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MARK KANE

2-speed transmission in an electric car is a rare sight.

Kreisel Electric automated 2-speed transmission for electric mobility applications

From time to time, news about 2-speed transmissions for electric cars appears and we’ve seen several prototypes over the years. The main advantage of having more than a single-speed is fun… that it enables to have both – high acceleration at low speed and higher top speed (without oversizing the motor).

The efficiency also should improve a little, but there are drawbacks such as higher costs, probably lower reliability, need to switch gears sometimes (not that often as in ICE) and slightly higher weight.

Recently, Kreisel Electric presented its own automated 2-speed transmission for electric vehicles, developed in partnership with Sala Drive. The transmission finds its way in sports car conversion that does 0-100 km/h (62 mph) in 2.5 seconds, reaches more than 300 km/h (186 mph) top speed and, using 54 kWh, can go up to 350 km (218 miles) on a single charge.

Kreisel’s 2-speed transmission is production ready, according to the press release, and can be used with one or two motors, for rear-wheel, front-wheel or all-wheel-drive configurations. Input power and torque stands at 600 kW and 900 Nm, respectively.

Not only halo cars could benefit from such a system, as according to Kreisel, small and medium-sized transporters up to 3.5 tons or trucks and buses up to 15 tons also could be handled.

Kreisel Electric automated 2-speed transmission for electric mobility applications

More about the transmission:

“„We have 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,“ says Markus Kreisel, CEO of Kreisel Electric. 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 continues.

For example, 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 a high-performance powertrain and a correspondingly powerful and lightweight battery, which was also specially developed for the vehicle. The result is at the same time an experience in itself and very impressive. The sports car, which was already on show at Techno Classica in Essen in April 2017, sprints from 0 to 100 km/h in around 2.5 seconds, achieving a top speed of above 300 km/h. And all this with a range that is not only impressive in the supercar category: with a single battery charge you can easily break the magic range limit of more than 350 km.

So what are the ingredients for the success of the Kreisel Electric 2-speed transmission? „An electric lube oil pump with integrated oil reservoir that self-enables on demand for maximum efficiency. Massively reduced drag losses due to a friction-optimized bearing arrangement. Electromechanical gear synchronization, which ensures the shortest torque interruptions through optimized torque and speed control of the electric drive during lightning-fast, 0.25-second gear shifts. In this way, any thermal impact by friction elements and possible wear effects on the shift components can be practically eliminated. A limited slip differential lock, which is also integrated, ensures uninterrupted torque transmission even in slippery road conditions. And last but not least, a modular interface that supports a wide range of applications for motor and transmission arrangements,“ explains Philipp Kreisel, who is also a CEO of Kreisel Electric. In a maximum expansion stage, e.g. through the use of more powerful electric motors, breathtaking output values of 600 kW and an input torque of up to 900 Nm can be managed in this way. Using innovative approaches to complete vehicle integration, the center of gravity of the lightweight sports vehicle was lowered even further to achieve optimum handling with a weight ratio of 37% (front): 63% (rear). There is also a great deal of intelligence, variability and flexibility in the entire setup. A large number of 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. And 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 easily be adapted to match.

All this is rounded off by the integration of the world’s leading battery solution from Kreisel Electric, with a nominal capacity of 54 kWh, which is exclusively used in the electric sports car. „Thanks to our patented technologies, unique thermal management and the laser-welding process of the battery packs, we are now able to offer the lightest battery with the highest energy density for the most diverse applications, whether mobile or stationary. This in turn results in unrivalled, fast charging times, long ranges and a long service life of our battery solutions,“ says Johann Kreisel, the third CEO in the Kreisel Electric group, completing the overall picture.”

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