How Do Electric Cars Work? Discover the Main Components and Their Functions

Feb 25, 2024

Even though EVs may look like regular cars from the outside, they actually work quite differently compared to combustion engine vehicles.

Most automakers try to make their electric vehicles look conventional so as not to alienate traditional buyers, but EVs operate quite differently compared to combustion cars. Their propulsion relies on completely different systems than those of a vehicle that runs on liquid fuel.

This is why car mechanics will usually refuse to work on an EV unless they’ve had special training. Knowing what makes an electric car go and what its main components are is important if you want to make the most of your EV ownership experience.

Here are the main components and systems that an EV needs to run.

The single biggest, heaviest, and most expensive component that goes into making an EV is its battery pack. Its role is to store significant amounts of electricity and also withstand repeated charge-discharge cycles in wildly varying weather conditions. In some EVs, the battery pack also acts as a structural member of the vehicle’s chassis.

EV battery packs are comprised of hundreds of individual cells linked together and vary in size from under 40 kWh in smaller vehicles to over 200 kWh in some electric pickup trucks. The GMC Hummer EV has one of the industry’s biggest batteries, a 205 kWh pack, which provides a claimed range of 329 miles. At the other end of the scale, we have the Mini Cooper SE, whose small 32 kWh battery packs can only take it 114 miles on one charge.

It’s also worth noting that manufacturers quote both the total and net (usable) battery capacity, which is why sometimes you see different capacities listed for the same EVs. Furthermore, two EVs with the same capacity battery probably won’t offer the same range since you also need to factor in how light the vehicles are and how much rolling resistance they have, which ultimately translates into how efficiently they use electricity.

An EV’s battery pack would be useless (and dangerous) without what is known as the battery monitoring system, or BMS for short. It serves the extremely important role of monitoring the battery pack and regulating its temperature, voltage, and current. It is also the BMS that gives you range and state of charge estimates, which it calculates based on how much current is left in the battery.

The BMS also monitors the health of the battery pack, both as a whole and each individual battery cell. More advanced EV users can also access the BMS' logs that track the battery’s performance and use patterns. These can then be analyzed in great detail to see how the battery is working and what can be optimized.

Another important role held by the BMS is controlling the battery pack’s thermal management system. This applies to all EVs that can control their pack temperature, which includes most modern EVs. Vehicles like the early generations of the Nissan Leaf and the BMW i3, as well as the Renault Zoe and Volkswagen e-Golf, all came without thermal management.

Managing temperatures in an EV works much in the same way as your combustion car’s cooling system. It relies on a liquid that’s pumped around the battery pack through a series of hoses and channels with the aim of taking heat away from these vital components so that they can run better and have a longer life.

Some EV manufacturers recommend checking and changing the coolant every few years, while others (like Tesla) say this is a fully sealed system that doesn’t need regular maintenance.

Heat pumps are also becoming increasingly common in EVs. These important pieces of hardware help heat the cabin as efficiently as possible by using residual heat from the battery pack and motor. They also help with cooling, as their operation can be reversed so that they can essentially act as air conditioning units.

The piece of hardware that actually provides propulsion in an EV is its electric motor. It converts electrical energy into mechanical energy that drives the wheels.

There are several types of electric motors, each with its own strengths and weaknesses, but all are made up of two major parts called the rotor and stator. The former is essentially an electric motor’s only moving part, while the latter is essentially the rotor’s housing, and it contains channels that liquid is pumped through in order to help the unit shed heat.

Many EVs are powered by what is known as a DC motor, which runs on direct current and comes in brushed and brushless configurations, with the latter being considerably more common. This type of motor is known for its high torque output and durability, but it does also have downsides, such as size, weight, and reliability (especially in the case of brushed motors).

Induction motors are also quite common in EVs, and they bring several advantages over DC motors. They are smaller, simpler, and easier to maintain, but at the same time, they can’t match the power output or efficiency of DC motors, especially ones that use permanent magnets.

Some higher-end EVs also use what are known as Permanent Magnet Synchronous Motors (PMSM), which are better than other types of induction motors in terms of power density and efficiency. Their biggest downside is their added complexity and higher cost.

Electric vehicles don’t need a traditional transmission. Their high torque output that is delivered at very low rpms negates the need to have multiple gears to change between as speed builds.

However, since electric motors have similar rotation speeds (or even higher) compared to ICE vehicles, they still need a reduction gear to help them achieve a good balance between acceleration and top speed. Differentials are present in EVs, and they work the same as in an ICE vehicle.

The only modern production EVs that actually have a geared transmission are the Porsche Taycan and Audi E-Tron GT, which, for their rear motors, have a two-speed automatic gearbox. It’s not clear if this solution will be retained in the future, as it has faced criticism for being an unnecessary overcomplication.

Other manufacturers have not announced plans to implement similar solutions, although there are companies like axle specialist Dana Incorporated in the US that do sell a two-speed gearbox designed to work with an electric motor.

All EVs have some kind of onboard charger, whose performance usually dictates the vehicle’s maximum rate of charge when using an AC (alternating current) charger. Its role is also to convert that into DC (direct current), which is then regulated by the BMS.

The power of onboard chargers in EVs ranges from 3.7 kW to 22 kW, and they can also detect whether the current that’s going through them is single- or three-phase alternating current.

Since most types of electric motors can also act as electricity generators, all EVs have what is known as a regenerative braking system. This relies solely on their motors, which can be used to scrub off speed and put juice back into the battery pack at the same time.

This dramatically increases the brake pad change interval for fully electric and some hybrid vehicles. It also allows EVs to offer what is known as one-pedal driving, which essentially means the driver is able to both accelerate and brake the vehicle using only the accelerator pedal, since when they lift off completely, the vehicle will automatically begin decelerating through motor resistance.

EVs also have a varying number of inverters, converters, and controllers. These are all vital for the correct running of the powertrain, as they help maximize power and efficiency through optimal use of the available current.

Inverters are responsible for converting DC into AC, while converters have the role of converting high-voltage DC drawn from the battery pack into a lower-voltage current that the vehicle needs to run various systems. Controllers are vital for power distribution as they help manage the flow of electricity to and from the battery pack; they are also what makes regenerative braking possible in an EV.

Electric vehicles may have fewer moving parts compared to combustion cars, but that doesn’t mean they aren’t complex pieces of engineering. Quite the opposite, actually, as they need a series of systems to work together in order to provide the power, efficiency, range, and dependability that consumers demand.

Breakthroughs and advancements in EV tech are common, and it’s best to at least have a basic understanding of how they work and what exactly is being improved. This knowledge is also important if you own an EV and are interested in knowing how to properly maintain it and how that differs from an ICE vehicle.

Andrei is the Section Editor for Electric Vehicles at MUO. He studied journalism and has over a decade of automotive content writing and editing experience. He also runs his own YouTube channel called One Tire Fire.