The most common off-grid question we get: how many batteries do I actually need? Oversize and you waste money and payload; undersize and you're chasing a dead bank every night. Here's a simple, honest way to size a lithium (LiFePO4) bank for your RV.
Shop RV lithium LiFePO4 batteries once you know your number.
Step 1: Estimate your daily watt-hours
List every load, multiply its watts by hours used per day, and add them up. A fridge, lights, water pump, fans, and device charging for a weekend camper often land around 1,000-2,000 watt-hours/day; add air conditioning or an inverter microwave and it climbs fast.
Step 2: Choose your days of autonomy
Decide how long you want to run without recharging - typically 1-2 days for a setup with solar topping up daily, more if you camp in shade or poor weather.
Step 3: Convert to amp-hours
Battery capacity is usually rated in amp-hours (Ah) at a given voltage. Divide your total watt-hours by your system voltage (12V, 24V, or 48V). Example: 1,500 Wh/day x 2 days = 3,000 Wh; at 12V that's 250Ah. Lithium lets you use most of its rated capacity, so you don't need to massively oversize the way you would with lead-acid.
Worked examples
- Weekend couple, solar daily: ~1,200 Wh/day, 1 day autonomy → ~100Ah at 12V.
- Family rig, some AC: ~3,000 Wh/day, 1.5 days → ~375Ah at 12V (or move to 24V/48V).
- Full-time off-grid with AC: often 400-600Ah-plus, frequently at 24V or 48V for efficiency.
When to move to 24V or 48V
Bigger banks and higher loads run more efficiently at higher voltage (thinner cables, less loss). If you're past roughly 300-400Ah at 12V, consider 24V or 48V - and match your inverter/charger to that voltage.
Frequently asked questions
Can I add batteries later?
With lithium it's best to plan the bank up front and add matched batteries; mixing old and new or different chemistries is not ideal.
How much solar do I need to recharge it?
Enough daily harvest to replace what you use - see how to build a Victron off-grid system and MPPT vs PWM.
Shop lithium batteries and the full Victron range. Ships from Upland, CA.