Belt alternator starter

General Motors introduced a mild hybrid system called belt alternator starter (or BAS) in the 2006 Saturn VUE Green Line. It operates similar to the "start-stop" system used in the Chevrolet Silverado Hybrid in that it shuts down the engine when the vehicle comes to a stop and instantly restarts it when the accelerator is pressed. A 48 volt electrical system is used to operate all accessory equipment, from the air conditioning to the lighting, making the system essentially invisible to the driver.

The BAS system goes slightly further than the Silverado, however, in providing some modest power assist for "acceleration feel", according to GM. Although not as effective as other systems, the BAS system is expected to provide about 15% fuel efficiency gain for the compact VUE.

One major benefit of the BAS technology is that it fits in the same space as a conventional engine. No modifications were required to the VUE's chassis to accommodate the BAS system, with the battery pack housed in the spare tire well. This allows the VUE Green Line to be produced on the same assembly line as the normal VUE, producing substantial cost savings and allowing the company to adjust production more easily.

The BAS system uses a conventional 4T45-E automatic transmission.

This system will eventually find its way to other GM models, including the Saturn Aura, and Chevrolet Malibu.