What Size Leisure Battery Do You Need for a Campervan?
Battery sizing is a chain of four numbers: what you use in a day, how many days you want off-grid, how much of the battery you are allowed to use, and the voltage. Get the chain right and the answer falls out.
Try it live
Size your battery bank live — calculator opens pre-configured for this setup
Step 1 — your daily watt-hours
Multiply each appliance's watts by the hours it runs, then add them up. A 45W compressor fridge cycling 10 hours is 450Wh. A 35W diesel heater on 4 hours is 140Wh. LED lighting at 12W for 5 hours is 60Wh. A modest weekend build lands around 800–1200Wh per day.
The trap is the fridge: "8 hours" is a guess people get wrong. In a warm van a compressor fridge cycles 30–50% of the time — 10–14h of run time is realistic in summer.
Step 2 — convert to amp-hours and multiply by autonomy
Divide daily Wh by 12 to get daily Ah, then multiply by the days you want to last without charging: 900Wh/day ÷ 12 = 75Ah × 2 days = 150Ah needed from the bank.
Step 3 — divide by usable depth of discharge
This is why lithium wins on weight: the same usable capacity needs barely half the rated bank. AGM looks cheaper per Ah until you buy twice as many.
| Chemistry | Usable DoD | 150Ah needed means | Cycles (roughly) |
|---|---|---|---|
| LiFePO4 | 80% | 190Ah bank | 3,000–5,000 |
| AGM / lead-acid | 50% | 300Ah bank | 400–800 |
Don't forget the BMS limit
Amp-hours is capacity; the BMS rating is how fast you can draw it. A 100Ah battery with a 100A BMS cannot safely run a 2000W inverter that pulls 170A — either a bigger bank or a high-discharge model is required. Check the inverter card for your DC draw.
Common questions
Is 100Ah enough for a campervan?
For lights, USB and a coolbox weekend build, yes. Add a compressor fridge and diesel heater and 100Ah lasts about a day — most weekend builds land at 150–250Ah of lithium.
LiFePO4 or AGM for a campervan?
LiFePO4 for almost everyone: 80% usable depth, a quarter of the weight, 5–10× the cycle life. AGM only makes sense for very occasional use or extreme cold without a heated battery.
How many solar watts per 100Ah of lithium?
Roughly 100–150W per 100Ah for UK conditions with a 30% real-world derate — more if you stay off-grid through winter.
Size your battery bank live