I've acquired some surplus solar panels that I'm going to mount on the roof of my motorhome.
One is a standard frame type that should be pretty straightforward to mount. However, I do have a question about that one... what's the advantage to using the "Z" mounts versus a simple "L" brackets? Also, if using the "Z" mounts, how do you account for the curve of the roof (this particular panel is 3" along its short axis)?
The other two panels have a channel underneath and would seem to require a special mounting system. Can anyone point me in the right direction on mounts? I'd like the find the least expensive effective option available.
I made my mounts with 6" long aluminum 2" angle from Home Depot. It is L shaped and 2" in both directions. I drilled a 5/16" hole into one side to mount the panel to the bracket, and 3 holes 3/16" to use #10 screws into the rubber roofing. I used a lot of rubber roof sealant, and that stuff pretty much holds the mount down by itself, the screws are mainly for show.
I drilled a 5/16" hole into the solar panel's frame, and inserted a Nutsert, it is a pop rivet of sorts that has a 1/4-20 nut in the center, and then you can install a bolt to clamp the panel to the bracket that is already installed on the RV.
On my 120 watt solar panels that are 4' wide, I had to first pop rivet 2" angle aluminum to the back side of the panel in the two curbside corners of the panel, then my bracket bolts onto that angle aluminum.
You might need to do the same thing, pop rivet some material to the back of the panel to mount a bracket that can bolt to the roof bracket.
You can get pop rivets at Home Depot. The Nutserts I bought at Graingers. The nutsert tool sometimes has a adapter for installing rivets, but I already had a rivet tool, used to install ductwork and other metal things.
I guess you already heard about running UV resistant direct burial wiring down the back side of the refrigerator, to a suitable place to mount the controller, then to the battery?
Having at least 1" of air gap below the panels is almost a requirement to ventilate and cool the panels, they don't make nearly as much power when hot. I see most of the panels are 36 strings of cells, that can go to one type of controller. The other one - I can not tell what voltage it would be because counting the cells is difficult. If the ratings are the same, or close, you can use the same 12 volt controller. Hopefully the extra large controller is not 60 volts, that would require a special controller of it's own, while the pair of 36 cell panels can use a standard 12 volt in and 12 volt out controller. By carefully disassembling the larger panel, you might be able to break it up into 3 - 36 cell panels that can be wired in parallel. (disassemble the factory wiring connections, not the panel itself).
What sort of controller are you planning on using?
What voltage and amperage is your panels?
Fred.
* This post was
edited 02/16/12 10:12pm by Golden_HVAC *
This is a picture of my roof, after coating it with Herculiner, and you can see some of the solar panels, the huge blue things in the front are my 120 watt panels, the right side is a pair of 45 watt panels (popular size in 1994) and a tilt bar made from 3/4" angle aluminum.
You can see they tilt in different directions, when the pair of 120 watt panels went on, there was no clear real estate that will also allow tilting side to side, so the choice was to not tilt any of them anymore.
Golden_HVAC wrote:
The ladder and it's mounts, well coated with bedliner, and the rear cap seam.
This is the roof looking forward, and the passenger side solar panel is propped up, so I can coat the roof. I need to turn it the other direction, and finish that last square foot.
Fred.
My guess is your large panel will need to go above the drivers seat, keep it rearward as much as possible, it can whistle if exposed to to much air in the front. That panel alone might power the RV. Yes you can buy a 60 volt input controller that puts out 12 volts.
SunElec.com has several controllers to pick from. If you click on laminates, and click on video on how to construct a electrical box on a solar panel, they demonstrate how to solder on a new bussbar, to make the panel from 24 volts to 12 volts.
When I talk about 12 and 24 volts, it is nominal voltage, not exact voltage. So 12 volt nominal is a solar rating from 16 to 23 volts at the panel under no load, and 24 volts is twice as high. I suspect the 108 cell panel is something like 60 volts open circuit? That would be 36 volts nominal, unless it has the ability to be split into 3 - 12 volt nominal circuits.
You will have to plan your layout well to keep them out of the shade.
Test them first, connected to a battery, to see how many amps and volts each one produces.
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I'm planning on mounting them all flat. They'll all be mounted about amidships or a little aft. Some shading is bound to occur depending on the season, time of day and orientation of the motorhome.
All three panels have an open circuit voltage of about 20v +/- .7v. The big discolored one has no labels and put out 97 watts pointed at the sun when I tested it in November. The bigger blue panel is labeled 75 watts and put out 51.6 watts while the small blue panel is labeled 50 watts and was putting out 28.2 watts.
I'm planning on using a Morningstar SunSaver PWM controller.
I don't want to get too elaborate on the mounts. "Z" brackets or "L" brackets are a cinch for the big panel and there is plenty of room with either method to use standard bolts and nylocks. It's the blue panels that look to need something special and compatible with the channel type frame.
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