Solar Requirements

A solar panel is used to keep the battery charged. Solar panels are generally rated for peak power, voltage, and current. Under the best sunlight conditions the panel will produce the given output.

Panel Power(peak) = Panel Voltage(peak) x Panel Current(peak) (5)

The panel voltage is selected to be larger than the battery voltage. For example, if the chosen battery is 12 Volts, then a 17 Volt solar panel or higher voltage is required.

The panel current should be chosen to provide the Total Supply Current plus additional current to charge the battery. For example, a typical 25-Watt solar panel will provide a peak voltage of 17 volts with a peak current of 1.5 A. In the above battery capacity example only 52 mA of current is needed on an on-going basis. This panel would produce and extra 1450 mA to charge a battery. However, we need to remember that a battery can be charged only part of the day during good sunlight.

The solar panel should never be directly connected to a battery. It can damage it by overcharging it and can even discharge the battery during times of poor or no sunlight. A solar charge controller must be purchased for the given voltage and current conditions to provide proper battery charging. The solar panel should be connected to the solar charge controller which in turn is connected to the battery.