Over here at Sun Electronics, we sell a lot of Specialty Concepts ASC charge controllers. They’re very simple, reliable units employing shunt regulation to halt battery charging once the battery is full.
By “shunt regulation”, this means they basically short out the input from the solar panel.
They’re very simple. There’s nothing to adjust, nothing to do but just hook it up and go. A small red LED on the top indicates that the solar power input is present and the batteries are charging (it goes out when the batteries are full and the controller is shorting out the output). The entire unit is “potted” in an epoxy filling and very moisture resistant – great for marine applications and severe humidity exposure.
Here’s one controller where you REALLY need to make sure that you’ve sized it correctly. Make sure that the total short circuit amperage (Isc) on your solar panels is lower than the controller’s rating… or you WILL blow the poor thing sky-high. Other than that, it’s pretty much set it and forget it. The switching is very slow, and the controllers are unlikely to generate any RFI. They’re very popular with our customers.
Click the block diagram to view it full size. This is what’s inside the unit. Please be sure you hook up the battery leads with the correct polarity, otherwise the controller just… ceases to be. The few damaged ones I’ve ever seen wound up failing with the battery terminals shorted. If proper fuses are used*, this would just blow the fuse between the controller and battery, preventing any damage or overcharge.
The AUX relay shown in the block diagram is provided on units with a low voltage warning/disconnect.
* Please properly fuse your system or I will throw things at you.