The on-board electrical system management of model series W221 was changed for modification year 08.
A new single-battery on-board electrical system is installed.
The on-board electrical system battery is no longer located in the trunk.
It has taken the place of the starter battery in the engine compartment.
The battery sensor is located on the ground terminal.
The battery sensor is connected to the driver-SAM via a LIN bus line.
This is located under the engine control unit.
On gasoline engines, the driver-SAM is installed in the control unit box.
On diesel engines, it is located under the engine control unit.
The SAM contains the on-board electrical system management software.
This controls the on-board electrical system functions.
The modified engine compartment with the on-board electrical system battery is shown on the left.
The engine compartment of an S-Class before the modification is shown on the right.
Instead of the on-board electrical system battery, the starter battery is still installed here.
The new single-battery on-board electrical system consists of the on-board electrical system management software in the SAM,...
...the no-load current switch in the prefuse box...
...and the intelligent battery sensor.
Together with the driver-SAM, the battery sensor is responsible for on-board electrical system management.
In critical on-board electrical system situations, measures can be initiated in order to stabilize the on-board electrical system.
These include dynamic idle speed control,...
... consumer reduction,...
... temperature-controlled charging voltage regulation, ...
... no-load current optimization by means of no-load current switches...
... and the battery quick charging function.
STAR DIAGNOSIS is used to read out the battery sensor and check the no-load current.
This is the same as on model series 204.
New: The data records of the battery sensor are no longer overwritten.
This does not happen either when the ignition is switched on or off.
The original data record is not overwritten until the vehicle is driven 100 m.
Exception: Entries generated due to high no-load current.
In this case, a new data record can still be created at the same kilometer reading.
Start the no-load current test via the driver-SAM.
Select 'On-board electrical system'.
Select 'Actual values'.
Select 'Current data of battery sensor'.
Select 'Battery current'.
Select 'No-load current behavior.
The last data records can be viewed here.
The no-load current can be read off.
When a data record is selected, the system displays the kilometer reading at which it was stored.
When charging the new single-battery on-board electrical system it is important that
only chargers with a charging current of at least 30 A are used.
Never charge the battery directly via the negative terminal of the battery.
Otherwise, the charging current will not flow through the intelligent battery sensor.
In addition, the system would still operate based on the old charge state of the battery.
Correct: Attach positive clamp to positive terminal of battery.
Alternatively, attach to the long-terminal stud on the prefuse box.
Attach the negative clamp to the front ground bolt on the wheel arch.
The charging current now flows through the intelligent battery sensor and is monitored.
Special considerations for jump starting:
The positive terminal point is not suitable for jump starting.
The contact pressure of the clamp is not adequate.
This can result in a high voltage drop during jump starting.
The clamp must therefore be clamped to the positive terminal of the battery.
The clamp for the negative terminal should still be connected to the ground terminal stud.
A correctly charged battery supplies all consumption points with power.
It ensures that the engine can be started.
If the on-board electrical system battery fails, the backup battery provides support.
The backup battery is installed behind the rotary light switch.
If the on-board electrical system battery fails, the backup battery activates the park pawl on vehicles with shift-by-wire.
The prefuse box houses another new technical feature.
It is located in the footwell of the front passenger seat.
It forms a node for power distribution to the vehicle interior.
The no-load current switch is also integrated inside it.
If necessary, it switches off circuit 30 G.
This takes place in three scenarios:
Firstly: The engine has been off for longer than six hours.
Secondly: The on-board electrical system voltage drops below 11.8 V.
Thirdly: The no-load current exceeds a value of 75 mA after approx. 75 min.
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30 авг 2016
