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

MODEL 166 as of model year 2016 

MODEL 292 

Function requirements, general 

IMPORTANT MODEL 166 (except 166.063) as of model year 2016

MODEL 292

The CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) sends the "Engine running" or "Drive train operational" status via chassis CAN 1 (CAN E1), the electronic ignition lock control unit (N73) and interior CAN (CAN B) to the SAM control unit (N10).

IMPORTANT MODEL 166.063 as of model year 2016

The ME-SFI [ME] control unit sends the "engine running" or "drive train operational" status via the engine CAN (CAN C1), powertrain control unit (N127), chassis CAN 1 (CAN E1), electronic ignition lock control unit (N73), and interior CAN (CAN B) to the SAM control unit (N10).

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).

Given that the power output of the alternator (G2) is dependent on engine speed and temperature, plus the fact that many consumers are used simultaneously, overload situations can arise that need to be buffered by the on-board electrical system battery. If such a situation lasts for an extended period or if the charging capacity of the on-board electrical system battery is low, a negative charge balance may result that impairs the starting capability of the engine. In situations where the on-board electrical system is overloaded for prolonged periods, engine on energy management works to increase the power output of the alternator or to switch off comfort-related electrical consumers in order to balance the charge/discharge ratio of the on-board electrical system battery.

Energy management for driving encompasses the following subfunctions:

Function sequence for voltage provision 

The voltage provision function sequence encompasses the following:

Function sequence for determination of charge level of on-board electrical system battery 

The state of the on-board electrical system battery is recorded by the battery sensor (B95). This calculates corresponding parameters by means of 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 of the on-board electrical system battery.

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 optimal manner. Depending on various factors, the specified voltage is determined using the alternator management or using the temperature-dependent charging characteristic including the quick charge function. 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.

The on-board electrical system battery in model 166.063 is mainly charged 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. 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.

IMPORTANT The rapid charging occurs with a charging voltage of U = 15 V and can last from t = 20 s to 1 h.

After this a transition is made to temperature-specific characteristic or the alternator management (as of T > 20 °C). Alternator management contains lowering the charging voltage (U = 12.7) and the possibility of regenerative braking (energy recovery) in the engine's decel mode.

When the alternator management is active, one of the front doors is open, and the ground speed is v = 0 km/h, the alternator management changes to the jump start mode or the workshop mode. The alternator voltage is raised here constantly to U = 13.9 V. This external starting aid or workshop mode is not canceled until the speed is v > 0 km/h.

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 (energy recovery) 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%.

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Function sequence for alternator regulation (alternator management) 

Alternator regulation (alternator management):

The alternator control actuates the alternator's power output. The SAM control unit reads in the on-board electrical system battery parameters as provided by the battery sensor via battery sensor LIN (LIN B15) and calculates the required alternator specified voltage. The SAM control unit then sends this value via the interior CAN, electronic ignition lock control unit and chassis CAN 1 to the CDI control unit or to the ME-SFI control unit. The CDI control unit or the ME-SFI control unit evaluates this value taking additional input factors (e.g. air conditioning ON) into consideration and calculates the optimum specified voltage for the alternator. The CDI control unit or the ME-SFI [ME] control unit then calculates the alternator specified voltage over the drive train LIN (LIN C1) to the alternator, which then sets it. 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 166.063 as of model year 2016

On model 166.063, the ME-SFI [ME] control unit sends the target alternator voltage via the engine CAN (CAN C1), powertrain control unit, and 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. The CDI control unit or the ME-SFI control unit sends information about the alternator operating rate via chassis CAN 1, the electronic ignition lock control unit and interior CAN to the SAM control unit.

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 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 therefore results from the overlay of the power management function and the alternator specified voltage sent by the SAM control unit.

IMPORTANT If a fault is found on the battery sensor, the on-board electrical system management switches to a fixed voltage of U = 14.3 V. This behavior can also be activated via the diagnostic system in order to check the alternator, for example.

Function sequence for dynamic idle speed control 

Dynamic idle speed control sets the engine's idle speed 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 sends the "Engine running" signal via chassis CAN 1, the electronic ignition lock control unit and interior CAN to the SAM control unit.

Information on condition, voltage and current is recorded by the battery sensor and it sends this over the battery sensor-LIN to the SAM control unit.

The rear SAM control unit reads and evaluates all relevant information and computes the required alternator current.

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 SAM control unit sends corresponding requests over the interior CAN, electronic ignition lock control unit and chassis CAN 1 to the CDI control unit or the ME-SFI [ME] control unit, which then raises the idle speed accordingly.

The idle speed is reversed under the following circumstances:

Function sequence for consumer reduction (deactivation of convenience functions) 

If the alternator can no longer provide the required electrical power, the load on the on-board electrical system is reduced by cutting back 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 consumer functions are reactivated when the alternator is able again to provide the requested electrical output to stabilize the on-board electrical system voltage.

The consumer reduction function is activated when the on-board electrical system voltage falls below U = 12.2 V. 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.

IMPORTANT Consumer 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 = 2s when the reversible emergency tensioning retractors are triggered in order to reduce the load on the on-board electrical system.

The SAM control unit sends targeted requests via the interior CAN to the respective control units, which are connected to the interior CAN and via the interior CAN, electronic ignition lock control unit, and chassis CAN 1 to the corresponding units.

The shutoff sequence is shown in the table below.

Sequence Shutoff stage Consumers with reduced or no power Responsible control unit Maximum Current in A
1 1 Heating level 6, PTC heater booster (R22/3) (with engine 642.8, 651.9), passenger side Automatic climate control and operating unit (N22/7) 18, 5
2 2 Heating level 5, PTC heater booster (R22/3) (with engine 642.8, 651.9), driver side Automatic climate control and operating unit (N22/7) 18, 5
3 3 Heating level 4, PTC heater booster (R22/3) (with engine 642.8, 651.9), passenger side Automatic climate control and operating unit (N22/7) 18, 5
4 4 Heating level 3, PTC heater booster (R22/3) (with engine 642.8, 651.9), driver side Automatic climate control and operating unit (N22/7) 18, 5
5 5 Heating level 2, PTC heater booster (R22/3) (with engine 642.8, 651.9), passenger side Automatic climate control and operating unit (N22/7) 18, 5
6 6 Heating level 1, PTC heater booster (R22/3) (with engine 642.8, 651.9), driver side Automatic climate control and operating unit (N22/7) 18, 5
7 7 Seat heater stage 3 (with CODE 873 (Seat heater for driver and front passenger)) Driver seat control unit (N32/1) (with CODE 275 (Memory package) over the interior CAN (CAN B), without CODE 275 (Memory package) over the center console switch LIN (LIN B12) connected) and the front passenger seat control unit (N32/2) (with CODE P64 (Memory package) over the interior CAN (CAN B), without CODE P64 (Memory package over the center console switch LIN (LIN B12) connected)) 13, 2
8 8 Seat heater stage 2 (with CODE 873 (Seat heater for driver and front passenger)) Driver seat control unit (N32/1) (with CODE 275 (Memory package) over the interior CAN (CAN B), without CODE 275 (Memory package) over the center console switch LIN (LIN B12) connected) and the front passenger seat control unit (N32/2) (with CODE P64 (Memory package) over the interior CAN (CAN B), without CODE P64 (Memory package over the center console switch LIN (LIN B12) connected)) 13, 2
9 9 Wiper park position heater (R2/10) via wiper park position heater relay (F58kS) Automatic climate control and operating unit (N22/7) 15, 0
10 10 Mirror heater (M21/1r1) and mirror heater (M21/2r1) Left front door control unit (N69/1) and right front door control unit (N69/2) 3, 5
11 11 Steering wheel heater (with CODE 443 (Steering wheel heater)) Steering column tube module control unit (N80) 8, 0
12 12 Rear window heater (R1) via rear window heater relay (F4kB) Automatic climate control and operating unit (N22/7) 30, 0
13 13 Rear blower motor (M2/1) P = 50 % Automatic climate control and operating unit (N22/7) 5, 5
14 14 Blower motor (A32m1) P = 50 % Automatic climate control and operating unit (N22/7) 16, 0
15 15 Fan motor (M4/7) P = 50 % Automatic climate control and operating unit (N22/7) 31, 0
16 16 Circuit 15R2 socket relay (F4kA) SAM control unit (N10) 6, 0...8, 0
17 18 Seat heater stage 1 (with CODE 873 (Seat heater for driver and front passenger)) Driver seat control unit (N32/1) and front passenger seat control unit (N32/2) 3, 3

When the on-board electrical system voltage has been stabilized to a value above U = 12.2 V, the convenience functions are switched on again in reverse order with a waiting time in each case of t = 1 s.

The on-board electrical system emergency mode represents a special case of consumer reduction. This is activated by the on-board electrical system management if a voltage threshold defined for the on-board electrical system battery is undershot for a certain period of time.

The on-board electrical system 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 SAM control unit activates the on-board electrical system emergency mode function.

The following functions are then activated:

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

In addition to consumer reduction the following consumers are switched off:

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 circuit status from circuit 15R to circuit 15C has occurred, the 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 via additional battery (without CODE B03 (ECO start/stop function) and without CODE ME05 (HYBRID DRIVE 80KW-VARIANT (INCLUDING PLUGIN))) or ECO start/stop function additional battery (with CODE B03 (ECO start/stop function) and CODE ME05 (HYBRID DRIVE 80KW-VARIANT (INCLUDING PLUGIN))) 

To allow selector lever position "P" to be engaged even when the on-board electrical system is overloaded, the electronic ignition lock control unit is also supplied with power from the additional battery or the ECO start/stop function additional battery.

The capacity of the additional battery is 1.2 Ah, that of the additional battery for the ECO start/stop function is 12 Ah.

The power supply function over the additional battery encompasses the following subfunctions:

Determine function sequence of status of additional battery 

The SAM control unit runs a battery state recognition immediately after the engine is started. This provides information about the electrical power of the additional battery. If the engine is switched off during the battery state recognition, the SAM control unit switches this off and discards the previous results. In addition to battery state recognition, the voltage of the additional battery is continuously checked. To perform this check, charging must be stopped for t = 20 ms. The check is performed every t = 5 s.

IMPORTANT

The battery state recognition can be started using the diagnostic system.

If voltage is not applied to the additional battery or if the additional battery is discharged or defective, the fault message "Backup battery fault" is shown in the multifunction display (A1p13) of the instrument cluster (A1). The SAM control unit sends the data required for this to the instrument cluster over the interior CAN.

Function sequence of charge additional battery 

The additional battery is charged as required after battery state recognition when the engine is running. Charging of the additional battery is controlled by the SAM control unit.

  Electrical function schematic for dynamic idle speed increase   PE54.10-P-2063-97NBA
  Electrical function schematic for alternator management   PE54.10-P-2064-97NBA
  Electrical function schematic for comfort function shutoff   PE54.10-P-2076-97NBA
  Overview of energy management system components   GF54.10-P-9990GN 
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