Pulse Width Modulation (PWM) is the most effective means to achieve constant voltage battery charging. When in PWM regulation, the current from the solar array tapers according to the battery's condition and recharging needs. PWM regulators 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. More modern charge controllers use Pulse Width Modulation (PWM) to slowly lower the amount of power applied to the batteries as the batteries get closer and closer to fully charged. This type of controller allows the batteries to be more fully charged with less stress on the battery, extending battery life.
Please note: PWM regulators are much cheaper than MPPT controllers, but are only suited for 36 cell panels for 12V systems and 72 cell panels for 24V systems. Do not use 60 cell panels on PWM regulators. Contact us for the correct sizing of your regulator. PWM regulators are rated according to the maximum current it can handle from the panels and are mostly available in 12V, 24V, and 48V for offgrid systems.
An MPPT, or maximum power point tracker is an electronic DC to DC converter that optimizes the match between the solar array (PV panels), and the battery bank or utility grid. To put it simply, they convert a higher voltage DC output from solar panels down to the lower voltage needed to charge batteries. The MPPT controllers are the most common these days and can gain you up to 30% more power than the PWM controllers. The MPPT controllers also allow the strings of panels to be connected in series for higher voltages, keeping the amperage lower and the wire size smaller, especially for long-wire runs to the PV solar array.
Please note: MPPT controllers are expensive and not always viable where you have a small 1-2 panel system. MPPT controllers are rated according to the maximum output current it can handle AFTER converting higher voltage from the solar array, and not like PWM regulators which are rated according to the maximum input current from the solar array. Contact us for the correct sizing of your MPPT charge controller.