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Battery company Kreisel Electric introduces automated 2-speed transmission for EVs

Austria-based battery pack provider Kreisel Electric (earlier post) has developed a production-ready, automated 2-speed transmission for electric mobility applications in combination with an integrated powertrain architecture specially developed in cooperation with Sala Drive GmbH—both designed for high performance and torque ranges.


Kreisel has applied the systems in an electric sports car, which accelerates from 0 to 100 km/h in around 2.5 seconds, with a top speed of 300 km/h (186 mph).

We set ourselves the demanding task of building an ultra-light, electric supercar based on a historic sports car as the ideal application for our transmission. The challenge here is that there is nothing even remotely like a standard component available here, no matter where you look. So we developed the essential components ourselves on the basis of our own requirements profile.

—Markus Kreisel, CEO of Kreisel Electric


The automated 2-speed transmission not only had to be able to guarantee unique acceleration values and top speeds, but also act as a reliable link between the high-performance powertrain and a correspondingly powerful and lightweight battery, which was also specially developed for the vehicle.

The Kreisel Electric 2-speed transmission features an electric lube oil pump with integrated oil reservoir that self-enables on demand for maximum efficiency. Drag losses are reduced due to a friction-optimized bearing arrangement.

Electromechanical gear synchronization offers the shortest torque interruptions through optimized torque and speed control of the electric drive during 0.25-second gear shifts. Further, this reduces thermal impact by friction elements and reduces wear effects. An integrated limited slip differential lock ensures uninterrupted torque transmission even in slippery road conditions.

The transmission also features a modular interface that supports a wide range of applications for motor and transmission arrangements.

At the high end, the transmission handle output values of 600 kW and an input torque of up to 900 N·m.

Sensors continuously monitor all relevant components and combine the collected data in real time in a transmission control unit (TCU). The modular powertrain arrangements allow for 1 or 2 motors per axle just as easily as a single motor. For applications that also require high torques, such as small and medium-sized transporters up to 3.5 tons or trucks and buses up to 15 tons, the automated 2-speed transmission can be adapted to match.



I'm surprised transmissions waited so long to be introduced; they give electric drivetrains the flexibility to improve efficiency and to operate at the best power levels for the load.


Well, it's really not that surprising. Tesla started the "bandwagon" for electric drives and their initial attempt at a two-speed tranny was a flop. They had excellent expertise as far as electronics and electrics were concerned but lacked entirely the necessary knowledge for encompassing mechanical engineering.
The big advantage of a transmission is the immense torque available to get a relatively high mass moving without taking huge gulps of current at the disadvantage of the battery. I.o.w. the transmission eases wear and tear on the battery and is life-prolonging on same.


Not just that.  The low speed range on the transmission allows the motor to operate at higher back EMF (higher efficiency) and lower current at low vehicle speed, reducing system losses.  Expect a substantial improvement in range from this, and likely lower demands on inverters as well.


The modular powertrain arrangements allow for 1 or 2 motors per axle just as easily as a single motor and differential slip limiting.
The link to Kreisel above has a utube presentation that shows the two motors per axle setup for 1-4 motors.
It is hard to determine from the presentation if each motor can be directed to one axle as that would make it highly versitile.
Many reasons to like this setup.


I like simplicity, this seems to head the other way.


What is complex about a two - or even three gear DCG in the sight of all the obvious advantages to be gained?


You do have more moving parts, but there's the factor that motor power is directly proportional to its speed (drive frequency).  The faster you can turn the motor, the more power you can get out of it.  If you have a 3:1 low gear, you can turn the motor 3x as fast in the low speed range and get 3x the power (torque) out of the same size/weight of motor.

Even with the added weight of the gearbox, the net can easily be a substantial reduction in weight and size.  Add in gains in efficiency and you've got a very attractive proposition.

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