Pulse Width Modulation (PWM) is the most cost effective means to achieve constant voltage battery charging by switching the solar system controller’s power devices. When in PWM regulation, the current from the solar array tapers according to the battery’s condition and recharging needs. The charge controller circuit of a MPPT controller (Maximum Power Point Tracking) unit is designed convert the voltage from your solar or wind power sources to the voltage optimum for maximum transfer of power to the battery or grid via a grid tie system. A PWM charge controller does not operate to optimize power transfer to the batteries; it is optimized to extend the life of the batteries. By applying higher voltage in short bursts a PWM controllers essentially clean off the lead plates that are a central part of the battery storage system. Charge controller selection depends on if it makes sense to optimize power transfer, with an MPPT controller, or to optimize battery life, with the PWM charge controllers.
Tip: "If you have a weekend cabin then we would suggest a PWM charge controller would be suitable and cost effective in maintaining battery condition and life. If you live with an off grid system everyday and optimizing power transfer to your batteries is crucial then an MPPT charge controller would be preferable"