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Wireless charging has an efficiency issue

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Editor’s take: Modern flagship smartphones are increasingly turning to wireless charging as a handy alternative to plugging in a physical cord to juice up. While the feature can be convenient, two major shortcomings – efficiency and range – will likely need to be addressed before wired chargers become obsolete.

On paper, wireless charging has its benefits. Being able to simply plop your phone down on a mat to recharge eliminates the potential for wear and tear on charging ports and cables. Others favor it due to sheer convenience.

But according to a recent report published by Medium’s OneZero, wireless charging is far less efficient at delivering power than you may realize.

Eric Ravenscraft used a Google Pixel 4 to test multiple wireless chargers and compared their efficiency to a standard block charger with a wired connection. To measure power draw, he used a “high-precision power meter” that sat between the charging block and the power outlet.

Charging from completely dead to 100 percent with a cable used an average of 14.26 watt-hours (Wh). With a flat Yootech wireless charger, Ravenscraft said a full recharge consumed around 21.01 Wh on average, or more than 47 percent more energy.

Worse yet, power consumption increased even further when the phone wasn’t perfectly aligned on the charger.

Results were a little better with Google’s official Pixel Stand charger, as it eliminates the possibility of vertically misaligning the phone during charging. In testing, the Pixel 4 consumed an average of 19.8 Wh. Still, that’s nearly 39 percent more power versus using a charging cable.

Also worth noting is the fact that both wireless chargers consumed a small amount of power even when no phone was being charged. Over a 24-hour period, this standby power draw amounted to around six Wh. In comparison, the standard charger cable didn’t exhibit any measure amount of standby power draw.

The extra power consumed by charging one phone with wireless charging versus a cable is the equivalent of leaving one extra LED light bulb on for a few hours. It might not even register on your power bill. At scale, however, it can turn into an environmental problem.

To get an idea of what it would look like at scale, Ravenscraft consulted with the crew over at iFixit.

Arthur Shi, a technical writer for the repair specialist, said that, “at 100% efficiency from wall socket to battery, it would take about 73 coal power plants running for a day to [wirelessly] charge the 3.5 billion smartphone batteries [in the world] once fully.” Now assume that everyone put their phones on the charger wrong and efficiency was cut in half, you’d suddenly need double the number of power plants in order to charge all of the theoretical batteries.

Image credit: Nor Gal, Andrey_Popov



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