With growing interest in electric vehicles much of the focus has been on developing improved power sources like batteries and fuel cells in order to deliver the range and performance drivers have become accustomed to with internal combustion engines (ICE). Transmissions on the other hand, despite being so important to ICE powered vehicles, are not given much thought when it comes to electric vehicles. This is because the wide torque curve of electric motors makes them largely irrelevant. In fact, nearly all electric vehicles have just one speed. However, it is time to rethink that approach according to U.K. based engineering firm Antonov. The company has produced a 3-speed transmission designed specifically for electric vehicles that promises to bring significant efficiency gains and a better driver experience.
Internal combustion engines usually reach maximum torque at between 3000 and 5000 rpm, so changing gears is needed to keep the engine in this operating range as the speed of the vehicle increases. Electric motors on the other hand have full torque at 0 rpm and a much wider operating range. This is why most EVs have a single speed transmission. Despite this, the efficiency of electric motors still varies at different speeds. They operate at a peak efficiency of around 90 percent, but this can fall to 60-70 percent, especially at low speed. Adding a multi-speed transmission to an electric vehicle can therefore optimize efficiency at all speeds.
During testing, Antonov’s 3-speed transmission improved efficiency by 14.7 percent while delivering the same performance as the same electric vehicle without it. This equates to a greater driving range and a smaller battery pack. Nearly 15 percent is significant and the 3-speed transmission has the potential to bring even more benefits. For example, adding the transmission allows a lower torque motor to be used which results in cost benefits as well as weight reduction. It can also offer better launch acceleration, lower noise and a higher cruising speed, while the hill climbing ability of utility vehicles can be improved. There is a strong possibility that future electric vehicles will come with a multi-speed transmission.