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Designing an RV lithium battery system? This guide covers capacity sizing, charging sources, BMS selection, and safety — everything you need to replace lead-acid with LiFePO4.
Sizing Your Battery Bank
Calculate daily consumption:
- List all DC and AC loads with wattage and hours
- Total Wh ÷ 0.85 (inverter efficiency) = battery Wh needed
- Add 20% margin for cloudy days
Example: 2,000Wh daily use → 2,400Wh battery minimum. Our 12V 200Ah dual-purpose LiFePO4 battery (2,560Wh) fits well for RV house loads with engine-start support. For larger systems, see our 12V 400Ah deep-cycle battery.
Charging Sources
| Source | Typical Power | Notes |
|---|---|---|
| Solar | 200–800W | MPPT controller required for LiFePO4 |
| Alternator | 30–60A | DC-DC charger required (not direct) |
| Shore power | 20–100A | LiFePO4-profile charger required |
| Generator | Varies | Via shore charger |
BMS Selection for RV
- Current rating: Size for max simultaneous load + 25%
- Low-temp cutoff: Essential for 4-season RVs
- Bluetooth monitoring: Highly recommended for RV use
See our BMS selection guide.
Wiring and Safety
- Use proper gauge wire (voltage drop <3%)
- Fuse within 18″ of battery positive terminal
- Ventilation not required for LiFePO4 (unlike lead-acid)
- Secure batteries against road vibration
Replacing Lead-Acid: What Changes
- Charger: Must switch to LiFePO4 profile
- Solar controller: Set to lithium mode
- Alternator charging: Add DC-DC charger (protects alternator)
- Battery monitor: Shunt-based recommended (voltage-only gauges don’t work on lithium)
Frequently Asked Questions
Can I mix old and new batteries?
No. Always use matched batteries of the same age, capacity, and brand.
Do I need to upgrade my converter?
Yes, if it doesn’t have a lithium profile. Lead-acid charging damages LiFePO4.
How many solar panels do I need?
Rule of thumb: 200W solar per 100Ah of 12V battery for full-time off-grid.
Contact LJY Energy for RV battery system sizing help.
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