Energy Management For ECO Start/Stop Function, Basic Function - GF54.10-P-1009A

MODEL ALL (CAR) 

Overview 

This document contains the following information:

• General 
• Function requirements 
• ECO stop 
• ECO start 
  • Vehicles with conventional drive concept (only combustion engine) 
  • Vehicles with 48 V technology 
  • Hybrid vehicles without backup concept 
  • Hybrid vehicles with backup concept 
• Forced engine start 

General 

The ECO start/stop function switches off the combustion engine under certain conditions when the vehicle is stationary. Switching off the combustion engine reduces the fuel consumption and therefore the carbon dioxide emissions.

In vehicles with conventional drive concept, the combustion engine is restarted when the driver wishes to move off.

Hybrid vehicles can also move off under purely electrical power depending on the charge level of the high-voltage battery. If the charge level of the high-voltage battery is too low, the combustion engine is started.

It is still possible to stop and start the combustion engine in the conventional way.

Function requirements 

• Combustion engine running and at operating temperature
• On-board electrical system battery charged sufficiently
• Vehicles with conventional drive concept:
  • Outside temperature -10 to 40 °C
  • On-board electrical system battery temperature 0 to 60 °C
• Hybrid vehicles:

• Outside temperature -40 to 60 °C
• On-board electrical system battery temperature -40 to 60 °C

ECO stop 

The combustion engine control unit checks all engine-relevant parameters and then issues the stop enable signal. The ECO start/stop function checks other input factors, e.g. the on-board electrical system load.

The energy management provides information which describes the on-board electrical system status or the demands on the on-board electrical system:

• Condition of the 12 V on-board electrical system battery
• Condition of the 48 V on-board electrical system battery (vehicles with 48 V technology)
• Condition of the ECO start/stop auxiliary battery (hybrid vehicles with backup concept)
• Load on on-board electrical system

After evaluating this information, the ECO start/stop function requests the combustion engine to be switched off. The combustion engine control unit stops the engine running and transmits the signal "Drivetrain operational" via CAN. This prevents the energy management system from reducing or switching off consumers if the "Engine running" signal is not sent.

After an ECO stop, only one further stop is permitted if a speed of 8 km/h is not exceeded. Then the speed of 8 km/h must be exceeded once. If the hood is opened during an ECO stop, the ECO start/stop function is switched off.

Vehicles with 48 V technology, hybrid vehicles 

The combustion engine can also be switched off in connection with system optimizations. For example, to convert the kinetic energy of the vehicle into electrical energy (recuperation).

ECO start 

The combustion engine is restarted when the driver wishes to continue his journey.

The following events lead to an ECO start:

• Vehicles with manual transmission:
  • The clutch pedal is depressed.
  • The vehicle moves off.
• Vehicles with automatic transmission:

• The brake pedal is released (when the HOLD function is not active and the selector lever position is "D" or "N").
• The accelerator pedal is operated.
• The transmission mode is changed.
• The selector lever position "R" is engaged.
• The selector lever leaves the "P" position.

The ECO start/stop function evaluates these events and requests the combustion engine control unit to start the combustion engine. When the engine speed reaches 400 to 700 rpm, the starting procedure is ended.

Vehicles with conventional drive concept (only combustion engine) 

The combustion engine is started with the starter. Due to the high start-up current of the starter during the ECO start, the on-board electrical system voltage drops severely. Active electrical consumers could be switched off briefly. A voltage dip limiter or a front-end relay prevents any excessively severe voltage drop. The power consumption of the starter is reduced during the startup phase of the combustion engine by the activation of a series resistor. If the on-board electrical system voltage drops too sharply, the voltage dip limiter or the front-end relay switches the series resistor off again.

Vehicles with 48 V technology 

The combustion engine is started with the starter-alternator. The power to start the combustion engine is provided by the 48 V on-board electrical system.

Depending on the number of 48 V consumers involved, a conventional alternator may be installed instead of the starter-alternator. In this case, the starting procedure is identical to that for vehicles with a conventional drive concept.

Hybrid vehicles without backup concept 

After an ECO stop, the combustion engine is started with the electric machine. The power to start the combustion engine is provided by the high-voltage on-board electrical system. If the charge level of the high-voltage battery is too low, the combustion engine is started with the starter. A voltage dip limiter or a front-end relay prevents any excessively severe voltage drop. The power consumption of the starter is reduced during the startup phase of the combustion engine by the activation of a series resistor. If the on-board electrical system voltage drops too sharply, the voltage dip limiter or the front-end relay switches the series resistor off again.

Hybrid vehicles with backup concept 

The combustion engine is started with the starter. The energy management connects the ECO start/stop auxiliary battery to the on-board electrical system. The ECO start/stop auxiliary battery takes over the power supply of the active consumers. The on-board electrical system battery is isolated from the on-board electrical system and provides the energy for starting the combustion engine. This prevents any voltage drop being noticed by vehicle occupants when the engine is being started (e.g. during radio or ventilation operation). After the starting procedure, the on-board electrical system battery is reconnected to the on-board electrical system and the ECO start/stop auxiliary battery is disconnected. The energy requirement of the on-board electrical system is then supplied again solely by the on-board electrical system battery.

Forced engine start 

To ensure that the on-board electrical system is also stable during an ECO stop, the combustion engine can be force-started. A forced start is also performed if, e.g. due to the requirement of load-intensive consumers, the stability of the on-board electrical system can no longer be guaranteed.

The following events result in a forced engine start:

• The on-board electrical system voltage decreases.
• The coolant temperature increases above 115 °C.
• The ECO stop lasts longer.
• The vehicle moves at more than 2 km/h forwards or it rolls backwards.
• The temperature in the vehicle interior moves out of the set range or the windshield is fogged on the inside.
• The vacuum in the brake booster decreases.
• The ECO start/stop function is deactivated.
• Vehicles with 48 V technology, hybrid vehicles

The combustion engine can also be force-started in connection with system optimizations. For example, when the charge level of the 48 V on-board electrical system battery or the high-voltage battery drops below a defined limit.

When the energy management is no longer able to guarantee the stability of the 12 V on-board electrical system, or if one of the events described above occurs, the combustion engine is started. If the stability of the on-board electrical system still cannot be guaranteed afterwards, the combustion engine is no longer switched off. The ECO start/stop function is deactivated.

	Function schematics
	Function schematic, ECO start/stop function energy management	Model 167 except code B01 (48V technology) except code ME05 (HYBRID DRIVE 80KW VARIANT (INCLUDING PLUGIN)) Model 177	PE54.10-P-2500-97A
		Model 167 with code B01 (48V technology)	PE54.10-P-2500-97B
	Additional basic functions
	Automatic start, basic function		GF07.10-P-1052A
	Automatic stop, basic function		GF07.10-P-1053A
	Combustion engine forced start, basic function		GF07.10-P-1059A
	Control units
	Combustion engine control unit, basic function		GF07.08-P-9890A
	Powertrain control unit, basic function		GF54.21-P-9894A
	Central controller unit, basic function	Model 177	GF54.21-P-9895A
	Front central controller unit basic function	Model 167	GF54.21-P-9896A