In this instructable, I will give you a practical guide to building a large solar panel from broken solar cells.
Step 1: Tools Needed
To start making solar panels from broken solar cells you need a few things.
1. 15-25 watt soldering iron
2. Light duty 60/40 electronics rosin core solder (radio shack $5.00 for a roll). You can use a silver solder, but I think its too expensive, and the difference in resistance is minimal. So I just use regular old electronics solder.
4. Pencil eraser
5. Solar tabbing pre tinned ribbing (ebay 100 feet is like $20 bucks)
6. A good flat sturdy working surface ( I use a piece of glass, but whatever you have will do)
Step 2: Overview
First get some solar sells.
Solar Cell Grab Bag
Electronics goldmine Solar cellsEbay
Thats just a few examples of where you can get solar cells, but it gives you a start.
First lest discuss parallel and series wiring
Parallel wiring increases amperage and voltage stays the same. Each cell in a parallel circuit is wired positive to positive and negative to negative.
Series wiring (mostly what you will use for solar cells} increases voltage and amperage stay the same. Each cell in a series circuit is wired positive to negative, the remaining positive and negative are you leads. You'll notice batteries in flashlights installed in series.
Now that you have your batch of solar cells we can get started!
First separate the cells in approximate similar sizes.
Remember if your wiring a group of cells together in series, the smallest cell in the circuit will dictate your panels amperage. Regardless of the size of your cells, each will produce about .5 volts. The bigger the cell typically the more ampreage you will get. So you wouldn't want five 6" cells with one 1" cell in series, because you would loose the amperage of the bigger cells and only output the amperage of the 1" cell. Basically try to keep the cells around the same size.
Most solar cells ( poly and mono crystalline) the positive side is the back of the cell and the negative is the front of the cell.
Step 3: Getting Started
Now that you have your batch of solar cells you must determine if each cell has tabbing on the busbar. If if does continue to the next step.
If your cell has no tabbing you must first use a pencil eraser to clean the surface of the busbar. Use a gentle hand as poly and monocrystalline cells are extremely fragile. Rubbing too hard will break the cell. Some of the dark spots on the busbar will hinder the solder from sticking so try to get these off. Don't go crazy if you can't, as long as a descent amount of solder sticks you are OK. The more you use the eraser the better.
Next you must tin your soldering iron with a nice blob of solder, and wait a few seconds until it stops smoking(some of the rosin burns off), then run it down the busbar. Don't beat yourself if you can't get every spot to stick as long as you can get a few spots you're good.
Now cut a piece of tabbing and use your soldering iron to melt the tabbing into the tinned busbar. Don't press down too hard let the soldering iron do the job. Thats why I suggest using a 25 watt minimum soldering iron so that you don't feel the need to press down on the cell so much.
Now that you tinned and tabbed your first cell continue and do the rest.
Now you must solder a lead to the back of the cell. Most polycrystalline cells have a dark area on the back, this is where you solder to. MonoCrystalline cells usually have small squares where you need to solder to. Just like before start by tinning your soldering iron with a good blob of solder and apply it to the underside of the cell directly under the busbar (makes it easier to line up the cells later). Then cut a small 1.5 inch of tabbing and melt it into the solder.
now that you have your leads soldered to the cell you are ready to move on to the next step.
Step 4: Wiring the Cells in Series
Now we can start wiring the cells in series. Using the tab we soldered to the back of each cell will now be used to connect to the front of the next cell.
Line them up and melt the tabbing from the underside tab on one cell to the top of the next cell. Keep doing this and you can get as many volts as you want. Remember if you don't plan on using a charge controller you will need to install a reverse flow diode on the positive side to prevent the batteries from draining during the night. You can get them at radioshack, or ebay or where ever you choose.
Thats basically all there is to it. Then all you have to do is make an enclosure of your liking, seal it all up and you have yourself a solar panel. I used a piece of painted plywood some pine peices for a frame and a piece of plexyglass all sealed together with silicone.
Step 5: You're Done
Put that bad boy in the sun and have pride when you tell people you made it yourself for pennies on the dollar.
Doug Brown made it!