The basic principles of wireless charging have been around many years, Nikola Tesla demonstrated magnetic resonant coupling, i.e. the ability to transmit energy/electricity through the air by creating a magnetic field between two coils.
The principals have been used in transformers, and also already in electric toothbrush chargers, where the toothbrush has no physical wire connected for many years. In principle these are called induction chargers, and with modern development they have become sufficiently efficient, that there are now around 6 different technologies about, used not only for smartphone charging, but also for laptops, kitchen appliances and motor vehicles!
The most popular wireless technologies now in use rely on an electromagnetic field between a two copper coils, which greatly limits the distance between a device and a charging pad. That’s the type of charging that Apple or Samsung has incorporated into their high-end phones.
September last year saw Apple joining other handset manufacturers by embracing WPC’s “Qi” standard, the same that Samsung and other Android smartphone makers use. That said, do make sure when you purchase a charging pad that it is indeed compatible with the technology used in your device to be charged!
Principally you now have 2 competing wireless charging standards groups, the Wireless Power Consortium (WPC) using “Qi” as their marketing name and AirFuel Alliance which includes the likes of Dell, Duracell, Samsung and Qualcomm using similar or alternative RF induction technologies.
The first question that actually comes to fore light is, is it bad to fully charge your smartphone all the time?
Although while you cannot overcharge a smartphone or tablet battery, as the electronics will not allow it, having it constantly charged will hasten its degradation. As a lithium-ion battery charges and discharges, ions pass back and forth between a positive electrode and a negative electrode. As those lithium ions move back and forth, the electrolyte that acts as the transport medium degrades over time. The higher the state of charge, the faster the electrolyte degrades.
Therefore, it’s best not only to keep your smartphone below its top charge, but also to keep the charging and discharging pendulum from swinging wildly. It is said that if you can cycle the battery between 45% and 55% that’s the best thing you can do. The other thing to keep in mind that most smartphone manufacturers design batteries to last two to three years, as most consumer typically replace their phone after that amount of time.
What needs to be understood is, that fully discharging a battery and then fully recharging it often, is not good for battery endurance. Generically a battery should not be left to discharge much below 50%. Having a wireless pad can simply lead to the user recharging the phone more often (as it is convenient vice trying to plug in a cable) and thus this leads to more cycle charges. Batteries are designed for around 500 charging cycles, and thus this “habit” would eat up that quota more quickly.
Further, when wireless charging, and with the device switched on, the battery is under constant use. When connected via cable, (and this is also manufacturer dependent!) the battery is bypassed and thus is not cycling.
But the fact that we charge wireless or wired has no significant difference, except that energy use efficiency is higher when it is wired charging. Wireless losses will always be higher than wired. Although technical development will decrease the difference between the 2 significantly over the coming years. And with the investment being placed on this technology, you will see more and more devices depending on wireless charging, as such the only thing that will ensure extended battery life is good habits and practices in ensuring that your devices batteries are cycled efficiently.