MPPT charge controllers use an algorithm to track the current output of the solar energy system and use this information to adjust the voltage and current it pulls from the solar panels to maximize battery charging. PWM or pulse width modulation controllers works by reducing how much power goes to the battery as it approaches a full charge. It prevents overcharging and can let power trickle into the battery to maintain an optimal charging level. While PWM controllers are more affordable and easier to operate, MPPT controllers deliver the best performance since these devices actively adjust how much solar power they pull from the solar array based on current production capacity.