Cellphone dead? This phone makes battery-free calls

Researchers at the University of Washington have developed what they call the first battery-free cellphone.

University of Washington researchers have built a phone that requires almost no power

The battery-free phone gets the minimal power it needs by harnessing ambient radio signals or ambient light. (Mark Stone/University of Washington)

One of the biggest challenges with cellphones is maintaining battery power, but new research is developing the technology for a battery-free phone.

Researchers at the University of Washington have developed what they call the first battery-free cellphone, which they discuss in an article published earlier this week in Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies.

Lead author Vamsi Talla told CBC News that, although the prototype doesn't work exactly like a standard phone, there are a lot of possibilities from a battery-free phone.

This battery-free technology could be useful in places where getting an electrical charge is difficult, he said, and could create a phone that lasts longer because it's not dependent on the shelf life of the battery.​

The main benefit would be the ability to make a phone call even if a cellphone's battery is low or even has zero power, Talla said.

The team created the phone from scratch, because existing phones use too much power to be modified to operate without a battery, he said.

"By re-engineering the way a cellphone operates, we can get down the power consumption to a few microwatts, which is about 1,000 to 10,000 times lower than a cellphone uses," he said. 

Low power needs

Battery-free calling operates by turning vibrations from a phone's microphone into analog signals that go to a customized base which then sends the message back to whoever is receiving the call, Talla explained. This base could potentially be built into existing cellphone towers or even Wi-Fi routers.

For their prototype, researchers made voice calls using Skype, sending information over an existing internet connection, Talla explained. 

To make the battery-free phone use minimal power, the device gathers the 3.5 microwatts it needs from ambient radio signals or light — the phone doesn't have its own radio signal or send information digitally, Talla said.

Sending analog information instead of digital saves a lot of power, he said.

Not a smartphone stand-in

Talla doesn't expect the battery-free phone to replace the iPhone or Android phones anytime soon, as great as it sounds to not need to recharge your phone.

"It's very unlikely you'll be making battery-free calls all the time," he said. "But I expect if your battery is low or your phone is dead then it's a good fail-safe mode to have where at least you can be guaranteed some options."

The current prototype is very basic, and in its first phase operates more like a walkie-talkie, with the user talking only or listening only, Talla said.

However, he said the technology is capable of a standard phone call where someone can talk and listen at the same time. The researchers are also developing a display similar to the Kindle for the phone as well as a camera, he said.

"It could be a complementary technology that gives you some functionality if the battery is low or you run out of battery."