Wireless Charging – A useful mechanism or a useless gizmo?

23-09-2020 |   |  By Robin Mitchell

While wireless chargers have been around for many years, their integration into smartphones seems to be taking its time with many mid to low range devices still not supporting wireless charging. What is wireless charging, how does it work, and is it really useful?

What is wireless charging?

Wireless charging does exactly what it says on the tin; it is charging, done wirelessly. However, it should be noted that the concept of sending power without the use of wires dates back to the time of the great Nikola Tesla, who had a vision of free power delivered via large scale EM toroids. While this idea has many flaws (such as who pays for the power and the efficiencies involved), wireless charging is practically achievable on small scales. One industry that has seen an increase in popularity in wireless charging is Smartphones, and multiple devices now support wireless charging stations whereby a phone can be charged by simply placing the phone on top of the charging station. 

How do wireless chargers work?

Wireless charging can be achieved using different technologies, including light (via lasers), and sound, but the most tried and tested method is using magnetic coupling (i.e. transformers). The charging base integrates a large coil that has an AC passed through it. A phone which supports wireless charging also integrates a large coil into its casing, and when the phone is placed close to the charging station, a current is induced into the smartphone’s coil via the charging station coil (i.e. transformer action). For the charger to work, it depends on the distance between the smartphone and the charger, as well as the orientation of the two coils relative to each other.


How efficient are wireless chargers?

One of the biggest challenges faced with wireless chargers is their efficiency, and this is becoming a more crucial issue in the engineering world. Reducing the distance between the two coils increases the efficiency, and a new charger developed by Xiaomi moves the internal coil so that it is in the optimal position for charging. However, even in the best of cases, wireless chargers are lucky to reach efficiencies greater than 70%, and this is compared to cable chargers (i.e. ignoring losses in the AC cable). The resultant efficiency not only makes such charging systems more expensive to run but also harms the environment. In a world where climate change is on the agenda, the use of devices that needlessly waste energy will begin to be frowned upon, and those that use wireless charging may be criticised for using such technology. Even if the changing climate is taken out of the equation, the additional production of CO2 and particulates that contribute to smog will have an impact on health. While the energy consumed by individual wireless chargers is very small, the use of wireless chargers may encourage the technology into other areas, and result in a more considerable impact on the environment.

What benefits do wireless chargers provide?

While wireless chargers can be inefficient methods for delivering power, their lack of connectors can make them ideal for a wide range of applications. The first significant advantage is the lack of cable and connector wear. While some connectors can be manufactured to handle many thousands of mechanical cycles, many of those used in production often do not last beyond several hundred. This may sound like plenty, but when considering that most devices are charged daily, the result is a worn connector after 100 days of use. The lack of connectors completely removes the need for mechanical resistance, and thus a wirelessly charged device has no limit on the number of times it can be charged (of course, the battery itself will wear down over time). The second significant advantage of wireless charging is the lack of a need for a mechanical connector. This makes it easier to design products with high IP ratings and therefore, can handle more harsh environments. The third significant advantage to wireless charging is convenience; devices can be placed onto a dedicated charger and left. 

Thus, wireless charging can find itself highly applicable in the consumer market, such as IoT devices and smartphones. Other products that would benefit from wireless charging include wearable electronics that require a high degree of environmental sealing, and automated systems (such as factory drones), that need to be mobile and use a simplistic charging method.

Conclusion

While wireless charging does have its drawbacks, it can be beneficiary at times. While wireless chargers with smartphones may be somewhat needless, such chargers can be highly ideal for lightweight, mobile applications where mechanical connectors can compromise a product, or the environment where the device is operating is unforgiving. 

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By Robin Mitchell

Robin Mitchell is an electronic engineer who has been involved in electronics since the age of 13. After completing a BEng at the University of Warwick, Robin moved into the field of online content creation developing articles, news pieces, and projects aimed at professionals and makers alike. Currently, Robin runs a small electronics business, MitchElectronics, which produces educational kits and resources.

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