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Energy Management, Function - GF54.10-P-0003KJE

MODEL 453.091/391/491 with ENGINE 780 14 volt on-board electrical system 

G12093874Courtesy of MERCEDES-BENZ USA

Energy management (14 volt on-board electrical system) in general 

Energy management (14 volt on-board electrical system) manages the provision (supply) and consumption (balance) of electrical energy to the 14 volt on-board electrical system. The goal is low energy consumption and an optimum charging process for the 12 volt on-board electrical system battery (G1).

The 14 V on-board electrical system is supplied using the DC/DC converter control unit (N83/1). The DC/DC converter control unit operates here like an alternator in a conventional combustion vehicle. The energy management function is integrated in the EDCU (N127). The following control units are integral parts in energy management of the 14 V on-board electrical system:

In detail the energy management encompasses the following functions:

General on-board electrical system support 

All installed control units are supplied by the 14 V on-board electrical system and the on-board electrical system battery (12 V battery).

On-board electrical system support ensures that the on-board electrical system battery is charged at all times. If the battery's charge level or the outside temperature undershoots a threshold value while driving, then the battery is charged by the DC/DC converter control unit. The DC/DC converter control unit converts the high voltage to the voltage level of the 14 V on-board electrical system to supply the 14 V consumers and to charge the on-board electrical system battery. To this end, the power electronics control unit regulates the DC/DC converter control unit using the drive LIN (LIN C1). The power electronics control unit receives this request and the corresponding circuit status from the electric drive control unit via the electric drive CAN (CAN EL). The electric drive control unit receives the battery voltage level from the driver-side SAM control unit via the interior CAN (CAN B). Malfunctions are indicated by the 12 V battery warning lamp (A1e75) in the instrument cluster. Error messages are shown via the multifunction display (A1p13).

On-board electrical system support during the charging process 

The high-voltage battery (G5) is charged externally by connecting the charging cable to a private (stationary service line) or public electricity network (charging station). As soon as the external power source is connected with a charging cable, the charging process monitoring control unit (except code 908 (22 kW on-board charger)) communicates with the control unit for high-voltage battery charger (7 kW charger). In code 908 (22 kW on-board charger), the control unit for high-voltage battery charger (22 kW charger) detects and monitors the charging process itself. The high-voltage battery is charged, and the control unit for high-voltage battery charger (7 kW charger) or the control unit for high-voltage battery charger (22 kW charger) communicates this via the electric drive CAN. The 14 V on-board electrical system charging process is initiated in the same way. In this case, the DC/DC converter control unit follows a time-dependent charging profile. In the first charging phase (0.5 h), the on-board electrical system battery is charged up to a maximum permissible voltage value (approx. 14.9 V). In the subsequent charging phase, the on-board electrical system battery is charged at a voltage value of 13.2 V to guarantee an optimal charging process. If the charging of the on-board electrical system battery is sufficiently complete, then after a period of approx. 8 hours, a minimum charging current is set, or charging is completely shut off to prevent the on-board electrical system battery from becoming irreparably damaged.

On-board electrical system support in delivery mode 

On-board electrical system support in delivery mode secures the system against the on-board electrical system battery discharging over the first 30 operational kilometers. To this end, a maintenance charging process is initiated every 30 days and the on-board electrical system battery is charged for a time period of approx. 6 hours.

The maintenance charging process is finished when:

Delivery mode is finished when the first 30 operational kilometers (odometer 30 km) are reached in the instrument cluster. An opened service flap is detected by the center SAM control unit via the EDW switch, battery (S85/4). The vehicle waking up is also detected by the center SAM control via the central locking system. The respective status is transmitted to the electric drive control unit via the interior CAN.

On-board electrical system support in customer mode during operation 

Additional function requirements:

If the on-board electrical system battery's charge level or the outside temperature exceeds a threshold value while driving, then the battery is charged via the DC/DC converter control unit. The 12 V on-board electrical system battery is charged in this way each time for approx. 30 min with a voltage of approx. 14.5 V and thereafter with a voltage value of 13.5 V. The on-board electrical system support starts from the beginning for every new driving cycle.

On-board electrical system support in customer mode during parking 

Additional function requirements

When the vehicle is parked and Comfort mode ended (15R OFF), then the on-board electrical system battery is charged if the on-board electrical system battery charge level is below approx. 70 % or if the outside temperature falls below a certain threshold value. In this case, the DC/DC converter control unit follows a time-dependent charging profile. During the first charging phase (0.5 h), the on-board electrical system battery is charged up to the maximum permissible voltage value. In the subsequent charging phase, the on-board electrical system battery is charged at a voltage value of 13.2 V to guarantee an optimal charging process.

IMPORTANT Comfort mode (run-on time): If the circuit 15R is switched off, then certain comfort functions (e.g. window lifter) can still be operated for t = 3 min as long as neither of the front doors have been opened. The status of the corresponding front door (open or closed) is registered by the center SAM control unit.

Comfort mode is also ended when the key is removed, as long as no front door has been opened.

Trickle charge during long-term parking 

Additional function requirements

If the high-voltage battery is fully charged and the on-board electrical system battery charge level is lower than approx. 70 %, then a trickle charge is initiated for approx. 6 hours and the on-board electrical system battery is charged with a voltage value of 14.5 V for the first 30 min and with a voltage value of 13.2 V thereafter. If the vehicle is not connected to a charging station, then trickle charge during parking does not take place.

  Electrical function schematic for energy management function   PE54.10-P-2072-97BEB
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