When I first set off on my See-the-USA-in-an-RV trip back in May of ’14 I brought with me a little, 120 watt portable solar panel kit with the idea it would generate a little electricity and cut down a little on how long each day I’d need to run my generator, and it has. As time has passed and my explorations into the scintillating world of sunshine and solar have progressed I’ve learned more and more about the whole solar thing. Learning about this sort of stuff is fun and has practical benefits, one of which led me to replace the controller on my solar panel kit and this has allowed me to go generator free for the most part since then.
One of the hard parts about making educated decisions about things such as which solar panel or system to buy is that you just can’t make an educated decision when “you be iggerunt”. Such was the case when I bought my GoPower PSK-120 portable solar panel kit which I’ve reported on separately here.
One of the things I wrote about in my report on the GoPower kit was the placement of the charge controller, the device that controls how much of the electricity generated by you solar panels is sent to your batteries and when. I’ve learned more about this very recently. I suppose it would be fair to say that in my initial report I complained that the controller was glued to the back of the solar panel which necessitated shipping the entire kit in the event the controller needed repair or replacement. Now that’s just dumb. Why not make it easily detachable so that you can send this itsy bitsy device, the controller, through the mail in an itsy bitsy package for a buck and change instead of having to deal with the huge hassle and expense of shipping a humungous 35 pound solar panel at great expense and inconvenience? It don’t make no sense. Its just plumb dumb. (Note: In July of 2015 GoPower informed me that they have modified the method by which they attach the controller in the PSK-120 kit so that it is no longer glued to the back of the panel.) It’s also dumb to put a non-waterproof device on a solar panel made for outdoor use. That’s all old stuff in my original report.
What I’ve recently learned, and from where the title of this article comes, is that there are a couple other reasons that gluing a charge controller onto the back of a solar panel is not a good idea. The first is that it might create a hot spot because it inhibits cooling in that area of the panel and may even generate heat as a byproduct of its operation. Hotspots on solar panels are not good and can ruin them. Next, every inch of wire between a solar controller and the batteries it is intended to charge represents a loss of voltage due to resistance inherent in the wire. I can understand why GoPower put the controller on the panel. I mean, where else can they put it if they want to sell a panel that is plug and play, where you don’t have to perform a separate installation of the controller? It’s just that I want you to know if you don’t know already that placing the charge controller as close to the batteries as possible is a better idea, especially when the wire run from the panel to the batteries is long.
Charge controllers are set-up to provide a certain amount of voltage to the batteries at certain stages of charging. Here I refer to multi-stage controllers which describes many if not most contemporary solar charge controllers. If there is a long wire run, or wire that isn’t heavy enough, or both, between your controller and your batteries, the amount of voltage sent by your controller can and most likely will be reduced due to the resistance in the wire. For example, your controller may be sending 14.4 volts but the batteries may only be receiving 13.4. This describes my situation where the wire run is 40′. The result will be batteries that never get fully charged. Then, when you decide you’re not getting enough electricity from your solar to run your TV, your Mr. Coffee… whatever, you go out and buy more solar panels and more batteries at great expense when really all you needed was to move your charge controller closer to your batteries. It’s 10 o’clock, do you know where your charge controller is? Are you with me now?
I am far from an expert on any of this, but I’m learning and have learned quite a bit. One resource from which I have learned quite a bit and which I have enjoyed is HandyBob’s Solar blog. If you’re keen on learning about solar for your RV and why much of the advice you get from solar dealers is to be trusted only about as far as you can throw a piano, start there, with his RV Battery Charging Puzzle. You’ll be doing yourself a huge favor. I have also condensced a lot of what I have learned into my article Things I have Learned About Solar Power which is jam packed with very useful information.