controllers work by slowly reducing the amount of power going into your battery as it approaches capacity. When your battery is full, PWM controllers maintain a state of “trickle”, which means they supply a tiny amount of power constantly to keep the battery topped off. Types of solar charge controllers There are currently two types of charge controllers commonly used in PV power systems : 1. Pulse Width Modulation (PWM), controller 2. Maximum Power Point Tracking (MPPT) controller In this tutorial, I will explain to you the PWM Solar Charge Controller.