Audi A4 Owners Manual
This system helps to ensure reliable starting
The power management controls the distribution of electrical energy and thus helps to ensure that there is always enough power available to start the engine.
If a vehicle with a conventional electrical system is left parked for a long time, the battery will gradually lose its charge because certain electrical equipment (such as the immobiliser) continues to draw current even when the ignition is off. In some cases there may not be enough power available to start the engine.
Your vehicle is equipped with an intelligent power management system to control the distribution of electrical energy. This significantly improves reliability when starting the engine, and also prolongs the life of the battery.
The main functions incorporated in the power management system are battery diagnosis, residual current management and dynamic power management.
The battery diagnosis function constantly registers the condition of the battery. Sensors detect the battery voltage, battery current and battery temperature. This enables the system to calculate the current power level and charge condition of the battery.
Residual current management
The residual current management reduces power consumption while the vehicle is parked. It controls the supply of power to the various electrical components while the ignition is switched off. The system takes the battery diagnosis data into consideration.
Depending on the power level of the battery, the individual electrical components are switched off one after the other to prevent the battery from losing too much charge and to ensure that the engine can be started reliably.
Dynamic power management
While the vehicle is moving, this function distributes the available power to the various electrical components and systems according to their requirements. The power management ensures that onboard systems do not consume more electrical power than the alternator can supply, and thus maintains the maximum possible battery power level.
- • The power management system is not able to overcome the given physical limits. Please remember that the power and life of the battery are limited.
- • A warning message will appear, “Driver message in the instrument cluster display” if the battery power has dropped to a level where reliable starting is impaired.
Points to remember
Starting ability has first priority.
Short trips, city traffic and low temperatures all place a heavy load on the battery. In these conditions a large amount of power is consumed, but only a small amount is supplied. The situation is also critical if electrical equipment is in use when the engine is not running. In this case power is consumed when none is being generated.
In these situations you will be aware that the power management system is intervening to control the distribution of electrical power.
When the vehicle is parked for long periods
If you do not drive your vehicle for a period of several days or weeks, the power management will gradually shut off the on-board systems one by one, or reduce the amount of current they are using. This limits the amount of power consumed and helps to ensure reliable starting even after a long period.
Please note that certain convenience features, such as the Audi advanced key*, the remote control key or the electrical seat adjustment may not be available when you unlock the vehicle. These functions will be restored when you switch on the ignition and start the engine.
With the engine switched off
If you listen to the radio or use the other MMI functions when the engine is not running, this will discharge the battery.
The MMI display will show this warning message before the battery power drops to a level where the starting ability is impaired.
Please start engine, otherwise system will switch off in 3 minutes.
This message warns you that the system you are using will be switched off automatically after 3 minutes. You should therefore start the engine if you wish to continue using the system.
When the engine is running
Although the alternator generates electrical power, the battery can still become discharged while the vehicle is being driven. This can occur when a lot of power is being consumed but only a small amount supplied, especially if the battery is not fully charged initially.
To restore the necessary energy balance, the system will then temporarily shut off the electrical components that are using a lot of power, or reduce the current they are consuming. Heating systems in particular use a large amount of electrical power. If you notice, for instance, that the seat heating* or the rear window heater is not working, they may have been temporarily switched off or regulated to a lower heat output. These systems will be available again as soon as sufficient electrical power is available.
You may also notice that the engine runs at a slightly faster idling speed. This is quite normal, and no cause for concern. The increased idling speed allows the alternator to meet the greater power requirement and charge the battery at the same time.
Driver message in the instrument cluster display
If battery power drops to a level at which you may encounter problems when starting the engine, the following message will appear in the instrument cluster display:
Low battery charge: Battery will
This message reminds you that the starting reliability may be impaired. The message will disappear as soon as you set off and the battery is charged.
Message comes on and goes out again
If the message appears in the display after the ignition is switched on or while driving, and goes out again after a period of time, the battery has been charged up again sufficiently while the vehicle was being driven.
Message comes on and does not go out
If the message appears in the display after the ignition is switched on or while driving, and does not go out again, the battery is not being maintained at the proper power level. Starting reliability may be impaired. You should have the battery checked by a qualified workshop as soon as possible.