Electric Vehicle Explainer

Jim Motavalli

Jim Motavalli | Aug 07, 2014

How do EVs work, anyway? 

The good news for you is bad news for your local mechanic: though there’s a lot of technology under the hood, EVs are, broadly speaking, simpler than gas cars. So, there’s literally less to break. Under the hood (or somewhere else; EV’s are flexible like that) is a relatively compact electric motor, which gets its electricity from a big battery pack that’s usually either under the passenger compartment or elsewhere towards the back of the car. In between the battery pack and the motor is a computer, called a controller, that decides if the electric motor needs power, and if so, just how much. When you press the accelerator (don’t call it the “gas pedal” because, hey, there’s no gas!) the controller analyzes how much electricity to send from the batteries to the electric motor.

No transmissions here! Under the hood on the Nissan Leaf.That’s about it— it really is just about that that simple. EVs have a lot fewer parts than a conventional, gas-powered car. For example, there’s no engine or gas tank, no fuel injectors, and no spark plugs. In place of all those parts, there’s a battery pack and the electric motor, which powers either the front or rear wheels. (EVs with electric motors at all four wheels are being tested now, but they haven’t yet made it into a production model.)
EVs don’t require a transmission. How can that be? The reason you need a conventional transmission in a gas powered-car, is because you need a lot of torque when starting from a stop, and you need a lot less torque when you’re up to full speed, and want the engine to be more efficient. Conventional engines can’t develop a lot of torque at low speeds—that’s where the gears in the transmission come in. The transmission multiplies the torque coming from the engine. An electric motor, however, develops just as much torque at one MPH as at 70 MPH. So, EVs don’t need a transmission to maximize. (For the engineers reading this: the torque curve of an electric motor is very wide—in fact, they have full torque at zero RPM!)
The motor can run in reverse as easily as forward, so there’s no need for a reverse gear, either.

Transmissions need not apply. Ford Fusion with inverter and small gas engine. (Jim Motavalli photo)EV Area Home

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