Everyone prices the battery. Almost nobody prices the bank. The difference is the reason a "cheap" lithium upgrade ends up costing 40% more than the number in the shopping cart — and knowing it up front is how you avoid a half-finished install sitting in your garage.
The hidden costs nobody budgets for
- Lithium-compatible converter: most factory converters use a lead-acid profile. They'll charge lithium to roughly 80% and then hold a float voltage lithium doesn't want. Budget for a swap.
- Cable and fusing: correctly sized copper cable plus an appropriately rated fuse or breaker. This is not the place to save money.
- DC-DC charger: without one, your alternator can't safely charge a lithium house battery while driving.
- Monitoring: free if you buy a Bluetooth cell; extra if you add a shunt later.
Three real budgets
| Setup | Capacity | What's included | Who it suits |
|---|---|---|---|
| Starter | 100Ah | Battery + cable + fuse, reusing an existing lithium-ready charger | Weekenders |
| Standard | 100Ah | Battery + converter swap + cabling + fusing | Most RVers |
| Full-time | 314Ah | Large cell + DC-DC charger + inverter cabling + monitoring | Boondockers, full-timers |
The number that matters: cost per cycle
Sticker price is misleading. What you're really buying is charge cycles:
| Battery type | Cycle life | Usable capacity (100Ah rated) | Cost per cycle |
|---|---|---|---|
| AGM (lead-acid) | 300–600 | ~50Ah | Highest |
| LiFePO4 | 3,000–5,000 | ~90–100Ah | Lowest |
Because lithium gives you nearly double the usable capacity and roughly ten times the cycle life, the cost per usable cycle works out dramatically lower — which is why lithium pays for itself if you camp more than a handful of weekends a year. Our lithium vs AGM comparison breaks down the full arithmetic.
Where to save (and where not to)
- Save: buy one large cell instead of several small ones — better price per amp-hour.
- Save: get a battery with Bluetooth built in and skip the separate monitor entirely.
- Don't save: on cable gauge, fusing, or a proper converter. These are safety items and the most common cause of failed installs.
What we'd buy
HumsiENK 100Ah LiFePO4 (Bluetooth)
Visit HumsiENK Store Visit Wattcycle Store
Frequently asked questions
Do I need to replace my converter for lithium?
Often yes. Many factory converters use a lead-acid profile that only charges lithium to about 80% and holds a float voltage lithium doesn't want. Budget for a lithium-compatible unit.
Is lithium actually cheaper than AGM?
Over time, yes. Lithium delivers 3,000–5,000 cycles versus 300–600 for AGM, and roughly twice the usable capacity per rated amp-hour. On cost per cycle, lithium is usually several times cheaper.
What hidden costs should I budget for?
A lithium-compatible converter if yours is older, correctly sized copper cable, an appropriately rated fuse, and possibly a DC-DC charger for alternator charging while driving.
Disclosure: RV Battery Hub is reader-supported and may earn from qualifying links at no extra cost to you. Prices change frequently — check the product listing for current pricing and confirm your RV's charger specification before buying.