Thread: Battery dead?
View Single Post
Old 06-02-2020, 08:12 PM   #10
Nick M3
Relic
 
Nick M3's Avatar
 
Join Date: Oct 2003
Location: Bethesda, MD
Posts: 12,439
Start by testing alternator output voltage. If it's above 13.5 or so, it's probably fine.

The battery will not stay over 12v for long once the alternator is off it.

If the alternator is good, disconnect the battery and see if it discharges overnight while not hooked up to anything.

Or, as an alternative, take it to an auto parts store and ask them to test it. The gigantic, expensive battery conditioners that they have can rehabilitate a battery that home chargers can't.
__________________
2011 M3
2006 Sierra 2500HD 4WD LBZ/Allison
2004 X5 3.0i 6MT
1995 M3 S50B32
1990 325is
1989 M3 S54B32

Hers:
1989 325iX
1996 911 Turbo


Nick M3 is offline   Reply With Quote