Transmissions in Electric Vehicles

Electric is the new black. At least, the is what one would think when watching the automotive industry. With one or two notable exceptions, almost every automaker in the world is now jumping on the electrically-powered bandwagon. Tesla certainly started something. The Mitsubishi i-MiEV and its cousins from Peugeot and Citreon, the Nissan LEAF and its no-nonsense baby brother eNV200, the Volkswagen eGolf, Mitsubishi’s Outlander PHEV, the Holden Volt (and all of its cousins), the list goes on.

Volvo has announced their intentions to stop developing diesel-powered products, Subaru is working on electric versions of all of their cars, Chevrolet has started manufacturing the Bolt (albeit in very limited numbers), BMW has committed to producing electric versions of their cars by 2020… the list goes on.

But that isn’t the point of this post. In this post, we will be examining a move that is questionable for any company making an EV: transmissions.

I don’t mean reduction gears that simply transfer power from the electric motor to the axle; I mean companies that are putting out EVs with multi-speed transmissions. Vehicles such as LDV’s new EG10, which features a six-speed automatic transmission, or the DS E-Tense concept, which sports a three-speed transmission.

The issue of a multi-speed transmission in a pure EV is simple: multi-speed transmissions were developed to optimise the power of an internal combustion engine, enabling it to run at the optimum speed as much as possible while also allowing the car to move at an appropriate speed.

Electric motors lack the volatility of combustion engines, and can move at almost zero RPM. This means that they technically have no need for a transmission at all – most of them only have the one-speed worm-drive to keep the motor off the ground! Transmissions inherently lose power as well – the power required to turn the gears and move the car is lost in the form of heat and noise. These things are a necessary part of any internal combustion vehicle – and they work well there – but they still lose large amounts of power as they do their job.

Electric vehicles have been demonstrated as not needing multi-speed transmissions. The Tesla Model S, Model X, Nissan LEAF, eNV200, Renault Zoe, Kia Soul EV, Chevrolet Bolt and the Mitsubishi i-MiEV all use reduction gears. There is no need for anything more than that.

While the ranges quoted on both the LDV EG10 (160kms) and the DS E-Tense (352kms) are at least acceptable, in both cases they could acheive a drastically longer range had they stuck with basic reduction gears. That would also make the vehicles easier to drive than their ICV equivalents, instead of making them feel like an ICV without the noise.