Practical tips
Sensors detect the battery voltage, battery
current and battery temperature. This ena-
bles the system to calculate the current pow-
er level and charge condition of the battery.
riod. Some convenience functions, such as
remote vehicle opening, may not be availa-
ble under certain circumstances. These
functions will be restored when you switch
on the ignition and start the engine.
Please remember that the power and use-
ful life of the battery are limited.
●
If there is a risk that the vehicle may not
start, the alternator electrical failure or low
battery charge level warning lamp will be
Residual current management
shown page 334 .
›››
With the engine switched off
The residual current management reduces
power consumption while the vehicle is
parked. It controls the supply of power to the
various electrical devices while the ignition is
switched off. The system takes the battery
diagnosis data into consideration.
For example, if you listen to the sound sys-
tem with the engine switched off the battery
will run down.
Flat battery
Starting ability has first priority.
If the energy consumption means there is a
risk that the engine will not start, a text will
be displayed in vehicles with a driver infor-
mation system.
Short trips, city traffic and low temperatures
all place a heavy load on the battery. In these
conditions a large amount of power is con-
sumed, but only a small amount is supplied.
The situation is also critical if electrical devi-
ces are in use when the engine is not run-
ning. In this case power is consumed when
none is being generated.
Depending on the power level of the battery,
switch off the individual electrical devices
one after the other to prevent the battery
from losing too much charge and to ensure
that the engine can be started reliably.
This driver indicator tells you that you must
start the engine so that the battery can re-
charge.
Dynamic power management
When the engine is running
While the vehicle is moving, this function
distributes the available power to the various
electrical devices and systems according to
their requirements. The power management
ensures that on-board systems do not con-
sume more electrical power than the alter-
nator can supply, and thus maintains the
maximum possible battery power level.
In these situations you will be aware that the
power management system is intervening to
control the distribution of electrical power.
Although the alternator generates electrical
power, the battery can still become dis-
charged while the vehicle is being driven.
This can occur when a lot of power is being
consumed but only a small amount supplied,
especially if the battery is not fully charged
initially.
When the vehicle is parked for long peri-
ods
If you do not drive your vehicle for a period
of several days or weeks, the power manage-
ment will gradually shut off the electrical de-
vices one by one or reduce the amount of
current they are using. This limits the
To restore the necessary energy balance, the
system will then temporarily shut off the
electrical devices that are using a lot of pow-
er, or reduce the current they are consum-
ing. Heating systems in particular use a large
amount of electrical power. If you notice, for
Note
●
Neither is the power management system
able to overcome the given physical limits.
amount of power consumed and helps to
ensure reliable starting even after a long pe-
338
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