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 LSC of 7.89 amp could potentially produce an extra 25% on a sunny day with very clear snow pack. (additional light reflected off the snow). This results in a possible maximum of 9.86 amp (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 5W – 45W:
Charge Controller 4A, 12V

12V solar panels up to 70W:
Charge Controller 7A – 12V

12V solar panels up to 120W:
Charge Controller 10A, 12V

12V solar panels up to 160W:
Charge Controller 25A – 12V
Charge Controller 12/24V, 20A
Charge Controller 10A, 12/24V

24V solar panels up to 160W:
Charge Controller 25A – 24V
Charge Controller 12/24V, 10A
Charge Controller 10A, 12/24V