Pulling a battery terminal on a running engine will cook the alternator 80% (or more) of the time. I think you have just exchanged a bad battery problem TO a bad battery plus cooked alternator problem. Sorry.
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i