To save energy and reduce the vehicle’s fuel consumption, this system controls the times at which the alternator charges the battery. Conventionally, a car’s alternator runs continuously and thus charging is always available to the battery; in the Gran Turismo, it charges only when the vehicle is decelerating or braking; otherwise, it freewheels, drawing virtually no power from the engine. An electronically controlled clutch, somewhat similar to that used with the air-conditioning compressor, is added to engage and disengage the alternator.
Accommodating the less frequent charging is a special, more powerful battery that can satisfy a contemporary vehicle’s high electrical demands without access to continuous charging. The battery uses a technology called “glass mat,” in which its internal plates are separated with saturated absorbent glass-boron silicate rather than the usual liquid electrolyte. This construction sharply reduces the battery’s conversion of charging energy to heat, and can provide the necessary electrical power for longer periods between charges.