Lead Acid vs Lithium RV Batteries
Last updated: September 3, 2026
The honest comparison
| Factor | Flooded / AGM lead-acid | LiFePO4 lithium |
|---|---|---|
| Usable capacity (planning rule) | ≈50% of rated Ah | ≈90% (BMS cutoff) |
| Weight (100 Ah) | ≈55–70 lb | ≈25–31 lb |
| High-discharge behaviour | Loses capacity at high amps (Peukert) | Barely affected |
| Charge acceptance | Tails off above ~80%; slow to full | Takes high current until nearly full — solar/alternator love it |
| Cycle life (to ~50%/90% DoD) | ≈300–1,000 cycles (flooded/AGM at deep discharge) | ≈3,000–5,000 cycles (manufacturer-rated) |
| Cold: discharging | Capacity drops 20–30% near freezing | Works, mild capacity loss |
| Cold: charging | Fine (slower when cold) | Must not charge below 0 °C without a low-temp BMS/heater — permanent damage risk |
| Upfront cost (100 Ah usable-equivalent) | Low (2× 6 V golf-cart ≈ $400–600) | Higher (≈$500–900 per 100 Ah; usable ≈180 Ah-equivalent of lead-acid) |
| Maintenance | Flooded: water levels; AGM: none; both: keep charged in storage | None; keep BMS firmware/app sane |
| Fail mode | Gradual capacity fade; sulfation from sitting discharged | BMS disconnect events (low voltage / low temp); usually abrupt, not gradual |
Ranges are industry-typical planning values; specific brands publish their own (often better) numbers — verify against your battery's datasheet.
Cost per usable amp-hour over time
Divide purchase price by (usable Ah × cycles). A $550 pair of 6 V golf-cart batteries: 220 Ah rated → 110 Ah usable × ~500 realistic deep cycles → ≈ $0.01 per usable Ah-cycle. A $700 100 Ah lithium: 90 Ah usable × 4,000 cycles → ≈ $0.002 per usable Ah-cycle — before counting weight saved and charge speed. The economics tilt toward lithium the more you cycle; toward lead-acid the less you do.
When each one wins
- Choose lead-acid if: budget decides, you plug in most nights, your usage is a few weekends a year, or you enjoy a proven system with a multimeter and a watering can.
- Choose lithium if: you boondock regularly, run an inverter or big 12 V loads, recharge from solar/alternator, count every pound, or plan to keep the rig 5+ years.
- Mixed answer for hard winter use: lithium discharges happily in cold but must not be charged below freezing without low-temp protection; AGM tolerates careless cold charging but delivers less. Neither is free — see the furnace-runtime realities in our furnace guide.
One thing no brand calculator tells you
Every brand calculator (battery and solar alike) ends in a cart for their chemistry. The physics above isn't brand-specific: usable capacity, weight, and charge acceptance are property-of-chemistry facts. Size your bank with the runtime calculator or solar calculator first, then shop brands on warranty and BMS behaviour.