Case Study: The RV Lead-Acid to Lithium Conversion
The same 200 Ah label means different things in the two chemistries — and the conversion decision is decided by the difference: usable energy, cycles, and cost per cycle.
The usable-capacity difference
At the recommended windows, the AGM bank offers 200 Ah × 50% = 100 Ah usable; the LFP offers 200 Ah × 80% = 160 Ah usable — 60% more energy from the same label (see capacity). The runtime calculator shows it: at a 10A house draw, the AGM runs ~10 hours, the LFP ~16.
The cost-per-cycle arithmetic
The original calculation that decides the purchase:
| AGM | LFP | |
|---|---|---|
| Purchase price (typical) | ~$400 | ~$1,200 |
| Cycle life (to ~80%) | ~500 | ~3,000 |
| Cost per cycle | ~$0.80 | ~$0.40 |
Typical order-of-magnitude figures — LFP costs three times as much upfront and roughly half as much per cycle, while also carrying 60% more usable energy per charge.
The three system changes the swap requires
- Charging profile — the converter and solar controller must switch to a lithium profile (3.65V/cell absorption, no equalization) or the LFP is charged wrong from day one (see lithium charging).
- Alternator protection — LFP accepts current far more eagerly than AGM; a DC-DC charger protects the alternator from the load (a BMS alone does not).
- Cold-weather charging — LFP refuses to charge below 0°C; winter users need heating pads or a charge-block strategy (see cold behaviour).
When the conversion is not worth it
Three honest counter-cases: the RV that sits plugged in (cycles never accumulate, so the per-cycle saving never materialises), the budget build (the upfront triple is real money), and the winter-only user (the cold-charge limits bite hardest exactly when the RV is used). The arithmetic says LFP; the usage pattern is the tiebreaker.
Our Read
My read: The RV conversion is the clearest worked example of battery economics anywhere — the same 200 Ah label, three times the price, half the cost per cycle — and the decision is decided not by the chemistry but by the usage pattern the owner actually lives.
Why: Cost per cycle plus usable energy is the correct frame, and the frame disciplines the decision: heavy users should convert, plugged-in users should not, and everyone should budget the three system changes before buying the battery — the battery is the cheap part of the swap.
My editorial view, not a purchasing guarantee.
Frequently asked questions
Is a lithium conversion worth it for an RV?
It depends on usage: LFP at ~$0.40 per cycle against AGM's ~$0.80 pays off only for batteries that actually cycle — heavy boondockers convert, permanently plugged-in RVs do not. Add 60% more usable energy per charge, and the heavy-use case becomes decisive.
What must change when converting an RV to lithium?
Three systems: the charging profile (lithium settings, no equalization), alternator protection (a DC-DC charger, because LFP draws harder than AGM), and cold-weather charging (LFP must not charge below 0°C). The battery is the cheap part of the swap.
Sources
Cross-verified from the engineering references cited on the linked pages.
- Manufacturer datasheets — AGM and LFP cycle life at rated depths.
- RV electrical practice references — DC-DC charging and lithium integration.
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