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AzNMpower32
01-05-2011, 01:43 PM
What's considered a normal battery voltage with the engine/alternator off?

In all three of our BMWs, the voltage is approx. 11,7-11,8 V based on the Board Computer. This is with all the electrics on, key position II, and the vehicle not started for at least one day.

In the X3 and 325i, voltage dips to 9,8 to 10,0 V when cranking, before quickly rising to a steady 14 to 14,4V (dependent on vehicle) while driving.

Tangent
01-05-2011, 04:31 PM
That seems normal. Keep in mind that the 11.7 - 11.8 is not an accurate reading of battery voltage because of all the electronics that's already on. If you were to read the battery with a multimeter with everything shut off you should get about 12.6 V. The ~14V is good alternator voltage.