How do MPPT charge controllers work?
The MPPT (Maximum Power Point Tracking) charge controller technology may significantly increase the efficiency of battery charging state.
The maximum power point tracking (MPPT) is a higher efficient DC-DC converter technology compared to "shunt controller" and "pulse width modulation (PWM)" technologies.
Using a non-MPPT charge controller is like connecting the battery directly to the solar module. A traditional charge controller may charge a battery with the voltage that is dictated by the battery. By nature, the voltage of a fully-charged battery is higher than that of a discharged-battery. Consequently, the power drawn by an empty battery is usually lower than that of a full battery.
The question arises when we notice that there is a power loss that we are not utilizing when our batteries are empty. Where did my power go?
The MPPT utilizes whole module power by dictating the voltage of the battery charging state. The charge controller keeps the voltage and current at an optimized level where the modules deliver the most juice. The
Let's explain with an example:
Assume that we are using an Evergreen ESA 210 Solar panel, (please not this module is just to illustrate the example and is no longer in production) which has the Vmp of 18.3 volts and the Imp of 11.48 amperes. (11.48A x 18.3V = ~210 watts)
An empty 12V battery may generally have 12.2 volts. Therefore the battery would charge by 11.48A x 12.2V = 140 Watts. It's significantly less than the maximum available output (210 watts) of the module.
What a MPPT charge controller does is that it boosts the voltage and the current of the system, as close as the I-V curve of the module. In this case, the MPPT charge controller charges the battery at almost 18.3 V and 11.48A, while using the most out of the solar panel.
One last note here is that Maximum Power Point Tracking technology has nothing to do with solar tracking. MPPT is only a control feature for a battery charger.
Here are two explanatory resources for further information: