When is a charge controller needed ?
 

I haven't found cheap/free 2nd hand solar panels yet, but thanks to Gascort I'm thinking about building my own... then I'm imagining where to put put these cells and so how to design the shape of the panels...

One question I have : when is a charge controller needed ?

My current cases are :

• a 1.5W panel connected to the car's battery, itself connected to the alternator.
• the old car battery in the trunk is connected to a 13W solar panel and this feeds my GPS navigator, a rear view camera and occasionally a computer.

I think that in both cases, the panels are too weak to damage the 50Ah 12V batteries. From which wattage does a charge controller is needed ?

Denis.

I think anything over 2A is probably good to have a charge controller for. But, that is a total guess. I say 2A just because thats what most trickle chargers put out. I'm not sure they lower their amperage after they hit full charge.