The house battery is the heart of your camp power system, and the choice almost always comes down to two chemistries: lithium iron phosphate (LiFePO4) and absorbed glass mat (AGM). AGM is the cheaper, familiar deep-cycle standard. Lithium costs more upfront but delivers far more usable power per pound and lasts much longer. Here’s how they really compare, and which one fits your build.
The short version
Lithium (LiFePO4) is the modern default for overlanding — lightweight, energy-dense, fast to recharge, and long-lived. AGM is cheaper to buy and a sealed, maintenance-free lead-acid battery, but it’s heavy, gives you less usable capacity, and wears out sooner. For most people building a serious rig, lithium wins on everything except sticker price.
Side-by-side
| Factor | Lithium (LiFePO4) | AGM (lead-acid) |
|---|---|---|
| Usable capacity | ~80–100% of rated | ~50% before harming the battery |
| Weight | Light, energy-dense | Heavy for the same usable Wh |
| Cycle life | Thousands of cycles | Hundreds of cycles |
| Recharge speed | Fast — as little as ~3 hrs | Slow, with a long absorption phase |
| Voltage under load | Flat — full power until near-empty | Sags as it discharges |
| Charging needs | Needs a compatible (DC-DC) charger | Tolerant, charges off most sources |
| Cold tolerance | No charging below freezing (some have heaters) | Charges in the cold |
| Upfront cost | Higher | Lower |
Where lithium wins
Usable capacity. This is the one that surprises people. A 100Ah lithium battery gives you roughly 80–100Ah you can actually use. A 100Ah AGM gives you about 50Ah before deep discharge starts damaging it. So a 100Ah lithium does the work of a ~200Ah AGM — and weighs a fraction as much.
Weight. Lithium is dramatically lighter for the same usable energy, which matters for payload, fuel economy, and where you can mount it.
Lifespan. Lithium delivers thousands of cycles to AGM’s hundreds. Over years of use, the higher upfront cost often works out cheaper per usable cycle.
Recharge speed. A lithium bank paired with a capable DC-DC charger can refill in as little as three hours of driving. AGM’s long absorption phase means it charges much more slowly, especially the last 20%.
Flat voltage. Lithium holds near-full voltage until it’s nearly empty, so your fridge and inverter get steady power. AGM voltage sags as it drains, which can trip low-voltage cutoffs early.
Form factors. Lithium comes in shapes to fit almost any compartment — GC2 (100Ah) and large GC3 (270Ah) cases, plus small 10/20/30Ah “base” units for light rigs, and both 12V and 24V configurations.
Where AGM still makes sense
Lower upfront cost. If your budget is tight and your needs are light, AGM gets you off the starter battery for less money today.
Charging simplicity. AGM tolerates charging from most sources without a dedicated DC-DC profile, and unlike lithium it can charge below freezing.
Cold-weather charging. Standard lithium cannot be charged below 0°C without damage (some packs add internal heaters). In sustained sub-freezing conditions, AGM avoids that limitation.
The charging catch with lithium
Lithium isn’t a drop-in replacement for AGM in every system. Most stock alternators can’t safely charge lithium directly, so a dual-battery system with a proper DC-DC charger is the right way to run it. Factor that charger into the cost when you compare — it’s part of doing lithium correctly.
Which should you pick?
- Pick lithium (LiFePO4) if you’re building a serious or full-time rig, run a fridge plus high-draw gear, care about weight, want fast charging, and plan to keep the system for years. It’s the right long-term choice for most overlanders.
- Pick AGM if your budget is tight, your loads are light, you camp in deep cold where charging below freezing matters, or you want the simplest possible charging with no DC-DC charger.
Whichever chemistry you choose, it has to be sized to your real daily draw and charged correctly. Map that in the dual-battery system guide and how much solar do you need, and see the power hub to fit the battery into the full system.