Looks to me like the master GND (negative) worked loose and as the full charging current also runs through here it got hot and burnt away the circuits print. I would suggest clean up area with a small fine wire brush and then clean area with meths/alcohol/jack daniels.

If there is some print left i would insert a small post or use thick copper wire. Solder this is the best you can. If there is no print left then follow the trace in a bit. If it is wide enough drill a very small hole and then follow my suggestion previously about a post.