Your first electric car driving experience may be full of surprises. The first one may be why isn’t this car shifting gears? You could be anticipating an upshift but it never comes. The reason for that is most electric vehicles have a single-speed gearbox. It doesn’t shift through the gears because it only has one!
Electric Vehicles are unique in many ways and one of those differences compared to a typical gas-powered car is that they have a single-speed transmission. One gear is all they need. If you think about it, it’s quite impressive. To see some electric cars, like the Tesla Model S, go from 0 to 60 in 2.4 seconds you can’t help but be amazed at the performance.
Why Does an EV Have Only One Gear?
There are a multitude of reasons why an electric vehicle has only one gear. The first reason is that the electric motors used by EVs rev at a much higher rate compared to a gas-powered (or ICE) vehicle. An electric vehicle motor can rev to 10,000 RPM, some even as high as 20,000 RPM, this is much higher than the typical 4,000 to 6,000 RPM you get out of an (Internal Combustion Engine) ICE powered vehicle.
We should also note that electric motors are very efficient when creating power throughout acceleration and deceleration. They have a very broad window where they obtain optimal performance.
What this means is an electric vehicle instantly produces torque from a standing position. This means they don’t need to stay at a certain RPM range when driving at low speeds or when under acceleration.
An ICE vehicle has to have a gearbox with many gears because the engine only has the ability to create good power and torque within a very narrow range of engine speeds.
The differing gear ratios help the internal combustion engine stay within that sweet spot of the power range at differing road speeds. As an example, a gas-powered car can accelerate to 20-30 mph in first gear without much effort but in order for it to get to a higher road speed, the engine needs to shift gears due to it reaching its RPM limit (also called redline). In the same regard, you will find it quite difficult to get your car moving if you where able to start from sixth gear because that ratio is designed for higher speeds.
In summary; an EV has no trouble reaching its top speed with a single gear electric vehicle gearbox without any downside when driving at low speeds.
One of the things an electric vehicle consultant does is pick the gear ratio that has a good balance between top speed and acceleration. If the ratio is numerically too low, the vehicle will accelerate quickly but it could be limited to a top speed less than desired. On the other end of the scale, if the gear ratio of the EV transmission is numerically too high, your electric vehicle may have a high top speed but the acceleration will not be optimal.
Benefits of Having a Single Gear
Efficiency - Less internal frictional horsepower loss
Less weight - Also adds to range efficiency and is easier to work with
Package - The small footprint leaves room for other components and offers placement flexability
Durability - With fewer gears, no clutches, no solenoids, no computer, the single speed gearbox is simple and strong, we like to call it bullet proof.