Your alternator is shot! Chances are the alternator bearing seized, and you don't get alternator roaring the whole time. Time to rebuild/replace that alternator.

GL


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01' 3.0i E53 (M54) with 164,000 miles
07' 3.0si E83 (N52) with 134,000 miles
08' 3.0si E70 (N52) with 91,000 miles