ECO Start/Stop Function Energy Management, Function - GF54.10-P-1040GW
Model 463 (except 463.342)
as of Model year 2013 up to Model year 2019
with code MJ7 (ECO start/stop function)
Model 463.342
with code MJ7 (ECO start/stop function)
The "Energy management for ECO start/stop function" is considered from an energy management viewpoint.
Function requirements, general
- Engine hood closed
- One-time over-speeding of v = 8 km/h with forward travel
- One-time over-speeding of v = 15 km/h with forward travel after a maneuvering process
- System diagnosis complete and fault-free
- Outside temperature T = -10 up to 40 °C
- Battery temperature 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 when the vehicle is at a standstill 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.
It is still possible to stop and start the engine in the conventional way.
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 (G1) 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 sub-functions:
- Engine stop
- Engine start
- Forced engine start
- Determine state of additional battery for ECO start/stop function
- Charge additional battery for ECO start/stop function
Additional function requirements for engine stop
- Engine running
- Stop enable issued by the CDI control unit or the ME-SFI [ME] control unit
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 energy management system provides information for this which describes the on-board electrical system status or the requirements for the on-board electrical system.
The SAM control unit reads in the data from the battery sensor (B95) via the battery sensor LIN (LIN B15) and evaluates it.
The SAM control unit then sends information which describes the onboard electrical system status or the requirements for the on-board electrical system, via the interior CAN (CAN B), electronic ignition lock control unit (N73) and chassis CAN 1 (CAN E1) to the CDI control unit (engine 642) or to the ME-SFI control unit (engine 157).
On vehicles with engine 176, the SAM control unit sends this information via the interior CAN, electronic ignition lock control unit, chassis CAN 1, powertrain control unit (N127) and drive train CAN (CAN C) to the ME-SFI control unit.
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
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 (engine 642) or the ME-SFI control unit (engine 157) then sends the "Drive train operational" signal via chassis CAN 1, the electronic ignition lock control unit and interior CAN to the SAM control unit.
On vehicles with engine 176, the ME-SFI control unit sends the "Drive train operational" signal via the drive train CAN, powertrain control unit, chassis CAN 1, electronic ignition lock control unit and interior CAN to the SAM control unit.
This prevents the energy management system from reducing or switching off consumers if the "Engine running" signal is not sent.
While the vehicle is at a standstill, the brake pedal must remain depressed or the HOLD function must be active. The blower setting 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 the engine has been switched off, maximum three engine starts within a period of t = 1 min (maximum idle time t = 3 min) without exceeding the speed threshold of v = 8 km/h are permitted.
Engine start
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 drop being noticed by vehicle occupants when starting the engine (e.g. during radio or ventilation operation).
The following events lead to an engine start:
- Release of brake (when the HOLD function is not active and gear range "D" or "N" is selected)
- Operation of accelerator pedal
- Selection of gear range "R"
- Shifting out of gear range "P"
- Unfastening of driver's seat belt
- Driver door opened
- Switch off of function via ECO start/stop function button (N72/1s50) in upper control panel control unit (N72/1)
- Activation of off-road ratio in transfer case
- Change to transmission mode "S" or "M" (except code ZU8 (USA national version) and as of Model year 2015 except code 990 (AMG vehicle documents/identification plate control))
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 the hot start signal over a direct line and actuates the ECO start/stop function additional battery relay and the ECO start/stop function diode.
The additional battery for the ECO start/stop function is then switched through to the on-board electrical system. The ECO start/stop function diode disconnects the on-board electrical system battery from the onboard electrical system during the starting procedure. The energy requirement of the on-board electrical system is now solely provided by the ECO start/stop function auxiliary battery. The on-board electrical system battery now supplies the energy required for the engine starting process.
As soon as the CDI control unit or the ME-SFI control unit detects an engine speed of n = 400 up to 700 RPM, it terminates the starting procedure.
The CDI control unit (engine 642) or the ME-SFI control unit (engine 157) then sends the "engine running" signal via chassis CAN 1, electronic ignition lock control unit and interior CAN to the SAM control
unit.
On vehicles with engine 176, the ME-SFI control unit sends the "engine running" signal via the drive train CAN, powertrain control unit, 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.
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 onboard electrical system stability can no longer be assured.
In addition, the following events lead to a forced engine start:
- Coolant temperature T > 125 °C
- Exceeding of engine stop period of max. t = 3 min
- Interior temperature outside nominal range
- Air conditioning requires engine to be running (e.g. fogging of windows)
- Vacuum in brake booster not in normal range (p = -1150 up to -130 mbar)
- Change of the steering wheel angle by more than a = 8°
- Vehicle speed v > 2 km/h with forward travel
- Recognition of reverse rollers
- System or communication error from one of the following systems: driver presence, steering, on-board electrical system, brake system, accelerator pedal, transmission, starter, engine As soon as the energy management is no longer able to ensure onboard electrical system stability, the SAM control unit sends a "start engine" request to the CDI control unit (engine 642) or to the ME-SFI control unit (engine 157) via the interior CAN, electronic ignition lock control unit and chassis CAN 1.
On vehicles with engine 176, the SAM control unit sends the "start engine" request via the interior CAN, electronic ignition lock control unit, chassis CAN 1, powertrain control unit and drive train CAN to the ME-SFI control unit.
The CDI control unit or the ME-SFI [ME] control unit then 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 on the basis of the data from the battery sensor, and sends this voltage via the interior CAN, electronic ignition lock control unit and chassis CAN 1 to the CDI control unit (engine 642) or to the ME-SFI control unit (engine 157).
On vehicles with engine 176, the SAM control unit sends the required alternator specified voltage via the interior CAN, electronic ignition lock control unit, chassis CAN 1, powertrain control unit and engine CAN
(CAN C1) to the ME-SFI control unit.
This makes the CDI control unit or the ME-SFI [ME] control unit start the alternator regulation (alternator management). For this purpose, the CDI control unit or the ME-SFI control unit evaluates the operating rate of the alternator (G2) and requests the corresponding specified voltage. The alternator and the CDI control unit or the ME-SFI [ME] control unit communicate with each other via the drive train LIN (LIN C1).
The CDI control unit (engine 642) or the ME-SFI control unit (engine 157) also sends information on the alternator operating rate via chassis CAN 1, the electronic ignition lock control unit and interior CAN to the SAM control unit.
On vehicles with engine 176, the ME-SFI control unit sends information on the alternator operating rate via the engine CAN, powertrain control unit, chassis CAN 1, electronic ignition lock control unit and interior CAN to the SAM control unit.
Illustration of power supply at engine start principle
Illustration of power supply when engine running principle
Determine state 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 information 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 tested 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 instrument cluster (A1). The request for this is sent by the Sam control unit over the interior CAN (except code E11 (Stealth lights with convoy marking)) or over the interior CAN, stealth lights control unit (N1) and the instrument cluster CAN (CAN KI) (with code E11 (Stealth lights with convoy marking)) to the instrument cluster.
Charge additional battery for ECO start/stop function
The charging strategy of the ECO start/stop function auxiliary battery must take into account two criteria:
- The ECO start/stop function auxiliary 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 voltage dip at engine start is too great (U < 11 V), an engine stop is suppressed for t = 5 minutes to recharge the additional battery for the ECO start/stop function. The additional battery for the ECO start/stop function is only switched in when alternator management is not active and the on-board electrical system voltage is high enough (U > 13 V). It is disconnected again when the alternator management is active or the on-board electrical system is severely overloaded.
| Electrical function schematic for energy management for engine start/stop | PE54.10-P-2070-97ZGA | ||
| Overview of energy management system components | Model 463 (except 463.342) as of Model year 2013 up to Model year 2019 with code MJ7 (ECO start/stop function) Model 463.342 as of Model year 2013 with code MJ7 (ECO start/stop function) |
GF54.10-P-9990GW |