Certain smartphones these days offer the useful function of wireless charging. For some people, this feature is essential, others think it's pointless. One question remains unanswered though: how is it possible to transfer energy without a cable?
Fast charging and electromagnetic induction
To fully understand how wireless charging works, you need to understand the concept of an electromagnetic field and, more generally, electromagnetic induction, which you may already be familiar with if you have an induction cooker in your kitchen. What is the link between an induction cooker and a smartphone, you ask? Electromagnetic induction is an energy transfer system, meaning that it can be stored (as in the case of the smartphone) or used.
So how does this energy get transferred? Well it's a question of forces. Imagine two people holding opposite ends of a rope: if one person decides to make waves with the rope, the other person will receive the waves as they travel down the rope. This is a very generalized way of explaining electromagnetic induction: a force sends energy from one point to another. The base unit (powered by electricity) transmits energy to the smartphone via electromagnetic fields. The sensors on the smartphone recover the energy and channel it to the battery for storage.
How is the charging speed calculated?
Again, it's all about the forces. As the energy is transmitted through electromagnetic fields, the speed depends on these fields. The bigger they are, the faster it will be. The problem is the fields are pretty small because the smartphone (because of the material (metal etc.) it's made from) leads to limitations.
Your smartphone therefore has a limited transfer speed for which the manufacturer specifies the voltage. The charger also emits energy at a regulated speed, as shown below.
What's Qi?
Qi is the most popular wireless charging technology. It is not restricted to a particular manufacturer, in theory all manufacturers can use it on their devices. Samsung and Apple are probably the most well-known brands that use it. Qi seeks to standardize wireless charging technology, which involves several safety rules that must be respected. These rules include power of the devices, which obviously plays a role in the charging speed.
Thanks to Qi, wireless charging technology has made considerable progress. Charging speed has increased considerably, and electricity no longer causes the unit to heat up significantly. Qi does not only use electromagnetic induction charging technology but also magnetic resonance technology.
Is my device compatible with induction charging?
Perhaps you've given it some thought and you want to give up on cable charging and opt for wireless charging instead. A question arises: is your device compatible with this technology? If you have a high-end Samsung smartphones, from the Galaxy S or Note series, then your device is probably compatible and Samsung has its own charger. The new iPhone 8 is also compatible with wireless charging, though if you have a less recent iPhone you can also use wireless charging but you'll have to buy a receiver such as the QInside Qi2001 first. Some Lumia, Motorola, Xperia and HTC smartphones are also compatible with Qi technology, as well as several Nexus phones (Nexus 4, Nexus 5, Nexus 6, Nexus 7, Galaxy Nexus).
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