216Ah 12V 4D SiO2 Battery. 4d battery voltage

Why you need to change your battery today:

The Silicon Dioxide Battery is a high performance battery comparable to Lithium-Ion in both depth of discharge and cycling capabilities for a third of its price. It even out-competes many similar Li-Ion batteries in longevity when subjected to the same discharge, temperatures, and partial state of charge abuse.

This means the SiO2 Battery boasts a fantastically low cost per Kilowatt-Hour over its entire lifetime. Each cent gives users more watts for longer to provide the best long-term solution with short-term costs. It even has a longer shelf life, only discharging less than 1.6% of its power over a month.

The SiO2 battery lasts 8-12 years, depending on use, thanks to its unique chemistry. The pH neutral electrolyte prevents sulphation and does not corrode the internal components.

Cold Weather Champion

The SiO2 Battery’s effectiveness in extreme temperatures stands out against all competition. The cold-resistant technology was developed for use in machinery up North and performs far better than any other battery technology on the market.

These batteries provide 40% more power than lead-acid battery at temperatures as low as.40 °C/F.

Safer, Easier, and Greener

The Silicon Dioxide battery is lighter weight than other types of Lead-Acid batteries and is easier to transport and install since it can be placed on any side or orientation.

These batteries are up to 99% recyclable and an excellent battery for environmentally-conscious users wanting to minimize the carbon footprint of their solar array.

These deep cycle batteries require no maintenance and are non-gassing. This makes them safer in high temperatures or remote battery banks and backup power storage. It is safe for air travel and can be used as marine batteries.

Settings for your SiO2 battery if you are choosing custom programming on your charge controller:

Equalizing Voltage. 14.6 or Shut off this function if available Boost Voltage. 14.6 Floating Charge Voltage. 13.6 Over-discharge Return Voltage. 12.7 Over-discharge Voltage. 11.8

Additional Information

SiO2 Composite Electrolyte Battery EFSN

Bright Way Group BW 4D Narrow Style. 12V 200AH SLA Battery

The Bright Way Group BW 4D Narrow is a 12-volt 200Ah sealed lead-acid battery that is brand new and ready to replace your existing battery (regardless of the original manufacturer).

8.4 in voltage!-

Voltage: 12 V
Terminal: IT
Amp Hours: 200 Ah
Height: 8.4 in
Width: 8.15 in
Length: 20.9 in
Weight: 115.5 lb

The Bright Way Group BW 4D Narrow is a 12-volt 200Ah sealed lead-acid battery that is brand new and ready to replace your existing battery (regardless of the original manufacturer).

This is a 12-volt (12v) battery. You should ensure that your current battery is a 12v battery. You can combine multiple 12v batteries in series if your equipment needs a higher voltage. (Reference your product’s manual for further details.)

The capacity of the battery is measured in amp hours (Ah), and this is a 200Ah battery.

The model number of this battery is BW 4D Narrow. Sealed lead-acid batteries (SLA) come in two variants: either gel or absorbent glass mat — this indicates the material inside the battery itself. This battery is the AGM variant.

This battery has an IT terminal. (Other terminal options may be available. See the difference between terminals.)

All SLA batteries are maintenance-free, can be used in any orientation, and are leakproof. They are exceedingly safe because they use a valve regulator to safely vent pressure. (You’ll see SLA batteries called VRLA, valve-regulated lead-acid.) In addition, these batteries have a wide operating temperature, a long service life, and the ability to recover from a deep discharge.

216ah, sio2, battery, voltage

Why use Bright Way Group batteries?

  • Always brand new, factory fresh, and high-quality batteries from a brand owned by Continental Battery
  • Always meet the Original Equipment Manufacturer’s battery specifications
  • Will work regardless of who made the original battery
  • Backed by the Continental Battery 1-year warranty

Common Questions

  • Does the battery arrive fully charged? It will arrive charged between 80-90%. We recommend installing the batteries and charging them for 24 hours before use.
  • Can this battery be used for my application? Almost always. This battery, or a similar version with a different capacity, has been used for UPS backup systems, alarm systems, mobility devices, emergency lighting, backup power systems, railway signaling systems, telecommunications systems, off-grid solar systems, and more.

This battery comes with a 1-year manufacturer’s warranty, processed by BatteryWholesale.com’s amazingly friendly customer support team.

This battery size is available in different capacities. This allows you to save money with a lower capacity (shorter battery run time), or increase your capacity within the same physical size.

Different capacities may have slight differences (less than half an inch), so double check the dimensions if your container is especially small

The Bright Way Group BW 4D Narrow is a 12-volt 200Ah sealed lead-acid battery that is brand new and ready to replace your existing battery (regardless of the original manufacturer).

This is a 12-volt (12v) battery. You should ensure that your current battery is a 12v battery. You can combine multiple 12v batteries in series if your equipment needs a higher voltage. (Reference your product’s manual for further details.)

The capacity of the battery is measured in amp hours (Ah), and this is a 200Ah battery.

The model number of this battery is BW 4D Narrow. Sealed lead-acid batteries (SLA) come in two variants: either gel or absorbent glass mat — this indicates the material inside the battery itself. This battery is the AGM variant.

This battery has an IT terminal. (Other terminal options may be available. See the difference between terminals.)

All SLA batteries are maintenance-free, can be used in any orientation, and are leakproof. They are exceedingly safe because they use a valve regulator to safely vent pressure. (You’ll see SLA batteries called VRLA, valve-regulated lead-acid.) In addition, these batteries have a wide operating temperature, a long service life, and the ability to recover from a deep discharge.

Why use Bright Way Group batteries?

  • Always brand new, factory fresh, and high-quality batteries from a brand owned by Continental Battery
  • Always meet the Original Equipment Manufacturer’s battery specifications
  • Will work regardless of who made the original battery
  • Backed by the Continental Battery 1-year warranty

Common Questions

  • Does the battery arrive fully charged? It will arrive charged between 80-90%. We recommend installing the batteries and charging them for 24 hours before use.
  • Can this battery be used for my application? Almost always. This battery, or a similar version with a different capacity, has been used for UPS backup systems, alarm systems, mobility devices, emergency lighting, backup power systems, railway signaling systems, telecommunications systems, off-grid solar systems, and more.

This battery comes with a 1-year manufacturer’s warranty, processed by BatteryWholesale.com’s amazingly friendly customer support team.

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.

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.

Комментарии и мнения владельцев

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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

216ah, sio2, battery, voltage

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?

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!

216ah, sio2, battery, voltage

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.

Lead Acid battery downsides

It is typically considered wise to use just 30% – 50% of the rated capacity of typical lead acid “Deep Cycle” batteries. This means that a 600 amp hour battery bank in practice only provides, at best, 300 amp hours of real capacity. If you even occasionally drain the batteries more than this their life will be drastically cut short.

2/ Limited Cycle Life

Even if you are going easy on your batteries and are careful to never overly drain them, even the best deep cycle lead acid batteries are typically only good for 500-1000 cycles. If you are frequently tapping into your battery bank, this could mean that your batteries may need replacement after less than 2 years use.

3/ Slow Inefficient Charging

The final 20% of lead acid battery capacity can not be “fast” charged. The first 80% can be “Bulk Charged” by a Smart three-stage charger quickly (particularly AGM batteries can handle a high bulk charging current), but then the “Absorption” phase begins and the charging current drops off dramatically.

Just like a software development project, the final 20% of the work can end up taking 80% of the time.

This isn’t a big deal if you are charging plugged in overnight, but it is a huge issue if you have to leave your generator running for hours (which can be rather noisy and expensive to run). And if you are depending on solar and the sun sets before that final 20% has been topped off, you can easily end up with batteries that never actually get fully charged.

Not fully charging the final few percent would not be much of a problem in practice, if it wasn’t for the fact that a failure to regularly fully charge lead acid batteries prematurely ages them.

4/ Wasted Energy

In addition to all that wasted generator time, lead acid batteries suffer another efficiency issue – they waste as much as 15% of the energy put into them via inherent charging inefficiency. So if you provide 100 amps of power, you’ve only storing 85 amp hours.

This can be especially frustrating when charging via solar, when you are trying to squeeze as much efficiency out of every amp as possible before the sun goes down or gets covered up by clouds.

5/ Peukert’s Losses

The faster that you discharge a lead acid battery of any type, the less energy you can get out of it. This effect can be calculated by applying Peukert’s Law (named after German scientist W. Peukert), and in practice this means that high current loads like an air conditioner, a microwave or an induction cooktop can result in a lead acid battery bank being able to actually deliver as little as 60% of its normal capacity. This is a huge loss in capacity when you need it most…

The above example shows specification of Concord AGM battery : this spec states that the battery can provide 100% of it’s rated capacity if discharged in 20 hours (C/20). If discharged in one hour (C/1), only 60% of rated capacity will be delivered by the battery. This is direct effect of Peukert losses.

At the end of the day, an AGM battery rated for 100Ah at C/20 will provide a 30Ah usable capacity when discharged in one hour as 30Ah = 100Ah x 50% DoD x 60% (Peukert losses).

6/ Placement issues

Flooded lead acid batteries release noxious acidic gas while they are charging, and must be contained in a sealed battery box that is vented to the outside. They also must be stored upright, to avoid battery acid spills.

AGM batteries do not have these constraints, and can be placed in unventilated areas – even inside your living space. This is one of the reasons that AGM batteries have become so popular with sailors.

6/ Maintenance Requirements

Flooded lead acid batteries must be periodically topped off with distilled water, which can be a cumbersome maintenance chore if your battery bays are difficult to get to.

AGM and gel cells though are truly maintenance free. Being maintenance free comes with a downside though – a flooded cell battery that is accidentally overcharged can often be salvaged by replacing the water that boiled off. A gel or AGM battery that is overcharged is often irreversibly destroyed.

7/ Voltage Sag

A fully charged 12-volt lead acid battery starts off around 12.8 volts, but as it is drained the voltage drops steadily. The voltage drops below 12 volts when the battery still has 35% of its total capacity remaining, but some electronics may fail to operate with less than a full 12 volt supply. This “sag” effect can also lead to lights dimming.

8/ Size Weight

A typical 8D sized battery that is commonly used for large battery banks is 20.5″ x 10.5″ x 9.5″. To pick a specific 8D example, Trojan’s 8D-AGM weighs 167lbs, and provides just 230 amp-hours of total capacity – which leaves you with 115 amp hours truly usable, and only 70 for a high discharge applications!

If you are designing for extensive boon docking, you will want at least four 8D’s, or as many as eight. That is a LOT of weight to be carting around that impacts your fuel economy.

And, if you have limited space for batteries on your rig – size alone of the batteries will limit your capacity.

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