Charge Controllers, what are they?

OK so we have covered what solar panels are, and how to design a solar array,  but what happens once your panels are generating power?  Well you obviously want to get them into your battery bank, but other than some very specific situations, you will charge your batteries through a charge controller.  So what is a charge controller...in essence, it is the device that regulates the amount of energy, both in terms of voltage and amperage, that goes from your solar array to your battery bank.

Charge controllers come in two primary modes, Pulse width modulation(PWM) and Maximum Power Point Tracking(MPPT).  Pulse Width Modulation Solar Charge Controllers reduce the amount of voltage applied to the batteries in an inverse relationship to the charge level of the batteries.  So as the state of charge goes up, the voltage is reduced so as not to damage the batteries.  MPPT Solar Charge Controllers match the incoming power from the PV array to the most efficient use of that power in terms of charging the battery.  This allows the array and the battery bank to be vastly different voltages.  The ability to step up the voltage and therefore reduce amps(because watts always equals amps x volts), especially if the array is sited a long distance from the charge controller, can allow a person to pay for the charge controller in wire savings.  This is because higher voltage/low amp power can run through thinner wires from the PV array to the Charge Controller.  To give you an example, using 6 gauge wire vs. using 2/0 gauge wire can save you nearly 70% in wiring costs.

We will dig into MPPT chargers in more depth at a later date.  Feel free to ask questions in the comment section below.