- Aug 19, 2011
Vocis says two-speed electric vehicle transmission will boost battery life
This will be the first public demonstration of the Vocis two-speed trans, which will be fitted to a prototype electric minibus developed in conjunction with powertrain supplier Zytek.
Vocis transmission guru Andy Turner explains, in simple terms, why two-speeds supposedly beat one:
Simulations have shown that Vocis' two-speed unit could reduce energy consumption by up to 10 percent, compared to a single-speed trans. Furthermore, Vocis says that its twin-speed setup doesn't cost much more than a one-speed unit and could even extend battery life. What's interesting is that Tesla learned the exact opposite lesson back in 2008.Electric motors have a very wide operating range, but that doesn't mean that they are equally efficient at every speed. The torque curve of a typical traction motor is well suited to vehicle propulsion, having maximum torque from zero speed and a wide constant power region. However, there is a sweet spot, typically at medium speed and medium to high loads, where the delivery of power is most efficient. A choice of gear ratios allows the motor to be kept in this operating region during more of the drive cycle.