Wireless charging may one day replace plugs and wires similar to how Bluetooth and Wi-Fi have modernized personal communication. The concept rests on inductive coupling using an electromagnetic field that transfers energy from the transmitter to the receiver.
Wireless transfer of power is not new. In 1831, Michael Faraday discovered induction in sending electromagnetic force through space. In the late 1800s and the early 1900s, Nicola Tesla demonstrated wireless broadcasting and power transmission. The experiments in Colorado Springs in 1899 lead to the Wardenclyffe Tower in New York. Tesla wanted to prove that electrical power could be transmitted without wires, but lack of funding halted the project.
It was not until the 1920s that public broadcasting began. Europe built massive transmitters to reach many countries. The transmitter at Beromünster in Switzerland could have transmitted at 600kW, but legislation on electro-smog and protests from the local population limited the power to 180kW. Smaller FM stations have since replaced these large national transmitters.
Wireless charging shares similarities with radio transmission transmitting power by electro-magnetic fields. Wireless charging operates in a near field condition in which the primary coil produces a magnetic field that is picked up by the secondary coil in close proximity. The radio transmitter, on the other hand, works on the far field principle by sending waves that travel through space. While the receiving coil of the wireless charger captures most of the energy generated, the receiving antenna of the radio only needs a few microvolt (one millionth of a volt) to recover a signal that become intelligent when amplified.
Last Updated: 26-May-2015
Batteries In A Portable World
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On March 29, 2019, john linhorst wrote:
What tests should be ran on wireless charging devices? There's not a lot about how to test
On February 12, 2016, Jim wrote:
Medical uses? I have a pacemaker with a battery that requires surgery when the battery nears the end of life. Some Pacemakers with a can use up their battery faster due to patient requirements. This seems to be an area that might fit wireless charging?
On October 12, 2015, peter connell wrote:
The oscillating magnetic field works within a one meter (3 feet) radius. To stay in the power field, the distance between transmit and receive coil must be within the 1/4 wavelength (915Mhz has a wavelength of 0.328 meters :( So its doable range is 80mm. or 4-5"! Screw more convenient phones and electric toothbrushes, but very exciting for EVs. "While a 3kW system for EV charging achieves an efficiency of better than 95 percent, a typical 100W system exceeds 90 percent" That's excellent. but beside the point if we can switch from ICEs and oil. and get 30% at best~ (tho the toyota "free piston" claims 40% (I will post on that later elsewhere)). If the epa wishes to apply the same standards to this EV opportunity as to wall warts, then that is truly absurd. An analogy i liked from the fuel cell section here, is its like having your battery charger on board. It cant deliver full power (that needs batteries), but a great range extender and small power boost when "connected".. In practice I see from trials, it looks incredibly easy infrastructure. Simply a strip in the middle of the lane, to all intents, normal roadway with a groove cut & filled with a "drive over flat cable" Do you get it? Its such simple, doable infrastructure. The car can be independent, but it gets a supplement up hills & is often recharging or moving without the battery during the trip. Aircon only when on the grid perhaps? We all use a smart phone app for metering power use. We still use a charger at home.