BMW E38 battery drains overnight
How much quiescent current is the E38 allowed to draw?
The car should go to sleep mode in about 15 minutes, and the allowed quiescent current is about 0.05 A. If the draw is higher than this, some module is not going to sleep.
How do you find the source of the E38's current drain?
Measure the current at the battery cable and remove the fuses one at a time until the reading drops. For example, cutting power to fuse 69 can bring the quiescent current down to about 50 mA when the culprits are the navigation and video module.
Which parts most commonly drain the E38 battery?
Common culprits are navigation and video equipment, the display wiring and the ignition switch base, which can prevent going to sleep mode. If the car flashes its indicators while locked, the alarm may have been triggered, and reading the fault codes shows which sensor is triggering.
Is the charging voltage enough in winter?
In winter, under 14 V is not enough to charge the battery, and the battery stays partly charged. Above +5 degrees the charging voltage is 14.4 V, and when colder 14.7-15 V depending on the model.