A system that produces green energy at home – solar panel, wind turbine or micro-hydropower plant – includes a controller, which adjusts the current and voltage that are sent to the batteries, protecting the installation. There are two types of charge controllers: PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking).
For maximum system efficiency you’ll want to install an MPPT device, which is 30% more efficient than a PWM.
PWM are fairly simple systems. They regulate the flow of power to the batteries and gradually reduce the current as the batteries reach full charge. In the case of a PWM controller it is necessary that the panels and the batteries have the same voltage. Such a controller offers a maximum conversion efficiency of about 75%.
MPPT technology explained, in brief
MPPT means tracking the maximum power point at which green energy producing systems can power batteries. The technology is compatible with photovoltaic panels, wind turbines or micro-hydropower plants and offers a very high maximum conversion efficiency of up to 97%. MPPT technology can work in systems where solar modules have a higher output voltage than batteries.
Also read: Survival Wind Turbine: portable, rugged and easy-to-use mini wind turbine
The MPPT controller optimises the parameters of voltage and current generation sources. These controllers convert a higher DC voltage (from the sources mentioned above) to a lower voltage needed to charge batteries or optimal for the utility grid.
Used for battery charging, MPPT controllers limit current according to the percentage of charge and include in the charge cycle a voltage regulation/equalisation time on the battery cells, which results in longer battery life because overcharging is avoided.
MPPT technology converts at high frequency (between 20-80 kHz) and increases the voltage until the sources enter the operating parameters needed to charge the batteries or required by the utility grid.
In summary, this technology offers the highest efficiency and protects the green energy producing system.
The disadvantage is that an MPPT controller can cost twice as much as a PWM controller.