I want to use an external charger to charge the battery in my US-market 2008 Jetta 2.5L SE with an OEM battery.
I need to figure out which nuts to get to fit the existing battery terminal bolt, in order to use the ring terminal attachment of the charger.
I've gotten some M6 nuts at Home Depot, however, they didn't seem to screw-on at all. I've then gotten 1/4" ones, and they only seem to screw between maybe 180° and 240° on one of the bolts, and maybe at most 90° onto the other bolt (I haven't tried using any tools, just hands).
Do I use 1/4" or M6? Or something else entirely?
What would be the best way to attach the ring terminals of the charger to the car?