WPT breaks all connections, Part 2

March 23, 2015 //By Sanjaya Maniktala
WPT breaks all connections, Part 2
Sanjaya Maniktala offers a second part of a high-level review of the current state of wireless power transfer (WPT).

Inductive Automotive Wireless Chargers
Doing a patent search we see that some of the earliest patents on wireless (inductive) charging were applied for by Hughes Aircraft Company in 1992.  Seems a strange choice, but this is how it played out :- In the mid-90s, Hughes Electronics, a subsidiary of Hughes Corp., released the Magne Charge interface, which was used for the first electric vehicles made by both General Motors (GM) and Toyota. Magne Charge was initially manufactured by the GM subsidiary called Delco Electronics. Note that this powerful yet spatially flexible wireless power transfer technology was inductive, not MPT-based. It operated between 80 to 350 kHz and consisted of a paddle containing the primary coil, about the size of a table-tennis (ping-pong) bat, which was inserted into a slot in the car for delivering up to 6.6 kW — without metal contacts, and with an impressive efficiency of 86%. This is still used by a few hundred first generation Toyota RAV4 EV electric vehicles. But as these retire from the road, Magne Charge will become obsolete.

The 2012 Gen 2 RAV4 EV, as well as the Nissan Leaf and Chevrolet Volt, use the new non-wireless SAE J1772 standard instead (it needs firm metal connections). The “older” Magne Charge wireless system is now referred to as the J1773 system.

Note that an older inductive patent was filed in 1975 too. See references below.


Electromagnetically coupled battery charger

Electric vehicle inductive coupling charge port

Battery charging system

Giving Teeth to Modern WPT

In the late 90’s, the basic induction principle behind inductive WPT found its way into homes through the strangest route: tucked away deep inside Braun’s latest Oral-B electric toothbrushes. Braun was part of The Gillette Company from 1984 to 2005. In 2005, Gillette along with Braun was acquired by Proctor and Gamble (P&G), making the latter the world’s largest consumer goods company. At almost the same time, rechargeable toothbrush technology appeared in the Sonicare brand from Optiva too, which was acquired by Philips in 2000.  These gadgets abound in homes today. However their form factor is clearly very different from what is considered acceptable or helpful for charging mobile phones. But the basic principle is the same. It is Faraday all over again.


Charging coil core insert for electric toothbrushes

Rechargeable toothbrushes with charging stations

Have a Heart

A Massachusetts-based company called AbioMed also pioneered inductive WPT at an early stage. They developed AbioCor, an artificial heart which could be fully implanted within a patient, due to a combination of technological advances in miniaturization, biosensors, plastics and energy transfer. The AbioCor ran on a rechargeable battery, charged by a “transcutaneous energy transmission” (TET) system. This was an under-skin transfer of power. There were no wires or tubes penetrating the skin, and therefore no risk of infection on that account. The aim of such systems is to transfer power across modest separations of 10-25 mm typically. On July 2, 2001, the first patient ever received the AbioCor.  By September 2004, 14 patients had received it — Faraday to the rescue once again.

Cleansing and Purification

A company called Splashpower was founded in 2001. It was a spinoff of Univ. of Cambridge UK. In Oct 2002, it announced its intention to soon release mobile phone and mp3 player wireless chargers in the form of a “transmitter” unit called “SplashPad” costing about $100. To pair up with the SplashPad, a “SplashModule” dongle costing ~$20 could be purchased as a “receiver” and plugged into a cell phone for example. But the development ran into a lot of unforeseen design problems and the commercial release got stalled for years. This should be an indication of the fact that these “mundane” wireless charging methods are in fact tricky, and are still being properly understood. Certainly, resonance is tricky business.

Splashpower filed several patents in inductive charging before they declared bankruptcy in April 2008. They were quickly purchased a month later by Fulton Innovation, a subsidiary of Alticor, the parent company of Amway, among others. With the help of Fulton Innovation, Splashpower wireless products did see the light of day in Aug 2008. They were then quickly reviewed by Gizmodo among others.

However, even prior to the Splashpower takeover, Fulton Innovation had been steadily working on developing their “eCoupled” technology of wireless charging. On April 6, 2008, they announced they would soon be releasing Amway’s bestselling portable water purifier called eSpring, with a wireless charging system based on Fulton’s eCoupled technology. That purifier was surprisingly the major impetus behind modern WPT. “eCoupled” was the underlying technology of the Wireless Power Consortium (WPC) to be founded very soon thereafter.

Note: The head office of Alticor is listed as 7575 Fulton Street East, Ada, MI 49355-0001, USA. So we can easily surmise where the name Fulton came from. But Fulton Innovation should not be mistaken for Fulton, a group of companies making boilers etc.  

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