BU-403: Charging Lead Acid. 48v battery percentage chart

BU-403: Charging Lead Acid

The lead acid battery uses the constant current constant voltage (CCCV) charge method. A regulated current raises the terminal voltage until the upper charge voltage limit is reached, at which point the current drops due to saturation. The charge time is 12–16 hours and up to 36–48 hours for large stationary batteries. With higher charge currents and multi-stage charge methods, the charge time can be reduced to 8–10 hours; however, without full topping charge. Lead acid is sluggish and cannot be charged as quickly as other battery systems. (See BU-202: New Lead Acid Systems)

With the CCCV method, lead acid batteries are charged in three stages, which are [1] constant-current charge, [2] topping charge and [3] float charge. The constant-current charge applies the bulk of the charge and takes up roughly half of the required charge time; the topping charge continues at a lower charge current and provides saturation, and the float charge compensates for the loss caused by self-discharge.

During the constant-current charge, the battery charges to about 70 percent in 5–8 hours; the remaining 30 percent is filled with the slower topping charge that lasts another 7–10 hours. The topping charge is essential for the well-being of the battery and can be compared to a little rest after a good meal. If continually deprived, the battery will eventually lose the ability to accept a full charge and the performance will decrease due to sulfation. The float charge in the third stage maintains the battery at full charge. Figure 1 illustrates these three stages.

bu-403, charging, lead, acid, battery, percentage

The battery is fully charged when the current drops to a set low level. The float voltage is reduced. Float charge compensates for self-discharge that all batteries exhibit.

The switch from Stage 1 to 2 occurs seamlessly and happens when the battery reaches the set voltage limit. The current begins to drop as the battery starts to saturate; full charge is reached when the current decreases to 3–5 percent of the Ah rating. A battery with high leakage may never attain this low saturation current, and a plateau timer takes over to end the charge.

The correct setting of the charge voltage limit is critical and ranges from 2.30V to 2.45V per cell. Setting the voltage threshold is a compromise and battery experts refer to this as “dancing on the head of a pin.” On one hand, the battery wants to be fully charged to get maximum capacity and avoid sulfation on the negative plate; on the other hand, over-saturation by not switching to float charge causes grid corrosion on the positive plate. This also leads to gassing and water-loss.

Temperature changes the voltage and this makes “dancing on the head of a pin” more difficult. A warmer ambient requires a slightly lower voltage threshold and a colder temperature prefers a higher setting. Chargers exposed to temperature fluctuations include temperature sensors to adjust the charge voltage for optimum charge efficiency. (See BU-410: Charging at High and Low Temperatures )

The charge temperature coefficient of a lead acid cell is –3mV/°C. Establishing 25°C (77°F) as the midpoint, the charge voltage should be reduced by 3mV per cell for every degree above 25°C and increased by 3mV per cell for every degree below 25°C. If this is not possible, it is better to choose a lower voltage for safety reasons. Table 2 compares the advantages and limitations of various peak voltage settings.

Maximum service life; battery stays cool; charge temperature can exceed 30°C (86°F).

Slow charge time; capacity readings may be inconsistent and declining with each cycle. Sulfation may occur without equalizing charge.

Cylindrical lead acid cells have higher voltage settings than VRLA and starter batteries.

Once fully charged through saturation, the battery should not dwell at the topping voltage for more than 48 hours and must be reduced to the float voltage level. This is especially critical for sealed systems because they are less tolerant to overcharge than the flooded type. Charging beyond the specified limits turns redundant energy into heat and the battery begins to gas.

The recommended float voltage of most flooded lead acid batteries is 2.25V to 2.27V/cell. Large stationary batteries at 25°C (77°F) typically float at 2.25V/cell. Manufacturers recommend lowering the float charge when the ambient temperature rises above 29°C (85°F).

Figure 3 illustrate the life of a lead acid battery that is kept at a float voltage of 2.25V to 2.30V/cell and at a temperature of 20°C to 25°C (60°F to 77°F). After 4 years of operation permanent capacity losses become visible, crossing the 80 percent line. This loss is larger if the battery requires periodic deep discharges. Elevated heat also reduces battery life. (See also BU-806a: How Heat and Loading affect Battery Life)

Permanent capacity loss can be minimized with operating at a moderate room temperature and a float voltage of 2.25–2.30V/cell.

Not all chargers feature float charge and very few road vehicles have this provision. If your charger stays on topping charge and does not drop below 2.30V/cell, remove the charge after 48 hours of charging. Recharge every 6 months while in storage; AGM every 6–12 months.

These described voltage settings apply to flooded cells and batteries with a pressure relief valve of about 34kPa (5psi). Cylindrical sealed lead acid, such as the Hawker Cyclon cell, requires higher voltage settings and the limits should be set to manufacturer’s specifications. Failing to apply the recommended voltage will cause a gradual decrease in capacity due to sulfation. The Hawker Cyclon cell has a pressure relief setting of 345kPa (50psi). This allows some recombination of the gases generated during charge.

Aging batteries pose a challenge when setting the float charge voltage because each cell has its own unique condition. Connected in a string, all cells receive the same charge current and controlling individual cell voltages as each reaches full capacity is almost impossible. Weak cells may go into overcharge while strong cells remain in a starved state. A float current that is too high for the faded cell might sulfate the strong neighbor due to undercharge. Cell-balancing devices are available compensate for the differences in voltages caused by cell imbalance.

Ripple voltage also causes a problem with large stationary batteries. A voltage peak constitutes an overcharge, causing hydrogen evolution, while the valley induces a brief discharge that creates a starved state resulting in electrolyte depletion. Manufacturers limit the ripple on the charge voltage to 5 percent.

Much has been said about pulse charging of lead acid batteries to reduce sulfation. The results are inconclusive and manufacturers as well as service technicians are divided on the benefit. If sulfation could be measured and the right amount of pulsing applied, then the remedy could be beneficial; however giving a cure without knowing the underlying side effects can be harmful to the battery.

Most stationary batteries are kept on float charge and this works reasonably well. Another method is the hysteresis charge that disconnects the float current when the battery goes to standby mode. The battery is essentially put in storage and is only “borrowed” from time to time to apply a topping-charge to replenish lost energy due to self-discharge, or when a load is applied. This mode works well for installations that do not draw a load when on standby.

Lead acid batteries must always be stored in a charged state. A topping charge should be applied every 6 months to prevent the voltage from dropping below 2.05V/cell and causing the battery to sulfate. With AGM, these requirements can be relaxed.

Measuring the open circuit voltage (OCV) while in storage provides a reliable indication as to the state-of-charge of the battery. A cell voltage of 2.10V at room temperature reveals a charge of about 90 percent. Such a battery is in good condition and needs only a brief full charge prior to use. (See also BU-903: How to Measure State-of-charge)

Observe the storage temperature when measuring the open circuit voltage. A cool battery lowers the voltage slightly and a warm one increases it. Using OCV to estimate state-of-charge works best when the battery has rested for a few hours, because a charge or discharge agitates the battery and distorts the voltage.

Some buyers do not accept shipments of new batteries if the OCV at incoming inspection is below 2.10V per cell. A low voltage suggests a partial charge due to long storage or a high self-discharge caused by a micro-short. Battery users have found that a pack arriving at a lower than specified voltage has a higher failure rate than those with higher voltages. Although in-house service can often bring such batteries to full performance, the time and equipment required adds to operational costs. (Note that the 2.10V/cell acceptance threshold does not apply to all lead acid types equally.)

Under the right temperature and with sufficient charge current, lead acid provides high charge efficiently. The exception is charging at 40°C (104°F) and low current, as Figure 4 demonstrates. In respect of high efficiency, lead acid shares this fine attribute with Li-ion that is closer to 99%. See BU-409: Charging Lithium-ion and BU-808b: What Causes Li-ion to Die?

At the right temperature and with sufficient charge current, lead acid provides high charge efficiency.

Argument about Fast-charging

Manufacturers recommend a charge C-rate of 0.3C, but lead acid can be charged at a higher rate up to 80% state-of-charge (SoC) without creating oxygen and water depletion. Oxygen is only generated when the battery is overcharged. The 3-stage CCCV charger prevents this from happening by limiting the charge voltage to 2.40V/cell (14.40V with 6 cells) and then lowering to a float charge about 2.30V/cell (13.8V with 6 cells) at full-charge. These are voltages below the gassing stage.

Test show that a heathy lead acid battery can be charged at up to 1.5C as long as the current is moderated towards a full charge when the battery reaches about 2.3V/cell (14.0V with 6 cells). Charge acceptance is highest when SoC is low and diminishes as the battery fills. Battery state-of-health and temperature also play an important role when fast-charging. Make certain that the battery does not “boil” or heat up during charge. Put an eye on the battery when charging above the manufacturer’s recommended C-rate.


Watering is the single most important step in maintaining a flooded lead acid battery; a requirement that is all too often neglected. The frequency of watering depends on usage, charge method and operating temperature. Over-charging also leads to water consumption.

A new battery should be checked every few weeks to estimate the watering requirement. This assures that the top of the plates are never exposed. A naked plate will sustain irreversible damage through oxidation, leading to reduced capacity and lower performance.

If low on electrolyte, immediately fill the battery with distilled or de-ionized water. Tap water may be acceptable in some regions. Do not fill to the correct level before charging as this could cause an overflow during charging. Always top up to the desired level after charging. Never add electrolyte as this would upset the specific gravity and promote corrosion. Watering systems eliminate low electrolyte levels by automatically adding the right amount of water.

Simple Guidelines for Charging Lead Acid Batteries

  • Charge in a well-ventilated area. Hydrogen gas generated during charging is explosive. (See BU-703: Health Concerns with Batteries)
  • Choose the appropriate charge program for flooded, gel and AGM batteries. Check manufacturer’s specifications on recommended voltage thresholds.
  • Recharge lead acid batteries after each use to prevent sulfation. Do not store on low charge.
  • The plates of flooded batteries must always be fully submerged in electrolyte. Fill the battery with distilled or de-ionized water to cover the plates if low. Never add electrolyte.
  • Fill water level to designated level after charging. Overfilling when the battery is on low charge can cause acid spillage during charging.
  • The formation of gas bubbles in a flooded lead acid indicates that the battery is reaching full state-of-charge. (Hydrogen appears on negative plate and oxygen on positive plate).
  • Lower the float charge voltage if the ambient temperature is higher than 29°C (85°F).
  • Do not allow a lead acid to freeze. An empty battery freezes sooner than one that is fully charged. Never charge a frozen battery.
  • Avoid charging at temperatures above 49°C (120°F).


[1] Courtesy of Cadex [2] Source: Power-Sonic

The material on Battery University is based on the indispensable new 4th edition of Batteries in a Portable World. A Handbook on Rechargeable Batteries for Non-Engineers which is available for order through Amazon.com.

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I have a lead Acid battery which is 12 volt 72AH. The load I applied to it is a fan of 12volt 9 amp. It only runs about an hour and slows down. As per my battery capacity it should run almost 7 to 8 hours. I have checked my charger’s charging voltages but it all fine. Also I have fully maintained my battery regarding its electrolyte level. Kindly could you please tell me what is the reason for that?

it is great and very knowledgeable. it hellps me in my research

A couple things confuse me here about SLA batteries. First, the presentation says these use the CCCV method, then goes on to discuss variable/multi-phase charging. So which are they really? Second, how does a vehicle alternator perform optimum charging of a SLAB? How does it prevent over or under-charging? Are alternators typically CCCV chargers?

@ Mark Hedge: Your battery manufacturer should specify the exact charging parameters. I would consult them for info.

This article is all well and good for a brand new, unused AGM type battery. For an AGM battery that has been in cyclic service for six months this article has a lot of faulty information. Charging a used AGM battery at 14.4 volts will kill that battery in short order due to over pressure gassing. By far, the most successful way to charge an AGM throughout its life at room temperature is using a maximum voltage of 13.8 volts. For long term float 13.3 volts is appropriate until a discharge occurs. Used batteries do not at all behave like brand new batteries and is especially true with AGM type.

1 Stationary lead-acid battery bank, valve regulated, voltage 48 vdc, nominal capacity 400 Ah, 24 cells of 2 vdc, with final voltage per cell of 1.75 Vdc at a discharge rate of 10 hrs and temperature operation 25 °C.

Please having read your article, especially on the temperature limit for charging lead acid batteries,may I ask if you will recommend buring battery for underground operations

I have a 1550 AH, 24V. 12 cell flooded battery which I am using to power my home. It is charged by solar. What would you recommend the Absorb charge voltage and how frequently should it be equalized and at what voltage and for how long? Thank you

Dear Sir, Please tel me a good battery additive or chemical for forklift battery desulphating. Thank You Thejamal

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Hi, Since you are controlling the charging manually you want to charge to 14.6 or so for a limited time and at a limited current. I have a 350AH flooded cell that I charge at 10 A. At 14.6 it levels off to about 5A, and I let it sit there for 12 hours. Below 13.5 V limit the current to C / 20 (About 20 amps for me). Charging above 13.8 will create gas. The logic varies with AGM do some reading. In most cases a lead acid battery should come to rest at 12.6V but the real test is specific gravity if it is flooded plate. What you never want to do is split water into gas. AGM will do some recombination, flooded plat creates bubbles so you replace water after a long time. You see a lot of manufacturers spec 13.2 to 13.8 and so. Charging at these lower voltages reduces gassing but takes a LONG time to reach full charge. Never over charge Gell Cells as the gas formation can push around the silica gell, at least so I was told. Bob K.

@Alex First of all, if you have the equipment, you have to calculate and set the charging voltage required based on ambient temperature. The formula for that, if I’m not mistaken, is: (2.4(number of cells))((difference between 25 degrees C and current ambient temperature)0.004(number of cells)) Here 2.4V is charging voltage for single cell required when ambient temperature is 25 degrees C and 0.004V is how many volts we compensate for each degree. Here are 2 examples: 12V battery, so 6 cells, ambient temperature is 30 degrees C. (2.46)((25-30)0.0046)=14.4(-0.12)=14.28V 12V battery, ambient temperature is 15 degrees C. (2.46)((25-15)0.0046)=14.40.24=14.64V Okay we’re done with voltage. The charging current should be limited to 1/10 of the battery capacity. You can stop charging when the current is no longer dropping as rapidly as it did before. Like if the current did not get lower by 0.1A in 1 hour, the battery is probably close to fully charged and can be disconnected.

Okay. I still dont get something. I am charging 12 volts car battery. When I measure voltage during charging its showing 13,20 volts. If I remove the charger, the volts rapidly drops to 12,40 or less for 30 min until stabilize and then slowly continue to drops. If I leave it to charge to higher volts, lets say 13,40, it is same, just the stabilization phase is higher. 12,60 volts. So: On what voltage indicator should I stop charging. 12,8 v. which showing me during charging, Or I should wait and stop charging on higher voltage, for instance. 14,5 and stabilization measuring 12,8 volts ?

Hi, I have two gelled electrolyte VRLA batteries a) 2 volts 225Ah and b) 6 volts 100Ah where earlier separator of thickness 4.9mm was used between the ve and.ve plates. Recently we observed failure in 2V 225Ah battery when separator of thickness 2.9mm was used therefore, we experimented using a 4.9mm separator. Unfortunately, we did not see any changes. what do you think is the reason for failure? Thanks in advance Vaish

to Mahmou Awad Lead batteries and NiCd are different tecnologies and has different voltage per cell for charging. normally NiCD are 1,42v per cell and Lead 2,27V (floating mode) normally Lead battery chargers MUST control both current and voltage during charging normally Lead batteries MUST be charged up to 10% of labeled Ah (100Ah = 10A max charging current. If you charge higher may overheat. loose life time or worst case. explode. In Open (top cup) Lead Acid battery it produce nocive gases. NiCD batteries are more permisive, but needs its own charger. I do not recommend the use of NiCD charger to Lead Acid battery.

to Ryan: I think your clear question can be answered with a simple yes. The charger in float mode gives 13.5. 13.8V. So both batteries will get that voltage, and assuming they are both in good shape and not defective (like a shorted cell or so), this will work.

Hi, I have a 7amp multi-stage charger which switches to a float charge. ( Says it’s rated to charge up to 140 Ah batteries) I have 90Ah starting battery and100Ah house battery in my boat. Question is if both batteries are fully charged and I connect my charger to one then let it cycle to float mode then connect the two batter in parallel will it maintain a float charge on both batteries? Thanks in Advance Ryan

Hi i have Lead acid battery No# 32batteries (UPS) ,but the UPS is faulty 6 month ago, right now i have traditional charger 110VDC,35A using for Nicd battery bank The question Is it possible to use this charger to charge the lead acid batteries and how Nr of batteries for right charging ,time? Sincerely

@Jeff If they are drawing 1.3A, they are not fully charged. Charge them separately with a constant voltage of at least 14.4V, something like 14.7V would be better of course. Any adjustable bench power supply would probably outperform an off the shelf battery charger if you’re looking to recover a battery or prolong it’s service life. Watch the current. If current starts going up it could be that the battery is starting to accept the charge better meaning that it’s recovering. At some point it should stop going up and start getting lower and lower. Stop charging if stayed the same for 2 hours (as well as the voltage).

I have 3 12V SLA batteries wired in series and found that the group wouldn’t charge. I individually trickle charged each battery and was able to get the three to charge back to 36v. But even when fully charged the group draws about 1.3A while connected to the charger so it won’t shut off. I found 2 of the charged batteries draw a couple hundred mA, but the third one draws way more and it increases while charging. The battery will start charging drawing

@Mark Ritchey How did you send the battery? Looks like 3 cells shorted out. This usually happens if battery is kept discharged for a while and then when charged cells short out because of hydration.

Hello, My battery should no signs of problems, but after a month in the body shop, it read 4.5 V. I sent the battery to the body shop and requested a 24 hour charge. When I got it back, it read 6.5V and was hot to the touch. After seeing the voltage was 4.5V, how many careless mistakes were made from that point in time? Thank You for your time and consideration? Sincerely, Mark Ritchey

Lol try proper full charge CaCa Calcium lead acid bateries with 14,4V. This is for old antimony lead alloy bateries. 14.2-14.4 is enough for this type.

to Tim: it all depends on the word approximately. With 12V, the battery will not charge or only draw a very small current. But then again, with the small current load, your generator voltage might be higher. So your system could find a balance itself. If not, a step-up converter will do the trick and load your battery with a decent current. Keep in mind that you won’t be able to load the battery with 4A; that is too high for a 9Ah battery. I suggest not to go above 1 A. (1/10 C) I looked in the Li-ion protectors, and they do what the are called: protect against overcharge, undercharge, and overcurrent. They are not battery chargers. E.g. the overcurrent values are way too high for your battery.

Hello, Sorry in advance if my question does not make any sense, I am quite new to the electronics world. Currently I am working on a small scale wind-turbine, where we’re using a DC motor that outputs approximately 12V, 4A at our desired RPM. If I wanted to charge a 12V 9AH led-acid battery, would I need to step up the voltage using a DC-DC converter to get a successful charge? And also, in terms of charge controls could I use a 3-5A 14.8V/16 Li-ion Battery Charger protection board? I read that you could use one for a led acid battery, and I have one just lying around. Again, sorry if this is incredibly incomplete.Thank you. Tim

I’ve tried to reply 3 times and apparently I type the captcha wrong every time and it deletes my whole text. I give up. Note from Moderator We are aware of this issue and are attempting to remedy. Thank you for your feedback.

Brand new 24V mobility scooter. 22Ah First trip

To lance a barker: you mean it is below 5.5V, and you cannot get it higher? I’m afraid it is dead. A 12V lead battery should never go below let’s say 10V. I keep them above 11V. Or is the voltage 5.5V, and when you connect a charger the voltage goes up but no current flows? Dead too. You can try to keep it connected for a long time and hope it recovers, but chances are small I’m afraid.

to Paolo: since a battery is not a resistor, the current is indeed changing all the time while the voltage stays constant. If you apply the charge voltage to an empty battery, the current will be way too high, but will keep on dropping until it reaches near zero (except for leakage current). To avoid that high current values, the current must be limited. A standard charger does that. The battery itself does not have a constant current phase; it is the charger limiting the current. So you are right about that.

i have a 12v 10ah battery which when its gets to 5.5 volts it wont charge anything up its like a dead battery can someone help me to solve this problem. many thanks

This ‘Constant Current’ nomenclature just seems deceiving. It’s not constant current. it’s current limit? Limit your charge current to 0.1C (or whatever you choose). the current will drop as voltage increases. There may be a ‘Constant Current’ phase but it’s only the limit you set.

I have an auto scrubbing floor cleaning machine that uses 6 12 volt lead acid batteries.To preserve the life of the batteries, is it best to recharge the batteries after EACH usage or wait until the batteries get low before recharging ?

Hi, I would suggest your voltage levels and timing logic is far from good. You want to charge to a much higher voltage. Let the battery discharge deeper. A lot depends on peak discharge currents. Go up to my sunduino.com web site you can download some docs that control charging. I think I have the setup for a 20AHr batter. Al I hte to tell you this temperature makes BIG difference. Bob K.

My standby charge for a 20Ah sealed lead-acid battery starts when battery voltage reaches 12.8V, after which I charge with constant voltage at 13.65V until charge current reduces to 50 mA. Here is my problem: Initially the discharge/charge cycle took some 9h, pushing some 0.7 Ah through the battery. This cycle time has gradually become shorter so that now the discharge/charge cycle is only about 30 minutes, pushing 0.07 Ah through the battery. This suggests the battery is becoming less efficient since the discharge time has decreased and the charge time has also decreased, and that what I am doing is not good for the battery. Any Комментарии и мнения владельцев or suggestions would be highly appreciated. Kind regards, Willem FergusonMy standby charge for a 20Ah sealed lead-acid battery starts when battery voltage reaches 12.8V, after which I charge with constant voltage at 13.65V until charge current reduces to 50 mA. Here is my problem: Initially the discharge/charge cycle took some 9h, pushing some 0.7 Ah through the battery. This cycle time has gradually become shorter so that now the discharge/charge cycle is only about 30 minutes, pushing 0.07 Ah through the battery. This suggests the battery is becoming less efficient since the discharge time has decreased and the charge time has also decreased, and that what I am doing is not good for the battery. Any Комментарии и мнения владельцев or suggestions would be highly appreciated. Kind regards, Willem Ferguson

Not having any luck finding an answer. Have a 16.5AH ATV battery with life left in it that I switched out with a new one for winter. Also have a 35 AH LG mower battery that’s dead. Both are 12 V batts. Is it not possible to use the 12V 16.5 AH ATV battery in the mower without sacrificing anything but CCAmperage. just having a much shallower ‘cycle’? The ATV is a 500cc High Output unit and the mower is a 155 LT.

Hello, I want to buy an intelligent charger for my vehicle batteries, one of which is a 65Ah and the other a 79Ah. I have seen a charger on the Internet, rated at 5. 20Ah https://www.bidorbuy.co.za/item/392591747/Battery_Chargers_12V_Intelligent_Pulse_Battery_Charger_5_20AH_Collections_are_allowed.html Does this mean that my vehicle batteries are beyond its capacity to recharge? Thank you, Keith Taylor.

I have a 20Ah Panasonic sealed lead acid battery for driving LED lighting during frequent electricity blackouts. I use a constant voltage charger with a maximum current of 2A and a voltage of 13.65V, charging the battery to around 13.5V (i.e. ~ 2.25V/cell). The battery voltage is monitored and when this falls below 12.9V, the charge cycle is repeated. Is there a need to improve this way of charging the battery? Are equalisation charges or anything similar required?

Response to Bob k Thank you for your response of 19th Oct The batteries are in a different country at the moment, so an exact response is difficult As I mentioned the batteries are part of a solar system ad electricity is something I have limited knowledge of. The system has worked fine for the past 3 years, the batteries are circa ten years old. I have not checked the voltage on each cell. From the limited time they run the house they are not fully charged. When I check with the Specific gravity meter the reading does not rise above the bottom of the scale. If I charge them from a generator say for four hours there is no significant change on the SG meter, the battery charger shows about 40 amps and this does not drop. The batteries fully discharge each evening as they have little capacity. Should I take the bank apart and try each cell separately?

hi, i have a strange thing going on with my lead acid battery. when i charge the 840ah (2v cells. 48v) all goes good, amps constant, volt goes to 60v. stays there in absorption, amps go down. TILL a point in time the amps dont drop anymore ( the voltage stays 60v stable). therefore the charger puts in the rest of the absorptiontime 30A into the battery. what is wrong here? thanks kristof

Hi Can a charger 5 amp 24 v damage batteries. 2 x 12 v 55 amp hour. over a period of time.if so what causes this to happen As I have had 2 sets of batteries in past 6 months fail. both at around 40%. which is strange as I would have thought if battery fails it would be only one Bath sets batteries failed after approx. 3-4 months. on both sets. and 2 different makes of batteries I am using same charger regards Patrick find this strange,

Hi, When you charge the batteries what voltage do they reach? Do not go adding any material to the batteries, charging well it the first issue. You also want to tell us the SG that you measure in the charged and discharged state. You want to tell us the capacity of the cells and how manny A Hr your are getting for discharge. Also tell us to what voltage you are discharging. Bob K.

Hi ! this is quit long so apologies in advance I have a solar battery system charged by solar panels It comprises twelve 2 volt batteries they were manufactured by Isofoton around ten years ago Replacement cost is around £800 per battery so there is a bit of incentive to find a miracle cure. I have read a lot about baking soda and Epsom salts and differing opinions. The batteries all seem to be in a similar condition, they hold a little charge but this quickly seems to run out, attempting to charge them with a generator has no effect ( shown by the specific gravity meter ). The batteries seem to have fallen of a cliff rather than a suffered a gradual deterioration. Given that replacement is circa £10k it would be very nice to find a way to reduce that. I have taken one of them apart. The negative plates were what I was expecting to find they are sheets of perforated lead with the perforations full of a paste (presumably this increases performance). The lead appears clean and does not appear to of deteriorated. Each plate is connected to a spreader bar which is in turn connected to the battery terminal post. If my understanding is up to speed the negative aide of the battery does not degrade ? The positive plates have thrown me a tad, instead of plates ( similar to their negative counterparts), connected to the spreader bar are twenty 3 to 4mm mm dia. Lead rods, these sit in a fabric sleeve and each rod is surrounded by paste. This paste is darker in colour then that in the negative plates. I could be mistaking this paste for shed lead. the spreader bar and terminal post are heavily covered with flaky pastry, presumably shed lead. The rods lie side by side to create a sheet of a comparable size to the negative plate This is the part where you get to fall over laughing. I was hoping to find the positive plates to be similar to their negative brothers, I was going to melt the down and re cast the positive plates, weld them back to the spreader bars. put it back together and hey presto, something resembling the performance of a new battery. NOW the questions Am I correct in my understanding the negative side is untouched by degradation ? What purpose do the individual rods serve, they are all connected to the spreader plate. Can I simply substitute the rods with a sheet of lead similar to the negative plate? Could I take the negative half of one battery to replace the positive side of another to make one good battery from two. Does the paste make a huge difference? Do I need to replace the electrolyte ? I have damaged the battery top, do you know a store that sells replacement, I seem to remember an online supplier selling the constituent parts but can’t find it now I want it

to Ben: the full battery won’t draw much current; the charger will take care of that. If you look at the drawing in the beginning of this article, you see that for an empty battery, the current is the highest and needs to be limited so the battery does not get damaged. But at a certain point, the voltage per cell reaches the maximum, and the current begins to drop down. You could drive the voltage higher and keep the current, but that will do permanent damage to the battery. So lead chargers have a voltage limit AND a current limiter.

The voltage of starter battery 75ah,lead acid sealed battery dropped from 12.75 to 12.20V within 6 weeks of production. What could be the cause and how will the problem be solved.

Hi, I’m hoping you may clear this up for me, If I had a charger for an automotive 12v lead acid battery that was current limited at say 150 A (unrealistic I know) and the battery was previously fully charged, how much current would be drawn from the charger if I were to measure it with a metre? Would a flat battery want to draw more current than a fully charged battery? Regards Ben

to Jerry: clear question, but I’m afraid the answer won’t be that clear. It all depends. I think that the charger circuit will not recognize that the battery is too small, and will charge with too high current and damage the battery. The charger cannot be damaged by that. (There is probably a way to reduce the charge current of the charger by changing some parts in the circuit, but you need the schematic for that.) But on the other hand, a lead charger works with constant voltage and current limiting, so after the initial current peak (with empty battery), the current might be quite acceptable. If you put a series resistor, it will indeed reduce the current, and it gives you the ability to measure the current: you measure the voltage over the resistor (volts), divide that number by the number of ohms of the resistor, and you have the current in Amps. E.g. you put 1 ohm and measure 0.8V over it, it means you have 0.8 Amps. For your 7.5Ah battery, charge current should be below 1 amp. But a 2 amp or even 3 amp peak for a few seconds won’t do harm. So a 1 ohm resistor in series would be a good idea to start with, but measure the current by measuring the voltage over the resistor. If current is low enough, you can try using a smaller resistor like 0.1 ohm. (0.08V over 0.1 ohm means 0.8 Amps) If that is fine too, you can completely remove it. But don’t forget you will have the largest current with an empty battery. You can put the resistor in or in. line; it doesn’t matter. Now for the load: your TV worked 13 minutes on a full battery. That means that the battery is delivering, very roughly, 30 amps. That’s a lot for a 7.5Ah battery. I got the feeling it won’t live long, and won’t enjoy its life either 🙂 Also, it won’t work with a 1 ohm resistor in series, so you must remove it before the load is connected.That’s no real UPS, is it. A diode over the resistor could overcome this issue, but it must be a BIG diode that can handle at least 50 amps, with as low as possible voltage drop. Don’t you have a second 7.5Ah battery? You can put it in parallel with the first one. 3 or 4 would be even better. Number of Ah is added then. With 2 batteries in parallel you get a 15Ah battery pack. They each get half of the charge current, and deliver half of the load current. Take care! Andre

Is it possible to charge a 12V 7.5Ah sealed battery using an Inverter rated 700VA 110Ah? I have an Inverter of 700 VA, (meant to work with 100. 135 Ah of 12 Volt Lead acid battery DC), I connected a fully charged 12 Volt 7.5 Ah Sealed maintenance free lead acid battery DC used in a UPS to the terminals and plugged in a Television to the inverter outlet and the TV ran for approximately 13 Minutes, which is to be expected of a UPS backup. Now my question is, Is it possible to Charge the same battery using the same inverter without blowing-up or damaging the 700VA inverter, 12v 7.5Ah battery, blowing some house fuse or overcharging. NOTE: The manual says, Charges at 10% of the battery’s rated Ah value. So for a 100-135 Ah battery it would be 10-13.5 Ah for 7.5 Ah it should be.75 Ah Will the Inverter do it automatically?? Can you reduce DC Ampere using resistors? serial or parallel. eg. (12V 11Ah DC) Resistor (OUTPUT 12V 1AhDC) If it isn’t much trouble, how much ohm resistor would be required to downgrade (12V ~10Ah) to (12V ~.75–1Ah) and should it be in the positive wire or negative wire? Thanks. 🙂

to Ahmad Rostami: NEVER full discharge. Half discharge and then refill is perfect. Lead, as well as Lithium, don’t like full discharge. to Wahid Anwar: probably the same answer for you. If you used your batteries until they are dead, you will need a replacement. For lead you can say: once dead = always dead. If you can fit a larger capacity battery it could help. If there is still like 20% charge left after your 36 holes, it is safe. Completely empty is never good. regards, Andre Regards, Andre

Hi, my 12V 36AH SLA battery which is about a year old suddenly won’t hold long.I use the battery with my motorized golf trolley which should carry me 36 holes.Now the battery barely able to finish 9 holes before going dead.How do I fix this problem.Thanka for your input.

In the name of God I have an electric motorcycle with lead acid batteries. I have an question: charge batteries when it completely discharge or charge it after half discharge(always be full charged?) Thanks

Hi, A small UPS is very inexpensive and you can add what ever battery size you wish. How much power do you require and for how long? Bob K.

Hello. i have a system with antenas working with 12 v. Now i want to put even batteries to make the system independent from the 220v AC power source. For this i do not want to use inverter or ups because they spent a lot of power instend of antenas itselfs. So i think the best solution is to work with only one voltage 12v. and make the battery work as in buffer state. so wen AC power fail the battery will be directly the power source for the antenas. On this point i want to know what type of charger should I choose and on witch voltage will the battery stay after full charge ? Thank you !

Yes, charging a battery is like voting in Chicago, do it early and often. So if it dies after 1.5 days then even at one day of operation the battery size might be a little Iffy. Consider operation on cold days as the battery ages. If you can not make it for a good day then you start to discharge deeper and that is worse. Battery life will shorten and expenses go up. Deep discharge is the kiss of death. Deeper you go the worse it is. Charging every night, or sooner if possible, is the right answer. Bob K.

I drive a ‘people carrier’ (large golf buggy) and the supplier tells me to only charge the batteries when they need it and not everyday. However a full charge easily lasts one day but not 2 which is a major problem as half way through the second day the batteries are drained. The vehicle has 8x 6 volt batteries and the charger is a massive 3 stage charger. Another place that has a similar buggy have told me that their supplier has told that it must be charged every night. I always understood a deep discharge was the worst thing to do to a lead acid battery. Please could I have a definite answer as I am sure only one supplier is right!

to Olaf Isele: in my opinion it won’t do any harm to not fully charge the battery after you bought it. Compare it with a car battery: it is mounted and immediately used to start the engine, drive a bit, stop, start again. Lead has a problem with too deep discharge, not with incomplete charge.

Does a first charge of a new Sealed Lead Acid AGM battery (60-70% charge when bought) have to go all the way to 100%? If only charging to 90 to 95%, and then using it to operate a fan or a pump, does that cause permanent damage to the battery? Or it is OK as long as during one of the next charges (let’s say after first use) the charge goes to 100% and then is stored (and checked every month)? I don’t have 24-36 hours to get to 100% before I need to use this just bought battery.

Which of the answer options would be applicable when charging a 100 amp-hour 12V lead-acid battery? The source of power for charging should be 2.3 to 2.45 volts per cell. The temperature of the electrolyte should not be allowed to exceed 32 deg C. Gassing within the battery DEcreases when nearing full charge and it will be necessary to reduce the charging current to a low finishing rate. The 1st option is correct according to this article. Could the 3rd option also be correct if there was INcreases?

I have an almost 20 year old 24V 1330AH Lead Acid Battery Bank which I charge by 3 seperate Solar Panel Arrays. Using a PLC, Current Sensor Relay and 3 Solar Chargers (2 dumb and 1 Smart) I can switch off the 2 dumb controllers when the Voltage reaches 28.8V and the Smart controllers current falls below a set point. My question is what is the maximum current I should be charging the battery at the Absorption stage?

To sureshbabu Yes of course it will take a long time, but the charger being soo small it will not bamage the batteries juste check occasionnaly that the battery voltage does not exceed 13.8V

To Mb Mubin the ideal charging time is 20 hours (most battery size) however there is not much gain compared to faster 16 hours charging time you can charge at faster rates (higher current) however this is detrimental to the battery usefull life (the number of charge / discharge cycles) on the other hand, if the battery is used rarely (like emergency back-up) then who caers if it only goind to do 5 or 10 cycles in its life, if this 5 or 10 cycles represent 15 years of service

to Kari: well, that was a clear explanation. I cannot match that. and my native language is Dutch 🙂 I don’t think it is the new batteries. When they get the proper voltage, which is equal for 4Ah or 7Ah, they will draw current, and the charger won’t say nothing is connected. So maybe something went wrong with the connections anyway, or with the charger itself. If you have a multimeter, you can test the DC voltage over the connected batteries. Should be like 13.xx volts each to charge. If the voltage is there, there is charge current, unless the batteries are defective. And the alarm system charger should give no alarm. If the voltage is not there, but is only 12.xx volts (the battery is delivering that voltage itself) it is not charging, and the charger is defective, or the connection between charger and battery. Or a fuse. Good luck!

I admit to being totally ignorant on this battery issue. I have an alarm system using two 12v 7AH batteries. They corroded setting off the alarm and I discovered that the installers had used two 12v 5AH batteries instead, but the system worked fine for about 8 years anyway. I reordered new batteries and after waiting for two days received two 12v 4AH batteries. The man working at the store said that these are fine, they just won’t hold a charge as long if the power goes out, which it does frequently here. I installed them and am getting a new power fault erroron one panel it shows No or low battery trouble and the main panel Switching Power supply fault. Is this due to the lesser batteries? I believe that I have hooked them up properly. In the process of doing so I discovered that the original installer didn’t follow the wiring diagram and made a complete mess so something else may be going wrong. Even the wiring schematic of what not to do looks likes heaven compared to what the guy did.

Hello, I have a question. What is the minimum charging time of a small capacity lead acid battery (12/15Ah )?? Can’t we reduce the charging time to 2/3 hours for this (small capacity SLA ) battery? ? Thanks

Hello, What is the minimum charging time of SLA batteries? ? Can’t reduce the charging time to 2/3 hours for small capacity battery such like 12,15ah? ? Thanks

please share me if there is any idea regarding the battery discharge we having any possible way to gain those current like power bank

to Barun: 14.4V drill battery means 12pcs 1.2V NiMH cells in one pack. When full, the voltage can be above 15V. These batteries can also deliver a lot of current. So when you connect the drill battery directly to the small lead battery, the current could be too high. You better add a resistor in series. So the. of one battery to the. of the other battery; the of the one battery to the resistor; the of the other battery to the other side of the resistor. The resistor can be e.g. 3.3 ohm 5 watt. You can also use a car halogen light 55W 12V instead of the resistor. It won’t give light 🙂 but it will limit the current to a safe value. If you have a multimeter you can measure the voltage over the lead battery you want to charge. You will see it raise slowly. It will go higher than 13.8V so you cannot keep it connected forever. But you can leave it raise up to 14.5V and then disconnect.

We have impact Silver Hi power souther batteries 12 V 200AH @ C20 @1.250Sp.Gr@27Degree C Can we charge this batteries with External Charger 12 V 6AH. Please reply

Hi everyone i have a 14.4v drill battery and i have a 12v 4.5 ah battery and i want to charge my 12v battery can i charge it with my drill battery

To Saravanan The voltage is draining That means there is some load on the batteries (something on the generator is consuming current) You have to get an electrician to find what is the trouble

Hi,my rc car has DJY NI-cd 700mAh AA battteries of 4 each I want to know how much time to take to full charge and how to know it is fully charged

dear, i have a doubt,so please anybody knows means,plz tell me the ans, i have battery charger model is adel CBI2410A,this charger used to charging the 12v 4 batteries connected in Diesel generator,the batery voltage is draining automaticalley, i thought may be batteries are faulty,so now i am replaced all batteries,but now also same problem,,so now the battery charger is faulty means it cannot give output voltage,but battery charger is in good condition,the battery charger shows an alarm indicator ,this indicator blinking three times,i checked internet,result three time blinking means battery internel element is short circuit. so what is the problem. how can i solve the issue,and stop the battery voltage draining

To Steve F when you say wont charge is that with your new or old charger? 10.2V, open circuit? sometimes it is normal when batteries are sulfated very difficult to evaluate keep on charger, sometimes it may take weeks! good luck

To Ankit most of your answers can be found at the beginning of this blog 12 to 16 hours how would I arrange to charge it from a rectifier? it depends on the machine. Usually there are no adjustments on low cost battery chargers just 2 wires to connect 90Ah, if new, should be charged at a max rate of 9A

A 12v lead acid battery of 90 A-h capacity is to be charged. What test would i make on the battery and how would I arrange to charge it from a rectifier? How many hours should the battery remain on charge?

to Md. Abdus Salam: right voltage is 2x 13.8 = 27.6V. When put in series, there is always a risk of unbalance when the batteries are not exactly equal. That means you get more voltage over one battery. Most discharged one has lowest voltage. Or if there is a defective one: it can be the one with the lowest OR with the highest voltage. Normally they tend to equalize during the charge, but one battery (with the highest voltage) could have a hard time and can even get damaged before it gets equal to the other. Take care the voltage does not exceed 14.5V for a longer time. In my opinion, if possible, charge them both separately to the exact same state. E.g. leave them connected for a day to 13.8V. You can place them in parallel to do so. After a day or so they will be equal charged. Now you put them in series again, use them, and charge them with 27.6V. If you still see a big difference again after a while, it means one battery has a lot worse condition than the other and should be replaced. Again, it is hard to tell which one it is. You should test them individually to know.

I have two 12-volt Deep Cycle marine batteries. During last fishing season, I was recharging them every week with an old 5A manual charger, watching the gauge and disconnecting when it approached 0. Recently I noticed the electrolyte levels were low. I refilled them with distilled water, but both don’t fully charge now. One has charged back to about 12.7 volts and the was at about 50% charged. 12.2 volts. When I put the second battery back on the charger for 6 hours the voltage dropped to 10.2 volts. What happened? BTW. I just purchased a NOCO Genius 3500 to replace my manual charger. Thank you for any advice you can provide. SF

To Mubeen Aslam when you say “but now” does that mean it was OKAY and now it is not OK? have you changed the charger? or something some chargers like DELL and HP look like identical twins, same voltage, same current, same connector but not software compatible, also the contacts are reversed PLS provide more information

To Feb Andre the device your mentioning seems a universal power supply these devices (most power supplies) are constant voltage devices to charge the battery you need a constant current charger one way to do that is using the 9V position, and connect a light bulb in series in the circuit to limit the current you will need wo watch the voltage ant stop when it reaches 6.9V

to Pierre Laliberté incroyable y a des autos, j’ai eu une Pontiac qui mangeait les alterneteurs! Y a des mystères dans les batteries même que la technologie date de plus de 100and Depuis plusieurs années j’ai de Mercedes. Je les laisse quand elles ont 10 à 14 ans Les batteries, jamais remplacé, même celle de 14 ans et ne montrait aucun signe de fatigue Les autos américaines, GM et Chrysler, les batteries durent 3 à 5 ans gros max Quand je mesure l’électrolyte c’est 1.275 à 1.300. il n’y a jamais de stratification Le voltage est très élevé, 14.7 de moyenne, 15.3 froid (0~-10°C) Dès que j’accélère un peu la charge cesse (le courant de batterie indique.20A) et reprend quand je cesse d’accélérer Je vous avoue ne rien n’y comprendre Les alternateurs, starter de BMW, AUDI et Mercedes, 1500 min! Portez attention si les lumières fluctuent (due au variation de voltage) si ça varie = pas bon signe Mesurez la densité de l’électrolyte, prenez-note Brassez l’électrolyte, il vendent des poires pour ça chez CDN Tire (pas cher et ça vaut pas cher) Je siphonne droit dessus, et injecte de côté pour faire tourner l’électrolyte pendant 5 minutes Si la densité change, c’est causé par la stratification (voir acid stratification)

Sir? I have firefly rechargeable sealed lead acid battery 4.5Ah 6volts FEL B6 4.5 How can i charge it directly to my DC voltage regulator with voltages of 3v, 4.5v, 6v, 9v, 12v?

Dear sir I bought laptop a few months ago but now it has a battery problem. The problem is that ma laptop battery can not store charging when the laptop is on (usage ),but it can store charging when my laptop is on sleep or shut down. please give me the solution.

Thanks, Germain. yeah, I read they’re like 90% efficient as opposed to what, 65-70% for the PWM. I might hook the PWM and run my LED lighting or USB charge ports through its load port. My greatest load will be a Coleman Powerchill cooler (50w at 4.2 amps). Not sure if the cooler can stand up to running full-time, though.

Hi Dave, Don’t use à PWM controller with an unefficient technology! Choose a MPPT one instead and you will be happy forever.

Hi all, I pretty new to 12 RV systems, and am kitting out a van for retirement. I’m going with a split charge system, with a solar back-up for when I’m parked. Any all advice would be greatly welcomed. Here’s my plan so far: 2AWG 80a fuse Pollak isolator switch 80a fuse 105Ah wet battery #1 (Two 105Ah deep cycle batteries in parallel) 100w solar panel 10AWG 40a fuse 30a PWM charge controller 30a fuse battery #2 (grounded to chassis) 6AWG from battery #2 30a fuse power distribution box (using maybe four ports) (The fuse sizes are what were recommended by the solar kit manufacturer and various other sources) I’ll use the split charge while driving, and the solar while parked. Since the panel won’t be attached to my van, it will be disconnected from the system while driving. My concern is the alternator over-charging the house batteries. Should I mount a battery monitor to the house batteries, or will the alternator sense a full charge stop charging them? My van is an ’89 Dodge Ram Wagon, 15 passenger, with a rear compartment a/c unit (now disabled), so I’m not sure if it’s a high-output alternator.

To Anita. Je n’ai pas de problème encore avec la batterie mais je les vois s’en venir. Un collègue a un Honda CRV 2011 et il en est à sa 4e batterie. J’ai acheté un testeur de batterie Ancel BA101 et ma batterie de Pilot 2017 est à 87% de State of Health mais 40% de SOC en revenant de 40 km de grande route. La batterie du CRV 2017 est à 87% de SOH mais était à 18% de SOC. Garder une batterie aussi bas sur une longue période va la tuer certainement.

To Wally it is not straight forward to modify vehicles I did have a camping trailer that the batteries were getting ultra hot on long driving my best advise is to contact the manufacturer, as they are the only one who knows the chemistry and the voltage and at the end, this will not tell you what you need to do I would suggest to make a 13.8V disconnect circuit

To Pierre Laliberté pas évident avec les autos moderne personellement j’ai toujours vu 13.8V ou 14.4V a froid 14.4 ça marche plus pour moins longtemps! 12.0 est trop bas, cen’est pas la première fois que j’entends ça de ne pas charger la batterie pour sauver du carburant C’est très difficile de savoir leur plan de match historiquement, sur les produits Chrysler les batteries duraient 3 ans (3 hivers) et la batterie pouvait faire un autre 2 hivers sur un véhicule GM sur des voitures Mercedes, j’en ai eu qui ont duré 12 ans sans problème ni faiblesses je ne sais pas à quoi c’est du Sur les Mercedes la batterie est plus grosse que les voitures Américaines comparable et beaucoup plus grosse que les Honda est-ce que la voiture ne démarre pas? pouvez-vous vérifier le niveau d’éectrolyte? parfois faut casser le couvercle et le recoller (pas évident) puis certains chargeurs sont des cuiseurs de batteries. ils font de domages que de bien bonne chance

To Niska Niska sorry for the delay 13.8V at 20°C, higher voltage at lower temperature I see 14.4 on automobiles at.40°C, 13.8 in summer Can you explain how ambient temperature are playing role fir battery voltage? I did not find exact charge profile. Battery University says not to charge above 49° what I find is these high voltage applications do not last as long as lower voltage higher current applications I would suggest to contact the manufacturer as they know their chemistries Best Regards

to Dr. Kalinba: Thanks for your clear story. The batteries you talk about are 7Ah sealed batteries, right? To be honest, it sounds to me that the built-in chargers are bad. Probably it is just a small transformer rectifier; no voltage and/or current regulation at all. There is a rule-of-thumb saying that the remaining capacity is the voltage above 12 x 100. So if you have 12.20V you have 20% capacity. Some questions:. Assuming your battery has 12.20V. Is it still the same voltage after a week or so? Or is it decreasing. If so, is there some sort of standby load of the amplifier? If the voltage is still 12.20V after one week, you don’t have excessive self-discharge and maybe your battery is not dead at all. You can try taking it out and charging it with a good charger If the built-in charger is indeed a slow unregulated charger, it is very well possible it never goes above 13V or so. You need 13.8V to fill the battery. But if you always charge with lower voltages, you can have sulfatation inside the battery. There exist de-sulfatation tools that give charging pulses (Amazon) but be careful; this is not a car battery we are talking about. A sealed battery should be charged now and then with 14.3. 14.5V until it is full, to avoid sulfatation. Always charging it with the safe 13.8V can already cause sulfatation over time, but charging it with a lower voltage could prevent full charge and will certainly cause sulfatation. I quickly looked at Amazon, and this one: MBC010 12V/1A Smart Battery Charger / Maintainer could do the job for your battery as charger. To test your built-charger: simply test the battery voltage while charging. If battery is empty it can be even below 13V, but over time it should certainly go up to 13.8V. If it doesn’t, you cannot fill the battery completely since it never goes to float charge mode. You cannot refill a sealed battery; there is no liquid water inside. I hope this helps.

Hi, My first through is this might be a Consumer Level product and if so I would first suspect the charger. The voltages you mention, 12.2 and 12.5 both sound low. At rest I would expect something like 12.6 though that will change a little depending on battery chemistry. You batteries don’t sound very old. I would expect longer life. The power here sound off. A 200 watt amplifier is probably 50% efficient so you are really pulling bursts of 400W For a 12V battery means 30 to 50 amp peaks. That is asking a lot from a small 7AH battery. Industrial chargers use multi phases of charging, but those typically run with larger batteries. What you might try is using a current limited lab supply (if you have on) to charge the new and old batteries You might also try for a very limited length of time a commercial car battery charger just to see if the batteries can be more fully charged. But watch out, over charging of a Gel Cell type battery could damage the battery. You must be careful as batteries can explode with over charging. Also, if you are running your battery down to a very low voltage, 9 volts or less, you could be doing them damage. Get back with the make and model of the batteries. Bob K.

I am so glad that I have found this comment section. I would love to be able to chat with a person, who truly understands acid-lead batteries and chargers, because non of my friends or people around me I feel cannot truthfully and knowledgeably answer my questions. THE STORY: I have several portable 200Watt speaker systems that I use for our outdoor events. They come loaded with a 12V 7A standard acid-lead batteries. When brand new, I can use such a speaker and almost max output for 3-4 hours. One year has passed and now their use time is down to 50min to maybe 1h. YES, I did by new 12V 7A batteries, but it seems such a waste to keep piling those batteries. Here are my questions regarding trying to understand the lifespan, quality of the batteries: 1. After fully charging all speakers, some show a rest voltage of 12.20V, another one is at 12.50V. Does it mean that somehow the 12.20V has a worse battery and I should change it first. 2. A brand new 12V 7A has a rest voltage of 12.70V after put in the speaker and charged. Is this OK? I read somewhere that maybe it should be 13.1-13.2. 3. Is there a way I can know whether the built-in charging system inside the speakers is a good/optimal one? Would I be able to get longer lifespan if the batteries are charged with one of those store-bought chargers with multi-step processes and what not. Would they be able to raise an old battery standing voltage higher than the 12.2V mentioned above. 4. At the end, my old batteries can still be used to for 30-40minutes but this is not optimal for my use. Is there a way I can revive them to be able to use them again for 3hours? Filling in with water or buying some commercial solution? Would that help? It seems such a waste to have numerous half-bad batteries, which are alright, but simply not good enough for me.

My application involves an auxiliary battery in my daily driver being charged from the truck’s alternator through an isolator. The alternator puts out 14.4 to 14.6 volts. I run various accessories off the auxiliary battery including an inverter for 120 volt devices. Some devices operate while driving, such as the CB radio. I was just sold a Deka 24M AGM deep cycle battery. I’m finding conflicting information about the proper charge voltage for this battery. Is it safe to charge this continuously from the truck’s alternator, or should I return it for a standard wet lead/acid battery? Is there a limit as to how much I should allow the alternator to charge in this way? Thanks

Thanks Ron. I have a feeling that the batteries are probably DEAD. The electrolytes are all very low 1.14 to 1.16. One cell is at 1.00 only. I wonder if that alone will casue the rise in temperature?? This was not happening before the MMPT was added to the system. I am also wondering if the temperature is is just co-incidental to one cell or may be more being RIP, the batteries are 7 years old and I believe that I did look after them well.

I have a stand alone system with 4 Rolls Batteries (600amphours) and after recently adding a MMPT 100, the batteries temperature during charging are up to 72 degrees C. Is this acceptable or will it destroy the batteries.

Hi! I have concerne in regard to the state of charge and condition of the 12 V battery in my car. The battery can be as low as 12V even after riding a few hours at high speed. Some reference says that a 12 V battery at 12 V is at 50% SOC. The problem come from the behavior of the algorythm that some car manufacturer use. The alternator is not fully charging the battery to save on fuel. I asked my Honda dealer and I was surprised by there answer. They say that the alternator is only there to power the accesories like lights, audio. heated seats but it will not charge the battery. They even asked us to put the battery on a charger on a regular base to recharge it with an external charger. The problem I see is that in very cold temperature, it is not a good idea to have a partielly charged battery. You are risking freezing it. Honda charging system can go in LOW mode where it will only apply 12.6 V in certain condition. It also has a HIGH mode where it will put 14.4 V on the battery. Many people in cold part of the country a suffering from premature battery failure. Can this be the cause? Would like to have some facts. Thank you very much.

I am interested in purchasing a battery charger for 12v lead acid batteries. Walmart offers two models 3/15/40A engine start and charger for 64.32 and 3/25/75A engine start and charger for 58.19. They are both Stanley brand products. It seems to me I should buy the 3/25/75A model because it is 6 cheaper and offers higher charging and jumping amps. The reviews on both products are mostly good except the bad reviews are related to this product won’t jump start a dead battery or charge a battery that has less than 2 volts. For the purpose I am using the product for is to keep batteries fully charged and maintained. I don’t expect my batteries to go below 10 volts so I would think I unit has enough current to jump a battery maybe after putting on charge for a little while. Does everyone agree with my logic?

Enda F wrote: I have eight 6 V Trojan batteries in an off-grid system. PV panels are the main source of energy with a generator for back-up. I am heading towards the shortest day of the year with many cloudy days but have managed to keep the sg reading at or slightly above 75 % SOC. 1. Will I be able to avoid sulfation? 2. After recharging on a good day (4/5 hours of sun) I don’t notice the sg readings changing all that much. Is that to be expected? 3. The last 10 % of charge seems to be the most difficult to achieve. What is the best method. Low current and voltage for a long time or a high voltage (say bulk voltage values) for a shorter time?

Is there a charging unit I could purchase that could be used to charge and jump start a 12 volt automobile and also have a setting to charge my 36 volt golf cart having automatic stage charging system?

Zia, Easy Question. When they make a battery they pre-fill the plate with Lead Dioxide. When you add acid you have a battery ready to go. Takes a few charge cycles to get all the plates completely filled. Bob K,

Please tell me. A brand new battery, when gets filled with electrolyte, why it gets charged 80% as per usual understanding, without connecting a charger. Is it already charged during manufacturing? Or what does happen inside that makes him charged? right after filling electrolyte. Please comment.

Thank you very much, Andre. In the meantime I read a bit about the state of charge of lead acid batteries (mostly Yuasa material) and concluded that, more or less, I should be fine trying to charge it. I charged the battery through a 2 ohm resistor to limit current to a bit below 0.1 C (oh yeah, and the battery has 7 Ah capacity) with a current of 600 mA initially. As the voltage of the battery gradually increased, this current decreased. I stopped charging when I reached 13.4 V. About 90 minutes after chargin I checked OCV and it resulted being 12.8 V, so I think this battery is pretty much OK. What you wrote, Andre, helped a lot to confirm that things are indeed in good order with my battery. Thank you very much!

to GM: you didn’t mention the capacity of the battery, but if it had 12V after 10 years it is still alive. I would have first charged it instead of loading it, but it seems you are not loo low on voltage. Charging is with 1/10 of the capacity. If it is a 50Ah, you can charge with 5A or lower. You talk about connecting a resistor and measuring the current, so I assume you know at least something about electronics. You can connect a DC power supply and set it to 13.8V, with a current limit of 1/10 your battery capacity or lower if you’re afraid something might happen. Lower will never do harm, just charge slower. Watch current and voltage. Case 1: When you connect the battery and the voltage drops a bit and current is limiting to the set value, the battery will be fine probably. Case 2: When the voltage stays at 13.8 and current is very low, the impedance of the battery has become too high. But leave it connected in that case, even raise the voltage to 14.5V. After some time, the current might increase and the battery can be charged and might be usable. Good luck!

to Edward King: I wouldn’t bother too much about 400 or 750mA. It depends on the build/brand of the charger of course, but I think it is comparable to a having a car engine of 2000cc or 1200cc. The 2000cc will consume more at full power, but might consume less at low power/cruise speed. The 750mA supply will deliver more initial current when connecting it to a discharged battery. But that will happen only once. The rest of the time the battery will be float charged with, say, a few mA. Then it depends on the efficiency and standby power consumption of the charger. Assume the charger has 0.2 Watts standby power (no battery connected, so this is lost power). A connected floating battery could take 5mA at 6.9V, or 0.0345 Watts. The efficiency of the charger will be low at low power, say 50%. So it is actually 0.069 Watts. Together with the 0.2 Watts standby power, it consumes 0.269 watts. (You see that the standby power will have the biggest influence!) So this setup will have to run for 3717 hours to consume 1kWh (and you know the price of that). That’s almost half a year. You could connect such a nice digital low-price power consumption meter and look back after a month or so to see if there is big difference, or to see how high the standby power of the chargers is. But to keep it a honest comparison, you will have to watch the number of times the alarm sirens work, how long they work, and so on. Anyway, it’s good to think green!

About 10 years ago I bought a valve-regulated lead-acid battery (6 cells) for a project which I never ended up doing. Now I have a bit more free time and enthusiasm, and decided to try it out. The open-circuit voltage was 12.0 V. After I loaded it with a high power resistor, causing it to produce 500 ma for a couple of minutes, the OCV went down to 11:92 V. Under load it drops to 11:55. Three questions, which I think you will easily answer: Is this battery dangerous to use? How much capacity may have it lost? How should I try to charge it (if it’s safe to use, see first question)?

Hi, I am making an adjustment to my house alarm so the 2 external siren boxes are powered by one lead acid battery (using in total about 25m of cable). Previously the siren boxes each ran on 6 D cells. I have a 6v 4ah lead acid battery, and a 3 stage (with float) 750ma charger which will be connected permanently to the battery. My Questions : I am now wondering whether 750ma is too much current, and whether 400ma would be more suitable? I believe the current will drop in the float stage but considering the charger will be running permanently for many years I’m wondering if the 750ma charger will be more expensive in electricity costs to run than a 400ma ? thanks kindly Edward

to Richard Szmidel: That’s a clear question! You need 6.9V 120mA approx. to charge very safe. Problem is that most chargers can deliver more current and are only limited at max current value, which is too high for your small battery. https://www.amazon.com/Sealed-Lead-Battery-Charger-D1724/dp/B001G8AIMU could be usable. Set it to 6V. The initial current will be a bit too high since this small thing can deliver 500mA, but it won’t do harm. Or you can put a 10 ohm 1 watt resistor in series (between of charger and of battery) to limit the initial current. Bypass it (remove it) after one hour or so. You can leave this setup connected for eternity, but when the battery was empty it will take like 14 hours to get if full. First solution can be a bit faster. If you have a multimeter capable of reading DC current, you can put it in series too (between of charger and of battery) to monitor the charge current. Current will be highest when just connected, and will slowly drop. When it drops to 10mA, you can assume the battery is as good as full. When it goes above 250mA and stays there for more than a minute, better add the resistor to protect your battery. As an alternative: if you have a small DC lab power supply, set it to 6.9V with the current limiter to 120mA approximately. (100. 150 is fine). Done. Upon connecting, (- to. and to ) the limiter will limit the current to the set value, and voltage will slowly rise to the setpoint 6.9V. There it will stay, and the current will start decreasing. At 10mA, the battery is full.

Hi please help me. I want to charge a Century PS612 6V 1.2 Ah sealed battery. How can I do this? What sort of charger do I need.

I’m having an SMF battery of capacity 150Ah@20hr which is used for my solar setup (250Wp) for LED lighting.The battery manufacturer recommended boost and float voltage setting are 13.8V and 13.5V (12V battery).I am using charge controller with 3 stage charging pattern. Problem is:- My charge controller default setting boost and float voltages are 14.6V and 13.6V respectively in SMF mode. Two modes are there Flooded (14.8V boost and 13.5 float),VRLA(14.6V boost and 13.6V float) Does this higher boost voltage will cause any problems to battery?? The ambient temperature is 22°C(winter) and 28°C(summer). The battery is discharged daily at current of 6.5Amps for 10-12 hours.

How much ampere rating charger can be used to charge 6V 7AH 20 HR battery so that it can be charged quickly and safely.

I have eight 6 V Trojan batteries in an off-grid system. PV panels are the main source of energy with a generator for back-up. I am heading towards the shortest day of the year with many cloudy days but have managed to keep the sg reading at or slightly above 75 % SOC. 1. Will I be able to avoid sulfation? 2. After recharging on a good day (4/5 hours of sun) I don’t notice the sg readings changing all that much. Is that to be expected? 3. The last 10 % of charge seems to be the most difficult to achieve. What is the best method. Low current and voltage for a long time or a high voltage (say bulk voltage values) for a shorter time?

To André Seoane: Theoretically, I think that is perfectly possible. But you should take care of the maximum current per battery. A question: what is the charger type you plan to use? Is it a 320 Amp charger. When you charge with C/10, each 18AH battery should get 1.8 Amp. So you take the current of your charger and divide it by 1.8. That gives you the number of batteries you should put in parallel. E.g. if your charger can indeed give 320 Amps, connect 177 batteries in parallel. The 320A is then divided over the 177 batteries, and each battery gets 1.8 A. But that is theory. When the batteries are not equal or there are bad batteries, the good ones might get too much current. Of course, there is some tolerance. C/10 is not a holy number. If some batteries get ‘some’ more current during the few initial minutes, it won’t do any harm.

To Gary Mendenhall: 2 things to keep in mind here:. voltage should be clipped at 13.8V for continuous connection to the solar charger. A good charger will take care of that, but if you build something yourself you should add a small circuit to limit the voltage to 13.8V. It will never overcharge then; you can keep it connected forever when there is no light, you should take care that the battery is not discharging through the solar panel. Again, a charger in between will take care of that. But a simple diode will do the trick too.

Hola, Tengo muchas baterías de 12voltios 18Ah. (acido de plomo) Estoy pensando en la posibilidad de comprar un cargador grande para disminuir el tiempo. ¿Está bien comienzo a usar un cargador de 12v y 320A? La idea es que se puedan cargar varias baterías al mismo tiempo.

I want to install a magnetic door lock that operates on 12 volts DC I also want a solar trickle charger is it possible to overcharge this battery with such a setup?

Hi we are using a charge voltage of 2.4V per cell in our power backup solutions can anyone help me out to know the water evaporation details considering a 30-40% DOD everyday for the batteries. Charge pattern for the system is 2.4V per cell CC followed by a CV tail of 2.5Hrs and than a 2.3V float level.

To Anita Thank you very much for response. We are using battery like stand by on UPS. It is writing on battery that is charging voltage for stand by use between 13.5 and 13.8 volts on 20ºC. In our case ambient temperature is 45ºC. I started fan and it is blowing straight to batteries. Now batteries voltage dropped. That mean with ambient temperature charging voltage is dropping or rising if I am correct. It looks like higher temperature higher voltage and lower temperature lower voltage. Also I adjusted voltage on regulator charge PCB with potentiometer to 13.5Voltes for each batteries (total 215 volts). It is confusing because it is writing with higher temperature charge with lower voltage.Our batteries are 45Ah. Can you explain how ambient temperature are playing role fir battery voltage.

To Niksa 15V is very high on a 12V battery It may be thr reason for the batteries to be bloated 13.8 is the usual voltage at 25ºC, less at hotter how much less depends on many factors. Consult the manufacturer 3Amps, it depends on the battery size the normal charge current is 1/10 the Ah rating of the battery the trimmer on the PCB, you need to get or draw the schematic to understand what it does If you provide make and model we may help some more Best regards Anita

Hello everybody, I have UPS system with 16 pieces of batteries. Each battery is 12VDC. Batteries are SLA Type. Batteries are connected in serial line. Batteries are charging via diode scr charger. Charger is controlled via charger regulator pcb. I can see that battery voltage during charging is 240 volts. 15 volts per each battery. Battery current is 3 amps during charging. It looks like overcharging. Also batteries are swell up. I tried to replace batteries but after some time it is happening same. Also I want to add that batteries are stored in very worm place(temperature is about 40 degrees. I tried to adjusted voltage during charging on PCB charger regulator via trimmer but nothing happening. Can someone give some advice? Thank you.

Baking soda and Epsom salts? How much? I would suggest ZERO. What makes you think this will De-Sulfate your battery? Bob K.

My Battery size is 19 7.5 15 (length width hight) all measurement in inches. now can you tell me how much backing soda and epsom salt is needed to clean and sulpate my battery respectively. Thank you for precending information.

Thanks you for valueable information. My Battery Size is (19 7.5 15)(lengthwidthhight) all measurement in inches. now can you suggest me how much backing soda and epsom salt is needed to clean and salpate my battery respectively.

Deepak, Did you read what I wrote just before your post? Unless the manufacturer advises otherwise You want to stick to 1/4 or 1/5 C as a starting point. So maybe 30A. Bob K.

Hello Everyone, Thanks a lot for information. I have a 150ah battery, what is the maximum amount of current I can give to this battery for charging. Plz reply at deepak.malik777@gmail.com

Xealgar, I recall from AGM docs that an AGM battery will accept high charge rates. You did not mention your battery size but I assume a 100 or 200A/hr. I would think (and don’t trust my thinking) that 1/4 or 1/5 C is a reasonable limit. The battery voltage will rise quickly and charging will taper off. There is very little advantage to trying to jam in current faster. If you can find specs on your batteries good, but search around on other similar units. If you generate gas you are not doing the battery any good. Slow down for longer life. You will probably only bring your battery up to 60% with a high bulk charge and you should not be too much below 40% when you start. So that bulk charge cycle at high currents will be quite short anyways. Bob K.

I have an extremely sophisticated mppt charge control unit connected to 1300 watts of solar. It is capable of producing 12v-18v easily with 0.1 amp. 56 amp. This is connected to a 3x 12v 100ah lead acid bank. I use in my rv. My question is the batteries recommend a 14.4 volt charge and 13.8 volt float. But it does not give any amp limitations. I understand that the higher the amp the faster the batteries heat up but can I dump all 56 amps in to get the batteries up to 14.4 in the bulk charge stage then reduce the amp to 2 and maintain 14.4 for several hours or should I drop it down to 13.8 with 2 amp or 14.4 with a lower amp. Basically I’m trying to get the best of both will the sun is up. Can you give a few helping pointers. Xealgar@gmail.com

I have drain my car’s battery for one or two weeks I think, it is a 12V 78Ah. So I took it out and charge by a charger with monitor function. It give out 2.XV in whole unit when I first remove from my car, after apply some voltage, it raise to 12.XV sharply then slowly ramp to 13.X. I charge it with 5A constant current but it voltage drop while it continues charged. I left it charged for around five hours but I turn it off at night, I resume the charge this morning. It begin with 12.77V and charged with 4.5A, it raise to 14.4V in 5min and my charger switch to CV mode. The voltage then drop again after another few minutes reducing current, my charger switch back to CC 4.5A charging while the voltage drop until 14.1V. I double checked the voltage with another multi-meter and it give out close enough reading. Is this normal for a recovering battery or it’s almost dead?

In response to Joe Elliott: I measured slightly over 14.5V in my own car, but I think that is quite high indeed. But I think the main risk in connecting a small battery while the engine is running is that the small battery will draw an almost unlimited current from the alternator car battery for a certain amount of time. There is some limitation from the copper wiring, of course. And a 1 ohm resistor in series will indeed keep the current to a safe value under all circumstances. A diode will give voltage losses, unless you use an electronic diode circuit (with mosfet as active switching element) instead. I have actually no idea if a charging current of several amps during some minutes or even seconds can harm a small 5Ah battery.

I disagree; the charging voltage with engine running shouldn’t exceed 14.3 V, which probably corresponds to the recommended charging voltage of the 5 A-hr 12 V SLA battery. It may not be good for it to be exposed to that voltage for an extended period of time, but I wouldn’t characterize it as dangerous. The real risks with what Doug proposes are 1) if it’s plugged in when you start the car, the starter motor may try to pull (excessive) current backwards from the small battery, potentially blowing a fuse in the vehicle or, worse, damaging the small battery and/or the car’s wiring (i.e. fire risk), and 2) when the car’s not running, very little charging may be accomplished. If we’re concerned about over-charging the battery when the car is running, perhaps a diode and a ~1 ohm power resistor would be a more elegant way to regulate the charging (with the diode also addressing my concern #1 above).

to Doug Anderson: see previous post. a direct connection between your 5Ah battery and the car battery could be dangerous. But of course there are ways to overcome this. Problem is that the voltage changes a lot. With the engine shut off, the voltage will be between 12 and 13V. With the engine running, it will be a lot higher, often 14.5 or more. I am talking about the measured car battery voltage, which I assume is the same as the lighter voltage (it is in most cars). Connecting your 5Ah battery to this high voltage can damage it (charge current will get too high). There is a simple solution: plug a 12V to 110V converter in your lighter! You have them in quite small versions, like this 12V to 110V 100W on Amazon (for 16): https://www.amazon.com/Power-Inverter-Outlet-Laptop-freezer/dp/B00SQUC0G8 Then plug the charger in the converter; it will never use 100W but stay way below that so you’re safe. Or you can buy a higher power / higher price version, if you want to use it to connect other things as well. Success guaranteed! Andre

I use a medical device at night that normally operates off a plug-in power supply which delivers 12 volts. When I go somewhere where I don’t have wall power I can use a 12V lead acid battery such as the 5aH battery I have. It runs the device for about 9 hr before cutting out (probably about 9V?). Good for one night. I can charge this battery with a charger but that also needs 110V power. Can I charge my battery using the lighter socket in my car? What would happen if I connected it directly to my car battery. would the current be too high? What other options could I explore?

to Pradeep M: your assumption is correct, but keep some details into account:. the battery won’t charge with 12V, it will need more, like 13.8V. So your charger must be able to give 13.8V, and your load must be able to handle 13.8V too when the charger is disconnected, the battery will deliver current to the load when they are simply put in parallel, without diodes in between. But diodes give losses, so must be taken into account to determine charger voltage when the battery is quite empty, the voltage is lower and the charger will put more current into the battery. When it is current limited, there is no problem, but your load will get less than 13.8V at that time. Depending on the load that is no problem actually, this is a simple UPS: you charge the battery and power the load. When the mains voltage drops out, you load will keep on working, powered by the battery. Just take care your charger does not consume any power when it is not connected to mains. Regards, Andre.

is it reccomended to use a battery when in charging mode ? if no why ? Consider this situation If the 12V battery is charging at 1A and if i add an another 12V load of 500mA its just two loads in parallel as like two LED’s in parallel each of them consuming their own current and the power supply is gonna deliver 1.5A is my opinion wrong ?How does the battery behave in such a circuit? Thank you 🙂

to Ricardo Fernandez: xCA means times battery capacity. So if you have e.g. a 50Ah battery, and you charge it with 5A, you are at 0.1 on the horizontal axis. When you charge it with 0.5A you are at 0.01 Best regards, Andre

I have purchased a solar panel to trickle charge my only occasionally used van. The rated output of the panel is 2.4w@17.5v. Even this seems too high a voltage, but on measuring the output it is between 19v and 20v. Is this why it fails to keep my less than one year old battery charged?

What are the safety concerns when attempting to recharge a 12Vdc lead acid battery when the voltages are less than 10.5Vdc? Is it worth while attempting to recharge a12Vdc lead acid battery if the voltage readings are less than 10.5Vdc?

Regarding figure 4, the horizontal axis reads “chargin current (xCA)”; what does xCA mean? Any clairification is welcome. Best regards Ricardo PS I wrongly select stopping to receive notices on this question; sorry for that mistake. I hope someone could answer my query. Regards Ricardo

Regarding figure 4, the horizontal axis reads chargin current (xCA); what does xCA mean? Any clairification is welcome. Best regards Ricardo

To Aas Mohammad Malik: A far as I understand (I am Dutch speaking 🙂 you want to make a charger for green batteries? Or do you want a green charger for standard lead acid batteries? What type of batteries exactly? How many Ah, voltage? Is it lead-acid? Since you are a battery manufacturer, I assume you want to charge many batteries together? Best regards, Andre

To Aas Mohamdad I cannot understand your question all I could do is Google translate ko ager ham kachchi plat me battery kar baad me charg kara to kiya rigelt milega I am sorry to say that I have the power to get my battery back to me. Get someone with more fluent English THX

hi dear sir and madam I am a manufactures off all type of motorcycle batteries in india how to mak new motorcycle batteries green charging with out formation mak battery charg and I writings in hindi bike battery ko ager ham kachchi plat me battery kar baad me charg kara to kiya rigelt milega

Afraid to say that you completely misunderstand the question. Clearly you have no understanding of campervan motor home wiring or electrics. On cranking the engine the vehicle engine electrics are automatically isolated from all of the motor home and the only power source is the starter motor. As to the notion that a 30 to 50A power supply is needed you should understand that a camper van is not an RV. 30 to 50 amp power units are never fitted or required. Maximum peak current draw from my 120Ah leisure battery is 15A for perhaps 30 seconds, and under normal circumstance continuous discharge is kept well below 6 A. and even when charging the current draw by any load comes from the battery not the charger! The Battery charger I am looking to replace is a permanently installed unit, but of the transformer type which energises and charges the batteries on connection to external mains supplies (EHU). The result is that when the camper is not in use but connected it charges and maintains two lead acid batteries one deep cycle and one starter. it is the fact that these two batteries have a differing charging profile which leads to my question

To Andy P usually in a camper the unit is a power supply (typically 30 to 50 Amps) with a built-in charger the batteries cannot accept such a large charging rate the best is to find another camper electric box and fit-it to your camper adding an automobile charger (some are 2, 10 to 15 Amps, some with 70 to many cranking assist Amps) totally not suitable for you under sustain load these chargers will burn out and may catch fire intelligent chargers are not that intelligent and are likely to misbehave under camper load you need 2 separate system. one to charge the batteries and one to supply the camper as you can see, your application is not a regular application for a regular automobile battery charger. This charger needs to be permanently installed automotive battery chargers are not designed for permanent installations

Ok I have camper van and when engine running both starter and leisure batteries are charged by the alternator via a Voltage Sensitive relay. With motor stopped and No electrical hook up batteries Isolated. With Electrical Hook up both batteries charged by onboard charger. This on board charger met with an accident and is no longer useable, ( I guess it didn’t like a gallon of water passing through it when on!) Looking for new charger, Original was a simple unregulated transformer type (Original Fitting) I now appreciate from your articles and others that an intelligent 3 stage type charger is required. Will this type of charger happily charge a starter battery and a deep cycle leisure battery in parallel and at the same time?

to Yuouonus your question is not too clear I imagine you mean 3 batteries from a 36V system it is better to charge the batteries individually, one by one at a rate of about 10% the Ah capacity tell us more about your charger and the batteries, what size, Ah.

To Sam 1 how do you conclude that the batteries are fully charged? 2 what is the voltage on each battery when fully charged? 2.2 what is the charging current at end of charge (trickle charge)? 3 how much current does the panel supply? 4 how much does the voltage drop after how many hours? it is normal for the voltage to drop to some extent possible cause, it depends on many variables did you measure for leakage current

I have 4 pcs 12v ,100Ah lead acid batteries connected in series.It is charge with an MPPT Solar controller, with a 1000 w solar panel. Batteries are 100% full in a day. After a few hours battery voltage drop even with out a load. My batteries are 2 years old. What are the possibilities of having a voltage drop? Your answer is highly appreciated. thank so much.

To Shaila Your transformer 15V center-tap with 2 diodes and the 18W bulb should work how long it takes your battery at 4.5Ah, you should charge at 0.45A for at least 10 hours if that does not work there could be something wrong with the battery (maybe one cell is dead. ) good luck

I have a 6 volt 4.5 Ah battery.I am trying to charge it with full wave center tap rectifier circuit. where each side have 6.72 volt in the secondary side.as my transformer is 15 volt I use a voltage divider circuit to minimize it to 6.72 each side. now I have two question 1) I have tried to discharge the battery with 5 volt 18 w bulb and 12v 9w bulb in different time.but it does not work properly. now my battery is not reaching 6 volt when I try to charge it fully.why?? 2) how long it actually take to charge a 6 volt 4.5 Ah battery with full wave center tap circuit and the other information given above. pls help me by answering this. thank u

To Dalton Bravo for being interested in engineering, I wish you all the success you deserve As you can see from the replies, the answer to your questions are somewhat complex It is not a simple task to get straight answers 350W is a good deal of power I am quite sure you can pedal this power for a while. The big debate is how long would the while be? And then someone may ask at what temperature, wind condition and yadi-yady The motor you refer to I assume it is a brushed type motor. Commonly called universal motor. The type you have in a vacuum cleaner or small hand drill, battery toys. Any other motor type is likely not suitable. If that motor was on your bike, mechanically hard connected. That means no one way bearing. Connected like the pedals on a tricycle. And if that motor was electrically connected to a battery through a switch. Once the switch is closed, the bicycle would move in one direction given the traction effort provided by the motor Reversing the battery polarity will reverse the direction of the traction effort Assuming, everything is fine and the bike is going at a certain speed, it will consume some current from the battery, and will go at some speed for some time. (distance) Now, if you add some load, like going uphill, the motor will consume more current. If you go downhill, as the bike pick-up speed it will consume less and less current from the battery. At some point, if it goes fast enough it will supply charging current to the battery. Adding a diode in the circuit, the motor will provide the same (or almost the same) traction effort but will no longer charge the battery when going downhill. It would be like a one way bering on a regular bicycle If you were to ask at what speed is all this going to take place This where the engineering comes into play, mechanical, electrical, electronics…and yes it is very complex I have an electric bicycle (that I am very fond of) to illustrate how complex. In the motor housing there are 14 distinct motors/generators and complex electronic controls to resolve this complex traction effort and speed combination, safety speed limit, regenerative braking….what to do when you need to brake and the battery is full. On a bicycle, the energy provided from the cyclist is not continuous. It starts with the crank (pedal) just past top dead center (12 O clock) and reaches maximum at 3 o-clock position The energy wave form is sinusoidal in nature, Google it up If you were to place a regulator or converter as you mentioned As the generator would spin faster (at 3 o-clock) it will become easier to spin. There would be a slipping effect, very similar to, but not as drastic, as if the chain would break Your other questions Will the 12 charging volts not charge… Lead acid batteries are generally charged till the voltage reaches 13.8V at 25ºC (more at colder, less at hotter temperatures) The rate of charge is generally limited at about 1/10 the Ah rating of the battery. Each manufacturer has their specs, depending on the application. … charging volts mean for the lifespan of the battery… Is a complex battery design criterion. IE. Emergency lighting, is used only a few cycles in its life as oppose to a laptop or cellphone battery … I did briefly look for a DC-DC battery charger… I need more details Will random fluctuations in voltage/current hurt the battery or create an unsafe situation? YES what will determine the amount of current produced in this circuit? How fast the motor is being turned This is part of the motor/generator design (how many turns of what gauge wire) You have to look at entropy, in electrical stuff it’s called impedance, it is expressed in Ohms For example you may have a 12v 100W lightbulb (100÷12=8.33Amps) 1.44 Ohms, lightbulb. The filament would be a certain length and thickness giving it these electrical parameters At 120V same 100W (100÷120=0.833Amps) = 144 Ohms lightbulb Therefore the filament would be 10 times longer and 10 times thinner I wish you all the best, as it is a wonderful experience I started with a small 3 wheel scooter from a garage sale, and…

Hi Dalton, Like Bob said: don’t bother too much because you probably can’t damage the battery anyway. Push in whatever you can. But it depends on the battery size of course. If it is a quite small battery, like 7Ah gel cell, you could damage it. To get the best efficiency and adjustable load for your legs, you can do it as follows:. The 24V DC voltage you make (I assume it is DC, otherwise use bridge rectifier capacitor) goes into the step-down converter. But with 12V the battery won’t charge at all, unless it is really really very empty). You need to adjust your output voltage to 13.8V, if possible. Advantage of using a step-down: for each amp input at 24V, you get 2 amps at 12V out load regulation: the step-down should have an adjustable current limiter. When you change the current limit setting, you will feel the difference in your legs. Would be nice, isn’t it? Now, if you have a DC/DC black box with 2 input pins and 2 output pins, you’re done: nothing to adjust there. But if you build your own circuit with one of the many DC/DC converter parts available, you can add current limit with this simple circuit: http://www.edn.com/design/other/4339031/Add-trimmable-current-limit-to-dc-dc-supply I hope this helps. André

Hi, You will be lucky if you get 300 watts out of a human powered generator. Probably more like 1/2 that. So your generator is more than sufficiently large. You want to look up generator characteristics but I suspect your generator will not magnetically Stall at 12Vs given the inability of a human to exceed the maximum current. Simply drive the 24v generator into the battery through a diode and fuse. When a battery voltmeter gets to about 14.4 get off the bike. You can also monitor the charging current, your human will FEEL IT when the battery starts charging. Your volt meter and amp meter will show you want is happening. Bob K

Hi all, For a little bit of fun, I’m attempting to convert an old bicycle into a generator. (There’s a bunch of Instructable-like articles out there if you’re really curious.) Here’s my problem: The bike’s chain will spin a 24 V DC 280 W motor. I want the generated current coming off that motor to charge a 12 V lead acid battery. I saw one guy who used a diode to make sure current goes from motor to battery (not visa versa) and a voltmeter to make sure his pedaling was giving off approximately 13.5 V to charge the battery appropriately. I don’t want the charging voltage to determine how fast I can pedal. I want to be able to pedal as fast as possible and ensure the battery is still getting a safe but appropriate voltage. I ordered a 24 V to 12 V step-down Buck converter before reading this article. After reading this, I’m thinking that 12 charging volts into a 12 V battery won’t charge it. My questions are: Will the 12 charging volts not charge the battery at all? Or will it just not charge as well as 13.5 V-14 V? What does 12 charging volts mean for the lifespan of the battery? Does anyone have any other creative solutions? (I did briefly look for a DC-DC battery charger but couldn’t find anything that fit my needs. If you know of something, please share links.) Also, how consistent does the charging voltage and current have to be for the battery? Will random fluctuations in voltage/current hurt the battery or create an unsafe situation? Lastly, what will determine the amount of current produced in this circuit? How fast the motor is being turned, or the charging resistance of the battery, or both? Please explain if you can. (I worded that last question poorly; I’m not sure how else to say it.) Thanks! Dalton

Hi Puria It is always best to charge at constant current rate is C10 (1/10 of Ah capacity 450mA in your case and stop at 13.8V at 25ºC maybe twice a year charge till 14~14.5V for 30 minutes consult your battery vendor

hello i have a circuit that needed battery back up. my battery back up is lead aid 12v 4.5 amper. what mode of charging needed to Increase life time of battery? note: current load is 400 mili amper.

Concerning Lead-Acid 12V battery’s. In trying to figure out what is the % discharge, how is the recovery voltage applied. See, I have this old Golf Cart that I put some old battery’s in it. When charged up reads 12.6V. When I do a short fun run the 12V battery’s drop to about 8V under load. When done with the fun run the 12V battery’s read about 11.2V. After I let them sit for a few hrs with no-loads the voltage reads 12.4V. So what is the % discharge taken from, 8V, 11.2V or 12.4V? I need this to apply the remaining life of the battery’s, per ‘% charge vs number of recharges’. charts. Thanks, Robert

what is the correct ambient temperature required for Charging 12V/160Ah SMF Battery for 300kva with 68 Batteries. My UPS Supplier saying it can be up to 37 deg. But my understanding is 27deg for Longer life of Battery.

years ago a car battery would give warning that it is near the end of its useful life by a slow turnover of the starter motor. this gave an opportunity to get to garage to buy a new battery. in recent years car batteries fail with no warning, frequently stranding motorists (i.e. me, twice). is there any action that can be taken to test if a modern battery is nearing failure so that being stranded can be avoided?

why charging time of lead acid battery is high? in which process the time is consumed? is it because slow chemical kinetics?

To Dilshan We cannot answer your question here, it would take enormous texting Where are you from? You may read all the literature right here from Cadex. Start at BU-001 and read on At the end you will be a battery expert

To Monir Usually it is 13.8V, however most UPS that I repair her (300W to 1000W) the charger charges the batteries to 14.4V once the utility power comes ON and seems to do nothing else (I use a separate constant voltage power supply set at 13.8V) I suggest to initially charge the batteries, do a power fail deep cycle, monitor the holding time Then do a short power fail cycle 6 month later, then once every 3 months…to once a month after 5 years Short power fail maybe ¼ the initial holding time

I like to start a battery supply, service and maintenance business but i do not have any knowledge about batteries. I am a Marketing Professional for construction machinery and equipment. can you advice where can i learn physically about the battery knowledge to set up my own business. thanks

@ Sandor: your assumptions are right. When the voltage reaches a certain value and you keep it there, the current will automatically start decreasing to near zero if you give it infinite time. A lead acid charger can be built with the 2 stages you describe, but often it is reduced to 1 stage: a current-limited voltage source. E.g. a 12V battery can be connected to a 13.8V voltage source with current limit depending on the battery size. Say it is a 7Ah battery and you decide to limit to 1A. When you connect the empty battery, 1amp will flow, and voltage will be 12.something. Voltage will keep on rising slowly to 13.8V, while 1A flows. But when 13.8V is reached, the current can’t stay at 1A anymore (because the voltage cannot rise any further) and the current will start decreasing. In case you want to give higher voltage than 13.8, e.g. 14.5, it is possible too, but you cannot keep the battery connected forever to that voltage; in that case you must manually disconnect or switch over to 13.8V when the current has dropped below a certain treshold, e.g. 1/10 of the initial value. You could do this every now and then, to avoid sulfation of the battery. But if you don’t. I think it is no big problem.

What will be the point cut off voltage for a Flooded 12V;50AH Lead acid battery. My battery fixed at the voltage 12.5V after fully charged by Inverter. Is it normal or battery problem.

Hello, Watching the graph http://www.batteryuniversity.com/_img/content/clead1xx.jpg of the charge of a lead acid battery there is a quetsion. At Stage1 a lead acid battery get charged with constant current at the given ~1A value and the voltage will go up 1.8V. If I give not more than 1.8V will the charging current decrease to the minimum of Stage 2 without any regulation or not? Or other way: Is it a right charger that has two units in serial: a voltage source and after it a current source? Where the voltage source is compensated for the voltage drop of the current source and provides the 1.8V. Do I need some switch that changes between the stages or it happens naturally as the battery get charged and we only need to limit the current and the voltage according to the graph.? Thanks for the answers in advance

@ Abishek I agree Anita and I want to add some ideas, based on my personal long experience and passion for batteries : I would not recommend connecting another battery in parallel, as large currents may flow and cause a fire or explosion ‘. but you can put an incandescent auto bulb 12V 21W.50W in series to limit the current that occur at the parallel connection. After some time (minutes. hours), the charger will start and you can disconnect the helping battery. If battery is sulfated.maybe you can revive the battery with a lab power supply, set it at 13.8V, with current limit to 1A. but if you don’t have lab PSU you can use a simple rough charger or an available AC adapter of the laptop, any type, 15.24V and two 12V bulbs in series having maximum 10W (the current must be limited to 1%.5% of battery capacity) and wait one or two weeks to reach results. the voltage will increase slow to 12.12,5V if battery is not defective. Then, connect a 3.5 stages charger to complete the charge process. Good luck ! 🙂

Abishek December 29, 2016 at 11:57pm 6.5V no load! this is very bad I would not recommend connecting another battery in parallel, as large currents may flow and cause a fire or explosion many (most) battery chargers need some voltage to start the charging process. This is to avoid sparks when connecting maybe you can revive the battery with a lab power supply, set it at 13.8V, with current limit to 1A depending what happened to the battery, it may take a while (days) to recover If with a lab power supply limited to 0.1A check how much voltage is needed to conduct 0.1A, if more than 13.8, much more (like 30 or even 60V) then the battery is sulphated

Bob, At this point we’re fair weather (May to October) campers so the temp doesn’t get that low I use 2ga. wire for my feeds, and the only motor is the water pump. I do understand your temperature. My load looks like 11.85amps overnight.

Salee, Slow cranking is more like 8V. If you check around you will find that cranking amps is specified at a very low voltage. After 10 minutes the engine is warm! With 14.4V fixed voltage charging you probably will not get anything near 70 amps charging. I would consider that 14.4V more like a High trickle. If it was continuous (car always running) yes it would be way to high. Much lower and you would not get much of a fast charge. It is a good compromise for a fixed voltage charger.

Gene, Ok, so you run from DC. AGM, yes I have played with a deep cycle 100AH batter in some detail. Going down to 60% is still a lot if the temp is low. Still depends on peak currents and the voltage required at those peaks. At 12V I suspect you have fairly long wires (long is greater than 3 foot) to your loads. I assumed you have an invert and like min very close to the battery ( 2 foot). Pulling 2KW is 200 amps and wire drop plus battery drop will drop out the inverter quickly. With your

Hi, I have just started picking up some knowledge about lead acid batteries and there is something I cannot understand. Every single article about charging lead acid batteries explains the critical C-rate, which should be gently kept within 0.1C and 0.3C depending of the exact type of the lead acid battery, and charging can take up something around 10 hours, or even more for the big guys. And of course after the topping charge, further charging should be reducet to float charge levels. However if I think of a poor car battery, that is ment to kept in conditions far away from this, having to suffer from very tough conditions. The car alternator does not used to be that soft, even my small gasoline car has a 70 Amps rated generator, which may pump 30-40 Amps (or even more) into the battery, after the start. This is almost 1C. over the voltage regulator never switches to floating voltage, it is ment to keep it around 14,4V. In cars charging rate is extremely fast. A cold, very slow cranking (guessing the voltage around 11V) morning after a 10 minutes driving the battery is well charged, spins the cranking like a turbine. My last battery worked for 5 years during these conditions. Well, of course I see the point, starter batteries are designed to live with these conditions, but it is not the same I can read about lead acid batteries.

Hi, Bob thanks for the response. I do not use an inverter, what I’m trying to do is just use my straight 12vdc for periods of time and then run the generator to recharge, unless we get back on the road. So, I guess I will have to experiment to find the length of time my batteries will last to a given charge percentage based on the output voltage of the battery set. Do you have any experience running AGM batteries, and if so is 60% a safe charge level to bring them down to before charging or is there a percentage I should use instead?

Gene, 50% sounds very low. A lot depends on temp. I can also see times where a motor starts, the battery voltage drops and almost instantly the inverter shuts down. Real Bad. Measuring your peak currents is a difficult measurement to make. And then knowing how your battery voltage will drop (don’t forget temperature) is also hard to figure. And the final number you get will vary wildly with state of charge and temp. So best I can suggest is play with it over time. There are just to many variable to do much design. I hate to guess at stuff but I don’t know what to suggest. What I have done is take a large load and a battery you know is at say 75%. Apply a load for 5 seconds, watch the battery voltage. When you get to a load that brings down the battery voltage to where your system fails you know your current limit. Compare that test load to your peak load and you know if your battery is too small. It is a big compromise. Bob K.

if my Battery gone to low 6.5 V DC(12 V/150AH).,How can i recharge again. since my Inverter not make it charge.since it is saying as battery voltage too low. But i heard from battery service engineer it can be charge while another 12 V battery takes in parallel. That means if i connect another battery 12V, total battery voltage will be 9V. is it ok for charging the same.

Hi Bob, I believe you are responding to my post, maybe not as I have not read all post’s earlier than mine. If this is the case, then Thank you for the response. My MH has a 4kW generator that will charge the batteries and we have done some dry camping on one coach battery. I just installed a second to bring my total power up to 184 amp hours. The two batteries are the same size and type (AGM, group 49). The question I am trying to get answered is how low I should allow the voltage to get before cranking up the generator. I see a lot of different opinions and am just not sure if I should discharge to 50% or 80%. Any idea?

Hi, I have played with this concept as an emergency power system for home. Major Params: 1. Size of batteries. 2. Load the motorhome, both continuous and burst. (For example motor starting of a refrigerator.) 3. Size of generator. I figure you want to use a very quiet gasoline powered generator. The small quiet units are typical about 1K watt. Some larger are 2KW. (Honda and similar) The major inconvenience is getting out the generator and starting it up. A larger battery/ small load helps here. The other issue is gasoline consumption. A tiny generator that runs full throttle can provide power for a charger and your DC to AC converter for a long period with less gasoline. The ECO system on small generators are not sufficiently fast to handle motor start transient, the generator output shuts down as the generator spins up. Together they need to work like a Hybrid Vehicle power system or as a UPS. You must be careful to use a DC to AC converter that will supply the peak power plus average draw. And I found a sine wave output invert is required for many loads. (Motors as in a refrigerator or the air blower in my gas furnace.) So my suggestion is get a tiny generator to drive your charger and run it as often as possible. Less wear on the battery system. If the load is lite and battery fairly large then let it run down to 70% or so then use the generator. Just watch out for peak loads, a partially discharged battery can have problems with peak currents. Also, If possible, wire the two batteries in series for 24 volts. Higher voltages mean less amps and this is much easier on cables. Next time I will move to smaller batteries but more in series, for 48V. Bob K.

HI, I’ve been referencing this site for a while and really appreciate the amount of effort it requires to maintain as new info becomes available. I do have a question: I have a small motorhome that has two 12v AGM batteries in parallel on a Smart charger. I want to use the batteries for short off the grid camping stints. I have a voltage monitor and would like to know how low I should allow the voltage to get before cranking up the generator. I see a lot of different opinions and am just not sure if I should discharge to 50% or 80%. Also is there a handy calculator available that would be helpful with different loads and time durations? Any advice will be taken into consideration. Thanks in advance.

I have a 36 volt floor scrubber/sweeper that has a qty of 6 6 volt 360 amp hr batteries. What size charger would I need to fully charge these batteries. The ones in the unit now are a little over a year old. When they were first installed the unit could be used almost all day (8 hrs shift) with out having to recharge. Now it will last about half that time. When the batteries are fully charged they have 37.89 volts which comes to 2.105 volts per cell.

Bob Kondner, thanks again for your input. I did another run test that ran the battery down to about 50% charge. Then I used the Plus Start charger until it quit. The SG at that point seemed too low for the known number of AH the charger had delivered, but it rapidly came up when I forced enough acceptance phase charging current to induce bubbling, and then continued to rise at a rate that looked right as this charging continued. At this point I was watching the voltmeter and reducing the current manually. I quit Monday evening when the indicated SG reached 1.270, but right now I am resuming it at 0.5A. Since this battery has been as high as 1.300, I will push it a while longer. I just found a PDF of Crompton’s book online, which I will consult. With this, along with your remarks and other sources I have found online, I would conclude that the tight voltage constraints specified above on this page are not to be taken as gospel. I am retired and as such I can pick times to charge manually and keep an eye on the voltage and current, rather than spend a lot of money for a Smart charger that may or may not deliver the goods with this particular battery.

I assume that during charging you have some gas forming, I would think even a small amount of gassing would stir up the acid. I played with this long ago by using the hydrometer rubber bulb to stir up the acid after charging, I did not see any affect of this manual stir. The 15 volts does not surprise me. Chargers I have seen always spec the 14.8. 15.0 as the maximum for a multiphase bulk charge. I would be curious as to any other specs. I would suggest you get a copy of Batter Reference Book by T R Crompton. You will find references to 2.65 V / cell (almos16V for a 6 cell 12volt battery). There are different constructions of batteries and various temperature affects. You probably want to charge at a low current (1/2 amp) for a long time watching the SG and voltage. Full charge is defined with the SG and battery voltage stop going up.

Now I am thinking I may have misread the hydrometer the first thing yesterday morning. After a couple of hours of trickle charge it was 1.230. After a few hours of about 1/2 amp and then letting it stand overnight on float charge with the Plus Start charger it is up to 1.250. As in a previous cycle I can forcibly charge it manually and the SG rises at a rate consistent with the current for a battery of this size, but by the book it is requiring excessive voltage, on the order of 15V. Nevertheless the battery is giving good run time on a test load. I remain as uncertain as ever about just what is happening here.

After letting the battery stand overnight I checked the SG Tuesday morning and it was unchanged at 1.185. I then let it charge all day with the Plus Start charger. The charging current held at 5.5A for several hours until the voltage reached 14.4V, and then started tapering off while the voltage held. The SG at that point was 1.200, which was well under the nominal 75% charge level specified for starting the acceptance phase, but by this morning it was up to 1.250, nominally 90%. The voltage this morning was about 13.4, right where it should be for the float charge. I am starting to think the charger is doing a satisfactory job with this battery, and that my immediate SG readings during the process were low because of stratification that clears up upon standing with a trickle charge. It makes perfect sense that the dense acid that forms between the plates would trickle down initially, and even if it didn’t, it would be slow in diffusing up to the surface layer I can reach with the hydrometer. Now I am forcing 1A manually for an hour, which I don’t think will hurt the battery, and I will then watch the SG for 24 hours on float charge to see what happens. At this point I am glad I did not jump the gun and order an expensive charger that may or may not be any smarter than the one I am using now.

Addendum to my battery and charger testing: I stopped my topping-up charging of the deep cycle battery when the SG reached about 1.270. After letting it stand for 24 hours the SG was up to 1.300, which some sources say is good for a deep cycle battery. Today I did a 48AH discharge over about 11 hours and an immediate SG reading was about 1.185, and I will check it again sometime tomorrow to see where it stabilizes. I will follow that with more charging tests. In the meantime I know someone who has a modern electronic multimeter and I compare my old voltmeters with it.

ankit, Please disregard my first answer, as I think I misunderstood you. If the big battery is fully charged, it will partially recharge the small one.

Hi, Look around the web for multi phase chargers and you will find many variations. You can look at my www.sunduino.com site where I have small battery chargers though I have played with larger lead acid, flooded and AGM. You almost need a charger with 4 phases where the user can adjust the setting for phases and their transitions. But that would be WAY to complicated for 99% of the users. I think your last statement about the charger not being really good for your deep cycle battery is correct. And a deep cycle is different from a starting battery so I am not surprised. Check out some multi phase chargers (Bulk, Taper and Trickle ) but be prepared to spend more. And don’t go for a lot of charging amps, all that does is bump you out of bulk early. And trickle charging without a timeout is not good for a battery. Give it 24 or 48 hours if you want the last few percent of capacity. Bob

ankit, That would depend on whether or not the two batteries reach acceptance phase at the same voltage. If they are mismatched as my batteries appear to be, getting to a full charge of the one that requires higher voltage will overcharge the other one.

can i charge 35ah,12v amaron battery from exide 150ah,12v battery by parrallel connection. please answer in yes or no. and why ?

I just did a momentary load test on the big battery. The voltage across the terminals dropped only about 0.1V with a 5A load. That suggests that there is not enough internal resistance to fool a properly programmed automatic charger into quitting when the battery is less than 50% charged. This brings me back to this other source where the author says that 15V is a normal acceptance phase voltage for a deep cycle battery. http://www.carbatterychargerscentral.com/deep-cycle-battery-charger-5-top-rated-Smart-chargers/ If they are right, it is simply that my cheap Plus Start charger, while satisfactory for a car battery, is not so for a deep cycle battery

After a couple of discharge-charge cycles I have estimated a nominal capacity of 75 AH for my battery. In delivering 60AH into a test load, the drop in SG showed about an 80% discharge. I compared the size and weight of this battery with those of a 90AH battery advertised online and these numbers were in good agreement. For measuring discharge I used a simple nichrome wire resistive load and monitored it with an ammeter. The voltage and current dropped during the run, so some rough and dirty calculus got the total discharge figures. The Plus Start charger delivers a steady 5 or 6 amps in a bulk phase until the voltage reaches 14.0, at which time it starts tapering off in what should be the acceptance phase to complete the charge. That works fine on the built-in 25AH battery in my DieHard 1150 portable power pack, but when it did this sequence on the deep cycle battery the SG indicated well under 50% charge. With the improvised manual charger I went from there with 4 amps, the most it can manage without overheating the Variac, until the SG got up to the 75% mark, and then manually tapered off while checking the SG frequently. The voltage during this acceptance phase was about 15 volts, which was too high according to some sources but was described as OK by others. With these conflicting opinions I cannot tell whether this battery has excessive internal resistance as a result of neglect or if it is normal. If the former, how is any automatic charger going to adjust to it? I am in a quandary about whether to buy an expensive charger or to make do with my manual setup.

A loco engine used batteries 3 x 8 v / 450 ah were put on charging at about 30 Amp. charging current, but 2 nos batteries busted after 3 hrs of period of charging. What may be the reasons of busting of batteries.

hi, i am doing CCCV charging for a lithium metal oxide cell. the max voltage is 4.1V, when the battery voltages reaches 4.1, the supply switches to CV mode but the current drops to 0 immediately and not gradually. anyone knows what i might be doing wrong? Thanks regards, PS

Great, You are getting good reasonable capacity. How did you set that 4.6A load? was it a fixed current or just a resistive load? If you look at various spec sheets you will find they typically discharge really deep. Probably not something good, discharge deep and life drops like a rock, at least that is what I read. Bob

I kept up the manual 1 amp charging until the SG reached 1.250, which is typically about 90% charged. Then I ran a 4.6 amp load until the SG got down to 1.100, a bit lower than I intended. That was 15.5 hours, which is about 70 AH. Clearly the battery is in much better shape than I originally thought, and simply was undercharged by a mismatched charger. It is now on the Plus Start charger for an overnight run, and I will follow up with the manual charger as needed.

About 8 hours since last post, specific gravity up to 1.235 average, only about.005 spread across all cells. This is a virtually linear progression since I started this constant 1 amp charge last night. I am going to let it run overnight at this rate and check it first thing in the morning. According to chapter BU-903, fully charged deep cycle battery can be 1.300 or more. This is reinforcing my idea about a wimpy charger and a defective voltmeter.

Hi, As for your battery with a Reserve Rating you really have no serious specs to go on. Once you get the SG to where it should be (by monitoring manual charging) you can then measure the capacity you get with your load current. The 14.8V is probably a good value, I would expect that. You need to drive to higher volts to push in the last remaining capacity. As for the charger it has almost zero specs about how it works. If the 6 amp setting completely terminates the charging then try the 2A which they call a trickle. You may need to add your own timer to limit charging. But make certain the charger does not discharge the battery once it is turned off. You have discovered how much logic is not provided in low cost chargers. And even with move expensive chargers you do not have access to all parameters. But 99% of folks are not concerned with the last 10%. Be real happy if you find a commercial charger that gets you to 90%. Bob K.

Battery: Sears DieHard #50124 Size JC-24CM (24M) 550 CCA, 140 minute reserve capacity, whatever that means. Charger: Plus Start #71228, bought at Sears. Yesterday I charged all day, until the Plus Start charger was down to less than 0.5 amp. Indicated voltage about 14.0 volt, specific gravity about 1.175. The charger would have quit within another hour. I then modified my 40-year-old charger, bypassing the voltage regulator and plugging it into a Variac to manually set the voltage. I have been giving the battery a steady 1 ampere the past 20 hours, and the specific gravity is now between 1.210 and 1.225. The external volt meter, also very old, is showing 14.8 volts. I am going to let it run a while longer and try to get the specific gravity up to 1.250, and then do another run time test at 5 amps or so. My hunch now is that the automatic charger function is maladjusted and that my old volt meter is reading high. Perhaps I should spend some more money for a good charger specifically designed for deep cycle marine batteries.

Folks, I have a 30 W solar panel with Voltage 17.5 current at 1.75A. I will insert a 6A. 12V PWM charge controller to charge lead acid battery. My question is what ,max capacity battery can I change with this solar panel. I have a 120AH Lead Acid battery with me. I have not connected these 3 yet as I am awaiting delivery of solar charge controller.

Bob, thanks again for your tips. I think I have enough stuff on hand to improvise a charger that can be forced to higher charging voltage and then be operated manually to deliver the charging sequences described in this article. I would monitor it carefully with the battery under an exhaust fan hood, and needless to say I would have acid splash protection on. It is a flooded battery, and I have distilled water I can add should my actions cause water loss from excess gassing. I charged the battery with an old charger before the camping trip over Labor Day weekend, but I did not check the level or the voltage under load before or afterward. I may or may not have been anywhere near a full discharge. I found this article just last week and then got the new charger and a hydrometer.

Hi Again, I am not a chemist but if you have a Car Sized Battery I would guess it is 100AH? Is that correct? Got a model numbers? For a 40 hours discharge at 1.3A you only got about 52 AH, that does not jive with the 50AH you got at the 4.5 A discharge rate! I suspect you are far from charging that battery to full. Suggestion: Put it on the Sears charger, let it charge. Then take a lab supply and charge it at 1 amp. Watch the SG of the acid. (This must be a flooded plat battery, (Hmmm I would thing a true deep discharge would be AGM?) If you charge at the 1Amp level for a while you should get full capacity and you should see the SP rise to the expected level. I suspect your Sears charger is not charging a deep cycle properly. Got a model number for that sears charger? Bob

Thanks, Bob, for your response. I got about 50AH out of the battery with a 4.5 ampere test load, to simulate running my telescope accessories overnight. That seems like a reasonable capacity for the size of the battery, which is about the size of a car battery for small or midsize cars. Sears does not give the courtesy of a published ampere hour capacity. All they give is cold cranking amps, which seems out of place here as this battery is designed for deep discharge cycles while running a small trolling motor, not for optimum bursts for starting a car. The battery kept a 1.3 amp load going for about 40 hours total during four nights at a remote camp site. Now that I think about it, maxing out the chemistry of the plates could leave the density lower if this particular battery has a larger volume of acid than does a typical car battery. To go to extremes, imagine putting the same plates in a huge vat of acid. There is a limited amount of lead to be charged or discharged, so I would expect less change in density if we have an excess of acid. Can any chemist help me with this line of thought?

Hi, From what I have read some vendors use a acid density under 1.25 to reduce corrosion, I do not know if that is true or not. I have some Rolls S-460 and the 100% point is specified at 1.265. The only way I get close to that is using a very low charge (like 1 amp) for a long time. I then see the density rise in that case. Getting a battery to more than 90% is difficult. The manufacturers are, I believe, in a specs war and they pull every string to get the numbers high. So yes my Rolls S-460 are rated at 350AHr (20Hr Rate) but at 100 hours it is 461 AH. Think of charging the same way, it takes 100 hours plus to fully charge, few if any chargers will do that. It also depends on how hard (as in how many volts) you want to use during charging. Higher voltages help complete the charging process faster but it also generates gas. I don’t drive hard or long and I am happy to get 275AH. These units have not required water in 4 years. I am guessing ( IE hope) that my gentle use prolongs life. I doubt you damaged thing with a heavy load on just 1 or 2 cycles. Also in some small 12 lead acid AGMs I have see it take a number of cycle to show a full capacity. I would suggest not worrying about the 90%. If you really need another 10% add a battery in parallel. Bob K

I just finished giving my Sears DieHard deep cycle marine battery a full charge with a new Sears automatic charger that stopped charging in what appeared to be normal operation, showing a green light to indicate full charge. After standing overnight the voltage is 12.6 with no load, about right for upwards of 90% charge, but the specific gravity is only about 1.175, as compared with 1.250 specified for 90% charge. My reading is what it should be at about 40% charge. The hydrometer checks out OK with concentrated salt water in that range. The battery is about 4 months old and has had a couple of deep discharges, the second of which was about 60 AH in a torture test of 24A for 2.5 hours, and pulled the battery down to under 8V under load. It recovered to over 11V no load after standing few minutes. I am now testing the battery with a 1A load to see how many AH it can deliver over the next two or three days. Does that low specific gravity suggest that my torture test may have damaged the battery?

New question: Two nights ago my charger automation failed, and the charger continued to charge the batteries for ~8 hr longer than it probably should havecurrent was just under 0.01C when the issue was discovered and the charger unplugged. Now the question is whether damage may have been done to the batteries. This is a converted EV application that has both flooded and AGM batteries in parallel; starting with the flooded ones (the AGM pack is harder to access to inspection purposes), I opened the electrolyte caps, expecting to see a lack of electrolyte (from boiling), but instead I saw electrolyte levels consistently ~0.1 higher than they had been previously! Can anyone tell me if this is this somehow normal (how?), or if it’s symptomatic of having damaged the plates of the batteries, or some other phenomenon? Thanks.

To Philip Joseph Re October 3, 2016 at 3:35am did you run your system to find-out? there seems to be several varieties of Xbox I have a power supply here that is 12V 16.5A output (over 200W) since it is 12V to start with, I would connect-it directly to the UPS battery to avoid converting to high voltage DC then to AC (in the UPS), then 120VAC back to 12V DC in the Xbox power supply If your system is 12V it will be far more efficient to run from the 12V battery let us know how it went Best Regards Anita

to David S Reynolds your question is a mater of personal choice/opinion technically, it is about the same. a bit more for the 3X batteries The 3 battery option is very likely to have less internal resistance meaning, it will suffer less in high power demand However, in my set-up I use the 3-4 battery option because it is lighter to handle! as oppose to one big battery and break my back

For Solar storage backup. is there an advantage for using 3 pcs of 12v 35ah batteries over a single 12v 100ah ?

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to Philip Joseph: I found these figures on the internet about your Xbox S compared with an older Xbox version: When watching TV, it’s ~30 watts, which is down from ~78 watts. When gaming, it’s ~50 watts which is down from ~110 watts. In instant-on standby, it’s ~10 watts which the same as the original. In instant-on standby while downloading, it’s ~20 watts, which is the same as the original too. Assume you are gaming and consuming 50 watts. Your supply can deliver 700VA. This is max load; it says nothing about how long it can deliver that. So like Anita said, more information is needed. But assuming it is a small UPS, let’s assume it can deliver 700VA for 5 minutes. VA is not equal to Watts; that depends on the load. An Xbox is far from ideal load, so let’s say you can deliver 400 watts for 5 minutes. Theoretically that would mean you can deliver 50 watts for 5 x (400/50) = 40 minutes. But to get a reliable real value: indeed, trying is the only option. Andre

To Philip Joseph cant answer your question, too many variables but the answer is somewhere between a few minutes and several minutes the best is for you to try-it out Best Regards

To Samuel It is strongly recommended to consult your vendor 12V 66Ah, what type of batteries? Usually batteries charge at 1/10 their C (Ah) value and at what voltage to stop depends on the battery itself If you decide to connect your panel to the batteries You need to watch that the voltage does not exceed the battery voltage some are 13.6V some are up to 15V Your battery vendor should tell you how to charge his batteries

Good day, I need to buy a mppt charge controller but I’m struggling to know which module I should buy in terms of the output current. I am using a 50W solar panel and I need to charge a 12V 66ah battery

Hey If i were to connect a Xbox One S to a UPS of 700VA, 230V, How long would I have before the Console goes off?

So Nitin what is the device? is it a resistive device? a constant current device? or a constant power device as Andre Van den explained you may want to read about Ohms law

to nitin: that is not much information, but I assume that you mean that your intention is to keep your power consumption constant, so you will change your circuit. That is the case when you use e.g. a switchmode power supply. Power P (watts)= voltage V (volts) x current I (amps). 12V x 2.5A=30 Watts. 30 Watts / 5V = 6 amps. So at 5V, your device will draw 6 amps to deliver the same 30 Watts. The story is different if you mean that you have e.g. a resistive load that you will connect to a lower voltage now. Then it will draw less current, according to ohm’s law: Voltage = current x resistance. Resistance is a constant in that case, so if your voltage is lower, your current will be lower and the load will get less power, since power = voltage x current. If it is a 12V light bulb, it will give a lot less light when fed with 5V.

my device took 2.5A current at 12v, my question is what if i transfer my device from 12v to 5v. what would be my current ?

To Matt the lower limit has to be above the self discharge of the battery generally speaking, a system should operate between 10 and 90% of its limits usually when operation below 1% and above 99% there are some undesirable effects that takes place self discharge is one example.

to Conundrum I have seen similar behaviour but at plateau current that is when the battery is fully charged and the current wont go down any further that when the battery is tilted, the plateau current increases sometimes 4 times (from 100 to 400 mA) and no change on some batteries. I tend to believe it is caused by stratification I tried mixing the electrolyte by pumping with the hydrometer, but no success I am tempted to empty the electrolyte in a container, mix-it, filter-it and put it back in the battery let me know if you find something THX

MattThe answer to your question is that no, there’s no harm in charging the battery with particularly low currents, but now you’ll presumably be faced with my earlier question (largely unanswered from my 06/06/2016 comment above) of how to calculate what the fully-charged charging voltage will be (i.e. when to shut off the charger) when charging with substantially lower-than-typical currents. (I’ve been researching/thinking about this for years, and so far the best input I’ve received is Anita’s suggestion to terminate charging based on temperature rise, but I’ve also found an old book [specifically this figure https://books.google.com/books?ID=mcL3P6x7xTcCpg=SA3-PA18img=1zoom=3hl=ensig=ACfU3U27by3zVPY9tyeq-LuYP0KsPhqrPQci=131,116,704,587edge=0 ] which also provides a clue, but my charging rates are so low that I end up in the truncated part of the curve [and, as with Anita’s suggestion, I’ll still need to make accurate temperature measurements before that chart from the book does me any good].)

to Matt: in my opinion, it won’t do any harm to charge with a lower than max current. It will just take more time to reach a full charge. And a full charge must be reached every now and then to avoid sulfation. See article http://batteryuniversity.com/learn/article/sulfation_and_how_to_prevent_it

Interesting fault here, bad battery which shows abnormally low voltage (ie 11.14V) but if the battery is tilted /- 45 degrees 20 seconds later it recovers back to 11.32V Any ideas? The charger shoots up to 14V and less than 1A drawn.

Les, thanks for your response but I don’t think it addressed my question. The question was if there would be any harm in charging the battery with particularly low currents. Not high currents, but low currents. When you say most batteries should be charged no faster than around C/4, does that imply that there is no lower bound? So if I felt like charging stage 1 at 10 mA (exaggerating) and wait for ages, that would be just fine?

Lets understand AH. The capacity of the battery is is listed in AH, but capacity, known a C is relative to the discharge rate. The faster you discharge a battery the lower it’s C. It is important to understand the at which discharge rate the AH capacity is based on. So it you buy a 9AH battery and the capacity is based on the C8 value then if you load it at 1.125A it should give you 8 hours of discharge current. But if you loaded it a 4.5A (4 times) discharge rate you will not get 2 hours of run time, actually you will be lucky to get one hour. Most batteries should be charged no faster than around C/4 where typically C is based on the C8 to C20 capacity so charge a 9AH battery at 2.25A and it will last but make sure you have the right type of battery for your application. A standby battery does not like to be discharged and will reach end of life quickly if discharged more than once in a blue moon. Cycle batteries can handle discharges and give the expected life. Remember discharging to a 20% (DOD) Depth Of Discharge will have a much longer life than a cycle battery taken to an 80% DOD.

Hello. Very nice write-up, thank you. I’m currently dealing with a BTX 12-134 battery and I am considering the charging options. The datasheet suggests a charge current of 0.25xCA for the stage 1, constant current charging stage. That’s 34 A and doing things at such high currents has lots of implications that I wish to get around, if possible. I am therefore wondering about disadvantages of charging at much lower currents (e.g. 5 A). Obviously this will dramatically increase the time spent in stage 1, but will it harm the battery? Regards and thank you.- Matt

to Muhammad Junaid Akmal khan the Cadex C8000 seems able to provide the testing you are looking for. check-it at http://www.cadex.com/en/products/c8000-battery-testing-system

AK47: Consider using simple diodes as switches. With both your input power and battery driving through ORing diodes you can run you light without draining during charging. Now this assumes you have access to power from the charger before it hits the charger current limit functions. But you can play a lot of games switching power circuits with simple diodes, and of course a FET can help! I use ORing diodes in my small circuits. I have schematics up on www.sunduino.com. Most of these products are for smaller instrument operation but the overall architecture will work at higher power. Bob K.

AK47, I’d like to add this: like Anita says, it depends on the current that the lamp consumes and the current that the charger can deliver. If your charger can supply more current than the lamp consumes, it will power the lamp and in the mean time keep on charging the battery. But your lamp will get the charge voltage, which is higher than 12V; more like 13.5. 14V. If your lamp can handle that, there is no problem. It will shine brighter 🙂 When your charger can deliver less current than your lamp consumes, it will deliver its max current to the lamp, and the battery will also deliver some current to the lamp. The water analogy might make this clearer: a T-piece connects 3 pipes. Water that flows in, flows out. If it flows in through 2 pipes, it comes out at the third. When it flows in at 1 pipe, if flows out at both others. The flow is the current. The water pressure is the voltage. Highest pressure (voltage) wins and pushes water (current) to the others.

Dear Sir, Hope you are doing well. We need a professional battery analyzer/tester to analyze Sealed Lead Acid Valve regulated batteries of different brands like YUASA, EXIDE, CSB etc. Please suggest us some renowned brands of battery analyzers in this regard. Please send us the maximum information about two or three different types of analyzer which you are going to suggest us along with the availability and Price. Tester must be compatible to analyze the batteries of 6Volts and 12 Volts with different ampere ratings like 4.5 to 200Ah.

To AK47 yes of course however to discharge the battery, the charger must either be disconnected or of a lesser value than the load otherwise the charger will supply the load

Can we use (discharge) a lead acid battery while charging it by connecting it with some load like table lamp?

To Khalid M. Almagrabi What is the optimal voltage as min / max points that will help to elongate their life you have to read all the stuff at battery university 14.5V is quite high (OK if ambiant is about.20ºC) at 25º, 13.6V (longer life) to 13.8V (more power less life cycles) min voltage! every time you use (charge/discharge) the batteries, you wear them some at 10.5, the damage is considered severe it is not recommended do discharge below 10.5V at that voltage there is not much energy left anyway Anita

Only a field trail can answer some of these questions. Your questions are far beyond the scope of a forum like this 2) How long will the inverter supply output? Quick answer is, about 30 to 45 minutes To charge the battery you need at least 13.6V preferably 13.8V and once in a while (twice a year 14.4V for 1 to 2 hours) when the batteries is/are new, more often when older If we refer to BU-403 article, it states 12 to 16 hours charging time. That translates to 185Ah/12h= 15 Amps and 11 Amps charging rate So the charger output current should be limited to these values to prolong the battery life One has to understand, every time we charge/discharge the battery we rob some of its useful life How much? It depends on the chemistry and how deep the discharge. Generally at 10.5V the wear (or damage) is considered severe! Regarding the charger’s efficiency (in terms of electrical voltage/current conversion) it depends where the prime energy comes from and a bunch of other factors 2) How long will the inverter supply output? Quick answer, about 30 to 45 minutes The battery rating 185Ah means the battery will supply 9 Amps and a bit for 20 hours Ah rating is always based on 20hours If you plan to use 58A as calculated, the battery would last about 0.6 hour for a flooded acid battery That is if the battery is less than 6 months old, and if the temp is between 0 and 85ºF… Wil last much longer if it is AGM type and even more if GEL type, for the same Ah rating Having said that, when you start, the battery voltage is more than 12, so the current may be less As the battery depletes towards 10.5V, the current will increase (to keep the Watts constant) and the “wire voltage drop” will increase due to the increased current demand (700/10.5= 66.6 Amps) Which will result in a sooner 10.5V than anticipated. The wire (copper) has a positive temperature slope It means the losses will increase with a rise in wire temperature, leading to more loss and more heat… …thermal runaway. This is the basis how a fuse works. As you can see the algebraic sum of all these factors is quite complex I hope I am not depressing you too much Best regards Anita

I am using regular car batteries (calcium) for solar power bank. my question is : What is is the optimal voltage as min / max points that will help to elongate their life. my solar controller will shut off charging batteries then their voltage reaches 14.5 V in order not to over charge them, but I want to know that is the minimum in order not to under deplete them.

Only a field trail can answer some of these questions. Your questions are far beyond the scope of a forum like this 2) How long will the inverter supply output? Quick answer is, about 30 to 45 minutes To charge the battery you need at least 13.6V preferably 13.8V and once in a while (twice a year 14.4V for 1 to 2 hours) when the batteries is/are new, more often when older If we refer to BU-403 article, it states 12 to 16 hours charging time. That translates to 185Ah/12h= 15 Amps and 11 Amps charging rate So the charger output current should be limited to these values to prolong the battery life One has to understand, every time we charge/discharge the battery we rob some of its useful life How much? It depends on the chemistry and how deep. Generally at 10.5V the wear (or damage) is considered severe! Regarding the charger’s efficiency (in terms of electrical voltage/current conversion) it depends where the prime energy comes from and a bunch of other factors 2) How long will the inverter supply output? Quick answer, about 30 to 45 minutes The battery rating 185Ah means the battery will supply 9 Amps for 20 hours Ah rating is always for 20h If you plan to use 58A as calculated, the battery would last about 0.6 hour for a flooded acid battery That is if the battery is less than 6 months old, and if the temp is between 0 and 85ºF… Wil last a lot longer if it is AGM and even more if GEL type, for the same Ah rating Having said that, when you start, the battery voltage is more than 12, so the current may be less As the battery depletes towards 10.5V, the current will increase (to keep the Watts constant) and the wire voltage drop will increase (700/10.5= 66.6 Amps) The algebraic sum of all these factors is quite complex I hope I am not depressing you too much Best regards Anita

@Muhammad: if the battery is empty, you need 185Ah12V=2220Wh=2.22kWh theoretically. This result x 1.4 like Anita said, due to efficiency, gives you 3.1kWh approximately. But then there is also the efficiency of your charger. If it has 80% efficiency, your total energy bill will be 2.22×1.4×1.25=almost 4 kWh. (1.25 = 1/0.80 for efficiency of charger). 2. When you consume the full 700W, you theoretically have 700/12=58 Amps charge current. quite a lot I think. You have 185Ah, meaning a charge of 1 amp can be delivered 185 hours. So 58 amps will last 185/58=3.2 hours. But this is theory. The less-than-100%-efficiency of the inverter must be taken into account. 80% maybe? So that is 80% shorter then. 3. For DC (battery voltage), V x I = W so I = W / V and V = W / I W x hours = Wh (watthours) One Wh = 1/1000 of a kWh kilowatthour For AC (230V or 110V inverter output), output watts = V x I x power factor. Power factor depends on the load. A resistive load like a standard light bulb has a power factor of 1.

Dear Muhammad 1 the answer to your question is it depends on any factors like what is the starting voltage… Typically to get 100W out of a battery it needs about 140W of charge when the battery is new this relates to the battery efficiency. This efficiency will gradually diminish as the battery gets used. It should take 10 hours or more to fully charge the battery The charging current should not be more than 18.5A for your application. All that depends on what is the life expectancy. For example, an emergency power system, which may operate 5 times in 10 years of service, would have very different design criteria than a solar power plant. 3 to calculate voltage and current, refer to Ohms law

I have a 12V, 185Ah battery and a 20amp charger for it. I want to know that: 1. How much energy in kWh is required to get the battery fully charged? 2. battery is attached to a 700W inverter. For how long would it continuousely supply AC current? 3. Can i calculate out put voltage V, amperes I and Watts W?

this is the first time ive charged a battery. what does it mean if the needle goes up when charging.is it good or bad

To Jay regarding your June 12th question Is there any rule of thumb or guideline for the allowable voltage drop between the battery charger and battery terminals? The answer is yes, and the applicable rule is “it depends” What you are asking is “what is, or how do I determine the ampacity of my wire/s” How much current can conductors carry is a function of safety and electrical parameters Generally at high voltages, operating temperature governs the limit, and at low voltage, voltage drop governs the limit In the case of battery chargers like you are asking, other than safety hazards (fires) there is no voltage drop to worry about Because at end of charge there is not much current, therefore, not much voltage drop if any The safety issues still prevail. Such as installing wrong batteries, IE 36V battery in a 48V system… For that reason, chargers and batteries systems should be designed with interlocking mechanism so that charging power is only available after a series of tests have been done If you look at your cell phone or laptop batteries, there is normally no power available at the contacts until both units are properly connected together Some of the criterions that governs what type of wire (wire alloys, and insulating jacket) is suitable are For example, a train catenary (overhead cable) it has to resist abrasion, from a voltage drop point of view, it can glow red if that is acceptable Some cables are made of steel for strength because they have to support winter ice Some are made of aluminum because of their light weight, sometimes reinforced with a steel core for added strength Some are bundled together with others in a hot conduit Some need to resist twisting and pulling like telephone handset Regards Anita

To Marc Saya You need to consult your charger vendor as they are the only people who know how the internal plumbing of the charger works How to set your charger depends on your batteries and the application, if flooded, AGM, gel cells. The application such as lift truck where the electrolyte gravity would be 1.3 (very stressed-out application) 1.2 in a telephone system application (very relaxed application) Generally 1.27 in automobile application (many cycles, shallow discharges but high energy demands) And again different in an emergency power system, few cycles, deep discharges You mentioned 200Ah batteries; this means the batteries will deliver 10Amps for 20 hours (not 200A for 1 hour. maybe 50 Amps for 3 hours when new) And should be charged at a C/10 rate of 20 Amps, but again, only the system designer knows all the answers Regards Anita

Can you help me configure my charger? I have a 48 volt 3 stages charger. I can adjust the voltage for going from constant current to topping charge and also for going from topping to float. I have 4 batteries in seie each is lead acid 12V 200Ah and the ambient temperature is 30 deg C. I have fixed the contant charging current to 30A for the first stage and would like to set correctly the voltage levels for topping and floating stages. Thanks in advance for your help.

To Jay Jay, it does not quite work like that! The battery is a very large capacitor (extremely large in your case) What will happen, depends on the internal plumbing of the power supply For example, a laptop power supply that is 19V at 90W can and will deliver 19V until 90÷19=4.73….Amps Beyond that, at some point it will shut down and restart a while later. This is called hick-up mode protection What you need is a constant current power supply, only lab power supplies or chargers have this feature. Nothing to do with switch mode! So, the current could be 9.5 Amps or whatever the limit is set at and it needs a voltage limit set at 135V (125 is too low, it will cause stratification and sulfating problem) If it is a rectifier that is designed to charge batteries, it will work fine your statement if float is set to 125V, resulting in a current of 1000/125 = 8A ? That is, the power supply will deliver 8Amps until the battery voltage reaches the set-point, then will taper off to near zero Amps all this provided that the power supply (rectifier) is intended for charging batteries

To Alvin Mallia Unfortunately, the answer is NO the reason being that there are too many variables 1,the connector has to fit, 2; the electrical parameters have to match. what I suggest is to go to a store where they sell those type of batteries they could see what is needed. the parameters you need is 13.6V with 0.45 or 0.5A current limit. (no hick-up mode. ) stay away from intelligent chargers if you have a multimeter, and have access to the terminals, you could get almost any “linear” power supply, provided that the current limit is not more than 500mA and watch the voltage, disconnect the charger when the battery voltage reaches 13.6V (30ºC) to 13.8 (20ºC) no sparks near the battery!

Basic question here. If I have a switched mode rectifier rated 1000W, while charging a completely discharged battery (end voltage 105V), will the current output of the charger be 1000W/105V = 9.5A in this scenario? Or would it be dependent on the float voltage, if float is set to 125V, resulting in a current of 1000/125 = 8A ?

I have a ride on car for my kid. It takes 2 6volts 4.5a valve regulated lead acid batteries. Recently my charger broke down and supplier does not have any spare. Please can you indicate what charger should I purchase and if there is on ebay indicate a suitable model

To Wilson How do I telly if my 15 year old charger is still working well or at all ? Can I do this with a multi meter ?? Usually yes, but not always what type of charger? automobile? plug-it in, try-it out, if you have a meter, check if come current is coming out (BE CAREFULL! no sparks near the battery) some chargers (small, 2A) starts on their own, larger ones (2A, 10A, boost) needs some battery voltage to start sometimes there is no contact, due to rusted clips, broken wires.

at one site there was 2Volt 300Ah ZTE battery and till Friday night there was 4.5 hour battery backup and there was city supply problem and we ran DG for whole night and in the morning when we stopped the DG immediately all equipment including MUX got down and we ran DG again and checked all battery of these two bank and got 5 Battery from two Bank was completely dead. what will be the technical reason behind this?

How do I telly if my 15 year old charger is still working well or at all ? Can I do this with a multi meter ??

To Anita: no idea about the chemistry involved, but speaking pure theoretically the difference would be that with 28A peak currents, the losses in the battery are higher. Losses are current x current x series resistance of the battery. If resistance is a constant, then the losses are quadratic with the current. Higher losses mean lower output voltage. So if you have a regulated inverter that keeps its output voltage constant, it behaves as a constant power load. It will draw slightly more current at its input since it gets a lower input voltage. Both effects will add up: more losses inside battery slightly higher load current. So it will make a small difference. If you know the battery Ri (resistance), you could make a guess. Andre

Hi Anita, Thanks for your reply. This is a commercial charger. Yes, 135vdc full charge and 105V end voltage. I calculated the recharging current to be about 75A, this results in the voltage drop in cables of about 4V. So with the commercial charger, should I be less concerned about this issue? Thanks

To Joe Elliott I suggest you read this article http://www.cdtechno.com/pdf/ref/rs_1476_0610.pdf it may answer many of your questions

To Jay how much voltage drop are you referring to? It depends, is this a homebrew, or commercial charger? generally voltage drop is not an issue at 135v, you are talking 105V dead, and 135V full charge, this is 35V difference the charger has to accommodate this variation, hence why it is “normally” not an issue

question in an inverter set-up, what would be the effect on reserve capacity minutes if the load has ripple current of 28A as oppose to if I put a capacitor in parallel with the battery and reduce the ripple to 14A the ripple is near triangular shape and 120Hz

to Joe Elliott generally lead acid batteries should be charged at a rate of C10. that is 1/10th the AH rating while the battery is charging, the temperature is stable = ambient when it is fully charger, the temperature starts to rise. 5ºC rise is considered the limit of a healthy battery, I have seen much more on old batteries (hot spots on the outer casing) very hot spot Of course an internal sensor is preferable, but life is life Use a thermocouple probe, there is some compound, very similar to chewing gum where you stick the temperature sensing wire close to the battery surface and wait 3~5 minutes for the sensor to stabilize Concerning your charger, it is wiser to use a higher voltage with a series resistor the output current is much more stable (due to line voltage variations, battery voltage etc. than a straight transformer) as opposed to just a transformer with diodes

Hi all, Was hoping someone could answer this question. Is there any rule of thumb or guideline for the allowable voltage drop between the battery charger and battery terminals? For my system, the battery float voltage is to be 135VDC. But if I have too large of a drop between the battery charger and battery bank, there could be a problem. Could an issue be that the battery will not float at 135VDC if the voltage drop is too much? Or would the charger simply output more current to compensate for the voltage drop in the cabling? I was thinking that a 3% voltage drop is okay, but i’m not sure. Thanks!

Hi I have 185AH Battry installed a heavy UPS for my home I have adjust charging volt 13.8V As the charger cut off the charging my Battry reads 12.9 volts which gradually drops to 12.35 volts in about 12 hrs and charger again starts automatically to charge battry and the Room temperature remains about 30℃ My Question is. 1. is my battry is over charged as i read in article that a fully charged battry reads 12.65 volts

Anita. To measure a temperature increase of 5° above ambient, would I need a temperature sensor inside the battery, or will this be measurable from the exterior of the battery? And can you point me to any of the applicable formulas? I’ve done quite a bit of searching and can’t seem to find anything that applies to my situation. Thanks!

To Mayur The minimum discharge voltage is always 10.5V for lead acid batteries for safety: no sparks or flame near battery, charge or discharge this means connect charger to battery first and 120/220V last 3.What considerations should I make while charging it with 12v, 10A Battery Charger? it depends, is it a commercial charger or a homebrew? you mentionned a 100Ah battery, 10A charging current is a very god value however, it would be necessary to look at the charger’s output, and the ripple current should not exceed 5% or more precisely, should not exceed 5% of the C/10 value 4.How should I discharge it using a DC load bank of 45kW(electrical calculation)? I don’t understand your question you discharge the battery by using the intended load. And you need to stop at 10.5V as below this voltage, the wear on the battery severely aggravates 5.Battery also shows charging current 6.5A. what does that mean? It should mean that 6.5A is going into the battery at that particular time. there are different types of battery chargers on the market. A low cost 10A charger, would recharge a 100Ah battery in about 10~12 hours a Smart charger for that specific battery (much more expensive) will recharge the same battery in maybe 2 hours

to Joe Elliott there are plenty of formulas here at battery university the terminal voltage varies with temperature. one method is when the battery temperature starts to rise. I would say to stop once the temperature reached 5ºC above ambient This is for a battery that has been in a stable environment for 24 hours

Maybe someone here can help me with a question I’ve been struggling with for yearshow do I know when a lead-acid battery is fully charged using a crude (transformer rectifier) charger that’s significantly undersized for the capacity of the batteries? (For example, it will barely supply 0.1C worth of current to a fully-discharged batteryby the time it approaches the battery’s recommended charging voltage the current has fallen to like 0.005C.) Is there a formula by which I can calculate a termination voltage for a given C-rate? Or a way to figure out how long to let it continue charging after it’s tapered off to 2.4 V per cell and 0.006C?

bu-403, charging, lead, acid, battery, percentage

I need Lead Acid Battery Specification in Jis Standard. Please Mail me if you have.35 my email address basharsel@gmail.com

I have a 12v, 100Ah, heavy duty battery. 1.what is the minimum discharge voltage? 2.What are safe n quick discharge methods? 3.What considerations should I make while charging it with 12v, 10A Battery Charger? 4.How should I discharge it using a DC load bank of 45kW(electrical calculation)? 5.Battery aslo shows charging current 6.5A. what does that mean? According to it what precautions should be taaken for charging n discharging of the battery?

I have a 12v, 100Ah, heavy duty battery. 1.what is the minimum discharge voltage? 2.What are safe n quick discharge methods? 3.What considerations should I make while charging it with 12v, 10A Battery Charger? 4.How should I discharge it using a DC load bank of 45kW(electrical calculation)? 5.Battery aslo shows charging current 6.5A. what does that mean? According to it what precautions should be taaken for charging n discharging of the battery?

How fast can I charge a flooded lead-acid battery? I have 6V 235Ah battery which I normally never discharge below 50%. My charger can provide 80 Amps, which is C/3. Will it damage the battery if I charge at this rate up to 70 or 80% (keeping Voltage below 7.2V), and then continue charging at a more moderate rate?

@André: thank you, I was aware of it, but halas some other curves on other Web sites show different voltage values.

@Germain: is this something: http://jgdarden.com/batteryfaq/carfaq9.htm There is a CA/Ca curve when you scroll lower. Andre

Thank you anyway for your fair answer ! It is sad we cannot found a lot of informations about how to charge these kind of Ca/Ca batteries because they are replacing more and more frequently the ancient Lead ones, for our vehicules at least.

@Germain: I would love to, but I am only a reader of these articles and can sometimes help with some advice on electronic circuits. I would have to look up all your questions myself, and probably make mistakes since I might misinterpret your situation. Depends on battery size and usage conditions. Andre

Hello André, Please could you answer to my question from November 11, 2015 at 11:23am just above ? Thanks in advance and kind regards, Germain

@salah: 1.2V x 165 = 198V. 12V x 15 = 180V and fully charged 13V x 15 = 195V. Looking at voltage: yes, it will work. But 1.2V is probably NiCd or NiMH; and 12V is probably lead, so your charging circuit will need a change. Andre

@Tele: If it works for a few minutes, I think the battery is not bad, but not charged. Since you connected them in parallel, your charger must have terminated charging for some reason. Since you bought a new battery, I assume your old one is getting defective. maybe the voltage is too low. This can prevent the new battery from charging, because the voltage never gets high enough. When in parallel, both batteries get the exact same voltage, but different currents. I guess it is best to simply install the new battery into your fan, and then charge it. No parallel connection with the old one. Good luck!

Hi,i bought new 12v 7.5ah lead acid batteries for my rechargeable fan. Since i was told to charge it for 20hrs i did a parallel connection to my old battery which is 12v7.0ah so it could charge,but i diconnected it when i wanted to use the fan. Now its been 20hrs. I connected it irectly to the fan. It came on for just 3minutes then went off. I tried it after a while without charging it and it did the same thing. Is the battery bad? Could it be a connection problem?please HELP.

I want to know what is the current drawn by VRLA Gel battery in float mode. When should the battery be put in boost mode while under float mode. I can measure the battery voltage and current both.

Hi ! can anyone tell me why the charge current of the battery fluctuate i have an acid batteries ( 4 12 =48 V ) and i have a solar pannels that gives me 17.33=52 V. and i use a regulator (MPPT) to which i hook my batteries. my solar pannels and a DC motor ( 3000kw) the problem is that when i have 3 panels in series in parallel with 3 other panel in serie i have a current that reaches 5.6 A5.6A= 11.2 A. the carge current of the batteries start to fluctuate

Hi any who can help me, let you know about I have a dream about, let you know that I have Westport trike 20: kent and also 48 volt dc ebike 1000 watt E-bike. ok I did not planing buy yet, first my question for you ok how is work? Harbor freight toll Gas motor 6.5 HP can use alternator or generator charge to 4 pc 12v 12ah= 48 v 12 ah? if yes what kind alternator or generator tell me how is work? My dream E bike can running from battery charge like long drive no stop keep going how?

If you could find a service door on your machine to access the interior it would help to demystify your conundrum. Without being able to visibly inspect your batteries you really cannot be sure if everything maintained it’s integrity during transportation. Can you take a reading on the voltage output of the batteries? I take it since they are not easily accessible they are sealed lead acid. What is the make and model of your unit? Any other symptoms or related malfunctions?

Wow! Thanks @ Jiffer. I really appreciate it. The issue is that the battery is inbuilt and I can’t see the connections and the machine is heavily sealed. On the other hand, I’ll have to confirm two things like you just mentioned, which is to be sure the charger was made to function at 110 or 220v and to confirm if the chargers output is actually 48. As for thr manufacturers part, I’m in Nigeria and the machine wasimported from China, I’ve written so many mails to the company and trued calling all to no avail, worst of all the instructions on the charger are written in Chinese. So I’m currently at a fix. I’ve also been searching for someone will same or similar machine over and Ive not had any breakthrough yet. Anyways, Thanks once again. I appreciate

First thing to check is if you have correctly configured your batteries in series because if your charger is 48v than your batteries must be set up in series which would make 4 x 12v equalling 48v- positive of one battery to negative of next, negative of first battery to positive of next. This way you increase 12v to the needed 48v. Second would be to check your battery’s individual voltage. It should be at least 12.0 or higher to start taking a charge. Anything less than that might indicate the batteries have set around to long without a charge and have started to sulfate from self-discharge. It might be able to come back to life from the 11.0v range but it can get kinda iffy. A real tell-tale indicator of your battery’s health is specific gravity taken with a hydrometer. This will give you an indication of what percentage the sulfuric acid is in your electrolyte. That is what provides the chemical potential for electricity generation. If the individual cells read low on the hydrometer than that would mean your battery is in trouble. Have you closely followed the manufacturer’s guidelines on how to wire up the connections of the battery? I would go back to ground zero as if it is the first time you have hooked everything up and make sure that you understand the way things are connected and don’t deviate from the instructions. If you have the wiring correctly positioned, than it is your batteries at fault. If your batteries all read within their specifications than I would check out the output of your battery charger to be sure it is delivering 48v. You can do that with a simple multimeter set on DC, probably in the 200v range. I would make sure the charger is meant to operate on 220v. There should be information on the charger that specifies what the electrical input should be: 120 or 240v (220- same as 240-just old school label basically). You have to be sure that it matches your country’s setup of 220v or it won’t work.

Hello, I just imported an LPG steam car washing machine from China to Nigeria and the machine has 4x12volts battery in it,the charger is also rated 48V,2.8A but each time I try to charge the battery, it doesn’t and it’s getting me insane as I need it to work so as to start up my business and the manufacturers are not responding. The power rating in Nigeria is 220V,could this be why it doesn’t charge? Please I need help asap. I’ve been thinking of buying a step up or step down but now I Dont really know what to do anymore. Please help. Thanks.

Can Some one plese tell me exactly how many litres of distilled water must be added to 150AH inverter Battery where the distilled water is critically low to fill it to the desired level

I have one normal car battery and one deep cycle battery in my 4×4, which is parked up for lengthy periods. I have a simple arlec 4 amp charger that switches on via a timer for 15 minutes twice a day 12 hours apart, the battery’s are connected in parallel. This seems to work out well but is it the right thing to do. An expert opinion would be great.

Here at work we use 36v forklifts with massive lead acid batteries. I’ve been informed that we may start to use an opportunity charging method (charge a little here and a little there while the lift is not in use, say an hour or two at a time). As a long time electric rc enthusiast i was trained that batteries have a limited number of charge cycles before declination of preformance, from li-ion in our phones to large industrial ni-zn and lead acid. My question, is it true that batteries such as water filled lead acid are limited in the number of charge cycles before performance decline whether it be charging from 60 to 75% or 10 to 100% as 1 cycle

i have 12v lead acid battery. please someone con tell me why my battery discharging so fast? and what is the proper reason of this quick discharging?

Hi, Many thanks for all those informations, I’ve spent or rather gained a lot of hours reading ! Please may I ask you some questions about charging a 12v Ca/Ca battery, as: 1) What are the proper voltages for the boost and float phases to stay on the left side of your table 2 above ? 2) What is recommended duration for the boost phase ? 3) What are the recommended voltage and duration for the monthly equalization ? As you guess, it is for a solar installation with a programmable controller… Thanks in advance for your appreciated help and kind regards, Germain

@umesh: I see that a 74Wp panel has a short circuit current of 4.55 Amp approx, and an open voltage of over 19V. So if you connect it directly, it will work, as long as the voltage stays below the maximum for the battery. As soon as the battery voltage reaches its max voltage, you should disconnect manually. Max voltage allowed: see article above. will be 14V or somewhere near, depending on temperature and other conditions. If you don’t disconnect, you can destroy the battery. Better and safer solution will be some charger circuit between panel and battery. See YouTube movie: Charging a Car Battery with a Solar Panel and Charge Controller Best regards, Andre.

My whole house generator uses a flooded lead acid (non-sealed) for starting. A 2amp heater was installed (under warranty) to prevent moisture condensation on the brushes of the A/C generator’s armature (which would cause a fault preventing starting). Do to the long run (about 80 ft one way) and thin gauge wire from where the battery charger is located to the battery, when the heater is on (below 38 degF), the voltage at the battery drops from 13.4v to 12.8 to 12.9v. Since the generator (when running) charges the battery at 14 volts, the 4 amp battery charger just needs to maintain the battery’s condition. My question: Is this low voltage during cold weather going to be a problem in maintaining the battery’s condition during winter or its longevity? Thanks in advance, DJ

Geezzz I can see that it will be a full time job to answer all these questions even just the ones that make sense. No thanks. I am ok after all.

Deep Cycle Battery FAQ

The links below are on this page. you can also just scroll down if you want to read them all.

This entire page is copyright 1998-2014 by Northern Arizona Wind Sun. Please do not use without prior permission.

  • What is a Battery?
  • Types of Batteries
  • Battery Lifespan
  • Starting, Marine, or Deep Cycle?
  • Deep Cycle Battery as a Starting Battery?
  • What Batteries are made of
  • Industrial Deep Cycle Batteries (forklift type)
  • Sealed Batteries
  • Battery Size Codes
  • Gel Cells (Gelled Electrolyte) (and why we don’t like them)
  • AGM Batteries (and why we do like them)
  • Temperature Effects
  • Cycles vs Lifespan
  • Amp-Hours. what are they?
  • Battery Voltages
  • Battery Charging (Here is where we get into the real meat)
  • Charge Controllers (for wind/solar)
  • Mini Factoids. Some small facts about batteries

The subject of batteries could take up many pages. All we have room for here is a basic overview of batteries commonly used in photovoltaic power systems. These are nearly all various variations of Lead-Acid batteries. For a very brief discussion on the advantages and disadvantages of these and other types of batteries, such as NiCad, NiFe (Nickel-Iron), etc. go to our Batteries for Deep Cycle Applications page. These are sometimes referred to as deep discharge or deep cell batteries. The correct term is deep cycle.

A printable version of this page will be available in Adobe PDF format when we finish updating this page for downloading and printing: Most of the charts have small images for faster downloading. To see the full size picture, just click on the small one.

What is a Battery?

A battery is an electrical storage device. Batteries do not make electricity, they store it, just as a water tank stores water for future use. As chemicals in the battery change, electrical energy is stored or released. In rechargeable batteries, this process can be repeated many times. Batteries are not 100% efficient. some energy is lost as heat and chemical reactions when charging and discharging. If you use 1000 watts from a battery, it might take 1050 or 1250 watts or more to fully recharge it.

Internal Resistance

Part. or most. of the loss in charging and discharging batteries is due to internal resistance. This is converted to heat, which is why batteries get warm when being charged up. The lower the internal resistance, the better. There is a good explanation and demonstration of Internal Resistance here.

Slower charging and discharging rates are more efficient. A battery rated at 180 amp-hours over 6 hours might be rated at 220 AH at the 20-hour rate, and 260 AH at the 48-hour rate. Much of this loss of efficiency is due to higher internal resistance at higher amperage rates. internal resistance is not a constant. kind of like the more you push, the more it pushes back.

Typical efficiency in a lead-acid battery is 85-95%, in alkaline and NiCad battery it is about 65%. True deep cycle AGM’s (such as Concorde) can approach 98% under optimum conditions, but those conditions are seldom found so you should figure as a general rule about a 10% to 20% total power loss when sizing batteries and battery banks.

Practically all batteries used in PV and all but the smallest backup systems are Lead-Acid type batteries. Even after over a century of use, they still offer the best price to power ratio. A few systems use NiCad, but we do not recommend them except in cases where extremely cold temperatures (-50 F or less) are common. They are expensive to buy and very expensive to dispose of due to the hazardous nature of Cadmium.

We have had almost no direct experience with the NiFe (alkaline) batteries, but from what we have learned from others we do not not recommend them. One major disadvantage is that there is a large voltage difference between the fully charged and discharged state. Another problem is that they are very inefficient. you lose anywhere from 30 to 40% in heat just by charging and discharging them. Many inverters and charge controls have a hard time with them. It appears that the only current source for new cells seems to be from Hungary. In the past they were often used by railroads as backup power, but nearly all have now changed over to newer types.

An important fact is that ALL of the batteries commonly used in deep cycle applications are Lead-Acid. This includes the standard flooded batteries, gelled, and sealed AGM. They all use the same chemistry, although the actual construction of the plates, etc varies.

NiCads, Nickel-Iron, and other types are found in a few systems, but are not common due to their expense, environmental hazards, and/or poor efficiency.

Types of Batteries

Batteries are divided in two ways, by application (what they are used for) and construction (how they are built). The major applications are automotive, marine, and deep-cycle. Deep-cycle includes solar electric (PV), backup power, traction, and RV and boat house batteries. The major construction types are flooded (wet), gelled, and sealed AGM (Absorbed Glass Mat). AGM batteries are also sometimes called starved electrolyte or drybecause the fiberglass mat is only 95% saturated with Sulfuric acid and there is no excess liquid.

Flooded may be standard, with removable caps, or the so-called maintenance free (that means they are designed to die one week after the warranty runs out). All AGM gelled are sealed and are valve regulated, which means that a tiny valve keeps a slight positive pressure. Nearly all sealed batteries are valve regulated (commonly referred to as VRLA. Valve Regulated Lead-Acid). Most valve regulated are under some pressure. 1 to 4 psi at sea level.

Battery Lifespan

The lifespan of a deep cycle battery will vary considerably with how it is used, how it is maintained and charged, temperature, and other factors. It can vary to extremes. we have seen L-16’s killed in less than a year by severe overcharging and water loss, and we have a large set of surplus telephone batteries that see only occasional (10-15 times per year) heavy service that was just replaced after 35 years. We have seen gelled cells destroyed in one day when overcharged with a large automotive charger. We have seen golf cart batteries destroyed without ever being used in less than a year because they were left sitting in a hot garage or warehouse without being charged. Even the so-called dry charged (where you add acid when you need them) have a shelf life of 18 months at most. (They are not totally dry. they are actually filled with acid, the plates formed and charged, then the acid is dumped out).

These are some typical (minimum-maximum) expectations for batteries if used in deep cycle service. There are so many variables, such as depth of discharge, maintenance, temperature, how often and how deep cycled, etc. that it is almost impossible to give a fixed number.

  • Starting: 3-12 months
  • Marine: 1-6 years
  • Golf cart: 2-7 years
  • AGM deep cycle: 4-8 years
  • Gelled deep cycle: 2-5 years
  • Deep cycle (L-16 type etc): 4-8 years
  • Rolls-Surrette premium deep cycle: 7-15 years
  • Industrial deep cycle (Crown and Rolls 4KS series): 10-20 years.
  • Telephone (float): 2-20 years. These are usually special purpose float service, but often appear on the surplus market as deep cycle. They can vary considerably, depending on age, usage, care, and type.
  • NiFe (alkaline): 5-35 years
  • NiCad: 1-20 years

Starting, Marine, or Deep-Cycle Batteries

Starting (sometimes called SLI, for starting, lighting, ignition) batteries are commonly used to start and run engines. Engine starters need a very large starting current for a very short time. Starting batteries have a large number of thin plates for maximum surface area. The plates are composed of a Lead sponge, similar in appearance to a very fine foam sponge. This gives a very large surface area, but if deep cycled, this sponge will quickly be consumed and fall to the bottom of the cells. Automotive batteries will generally fail after 30-150 deep cycles if deep cycled, while they may last for thousands of cycles in normal starting use (2-5% discharge).

Deep cycle batteries are designed to be discharged down as much as 80% time after time and have much thicker plates. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates. not sponge. This gives less surface area, thus less instant power like starting batteries need. Although these can be cycled down to 20% charge, the best lifespan vs cost method is to keep the average cycle at about 50% discharge. Unfortunately, it is often impossible to tell what you are really buying in some of the discount stores or places that specialize in automotive batteries. The golf cart battery is quite popular for small systems and RV’s. The problem is that golf cart refers to a size of battery case (commonly called GC-2, or T-105), not the type of construction. so the quality and construction of a golf cart battery can vary considerably. ranging from the cheap off brand with thin plates up to true deep cycle brands, such as Crown, Deka, Trojan, etc. In general, you get what you pay for.

Marine batteriess are usually a hybrid, and fall between the starting and deep-cycle batteries, though a few (Rolls-Surrette and Concorde, for example) are true deep cycle. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries. It is often hard to tell what you are getting in a marine battery, but most are a hybrid. Starting batteries are usually rated at CCA, or cold cranking amps, or MCA, Marine cranking amps. the same as CA. Any battery with the capacity shown in CA or MCA may or may not be a true deep-cycle battery. It is sometimes hard to tell, as the term deep cycle is often overused. we have even seen the term deep cycle used in automotive starting battery advertising. CA and MCA ratings are at 32 degrees F, while CCA is at zero degrees F. Unfortunately, the only positive way to tell with some batteries is to buy one and cut it open. not much of an option.

Deep Cycle Battery as a Starting Battery

There is generally no problem with this, providing that allowance is made for the lower cranking amps compared to a similar size starting battery. As a general rule, if you are going to use a true deep cycle battery (such as the Concorde SunXtender) also as a starting battery, it should be oversized about 20% compared to the existing or recommended starting battery group size to get the same cranking amps. That is about the same as replacing a group 24 with a group 31. With modern engines with fuel injection and electronic ignition, it generally takes much less battery power to crank and start them, so raw cranking amps is less important than it used to be. On the other hand, many cars, boats, and RV’s are more heavily loaded with power sucking appliances, such as megawatt stereo systems etc. that are more suited for deep cycle batteries. We have used the Concorde SunXtender AGM batteries in some of our vehicles with no problems.

It will not hurt a deep cycle battery to be used as a starting battery, but for the same size battery they cannot supply as much cranking amps as a regular starting battery and is usually much more expensive.

What Batteries Are Made Of

Nearly all large rechargeable batteries in common use are Lead-Acid type. (There are some NiCads in use, but for most purposes the very high initial expense, and the high expense of disposal, does not justify them). A few Lithium-Ion types are starting to make their appearance, but are much more expensive than Lead-Acid and most charge controllers do not have the correct setpoints for proper charging.

The acid is typically 30% Sulfuric acid and 70% water at full charge. NiFe (Nickel-Iron) batteries are also available. these have a very long life, but rather poor efficiency (60-70%) and the voltages are different, making it more difficult to match up with standard 12v/24/48v systems and inverters. The biggest problem with NiFe batteries is that you may have to put in 100 watts to get 70 watts of charge. they are much less efficient than Lead-Acid. What you save on batteries you will have to make up for by buying a larger solar panel system. NiCads are also inefficient. typically around 65%. and very expensive. However, NiCads can be frozen without damage, so are sometimes used in areas where the temperatures may fall below.50 degrees F. Most AGM batteries will also survive freezing with no problems, even though the output when frozen will be little or nothing.

Industrial Deep Cycle Batteries

Sometimes called fork lift, traction or stationary batteries, are used where power is needed over a longer period of time, and are designed to be deep cycled, or discharged down as low as 20% of full charge (80% DOD, or Depth of Discharge). These are often called traction batteries because of their widespread use in forklifts, golf carts, and floor sweepers (from which we get the GC and FS series of battery sizes). Deep cycle batteries have much thicker plates than automotive batteries. They are sometimes used in larger PV systems because you can get a lot of storage in a single (very large and heavy) battery.

Plate Thickness

Plate thickness (of the Positive plate) matters because of a factor called positive grid corrosion. This ranks among the top 3 reasons for battery failure. The positive plate is what gets eaten away gradually over time, so eventually there is nothing left. it all falls to the bottom as sediment. Thicker plates are directly related to longer life, so other things being equal, the battery with the thickest plates will last the longest. The negative plate in batteries expands somewhat during discharge, which is why nearly all batteries have separators, such as glass mat or paper, that can be compressed.

Automotive batteries typically have plates about.040 (4/100) thick, while forklift batteries may have plates more than 1/4 (.265 for example in larger Rolls-Surrette) thick. almost 7 times as thick as auto batteries. The typical golf cart will have plates that are around.07 to.11 thick. The Concorde AGM’s are.115, The Rolls-Surrette L-16 type (CH460) is.150, and the US Battery and Trojan L-16 types are.090. The Crown L-16HC size has.22 thick plates. While plate thickness is not the only factor in how many deep cycles a battery can take before it dies, it is the most important one.

Most industrial (fork lift) deep-cycle batteries use Lead-Antimony plates rather than the Lead-Calcium used in AGM or gelled deep-cycle batteries and in automotive starting batteries. The Antimony increases plate life and strength, but increases gassing and water loss. This is why most industrial batteries have to be checked often for water level if you do not have Hydrocaps. The self discharge of batteries with Lead-Antimony plates can be high. as much as 1% per day on an older battery. A new AGM typically self-discharges at about 1-2% per month, while an old one may be as much as 2% per week.

Sealed Batteries

Sealed batteries are made with vents that (usually) cannot be removed. The so-called Maintenance Free batteries are also sealed, but are not usually leak proof. Sealed batteries are not totally sealed, as they must allow gas to vent during charging. If overcharged too many times, some of these batteries can lose enough water that they will die before their time. Most smaller deep cycle batteries (including AGM) use Lead-Calcium plates for increased life, while most industrial and forklift batteries use Lead-Antimony for greater plate strength to withstand shock and vibration.

Lead-Antimony (such as forklift and floor scrubber) batteries have a much higher self-discharge rate (2-10% per week) than Lead or Lead-Calcium (1-5% per month), but the Antimony improves the mechanical strength of the plates, which is an important factor in electric vehicles. They are generally used where they are under constant or very frequent charge/discharge cycles, such as fork lifts and floor sweepers. The Antimony increases plate life at the expense of higher self discharge. If left for long periods unused, these should be trickle charged to avoid damage from sulfation. but this applies to ANY battery.

As in all things, there are trade offs. The Lead-Antimony types have a very long lifespan, but higher self discharge rates.

Battery Size Codes

Batteries come in all different sizes. Many have group sizes, which is based upon the physical size and terminal placement. It is NOT a measure of battery capacity. Typical BCI codes are group U1, 24, 27, and 31. Industrial batteries are usually designated by a part number such as FS for floor sweeper, or GC for golf cart. Many batteries follow no particular code, and are just manufacturers part numbers. Other standard size codes are 4D 8D, large industrial batteries, commonly used in solar electric systems.

Some common battery size codes used are: (ratings are approximate)

U1 34 to 40 Amp hours 12 volts
Group 24 70-85 Amp hours 12 volts
Group 27 85-105 Amp hours 12 volts
Group 31 95-125 Amp hours 12 volts
4-D 180-215 Amp hours 12 volts
8-D 225-255 Amp hours 12 volts
Golf Cart T-105 180 to 225 Amp hours 6 volts
L-16, L16HC etc. 340 to 415 Amp hours 6 volts

Gelled Electrolyte

Gelled batteries, or Gel Cells contain acid that has been gelled by the addition of Silica Gel, turning the acid into a solid mass that looks like gooey Jell-O. The advantage of these batteries is that it is impossible to spill acid even if they are broken. However, there are several disadvantages. One is that they must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells. They cannot be fast charged on a conventional automotive charger or they may be permanently damaged. This is not usually a problem with solar electric systems, but if an auxiliary generator or inverter bulk charger is used, current must be limited to the manufacturers specifications. Most better inverters commonly used in solar electric systems can be set to limit charging current to the batteries.

Some other disadvantages of gel cells is that they must be charged at a lower voltage (2/10th’s less) than flooded or AGM batteries. If overcharged, voids can develop in the gel which will never heal, causing a loss in battery capacity. In hot climates, water loss can be enough over 2-4 years to cause premature battery death. It is for this and other reasons that we no longer sell any of the gelled cells except for replacement use. The newer AGM (absorbed glass mat) batteries have all the advantages (and then some) of gelled, with none of the disadvantages.

AGM (Absorbed Glass Mat) Batteries

A newer type of sealed battery uses Absorbed Glass Mats, or AGM between the plates. This is a very fine fiber Boron-Silicate glass mat. These type of batteries have all the advantages of gelled, but can take much more abuse. We sell the Concorde (and Lifeline, made by Concorde) AGM batteries. These are also called starved electrolyte, as the mat is about 95% saturated rather than fully soaked. That also means that they will not leak acid even if broken.

AGM batteries have several advantages over both gelled and flooded, at about the same cost as gelled:

Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken. This also means that since they are non-hazardous, the shipping costs are lower. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage.

Nearly all AGM batteries are recombinant. what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99% efficient, so almost no water is lost.

The charging voltages are the same as for any standard battery. no need for any special adjustments or problems with incompatible chargers or charge controls. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. The Concorde (and most AGM) batteries have no charge or discharge current limits.

AGM’s have a very low self-discharge. from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries. The Concorde batteries can be almost fully recharged (95% or better) even after 30 days of being totally discharged.

AGM’s do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM’s are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. AGM’s will cost about 1.5 to 2 times as much as flooded batteries of the same capacity. In many installations, where the batteries are set in an area where you don’t have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice. AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Not everyone needs these features.

Temperature Effects on Batteries

Battery capacity (how many amp-hours it can hold) is reduced as temperature goes down, and increased as temperature goes up. This is why your car battery dies on a cold winter morning, even though it worked fine the previous afternoon. If your batteries spend part of the year shivering in the cold, the reduced capacity has to be taken into account when sizing the system batteries. The standard rating for batteries is at room temperature. 25 degrees C (about 77 F). At approximately.22 degrees F (-27 C), battery AH capacity drops to 50%. At freezing, capacity is reduced by 20%. Capacity is increased at higher temperatures. at 122 degrees F, battery capacity would be about 12% higher.

Battery charging voltage also changes with temperature. It will vary from about 2.74 volts per cell (16.4 volts) at.40 C to 2.3 volts per cell (13.8 volts) at 50 C. This is why you should have temperature compensation on your charger or charge control if your batteries are outside and/or subject to wide temperature variations. Some charge controls have temperature compensation built in (such as Morningstar). this works fine if the controller is subject to the same temperatures as the batteries. However, if your batteries are outside, and the controller is inside, it does not work that well. Adding another complication is that large battery banks make up a large thermal mass.

Thermal mass means that because they have so much mass, they will change internal temperature much slower than the surrounding air temperature. A large insulated battery bank may vary as little as 10 degrees over 24 hours internally, even though the air temperature varies from 20 to 70 degrees. For this reason, external (add-on) temperature sensors should be attached to one of the POSITIVE plate terminals, and bundled up a little with some type of insulation on the terminal. The sensor will then read very close to the actual internal battery temperature.

Even though battery capacity at high temperatures is higher, battery life is shortened. Battery capacity is reduced by 50% at.22 degrees F. but battery LIFE increases by about 60%. Battery life is reduced at higher temperatures. for every 15 degrees F over 77, battery life is cut in half. This holds true for ANY type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever. This is actually not as bad as it seems, as the battery will tend to average out the good and bad times. Click on the small graph to see a full size chart of temperature vs capacity.

One last note on temperatures. in some places that have extremely cold or hot conditions, batteries may be sold locally that are NOT standard electrolyte (acid) strengths. The electrolyte may be stronger (for cold) or weaker (for very hot) climates. In such cases, the specific gravity and the voltages may vary from what we show.

Cycles vs Lifespan

A battery cycle is one complete discharge and recharge cycle. It is usually considered to be discharging from 100% to 20%, and then back to 100%. However, there are often ratings for other depth of discharge cycles, the most common ones are 10%, 20%, and 50%. You have to be careful when looking at ratings that list how many cycles a battery is rated for unless it also states how far down it is being discharged. For example, one of the widely advertised telephone type (float service) batteries have been advertised as having a 20-year life. If you look at the fine print, it has that rating only at 5% DOD. it is much less when used in an application where they are cycled deeper on a regular basis. Those same batteries are rated at less than 5 years if cycled to 50%. For example, most golf cart batteries are rated for about 550 cycles to 50% discharge. which equates to about 2 years.

Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Obviously, there are some practical limitations on this. you don’t usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The most practical number to use is 50% DOD on a regular basis. This does NOT mean you cannot go to 80% once in a while. It’s just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor. Also, there is an upper limit. a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the the positive plates rather in an even film. The graph above shows how lifespan is affected by depth of discharge. The chart is for a Concorde Lifeline battery, but all lead-acid batteries will be similar in the shape of the curve, although the number of cycles will vary.

Battery Voltages

All Lead-Acid batteries supply about 2.14 volts per cell (12.6 to 12.8 for a 12 volt battery) when fully charged. Batteries that are stored for long periods will eventually lose all their charge. This leakage or self discharge varies considerably with battery type, age, temperature. It can range from about 1% to 15% per month. Generally, new AGM batteries have the lowest, and old industrial (Lead-Antimony plates) are the highest. In systems that are continually connected to some type charging source, whether it is solar, wind, or an AC powered charger this is seldom a problem. However, one of the biggest killers of batteries is sitting stored in a partly discharged state for a few months. A float trickle charge should be maintained on the batteries even if they are not used (or, especially if they are not used). Even most dry charged batteries (those sold without electrolyte so they can be shipped more easily, with acid added later) will deteriorate over time. Max storage life on those is about 18 to 30 months.

Batteries self-discharge faster at higher temperatures. Lifespan can also be seriously reduced at higher temperatures. most manufacturers state this as a 50% loss in life for every 15 degrees F over a 77 degree cell temperature. Lifespan is increased at the same rate if below 77 degrees, but capacity is reduced. This tends to even out in most systems. they will spend part of their life at higher temperatures, and part at lower. Typical self discharge rates for flooded are 5% to 15% per month.

Myth: The old myth about not storing batteries on concrete floors is just that. a myth. This story has been around for 100 years, and originated back when battery cases were made up of wood and asphalt. The acid would leak from them, and form a slow-discharging circuit through the now acid-soaked and conductive floor.

State of Charge

State of charge, or conversely, the depth of discharge (DOD) can be determined by measuring the voltage and/or the specific gravity of the acid with a hydrometer. This will NOT tell you how good (capacity in AH) the battery condition is. only a sustained load test can do that. Voltage on a fully charged battery will read 2.12 to 2.15 volts per cell, or 12.7 volts for a 12 volt battery. At 50% the reading will be 2.03 VPC (Volts Per Cell), and at 0% will be 1.75 VPC or less. Specific gravity will be about 1.265 for a fully charged cell, and 1.13 or less for a totally discharged cell. This can vary with battery types and brands somewhat. when you buy new batteries you should charge them up and let them sit for a while, then take a reference measurement. Many batteries are sealed, and hydrometer reading cannot be taken, so you must rely on voltage. Hydrometer readings may not tell the whole story, as it takes a while for the acid to get mixed up in wet cells. If measured right after charging, you might see 1.27 at the top of the cell, even though it is much less at the bottom. This does not apply to gelled or AGM batteries.

False Capacity

A battery can meet the voltage tests for being at full charge, yet be much lower than it’s original capacity. If plates are damaged, sulfated, or partially gone from long use, the battery may give the appearance of being fully charged, but in reality acts like a battery of much smaller size. This same thing can occur in gelled cells if they are overcharged and gaps or bubbles occur in the gel. What is left of the plates may be fully functional, but with only 20% of the plates left. Batteries usually go bad for other reasons before reaching this point, but it is something to be aware of if your batteries seem to test OK but lack capacity and go dead very quickly under load.

On the table below, you have to be careful that you are not just measuring the surface charge. To properly check the voltages, the battery should sit at rest for a few hours, or you should put a small load on it, such as a small automotive bulb, for a few minutes. The voltages below apply to ALL Lead-Acid batteries, except gelled. For gel cells, subtract.2 volts. Note that the voltages when actually charging will be quite different, so do not use these numbers for a battery that is under charge.

Amp-Hours. What Are They?

All deep cycle batteries are rated in amp-hours. An amp-hour is one amp for one hour, or 10 amps for 1/10 of an hour and so forth. It is amps x hours. If you have something that pulls 20 amps, and you use it for 20 minutes, then the amp-hours used would be 20 (amps) x.333 (hours), or 6.67 AH. The generally accepted AH rating time period for batteries used in solar electric and backup power systems (and for nearly all deep cycle batteries) is the 20 hour rate. (Some, such as the Concorde AGM, use the 24 hour rate, which is probably a better real-world rating). This means that it is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours it supplies is measured. Sometimes ratings at the 6 hour rate and 100 hour rate are also given for comparison and for different applications. The 6-hour rate is often used for industrial batteries, as that is a typical daily duty cycle. Sometimes the 100 hour rate is given just to make the battery look better than it really is, but it is also useful for figuring battery capacity for long-term backup amp-hour requirements.

Why amp-hours are specified at a particular rate:

Because of something called the Peukert Effect. The Peukert value is directly related to the internal resistance of the battery. The higher the internal resistance, the higher the losses while charging and discharging, especially at higher currents. This means that the faster a battery is used (discharged), the LOWER the AH capacity. Conversely, if it is drained slower, the AH capacity is higher. This is important because some manufacturers and vendors have chosen to rate their batteries at the 100 hour rate. which makes them look a lot better than they really are. Here are some typical battery capacities from the manufacturers data sheets:

Battery Type 100 hour rate 20 hour rate 8
Trojan T-105 250 AH 225 AH n/a
US Battery 2200 n/a 225 AH 181 AH
Concorde PVX-6220 255 AH 221 AH 183 AH
Surrette S-460 (L-16) 429 AH 344 AH 282 AH
Trojan L-16 400 AH 360 AH n/a
Surrette CS-25-PS 974 AH 779 AH 639 AH

Here are no-load typical voltages vs state of charge

(figured at 10.5 volts = fully discharged, and 77 degrees F). Voltages are for a 12 volt battery system. For 24 volt systems multiply by 2, for 48 volt system, multiply by 4. VPC is the volts per individual cell. if you measure more than a.2 volt difference between each cell, you need to equalize, or your batteries are going bad, or they may be sulfated. These voltages are for batteries that have been at rest for 3 hours or more. Batteries that are being charged will be higher. the voltages while under charge will not tell you anything, you have to let the battery sit for a while. For longest life, batteries should stay in the green zone. Occasional dips into the yellow are not harmful, but continual discharges to those levels will shorten battery life considerably. It is important to realize that voltage measurements are only approximate. The best determination is to measure the specific gravity, but in many batteries this is difficult or impossible. Note the large voltage drop in the last 10%.

State of Charge 12 Volt battery Volts per Cell
100% 12.7 2.12
90% 12.5 2.08

Why 10.5 Volts?

Throughout this FAQ, we have stated that a battery is considered dead at 10.5 volts. The answer is related to the internal chemistry of batteries. at around 10.5 volts, the specific gravity of the acid in the battery gets so low that there is very little left that can do. In a dead battery, the specific gravity can fall below 1.1. Some actual testing was done recently on a battery by one of our solar forum posters, and these are his results:

I just tested a 225 ahr deep cycle battery that is in good working order. I put a load on it 30a for 4 hrs it dropped its voltage to 11.2 I then let it cool down for 2 hrs

then put the load back on again in 1hr 42 mins it dropped to 10.3v 35 mins under 30a load 9.1v (273w) 10 mins later max output current 11.6a 8.5v (98.6w) 5 mins later max output current 5.2 amps 7.9v (41w) 3 mins later 7.6v and 2.3a (17.5w)

This shows after it gets below 10.3 v you only have 35 mins of anything useful available from the battery.

battery is now dead and most likely will not fully recover

Battery Charging

Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.

Bulk Charge. The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no correct voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.

Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts. (The internal resistance gradually goes up because there is less and less to be converted back to normal full charge).

Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it’s main purpose is to keep an already charged battery from discharging. PWM, or pulse width modulation accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called pulse width because the width of the pulses may vary from a few microseconds to several seconds. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.

Chargers: Most garage and consumer (automotive) type battery chargers are bulk charge only, and have little (if any) voltage regulation. They are fine for a quick boost to low batteries, but not to leave on for long periods. Among the regulated chargers, there are the voltage regulated ones, such as Iota Engineering, PowerMax, and others, which keep a constant regulated voltage on the batteries. If these are set to the correct voltages for your batteries, they will keep the batteries charged without damage. These are sometimes called taper charge. as if that is a selling point. What taper charge really means is that as the battery gets charged up, the voltage goes up, so the amps out of the charger goes down. They charge OK, but a charger rated at 20 amps may only be supplying 5 amps when the batteries are 80% charged. To get around this, Xantrex (and maybe others?) have come out with Smart, or multi-stage chargers. These use a variable voltage to keep the charging amps much more constant for faster charging.

We stock all of the Iota Engineering battery chargers.

Charge Controllers

A charge controller is a regulator that goes between the solar panels and the batteries. Regulators for solar systems are designed to keep the batteries charged at peak without overcharging. Meters for Amps (from the panels) and battery Volts are optional with most types. Some of the various brands and models that we use and recommend are listed below. Note that a couple of them are listed as power trackers. for a full explanation of this, see our page on Why 130 watts does not equal 130 watts.

Most of the modern controllers have automatic or manual equalization built in, and many have a LOAD output. There is no best controller for all applications. some systems may need the bells and whistles of the more expensive controls, others may not.

These are some of the charge controllers that we recommend, but almost any modern controller will work fine. Exact model will depend on application and system size, amperage and voltage.

Xantrex Morningstar Midnite Solar Outback Power Steca You can find all these brands, as well as others, in our charge controller section.

Using any of these will almost always give better battery life and charge than on-off or simple shunt type regulators

Battery Charging Voltages and Currents:

Most flooded batteries should be charged at no more than the C/8 rate for any sustained period. While some battery manufacturers state a higher maximum charge rate, such as C/3, higher charge rates can result in high battery temperatures and/or excessive bubbling and loss of liquid. (C/8 is the battery capacity at the 20-hour rate divided by 8. For a 220 AH battery, this would equal 26 Amps.) Gelled cells should be charged at no more than the C/20 rate, or 5% of their amp-hour capacity. Concorde and some other AGM batteries are a special case. they can be charged at up the the Cx4 rate, or 400% of the capacity for the bulk charge cycle for a short period. However, since very few battery cables can take that much current, we don’t recommend you try this at home. To avoid cable overheating, you should stick to C/4 or less.

Charging at 15.5 volts will give you a 100% charge on Lead-Acid batteries. Once the charging voltage reaches 2.583 volts per cell, charging should stop or be reduced to a trickle charge. Note that flooded batteries MUST bubble (gas) somewhat to ensure a full charge, and to mix the electrolyte. Float voltage for Lead-Acid batteries should be about 2.15 to 2.23 volts per cell, or about 12.9-13.4 volts for a 12 volt battery. At higher temperatures (over 85 degrees F) this should be reduced to about 2.10 volts per cell.

Never add acid to a battery except to replace spilled liquid. Distilled or deionized water should be used to top off non-sealed batteries. Float and charging voltages for gelled batteries are usually about 2/10th volt less than for flooded to reduce water loss. Note that many shunt-type charge controllers sold for solar systems will NOT give you a full charge. check the specifications first. To get a full charge, you must continue to apply a current after the battery voltage reaches the cutoff point of most of these types of controllers. This is why we recommend the charge controls and battery chargers listed in the sections above. Not all shunt type controllers are 100% on or off, but most are.

Flooded battery life can be extended if an equalizing charge is applied every 10 to 40 days. This is a charge that is about 10% higher than normal full charge voltage, and is applied for about 2 to 16 hours. This makes sure that all the cells are equally charged, and the gas bubbles mix the electrolyte. If the liquid in standard wet cells is not mixed, the electrolyte becomes stratified. You can have very strong solution at the bottom, and very weak at the top of the cell. With stratification, you can test a battery with a hydrometer and get readings that are quite a ways off. If you cannot equalize for some reason, you should let the battery sit for at least 24 hours and then use the hydrometer. AGM and gelled should be equalized 2-4 times a year at most. check the manufacturers recommendations, especially on gelled.

Battery Aging

As batteries age, their maintenance requirements change. This means longer charging time and/or higher finish rate (higher amperage at the end of the charge). Usually older batteries need to be watered more often. And, their capacity decreases while the self-discharge rate increases.

Mini Factoids

Nearly all batteries will not reach full capacity until cycled 10-30 times. A brand new battery will have a capacity of about 5-10% less than the rated capacity.

Batteries should be watered after charging unless the plates are exposed, then add just enough water to cover the plates. After a full charge, the water level should be even in all cells and usually 1/4 to 1/2 below the bottom of the fill well in the cell (depends on battery size and type).

In situations where multiple batteries are connected in series, parallel or series/parallel, replacement batteries should be the same size, type, and manufacturer (if possible). Age and usage level should be the same as the companion batteries. Do not put a new battery in a pack which is more than 6 months old or has more than 75 cycles. Either replace with all new or use a good used battery. For long life batteries, such as the Surrette and Crown, you can have up to a one year age difference.

The vent caps on flooded batteries should remain on the battery while charging. This prevents a lot of the water loss and splashing that may occur when they are bubbling.

When you first buy a new set of flooded (wet) batteries, you should fully charge and equalize them, and then take a hydrometer reading for future reference. Since not all batteries have exactly the same acid strength, this will give you a baseline for future readings.

When using a small solar panel to keep afloat (maintenance) charge on a battery (without using a charge controller), choose a panel that will give a maximum output of about 1/300th to 1/1000th of the amp-hour capacity. For a pair of golf cart batteries, that would be about a 1 to 5-watt panel. the smaller panel if you get 5 or more hours of sun per day, the larger one for those long cloudy winter days in the Northeast.

Lead-Acid batteries do NOT have a memory, and the rumor that they should be fully discharged to avoid this memory is totally false and will lead to early battery failure.

Inactivity can be extremely harmful to a battery. It is a VERY poor idea to buy new batteries and save them for later. Either buy them when you need them or keep them on a continual trickle charge. The best thing. if you buy them, use them.

Only clean water should be used for cleaning the outside of batteries. Solvents or spray cleaners should not be used.

Some Peukert Exponent values (not complete, just for info). We don’t have a lot of data. Trojan T-105 = 1.25; Optima 750S = 1.109; US Battery 2200 = 1.20.

information. Manufacturers Websites

Trojan Battery. not a lot of real technical info here, but has all the specifications.Rolls Battery. Specs and data on the Rolls Surrette deep cycle and marine batteriesConcorde. specs and data on all the Concorde batteries, including Lifeline.Discover Battery. Lots of info on the Discover Battery brand of batteries.Discover Solar. A solar specific site for the Discover Battery brand.SimpliPhi

What is a Battery. A Complete Guide to Battery Basics

If you have done any research on how batteries work or what you should look for when selecting the best high performance battery, you’re probably buried in information, some of which is conflicting. At BatteryStuff, we aim to clear that up a bit.

You’ve most likely heard the term KISS (Keep It Simple, Stupid). I’m going to attempt to explain how lead acid batteries work and what they need, without burying you with a bunch of needless technical data. I have found that battery data will vary somewhat from manufacturer to manufacturer, so I will do my best to boil that data down. This means I may generalize a bit, while staying true to purpose.

The lead acid battery has been used commercially for over 100 years. The same chemical principle that’s being used to store energy is basically the same as our great grandparents used.

A battery is like a piggy bank. If you keep taking out and putting nothing back, you’ll have nothing left. Present day vehicle or powersport vehicle battery power requirements are huge considering all the stock electrical devices that must be supplied with power. All these electronics require a reliable source power, and poor battery condition can cause expensive electronic component failure.

Did you know that the average auto has 11 pounds of wire in the electrical system? Look at RVs and boats with all the electrical gadgets that require power. It wasn’t long ago when trailers or motor homes had only a single 12-volt house battery. Today recreation vehicles use their rv batteries to power inverters up to 4000 watts.

Average battery life has become shorter as energy requirements have increased. Life span depends on usage and depth of discharge—usually 6 to 48 months—yet only 30% of all batteries actually reach the 48-month mark. If your unable to maintain the battery with an battery charger you can extend your battery life by hooking it up to a solar charger during the off months.

If you can grasp the basics, you’ll have fewer battery problems and will gain greater battery performance, reliability and longevity. I suggest you read the entire tutorial; however, I’ve indexed all the information for easy reference.

A Few Basics

The lead acid battery is made up of plates, lead, and lead oxide (various other elements are used to change density, hardness, porosity, etc.), with a 35% sulfuric acid and 65% water solution. This solution is called electrolyte, which causes a chemical reaction that produces electrons. When you test a battery with a hydrometer, you are measuring the amount of sulfuric acid in the electrolyte. If your reading is low, that means the chemistry that makes electrons is lacking. So where did the sulfur go? It’s resting on the battery plates so that when you recharge the battery, the sulfur returns to the electrolyte.

  • Safety
  • Battery Application: Deep Cycle vs. Starting
  • Wet Cell, Gel-Cell and Absorbed Glass Mat (AGM)
  • Lithium-Ion LiFePO4
  • CCA, CA, AH and RC; what’s that all about?
  • Battery Maintenance
  • Battery Testing
  • Selecting and Buying a New Battery
  • Battery Life and Performance
  • Battery Charging
  • Battery Do’s
  • Battery Don’ts


You must think safety when you’re working around, and with, batteries. Remove all jewelry. (After all, you wouldn’t want to melt your watchband while you’re wearing it!) The hydrogen gas that batteries make when charging is very explosive. We have seen several instances of batteries blowing up and drenching everything in sulfuric acid. That was no fun, and would have been a good time to use those safety goggles hanging on the wall. Heck, you could even break out your disco outfit. Polyester isn’t affected by sulfuric acid, but anything with cotton will be eaten up. If you don’t feel the need to make a fashion statement, just wear junk clothes—after all, polyester is still out of style.

When doing electrical work on vehicles, it’s best to disconnect the ground cable. Just remember that you’re messing with corrosive acid, explosive gases and hundreds of amps of electrical current.

Battery Types: Deep Cycle vs. Starting

Basically, there are two types of lead acid batteries (along with three sub categories). The two main types are starting (cranking), and deep cycle (marine/golf cart). The starting battery (SLI starting lights ignition) is designed to deliver quick bursts of energy (such as starting engines) and therefore has a greater plate count. The plates are thinner and have somewhat different material composition.

What is a deep cycle battery? The deep cycle battery has less instant energy, but greater long-term energy delivery. Deep cycle batteries have thicker plates and can survive a lot of discharge cycles. Starting batteries should not be used for deep cycle applications because the thinner plates are more prone to warping and pitting when discharged. The so-called Dual Purpose Battery is a compromise between the two types of batteries, though it is better to be more specific if possible.

Lead Acid Battery Types: Wet Cell vs. Gel Cell vs. AGM

The gel cell and the AGM batteries are specialty batteries that typically cost twice as much as a premium wet cell battery. However, they store very well and do not tend to sulfate or degrade as easily as wet cell. Although not impossible there is little chance of a hydrogen gas explosion or corrosion when using these batteries; they are the safest lead acid batteries you can use. Gel cell and some AGM batteries may require a special charging rate. If you want the best and most versatile battery, then consideration should be given to the AGM battery type. AGM batteries are great for applications such as Marine, RV, Solar, Audio, Power Sports and Stand-By Power just to name a few.

If you don’t use or operate your equipment daily, AGM batteries will hold their charge better than other types. If you must depend on top-notch battery performance, spend the extra money. Gel Cell batteries still are being sold, but AGM batteries are replacing them in most applications.

There is common confusion regarding AGM batteries because different manufactures call them by different names. Some of the more common names are sealed regulated valve, dry cell, non-spillable, and valve-regulated lead acid batteries. In most cases, AGM batteries will give greater life span and greater cycle life than a wet cell battery.

SPECIAL NOTE: It’s common for individuals to use the term gel cell as a generic term when referring to sealed, maintenance-free batteries, much like one would use Kleenex when referring to facial tissue. As a result, we get lots of requests for a gel replacement battery or gel battery charger when in fact the battery is an AGM. For this reason, we always recommend verifying the battery type when purchasing a replacement or looking for a charger to maintain the battery.

Wet Cell

The wet cell comes in two styles: serviceable and maintenance-free. Both are filled with electrolyte and are basically the same. I prefer one that I can add water to and check the specific gravity of the electrolyte with a hydrometer. Also, the serviceable type tends to last a little longer since you can add distilled water when evaporation occurs and treat the battery with an inhibitor such as Battery Equaliser to prevent sulfation. In contrast, with the maintenance free, you cannot do either of the servicing features.


The Absorbed Glass Mat construction allows the liquid electrolyte to be suspended in a fiberglass matting. This matting surrounds the plate’s active material and in theory this enhances both the discharge and recharge efficiency. AGMs are commonly manufactured for applications that include high-performance engine starting, power sports equipment, deep cycle, solar and storage battery. The larger Deep Cycle AGM Batteries we sell typically offer great cycle life if recharged before they drop below the 50% discharge rate. When deep cycle AGM batteries are discharged to a rate of no less than 60%, the cycle life will generally increase by 300 plus cycles.

The Scorpion motorcycle batteries we carry are a meet or exceed the specification for the OEM battery. We also carry the Motocross branded batteries for those that have brand loyalty to the OEM battery as they are Yuasa’s aftermarket battery.


The gel cell battery is like the AGM battery in the fact that it is considered non-spillable, but the electrolyte is not a wet liquid. The electrolyte in a gel cell has a silica additive that causes it to set up or stiffen. In most cases the recharge voltage on gel battery is typically lower than a standard flooded wet cell battery or AGM battery, apart from those made by MK Battery where their 12-volt batteries can accept up to 14.6 volts. Most gel batteries can only be charged as high as 14.2 volts per 12-volt battery and are probably the most sensitive battery in terms of adverse reactions to over-voltage charging. Gel Batteries are best used in VERY DEEP cycle application and may last a bit longer in hot weather applications or application where the battery gets excessively discharged. If the incorrect battery charger is used on a gel cell battery, poor performance and premature failure is certain.

Lithium Battery Types: Lithium-Ion vs LiFePO4

The new premium battery on the market is the Lithium battery, often referred to as a Lithium-Ion or LiFePO4 battery. In most cases, they are the same battery as Lithium-Ion is the parent category of the LiFePO4 battery, so some manufacturers use the parent term vs. the specific term.

Deep cycle lithium batteries generally offer up to 3x the cycle life compared to lead acid batteries. Most are designed with a long service life of 10 years. Lithium also offers a 60% reduction in weight compared to lead-acid batteries.

For comparison, our best lead acid battery is a Lifeline AGM battery that offers about 1000 cycles at 50% depth of discharge. The BSLBatt Lithium Battery we carry offers over 2000 cycles at a 50% depth of discharge and up to 8500 cycles at a 30% depth of discharge. They were designed for a 15 to 18-year service life, whereas a Lifeline is estimated to have about a six year service life.

This article covers the Lithium topic from the deep cycle battery perspective. If you are looking for a starting battery, we offer plenty of choices for motorcycles, ATVs, and various other powersport applications. You can learn more about lithium batteries for powersport applications via our Lithium Battery Buyers Guide.

CCA, CA, AH and RC Explained

All of these terms are widely used by battery manufacturers. Look under the hood, and you will most likely see a battery rated with one or more of these terms. The first two in the list below are cranking terms, and the second two are capacity terms. Let’s break them down!


Cold cranking amps is a measurement of the number of amps a battery can deliver at 0°F for 30 seconds and not drop below 7.2 volts. So a high CCA battery rating is especially important in starting battery applications, and in cold weather. This measurement is not particularly important in deep cycle batteries, though it is the most commonly known battery measurement.


Cranking Amps are measured at 32°F. This rating is also called marine cranking amps (MCA). Hot cranking amps (HCA) is seldom used any longer but is measured at 80°F.


Reserve Capacity is a very important battery rating. This is the number of minutes a fully charged battery at 80°F will discharge under a 25 amp load until the battery drops below 10.5 volts.


An Amp/Hour is a rating usually found on deep cycle batteries and is a capacity rating. The standard rating is a based on how many amps you can pull out of the battery over a 20-hour period. For a 100 AH rated battery this means you can draw from the battery for 20 hours, and it will provide a total of 100-amp hours. That translates to about 5 amps an hour (5 x 20 = 100). However, it’s very important to know that the total time of discharge and load applied is not a linear relationship. As your load increases, your realized capacity decreases. This means if you discharged that same 100 AH battery by a 100-amp load, it would not give you one hour of runtime. On the contrary, the perceived capacity of the battery will be that of 64-amp hours.

Battery Maintenance

A properly maintained battery is important for the ultimate in service life. Consider these points on a regular basis:

  • The battery should be cleaned using a baking soda and water solution; a couple of tablespoons to a pint of water.
  • Cable connections need to be cleaned and tightened as battery problems are often caused by dirty and loose connections.
  • A serviceable battery needs to have the fluid level checked. Use only mineral-free water; distilled is best as all impurities have been removed and there is nothing left that could contaminate your cells.
  • Don’t overfill battery cells, especially in warmer weather because the natural fluid expansion in hot weather can push excess electrolytes from the battery.
  • To prevent corrosion of cables on top-post batteries, use a small bead of silicone sealer at the base of the post and place a felt battery washer over it. Coat the washer with high temperature grease or petroleum jelly (Vaseline), then place cable on the post and tighten. Coat the exposed cable end with the grease. The gases from the battery condensing on metal parts causes most corrosion.

Battery Testing

This can be done in more than one way. The most accurate method is measurement of specific gravity and battery voltage. To measure specific gravity, buy a temperature-compensating hydrometer. To measure voltage, use a digital D.C. Voltmeter. A quality load tester may be a good purchase if you need to test sealed batteries.

For any of these methods, you must first fully charge the battery and then remove the surface charge. We recommend letting the battery sit for several hours to remove the surface charge (I prefer at least 12 hours). Letting the battery sit gives you the most accurate result on how the battery will normally act. However, if you need to remove the surface charge faster it is possible to discharge the battery for several minutes. For deep cycle batteries you could simply power the device that uses the battery for several minutes. For starting batteries simply powering the headlight using the high beam can work as well. Once the surface charge has been removed you can begin testing.

State of ChargeSpecific GravityVoltage
12V 6V
100% 1.265 12.7 6.3
75% 1.225 12.4 6.2
50% 1.190 12.2 6.1
25% 1.155 12.0 6.0
Discharged 1.120 11.9 6.0

Load testing is yet another way of testing a battery. A load tester removes amps from a battery much like starting an engine would. Some battery companies label their battery with the amp load for testing. This number is usually half of the CCA rating. For instance, a 500 CCA battery would load test at 250 amps for 15 seconds. However, most load testers will either allow you to input the CCA or in the case of an analog tester it will show you a graph the battery should test at.

A load test should only be performed when the battery is at near or full charge. If you don’t own or want to buy a load tester, then simply charge the battery, wait 12 hours, and then take it to an automotive shop for testing. Avoid taking a discharged battery to an automotive shop for testing as the test will only indicate something you already know.

The results of your testing should be as follows:

  • Hydrometer readings should not vary more than.05 differences between cells.
  • Digital volt meters should read as the voltage as shown in this document. The sealed AGM and gel cell battery voltage (fully charged) will be slightly higher in the 12.8 to 12.9 range. If you have voltage readings in the 10.5 volt range on a charged battery, that typically indicates a shorted cell.
  • If you have a maintenance-free wet cell, the only ways to test are volt meter and load test. Any of the maintenance-free batteries that have a built in hydrometer (black/green window) will tell you the condition of 1 cell of 6. You may get a good reading from 1 cell but have a problem with other cells in the battery.
  • When in doubt about battery testing, call the battery manufacturer. Many batteries sold today have a toll-free number to call for help.

Selecting Buying a New Battery

When buying a new battery, I suggest you purchase a battery with the greatest reserve capacity or AH rating as possible. Of course, the physical size and terminal type must be a consideration. You may want to consider a gel cell or an absorbed glass mat (AGM) rather than a wet cell if the application is in a harsher environment, or the battery is not going to receive regular maintenance and charging. AGM and Gel cell batteries typically have a lower self-discharge rate so they can last longer when not being maintained.

Be sure to purchase the correct type of battery for the job it must do. Remember that engine starting batteries and deep cycle batteries are different. Freshness of a new battery is very important. The longer a battery sits the more damaging sulfation build up there may be on the plates. Most batteries have a date of manufacture code on them. While the date code isn’t always apparent many manufacturers or dealers will indicate the month with a letter, such as the letter with A being January. The letter is then followed by a number such as “4” corresponding with the year 2021. C4 would tell us the battery was manufactured in March 2021. Remember the fresher the better. The letter I is not used because it can be confused with the number 1.

Battery Warranties

As with most warranties, they are often favored by battery manufacturers. Suppose you buy a 60-month warranty battery, which lasts 41 months. The warranty is pro-rated, so when taking the months used against the total retail price of the battery, you end up paying about the same money as if you purchased the battery at the sale price. This makes the manufacturer happy.

What makes me happy is to exceed the warranty. As of the writing of this article, we currently carry motorcycle and ATV batteries by Scorpion and Motocross that come with a replacement warranty. For deep cycle batteries, the MK Battery and Universal Battery line currently have a 1-Year Replacement, and some of our higher-end manufacturers we carry offer higher warranty terms depending on their installed applications.

Battery Life and Performance

The average battery life has become shorter as energy requirements have increased. Two phrases I hear most often are my battery won’t take a charge, and my battery won’t hold a charge. Only 30% of batteries sold today reach the 48-month mark. In fact 80% of all battery failure is related to sulfation build-up. This build-up occurs when the sulfur molecules in the electrolyte (battery acid) become so deeply discharged that they begin to coat the battery’s lead plates. Before long the plates become so coated that the battery dies. The causes of sulfation are numerous:

  • Batteries sit too long between charges. There are two states when it comes to batteries: They are either being charged or they are self-discharging.
  • Battery is stored without some type of energy input. Even if you disconnect the battery it will still self-discharge.
  • Deep cycling an engine-starting battery. Remember these batteries can’t stand deep discharge.
  • Not completing the charge cycle. Undercharging a battery will allow the sulfation buildup that occurred during discharge to harden. When this happens, it reduces the area on the lead plates for the chemical reaction to occur thereby reduces the capacity of the battery.
  • Heat of over 100°F increases internal discharge. As temperatures increase so does internal discharge. A new fully charged battery left sitting 24 hours a day at 110°F for 30 days would most likely not start an engine.
  • Low electrolyte level. Battery plates exposed to air will immediately sulfate.
  • Incorrect charging levels and settings. Most cheap battery chargers can do more harm than good. See the section on battery charging.
  • Cold weather is also hard on the battery. The chemistry does not make the same amount of energy as a warm battery. Also a deeply discharged battery can freeze solid in sub zero weather. We recommend gel batteries by MK Battery for subzero weather as some of their batteries are rated down to.76°F.
  • Parasitic drain is a load put on a battery with the key off. Depending on the parasitic load we have seen batteries discharged in a few days to a few months. We recommend testing your parasitic load so you know what to expect.

Increase Life

There are ways to greatly increase battery life and performance. All the products we sell are targeted to improve performance and battery life.

An example: Let’s say you have toys such as an ATV, classic car, antique car, boat, Harley, etc. You most likely don’t use these toys 365 days a year as you do your car. Many of these toys are seasonal, so they are stored. What happens to the batteries? Most batteries that supply energy to power our toys only last 2 seasons. You must keep these batteries from sulfating or buy new ones. We sell products to prevent and reverse sulfar buildup on batteries. The BatteryMINDer products are patented electronic devices that reverse and prevent sulfation. Also Battery Equaliser, a chemical battery additive, has proven itself very effective in improving battery life and performance. Other devices such as solar trickle chargers are a great option for battery maintenance.

Parasitic drain

Most vehicles have clocks, engine management computers, alarm systems, etc. In the case of a boat, you may have an automatic bilge pump, radio, GPS, etc. These devices may all be operating without the engine running. You may have parasitic loads caused by a short in the electrical system. If you are always having dead battery problems, most likely the parasitic drain is excessive. The constant low or dead battery caused by excessive parasitic energy drain will dramatically shorten battery life. If this is a problem you are having, check out PriorityStart! battery switches to prevent dead batteries before they happen. This special computer switch will turn off your engine start battery before all the starting energy is drained. This technology will prevent you from deep cycling your starting battery.

Battery Charging

Remember, for proper battery maintenance you must put back the energy you use immediately. If you don’t, the battery sulfates, which will affect performance and longevity. The alternator is a battery charger. It works well if the battery is not deeply discharged. The alternator tends to overcharge batteries that are very low and the overcharge can damage batteries. In fact, an engine-starting battery on average has only about 10 deep cycles available when recharged by an alternator. Batteries like to be charged in a certain way, especially when they have been deeply discharged. This type of charging is called 3-step regulated charging. Please note that only special Smart battery chargers using computer technology can perform 3-step charging techniques. You don’t find these types of chargers in parts stores or big box stores.

  • The first step is bulk charging, where up to 80% of the battery energy capacity is replaced by the charger at the maximum voltage and current amp rating of the charger.
  • When the battery voltage reaches 14.4 volts this begins the absorption charge step. This is where the voltage is held at a constant 14.4 volts and the current (amps) declines until the battery is 98% charged.
  • Next comes the Float Step. This is a regulated voltage of not more than 13.4 volts and usually less than 1 amp of current. This in time will bring the battery to 100% charged or close to it. The float charge will not boil or heat batteries, but it will maintain the batteries at 100% readiness and prevent cycling during long term inactivity. Note: Some gel cell and AGM batteries may require special settings or chargers.

Battery Don’ts

While that was a detailed look at battery types and how to maintain them, there’s always more to learn.

StevenJust trying to understand the AGM batteries behavior. I have 8-6v batteries used for a small solar system of 48v. When charging the batteries get up to 57v, but when discharging they start out at 50v and then slowly discharge. Why does it start discharging at such a low voltage

TECHWhile a 48v system may charge in the 59v range and float and maintain in the 56v range, they are still considered 100% fully charged off the charger at 50.92v. So, depending on the load, a voltage reading of 50v would seem perfectly normal. While it is good to know how your battery reacts under load, knowing the recovery voltage and how to interpret the voltage in terms of capacity is also important. In a 48v system, it is considered 50% discharged when the voltage reaches 48.4v in an open circuit reading.

Joslyn SchicchiI have a 2009 tao tao moped with a TPE Lithium Motorcycle Scooter Battery. im having issues getting it connected again when j do screw thevterminals in therss no power i also did charge after use

TECHUnfortunately, we do not sell that brand, but it sounds like the battery has been excessively discharged if there is no voltage. I suggest contacting the supplier and talking to them regarding their troubleshooting steps. Typically, you will need a lithium charger with a safe recovery mode, such as the Optimate TM-471 we sell, but I would follow up with them before purchasing anything.

Steve ZDoes a deep cycle lead acid battery discharge faster than it charges? I ask because I am using an 80ah battery to power the small refrigerator in my camper when I’m boondocking. I have a 200w Solar suitcase and a 100 watt panel on the camper. Their controllers are often in a “float” or “full” state when the sun is out and the fridge is on. indicating the battery won’t take any more charge. But the battery monitor shows it is just at 60 or 70 percent capacity. Does this make sense? Thank you!

BatteryStuff TechSteve, as far as if a battery discharges faster than it charges depends on the amperage being pulled from a battery and the amperage charging the battery. Typically, most Smart chargers will taper off the amperage towards the end of the charge to not heat the battery, so that can add about 10 to 20% extra time than the straight math might indicate. However, I think your issue might be a different problem. It sounds as if your controller is shutting down prematurely or is set to go to a float mode after it has been charging for a certain amount of time. I would suggest contacting the manufacturer of the controller to determine why it would be going into float mode when the battery is not full. You may also consider an MPPT controller such as our Victron Controllers as they can be programmed via a smartphone and give you more options to control your charging.

Carl OhHi great article…I have a TT with 2 trojan 6v batteries hooked up to a renogy 30amp controller and a LG 350 solar panel When I hooked them up at the beginning of year the hydrometer reading was 1265. Now the reading is 1225 but the controller says 100% 13.4v. I have been watching and the controller does boost and float and is always at 100%. Why is the hydrometer reading in the recharge area. The whole system is only 1 year old.

BatteryStuff TechCarl two things maybe happening. The batteries could be sulfated and while the controller is able to bring them full charge the batteries will not hold their after they are disconnected. Or, the controller is simply not charging the batteries correctly. I would suggest charging the batteries with your normal plug in charger and see if it is able to get the batteries to full charge with a good specific gravity reading. If it is then you know the solar charge controller isn’t functioning properly. If it isn’t then you know your batteries maybe sulfated.

AlexDo I need to disconnect battery banks to measure CCA? I have (2 x 12v in serie) x2 of this in parrallel. So basicaly 24v with 4 x 12v batteries.

BatteryStuff TechIn parallel you are going to get double the CCA, so you may want to disconnect the parallel connections to measure your CCA with a tester. Once the parallel connections are removed you can test each battery individually even with the series connections in place as the tester will only see what is in-between the testers positive and negative connection.

TimI have a flat plate AGM Deep cycle 135aH battery. It’s brand new and is sitting at 13 volts. I recently bought a load tester off ebay and when I go to load test the battery it is asking for the CCA. How do I calculate the CCA if the CCA is not displayed on the battery sticker? I assume the CCA is not displayed because this battery is not a cranking battery.

BatteryStuff TechThe easiest method might be to contact the manufacturer of the load tester as they may have a AH to CCA conversion table for testing deep cycle batteries with their load tester. We sell a PulseTech unit that has such a table, but if your manufacturer doesn’t you can simply contact the manufacturer of the battery in question as they often have a CCA specification on file even if it is a deep cycle battery.

Andy SchoutetenWe have an off gritt solar system that supports a home with 240v electricity for fridge, dishwasher, washing machine and all lighting. We have around 3kw of solar panels and a 2,5 kw inverter. We store electricity in 24 6v 225ah lion batteries. We are thinking of replacing these batteries because they are more than 10 years old. We also would like to reduce the number of batteries but still have the same or better storage capacity. What would be your recommendations

BatteryStuff TechUnfortunately, we don’t specialize in deep cycle lithium batteries at this time. I would suggest contacting another source if your still looking to stick with lithium.

Jim NavotneyAnd despite all the YouTube videos never runn your engine with the car battery dissconnected

Eileen McCrackenThis is helpful. For the existing deep cell in our rv we should not use more than 50% of charge. If we upgrade to agm can we use more? Reading the article there are a lot of maintenance and life span advantages but I’m not clear if I can run my fridge longer! Thanks so much

BatteryStuff TechAGM’s can hold under higher amp loads at lower depths of discharge, but they are still considered a lead acid battery and do not like being discharged below 50% as it effects their cycle life. The fridge may be able to run longer when the battery is getting excessively discharged, but the batteries cycle life will still be drastically affected anytime you take the battery below 50%. If you plan on excessively discharging the battery below 50% you may want to consider a gel battery as they withstand excessive discharge better and tend to start with a higher cycle life.

Dhika RI’ve got a 100 ah battery (i’m told by the ebay seller its gel) that has a maximum voltage of 15v similar to an AGM written on the case. Its still brand new and I wanted to get a second one to wire in series but found out that they are not selling this product anymore. I wonder if I can get away with a 100ah AGM battery as the second unit in series. Also wondering if this battery is actually a gel cell if it has a maximum voltage of 15v. Thanks The battery is an eco-worthy VT12100 (green)

BatteryStuff TechWe would not recommend putting batteries together unless they are the same type, age, and chemistry. Basically, they should be the same battery from the same batch otherwise they will never be balanced to each other, which can lead to a battery failure.

Brian ApI use two lead acid batteries of field charging of hobby batteries. I bought a min kota digital precision dual bank charger to charge them. This charger uses what they call a mild equalization phase in the bulk charge cycle. I have come back to find the charger stuck in this phase for over 24 hours. Basically it can never get past this part and there is no fault timer to kick it out of this phase. I noticed that the batteries were boiling in this phase so I stuck a voltmeter on to see what it is doing. What they call mild equalization is just going up to 14.7 volts for the bulk phase. The charger is obviously looking for something to get past this phase. I can only guess that it wants to see some higher voltage to move on to the float charge. I was very annoyed that it would just go ahead and boil off most of the water with no signs of stopping. When I called tech support they said that I must just have worn out batteries since they don’t have a problem with this line of charger. Are my batteries to blame or is the charger wearing them out by bulk charging at 14.7 V? They were 4 yrs old at the time and could indeed be old.

BatteryStuff TechIt could be either the charger or the batteries. Most marine Smart chargers have built in time limits to prevent chargers from being in operation for extended amounts of time. Unfortunately, it sounds like yours doesn’t have that feature, so it might be wise to look at getting an new charger in the end just to prevent this issue from arising. If you would like a recommendation feel free to contact our tech department. Eithew way I would also suggest taking your batteries to a local battery shop to have them tested, so you can determine if it is the charger or the batteries.

Jack MartinWhat minimum voltage is acceptable for a 12V AGM (and other lead-acid) batteries upon receiving after shipment? The issue came up when I received a new AGM battery that arrived at X volts, and it seemed too low for a proper storage voltage, suggesting the battery may have arrived already a bit damaged.

BatteryStuff TechA lot depends on where you are getting the battery. If the battery comes from our store like us, then chances are the battery is going to be load tested prior to it leaving the warehouse to ensure the battery is good. Our 100 Amp load test can take anywhere from 5% to 25% off the battery depending on the battery size. This means the battery may be received by the customer between 12.3 to 12.6 volts. If the battery comes from a big box retailer or online store that’s primary FOCUS isn’t batteries, then chances are the battery isn’t being tested. If the battery arrives discharged from these type of stores it would most likely indicate that it has been sitting on the shelf for awhile, or stock wasn’t being rotated correctly. So, the real question is what the voltage is 12 hrs after its been charged? That voltage will give you a good indication on the state of the battery and if it is sulfated. Ideally, any battery with an open circuit voltage of 12.7 volts or higher for a 12v battery is considered 100%. However, very fresh and new batteries will typically have an open circiut voltage of 12.9 to 13.2 volts 12hrs after charge.

Michael TrivetteI have a Kangaroo golf cart and it recommends a 12v Deep Cycle Gel with a minimum 31ah. What battery and charger do you recommend. The current one does not hold a charge for an entire 18 holes of golf. Thank you.

BatteryStuff TechMichael, it is hard to give a recommendation with the information given. Ideally, you do not want to discharge your battery beyond 50%, otherwise you would be excessively discharging the battery. This means if you want to play 18 holes of golf your battery should be able to withstand that, and still be at least 50% charged when you get back home. The manufacturer of your cart has given you are minimum recommendation, but if you can’t even get through a round of golf on that recommendation, then you need to figure out approximately how far you have gone. Let’s say you done 14 holes and your battery has gone dead. This means the golf cart lasted 77% of the course leaving 23% left. In the end you need a battery with 146% higher in capacity than your current battery. Basically, you are doubling your 77%, which is the 100% increase, and you still have 23% more of the course left to play, so 46% is the extra 23% left on the course plus the extra needed not to discharge the battery below 50%.

DennisoxYpeI simply wish to say I am newbie to blog and actually relished you’re site. Most likely I’m want to bookmark your website. You certainly come with great posts. Thanks a lot for exposing your blog website.

C JosephThis article was outstanding the best I’ve ever read regarding everything you want to know about the various types of batteries, functions, etc. Thank you. Good job!

JaimeOxyncGood post! I read your blog often and you always post excellent content. I posted this article on and my followers like it. Thanks for writing this!

JerryHello, I have a Ford Transit with a single battery system. I also have a 1000 Watt inverter that I use to keep my phone and laptop charged. I have drained the battery to the point it will not start the Transit so I am trying to add additional power to keep from drawing the battery down for a longer period of time. After reading your article, it sounds like I should avoid drawing the vehicle battery down too low. Would you recommend dual batteries, a deep cycle battery, or…? I would greatly appreciate any ideas. Thank you!

BatteryStuff TechIf the battery is going to be inside the vehicle we recommend an AGM battery or Gel battery. If you plan to have the vehicles alternator to charge the battery your best bet is to go with an AGM. You would need to isolate the vehicle battery from auxiliary battery using a Battery Isolator. Be aware that if you plan to go this route the chemistry of the vehicle battery, and the auxiliary battery need to be the same, otherwise the isolator may overcharge one battery.

NateWhat is your advice on the best battery for a backup sump pump application? From 0 to 2 times per year our AC power goes out when it is raining. Perhaps once every 5 years it goes out when Niagara Falls is flowing into our sump pit. When this occurs is it profoundly essential the backup system work. Most backup sump systems appear to be sold with 12V maintenance free deep cycle 75 or 100 AH AGM batteries. Does this seem like the best choice? Also, the systems are sold with controllers that charge the batteries occasionally. I assume this is important to obtain maximum battery life. Any advice here on ways to ensure periodic charging is occurring? Finally, any other overall advice? thanks much nate

BatteryStuff TechI find most people with sump pumps have at least a 100 AH battery, but it is best to go with whatever the manufacturer recommendation at a bare minimum. The higher the capacity the longer your pump can run if AC power goes out. As far as the charger is concerned we recommend a power-supply / converter chargers if the battery will be in use while charging. Most sump pumps will come with a charger that has demand sensing technology, so you don’t end up overcharging your battery. However if your charger ever goes out, and you need to replace, be sure to get one that does work as a power-supply / converter charger, otherwise you may overcharge some batteries and learn the lesson the hard way.

Mohamed OmerThis article is very helpful for me. But i have one more qn to ask. I bought a new 12v 200Ah battery.but there is no electrolyte.just empty. I poured distilled water and made to charge.after two days the plates getting coated with some white sludge.so what shud i do now.help me please.

BatteryStuff TechReally hard to say what happened, as someone could have already contaminated the battery before you.

KwakuHow can one determine the number of plates in a battery by the batteries amp-hr? Is there a formulae to calculate the number of plates in a battery? Thanks

BatteryStuff TechThere is no correlation between the to for such a calculation. Capacity generally follows the amount of lead in the battery, so the more lead the higher capacity.

BatteryStuff TechGenerally those batteries are recharged in a battery pack of at least 12v, so you would need more than one battery in order to recharge in most situations.

KevinI am installing a 36 volt trolling motor and it calls for 6 gage wire. The boat had a smaller trolling motor installed on it previously and it had 2. 10 gage wires together for the positive and 2. 10 gage wires together for the negative. Will 2 10’s be sufficient to carry the amp load of a 6 gage or do I have to replace the 4 10’s with 2. 6’s. Total lengths is 20 feet. but that should only affect voltage drop

BatteryStuff TechThe amperage your motor pulls may be the reason the manufacturer suggest 6 gauge wire to be the best selection. I know out of experience that our 10 gauge custom cable that is 8ft long only handle up to 30 amps. Given your distance and the amperage the motor pulls you could very well need the 6 gauge cable. If you are looking to substitute with a different gauge i would suggest talking with the manufacturer.

DerekHi I have a 100ah agm battery in my caravan which has buckled and wont hold a charge. I am about to buy a new agm battery but hope you can advise me on the following. When I head off on a trip I have the battery fully charged. I have an Anderson plug charging the battery whise we are driving, the question is, can a fully charged agm battery be damaged by overcharging by the charge it receives from the car while I am driving. Regards

BatteryStuff TechWe recommend that you use a Battery Isolator when charging through the alternator so you don’t overcharge a battery. They are designed to charge not only the caravan’s battery in your case, but an additional battery pack. The key thing you need to know with isolators is that you need to match the chemistry so that it knows how to charge the battery correctly. Another words if you have an AGM battery for your house battery, then you should have an AGM under the hood as well. This will ensure the isolator charges the batteries correctly and doesn’t overcharge the battery. I have heard of isolators that can determine the charge if chemistry doesn’t match, but they are extremely expensive, and I’m not sure how reliable they really are. It is best to just match chemistry in my opinion.

Dave BrennanI built a paddlewheel for my pontoon boat using motors from a power wheelchair. I used the original batteries from the chair.2×12=24v.will I burn out the motors by changing to full size batteries or is 24 volts 24volts ?

DeanIm a designer/installer and have read literally hundreds of guides and tutorials over the years and none are a patch on this – hats off, you’re brilliant – and crazy helpful to have provided answers to every question posted here individually, for free, despite you having already answered 99% of them in your other excellent articles! People, don’t be lazy, sure this guy has a life so read ALL the FREE guides provided for you here before asking. Big respects

Mike CoshanFantastic article though I admit even the laymans terms seems to go over my head. I live in the UK and have a QUICKIE Jive Midwheel drive wheelchair made by Sunrise Medical which uses 2 × 12volt 70 amp sonneschein GEL Batteries I Have a 8amp Gel battery charger but in the 27 months I have owned the chair I’ve had to have 4 sets of replacement batteries as they fail after 6 months apparently ( according to the manufacturer) because of a faulty Cell. I have followed the manufacturers guidelines with charging the battery, which states as soon as you’ve finished using the chair put it on charge Though I often wait about 5 hours to put the chair on charge. I do this and then leave it. So the chair gets between 13 18 hours charge even if I have done only 5 miles, which is my about my average daily use. Should I put the chair on charge straight away the leave it alone even If I need it? I have my manual wheelchair to get about in inside my house. Any help to prolong the battery life is greatly appreciated. I have repeatedly asked both Sunrise medical sonneschein for help over the past 2 years with n how to alleviate this problem but have had no reply.

BatteryStuff TechI would definitely not leave the batteries sitting in a discharged state, plus it is never recommended to discharge a battery more than 50% so if your 5 mile run does this then that could be affecting the batteries life. If you are not running them below 50% then I would look to the charger, and be sure it is at least a 3 stage charger, anything less is not recommended for those size batteries. Feel free to contact our Tech Department for assistance.

BatteryStuff TechThe rating reflects how many amps you can pull from that battery over a specific period of time. In general the ratings goes down the quicker you pull a load out of a battery, so a 200AH 10 Hr rated battery will have a higher capacity than a 200AH 20 Hr rated battery.

KanziI am in the process of upgrading my solar electricity in my house and need information regarding what electrical appliances 8 AGM batteries will be able to power. I already have a solar panel array in place that is powering a solar water pump very effectively. I suppose I need to tell you the amount of watts the panel produces but do not have that info. at this time. Is it likely that I can replace my propane frig. with an electric refrigerator, run power tools without the generator on, etc.? Thank you! Sandra

BatteryStuff TechAs solar is basically a math problem I would suggest reading our article Solar Systems The Right Way as a start, or Contact Our TECH Department for further assistance. Please be aware that we are not home solar experts, and it might be best to contact a local home solar expert.

DaveTGreat article. However, it seems that no matter how many articles I read on batteries, I can’t seem to grasp a full understanding of how it all works. And I say that because 6 years ago I purchased a highly modified EZ-GO golf cart that I use to get around the woods of southwestern Pa. year round. Our temps run in the high 80’s in the summer to the mid teens in the winter, and at times lower. I have a 48-volt system using 8 six volt T-105’s and a Smart charger for the cart, and for my headlights and winch a separate vehicle 12-volt battery. Now, I’ve read that I should not discharge my flooded T-105’s below 50%, but in all honesty, that is at times impossible to do. The woods are not that short in places, and at times…well mud is mud and you can’t predict it. However, I always check my water levels…they seem to remain a constant…and I always clean my terminals monthly, even if they don’t seem to need it. Your suggestions of using grease is great and I will do that on my next cleaning session. Now, I have installed a new Warn winch and I winch my cart on and off my truck. I currently have one 12-V auto battery in the cart, but I am concerned that I may be “out there” and the 12-V simply run out of charge. So, what I have been thinking of is replacing the one 12-V with two 12-volts and wiring them to still have a 12-volt output, but have a longer output “time” if you understand what I’m saying. I have enough room under the cart seat for the average width of a car battery, and about 24” in length. What type of batteries would you suggest would work the best in my situation?

BatteryStuff TechDave I would recommend our Calculator | Sizing a 12 Volt Battery to a Load to really determine your need. If you have further questions I would suggest contacting our Tech Department.

Earthrealmlease, am a little confused. whats the difference between a 200ah 20hr rated battery and a 200ah 10hr rated battery. am trying to buy a deep cycle battery and i see 10hr on one and 20hr on the other. which one is better?

StellaThank you so much for writing this. I am certainly going to give to my husband to read and for reference. I just purchased a yamaha 36v golf cart that needs new batteries. There are 6 each, 6 volts batteries, which would you suggest? thank you !

BatteryStuff TechWe carry some of the best Golf Cart batteries available. Any of the batteries listed in our Golf Cart Section would be recommended.

DarrenHi, I have been getting a headache with all the conflicting advice on my current and planned dual battery setup. I have a 105 Landcruiser with 4.2 diesel and standard 110 amp alternator. I have a dual battery system with a Delkor 27HR-70 Calcium and a brand new Optima Blue Top D27M AGM (replaced the other Delkor which died) as the secondary battery for running utilities (fridge etc). They are parallel connected through a RedArc 100 amp isolator. I also have a RedArc 120W portable solar setup to assist with powering for extended camping etc. Firstly, is this current setup likely to damage Optima through lack of charging output. And if so would an in car BC/DC charger resolve the issue. Secondly, as I am not sure of the age / condition of the Delkor I am thinking of replacing it with a new Optima Yellow Top D27F. Would this make my current setup sufficient? Or is the standard 110 amp alternator still not up to fully charging the AGM ’s? Would really appreciate some feedback and guidance Cheers We would require more information about your situation. Please contact one of our techs at tech@batterystuff.com.

SuzWow…thankyou for existing. We are beginning to get a solar set up organised for free camping and I have a plethora of questions that hopefully you can answer for me. We intend to run a 12v52 litre fridge and strips of led lights. What do I need to know about these applicances when planning the battery set up. We are looking at a 12v 260 AH AGM battery using a 140W solar panel to charge. Would one battery be enough or should we look at two – the fridge needs to run most of the time but the led lights would be just at night. If we did get two what is the difference between wiring in series and in parallel ….is one way better than the other?? And I need reminding … In paralel is it positive to posiive and neg to neg. Thank you so much for your time and expertise……cheers Suz from Oz

TECHSuz I would suggest reading our article: Solar Systems the Right Way. This will help you gather the proper information to determine if your panel and battery setup would be sufficient. As far a series vs parallel I suggest looking at our article: Battery Bank Tutorial – Series and Parallel. This article will show you possibilities of creating different type of battery banks, and maybe the possibility of going to two 6 volts batteries for less than two 12 volts batteries would be for the same Amp/Hr capacity.

TECHIf your existing battery is a WET cell then you can use an AGM. However if your original battery was a GEL then you would have to contact BMW to verify that your charging system will charge and AGM as they charge at a higher rate.

KylaGreat article, easy to understand and informative. I have a few questions about my RV battery cables. I was about to replace the 2 12v marine batteries on my RV with 2 6v deep cycles, when I realized the cable situation seems strange and possibly scary The ends of the cables, for about a foot before the terminal connectors, are all taped up and homemade. Should I be concerned about that? – How do I know if they’re an appropriate size for the battery size? – There is a thin black ground wire coming from the taped up part of the cable, which is bolted to the trailer frame. Why would the cable be grounded? Isn’t that what the – cable is for?! The 2 cables that were used to connect the 12v batteries in parallel are also of this taped-up homemade variety. I was going to use one of them to connect the 6v in series, but now am unsure whether I should use ANY of these cables at all. Wiring in new cables seems really daunting because I can’t see an obvious way to access where they run up into the bottom of the trailer. But I don’t want to be unsafe, so… Thanks in advance 🙂

TECHI would talk to your local RV Service Center if you feel the homemade cables are questionable. If you plan on rewiring the the connections to replace the existing cables we recommend staying with the same gauge wire that originally came with your RV. Obviously the last foot or so you said is homemade, so you would want to look further up to see what size the original cable is. If your changing charger, converter, or inverter (or an all in one) then we recommend you look to that manufacturer for recommendation.

JoelHi, I bought a sailboat with 2 batteries and a selector which reads off/1/both/2 My question is about what you say about batteries being the same size, rating and type. Of the 2 that came with the boat, #1 is a reg. acid starting battery and #2 is a deep cycle used as a house battery. Is that bad? should I avoid the “both” position of the selector?

BatteryStuff TechGood Question! The selector switch is designed to get the boat out of a bad situation, say for instance you were unable to start the boat. This enables you to bank the other battery together in such situation to get the boat going again. You do want to avoid tying them toghether unless your are in a problematic situation.

MauriceIf AGM batteries aren’t damaged by a car’s alternator charger why do they need a special charger?

BatteryStuff TechThey really only need a specific charger if they are being maintained long term with a constant charger. The exception is specialty AGM s such as Odyssey batteries or aircraft batteries.

T-ManThank you for some great info. We have a travel trailer that we have parked at a camp area on the back the farm. It hasn’t moved since we bought it 5 years ago. We charge the battery with a Honda 3000 generator. After many years of frustration using a flood cell deep cycle battery we just installed a AGM battery. (I believe we brought the charge down on the batteries too far, too often). Anyway we just bought the AGM battery because we understand it will charge much quicker than a flood cell. My question is using this type generator on a trailer, will that work for a AGM or should we do anything different for charging? Thanks again.

Laura HargisWe have a John Deer Gator (riding toy)for our Granddaughter. The connection for the battery has corroded down inside. Is there a safe way to clean it out? It is a very tight area.

Md. Saiful Haque KhanI have two 12v 100AH battery it is connected with IPS recently I see the battery is very HOT IPS Full Charge indicator not showing full charge. I check Battery Water Level ok. Then I disconnect all battery from IPS 2 days take time to cool the battery after battery fully cold I connect it to IPS but again the battery is very HOT. What is just happening Can you tell me please. My battery Name Lucas AP 100 12V 100AH 21 Plate made by Rahimafrooz Bangladesh. Please give me the repply. Thanks Saiful Haque Khan Bangladesh saiful6848@gmail.com 8801716579824 We would require more information about your situation. Please contact one of our techs at tech@batterystuff.com

GarthJI have a boat with a normal marine 12v lead acid battery I would also like to add a second battery to provide for lets say a 12v access port for accessories. Unfortunately I have limited space for a second full sized battery. Could I use a smaller lets say ATV type twelve volt battery connected through a dual battery charger relay isolator so that both would charge when the motor is running but both would not drain when the motor is not running. We would require more information about your situation. Please contact one of our techs at tech@batterystuff.com.

ArieSI have a few questions on battery reconditioning, based on reading of various How To and DIY sites, and hope that you are able to help: 1 – The powder that everyone seems to suggest is Epsom salts, is that correct? 2 – Is there a specific type of these Epsom salts that is appropriate? 3- What are the mixing specs for the solution? Thanks a lot! We would require more information about your situation. Please contact one of our techs at tech@batterystuff.com.

TracyI have installed a few advanced GPS devices on a fleet of vehicles. The manufactures paperwork says they should be wired into an output capable of at least 13 volts. I have not had any problems with the devices on vehicles with a normal 12 volt car battery and wonder if there would be any possible problems if I wanted to install them on a recreational vehicle like a Polaris ATV /Quad or a Side X Side with a 12 volt battery?

ZareefI had solar system, Know I want to add new set of batteries with old one for charging purpose, both pared as 24V sets. 24V old set and 24v new set. is this work or any problem, i will face during charging for solar panels. or should i charge separtly and use dual purpose. Once charge new and than Old. In house for electric city,Should i combine both sets, or I use old to discharge than switch to new for use.

BatteryStuff TechI would recommend charging separately. Mixing old and new batteries is asking for trouble.

RandyWe have a few 10 tonne dump trailers that are towed behind a few chev 2500 3/4 ton trucks (1 alternator)1 battery. Also towed by 2 FORD 1 tons which have dual batteries in them. We are using deep cell wet batteries 175AH (D27’s) one battery in each trailer. The batteries in the trailers only get a 1/2-1 hour charge from the 7 way trailer plug when they are ran to site and dumped. I don’t have the amp draw of the “Dyna-Pack) electric/hydraulic motor/pump unit yet. It takes 15-30 seconds to fully dump the trailer. The batteries don’t seem to last too long to these guys. The charge from the tow vehicle may be to low as the voltage drop in the 12 or 14 ga. wire used in the typical trailer tow package. I was thinking about wiring in #4 ga. from the font to the rear trailer with a battery isolator so the trailer battery could receive a better charge rate., specially if being dumped every hour or two and only getting 1/2 or little more charge in between. Is it worth it 150 isolator. I can install and get reasonable pricing on wire terminals etc. Also what is the best battery to use as the trucks have different batteries in each of them?? Good site for info I must add.

JeremyJim, Technical questions can be submitted using the “contact us” tab at the top of the website. The Комментарии и мнения владельцев for articles are not always reviewed by Techs, so the best way to get an expedient answer to a question, is to contact the correct department directly. Thanks

Frank TuckerI have n ABM 12volts, 120AH battery and a Wet Cell 12volts ,120AH battery can I connect both of them to my solar system in parallel

SamWith a BS in Chemical Technology and eperience with batteries, I congratulate you for this article where expertise and general public understanding are mixed in a state of the art level. Talking for shalow cycle batteries where Ah has no sense because CCA matters people has to be aware that this battery has to be fully charged, and if discharges only 20% i.e below 12.6 V affects the life of the car battery. The status of battery has to be checked every weak, while you check the cold inflation pressure of the tire. To have a optimal inflated tire, means an optimal tire foot print i.e an optimal tire grip. So at this time check the battery voltage in your car parked overnight, start engine check again and you’l get 13.5 to 14.5 i.e. this is the status of alternator and voltage regulator in your car. If not using a vehicle use a battery tender that start charging at 12.6 V and stops at 14.2 – 14.5 V. Not hapy with comercial battery tenders, I made my own using a NE555 timer as precission comparator an more component. I can adjust ON at 12.6 – 12.7V and of at 14.2 to 14.5 volts according to the status (age ) of the battery. Increasing the battery voltage above 13.2 V, starts equilizing process. The weak cealls continue to charge and the strong start boiling. I do this proces at 250mA untill battery saturated, and after turns OFf to let battery to relax. I never buy a maintenance free battery, because I must check the electrolyte, level, top with H2O, and if necessary check the density.

MarieSir Good day! i need with my newly bought gel battery, i dont know if i have to add sulfuric acid… i used it with my u.p.s. and it cant five any power to my computer when i unplug the power cable of the u.p.s.when i read the power rating 12.5V i dont know the ampere since i dont have amp meter. but in the battery it says 7Ah/10H. i thought it is better than my old VRLA with 12V 4.5Ah rating

JeremySounds like you should talk to the manufacturer. If its gell, then you wouldn’t add any acid, and most cases if its AGM it would come prefilled. The 7AH will last longer than the older 4.5AH one.

Dave MCan you use a AGM battery by laying it on it’s side or must it be in the upright position? If so, does it make any difference what side it lies on (battery posts toward the top vs toward the bottom)

Anders DBest written, most through article I have read regarding batteries, thank you! I have a BMW with AGM battery that was just replaced. I purchased a CTEK multi us 4.3 Smart charger to lengthen the life of this new battery. I attempted to charge 3 days after installation, but became concerned as the charger was hot to the touch after 2 hours and still in the bulk charging state. Should I be concerned by the heat? There was no indication of anything awry other than the charger itself being hot. Interestingly, the old battery never remained in the bulk charging state this long and I never experienced the charger ever being warm.

JeremyI would not be concerned if it is hot after 2 hours, but if it has not entered into maintenance mode after 12 hours, I would check the battery to ensure it is good.

AtharDuring periodic check when I observe that water level is low, I add distilled water to cells of lead acid battery. After a short time the fluid starts oozing out from the caps. It continues for about 12.15 hours. What is the cause of this problem and how it can be rectified?

HaroldThanks for a very informative article. I own an older Honda Goldwing with lots of electrical gizmos. I have replaced the battery twice in last year. My dealer replaced the last under warranty about three months ago. The new battery worked fine when I was driving the bike frequently. But after letting the bike set for about two weeks I now have another dead battery. I hooked up my trickle charger, it only has a light that tells me it is charging, I left in on for about a week it did not recharge. I then hooked up my battery charger, it tells me it the battery is fully charged at 6 volts. Does this mean I have three bad cells? This is the second time this has happened, the first new battery lasted about six months this one about three. Do you think I got bad batteries. One I think maybe, but two in a row.

LarryWhat a well written article. Thank you! My interest in the topic comes from wanting to maintain our trailer’s 12v AGM battery over the winter. We brought it home and put it in the basement workshop, but I discovered tonight that it was down to 10 volts. I’d like to put it in the cold room where there’s an unused plug but was worried about the “well ventilated area” instructions. The article says AGM batteries are the safest type, so would it be safe to charge it in the cold room? (10 × 4 × 7 feet, with top and bottom 4” pipe vents)

JohnBrilliant article. Has really explained the internal working of various makes of batteries, better than anything I have come across here in the U.K.

PulkitHi. I have 2 12 Volt batteries and want to use them both/ But i still want to use them for 12 volts. I just want extra backup. Please reply me anyone ASAP.

Robin BrokawHere is an article that explains the answer to your question. Should you have any further questions please feel free to email our tech guys at tech@batterystuff.com. www.batterystuff.com/kb/aricles/battery-articles/battery-bank-tutorial.html

SandieI am battery deficient. I am charging a battery on trickle charge, I know that much, but how do I know what the red and black bits on the charger mean? And how long til it charges? My hubby used to do all this but alas he is no longer here. Thanks for input

Jeremy FearI appologize, but I‘m not quite sure what you are reffering to by the ‘red and black bits’. If you want to send me a photograph of the charger in question, my email is tech@batterystuff.com, then I will be more than happy to assist you from there.

DonnaI need a battery for a lighting setup for artfair booth (outdoors). I want to use 6 LED lights (14-watt Par30 bulb 3500K). also use of a fan for cooling the booth. which type of battery do you recommend.

DavidIs it possible for a AGM battery to test 100% on a load test and still be bad? My battery shows 12.8v unconnected. In the motorcycle it shows 12.6v and with the key on it drops to 12.1 and won‘t start the bike.

Jeremy FearYes, it i s possible for it to have an internal ‘open’ in the cell. This happens when a weld point begins to come loose in the battery and it is unable to pass any significant current along the now thin connecting point.

JohnI have a 12v 100 amp hour wet cell battery at work. It was taken out in the fall and put on a Smart charger. Now I was going to reinstall it back into our equipment. I noticed that the end with the negative post is swollen. With a load test it passes at 9.5v‘s. no other physical damage is found on the case. Could the one cell have pressured up and not vented?

Jeremy FearIt could have had some gassing at some point without actually damaging the cell, as may be indicated by the continued performance.

SeanQuestion, i have access to some lead acid batteries with much more life left in them….more than i need at any one time. I want to put some in extremely long storage (5to10) yrs) Can i remove the electrolyte, flush then store? I read somewhere after flush to refill with ph neutral water and storing worked well. Another that after flushing used inert gas argon and sealed battery vents. Not concerned with losing a little capacity as these are very robust batterys. what would you recommend. I would charge these fully then remove electrlolyte and store it properly until redeployment.

TimGreat Article. If I have a 80 Amp Hour battery and use a winch that is drawing 435 Amps under load with a 90 Amp alternator on the vehicle, how many minutes can I winch before I fully drain the battery or cause the vehicle to turn off? What formula are you using?

DonnyDo you recommend a 2 battery solution for a boat? 1 for starting and 1 for deep cycle? Or would a dual purpose battery be sufficient? The engine is a 90 HP outboard.

BatteryStuff TechWe recommend using a dual battery setup versus the dual purpose batteries. You get better performance for your needs this way (starting the engine and running your electrical system).

Jerry AndersonI have a Yamaha golf cart I purchased 4 yrs ago. Last winter I parked the cart in my heated garage and did not recharge the batteries during the 3 1/2 month period. By spring the batteries were so discharged thatmy cart charger would not work. I used a car battery charger to charge the 4 12V batteries separately. I limped through last summer having to charge to cart every 18 holes. I haave recently read about de sulfating the batteris. I was thinking about trying this before I spring for new batteries. Can you recommend a product to do this and if I can use the cart charger when doing this or would I have to charge the batteries individually. Thanks for the great article.

BatteryStuff TechI recommend using the liquid additive called BATTERY EQUALIZER and also the PP48L ON- BOARD DESULFATOR by Pulse Tech.

Reg RaynerSir, Thanks for the article. I Have a yacht with 4 Trojan T105‘s(6v – 2 in series- paralleled X 2) as one bank and a truck and tractor battery as the other bank. These are constantly charged by both solar panel and wind generator ( through a regulator) and also charged when the motor is running by alternator. My question;- Can I replace these wet cells with AGM batteries without changing any charging facilities? and if this is OK, do I replace them all with dual purpose AGM ‘s or do I have 2 different banks, 1 starting. 1 deep cycle. I have a manual(idiot) switch, for selecting each battery bank or both. My motor is a Ford Lees 85 HP deisel. Thanks in advance.

BatteryStuff TechMost AGM batteries require no special charging accommodations. I recommend using deep cycle and starting batteries for their respective purpose. That way, you‘re getting the best performance based on the demand.

NickiHi, my husbands 650cc motorcycle wasn‘t turning over so we figured it was the 12v battery. In order the check that it wasn‘t anything else we hooked up my new smaller scooter 12v battery to his bike and got it running. Now the scooter battery won‘t even turn the lights on the scooter even though the voltage meter says its fully charged. Could we have damaged the battery by using it in a different machine? The bikes take different size batteries with different amps but both 12 volts. thanks.

BatteryStuff TechThere should be no issue using a smaller 12 volt starting battery for the motorcycle. I‘m surprised if the bike was able to start with a smaller battery. If the battery is truly fully charged, can you provide a resting voltage reading (bike off)?

Mizanur RahamanSir, I want to know a matter. When a 12V, 7.2AH rating battery is fully charged, is there any current flow to the battery where the charger is still plug in? and what is the actual voltage when the battery is fully charged? Please ans. to me. Thanks in advance.

BatteryStuff TechWhether or not current is going into the battery after being fully charges is entirely dependant on the model charger you use and therefore I cannot answer your question. Micro processor controlled chargers will ‘float’ a battery after full charge. This is usually ~13.4 volts with little to no current. However, if you want to know what resting voltage (off charger) on the battery itself is considered full charge, please refer to this article for the answer.

Ms. Safetyspan THANK YOU. The information on this page was GREAT. It is now my “Go-To” reference for batteries.

SilasSir I will be very thankful if you guide me to build a charger of a 4 volt Li-ion battery(which I have dismantled from my old laptop battery)……Thank You.

BatteryStuff TechWe are unable to provide you the information you need. We are a reseller. We do not build or manufacture any chargers.

Adda LamonI found the article SUPER helpful, because the guys at the auto parts store we talked with did a few confusing things. One guy called a battery looking like a 6-pack of soda cans a gel battery, where as the guy he called in for more info called it AGM. which it probably actually is. However, the guy who actually did know it was an AGM battery told us specifically that it wouldn‘t have any problems if it was completely discharged…which sounded quite attractive. We‘re still planning on purchasing the AGM batteries, but if I hadn‘t found the web page and wised up on the great info and tips you folks provided, we might have blithely followed his information and totally killed our battery (sucksville!). Thanks for a great website.

bu-403, charging, lead, acid, battery, percentage

Mike SmithVery Informative! (I assume 1 to be the highest rating). I have an ‘85 Ford class C motorhome with 2-12v batteries. Not sure if they‘re connected in series or parallel. It has a single alternator and a separate voltage regulator. With the engine running, one battery reads 12.4v, the other reads 16v. I assume this means the alternator is trying to charge this battery more? I first thought the regulator was bad replaced it. At that time, one battery was reading 16.4v the other 16.2. I discovered I had bought the wrong regulator, so I bought a second one. It read 16v and 17v. I put the original regulator back in, leading to my assumption that one battery won‘t hold a charge and the alternator/regulator is trying “harder” to charge it. The batteries were in it when I bought it, but they‘re different brands I have no way of telling when either was purchased. Would my assumption be correct, and should I replace the battery with the higher voltage reading (or both)? What started this was when I bought the rv, before driving home I turned on the headlights and one went out immediately. I turned them off the seller turned them back on the second headlight went out. I left it for him to fix. He replaced both headlights. The first time I used them the new ones went out together. I switched to high beam after about 10 seconds they both went out. I knew something was wrong suspected the regulator first.

BatteryStuff TechThey do make 16 volt batteries and alternators. They are commonly found in race cars. 16 volts is too high for a 12 volt system. You could be overcharging your batteries.

Garry McdonaldRE; Can anyone please help? Scooter battery problem, will not take a charge. It appears that there may not be anything wrong with my batteries. I was told that the batteries must be charged every month or two or sulfation would set in. But the batteries not excepting a charge after 4 months was concerning. With no answers I decided to drain the batteries of two scooters by running the motors with the throttle on full and turning the lights on. However after 5 hours of constant running the scooters meters were still showing full and the volts where at 48.7 and my volt meter was showing 48.6 volts. After 5 hour only dropped 2 volts while protection shutoff is 42 volt. The next day I charged the batteries and yes they took a good charge, 7 hours and still taking a charge when I left for the day (I have them on a 12 hour timer). These Chaowei deep cycle gel batteries must be very good with little self discharge to not except a charge for 4 months.

BatteryStuff TechI‘m glad your batteries are fine now. But for the future, it‘s not necessary to discharge these batteries down. They are not like NiCD batteries, there is no ‘memory effect’ or need to cycle charges. Batteries that are fully charged for a 48v system should give you 51.2 volts or more.

Louw Penni NgHi, Very informative article, thank you. I have a problem with my camper van, 24 volt system for the truck, 25 amp alternator, fridge in the house on the truck that draws current from the 2 × 12 volt in series truck batteries. When ignition is off, the fridge stop drawing current. However, the truck batteries constantly run flat during driving, all well while I drive (diesel truck), but next morning the truck batteries are almost flat. The camper van house has it‘s own 12 volt battery, charged from solar, it performs OK. Currently the 12 volt fridge element draws amps from the second 12 volt truck battery, this implies that the fridge uses the power from the battery, not directly from the alternator. Is it possible that the power outflow from the battery is more than the charge inflow into the battery? How many Amps can a battery continuously take while charging? I now think I must tap the 24 volt directly from the alternator, then put it through a rectifier to get 12 volt, and then onwards to the fridge. This will leave the truck batteries free to charge at will without being drained by the fridge. If the truck batteries can only charge at say 6 amps, while the fridge draws 10 amps, the current set up will always discharge and leave me with flat batteries. Am I correct in my reasoning? Please advise asap, Many thanks, Louw

BatteryStuff TechThere is no limit to what a battery can or cannot accept. A battery cannot say ‘no’ to charge. However, there is a safe range, up to 25% of the battery capacity, should be the max amperage charge rate. For a 50 AH battery, that would be a max of 12.5 amps per hour. Alternators usually don‘t have problems with overcharging, because of the electronic control unit. It sounds to me like you have a 24 volt battery system, but a 12 volt alternator. It seems like the fridge only takes 12 volts to run. What part of your system actually draws from 24 volts?

Edi have 3 sb 12100-s 12 volt 10 amp batteries for my bike which were stolen how do i wire the new ones?

Edi have 4 batteries ps 1272 fs 12 volt 7.2 amp batteries were stolen how can i wire theser my bike?

MikeI use 4 – 12 volt dcm0035 interstate batteries hooked up to 48 volt configuration to power my pedicab. I have 2 sets-8 batteries total. They have had 11 months of being drained to approx 12 volts on the meter 3 times a week. I use 2 noco gen 4 chargers. Mostly in the 10 amp mode….but sometimes doubled up on one battery set. Weather conditions from 35 – 110 F. How can I determine how much life is left? Besides the obvious based on how long they run before being drained. It seems they are at about 50% of new. Also…does my charger do a real 100% charge

BatteryStuff TechThere is no magical formula to predict the length of life remaining in a battery. Yes, the Gen 4 charger should bring the batteries to full charge before entering the gentle float mode on/off cycle. 12.0v on the meter is more than 50% discharge, which is more than we recommend for optimal performance.

AndyI purchased a used boat in 2009, it has 2 identical West Marine starter batteries 650 CCA with a Perko 3 way switch, 1, 2 both or off). I‘ve never charged these batteries other than while running my boat, which is probably less than 50 hours per year. The engine is a 175HP Suzuki, with a 44 amp alternator. I feel like I‘m running on borrowed time and want to replace these batteries with AGM s. Should I go with 2 starter type batteries or 1 starter and 1 house? While boat is running is the alt charging both battery at the same time or does it follow the path of the Perko switch? Thanks, great site.

BatteryStuff TechSince the batteries will be connected together via switch, I recommend using two of the same battery types and sizes. Therefore, if the batteries are used to start the engine I recommend two starting batteries. I recommend a deep cycle battery if you need 12v power while the engine is off.

BatteryStuff TechNo. If you are charging a battery and then you use it at the same time, the charger will attempt to supply the load. Depending what the load amount is, and if the charger can supply it, the battery may be charged at a lower rate or not at all and start discharging instead.

Murugan(continued…) I am using a 17 inch CRT monitor which consumes 80W power. Here in India we use 220V Ac for our appliances.

Murugani bought a 12Volt battery 22months back with inverter for my desktop computer only. It reads GT-2100 C20 210AH. It‘s a lead acid battery. The dealer told me that i can use it for 10 and half hours for to power my computer only. from internet i came to know that one should not fully discharge a battery. i till date only once i used it up to 9 1/2 hours. never seen ‘battery low’ blinking any time till date. I always carefully kept the water level full by regularly checking the level indicators. On an average i use the battery up to 7 to 9 hrs these days because of big power cuts here and see it charged fully immediately when power comes. One problem is that if i use the battery for 9 hours then there has to be continuous power supply for at least up to 8 hours(minutes) to get fully recharged. but here they are supplying power only on alternate hours. i.e, one hour power supply – one hour power cut – one hour power supply. and that too during the night only. during day time only for four hours power in given- morning 8to10 and evening 4to6. rest all day power cut. only in the past 3 months power supply became like this. i have been forced to use my battery very carefully and judiciously. My questions is will it affect my battery life by leaving it to be charged in alternate hours?(i don‘t use it during night while being charged). i am really worried. we have abundant sunshine here. so i am willing to explore the possibilities to charge it using a solar panel. i want to know the maximum wattage or voltage should i supply to charge it in the minimum amount of time possible. tell me this much wattage up to this much hour. here we have 10~ hours of bright sunshine. please help.

BatteryStuff TechIt‘s okay if the battery is receiving charge during irregular intervals. It‘s not the best situation, but it‘s not going to destroy the battery immediately. The truth is, the battery is going to build sulfation when its in a discharged state. Re-charging it will reverse this. That‘s good practice, but I understand if your situation prevents you from doing that in the best way possible. If you‘re looking for solar charging, the largest panel I recommend you can use to safely recharge the battery in the quickest time is a 900 Watt solar panel. This will charge at a rate of 73 amps per hour (35% of battery capacity). Less is fine, but no more for safe re-charging.

FawadMy AGM 100amps battery for UPS is acting strange it gains full charge with 30-50 mins while it also discharges with 30-40 mins, my UPS is charging the battery on 10-12 amps. Any Help

FawadI don know exactly but its has a Samsung 42” Plasma TV and and small Satellite receiver, that‘s all. And with the same load it gave me a Backup time of almost 2 to three hours.

BatteryStuff TechIf I understand you correctly, your battery isn‘t lasting as long as it used to, and it charges quickly, too? Short charge/discharge periods? Sounds like the battery has sulfate crystal buildup on the plates. Sulfation causes batteries to age quickly. Refer to our other technical articles about how to remove sulfation.

Greg”… An amp hour (AH) is a rating usually found on deep cycle batteries. The standard rating is an Amp rating taken for 20 Hours. What this means, say for a 100 AH rated battery is this: Draw from the battery for 20 hours and it will provide a total of 100 amps …” Should say … ”… and it will provide a total of 100 amp-hours …”

David CuneoThank you for your article, I have a question. I bought a 2 month old ( STICKER ON IT) battery from junkyard, outside cell was punctured in a crash, looked inside all electrolyte was gone from the one cell. I repaired the plastic casing,it could now hold liquid safely. Could i add electrolite from an old battery or would that have too many sulfites. it would be better to get a motorcycles worth at autozone? I am going to turn in my old battery anyway as it is a core charge… What do you think?

BatteryStuff TechThe moment oxygen hits activated plates in a cell, sulfation will form rapidly. My opinion is that it’s not worth the effort or the risk. I recommend buying a new battery. Even if you were able to restore this one a bit, I doubt it will last very long and it would not be safe as the internal resistance when charging will be greater than a healthy battery, which you will risk the battery overheating as a result.

Wilfred KubeI have a Toyota Coaster bus which is fitted out as a motor-home. The vehicle was manufactured with a 24 volt electrical system, which uses two batteries in series, of 12 volts each. I have outlined a description of the auxiliary electrical system below, but my basic question is, how can I know how depleted my auxiliary batteries are at the end of a day in which the refrigerator has been working for a long time? I think the basic rule is that the batteries should not be discharged below 50% of their capacity, but what reliable method can I use to determine when they have reached this point? There are two auxiliary 12 volt batteries in series, each 120 amp-hour, to provide power for the “house system” – namely refrigerator, lights, water-pump, and various 12 volt power outlets. The refrigerator is the major user of battery power, because it is a compressor fridge which uses the equivalent of 12 volts 8amps (i.e.96 watts) while it is running, and it runs for approximately 8 to 12 hours in each 24 hour period depending on how hot the weather is. The auxiliary batteries are charged by two solar panels of 80 watts each, and receive additional charging from the vehicle alternator when the engine is running. There is a battery isolator which automatically disconnects the auxiliary batteries from the vehicle electrical system when the engine is not running. The voltage regulator for the solar panel charging system provides a constant display for the auxiliary system, including the auxiliary battery voltage. I have been in the habit of checking the voltage last thing at night, and first thing in the morning, to find how much power the fridge has taken from the batteries. If the night time voltage is below 24.8volts, then the morning reading is below 24.0 volts. The problem is that if we have not done much driving on a particular day, and the solar panels have not done much charging because of cloudy weather, the night-time voltage may only be 24.2 volts, and the morning voltage not much above 23 volts. If the battery is at 24.2 volts when the fridge is not running, then when the fridge starts running the voltage reading drops down to about 23.5 volts. And so my question remains, what is the lowest acceptable voltage for my auxiliary battery system, so that the batteries are not damaged by being discharged too much. Thank you for reading through a long and detailed letter, but I wanted to provide sufficient background information.

BatteryStuff TechResting voltage of 24.4 volts is 50%. When you reach this point, stop using the batteries until you can recharge them again.

Yves Van DammeI do have the same system as Wilfred, although I use a Tripp Lite to invert current from 12V to 110V (2,400 Watts) I have always used 3 cheap regular truck size batteries, charged by the alternator and, with the almost every WE driving, had no problem running everything for 3 years without having to charge the batteries with an external charger Recently, to lower the weight, I bought 2 trojan deep cycle batteries 225 that almost totalled the same Amp as the 3 previous ones To my surprise, these batteries have gone dead last week after 6 months of use, although well maintained as far as water and regular charging through the alternator The Tripp Lite works fine and we always avoid to use the battery lower than the yellow and red lights which indicate a battery load of 50 % We did have a 2 minutes run on red light 2 weeks ago (as much as 80% discharge) and to prevent any further problem I recharged the batteries with an external charger together for 20 hours (for the first time in the last 10 years); the charger indicated 14V at the end of the charging process. Unfortunately, on a trip last week I lost power faster then ever and ended up having to only use the refrigerator while driving, forgetting about the water pump or the coffee maker; I tried to recharge the batteries since then but the charger wont go over 10 volts and goes down to 8 and 7 after 10 hours My question: since these trojan batteries are very expensive where I live (Peru) should I invest in a charger, what kind, and should I charge the batteries everyday from my house? The car is in the street and I cant go check every 2 hours what the voltage is, so is there a charging process that is safe, guaranteed on the long term for these batteries? Once again this is the full description of my configuration: bus sprinter with alternator of 100 Amp starter battery of 120 Amp 2 trojan deep cycle 225 130 amp each output 12V one tripp lite inverter 12-120V 2,400 Watts Thank you so much for your answer which should interest many people like me who just want to understand how to run a simple 3 or 4 devices in their camper

BatteryStuff TechIt sounds to me like your current charger is probably fine but the batteries may be defective or had their life significantly reduced when they were overly discharged those 2 weeks ago.

PeterThank you for your great work! I have learned a lot. I have a Die Hard 1150: 20ah AGM power pack. As per your explanations, I leave it plugged in because it has an integrated Smart charger that is supposed to provide a safe float charge to maintain the battery‘s health. I have two questions relative to this: 1. Is it normal that the battery is slightly warm to the touch when it is plugged, has reached 100% and is receiving a maintenance charge? 2. Are dangerous gases given off while the battery is plugged in and receiving a trickle charge? My battery is plugged in in the basement workshop in a fairly large house. Thanks for any information you can provide and take care. Peter

BatteryStuff TechIf the battery is warm, it‘s because there is more resistance in the battery internally than normal. There is probably a good amount of sulfate crystals on the plates in the cells, which would cause the charger to work harder to maintain the float mode. Sulfation robs the battery of power, but can be reserved with de-sulfation units and chargers. Gassing should not be an issue if the battery is healthy. Only significant over-charging should cause an AGM to vent excessively.

MattGreat article. I learned more than I‘ve ever known about batteries, but I still don‘t know much. I am wondering, I recently purchased a year round ice fishing house / camper. I‘m looking at batteries now and am leaning towards an AGM. Is that what you would recommend? Again, this battery will be used year round. Freezing cold when it sits for 4-5 days at a time without being used, then it will be used on the weekends when I go fishing. Then during the summer it will be used in the heat. I‘ve also seen a couple mentions of solar chargers. I do have a generator that i plan to use to recharge the battery when necessary, but am wondering if it would make sense to leave a solar charger hooked up to the battery constantly. The location of the battery in the house would make it very simple to hook a solar charger up and have it mounted either directly in the window, or just outside attached to the side of the camper/fish house. Then even when in use, the battery would be charging, right? Thanks in advance for any response.

BatteryStuff TechFor extreme temperatures, the Gel batteries are the best. They also have the slowest discharge rate. Having a solar panel is a great idea, and perfectly safe even if a generator is on or you are using the batteries, if you are also using a solar controller (which regulate safe charge voltage levels, and prevents back feed into the panel). But yes, if a solar panel is receiving sunlight, the battery will also be charging as well.

TimGreat Article ! For what it‘s worth. I use NorthStar pure lead AGM batteries. They have the widest operating temperature range (-40 deg F to 149 deg F) and have a two year shelf life. Never saw a gel battery with that type of operating temperatures. I have one in in my truck. Never a minutes worth of problem.

BatteryStuff TechPure lead vs recycled lead does make a difference in performance. NorthStar batteries sounds like good batteries.

Adam JohnsonThank you for your opinion….I would like to use an electric golf cart for in-town transportation in a small town in the San Juan Mountains of Colorado, year around. I am a teacher and typically only drive it back and forth once or twice a day, about one mile each way. 1st question: It can be very cold here on winter mornings, (-20 degrees and more),but then warm-up to 30 degrees on the same day, is there a battery that can handle the temperature range, and still have a reasonable life length? 2nd question: I have a solar panel that I could place on the roof, get a charge controller, and have the batteries always trickle charging, how will that effect the battery life? I have a 36 volt charger that came with the cart. The cart is perhaps 20 years old. The batteries it came with were all exhausted, I took them to a recycler. I was thinking of spending the 150.00 each ( including core fee) for 6 batteries, and stop driving my gas vehicle. I‘d appreciate some advice.

BatteryStuff TechFor the greatest range of operating temperature, the gel batteries would work the best. For a solar panel, you would either need a single 36 volt panel, or 3 12 volt panels in series. That‘s a good idea if you want to see the longest lifespan from the batteries. The charge controller, make sure it‘s safe for gel batteries, which require a slightly lower voltage charge than most other batteries need. We sell Trojan T-105 6 volt batteries for 139 each. No core needed.

BatteryStuff TechThere are some step up converters to increase voltages, but we do not sell them. Additionally, I think it may be hard to find one that will step up to 180 volts.

Selvan AlbertHi all, Current setup: 1) Two UPS s. Both are independent systems. 2) Both are identical; Manufacturer: Delta; Model:J-Series 7 KVA. Each capacity: 5000 Watt, 230 Volt AC. 3) Each has 20 numbers of 12 Volt 26 AH batteries connected in series for a 240 Volt DC, 26 AH battery bank. Objective: a)Design a battery bank in such a way that even if one battery fails, the bank would still be operational and keep the UPS running until the failed battery is replaced. b)Try reconfiguring existing battery bank so that cost is minimized. Proposed setup: 1)Instead of two identical but separate battery banks as configured now, reconfigure the 40 batteries in one battery bank. 2)Batteries will be connected in series and also in parallel as listed in the diagram. 3)Two batteries will be connected in parallel to form one 12 Volt 52 AH parallel battery bank pair. Twenty such pairs will be linked in series to form one 240 Volt DC 52 AH bank. 4)Connect both UPS s to this one battery bank. 5)The 230 Volt AC “Output” of the UPS s would remain independent as they are now. Attached Diagram: Both the current setup as well as the proposed setup are illustrated. (No change in the independent “Outputs” of the two UPS s. The 230 Volt AC “Output” of the two UPS s would remain the same (as independent outputs) in the proposed setup as they are now in the existing setup.) Advantages: 1)When any one battery fails, the entire bank would still be operational. (Hence, the UPS s will not fail.) 2)So long as “both” batteries connected in any parallel pair do not fail, the bank would still be operational. Question: 1)Would the battery charging circuits in each UPS somehow interfere with each other? 2)Are there other issues and/or disadvantages in the proposed system that are overlooked? When electrical power is On, would the battery charging systems in each UPS interfere with each other when charging the single battery bank? In other words, currently just as one UPS charges its own battery bank, would the two UPS s charge the single common battery bank without issues? We would be very thankful to you if you can please give us your valuable feedback on our proposed battery bank set up. Selvan Albert.

BoHi James, thank you for the information and excellent explanations! How can I figure out what type of battery in my car (2007 BMW X3)? The battery is a sealed maintenance free battery. It’s the original battery. The part number is S: 61 21 8 385 398, and the label says it’s 90 AH and 720 CCA. but no manufacture name on it though. I called couple of BMW dealers, but they didn’t know. Hopefully you can help me out. Thanks in advance!

BatteryStuff TechSounds like an AGM or a VRLA battery. Both are different types of lead acid batteries, the sealed ones as apposed to the conventional flooded type. It‘s not going to be a gel, I can almost guarantee that. Gel batteries are completely sealed. If there any ventilation or even vent slits on the top of the case, then it‘s not a gel. That‘s good too, because gel batteries don‘t make good starting batteries. They‘re fragile.

BoThank you very much for your answer. I have a battery charger, and I need to choose one of Standard, AGM. and GEL battery type. Which type should I select?

BatteryStuff TechGel is the safest, because it uses the lowest charging voltage of the three. If you are not sure, the gel setting is always a safe option. Otherwise, if you think it‘s an AGM (check to make sure there are ventilation slots to confirm it‘s not a gel) then use the AGM setting.

Charles WehlandI have an electric 2-wheel scooter that my wife uses. It has 3-batteries linked together. How do I hook-up the cables on my battery charger to charge this bank of 3-batteries?

BatteryStuff TechIt depends entirely if the batteries are suppose to be in series or parallel. The answer to this question depends if the scooter runs off 12 volts, or 36 volts. But the surest place to connect your charger to are the same terminals that the scooter‘s motor is connected to in order to run.

BobWhen using a deep cycle battery in a Solar system, using DC 12 volt lights. Is there a way to automatically shut off the lights before it discharges the battery too far?

BatteryStuff TechYes, you would need a battery disconnect or a power switch. Priority Start and Battery Guard are two brands that will do this automatically. We sell these in our battery accessories category.

John FetterThis is a philosophical comment. Lead-acid batteries suffer from self discharge. Batteries actually spend overwhelmingly most of the time not on charge but doing absolutely nothing at all. This is what causes sulfation. So what do the experts recommend battery users do? Treat the sulfation. A hundred year old cure! How about treating the battery with something that stops the self discharge?

BatteryStuff TechKeeping a battery on a trickle charger will prevent self discharge. Beyond that, asking a battery not to self discharge is like asking a person not to age. It‘s a chemical issue, and healthy batteries will self discharge at a lower rate than older batterie or cheap batteries made from lesser quality materials.

Will HelbichI have new replacement 4 × 12v 18 ah deep cycle agm batteries wired in series for an e-bike, the 48 v charger charges the bank at around 54-55 v, Now,the original batteries performed the last 2 years as expected for 300- 400 cycles with good range. but these new replacement batteries are failing within weeks, less than 30% range than originals. When testing the charging voltage going to each individual battery in series. it varies from 14.1 V- 15.9 V from one battery to the next. and under a timed load test on each charged battery, they range from 2 min to 55 min before dropping below 11.5 /cell. Are the batteries poorly constructed or is it a charger issue? Thanks for any insight you can provide.

BatteryStuff TechHow much was the load amount for the test? 15.9 volts is on the high side as far as charging goes.

JeffHi, just got a new kirkland battery and it has the 6 cells under the cap. Not all of the cells have liquid in them to the top. is this normal for some cells to have more liquid than others, should they all be filled to the top? I could not see any fill lines as to where the level should be. thanks

BatteryStuff TechYes, the cells should be balanced, even as far as liquid levels. Please only use distilled water. They do not need to be filled to the rim, but definitely the plates should never be exposed. If this happens, the plates react with the oxygen in the air and form sulfation rapidly. I hope this answers your question.

Qusayhello i have 8 deep cycle battery 12v 200Ah connected series/parallel to supply a ups system and it charged by acostant charger 52.5 V 35A its working abot 18 month every day about 6hr on the UPS and now begin loose its capacity when i check the voltage for each battery while the charger working some of them give 13,4v and other 12.66 and 12.9 so it the sulfated or need for reacharging with a Smart charger. thanks

BatteryStuff TechI don‘t know what the load is, but for a 48 volt system the charger seems a little too low if it‘s charging at 52.5 V. It should be 56 V or so under the bulk charge mode. For float, 52.5 is okay. I‘m not sure what your question is about. If the batteries are individually reading different voltages, that‘s not good for the system. Are the batteries the same age? 13.4 v is a little high but good full charge, while 12.9 v sounds just about right. 12.66 v could use more charge. If it‘s not able to reach any higher voltage, sulfation is a good cause of that. An onboard de-sulfator like the Power Pulse or ODB from Battery MIND er would be recommended to fix that battery. No need to disconnect it from the others or change your system.

Qusaythanks alot for your assistant 1- my battery have the same age 2- i cant increase the charger voltage because its max volt is 52.5 also till now i dont try another charger or charge each battery individually 3- these readings for each battery but while they connected to the charger and for example when im add all the reading ( 13.412.6612.913.54) its equal to 52.5 which is the charger voltage and when im disconnect the charger and after 1 hr battery reading is ( 12.7. 12.5. 12.7. 12.6 ) i think battery No 1 and 4 prevent the voltage to rais in battery 2 and 3 so they cannot charge fully. also at the first 8 month all the battery have the same reading when charging. do recommend individually charging for each battery to force it reach to 13.6 v and accept current. like using 48 v charger with 4 bank or its no problem to use 48 v charger with one bank also if i want to desulfate it it is better to use obd-12 for each on or use obd 48 for each 4 batteries also what is the recomended methode to charge and maintain this system to get maximum life for the batteries. thanks best regard

BatteryStuff TechA 4 bank 48 volt charger would charge the batteries individually, which may solve the problem. 52.5 volts is good if the batteries are fully charged. But since they are not all charged, I recommend the charge rate should be higher for the two to charge up. If you use the OBD.12, you‘ll need one for each battery. Otherwise, you can use a single OBD.48 for all four batteries in series.

Qusaythanks to helping me to solve the problem and thanks for the site which give this amount of data for users. really great site and great staff thanks again with my best regards

Max WilliamsHi I have (8) x 6V x 125AH deep cycle batteries producing 24V in a series/parallel config charged by a 250W x 24V solar panel,powering a 24V fridge/freezer 24/7 drawing 2A when running. Am i correct in assuming my total stored AH capacity should be sufficient to run the fridge with minimal sunlight for a few weeks. Cheers Max

Jeremy FearAs long as you rpanels recieve at least 5.5 hours of direct sunlight on the panel then you should be good. If you have any further technical questions, please email them to Tech@batterystuff.com

Bobhi, i have a solar system i am using a device that measures the voltage of the batteries and send it through a serial port to the computer, that can show me the health at anytime of the day. i have 8 batteries connected in parallel, and the problem that i am trying to think of a solution is that the measuring device is treating the 8 batteries as one, and gives me a single reading. But in order for my monitoring project to work, i want to be able to measure each battery alone, even when they are connected in parallel together… I know this sounds impossible, but I still need to think of all possibilities. Anyone with any clues would be very helpful. Thanks.

Jeremy FearAny technical questions can be emailed directly to Tech@batterystuff.com for the fastest response. To answer, at least the best I can, I would personally hook up the tester that you are using to an 8 point switch, where each of the 8 modes were connected to one of the batteries directly. You could then switch the connection on the monitor to each battery individually, even though they are all hooked up together. The only real downside to this would be that if your device is one of the more accurate types, then it will be thrown off by resetting it on each battery and will cease to be as accurate. On the other hand, if it is not a super accurate one, then I wouldn‘t bother setting it up this way anyways. So while its not completely impossible, its a bit of a catch 22. The accurate one will cease to be so, and the not as accurate one falls in the ‘why bother’ catergory. Hope that helps! 🙂

BobHi, First of all I want to say that your tutorials have been very useful for me and I have learned very much. I have an off grid house that I power with four 12V 245AH 8D AGM batteries wired in Parallel which are connected to a xantrex 3000W sine wave inverter/charger. I have a xantrex link pro battery monitor that has a programable alarm relay that I have set to start the generator when the batteries get down to 55% state of charge and to turn off again at 85%. occasionally I turn the generator on manually to bring the batteries up to 100% charge to synchronize the monitor. I just set the system up a few weeks ago and it is working very well so far. I am not there very often but whenever I check on it, the batteries are within range and the generator runs for 4 or 5 hours a week. The only thing running while I am gone is the refrigerator and a half dozen 7w led lights that I have come on after dark. I don‘t have any other source to charge the batteries yet (solar or wind). I have a couple of questions: Do you think this system will work well in terms of longevity? Is there something I should be doing differently, such as setting up the monitor to keep the batteries at a different state of charge (more or less discharge)? The reason I don‘t bring them to 100% every time is that the generator needs to run for quite a long time to get the extra 10-15% into the batteries and it seems like a waste of fuel. Second, if I had an always on wireless internet connection, do you know of a way that I could monitor the battery condition from far away via the internet? So that I would know if there was a problem with the generator not coming on. I don‘t know if there is a battery monitor available set up to do that. Any ideas you might have would be geatly appreciated. Thank you.

BillI have an old (‘85) Honda ATV. After some reading (obviously not enough)I purchased a gel cell battery that was advertized as appropriate for my ATV. It did not take long for the battery to reach a point where it would light lights but not turn over the electric starter. After more reading, it would seem that the alternater would need some “adjusting” to keep this battery charged. I can find many references to external chargers, however I have, so far, been unable to find any information on what needs to be done to upgrade the charging system of the ATV for gel. Any help here?

BatteryStuff TechWe do not sell anything that would regulate an alternator to a safe voltage for Gel batteries (no more than 14.2 volts). I imagine it would be costly. It‘s easier to simply purchase an AGM battery for the ATV and not have to worry about charging differences.

Cpt Crunchspan THANK YOU FOR SHARING YOUR KNOWLEDGE ! WOW ! I have been working with batteries for years, yet never really understood their differences, much less how to match them with various applications. Here I have been buying based on the highest amp/hr AND CCA. when I should be looking harder at one or the other. And now there‘s an AGM. Okay, ….a question: The GPS /Fish Finder on our boat uses around one-third of an amp. My typical day of ocean fishing is between 8 and 10 hours. I do not like it on the starting battery and am looking for options. The first question is AGM or a small gel cell? I am looking to understand the balance between them, in particularly, the lesser chance/lower cost of replacing it in the event I trash it, …which I am convinced is destiny – or the higher cost of a gel that I will not trash. (While I think I am very easy on batteries, evidence shows they do not seem to like me.) So, is it just math, or are there other considerations I should be looking at? If using an AGM. the YT4L-BS will give me 9 hours of GPS. Correct? Or should I be looking at double that size, like the YT6.5L 12v AGM ? I just cannot see spending 140 for something a 41 battery will do just as well for. Prior to reading your pages, I had heard of AGM s, but the information was skewed. I was told they are just like gel cells, which I now know is only a half-truth. I can clearly see the differences over wet and gel, but I am most attracted to the low replacement cost if I, indeed, trash it. Which one do you recommend? Again, thank you for the site, …and I welcome your sagacity.

BatteryStuff TechAGM batteries can be recharged with any battery charger. Gels are more fragile, and they need a charger with a safe voltage profile for charging. Gel batteries can be discharged further without the damage it would cause an AGM. We recommend no more than 50% for AGM. The Gel can go as much as 80% discharged. For your GPS/Fish Finder, I recommend a deep cycle battery. The YT4L and YT6.5L are motorcycle starting batteries. I recommend a sealed lead acid deep cycle battery. Having one at least 9 AH in capacity should give you 10 hour of safe runtime given the 300 mAh draw.

SteveThank you for your great information. It always helps to read it rather than using guess work! I do have a question for you that I hope you can help with please. I have had our motorhome for nearly 2 years and it came with a couple of solar panels – one of which is rather large. However we have had a couple of problems with cooked batteries! Basically, we discovered our battery was being cooked by one of our solar panels as the regulator was not working. We got that sorted and replaced the very smelly leisure battery. But just recently the same thing happened again and we discovered that our very large solar panel didn‘t have a regulator on it at all. We realised very quickly and disconnected the battery which was beginning to sulphar up and smell. We have since added a regulator and although the battery was able to be cleaned up we are finding that it now will take a decent charge but is only holding that charge for about 45 minutes. So we have 2 great solar panels and no holding charge. Do you think that this is due to the damaged battery or could it be something else? It is a sealed battery and so we cannot tell what state it is in internally. Thank you.

BatteryStuff TechIf the issue was sulfation, then the solution would be to try to restore the battery with an on-board pulse de-sulfator. But if the batteries have been over-charged, and they drain very quickly, then there really is nothing else you can do. Overcharging can dramatically age a battery rapidly. Can you provide some voltage readings? Say, one at rest. While on the charger. And finally, a reading 45 minutes after off the charger. With these numbers, I can more accurately diagnose the battery.

RogerA really helpful, first rate site. Thanks! My question relates to appropriate charging of an AGM (or alternatively, a Gel) battery on a vintage, generator equipped car. The generator and standard regulator setup are inadequate to operating the car with headlights AND. say, windshield wipers or heater blower. The set-point of the regulator has to be raised to 16 volts to avoid battery drain whilst driving, and so after starting, and within about 5 minutes, as the voltage reaches 16, I switch on the headlights to load the generator down to about 14.5 volts. After several hours drive, or when other loads are added, this voltage will fall below 14 volts. Is this procedure good enough to maximize the life of an AGM or Gel battery? An alternator conversion is being considered. Comparing say a Delco 10Si with a Mitsubishi that might be used for tractor or marine purposes, what should I be careful about? I am thinking of the different battery applications, tractor, marine, etc, versus the Delco regulator of 14.4 volts. Thanks.

BatteryStuff Tech16 volts is too high and will damage a gel battery. volts for an AGM is just right. If you need to charge a gel battery, a regulator will be needed to keep the voltage from exceeding 14.2. An alternator would be a good idea. Regularly pumping 16 volts in a battery will cause the internal resistance in the battery to spike and heat up. It‘s not recommended for the long run.

BatteryStuff TechNo. This will be like trying to run a gasoline car on diesel. You can either use a 6 volt panel for the car battery, or series the battery with another of identical specs to create 12 volts.

MarissaI just bought a JL 50 scooter and the battery it came with is a12. Battery which came with the liquid which instructed me to put liquid into the cells and then cap it with the plastic cap plate that came with it and then charge fully before using. I filled it with the liquid two days ago but have not been able to go buy the charger which I Plan on buying at wall art tomorrow. Last night and one time today the battery cell cap has popped open on only one cell (the last one) loud enough for me to here it ( it is in the same room with me). I am worried something is wrong, should I be concerned? Is this normal ? Is it because I squeezed the bottles when adding the liquid?

BatteryStuff TechCongratulations on the new scooter! Squeezing the battery would not be a problem. It usually takes hours for the acid to become fully absorbed. The only cause I can think of for the caps popping off is overheating. Is the battery in the garage? Did you install the vent tube that comes off the side? Something is causing the battery to build pressure, and it‘s not venting fast enough. If the liquid levels decrease, please add distilled water. But other than that, everything else should be fine. Venting is normal, but caps popping off is not. You definitely don‘t want that happening while on the road.

FranciscoHi Can I charge a wet lead acid battery SLI in paralel whit a AGM deep cycle whit only one alternator? A relay disconnect de paralel when the motor is off. Thanks

BatteryStuff TechFor a situation like yours, I recommend using a battery isolator switch, which can be used on up to 120 amp alternators to conveniently allow for adding a spare battery in your car, boat, or RV. The unit is a fully automatic switch that allows the engine alternator to charge 2 batteries, while keeping them electrically isolated from each other. This will prevent current flow from one battery to another, thus allowing each battery to be an independent power source. You can see it here: /battery-products/switches/Bi303303.html

TrevorShouldn‘t this battery be dead? Why is it working? I just bought a 12v 7.2ah Valve regulated Lead acid battery for 5.00 I tested the volts and it‘s at 12.75 a sticker reads “Top Charge Date 4/26/2007 I ran a motor from it for 2 minutes and it held up. I charged it and it took a charge. Should I run a cordless drill motor from it for as long as I can to see how long it last? Or should I leave well enough a lone? Thanks Trevor

BatteryStuff Tech12.75 is good voltage. If the battery was kept maintained fully charged, there‘s no reason not to use it as long as there‘s nothing physically wrong with the battery. Draining it down with lights, drills, motors is good, you should measure the voltage under the load to see if it holds up and doesn‘t crash. When you‘re done testing it, it‘s good to recharge it ASAP and keep it charged when you‘re not using it.

KyleIf you have a bunch of 12V deep cycle batteries paralleled (or groups of series 6‘s then paralleled to make 12V) – is it best to isolate each group so that at night the batteries are not fighting each other. I mean isolation as in commercial heavy duty battery isolators. Is this much more necessary if the bank is not typically receiving a daily charge top up (i.e. solar)?

BatteryStuff TechIf the batteries in the bank are charging and discharging together, and they are of the same type, size, and age, then there is no need to disconnect them. They act together as a single batery unit. But if the batteries are unevenly charged and/or different capacity, they will try to equalize and balance. This is can harm a small battery if connected to a large battery, which is not recommended. Different age and type of the batteries can also cause inbalance.


BatteryStuff Tech7-8 volts is extremely discharged. The batteries are probably beyond repair due to sulfation. If they cannot reach 12 volts, they‘re no use for them. I recommend replacing them. As far as which batteries to use, I suggest deep cycle batteries, not car batteries. They can be flooded…but for mobility scooters its best to use sealed batteries like AGM or Gel.

Steve TannenbaumI have a question about battery charging from a solar panel. The solar charge controller uses a mosfet to act as a switch. If the voltage on the battery increases to a certain level, then the mosfet opens and disconnects the solar panel. What happens if my solar panel puts out 24 volts instead of 15-16 volts? Will the higher voltage but lower current of the panel cause any charging problems?

BatteryStuff Tech12 volt solar panels can reach as high as 21-24 volts if the sunlight is direct. The controller should have specs regarding the maximum voltage input it can handle. Even though the controller is, like you said, a switch, it also lowers the charge voltage, too. Most of our controllers lower the voltage to a safe 14.4-14.8 volts. Therefore, 24 volts incoming from the panel is no problem for the battery.

Joshin a 24 volt system, batteries connected in series, if one battery happens to fail, should both batteries be changed regardless of whether or not the 2nd battery tests out fine? also, in the same system, if one would be required to boost the 24volt system from a another source being a 12 volt source… does one connect battery positive from boosting source to battery positive of battery require boosting, negative to negative of only one battery? This seems like it could cause a problem as battery 1 is connected to battery 2 in series which means, battery of one is connected to battery – of the second, wouldn‘t boosting cause problems?? how does one go about doing this safely to himself and the machine being boosted.

BatteryStuff TechIf one battery fails, it‘s recommended to replace both because battery banks composed of batteries of different ages will charge and discharge unevenly. With the 12 volt boost, it looks like one battery is being discharged more than another. This is a problem. The second battery, even though connected in series with the first, is untouched by the boost because the connections are only attached to the first battery. But having a 24 volt system, both batteries act as one single unit. Uneven charge levels will cause early battery failure and poor performance. I would use the boost option as sparingly as possible.

Graham BennettDear Sir,What is the best/correct proceedure when charging a 12v battery,used for a golf trolley.When fully charged,is best to keep it on charge,or remove it from the power supply? Thanks.

BatteryStuff TechThe best thing you can do for batteries is keep them in a fully charged state whenever possible. If your charging system will not overcharge, but will adjust and trickle down to a float charge, then it‘s safe to leave on indefinitely. If not, please remove after it‘s done charging.

Graham BennettMy question is,do you keep a 12volt battery(used for a golf trolley)constantly on charge,or remove from charge when fully charged?thanks.

BatteryStuff TechIt really depends on the charger you use. If it is a manual constant current charger, then I would remove the batteries after they‘re fully charged. If the unit is a Smart charger, like the 3-stage microprocessor controlled chargers we sell, then it‘s safe to leave on the battery forever. Keeping the battery in the “float mode” will ensure full charge at all times, which is the healthiest thing you can do for a battery.

TimI live in a 3rd world country. Distilled water is not available here. Can I safely use the water out of my Katydyn Filter to add back water to my starter battery? The water going in is either rain water or river water; it is not treated chemically. If it is not acceptable for the battery, what are my options for adding water to the battery? Thanks in advance!

SamDistilled water is just captured steam. If you boil water and capture/cool the stream back into water, that‘s distilled water. You can pretty easily make your own with household supplies or even camping supplies. There are several methods out there. Google “How to distill water.”

BatteryStuff TechDistilled water is best because there are no impurities. Using other water will technically work, but the battery will not perform or last we long as it would otherwise. Having foreign contaminants and minerals will throw off the delicate chemistry of the electrolyte, and throw of the pH levels, too. Filtered water will work better than rain water. But anything more than pure H20 will negatively affect the battery.

Fred HarrisGreat article, Learned much, but, and there is always a but, started looking at batteries and found the amp hour rating listed in different ways – examples: 20 amp hour rate:55 35 Amp Hour 32 Min @ 10 Amp So I am again confused about the true meaning of the amp hour. I think this is what I need to look for as I am looking for batteries for a trolling motor.

BatteryStuff TechAmp ratings are tricky. They really depend on two things: Draw amount, (Amps) and time. The first rating, 55 AH at 20 hours means that during a 20 hour load time, it takes 55 amps to discharge the battery completely. I do not know what time frame the second rating is for, possible taken at 10 hours? The third rating tells you if you draw a steady amount of 10 amps, the battery should last you 32 minutes. The first rating, 55 AH, is equivalent of 2.75 amps an hour. But if you bump it up to a rate of 10 amps per hour, your duration is drastically cut to 32 minutes. Check out our battery load run time calculator to figure out what length of time a battery would give you under a load of your choice. Plus, there‘s also an article about Pukert‘s Law, which explains all about Battery Capacity. You should find that very informational.

ArtI have two deep cycle dp24 12 volt batteries. One is rated 685 CA 32degrees and the other is 505 ca 32 degrees, the first is rated at 140 minutes and the other is 120 minutes. Can these be connected in parallel without problems? Can they also be charged in parallel using one charger?

BatteryStuff TechYes, they can be paralleled together, but it‘s not advised. It will technically work. But charging and discharging will be un-even. There‘s no way around that. If you desperately need it, I say go ahead. But in the long term there may be some issues and maybe shortened battery life as a result.

JimSounds like a similar problem we have had with one of our vehicles. It is an F350 Truck with a box that has a communications package. The truck has two batteries under the hood with green eyes. There is a third and much larger battery in the box that powers the inverters for the comms. Twice over the past 3.5 years the charging system has overheated the large battery until it failed. Last time the battery boiled over and we had a mess to clean up. The charging system is powered by a shore line that plugs into 125v wall receptacle. There has been some modifications to the systems and there is not sufficient info with the vehicle from the manufacturer that explains the 12 vots systems, but from what I understand the shore power charges all three batteries. I assume I need to check if all three are charged by the same charger. What happens to MFLA batteries if they are mixed like this?

Gary MackI have recently purchased four new US Battery 12V Deep Cycle golf cart batteries for my 2006 Club Car, which has a 48V motor. I don‘t drive the cart more than 1-2 miles on a given day but always recharge the batteries every day of use. The Club Car charger is left plugged into the cart at all times the cart is not in use. I am getting an awful smell after the meter on the charger drops to about 4 amps…on its way to zero on the charging cycle. I can hear the electrolyte bubbling inside the batteries and they do not get hot whatsoever. Once the meter reads zero amps and the charging cycle has ended, the smell stops. Is this normal? Factory personnel tell me they will always smell when recharging….but I have never experienced this with former Trojan (Club Car) batteries. The local dealer says the smell should stop shortly…otherwise there may be a problem with one of the new batteries. My voltmeter shows 12.7v in each of the four batteries after charging.

BatteryStuff TechSome bubbling and smell of sulfur is normal for large flooded batteries. 12.7 volts is good voltage. As long as you monitor the water levels, it sounds like everything else is fine. If the electrolyte boils over, or completely evaporates, that‘s a problem.

CarlosI have four 110AH leisure batteries for my small hybrid solar system. The batteries are all 2yrs old and are not holding their charge like they once did. I read somewhere that I could empty and wash them out then replace with a mixture of sulphuric acid(96%) with distilled water to the correct gravity, put them on a trickle charge for 36hrs and then they will be better than new… Is this true? And if so, how can I be sure my mixture is correct? I do have a basic hydrometer. Many thanks!

BatteryStuff TechWe strongly advise against emptying out the electrolyte. Bad batteries are not a result of the electrolyte being “bad”, but usually there is a build up of sulfation on the plates in the cells. When exposed to oxygen, the sulfation will rapidly increase. Putting new acid sounds nice, but here‘s the problem. Sulfation is like trying to wash your hands while wearing gloves. You still won‘t see a full charge. On top of that, if you remove the sulfation from the plates using a pulse charger/unit, then it will become electrolyte and throw off your pH levels again when mixed with the new stuff. It‘s safer to simply use a de-sulfation unit like Battery MINDer or Pulse Tech for an extended period of time. That‘s what we do.

Timothy LeeI have a 12V marine deep cycle battery which is marked 875 marine cranking amps, 675 cold cranking amps, and 125 amp hours. I have been using the battery on my boat for about two years since I purchased it. It was charged every couple of months by either running the engine (a 9.9 HP outboard with an alternator which puts out less than 10 amps at full throttle) or by using a regular car battery charger with a pulsating charge of 10 amps(duty cycle= 10 sec. on, 140 sec. off). It only serves the bilge pump when the boat is not in use, and the pump only runs a few times a day for a few seconds. After not checking it for about two months, I found that my battery was not working (boat bilge was flooded) so I brought the battery out of the boat to my house. Prior to charging, it read about 6 volts on the meter, and it was low on water. Each cell had about 1/4 in. of the cell showing, and I added about 4 oz. of distilled water to each cell. I charged it for about 50 hours with the 10 amp charger, and after reading your article, I changed to a 1 amp charger. I now have access to a hydrometer, and I will stop the 1 amp charge tomorrow morning, and let the battery set for a while before checking with volt meter and hydrometer. The 10 amp charger still reads about 9 amps on its meter when charging, and immediately after I disconnected it, the voltmeter showed 12.46 volts. All cells were bubbling, and the battery was warm, about 100 F. What have I done wrong so far? Could I have damaged the battery? Do you think it will recover from the deep discharge?

BatteryStuff Tech12.46 volts is good progress. You probably won‘t be able to see a full charge because of sulfation build up. It‘s like trying to wash your hands while wearing gloves. I don‘t believe the battery is beyond repair, but I strongly recommend a desulfator or charger with desulfation pulse mode (not voltage pulse, like some chargers do). Try a Battery MINDer or Pulse Tech unit.

BatteryStuff TechYes, but not fully. Proper charging requires inputting a higher voltage in order to bring up the battery voltage. For example, if your 12 volt battery is reading less than 6 volts, you can use a 6 volt charger to bring it up to 6.6 volts. At this point you may use an 8 volt charger. But a 12 volt battery reading less than 10 volts is still EXTREMEMLY discharged, and should be brought back ASAP to avoid sulfation and decreased battery life. Please use a 12 volt charger, or make sure the charging system in your application is strong enough, usually 14.6 volts is normal.

VinceI have a cpep that uses 2.2 amp I need to run it of a deep cell and a inverter for 8 hour for camping what what size inverter and deep cell battery would I need?

BatteryStuff TechPlease use our online calculators to find the answer. They are located at /kb/tools/ and they are very easy to use.

Justini have a 12 volt trolling motor and i just purchased an optima bluetop battery. These batteries are marketed as being dual purpose (deep cycle and cranking). is it possible to connect two 12 volt batteries to power my trolling motor (i want to be on the water as long as possible) and if so could i than use one of those 12 volt optima blue top dual purpose batteries as my cranking battery for my engine? if any of this sounds dumb im sorry im very new to boating and im trying to figure all this out.

BatteryStuff TechDeep Cycle batteries have a CCA rating as well. If you have a starting battery and a deep cycle battery of the same physical size, the starting battery will have far more CCA. It has to do the the thickness and number of the plates per cell. But if you have a large marine battery, there‘s a good chance there will be enough CCA to turn over your engine. It‘s not unheard of. There‘s no harm in trying it out. It will either work or it won‘t.

Kamran JabbarWhen we use two batteries 12V each in a 24V system connected in parallel. There will be a possibility of unbalancing if both the batteries have different manufacturing date or batch. The charger only knows to charge 24V even if one battery is at 14 and other one is at 10. So it is thumb rule always connect same batch batteries in series and never replace one battery in a series. Replace the whole bank to avoid unbalancing. Unbalancing can damage one battery earlier than expected life.

YloonI have been charging my dead battery for 4 months using pulsetech Smart charger. This dead battery has been leaving there for 1 year. I got back my voltage of 13.7v and the Smart charger is pulsing without mass charging for 1 week. However the battery still unable to start my car. The battery can supply headlight, horn and etc. Should i give up this battery or any other way to try it out? I notice 1 of the electrolyte‘s in a cell is not drying up even after a long charge. the other cells always keep drying up and require to top up with battery water. Is the cell dead and cannot be revive anymore? thanks.

BatteryStuff TechPlease refer to our article about Battery Troubleshooting. As far as battery water goes, as long as it‘s distilled water, that‘s fine.

S.My husband just added acid instead of distilled water to my motorcycle battery after it had been sitting all winter. Is it ruined?

BatteryStuff TechPossibly. The sulfuric acid never leaves the battery, it‘s only the water that evaporates and needs replenishment. If more acid was put in, the pH levels are probably out of balance. The battery may still work, you should test it before going on the road with it.

JimOff the beaten track but several years ago my Dad bought me a 16V Craftsman drill. I used it a couple times and put it in the garage. Recently I was cleaning up and found that drill but the battery was dead and refused to take a charge no matter what. A new battery (when they can be found) is 55 plus. Do you know of any way to get this battery working again? Thanks.

BatteryStuff TechWe sell a variety of power tool replacement batteries. You can view our selection at /batteries/power-tool-batteries/ Rebuilding a power tool battery pack will run around 30-35 and up. We will be offering battery rebuilding in the near future.

Jack GilbertGreat info, my battery died today, so, the AAA guy said that my old battery was below 12.5 volts and that it wouldn‘t have or hold the amps?? what does this mean

BatteryStuff Tech12.5 volts is partially discharged, 70% capacity remaining. When a battery is put under a load and there are no “amps” going through, it‘s usually a result of an open cell. The intense heat of a load can cause a separation in a cell connector, and this will cause current to decline or cease entirely. But when the load if taken off, the metal cools enough to touch and give a false voltage reading. It‘s very misleading and a result of poor construction at the factory level.

Trevi might have missed this in the article but, why is it not recommended to mix battery sizes, and not to mix battery types? cheers

BatteryStuff TechBatteries of different types and sizes will charge and discharge unevenly. When batteries are configured in parallel or series (or both) they behave as a single unit. If there is an imbalance it could mean a shortening of overall battery life, as well as potential harm in recharging.

DaveI have a question. I purchased a Minn Kota Endura 50 trolling motor 2nd hand. It‘s for an aluminum fishing boat I have access to once a year for a week. I‘m a casual fisherman who takes the boat out maybe for an hour a day. I bought a deep cycle AGM 12 Volt 12 amp hour with a charger for agm and gel batteries. I had trouble finding what kind of draw the trolling motor places on the battery at the Minn Kota site. Did I buy an undersized battery for my causal usage?

BatteryStuff TechSpeaking from experience with other customers with trolling motors, I can‘t imagine the motor pulling anything less than 15 amps/hour from the battery. A 12 AH battery would not be able to supply more than 1/2 hour of power to the motor, if even that much. A larger capacity deep cycle battery would be highly recommened.

DaveI was afraid of that. Any suggestions as to what would fill my needs but would not be overbuying for what I do? I see some of the deep cycles run 400 or more. I don‘t think I need that much power. Thanks for your reply. Obviously I‘m new to making these calculations and a little leery of just walking into a store and having them sell me something.

BatteryStuff TechIf the motor drew at a rate of 15 amps an hour, I recommend using a group size 24 marine battery. This 12 volt, ~75 Amp Hour battery should give you 2 hours of uninterrupted runtime, and only discharge the battery to the safe 50% capacity remaining. We sell these batteries for 200-250.

BillHello, I asked a question a few weeks ago and have been looking for a reply. My question is about running LED lights on a 12v vs a 24 volt system. I have 17 lights that are 27 watts each and want to get the maximum runtime. I have seen your calculators but do not have all the imput parameters. The batteries I am thinking about are deep cycle with 210 reserve capacity. Thanks.

BatteryStuff TechMy question is this: what voltage are those lights rated for? If it doesn‘t say on the lights, you should find out by calling the maker. It‘s important to keep the voltage the same. Running a 12 volt rated LED light bulb will blow up if you use 24 volts (2 batteries in series). Maximum runtime is ensured not my increasing the volatge amount, but the capacity (Amp Hours).

FrankVirgin lead vs. recycled lead? Is there a life span difference between batteries constructed with virgin lead compared to one made with recycled batteries, assuming that all other conditions are equal? If there is a difference, is it a noticeable one?

BatteryStuff TechYes. Batteries made from virgin-lead perform better and will last longer. High performance batteries, such as Odyssey, also have 2 year warranties.

BudgeI have a 12 volt portable battery (Sears Diehard Portable Power 1150) that I use for car camping trips and the occasional jumpstart. I wasn‘t keeping it charged all the time and the battery finally wouldn‘t take a charge anymore. So I was convinced to replaced it with a deep cycle agm battery. After reading your article, it seems apparent that I should not have used a deep cycle because it‘s not appropriate for jumpstarts. However, I have also found that after the first time I used the battery for a weekend of camping, I had drained it down to 10% and now it will not charge. Is it possible that the unit is not compatible with deep cycle batteries, or is it more likely that I overdrained it and the unit isn‘t registering a battery to charge? I was told that I can connect this unit to my car battery (or any other charged 12 volt battery) and that should trick the unit into charging the battery. What do you think?

BatteryStuff TechDeep Cycle batteries have CCA ratings as well. However, for the same physical size battery, if you compare it to a starting battery, the CCA will be much less. But a deep cycle battery is fairly common in jumpstarts because they are also used as 12 volt power sources and some even have built in inverters for AC power. The batteries in the units are large enough where the CCA can jump start a car. In doing so, 25% of the battery‘s capacity can be drained just like that. If batteries read severely low voltage, most automatic chargers have trouble charging. Connecting another battery in parallel with the drained battery is a good method of bypassing the “low voltage disconnect” filter of the charger.

TomLots of good stuff here—-and well written so that weekend mechanics like me can understand it. I have a 36v Western Golf Car with 2 year old batteries. The charger came with the car and I recharge after every use. None-the-less, two cells have failed on each of two of the batteries. Your article recommended that I should not ‘mix and match’ batteries, but I would like to replace the two failing batteries with new ones to get another year or so out of the remaining 4 old batteries. They cost about 125 each so my fix would invest 250 now to stave off a 750 pay out for another year. Bottom line: If I follow your advice, I replace all batteries at the same time and chuck 4 fairly good batteries (with no resale value). Is there a middle ground—-such as using some of your products to bring the two batteries back to service??

BatteryStuff TechThe choice is yours. The reason we recommend using batteries of the same age is because you will see overall better performance and lifespan of the whole bank if you do this. But if you feel it‘s not practical, you buying 2 new batteries will make your bank work and it might be just fine for you. It‘s not optimal, but it makes more sense. If your old batteries have shot cells, there is no product that can reverse that.

ChadExcellent information. Thanks. Just bought a DieHard Platinum Marine Group 31 for my boat. The reviews on this battery are excellent and I plan to use it for both starting the boat and running the trolling motor. You mentioned needing a special charger for AGM batteries. I have a Stanley BC4009 40 amp 3 stage charger. Is this charger OK to use with the AGM battery? Do I have to disconnect the battery from the power cables to charge it? Thanks for your help!

BatteryStuff TechAGM Batteries can be charged with most standard chargers. It‘s the Gel batteries that require a special charge profile. If you charge your battery, you don‘t have to disconnect the power cables as long as the battery isn‘t being used while you charge it, unless your charger is also a power supply. If you draw on the battery while the charger is turned on, the charger will attempt to supply the demand.

JohnWell then, if a modern automobile with all it‘s current drawing electronics is to be charged using a Smart charger, are you suggesting that the cables be disconnected while charging the battery? What difference would it make if cables were left on during the charging process? Thanx

BatteryStuff TechHaving the battery connected to the vehicle will cause a slight discharge as a result of the electronics. But normally it‘s not much. A charger will stil charge just fine but if the draw amount of the car is excessive, it can cause the charger to become less efficient.

BobbyA very useful site, and highly informative – well done! I have two flooded lead acid for my domestic bank, and have added a small AGM for the engine start. The mains charger can be configured for one type or the other – in my situation would it be better to set the charger to AGM type? bob

BatteryStuff TechFrom our experience, Flooded and AGM batteries can be charged at the same charge voltages. It should be safe either way.

RichJames, I have a boat with 2 cyl diesel engine and currently 2 series 27 wet batteries set as two banks. I would like to add another 2 batteries because the engine does not start easily when cold. The question is whether it is advisable to mix AGM ‘s as one bank with wet cells as the other. I would like to change to AGM ‘s, but hate to lose the investment already made in the two wet batteries. For starting, I do have a standard A/B or BOTH as a switching option for the banks.

James VilleWhen constructing battery banks, it‘s highly recommened to use batteries of the same type (Flooded, AGM. Gel), voltage, AH rating, and even age. Although you can technically build your banks by adding AGM batteries, having these differences will cause an inbalance of discharge and recharging.

Bill SmithThank you for that info. Well meaning folks online were driving me nuts telling me that a deep cycle battery that is often discharged to 50 percent will greatly shorten the life of a small alternator. But I couldn‘t find any info like that at a reputable web site and I‘m glad to hear it isn‘t really true. I had been looking at a VSR (voltage sensitive relay) for the part of the wiring you mentioned. These (I guess they are all the same) charge the starting battery first and then switch the charging current to the auxiliary battery. Does the isolator you mentioned work that way? If not, which method do you think is best. I know the companies that make the VSR devices are always touting the fact that there is no voltage drop with their devices which I gather there is with a device that uses a solenoid.

Andrew D-HAwesome article – thanks. I have a question. I have a YP17-12 (12V17AH) Maintenance Free Lead Acid battery in my Bushranger Power Tank (for jump starting). It‘s was showing over 12 volts after about 10 hours at 1 amp. I tried to load test (it failed) and it‘s now just under 12 volts. It has a plastic strip which when I popped it off with a screwdriver there were little caps on each filling hole. Can I add distilled water to it even if it had gel. I up-ended it with caps off over a container and not a single drop of liquid came out making me think it is not a wet acid type. Your thoughts would be greatly appreciated.

James VilleIf the battery is indeed maintenance free, it is not designed to be opened and water added. Low voltage is not a result of low fluid levels, in this case. A fully charged battery should read 13.2-12.8 volts. If you read 12.0 or 12.2 volts, that‘s severely discharged. If you load test at this poin, you‘ll only further discharge the battery. I recommend putting the battery on a charger immediately and load testing once it‘s fully charged. If the battery is draining rapidly in 10 hours at 1 amp, I recommend you use our online tools to calculate if that‘s a good size battery for that amount of draw, or if the draw time should be shortened for the sake of the battery. /kb/tools/

ShawnThe article above suggests you know what you‘re talking about. I don‘t know jack, but have read a little online and am trying to use a deep-cycle battery to power a projector for a public art project. Any chance you‘re available to help me trouble-shoot? I borrowed a neighbor‘s charger and charged a brand new battery up for about 15 hours. I then hooked up a 1000watt inverter and plugged the projector in. It worked great, for about 25 minutes, but then just died with a Low Voltage error message. Does this mean the battery wasn‘t charged all the way or am I doing something else wrong? According to the projector specs, the max wattage it uses is 288. Would really appreciate any input you‘ve got. I‘m out of my league here.

James VilleBased on the information you provided, you‘re drawing around 23 amps from a 12 volt battery. That‘s a lot of juice since it‘s a constant draw, not a quick burst. Without any information about the battey itself, or the charger, I cannot determine what the problem was. If the battery did not have the capacity to handle the load, you may need something with more AH (Amp Hours). It might be helpful if you run your numbers through our calculators. /kb/tools/ Or give our tech guys a call at 541-474-4421

CainHi, I only use my car on weekends. My question is: Can I use a Smart Charger whenever the car is stopped? This will not overcharge the battery? My car has an AGM battery. Thanks in advance for your help.

James VilleIf you use an AC charger, parking the car and turning off the engine is fine. If you are refereing to a solar charger, it‘s also designed to charge the battery, not only when the car is stopped, but the engine is off as well. Plugging a Smart charger on the car during the weekdays is very healthy for the battery. No overcharging if you make sure the charger is fully automatic. Our chargers are. 🙂

Bill SmithThank you for the excellent article and taking the time to answer everyone‘s questions. I want to install a dual battery system in a small car that has an 80 amp alternator. The 2nd battery will be dedicated to one appliance that has a low current draw. A small deep cycle AGM like those used in mobility scooters will do the trick (about 35 Ah). I don‘t want to upgrade the alternator but I also don‘t want to overly stress the one I‘ve got by having it regularly recharge a battery that is often going to be drained close to max (50 percent). Is there a way that I can limit the current to the second battery so that it charges at 10 to 15 amps? That would be equivalent to driving with lights on and so I know it would not have a big negative effect on the alternator as long as I am not using the lights.

James VilleIf you want to charge your vehicle‘s starting battery as well as a separate auxiliary battery, I recommend using the Battery Isolator Switch (Bi303303). Having a 35 AH spare battery should not be too much for your 80 amp alternator. It‘s an automatic device, there is no “preset” amperage setting. The charge allocated to the batteries really depends on the status of each one. With the rise in resistance in one battery, charge will be directed to the other until they are both stable and full.

Garyhave a 6 volt dry cell batt. in a old bike. is there a way of protecting the batt. from being over charged? thank you for your time.

James VilleThe best method to preventing battery from being overcharged is to use a micro-proccessor controlled “Smart” automatic battery charger. If the bike itself is over-charging, then there is a problem with the bike‘s charging system, the stator.

Toni RoddeyFantastic information. Thanks so much for your service to those of us struggling to understand through all the hype. My question is for a marine application. I have a bank of 4 Trojan lead acid batteries for my house bank and another lead acid starter battery. My starter battery died and I‘d like to replace it with a maintanence-free option but have heard not to mix battery types. I‘m not ready to replace the Trojans, so should I just buy another lead-acid starter to tide me over until my Trojans die? Thanks for any suggestions you can give.

James VilleIf your starter battery is not connected to the house bank, then it‘s fine to upgrade it to a sealed type. You can even use the same charger if you go with an AGM. Within a battery bank it‘s recommended to use the same battery type. Because your boat draws from the house bank and the starting batteries separately, then you‘re okay.

Jummyhello Jamie, I am currently working on a research about Solar- hybrid off-grid instalations, I have my battery amp hour for 20hrs discharge but i need the battery to store enuf cahrge for 3 days, so ut is trippled, do i still use the C20 rating or do i use the C72hrs rating for it? i am confused. and the needed Current is about 6000Amp-hour

James VilleIf you parallel your batteries, the capacity (AH) will increase. The rating will still be at 20 hrs, but the number will triple. If you have your batteries and draw amount, please use our battery calculators to help you figure out how long they will last, or if you need another battery based on your load. /kb/tools/

Mel SchallotVery good overview of lead-acid batteries. How do I submit a question? What type of sealed lead-acid battery would a handicap scooter likely have: AGM or Gel? I need to know in order to select the right charging mode for a Schauer automatic charger.

James VilleMobility Scooters use both AGM and Gel batteries. I cannot verify what you have. However, if you‘re unsure, I recommend using the Gel setting. This is a lower voltage that is safe for gel, but the AGM will accept it also. It‘s the other way around that is not recommended.

PhyleusWonderful article. Just had a question though. How does one test SMF batteries on-site for e.g. Server UPS batteries. ? The test-gig should be portable though.

James VilleWhat do you need to test for? Voltage readings with a volt meter is always helpful. This gives you a good idea of the state of charge of the batteries. A Load tester is good for measuring CCA and durability under a load. Even our comprehensive digital battery conductance analyzer is portable. All of our testing units are located in the Battery Accessories category on our website. See for yourself. 🙂

Greg WhiteJames, this is a great site! Maybe you can help me: I have 3 8D AGM marine batteries on my boat with a xantrex charging system. The boatyard said they would plug the boat in over the winter in the warehouse but did not. Nor did they shut the breakers off. So, the batteries were depleted to zero over the last 5 months. How can I tell what damage was done? How can I calculate the liability the boatyard has?

Knobby Ionshi all i bought a AGM battery for my kawasaki vn 1500, great more ca,s no probs with it until i went overseas to work and made the mistake of leaving the ignition switch turned to park!, THIS in turn left the rear lamp illuminated, returned back home 6 weeks later ZILCH ,visited my local bike guru in redcar he put slow charges, then fast charges into it over a period of two days, its gone from an initial reading of 0.3 v to a steady 12.9, hope this helps the guy with the boat.

BatteryStuff TechHey, that‘s great that your batteries came back! 12.9 is very good voltage. Thanks for sharing!

James VilleWhile it‘s difficult to quantify the damage, I have some recommendations. First, you should take a voltage reading from the batteries. If indeed you‘re reading 0 volts (which is unlikely) then I would try to charge them with a low voltage start charger ASAP. Most automatic chargers have a cut-off voltage of 6.5 volts before they will start. This prevents you from bringing back severely discharged batteries. Interacter makes a charger that starts charging with a reading as low a 1-2 volts. Second, sulfation has most definitely occurred, so I would also advise putting a de-sulfator unit on the batteries as well, such as the OBD12V. If these do not bring the battery back to working condition, then I would suggest the batteries have passed the point of no return.

EagleyeThank you James, for all the great information! Ive got an electric scooter (xtreme xb-600) and need to replace the 12v22ah SLA. Ive looked around and was told that the EVX12200 or EVH12240 Deep Cycle Battery would be the way to go. Your opinion would be muched valued and appreciated!

James VilleYes, those batteries will work as they are the same dimensions as any 12 volt 22 AH SLA Battery. The difference between the EVX12200 and the EVH12240 is AH rating. The higher the AH, the more runtime you‘ll have.

Rick EcholsHi, I have four 6 volt house batteries for my RV. We do some warm weather dry camping. How low should I let the voltage drop before recharging with the generator? Thanks, Rick

James VilleLead Acid Batteries, doesn‘t matter the voltage, should never be left to drop in voltage. That is only common practice with NiCD batteries. Discharging your batteries severely before recharging them will cause sulfation and early battery failure. The healthiest thing to do is keep them fully charged as often as possible.

Rick EcholsSo how can I expect to be able to use my house batteries for dry camping without losing any voltage? I would think that I should be able to use my lights inside and radio without runnung my generator. I don‘t want to have to run my generator all the time.

James VilleLosing voltage is normal. Good battery maintenance is as follows: Re-charge battery at the soonest possible after using the battery. When drawing from the battery, avoid discharging below 50% capacity. This is the danger of having a battery sit in storage for months at a time. You will see early battery failure. Charging regularly or keeping a trickle charger is the best solution. Surely batteries are meant to be used. But the myth of “battery memory” does not apply to lead acid batteries. It is not healthy, and unnecessary, to discharge all the way and recharge again.

John PaciorekI have a Sportster scooter which is seven years old and has two 12V deep cell GEL type batteries. It has been used very little. These batteries won‘t take a charge. When I disconnect them to read the voltage I get 11 volts on one and 13 volts on the other. Gel types (80AH) for this unit are super expensive. (1)Could I try to replace the 11 volt battery only, presuming its a dead cell? (2)Would you recommend that I replace these batteries with two AGM batteries with a comparable AH rating? Can I use the same charger on these batteries? (3) Any other way out of this dilemma, such as using a maintenance-free lead acid battery with a comparable AH? Thanks very much, John Thanks very much

RangerHow is that one would determine that an 11 volt reading is not associated with a shorted cell?

BatteryStuff Tech11 volts cannot be a short cell, as each cell can read 2 volts or more. Therefore, a battery with a short cell typically reads 10.5 volts or less. But an open cell is different. This has to do with a weld piece disconnecting under the load, and voltage usually drops significantly or sometimes flatlines when this happens.

James Ville1) If you‘re reading 11 volts, there is no short or dead cell. It‘s much less expensive purchasing a de-sulfator unit to restore the battery than to buy a new one. If the batteries are still holding a charge, they can be restored. 2) If you do decide to upgrade to AGM. your Gel charger will work. Commonly, AGM batteries charge best at a higher voltage, but those chargers would damage the Gel. 3) When creating a battery bank, it‘s recommended to use batteries of the same voltage, AH rating, and type. 80AH AGM batteries will work for your system just fine, but good battery maintenance is still recommended, regardless of the battery chemistry type.

Tom ZI have an interesting battery question for AGM battery charging. I recently purchased a 12 volt 7 amp battery for my roboduck, I used my older 1/2 amp charger adn about two hours later, I noticed the battery had a puddle of clear water around it‘s base. It was acid! How on earth could a glass matt battery generate that much fluid (about 1/4 cup). I did nto even think there was that much fluid in the battery! What is going on?

James Villespan AGM batteries are sealed. If there is a large pool of electrolyte, there must be an opening in the case. If the liquid is not coming from the ventilation holes on the top, there must be physical damage elsewhere, possible near the base. The electrolyte in the battery is absorbed, but it can be forced out if there is enough pressure in the case or if it hasn‘t had time to fully absorb (for instance, it if was a freshly activated battery).

YancyI‘m shopping for a couple of off-grid batteries. I‘m curious when purchasing a new battery, what is the typical warranty length, in case you bought a dud that was sitting in the heat in storage for 12 months. Thanks, great info BTW

James VilleAll of our batteries have their warranties listed on the product pages. Typical warranties start at 1 year for most of our powersports batteries. Shorai and Odyssey high performance batteries have 2 year warranties.

John CGreat informative article. Just wondered if you or any of your readers have experienced or heard of problems with BMW automobile batteries? This is a well know and documented issue by many BMW owners and dealers? Due to the inordinate number of battery life failures BMW no longer honors their new car battery warranty. By downloading historical information from the automobile‘s computer the dealer will look for any excuse for blaming the problem on the car owner, e.g., leaving the door open, leaving the key in the car, or not driving the car for several weeks. It seems to me that BMW has a problem with parasitic drain on their cars from about the time that the 2008 models came out. The car computer remains active when the engine is off, still controlling functions that I cannot explain. BMW has not compensated for this parasitic drain by installing a heaver duty (more Amp Hours) battery. I can‘t believe their engineers are this ignorant. An easy saluting would be to parallel two batteries but this would increase the cost of the vehicle by several hundred dollars. That is probably why BMW has taken no action to correct the problem. It is possible that other automobile manufacturers have similar problems. My opinion is that if new batteries cannot be designed to compensate for the heavy parasitic drain then the manufactures need to install two parallel batteries or come up with procedures to connect an external battery trickle changer when the car is parked overnight.

Keith Vandereespan BMW cars and some Mercedes Benz have had issues with on board computers,after disconnecting the engine heater wiring and computer reset the problem was solved. Disconnect the battery,disconnect the heater wiring at engine, reconnect battery, turn on ignition 20 seconds, turn off. Then start engine, if no startyou have to reconnect the wiring on some models warning fault light will stay on for some time. Our workshop solved most problems. Over sophisticated temp (seats, engine) and security sensors and free radical computer connections can create the power use problem. If you can find a reset button/or code it helps.

James VilleThat‘s a good suggestion. A Trickle Charger is the best step to take in extending the life of the battery. It‘s less expensive than a new battery, that‘s for sure.

ToddI am purchasing a 125 watt solar panel and want to purchase two 12 volt RV batteries.I dry camp alot and want to be able to maximize my reserve capacity using the solar charging to replenish the drain on the batteries. My question is what size battery re the 20 hr amp rating would you recommend using two twelves and AGM or Gel? I do not winter camp so majority of use is April to Oct. Apprecite your expertise. Thanks TP

James VilleIf want to size the batteries, you will need to know your load amount. If you have this, please use our Sizing a 12 Volt Battery to a Load Calculator found here: /kb/tools/calculator-sizing-a-battery-to-a-load.html If your solar controller has a gel profile, then having a gel battery is not a problem. They can deep discharge better than AGM. but are more expensive.

ZI have a few questions about sulfation removal. 1. How can a person determine how much sulfation has occurred inside a battery? 2. Which de-sulfation device do you most highly recommend to remove sulfation from battery plates? 3. How much time is required to fully de-desulfate a battery? If the de-sulfation device isn‘t capable of fully de-sulfating a battery, can you let me know how much de-sulfation such a device can provide. Thx, Z

James1)There is no exact way to determine the amount of sulfation, but a hydrometer is helpful. By telling the specific gravity, you can determine the strength of the electrolyte. Typically, the more sulfation on the plates, the weaker the strength of electrolyte. If you have sealed batteries, a hydrometer will not work. 2)If you have a flooded battery, I recommend using Battery Equalizer in conjunction with a pulsing charging, such as Battery MIND er or PulseTech. Exact model will depend on the capacity of your battery. 3)You’ll see the most dramatic results after about 2 weeks of continuous pulsing. The harder, crystallized sulfate which took a long time to build up may take an additional 2 months before reaching a another restore point. On average, a de-sulfated battery may be restored up to 80% of its original factory capacity.

Kris Fhey, i am trying to charge 2 deep cycles in parallel with a 6 amp charger (12v) is this any diffrent than charging a single?

JamesWhen you charge 2 deep cycle batteries in parallel, you’ve essentially doubled your capacity. The charger will recognize your battery bank as a single battery. If your 6 amp charger took 4 hours to charge one battery, it will now take 8 to charge both. The resistance has increased with the increase in capacity, so it will take longer to charge. As for the connections, you can hook your charger to the positive and negative terminal from one battery or both. For a 2 battery system, it doesn’t make a difference.

Paul“The resistance has increased with the increase in capacity,” Not so, resistances in parallel decrease. It takes longer to charge because you are charging two batteries at the same time instead of one.

BatteryStuff TechResistance is based on the internal battery chemistry. It‘s not constant, but it relates to the strength of the charge rate versus the state of charge in the batteries. Two batteries in parallel will indeed lower the resistance. The charge time may not be quicker, but it will be more efficient.

Denise Keilholtzhi I am extremely interested in the subject and would like to thank you for clearing up a few things that i had previously not known.

Bob GTwo weeks ago I purchased a new car Buick Enclave that had been on the lot for an extended period of time. Everything seemed to be fine until I took a long trip (10hrs). The next morning I used the remote start to warm up the car then turned it off and continued to load the car using the remote hatch lift several times. About ten minutes later I got in the car and didn‘t have enough battery to start it. I was able to get a boost to start the engine and return home (10hrs). I took the car to the dealer the next morning to have it checked out and was told the battery was good as it checked out at 12.3 volts. Doesn‘t that show a discharged battery? Should the charging system maintain the battery at 12.6 to 12.8 volts? The next step is to have the electrical output checked. I would appreciate your input as to what I should have them check next. Thanks

James VilleHello Bob, You are correct. The battery should be reading more than 12.3 volts. If the battery cannot reach over 12.6 volts, then there is likely a sulfation problem. the more sulfation on the plates, the less surface area. in turn, that results to less power and pre-mature failure.

Lester CheeksOptimum battery voltage is 12.6 volts at 70 farenheit. Specific gravity and voltage will drop with temperature. 12.3 is a good voltage. What the battery loads down to is more important.

BertHi, I have an older 4 ×4 truck with no electronics. However, I have an inverter to power (mainly laptops, gadgets), two external lights but no winch. My current alternator is rated at 75amps and my current battery at 80ams / CCA 780 / CR 120. I want to install a split batteyr system (solenoidmonitor) along with another batter (same power or slightly higher). Do I need to upgrade my alternator. say to a 100 amps? Can a 75amp alternator comfortably charge both batteries.given than I‘m using a “Smart” split battery charging system? or am I asking for trouble….ie: a dead alternator? Thanks

JeremyYou would be best off going with the larger alternator. 75 amps may be enough, but upgrading to the 100 amp system would make sense.

JAYANTIVery important article on rechargeable batteries. We are planning to install Lead Gel batteries in our AS/RS equipments. Shall we go for Lead Gel or AGM type of batteries ? Why ? Give us advantages in terms of cost safety while selecting the type of battery. Pls help us to decide. thanks

James VilleHello, Gel and AGM batteries are both nice because of the maintenance free nature and sealed case. The Gels are able to deep discharge better (well, with less negative effects than the AGM ). However, the Gel battery requires a compatible charger/regulator. Normal wet cels and AGM batteries effectively charge at 14.6 volts or higher. But the Gel battery should be no more than 14.2 volts. It really does make a difference. They are more fragile and can be damaged easier when charging. For more information, please read GEL Vs. AGM. /kb/battery-articles/gel-vs-agm.html

Johnif i could rate your article out of ten, i would give it ten. very informative alas i did not solve my problem what is the method of getting a rechargable battery to hold charge, will short overcharging periods do the trick?

JamesIf you‘re referring to a rechargeable lead acid battery, then there could be many reasons why a battery does not “hold a charge”. There could be a parasitic drain. There could be a short or open cell. There could be an internal defect such as a weak weld. Or the battery could simply be deeply discharged, and if you‘re using a Smart charger, find that the charger simply will not charge the dead battery. This is primarily due to the low voltage safety disconnect found in most microprocessor controlled chargers.

LarryIs it possible to have 12 volts from a battery and low or weak cca ? Also tell me if im thinking wrong. but I have theory. that a battery is allot like your arm. you arm has the 12 volts and the muscles in your arm potentially are your amps. you can with stand holding weight for a certain amount of time until you become weak and need to relax for a few moments before you can “crank” again. would you say that would be a good example if i were to try and explain how a battery functions to people who don‘t speak english ?

JamesThat is a good example, yes. Some arms have less muscle mass and others have more. But all the same number of muscles in the arm. 12 volt batteries all have 6 cells. Each cell is 2 volts. 2 × 6 = 12. But the cells have plates inside of them. The more plates, the more current can run through, thus more CCA. Large and small batteries all have 6 cells, but the size and number of plates can vary greatly. I hope this helps.

John HackneyOver the last 40 years I have puchased endless numbers of leisure batteries for my caravans none have ever lasted more than 12 mounths althouth I have charged them regularly.My latest one has just failed after 6 mounths and the manufacturers stamp 15 indicates January 2005 surerly this must be one of the reasons they do not last the coarse.I have found out more about batteries since reading Battery Stuff.com although I am a retired motor engineer,Well Done.

Eric Robertshi this is a common problem, many battery manufacturers make batteries that they claim are leisure batteries. the advice i will give is that you should buy a battery with the largest amps as possible that will fit in the space that you have, in my opinion you should buy an AGM battery as this will discharge and recover better after use, they are more expensive but should last much longer. thanks eric roberts www.batteriesontheweb.co.uk

Jamiespan AGM batteries do not last much longer than lead acid batteries, if they last an longer at all.

BatteryStuff TechAGM technology is essentially the same as a lead acid battery. The only difference is the electrolyte is not free to spill, but absorbed. This eliminates the need to maintain fluid levels, thus preventing a lot of premature failure caused by reflectance. But maintenance free does not mean the freedom from having to charge regularly. All lead acid batteries self discharge, and the best way to see longest life is to keep fully charged as often as possible. Maybe you‘ve had some bad experiences with AGM batteries. That‘s unfortunate.

SergioAgreed, if properly maintained, a wet battery will last just about as long as an AGM battery. BUT. very few people actually do the proper maintenance. Because AGM batteries are valve-regulated, have a slower self-discharge rate, recharg faster, etc, etc, they are more resilient than wet batteries and therefore, in real world use DO last much longer than wet batteries.

Keith ClemensJust to let you know that your battery basics piece was well written and useful. I appreciate your hard work and your passion for your subject.

JamesIf you have 2 batteries in series, the voltage increases. The most common form of 24 volt systems involves two 12 volt batteries connected together, a wire from the positive terminal of one battery to the negative on the other. For more information about constructing battery banks, read this helpful article. /kb/articles/battery-articles/battery-bank-tutorial.html If you have a 24 volt charger, you must treat your two 12 volt batteries as if they were a single battery. The open terminals on both ends would be the required positive and negative access points.

DesmondThis is just what I need to give me confidence in dealing with a battery issue. Much appreciated.

Wire Sizing Chart for 12V, 24V, and 48V DC Systems

Properly sized wire can make the difference between inadequate and full charging of a battery system, between dim and bright lights, and between feeble and full performance of tools and appliances. Designers of low voltage power circuits are often unaware of the implications of voltage drop and wire size.

In conventional home electrical systems (120/240VAC), wire is sized primarily for safe amperage carrying capacity (ampacity). The overriding concern is fire safety. In low voltage systems (12, 24, 48VDC) the overriding concern is power loss. Wire must not be sized merely for the ampacity, because there is less tolerance for voltage drop (except for very short runs). For example, a 1V drop from 12V causes 10 times the power loss of 1V drop from 120V.

Use the following chart as your primary tool in solving wire sizing problems. It replaces many pages of older sizing charts. You can apply it to any working voltage, at any percent voltage drop.

Universal Wire Sizing Chart

This chart works for any voltage or voltage drop, American (AWG) or metric (mm2) sizing. It applies to typical DC circuits and to some simple AC circuits (single-phase AC with resistive loads, not motor loads, power factor = 1.0, line reactance negligible).

Step 1 – Calculate the following:

VDI = Voltage Drop Index (a reference number based on resistance of wire)FEET = ONE-WAY wiring distance (1 meter = 3.28 feet)%VOLT DROP = Your choice of acceptable voltage drop (example: use 3 for 3%)

Step 2 – Determine appropriate wire size from the chart below. Compare your calculated VDI with VDI in the chart to determine the closest wire size. Ampacity rating of wire size must be at least 125% of the continuous current passing through it.

Wire Size Copper Aluminum
AWG # Area(sq. mm) Wire Availability(sq. mm) VDI Ampacity VDI Ampacity
16 1.31 1.5 1 10 Not Recommended
14 2.08 2.5 2 15
12 3.31 4 3 20
10 5.26 6 5 30
8 8.37 10 8 55
6 13.3 16 12 75
4 21.1 25 20 95
2 33.6 35 31 130 20 100
0 53.5 70 49 170 31 132
00 67.4 70 62 195 39 150
000 85.0 95 78 225 49 175
0000 107 120 99 260 62 205
Metric size by cross-sectional area Copper(VDI x 1.1 = mm 2 ) Aluminum(VDI x 1.7 = mm 2 )
Available sizes: 1 1.5 2.5 4 6 10 16 25 35 50 70 95 120 mm 2
EXAMPLE:20-amp load at 24V over a distance of 100 feet with 3% max voltage drop
For copper wire, the nearest VDI = 31.This indicates #2 AWG wire or 35mm 2
bu-403, charging, lead, acid, battery, percentage

NOTES: AWG = American Wire Gauge. Ampacity is based on the National Electrical Code (USA) for 30°C (85°F) ambient air temperature, for no more than three insulated conductors in raceway in free air of cable types AC, NM, NMC and SE; and conductor insulation types TA, TBS, SA, AVB, SIS, RHH, THHN and XHHW. For other conditions, refer to National Electric Code or an engineering handbook.

Did you know altE offers free solar system design consulting? Call us at 877-878-4060 or tell us about your desired system using our free quote tool.

Determining Tolerable Voltage Drop for Various Electrical Loads

A general rule is to size the wire for approximately 2-3% drop at typical load. When that turns out to be very expensive, consider some of the following advice. Different electrical circuits have different tolerances for voltage drop.

LIGHTING CIRCUITS, INCANDESCENT AND QUARTZ HALOGEN (QH): Don’t cheat on these! A 5% voltage drop causes an approximate 10% loss in light output. This is because the bulb not only receives less power, but the cooler filament drops from white-hot towards red-hot, emitting much less visible light.

LIGHTING CIRCUITS, FLUORESCENT: Voltage drop causes a nearly proportional drop in light output. Fluorescents use 1/2 to 1/3 the current of incandescent or QH bulbs for the same light output, so they can use smaller wire. We advocate use of quality fluorescent lights. Buzz, flicker and poor color rendition are eliminated in most of today’s compact fluorescents, electronic ballasts and warm or full spectrum tubes.

DC MOTORS may be used in renewable energy systems, especially for water pumps. They operate at 10-50% higher efficiencies than AC motors, and eliminate the costs and losses associated with inverters. DC motors do NOT have excessive power surge demands when starting, unlike AC induction motors. Voltage drop during the starting surge simply results in a “soft start”.

AC INDUCTION MOTORS are commonly found in large power tools, appliances and well pumps. They exhibit very high surge demands when starting. Significant voltage drop in these circuits may cause failure to start and possible motor damage. Follow the National Electrical Code. In the case of a well pump, follow the manufacturer’s instructions.

PV-DIRECT SOLAR WATER PUMP circuits should be sized not for the nominal voltage (i.e. 24V) but for the actual working voltage (in that case approximately 34V). Without a battery to hold the voltage down, the working voltage will be around the peak power point voltage of the PV array.

PV BATTERY CHARGING CIRCUITS are critical because voltage drop can cause a disproportionate loss of charge current. To charge a battery, a generating device must apply a higher voltage than already exists within the battery. That’s why most PV modules are made for 16-18V peak power point. A voltage drop greater than 5% will reduce this necessary voltage difference, and can reduce charge current to the battery by a much greater percentage. Our general recommendation here is to size for a 2-3% voltage drop. If you think that the PV array may be expanded in the future, size the wire for future expansion. Your customer will appreciate that when it comes time to add to the array.

WIND GENERATOR CIRCUITS: At most locations, a wind generator produces its full rated current only during occasional windstorms or gusts. If wire sized for low loss is large and very expensive, you may consider sizing for a voltage drop as high as 10% at the rated current. That loss will only occur occasionally, when energy is most abundant. Consult the wind system’s instruction manual.

Techniques for Cost Reduction

ALUMINUM WIRE may be more economical than copper for some main lines. Power companies use it because it is cheaper than copper and lighter in weight, even though a larger size must be used. It is safe when installed to code with AL-rated terminals. You may wish to consider it for long, expensive runs of #2 or larger. The cost difference fluctuates with the metals market. It is stiff and hard to bend, and not rated for submersible pumps.

HIGH VOLTAGE PV MODULES: Consider using higher voltage modules (18 volts peak power point, like our BP-585 and BP-590) to compensate for excessive voltage drop. In some cases of long distance, the increased module cost may be lower than the cost of larger wire.

SOLAR TRACKING: Use a solar tracker (by Zomeworks) so that a smaller array can be used, particularly in high summer-use situations (tracking gains the most energy in summer when the sun takes the longest arc through the sky). The smaller PV array will require smaller wire.

WATER WELL PUMPS: Consider a slow-pumping, low power system with a storage tank to accumulate water. This reduces both wire and pipe sizes where long lifts or runs are involved. A PV array-direct pumping system may eliminate a long wire run by using a separate PV array located close to the pump. The SunRise Submersible, Solar Slowpump, Flowlight Booster Pump and Solar Force Piston Pump are highly efficient DC pumps that are available up to 48V. We also make AC versions and converters to allow use of AC transmitted over great distances. These pumps draw less running current, and far less starting current than conventional AC pumps, thus greatly reducing wire size requirements.

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