Electric energy storage is provided by a 42-cell, 300-volt lithium-ion battery bank. Its performance is carefully monitored and governed by an electronic control unit, through which electric current from the engine is fed.

This power pack is accommodated under the floor of the trunk, without taking up any stowage space, as demonstrated in the Stockholm show car.

The battery supplies a compact 38 kW electric motor located between the rear wheels which powers a transmission differential and drive shafts. At low speeds, this Rear Drive Unit (RDU) is able to briefly generate 666 Nm of additional torque.

In reverse operation, the motor acts as a generator to provide 'regenerative braking'. It automatically recovers kinetic energy otherwise lost during braking and converts this into additional battery charging. It also performs the same function whenever the driver lifts off the throttle, harnessing the energy in the rotating drive shafts. This is achieved without any perceptible change in the rate of deceleration.

The second electric motor is the integrated starter generator (ISG) located within the flywheel between the engine and main transmission. On demand, it contributes 15 kW of additional power and 120 Nm of extra torque to the output of the engine through the front wheels.



Driving Benefits

The sophisticated electronic control of the hybrid componentry is matched to the operating parameters of the BioPower engine to provide seamless power assistance and power saving functionality.

Under transient driving conditions, both electric motors are activated to augment the power of the engine, increasing standing start acceleration and in-gear performance for safe overtaking. This briefly raises total power by as much as 28 per cent - without raising fuel consumption.

At take off, the Saab BioPower Hybrid Concept also exploits the instant torque generation of its electric motors, smoothly adding strong, accelerative power during the engine's pick-up, from tick-over to about 1,500 rpm. It is during this phase that the available pulling power, or torque, is more than tripled.

An estimated fuel of saving of 5-7% is provided by the automatic engine stop/start function. Whenever the vehicle is stationary, the engine is immediately shut-off to save fuel. As soon as the brake is released, it is automatically started again by the powerful ISG. The operation is carried out seamlessly and requires no input from the driver.

In congested driving conditions, fuel saving is taken a step further by the Saab BioPower Hybrid Concept's 'Zero Mode' operation - giving zero fuel consumption, and, of course, zero emissions - which can be selected by the driver via a button in the central console. At speeds below 50 kph, 'Zero Mode' will shut off the engine and again switch the car over to electric power only through the RDU. In this mode, the battery bank provides a range of between 10 and 20 kilometers. The engine is smoothly re-engaged whenever the battery status approaches a low charge level or the electronic throttle opening requires acceleration beyond the 50 kph operating limit.

Whenever the engine is shut down, all auxiliary functions, such as the power steering, air conditioning and lighting, remain unaffected because they are now permanently electrically-powered through the battery. The removal of unnecessary loadings on the engine further contributes to fuel economy and in mixed driving the estimated range of Saab 9-3 BioPower Hybrid Concept test vehicles, with a standard 62 liter tank, is a competitive 800 kms.

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