LiFePO4 vs AGM: Which Battery for a Camper Van Build?
For a camper van, the battery choice is really LiFePO4 (lithium iron phosphate) versus AGM (a sealed lead-acid type). Flooded lead-acid rarely makes sense in a van because it vents gas and needs maintenance. The decision comes down to usable capacity, weight, lifespan, cold behavior, and lifetime cost — not just the sticker price.
Usable capacity is the real number
A battery's rated amp-hours are not all usable. LiFePO4 lets you draw about 80% before you should recharge; AGM only about 50% if you want it to last. So a 100Ah LiFePO4 gives roughly 80Ah usable, while a 100Ah AGM gives about 50Ah. To store the same usable energy, an AGM bank has to be far bigger — often three times the amp-hours once you account for both depth of discharge and the extra autonomy AGM needs to avoid deep cycling. See the numbers side by side on the LiFePO4 vs AGM sizing page.
Weight and space
LiFePO4 is roughly a third the weight of AGM for the same usable energy — a decisive advantage in a payload-limited van. A 200Ah LiFePO4 weighs about 50 lb; the AGM bank needed to match it can top 200 lb. In a build where every pound competes with water, gear, and passengers, that gap alone often decides it.
Lifespan and cost over time
LiFePO4 typically lasts 3,000–5,000 cycles; quality AGM manages 300–500 in deep-cycle use. Even though LiFePO4 costs more up front ($200–$700 per usable kWh versus $150–$350 for AGM), it usually wins on cost per usable kWh over the life of the build because you replace it far less often. If you full-time, you may outlast several AGM banks with a single lithium one.
The cold-weather catch
LiFePO4 has one hard limitation: it must not be charged below 0 °C (32 °F), or it suffers permanent lithium plating damage. Discharging in the cold is fine, but usable capacity drops about 20% near freezing. The fix is a self-heating battery or an external heater pad plus a charger that blocks cold charging. AGM can accept a charge below freezing (slowly), which is its one genuine edge for unheated winter rigs.
Safety and chemistry
LiFePO4 is the safest lithium chemistry for vehicles — it does not have the thermal-runaway reputation of the lithium chemistries used in laptops and phones. A quality battery management system (BMS) handles cell balancing and cutoffs. AGM is inherently stable and sealed, with no venting in normal use, which is why it remains a reasonable budget choice.
Bottom line
- Full-time, weight-sensitive, or heavy daily use: LiFePO4. It is the default for good reason.
- Tight budget, light or occasional use, or unheated sub-freezing charging: AGM can still make sense.
Whichever you pick, size it to your actual daily load. The calculator switches depth of discharge automatically when you change chemistry, so you can compare both banks in seconds.