Which is better PWM  or MPPT Solar Charge Controllers?

Which is better PWM or MPPT Solar Charge Controllers?

The charge controller is a very important component of a solar Plant and defining the best one for the solar system requires deep analysis. We try to define PMW & MPPT technologies below.

The two types of charge controllers generally used in today’s solar power systems are PWM (Pulse width modulation) and MPPT( maximum power point tracking). Both charge controllers adjust charging rates depending on the battery’s charge level to allow charging closer to the battery’s maximum capacity as well as monitor battery temperature to prevent overheating.

MPPT controller is proving better charging capacity than PMW. But the two technologies are different, each with its own advantages. The choice of solar charge controller depends on solar system  conditions, system components, size of array and load, and finally the cost for a particular solar power system.

An MPPT controller is better suited for colder conditions. As solar module operating temperature goes down, the Vmp increases. That’s because the voltage of the solar panels operating at their peak power point at Standard Testing Conditions (STC is 25C°) is about 17V while the battery voltage is about 13.5V. The MPPT controller is able to capture the excess module voltage to charge the batteries.  As a result, a MPPT controller in cool conditions can produce up to 20 – 25% more charging than a PWM controller.

In comparison, a PWM controller is unable to capture excess voltage because the pulse width modulation technology charges at the same voltage as the battery. However, when solar panels are deployed in warm or hot climates, their Vmp decreases, and the peak power point operates at a voltage that is closer to the voltage of a 12V battery. There is no excess voltage to be transferred to the battery making the MPPT controller unnecessary and invalidate the advantage of an MPPT over a PWM.

In a scenario where the solar array is large relative to the power draw from the batteries by the load, the batteries will stay close to a full state of charge. A PWM controller is capable of efficiently maintaining the system without the added expense of an MPPT controller.

MPPT controllers are typically more expensive than PWM’s but are more efficient under certain conditions, so they can produce more power with the same number of solar modules than a PWM controller. One must then consider that the MPPT can indeed perform more efficiently when used in that system’s given set of conditions.