Zombie technologies of electric vehicles: wireless charging
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Oct 30, 2019
James Carter

In the third of our Halloween-themed series on zombie electric vehicle technology, James Carter explains the challenges of wireless charging for electric vehicles

This is the third in a series of articles that will culminate on Halloween, in which we present four zombie technologies that display zombie characteristics

We’ve all seen it: great new technologies with huge potential from a central promise to revolutionize what we do. However, each comes with a challenging list of problems that — when viewed objectively — relegate the technology to prototype form with limited commercial value. These problems could include available technology, cost, business model, and in some cases, the basic laws of physics.

However, these problems aren’t enough to stop hardy groups of individuals from continuing their development and promotion, fuelled by the promise of fulfilling those technologies’ potential.

New Mobility is no exception. In this short series of Halloween-themed articles, James Carter and Paul Martin analyze four technologies that display zombie characteristics.

Zombie Technology 1Solar panels on cars
Zombie Technology 2Hydrogen fuel cell cars
Zombie Technology 3: Wireless charging
Zombie Technology 4: E-roads

Zombie Technology 3: Wireless charging

The dream 

Charge your electric vehicle without ever having to plug in, allowing for convenient and regular opportunity charging. It offers a cordless aesthetic and also close to zero maintenance as no connectors ever touch.

How it works 

Wireless charging, aka inductive charging, involves passing a high-frequency alternating electrical current through a transmitting coil to create an alternating magnetic field. When a device with a receiving coil is placed nearby, the electrons in the receiving coil are induced to move, creating an electric current to charge a battery.

Why it should die (or how it could live)

Like most zombie technologies, the devil is in the details and the (lack of) support of wider stakeholders.

The first problem is efficiency. While lab tests have shown that inductive charging can achieve over 90% efficiency in an ideal laboratory environment, real word results are often much lower, due to problems such as alignment and exterior conditions like snow, ice, rain and road grime. A 90% efficiency result is also far less than the best conductive (plug-in) charging systems, which can achieve over 99% efficiency. To best understand efficiency, imagine you are filling your car with 10 litres of fuel; however, one litre of fuel always leaks out through the pump hose. This would make you quite annoyed, right? The same goes for charger efficiency, it’s just that you don’t physically see the result.

The second problem is the need for exacting alignment of the two coils. A misalignment of more than an inch or two can cause efficiency to quickly drop off. This means that vehicles must be positioned exactly over the pad — a difficult job for most drivers when the charging pad can’t be seen. BMW’s beta test wireless charging system on their 540e comes with a locator system built into the dash to help overcome this issue. However, maneuvering your car multiple times to ensure correct alignment, even with a guide, is far from the convenient promise that wireless charging holds up.

Wireless charging systems also create high electromagnetic radiation, particularly from high-intensity electric fields created from the switching elements in the built-in power conversion block. This generates noise in nearby electronics and can be of significant concern from a health perspective. That is why protective shielding is needed for these elements of the system.

The magnetic field component of the system can also heat up ferrous objects that are close by, causing a potential fire hazard. This is particularly the case around buildings and structures, especially those that use steel rebar in reinforced concrete floors or walls, nails or screws in wooden buildings, and even metal parts in a car. Any type of ferrous metal must be cleared from under or around the charging pad, as well as ensuring that there are no foreign metal objects nearby. Practically, this could mean digging up the floor or foundation in a garage and ensuring that objects like golf clubs, wheels or tools are stored well away from the charging pad.  

To counteract these problems, wireless systems must be fitted with large, heavy shields on the vehicle and surroundings to make it safe. Furthermore, a safety detection method in the system is needed to confirm through radio interface that no significant system leakage is detected.

An issue that many automotive engineers regularly fight is reducing weight to preserve efficiency and performance. Yet wireless charging adds significant weight to any vehicle through the charging pad, shielding requirements and additional power electronics on the vehicle. Few OEMs will accept such a compromise and have so far shown little enthusiasm towards wireless charging beyond lab testing.

The last problem is charging speed. Most inductive charging systems charge at 3kW, about the same as the maximum capacity of a European house plug, with some capable of 11kW, equivalent to a household Level 2 EV charger. There are a few higher-power prototype inductive charging systems running at 200kW for heavy duty vehicles, but these are rare and not commercially available. Given the move toward EV fast chargers for regular vehicles and the adoption of higher conductive power standards by most heavy-duty OEMs, the inability of inductive charging to keep up is problematic.

The final blow for wireless charging is that almost no OEMs have supported it beyond laboratory and prototype testing due to the challenges cited. If there are no cars that use a wireless charging standard, supplying wireless charging infrastructure is not commercially viable, meaning the technology is dead.

Our Halloween conclusion

Leave wireless charging for low-power household electronics where efficiency and EMF matters a lot less.

In this series

Zombie Technology 1: Solar panels on cars
Zombie Technology 2: Hydrogen fuel cell cars
Zombie Technology 3: Wireless charging
Zombie Technology 4: E-roads

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James Carter Vision Mobility

James Carter is Principal Consultant of Vision Mobility, a Toronto-based consultancy that provides services to OEMs, Tier 1s, dealers, startups, industry organizations and companies on strategies to succeed in a New Mobility environment. Prior to that, James worked for Toyota for 19 years in Australia, Asia and North America.

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