A charge controller is an essential component of any battery-based RE system because it protects the batteries from excessive overcharge, which can shorten their life and create hazardous conditions.

Some charge controllers work by opening the charge circuit (or 'turning off' the PV array) when the batteries near full charge. Other controllers work by reducing the charge current into rapid 'pulses' of current keeping the batteries at a constant voltage. A third type of controller, diversion controllers, work by diverting portions of the charge to external loads (like water heating elements or other types of resistive loads) when the batteries near full charge. Diversion controllers are the choice with wind and hydro systems and they can work in conjunction with solar controlling the charge to the same battery.

For optimum efficiency charge controllers should be sized proportionally to the maximum charge current in the system. If you plan on increasing your charge capacity in the near future, oversizing the controller initially is a good idea.

Products Available:

Outback MX60 MPPT Charge Controller
Xantrex C-35, C-40 & C-60 Charge Controllers
Xantrex C-12 Charge Controller