How does wireless charging work?

Wireless charging allows you to charge your gadgets without connecting a USB cable. It’s pretty neat, but how does it actually work? Why even bother? What are the disadvantages?

We cover everything you need to know about how wireless charging works here. You soon forget what all that mess with cables was like!

A matter of induction, my dear Watt (son)

In general, wireless chargers use a property of magnetism and electricity known as “induction” charging. Basically, electric current is converted into a magnetic field. This field then generates an electrical current in the device you want to charge.

That’s a bit of an oversimplification, but it’s essentially what happens in the wireless charging process. There are two coils, one in each device, that convert the energy from one form to another.

This is the most common form of wireless charging that you are likely to find in personal gadgets such as smartphones or smart watches. Inductive charging only works over very short distances. Usually 10mm or less. So even though the power is “wireless”, you usually have to place the device on some sort of charging pad for the power to flow. Inductive chargers like this one use low-frequency signals to move current from the charger to the device.

The Resonating Alternative

Wouldn’t it be cool to just walk into a room and have all your devices powered? That’s the promise of resonant charging. Using high-frequency radio waves to wirelessly send power to devices.

The main advantage of this method is that the relatively high-frequency waves can travel much further than induction chargers can handle. We are talking about several feet. So as long as you stay within range of the coil, your device will turn on.

It’s a futuristic idea, but electro pioneer Nikola Tesla did it more than a century ago† If history had gone in a slightly different direction, wireless electricity could be the standard way of doing things today.

A race with two horses

There are different approaches to how wireless charging works, each with their own pros and cons. Different companies have different visions about how we all want to use wireless power in everyday life. This has led to multiple standards for wireless charging and, as you’ve probably guessed, these standards don’t work together.

Qi wireless chargers use the short range induction method and this is what you will find in most personal devices that charge wirelessly.

The AirFuel stand uses the long range resonance method and you probably won’t find it in your gadgets yet. However, you can buy special charging cases for smartphones that add AirFuel capabilities to them.

Faster! Faster!

One thing you might notice about wireless charging, regardless of the standard, is that they don’t offer that much power. Fast charging has pretty much become the standard when using a cable. Modern USB-C smartphones and laptops can often handle anything between 40 and 60 watts. USB-C Power Delivery lets you move 100W of power over a USB-C cable, but current lithium-ion batteries in a phone can’t accept that.

Qi or AirFuel chargers don’t offer nearly as much power, but both standards are evolving. At the time of writing, 40W wireless fast charging has hit the market and AirFuel hopes to reach 100W in the future. We can also expect battery technology to improve, making it easier to charge devices faster.

At the moment, however, a major drawback of wireless charging is that it is slower than using a direct wire connection and cannot actively power devices that require even a moderate amount of power to operate.

One charger to rule them all

One big advantage of wireless charging is that it does away with all the different cable standards. We will. that assumes all your devices use the same standard, but Qi charging is becoming quite ubiquitous for devices like smartphones.

So anyone with a Qi-enabled device can just put it on your pad and charge it. That’s cool, but the real killer feature is the ability to charge multiple devices simultaneously on the same charging pad. You need a charger with one coil for each device you want to charge.

For example, “triple chargers” have three coils and thus three charging points. You can put three devices next to each other and have them charge at the same time. That can be a pretty elegant solution. For example, if you place a triple charger on a side table in your living room, it is a central place where people can store their devices.

Devices that only charge wirelessly

Most devices that charge wirelessly, such as smartphones, also offer you the option of wired charging. However, there are some devices that only allow you to charge them wirelessly. Smartwatches are an example of this and if you think about it, it makes sense.

If you want to make a device that is truly dust and waterproof, having a ton of ports can be a pain. Not to mention that small devices like wireless earbuds or smartwatches often don’t have room for standard connectors anyway.

How does wireless charging work on larger devices? While there aren’t any phones, tablets, or laptops we’re aware of yet with wireless charging exclusive, don’t assume it never will. A fully enclosed device using only wireless communication and charging would open new doors when it comes to ruggedness and design.

Phones and power banks that enable wireless charging

Wireless chargers themselves have gone wireless in the sense that you can now get power banks and even smartphones that can charge devices wirelessly using the Qi standard.

Smartphones like the Note 10+ have a feature known as “Wireless Powershare” and it is very useful for charging devices such as wireless earbuds or smartwatches. Wireless power banks are of course also useful for that use, but it also brings up the interesting possibility of sticking your phone to the power bank and temporarily using it as one cable-free piece.

A wireless future

Short-range Qi inductive charging is definitely here to stay, but we’ve seen some impressive demonstrations of long-range charging using the resonance method. If you place an LCD TV with a receiver coil, you can simply place it within reach of another coil in a wall to turn it on.

Now that both power and data transfer is wireless, there are new avenues for product designers to take. We may be in for an interesting future of devices that always have power, don’t need to be opened, and in some cases don’t need batteries to operate.

It will of course take some time before long-distance wireless power becomes the norm. You can certainly expect quite a bit of pushback as well. There are already many (mostly unfounded) concerns about electromagnetic radiation technologies, such as 5G, causing health or environmental problems. We expect the same types of complaints to arise as long-distance wireless power transmission becomes more common.

For now, however, no one seems to have a problem with inductive charging at very close range. How many of your devices can be charged wirelessly? How often do you use that feature? We’d love to hear about it in the comments.

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