Supplemental Power

My brain’s been wandering around several different topics while sitting here in a van down by the river. Ways to address my power deficit during the shortest days of the year are among them. (Ironic, since we’re getting into the longest days of the year right now.)

My original plan had been to simply add a third Renogy 175-watt flexible solar panel to the two I already have, boosting me from 350 to 525 watts on the roof. I designed my charging system with enough reserve capacity to be able to plug in another panel and be done. However, I’ve discovered a major flaw in this plan. This third panel is six inches longer than my remaining roof space. I don’t know how I missed this before. I could’ve planned slightly better and saved maybe an inch or two by cramming my existing panels and roof vent closer together, but I couldn’t have saved the six inches I need. Regardless, it is what it is.

I can’t mix and match different kinds of solar panels in the same charging system. The output of all panels will be drawn down to the lowest common denominator, negating any real advantage I’d hope to gain. So adding one or two 100-watt panels to my existing system won’t work.

I have, however, figured out three alternatives that would give me that extra power boost I need during the winter.

The Temporary Solution

I can still get a third 175-watt Renogy flexible solar panel, but instead of mounting it to the roof, I can temporarily (not like this picture) attach it to the side of my van while I’m parked. I’m specifically looking to improve my charging situation in the middle of winter when the sun is low in the sky. I already try to park with my side doors facing south for maximum sun. I could figure out a way to attach this third panel to the side of the van, behind the side doors, for a pretty good shot at the sunlight coming from that low elevation.

I’d have to run a second set of cables from my charger to the new panel. I’d also have to figure out how to run them out the side of the van without getting damaged, which might happen if I just run them through the door opening. I’d also have to figure out a system for mounting the panel on the side of the van. I don’t intend to use it while driving (I can store the third panel in the trailer when not in use), but I do need it to stand up to high winds in the Arizona desert. I can make all this work. It’ll just take a little engineering.

Cost: $264 + whatever hardware I need to mount the van + cables

The Permanent Solution

Like I said, I can’t mix and match different size and wattage solar panels with my existing setup. But, I can run different size and wattage panels through their own charge controller! I could easily fit a pair of smaller 100-watt solar panels side-by-side on the remaining open roof space. They’d have their own cables going down to a 20-amp charge controller, which would then connect to my battery bank. This would add slightly more charging, 200 watts, than the single 175-watt panel would. Also, I’d have two independent charging systems, so that if one fails, I’d still get at least some charging out of the other.

This would take the most work to install. It would also be the most expensive of my three options. But once installed, it would just work. I wouldn’t have to think about it.

Cost: 2 x $120 solar panels + $88 charge controller = $328 + cables

A Generator

Last winter, Misty plugged me into her generator for a few hours every few days, and the boost was enough to keep my house batteries going through the shortest days of winter. This particular one costs $299 on Amazon. That’s right in the same price range as my solar options.

Generators have some downsides. They make noise. They’re not great for the environment. They require maintenance, oil changes, and so on. They’re bulky to carry around, set up, and take down. On the plus side, it would be no problem to carry one in the trailer. I already carry a gas can, which I can use to fuel a generator as well. It’s the simplest solution since I can just plug it into the shore power plug and 10-amp charger I already have. And I won’t have to worry about it blowing away in a strong wind.

This also opens up possibilities beyond just keeping my batteries charged in winter. I could replace one of my back windows with a solid panel and a tiny air conditioner, and run it off the generator on particularly hot days. This isn’t something I need to do, but I could. If gas prices stay sky high, it might cost less to run the generator for the AC than to drive to cooler locations. All I’d need is the smallest window AC available. It would cool my small “room” just fine, and it would draw a minimum of electricity — more than my current system can handle, but well within what a generator can provide. Who knows what other uses I’d find for the additional power a generator can provide.

Cost: $299 for this particular model

What To Do?

I don’t have to make any decisions right now. Whichever solution I use, I probably won’t buy it until I settle down in Quartzsite this fall, and will install it while I’m there before the days get short. So I have months to ponder this.

I’m probably not going to go with the permanent solution. It’s the most robust, and easiest to maintain because there’s no maintenance at all. But it’s the most hassle to install and let’s face it, I’m only short on power for a few weeks surrounding the winter solstice. I don’t need a solution this sophisticated for that.

I’m leaning toward either the generator, or the temporary panel on the side of the van. I can mount the panel to an angle iron frame to give it rigidity. (Remember, I can’t mix and match different types of panels, so I need the same flexible panel that I already have on the roof even though a rigid panel would be better for this application. I did compare the specs of Renogy’s rigid and flexible 175-watt panels, but they’re still too different to use together.) I could clamp/hang that metal frame from the rain gutter, and use some strong magnets to attach it to the body under the windows. It would take some finagling, but it would work. I also like the principle of using only the sun instead of gas to run my house batteries. (Yes, I do charge them off the alternator, but only when I’m already driving somewhere anyway. I’m not running the engine specifically to charge the batteries unless I have absolutely no alternative.)

Or, I could just buy a generator, solve this problem, and give myself the option of AC and other high-power tools or accessories. I could help keep other people charged up the way Misty helped me. It would be an investment for the future. Though that future would depend on gas, whose availability is less reliable than the sun that’s guaranteed to keep burning for another 5 billion years — longer than I’m going to be around, at any rate.


  1. Hi Justin,
    Would it make any sense to install a 175-watt Renogy flexible solar panel on the roof of your trailer and plug it in to your existing power system through an external connector?

    Liked by 1 person

    1. I could. When I’m parked somewhere for a while, like in Quartzsite, I don’t always park right next to the trailer, though. Sometimes I park some distance away and put up a shade cloth between the van and trailer. It’s probably just as much/little work to temporarily attach it to the van instead. Good thought, though, and definitely an option! I’ve also considered giving the trailer its own solar and battery system, using less expensive, more durable rigid panels attached to roof racks. I don’t have a need for that at this point, though.


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