Enter what you run in your van and how long you’ll go between charges. The calculator estimates the battery bank’s rated capacity in amp-hours (Ah) and watt-hours (Wh).
Camper Van Battery Size Calculator
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How the estimate works
Multiply each appliance’s wattage by the hours it runs in a day. For a fridge, use its compressor run time, or enter the average wattage from a full day of measurements and set it to 24 hours. Add any inverter standby draw as a separate DC load if you know it.
The calculator divides AC appliance use by the inverter efficiency, then adds the DC loads. It multiplies that daily total by the days between charges and adds the extra capacity you selected. Dividing by the usable share gives the rated capacity in Wh. Dividing that result by the battery bank’s nominal voltage gives Ah.
If your van uses 600 Wh per day at the battery, two days without charging take 1,200 Wh. At 80% usable capacity with no extra margin, the bank needs a rating of at least 1,500 Wh. At 12.8 V, that rounds up to 118 Ah.
Before choosing a battery
Use the usable capacity from your battery’s documentation. Check the bank’s continuous and surge discharge limits separately, especially if you run a large inverter. The estimate starts from a full bank and assumes no solar, alternator, or shore charging during the selected period.
For more detail, see Renogy’s guide to sizing a battery bank and Van Clan’s camper van battery guide.
