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For the past month or so, my electric toothbrush has been charging wirelessly, but not the way you think. My toothbrush charger is not plugged into an outlet. There are no wires or cables. The charging cradle can sit anywhere on the bathroom counter and continue to charge my toothbrush. This is because I am beta testing a prototype from Wi-Charge, an Israeli company that employs infrared technology to deliver wireless power across distances of up to 30 feet.
Several companies have demonstrated wireless power over distance in the past decade, but tangible products have failed to materialize. More than a century has passed since Nikola Tesla thought up the idea of transferring electrical energy through the air, so you could be forgiven for thinking it's simply not feasible (or at least not profitable) to implement. I've been watching this space for over five years and have grown increasingly skeptical.
But now I have a working example in my home. While most distance wireless power technologies rely on radio frequency transmission, Wi-Charge sends focused laser beams of infrared light. The advantage is higher efficiency and power delivery up to 2 or 3 watts, but the catch is that the technology requires a line of sight to a receiver. I'll dig deeper into the pros and cons, but here's a look at what it's been like to live with this technology, and how it works.
Wireless Wonder
The Wi-Charge receiver is a little bigger than a regular toothbrush charger. It has a photovoltaic cell (like a tiny solar panel) measuring 1.5 x 1 inches, and it harvests power transmitted by a puck-shaped device embedded in the ceiling. The transmitter resembles an oversized recessed spotlight and can power multiple receivers within the 80-degree cone beneath it. For example, a single transmitter could supply up to 10 toothbrush chargers. The maximum range is around 30 feet, but in this case, the transmitter sits around six feet above the receiver.
To install the system, I had an electrician add an outlet in my loft and cut a hole in the bathroom ceiling for the transmitter. A light on the transmitter turns green when it's powered but not charging. Both the transmitter and receiver display a blue light when connected and when charging is in progress. The toothbrush charger has a 500-mAh battery inside, which the transmitter keeps topped up.
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My family has been charging two regular Oral-B electric toothbrushes (used twice every day). The transmitter has kept them both fully charged for the past five weeks. When I block the line of sight with my hand or move the receiver, the transmitter goes green and stops charging immediately. With the line of sight restored, it usually takes a few seconds, occasionally up to a few minutes, to turn blue and start charging again.
I’ve tried various positions on the countertop, and it works as long as it has a line of sight. The top of the receiver has occasionally gotten toothpaste smears, but I’ve wiped it clean with a wet cloth. It stopped working for a day or so in the first week, but Wi-Charge pushed a firmware update, and it has been smooth sailing since. The transmitter also connects to my Wi-Fi network, allowing Wi-Charge to remotely monitor, debug, and tweak the system.
Cost of Convenience
Wireless power over distance is sometimes described as a solution in search of a problem. In this case, it’s a convenience rather than a necessity. UK bathrooms cannot have regular power outlets, only shaver electrical sockets, and we don’t have one in ours. I'm quite happy that we don't have to rely on a line of toothbrushes charging in the upstairs hall anymore—our carpet has seen a sharp downturn in toothpaste stains too.
The electrician who installed the Wi-Charge receiver did point out that it would've been easy to install a shaver socket to power the toothbrush charger, but it would still have a cable. I love the elegance of a truly wireless charger like this. No unsightly wires to hide, no tangle of cables to negotiate. But this convenience comes at a cost.
I used an Emporia smart plug to track the transmitter’s energy usage. The smart plug also lets me turn the Wi-Charge system on or off remotely, though I have left it on all the time for the past month. With an average draw of 7 watts, it has been pulling roughly 1 kilowatt hour weekly. Here in Scotland, that costs around 30 pence (£15.60 per year). In the US, the average cost for 1 KWh is 17 cents, but you could pay up to 30 cents depending on your state. At 17 cents, the cost is less than $9 a year. But remember—I'm just using this for two toothbrushes.
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I tracked a regular toothbrush charger with two toothbrushes on another smart plug to compare. Extrapolating that data, it would use around 5 kWh for the year (£1.50 for me, or less than $1 in the US). Much depends on your toothbrush, and smart plugs are not always accurate, particularly with small variable loads. But you get the idea.
Wi-Charge says the current power usage is higher than in a finished product because the development kit is always on and sending data for the beta test. Without telemetry, only powering on when required, the company says it will use at most one-fifth the power, bringing the cost down to around $1 or $2 a year for a single toothbrush.
Blocking Wireless Power
There are several good reasons why wireless power over distance has yet to take off, and why, even with proven examples, enough obstacles remain to encourage healthy skepticism. To simplify massively and pick just two: It is inefficient (much of the power transmitted is lost), and only relatively small amounts of energy are realistic with current limitations and safety in mind. Wi-Charge may be ahead of the competition on these points, but it is still not as efficient, as capable, nor as safe as a wired connection.
You can argue that inductive coupling is common, and we accept inefficiency where it brings convenience. The wireless chargers we use with our phones are not as efficient as cables, for example, and we connect to Wi-Fi rather than use Ethernet. But it’s hard to paint that as a good thing given the current climate crisis. If our power came from renewables, it wouldn’t necessarily be a problem, but we are not there yet. (For the record, I am lucky enough to have solar panels, and my energy pro, Octopus, delivers 100 percent renewable electricity, but I’m in the minority.)
There are scenarios where this technology can be an eco-friendly alternative. One of the few places wireless power over distance is already working is for electronic price tags (e-ink that shows pricing) in retail stores. It is far more environmentally friendly than disposable lithium coin batteries. Ditching the batteries in small devices could also reduce lithium demand and problematic e-waste. Even cables require mined resources and have an energy production cost.
In some cases, devices might switch to supercapacitors, but even where they retain a rechargeable battery, technology like Wi-Charge could help extend battery life. Charging slowly and keeping a battery between 20 and 80 percent can significantly extend its useful lifespan. But these are all potential benefits. Much depends on how the technology is used. I can’t see any positives in retail stores installing advertising screens (something else Wi-Charge has prototyped), for example.
As for safety concerns, Wi-Charge has FDA and UL approval in the US, and UL and IEC approval in the UK. Wi-Charge CBO Ori Mor told me that the FDA and UL certified the technology as “safe under all conditions.” Unlike technologies based on radio frequency transmission, Wi-Charge transmits power in a narrow beam focused on the receiver and cuts out when the line of sight is blocked, minimizing potential exposure for people.
It's Finally Coming … Maybe
The toothbrush charger is still a prototype. Wi-Charge is widening the beta test, and I have agreed to test the next version. While it remains to be seen whether manufacturers will take this beyond the research and development phase, what many have written off as vaporware is beginning to solidify.
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Wi-Charge has partnered with Alfred Smart Locks. Its ML2 Smart Lock is on the market, using a similar but lower-power Wi-Charge transmitter to the one I tested. The price is not public, and the cost of Wi-Charge as an optional extra depends on the installation. I have inquired, but the old adage about having to ask occurs. (We can safely say north of $1,000).
Aside from toothbrush chargers, touchless faucets are another bathroom-based device that could work well with Wi-Charge. Security cameras and video doorbells seem like low-hanging fruit after smart locks. Any device with modest power requirements and space for a receiver is a possible candidate. Mor likens the manufacturers to penguins huddled on a rock getting ready to swim. He believes when one or two dive in, the rest will follow.
It does feel like a chicken-and-egg situation. A single transmitter can serve multiple devices, but you need devices with infrared receivers to make it worthwhile to buy a transmitter. If you have only one or two gadgets with receivers, would you want to drop $300 on a transmitter? Will device manufacturers want to sell transmitters alongside their devices?
Sadly, many small devices you might immediately imagine benefitting from wireless power over distance, like earbuds, won’t accommodate a Wi-Charge receiver (though they may work with other kinds of wireless power). Realistically, a limited charge like this is not enough to justify the expense for larger devices like smartphones or laptops. To get a line of sight, you’d need to put your smartphone down, and if you’re going to do that, you may as well put it on a faster and cheaper Qi charger. Incidentally, Wi-Charge has a prototype Qi charger with a battery that can charge from a transmitter. It could appeal where power outlets are in short supply or cables present a problem.
While I’m not bullish about wireless power over distance in the short term, having used Wi-Charge’s technology I can see a future path emerging. I couldn’t justify the expense of an installation like this, but high-end rentals and wealthy smart-home pioneers are different. I can see it carving out a niche, and say some clever manufacturer finds a way to fold the technology into a light bulb replacement, that would be a much easier sell for folks. If a big enough penguin takes the plunge, who knows?
