# Oxford startup magics up metamaterials for next-gen charging

Imagine throwing your phone onto a car dashboard or table, knowing it'll power up. And imagine that tabletop or dashboard powering up several randomly aligned devices at once. Above an unassuming street in Oxford, engineers are ironing out the problems. Metaboard with three smartphones Metaboards labs testing gear: the LEDs …

1. I thought one of the problems was that wireless charging is more wasteful which usually manifests itself as heat, which as anyone knows is murder on these batteries...especially those that can't be replaced by the user when (not if) they start to break down.

1. I was going to make a similar comment - what is the electrical efficiency of such a system? Charging systems are bad enough as it is without introducing another wholly inefficient coupling system 'just for convenience'.

1. "What is the electrical efficiency of such a system?"

About 83% - that's the power into the transmitter unit vs. power out of the receiver. Your AC to DC conversion to supply the transmitter and the battery current to battery charge conversion are separate. To put it in perspective: your average phone charging at 2A consumes 10 watts from a 5V USB supply. If we are using a USB cable with 28AWG/0.32mm wires, the resistance of a 1m long cable is 0.212 ohms for a loss of 1.7W (two 1m long runs - supply and return). In comparison, the wireless charger has a system loss of 2.0W if adjusted to give 10W output.

A datasheet for a typical system is here:

There are some pretty clever ways they can detect foreign objects on the transmitter antenna.

2. Yes, wireless charging is an insane proposal in a world that is already choking on carbon emissions from coal plants.

Check it out here.

3. #### @Charles 9

Yes, it's inefficient, but that's because most of the energy emitted from the charging pad doesn't reach the device. So it won't be the battery that heats up, it'll be the pad* and anything else conductive within range.

* Only slightly - you're not going to burn yourself - but it's still a waste, particularly if you think of 50 million phones in the UK alone being recharged almost daily.

1. #### Re: @Charles 9

@Chris Miller

I think Charles is right, not necessarily because you are wrong but batteries warm as they charge anyway and becasue the phone is also sat on the warm pad everything heats up just a little bit more from being in direct contact with it. Further to that I expect that if left on the pad after charging will probably stay warm for longer too

1. #### Re-use

If said charging phone can tap into your smart heating to reduce the boiler very slightly (in fact this is unnecessary as we all have thermostats) then this heating is only lost in summer. For the most part charging overnight is (housewise) energy lossless. Same with those old light bulbs. The energy isn't wasted.

2. #### Disco Dancing.

I like hovering my phone above the pad in the pub and explaining the history, physics and chemistry plus creating a flashing light and generally looking the business. With £5m you can have anything you like up north. #thebigNkeepgoing

3. #### I have another theory

I have one, and I do use it, but I dont think its mystery why Qi pads havent taken off

1. they cost more than a standard cable

2. most are slower than a standard cable

3. for the environmentally concious they take up more resources than a cable and are less energy efficient

4. its just one more item of clutter in the home - and it still needs the same cable sticking out of it

5. its a proper first world problem that doesnt really need a solution (it not actually that hard to plug in a phone esp usb c)

6 if you charge on the move its yet another thing to take with you

7 if you charge in multiple locations and dont take one with you thats multiple more charging pads to buy

1. #### Re: I have another theory

8. If you use a case you typically have to remove it

1. #### Re: I have another theory

9. its difficult to continue using the device whilst its charging.

1. #### Re: I have another theory

9. its difficult to continue using the device whilst its charging.

This is why I didn't go back to wireless charging after my Palm Pre (a decade ago!). While it was rather nice to be able to just throw the phone onto the charging pad and not have to deal with fiddly little connectors, if you wanted to use it you'd have to take it off the pad which obviously stopped charging. Now with Lighting/USB-C, the "big hassle" - looking at the end of the connector to see which way to insert it - is behind us. I suppose there is still an argument to be made about connector longevity, but that still isn't enough to get me to switch back over to wireless.

1. #### Re: I have another theory

There's only one reason I'd use Qi charging: to free the port to use USB On-the-Go. Simply put, you can't charge and use USB OTG at the same time (the design prevents this, so don't believe any ads). Thankfully, someone thought about that and at least one tablet I use has TWO USB Micro sockets: the second dedicated for OTG use.

2. #### Re: I have another theory

10. It avoids wearing out the USB port/cable end which although isn't a huge deal on my Nexus 5, it's a big enough deal that I would rather avoid it.

1. #### Re: I have another theory

If you fear for the longevity of your phone connector, there are other ways to do it, including 90-degree pigtails that fit neatly into the socket and then run a short bit up the back, leaving only a minor inconvenience. Besides, USB Micro and Type C connectors are designed to focus the stresses on the plug more than the socket.

3. #### Re: I have another theory

Totally agree. I remember saying that I thought wireless charging was useless and some people said I was only saying that because I was an iPhone user and was excusing Apple being behind Android on that front. Others said wireless charging was a niche then only because it hadn't reached critical mass, but once Apple went all in and sold 200 million wireless charging capable phones in a year the market would explode.

Well, Apple is selling those 200 million wireless charging capable phones a year now, but I still think it is useless and it still hasn't taken off. Clearly it isn't a market that was waiting for critical mass of phones to increase adoption. The only place where I think wireless charging makes sense is mousepads, so you'd never need to recharge your wireless mouse. One designed to sit under a laptop and keep it charged while you use it wouldn't be bad either (be nice to build into cubicle desks in an office)

Having a mat next to your bed might sound more convenient than fumbling for the cable in the dark, but if there's any waste heat your cat will claim the spot and push your phone off onto the ground during the night, eventually cracking the glass back!

4. #### Re: I have another theory

> 3. for the environmentally concious they take up more resources than a cable and are less energy efficient

We don't need to worry about efficiency as standardized ubiquitous wireless charging should become available around the same time as nuclear fusion starts feeding the power grid. So, 50 years or so?

4. #### Great news, then

We're going to get mass wireless charging by next year, instead of getting any of those recharge-in-a-minute carbon nanotube batteries we've been promised for a decade.

Figures that we'd get a more wasteful way of recharging before getting a better way of storing energy.

5. #### "that turned a surface into a speaker"

After all, the Vogons managed to do it - how hard can it be?

6. Above an unassuming street in Oxford...

I know Oxford moderately well, but I never realised the streets could be rated according to their pretensions. I read to the end of the article in the hope that the unassuming street would be named, but it wasn't, so I'm left speculating.

Obviously streets like High St, Broad St, St Aldate's and St Giles are among the most assuming. I suppose the unassuming ones are too modest to have attracted attention.

1. It's a very positive indicator, as we know that assumption is the mother of all f*ck ups

2. #### Well--

Using the wonders of "t'web" I see 23 Park End St, down by the station. Definitely unassuming.

1. #### Re: Well--

> Using the wonders of "t'web" I see 23 Park End St, down by the station. Definitely unassuming.

Well not any more. Now you've spoiled it.

2. #### Re: Well--

Funnily enough, I wondered whether to cite Park End St as an example of an unassuming thoroughfare. I used to know someone with a flat there.

7. #### So much research for waht?

It's a pity that all this research efforts are wasted to circumvent the standardized recharging and create another expensive recharging system incompatible with what people can easily find wherever they go.

8. #### I^2 losses

I have never really understood the hype over wireless charging, or as we used to call them, air core transformers. And if you have a device so equipped, can't you just charge it anywhere there is some spare EM floating around, like a wall wart or pretty much any electrically powered device, anywhere, anytime, for free??

9. Oh joy... more gadgets we never knew we needed, chucking out RF in the HF bands...

10. #### Niche use case

If you have a working USB port then why do you need this wireless charging?

It comes into its own when you drop the device and it lands on the USB plug and buggers the internal connection.

I thoughts I had been robbed when I bought the charging stand for my Sony Xperia tablet and found that it blanked off the USB port when charging through a couple of external contacts. I thought I could connect USB devices and use it like a little PC.

A few years later and an accidental breaking of the USB port and I can still charge it. Saving me from a tech refresh (or a repair which may or may not work). I know you can prise the back off and get at the internals but long experience suggest that when you go down that route you end up with new and different problems.

1. #### Re: Niche use case

Niche indeed.

The only real benefit that i can think of from wireless charging is that now that most* phones don't have a headphone socket, but give you a nice usb - headphone dongle, then you can plug your headphones / speakers/whatever in, and still charge.

Good for in a car, you can have wireless pad (plugged in by a wire into the cars USB socket) and the phone plugged into the stereo

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