Wireless charging is one of many new features appearing in the latest smartphones, from Google's Nexus 4 and Samsung's Galaxy S4 to Nokia's Lumia 920. There are even cases that add wireless charging capabilities to Apple's iPhone 5.
Wireless chargers use magnetic induction. They offer the promise of being able to place a device on a surface and have it charge automatically — no fiddling with cables required.
How Wireless Charging Works
Wireless charging is immediately appealing because it allows you to charge your smartphone without fiddling with USB plugs. Just place the smartphone on a wireless charger and it will start charging. Of course, the wireless charger itself must still be plugged into the wall. The requirement for a separate device that must be plugged into the wall has led Apple's Phil Schiller to argue that wireless charging is actually, for most situations, more complicated — which is why the iPhone hasn't adopted wireless charging.
Wireless charging is more accurately described as "inductive charging" because it uses magnetic induction. The short explanation is that it uses magnetism to transmit energy. The current coming from the wall power outlet moves through the wire in the wireless charger, creating a magnetic field. The magnetic field creates a current in the coil inside the device. This coil is connected to the battery and the current charges the battery. Devices must have the appropriate hardware in them to support wireless charging — a device without the appropriate coil can't charge wirelessly.
We're focusing on smartphones here, but you may already use a device with wireless charging. If you have an electric toothbrush, there's a good chance it uses wireless charging technology — otherwise, there would be a risk of an electrical shock considering how wet the toothbrush and its charger could be.
is becoming more and more common. You can buy phones with wireless charging coils inside them, purchase wireless charging mats from tech stores, and businesses like Starbucks are beginning to roll out wireless chargers, so you can put your smartphone down on the tablet and recharge it while you are drinking a coffee.
There's one problem: The companies involved haven't settled on a single standard for wireless charging.
''The great thing about standards is that there are so many of them to choose from.” – Grace Murray Hopper
The standards are designed to ensure that devices and wireless chargers from different companies can work together. There are three standards: Qi, PMA (Power Matter Alliance) Powermat, and A4WP (Alliance for Wireless Power). Things are very much in flux at the moment. For example, Google currently backs Powermat's PMA technology. However, Google's own Nexus 4 and its wireless charger use the Qi standard because it's manufactured by LG. However, LG has also now joined the PMA.
While current devices overwhelmingly use the Qi standard, it looks like the PMA standard may be the most popular one in the future — which means that current devices may be incompatible with most wireless chargers in the future. It's also possible that another standard may take over.
How You Can Use Wireless Charging Today
To use wireless charging with a smartphone, you'll need a smartphone that supports wireless charging and a wireless charging mat to place the device on.
Popular smartphones that support wireless charging include:
Google Nexus 4
Samsung Galaxy S4: You'll need an official "wireless charging cover" that replaces the Galaxy S4′s back panel.
HTC Droid DNA: Other HTC phones, like the new HTC One, do not have wireless charging support.
Nokia Lumia 920 and Lumia 820
Apple iPhone 5: Wireless charging is not included in the iPhone 5, but you can buy a Powermat case that adds wireless charging capability to your iPhone.
All of the above smartphones use the Qi standard, except from the Apple iPhone 5 case made by Powermat, which uses Powermat's own standard.
Be careful when purchasing a wireless charger mat and ensure that it works with your smartphone. While wireless chargers are supposed to work with all certified smartphones supporting the standard — a Nexus 4, which uses the Qi standard, is supposed to work with all Qi chargers — some users have been dismayed to find that their Nexus 4 doesn't work with certain Qi chargers. These are early days for the smartphone wireless charging, and it appears that the standards still have some kinks to work out.