Lexus GS 450h Hybrid Synergy Drive in Operation
Over the course of any journey, Lexus Hybrid Drive operates in several different modes to maximise efficiency. At start-up and low to mid-range speeds, the vehicle runs on the electric motors alone, eradicating both engine noise and carbon dioxide emissions.
In normal driving conditions, the V8 engine is the main power source, with output divided by the power split device, both to drive the wheels and power the generator, which in turn charges the high-voltage battery. This power allocation is constantly monitored and adjusted between the engine and electric motor to maximise efficiency.
When full acceleration is required, engine and electric motor again work in tandem, with extra power supplied by the battery to boost acceleration.
During deceleration, the engine switches off as the driver lifts off the throttle and the electric motor acts as a second generator to initiate regenerative braking, recovering energy that would normally be lost as heat as electrical energy for storage in the battery. Over the course of any journey, the Lexus Hybrid Drive system will operate in several modes to maximise the GS 450h’s overall efficiency. When the engine is cold and the ignition is switched on, the system will start the engine to warm the unit. Thereafter, when the vehicle comes to rest, the engine stops automatically to conserve fuel. However, if the vehicle is at idle for prolonged periods, the engine will automatically run when necessary to charge the high-voltage battery via the generator.
In conditions where engine efficiency is low, such as during start-up and at low range speeds, the GS 450h runs on its electric motor alone, reducing exhaust emissions to zero. The system also gives the vehicle an in-gear ‘creep’ quality, similar to that of a conventional automatic transmission.
In normal driving, engine output is divided by the Power Split Device to drive the wheels directly and to power the generator, which in turn drives the electric motor and simultaneously charges the high-voltage battery. In these circumstances, power allocation is constantly monitored and adjusted between engine and motor to maximise efficiency. When sudden acceleration is required, the engine and electric motors again operate in tandem, with extra power from the battery to boost motor response.
During deceleration and under braking, the engine switches off and the electric motor acts as a high-output generator to effect regenerative braking, optimising energy management by transforming kinetic energy into electrical energy for storage in the high-output battery.
Under all driving conditions, the battery power level is constantly managed via the engine-drive generator, so there is no need ever to recharge the system from an external source.