ECO Start/Stop Function Energy Management, Function - GF54.10-P-1040GR

MODEL 166 up to model year 2016 with CODE B03 (ECO start/stop function) 

The "energy management for ECO start/stop function" subfunction is considered from the viewpoint of the energy management. Information on the subfunction "Engine timing, start/stop function" is documented in the function description "Common rail diesel injection (CDI), function" (diesel engine) or "Gasoline injection and ignition system with direct injection, function" (gasoline engine).

Function requirements, general 

• Engine running and at operating temperature
• Engine hood closed
• One-time overspeeding of v > 15 km/h in forward travel
• System diagnosis completed
• Outside temperature T = -10 up to 40 °C
• On-board electrical system battery temperature (G1) T = 0 up to 60 °C
• A/C regulated

Energy management for ECO start/stop function in general 

For a stationary vehicle, the ECO start/stop function switches the engine off automatically and starts it again, as soon as the driver wishes to drive off. Switching of the engine during standstill periods of the vehicle reduces the fuel consumption and therefore the carbon dioxide emissions. The master control unit for the ECO start/stop function is the CDI control unit (N3/9) (diesel engine) or ME-SFI [ME] control unit (N3/10) (gasoline engine) which records and evaluates all influencing factors.

Conventional cut out and starting of the engine with the transmitter key (A8/1) or over the Start/Stop button KEYLESS-GO (S2/3) (with code (889) Keyless Go) continues to be possible.

Through the use of the additional battery for ECO start/stop function (G1/13) with a capacity of 12 Ah, the starting voltage dip is avoided while the engine is being started. The additional battery for ECO start/stop function then assumes the power supply for the active consumers in the process while the on-board electrical system battery is isolated from the on-board electrical system (at engine start). Active comfort functions are not switched off. Immediately after the engine's cold start, the CDI control unit or the ME-SFI [ME] control unit runs a system diagnosis [SD] and evaluates the functional capability of the ECO start/stop function. In addition the SAM control unit (N10) checks the function of the components involved in isolating the on-board electrical system battery and connecting the ECO start/stop function additional battery.

The additional battery for the ECO start/stop function is activated by actuation of the ECO start/stop function additional battery relay (K114). The on-board electrical system battery is decoupled from the on-board electrical system by actuating the ECO start/stop function diode (V19).

The ECO start/stop function encompasses the following subfunctions:

• Function sequence for engine stop 
• Function sequence for engine start 
• Function sequence for forced engine start 
• Function sequence for determine condition of additional battery for ECO start/stop function 
• Function sequence for charge ECO start/stop function additional battery 

Additional function requirement for engine stop 

• Stop enable issued by the CDI control unit or the ME-SFI [ME] control unit

Function sequence for engine stop 

As the master control unit for the ECO start/stop function, the CDI control unit or the ME-SFI [ME] control unit checks the various influencing factors for the stop enable.

The SAM control unit reads in the data from the battery sensor (B95) via battery sensor LIN (LIN B15), evaluates it and transmits information about the on-board electrical system status or the requirements for the on-board electrical system to the CDI control unit or ME-SFI control unit via interior CAN (CAN B), electronic ignition lock control unit (N73) and chassis CAN 1 (CAN E1).

The following information is included in it:

• State of on-board electrical system battery
• State of additional battery for ECO start/stop function
• On-board electrical system status
• Requirements for load-intensive consumers (e.g. A/C)

The CDI control unit or the ME-SFI [ME] control unit evaluates all the relevant data, issues the stop enable and switches the engine off. The CDI control unit or the ME-SFI [ME] control unit then sends the signal "Drive train ready" over the chassis CAN 1, electronic ignition lock control unit and interior CAN to the SAM control unit. This prevents the energy management from starting the process of consumer reduction or consumer shutoff as the "Engine running" signal is not sent.

While the vehicle is at a standstill the brake pedal must remain pressed or the "Hold" function be active. The blower output is reduced when the automatic blower speed function of the air conditioning is active. In high ambient temperatures the system changes into air circulation mode depending on the specified temperature adjusted. After an engine stop a maximum of three engine starts is permitted without exceeding the speed threshold of v = 8 km/h.

Function sequence for engine start 

The engine is started with the actuation of the accelerator pedal.

During the starting procedure the on-board electrical system battery is isolated from the on-board electrical system. The power supply for the active consumers is now provided by the additional battery for the ECO start/stop function. This serves to prevent any voltage dip as perceived by vehicle occupants when starting the engine (e.g. during radio or ventilation operation).

The additional battery for the ECO start/stop function is then switched through to the on-board electrical system. Shortly after this the ECO start/stop function diode isolates the on-board electrical system battery from the on-board electrical system during the starting procedure. The energy requirement of the on-board electrical system is now solely covered by the ECO start/stop function additional battery. The on-board electrical system battery provides the energy required for the engine starting procedure.

The CDI control unit or the ME-SFI [ME] control unit evaluates all relevant influencing factors and then issues the start enable (hot start signal). The SAM control unit reads in this hot start signal over a direct line, and actuates the ECO start/stop function additional battery relay on the ECO start/stop function additional battery and the ECO start/stop function diode in the engine compartment prefuse box (F32/3).

As soon as the CDI control unit or the ME-SFI control unit detects an engine rpm of n = 400 to 700 rpm, it stops the starting procedure and sends the signal "engine running" via chassis CAN 1, electronic ignition lock control unit and interior CAN to the SAM control unit. The SAM control unit then actuates the ECO start/stop function diode and the ECO start/stop function additional battery relay.

The ECO start/stop function diode then switches the on-board electrical system battery through to the on-board electrical system. The additional battery relay for ECO start/stop function disconnects the additional battery for ECO start/stop function from the on-board electrical system. The energy requirement of the on-board electrical system is now supplied again by the on-board electrical system battery.

Function sequence for forced engine start 

To ensure that the on-board electrical system stability is also given during engine OFF, the CDI control unit or the ME-SFI [ME] control unit can also force the engine to start. A forced engine start is also conducted if, as a consequence of load-intensive consumers, the on-board electrical system stability can no longer be assured.

Load-intensive consumers can also be requested by the following systems:

• Air conditioning
• Steering

As soon as the energy management is no longer able to ensure on-board electrical system stability, the SAM control unit sends a "Start engine" request to the CDI control unit or to the ME-SFI [ME] control unit via interior CAN, electronic ignition lock control unit and chassis CAN 1. The CDI control unit or the ME-SFI [ME] control unit receives this and starts the engine.

If, following this, the on-board electrical system stability can still not be assured, the engine is no longer switched off. The ECO start/stop function is switched off.

The SAM control unit calculates the required alternator specified voltage based on the data from the battery sensor and transmits this to the CDI control unit or to the ME-SFI control unit via interior CAN, electronic ignition lock control unit and chassis CAN 1. This makes the CDI control unit or the ME-SFI control unit start the alternator regulation (alternator management).

Detailed information about the alternator regulation can be found in the subfunction "engine ON energy management function".

Illustration of power supply at engine start principle 

Illustration of power supply when engine running principle 

Function sequence for determine condition of additional battery for ECO start/stop function 

The SAM control unit runs a battery state recognition immediately after the engine is started. This provides regarding the availability of electrical power to the additional battery for the ECO start/stop function.

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 for ECO start/stop function mode in the ECO start/stop function mode is measured after every engine start.

The battery state recognition can be started using a diagnosis tester.

The additional battery relay for the ECO start/stop function is no longer actuated under the following conditions:

• Additional battery for ECO start/stop function deep discharged
• Internal short circuit
• Short circuit in positive line of additional battery for ECO start/stop function

In order to establish this, the voltage of the ECO start/stop function additional battery is compared with an internal value. A corresponding fault message is shown in the multifunction display (A1p13) of the IC (A1). The SAM control unit transmits the data required for this to the instrument cluster over the interior CAN.

Function sequence for charge ECO start/stop function additional battery 

The charging strategy of the additional battery for ECO start/stop function must take two requirements into account:

• The ECO start/stop function additional battery must always be sufficiently charged.
• The number of additional battery relay for the ECO start/stop function actuations and the related load on the additional battery for the ECO start/stop function must be minimized as far as possible.

If the open circuit voltage of the additional battery for ECO start/stop function is too low (U < 12.5 V), the alternator's power limit (alternator management) is deactivated so that the additional battery for ECO start/stop function can be charged.

If the voltage dip is too large (U < 11 V) at engine start, an engine stop is deactivated for t = 5 minutes (up to 30.06.2012) or for t = 1 minute (as from 01.07.2012) to recharge the additional battery for the ECO start/stop function.

The additional battery for ECO start/stop function is only connected when the alternator's power limit (alternator management) is not active and the on-board electrical system voltage (U > 13 V) is high enough. It is cleared again when the alternator's power limit is active or the on-board electrical system is severely overloaded.

	Electrical function schematic for energy management for engine start/stop		PE54.10-P-2070-97NAA
	Overview of energy management system components		GF54.10-P-9990GR