(I’m writing this having already built the panel so the step by step process is using leftovers)

First I bought ~40 photovoltaic solar cells off of eBay. The cells are “B grade”, meaning they are factory rejects. They still perform quite well; the cells may have slight discolorations or cracks but for the price you pay I wouldn’t complain. B grade cells are the best you can get reasonably. Anyways, the cells I bought were untabbed, see the cell to the right in this picture. They’re very fragile!

After metering each cell I threw out the bad ones. It’s important to do this because the strength of the overall panel is dependent on the weakest cell. One bad cell could ruin everything. Afterwards, I soldered tabbing wire (just flexible metal, really) to the back of each of the good cells (see to the left in the same picture above. I did this 36 times). After each cell had tabbing wire, I soldered them together like this in strings of 9. I couldn’t find my soldering iron so try and use your imagination and picture those soldered together. Once I got a string of 9 finished, I put it on a piece of white pegboard. I forget which type of adhesive I used.

After getting my 36 cells in 4 strings, I connected them with bus wire as you can see here. This is necessary so your cells remain in series while also fitting into a more reasonable shape. Without the bus wire you’d have a 36×1 solar panel… not too attractive!

Once I drilled a hole for positive/negative wires (bottom & top) I nailed the pegboard to a piece of plywood and encased it under plexiglass.

The positive and negative wires go to a solar charge controller. This tells me the status of the panel and the battery. It also acts as a diode, preventing the flow from the battery to the panel. This is important because without anything stopping the current at night the battery would fry the weaker cells. The wires leaving the controller just go to a deep cycle 12V car battery.

Finally, I applied silicone to the outside edges of the panel. It’s very important to make sure the panel is airtight. Once water is able to get in (even vapor), your panel is done. The cells are very sensitive to moisture.

The only reason this isn’t mounted is because, well, I don’t have a use for it. I was interested in solar panels so I gave it a shot. One additional step before I mounted it on a roof would be to add a sloped surface towards the bottom of the panel so water didn’t get stuck. See this picture. The white piece of wood is raised, and water would get stuck above it. Otherwise, this is a finished product.

The overall panel is about 18V and ~64W in direct sunlight. The panel also gets about 3.6 Amps. The 18V is necessary to charge the 12V battery. Here’s a picture of the finished panel.