How Do I Size a Solar Charge Controller ?You'll notice that solar charge controllers are specified by both amperage and voltage. You will need a solar controller that can support the voltage of your solar panel array, and then output to the battery bank's voltage (usually 12, 24 or 48VDC).
Next, you'll want to make sure the solar charge controller has enough capacity to handle the current (in amps) from your solar panel array. Take the wattage of your solar panels and divide it by the battery bank's voltage to get a rough estimate of how many amps the controller needs. See more detailed information in our video on how a solar charge controller works in a solar power system:Read more +
The basic formula for sizing a solar panel charge controller is to take the short circuit current (Isc) of the array, and multiply it by 1.56. (What is short circuit current? Glossary of Alternative Energy Terms & Why 1.56? See Sizing PWM Solar Charge Controllers and Sizing MPPT Charge Controllers). Be sure that the solar controller you select can handle at least that many amps.
Please protect this important part of your system with appropriate overcurrent protection before and after the solar controller (see Enclosures, Electrical & Safety for options).
Additionally, some solar controllers offer adjustable control voltage set points, low voltage disconnect, overload protection and displays and metering. If you plan to run a DC load, you can connect it directly to the solar charge controller. If the solar controller is equipped with a low voltage disconnect (LVD), then the solar charge controller can detect when the battery is low and shut off the DC load until the battery is charged. Is all of this still confusing? Give us a call and let us know the short circuit current of your solar panel array (or at least the brand and size of your solar modules) and the system voltage (12, 24, 48 VDC) and we'll be glad to help with a recommendation.