Generator
Generator
Liquid-cooled generator, 190A of nominal power, depending on temperature and adjustment, 350A of power can be generated.
- Voltage regulation = BSS voltage regulator (Bit Synchronous Single-Wire technology)
- Vehicle electrical system voltage potentially greater than 15V, depending on vehicle electrical system requirements
The generator delivers the electrical energy required to supply the electric/electronic components and systems in the vehicle. The voltage is largely independent of load and is set by an integrated BSS regulator in accordance with a predefined characteristic.
Generator Control
The battery sensor transmits information (battery voltage, charging current, battery temperature) = battery condition to the gateway, the gateway calculates the energy requirements and sends this requirement request signal via DFI to the BSS generator regulator. The BSS generator regulator controls the exciting voltage according to requirements (charging current) and communicates the generator's utilization status to the gateway.
The chip temperature of the BSS regulator is used for overload protection: if the temperature is too high (coolant temperature high, excessive charging current), the field current is limited to reduce the temperature.
The interface regulator is designed as a LIN slave for the DFI control unit (LIN master). A second-generation bit-synchronous serial interface (BSS2) enables communication between the regulator and the control unit.
NOTE: BSS regulators have been installed since model year 2007 except (GT3).
Load-Response Start (LRS)
This function prevents the generator from generating charging current during and immediately after starting. This means that the starting process is not impeded or prolonged by the braking torque of the generator. Exciting voltage/utilization signal (DFM) Dynamo Field Monitor Signal (PWM) reflects the pulse/duty factor and is a measure of the utilization rate of the generator. The pulse width depends on the operating point of the generator (load, engine speed and temperature).
Generator Control Communication
Energy Management
Battery management takes place in the gateway.
Task:
Battery management must ensure that the vehicle can start in all operating conditions.
Objective:
In order to be sure that the vehicle will start every time, electrical energy consumption must be reduced, depending on the battery charging condition.
A distinction between interventions in battery management in the following situations:
- When the engine is running
- When the engine is off (Start Stop operation)
- Closed-circuit current management (engine is running, generator is not activated)
- If there are problems with the vehicle electrical system or generator an emergency load switch-off is activated. This also happens if a pyrofuse is triggered in the power distributor.
Closed-Circuit Current Management
In the case of long transport times and idle periods, the vehicle battery discharges due to closed-circuit current loads to the extent that the battery becomes damaged or unusable. Discharged batteries sulphate and are subsequently permanently damaged.
To increase startability of the vehicle, electrical energy consumption must be reduced, depending on the battery charging condition. Electrical energy consumption should be reduced during prolonged idle periods and during transport by switching off subsystem software (existing control units).
Measures for Reducing Parasitic Drain
- Reduce closed-circuit current
- Reduce loads with controlled run-on time after terminal 15 is switched off
- Reduce operating current when vehicle is stationary
- Switch off lighting after a defined run-on time through terminals G1 (Switching off comfort lighting in the passenger compartment) and G2 (Switching off security lighting in the passenger compartment)
- Switch off terminal 30 F in the event of a vehicle electrical system fault after a defined run-on time after terminal 15 is switched off
Switch-off Levels
In the event of a critical vehicle electrical system status, the escalation stages proceed step by step; when the vehicle electrical
system recovers, the escalation stages are scaled back accordingly.
Operating current loads are loads that can be activated and deactivated manually by the driver when terminal 15 is off/on and the engine is not running, e.g. radio, television, residual heat, interior lighting etc. Loads with controlled run-on time are loads that switch themselves on independently or remain on after terminal 15 is switched off and then switch off independently after a specified run-on time. The run-on times can vary. Examples include engine cooling, engine control unit, steering-angle sensor etc.
Closed-circuit current loads are electrical loads that must be powered indefinitely after terminal 15 is switched off while the vehicle is stationary. Examples include interior surveillance, interfaces, sensors, receivers etc. Comfort loads with "engine off"
Comfort loads with high static current consumption are prohibited when the engine is off, e.g. the heated rear window, mirror heating, windshield heating, heated seats, heated steering wheel.
Terminal 30F
Switching off terminal 30F helps to reduce energy consumption in the vehicle in the event of a faulty battery and vehicle electrical system before the startability limit is reached. The terminal is only switched off once all of the following conditions have been met:
- The minimum run-on time of 32 minutes has expired
- The ignition has been switched off
- The S contact is "off" (the key is not inserted)
- The alarm system is not active
- The diagnosis session is not active
- There is a fault in the vehicle electrical system
Terminal 30F
- Switching off terminal 30F when battery charging condition is critical
Transport Mode (hardware connector)
Two independent transport modes have been implemented to reduce energy consumption to a minimum during production and transport. With the first mode, a hardware connector is activated in the power distributor. The power distributor is supplied with the hardware connector inserted. It remains inserted during production and transport and is only disconnected when it reaches the dealer and the vehicle is driven.
During transport, all terminal 30TP control units are connected to terminal 30F via the transport connector. Use of the transport connector is displayed in the instrument cluster.
Transport Mode (PIWIS Tester)
The second transport mode is activated using the PIWIS diagnostic tester (PIDT).
NOTE: If terminal 30F is switched off in transport mode, terminals G1/G2 and the plug sockets are deactivated simultaneously.
Switching Off Interior Lighting
Switching off the interior lighting helps to avoid the unnecessary energy consumption caused mainly by this when the vehicle is stationary (terminal 15 is switched off) and to switch it off centrally. When terminal 15 is "off" the gateway sends a switch-off signal to the individual control units via the vehicle network.
Switching off comfort lighting in the passenger compartment: Terminal G1 Switching off security lighting in the passenger compartment: Terminal G2
The run-on times of both signals depend on the vehicle status.
- When the vehicle is locked, the gateway sends signals to the load switch-off immediately locking.
- When the vehicle is unlocked, the gateway sends the switch-off signal for terminal G1 after 16 minutes.
- When the vehicle is unlocked, the gateway sends the switch-off signal for terminal G2 after 32 minutes.
Switching Off Plug Sockets - Idle State
Switching off the plug sockets helps to improve a critical system status by reducing load current. In the idle state, the plug sockets are always switched off after a minimum run-on time of 10 minutes plus a run-on time of 60 minutes after terminal 15 is switched off. Switching off of the plug sockets may be necessary before the end of the run-on time if the system status is critical.
If the plug sockets are switched on, the gateway issues a network message requesting that they be switched off if the following conditions have been met:
- The diagnosis session is not active
- No external charging is taking place
- Terminal 15 is off
Measures for Reducing Energy Consumption
When the battery's voltage limit is reached (vehicle startability still just ensured) stage 3 is sent by the gateway.
Exceptions:
- Terminal 15 on = wake-up
- Front-end/rear-end electrics
- Remote control
- Triggering of alarm system
- Hazard warning lights
- Rotary light switch
Once stage 3 has been sent by the gateway, wake-up by means of bus nodes is no longer possible. In addition to the wakeup lock, terminal 30F is also deactivated if all switch-off conditions have been met (minimum waiting time, terminal 15 is switched off etc).
Switch Off Stages
DC/DC Converter (Start Stop)
The DC/DC converter is only installed in vehicles with Start Stop systems. The DC/DC converter is installed in the luggage compartment, underneath the luggage compartment cover and above the battery.
Situation:
- and various components are no longer supplied with the usual 12V voltage. This can result in a system failure.
Solution:
- starts and delivers this missing voltage to the vehicle electrical system.
During Start Stop operation, the Start Stop coordinator (DME) decides to switch off the engine. When the engine is off, the electrical loads are supplied with energy by the vehicle battery reserves. The battery voltage falls many times below the cell open-circuit voltage (2.1V/cell).
When the engine is started, voltage drops occur (when the starter engages and a second voltage drop when the main contacts of the starter are closed and the engine breaks away). Afterwards, the voltage recovers as a function of the starter speed when the starter is switched off and disengages, generator charging then commences and the charging voltage is reached. The size of the voltage drop depends on the temperature of all the relevant components in the current path, internal resistance and the age of the battery as well as the engine resisting torque when it is turned.