Charging stations are necessary for electric vehicles to charge the battery to power the vehicle. Wireless charging for electric cars is an interesting technology that makes electric vehicle charging very convenient.
Today, we will discuss “how does wireless charging work?”, “wireless charging technology,” “advantages of wireless charging for electric vehicles,” “disadvantages of wireless charging of electric vehicles,” “Wireless charging standards”, and “a few electric cars with wireless charging facilities”.
Charging stations are classified into the home, private, and public charging stations. I hope you had read the articles about charging stations.
There is a 5 part blog series published about electric vehicle charging. Vehicle to Grid, Vehicle to Home, Vehicle to Vehicle, and Solar charging are explained there.
Wireless charging technology
Energy can be transferred from one point to another without a direct-wired connection.
There are different types of wireless charging technology that in use.
- Inductive wireless charging
- Resonant Inductive Coupling
- Capacitive wireless charging
- Light waves
We focus of Inductive and Capacitive wireless charging
#1 Inductive Wireless Charging
The principle behind wireless energy transfer is mutual induction – the same principle of a transformer.
Mutual induction is the property of a coil due to which it opposes the change of current in the adjacent coil
Wireless chargers for mobile phones are popular due to the convenience of use.
Electricity is induced in a coil that kept in an alternating magnetic field. The alternating magnetic field is generated by supplying alternating current to the coil.
The frequency of the alternating current in the coil determines the size of the coil. For example, a high-frequency current helps out to reduce the number of turns in the coil to have the same flux density.
If the alternating current passes through a coil then electricity will be generated in the adjacent coil. The gap between the two coils, the number of turns in the coil, etc. affect the magnitude of the generated electricity.
The principle of inductive wireless energy transfer is simple and it is mutual induction. Wireless charging for electric cars is based on this principle.
#2 Resonant Inductive Coupling
This is a modified form of inductive charging where the range of the charging is a few meters where as the inductive charging has very short range.
Resonant inductive charging is the method that commonly used for electric vehicle wireless charging.
Do you remember the tuning fork experiment that you did on your school? The resonance causes objects to reverberate when energy of a certain frequency is applied.
In resonant inductive charging, two copper coils are used to transfer the energy.
Both the coils are tuned to the same electromagnetic frequency and one coil will be energized from the external supply. Then the energy will be transferred to the other coil that has been tuned to the same frequency.
To charge an electric car, the garage and car would both equipped with copper coils. The transmitter coil is connected to the power socket supplies the room with a non-radioacive magnetic field. It transfers power to the receiver coil connected to the car battery.
#3 Capacitive Wireless Charging
There is another technology in wireless charging which is based on capacitance. It’s is known as capacitive wireless charging.
In this method, instead of mutual induction, electrostatic power transfer happens. A plate of the capacitor is installed on the road and other plates will be there at the bottom of the electric car.
Electric power transferred from the charging station to the battery through electrostatic effect. High-frequency AC transfers power to the battery from the charging station.
Wireless Charging Standard
SAE J2954 is an emerging standard for wireless power transfer for electric vehicles developed by SAE International.
It defines three classes of charging speed, WPT 1, 2, and 3, at a maximum of 3.7 kW, 7.7 kW, and 11 kW, respectively. This makes it comparable to medium-speed wired charging standards like the common SAE J1772 system. A much more powerful WPT9 is being defined in J2954/2 for 500 kW charging for heavy-duty vehicles which have the room necessary to mount the larger induction plate.
This system has a demonstrated efficiency of 85 % and sometimes can achieve an efficiency of 94 % as well. [Reference]
How does wireless charging for electric cars work?
Let’s check out how wireless charging for electric car works.
When the electric car parked on a charging slot where wireless charging technology is installed, the vehicle battery starts charging.
Beneath the parking area, coils are installed to generate an alternating magnetic field to enable wireless charging. An electric car with wireless charging would also be installed with coils to generate electricity from the alternating magnetic field.
The vehicle parks above the charging spot where the wireless charger is installed. Then high-frequency electricity passes through the wireless charging station.
As a result, alternating magnetic fields are generated and electricity is induced in the adjacent coils in the car. The generated electricity is converted into DC using a rectifier (AC-DC converter) and charges the battery.
Advantages and disadvantages of wireless charging of EVs
Wireless charging happens in an electric vehicle when the vehicle parked above the wireless charger. The proximity of the wireless charger decides how efficiently transfer energy from the charger to the battery of EV.
Wireless charging for electric cars has advantages and disadvantages. Let’s have a look at the advantages and disadvantages of wireless charging for EVs.
Advantages of wireless charging of electric car
Following are a few advantages of wireless charging for electric vehicles
- No need to carry bulky charging cable in the car
- Convenient to use the charger
- Safe since the absence of wired connection
- Immune to dirt and water
The space utilization inside the car would be increased if the wireless charging stations are popular. The regular maintenance of the power plug is avoided in the wireless charging. The charging station can be easily made immune to dirt and water.
What are all other benefits of wireless charging?
Disadvantages of wireless charging of electric cars
Even though electric car wireless charging is an attractive option, there are a few disadvantages as well. The disadvantages are
- Standardization of charging system
- The difficulty of installation of a wireless charging system
- The vehicle has to park on the exact location where charger coils installed to charge the battery
Electric cars with wireless charging facility
Do you know there are cars with wireless charging technology installed?
Electric car manufacturers introduced wireless charging enabled electric cars. BMW introduced wireless charging for 530e performance plug-in hybrid electric vehicles.
Along with BMW, other vehicle manufacturers and industries produce their own wireless charging facilities. See the list of a few wireless charging providers for electric cars
You may explore the list of electric cars available in the market
What’s next in wireless charging?
Wireless charging technology grows to another advanced level where the vehicle could charge when it is being driven!
In wireless charging at run technology, the vehicle runs on a road where the coils are installed and connected with the charging station’s power supply at high frequency. Energy transfers from the coil beneath the road to the coil at the bottom of the car even if the vehicle runs.
It’s not a hypothetical charging technology but a proven method. I think we could expect to charge electric cars when it travels.
Just think of the possibilities that wireless chargers installed beneath the road near traffic signals, junctions, parking areas, and on highways.
An electric car can then be charged on the go!
Are you interested to do projects on electric vehicles?
You can check: List of 50 electric vehicle project ideas
Wireless charging is a convenient method to charge an electric vehicle. It avoids the use of a long bulky cable to connect to the plug point to charge the battery of an electric vehicle.
Mutual induction generates electricity in the coil at the bottom of the electric vehicle when it parks above the wireless charger. Charging an EV while driving is an advancement of wireless charging.
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- Wireless charging is the most convenient method of EV charging available
- Two types of wireless charging are inductive and capacitive
- The vehicle can charge even it is being driven
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