Connecting solar panels to MPPT Charge Controller

High voltage solar panels connected in series diagram

High voltage solar panels connetced to MPPT Charger

This diagram has 2 high voltage solar panels connected in series to an MPPT Charge controller. An MPPT Charge controller has the ability to convert the high voltage output solar panels into a lower voltage suitable for charge the batteries. On the diagram there are the two different current calculations for this setup. The first, high voltage, solar panel side and the second, lower voltage battery charging side.

To calculate how big a charge controller we need (the power rating) we need to calculate the current flowing in the lower voltage, battery charging side of the circuit. (Not the primary solar panel circuit)

According to to Current is always Power (Watts) divided by voltage (Volts) so in this example solar power system it’s 450 / 24 = 18.75 Amps. The Tristar MPPT 45 shown here will be fine for this purpose as it is a 45Amp solar charge controller.

Having a higher voltage on the solar panel side of the circuit is an advantage if you need to use longer, smaller diameter cables.  Solar cable is expensive so using use smaller diameters we can save some money. A higher voltage means less of a voltage drop over the cable length. Less voltage drop can mean a more efficient system. But a little of the gained efficiency can be lost in the more complex circuitry of an MPPT charge controller. Roundabouts & Swings :-)

A selection of our MPPT Solar Charge controllers