Wireless charging has been around since the late 19th century, when electricity pioneer Nikola Tesla demonstrated magnetic resonant coupling – the ability to transmit electricity through the air by creating a magnetic field between two circuits, a transmitter and a receiver. But for about 100 years it was a technology without many practical applications, except, perhaps, for a few electric toothbrush models.
Today, there are nearly a half dozen wireless charging technologies in use, all aimed at cutting cables to everything from smartphones and laptops to kitchen appliances and cars.
The most popular wireless technologies now in use rely on an electromagnetic field between two copper coils, which greatly limits the distance between a device and a charging surface.
Before we go into how wireless charging works, it is important to note that there were two charging standards when this concept took off. Qi (pronounced “chi”, or “chee”) was a standard by the WPC (Wireless Power Consortium), and PMA was promoted by the Power Matters Alliance. Both are based on inductive charging, but Qi has been widely adopted by electronics manufacturers and is now the de facto standard, which eliminates compatibility issues.
HOW WIRELESS CHARGING WORKS
The secret to how wireless charging works is electromagnetic induction:
A transmitter coil in the charging base sends out a signal.
The signal searches for a receiver coil, like the one in your compatible smartphone.
When it senses one, electromagnetic induction begins.
The electrons (electricity) inside the transmitter coil start to flow around in the coil.
This generates a magnetic field, which is sensed by the electrons in the receiver coil
The electrons trapped inside the receiver coil start to flow around the coil due to the magnetic field
This flow of electrons inside the receiver coil is the electricity powering the battery in your smartphone.
Accessory manufacturers have started designing chargers with more than one coil for better coverage, and also to be able to charge more than one device wirelessly at a time. These wireless chargers come in various shapes and sizes and have anti-slip materials. You get charging pads that lay flat on a table as well as stands with cradles that let the phone rest at an angle so that the display can be viewed. For example, Samsung and Google both have wireless chargers for their products, but thanks to the Qi standard, they are compatible with a lot of other products as well. Apple also announced its own AirPower wireless charger which was supposed to be able to work with multiple devices at the same time, but was never released.
REVERSE WIRELESS CHARGING
The concept is very similar to wireless charging, but in this case, it is a smartphone that uses its own battery power to charge another device wirelessly. The coil in the smartphone is used as a transmitter, to charge smaller devices such as wireless earphones or activity trackers. Very few smartphones support reverse wireless charging. A few of the popular ones are the Samsung Galaxy S10, Galaxy S20, and Galaxy Note 10 series. Reverse wireless charging also is also slow and relatively inefficient, and we recommend that you use it only when really needed.
And that is how wireless charging works compared to traditional (wired) charging.