How To Build A Campervan Part 3: POWER!

When I first started thinking about converting a van, one of the main things I wanted was power. Solar power to be precise, with batteries to store it during the day so I could have lights and more at night. From RVs to sailboats, this has become increasingly common. As such, there are a bunch of companies that offer everything from individual products to full kits with everything you need.

But what do you need? While there’s a massive amount of information out there, most of it is for larger Sprinter van and RV-sized installs. For something small, more minivan sized, there’s a lot less info. There are also certain expectations. Most notably that you won’t have a significant load since there isn’t the physical space to have a lot of energy-draining devices. That’s fair, to be honest, but I wanted a fridge, lights, enough energy to charge cameras and a laptop, and ideally all that for a few days off the grid (or at least, not connected to “shore power” at a campsite).

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I also wanted what in my head I called “significant redundancy.” I didn’t want to be constantly worrying about how much power I had in my batteries, or if I’d run out if it was cloudy for a few days. In the end, my final build ended up being more than I needed. However, the price difference between that and a build with less overall capacity wasn’t a huge difference (with one exception, which I’ll explain). So here’s what I learned, what I bought, and what you might want to do instead if you’re building out a small campervan.

Solar Panels

Solar panels are surprisingly cheap. There are foldable/storable options, but I wanted to mount them on the van. One less thing to set up when arriving at a campsite. This would also have the advantage of charging while I was driving. The full-size panels like what you’d mount to a vehicle are generally in the 100-watt range, per panel. For your calculations, remember that’s best-case. If it’s cloudy, rainy, etc, you might not get any power at all, or way less.

Some options have rigid frames, but there are also flexible panels that you can glue to your roof. I couldn’t do the latter because of my panoramic moonroof, and because of some specific requirements that I’ll detail in the next article, so I went with rigid.

In the first example of going with more capacity than I would really need, I went with two 100-watt panels. I probably could have gotten away with just one, but given how inexpensive they are, I didn’t see any reason not to get two. The biggest “cost” would be the install in general, which I’ll get to in the next article, and having two panels instead of one wasn’t going to add much.

Charge Controller

You can’t connect solar panels directly to a battery. I mean, I suppose you could but it’s not a good idea. You need a “brain” to figure out what the batteries need. This brain is called a charge controller, and it goes in between your panels and your battery.

There are two types of charge controllers, PWM and MPPT. PWM, or Pulse Width Modulation controllers are older, less efficient, but cheaper. MPPT, or Maximum Power Point Tracking, is newer, more efficient, but more expensive. They do a better job regulating and adjusting the power between the panels and the battery.

Unless you’re on a very tight budget, you should get MPPT. The difference in price isn’t huge, and the extra money is worth it in terms of efficiency and flexibility. Make sure you get a charge controller that can handle the power expectations of your system, which in fairness isn’t going to be a lot for a minivan build. I went with a 20 amp model as it came with the kit I bought, which is plenty for 2 panels. If you have more panels you’ll want a higher capacity charge controller. The price difference between MPPT controllers in this range is negligible.


Batteries are the single biggest cost for a solar system. These might look like car batteries, but they’re far from it. Well, at least most of them are. Their capacity is rated in amp hours. So if you have a fridge that draws 5 amps, and you have a 50 amp hour battery, then you can run that fridge for 10 hours. The three types are batteries are:

Lead Acid: OK, these are like what’s in every modern car. They are extremely heavy, but the cheapest of the three options. They’re not really designed to do what we’re trying to do here, so again unless you’re on a really tight budget, you’re better off with one of the other options. One important aspect to keep in mind, you shouldn’t let them drop below 50% capacity. As such, however much capacity you want for your system, you need to buy twice that.

GEL and AGM: These are sealed lead acid batteries that are more forgiving for campervan usage than repurposed car batteries. They’re more expensive than those, but much cheaper than lithium (which we’ll discuss next). However, they don’t last as long and have the same 50% issue of traditional lead acid.

Lithium: Lithium Iron Phosphate (LiFePO4) batteries are similar to what you have in your phone (lithium ion), except they’re a safer, more stable design. They’re relatively lightweight, long-lived if you take care of them, and are designed to work with the drain-and-charge cycles of the typical campervan. They’re also significantly more expensive than the other types, however prices get better every year.

I went with lithium, which I don’t regret, but I got two 100Ah batteries which… OK, I don’t regret getting two but this was where my desire for extra capacity definitely cost a bunch of money. About 25% extra to be precise. Having used the system for months, even on days where I’ve used the batteries a lot, I have yet to fall below 60% of my system capacity. That said, it’s done and paid for, and it’s nice having the headroom to add more electrical devices without having to worry about running out of power in the middle of the night.

Optional Extras

For most builds, the above three items are all you really need. Solar to charge, charge controller to control, and batteries to store. You can power your devices either through the charge controller, or off the batteries directly.

I purchased two additional items that I thought I would need or want. I’m not currently using either for different reasons.

DC-to-DC charger: If you want to be able to charge your batteries from your vehicle’s alternator, you need a DC-to-DC charger. I thought this would be a great accessory in case I was stuck in the rain for a few days and wanted to charge my battery. The back of my van has a separate fuse box, which made the install easy, and the trim level of my Transit Connect has a 150-amp alternator.

While I don’t regret buying or installing it, I had a kill switch put in line which is currently set to “off.” The problem, if you can call it that, is it’s pretty rare I’d stick around somewhere if it was raining long enough to deplete my batteries. Also, it’s basically always running if the batteries dip below 100%. That’s as designed, and not an issue, but the panels themselves are also charging so it seemed a duplication of effort, and one that was reducing my fuel economy by some tiny amount. So this is nice to have, but in hindsight, definitely optional. At least, for my kind of campervan build. If you’re living in your van, perhaps you’d get more use out it.

Inverter: If you want to run standard household appliances, or you want to plug into power at a campsite or house, you need an inverter. This converts the AC power you get from a regular power outlet into DC power that your batteries and other car devices use. It’s like a big version of a phone charger.

The problem is, scale that up to work with the above equipment, and it’s a huge and heavy device. While I could theoretically find the room in my van, I have yet to actually need it. My over-capacity design means I rarely use that much of my battery capacity, so I haven’t needed shore power. I also hate cooking, and have found that a simple camp stove suffices for my needs instead of a hot plate and a rice cooker (which was the original plan). While I was hoping to go completely fossil fuel-less with this design (other than the van’s engine), the infinitesimal amount I use to cook was likely less than what I would burn lugging around a heavy inverter. So, again, useful for some people for sure, but for me it wasn’t necessary.

All told, I spent about $2,500 on all the above, including taxes. If I was buying it all now with what I know, I’d skip the inverter and one of the batteries for sure, and maybe also the DC-to-DC charger. That’d put the cost around $1,100. This was all with Renogy, and the prices for all this equipment has fallen even since I started my build. I went with them because they had some good package deals, lots of info on their site, and helpful tech support. I paid full price for all the gear, they don’t sponsor me or anything.

For more info, check out the video above. Up next, getting it all installed and running. Stay tuned.

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