July 27, 2023
How does an EV work?
Electric vehicles look and feel very similar to other cars on the road, but what's happening under the bonnet is something very different.
How does an EV work?
Simple Explanation:
An electric vehicle (EV) is like a normal internal combustion engine (ICE) car, but instead of a petrol or diesel engine, it has an electric motor and a big battery. The battery provides electricity to the motor, which then turns the wheels. When the battery runs low, you plug the car into a charger to fill it up, just like you'd charge a mobile phone. Unlike petrol or diesel cars, EVs don't have gears, so driving them can be smoother and simpler.
Detailed Explanation:
- Battery: The battery in an EV is usually a large lithium-ion battery pack. The battery doesn't just power the motor; it also powers everything else in the car, like the lights, the radio, and the heating and cooling system. Over time, the battery can lose some of its ability to hold a charge, a process known as degradation. Many factors can influence this, including how often the car is used, how it's charged, and the climate where it's driven. (See our article on battery degradation in EVs)
- Motor: EVs use electric motors, which are more efficient than the internal combustion engines found in petrol or diesel cars. There are different types of electric motors, but many EVs use what's called a permanent magnet synchronous motor. These motors convert the electrical energy from the battery into mechanical energy to turn the wheels. When you press the accelerator, the car's control system sends more electricity to the motor, making it spin faster and increasing the speed of the car.
- Charging: To charge an EV, you plug it into a power source. This could be a normal wall socket (slow), a special home charging station (faster), or a public charging station (fastest). The charger converts the AC power from the grid into DC power that can be stored in the battery. Charging speed depends on both the power of the charger and the car's onboard charging system. Some cars can also use regenerative braking to charge the battery a little bit while driving. (See our article on AC vs. DC charging)
- No Gears/Transmission: Most EVs have a single-speed transmission and don't have a traditional gearbox like petrol or diesel cars. This is because electric motors can operate efficiently over a wide range of revolutions per minute (RPM), so they don't need multiple gears. This can make EVs simpler to drive and can also reduce maintenance needs.
How does the battery work?
The battery in an electric vehicle (EV) is not a single battery, but a pack made up of many smaller batteries, called cells, linked together. These cells are similar to the rechargeable batteries you might find in a laptop, mobile phone or the traditional AA and AAAs that we’re all used to. In most EVs, the cells are lithium-ion, a type of rechargeable battery that's popular because it's lightweight, compact, and can hold a lot of energy. Lithium-ion refers to the chemical composition of the cell, it means there’s a high proportion of lithium metal inside.
Charging: When you plug in the EV to charge, electricity flows into the battery. This electricity forces the lithium ions to move from one side of the battery cell (the cathode) to the other side (the anode), through an electrolyte. The electrolyte is a chemical medium that allows ions to move but doesn't let the electrons through. This movement of ions from the cathode to the anode stores energy in the battery.
Driving: When you drive, the process is reversed. The lithium ions move back from the anode to the cathode. As they move, they force electrons to flow through an external circuit, creating an electric current. This current is what powers the electric motor and makes the car move.
Over time, the constant movement of lithium ions back and forth can cause the battery to degrade, meaning it can't hold as much charge as it used to. This is why the battery's capacity might decrease over time. The rate of this degradation depends on many factors, including how the battery is used and the conditions it's used in.
How does the motor work?
Most electric vehicles use a type of motor called a "permanent magnet synchronous motor," but we'll keep the explanation general to cover how most electric motors function.
An electric motor's operation is based on the principles of electromagnetism. At its core, it's all about magnets and how they interact.
Simple Explanation:
Imagine two magnets: one is fixed in place and the other is free to move around. If you bring the movable magnet close to the fixed one, it will either be attracted and move towards the fixed magnet, or it will be repelled and move away from it, depending on the orientation of the magnets. This is the basic principle behind how an electric motor works.
More Detailed Explanation:
An electric motor has two main parts: the stator (which stays still) and the rotor (which rotates).
- Stator: The stator is made up of a series of coils, called windings, arranged around a ring. When electricity passes through these windings, they become electromagnets, creating a magnetic field.
- Rotor: The rotor is located in the middle of the stator and is also made of magnetic material or contains permanent magnets. When the magnetic field from the stator is applied, it generates a force that causes the rotor to spin.
The key to making the motor work is to continuously switch the magnetic field generated by the stator. By quickly switching the direction of the current flowing through the windings, the motor can flip the magnetic field's orientation. This changing field keeps pushing or pulling the rotor around, causing it to spin continuously.
This rotation of the motor's shaft can then be used to turn the wheels of the electric vehicle. And by controlling the amount of electric current, you can control the speed of the motor and thus the speed of the car.
