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That is a good question but if you look at this:
https://www.wirelesspowerconso...

There are surprisingly few phones that are certified for > 5w Qi charging. I'm guessing there's gotta be a reason for that.

It's a lot slower than a wire. but the fundamental reason it really sucks is, THERE IS STILL A WIRE that goes to whatever wireless charging plate you have. I would way rather just have a small cable with me that I can plug into any USB slot, which are in quite a few places now, since I have to have a wire anyway.[/quote]

I would not mind it to save wear and tear on the physical charging connection.

The apple product in particular also did not seem very useful to me in that what I set stuff down by the bed at night I don't necessarily want everything flat. I have a stand I can leave the watch on to charge so it's at a nice angle to read, and even the phone I would prefer angled up so I could quickly glance to see in the morning if I have important messages waiting.

Sounds like an opportunity to sell a second device.

It is kind of funny to watch Apple stalinize a product though... it's like, dude, just admit it didn't work out!

You can read some more details about the technology at the links below:

https://appleinsider.com/artic...
https://www.wirelesspowerconso...

It looks to me like Apple got scammed because of lack of engineering review. The tests were only done under small signal conditions where efficiency on the transmitter's side is not a problem.

Relevant is: how much energy does an EV comsume while [traveling]

I will now attempt some back-of-the-envelope calculations. Corrections cheerfully accepted if I screw anything up.

Desired: a highway that can use solar power to drive all its traffic. We assume all traffic is electric cars of comparable efficiency to a Tesla Model S. (Note: the article specifically said that the road was to have no heavy trucks on it.)

Rule of thumb: one kilowatt-hour is good for about three miles of driving. (It's actually a touch higher than that but reasonably close to 3, and 3 makes the math easier.) So assume we need something like 330 watt-hours per mile. Converting to metres, we need about 0.205 watt-hours per metre.

But we can't wait an hour to get it... at 60 miles per hour it takes one minute to drive a mile, and one second to drive 1/60 of a mile. Converting to metres we get 26.8 metres per second. Therefore in a second of driving we will need 26.8 * 0.205 == 5.5 watt-hours. There are 60 minutes in an hour, 60 seconds in a minute, so 3600 seconds per hour. To deliver 5.5 watt-hours in one second we need 5.5 * 3600 watts, or 19800 watts.

If Solandri did the math correctly, we get about 0.336 Watts/m^2 from the road. A standard highway lane in America is about 3.5 metres. Therefore for each metre of lane we can hope to gain 0.336 * 3.5 == 1.17 watts.

To get 19800 watts from such a highway we would therefore need 19800 / 1.17 == 16900 metres of lane per car.

Except that we are talking about driving the cars in real-time with an inductive charger. We need to account for the efficiency of the inductive charger. Let's assume an inductive charger can be 75% efficient (which I think is very generous... it's at the high end of numbers from this paper), then we would need about 22500 metres of lane per car. That's one car per 22.5 km (or one car per 14 miles).

Let's work it the other way. I was taught that for safety I should not be closer than 3 seconds of driving time to the car in front of me. If everyone uses that rule, how many metres of road will one car take up at 60 mph/96 kph? 96000 metres / 3600 seconds per hour * 3 seconds == 80 metres

(Note: let's assume that 80 metres is always enough. When cars drive more slowly they pack closer together, with the worst case being bumper-to-bumper traffic where the road is tiled with cars. But electric cars get more efficient when they drive more slowly, so let's just assume it all works out. I feel I've done enough math already.)

So we need 19800 watts from 80 metres of road at 3.5 metres width... we need 19800 / (80 * 3.5) == 70.7 watts/m^2 (about 210 times more efficient than what Solandri calculated).

Or, factoring in a 75% efficient inductive system we would need 94.3 watts/m^2 (about 280 times more efficient than what Solandri calculated).

So we need a solar panel setup that nets 9.4% efficiency in converting solar power: 750 watts/m^2 solar power in, 70.7 watts/m^2 out, 70.5/750 == about 9.4%

Or, factoring in a 75% efficient inductive system we would need a net 12.6% efficient solar panel setup.

Again assuming 0.16 efficient solar cells, we need a capacity factor of about 0.588 to make it work, or 0.786 assuming the inductive system.

If we put solar panels on roofs over highways, it looks to me like we can come surprisingly close to break-even (being able to power the cars on the road purely from the solar panels). If you assume the panels are a bit more than 16% efficient maybe break-even is possible.

But burying the solar panels in the road under translucent concrete means you don't get 100% transmission of light to panels, and you can't angle the panels to improve capacity factor. Also your capacity factor takes a hit as cars put panels into shadow. (If you ever permi

11 comments and nothing but complaints and grousing. Where's the apps guy, to accuse you all of being Luddites?

I've been using a cordless keyboard and mouse since 2001, Logitech's very first model with a USB antenna. They're a marvelous invention. The antenna is a brick as big as the mouse with a four foot cable coming out of it with two separate USB connectors on the end. Still works beautifully, even though it looks like something from the last century. Admittedly it didn't cost $200-$250, even though I bought it when it was a brand new product, so I'm not impressed with the price point of this product, but the concept is immensely appealing. Not having to pop the batteries out of the mouse every few weeks and muck around with the battery charger is just the sort of tiny little convenience my lazy ass desires. (Why do I have sometimes have to rotate the batteries with my thumb after I plug in the charger before the charge light will come on?)

In the immortal words of Arnold Schwarzenegger, stop whining!

Instead, let's speculate about why Logitech is lying about their inability to use Qi. The Wireless Power Consortium has published a paper about how to use multiple cooperative flux generators to provide charging over an arbitrarily large surface, while not wasting power energizing coils that aren't underneath a receiver. Considering the size of the receiver puck in the picture of the Logitech product, it's obvious they're using precisely this technique in the mouse pad. Qi could have been used just fine, especially since the part that makes Qi what it is is the communications protocol between the receiver and the transmitter. Qi uses backscatter modulation from the receiver to tell the transmitter to give it power. When there's no receiver present, the Qi transmitter uses only 70 mW. With a receiver present and the protocol negotiated successfully, the transmitter ramps up to the power level requested by the receiver, up to 7.5W in the v1.2 standard.

I assume Logitech doesn't want to submit to any standards verification and doesn't want people to be able to use their mousepad to charge their Qi-enabled phones because Logitech hates their customers and wants them to die. I invite other opinions...

My phone has a micro USB port like any other phone. I however have a QI charger in the car and house.

The freight train of fail would be on your end, not mine. Everyone does things your way, therefore there can be no other way. When I point out that you are incorrect, you try to derail what I am saying by coming up with all these convoluted solutions to something exceedingly simple and elegant. I would like to point out where this train started so you can see why you are the one failing at seeing the utility, and I am pointing out to you that it already exists and is in wide use:

Regardless... no one using this tech is doing it for water proof cellphones.

As there are numerous vendors creating phones that wirelessly charge to reduce strain on the power plug and to increase water resistance, YOU ARE WRONG. I pointed you to one such phone, and you persist in trying to come up with a reason that no one makes cell phones with wireless charging to increase the water resistance, well that statement is wrong. Get over yourself.

Wireless charging serves many purposes, which is why people buy QI compatible phones. If it had no purpose, there wouldn't be a huge industry built around it.

http://www.qinside.biz/en/supp...

Just because you willfully can't see the utility in wireless charging because "it isn't wireless!" doesn't mean many others haven't seen the usefulness of wireless charging. Not having to plug anything into my phone to have it charge is wonderful. I get into my car and drop my phone into it's mount, and BOOM, it is getting power from the car. I get home, and I drop the phone into its cradle, and BOOM, it is getting power. I never have to plug it into anything, figuring out which direction the plug goes, dealing with loose plugs or plugs where the catch has broken and they just fall out. I also don't have to worry about my phone getting wet, I just don't worry about it at all.

http://smile.amazon.com/Itian-...

http://smile.amazon.com/Itian-...

Also, QI is 60% efficient (including the AC-DC step that wired power has), it isn't as efficient, but the convenience it great, which more than balances it out.

http://www.wirelesspowerconsor...

You don't have to get it, but calling other people names because you don't get it just makes you look ignorant. QI is taking off, as evidenced by the number of QI chargers on Amazon, and the number of phones that support it. You don't want one, fine, don't get one.

Wireless charging is only slightly worse than a good quality wired charger.

http://www.wirelesspowerconsor...

I've checked a few places and it seems as though you can expect a 70% power efficiency with this type of inductive charger. Some of the higher end models reach as much as 85%.

It strikes me as odd that in a time where we want as much energy efficiency as possible, we'd push towards something much less efficient with the potential to be so widespread.

Sources:
http://www.wirelesspowerconsortium.com/technology/total-energy-consumption.html
http://en.wikipedia.org/wiki/Inductive_charging

A phone battery is so small that it's not really that much power -- throwing away 30% of a 3.7V 2300mAh battery's capacity is 2.5 watt-hours, or just under a killowatt-hour in a year's time if you charge your battery daily - less than 15 cents for most people.

Seems like a small price to pay for the convenience. if it saves just 1 second/day in a year's time, it will have saved around 6 minutes/year, or $1 worth of labor for someone that earns $10/hour.

If you want to make up for it, walk or bike instead of driving - gasoline contains around 35KWh of energy per gallon, so if you bike or walk for 1 mile instead of driving, you'll have saved an entire year's worth of wasted power from a wireless charger.

I've checked a few places and it seems as though you can expect a 70% power efficiency with this type of inductive charger. Some of the higher end models reach as much as 85%.

It strikes me as odd that in a time where we want as much energy efficiency as possible, we'd push towards something much less efficient with the potential to be so widespread.

Sources:
http://www.wirelesspowerconsortium.com/technology/total-energy-consumption.html
http://en.wikipedia.org/wiki/Inductive_charging

..I don't see why it can't exceed 90%

<citation needed>

http://www.wirelesspowerconsortium.com/technology/transfer-efficiency.html

A high efficiency (>90%) can be achieved at close distance (z/D < 0.1) and for coils of similar size (D2/D = 0.5..1)

This article is a pitch for the Qi standard. The "widely accepted Qi standard" is still one of several competing technologies. Neither Apple nor Google is a member of the Wireless Power Consortium. There are 91 Qi compatible products, but most of them are chargers or add-on power receivers. Other than NTT DoCoMo, almost no manufacturer makes phones tablets with the Qi technology. Nobody seems to make a tablet or laptop with it built in.

One thing they got right is that there's minimal communication between power receiver and transmitter. There's just enough one-way communication for the power receiver to send "I want power" or "I don't want power". This shuts down the transmitter when the battery is fully charged. There is no data path from power transmitter to receiver, which avoids the use of this as an attack vector. That's been a problem with public USB charging ports. Another thing NTT/Panasonic got right is that their Eluga Eluga V P-06D phone, which has Qi charging, is waterproof.

Outside of the NTT/Panasonic world, though, there are few devices with integral Qi charging. Panasonic has been getting charging pads into a few coffee shops in Japan, but widespread adoption by the big chains hasn't happened.

Indeed. There is nothing 'green' about it, though I'm sure the iPhone crowd will probably find they can't do without it.

It just bleeds energy into the atmosphere. Running your GPU at full tilt to generate BitCoins might be less dangerous.

What are you talking about? A wireless charger doesn't radiate Watts of energy into the air when there's no device on the charging mat. Standby power use should be around the same as a traditional charger - the wireless power consortium claims they have test devices that are as low as .0001W of standby power, but they don't say what currently shipping chargers are at.

Seriously, this. I just don't get why this is such a popular idea, unless I remind myself that the average person is more or less technically uneducated, and doesn't understand that it's wildly energy inefficient. Also, echoing other comments on this topic: This is far from a new idea, and again: there are reasons we haven't gone this way before, but nobody seems to understand that.

Nothing serious about the inefficiency. We are not talking about cars, we are talking about 5W chargers...

I would read this with a pinch of salt (I probably would not often charge two devices at the same time), but it is pretty informative. http://www.wirelesspowerconsortium.com/technology/total-energy-consumption.html

FYI, this whole thing is just IDT's implementation of the Qi standard... http://www.wirelesspowerconsortium.com/

Inductive charging is a good idea, but there are at least three competing standards, which is why it isn't going anywhere. If the industry would settle on a standard and get business hotels to put a charging pad in hotel rooms, this mgiht get deployed.

So when they make a Pixel Qi Adam Slate that can be charged wirelessly, it will be called Qi Pixel Qi Adam Slate? Gee, Pikachu's late, too.

The group developing a standard for wireless charging expects to complete its first specification within six months, opening
the door for makers of cell phones, digital cameras and other devices to bring compatible products to market.

Wireless charging lets consumers place gadgets on a mat that plugs into a wall outlet, and have the devices recharge automatically
without needing to plug in each one. Apart from the gee-whiz factor, it's supposed to make life more convenient by letting
people walk into their home or office, toss their gadgets onto a mat to recharge and forget about them.

There are still questions about when standardized products will come to market and how they'll be received, but the Wireless
Power Consortium aims to finish its first standard before the middle of the year, said Menno Treffers, a Philips executive
who is chairman of the consortium. If it's not ready by then, "I will eat my hat," he told a group of vendors at the Consumer
Electronics Show in Las Vegas on Friday.

The consortium has 27 members including Nokia, Research In Motion, Philips, Sanyo, Samsung Electronics, Energizer and Hewlett-Packard, as well as component
and wireless-power technology companies such as Texas Instruments and Fulton Innovation.

The standard is for a technology called magnetic induction, in which power is transferred between metal coils built into the
device and the charging mat when they are placed close to each other. The standard is for delivering up to 5 watts of power,
which covers most smaller devices. A further standard will be needed for laptops and larger products. "We want to start on
that as soon as possible, but for now we don't want to dilute our engineering efforts," Treffers said.

Consumers will know which products are compliant because they'll carry the consortium's "Qi" logo (pronounced "chee" after the Chinese for life force). Initial products are likely to come bundled with a small charging mat
of their own, but if the technology takes off other companies are likely to sell mats that can charge multiple devices at
once.

Several wireless power products are already in the market, including a Nintendo accessory from Energizer for recharging Wii
game controllers, a Dell Latitude Z business laptop that can be recharged by placing it on a stand, and products from Powermat
for charging phones and other devices. Bosch has shown power tools that are recharged by laying them on a workshelf.

But a standard is seen as important to wider adoption because it ensures that devices will interoperate. Until it arrives,
some vendors won't release any further products. "We're done for now until the standard is complete," said Serge Traylor,
brand manager for charging and rechargeable systems with Energizer. When the standard is done, Energizer will release a mat
for charging as many as two devices, for about $100, and charging sleeves for iPhone and Blackberry devices, for $30 to $40,
he said.

The standardization effort faces several challenges, though. Powermat, one of the leading wireless power companies, has not
joined the consortium and is selling products using its own technology, which Treffers acknowledged could create confusion
in the market.

Some of the most popular gadget makers also are not on board, including Apple. "I have not heard from them," Treffers said.

He admitted also that the public may have concer

The group developing a standard for wireless charging expects to complete its first specification within six months, opening
the door for makers of cell phones, digital cameras and other devices to bring compatible products to market.

Wireless charging lets consumers place gadgets on a mat that plugs into a wall outlet, and have the devices recharge automatically
without needing to plug in each one. Apart from the gee-whiz factor, it's supposed to make life more convenient by letting
people walk into their home or office, toss their gadgets onto a mat to recharge and forget about them.

There are still questions about when standardized products will come to market and how they'll be received, but the Wireless
Power Consortium aims to finish its first standard before the middle of the year, said Menno Treffers, a Philips executive
who is chairman of the consortium. If it's not ready by then, "I will eat my hat," he told a group of vendors at the Consumer
Electronics Show in Las Vegas on Friday.

The consortium has 27 members including Nokia, Research In Motion, Philips, Sanyo, Samsung Electronics, Energizer and Hewlett-Packard, as well as component
and wireless-power technology companies such as Texas Instruments and Fulton Innovation.

The standard is for a technology called magnetic induction, in which power is transferred between metal coils built into the
device and the charging mat when they are placed close to each other. The standard is for delivering up to 5 watts of power,
which covers most smaller devices. A further standard will be needed for laptops and larger products. "We want to start on
that as soon as possible, but for now we don't want to dilute our engineering efforts," Treffers said.

Consumers will know which products are compliant because they'll carry the consortium's "Qi" logo (pronounced "chee" after the Chinese for life force). Initial products are likely to come bundled with a small charging mat
of their own, but if the technology takes off other companies are likely to sell mats that can charge multiple devices at
once.

Several wireless power products are already in the market, including a Nintendo accessory from Energizer for recharging Wii
game controllers, a Dell Latitude Z business laptop that can be recharged by placing it on a stand, and products from Powermat
for charging phones and other devices. Bosch has shown power tools that are recharged by laying them on a workshelf.

But a standard is seen as important to wider adoption because it ensures that devices will interoperate. Until it arrives,
some vendors won't release any further products. "We're done for now until the standard is complete," said Serge Traylor,
brand manager for charging and rechargeable systems with Energizer. When the standard is done, Energizer will release a mat
for charging as many as two devices, for about $100, and charging sleeves for iPhone and Blackberry devices, for $30 to $40,
he said.

The standardization effort faces several challenges, though. Powermat, one of the leading wireless power companies, has not
joined the consortium and is selling products using its own technology, which Treffers acknowledged could create confusion
in the market.

Some of the most popular gadget makers also are not on board, including Apple. "I have not heard from them," Treffers said.

He admitted also that the public may have concer

• Radiative transfer: send a directed beam of energy from a source to a receiver. The advantage is that this can work over long distances, the disadvantage is that you need to either have fixed locations or some active tracking system to keep pointing at the receiver as it moves around, and you need some kind of automated kill switch to make sure you don't accidentally fry anything that walks between the transmitter and receiver or waste power when the receiver is not there. It looks like PowerCast and PowerBeam fall into this category.
• Traditional inductive, non-radiative power transfer. This works well, and does not transfer power when the receiver is absent, but is extremely short-range if you want any kind of efficiency; typically, the device to be charged must be sitting directly on or adjacent to the charger. The Wireless Power Consortium is pursuing this kind of approach.
• Resonant, non-radiative power transfer. This relies on the source and receiver being electrical resonators at the same frequency, so that they preferentially transfer energy to one another rather than to other objects in the environment via resonant coupling. This is the approach being pursued by WiTricity, where they additionally rely on resonators that couple primarily via magnetic fields (the electric-field energy is mostly in capacitors inside the devices), which have the advantage that most materials are non-magnetic at these frequencies so the power source dissipates very little energy into extraneous objects (or people). (In contrast, Tesla coils produce strong electric fields external to the device, which interact much more strongly with matter; it's no coincidence that Tesla coils are used as lightning generators.) This operates efficiently at mid-range distances although not as far as radiative transfer (meters at most), does not transfer or dissipate power when the receiver is absent, and is not directional so does not require active "pointing" of the power at the receiver. But it is more complicated than the short-range non-resonant inductive transfer, and requires careful impedance-matching of the source and receiver.

Full disclosure: I know Prof. Soljacic at MIT, who founded WiTricity, although I personally have no financial interest in the company; all of the above information is public and published, however.