Keep your phone charged for 30% longer

The Ohio State University has developed technology that makes mobile phone batteries last up to 30% longer on a single charge. The patented circuitry converts some of the radio signals emanating from a phone into direct current (DC) power, which then charges the phone’s battery.

“When we communicate with a cell tower or Wi-Fi router, so much energy goes to waste,” explained Chi-Chih Chen, research associate professor of electrical and computer engineering. “We recycle some of that wasted energy back into the battery.”

According to Robert Lee, professor of electrical and computer engineering reckoning, nearly 97% of mobile phone signals never reach a destination and are simply lost. Not all of it can be recaptured, but some can.

“No-one can charge a cell phone from the air, but we can reduce power consumption by retrieving some of those lost milliwatts,” said Lee. “Think of it as a battery extender rather than a charger.”

The idea of converting radio signals into battery power relies on the fact that radio waves are actually just a very high-frequency form of alternating current (AC). The power grid supplies AC, but most devices need DC to operate. So electronics manufacturers use a special kind of electrical circuit called a rectifier to convert AC to DC.

Today’s portable devices broadcast radio signals - that is, high-frequency AC - a portion of which the Ohio State rectifier system captures and converts back to DC. The trick is to siphon off just enough of the radio signal to noticeably slow battery drain, but not enough to degrade voice quality or data transmission.

But there’s plenty of wasted radio signal to utilise, as mobile phones broadcast in all directions at once in order to reach the nearest cell tower or Wi-Fi router. Chen and his colleagues came up with a system that not only identifies which radio signals are being wasted, but efficiently gobbles up the maximum amount of them that won’t compromise phone function.

It works only when a phone is transmitting - when a person is sending email, texting or talking on a phone. Phones expend most of their energy in voice and data transfer, so the rectifier helps out by slowing battery power loss by up to 30%.

Lee noted that there are some products that harvest stray radio signals to charge tiny wireless devices such as temperature sensors, but claimed the Ohio State invention is many times more powerful and efficient.

“These other devices are trying to harvest little bits of energy from the air,” he said. “Our technology is based on harvesting energy directly from the source. They can capture microwatts or even nanowatts, but cell phones need milliwatts or higher.”

Chen joined with Lee as well as John D Bair, Rodolfo Bellesi, Flavio Lobato and Will Zell to form Nikola Labs, the company that will develop the technology through a Kickstarter campaign to be launched in June. Researchers estimate that it will cost around $100.

The engineers plan to insert the rectifier system into a ‘skin’ that sticks directly to a phone. Eventually, they would like to partner with a manufacturer to build it directly into a phone, tablet or other portable electronic device.

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