Lead Acid Battery Maintenance Mistakes
For companies that use lead acid batteries to power their material handling equipment, how long their batteries last and how well they perform is critical to their operations.
The maintenance of lead acid batteries plays an important role in both of these outcomes. If not properly maintained, a battery’s lifespan and performance can diminish. impacting efficiency and increasing costs.
Here are some of the most common maintenance mistakes that companies make when servicing lead acid batteries and why lithium-ion batteries are a better alternative that avoids or reduces the likelihood of these issues occurring.
Under Charging
If a lead acid battery is not returned to its full charge after it has been used, it will be undercharged and there is a risk of damaging it.
Partially charging a lead acid battery can cause sulfating, which is the formation of lead sulfate that occurs on the battery’s plates. This diminishes the battery’s performance. It can even lead to battery failure, a costly mistake if your goal is to use a lead acid battery for its estimated lifespan (an average of 1,000 charging cycles).
Why Lithium-ion Batteries are Better:
Unlike lead acid batteries, lithium-ion batteries can be opportunity charged. Partially charging a lithium-ion battery does not damage it and is more convenient because equipment operators can charge the battery as needed during breaks or shift downtimes. And, this doesn’t impact its average lifespan of 2,000 cycles.
Over Charging
Overcharging a lead acid battery can be just as harmful as undercharging it. If workers leave the battery in a continuously charging state for long periods of time, corrosion of the positive battery plates can occur.
Lead acid batteries can also get very hot while charging. So, if workers overcharge a battery, it can cause damage on the inside due to longer exposure to excessive temperatures.
The odds of this occurring are greater when workers allow the battery to experience a deep discharge, requiring extended time to return the battery to full charge.
If a lead acid battery overcharges and overheats, pressure generated from the hydrogen and oxygen gas must be relieved or it can rupture.
Why Lithium-ion Batteries are Better:
Lithium-ion batteries feature a state-of-the-art battery management system that tracks cell temperatures while charging to ensure they remain in safe temperature ranges. Unlike lead acid batteries, lithium-ion batteries do not require separate charging and cooling areas because of the risks outlined above.
Built-in controllers prevent overcharging, in order to prevent dendrites from forming that can cause significant damage to lithium-ion batteries.
Under Watering
lead acid batteries are filled with an electrolyte solution (sulfuric acid and water) and feature a removable top. They generate electricity through a chemical reaction of the lead plates and sulfuric acid. This type of battery requires regular refilling with water or the chemical process will degrade and the battery will suffer an early failure.
One of the biggest mistakes workers make is under watering the battery. If water that is lost during the charging process is not replenished and the electrolyte levels drop below the top of the plates, significant damage can occur.
In hotter environments, water depletion can occur at an even faster rate.
Why Lithium-ion Batteries are Better:
Because of the way lithium-ion batteries are designed, they do not require watering. Lithium-ion batteries are sealed shut, which means the electricity-generating chemicals stay inside.
Over Watering
Over watering can cause significant damage to a lead acid battery as well. When a battery is over watered, the electrolytes become diluted. This will diminish the battery’s performance.
Over watering also creates the risk of the spillage, which is a dangerous mixture of toxic sulfuric acid.
Why Lithium-ion Batteries are Better:
Again, lithium-ion batteries do not require watering because of the way they are designed. Lithium-ion batteries are sealed shut, so workers do not have to monitor water levels or worry about spills of highly-toxic sulfuric acid occurring.
Sealed lead acid SLA battery charging and flooded lead acid battery charging technologies
- Coulometric Efficiency
- Minimum voltage
- Cyclic versus Standby charging
- Temperature compensation
- Unregulated Transformer-based Chargers
- Taper Charging
- Constant Voltage Charging
- Constant Current Charging
- Fast Charging Options
- Three step chargers
Lead acid batteries have come a long way. They have an incredible number of man-hours in research, science, and manufacturing technology. The high voltage, robustness, infrastructure and low cost will make sure they stick around for a long time.
Weight We have visited at least 10 factories in China. One interesting thing that I learned is that you can judge a sealed lead acid battery by its weight. They said If you want a cheaper battery, no problem, we will just use thinner plates and less lead. Of course the thinner plates will fail faster and give less lifetime. That is the trade-off. All the battery factories in China run off the same basic profit margin, so if the battery is significantly cheaper, now you know why. You can judge the quality of a sealed lead acid battery by its weight.
Coulometric Efficiency. This is the efficiency of battery charging based solely on how many electrons you push in. If you compare watts in to watts out you have to take into account that the battery charging voltage is higher than the battery discharging voltage. The coulometric charging efficiency of flooded lead acid batteries is typically 70%, meaning that you must put 142 amp hours into the battery for every 100 amp hours you get out. This varies somewhat depending on the temperature, speed of charge, and battery type.
Sealed lead acid batteries are higher in charge efficiency, depending on the bulk charge voltage it can be higher than 95%.
Minimum voltage
Anything above 2.15 volts per cell will charge a lead acid battery, this is the voltage of the basic chemistry. This also means than nothing below 2.15 volts per cell will do any charging (12.9V for a 12V battery) However, most of the time a higher voltage than this is used because the battery will accept higher currents, enabling the charging reaction to proceed at a higher rate. Charging at the minimum voltage will take a long long timeover 200 hours. At 2.25V per cell (13.5) it would take 85-120 hours to fully charge. As you increase the voltage to get faster charging, the voltage to avoid is the gassing voltage, which limits how high the voltage can go before undesirable chemical reactions take place. Charging voltages range between 2.15V per cell (12.9V for a 12V 6 cell battery) and 2.35V per cell (14.1V for a 12V 6 cell battery). These voltages can be applied to a fully charged battery without overcharging or damage, since they are below the gassing voltage, and cannot break down the electrolyte. If the battery is not fully charged you can use much higher voltages without damage because the charging reaction takes precedence over any over-charge chemical reactions until the battery is fully charged. This is why a battery charger can operate at 14.4 to 15 volts during the bulk-charge phase of the charge cycle. Using modern precision chargers allows both a fast charge and safe floating voltages, allowing them to be left on the battery continuously.
6V batteries need to stay below 7.1V to avoid gassing, and typical charge voltages are 6.9V (float) to 7.5V (bulk charge).
The basic lead acid battery is ancient and a lot of different charge methods have been used. In the old days, when voltage was difficult to regulate accurately, flooded lead acid batteries were important because the water can be replaced. The lead acid chemistry is fairly tolerant of overcharging, which allows marketing organizations to get to extremely cheap chargers, even sealed lead acid batteries can recycle the gasses produced to prevent damage to the battery as long as the charge rate is slow. We offer a range of chargers from inexpensive to very sophisticated, depending on the requirements of the customer, but all of the chargers we sell off-the-shelf are highly regulated sophisticated chargers that cannot overcharge the battery.
Cyclic versus Standby charging.
Some lead acid batteries are used in a standby condition in which they are rarely cycled, but kept constantly on charge. These batteries can be very long lived if they are charged at a float voltage of 2.25 to 2.3 volts/cell (at 25 degrees C) (13.5V to 13.8V for a 12V battery). This low voltage is to prevent the battery from losing water during long float charging. Those batteries that are used in deep discharge cycling mode can be charged up to 2.45 volts/cell (14.7V for a 12V battery) to get the highest charge rate, as long as the voltage is dropped to the float voltage when the charge is complete.
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.
Replace Lead Acid with Lithium Batteries for RVs and Marine – Why How
It’s time. Your RV or boat’s lead acid battery bank had a good run, but just isn’t able to hold a charge anymore – so what should you do? Using battery desulphators could help squeeze some more life out of it, but instead of asking how to restore lead acid batteries that are clearly past their prime, the question you should be asking is: Can I replace lead acid batteries with lithium batteries in my boat or RV? After all, lithium batteries are becoming the standard for renewable energy storage.
The answer is YES, you can absolutely replace lead acid batteries with lithium in marine and RV applications – but here are a few considerations to help you decide if upgrading to lithium batteries is the right lead acid battery alternative for your boat, camper, or RV.
Why Replace Lead Acid Batteries with Lithium in a Boat or RV?
Lead Acid vs. Lithium: Depth of Discharge
Depth of Discharge, or DoD, is how much of your battery bank’s stored energy can actually be used without dramatically reducing its life. For example, a 100Ah (amp hour) lead acid battery rated for 25% DoD means you need to plan to use only ¼ of its rated capacity (so 25Ah), leaving the other ¾ in the battery, unused.
- DoD for lead acid batteries – both flooded (which you have to add water to periodically) and sealed (“maintenance-free”) – is typically in the 25% – 50% range. Your battery will last at least twice as long if you regularly discharge it 25% than if you regularly discharge it 50%. Keep in mind that if you don’t have a sunny day to recharge your batteries after a day of use, the DoD will go down again the next day – so planning to use 25% per day will allow you to use less than the 50% maximum after two days of use.
- On the other hand, DoD for lithium ion batteries is 80% or more, allowing you to use most or even all of the battery’s stored energy. That means a 100Ah lithium battery rated for 80% DoD can safely provide you with 80Ah without being harmed.
As a result, a lithium battery bank can be much smaller than a lead acid battery bank to provide the same amount of usable energy. For example, if you need 100Ah of energy a day, you would need a 400Ah lead acid battery bank to stay at 25% DoD, but would only need 125Ah of lithium at 80% DoD. That is a significantly smaller battery bank with lithium batteries.
Lead Acid vs. Lithium: Cycle Count
Cycling a battery means discharging it to any amount and recharging it to a fully charged state. If you cycle your battery bank every day for a year, that’s 365 cycles. If you only use it on the weekends, and keep the bank topped off the rest of the time, that’s 104 cycles a year.
A cycle is a cycle regardless of how deep the discharge is, but the depth of discharge directly affects how many cycles you can expect your battery to last. A battery’s specs will tell you how many cycles to expect from it when discharging to its rated DoD.
- A standard flooded lead acid battery can have about 2500 cycles at 25% DoD
- A standard sealed lead acid battery can have about 1200 cycles at 25% DoD
- Unlike lead acid, lithium batteries don’t have a cycle curve under 80% DoD. Beyond 80%, the cycle count can drop dramatically. A typical lithium battery can have 5000 cycles at up to 80% DoD. That’s 4x the cycles at over 3x the DoD. That’s a much longer lived battery bank with lithium batteries.
Lead Acid vs. Lithium: Charge/Discharge Rate
In addition to how much of a battery’s capacity you use, it also matters how fast you use it. Again using the 100Ah battery example, if you have a 10 amp (A) load, that can drain the battery completely in 10 hours (100Ah ÷ 10A = 10 hours). That is considered a C/10 rate. Likewise, if you have a 50A load on the same battery, that would drain it in 2 hours (100Ah ÷ 50A = 2 hours). That is a C/2 rate. Most batteries are rated at their C/20 rate, emptying the battery in 20 hours.
If you have a high-current load in your system, or are charging it very quickly with a high current, such as your alternator or shore power, you need to consider the charge/discharge rate of the battery bank. If you need a higher rate than the batteries can handle, you would need to increase the battery bank by adding more batteries in parallel so that the batteries can share the current between themselves. This may result in needing a battery bank that has a higher Ah capacity than you need to power your loads, just to handle the high current.
Likewise, too slow of a charge of lead acid batteries can cause premature sulphation, shortening their life. This is not a problem with lithium.
- Lead acid batteries tend to perform best between C/8 and C/12 rates. So our 100Ah battery would want to be charged or discharged at between 8A and 12A. Wiring three batteries in parallel would permit three times the rate, as it shares the current between the three, so 24A to 36A.
- Some lithium batteries can generally handle a C/1 rate, or even higher for short periods depending on the battery. This means a 100Ah lithium battery can handle 100A (or more) of charge/discharge current. Most manufacturers recommend no more than a C/2 rate on a regular basis for best battery life, but it is good to know the extra power is there with lithium batteries if you need it. Be sure to check the manufacturer’s specs when selecting a lithium battery, as some do not support as high of a current as others.
Lead Acid vs. Lithium: Voltage Sag
You may be familiar with the voltage of your boat or RV’s battery bank sagging, or dropping to 11V or lower when trying to run a high–power load such as your winch, windlass, or air conditioner. When running a heavy AC load off the inverter, the voltage could drop below the low voltage cutoff, causing the inverter to turn off when you need it most. Likewise, if you are running a DC load like your bow thruster directly off the battery bank, you need it to maintain a high enough voltage for it to work when you really need it to work. Due to lithium batteries’ voltage curve and ability to handle high current, loads like these will not cause the voltage to drop dramatically, eliminating the problem of voltage sag.
Considerations When Replacing Lead Acid Batteries with Lithium in a Boat or RV
Now that you’re convinced lithium is the best way to go, you need to be aware of a few things when replacing a lead acid battery with lithium. The term “drop-in replacement” has become popular, but the reality is there are a few other things you’ll need to do to safely upgrade from lead acid to lithium batteries in your boat or RV.
Charge Controller/Charging Profile
If you are currently charging your lead acid batteries with solar, your alternator, and/or shore power, you may be able to keep your existing charge controller or inverter/charger. The charging and low voltage cutoff profiles for lithium batteries are a little different from lead acid, so you need chargers that have adjustable charge rates. Different batteries will have different preferences, so be sure to see the manufacturer’s recommendations when configuring your charger. They will often recommend a Bulk and Absorb rate of around 14V, with an Absorption time of as little as 2 minutes, significantly less than the standard for lead acid. With a Float voltage of just below 14V, you can maintain the charge without overcharging it. Because lithium has a very narrow voltage window, 12V is generally the lowest voltage you want before you shut off your loads.
Note: Unlike lead acid batteries, lithium batteries do not always need to be recharged to their full 100% capacity. They actually prefer being in a partial state of charge. If you are going to be leaving your boat or RV for a season of storage, it is recommended that you leave the battery bank at around 90% state of charge. This leaves plenty of energy for small loads like the bilge pump or CO2 alarm, but helps maintain a healthy battery bank until you can get back to normal use.
Cranking Amps / Starter Battery
With lead acid batteries, we are used to seeing a rating of CCA (cold crank amps) to show how many amps can be used to start an engine in the cold weather. Lithium batteries do not have the CCA rating. If you intend to replace a lead acid battery with lithium for your starting battery, make sure the new lithium battery is rated to handle enough current to do so. Not all of them are. We see a lot of people continue to use a lead acid battery as the starter, with lithium used only for the house/service battery. This also gives you a bit of a backup, so that if everything goes wrong with your house/service battery, you still have the starter battery available.
Alternator
Unlike lead acid batteries, lithium batteries have very little internal resistance and can take as much charging current from the alternator as needed. But since alternators are not designed to run at full speed for long periods, this can result in the alternator working too hard, overheating, and damaging itself. There are a few ways to prevent this from happening.
Use a DC/DC Converter
By installing a DC-to-DC converter between the alternator and the lithium battery bank, you can limit the amount of current the battery draws from the alternator. It is recommended that you only draw from the alternator at half its rating, so for a 60A alternator, a 30A DC/DC converter like the Bluetooth-enabled Victron Energy Orion-Tr Smart 12/12-30A charger is a good option. You can use multiple DC/DC converters in parallel to increase the rate for larger alternators.
Victron Orion-TR Smart DC/DC Converter setup
Replace the Alternator
You can replace the alternator with one designed for higher amperage charging and temperature control. Balmar makes great alternators and external regulators for this. They monitor the temperature and will wind down to appropriate amperage if the alternator gets too hot. If you currently have a V-belt, you may need to modify the engine for a serpentine belt before you can use the larger Balmar alternator.
Low Voltage Disconnect
The ability to automatically disconnect your DC loads gives you control over how low you discharge your battery bank. An automatic switch such as the Victron Energy Smart BatteryProtect can be configured via Bluetooth for excellent control of your system. It can turn your non-critical loads on or off based on a configurable voltage setting.
Battery/Bank Monitoring
KiloVault CHLX Bluetooth App
Any good battery system should have the ability to monitor both the individual batteries, and the whole battery bank. Watching more than just the voltage, but also how many amps go in and out of the battery bank and the temperature gives you a complete view of the health and state of charge of the entire bank. Some lithium battery Battery Monitoring Systems have Bluetooth or Wi-Fi built in to allow you to monitor it from the phone. For example, the KiloVault HLX and CHLX batteries have Bluetooth to your Smartphone to see down to the cell level of each battery.
It’s Time to Mobilize with Lithium Batteries for Marine and RV Applications
Whether you are looking for a new battery bank for your RV or boat or considering replacing your aging lead acid batteries, deep-cycle lithium ion batteries – specifically LiFePO4 batteries – are an excellent solution. Compared to lead acid batteries, LiFePO4 batteries offer more power, higher current, a longer life, smaller footprint, lower weight, and safe, maintenance-free operation. Are you ready to mobilize and go lithium?
See more options for lithium batteries at our website or contact us at 877-878-4060 to help you select the right lithium batteries for your specific needs.