You’ve probably grown up hearing about cars that have internal combustion engines and gears. Different types of cars might burn different fuels in these engines and require changing gears manually or automatically. But the very presence of the two drivetrain components is inseparable from the idea of a car. That is why when electric vehicles (EVs) charged onto the scene—pun intended— they were revolutionary. These cars did away with the internal combustion engine and (less obviously) the gearbox that so many are used to.
Most EVs, like the MG ZS, do not have multiple gear ratios. The power stored in the batteries is channelled to the electric motors (and through them, the wheels) via a single-gear transmission. This is possible due to the inherent difference between how internal combustion engines and electric motors generate torque.
Torque Generation: Internal Combustion Engine vs Electric Motor
Internal combustions engines can safely and reliably spin only up to a certain rate, around 7,000 RPM in the average fuel-powered car. Within the confines of this limit, they produce usable torque and power in an even narrower rev range. As such, a multi-ratio gearbox is needed to provide a wider range of torque and power to suit different driving conditions.
When a car starts from a stationary position, a higher amount of torque is required to overcome its initial inertia; in such a case, a large cog provides more leverage. As the car speeds up, you exhaust the functional rev range quickly. Without gears, it wouldn’t be possible to drive your car very fast at all. When you’ve worked your way through the first couple of gears and hit cruising speed, a smaller cog starts to spin faster to provide you with more power to sustain that speed. Different sized gears in cars with internal combustion engines, thus, provide different levels of torque and power to suit varying driving conditions, all the while keeping the engine spinning happily in its ideal rev range.
<Image of MG ZS engine>
The workings of an EV motor
Things work differently with an electric motor. By design, an electric motor generates the full amount of torque for the car right from the get-go. This torque output is fairly consistent throughout the rev range, which, unlike an internal combustion engine, usually stretches to 20,000 RPM. As such, an electric motor can cater to pretty much any driving condition without needing the leverage provided by multiple gear ratios. Need to get your EV in motion from a standstill? All of the motors’ torque is at your disposal. Need to accelerate quickly to overtake another vehicle? Same story. Need to cruise on the highway at a steady speed? You guessed it — your EV’s rev range makes this possible without having to shift gears!
Can EVs Even Have Gears?
Technically, an EV can have a set of gears. Depending on the vehicle, multiple gears could give an EV better acceleration at lower revs or higher efficiency when cruising (which would lead to a better range). However, the pros of a multi-ratio gearbox need to be weighed against the cons, quite literally. A gearbox will add quite a bit of weight to the EV while also increasing its complexity. The additional weight could eliminate any gains in efficiency.
Do You Need Gears in an EV?
The question then is: Do you really need gears in an EV? In a nutshell, not really. Gearboxes are heavy, complex pieces of machinery that leak quite a bit of the power generated by the engine (or taken from the battery) in the form of friction losses. By eliminating gearboxes, EVs like the MG ZS are lighter, simpler, and more efficient. And as for speed and acceleration? You get plenty of that on account of the electric motors’ torque being available on demand. The MG ZS, for instance, can barrel from 0-100kph in a matter of 8.5 seconds. And yes, it does so with just a single-gear transmission.