MPPT Charge Controller

MPPT stands for Maximum Power Point Tracking. A solar panel's output voltage shifts with sunlight and temperature; an MPPT controller continuously finds the voltage at which the panel delivers the most power, then converts it down to the battery's charging voltage with little loss.

The practical payoff in a van: an MPPT controller typically harvests noticeably more energy than a cheaper PWM controller — the gain is largest when panel voltage sits well above battery voltage. You size it by the panel array's wattage and the controller's rated charge current (amps). It is the third pillar of the charging trio alongside the alternator's DC-DC charger and, when on a campsite, mains hook-up.