Camper Power Mk2

For various reasons our setup is not typical of the best way of doing this - in an ideal world we'd have waaay more battery capacity and consequently less (or zero) solar, but here we are. The main reason is purely that we don't want to make more holes in the vehicle to fit extra batteries in or cram big batteries under the seat (it's doable but it makes for ugly under-seat wiring with BIG wires which gives me the jeebies).

There are a few compromises we've made that you might not have to;

• More battery capacity trumps everything, if you can fit it in.
• Ventilation / insulation for the fridge makes a huge difference
• Not being inside a dark green metal box in direct sunlight would probably help a lot too. There's a reason most campers are white.

First step in any setup is working out what you need to power and for how long. Our setup is fairly basic;

• Waeco CRX50 fridge = 15W average (ish)
• LED Interior lights - 3W / 9W
• Water pump - occasional
• Eberspacher - occasional
• Phone charging - occasional

By far the biggest load (and most important) is the fridge - without cold beer we may as well be living in a cave like savages, or worse, a travelodge .

Extensive testing under the arduous conditions of the 24 Hours Of LeMans revealed that, when the sun's blasting and you're removing cold beer and replacing it with warm beer at a fair rate (for science!), the fridge actually uses a LOT more than its average power rating, maybe 50W when it's trying hard. Also when you're parked under or near trees, your solar performance drops massively.

So, our criteria are:

Now, this is very back-of-the-envelope-after-a-beer but just to show a rough sketch of how to do this…

Just to be clear - when doing these sorts of calculations you don't need to be very accurate, just round up to the nearest sensible number, using Fermi Estimation is pretty much fine as there's so much variation in the real-world use case and you'll always want a bit of headroom anyway.

We're running a Varta stop/start AGM battery which is ~80Ah, a leisure battery might manage a few more Ah on paper (100Ah is average for the physical size) but the Varta one is designed for more abuse and can take a heavy charge (we've seen 80A from the alternator into it!).

This is basically the most / best battery we can fit without making mods to the vehicle, no great science to that bit!

It sits in the Mk2 battery cradle which bolts between the two outriggers on the chassis.

We have a 100A Smart-relay feeding the 2nd battery, via a battery cutoff switch - cheap and simple.

What we've ended up with (as of 2019) are;

• 2x 100W Bosch panels from Alpha Batteries
• 2x 30A “MPPT” (probably) cheap eBay controllers
• 4-way fusebox and isolator switch

All mounted in the little alcove above the passenger's head.

Basically we started with one panel & controller and then just doubled up as it was the simplest and cheapest option and gives some redundancy.

Now, there are all manner of complications that set in when you throw campers into the equation - a lot depends on what exactly your camper's fitted with (does it have any mains-powered stuff or is it all 12v?) and what you're doing with it (some people go camping to sit in their camper and watch TV… no, I don't know why). As mentioned in the Solar Panels for your Camper page, driving about charges the battery relatively quickly anyway (if you have a good split charge unit), and when your house is also your transport you're unlikely to be parked for long periods. Caravans, by contrast, can get parked up for ages while the tow vehicle goes out having all the fun.

As we're not in the Winnebago league of having a full-size dishwasher and 24/7 air-con, and we're not in the boondocking category of parking up for extended periods with no activity, we just need cold beer and a light to drink it by when parked up for a few days in a field at an event.

Everything in the vehicle is 12v, so adding a mains hookup would only be charging the battery, at which point you're reliant on a chunky charger to make best use (and finding a charger which can tolerate being connected to a driving vehicle).

This issue came to a head for the 24 Hours Of Le Mans, which meant we'd be camped in a field for ~4 days straight. Cold beer is an essential requirement at this event so something must be done!

So the challenge is:

• Keep the beers cold for up to 5 days
• NO mains available
• NO driving about
• North-European weather (could be hot, could be cloudy)

The Mk1 fridge (standard 3-way caravan fridge) would consume a constant 100w day & night.

Solar panel from Alpha Batteries

Here's the 3-way running on 12v Vs the CRX50 running on 12v, as you can see, there's a fair difference!