Solar Projects for Students – Build a Solar Battery Charger

You can build a solar battery charger using photovoltaic cells as an experiment to understand the basic principles of photovoltaic power. It is an effective way of conserving energy, as well as saving money required for new batteries.

The example given below is a basic design for a solar battery charger:

You can experiment using more solar cells, or using other types of batteries like “AAA” or “D” or “C”.

Find out what happens if the cells are connected in parallel versus series.

Materials Required:

• Silicon Solar Cells (3)
• Two “AA” rechargeable batteries
• 2 Single Battery Holders for “AA” battery
• Wire for connecting the cells and holder (preferably #26 gauge or less)
• Small soldering iron (less then 50 watts)
• Solder material (e.g. Rosin Core solder)
• Flat board for mounting the cells and battery holder (e.g. perfboard)
• Self-sticking fasteners like Velcro

Procedure
(1) Solder the three solar cells in series with the help of connecting wire, as shown in the diagram. When the cells are connected in series, the voltage is increased by three times, which is sufficient to charge the battery (the voltage of a single battery is 1.25V). The current remains the same. Each 2×4 cm solar cell will produce about 0.45 volt and 0.275 amp of usable current.

(2) Mount the cell on a board with the help of Velcro or any other material you can think of (e.g. Self-sticking Hoop-And-Loop Fasteners).

(3) Connect the battery holders in parallel.

(4) Connect the battery holder to the solar cells.

(5) Mount the battery holders with the rechargeable batteries, on the board.

(6) Place the board with the cells and battery holder in direct sunlight. It can be laid horizontal, but it is better to tip up the board towards the direction of the sun. This increases the efficiency of the solar cells.

(7) Use rechargeable batteries that are dead.

(8) If you have a voltmeter at home, you can check the voltage in the batteries, at intervals.

(9) It should take approximately a day to charge the batteries.

Precautions

Make sure that the solar cells are placed in full sunlight with no shadows falling over them. Be careful while handling the soldering gun. Wear safety glasses! If you want to avoid the soldering, an enclosed solar module could also be used for this experiment. Note: The battery holders have batteries connected in parallel; therefore, the voltage remains the same and the current is divided.

You can find most of the material required around the house, like the wire or board. However, for your convenience, listed below are all of the items required for the experiment, which are available at Radio Shack.

Material Specifications:

• Silicon Solar Cell (3) 276-124 4.49 Or Enclosed Solar Module RSU 11903085 10.99 (1.5V, 200mA)
• 2 “AA” Batteries (1 pack) 23-125 5.49 Rechargeable Ni-Cds
• 2 Single Battery Holders 270-401 0.79 (For 1 “AA” no.26)
• Prepunched Perfboard 276-1394 2.39 (41/2 x 6”)
• Hook-And-Loop Fasteners 64-2345 2.69 (self-sticking 3-inch Strips)
• Rosin core solder 64-001 1.19 (0.062”, 0.5 oz)
• Wire (#26 gauge or less)

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