Battery Chemistry Comparison Chart: LiFePO4, AGM, Gel and Lead

Battery chemistry is decided by three numbers and not by the one printed on the label: how much of the nameplate capacity you can safely use, how many times you can use it, and what each of those cycles costs you. Two batteries both labelled 100Ah can differ by 70 percent in usable capacity, by a factor of six in cycle life, and by a factor of eight in the real cost of the energy they deliver. Nameplate amp-hours is close to meaningless as a comparison unit.

How do the five chemistries compare on the numbers that matter?

Everything below is per 100Ah of nameplate capacity, so the columns are directly comparable. The usable watt-hours figure is the nominal voltage times 100Ah times the safe depth of discharge, and it is the honest measure of what one battery holds. Prices are representative rather than quoted, because the same chemistry spans a wide range depending on the maker, and cycle life is the figure at the stated depth of discharge rather than a best case at a shallow one.

Start with usable capacity, because it is the column people skip. A 100Ah LiFePO4 battery holds 1,280 watt-hours and gives up 85 percent of it without harm, which is 1,088 watt-hours or 85 amp-hours. A 100Ah AGM holds 1,200 watt-hours and gives up half, which is 600 watt-hours or 50 amp-hours. Those two batteries are sold under the same headline number and one of them holds almost twice as much energy you can actually take out. Two AGMs are needed to match one lithium battery, and those two AGMs weigh about 130 lb against 27.

Then look at charge acceptance, which is the column that decides whether alternator charging is worth doing. A LiFePO4 pack will accept 0.5C to 1C, so a 100Ah battery takes 50 to 100A and refills in roughly an hour and a half of driving. An AGM accepts 0.2C to 0.3C and tapers early, so the same 100Ah takes four to six hours. That difference is why a Litime 12V 100Ah LiFePO4 Battery (Group 24) paired with a DC-DC charger makes a two hour drive genuinely useful, and an AGM bank does not. The DC-DC charging guide covers how to exploit it.

Weight is a payload question rather than a preference. Every pound of battery comes out of the figure on the door jamb sticker, and 400Ah of AGM is roughly 260 lb against 100 lb of the lithium equivalent. On a mid-size 4x4 with 1,100 lb of payload, that 160 lb difference is a passenger. Run the numbers through the payload weight calculator before you commit, because it is a harder limit than the electrical one and it catches people late.

What does the resting voltage tell you about state of charge?

On lead acid, a useful amount. On lithium, almost nothing, and this surprises people who have spent years reading a voltmeter on a boat or an RV.

The LiFePO4 column moves 0.6V across the entire range from full to nearly empty. The AGM column moves 0.9V, and more importantly it moves in a curve you can actually read: 12.7V is full and 12.2V is the floor. On lithium, the difference between 90 percent and 30 percent is 0.3V, which is smaller than the voltage sag a fridge compressor causes when it starts. Reading a lithium battery by voltage is not conservative or approximate, it is guessing.

These are typical published figures and vary by manufacturer and temperature, so treat them as the shape of each curve rather than as a calibration, and note that they only apply after the battery has rested with no load and no charge for a while. The usable amp-hour columns count down from the safe floor of each chemistry: 15 percent remaining for LiFePO4 at an 85 percent depth of discharge, and 50 percent for AGM.

The practical consequence is that a lithium bank needs a shunt and a lead acid bank can survive without one. A Victron SmartShunt 500A Battery Monitor sits in the negative line and counts amp-hours in and out, which is the only honest state of charge reading on a flat discharge curve, and it also catches the parasitic loads nobody knew about. A AILI TR16 Shunt Battery Monitor (500A, 8 to 120V) does the same counting without an app if the budget is tight. The battery monitor roundup compares them, and the same voltage table appears there so the two pages agree.

What does each chemistry actually cost per usable amp-hour?

This is the table that decides the purchase, and it is the one nobody puts on a product page. Two costs are worth separating. Cost per usable amp-hour up front is what you pay today for capacity you can actually use. Cost per usable kilowatt-hour over the life of the battery is what each unit of energy costs you across every cycle the battery will deliver, which is the honest measure of ownership.

Read the last column and the argument ends. LiFePO4 at roughly nine cents per usable kilowatt-hour over its life against seventy-three cents for AGM, sixty-three for flooded and seventy-two for gel. That is a factor of seven or eight, and it comes almost entirely from cycle life rather than from the purchase price: lithium costs more up front and then delivers six times as many cycles with 80 percent more usable energy in each one.

Two honest caveats on those figures. First, the prices are representative and the cycle lives are manufacturer claims. A budget cell like the Lithova 12V 100Ah LiFePO4 Battery (Group 24, 100A BMS) at $144 buys into lithium for less than an AGM costs, and the correct way to read that is that the price is the point and the cycle life claim is optimistic. Even at half the claimed cycles it still wins the last column comfortably. Second, cycle life depends heavily on how you treat the battery: shallow cycles extend it substantially for every chemistry, and leaving lead acid partially discharged for weeks destroys it far faster than the cycle count implies.

There is a third consideration, and it cuts against lithium: none of the arithmetic above matters if you replace the vehicle in three years. A 3,000 cycle battery used 150 times a year has a 20 year life you will not use. For a weekend build that camps thirty nights a year, the up-front cost columns are the relevant ones and AGM is genuinely defensible. For anything approaching full-time use, the lifetime column is the only one worth reading. The lithium versus AGM comparison works through where that line falls.

What happens to each chemistry below freezing?

This is the one genuine weakness of lithium in a vehicle, and it is worth understanding properly rather than treating as a marketing line for heated batteries.

The mechanism is lithium plating. When charge current is pushed into a cold lithium cell, lithium metal deposits on the anode instead of intercalating into it, which permanently removes capacity and can eventually create an internal short. It is not recoverable and it does not announce itself. Because of that, essentially every LiFePO4 battery management system blocks charging below roughly 32F while continuing to permit discharge. The battery will happily run your fridge all night at 20F and then refuse every amp the solar controller offers it in the morning.

There are three ways to deal with it. The first is a self-heating pack, which uses a heating element powered from the charge source to warm the cells above the threshold before it accepts charge. It costs you charging time in the cold rather than stored capacity, which is exactly the right trade, and a Renogy 12V 100Ah Self-Heating LiFePO4 Battery (DuoHeat, Mini) is the cheapest sensible way in. The second is to put the battery inside the heated living space rather than in an exterior locker or under the vehicle, which works for most people most of the time and is free. The third is to accept it and charge only while the vehicle is warm, which is fine for occasional cold nights and a genuine problem for a winter season.

Lead acid has the opposite failure. It accepts charge below freezing, slowly and inefficiently, so it does not lock you out. But a discharged lead acid battery freezes at a much higher temperature than a charged one, because the electrolyte is closer to water when the battery is flat, and a frozen lead acid battery cracks its case. It also loses far more usable capacity in genuine cold: 40 to 50 percent at 0F against 10 to 20 percent for lithium. In a real winter build, lithium with a heater beats lead comfortably, and the winter camping power guide covers the rest of the cold weather system.

Which chemistry should go in your build?

LiFePO4 for anything that gets used regularly, which is most builds. The usable capacity, the weight, the charge acceptance and the lifetime cost all point the same way, and the freezing problem has a solved answer that costs about a hundred dollars. This is not a close call any more, and it stopped being close when prices fell to where a 100Ah lithium battery costs less than a good AGM.

AGM for a budget weekend build that will not accumulate cycles, for a replacement in an existing tray where the charging system is old and configured for lead, or where a vehicle spends months parked and nobody wants a BMS drawing anything. It is also the right answer where the charging source is small: an AGM that only ever gets a slow trickle is not being punished by its own low charge acceptance.

Flooded lead acid only where budget dominates completely and the battery can live in a properly vented box outside the living space. It is the cheapest way to buy amp-hours and the most expensive way to own them. Gel is a narrow product that suits deep slow discharges and is intolerant of overcharge, and in a vehicle it is usually the wrong price for what it delivers. NMC is the right chemistry when weight and volume dominate everything, which in a vehicle is almost never true for a house bank.

Whichever you choose, three pieces of hardware are not optional. A NOCO BT31S Group 31 Heavy Duty Battery Tray and Hold Down keeps a 60 lb mass from becoming a projectile in a crash or shorting itself against something on a washboard road. A Blue Sea Systems 5191 MRBF Terminal Fuse Block (30 to 300A) or a Class T fuse sits within a few inches of the positive post so the main cable is protected from its first inch. And a Blue Sea Systems m-Series Battery Switch, On/Off with Knob (6006) lets you isolate the whole system by hand for maintenance, storage and emergencies, which no fuse can do.

Everything on this page is compiled from published manufacturer specifications, datasheets and standards documents rather than measured by us. Cycle life figures in particular are manufacturer claims at a stated depth of discharge and temperature, and real service life depends on how the battery is charged and how deeply it is cycled. This is researched guidance rather than an electrical certification, it does not replace ABYC E-11 or your battery manufacturer's manual, and a lithium installation should be inspected by a qualified installer before it carries load.

Where to go next

• Lithium versus AGM batteries, the same decision argued in full.
• Battery bank calculator, turning a daily load into a bank size.
• Best lithium batteries for a van, the packs themselves compared.
• Appliance power draw chart, to find the daily load first.
• How to size a battery bank, the full method end to end.