Virtually all modern EVs send their power to the road via a direct drive and reduction gear system - they are single-speed machines. No shifting of gears or variable ratios in sight and manufacturers rely on electric motors’ well known torque to provide a blend of acceleration, efficiency and higher speed cruising ability.
The only current vehicle that has a geared transmission is the Porsche Taycan (and its sister model, the Audi E-Tron GT), which gets a two-speed gearbox for the rear motor, but it is an exception. There was also the unsuccessful Coda Sedan that tried to adapt a CVT (continuously variable transmission) to make the most of its electric motor, but sadly there are none around to see how that might have worked.
So perhaps a CVT is better suited as an EV transmission, since it can vary the ratio continuously to either make the vehicle run at its most efficient, or allow it to make the most of what power and torque it has, depending on the given situation. And this is not us just thinking out of the box, as this information comes from German automotive giant Bosch.
It has been touting its EV-specific CVT as providing two key benefits: improving an electric vehicle’s range and performance. The company says the transmission itself is a lightly modified version of a traditional pushbelt CVT, which it calls CVT4EV. Bosch says that with this transmission installed, the vehicle gets improved acceleration, top speed, and because torque demand on the traction motor is reduced, it is also more efficient.
According to Gert-Jan van Spijk, the boss of the CVT program at Bosch Transmission Technology,
The CVT4EV expands the electrical car’s repertoire.
He also says that through using this transmission, electric motors don’t have to be as powerful as they are today, and battery packs can also be slightly smaller too. CVT4EV should also provide extra torque for towing duties, and it should also improve the performance of off-road vehicles.
The company also mentions the estimated efficiency gain through using CVT4EV and it is around 4 percent, although it doesn’t provide a similar figure for performance gains. The transmission is currently being tested in a Volkswagen e-Golf by Bosch Transmission Technology, a Dutch subsidiary of the company, but so far no commercial application for it has been announced.
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Source: Bosch