Solar charge controllers regulate and control solar batteries. They prevent overcharging and block reverse current from affecting the PV cell in order to lengthen battery life.
Most charge controllers use simple circuits comprised of basic components to block reverse current and to pre-set the maximum battery charge value. More sophisticated and expensive devices use pulse width modulation (PWM) or maximum power point tracking (MPPT) to accomplish these functions. PWM and MPPT allow for batteries to charge closer to their maximum capacities.