Project: DIY Solar Panel
One cool thing about solar panels is that you are not limited to just one. You can take a bunch of separate panels, or even fragments of panels, and solder them together to make a larger one. You can do this one of two ways. The first is to connect them in series, which means that the negative lead of one cell connects to the positive lead of the next. When a number of cells are connected this way, the voltage is the sum of the various panels and the amps remain the same. For example, two 12V 3.5-amp cells wired in series output 24V at 3.5 amps. By contrast, if you were to wire those cells in parallel, where all the positive leads are connected together and all the negative leads are connected together, you’d get an output of 12V at 7 amps.
Why would you want one over the other? It all depends on what you’re using it for. Motors use a lot of amps, for instance. Go ahead and try both ways of wiring up your panels, testing each way with a multimeter. See Chapter 9, “Robot-Builder’s Tool Box,” to learn more about this great tool.
To make your own multicell solar panel, you’ll need the following parts. Follow along with Figure 4.21:
- Pieces of solar panel or a number of separate panels. One option is the Jameco Solar Cell Grab Bag (jameco.com, P/N 2113666), which consists of factory-extra solar cells in irregular shapes. The downside to that option is that you have to solder all the parts together. Another option is to buy individual solar panels already equipped with wires, and then manually connect them.
- Stranded hookup wire like Sparkfun P/N 11375.
- Soldering supplies (optional). If you decide to solder and need help, I teach you how to solder earlier this chapter.
- A board or other surface on which to stick the solar cells.
Hot glue or some other kind of adhesive.
FIGURE 4.21 You’ll need the following parts to make your DIY solar cells.
Follow along with these steps to build your DIY solar cells:
STEP 1 Decide how many volts and amps you want. Measure each panel’s output and determine whether to go with serial or parallel. If in doubt, I suggest serial because it’s easier to wire together! In Figure 4.22, I show two solar panels soldered in series, connected to a multimeter. Note that I used solid hookup wire when prototyping this project. Big mistake—the solid wire is too stiff. Stranded wire is more flexible, which is easier on fragile solder joints, and it lays flat better.
FIGURE 4.22 Connect your solar cells in series.
STEP 2 Connect the cells together in series. This means the positive wire of one cell connects to the negative wire of the next cell. On cells without wires, you will need to solder them on. The entire metallic backing of the cell is the positive lead, and the shiny strips on the front are negative, as shown in Figure 4.23. However, if your solar cells have wire leads, you don’t have to bother with all that.
FIGURE 4.23 Solder one wire to the positive and one to the negative lead.
STEP 3 Glue the cells to the board. You may want to secure the solder joints with a little hot glue as well, as shown in Figure 4.24.
FIGURE 4.24 A little hot glue can help keep the solder joints secure.
STEP 4 Hook up the cells as shown in Figure 4.25—each positive wire is plugged into its neighbor’s negative wire.
FIGURE 4.25 Hook up the solar cells in series.