The ground (black) terminal clamp on the battery in my 2007 Mazda-6 has become loose to the point that sometimes the start motor will drain the whole electrical system before it engages. At that point I have to pop the hood and shimmy the clamp to get a connection sufficient to start the car.
I have hit the limit tightening the clamp nut but I can still turn the clamp without much effort. (Maybe this is a consequence of differential metal shrinkage as temperatures have recently been below freezing?)
What is an expedient or proper fix for this? I don't see any corrosion on that terminal. My first inclination was to shim it with some copper wire between the clamp and the terminal, but for all I know that will cause galvanic corrosion.