How does Tesla work

How does an electric car work?

At first glance, electric cars can hardly be distinguished from a conventional vehicle with a combustion engine from the outside. If you take a look at the heart of an electric car - the engine - you can see significant differences in the inner workings, both in terms of size and the arrangement of the components: Some components that a diesel or gasoline engine absolutely needs do not appear in the electric car. Whether this is a catalytic converter, the spark plugs or the starter - that and much more is superfluous with an electrically powered vehicle. Instead, other components are required.

In this overview you will find out why drive technology is so future-oriented and how an e-car works in the first place.

1. Basic principle of the motors of electric cars

In order for an electric car to start moving, it needs two components that are to be understood as essential. On the one hand, there is the battery as an energy supplier and the electric motor, which embodies the drive element. Instead of the rechargeable battery, one often speaks of a battery, which ultimately aims at the same component. This stores the previously supplied electrical energy so that it can be converted into mechanical energy - i.e. kinetic energy - by the motor.

First, the energy of the battery flows in the direction of the motor. An integrated management system regulates the battery cells and thus ensures that they all have the same voltage and provide the required power. In this way, this controller is able to extend the life of the battery installed in the car and to ensure that it works as economically and reliably as possible.

There are two different types of magnets in the motor. The stators are - as you can see from their designation - firmly integrated. There is also a rotor that turns. As is known, two magnets attract each other when the poles are different, but repel each other when the poles are the same. The stators permanently change their poles due to the energy coming from the battery. Meanwhile, the rotor in the middle is alternately attracted and repelled by the other magnets, causing it to rotate around its own axis. The result is a rotation, a turning movement. It ensures that the wheels of the electric car are ultimately set in motion.

So that the required energy is always provided while driving, so-called potentiometers are located between the accelerator pedal and the controller. They convey the information about how much electrical energy the battery should release. A regenerative braking system is also widespread in e-cars. Alternatively, one can also speak of a regenerative brake. It is used for recuperation, which means nothing more than recovery. And the kinetic energy that has already been generated is recovered. When the electric car brakes, some of it can be converted back into electrical energy.

Electric motors have the decisive advantage that they can provide their full torque even when the vehicle is stationary. The complete traction is therefore available from the start. This allows enormous comfort when starting off. Internal combustion engines, meanwhile, only achieve their tractive power in the range between 800 and 1,000 revolutions per minute. Shifting operations are no longer necessary in an e-car, which is why it works without a multi-stage gearbox and a classic clutch.

It is also important to mention that the electric motor works with extremely low friction and therefore without any real loss of energy. The efficiency is a physical quantity that describes the relationship between the energy supplied and the energy actually used. E-car motors have a very high degree of efficiency, which is often 80 to 90 percent. Sometimes there is even talk of 95 percent. This means that only a very small amount of the supplied energy is not used for driving. The balance sheet for internal combustion engines is much worse. On average, gasoline engines achieve an efficiency of around 30 percent, while diesel vehicles are slightly higher at 40 percent. The rest is converted into heat, which is irrelevant for driving itself.

A special feature of e-cars results from the different manufacturer concepts where the engines are installed in the vehicle. Some have the classic electric motor under the bonnet, others have two electric motors, one for each axle. As a result, e-cars often have all-wheel drive. Third and last variant - implemented in the Tesla Model S, for example - each individual wheel is driven by a separate electric motor, with each one being fed by a large battery. This variant opens up a completely new division of space and enables sportier driving behavior. Said Model S, for example, has capacity for a trunk in the front and one in the rear, since the engine does not take up this space. In addition, the design results in an extremely low center of gravity of the vehicle, which promotes traction and thus sporty driving behavior.

2. Types of engines

In addition to the battery as an energy store, the motor is the most important part of an electric car. Electric motors are considered to be trend-setting because they do not use any fossil fuels and therefore do not generate any exhaust gases. Then it is said that they are emission-free.

Basically, the motors of electrically powered mobiles are divided into two categories, which are to be presented here in more detail.

2.1 DC motors

DC motors got their name from the flow of current. This moves constantly in one direction. The engine type is characterized by a comparatively high weight and large dimensions. It is therefore clear that engines of this type do not have the ideal properties to be installed in an electric car. On the one hand, this would increase the total weight of the vehicle, which reduces the range. On the other hand, e-cars could be designed to be less compact due to the volume of the motor.

2.2 AC motors

Instead of DC motors, AC motors are the first choice in electric cars. They show far more advantages and thus have a clear raison d'être. As the name indicates, these machines have the option of changing the direction of the current flow. The result is that different voltages can be converted ideally. AC motors are also more compact, so that they take up less space inside the electric car. At the same time, their weight is lower, which is particularly relevant for electromobility. Ultimately, the lighter the vehicle, the less energy has to be used to drive it. AC motors can also reach extremely high speeds of up to 20,000 revolutions. For AC motors, a distinction is also made between asynchronous motors and synchronous motors.

2.2.1 Asynchronous motors

The designation of asynchronous motors can be traced back to the generation of the magnetic field between the rotor and the stators. It runs with a certain time delay, which is why it is described as asynchronous. This type of engine is characterized by a very simple structure. The rotor only consists of a laminated core and a short-circuit winding. The low wear is an advantage when using asynchronous motors. It also reaches high speeds. It should not go unmentioned that the use of so-called rare earths is not necessary. Rare earths are expensive and rare industrial metals, such as dysprosium or neodymium. These occur as components in magnets. However, asynchronous motors are only of limited relevance for e-cars.

2.2.2 Synchronous motors

Compared to asynchronous motors, synchronous motors were able to prevail in electromobility, as they offer an even higher power density and more optimal efficiency. They are able to convert as much of the supplied electrical energy as possible into actual mechanical energy. In these machines, the rotor moves synchronously with the rotating magnetic field - hence the name. Almost all manufacturers of e-cars are now using synchronous motors.

3. Other essential components of the electric car

Basically, it should be clear: an e-car does not need fossil fuels to drive it, only electrical energy. This eliminates a whole series of technical elements without which a vehicle with an internal combustion engine cannot work. Starting with the tank, through the radiator or the catalytic converter, to an exhaust system, the electric car can do without all of these components. A different type of drive also means that correspondingly different components work together to ensure that the vehicle functions properly. You will find the most important of these in this overview.

3.1 High-voltage battery (traction battery)

The high-voltage battery in an electric car is comparable to a cell phone battery for smartphones. Only the size, the necessary capacity and of course the performance are significantly higher. In a sense, it could also be called the “tank” of the electric car. As a rule, the high-voltage battery is the largest component in the vehicle and is often located lengthways under the passenger cell of the car.

The battery consists of several individual battery modules. In these, in turn, there are individual cells connected in series. In total, they result in the voltage that is necessary to drive the electric car. When the high-voltage battery is charged, it receives electrical energy, which it stores as chemical energy. As soon as their capacity for driving is required, this energetic process is reversed and electrical energy is available.

Currently, lithium-ion batteries for electric vehicles have proven to be the ideal solution, so that almost all manufacturers trust them. The battery type provides a number of arguments. It offers a high energy density, a large storage capacity, is long-lasting and, above all, is also suitable for quick charges. The latter aspect is particularly important for the everyday suitability of e-cars with regard to the charging time.

The research and development for even more powerful accumulators is far from over - up to 30 times the current capacity is technically conceivable. This can be used to extend ranges or, alternatively, to compress the batteries.The most innovative and promising technology seems to be the lithium-oxygen battery. Let us be surprised what the future has in store.

3.2 Low-voltage battery (on-board power supply battery)

The battery supplies the electric car with energy. The low-voltage battery with a voltage of 12 volts supplies consumers and devices inside an electric car with energy. This component got its name from the significantly lower energy. Meanwhile, the drive battery has a much higher voltage of 350 volts - it is therefore called a high-voltage battery.

Back to the low-voltage battery: It primarily serves the purpose of a buffer storage tank. Far away from the engine, it supplies the consumers in a vehicle with electricity. These include in particular:

  • On-board electronics
  • Indoor and outdoor lighting
  • Seat heating
  • Ventilation / blower
  • Window regulator
  • Door opener
  • windshield wipers
  • Radio and possibly other multimedia devices

The part, also known as the on-board network battery, plays an important role when the vehicle is started: It checks the entire system of the electric car and activates the high-voltage battery. Even small currents are sufficient for this. The low-voltage battery also exists in cars with internal combustion engines. There it is known to be charged via the alternator while driving. In an electric car, part of the recuperation energy, i.e. the energy gained during braking, flows into the 12 volt battery.

It is worth mentioning at this point what happens in the event of an accident. For safety reasons, the high-voltage battery in an electric car is deactivated immediately. Explosions or fire hazards are therefore categorically excluded. However, the low-voltage battery remains in operation to supply the on-board electronics. This means that the windows and doors of the vehicle can be opened and closed.

3.3 Power electronics

The power electronics act as a link between the electric motor and the battery. Its essential task can be summarized in a simplified way: It converts the current as required in terms of shape, strength and frequency. After all, the battery provides direct current, while the common motors in electric cars each require an alternating voltage. This is where the power electronics do their job just as they do in cases where the vehicle is connected to the public grid for charging: it transforms the incoming alternating current into direct current for the battery.

If the braking energy is converted into electrical energy through recuperation, the power electronics use it to generate direct current for the battery. It is a kind of center for the high-voltage on-board network, since all connections come together there.

3.4 Charging port

What the tank cap is for gasoline and diesel vehicles is embodied in the charging connection for e-cars. This is usually located on one of the rear fenders or directly on the front of the bonnet under the brand emblem. The charging connection represents the interface between the car and the power grid. Charging with electricity is possible at the charging stations provided for this purpose, as well as at wall boxes (wall charging stations) or conventional sockets. However, there are different types of plugs on the vehicle side and on the charging station side. Accordingly, adapters often have to be used for compatibility. You can find more information on this in our FAQ section with a focus on batteries and charging.

4. Ancillary units

Auxiliary units perform various tasks. In internal combustion engines, for example, they are responsible for cleaning exhaust gases. This job is self-explanatory for e-cars, but there are still aggregates. Depending on your task, they are powered by the vehicle's high or low voltage battery. You are responsible for safety, comfort or ensuring that the vehicle is in operation:

  • Illumination of the vehicle inside and outside
  • Heating or air conditioning
  • Air conditioning of the battery
  • Braking assistance
  • Steering assistance

In the classic sense, the electric motor does not have an idle speed as is known from an ordinary car. When idling, the temperature and energy are generated there in order to operate the functions mentioned above and to regulate the engine temperature. In an electric car, no electricity is used for the motor when it is stationary, but all other consumers such as heating and light access the stored energy of the battery. Incidentally, air conditioning is the most energy-intensive topic. On the one hand, it is about the temperature for the passengers in the car, but on the other hand, it is primarily about regulating the temperature of the battery. If the outside temperature is particularly cold, it must be warmed up; if the outside temperature is high and the outside temperature is high, cooling must be used. All of this naturally costs the battery electricity and ultimately range. In these areas in particular, engineers are working flat out on solutions and efficiency improvements.

5. Body

A great deal of attention must be paid to the body of e-cars. In any case, it plays an important role in all types of vehicles when it comes to protecting the occupants and all components installed inside as well as possible. On the other hand, as a form-giver, it contributes to the look and aesthetics of the vehicle in order to create a high recognition value and to differentiate it from other models. In recent years, there has been a noticeable leap in the design of e-cars. While the first e-cars did not meet the tastes of car enthusiasts, there are now all design variations, from sporty to luxurious. The reason for these initially strange body shapes of e-cars is simply the air resistance and weight, more details can be found in the following lines:

5.1 Conversion Design

The English term conversion means translated into German something like a conversion or a remodeling. Applied to the body of an electrically powered car, this idea aims to simply use the design of an existing vehicle with a combustion engine. The original model is then transformed into an e-car, as it were, by only adapting the components required for operation.

For the manufacturer himself, this principle makes sense and optimizes costs. The effort and cost factor for a new development would be much higher. If a cCnversion design does not make it into series production, the damage is manageable. There are also fewer problems with repairs to the body, as the blueprints and spare parts can be adapted, so the handling in the workshops for the mechanics performing the work does not change that much.

The disadvantage of this model is the basic concept of the vehicle for an internal combustion engine. The possibilities of placing electric motors and batteries are much more diverse than an internal combustion engine and the associated tank. Prefabricated spaces for the gearbox, exhaust system or even the gear knob in the interior are suddenly superfluous. It is therefore a compromise-ready merging of old and new.

5.2 Purpose design

While conversion design is used to adapt the existing, purpose design aims to create a vehicle that is completely optimized for electromobility. It is the consistent design of an e-car without having to make compromises with the conditions from combustion technology.

In terms of shape and material, the design is geared towards generating as little driving resistance as possible. This is created by:

  • Air resistance
  • Incline resistance
  • Rolling resistance
  • Acceleration resistance

Purpose design brought to light the use of more suitable materials such as various plastics or carbon fiber.

For the manufacturer, the purpose design is a higher risk. Not only are the investments for a completely new concept car, including the time and resources required, expensive, but also the entire manufacturing process, including the purchase of parts from suppliers, has to be recreated.

6. Maintenance of an electric car

The electric car is generally considered to be much less vulnerable and requires less maintenance than a diesel or gasoline engine. The reason for this is obvious: a large number of technical components simply do not appear in the vehicle. These include the clutch, the spark plugs, the catalytic converter, the oil filter, the exhaust system, the alternator, the carburetor or even the air filter. At the same time, there is no need to change the oil and the brake pads of an e-car are subject to significantly less wear, as recuperation (energy recovery when braking) already decelerates the vehicle.

Nevertheless, an e-car must also be subjected to regular service intervals and checks. As with conventional vehicles, the manufacturer's guarantee is linked to it. What is special, however, is that not every manufacturer insists on their own authorized workshops, but there can also be so-called service providers. In particular, start-up companies that have developed vehicles and cannot fall back on their own comprehensive network of service points use external partners for this. The vehicle "e.Go life" from a newly founded company from Aachen (GER), which has been outsourced to Bosch Car Service, will serve as an example.

Which parts of an e-car now have to be checked and serviced regularly? Primarily bearings and hubs, lights including the headlights, mirrors and windows, washer fluid and of course brake pads, brake disks and brake drums. The charge level of the low-voltage battery should be checked. It is obvious from this list that the components involved are much less maintenance-intensive. If these parts are defective, repairs can also be carried out quickly and cheaply.

From the point of view of maintenance, a study by the Institute for the Automotive Industry (IFA) is worth mentioning. She compared the maintenance and repair costs for e-cars with petrol and diesel vehicles. A small car served as the basis, which was observed over a period of eight years. The end result was that the cost of an electric car was around 35 percent lower.