Charge Controller

A charge controller makes sure that your batteries do not get overcharged, and disconnects the solar panels at night to avoid leaking current from the batteries through the cells.

You can use a charge controller either in 'charge' mode, or in a special mode called 'load diversion' where whenever the battery voltage exceeds a preset limit the charge controller enables a 'dump' load such as an electric heater to get rid of the excess energy that the panels are making.

Either scheme should protect your batteries against overcharging (which would damage them and reduce their lifespan).

In our system we used a Trace C-40 charge controller.

Update !

Our first charge controller died after about a week of service, it has since been replaced, and the new one seems to be working fine (so far :).