I have happened upon an interesting problem in my 2007 XK. My battery ground battery clamp was hot enough to cause a painful finger burn after a short run with the engine on.

I tried cleaning and tightening the clamps and posts and it made no difference.

Based on measurement I have taken I see as much as a .4-.5 volt drop at the crimp on the cable under a running load. I am sure it is considerably more during starting (I did not measure).

I have replaced the cable/clamp assembly, and now the clamp runs cold and there is no significant voltage drop.

Although the battery remains the prime suspect for the common electrical problems on this car, anyone with problems should run the vehicle for 10 -15 minutes and see if their battery clamp is hot. The cable/clamp assembly should be replaced if the problem remains after cleaning and tightening.

 

Been there, done that, multiple times. Back in the dear dark days beyond recall I lived in England and ran a 1969 Vauxhall Viva. That had a battery negative cable that you could swing on, but it didn't carry current worth a damn.