necessary for the system to start the combustion engine even when the vehicle is not moving. With prolonged driving in traffic jams, the combustion engine will be switched on and off to charge the high-voltage battery for the following start-stop phase.
Sailing
If the accelerator is not depressed and the lever is in Drive (D), the internal combustion engine is switched off even at higher speeds. The vehicle then decelerates slower than conventional vehicles.
This feature can be used to help reduce fuel consumption when you keep traffic conditions in mind and can anticipate the vehicles power requirements. Even in this case, the rev counter in the instrument cluster displays zero engine speed (0 engine revolutions). The instrument cluster powermeter shows zero.
Brake energy regeneration (Recuperation/charge)
When the vehicle brakes, the electrical energy is generated by the electric motor, which works as an alternator and charges the high-voltage battery. The same thing occurs while the vehicle is coasting to a stop or driving downhill.
Energy regeneration is shown in the instrument cluster display or on the Infotainment System screen. The combustion engine may be switched off automatically in this situation. The instrument cluster tachometer will show zero engine speed (zero engine revolutions). The instrument cluster powermeter shows zero.
Automatic starting - combustion engine
The combustion engine is started automatically in a number of situations.
x Engine temperature is too low.
x Catalytic converter temperature is too low.
x High-voltage battery being charged at high rate when decelerating. The high-voltage battery cannot absorb any more energy and for this reason the electric motor cannot brake the vehicle. The combustion engine comes on to help slow the vehicle down (engine brake).
x Engine hood is open.
x Leaving the vehicle when the electric motor is still “live”. The status of the electric motor is not always obvious, particularly when the combustion engine is not running. The combustion engine will therefore start if the driver's safety belt is unlatched or the driver's door is opened when the
transmission is in Park (P) or Neutral (N) ⇒ Warning when leaving the vehicle.
Energy flow display
Fig. 261 Energy flow display (Variant 1). Left: Instrument cluster. Right: Infotainment System.
The on-board electrical system management cannot always keep the battery from being drained. For example, the battery will drain if the engine is not running, but the ignition is switched on or the parking lights are left on for a long time when parked.
Battery disconnection in an accident with airbag deployment
In vehicles with a battery in the luggage compartment, the electrical connection to the battery is disconnected automatically in a collision with airbag deployment. This helps to prevent a short-circuit.
What drains the vehicle battery?
x Long periods when the engine is not running, especially when the ignition is on.
x Using electrical systems or devices when the engine is switched off.
x Leaving the vehicle unlocked for several days when not in use.
x The selector lever is left for a long period of time in any position other than (P) when the ignition is
switched off ⇒ Automatic transmission: Selector lever.
WARNING
Failure to use the proper battery with proper mounting and connections may cause short circuits, fires, and serious personal injuries.
x Always use only maintenance-free or cycle-free, leak-proof batteries with the same specifications and dimensions as the original equipment battery. Specifications are listed on the battery housing.
WARNING
When the vehicle battery is charged, it produces highly explosive hydrogen gas.
x Charge vehicle batteries only in well-ventilated areas.
x Never charge a frozen or thawed battery. A dead battery can freeze at temperatures around +32 °F (0 °C). Always replace a battery that has frozen.
x You must replace the vehicle battery if it was frozen.
x Incorrectly connected cables can cause a short-circuit. First connect the positive cable (+) and then the negative cable (-).
NOTICE
x Never disconnect a vehicle battery or connect 2 vehicle batteries to each other when the ignition is switched on or the engine is running. Using the wrong battery can damage the electrical system or electronic components and cause electrical malfunctions.
x Never use a vehicle battery that does not meet specifications for the vehicle battery for your vehicle. Using the wrong battery can damage the electrical system or electronic components and cause electrical malfunctions.
x Never connect power generating equipment, such as a solar panel or battery charger, to the 12 Volt socket in order to charge the vehicle battery. This can damage the vehicle's electrical system.
Dispose of the vehicle battery according to regulations. Vehicle batteries contain poisonous substances such as sulfuric acid and lead.