When it comes to modern solar controllers, there are 2 main characteristics that needs to be considered:
- PWM (Pulse Width Modulation) controllers – Cheaper but less efficient controllers. The PWM controller is in essence a switch that connects a solar array to a battery. The switch is “flicked” ON and OFF as needed (pulse width modulated) to hold the battery voltage at the absorption voltage. The result is that the voltage of the array will be pulled down to near that of the battery.
- MPPT (Maximum Power Point Tracking) controllers – More expensive but more efficient controllers. The MPPT controller could be considered to be a “smart DC-DC converter”, i.e. it drops the panel voltage down to the voltage required to charge the battery.