MPPT Charge Controllers

MPPT controllers convert a higher-voltage string down to battery voltage and take more energy from the panels. Two numbers decide the size. Keep the string's cold-weather Voc under the controller's maximum PV input voltage, with room to spare, and size the maximum charge current on your array's wattage divided by the battery voltage. The Victron SmartSolar and the MidNite Classic here each come in several sizes, so pick the size on those two numbers.