5 Series E60 525d (M57TU) SAL
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Output signals
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Idle-speed control
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Nominal value for charging voltage
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Auxiliary consumer shutdown
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Load peak reduction
Power management registers the battery charge state and the battery condition.
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Battery charge balance
The charge balance of the battery is determined by the charge quantity flowing into and out of the battery. Two
counters are provided in the power management to give a running balance of the battery's charge state. One of
the counters counts the charge quantity taken up by the battery. Another counter counts the charge quantity
discharged from the battery. At the factory, the counters are calibrated for the battery fitted. The IBS transmits
the data to power management in the DME / DDE. Data is transmitted via the bitserial data interface (BSD).
The difference between the two charge levels is the battery charge state (SoC: "State of Charge"). Following an
engine shutdown, the power management computes the current battery charge state for the next engine start.
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Battery condition
The battery condition (SoH: "State of Health") is derived from the drop in battery voltage and the current drawn
during engine start. These data are measured by the IBS during the starting procedure. The average value of
the starting current in the start phase and the value of the voltage dip are transmitted to the DME / DDE via the
bit-serial data interface (BSD). The starting procedure is indicated to the IBS by currents greater than
200 ampères (A). The "engine running" signal is output by the DME / DDE as soon as the engine starts.
The power management system calculates the battery's internal resistance from the average value of the
starting current and the value of the voltage dip. Conclusions about the battery's condition can be drawn from its
internal resistance.
Variable charging voltage
The variable charging voltage for the battery ensures that an optimal battery charge state is maintained, even in
unfavourable driving situations. Unfavourable driving situations are, e.g. city traffic and driving in congested traffic.
The charging voltage varies, depending on
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Battery temperature and
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Consumer current.
Battery temperature
The temperature-dependent adjustment of the battery charging voltage prevents an undesirable increase of the
battery temperature during recharging.
Moreover, the battery temperature remains lower, even at higher ambient temperatures. This reduces the
amount of gas generated during charging and the amount of distilled water consumed.
Consumer current
The level of consumer current is measured by the IBS and transmitted to the power management via the bit-
serial data interface (BSD). From this, the power management derives the charging voltage level to be
generated by the alternator. This charging voltage nominal value, as derived by the power management,
determines the level of the charging voltage generated by the alternator. This determines the battery charge
current, which in turn influences the battery charging process, and ultimately the vehicle's consumer current.
Idling speed increase
The idling speed of the engine is raised by the DME / DDE to 750 rpm if the specified battery charging voltage level
is not achieved.
The idling speed is raised when
SBT Power supply E60, E61, E63, E64
BMW AG - TIS
12.02.2013 16:01
Issue status (12/2007) Valid only until next DVD is issued
Copyright
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