Posts of varying effort on technology, cybersecurity, transhumanism, rationalism, self-improvement, DIY, and other stereotypical technologist stuff. Crazy about real-world functional programming.

Adding solar power to the camper van

We added solar power system to the camper van. It was delightfully easy.

First, we sized the system to our modest electrical needs: have power to run the exhaust fan, charge some cell phones and plug in random knick-knacks that take AC adapter plugs.

We settled on a 100 watt solar panel, with a 35Ah capacity lead-acid battery and a small inverter. A 35Ah battery can provide 420 watts of power from fully charged. The modest sized battery only takes a few hours of sunlight to charge fully. It won't run an air conditioner or a power tool, but for minimalist camper life-style stuff it works perfectly.

Next, selecting stuff to buy. It turns out there are kits that take away a lot of the guesswork. I bought this kit by Renogy. Also this inverter and this battery.

Let's look through the list of components.

  • Solar panel: everyone knows what a solar panel does. It's a screen that takes in sunlight and puts out electricity. In this case it puts out DC power at 12 volts. The same thing the battery works with.

  • Lead-acid battery: everyone knows what a battery does. It stores energy. Lithium-ion batteries are all of the rage these days, and last significantly longer, but they're also more expensive. Although lead-acid batteries are a little more risky (they're full of acid) and don't last as long, the lower cost meant we could get this system off of the ground more easily.

  • Charge controller: a device that takes power from the solar panel and uses it to charge a battery. Why can't you plug the solar panel directly into the battery? Well, you could, but then there'd be nothing to tell it to stop charging the battery once it's full. Batteries don't like being over-charged. It's apparently dangerous, even. So that's why there's a charge controller. It watches the line to the battery: when the battery is empty it charges it at full blast. When the battery is full, the controller backs off so it won't overcharge.

  • Inverter: changes DC power to AC power, so we can plug in devices that expect a AC wall-style power.

Here's a diagram of how we wired it.

Probably the hardest part was figuring out how to run the cables from the solar panel on the outside to the charge controller and battery on the inside. There's a lot written on the internet on how to run cables through things and waterproof them. You can seemingly spend a sizable amount of money by using special adapters. What I ultimately settled on was something much simpler: grommets and caulk. I drilled a hole slightly bigger than the thickness of the cable, put a 20 cent rubber grommet into the hole, and then stuffed the cable through the grommet. I sized a grommet just barely big enough that it took some force to push the cable through. In some cases I had to moisten the cable a bit to make it stuff through more easily.

Once all of the cables were connected and cut to size, I clamped them down so they wouldn't slide and applied caulk over the grommets from both the roof side and the inside. I let the caulk dry and then applied it again. Seems fine so far.

It works. We've gone on extended camping trips, had power for our phones, and been able to keep ourselves cool at night by having airflow without ever having to risk the van's startup battery to do it. Pretty excited by the result and it cost about $300 in all.

Here's what it looks like mounted to the "roof rack". You can also spend a small fortune on these too, offered by brands like Thule and Yakima, but what I settled on here was a $60 commercial ladder rack found on ebay.

Inside, tucked away, we have the charge controller, inverter and battery.

The only part of this system that I'm not fully thrilled with is that there's no intelligent cross-over between van power systems. Ideally once the leisure battery was charged the solar panel would then work on topping up the van battery if needed. Vice versa too; it would be nice to charge the leisure battery off of the engine alternator, but otherwise ensure the van didn't try to draw power from the leisure battery and vice versa.

I'm still evaluating options for when I do a power system refresh, but in the meantime there's plenty to be happy with: free and clean mobile power!

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