Belt Alternator Starter (BAS)

The Belt Alternator Starter or BAS-hybrid vehicle is a new trend in hybrid vehicles. This type of system is often referred to as a mild hybrid. Rather then have an expensive full hybrid system in a vehicle for maximum fuel economy a relatively cheap BAS can be added to a vehicle line to make modest consumption reductions for a much lower price. For example, the Saturn Vue Green Line uses this system to gain a respectable 20% gain in fuel economy over the non-hybrid Vue.

Saturn Vue Green Line BAS System

A sophisticated computer system controls an alternator generator mated to the engine to stop the conventional powerplant in idle or deceleration as well as offer added torque in certain situations. Typically a large battery (usually a 36-Volt NiMH) stores electricity to help restart the engine when the driver releases the brake pedal.

Most BAS-Hybrid systems aslso include regenerative braking and optimized charging combined with an energy storage system. This provides enhanced fuel economy while maintaining all vehicle accessories and passenger comfort systems during the periods when the engine is temporarily shut off.

Some BAS-hybrid systems like the one devloped for the Saturn Vue Green Line provide an electric motor boost during acceleration when needed. There can be as much as 110 lb-ft (150 Nm) of auto-start torque. For example, during an aggressive passing maneuver, the system improves vehicle launch and acceleration feel by assisting the engine to achieve maximum power.