Mild hybrid
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Mild hybrids are essentially conventional vehicles with oversized starter motors, allowing the engine to be turned off whenever the car is coasting, braking, or stopped, yet restart quickly and cleanly. Accessories can continue to run on electrical power while the engine is off. The larger motor is used to spin the engine up to operating rpm speeds before injecting any fuel.
Many people do not consider these to be hybrids at all since they do not have hybrid drivetrains (there is no electric motor to drive the vehicle), they don't have battery storage and do not achieve the fuel economy of full hybrid models. A major example is the 2005 Chevrolet Silverado Hybrid, a full-size pickup truck. Chevrolet was able to get a 10% improvement on the Silverado's fuel efficiency by shutting down and restarting the engine on demand.[citation needed] Mild hybrids often use 48 volt systems[citation needed] to supply the power needed for the startup motor, as well as to compensate for the increasing number of electronic accessories on modern vehicles.
Compared to a "full" hybrid vehicle, however, mild hybrids may provide some of the benefits of the application of hybrid technologies, with less of the cost/weight penalty that is incurred by installing the parallel (electric) hybrid drivetrain. Fuel savings would generally be lower than expected with use of a full hybrid design, as the design does not normally allow regenerative braking or the use of smaller, lighter, more efficient internal combustion engines. BMW, however, succeeded in combining regenerative braking with the mild hybrid "start-stop" system[1] in their current 1-series model. GM's Belt alternator starter mild hybrid system also utilizes regenerative braking, by back-spinning the electric motor during coasting and deceleration to generate electricity used to charge the system's battery.
General Motors followed the pickup truck hybrid with their Belt alternator starter (BAS) hybrid system, used in the 2007 Saturn Vue Green Line. It operates in much the same manner as the "start-stop" system in the Silverado, but the electric motor can also provide modest assist under acceleration.
Citroën proposes a stop and start system on its C2 and C3 models [2]. The concept-car C5 Airscape has an improved version of that, adding regenerative braking and traction assistance functionalities, and ultracapacitors for energy buffering [3].
VW brought two concept cars to Shanghai for the Challenge Bibendum. [4]
