Engine Off Energy Management, Function - GF54.10-D-1050TSA

Model 907

Function requirements in general

"Engine running" or "Drivetrain operational" signal not set (engine switched off).

Engine OFF energy management, general

Engine OFF energy management ensures the stability of the on-board electrical system and the starting capability of the engine when the vehicle is parked.

This functionality is integrated in the SAM control unit (N10) and allows the on-board electrical system battery (G1) to have extended non-operational times. To achieve this, active comfort functions or consumers are switched off or disconnected from the power supply (terminal 30t) as necessary.

Engine OFF energy management encompasses the following subfunctions:

Deep discharge protection
Consumer shutoff
Remote charging/jump start

Function sequence for deep discharge protection

The purpose of the deep discharge protection system is to prevent impermissible deep discharging of the on-board electrical system battery during vehicle downtimes (inactive phase). This function should ensure the startability of the vehicle over an extended period of time or in the event of elevated quiescent currents.

It also briefly interrupts the power supply to components causing elevated quiescent currents (control unit reset). Only if several interruptions do not rectify the quiescent current problem will the battery disconnect switch (BTS) open and stay open.

Deep discharge protection encompasses the following subfunctions:

BTS reset at elevated quiescent current
BTS opening at low state of charge
BTS opening for extended non-operational time ("hibernation mode")

BTS reset at elevated quiescent current

After switching off the engine, the system checks the quiescent current cyclically every 15 minutes. If the quiescent current does not drop below a certain threshold after a tolerance period has elapsed, the tml. 30t power supply is briefly interrupted (BTS reset).

If there is a CAN bus fault because the electronic ignition lock (EZS) control unit (N73) reports a bus keepawake event, the tolerance time is not waited for and the BTS reset is activated.

Preconditions:

Ignition OFF
The state of charge of the on-board electrical system battery is below a predefined threshold.
There is no reason for prevention of a reset (see section "Prevention of reset")

The BTS reset is triggered if one of the following conditions is present:

The tolerance time has elapsed and the quiescent current exceeds the quiescent current limit.
The electronic ignition lock (EZS) control unit reports a bus keepawake event.

Execution of function:

The SAM control unit sends a pre-warning signal on the interior CAN (CAN B), so that the components located on the interior CAN can prepare for a supply voltage shutdown. After the pre-warning time has elapsed, the SAM control unit opens the BTS. It is automatically closed again after the relay has opened.

If a reset inhibitor occurs during the tolerance time, the time is reset and the counter restarts once the reset inhibitor is no longer present.
If a reset inhibitor occurs during the pre-warning time, the time is reset and the counter restarts once the reset inhibitor is no longer present.

If, after a BTS reset and expiry of a new tolerance time, the quiescent current still does not drop below the threshold, or if a bus keepawake event occurs, the reset procedure is repeated. A maximum of 3 resets in succession are possible. If these fail, the BTS remains closed until the system reaches the function status of "low state of charge".

BTS opening at low state of charge

After the engine is switched off, the system checks the condition of the on-board electrical system battery.

If the voltage of the on-board electrical system battery is below 11.4 V or if the state of charge drops below a predefined threshold, the on-board electrical system battery is in a state that jeopardizes the starting capability of the engine. The BTS is then opened.

Preconditions:

Ignition OFF
There is no reason for preventing opening (see section "Prevention of opening").
The anti-theft alarm system is not active or must not prevent monitoring.

Opening is triggered if one of the following conditions is present:

The state of charge of the on-board electrical system battery drops below a predefined threshold.
The voltage of the on-board electrical system battery drops below 11.4 V.

Execution of function:

Due to various control unit run-on operations (e. g. for cooling, tank leak diagnosis, etc.), a certain amount of time needs to elapse after switching off the vehicle before the BTS is allowed to open. A run-on time has been introduced for this purpose, which starts as soon as the vehicle is stopped.

After the run-on time has elapsed, all conditions must then be present for a specific monitoring period, before the BTS is opened. The SAM control unit then sends a pre-warning signal on the interior CAN so that the components located on the bus system can prepare for a supply voltage shutdown. After a pre-warning time has elapsed, the SAM control unit opens the BTS.

If an opening inhibitor occurs during the monitoring time, the time is reset and the counter restarts once the opening inhibitor is no longer present.
If an opening inhibitor occurs during the pre-warning time, the time is reset and the counter restarts once the opening inhibitor is no longer present.
BTS reset and BTS open are independent of each other. If the conditions for a BTS opening are met immediately without the conditions for a BTS reset being present, an opening without preceding resets is requested directly. However, the on-board electrical system does not generally reach the critical status until after a phase of elevated quiescent current, i.e. a BTS reset usually precedes the BTS opening.

If the vehicle is unlocked, the electronic ignition lock (EZS) control unit sends a corresponding signal to the SAM control unit. This then closes the BTS again.

BTS opening for extended non-operational time ("hibernation mode")

The "hibernation mode" function can be activated via the head unit (A26/17) to extend the non-operational time by opening the BTS early.

After activation, the display shows the maximum remaining non-operational time in weeks and the current state of charge of the on-board electrical system battery.

Preconditions:

The terminal status is terminal 15R or higher.
The state of charge of the on-board electrical system battery is over 70 %.
No reason to prevent hibernation is present (see section "Prevention of opening in "hibernation mode"").
The function is enabled by the electronic ignition lock (EZS) control unit.

Trigger:

The function is switched on via the head unit.

Execution of function:

If the function is switched on, the head unit sends a corresponding signal to the SAM control unit.

The SAM control unit transmits the possible remaining non-operational time, based on the current state of charge of the on-board electrical system battery, to the head unit. If the state of charge is too low, the display indicates that the on-board electrical system battery should be charged (by running the engine or using a charger).

After the function is switched on, the activation time must be waited for; the ignition must not be switched on during this time. The debounce time (5 minutes) followed by the regular pre-warning time must then elapse. The SAM control unit then opens the BTS.

If the vehicle is unlocked, the electronic ignition lock (EZS) control unit sends a corresponding signal to the SAM control unit. This then closes the BTS again.

If an opening inhibitor occurs during the debounce time, the time is reset and the counter restarts once the opening inhibitor is no longer present.
If an opening inhibitor occurs during the pre-warning time, the time is reset and the counter restarts once the opening inhibitor is no longer present.

Prevention of a reset

The following states can prevent a reset of the BTS:

The BTS must remain closed.
The hazard warning lights are switched on.
The key is inserted into or removed from the ignition lock.
The terminal status is terminal 15R or higher.
The alarm system is switched on.
The parking lights are switched on.
Hill-Start Assist is active.
The air conditioning system is heating or ventilating.
Evaporator drying of the air conditioning system is active.
The "Extended session diagnosis mode" is active.
The head unit is switched on.
The electronic ignition lock (EZS) control unit requests a closed BTS.
The central locking is actuated.
A door is unlocked or opened.
A seat is adjusted electrically.
The residual heat utilization function is active.
External charging is detected.
Quiescent current measurement is active.
The vehicle moves.
BTS opening is requested via diagnosis.

Prevention of opening

The following states can prevent the BTS from being opened:

The BTS must remain closed.
The hazard warning lights are switched on.
The key is inserted into or removed from the ignition lock.
The terminal status is terminal 15R or higher.
The alarm system is switched on.
Hill-Start Assist is active.
The "Extended session diagnosis mode" is active.
The electronic ignition lock (EZS) control unit requests a closed BTS.
A door is unlocked or opened.
External charging is detected.
Quiescent current measurement is active.
The vehicle moves.
BTS opening is prevented via diagnosis.
The engine is running.

Prevention of opening in "Hibernation mode"

The following states can prevent the BTS from being opened:

The hazard warning lights are switched on.
The alarm system is switched on.
The "Extended session diagnosis mode" is active.
The electronic ignition lock (EZS) control unit requests a closed BTS.
Quiescent current measurement is active.
The vehicle moves.
The state of charge of the on-board electrical system battery is over 70 %.
External charging is detected.
The engine is running.
There is a BTS fault.

Consumer shutoff function sequence

The consumer shutoff function is integrated into the SAM control unit and serves to extend the non-operational time of the on-board electrical system battery. To this end, active comfort functions or consumers are gradually switched off as necessary.

Default condition:

The engine does not run.
Consumer shutoff is triggered if one of the following conditions is present:
The voltage of the on-board electrical system battery drops below 11.8 V.
The state of charge of the on-board electrical system battery reaches a predefined threshold.

Execution of function:

If the voltage of the on-board electrical system battery falls below 11.8 V, the electrical consumers are switched off in succession at specific time intervals; this shutdown continues for as long as the voltage remains below 11.8 V. If the voltage increases to ≥ 11.8 V, the shutdown stops. It will only resume if the voltage drops below 11.8 V again.

Remote charging/jump start

If the on-board electrical system battery does not have enough capacity to start the engine, the on-board electrical system battery must be charged or a jump start carried out.

Once switched off, the consumers are not switched on again until the engine is started.

During a jump start procedure or during any testing in the workshop one of the front doors must be opened so that the alternator management can switch to jump start mode or workshop mode, thereby increasing the alternator voltage to 14.3 V.

Overview of energy management system components

GF54.10-D-9990TSA