Electric Car Wireless Charging – The Now And The Future, Pros And Cons

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By Miro Stoichev

While wireless charging for electric cars has been “in rumor” for some time, the technology appears to be evolving and there will be consumer-ready products available for purchase, standardization efforts, and more development ideas. We have tried to collect every single note we could find about this technology into one article so that we can present a comprehensive view.

Electric Car Wireless Charging – The Now And The Future, Pros And Cons (1)

Wireless charging: The present and the future

The announcement from BMW regarding the launch of its own wireless charging system was one of the driving forces behind the content. Only for the BMW 530e hybrid at this time, but possibly for the whole lineup of BMW’s electrified vehicles, including electric and rechargeable hybrids. The fundamentals of BMW wireless charging are the same as those already found in the realm of smartphones: an electromagnetic field that exists between a transmitter and receiver in the form of coils. Up until now, every element has a distinctly larger size. The transmitter is a plate that can be fixed permanently or left on the floor of a parking lot or garage. The hybrid or electric car’s bottom mounts the receiver, which is wired to the traction battery.

Generally speaking, the concept is not new; Mercedes has also used a similar approach for its rechargeable hybrid S-Class. Remarkably, the two vehicles mentioned above are rechargeable hybrids with traction batteries that have a capacity of approximately 9 kWh and require 3.5 hours to fully charge. Because of what? Due to the fact that current production samples of wireless chargers “for customers” have ratings of roughly 3-3.5 kW, which is equivalent to using a 220V outlet to charge. It’s also noteworthy that Renault, in addition to Mercedes and BMW, is developing wireless charging technology, and Qualcomm innovations are utilized in each of these three instances.

Wireless Electric Vehicle Charging

We are discussing the Halo WEVC (Wireless Electric Vehicle Charging) system, which promises high wireless transfer efficiency (90%) and allows you to operate with power up to 20 kW. Тoday’s hybrid cars only need 3-3.5 kW of power to run (this is just for everyday convenience; you don’t need to constantly plug in a cable for faster charging). However, the Renault ZOE electric car actually needs up to 20 kW of power.). However, the Renault ZOE electric car actually needs up to 20 kW of power.

Furthermore, Renault has concepts for wireless charging integrated into the pavement. The engineers at the company calculated that installing one charging point every 250 meters would be sufficient to fully recharge an electric car before a lengthy journey. With Qualcomm components and an operating power of 5–20 kW, Renault is currently testing wireless charging. However, the technology is anticipated to be released by 2025–2027, most likely on the ZOE model that will follow.

Concerning Renault, we are already considering the near future: wireless charging zones on highways and high charging power (China and the UK have already implemented such developments). Apart from BMW, Mercedes, and Renault, other automobile manufacturers are also operating in this region. For GM, Honda, Hyundai, and Nissan, for instance, WiTricity is already producing wireless charging (7–11 kW). Although they were only revealed as concepts, the collaboration has already begun, especially since all the aforementioned automakers are looking to produce plug-in hybrids and electric vehicles. This means that if only to stay competitive in the eyes of consumers, they will soon need wireless charging technology.

Non-automotive companies

When it comes to companies that are not directly associated with auto brands, there are other IT-sector companies operating here besides Qualcomm. For instance, Google and two businesses are collaborating to determine the best wireless charging option for electric and driverless vehicles. We have discussed partnership agreements and the testing of multiple wireless charging systems from Momentum Dynamics and HEVO Power. The first example involves the wireless charging project HEVO Power, which has power outputs between 1.5 and 200 kW. It also features a proprietary app that enables reserved space, remote charging control, and the correct alignment of the electric vehicle or hybrid over the wireless charging work grid.

In the second instance, Momentum Dynamics has completed fast wireless charging projects for electric buses and has ceased to even have plans: 200 kW. We are discussing 200 kWh batteries in BYD electric buses, which can be charged at a rate of roughly 3-3.5 kWh per minute in approximately one hour. As of right now, the 200 kWh operating power appears to be a record for wireless chargers used in actual use.

Even so, Momentum Dynamics also provides 50–75 kW chargers, and other businesses have already had success with comparable outcomes. For instance, Oak Ridge National Laboratory, which works with electric cars made by Toyota, has reached an operating power of 20 kW and is currently striving to reach 50 kW. Even though they guarantee charging efficiencies of 90% or more. In summary, if wireless chargers were initially developed to replace regular outlets with a power of 3-3.5 kW, we can now discuss how their power will increase in the near future. As you can see, there are actual, operational projects with a power of up to 200 kW. The size of the transmitter and receiver only increases proportionately to the increase in power. Furthermore, the shorter the distance between them, the more efficient the power transmission will be. Because of this, a 200 kW power source is only appropriate for an electric bus or truck; in fact, the entire parking area of the device is one big transmitter that occupies 15-20 square meters.

Not overwhelmed by the sheer number of businesses and companies involved in this issue yet? There is always this “disorder and confusion” when developing a completely new product, which makes everything need to be streamlined.

The initial attempts at standardization for wireless charging

The SAE J2954 standard is the first—and, it appears, the only—attempt to establish order in the field of wireless charging for hybrids and electric vehicles. Furthermore, these are not even “rules” in the sense that we understand them: the SAE organization originally published the so-called “recommendations” under the J2954 number. This took place in 2012, and the goal was to make these “recommendations” a recognized standard only a year later.

All wireless chargers have to be divided into three WPT (Wireless Power Transfer) types in accordance with SAE J2954. One standard type of working (transfer) coil array is included, and the first type can handle up to 3.6 kW, the second up to 7.7 kW, and the third up to 11 kW. Even though SAE J2954 was merely a “recommendation” at first, businesses needed something to “fix” their advancements, so J2954 ended up becoming the de facto accepted “default” standard for wireless charging. Actually, this is the initial phase in the process of developing chargers that work with various manufacturers.

Furthermore, the influence of transmit and receive array-coil shape on handling power is still being investigated. When the power is more than 11 kW, we can discuss solutions that surpass the J2954 standard. Furthermore, the operating frequency has not yet been decided upon in its entirety. Numerous studies indicate that the electromagnetic field’s ideal frequency is between 22.5-22.7 KHz; at this range, power transmission efficiency can be achieved almost regardless of power, with the best efficiency (between 85 and 90%). Nevertheless, developers typically stray from the generally accepted guidelines in an attempt to boost their wireless charger’s efficiency and display a “nice” efficiency figure of up to 92–95%, which leads to incompatibilities between various wireless chargers.

The initial attempts at standardization for wireless charging

Simply put, everything should function at the level of technological compatibility—that is, an electric car made by Renault should be able to be charged by a BMW charger and vice versa. This is not a security risk; if you need to disable the charger so that other electric vehicles or hybrids can’t use it, there are a number of technologies available that can identify “friend/foe” (a variety of RFID tags).

When it comes to charging compatibility for electric cars, the problem should be addressed early on in the technology introduction process. Consider cell phones from ten to twenty years ago, each with a unique charging connector, and compare that to what everyone has today. Compatibility is merely one of the problems that wireless charging may face in the future.

Wireless charging: summary and conclusions, pros and cons

It may not look like it at first glance, but wireless charging technology is a mini revolution with a really useful result. After all, there are a number of noteworthy benefits to wireless charging. First, it’s convenient – to charge an electric car you don’t need to connect wires and think about the compatibility of charging connectors, you just need to put the electric car in the right parking space with a wireless charging system. Second, a small but crucial point to remember is that you can reduce the size of the battery in your electric car by using wireless charging. Now an electric car or hybrid can be recharged during intermediate stops, and when driving on the highway with built-in wireless charging, the traction battery will act as a buffer or backup for a short autonomous trip. Thirdly, wireless chargers—also referred to as “Vehicle to Home” or “Vehicle to Grid”—are already being developed with the ability to transmit electricity from an electric vehicle to the home grid. This demonstrates that improving wireless charging functionality in comparison to a traditional wired connection is just as important as increasing power.

But there are also sufficient observations. For instance, building a track with integrated charging will cost money (current experimental projects span only a few kilometers at most). Building highways with a single charging lane is a feasible way to cut costs (for public transportation and electric cars, for example). However, who will keep an eye on this lane and prevent different offenders from using it? The effectiveness of charging is the next point to note: Typically, 90% efficiency is stated, however several businesses point out that power losses occur even in common wires and outlets/plugs. Indeed, it does. However, the transmitting unit of the wireless charger is also wired to the power source, so the losses must be totaled. This brings up another important but less obvious observation: the more losses an electric car experiences, the less clear the concept of its economic and environmental benefits becomes. This is especially important for individuals who choose to use electric cars “with a calculator in their hands” or based solely on their own environmental convictions. But we are all aware of what propels advancement. We return to the primary benefit of these systems, which is their convenience: there is no need to worry about charging connector compatibility or plugging in a cable. As a result, wireless charging for electric vehicles will undoubtedly become commonplace.

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