How do electric cars work? EV motors and batteries explained

Electric vehicles function in fundamentally different ways than traditional cars. Internal combustion engines have loads of moving parts, and while EVs have their own complexities, they’re much more digital than mechanical. Let’s take a closer look at exactly how electric vehicles work.

How does an EV battery pack work?

Instead of gasoline, EVs derive their power from a battery pack, which usually stretches along the underside of the car to keep the weight as low as possible. It’s composed of multiple modules, which are in turn broken down into individual battery cells, similar in size to AA batteries. A layer of coolant runs between cells since hot batteries are explodey batteries. A battery management system regulates that coolant and ensures that each cell drains at the same rate, which prolongs the life of the pack.

A battery diagram shows movement of lithium atoms and their associated electrons.
Sdk16420 / Wikimedia Commons

We have an entire article on how batteries work, but the short version is that electrons are drawn through a circuit by moving lithium atoms from one side of a battery to another. The electrons want to follow those lithium ions, but a separating membrane within the battery prevents them from coming along for the ride. As a result, they have to run through wires that also power our phones, tablets, light bulbs, computers, and cars. When you charge a battery, you attract the lithium atoms back to their original side of the battery by loading it up with electrons.

How does an EV inverter work?

Most of your home electronics work on alternating current. This means the electrons are perpetually going back and forth through the wires at set intervals. Batteries, however, operate on direct current, so electrons just get blasted in one direction in a consistent stream. An EV uses an inverter to change its battery pack’s current from direct to alternating before it reaches the motor. This is an important step since the change in AC frequency made by the inverter directly affects the electric vehicle’s speed.

How does an EV motor work?

EV motors turn electricity into motion by creating a rotating magnetic field. A cylinder called the stator contains tightly-wound copper wires, which the alternating current coming from the inverter runs through. Because the current alternates, the north and south poles of these magnetic fields switch back and forth. By running different circuits at slightly different electrical frequencies, the overall magnetic field rotates.

Inside the stator, a free-floating rotor feels the effect of all these rotating magnetic fields. As the current runs through the stator, the magnetic attraction causes the rotor to spin in order to catch up with it. After all, the rotor’s magnetic poles opposite of the stator’s will be attracted, and the alike poles will repel. The more power that gets pumped through the stator, the faster the magnetic field spins. The rotor moves an axle, which spins the EV’s wheels. Since the power generated by an EV motor is significant, a necessary component called a reducer brings the force down to the desired level before going from the rotor on to the wheels.

EV motors aren’t just motors — they can also act like generators. When you brake your EV, the mechanical force of the slowing vehicle spins the rotor, which produces current flowing through the stator, back up to the battery.

Since much of the force needed for slowing down a vehicle is pushed into regenerative braking, an EV’s brake pads see less wear than a normal car. EVs deal with much less mechanical stress across the board, not just in braking. EV motors aren’t dealing with repeated explosive chemical reactions like internal combustion engines, transferring the linear force of a piston into rotational force (torque) via a crankshaft, or relying on a flywheel to stabilize varying force input. Overall, this is good news for EV repair costs.

Hopefully, this provides some insight into an electrical vehicle’s inner workings. EVs are taking over the world, so it’s probably a good thing you know a thing or two about how they work.

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