Engine On Energy Management, Function - GF54.10-S-1060TRA
Model 447, 448
Function requirements, general
- "Engine running" signal set.
The CDI control unit (N3/33) (model 447 with engine 651.9) or the CDI control unit (N3/36) (model 447.6/7 with engine 622) or the ME-SFI control unit (N3/34) (with engine 274) sends the "Engine running" signal via chassis CAN (CAN E), electronic ignition lock (EZS) control unit (N73) and interior CAN (CAN B) to the signal acquisition and actuation module (SAM) control unit (N10/1).
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 this case, a stable supply of all electrical consumers is no longer ensured.
In situations where the on-board electrical system is overloaded for prolonged periods, the engine ON energy management increases the power output of the alternator (G2). 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.
- Function sequence for dynamic idle speed control.
- Function sequence for switching off comfort functions.
Function sequence for voltage provision
The voltage provision function comprises the following subfunctions:
- Function sequence for determination of charge level of on-board electrical system battery.
- Function sequence for charging on-board electrical system battery.
- Function sequence for alternator management.
Function sequence for determination of charge level of on-board electrical system battery
The charge level of the on-board electrical system battery is recorded by the battery sensor (B95).
The battery sensor 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. This, along with the battery capacity, is then used to compute the charge stored in the on-board electrical system battery.
The signal acquisition and actuation module (SAM) control unit reads in the data from the battery sensor via the battery sensor LIN (LIN B15), additionally measures the voltages at circuit 30 and circuit 30g and calculates the specified alternator voltage required to meet the energy demand.
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 various factors, the specified voltage is determined using the alternator management or using the temperature-dependent charging characteristic.
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.
Rapid charging is performed with a charging voltage of 15 V at the alternator and can take 20 s to 1 h. Only following this, a temperature-dependent characteristic or the alternator management function is used.
The alternator management system includes the lowering of the charging voltage to 12.6 V and the possibility of regenerative braking (energy recovery) when the engine is in overrun mode. When the alternator management is active, one of the front doors is open and the vehicle speed is 0 km/h, the alternator management changes to the jump start mode. At the same time, the alternator voltage is increased constantly to 14.3 V. This jump-start mode is not canceled until the vehicle speed is > 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 in cases of high voltage combined with low power consumption. If the onboard electrical system battery becomes fully charged (for example after driving in the cold or after long downhill travel), the voltage is lowered further to return the battery to its optimum charge level of 80 %.
Voltage provision
Quick charging:
- Voltage up to 15 V
- Once after circuit 50 "ON"
- Optimized charging of on-board electrical system battery, incl. during short trips
- Duration 20 s to 1 h
- End of rapid charging if battery voltage is ≥ 14 5 V and battery capacity is ≤ 30 Ah
- No quick charging when towing a trailer
- No quick charging when the on-board electrical system battery is too warm
Temperature-based charging:
- Temperature of on-board electrical system battery ≤ 15°C
- Outside temperature ≤ 15°C
- Quick charging ended alternator management not possible
- Voltage range 13 5 to 15 V
- Linear charging characteristic (temperature-dependent)
Transition to alternator management:
- Quick charging ended
- Stable engine operation
- Temperature of on-board electrical system battery ≤ 15°C
- Outside temperature ≥ 15°C
- Charge level of on-board electrical system battery ≥ 70 %
- No trailer operation
- Vehicle speed ≥ 3 km/h
Alternator management:
- Voltage 12.6 V, with some exterior lamp functions 13.5 V
- Charge level of the on-board electrical system battery 80 %
- Reduced consumer power consumption
- With air conditioning system "ON" and high blower setting 14.3 V
- With the windshield wiper system "ON" the voltage increases to 13 5 V If the power demand is too high, alternator management is switched off.
Transition to charging in deceleration mode:
- Stable engine operation
- CDI control unit or ME-SFI control unit detects overrun mode.
Charging in deceleration mode:
- Voltage up to 15 V
- Activated by CDI control unit or ME-SFI control unit.
- On-board electrical system battery charged when "free" energy is available.
Function sequence for alternator management
The alternator management:
- Takes place in the CDI control unit or ME-SFI control unit.
- Sets the specified voltage of the energy management.
- Switches to regenerative braking voltage in deceleration mode.
- Sets a lower voltage in exceptional cases (e.g. stall prevention, cold start at high altitude, catalytic converter heater).
The alternator management controls the power output of the alternator. The CDI control unit or the ME-SFI control unit communicates with the alternator via drivetrain LIN (LIN C3) and evaluates the alternator operating rate. The CDI control unit or ME-SFI control unit then sends information on the alternator operating rate via chassis CAN, electronic ignition lock (EIS) control unit and interior CAN to the signal acquisition and actuation module (SAM) control unit.
The state of the on-board electrical system battery is recorded by the battery sensor. The battery sensor sends corresponding parameters of the on-board electrical system battery via the battery sensor LIN to the signal acquisition and actuation module (SAM) control unit. The signal acquisition and actuation module (SAM) control unit evaluates all relevant information and calculates the specified voltage required for the alternator. The signal acquisition and actuation module (SAM) control unit then sends this value via interior CAN, electronic ignition lock (EIS) control unit and chassis CAN to the CDI control unit or ME-SFI control unit.
The CDI control unit or the ME-SFI control unit evaluates this, taking additional input factors (e.g. A/C "ON") into consideration, and calculates the ideal specified voltage for the alternator. Next, the CDI control unit or the ME-SFI [ME] control unit sends the calculated specified alternator voltage over drivetrain LIN 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.
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 onboard electrical system voltage is not high enough, the power management is gradually reduced. The alternator can then make its full output available.
The power management in the CDI control unit or ME-SFI control unit adopts the alternator specified voltage values of the signal acquisition and actuation module (SAM) control unit as a guideline value only because certain vehicle conditions (e.g. idle stability, engine start and 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 signal acquisition and actuation module (SAM) control unit and that of the power management into account.
If a fault is found on the battery sensor, the energy management switches to a fixed voltage of 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. Idle speed increase is performed 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:
- Alternator excitation current
- Alternator operating rate
- On-board electrical system battery voltage
- On-board electrical system battery current
- State of on-board electrical system battery
- Engine speed
- Consumer reduction shutoff stage
- Engine start
The CDI control unit or the ME-SFI control unit communicates with the alternator via drivetrain LIN and evaluates the alternator operating rate.
The CDI control unit or ME-SFI control unit then sends the "Engine running" signal and information on the alternator operating rate via chassis CAN, electronic ignition lock (EIS) control unit and interior CAN to the signal acquisition and actuation module (SAM) control unit.
The state, voltage and current of the on-board electrical system battery are detected by the battery sensor. The battery sensor sends corresponding parameters of the on-board electrical system battery via the battery sensor LIN to the signal acquisition and actuation module (SAM) control unit. The signal acquisition and actuation module (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 possible excitation current is used to calculate the maximum possible alternator current at different idle speeds.
The signal acquisition and actuation module (SAM) control unit sends corresponding requests via interior CAN, electronic ignition lock (EIS) control unit and chassis CAN to the CDI control unit or ME-SFI control unit, which then increases the idle speed accordingly.
The idle speed increase is reversed under the following circumstances:
- Engine off or alternator defective
- Simultaneous occurrence of the following conditions:
- Consumer reduction not active
- Consumer load no longer high
Function sequence for switching off comfort 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 comfort functions are reactivated when the required electrical power to stabilize the on-board electrical system voltage is available again.
The consumer reduction function is activated when the on-board electrical system voltage drops below 12.2 V. The first consumer's power consumption is reduced 20 s after engine start.
Consumer reduction during PRE-SAFE® triggering (models 447, 448.8 with code JP1 (PRE-SAFE)):
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 are deactivated completely as quickly as possible for approx. 2 s when the reversible belt tensioners are triggered in order to reduce the load on the on-board electrical system.
The signal acquisition and actuation module (SAM) control unit sends the consumer shutoff request via interior CAN to the corresponding control units, and also via interior CAN, electronic ignition lock (EZS) control unit and chassis CAN to the CDI control unit or ME-SFI control unit.
The shutoff sequence "Comfort" is shown in the table below.
| Deactivation sequence | Consumers with limited or no power | Responsible control unit |
|---|---|---|
| 1 | PTC heater booster control unit (N33/4) stage 1 (model 447 with code HZ0 (Electric auxiliary heater)) | Automatic climate control (AAC) control unit (N154) (models 447.8. 448.8 with code HH4 (THERMOTRONIC automatic climate control)) or Air conditioning system control and operating unit (AAC-V & AAC-H) (S98) (models 447.6/7, 448.7) |
| 2 | PTC heater booster control unit stage 2 (model 447 with code HZ0 (Electric auxiliary heater)) | See under cutout point "1" |
| 3 | PTC heater booster control unit stage 3 (model 447 with code HZ0 (Electric auxiliary heater)) | See under cutout point "1" |
| 4 | PTC heater booster control unit stage 4 (model 447 with code HZ0 (Electric auxiliary heater)) | See under cutout point "1" |
| 5 | PTC heater booster control unit stage 5 (model 447 with code HZ0 (Electric auxiliary heater)) | See under cutout point "1" |
| 6 | PTC heater booster control unit stage 6 (model 447 with code HZ0 (Electric auxiliary heater)) | See under cutout point "1" |
| 7 | All seat heating stage 3 (model 447 with code H16 (Seat heater for driver)) | Driver seat heater/ventilation control unit (N32/3) or Driver seat heater/ventilation control unit (N32/4) (with code ZM3 (RHD version)) |
| 8 | All seat heating stage 2 (models 447, 448.8) | For model 447: Driver seat heater/ventilation control unit (with code H16 (Seat heater for driver)) Driver seat adjustment control unit with memory (N32/5) (with code SF1 (Electrically adjustable luxury driver's seat)) Front passenger seat adjustment control unit with memory (N32/6) (with code SF2 (Electrically adjustable front passenger seat)). For model 447.8: Seat heater/ventilation control unit, rear seat, 1st seat row, left (N32/12) (with code H05 (Seat climate control in rear passenger compartment, 1st seat row)) The seat heater/ventilation control unit, rear seat, 1st seat row, right (N32/13) (with code H05 (Seat climate control in rear passenger compartment, 1st seat row)) Seat heater/ventilation control unit, rear seat, 2nd seat row, left (N32/14) (with code H07 (Seat climate control in rear passenger compartment, 2nd seat row)) Seat heater/ventilation control unit, rear seat, 2nd seat row, right (N32/15) (with code H07 (Seat climate control in rear passenger compartment, 2nd seat row)). For model 448.8: Driver seat adjustment control unit with memory (with code SF1 (Electrically adjustable luxury driver's seat)) Front passenger seat adjustment control unit with memory (with code SF2 (Electrically adjustable front passenger seat)) Seat adjustment control unit with memory, rear seat, 1st seat row, left (N25/20) (with code U90 (Luxury seat, 1st seat row, left)) Seat adjustment control unit with memory, rear seat, 1st seat row, right (N25/21) (with code U91 (Luxury seat, 1st seat row, right)). |
| 9 | Wiper heater, front (cannot be used for models 447, 448) | - |
| 10 | Mirror heater, left (M21/4r1) and mirror heater, right (M21/5r1) (with code F68 (Outside mirror, electrically adjustable and heated) or code F69 (Rearview mirror, electrically adjustable and heated with integral turn signal light)) | Left front door control unit (N69/3) and Right front door control unit (N69/4) |
When the on-board electrical system voltage has been stabilized to a value above 13.5 V or when the permissible discharge current is undershot, consumer output limitation or deactivation is canceled in the reverse order.
The on-board electrical system emergency mode represents a special case of consumer reduction. This is activated by the energy management in the signal acquisition and actuation module (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 10.6 V for 10 s, the signal acquisition and actuation module (SAM) control unit activates the on-board electrical system emergency mode function.
This causes the activation of the following engine on energy management functions:
- Idle speed increase
- Deactivation of alternator management
- Consumer reduction with shutoff of short-term consumers
Unlike consumer reduction, consumer output limitation or deactivation is done with a cycle time of 200 ms.
As soon as the on-board electrical system voltage has been stabilized to a value of 11.8 V for 10 s or a change in circuit status from circuit 15R to circuit 15C has occurred, the signal acquisition and actuation module (SAM) control unit ends the on-board electrical system emergency mode function. Consumer output limitation or deactivation is canceled.
| Electrical function schematic for dynamic idle speed increase | Model 448 | PE54.10-S-2063-97VDA | |
| Model 447 | PE54.10-S-2063-97TRA | ||
| Electrical function schematic for alternator management | Model 448 | PE54.10-S-2064-97VDA | |
| Model 447 | PE54.10-S-2064-97TRA | ||
| Electrical function schematic for comfort function shutoff | Model 448.7 | PE54.10-S-2076-97VDB | |
| Model 448.8 | PE54.10-S-2076-97VDA | ||
| Model 447.6/7 | PE54.10-S-2076-97TRB | ||
| Model 447.8 | PE54.10-S-2076-97TRA | ||
| Overview of energy management system components | Model 447.6 Model 447.7 except code ZH6 (Marco Polo ACTIVITY) Model 447.8 except code ZK7 (Equipment line MARCO POLO) Model 448 |
GF54.10-S-9990TRA |