M6 electrical problems

[Xuliganf10]

I bought my 2016 bmw m6 gc in 6spd couple months ago and rebuilt it my self, the airbags had blown so i changed the battery and the positive cable, and fixed everything wont go into detail as I believe its not relevant. After driving the car for a month or so the battery died after a short drive so i jumped it, thought it was weird since i replaced the battery with 950amp hour agm battery and coded, then after short while the car wouldn't start again, so i jumped it and let it idle with the jumper connected for 2-3 mins then drove a block into my driveway and smelled burning plastic, opened the trunk and the positive cable that I replaced had melted, ran diagnostics on ista+ before and after replacing the cable there was no codes. After a week the car started having trouble starting but would start and the issue kept getting worse until the point where mid drive the car would shut of and bump start since its a manual car, i have replaced the battery to oem replaced the postive cable to oem checked the engine ground cable, cant find anything problem, every possible code is coming up on ista. Took it to indy shop that every person that has a bmw recommended, he is verry busy and told me that it would take a while to diagnose root problem, please some one help if you had any of these issues

1. the car clicks and wont start on first couple tries, 50% of the time

2. Even if does start it wants to shut off/ idle verry rough once i rev it little bit goes back to normal

3. Will shut off mid drive and bump start

4. Some times it misfires and goes into limp mode on pulls some times its perfect

5. On idle with everything off ive seen down to 8 volts on ista, when it idles fine i see 14-15.5 volts on voltmeter and ista

All the issues are intermittent some times it drives prefectly.

[crazyinp]

My suggestion would be to trace the positive cable all the way to the starter and from the alternator back. You said that you fix the car yourself, I would assumed that was in some sort of collision. Very well there might be short somewhere that is causing the issue.

[Xuliganf10]

Will have to yes the car was hit from the passenger side front, not sure how the because the the positive wire for the batter bolts to the floor of the trunk and i dont know how to inspect that wire from the bolt towards the engine.

[m5bbq]

positive short will blow a fuse. check the ground bro.