How does wireless mobile charging work?

Wireless Charging Station: Ghost 100

Wireless chargers are those enigmatic wonders of science that are just as frightening as they are fascinating.

How is it possible that I can charge my smartphone without a wire and what exactly does that mean anyway?

The first time I placed my Galaxy S4 on the wireless charging mat I honestly felt apprehensive.  I discovered the following thoughts swirling through my mind:

  • Can I get cancer by being within the proximity to this power mat thing?
  • Is electricity somehow being sent through the air – will I spontaneously get electrocuted?
  • How exactly does wireless charging work and why is it so cheap?

Now unless you have a firm understanding of electricity, specifically electromagnetism, wireless charging is a completely opaque idea.

I’m not an expert and don’t have an aptitude for this but I’m extremely inquisitive and have an insatiable desire to understand how stuff works.  So I spent some time researching how wireless charging works and now can tell you with confidence that you have nothing to fear.

It may take a while to assimilate all the concepts; however, at the end of this article you’ll not only know how it works but also have a good understanding of electricity and the benefits and disadvantages of using wireless chargers.

Let’s start with a quick primer on electricity.  We need to understand some rudimentary concepts before I disclose the mysteries of wireless charging.

Electricity 101

It’s time to get tiny.

To explain electricity we need to shrink ourselves down to the infinitesimal size of atoms.

When I say infinitesimal you’re probably bemused because it’s hard to imagine just how freggin’ small atoms are.

In his book, Electronics for Dummies, author Doug Lowe puts it this way:

Suppose you could enlarge the period at the end of this sentence until it was about the size of Texas.  Then, each atom would be about the size of — you guessed it — the period at the end of this sentence.

But believe it or not, atoms aren’t the smallest units of matter in the universe; as you approach the surface of the atom you’ll encounter a dense cloud of hyperactive negatively charged particles called electrons.

The electrons zip and zoom around the atom’s nucleus at an extremely high velocity and have one defining characteristic:

They hate each other, that’s why they’re called negative.

That’s right, electrons abhor each other.

In fact, electrons find other electrons abominable and would love nothing better than to get as far away from each other as possible.

The mutual repugnance electrons feel toward one other forces them to continuously repel in a random fashion.

But this is the thing: if we can find a way to give those jittery electrons a nudge, a push as it were, then they’ll all start moving in the same direction – and when that happens you get electricity.

That little push is known as voltage (measured in volts) and the speed or rate that the electrons hop from one conducting atom to the next is known as current (or amps).

It’s all about induction baby

So what does all this have to do with wireless cellphone charging?

If you wrap a cylindrical container with a conductor such as copper and pass a magnet through the interior something really cool happens:

You’ll induce a current on the coiled wire.

Many people adduce Hans Christian Orsted as the first person to discover this interesting phenomenon.  It has a fancy name too:

Electromagnetic Induction

We call it electromagnetic induction because we’re using a magnet to induce an electrical current on a conductor.

Or here’s another way to think of it:

Grab a standard 9V battery, some wire and a nail.  Now wrap the wire around the nail and attach one end of the wire to one of the battery terminals.

Alright, now remember what I said about all those electrons hating each other?  Think of your 9V battery as a jail for all those haters.

In other words, there are abounding electrons all crammed into that 9V battery so as you could imagine they all want to get out.  Life in the battery sucks for electrons but they can’t get out because there’s no path or conductor for them to travel on.

By conductor I mean there’s no substance made the kind of atom that is willing to give up its own electrons with anyone else.  Stingy atoms are called insulators and are rather unexciting; however, conductors are the antithesis of their parsimonious peers because they graciously give up their electrons to stabilize themselves.

Conductors are benevolent elements who freely pass on electrons. And since electricity is basically just the flow of electrons in a specific direction, conductors provide a path for those angry electrons to run along.

The electron run

Now as those electrons hurry along the copper wires they automatically generate an electromagnetic field around the wire.

Why does this happen? Because that’s the way God designed it!

Seriously, it’s just one of axioms of the natural order that no one really understands.  In my mind every “why” terminates in the wisdom of God and I’m okay with that.

Now, if you’re agnostic or an atheist just realize that I respect your right to choose your beliefs; however, I think you’re wrong for several reasons.

But that isn’t really what I want to talk about today – but hey – if you want to talk religion please email or tweet me because I love hearing other peoples arguments for why they believe what they believe.

Back to the electromagnetic field thingy…

If you placed two wire coiled nails in proximity to one other, each receiving power from its own battery source, you’ll notice that the magnetic field created from the first coiled nail is inducing a current on the second coiled nail.

In other words, as the magnetic field of the first coiled nail moves near the other nail it excites the electrons in such a way that they all start moving in the same direction.

The last thing we need to do is to make sure the current is always changing direction.

The battery provides direct current meaning the electrons keep flowing from one side of the battery through the wire to the other side; however, to induce electricity the current needs to oscillate many times per second so that the magnetic field is constantly in flux.

Constantly alternating the direction of electron flow through a coil is what allows the wireless stations to work.

How wireless charging works

Wireless chargers comprise two elements:

  1. The wireless charging base that has the inductive coil that generates the electromagnetic field
  2. A smartphone case or cover with an inductive coil that passes into the electromagnetic field created by the base and therefore produces a current that can charge a battery

First let’s clarify a few things:

Electromagnetic induction isn’t new

Contrary to what the media probably wants you to know: wireless charging isn’t a novel idea.

Way back in the early 1900’s a really smart guy named Nikola Tesla countenanced the idea of transmitting electrical power between conductors without wires.

Unfortunately, the day he envisioned never came to fruition during his lifetime; however, his patent on an Apparatus for Transmitting Electrical Energy left an indelible mark in the scientific community and it provides the foundation for why wireless charging works.

Check out that patent by the way, it’s a really cool document.  It’s only 4 pages on the United States Patent and Trademark Office.

Nikola Tesla's Apparatus for Transmitting Electrical Energy

Wireless charging isn’t really wireless

Secondly, the phrase “wireless charging” is a misnomer because it isn’t actually wireless in the same way that you think of wireless internet or wireless radio signals.

The wireless base (or charging station) isn’t wireless.  You have to plug it into the wall so it can use the alternatating current (AC) flowing from the plug to generate the electromagnetic field.

The good and the bad

So wireless charging principles are ancient; only recently has it come into the limelight.

Good stuff

On the one hand it can mitigate the tangled wire mess under our desks and beds.  The wireless charging station makes it easy to keep things tidy and is also easy to use.

Just place the phone on the pad you’re good to go.

In addition, most wireless chargers conform the standards of the Qi wireless power consortium.  By the way, it’s pronounced “Chee” and is a derivation of the Chinese word for life force.

Qi is the official governing body that exists to make sure than any Qi wireless charging systems play nice together.  So you can take your Qi phone and drop it on your friends Qi charging base and it’ll charge just fine.

Furthermore, most new phones are already Qi enabled by default which makes this really convenient.

Not so good stuff

On the other hand, it make take slightly longer to wirelessly charge your phone; however, if you charge it overnight the difference isn’t relevant.  When I charged my Galaxy S4 overnight with the Ghost 100 charging base, it’s always ready to go in the morning.

There aren’t any reviews on Amazon for the Ghost 100 yet but I can attest that it works.

But the one thing that bugs me is that it’s pretty expensive.

My wireless charger costs $40 hard-earned bucks which is significantly more expensive than a $1 USB cable on Amazon.

This is biggest obstacle to universal acceptance in my mind; the cost needs to dip before people jump in.

The Bottom Line

Wireless chargers are technological marvels and now you know how they work.

It’s really just basic physics packaged in a new way.  People have known about electromagnetic induction for years but it wasn’t until the last five years or so that we’ve harnessed its power to do cool things with gadgets.

In summary wireless chargers work by sending an alternating current through an induction coil to create an electromagnetic field around the charging station.

When you attach another induction coil to the battery of your phone and place it on the charging base it enters that electromagnetic field which automatically generates a current on your phone.

If you think wireless chargers are cool please share in the comments below!

Update December 15, 2014!

Robert Kramers at PowerbyProxi sent me two excellent diagrams clarifying how wireless power works.  I’ve posted them below!  Enjoy.

Wireless Charging Example from PowerbyProxi

Wireless Power Example from PowerbyProxi

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