I'm building a solar panel for the first time and have the tabbed solar cells. I put together 4 strings of 9 cells. And the cells are each 0.55V, 3.6A.Because I'm going to be using the panel indoors and leaning it up against a window pane, I put them in a 24x36 inch poster-size frame. The frame has a plexiglass cover and a thick cardboard backing. My question to you is this. Will the cardboard backing up against the metal underside (positive side) of the solar cells be ok? I don't know if it may catch fire or if holes may burn through when there's full sun.My guess here is it should be ok. But maybe I'm wrong. If I am wrong, or if something should be put in between, please let me know what I should use.Thanks everyone!
No,do not use card board because your cells are quite powerful. Accident short might cause fire. Replace it with another piece of plexi-glass.
In commercial panels some sort of polymer is often used for backing. With a 2V panel there are 36 cells, which means they can still output about 4V for charging a 2V battery even when hot. The voltage reduces about 2.2mV per degree C per cell. Commercial panels are meant to work up to about 60 degrees C, which is quite normal in the sun. I have found just lying them on the grass the air circulation is reduced, and they get too hot to charge a 2V battery. This means the backing should have good thermal conductivity while being an electrical insulator, as well as mechanical strength. The cells are often encapsulated in a thermosetting plastic first, then laid face down so a liquid polymer can be poured as backing.. I have removed commercial panels from their frames and re-packaged them to work in a very wet environment. I suppose cardboard would work, but it is unlikely to have good cooling so the expected voltage would be lower. As you intend to only operate indoors I suppose it is unlikely you have full sun most of the time anyway, so there could be less heating and less output current accordingly. I think the cardboard is only useful for a short time, and is not strong enough. Temperature wise it is marginal. The link below uses plywood for the backing. The backing is supposed to provide strength too. A sheet of some sort of plastic or laminate (including melamine laminate as in kitchen bench tops) comes to mind too. The cells are supposed to be bonded to the backing for better thermal conductivity. Use silicon RTV to stick cells to the backing, very thinly.
