"Unplugged Site" Analysis of Pure Electric EV Inductive Charging Technology

This week, NetEase Auto reported on the current status of electric vehicle projects in Beijing, Taiyuan and other places. In the face of facts and evidence, one cannot help but question the current development status of electric vehicles in my country. Although pure electric EVs are far from being popularized, the wheel of history is constantly moving forward, promoting the development of pure electric EVs, and one day people will usher in a fully EV-based transportation. However, just as too many cars will cause oil shortages, too many EVs will also have their own problems, that is, the difficulty of charging.

When an EV is parked for a long time, it takes a lot of time to find a charging station or charging pile, and it takes a lot of time to plug in the power supply to charge. The exposed charging cable always gives people an uneasy feeling. In addition, multiple plug-in EV technology schools also have their own technical standards. In the future, when large-scale universal charging stations appear, we can't require every plug to have them, right? Therefore, "wireless charging" has begun to attract the attention of car companies. Humans have mastered the technology of transmitting energy using wireless electromagnetic waves for more than a hundred years, but it is only in recent years that energy-intensive transmission has been truly achieved. There are already many types of mobile phone wireless chargers on the market, and the charging performance is comparable to wired charging.

A variety of mobile phone wireless chargers

EV Unplugged

Unplugged is a form of performance of rock bands' live performances, but it has a different meaning in the automotive field. Recently, Volvo Cars officially launched a joint research project called CED (Continuous Electric Drive) and began to modify a Volvo C30 electric car for inductive charging, which means that wireless charging technology has officially entered the automotive field, making a strong mark in the history of EV development.

Inductive charging is a future smart solution to charge electric vehicles. Electric vehicles no longer need power sockets or charging cables. Using the inductive charging method, electrical energy is wirelessly transmitted to the car's battery through a charging plate buried in the road surface, so that the car can be charged directly from the road surface. To put it simply, it uses electromagnetic induction to transfer energy. The principle is somewhat similar to that of microwave ovens and induction cookers, but the energy is not converted from electrical energy to heat energy, but first converted into magnetic field energy and then reversely converted into electrical energy.

In an inductive charging system, a charging pad is buried underground, such as under the driveway of a home. The pad consists of coils that generate an electromagnetic field. When a car is parked on top of the pad, electrical energy is transferred directly from the pad to the car's inductive receiver in the form of alternating current, which is then converted to direct current in a voltage converter inside the car to charge the car's battery pack. The advanced feature of this system is that the entire charging process does not require direct contact between the car and the pad.

This technology will greatly reduce the charging time. When the battery is fully discharged, it is estimated that it will only take one hour and twenty minutes to fully charge a 24 kWh battery pack. This is of great significance, that is, there is such a possibility that your EV can charge itself when it is parked on the roadside. The owner does not need to laboriously connect the high-voltage cable to the charging port and the charging pile, and naturally does not avoid the trouble of various interfaces, as long as the battery supports wireless charging.

Concerns and risks that still exist with this type of technology

Under the temptation of the novel user experience of wireless charging technology, we have to calmly think about some deeper topics. First of all, will wireless charging technology kill the emerging plug-in EV? The answer is obviously no. Just like the inherent disadvantages of wireless networks compared to wired networks, wireless technology lacks a continuous and stable medium, and its energy transmission rate and energy utilization are relatively low. Under the same conditions, the charging rate is still slower than wired charging, and the energy conversion efficiency is low.

The status of plug-in EVs is still unshakable

Secondly, we also have the issue of human health. Radio means radiation. The greater the power of the radio, the greater the radiation, and the more severe the damage to the human body. Just as some people feel headaches after long mobile phone calls, the amount of electromagnetic radiation released during long wireless charging is also considerable. Even if some peripheral technologies are used to improve the energy directivity and shorten the contact distance, no one can stop the radiation of electromagnetic waves. Moreover, the fast charging technology that is increasingly being raised as an issue, the efficient charging technology that can fully charge the battery in half an hour, if it is replaced by wireless charging, I am afraid that the radiation will be even more alarming.

Tesla's wireless charging technology

GM and Plugless Power develop wireless charging for Volt

Even though wireless charging technology has many obstacles and shortcomings, many automakers and technology companies are currently conducting research in this area. General Motors, Tesla, Nissan, Volvo, etc. are already at the forefront of the world. Smart people may wonder, how to calculate the electricity bill for wireless charging? Don't worry, the comrades in the power grid will definitely have a way at this time, and billing technology will definitely be the top priority...

Nissan's wireless charging technology architecture