My next step in getting some electricity going in the Magic Bus, was to build some solar panels. I purchased some solar cells from ebay. These were six inch square solar cells. I got them for about $1.70 a piece. There was ten of them. Then I purchased some used ones that were removed from other panels. I got forty of those, but only about thirty were usable. It ended up being close to the same price as the new ones, but these did come with all of the metal tabbing I was going to need, and they do work.
If you have never touched one of these solar cells, well let me tell you, they are brittle. Now I don’t mean you just have to be gentle with them, no I mean you have to treat them like they are a rare find from some ancient archaeological dig or you will break them. If you dissolved a whole bunch of sugar in water until it was nice and thick, and then poured it out about a sixteenth of an inch thick, and then let it dry out and harden. It would be about the same. They are that brittle. They break just by looking at them wrong, and you have to solder a big wire on these things. Matter of fact, you have to solder several big wires on them. Each cell has to have two pieces of tabbing on them and they have to connect to the next one in a series. So technically, each cell gets soldered four times. These thin brittle pieces of sugar glass have to be soldered four times! Not only that!! You will need at least a sixty watt soldering iron to get them hot enough for the solder to stick. In other words, this part sucked even for me, and I can solder like a robot.
Each cell has to be soldered on each side, twice. At times I found it very hard to get the solder to stick to the cells. Rosin helped for the most part, but at times I couldn’t even get it to stick with that. I don’t know what it was. I am sure I was using the wrong type of solder, but I was using the solder that I had. It worked good enough, but I broke several of the cells. Several.
I won’t go into how to solder them all together. There are plenty of instructions online. Basically the bottom side of the solar cell is positive, and the top side is negative. You want to wire them up in a series so that the voltage increases. I ended up with thirty cells. Two sets of fifteen. Each cell puts out four watts at the max. Which is in the form of a half of a volt, at eight amps. Wired in a series, thirty cells would give me fifteen volts at eight amps. When I put mine out in the hot Texas sun, I got close to that, but not quite that much. At top, I was getting about fourteen volts and the amps were about seven and a half. Well, close enough, considering the outcome… keep reading.
So these fragile cells, that are all soldered together, have to be put on top of a van and not break. Not an easy task, especially when you are trying to keep the weight to a minimum to save on gas. I could easily get a big thick piece of plywood or something to put them on, but that’s too much weight. So I decided to build it frame style. I ripped down some white pine, three quarters by three quarters, and built a frame structure where I notched each joint. This worked really well. It did not flex hardly at all. When I have to rebuild these, and I will, I will be doing the same thing. Although, I might go even smaller, but with more sticks.
On the first frame I made, I used a corrugated plastic to skin it. It is basically cardboard, but made out of plastic. It was stiff. It was super lightweight. It looked perfect. So I glued and stapled the plastic onto the frame. At this point it was very light and looked perfect, but it was not to be. Little did I know that it was going to warp in the hot sun, but I am skipping ahead. I then used three quarter inch corner molding to frame the frame. It being corner molding, it gave me more meat to attach it with, because this is what the plexiglass piece sits on.
On top of the plastic sheet, I laid down a layer of foam sheeting that is used under hardwood floors, using spray glue. First, I cut holes where the center of the solar cells would lie, in the foam sheet. I then took thick silicone and filled the holes. Then I laid the soldered cells down. The cells were attached to the panel by a single blob of silicone in the center of each cell. All while sitting on a foam layer that is sitting on a framed out piece of plastic, attached to a wooden frame. It came out decent. After painting with oil based enamel, I then screwed the plexiglass down on the corner molding and it was done. This seemed perfect. Not too heavy at all. So I decided to give her a test.
As I said, I wasn’t getting the maximum from the cells, but it wasn’t too bad. I walked away, and I left it out in the sun. I came back later to test it again, and the electrons were still flowing strong. The only thing, the corrugated plastic had started to bow up in between each grid piece of the wooden frame. The plexiglass started warping too, but I didn’t really care about that. I was more worried about the bowing that was flexing those fragile solar cells. Two of the cells did crack and break, but oddly enough they are still working. So I decided that I will just leave it like it is and when it stops working, I’ll build another one.
The second panel I built the same way except I used masonite instead of the plastic. It doesn’t warp or bow in the sun, but it’s also not as lightweight as the plastic. I really like the idea of the plastic. I am thinking it would be better to build a more elaborate wooden frame system and still use the plastic. If the grid was smaller, I don’t think the plastic could bow as much. I am thinking half inch by half inch wooden sticks, interlocked with notches, should do the trick. Then the plastic. Then the foam. That will be the next way I would do it.
But you know what… That was such a pain in the ass… I might just buy them already made.