Thread: Battery Drain
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Old 03-17-2011, 06:10 PM
gahawkins gahawkins is offline
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Location: Rochester, NY 14506
Join Date: Jul 2009
Posts: 21
Mein Auto: 1991 M5
sad battery

If you only drove 20 minutes, I don't think a new battery would be discharged even if the alternator was inoperative. To check the alternator, measure the battery voltage when running: it should be about 13.5 volts and should drop about a volt when the car is turned off. If the alternator is ok, then some light, heating element (door locks), or other malfunctioning device is using an amp or three all the time. Start pulling fuses and measure the current drain on the battery!
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