How to Build a Solar USB Charger
- 1). Connect two solar cells in series by soldering the positive lead on one solar cell to the negative lead on the next. Heat the soldering iron and apply just a little solder to one end of a piece of wire 2 inches long, then apply a little solder to the positive terminal and join the wire to it. Heat the joint between the wire and the terminal, and allow the rosin-core solder to melt onto the joint while holding the solder on the opposite side of the joined wire and terminal. Solder the wire to the negative terminal the same way. Now do the same on the second set of solar cells. Use this same soldering procedure on all soldering. Connecting the solar cells in series like this adds the voltage of the two cells together so the two cells put out 5 volts instead of 2.5 volts.
- 2). Solder the Schottky diode to the positive terminal on one of the photovoltaic cells -- which one makes no difference. One end of the Schottky diode has a white line and the other end does not; solder the end of the Schottky diode without the line to the positive lead.
- 3). Cut off the end the USB extension cable containing the small square socket and strip back 2 inches from the wire to expose the black, red and white wires. Do not cut the end that plugs into USB devices. Now solder the red wire to the end of the Schottky diode that is not soldered. Then, solder the black wire to the unused negative terminal on the other pair of solar cells.
- 4). Connect the two pairs of solar cells together in parallel by soldering the positive terminal on one pair to the positive terminal on the other pair of solar cells. Then do the same for the negative terminals, soldering the negative terminal on one pair to the negative terminal on the other pair. Parallel wiring doubles the current output but does not change the voltage.
- 5). Stick a piece of double-sided tape onto the back of each solar cell, then slide the cells into the CD slipcover and stick the other side of the tape to the inside of the slipcover. Next, tape the slipcover closed with clear tape, and reinforce the USB cable with more clear tape so it will not get pulled out accidentally. The solar USB charger is ready to start charging.
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