Sizing a battery bank for a campervan

The first step in sizing a campervan battery bank is to work out what your daily energy budget is.

Which is what is the total of all the things that consume electrical energy in your camper van in a day. List each load, what it draws and how many hours it runs, total it, you can work in either amp-hours or kilowatt-hours.

This exercise beats guesswork every time. And once you have it, your next task is to match that to your generation. Typically, the generation options in a camper van are solar and charging from your DC-DC charger. Also, a factor is campground power if you frequent campground sites and don't freedom camp for more than 1 or 2 days. Otherwise, you're wholly reliant on your self generation, and that's the only thing you should consider.

You need to be generating at least what you're consuming every day, with some amount of generous safety factor on that (because some days there's less generation, more consumption, and there are also losses in the system). An extra amount more is a good idea, and the more that extra amount is, the more certain and reliable your energy solution is going to be.

If your camper has a fridge, it is likely the fridge's installation and efficiency will dominate your install requirements. Specifically the fridge's energy efficiency and installation, meaning ventilation around the condenser rather than packed against a wall, and whether the fridge is AC or DC, and what its power rating and energy consumption per day are.

When you add an inverter your budget jumps twice: once for what you run through it, and again for the inverter itself, because an inverter switched on and powering nothing still draws its idle current. On our NPS range that's 0.6A for the 700W, 1.1A for the 2200W and 1.5A for the 4500W at 12V, which is 14 to 36Ah a day if it's left on, and it's the single most common phantom load we diagnose. Our standby draw guide has the details.

Batteries in a camper, there are three choices of chemistry: AGM, lead-carbon, or lithium.

• AGM is the cheapest and suits the lightest duty.
• Lead-carbon gives you long life and a highly flexible install.
• Lithium gives you long life, but also has some restrictions on where you can place it.

Specifically, the two requirements for lithium in campers are. Where the bank lives is decided by the placement rules for connectable installations, and for lithium in a habitable area that means a sealed, externally vented enclosure with a BMS, certified to AS IEC 62619, so read the lithium-in-caravans guide before you build the battery box.

Charging

A DC-DC charger brings in roughly its rated current for every hour you drive, so a 20A unit is about 20Ah an hour into the battery.

Solar is the other source and it's seasonal, so consider how much of your use is going to be during summer and how much during winter, and is it going to be North Island or South Island? There's a massive difference between flat mounted solar on a camper's generation in the North Island during summer versus the generation for the same solar in the South Island during winter. You'll be looking at a factor of four difference between those two scenarios. Budget that different use case into your expectations of how much energy you're going to end up with each day from solar.

You can compensate somewhat for lack of generation by increasing the battery bank, which will give you a greater reservoir to draw from and then more time until you get a decent amount of generation or access to campground power. It is not a complete solution by itself, but it may give you more flexibility if your generation options are restricted.

Send us your load list and travel style and we'll run through the whole energy budget with you.