Most drivers in the UK will have spent their teenage years learning how to dip the clutch and make smooth gear changes - we all stalled at the lights in a driving lesson or two!
So it may come as some surprise to find out that not only do electric cars not have manual gearboxes, but they also don’t technically even have “gears”.
Virtually every EV on the market has just one single gear ratio that it uses to drive the car all the way from standstill to its maximum speed – and in reverse. That means there isn’t a single gear change throughout every journey you make.
An electric car is sort of like a single speed bicycle... being ridden by Bradley Wiggins.
The effect is noticeably different, with electric cars offering a smooth and silent ‘magic carpet’ ride as you accelerate away without the obvious ‘dips’ in forward momentum you get as a gearbox changes up or down.
That absence of a complicated, multi-ratio transmission is one of the biggest differences between electric and combustion-engined cars. But to understand why they’re missing in an EV, it’s first important to understand why they’re needed in the cars we’ve been driving for the past century and more.
Why Do Normal Cars Need A Gearbox?
While combustion-engined cars are capable of producing prodigious amounts of power, they can only generate that oomph in a fairly narrow band of the rev range.
You will have noticed this if you try to pull away from a standing start without enough revs, if you try to accelerate in too high a gear. Your car just won’t respond in the way you want it to because it’s not operating within its power band ‘sweet spot’.
To get around that fundamental problem, engineers created multi-ratio gearboxes, which allow the engine to stay within its preferred power band as you go up and down through the gears. By making sure you are always in the right gear, you always have power on tap and generally will be running with the most efficient use of your fuel as well.
So Why Don’t Electric Cars Operate The Same Way?
The answer to that lies in two unique properties of the electric motors that drive your car.
The first is their ability to spin in a manner that would blow a combustion engine to smithereens. While a conventional car might have its rev range limited to around 6000 revolutions per minute (RPM), electric motors have a much higher rev range – more than three times the speed of a standard petrol-engined car.
And that ability to turn as fast as 20,000 revs a minute means that there just isn’t the constant requirement to move up through the gears to lower the motor’s RPM and stay out of the ‘redline’.
The second remarkable feature of an electric motor is the fact that it can produce its best power output almost regardless of the speed it is turning. So with an EV, the days of narrow power bands are gone and you will be able to call upon instantaneous acceleration at any time – from standstill or when it’s time to overtake.
Combine those two properties and it’s clear that with massively improved revs and a much wider power band, an EV simply doesn’t have the requirement for multiple gears. It will happily function with just one forward speed, whether you’re pootling around in town or zipping down the motorway.
And even when you need to back out of a parking spot, your EV won’t need to select a separate reverse gear. From inside the cabin you simply press a button or flick a switch to choose reverse. No gears are changed within the powertrain, instead the car simply spins its electric motor in reverse, thereby turning your wheels in the other direction. You’re in the same gear as always, just travelling backwards…
But Don’t Some Electric Cars Use More Than One Gear?
As always in the world of automotive engineering, car designers are looking to find ever more performance, particularly in more sporting EVs.
That’s why we’re beginning to see the use of two-speed gearboxes in some of the highest performing sports models on the market like the Porsche Taycan.
In most EVs a single ratio is a totally acceptable compromise for providing both good low-speed acceleration and a sufficiently high top speed. But it is still a compromise.
For sportscar owners who are used to really high top speeds and are unwilling to make sacrifices, a single gear EV can’t always offer the ultimate performance they are expecting. That’s where a second gear comes in.
The all-wheel drive version of the Porsche Taycan uses two motors – one on each axle. For the front wheels the motor drives a single ‘compromise’ gear that is designed to blend good acceleration and top speed.
But on the rear axle, a two-speed gearbox that is unique to Porsche allows the rear wheels to change down a gear to provide maximum acceleration when called upon, before moving up into a second gear that matches the one driving the front wheels. It’s an elegant solution for a car with performance at its heart.