Wireless Charging and the Technology Behind It

Reviewed by Peter Kendall, Technical Support Engineer (June 2024)

What is wireless charging? Imagine a wi-fi system transmitting electrical power instead of data, and you’re thinking of something akin to wireless charging. With wireless charging, instead of relying on a cable to transfer power, the battery in a portable device can be charged by placing the device on a wireless charging system. Because these systems can be interoperable with Bluetooth and other near-field communications technology, this means mobile phones that are paired together can charge each other up, too. 

Wireless charging relies on principles of electromagnetic induction discovered in the 19^th century by English scientist Michael Faraday. Its applications are numerous, including not just mobile phones but also tablets, portable media players, digital cameras, and wearable electronics such as smartwatches. On a larger scale, electric vehicles can also be charged using wireless charging technology. 

One common question is how efficient is wireless charging compared to traditional charging methods. The answer is that wireless charging is about 70% efficient. The energy that is lost during charging dissipates as heat, which is why your mobile phone may feel warm to the touch during the charging process.

So, how does wireless charging work? Wireless charging typically relies on induction charging, in which a charging station sends an electric current through an internal induction coil. This creates a magnetic field, which in turn generates electric current in an induction coil within the portable device; current usable for charging or operation without the need for a cable. 

Induction charging is commonly used to power smartphones, smartwatches, earphones, and other consumer electronics, but it’s not the only type of wireless charging technology out there. Radio frequency charging employs radio waves to transmit energy, while resonant inductive charging works over bigger distances than induction charging.

Inductive wireless charging (or induction charging) uses the science of electromagnetic induction to work. Although electricity can be transferred from the charger to the device without wires, typically the charger and the device need to be close to each other or touching. This means induction charging is what’s known as a ‘near field’ technology. 

What is Qi wireless charging? The Wireless Power Consortium launched the Qi standard in 2009. The standard relies on closely coupled electromagnetic induction, with the portable device placed on top of the coil on the Qi wireless charger. The advantage of the Qi wireless charger is that it can be used with any Qi-compatible portable device. For example, you can use a Samsung Qi wireless charger to charge an Apple iPhone.

Resonance, or resonant, wireless charging is similar to induction charging. Resonance or resonant chargers work by using oscillating current in a highly resonant coil combined with a capacitor. Like induction charging, this creates an electromagnetic field. A second coil and capacitor (a resonant circuit) in the device operating at the same frequency takes the power and converts it back into electrical current. 

Resonance charging is advantageous for applications where longer distances are needed between the charging station and the device being charged. One charger can also charge several devices at the same time. One disadvantage of resonance wireless charging technology is that it is more complicated than induction charging and requires extra components. 

Wondering how to use a wireless charger? Wireless charging pads are designed to be straightforward to use. First, connect the charging pad to a source of power. Next, put the charging pad on a flat surface. Place the device you are charging on the centre of the charging pad with the display facing upwards. Your device should start to charge automatically.

Wireless charging made its big breakthrough in consumer electronics, especially mobile phones. Today, wireless charging is used to charge many other types of portable electronic devices like tablets, digital cameras, and smartwatches. Car manufacturers have also been experimenting with the potential of wireless charging for EVs for some years. In the industrial space, that effort continues with examining the possibility of wireless charging of forklift trucks and other electrified handling equipment. 

Electric vehicles are a key area for development when it comes to the future of wireless charging. Wireless charging has the potential to make it possible to embed a wireless charging system in the floor of a garage, or in the road, doing away with the need for a charger using cables and plugs. 

As wireless charging technology develops, manufacturers will focus on greater wireless charging efficiency and speed while dealing with bigger power outputs. And when it comes to resonance charging, the focus will be on charging across greater distances. 

In short, with the ever-increasing electrification of the economy, wireless technology will play a key role in making charging safe, convenient, and cable-free. 

Do you need charging equipment? We’ve got you covered. Explore RS’ range of power bankshere.