New Two-Speed EV Transmission Promises Better Range, Battery Life

By KBB.com Editors on May 18, 2009 1:29 PM

UK-based Vocis Driveline Controls has developed a new two-speed transmission for electric vehicles that it contends can cut the amount of energy required to operate the motor by 5-10 percent and help extend the service life of the battery pack. Presented at the Electric Vehicle Symposium in Norway last week, Vocis also claims its still-experimental transmission would bring no cost or packaging penalty -- and that it has the potential to substantially reduce the size of the motor/battery pack. Key to the efficiency of any two-speed EV gearbox is its ability to keep the motor revving in the "sweet spot" of its output curve for a greater part of the operating time than a conventional single-speed setup. Having a lower gear to better match elevated system demands during initial startups or when climbing hills but a "taller" ratio for cruising allows more effective use of the power in the battery as well as more efficient scaling of all components in the drive package, including ancillaries like the cooling system. According to Vocis Managing Director Mike Everitt, his firm's new design also would lower the frequency of deep-discharge cycles that can result in shortened battery life. By combining a conventional twin-shaft design with a sophisticated electronic controller, the Vocis transmission allows all changes to take place with no break in torque delivery and can be tuned and optimized for individual applications, including other multi-ratio configurations.

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