Electric vehicles in a nutshell
Talent is like electricity. We do not understand electricity. We use it.
In 2020 sales of electric vehicles represented 4.2% of the global car market and it is estimated that in 2021 the EV market will double.
But are these vehicles all the same? No!
There are different types of electric vehicles which differ for degrees of “electrification”.
Car manufacturers use terms such as hybrid, plug-in, full hybrid, etc. to advertise their electric vehicles.
But, what do all these terms mean?
In this article we will clarify this “chaos”.
…Let’s start with some basic concepts.
What is an Electric Vehicle (EV)?
An Electric Vehicle (EV) is a vehicle that uses one or more electric motors for propulsion.
An electric car is just a type of EV because in general it’s possible to equip any kind of vehicle with an electric powertrain.
The most popular EVs that we see in our cities are: e-cars, e-scooters, e-bikes, electric trams, electric buses, etc.
In this article, we will focus on Electric Cars.
An Electric Car consists of three main components:
- Electric Motor
In simple words, an electric motor needs electric power to move the vehicle.
The electric power is taken from the Battery, the “fuel tank” of the car, and it is given to the Motor by the Controller.
How does an electric motor work?
Electric Motor is the “hearth” of the electric propulsion.
Let’s examine in detail how an electric powertrain works.
An electric motor is a device which converts electrical energy into mechanical energy.
By simplifying the structure of the electric motor, you can identify two main parts:
- Stator: the stationary electrical part of the motor.
- Rotor: the rotating part of the motor.
These two elements generate two magnetic fields whose interaction produces the electric propulsion (aka “driving torque”). To generate the magnetic fields, in general, the rotor and stator are powered by current.
The motor type used on electric cars is usually a brushless motor with the following characteristics:
- Rotor has no coils or copper wires but “permanent magnets”.
- Only the stator is powered by current.
On an electric car, the speed of the car is adjusted by varying the frequency of the current in the stator: the controller has the function of responding to the commands of the accelerator pedal.
Electric motor vs Endothermic motor
The endothermic motor, also known as internal combustion engine, is the motor used in petrol cars. It converts chemical energy (petrol) into mechanical energy.
The main differences between electric and endothermic motor are:
- Energy efficiency
Movement is generated by combustion where over 50% of the energy is released into heat and the remaining becomes kinetic energy.
Motion must be transformed from linear (piston moving in a straight line) into rotary through a complex system.
Energy conversion results in a quicker rotation response, with fewer moving parts than the endothermic motor.
- Drive torque
Maximum drive torque is achieved at high motor revolutions (3000–4000 rpm).
The maximum drive torque is reached at the moment when the motor starts.
- Energy density
Gasoline has a high energy density. This means that the gasoline tank of an internal combustion motor is smaller than an electric car battery.
Batteries have a lower energy density compared to gasoline. This means that the battery of an electric car has to be 5 times bigger than a tank of a gasoline-powered car with the same range.
Battery: “fuel” for EV
Battery is the “fuel tank” of an electric vehicle.
The most common type of battery, used in electric cars, is the Lithium-Ion (Li-Ion). It’s a rechargeable battery also used in portable devices (e.g., smartphones, etc.).
Li-Ion batteries are able to be recharged hundreds of times and are more stable. They have a higher energy density, voltage capacity and lower self-discharge rate compared to other rechargeable batteries.
But they also have two strong limitations:
- Subject to aging (even if not in use).
- Expensive to manufacture. (It’s the most expensive component of an electric car…)
Batteries’ companies are constantly working on finding chemistries that are cheaper, denser, lighter, and more powerful than Li-Ion batteries.
The biggest challenge of batteries’ companies is to reduce the battery charging time.
A modern electric car needs approximately 3–6 hours to fully recharge its battery. This is no way comparable with gasoline cars where it takes only few minutes to refill their gasoline tank.
The electric car described so far is what it’s called Battery Electric Vehicle (BEV or EV), in which the propulsion is only supplied by an electric motor and the only source of energy is the battery.
But BEVs are not the only types of EVs available on the market. There is a category of vehicle called Hybrid in which electric motor and endothermic motor coexist in the same vehicle.
There are 4 types of Hybrid vehicles:
- Micro Hybrid Electric Vehicle (mHEV)
- Mild Hybrid Electric Vehicle (MHEV)
- Full Hybrid Electric Vehicle (FHEV or HEV)
- Plug-in Hybrid Electric Vehicle (PHEV)
Micro Hybrid Electric Vehicle (mHEV)
mHEVs don’t have an electric motor used for traction but they have an efficient electrical system.
For instance, the start & stop system allows energy recovery during the stop phase.
We can consider all modern internal combustion engine vehicles as Mild Hybrid EV.
Mild Hybrid Electric Vehicle (MHEV)
MHEVs have an electric motor that only works in specific moments: low speed driving (about 40 km/h) and the starting phase. While, in all the other situations it’s the internal combustion engine that kicks in.
Full Hybrid Electric Vehicle (FHEV or HEV)
FHEVs have an electric motor that works independently or in synergy with the internal combustion engine.
The battery is recharged using the energy that is produced by the internal combustion engine and during the decelerations.
Plug-in Hybrid Electric Vehicle (PHEV)
PHEVs are similar to FHEVs. They have an electric motor that can work independently or in synergy with the internal combustion engine.
The main difference is that the battery is recharged either with domestic socket or an electric column.
(Battery) Electric Vehicle (BEV or EV)
BEVs have only an electric motor and the source of energy is the battery.
This is a very short “survival guide” about electric cars.
Electric mobility is a huge subject, but I hope this brief article will help you to better understand what kind of cars the automarkers are selling.
If you’re interesting to go in depth on how an electric car works, I suggest this 10-minute video that describe the functioning of the Tesla Model S: the BEV with the longest range and highest acceleration.