When will your phone charge wirelessly in your pocket? We asked an expert

A main limitation of smartphones is battery life. Despite some improvements in charging speeds and power efficiency over the last couple of years, longer battery life still tops the wish list for most smartphone owners, according to a YouGov poll. Having to plug in and charge our phones every day or two is a real annoyance.

Wireless charging, as we currently know it — through wireless charging pads employing the Qi standard — definitely reduces the friction. It dispenses the need to fumble with wires, but it still requires contact. What we really picture when we hear wireless charging is the prospect of our smartphones charging up in our pockets or bags, with power sent wirelessly across distance.

The technology to achieve wireless charging over distance has been around for a few years. The science is sound. While there are some companies working to increase the range of magnetic induction, which is what Qi is based on, most wireless charging over distance technologies employ radiofrequency (RF) signals. A transmitter sends out the RF signals, much like a Wi-Fi router does, and a small antenna on the device being charged picks it up and channels it into the wireless power receiver.

It definitely works

We have seen several demonstrations of wireless power over distance technology over the last few years from companies like Energous, Ossia, and TechNovator, and it definitely works. But there are some caveats. Qi wireless charging pads take longer to charge our phones than wired connections, and wireless charging over distance is even slower.

The most impressive demo we’ve seen yet came from Ossia with its Cota technology. The transmitters were in two large tiles, a couple of feet across, and they were able to deliver power to a Galaxy S7 (with a receiver embedded) continuously as it moved around the room up to distances of around 10 feet away.

“As you get further and further away you get less power,” Ossia’s Chief Technology Officer, Hatem Zeine, told Digital Trends.

“What you can see is a phone charging at distance as I’m walking around,” he said. “No one else can show you this demo.”

The maximum range is somewhere around 30 feet, but at that distance you can only receive a very small amount of power. Within 6 feet of the transmitter, you’ll get somewhere around 1 watt from the 10 watts being transmitted. At longer distances, you might expect 100 or perhaps 200 milliwatts, which isn’t enough to charge up a smartphone, though it can slow down the discharge.

“I wasn’t trying to do wireless power when I came up with this 16 years ago, I was trying to optimize Wi-Fi,” said Zeine, who is also chief scientist, founder, and chairman of the board of Ossia. “Wi-Fi signals really sucked back then; dead spots in the house and slow speeds were common. As a physicist, I knew using more antennas could improve that.”

Zeine continued to add more and more antennas and found that it not only improved the Wi-Fi signal quite dramatically, but it also had the potential to deliver a useful amount of power. The tiles used in the demo contain 256 antennas each. By adding multiple tiles, it’s possible to boost the distance and the potential power delivery.

He moved freely around the room and the phone continued to charge. It also continued to charge when he placed the receiver in his pocket, because clothes don’t block radiofrequencies.

“What you can see is a phone charging at distance as I’m walking around,” he said. “No one else can show you this demo.”

That’s true, but the first question everyone asks about technology like this is inevitably: “Is it safe?” They want to know that they’re not being washed in dangerous radiation.

So, is it safe?

With Ossia’s Cota technology the receiving device sends a beacon signal to the transmitter which then captures the shape of the incoming wave, and plays it back to deliver power.

This technology achieves the same level of safety as Wi-Fi and Bluetooth, so there is no issue with exposing people.”

“You have to spend power to get power,” Zeine said.

This enables it to bounce RF signals off the walls or ceiling, but also to avoid firing them directly at people. Since our bodies block the beacon signal, which is sent out 100 times per second, the transmitter shouldn’t ever be hitting us directly. But clothes, plastic and rubber don’t block RF, so the technology should work fine when phones are in cases, pockets or bags.

“We have established that this technology achieves the same level of safety as Wi-Fi and Bluetooth, so there is no issue with exposing people,” Zeine said.

You’d be forgiven for not taking his word for it.

“We are working with the FCC very closely, hopefully soon we’ll be able to announce something.”

The path to FCC approval

While Ossia’s demo is more impressive, one of its biggest competitors, Energous, appears to be closer to getting certified as a safe product on the market. The FCC approved the WattUp Mid Field transmitter in December. It’s capable of delivering power to devices up to three feet away.

“What we got in December is FCC approval for Part 18,” Gordon Bell, vice president of marketing for Energous, told Digital Trends.


While Part 15, designed for telecommunications devices, limits power transmission to 1 watt, Part 18 has no limitations on power or distance, provided it can be delivered safely. This means adhering to guidelines regarding things like SAR (specific absorption rate), which measures the rate at which energy is absorbed by the human body when exposed to radio frequencies.

“The amount of power we’re sending out is very small,” Bell said. “It’s much smaller than a lot of things that are already present in your life. When we’re charging a fitness band, we’re charging it at 100 milliwatts maybe 200 milliwatts, while you’re walking.”

There are limitations to what you can safely do, and this is perhaps the biggest stumbling block.

There are limitations to what you can safely do, and this is perhaps the biggest stumbling block for wireless charging over distance technology today. While there are many competitors emerging, winning approval can be tough.

“If they’re going to be on the market, they need to go through the regulatory process,” Bell said. “We’re the only company that does wireless charging at distance that’s public and we’re the only company that vetted the technology through a third-party.”

The only other company that currently has FCC approval is Powercast, which has a range of up to 80 feet.

Other devices will come before phones

Because these technologies are currently delivering a very small amount of power, the companies behind them are not focusing on smartphones. Instead they’re looking at devices like game controllers, remote controls, fitness bands, hearing aids, and headphones.

“The transmitter is not like a Wi-Fi router that blasts Wi-Fi 24/7,” Bell said. “When it’s plugged in, there’s no power coming out of it. What it does is see the different devices within Bluetooth range, sees which ones are close enough to be charged, and checks if they’re authorized on the network.”

wireless charging over distance barriers cota chip
Ossia Cota charging chip Android Authority

The technology can determine a charging schedule automatically, topping up your wireless keyboard and mouse at work, for example, on a Saturday at 4 a.m. when it knows no one is around. The Bluetooth handshake establishes all the details and allows the transmitter to track and target the device. That means you can specify precisely which transmitters should charge which devices, when, and how much.

Energous’ December approval was followed this month by certification for its near field charging, which is a lot like the Qi charging we’re used to, but with a few important advantages.

Foreign object detection can be a problem for Qi. If you have a coin or the metal kickstand of a case between your phone and the charging pad it will heat up and disrupt the charging process. Qi wireless charging is also based on coils which must be aligned, and sometimes your phone is not perfectly placed or slides off the sweet spot. Though this issue has been alleviated somewhat by pads with multiple coils, it still presents design limitations.

“We can get very small,” Bell said. “You see the big coils in Qi, which is not adopted in a lot of different products as it’s too big in some circumstances and needs a flat surface.”

Energous can also put antennas in flexible material like around the watch strap, while the receiver is in the body of the watch.

“Every battery costs 5000x more than the equivalent power coming from the wall socket.”

“With an Apple Watch you have to take it off to charge,” Bell said. “But with the antenna around the strap it could charge up while you’re wearing it and typing at your computer.”

Energous continues to work towards increasing the safe range of its technology, but acknowledges that, at least for now, wireless charging at distance is going to be a trickle charge, not something that can refill your smartphone battery. It might charge up your mouse, headphones, or even your smartwatch at a distance, but for now you’ll want to put your smartphone on, or right next to, the transmitter much like you would with a Qi pad, though you don’t have to be quite as precise.

Ossia is also in talks with phone manufacturers and chip makers, but its first product is likely going to be the Forever Battery. It’s a smart retrofit solution that could allow us to keep our remote controls, toys, and smoke detectors working without ever having to swap batteries. This product also combats one of the main criticisms of wireless power over distance, which is its massive inefficiency.

wireless charging over distance barriers hatem zeine ossia getty
Ossia Chief Technology Officer, Hatem Zeine Steven Jennings/Getty Images

“A single disposable battery gives you 1-watt hour and costs 50 cents,” Zeine said. “1 kilo watt hour from the wall socket costs 10 cents. Every battery costs 5000x more than the equivalent power coming from the wall socket.”

Even with the power loss over distance, a Cota transmitter powering a battery would still be more efficient than a disposable battery. It’s easy to see how this argument could extend to IoT sensors and other devices with modest power needs.

Ossia is working with Motherson Innovations to build transmitters into car dashboards to power sensors and smart mirrors that currently need to be wired. It’s also in talks with retailers about electronic price tags.

When do we get wireless charging over distance then?

Energous showed us various concepts, suggesting that transmitter antennas might be embedded in things like TV bezels, lighting, smart speakers, or sound bars.

“We see our technology coming into the home embedded into devices you already have,” he said.

To that end, the company has partnered with Dialog Semiconductors to integrate the technology into a chipset that device manufacturers can buy off the shelf. Though we know Energous has been working with a big phone manufacturer that will license their technology – there were rumors it’s Apple – there’s no telling when they’ll deem it ready for primetime.

“When you’re introducing a brand-new technology into an emerging market, you get a bunch of people who want to be super secretive about what they’re doing because they think they’ve got an edge to help them differentiate their product,” Mark Hopgood, senior director of Strategic Marketing & Corporate Strategy at Dialog Semiconductor, explained to Digital Trends.

Big companies are happy to let smaller players be first to market with new technologies like this, because they represent some serious risk.

“Very few tier ones are risk takers,” Hopgood said.

“This year is the year that we’ll see products from partners and 2019 will see a broader launch.”

Perhaps it shouldn’t be a surprise, then, that the first product announced that will use Energous’ WattUp charging was Myant’s Skiin fitness tracking underwear. Bell assures us more will follow.

“This year is the year that we’ll see products from partners and 2019 will see a broader launch.”

Make no mistake, wireless charging over distance is coming, but it’s going to start small. Once the technology has won regulatory approval worldwide and some smaller manufacturers have proven its effectiveness in niche devices, we may finally see a major player step in and integrate it into their next flagship phone.


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