BMW explores the limits of electric drives
The Power BEV has three electric motors of the fifth generation and a system output of 530 kW (720 HP). Driven in this way, it can accelerate from 0 to 100 kmph in less than 3 seconds. However, the developers did not only want to implement the most impressive longitudinal dynamics possible, but also the same transverse dynamics – in other words, it should take curves about as fast as a fighter plane.
From the designers’ point of view, the decisive factor is therefore the fact that the two electric motors on the rear axle can be controlled separately. In this way, torque vectoring can be achieved in which as much drive power as possible can be converted into propulsion, even during highly dynamic driving manoeuvres. The electronic control for torque vectoring is more sensitive and at the same time more effective than a mechanical limited slip differential, the designers say. The reason: While a limited-slip differential always only reacts to a speed difference at the drive wheels, electronic torque vectoring enables actively targeted interventions in any driving situation.
The powertrain is made up of three drive units of the fifth generation, each of which houses an electric machine with the associated power electronics and the output in a common housing. One is installed on the front axle, two on the rear axle, designed as a double drive unit. In addition to the performance, it is remarkable that this generation manages completely without rare earth materials.
The Power BEV test vehicle was based on a current production vehicle from the BMW 5 Series. The integration of such a drive into a production vehicle is considered an essential engineering achievement. Thus, the entire passenger compartment of this vehicle was completely preserved without any restrictions. This makes it easier to assess the drive concept in comparison with others. The engineers were thus able to better analyse the possibilities offered by two separately controllable e-machines with E-Torque vectoring on the rear axle. This makes it possible to select the appropriate technology for future series vehicle projects. Thus, it will also be possible in the future to provide the customer with the appropriate technology in the respective vehicle concept.
BMWs engineers were also musing about an electric drive for its motorcycles, which perhaps could replace the traditional boxer engine. As a result of its thinking process, the company presented the Vision DC Roadster, a “naked bike” with electric drive.
In a motorcycle, the engine is the core, a supporting functional element. It forms the basis for the entire architecture. However, electric drive components place completely different demands on the installation space. While the engine size of an internal combustion engine is primarily determined by its displacement, the battery is the most expansive element in electric drives. The electric motor itself is relatively compact.
The previous engine is replaced by a vertically installed, longitudinally oriented energy storage unit. Two elements with cooling fins and integrated fans protrude sideways to cool it. The cylindrical electric drive is located under the energy storage unit and is directly connected to the cardan shaft. The company did not provide any further information on the technology – whether the motorcycle is equipped with modern stabilisation and driver assistance systems remains in the dark for the time being.
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