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Continental supplying 48-volt belt starter generator with integrated power electronics for Audi A8

Continental is supplying the 48V belt-starter generator with integrated power electronics that is at the heart of the mild-hybrid (MHEV) system that is standard on Audi’s new A8. (Earlier post.)

The system replaces a conventional starter pinion and is driven by a belt connected to the engine crankshaft. Together with a lithium-ion battery the belt-starter generator forms the heart of the electrified drivetrain.


With a starter output of eight kilowatts and peak transient torque of up to 60 N·m, the asynchronous motor developed by Continental achieves new benchmarks. It has a continuous power rating in generator mode of up to 5 kW, with peak output of up to 15 kW available for short periods.

This is made possible by a water-cooling system that protects the motor, and particularly the power electronics, from overheating. The coolant is supplied by the regular engine cooling system, eliminating the need for a second, low-temperature cooling circuit.

When coasting to a halt at a red light, the engine in the new Audi A8 shuts down at 22 km/h (14 mph)—much earlier than with a conventional stop-start system. The engine also shuts down periodically during steady-state cruising at speeds between 55 and 160 km/h (34 and 99 mph), restarting instantly when the driver wants to accelerate.

Additionally, when the driver applies the brakes during everyday driving, the A8 converts a large percentage of the braking energy—normally lost in the form of heat—into electrical energy for future use.

The combination of zero-emission coasting, earlier engine shutdown by the stop-start system and improved braking energy recuperation results in fuel savings of up to 0.7 liter fuel per 100 kilometer in real driving situations. At the same time, the 48 volt board net makes it possible to provide four times as much electrical power at short notice, at the same current. This clears the way for adaptive suspension systems like the new predictive active suspension in the Audi A8.

We see 48-volt electrification as a key technology which in terms of improved comfort and fuel economy offers promising potential in all vehicle classes and in all markets. Additionally, the 48-volt technology is capable of achieving up to double-digit percentage fuel savings and offers a low-cost way to reduce fleet fuel consumption.

—José Avila, Member of the Executive Board of Continental and Head of the Powertrain division

Continental has been producing the belt-starter-generator with integrated power electronics on highly automated production lines at its Nuremberg plant since 2017. The system is based on a modular concept that can be adapted to meet the needs of all automakers.

For example, Audi’s emphasis on high performance has been met by increasing the length of the stator, which instead of windings consists of welded copper rods. The collaboration with Audi was not just limited to the hardware.

Together with Audi we also further refined the software functions of this system. The intelligent control system plays a key part in meeting the high performance requirements.

—José Avila

Following the new Audi A8, Audi plans to use this system in other model ranges too.


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