How to Build a Solar Cell Charger
A solar cell powered electric battery charger can be a helpful and practical addition to any household taking steps towards going green. Solar cell battery chargers can work with any standard format rechargeable battery, such as AAA or AA as well as more exotic formats if specifically designed to do so. Most household rechargeable batteries are either AA or AAA, making these the most common source for a solar cell charger.
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Things You'll Need
- Soldering iron
- Soldering wire
- Photovoltaic cells
- Copper wire segments with half-inch stripped ends
- 35-45° angle book stand (wood or heat resistant plastic)
- Electrical tape
- Diode
- Resistor
- Prefabricated battery case
- Multimeter
- Notebook
Instructions
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Constructing the Cell Charger
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1
Solder the individual solar cells together in series at their lead points with the copper wire. To effectively solder one wire to a lead point, hold the stripped end of the wire to the solar cell contact point and apply heat with the soldering iron in your right hand while feeding soldering wire to the soldering point with your left hand. Consult the soldering iron's manual for additional technique help.
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2
Tape individual solar cells to the book stand using electrical tape. Use a light touch to avoid breaking the fragile photovoltaic cells. Solder the diode into the series circuit before the point where it would connect with the battery case. Solder a length of copper wire from the unattached end of the diode to continue the circuit.
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3
Solder the resistor into the circuit after the diode. Solder a link of copper wire to the end of the unattached resistor lead to extend the circuit. Solder the positive and negative leads from the solar cell array to the battery case. Tape the battery case to the underside of the book stand with the electrical tape. Insulate any exposed wiring by wrapping it with electrical tape.
Testing the Charger
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4
Drain one or more batteries (enough to fill the battery case of the charger) until they no longer provide enough energy for regular use. Test the voltage output of the battery in its drained state using the multimeter probes on each battery contact and record the results in a notebook.
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5
Insert the batteries into the battery case of the charger.
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6
Align the battery charger's solar array with the sun and wait at least 4 to 6 hours before removing the batteries that have been charged. Do not leave the batteries themselves in direct sunlight. Test the voltage output of the battery in its charged state; if the charger is functioning properly, the voltage should have increased slightly from the drained state.
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7
Test the charged batteries in a household device, preferably one with its own battery charge indicator. If the device works and indicates a full charge, then the solar charger works.
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1
Tips & Warnings
The number of solar cells needed to charge a battery varies depending upon the size and brand of solar cell, as well as the voltage requirements of each individual battery. Adjust the size of your solar array accordingly.To determine the number of solar cells needed to power the charger check the voltage output per solar cell as listed on the packaging. The combined rated voltage on the solar array should be equal to the voltage of one of the batteries being charged plus 20 percent to allow for charging in less than ideal light conditions.
To determine the correct voltage for the diode and resistor for the project read the label on the rechargeable battery. Match the resistor and diode to the voltage of a single battery, this allows for a slow steady charge which will reduce the chance of overcharge damage to the battery.
Use safety goggles and have a fire extinguisher available while soldering to prevent fires.
Only attempt to charge batteries that specifically state that they are rechargeable.
Wear non-latex based plastic gloves while handling batteries after the first charge and inspect the batteries closely for acid leaks, which can be a sign of overvoltage damage. If this occurs, remove some solar cells from your array and try again with new batteries.
References
- Photo Credit Sun image by KPICKS from Fotolia.com
