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BMW developing wireless inductive charging system for electric vehicles

By

July 8, 2014

The BMW charging system uses a primary coil in the floor and a secondary coil in the car

The BMW charging system uses a primary coil in the floor and a secondary coil in the car

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Electric vehicles and plug-in hybrids may be green and sustainable, but that doesn't mean much if you forget to plug them in the night before. To overcome this frustrating morning surprise, BMW Group is developing a new generation of wireless inductive charger technology that’s comparable in speed to cables, but requires no more effort than parking and pressing a button.

BMW sees premium market electric cars as a major part of the automotive future. The company already has its all-electric i3 and i8 plug-in hybrid sports car, both of which are designed for quick charging using the BMW i Wallbox. Now the company wants to take this a step further with an induction charging system as a way to make electric cars more attractive to the public.

The new induction system is designed to work with the BMW i car batteries and those under development by the company. In addition, Daimler and BMW have entered into joint development of standardized inductive chargers with the aim of making electric cars more mainstream. Inductive charging has the advantages of being user friendly and there’s no need for connectors, which BMW sees as the crucial advantage of the new charger.

Architecture and structure of inductive charging

Not having connectors means one less thing to remember and one less thing to suffer from mechanical wear. Without the need for a connection, the driver has only to drive over the charge station, activate it with a press of a dashboard button. The system then does the rest while keeping the driver updated on charge status and time remaining by means of a Wi-Fi connection between charger and car and a smartphone app. BMW says the app can even help the driver park the car properly over the charger.

How it works

The system consists of two components – a primary coil that is installed in a base plate on the floor of a garage or car port, and a secondary coil that is installed in the floor of the car. Both coils are circular to keep them compact, lightweight, and the magnetic field confined to a small area for safety. An alternating magnetic field in the primary coil transmits power to the secondary coil at a rate of 3.6 kW, which is enough to fully charge the high-voltage batteries in many plug-in hybrids in under three hours.

BMW says that the prototype system has an efficiency of 90 percent and can charge the BMW i8 in less than two hours. To make the charger suitable for all electric cars instead of hybrids, the company is working on boosting the charge rate to 7 kW, which would charge a BMW i3 overnight.

Since all the system's conductive components are protected, weather conditions don't have an effect on the power feed, meaning it can be installed indoors or out. The system continually monitors the space between th primary and secondary coils, so that If a foreign object enters the field, the system cuts out automatically.

BMW says its medium term goal is to put into production a user-friendly inductive charging system that is reliable and non-wearing that will be compatible with the batteries in its existing i cars, as well as the high-voltage batteries in future plug-in hybrid models.

Source: BMW

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past.   All articles by David Szondy
10 Comments

So to the question on efficiency and whether the 10% loss during charging would be incorparated into the miles per charge equation - my guess is it would probably be not

myale
9th July, 2014 @ 03:35 am PDT

I'm going to need a warning when I open the driver's door that I haven't switched it on. Failing that, there will some tantrums the following morning, and I cannot guarantee that naughty words won't be used.

On an even more serious note, how can we say that electric cars are any real replacement for petroleum fuelled ones when it is going to take overnight to charge some of them.

What an awful situation. After a lovely meal, the girlfriend asks you if you would like to go back to her place for a 'coffee' and you have to worry about not being able to get to work in the morning. I know what I would choose (I never really did like the job, all that much, anyway.)

Mel Tisdale
9th July, 2014 @ 05:52 am PDT

So what would happen to all the magnetically conductive components of the car that fall within the field of the charge system ? Won't this also act as an induction hot plate? One could probably cook a meal sliding a pot under the car !

pmshah
9th July, 2014 @ 09:21 am PDT

Mel: make sure your date does NOT know she was chosen because she was less than 50% of your vehicle's range from home. This small bit of information probably would not be interpreted kindly. This is sort of like Elaine, (on Seinfeld), deciding if a possible date is "spongeworthy" or not.

StWils
9th July, 2014 @ 10:37 am PDT

Obviously there will be a warning light & alarm as a reminder to press: "charge". And every shopping mall will provide chargers. probably free. This is so much better than plugging in. It allows charging while out & about or at work without hassle. And if you just make it to the charger on empty, your phone will alert you when the battery will get you home. It may mean waiting an extra 30-90 minutes but this is a learning curve. Soon, you will know the waiting time for all your destinations, and can plan accordingly.

Don Duncan
9th July, 2014 @ 10:47 am PDT

I have been wondering about a special lane on the highway that would provide induction charging for cars and trucks so that they could charge on the go. Putting these on uphill grades could greatly extend the range of electrics.

Bob
9th July, 2014 @ 05:51 pm PDT

Sorry...don't want to plan around my car. I don't need to now, so why should Electric Car be any different. Too busy and time is money. Is that advancement when you need to wait? No, it's not. I want my future vehicle to be more efficient and better all the way around...or scrap it.

Foofaraw
9th July, 2014 @ 06:51 pm PDT

Conductive tires and a charge-grid-floor, just like dodgem/bumper cars use at the showground, sounds a much more sensible idea.

christopher
9th July, 2014 @ 08:57 pm PDT

@pmshah I don't think this is normal induction charging method, like the one in toothbrushes. I believe it can span that much larger distance due to resonant inductive coupling.

on a side note this does solve some problems in the future, eventually it could be more like a supercharger or even more. One of the problems is for high amperage situations, very large bulky cables are required

Jacob Hernandez
10th July, 2014 @ 06:37 pm PDT

I planned about this system few years ago, to cars' blockheater for winter time in Finland.

100% of the cars have to be plugged in every day if you want to start it in the next day without blowing up the engine in -20-30c environment.

I cancelled the project due to lack of resources, and possible hazards due to retrofitting high energy magnetic fields without having all around protection to the car's electronics.

I wish this system becomes available soon. Plugging wires everyday is so 1940s.

Tuppe
19th July, 2014 @ 09:29 am PDT
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