Mobile Phone Without a Battery

The quest for better batteries may be the ultimate technology industry arms race as phones, cars, and other power-hungry devices proliferate in our lives. But researchers at the University of Washington may have upended that equation, making what they say is the first cellular call from a mobile phone with, well, no battery at all.

The prototype phone, built with off-the-shelf components, runs on a combination of wireless power and tiny solar chargers. It’s certainly barebones: the phone can send and receive voice signals, drive a pair of head phones, and not much else. It has neither screen nor memory. Once you connect a call using the device, you have to push a button to talk.

The phone must rely on a nearby base station that relays its signal to the cellular network, in this case via Skype. The base station provides the bulk of the phone’s operational power, which the phone harvests from radio signals.

The phone generates its own signal using backscatter, a technique already common in RFID—as in radio frequency identification—chips that encodes existing radio signals with new information and reflects them back to a receiver.

One of the phone’s key innovations is the use of analog rather than digital voice encoding, which the researchers say saves a substantial amount of power. Supplemental power to increase the device’s range comes from photodiodes, essentially tiny solar panels.

In short, don’t expect to play endless games of Candy Crush on this device anytime soon. But the researchers envision a future where similar wireless technology is widely integrated into cell towers or Wi-Fi routers, making battery-free phone calls ubiquitous—assuming, of course, that we don’t give up on voice calls entirely in favor of text messages, Snap Stories, or other communications methods.

The phone is described in detail in a research paper published on June 30th.


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