Wireless Charging in a Nutshell


Wireless charging seems so great, I plug this thingy in and then set this other thingy on it and then there’s power! But how the heck does electricity get from the wall into my phone? You’re probably reading this article via a device that has a battery–laptops, mobile phones, toothbrushes, though. All these things need charging and for the moment we’re still using cords and plugs for this. Inductive charging isn’t new, it’s been used since the early 1990s in electric toothbrushes, and for surgically implanted devices like artificial hearts. You’ve even heard of this in pop culture! In the late 1800s, Tesla was allegedly able to power light bulbs with no wires, and claimed to be able to transmit power from one location to another with no wires. To make it work relies on simple physics.

If you ever wrapped a coil of wire around a nail and attached a battery, then you know the electricity in the battery runs through the wire creating an electromagnetic field, or flux. Do it at home, it’s fun and you can use it to pick up paperclips or whatever. With that same principle, a coil of wire, magnet, battery, you can make it go the other way too. Spin a magnet in the coil and you’ll generate electricity by taking that magnetic flux and moving it through that coil to create electricity. The battery creates a stable electromagnet because it’s direct current, it’s going one way. The power from your walls is alternating current, changes direction 60 times a second — or cycles at 60 hertz — so the electrons are moving back and forth — remember that because that’s the key to the charging.

Wireless inductive charging gets its name from that magnetic field interaction, called induction. Inside of the charging pad, and the inductive charging device are tiny coils of wire. The pad, being plugged into the wall, is fully powered — and the power is cycling. When the other coils come within a short distance their flux will interact with the flux in the device, move the electrons around and charge the battery. Chances are, the number of cycles per second isn’t going to be 60 hertz, but like, 5 or 10, so it doesn’t mess up other things in your house. Your WiFi network cycles at 2.4 gigahertz or 2.4 billion cycles per second, so it’s DEFINITELY not going to mess THAT up, but with all the radio waves flying around, you can’t be too careful. If it’s that easy, you’d think it would be everywhere, but the problem is efficiency. You waste a lot of power filling up two coils and letting them talk to each other. It’s SO much better to just plug right in. The future of wireless charging is unclear. It seems like a great idea, but it’s still going to be a short-distance system for a while.