How do electric cars work?

1. An electric car plugs into a charger instead of visiting a gas station. Electricity flows through the cable and is stored in the battery.
2. The battery is a flat pack under the floor, made of thousands of small cells joined together. Keeping it low helps the car stay steady around corners.
3. When you press the pedal, electricity flows from the battery to the motor. Inside, electromagnets switch on and off in turn, pulling the magnets on the spinning part around.
4. A simple set of gears carries the motor's spin to the wheels. Electric motors push hard right away, so the car speeds up smoothly and quietly, with no exhaust pipe.
5. When the driver slows down, the motor works backward as a generator. The turning wheels make electricity, which charges the battery a little. This is called regenerative braking.
6. Electric cars waste much less energy as heat than gasoline cars. Most of the battery's energy ends up turning the wheels.

Tap each part to follow the energy from the plug to the wheels.

• Charge port. The charging cable plugs in here. Electricity flows in from a charger at home or at a charging station.
• Battery pack. The battery pack is made of thousands of small cells. It stores energy as chemical energy and gives it out as electricity.
• Inverter. The inverter is the car's power controller. It changes the battery's electricity into the kind the motor needs, and sends more when you press the pedal harder.
• Electric motor. Inside the motor, coils of wire become electromagnets that push and pull on the spinning rotor. The motor can also work backward to make electricity.
• Reduction gear. A small gear on the motor turns a bigger gear on the wheel axle. The wheels turn slower than the motor but with more force.
• Wheels. The wheels push on the road. Tires grip the road, so the car moves forward when the wheels turn.
• Friction brakes. Electric cars still have ordinary brakes for quick stops. Pads squeeze a disc, and the car's motion energy turns into heat.
• Cooling system. Pipes of coolant carry heat away from the battery and the motor, like sweat cooling you down on a hot day.

Speed up, coast and brake. Watch which way the energy flows and what happens to the battery.

Experiment: When the car slows down with regenerative braking, what happens to the battery?

1. Press Go and watch the battery level and the energy dots.
2. Press Brake while the car is moving.
3. Watch the dots turn green and flow back to the battery.

What we found: Regenerative braking turns the car's motion back into electricity and puts a little charge back in the battery. Normal brakes would turn that motion into heat instead.

Turn on JavaScript to try it yourself.

The battery is almost empty! Drive over the hill, stop at the stop sign, and stop at the charger to plug in. Use regenerative braking to save energy.

An electric car has no gas tank and no engine. Instead, it has a big battery under the floor and one or more electric motors. When you press the pedal, electricity flows from the battery to the motor, and the motor turns the wheels through a few gears.

Inside the motor are coils of wire. When electricity flows through them, they become electromagnets. They switch on and off in turn, pulling magnets on the spinning part of the motor around and around.

When the car slows down, something clever happens. The turning wheels spin the motor, and the motor works as a generator, making electricity that goes back into the battery. This is called regenerative braking. It saves energy that ordinary brakes would waste as heat.

When the battery runs low, you plug the car in to charge it, at home or at a charging station. Electric cars make no exhaust fumes on the road, and how clean their electricity is depends on how it was made, for example from sunlight, wind, water or fuel.

Key words

Battery

A store of chemical energy that gives out electricity.

Electric motor

A machine that uses magnets and electricity to make something spin.

Generator

A machine that turns spinning motion into electricity, like a motor running backward.

Regenerative braking

Slowing the car by using the motor as a generator, which puts energy back into the battery.

Inverter

Power electronics that turn the battery's direct current into alternating current for the motor, and back again.

Kinetic energy

The energy something has because it is moving.

Check your thinking

1. What turns the wheels of an electric car?

   Show the answer

   An electric motor. Electricity from the battery runs the motor, and the motor turns the wheels through gears.

2. What is regenerative braking?

   Show the answer

   Using the motor as a generator to charge the battery while slowing down. When the car slows, the motor makes electricity instead of using it.

3. Why do electric cars need only one gear?

   Show the answer

   Electric motors push hard at low and high speeds. A motor makes strong turning force from a standstill all the way to high speed, so no shifting is needed.

4. How do you add energy to an electric car?

   Show the answer

   Plug it into a charger. A charger pushes electricity into the battery, where it is stored.

5. Where does the energy go when ordinary friction brakes stop a car?

   Show the answer

   It turns into heat in the brakes. Friction turns motion into heat, which is why brakes get hot.