Once your solar panels are up and running, the next obvious requirement is some sort of charge controller, since continuous overcharging will ruin the expensive battery bank.

Charge controllers intended for solar panels work by monitoring the battery voltage, and once it reaches full charge, the controller simply short the solar panel leads together. This doesn’t harm the solar panels but it does waste whatever power they are generating. The energy ends us up heating the transistors in the controller instead.



Simple Charge Controller Circuit

Charge controller

In a typical charge controller for a solar panel, the incoming battery voltage is divided in half by a pair of 3.3K resistors, so the trip points are adjusted to one-half the desired levels. Start at 14 volts for the trip points. The actual trip points will depend on your particular batteries, but a good starting point is 14.5 volts for full charge, and 11.8 volts for discharged. In this case, the trimpots should be adjusted to read 7.25 volts at TP-A and 5.9 volts at TP-B.

You will probably need to monitor your battery voltage through several charge cycles to determine the perfect trip points for your system.



Simple Wiring Diagram Showing the Charge Controller and Batteries.

Wiring diagram for charge controller and batteries

You can easily buy a charge controller or build your own custom made if you know how. Certainly the best option is buy an already built controller as this is a critical part of solar panel energy system.

In our next post we shall discuss the main points on building the battery bank. Until then…

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