RV battery types: AGM, gel and LiFePO4 compared
“100 Ah” is printed on almost every house battery – but how much of it is really usable, how often the battery can be recharged and how it behaves in the cold depends on the type. This article explains the differences between lead-acid technologies (AGM, gel, flooded) and lithium iron phosphate (LiFePO4) so you can put the numbers in the calculators into perspective.
Rated capacity is not usable capacity
Lead-acid batteries age quickly when discharged deeply. Rule of thumb: not below 50% state of charge. Of 100 Ah, about 50 Ah (600 Wh at 12 V) is practically usable. LiFePO4 cells, on the other hand, tolerate 80–90% depth of discharge over thousands of cycles – 100 Ah become about 80–90 Ah (1,000–1,150 Wh at 12.8 V).
On top of that, lead-acid has the Peukert effect: capacity is rated for a 20-hour discharge (C20). If you discharge faster – say with an inverter – you get noticeably less. At 50 A from a 100 Ah AGM it's only about 63 Ah by calculation. LiFePO4 practically doesn't have this effect.
Battery runtime calculator – accounts for depth of discharge and the Peukert effect automatically
The technologies at a glance
| Feature | Flooded (lead-acid) | AGM | Gel | LiFePO4 |
|---|---|---|---|---|
| Nominal voltage 12 V system | 12.0 V | 12.0 V | 12.0 V | 12.8 V |
| Recommended depth of discharge | ≈ 50% | ≈ 50% | ≈ 50% | 80–90% |
| Cycles (at recommended DoD) | 300–500 | 400–700 | 500–900 | 2,000–5,000+ |
| Weight per 100 Ah | ≈ 55–66 lb (25–30 kg) | ≈ 62–70 lb (28–32 kg) | ≈ 66–75 lb (30–34 kg) | ≈ 24–31 lb (11–14 kg) |
| Charge efficiency | ≈ 80% | ≈ 85% | ≈ 85% | ≈ 95–99% |
| Charging below 32 °F (0 °C) | possible (slow) | possible | possible | only with heating / BMS lock-out |
| Maintenance | top up water, gassing | maintenance-free | maintenance-free | maintenance-free |
AGM (absorbent glass mat) is the standard in factory-built RVs: robust, inexpensive, high currents possible, but heavy and short on cycles. Gel batteries tolerate deep discharge a bit better but don't like high charging currents. LiFePO4 is light, cycle-proof and delivers stable voltage to the end – but needs a matching charger and protection from cold.
Charging: what changes with LiFePO4
- Charge profile: LiFePO4 wants 14.2–14.6 V without a long float charge at 13.8 V; chargers, DC-DC chargers and solar controllers need a lithium profile.
- DC-DC charger instead of an isolator relay: the low internal resistance of lithium cells can overload alternators; a DC-DC charger limits the current.
- Cold: no charging below 32 °F (0 °C). Good batteries have a BMS with a temperature lock-out, some an integrated heater.
- BMS limits: the maximum continuous current (often 100 A at 100 Ah) limits the inverter size.
Battery charge time calculator – with absorption phase for lead-acid and CV phase for LiFePO4
How much capacity do I need?
The starting point is the daily consumption in watt-hours. Frugal users are at 300–500 Wh, with a compressor fridge and laptop at 600–1,000 Wh, with an inverter for coffee or induction well above. For two days without recharging at 800 Wh daily consumption you need about 200 Ah LiFePO4 or 320 Ah AGM – at roughly a quarter of the weight.
LiFePO4 battery size calculator – converts daily consumption and off-grid days into rated capacity
Bottom line
For occasional camping with shore power, AGM remains a solid, inexpensive choice. If you regularly boondock, use solar or need to save weight, LiFePO4 is the better long-term choice – provided charger, DC-DC charger and solar controller match.
Sources
- Manufacturer data sheets for AGM, gel and LiFePO4 batteries (cycle counts, depths of discharge, weights)
- Peukert's equation (standard battery engineering literature)
Published 09/19/2026.