7 Series E38 750iL (M73) SAL
In starting sequence with system battery flat/faulty
When terminal 15 is detected, the voltage here of the system battery (55 Ah) must be >1.5 volts and the
electronic disconnecting switch closes for 30 seconds. Electrical system is thereby supplied via starter battery
(110 Ah). The starting sequence must now follow within this period of 30 seconds. Starting sequence can be
repeated several times by detecting terminal 15 again. If system voltage is < 1.5 volts: starting is no longer
possible.
In starting sequence with starter battery flat/faulty
Engine starting is no longer possible if the starter battery is flat/faulty. The assistance of the system battery is
not possible as the electronic disconnecting switch is only designed for a maximum current flow of 60 A and
this is exceeded during the starting sequence.
Stationary operation/neutral position
In stationary operation/neutral position, the electronic disconnecting switch is in "Sleep mode". A closed-circuit
current of > 1 mA is essential for this. The electronic disconnecting switch is always open in stationary
operation/neutral position. The closed-circuit current flows exclusively via the system battery (55 Ah). This
prevents the starter battery (110 Ah) from discharging via the vehicle electrical system. The electronic
disconnecting switch is activated either with detection of terminal 15 or at a battery voltage of > 13.5 V
(charging operation).
Driving/charging operation (alternator)
The alternator charges the starter and system batteries in parallel. The starter battery is disengaged if now the
voltage of the starter battery is greater than the alternator voltage. Only the system battery is charged. If now in
driving operation the system voltage drops below 9 V
±
0.5 V, the starter battery is cut in to support the
electrical system. This can result in both batteries discharging.
Charging operation with battery charger
In the case of charging with a battery charger in the engine compartment, the starter battery is charged via the
B+ support point at the front of the engine. In the case of charging with a battery charger, the system battery is
charged at the rear B+ support point on the left wheel arch in the engine compartment.
Note:
In the event of repairs or during diagnosis with terminal 15 activated, the battery charger must be connected to
the rear B+ support point (engine compartment, wheel arch, left) in order to prevent the system battery from
discharging.
RA Notes for cars with twin-battery system
BMW AG - TIS
21.02.2013 03:22
Issue status (12/2007) Valid only until next DVD is issued
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