Wireless charging is becoming more prevalent and integrated into daily life, as modern day society morphs into a lifestyle of convenience.
The latest example? The split second saved by placing your phone on a wireless charger instead of plugging in a charging cord.
Wireless Charging in Modern Technology
Wireless charging did not become mainstream in phones and mobile devices until relatively recently. Samsung first introduced integrated wireless charging in a mobile phone in their Galaxy S6 & S6 edge models in 2015. In 2017, Apple released the iPhone 8 with wireless charging capabilities.Wireless charging existed with many products before it debuted in mobile devices: headphones, kitchen appliances, and power tools are all capable of charging without a cord being connected. True, there is a wire connecting the wireless charger to an outlet, but the device does not have to have a cord, making it less of a hassle to charge.
Who Invented Wireless Charging?
Though it has only started to integrate with consumer electronics in recent years, wireless charging technology has actually been around for over 100 years.How Does Wireless Charging Work?
Magnetic Induction
Inductive wireless charging uses a low-frequency oscillating field between 110 and 205 kHz to generate an electric current with a magnetic field. It transfers power easily between non-resonant but closely coupled coils.The process behind wireless charging through magnetic induction is pretty straightforward. When a device with a wireless receiver coil is placed directly on top of a charging pad with a transmitter coil, the device battery is able to charge by intercepting the magnetic field created by the charging pad. The larger the coils, the larger the magnetic field.
The benefit? Very high efficiency when the coils are perfectly aligned, with 30-60% of the energy created being transferred to the receiver coil.
The drawback? The coils must be closely coupled and precisely aligned; even a vibrating text message can move the phone enough to stop the magnetic induction.
Resonant Wireless Charging
The Massachusetts Institute of Technology (MIT) sought to improve the efficiency of the inductive wireless charging system detailed above. They came up with a more complex way to transfer power between two coils operating at the same resonant frequency.This method generates a higher frequency oscillating magnetic field of 6 MHz (6000 Hz). While it is still inductive, since the current in the first coil induces a current in the receiver coil, it uses the resonant coils’ strong coupling to allow the coils to be tens of centimeters apart.
The benefit? Multiple devices can charge in close proximity, and there can be a greater distance between the coils.
RF Wireless Charging
Another form of more recent wireless charging uses radio frequency (RF). Instead of simply producing an electromagnetic field, the charger radiates EMF waves or radio frequencies. It transmits energy to the device via radio frequency waves, and the device converts that energy to electricity, which charges the device.RF charging provides the opportunity for far-field charging, which allows for an increased distance between the charger and the device, for more than one device to charge at a time.
While RF charging hasn’t deployed in commercial products yet, it has been shown to charge multiple phones simultaneously up to 15 feet away. This type of wireless charging is potentially the most harmful, since a device is sending higher frequency EMF waves through the air to a device far away.
EMF Radiation Concerns for Wireless Chargers
Wireless device charging that harnesses magnetic induction creates a pretty small electromagnetic field that’s only a few millimeters wide, and is between 5 and 15 watts.When a wireless charger is simply plugged in, it actually only emits trace levels of ELF. When your phone is sitting on the charger and the coils are aligned, the transfer of energy increases emissions to around 3 milligauss (mG).
Let’s compare that to other devices you might have around your house.
The EPA advises to keep daily exposure to under 4 mG, although we recommend a limit of 2 mG to be extra cautious. An inductive wireless charger sits right in that gray zone, meaning it shouldn’t be ignored, but it also isn’t a big concern. However, if you are sensitive to EMF radiation, you may be at risk of experiencing negative symptoms.
Resonant and RF charging, however, allows for more space between the charger and the device, meaning more power and higher frequencies, transmitting over a longer distance.
As the capabilities of wireless chargers grow to more complex models that can charge over longer distances, the EMF radiation produced will only intensify, thus increasing the health risks associated with wireless charging.
What We Recommend
Stick to cords. Having wired devices is always better than wireless because it eliminates a source of transmissions. Plugging in your device takes only a second or two, and because most of us are constantly surrounded by various sources of EMF, anything we can do to reduce the number of sources will benefit our health in the long run.Our Final Take?
The small increase in convenience of placing a phone on a charger instead of plugging a charging cord into your phone might not be worth the cost for most of your devices.Plus, they can be annoying. You can’t really use your phone while it is charging, and you might have to remove your phone case (*note: DefenderShield cases are not compatible with wireless charging stations). For Qi inductive chargers, they have to be perfectly aligned to get an efficient charging experience.
Overall, wireless chargers—while actually a pretty safe wireless accessory—still add to the ambient radiation in our everyday environment, and we wouldn’t recommend being in close proximity to one for a long period of time.
