LiFePO4 vs AGM for an RV: usable energy and tradeoffs
Compare battery chemistries for RV duty cycles using usable capacity, charging limits and real total cost criteria.
comparison · transparent planning
A 100Ah label does not make two battery chemistries interchangeable. Focus on documented usable energy and system compatibility, not just the purchase price.
Compare usable watt-hours fairly
Start with the specific battery's documented voltage and capacity, then choose a discharge window. The worked comparison below separates a named manufacturer's LiFePO4 rating from an illustrative AGM scenario and shows how a reserve choice changes available energy.
Charging and temperature matter
Check the charge controller profile and the battery maker's stated temperature limits. Lithium systems may have protection electronics and low-temperature charge restrictions; lead-acid batteries also have charge-stage and life-cycle constraints. Do not use an existing charger merely because connectors fit.
Compare lifetime economics only with evidence
A credible comparison needs a delivered price, the exact battery's cycle-life conditions, documented warranty, expected duty and charger replacement requirements. The source-backed cycle figures below are manufacturer claims for one range; they do not establish a guaranteed lifetime cost for your use.
Decision checklist
Record battery mass and installation space, expected winter temperatures, compatible charging equipment, monitoring needs and your budget. Seek qualified installation advice when changing chemistry in a built-in system.
A documented LiFePO4 example, with cycle conditions
Victron rates its LFP Smart 12.8/100 at 100Ah / 1,280Wh at 25°C (capacity rated at discharge current ≤1C). The range's published cycle-life figures are 2,500 cycles at 80% depth of discharge and 5,000 at 50%, with remaining capacity at least 80% of nominal. These are manufacturer ratings, not our tests or a guarantee that another LiFePO4 battery behaves the same way.
Separate published ratings from your reserve choice
| Reference or scenario | Nominal Wh | Chosen usable window | Wh before delivery losses |
|---|---|---|---|
| LFP Smart 12.8/100; 80% scenario | 1,280 | 80% | 1,024 |
| Same LFP rating; 50% scenario | 1,280 | 50% | 640 |
| Illustrative 12V 100Ah AGM; 50% scenario | 1,200 | 50% | 600 |
The table is an energy worksheet, not a claim that every AGM must stop at 50% or every LiFePO4 should be discharged to 80%. Victron's AGM curves show that discharge rate and discharge depth affect usable capacity and cycle life. Select the product's operating window for your required life and load, then apply actual delivery losses separately.
Temperature and charging can decide the choice
The cited LFP Smart range specifies charging from +5°C to +50°C. A different battery with a heater or different protection may have different limits; the word “lithium” alone does not establish winter charging suitability. Verify the exact battery, charger, BMS, alternator interface and installation requirements before replacing an existing bank.
Use cycle counts as one input to total cost
Compare current delivered prices for complete compatible systems, the storage you actually need, expected temperature and documented warranty. A cycle rating is not a number of years: calendar aging and a lightly used vehicle can dominate. Do not multiply a manufacturer rating into a guaranteed lifetime saving, or compare ratings taken under different conditions as if they were one controlled test.
Sources and calculation notes
- Victron Lithium Battery Smart datasheet — capacity, cycle-life conditions and temperature limits
- Victron AGM/Gel datasheet — discharge-rate ratings and depth-of-discharge tradeoffs
Documentation checked 2026-10-24. Manufacturer specifications describe the named product or range, not every battery of that chemistry. Tables are our arithmetic under stated assumptions; they are not hands-on discharge tests or product recommendations.
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No fabricated product tests or affiliate claims. Compare verified specifications before buying.