PWM Charge Controllers

PWM controllers are simple and inexpensive, and they suit small systems: a 12 V panel charging a 12 V battery on a trailer, a gate opener or a shed light. The panel's voltage has to match the battery's, because a PWM controller can't step a higher string down the way an MPPT can. Check the controller's amp rating against the short-circuit current on your panel's datasheet. A low-voltage disconnect protects the battery by switching the load off before it's drained too far.