GF54.10-P-0001TX 2-Battery on-Board Electrical System, Function

GF54.10-P-0001TX 2-battery On-board Electrical System, Function

Component Identification:

The battery control unit (N82) is integrated into the vehicle's power supply. The battery control unit increases the availability of the vehicle power supply by introducing energy management measures. To do this, it determines the load capacity of the battery (G1).
The Battery control unit (N82) is designed for an on-board electrical system voltage of up to 14 V and connected to the battery (G1), a 12-V battery in mat-battery technology. The additional battery (G1/7) is integrated into the circuit to backup the on-board electrical system in certain situations, or to charge itself. Activation of the additional battery (G1/7) is managed by the battery control unit (N82) via the additional battery relay (K57/2).

Function conditions
The battery control unit (N82) operates within the specified voltage and temperature limits when the on-board voltage is supplied.

It is not permitted to connect electrical devices (consumers or charger) directly to the battery terminals of the battery (G1) by bypassing the current sensor.

Function sequence
The battery control unit (N82) measures the current from the negative terminal of the battery (G1) and the currents of both batteries if the auxiliary battery (G1/7) is also activated. Circuit 30, which serves simultaneously to supply the battery control unit (N82), is used to determine the battery voltage (G1). By using an internal temperature sensor the battery temperature (G1) can be determined. To this end the interior temperature of the overhead control panel control unit (N70) is used as a reference. The voltage of the auxiliary battery (G1/7) is also measured.

The following data on the vehicle status is also received over the Controller Area Network bus Class B (interior) (CAN-B):
^ Engine speed
^ Vehicle speed
^ Circuit 61
^ Interior temperature

From the recorded current and voltage values an algorithm continuously determines the dynamic internal resistance of the battery (G1). When the alternator (G2) is running this is the basic parameter for the following functions:
^ Consumer shutoff
^ Idle speed increase
^ Activation of additional battery (G1/7)

The maximum current demand of the vehicle is limited to I ≤100 A by switching off consumers. The voltage output when the battery (G1) has a load of I = 100 A applied to it is also calculated.

This is a measure for the load capacity of the battery (G1). If the alternator (G2) fails, 100 % of the power required is provided by the battery (G1).
The effective characteristics of the battery control unit (N82) is determined by the vehicle's overall status.
The battery control unit (N82) actuates the cutoff relay for interruptible loads (K75) for the shutoff of the consumer directly, the additional battery relay is actuated for connecting the additional battery (G1/7)K57/2.
If the rear SAM control unit with fuse and relay module (N10/2) detects that the trunk lid is open when the engine is started, the control unit checks if the engine has been started externally.

During the engine starting procedure, the battery control unit (N82) switches to the start measuring mode to determine the internal resistance of the battery. However, the battery control unit (N82) is not able to predict battery defects.

Consumer shutoff:
In the event of faults in the 2-battery on-board electrical system various messages are displayed in the multifunction display (A1p13) in the instrument cluster (A1).
If the battery control unit (N82) detects a fault in the power consumption or a bad condition of the battery (G1), the driver is informed about the corresponding charge level by the multifunction display (A1p13) in the instrument cluster (A1).
Messages displayed in white are of an informative nature only. They indicate that consumers, which do not impair driving safety, will be deactivated until the general status of the on-boar electrical system has stabilized again.
The consumer shutoff is, e.g. signaled by the function LED on the heated rear window switch (N22s1) flashing on and off.

The following message is displayed white in the multifunction display (A1p13) in the instrument cluster (A1):
^ "FAULT ELECTRICAL CONSUMER DEACTIVATED" message; this message appears when the charge level of the battery (G1) is too low and a consumer shutoff to shutoff level 1 takes place, and when the charge level of the battery (G1) is very low and a consumer shutoff to shutoff level 2 takes place.

The following messages are displayed in red in the multifunction display (A1p13) in the instrument cluster (A1):
^ "BATTERY/GENERATOR: VISIT WORKSHOP" and "ELECTRICAL CONSUMER DEACTIVATED" messages; the circuit 61 signal cannot be read in over CAN-B. Consumer shutoff occurs.
For fault code 9051 shutoff level 1 is activated.
For fault code 9050 shutoff level 2 is activated.
For fault code 9092 the voltage of the additional battery (G1/7) < 10.5 V or the line to the battery control unit (N82) has an open circuit or a short circuit.

^ "BATTERY/GENERATOR: STOP" message; the on-board electrical system limp-home mode, the additional battery (G1/7) is activated. Consumer shutoff occurs.
For fault code 9051 shutoff level 1 is activated.
For fault code 9050 shutoff level 2 is activated.

The fault codes do not appear in the multifunction display (A1p13) in the instrument cluster (A1). They can only be read out using STAR DIAGNOSIS.

The following consumers are deactivated at shutoff level 1:
^ STH heater unit (A6)
^ Blower motor (A32m1) (reduced to 69 %)
^ Steering wheel heater electronics (A74)
^ Front left door warning lamp (E17/19)
^ Rear left door warning lamp (E17/20)
^ Front right door warning lamp (E17/21)
^ Rear right door warning lamp (E17/22)
^ Left front door entrance and exit lamp (E17/3)
^ Right front door entrance and exit lamp (E17/4)
^ Left rear door entrance and exit lamp (E17/5)
^ Right rear door entrance and exit lamp (E17/6)
^ SRA pump (M5/2)
^ Left front seat cushion ventilation motor group (M18/9)
^ Left front seat backrest ventilation motor group (M18/10)
^ Right front seat cushion ventilation motor group (M18/11)
^ Right front backrest ventilation motor group (M18/12)
^ Driver seat adjustment motor group with memory (M27)
^ Front passenger seat adjustment motor group with memory (M28)
^ Driver-side front seat adjustment control unit, with memory (N32/1)
^ Passenger-side front seat adjustment control unit with memory (N32/2/)
^ Heated rear window (R1)
^ Left front seat heated cushion (R13/1)
^ Left front backrest heated cushion (R13/2)
^ Right front seat cushion heater element (R13/3)
^ Right front backrest seat cushion heater element (R13/4)
^ Left rear seat heated cushion (R13/5)
^ Left rear backrest heated cushion (R13/6)
^ Right rear seat heated cushion (R13/7)
^ Right rear backrest heated cushion (R13/8)
^ Left rear side piece heated cushion (R13/9)
^ Right rear side piece heated cushion (R13/10)

The following consumers are deactivated at shutoff level 2:
^ Blower motor (A32m1) (reduced to 53 %)
^ Left front reading lamp (N70e2)
^ Right front reading lamp (N70e3)
^ Ambient lamp (A67e3)
^ Rear interior lamp (E15/3)
^ Right front footwell lamp (E17/15)
^ Left front footwell lamp (E17/16)
^ Right rear footwell lamp (E17/17)
^ Left rear footwell lamp (E17/18)
^ Trunk lid drive motor (M51/2)
^ Left electrically adjustable and heated outside mirror (M21/1)
^ Right electrically adjustable and heated outside mirror (M21/2)
^ PTS control unit (N62)
^ Washer nozzle heating (R2/1)
^ Washer nozzle hose heater (R2/11)
^ Illuminated cigar lighter (R3)