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Engine On Energy Management, Function - GF54.10-P-1060LF

Model 217, 222 

Function requirements, general 

IMPORTANT The CDI control unit (N3/9) (diesel engine) or the ME-SFI control unit (N3/10) (gasoline engine) sends the signal "Engine running" via drive train CAN (CAN C1), powertrain control unit (N127), chassis FlexRay (Flex E), electronic ignition lock control unit (N73) and interior CAN (CAN B) to the front SAM control unit (N10/6).

Engine on energy management, general 

Engine on energy management ensures the stability of the on-board electrical system as well as an even charge balance in the on-board electrical system battery (G1).

If lots of electrical consumers are operated simultaneously, overload situations may occur, which have to then be buffered by the on-board electrical system battery. If such an overload situation lasts for an extended period or if the charging capacity of the on-board electrical system battery is low, a negative charge/discharge ratio could arise. In such an instance, the mobility and the stable supply of all electrical consumers can no longer be assured. The engine ON energy management increases the power output of the alternator (G2) if the on-board electrical system remains overloaded (except model 222.004/057/104/157/163/173 and except model 222 with code B01 (48V technology)) or the energy transfer from the high-voltage on-board electrical system through the power electronics control unit (N129/1) (model 222.004/057/104/157/163/173) or the energy transfer from the 48 V on-board electrical system through the DC/DC converter control unit (N83/1) (model 222 with code B01 (48V technology)). The energy management also reduces the comfort consumers to enable an equalized charge balance for the on-board electrical system battery to be achieved.

Energy management for driving encompasses the following subfunctions:

Function sequence for voltage provision 

The voltage provision function comprises the following subfunctions:

Function sequence for determining charge level 

The condition of the on-board electrical system battery is detected by the battery sensor (B95) (except engine 157, 279) or by the control unit in the on-board electrical system battery (engine 157, 279).

The battery sensor or the control unit in the on-board electrical system battery calculates corresponding parameters on the voltage, current and temperature measurements on the on-board electrical system battery. The charge level of the on-board electrical system battery is the ratio of the current charge to the maximum storable charge. This is based on the calculation of the internal resistance. This, along with the battery capacity, is then used to compute the charge stored in the on-board electrical system battery. The front SAM control unit reads in the data from the battery sensor or the control unit in the on-board electrical system battery over the battery sensor LIN (LIN B15), it also evaluates the voltages at circuit 30 and circuit 30g and the specified voltage of the alternator required to provide the requested energy (except model 222.004/057/104/157/163/173 and except model 222 with code B01 (48V technology)) or the required energy transfer from the high-voltage on-board electrical system through the power electronics control unit (model 222.004/057/104/157/163/173) or the required energy transfer from the 48 V on-board electrical system through the DC/DC converter control unit (model 222 with code B01 (48V technology)).

Function sequence for charging on-board electrical system battery 

Charging of the on-board electrical system battery requires that the specified voltage be determined. The specified voltage is the voltage that must be present at the terminals of the on-board electrical system battery in order to charge the on-board electrical system battery in an optimum manner.

Depending on the various factors involved, the specified voltage is determined on the basis of the alternator management (except model 222.004/057/104/157/163/173, and except model 222 with code B01 (48V technology)) or the required energy transfer from the high-voltage on-board electrical system through the power electronics control unit (model 222.004/057/104/157/163/173) or the required energy transfer from the 48 V on-board electrical system through the DC/DC converter control unit (model 222 with code B01 (48V technology)) or on the basis of the temperature-specific charging characteristic with quick charging function (except engine 157, 279). After the engine is started, quick charging is performed first at high voltage until the charge level of the on-board electrical system battery is recognized as being sufficient (except engine 157, 279).

Model 222.004/057/104/157/163/173:

The on-board electrical system battery is charged primarily using energy from the high-voltage on-board electrical system. To this end, the energy stored in the high-voltage battery (A100g1) is fed by the power electronics control unit to the 12-V on-board electrical system (up to approx. I = 100 A). If the energy made available by the power electronics control unit does not meet the existing energy requirements, the alternator will be switched on for support.

Model 222 with code B01 (48V technology): 

The on-board electrical system battery is charged using energy from the 48-V on-board electrical system. To this end, the energy stored in the 48-V on-board electrical system is fed by the DC/DC converter control unit to the 12-V on-board electrical system. The front SAM control unit sends information on the on-board electrical system capacity utilization over the interior CAN to the DC/DC converter control unit.

IMPORTANT Model 217 with engine 278

Model 222 with engine 276, 277, 278, 642, 651

The rapid charging occurs with a charging voltage of U = 15 V and can last from t = 20 s to 1 h. Only following this, a temperature-dependent characteristic or the alternator management function is used.

IMPORTANT An emergency shutoff is activated when driving down long hills in order to avoid overcharging of the on-board electrical system battery resulting from long periods of deceleration fuel shutoff. This emergency shutoff deactivates regenerative braking in cases of high voltage combined with low power consumption. If the on-board electrical system battery becomes fully charged (for example after driving in the cold or long downhill travel), the voltage is lowered further to return the battery to its optimum charge level of 80%.

G15299355Courtesy of MERCEDES-BENZ USA

Voltage provision 

Rapid charging (except engine 157, 279): 

Temperature-based charging: 

Transition to alternator management (except model 222 with code B01 (48V technology)): 

Alternator management (except model 222 with code B01 (48V technology)): 

Transition to charging in deceleration mode: 

Charging in deceleration mode: 

Function sequence for alternator control (alternator management) (except model 222 with code B01 (48V technology)) 

Alternator regulation (alternator management):

The alternator control actuates the alternator's power output. The CDI control unit or the ME-SFI control unit communicates with the alternator via the drive train LIN (LIN C1) and evaluates the alternator operating rate. The CDI control unit or the ME-SFI [ME] control unit sends information on alternator capacity over the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and the interior CAN to the front SAM control unit.

The state of the on-board electrical system battery is recorded by the battery sensor or by the control unit in the on-board electrical system battery. The battery sensor or the control unit in the on-board electrical system battery sends corresponding parameters of the on-board electrical system battery to the front SAM control unit via the on-board electrical system LIN. The front SAM control unit evaluates all of the relevant information and calculates the specified voltage required for the alternator. The front SAM control unit then sends this value to the CDI control unit or the ME-SFI control unit via the interior CAN, electronic ignition lock control unit, chassis FlexRay, powertrain control unit and drive train CAN. The CDI control unit or the ME-SFI [ME] control unit evaluates this, taking additional input factors (e.g. A/C ON) into consideration, and calculates the ideal specified voltage for the alternator. The CDI control unit or the ME-SFI control unit then requests the calculated specified voltage of the alternator via the drive train LIN at the alternator; the alternator then sets this voltage. In addition, the CDI control unit or ME-SFI [ME] control unit checks the input factors for plausibility in order to rule out any overcharging or faulty charging of the on-board electrical system battery.

IMPORTANT Model 222.004/057/104/157/163/173

The specified voltage request is sent by the CDI control unit or the ME-SFI [ME] control unit over the drive CAN, powertrain control unit and the hybrid CAN (CAN L) to the power electronics control unit.

The CDI control unit or the ME-SFI control unit compares the optimum specified voltage for the alternator with the actual alternator power and is thus able to determine the energy state of the on-board electrical system. The continuous comparison of these two values and the corresponding corrections are designated as power management. As soon as it becomes apparent that the on-board electrical system voltage is not high enough, the power management is gradually reduced. The alternator can then make its full output available.

The energy management in the CDI control unit or in the ME-SFI [ME] control unit adopts the alternator specified voltage values for the front SAM control unit as a guideline value only, because certain vehicle conditions, e.g. engine comfort, idle stability, engine start, irregular engine operation have to be taken into consideration. The actual specified voltage of the alternator is therefore obtained by taking both the specified voltages sent by the front SAM control and that of the energy management into account.

IMPORTANT If a fault is found in the battery sensor or in the control unit of the on-board electrical system battery, the energy management switches to a fixed voltage of U = 14.3 V (except engine 157, 279). With engine 157, 279, the value of U = 14.4 V must not be exceeded. This behavior can also be activated using a diagnosis service in order to check the alternator, for example.

Function sequence for dynamic idling speed control (except model 222 with code B01 (48V technology)) 

Dynamic idle speed control sets the engine's idle speed and thus the power output of the alternator such that no current needs to be drawn from the on-board electrical system battery when the vehicle is idling.

The idle speed is increased for a higher consumer load. The idle speed is increased as a preventive measure. In other words, the system does not respond to a lack of electrical energy, but rather sets the required idle speed based on the present load.

The following factors are used for dynamic idle speed control computations:

The CDI control unit or the ME-SFI control unit communicates with the alternator via the drive train LIN and evaluates the alternator operating rate. The CDI control unit or the ME-SFI [ME] control unit sends information on alternator capacity over the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and the interior CAN to the front SAM control unit.

The state, voltage and current of the on-board electrical system battery is recorded by the battery sensor or by the control unit in the on-board electrical system battery. The battery sensor or the control unit in the on-board electrical system battery sends corresponding parameters of the on-board electrical system battery to the front SAM control unit via the on-board electrical system LIN. The front SAM control unit evaluates all relevant information and calculates the energy required. If the energy required is more than what the alternator can supply, idle speed increase takes effect. The maximum possible excitation current is calculated from the current excitation current and the alternator utilization. The maximum excitation current is used to calculate the maximum possible alternator current at different idle speeds. The front SAM control unit sends corresponding requests over the interior CAN, electronic ignition lock control unit, chassis FlexRay, powertrain control unit and drive train CAN to the CDI control unit or the ME-SFI [ME] control unit, which then raises the idle speed accordingly.

The idle speed increase is reversed under the following circumstances:

IMPORTANT Model 222.004/057/104/157/163/173

The CDI control unit or the ME-SFI [ME] control unit sends the requests of the front SAM control unit over the drive train CAN, the powertrain control unit and the hybrid CAN to the power electronics control unit.

Function sequence for consumer reduction (deactivation of convenience functions) 

If the alternator (except model 222 with code B01 (48V technology)) or the DC/DC converter control unit (model 222 with code B01 (48V technology)) can no longer provide the required electrical output, the on-board electrical system load is reduced by shifting down from comfort functions. This serves to avoid any significantly negative charge balance for the on-board electrical system battery. This in turn retains the engine's starting capability. The comfort functions are reactivated when the required electrical power to stabilize the on-board electrical system voltage is available again.

IMPORTANT Detailed information on evaluation of alternator operating rate can be found in the section "Alternator regulation".

Consumer reduction is activated when the on-board electrical system voltage drops to below U = 12.2 V (except engine 157, 279) or the maximum discharge current is reached (engine 157, 279). The first consumer's power consumption is reduced at t = 20 s following engine start. If the cutback conditions remain unchanged, the power consumption of one further consumer will be reduced every following second.

The front SAM control unit sends the request to limit power or to shut down consumers over the interior CAN to the control units that are connected to the interior CAN, and over the interior CAN, electronic ignition lock control unit and suspension FlexRay to the steering column tube module control unit (N80), and over the interior CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit and powertrain CAN to the CDI control unit or ME-SFI [ME] control unit.

IMPORTANTConsumer reduction in case of PRE-SAFE® deployment: 

The front left reversible emergency tensioning retractor (A76) and the front right reversible emergency tensioning retractor (A76/1) have very high starting and operating currents. The power consumption of some high power consumers is therefore reduced or the consumers shut off altogether as quickly as possible for approx. t = 2 s when the reversible emergency tensioning retractors are triggered in order to reduce the load on the on-board electrical system.

The "De-icing" shut-off sequence (t ≤ 10 min.) is included in the following table. A switch is then made to the "Comfort" shut-off sequence.

Sequence Shutoff stage Power-reduced or deactivated function Responsible control unit
1 1 PTC 1st branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
2 2 PTC 2nd branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
3 3 PTC 3rd branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
4 4 PTC 4th branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
5 5 PTC 5th branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
6 6 PTC 6th branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
7 7 Seat heater, wall heating stage 3 (with code 401 (Seat climate control for driver and front passenger) or code 873 (Seat heater for driver and front passenger) or code 432 (Left and right dynamic multicontour seat)) Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
8 8 Seat heater, wall heating stage 2 (with code 401 (Seat climate control for driver and front passenger) or code 873 (Seat heater for driver and front passenger) or code 432 (Left and right dynamic multicontour seat)) Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
9 9 Steering wheel heater (with CODE 443 (Steering wheel heater)) Steering column tube module control unit (N80)
10 10 Blower in rear (with CODE 582 (Air conditioning system in rear)) P = 50 % Climate control control unit (N22/1)
11 11 Blower in front P = 50% Climate control control unit (N22/1)
12 12 Fan P = 50% CDI control unit (N3/9) (diesel engine) or ME-SFI [ME] control unit (N3/10) (gasoline engine)
13 12 Windshield heater (with code 597 (Heated windshield)) P = 50 % Climate control control unit (N22/1)
14 13 Trunk socket, cigarette lighter (with CODE 301 (Smoker package)) Front SAM control unit (N10/6)
15 14 Mirror heater Left front door control unit (N69/1) and right front door control unit (N69/2)
16 15 Spray nozzle hose heater, wiper blade heater (with CODE 874 (MAGIC VISION CONTROL, heated)) Front SAM control unit (N10/6)
17 16 Rear refrigerator box (with CODE 308 (Refrigerated compartment)) Rear SAM control unit (N10/8)
18 16 Wiper park heater Front SAM control unit (N10/6)
19 17 Rear window heater Rear SAM control unit (N10/8)
20 19 Windshield heater (with CODE 597 (Heated windshield)) P = 0 % Climate control control unit (N22/1)
21 20 Seat heater, wall heating stage 1 (with CODE 401 (Seat climate control for driver and front passenger) or CODE 873 (Seat heater for driver and front passenger) or CODE 432 (Left and right dynamic multicontour seat)) Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
22 20 Seat ventilation (with CODE 401 (Seat climate control for driver and front passenger)) Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)

The shutoff sequence "Comfort" is shown in the table below.

Sequence Shutoff stage Power-reduced or deactivated function Responsible control unit
1 1 PTC 1st branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
2 2 PTC 2nd branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
3 3 PTC 3rd branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
4 4 PTC 4th branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
5 5 PTC 5th branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
6 6 PTC 6th branch, heat boosting (engine 642, 651) Climate control control unit (N22/1)
7 7 Windshield heater (with code 597 (Heated windshield)) P = 50 % Climate control control unit (N22/1)
8 8 Rear refrigerator box (with CODE 308 (Refrigerated compartment)) Rear SAM control unit (N10/8)
9 8 Wiper park heater Front SAM control unit (N10/6)
10 9 Spray nozzle hose heater, wiper blade heater (with CODE 874 (MAGIC VISION CONTROL, heated)) Front SAM control unit (N10/6)
11 10 Mirror heater Left front door control unit (N69/1) and right front door control unit (N69/2)
12 11 Seat heater, wall heating stage 3 (with code 401 (Seat climate control for driver and front passenger) or code 873 (Seat heater for driver and front passenger) or code 432 (Left and right dynamic multicontour seat)) Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
13 12 Rear window heater Rear SAM control unit (N10/8)
14 13 Steering wheel heater (with CODE 443 (Steering wheel heater)) Steering column tube module control unit (N80)
15 14 Seat heater, wall heating stage 2 (with code 401 (Seat climate control for driver and front passenger) or code 873 (Seat heater for driver and front passenger) or code 432 (Left and right dynamic multicontour seat)) Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
16 15 Blower in rear (with CODE 582 (Air conditioning system in rear)) P = 50 % Climate control control unit (N22/1)
17 16 Blower in front P = 50% Climate control control unit (N22/1)
18 17 Fan P = 50% CDI control unit (N3/9) (diesel engine) or ME-SFI [ME] control unit (N3/10) (gasoline engine)
19 18 Trunk socket, cigarette lighter (with CODE 301 (Smoker package)) Front SAM control unit (N10/6)
20 19 Windshield heater (with CODE 597 (Heated windshield)) P = 0 % Climate control control unit (N22/1)
21 20 Seat heater, wall heating stage 1 (with CODE 401 (Seat climate control for driver and front passenger) or CODE 873 (Seat heater for driver and front passenger) or CODE 432 (Left and right dynamic multicontour seat)) Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
22 20 Seat ventilation (with CODE 401 (Seat climate control for driver and front passenger)) Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)

When the on-board electrical system voltage has been stabilized to a value above U = 12.2 V or when the permissible discharge current is undershot, power output limitation or consumer shutdown is canceled in the reverse order with a waiting time between each of t = 1 s.

The on-board electrical system emergency mode represents a special case of consumer reduction. This is activated by the energy management in the front SAM control unit if the voltage of the on-board electrical system battery remains below a defined voltage threshold for a certain period of time. The energy management uses all options available through dynamic power management to enforce a positive charge balance.

If the on-board electrical system voltage drops below U = 10.6 V for t ≥ 10 s, the front SAM control unit activates the on-board electrical system emergency mode function.

This causes the activation of the following engine on energy management functions:

Unlike consumer reduction, power output limitation or consumer shutoff is done with a cycle time of t = 200 ms.

As soon as the on-board electrical system voltage has stabilized for t ≥ 10 s at a value of U = 11.8 V or a change in terminal status from terminal 15R to terminal 15C has occurred, the front SAM control unit ends the on-board electrical system emergency mode function. The switched off or power reduced consumers are switched on again.

Function sequence for power supply through ECO start/stop function auxiliary battery (model 217, model 222 except code B01 (48V technology)) or through the park pawl capacitor (model 222 with code B01 (48V technology)) 

To enable the selector lever position "P" to still be engaged when the on-board electrical system is overloaded, the electronic ignition lock control unit is also powered through the ECO start/stop function auxiliary button (model 217, model 222 except code B01 (48V technology)) or the park pawl capacitor (model 222 with code B01 (48V technology)).

  Electrical function schematic for alternator management Model 217 Model 222 except code B01 (48V technology) PE54.10-P-2064-97SEA
  Electrical function schematic for dynamic idle speed increase Model 217 Model 222 except code B01 (48V technology) PE54.10-P-2063-97SEA
  Electrical function schematic for comfort function shutoff   PE54.10-P-2076-97SEA
  Overview of energy management system components   GF54.10-P-9990LF 
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