In my experience, permanent installation of solar panels on a rig, such as flat on top of a trailer or vehicle, is nowhere near as effective as panels that can be moved about, because of optimum angle and efficiency.
I’ve used a portable 120w folding panel while camping in a variety of places, both open and forested over the last few years and have had great luck.
It’s all I used to charge 100ah of deep cycle Odysseys for up to five weeks straight at a time, which in turn provided all my power needs; some LED trailer lights, water pump, charged multiple mobile devices, power packs, multiple battery chargers (for AA, AAA, and camera batts), misc USB stuff, and my power-hungry 48v ebike battery. Sounds like a lot, but I was surprised how little 110 power I actually needed and how easy it is to live on primarily 12v alone.
So, no shore power, no other power in camp or from my van to charge the deep cycles for over a month at a time, just the 120w folding solar panel. Could easily go longer depending on only the solar panels, without shore power or my van charging the deep cycles; I just wanted to get moving again.
If my panel was stationary on my rig, it would be nowhere near as efficient. I can move my 120w folding panel anywhere within about a 45′ radius of my trailer and the deep cycles. I use a #10 gauge cable to minimize transmission loss and made up my own cable with Andersen plug ends. Then you want a fairly decent charge controller, too, to regulate the amps generated and manage how it’s distributed to your deep cycle(s).
Having your panel on your rig permanently means you’ll be parking in the sun more often than you might want to get sun on the panels, and may need to move your rig more often than you’d like to keep them in the sun. Having panels you can move lets you park your rig in the shade and leave it that way.
When you have clear sky and no obstruction, it’s far simpler to track the sun and aim your panels throughout the day and you won’t have to move them around as much, but aiming with proper angle and direction will dramatically increase efficiency. When you have a canopy of branches and leaves overhead–like I had in the Smoky Mountains for five weeks–you’ll find much greater efficiency if you can move the panels periodically to be in the sun wherever it peeks through the canopy and aimed just ahead of where the sun will be. Newer panel technology allows better panels to still harvest power even if part of the panel is shaded or of the sky is overcast. Older and less-efficient panels often lose efficiency or don’t draw any power at all if even one cell of the panel is shaded or if the sky is even mildly overcast.
I devised a tiny sundial of sorts with my mini-Streamlight flashlight, where I’d simply hold it on the face of my panel, sticking straight out, then aim the panel so the Streamlight cast no shadow. Then I knew the panel was aimed as directly at the sun as could be and was working to its maximum efficiency. You can actually see the amps increase on your charge controller. They make commercial sundials for aiming solar panels, but I just used my mini-Streamlight, as it is always in my pocket.
Here’s a post I made about it on instagram one morning that explains it a little more:
You’re dealing mostly with two angles when aiming your panels; relative to the ground and side to side as the earth turns. You’ll find most movable or folding panels can be set to 45º or less, and that is not always what you need, nor are they always as stable as you might like. I took to using a folding painter’s bench behind my folding panel, on which I often set other solar devices. That way, when I aimed my panel, my other devices were also aimed. I could stand my panel almost straight up for early morning sun and adjust it anywhere to as low as I wanted for overhead noontime sun.
I learned pretty quickly to aim the panel just ahead, to the middle of where the sun would be over the next hour, or however long I wanted before re-aiming the panel. IF you have time to do that in camp–and I did because I was fascinated at tracking the sun and learning how to best use the panels–then you’ll be using it to it’s best ability. If you know you’re going to be gone for a few hours or longer, aim it to the middle of where you know the sun will be be over the time you’re gone.
When your panel is not aimed as directly towards the sun as can be, as is the case when its laying flat on the top of a rig or simply at a 45 all day, it’s only working to its best ability for an hour or so each day. You can rig up actuators so your panel tracks the sun throughout the day, but that’s typically more for off-grid ground installation, not mobile camp use. I’m looking into it, though, for night photography as well. There are tripod heads available (as well as some really clever DIY solutions) that raise and lower in time to the earth’s rotation.
I’m working on a design so I can have a couple larger, more powerful, panels that are meant to be stationary, but store them in tracks under my raised platform on the trailer (like a Frontrunner table) so I can slide ’em out and tilt them on two axis (both down and side to side) on the rack, or take ’em all the way off and move them around camp.
Just my way of thinking and doing things, but I don’t find it very useful to spend that many pesos to buy a good panel and make it permanently stationary when you can get far more bang for your buck in generating your own power if you are willing to move your panels.
Good luck with figuring out the best way to generate power for your rig and your needs!
Dry roads and open skies,
Road
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