How to Recharge Batteries with Solar Cells
To recharge a battery with a solar cell, all you need is a solar cell that outputs the current necessary to recharge the battery as well as a diode.
-Battery Holder (for battery to be recharged)
-Battery(s) to be recharged
When recharging a rechargeable battery, the battery comes with a specification to the amount of current that is needed to recharge this. This is the current that you have to make sure to feed the battery in order for it to charge properly to full strength.
When you are arranging your solar cells, check the current specification to see how much current it can output up to in bright light.
In our example, we will use a solar panel that can output a maximum of 3 volts and a maximum of 0.1A (or 100mA) when exposed to bright light. Let's also say that the battery we want to charge, a 'AA' Duracell 2650mA needs 270mA for 16h in order to charge to its full potential.
Since each solar cell can only output 100mA and the battery needs 270mA to charge, we need to take 3 solar cells and place them in parallel in order to increase the current output to acceptable charging levels for the battery.
When recharging batteries, the circuit will be arranged like this:
Once we have the 3 solar panels in parallel, the current output will be about 300mA. The reason we connect a diode in the circuit is to keep the charged battery from leaking back current into the solar cells. We have omitted the battery holder and alligator clips in this above illustration, but you will need these for connecting the circuit.
All one must do is keep this circuit exposed to bright light for about 1 day or 2
days and the battery will be fully charged. This is how solar panels can charge batteries.