How much battery capacity does a campervan need?
There is no universal right answer — the honest figure comes from adding up what you actually use in a day, then making sure you can recharge it. A bigger battery is not automatically better; a battery you cannot keep charged is just expensive dead weight. Here is how to work it out properly rather than guess.
Start with a power budget, not a battery
The right way round is to work out your daily energy use first, then size the battery (and the charging) to suit. List everything electrical you use and roughly how long each runs in a day — lighting, fridge, water pump, phone and laptop charging, fans, heating, any mains appliances through an inverter. Each one draws a certain amount, over a certain time, and the total is your daily budget. That number, not a sales figure, is what your system should be built around.
The big loads dominate
A few items usually swamp everything else. A compressor fridge running day and night, an inverter feeding an induction hob or kettle, and electric or diesel heating dwarf the lighting and charging. If you have any of these — and especially all of them, as on a gasless van — your budget is far higher than a hook-up weekender's, and your battery needs to reflect that.
Usable capacity, not headline capacity
Remember that headline capacity is not what you can use. With lead-acid you can realistically use only about half before harming it; with lithium, most of it. So the chemistry changes how big a battery you need to meet the same budget — a point we cover in our guide on lithium versus lead-acid. Size around usable capacity, not the number on the label.
How many days between charges?
The other half of the sum is how long you need to last before recharging. A van that drives most days, or sits in good sun, refills regularly and can run a smaller bank. A van that sits still for days off-grid in poor weather needs to store far more, because nothing is coming in. Your battery size is really 'daily use multiplied by the days you need to be self-sufficient' — minus whatever your charging reliably puts back.
The mistake that strands people: ignoring charging
This is the one we see most. A big battery with too little charging capacity still leaves you flat — it just takes a bit longer to get there. Battery capacity and charging (engine/DC-DC, solar, hook-up) have to be reconciled against your real daily use, season by season. A modest battery that is reliably refilled can outperform a huge one that never gets full. Size the whole system together, or the headline battery figure means nothing.
So, a realistic approach
- Add up your honest daily energy use.
- Decide how many days you need to last without charging.
- Size usable capacity to cover that — allowing for your battery chemistry.
- Then check every charge source can realistically refill it where and when you travel.
- Leave headroom. Systems run at their absolute limit disappoint.
How we would help
This calculation is the foundation we build every system on — it is the first thing we do on a new build, and the first thing we check on an upgrade. Tell us how you use your van and where you take it, and we will work out the capacity you genuinely need, and the charging to keep it there.