As of model year 03/05, the following additional functional description with regard to disconnecting terminal LM is to be observed:
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The power module has the task of securing the charge of the battery
The electronic batter master switch connects the input terminal 30 with the outputs terminal 30U and terminal 30B on the power module.
The following functions are controlled by means of the power module according to the position of the battery switch:
For brief periods, currents of up to 220A can flow across the high-current sockets for terminals 30, 30U and 30B.
The battery switch has the following switch positions:
Measures the temperature directly on the battery negative terminal
The optimum charge voltage is set according to the charge condition and battery temperature. Maximum 16V. The power module knows what the charge level of the battery is by calculating the battery current when the vehicle is being driven and measuring the discharge current. When the vehicle is not in use, the charge level is calculated and updated by measuring the quiescent battery voltage. If the charge level falls below the calculated minimum level for starting, the idling speed is increased to improve the charge balance.
If battery discharge is detected while the engine is running (despite increased idling speed), the power supply to electrical consumer units is gradually reduced or completely shut off according to a table of priorities.
These consumer units are
If the battery voltage drops below 10.5 V (for 5 seconds) due to high load levels, the power module sends out an instruction to increasing the idling speed and to activate prioritized shutdown of electrical consumer units. At the same time, the power outputs of the power module (interior lights, isolation of consumer units in roof/body zones) are switched off. A Check Control message is output.
In order to ensure that the car is capable of starting, the charge level of the battery is also monitored when the vehicle is not in use.
Dependent on
a minimum battery charge level required to ensure that the car can be started again is calculated.
If the charge level of the battery gets close to that minimum level as a result of running an auxiliary consumer unit, the power module instructs that unit to switch off.
In the case of auxiliary consumer unit shutdown, two operating states must be distinguished:
Auxiliary consumer units at terminal R
With the change from terminal 15 to terminal R, the information priority 1 is transmitted. The reduction of the power consumption is reduced according to the corresponding table.
The charge of the battery is calculated. If the value of starting capability is still not reached, a Check Control message is displayed.
If the charge condition does not improve, the power module sends the message ”Shutdowncounter” after 5 minutes.
After a further 90 seconds, the vehicle's electrical system is shut down.
The condition here is that no legally prescribed consumer units are switched on.
The message Shutdowncounter reports to all control units that the battery will be shut down in 90 seconds. This gives all control units with memory function the possibility to write their data in the EEPROM.
If the switched on consumer units include legally prescribed consumer units, the battery is not shut down. Complete discharge of the battery is permitted.
Auxiliary consumer units at terminal 0
If the driver switches on an auxiliary consumer unit, this logs onto the power module with the message ”Powermanagement auxiliary consumer units”. This logon enables the power module to calculate the charge more precisely.
Following correct logon, the auxiliary consumer unit goes into operation and the charge level of the battery is monitored. If the limit for start capability is not reached, a Check Control message is issued.
After another 5 minutes, the power module switches over to quiescent current monitoring. Precondition: No legally prescribed consumer units are activated.
When Terminal 0 is active, the power module switches over to closed-circuit current monitoring after 60 minutes. If an operation is performed on the car before 60 minutes has elapsed (e.g. operation of the interior lights, central locking system), the timer for closed-circuit current monitoring restarts.
Once that period has elapsed, the closed-circuit current should not exceed 80 mA. If the closed-circuit current exceeds 80 mA, after 5 minutes the message ”Shutdowncounter” is transmitted by the power module. After a further 90 seconds, the vehicle's electrical system is shut down for 5 seconds. This shutdown for 5 seconds resets the hardware of the control units. This places the control units in a defined initial state. A control unit that may be defective can be returned to proper functioning by this operation.
If the closed-circuit current still exceeds 80 mA when the system is switched on again, the sequence described above is repeated.
If the closed-circuit current is then still over 80 mA, the system is permanently shut down via the battery master switch.
The reason for the shutdown is stored in the power module.
At terminal 15 On, the electronic battery main switch is closed and a Check Control message is displayed.
Note:
After disconnecting terminal R, an additional immediately current monitoring run is carried out. If the measured current exceeds 120 A, the interior lights, consumer units in the roof and body zones are switched off immediately.
By switching over the battery switch to the OFF position, the power module goes into distribution mode function 30 minutes after Terminal R switches off. Before disconnecting, the power module sends out the ”Shutdown” signal. After a further 90 seconds, the shut down is executed.
After terminal R On, a Check Control message is displayed to inform the driver that the vehicle is in the distribution mode.
When the signal terminal 15_w (from the Car Access System) is detected or the battery switch is set to ON (closed-circuit current monitoring), the electronic battery main switch is closed.
The vehicle can also be started and driven in the distribution mode. All systems are able to operate. The Check Control message remains active. With terminal R Off, the shutdown is initiated once again after 30 minutes as described above.
If no function of any kind is activated over a period of 3 weeks, the battery is disconnected from the vehicle electrical system. This prevents battery discharge. This function can be coded.
In order that the battery is not discharged when consumer units are left continuously on (interior lights, consumer units in body and roof zones), they are switched off centrally.
The deactivation times after terminal R Off are:
If a short circuit current of over 250 A is detected, the battery master switch is opened. Only when the prompt signal 15_w (from the Car Access System) is detected is an attempt made to close the battery master switch again. This procedure is repeated continually until the short circuit has been eliminated.
The power module continuously measures the battery voltage. This information is made available to all other control units via the bus link.
Central battery voltage notification dispenses with the need for individual measurement of battery voltage by each control unit.
The electronic rear window heater output stage on the PM is activated by a K-CAN message from the IHKA control unit.
The interior lighting is subdivided among three outputs (groups).
The interior lights are controlled by the power module. The voltages of the outputs have been stabilised.
The power module controls the following boot lid / tailgate related functions of the body-zone electronics:
The data memory stores data relevant to the vehicle. That information provides a status read-out of the battery load and life.
The data memory will be used in future to obtain a load profile of the battery in normal operation.
Battery temperature sensor
In the case of an interruption, short circuit or an implausible value, a default value of 20 degree Celsius is assumed. This corresponds to a charge voltage of 14.3 V at the battery.
Battery switch
If the battery switch is detected as defective, closed-circuit current monitoring is activated.
Terminal 15_w
Switching off the power module without terminal 15_w is prevented by the following signals:
Bus communication
If no bus communication possible, all the information is frozen.
The power module can issue the following Check Control messages:
All inputs and outputs that are part of the power module functions can have their status checked by diagnosis functions. The outputs can be activated individually.
All electronic circuit breakers and the electronic battery master switch are monitored for short circuits/circuit breaks.
In the event of a fault, an appropriate entry is made in the fault memory and, if appropriate, a check control message is initiated.
Power Down command
This function enables the control units to be placed in sleep mode.
Battery replacement
This function informs the power module of a battery change. The following operations are performed:
The seasonal temperature is an average battery temperature value spread of the last few days
Values for the charge level following the diagnosis command ”Register battery replacement” dependent on the seasonal temperature.
Seasonal temperature |
Capacity value |
< 25 °C |
98 % |
-10 °C |
68 % |
0 °C |
66 % |
10 °C |
63 % |
20 °C |
61 % |
>30 °C |
58 % |
This value is retained until the vehicle has been deactivated for at least 6 hours. Thereafter, an open-circuit voltage measurement determines the capacity. The value determined in this way is entered in the power module.
Charging the Battery
As with previous models, a battery charger can be connected in the engine compartment to the battery earthing point or directly to the battery at the back. The power module detects an external battery charger after 1 hour and a battery voltage > 13.2V without engine operation. Following detection of external battery charging, a battery charge level of 80 % is reported to the diagnosis function even if the charge level is higher or lower than that figure.
Cigarette lighter battery charging function
A trickle charger can also be connected to the cigarette lighter. However, the cigarette lighter is supplied by the body-zone consumer unit isolation circuit via a relay. If the Terminal R Off signal is present for more than 60 minutes, that relay will be tripped by the consumer unit shutdown function. That would mean that a charger connected to the cigarette lighter would be disconnected from the battery. To prevent this, the consumer unit shutdown function can be deactivated.
Procedure:
Switch battery switch off and on again twice within two seconds.
The function is cancelled by