How to Build Solar Battery Chargers
A solar battery charger is a simple, fun device to construct that offers some practical applications. At its simplest, it requires very few components to construct and is open to a wide number of user modifications. It can be used to charge electrical devices where electricity is not readily available - such as the outdoors - or for educational purposes.
For this project, you will need:
- Solar cell(s) of any voltage. The combined voltage of the solar cells must at least be greater than that over the battery being charged.
- A battery of any voltage.
- Copper wire.
- Cellotape or a soldering iron.
- An electric trackboard (optional).
- A battery holder (optional).
- A diode (optional).
- Familiarize yourself with charging principles. In order for your battery to charge, there must be a difference in voltage between the solar cell apparatus and the battery. If you have a 2-volt battery, a 3-volt solar cell will charge it, but not a 1-volt solar cell (though three 1-volt solar cells in series could.). Diodes function like electric valves, preventing energy loss in your battery during low-voltage (cloudy) conditions.
- Attach wire to your cells. Using cellotape or a soldering iron, attach one length of copper wire to each terminal on your solar cell. If you are using many low-voltage solar cells to charge a higher-voltage battery, connect your cells in series such that they electrically become one unit. Do this by attaching each cell's negative end to another cell's positive end until you only have one positive and one negative wire free from the assembly.
- Insert your optional components. If you are using an electric trackboard, place your copper wires into it now. If you are using a battery holder, insert your battery. If you intend to use a diode, place it in the circuit through taping, soldering, or insertion onto the track. It should be between the positive ends of the solar cell apparatus and your battery.
- Complete the circuit. Attach the battery to the solar cells. Keep your alignments straight: the positive lead of the apparatus will enter the positive side of the battery, the negative side of the battery connects to the negative side of the apparatus. At this point, your solar cell charger is complete.
- Experiment! It is possible to add multiple batteries in series to charge them simultaneously. It is also possible to connect multiple solar panels in parallel to boost current, and thus charge batteries faster. Use different arrangements to try to achieve the optimum charge-rate for your needs.