Solar Car Battery Charger DIY

Step 2 Overvoltage Disconnect

They call this item a "7 amp charge controller" at [campingworld.com Camping World] and charge $25 or so for it.
All it does is disconnect the panel from the battery when battery voltage goes over 14 volts.
Home Power Magazine Has published schematics for circuits that do the same thing.

You can still overcharge a battery through one of these units if your panel is big and your battery is small. The bubbling sound you hear in your overcharging battery is water (H2O) being broken down into hydrogen and Oxygen, which then bubble out to join the atmosphere. Eventually the battery will run out of water. Eventually the exposed parts of the battery's lead plates will oxidize and the battery won't take a charge, even if you add distilled water to it.

Comments

[irritant#9]

The ICP charge controller shown above is a poor choice for maintaining a battery. Consider any other product but this one. I have used the ICP charge controller and it yielded poor results. Field testing using a 30W array and a new 16Ah SLA battery ended with a damaged battery that never achieved a full charge(green light). This was with an unloaded battery. I have had good success with the Morningstar charge controllers. Batteries are expensive and environmentally hazardous. You shouldn't go cheap on a charge controller that will damage your battery and create something else for the landfill.