Elements of the Bosch Start-Stop system. Click to enlarge.

While only 5% of all new vehicles in Europe were equipped with this system in 2008, Bosch predicts that this share will increase to 50% by 2012. Bosch start-stop technology already features in models made by BMW and Mini, Fiat, Kia, and Volkswagen, among others.

Start-stop systems stop the combustion engine when the vehicle comes to a halt at a red light or in a traffic jam, starting it again automatically when the clutch is depressed and the vehicle is put back into gear. For this system, Bosch supplies a special starter, whose electric starter motor as well as low-noise, enhanced meshing mechanics provide safe, fast, and quiet engine starts.

The system also includes control software, which is generally integrated into the engine ECU, and a battery sensor, one of whose tasks is to record the current battery charge and relay this information to the energy management system. This ensures that the engine is only stopped if the battery has stored enough energy to start the engine again quickly. The system is rounded off by a crankshaft sensor, sensors on the pedals, and a deep-cycle resistant battery.

For start-stop operation that is as uninterrupted as possible, Bosch also offers a new series of alternators. In the models of the “Efficiency Line” (EL) series, Bosch engineers have improved the electrical design and used new diodes, and in this way achieved an efficiency of as much as 77%. In addition, these alternators ensure that the battery is well-charged even when the engine is idling or running at low revolutions. A well-charged battery is a condition for start-stop. The combination of Bosch EL alternator and start-stop system can reduce fuel consumption (and thus also CO₂ emissions) in urban driving by as much as 10%.