Electricity, Solar, Sustainability

Solar Charge Controller: MPPT vs PWM

Solar Charge Controllers are specialized 12/24v battery chargers that regulate the voltage coming from the solar panels, going to the batteries. Often, these are very specialized deep-cycle battery chargers. There are two main types of controllers: PWM and MPPT.

PWM (Pulse Width Modulation) Chargers slowly lower the applied voltage to the batteries as they come closer and closer to a full charge. PWM chargers have their place, in that they cause less stress on the battery, while obtaining a fuller charge. Often included with “solar kits” directed at new buyers. These chargers are the lower to mid-range quality chargers.

MPPT (Maximum Power Point Tracking) Chargers are the most recent and best style of solar charge controller. MPPT Chargers are able to convert excess voltage into charging amperage! Thus, by converting the excess voltage into amps, the charge voltage can be kept at an optimal level, while reducing the total time to charge. MPPT Charges are up to 30% more efficient. MPPT charges can typically run 2x the price of their PWM counterparts, however the pros outweigh the cons for us.

Remember how 24v panels lowest produced voltage is 24v? Combine that with the fact that MPPT chargers can convert voltage into amperage, and you have a recipe for success. Instead of waiting for the sun to be high overhead, we can harness the morning sun more efficiently with 24v panels and an MPPT charger.

We know we will be using a MPPT Charger to reap the benefits of higher voltage panels. However we haven’t settled on a specific charger; though, personally we are considering the Outback FM-80,  and the Morningstar TriStar 60 Amp, they are of the most versatile MPPT chargers currently available.

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