Phone can make calls without battery

If it becomes a reality, the practical applications of the new technology are virtually limitless. But to get there, the research team at the University of Washington still has a long way to go before commercializing this product.

“Hello, hello, I’m calling from a battery-free phone,” was the message Vamsi Talla transmitted from inside a busy lab at the University of Washington in Seattle. And Talla’s greeting was heard coming from a nearby Android phone. This was revolutionary, because the cell phone Talla used to make the call had no battery.

According to Wired, the prototype phone (without battery) below is the best result of years of research by Talla, who is currently a research associate in the lab of Joshua Smith (a computer science and electrical engineering researcher at the University of Washington).

“If you had to choose a device that didn’t use a battery, what would you choose?” Smith asked, adding: “Mobile phones are one of the most useful things in the world. Imagine how great it would be if your phone ran out of battery but you could still send texts and make calls.”

The new vision forces us to rethink how our current mobile phones work. In order to operate without a battery, the phone would have to draw some energy from its surroundings.

Ambient light can be converted into electricity using solar panels or semiconductor photodiodes. Radio frequencies from TVs and Wi-Fi waves can be converted into energy using antennas.

A hybrid system using both technologies can generate power of around a few tens of μW (micro Watt). The problem is that a traditional mobile phone when making a call uses much more power, around 800 mW (Mili Watt).

Prototype phone that can make calls without using battery.

The first thing the team had to tackle was communication. Smith's lab developed a technique called "backscatter," which allows a device to communicate by reflecting radio waves back to it, much like an injured hiker sending a distress signal using a mirror and sunlight.

Smith also developed a solution called Jeeva Wireless and commercialized what he called “passive Wi-Fi” technology—which used digital “backscatter” techniques for ultra-low-power Wi-Fi devices. However, even low-power “passive Wi-Fi” was not enough for the mobile phone his team was pursuing.

“Converting human speech from analog to digital consumes a lot of power,” says Talla. “If you could communicate using analog technology, it would be really energy efficient.” So while cell phones use digital signals to dial, the “backscatter” process for calling uses analog signals.

While developing the technique of “Backscatter” using analog signals, Smith realized that he was reinventing the spy technology used during the Cold War. In 1945, the Soviet Union presented the US Ambassador in Moscow with a gift in the shape of the Great Seal of the United States. Inside it was a listening bug, activated by radio waves of a precise frequency, and powered by the energy of those radio waves.

"My dad was a spy during the Cold War, so I heard stories about the Great Seal when I was a kid," Smith said, adding, "I wondered if it was possible to use software to control the operation of the analog "Backscatter" technique, turning what was once a seemingly esoteric curiosity (only known to those who read about espionage stories) into something everyone could use."

Like the bug used in war, some of the key components of the phone under study are located far away to save power. A nearby base station has circuitry to convert and connect to the digital cellular network, currently via Skype.

The prototype base station uses unlicensed frequencies, limited to low-power transmissions. And because the phone draws power based on the signal it receives, the base station is currently only about 15 meters away from the phone.

To commercialize the phone, it would be necessary to create a switching circuit system inside a home Wi-Fi router or traditional base station. "Traditional base stations are a hundred times more powerful, which can increase the distance (between the phone and the base station) up to 1km," said Talla.

There’s still a long way to go before that happens. The phone we’re testing has only a few basic touch buttons, and its only “display” is a tiny red LED that lights up when a key is pressed. A larger touchscreen would require around 400mW—about 100,000 times the power of the phone Talla has in his hands right now.

Most importantly, making calls is still a pain. You have to press a button to switch between listening and talking walkie-talkie style, and making calls through clouds of static is impossible.

Talla promises better call quality and a next-generation E-Ink display, with the ability to add a camera for selfies. Smith says the team bought the components for the prototype off-site, but they’re much cheaper than regular phones, and if it were built on an industrial scale, it would be cheaper. And best of all, you’ll never have to worry about leaving your charger at home again!

According to VnMedia