Everything you need to know about wireless charging
When wireless charging first hit mainstream devices in around 2012, it was hailed as a futuristic move by the media. Visions of people tossing their charging cables aside and plopping their phones on a table, bowl or desk to charge them were the fantasy of the week. The reality, alas, would take a much longer time to materialize.
Office desktop with a phone charging wirelessly.
Fast forward to today where nearly every new phone supports Qi, the most popular wireless charging standard, and wireless charging efficiency is improving with every technological cycle. It seems that the time to go wireless has truly arrived.
How does wireless charging work?
Wireless charging works off the principle of electromagnetic induction. This is similar to what drives those induction stoves that have been around for years.
Essentially, both charger and receiving device contain wireless charging coils. The transmitting coil converts electricity and emits an electromagnetic field. When the receiving coil is within this field, it converts the energy into an electric current that is sent to the battery.
The transmitting coil send power to the receiver which is installed in your phone.
In the case of a phone-charger system, the transmitting coil (often shortened to Tx) is located in the charging pad while the receiving coil (Rx) is located at the back of the phone and connected to the battery.
History of wireless inductive charging
Wireless power transmission has a long history.
Michael Faraday is credited with the discovery of electromagnetic induction in 1831, during an experiment where he demonstrated that a rotating electric current in a coil of wire could induce a current in another nearby coil of wire.
Nikola Tesla experimented with wireless power transmission in the late 19th century, using a huge 200-foot-tall tower called Wardenclyffe Tower as a radio energy transmitter, though he ultimately failed because the radio waves spread out in all directions.
Nikola Tesla proved wireless power transmission was possible back in the 19th century.
Much research in inductive charging would continue throughout the 1960s to the 1980s, but the true technological breakthrough that would lead to modern wireless charging was a principle known as resonant inductive coupling. This principle had long been known as a wireless power medium, but was refined into viable technology by researchers at MIT in 2006.
Companies scrambled to take advantage of the new technology, and from here, two competing standards were formed. The first to make any headway was the Qi standard, which was formed in 2009 by the Wireless Power Consortium. Its primary competitor, Powermat, was developed earlier in 2006, but it became a competing wireless charging standard upon the formation of the Power Matters Alliance in 2012.
Both standards clashed viciously in the beginning, with users having to choose one or the other depending on the brand of smartphone or device they purchased. Samsung was one of the few manufacturers to have wireless charging support for both standards.
It was a war of marketing as well, as Powermat became the official charging partner for major companies like General Motors, Starbucks, and Delta Airlines.
Eventually, the Qi standard won out, a decision that was ultimately cemented by Powermat becoming part of the Wireless Power Consortium in 2018. Today, almost every wireless charger, and device that supports wireless charging, uses Qi.
The Qi standard
Qi, pronounced “chee,” is named after the Chinese concept of the flow of vital energy through every living thing.
The Qi standard describes various power specifications that correspond to how much energy can flow from charger to device. The “Low” power specification allows for 5-15 watts of power, while the “Medium” power spec supports battery powered products that operate in the 30-65 watt range. A data transfer spec is also included, allowing the device to request the optimal amount of power from the wireless charger.
Many high-end smartphones today have glass backs. Although Apple started this trend back in 2012 with iPhone 5, it quickly caught on with the major manufactures with the rise of wireless charging as metal backs greatly reduce the efficiency of wireless charging. This isn’t a part of the Qi standard, but it’s pretty much a requirement for a phone to have a glass back if it wants to charge wirelessly.
The Wireless Power Consortium (WPC) has defined 3 specs for wireless power transmission.
Advantages of wireless charging
The foremost advantage of wireless charging is right there in the phrase - wireless. With wireless charging, you reduce the clutter of charging cables, limiting it to just the power cable of the charging pad. You don’t need to think about the hassle of plugging in your cable, either - all you have to do is place your phone onto the charging pad and it starts charging right away.
With the lack of charging cables comes the elimination of that timeless problem among tech enthusiasts - all those different connectors! You don’t need to worry about not having a Lightning, USB-C, or micro USB cable on hand anymore. All Qi-supporting devices will work on all Qi charging pads.
The elimination of repeated cable plugging and pulling will also reduce wear and tear on the charging port, making your phone last longer, as the charging port is a common point of failure for many devices.
Your friend asks to borrow a charger and you reply, “do you have Apple or Samsung or...?” Wireless charging fixes this problem because all Qi-enabled phones can be powered up with the same charger.
Myths about wireless charging
Many people still have concerns about wireless charging, that are often a holdover from its old days when the standards weren’t quite as refined.
Here are some of the main myths and misconceptions busted.
Wireless charging is slow
This may come from a time when people tried out wireless charging in its 5-watt days. It was definitely slow back then. But today, there are fast wireless charging pads that can provide 10 or even 15 watts of power. That’s potentially faster than 5V/2A fast charging in standard phones, and almost as fast as the variety of higher-end fast charging standards such as Qualcomm Quick Charge.
Wireless charging is inefficient
Just because there’s a conversion from electric current to electromagnetic field and back, this doesn’t cause a significant loss in efficiency. You can recover as much as 80% of the input wattage when wirelessly charging, though this may go down depending on whether you use a phone case, and how thick it is.
Wireless charging is dangerous
Some people think that the energy transmitted wirelessly over the charging coil could be dangerous to your body. After all, there’s a reason why those charging cables are insulated. However, organic creatures don’t react very strongly to the magnetic field frequencies used by efficient wireless charging, and the power output isn’t high enough to be a risk factor.
The future of wireless charging
Wireless charging has a bold, bright future ahead of it. Already more and more manufacturers are putting Qi support in their phones, while peripheral manufacturers are adding Qi charging to more devices.
Advanced applications of the technology are getting interesting as well. Manufacturers like Huawei and Samsung are implementing reverse wireless charging, allowing phones to wirelessly charge other phones and smaller devices.
In the future it may be possible for your phone to power up a friend’s, wirelessly.
The charging pad itself could be getting a makeover. Some devices like monitors and mousepads are integrating wireless charging. Even furniture makers for tables and desks are getting in on the Qi action, fulfilling the original promise of the future that wireless charging held.
Wireless charging is only going to become more prevalent and more interesting. There’s never been a better time to adopt the new technology.