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Two batteries for vehicle power supply, function - GF54.10-P-1001T

MODEL 211.0/2 up to 31.5.06 except CODE (494) USA version except CODE (498) Japan version 

MODEL 211.0/2 up to 30.6.06 with CODE (494) USA version with CODE (498) Japan version 

Fig 1: Power Supply System Components And Battery Locations
G07284377Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Installation survey of batteries shown on model 211.0 

Interlinkage of components 

Fig 2: Interlinkage Of Components
G07284378Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The battery control unit (N82) is integrated in the power supply of the vehicle. 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 planned for a 14-V-on-board electrical system with the battery (G1), which is designed as a 12-V-lead battery (AGM- or wet battery). The additional battery (G1/7) is connected for charging if necessary in order to assist the on-board electrical system in particular situations. Via the additional battery relay (K57/2) the additional battery (G1/7) can be connected through the battery control unit (N82).

Function conditions 

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

Connection of electrical devices (consumers or chargers in the broadest sense) direct to the battery post of the battery (G1) while bypassing the current sensor is not permissible.

Function sequence 

The battery control unit (N82) records the current from the negative terminal of the battery (G1) or if the additional battery (G1/7) is connected, the current from both batteries The voltage of the battery (G1) is determined via circuit 30 which simultaneously serves the supply of the battery control unit (N82). An internal temperature sensor is used to draw conclusions about the temperature of the battery (G1)

The voltage of the auxiliary battery (G1/7) is also measured.

IMPORTANT Should the battery (G1) and/or the additional battery (G1/7) be replaced, then only the replacement parts used by DaimlerChrysler AG be used.

The buffer algorithm continuously determines the dynamic internal resistance of the battery (G1) from the recorded current and voltage values. When the alternator (G2) is running this is the basic parameter for the following functions:

The maximum current demand of the vehicle is limited to I ≤ 100 A by switching off consumers. A calculation is also made as to which state of charge prevails when the battery is loaded (G1) with I = 100 A. 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 overall condition of the vehicle and determined in the integral linking part.

The battery control unit (N82) actuates both the cutoff relay for interruptible loads (K75) directly to deactivate the consumer socket as well as the additional battery relay (K57/2) to activate the additional battery (G1/7).

IMPORTANT Once the battery has been disconnected (G1) the vehicle must be started because this is how the battery control unit (N82) determines the start value for internal battery resistance.

IMPORTANT The battery control unit (N82) is not able to predict battery defects.

Consumer shutoff: 

In the event of problems in the two-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 poor condition of the battery (G1), the driver is informed through the multifunction display (A1p13) in the instrument cluster (A1) about the corresponding charge level. Messages which are displayed in the color white, only have information functions, so that consumers which do not impair driving safety are switched off until the overall condition of the on-board electrical system has stabilized again.

Amongst others the consumer shutoff is signaled by the flashing on and off of the switched-on heated rear window or heated seats.

The following messages can be displayed in white in the multifunction display (A1p13) in the Instrument cluster (A1):

The charge level of the battery is too low (G1).

Cutout stage 1 is activated at a voltage of approx. > 11 V.

Cutout stage 2 is activated at a voltage of approx. > 10.5 V.

The following messages are displayed in red in the multifunction display (A1p13) in the instrument cluster (A1):

the signal of circuit 61 cannot be read in via the interior CAN. The message appears, if the battery control unit (N82) is defective, the alternator (G2), the additional battery relay (K57/2) or the additional battery (G1/7) are defective.

This message appears when the vehicle rolls without the engine and the battery is flat (G1) or when the engine is running the additional battery (G1/7) is connected but the on-board electrical system is still unstable.

IMPORTANT The two-battery on-board electrical system can be diagnosed via STAR DIAGNOSTIC.

The following consumers are switched off during consumer cutoff stage 1:

The following consumers are switched off during consumer cutoff stage 2:

Auxiliary battery relay, location/task GF54.10-P-4201T 
Battery control unit location/task GF54.21-P-4121T 
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