Why don’t electric-powered cars have transmissions?
Dear Car Talk: Why do electric-powered cars not have transmissions?
I understand that electric motors have full torque from the first spin, thus do not need a low gear, but don’t they waste battery when spinning at a very high RPM while being driven fast on level interstates? — Joseph
Joseph: The vast majority of electric cars don’t have transmissions because they don’t need them, Joseph.
The reason gas-powered cars have transmissions is because they have very little torque (“twisting power”) at low speeds.
So, from a dead stop, a gasoline engine needs a transmission’s low gear to multiply the engine’s power by four or five times to get the vehicle moving.
But, by the time a gas-powered car is at highway speed, there’s almost no transmission involved, and the ratio between engine speed and wheel speed is close to 1:1 – sometimes even less.
Electric motors don’t need to have their power multiplied. You get full torque at very slow motor speeds. So, the electric motor can simply spin slowly when the car is moving slowly and spin faster as the car speeds up.
And, while you might be able to add a little bit of efficiency, or excess speed, to an electric car by employing a transmission, think about the downsides.
First of all, transmissions are expensive, so if you’re only getting a marginal benefit, do you want to pay thousands more for your car?
Second, transmissions are heavy. So, they add weight, which reduces range and efficiency.
Technology may come along that changes the equation at some point. But right now, with the exception of an EV super-car like the Porsche Taycan, which uses a two-speed transmission to achieve higher speeds and typically sells for about $200,000, you really don’t see transmissions on electric cars for pretty good reasons.
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