The solar charge controller is the heart of your solar system’s operation, which is why it’s important that you have the best one possible when installing your system. When picking a solar charge controller, you’ll come across two different types – PWM and MPPT, and you’ll have to choose which one fits your needs best. While a part of the decision will come down to personal preference, there are a few key differences between the two types that you should be aware of in order to make the best choice possible.
A PWM solar charge controller acts as a switch that connects the battery to the solar array, which results in the voltage of the array being pulled down to the voltage of the battery. An MPPT solar charge controller, on the other hand, is the more sophisticated and thus more expensive option. It adjusts the input voltage to collect the maximum amount of power from the solar array and transform it to supply the voltage requirement of the battery plus its load. This basically allows you to have a 12V battery on one side of the MTTP controller, and a large number of cells wired together to produce 36V on the other.
In other words, a PWM solar charge controller slowly reduces the amount of power drawn by the batteries as the batteries get closer to being fully charged. This allows the batteries to be fully charged without putting much stress on them, thus improving their lifespan. This also allows PWM controllers to keep the battery in a fully charged state indefinitely, which makes them the more complex type. However, PWM charge controllers don’t have mechanical connections that can break.
On the other hand, MPPT charge controllers convert excess voltage into amperage, which is beneficial in many different areas. For instance, most solar systems use 12V batteries just like the ones found in most vehicles. Sometimes, the solar panels deliver much more voltage than necessary to completely fill the batteries, thus keeping the charge voltage at optimal levels while reducing the time required to charge the batteries at the same time. This makes the solar power system operate optimally all the time.
Regardless of what type of charge controller you end up choosing, you’ll get the benefit of reverse-current flow prevention. When solar panels aren’t gathering power throughout the night, electricity can flow in the opposite direction – from the batteries and down the panels, thus draining the batteries, which is very counter-intuitive. Solar charge controllers detect when there’s no energy coming from the panels, and they disconnect the panels from the batteries to prevent reverse current flow.