PWM Solar Charge Controller

The 

The pulse width modulation controller was the original charge controller used and are simpler and less expensive than MPPT controllers. PWM controllers regulate the flow of energy to the battery by reducing the current gradually, called "pulse width modulation". When batteries are full, PWM charge controllers continue to supply a tiny amount of power to keep batteries full. PWM controllers are best for small scale applications because the solar panel system and batteries have to have matching voltages. This becomes a much more difficult with larger installations.