A solar charge controller is a device included in most photovoltaic systems to protect the batteries from overcharge and/or excessive discharge. The minimum function of the controller is to disconnect the array when the battery is fully charged and keep the battery fully charged without damage. The charging routine is not the same for all batteries: a charge controller designed for lead-acid batteries should not be used to control nickel-cadmium batteries.

 

The basic criteria for selecting a controller includes the operating voltage and the PV array current. Controllers are critical components in stand-alone PV systems because a controller failure can damage the batteries or load. The controller must be sized to handle the maximum current produced by the PV array.

 

There are two types of controllers: series and shunt. Series controllers stop the flow of current by opening the circuit between the battery and the PV array. Shunt controllers divert the PV array current from the battery. Both types use solid state battery voltage measurement devices and shunt controllers are 100% solid state.