Vehicle System Power Supply
Vehicle System Power Supply
Power supply F01/F02
The continuous increase in the number of electric functions in the areas of comfort, communication and safety in BMW vehicles means that increasing importance is attached to the power supply.
Two separate distribution boxes are fitted in the F01/F02. The front distribution box is located in the vicinity of the glove box; the rear distribution box is on the right side of the luggage compartment.
Brief description of components
The following components for power supply are described:
- Battery
- Intelligent battery sensor
- Alternator
- Fuse block on the battery
- Rear distribution box
- Distribution box at front in the junction box
- Distribution box in the engine compartment and E- box
- Battery cables
- Car Access System (CAS)
- Junction box electronics (JBE)
System circuit diagram
Battery
The vehicle battery is fitted in the centre at the back of the base of the luggage compartment. An AGM battery is always fitted in the F01/F02. The AGM battery has a capacity of 90 Ah.
The AGM battery provides above all the advantage of higher cycle resistance.
IBS: Intelligent battery sensor
The intelligent battery sensor (IBS) is a mechatronic component with its own microprocessor for monitoring the battery status. The IBS continuously measures the following values on the battery:
- Voltage
- Charge and discharge current
- Battery temperature
For data transmission, the IBS is connected to the DME (Digital Motor Electronics) or DDE (Digital Diesel Electronics) via a Local Interconnect- Network bus (LIN bus).
Alternator
With the engine running, the alternator generates a variable charge voltage for battery charging. The variable charge voltage is influenced by the power management depending on the temperature and current by the DME/DDE raising the engine speed.
Fuse block on the battery
The fuse block can only be completely replaced. The fuses can not be replaced individually.
The fuse block contains fuses for the following consumer units:
- Distribution box at front in the junction box
- Rear distribution box
- Distribution box in the engine compartment for electric auxiliary heater or electric fan (850 W or 1000 W)
- Valvetronic, common rail (fuel injection for diesel), electric coolant pump (100 A)
- Intelligent battery sensor IBS
Rear distribution box
The rear distribution box is located in the luggage compartment on the right. Alongside the fuses, a number of relays are also plugged into or soldered onto the circuit board. If one of the soldered relays is defective, the complete distribution box must be replaced.
Distribution box at front in the junction box
The front distribution box is located below the dashboard on the right side, behind the glove box. There is an internal plug- in connection for the junction box electronics (JBE) in the right area of the distribution box. When assembled, the front distribution box and JBE are one unit: junction box.
The components distribution box and JBE are to be replaced individually.
There are a number of relays in the front distribution box. The relay for terminal. 30B is plugged; the others are soldered onto the circuit board:
- Bi-stable relay terminal 30F
- Relay terminal 15N
- Relay for headlamp cleaning
- Fanfare horn relay
Distribution box in the engine compartment
The purpose of the distribution box in the engine compartment is to provide the power supply for the electric auxiliary heater and electric fan.
The Valvetronic, common rail (fuel injection for diesel) and electric coolant pump (100 A) are supplied via the E- box.
Battery cable
On the F01/F02, three battery cables run on the underbody from the fuse block on the battery to the engine compartment:
- One of the battery cables leads across the battery positive support point to the starter motor and to the alternator. This battery cable is monitored by the crash safety module.
- One cable supplies the engine electronics (E- box) with voltage.
- One cable leads to the distribution box in the engine compartment.
Depending on the version, different cable cross- sections are used.
Car Access System (CAS)
The CAS is involved in terminal control (terminal R, terminal 15, terminal 15N and terminal 30B). The terminal control supplies important messages for the power supply. The CAS controls the relays for terminal 30B and terminal 15N.
The CAS is attached to the bus of the K- CAN2.
Junction box electronics (JBE)
The JBE controls the bi- stable relay of terminal 30F at the request of the following components:
- Central gateway module (ZGM) for inhibited sleeping or unauthorised waking.
- Intelligent battery sensor (IBS) for closed- circuit current fault or reaching the starting capability limit.
System functions
The following system function for power supply is described:
- Terminal control (terminal 15N, terminal 30B and terminal 30F)
Terminal control (terminal 15N, terminal 30B and terminal 30F)
Terminal 15N, terminal 30B and terminal 30F are switched terminals that provide the power supply for control modules and components in the vehicle network. The switched terminals enable optimization of the power consumption in the normal operating mode, in the stationary operation (closed- circuit current) or in the event of faults.
Terminal 15N
Terminal 15N provides the power supply for control modules and components required at ignition on.
Terminal 15 N is activated together with the logical terminal 15 by operating the START- STOP button. Terminal 15N is switched off with an after- run time of 5 s after switching off the logical terminal 15.
Terminal 30B
Terminal 30B provides the power supply of control modules and components that in the normal operating mode are required when the driver is present. Terminal 30B is controlled by the CAS. Terminal 30B is activated with the following events:
- Unlocking, locking or deadlocking the vehicle.
- Changing a door contact (driver's side front or rear, passenger's side front or rear).
- Changing the luggage compartment lid contact switch or actuating the luggage compartment lid button.
- Actuating the START- STOP button.
- Request from the Telematic Control Unit (TCU).
Terminal 30B is switched off with an after- run time that depends on the state:
State After-run time
Unlocked vehicle or opened luggage compartment lid. 30 min
After waking by the TCU 3 min
Deadlocked vehicle and closed luggage compartment lid 1 min
Reaching the starting capability limit 1 min
After sending the 'power down' command 10 s
The after-run time of terminal. 30B can be extended at the request of auxiliary consumer units. Auxiliary consumer units are for example the independent ventilation or independent heating function, TCU and electric fan.
Terminal 30F
Terminal 30F provides the power supply for control modules and components that in the normal operating mode require continuous + but can be switched off in the event of faults. Terminal 30F is controlled by the JBE.
In the event of a fault, a reset of terminal 30F is carried out first. If the fault persists, this is followed by a shutdown. The following faults lead to a reset or shutdown of terminal 30F:
- Prevents sleeping after terminal 30B off
- Unauthorised waking after terminal 30B off
- Closed- circuit current infringement
- Reaching the starting capability limit
Terminal 30F is reactivated together with terminal 30B.
Notes for Service department
General information
NOTE: Charging and trickle charging of the battery.
The battery may only be charged using the BMW- approved chargers at a constant charge voltage of 14.8 V.
If possible, the battery temperature during charging should be between 15 °C and 25 °C. Under these conditions, the battery is adequate charged if the charge current has fallen below 2.5 A. If the charging process is carried out at low temperatures, it is only to be terminated after the charge current falls short of 1.5 A.
If the battery is charged when fitted, the charging process must take place via the starting- aid terminal. This is the only way to ensure that the charging process is detected correctly by the vehicle electronics on vehicles with an intelligent battery sensor (IBS).
If the battery is charged directly at the battery terminals, misinterpretations of the battery status and, under certain circumstances, unwanted Check Control messages or fault memory entries can occur.
The cigarette lighter is supplied with voltage by the front distribution box via switched terminal 30B. After terminal 30B off, the relay de- energizes. This means that a trickle charger connected at the cigarette lighter would be disconnected from the battery. Only charge the battery via the starting-aid terminal.
Diagnosis instruction
Power diagnosis
A breakdown due to a flat battery or problems in the vehicle electrical system can have wide variety of causes. In most cases, the cause does not lie with the battery itself. For this reason, replacing the battery will only rarely provide a sustained solution to the problem.
Instead, a systematic diagnosis of the source of the fault is necessary.
Faults are often no longer present when the vehicle comes to the workshop. This is why data stored in the vehicle is the basis for diagnosis. Information on the battery status as well as functional processes in the various bus systems are stored in the corresponding control modules.
This information can be called up and evaluated by the BMW diagnosis system. The BMW diagnosis system has a test module for this. The test module for energy diagnosis reads all the relevant data from the corresponding control modules.
Notes on encoding / programming
The battery and battery capacity are coded in the Car Access System (CAS). The data can be read out using the BMW diagnosis system.