The answer is almost always YES, apart from a really small battery and solar panel. So, you ask what is a real small solar panel… about 5 watts or less, but can’t a 5-watt panel overcharge a small 12-volt battery that’s not being used? YES, it can.

The answer is almost always YES, apart from a really small battery and solar panel. So, you ask what is a real small solar panel… about 5 watts or less, but can’t a 5-watt panel overcharge a small 12-volt battery that’s not being used? YES, it can.

This begs the question why not just get a small charge controller and not take the chance. If you read my article on “what does a charge controller do?” you know that charge controllers also prevent the battery from leaking back to the solar panel at night.

We have used a 5-watt panel on an AC generator, with a digital regulator, to keep the starting battery from draining to dead after two weeks, but there is always a load from the generator regulator thus preventing an overcharge of the battery.

So, while the answer to the question might rarely be no, just consider the answer as YES! You do need a charge controller.