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How To Make A Solar Battery Charger

     You will need to understand the difference between wiring in a SERIES or in PARRALLEL. A SERIES is when each Cell (Solar or Battery) is wired Positive to Negative to Positive to Negative and so forth. A SERIES will increase Voltage while maintaining Amperage. PARRALLEL is when each Cell is wired Positive to Positive to Positive and then Negative to Negative to Negative. PARRALLEL increases Amperage while maintaining Voltage.

     You will need to configure the Solar Cells to produce 1.2-1.5 VDC or Volts in Direct Current. To increase Voltage, while maintaining Amperage, wire the Cells in a SERIES. Three Cells producing 0.5 Volts each wired in a series produces 1.5 Volts. The alternative to wiring in a SERIES is to wire in PARRALLEL which will increase Amperage while maintaining the Voltage of a single Cell. Three Cells producing 0.6MA and 0.5 Volts each wired in PARRALLEL will produces 1.8MA at 0.5 Volts. MA stands for Millionths of an Amp.

     A Diode is a one-way switch for elecrical current. Current flows from Cathode to Anode but not Anode to Cathode. If the band marking Cathode is not visible, you must contact Radio-Shack to find out which end is which. I did this but had a really hard time with their phone support, eventually someone helped me!

     Most if not all battery holders come prewired in a SERIES. You want the batteries to be in PARRALLEL with one another. They will currently be positive to negative to positive to negative, etc.. You want them to be positve to positive to positive and then negative to negative to negative.

     Radio Shack sells a Silicon Solar Cell which is 2x4cm and delivers 0.3amp at 0.55VDC. We want the Voltage to be 1.2-1.5V so we will take 3 of these and wire them in a SERIES to give 0.3 amps at 1.65 volts. If we wanted more Amperage, we would wire another set of 3 Cells and wire the 2 sets together in PARRALLEL to produce 0.6 amps at 1.65 volts.

     To wire the Solar Charger together, you will put the diode on the negative wire between the Solar Cells and the Battery Cells. The Negative wire on the Solar Cells should be soldered to the Cathode and then the Anode should be soldered to the Negative wire of the Battery (holder). So the one-way current is from Solar Cells to Battery Cells which is Cathode to Anode. The positive wire on the Solar Cells will be connected directly to the positive wire on the Battery Cells.

     Packaging the Solar Charger is up to you. The 2x4cm cell used in the above example is very breakable and must be protected in some fashion. Radio Shack sells pre-packaged cells which have a plastic case with a translucent top. They come in a variety of Voltages and Amperage. You can modify the charger with plugs so you can change out battery holders to different sizes as needed.

     The following is a list of Radio Shack catalog numbers and specifications for Solar Cells.
Catalog Number Specifications Description
RSU 12037115 050MA at 4.0VDC Flexible Solar Cell
RSU 11903101 300MA at 0.5VDC Enclosed Solar Modules
RSU 11903085 200MA at 1.5VDC Enclosed Solar Modules
RSU 11903093 050MA at 6.0VDC Enclosed Solar Modules
276-124 0.3Amps at 0.55VDC Silicon Solar Cell