Each time you charge deep cycle batteries with solar panels, it’s necessary to use a charge controller in the circuit in order to protect the battery from overcharging or from over discharging. The exception to this rule is when using solar panels smaller than 5 Watts.
SOLAR CHARGE CONTROLLER
Choosing the most suitable charge controller is simple and only requires two steps:
Step 1 – Voltage selection
Select a charge controller that is compatible with the system voltage. The standard configurations are 12, 24, and 48 volts. If you are wiring your batteries for 24 volts you need a charge controller that is rated at 24 volts.
Some controllers are voltage specific, meaning that the voltage cannot be changed or substituted. Other more sophisticated controllers include a voltage auto-detect feature, which allows it to be used with different voltage settings.
Step 2 – Current capacity
Select a charge controller that can handle the maximum output current of the solar panel (or solar array). The maximum possible current that a PV panel can generate is the “short circuit current,” indicated as Isc in the panel’s label or specs sheet.
It’s recommended to include a safety factor for isolated events as well. For example, a solar panel with a ISC of 7.89 amp could potentially produce an extra 25% on a sunny day with very clear cloud. (Additional light reflected off the snow). This results in a possible maximum of 9.86 amps (7.89 x 1.25 = 9.86 amp). In this case, a 10 amp charge controller would be recommended.
Below you will find a quick guide to choosing the proper charge controller for several popular solar panel sizes.
12V solar panels 30W – 150W:
Solar Charge Controller 12V/24V - 10A/20A PMW
12V and 24V solar panels From 150W and Above:
Solar Charge Controller 12V/24V - 30A PMW
24V and 48V solar panels From 200W:
Solar Charge Controller 48V- 60A PMW