Power Supply
Power SupplyECM Main Relay
The ECM main relay in the E60 is supplied with power by the ECM throughout the PTCAN bus activity. Voltage is supplied to all the output actuators (which receive power via KL 87 from the relay) throughout the PTCAN bus activity.
The activation of main relay (525i / 530i in E box, 545i in IVM) KL 87 is necessary for the function of the bitserial data interface (BSD). The BSD is supplied with power by the ECM via KL 87 and a pull up resistor. The following components communicate with the ECM via the bitserial data interface:
^ Alternator
^ Intelligent Battery Sensor (IBS refer to Voltage Supply and Bus Systems for more detailed information)
Lead to Car Access System (CAS)
A lead is installed between the ECM and the CAS for vehicles with automatic or SMG transmissions and the comfort starting function. The CAS contains the function of the electronic immobilizer (EWS as in the E65) and the starter relay.
The ECM supplies the CAS with the signal for start enable. This facilitates the comfort starting function and prevents starter engagement while the engine is running.
Intelligent Battery Sensor (IBS)
The IBS sends the calculated battery values to the ECM via the BSD. The IBS calculates changes in battery SoC (state of charge)/SoH (state of health) based on information received from the ECM on the battery during the period of time between engine OFF and deactivation of the ECM main relay. After the ECM main relay has been switched off, the IBS continues to constantly observe the SoC (state of charge) of the battery.
Terminal IBS Wake Upm
When the key is switched off, before the ECM enters sleep mode, the ECM informs the IBS of the current SoC (state of charge) of the battery. The IBS monitors the SoC (state of charge) and when it drops below the programmed threshold, a terminal 15 wakeup signal is sent to the ECM. The ECM wakes up, obtains information on the current SoC (state of charge) of the battery from the IBS and requests the auxiliary electrical loads to switch off.
After one wakeup sequence the IBS is prohibited from waking the vehicle again during this key off cycle. The vehicle subsequently reassumes sleep mode.
The ECM reads the histogram after starting the vehicle. A corresponding entry is made in the ECM fault code memory if a closed circuit current infringement is determined.
IBS Diagnosis
The IBS features a fault code memory that is read out by the ECM. Self diagnosis checks the voltage, current, temperature measurement, terminal 15 wake up as well as system errors in the IBS.
Alternator
Bosch and Valeo alternators are installed in the E60. The alternators are fitted depending on the type of engine and equipment configuration. They differ with regard to their rating of 140 A and 170 A and are air cooled.
Power Management
The power management software is contained in the ECM. When the vehicle is at rest, the IBS is partially responsible for power management. The tasks of the power management system include:
^ Adaptation of the alternator charging voltage
^ Idle speed boost for increasing the power output of the alternator
^ Reduction of peak loads in the event of a shortfall in coverage provided by the vehicle electrical system
^ Deactivation by means of bus messages of electric loads such telephone, on reaching the start capability limit of the vehicle
Variable Battery Charging Voltage
The variable battery charging voltage function ensures improved charging management of the battery in unfavorable driving situations. The power management controls the temperature dependent voltage for the charging voltage of the alternator via the BSD line.
Idle Speed Boost
The idle speed can be increased in situations where the battery does not cover power requirements. When the specified voltage alone is no longer sufficient, the ECM boosts the idle speed corresponding to the engine status.
Reducing Peak Loads
The peak load of the vehicle electrical system is reduced when there is still a shortfall in battery coverage despite boosting idle speed. Peak load reduction is accomplished by:
^ Reducing power output, e.g. by controlling the clock cycles of the rear window defogger
^ If reducing the power output is not sufficient, individual electric loads can be switched off in extreme situations
Electric Load Cutout
The electric loads in the E60 are divided into the following categories:
^ Comfort loads, e.g. window defogger, seat heating, steering wheel heating
Electric loads switch off automatically after engine OFF. These electric loads can be activated again after the vehicle has been restarted.
^ Legally required auxiliary electric loads, e.g. side lights, hazard warning lights
Legally required auxiliary loads must be operational for a certain period of time after engine OFF. These legally required electric loads are not switched off even on reaching the start capability limit of the battery.
^ Auxiliary electric loads, e.g. independent heating, independent ventilation, communication components such as central information display, telephone, telematic services
Auxiliary loads can be switched on after engine OFF. The comfort electric loads switch off automatically on reaching the start capability limit of the battery. Switch off is requested by the ECM in the form of a CAN message.
^ System related after running loads, e.g. electric cooling fan
System related after running loads can maintain operation for a defined period of time.
Battery Charge Management
There are 2 counters in the ECM power management module. One counter is responsible for the battery charge and the other for the battery discharge level. The state of charge (SoC (state of charge)) of the battery is formed by the difference between the charge acceptance and draw level.
The power management calculates the current SoC (state of charge) value on restarting the vehicle. The power management receives the corresponding data from the IBS via the BSD.
Battery State of Health
The IBS measures the drop in the battery terminal voltage and the starting current of the starter when the vehicle is started. The IBS detects vehicle start based on current draw in excess of 200A. The engine running signal is made available by the ECM. Internal resistance of the battery is calculated from the current and voltage drop.
Starting current and voltage drop determined during the start phase are transferred via the BSD to the ECM. From this data, the power management calculates the battery state of health (SoH (state of health).
Data Transfer to the IBS
The following data is transferred via the BSD to the IBS before the ECM assumes sleep mode:
^ Battery SoC (state of charge)
^ Battery SoH (state of health)
^ Outside (ambient) temperature
^ Available discharge level
^ Terminal IBS wakeup enable
^ Terminal IBS wakeup disable
^ ECM enters sleep mode