Head unit losing memory after a few days

[D-Day]

Well, I think I found the problem. After going to the store and stopping at a gas station to get some smokes, I came back and turned the key to the old familiar sound of rr-rr-runt...rr-rr-runt. Excuse me? 180 amp HD alternator and 1500 amp dry cell military grade battery and not starting? What the hell?!

I popped the hood, and smoke was billowing off this one ground wire that was melting. Trying to see what it went to, I knew it couldn't be good, so I took out my knife and sliced it. Shut the hood, turned the key and it fired right up. I have no idea what that wire was doing.

Upon getting home, I looked and saw that it was a black ground wire coming off the negative post...grounded to the front end. What the hell? Why was this there? How long had it been like that? I can not remember ever putting it that way. Having a ground wire running from the body to the negative post of the battery can't be good.

It'll be interesting to see if this removes my head unit problems, and the oddly slow starts lately. On the way home, nothing seemed amiss...stereo system, vacuum gauge, tach, fuel mixture meter, manual lock up for my overdrive trans, etc., all fine; all stuff that would have been added on myself. But I cannot remember what purpose that ground wire went to...it went to no other operating component. It puzzles the hell out of me.