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After a User Dies, Apple Warns Against Counterfeit Chargers
After a Chinese woman was earlier this month evidently electrocuted while talking on her iPhone while it was plugged in to charge, Apple is warning users to avoid counterfeit chargers. From CNet:
"Last week, reports surfaced in China that suggested the woman, Ma Ailun, might have been using a third-party charger designed to look like the real thing. Although third-party chargers are not uncommon, they vary widely in terms of safety and quality.
Earlier this year, safety consulting and certification company UL issued a warning that counterfeit Apple USB chargers were making the rounds and that consumers should be on the lookout for them due to their lower quality and possibly dangerous defects. The company posted the guidance on its site after a woman was allegedly electrocuted while answering a call on her iPhone."
Whether or not the counterfeit charger was the cause, they have reinforced their image and promoted their chargers (as well as discouraging customers from buying their chargers elsewhere).
There are lots of "third-party" Android chargers out there -- ordinary MicroUSB things. If "counterfeit" (i.e. non-Samsung, or whatever) chargers were a problem, wouldn't this happen all the time with Androids?
Sounds like Apple is just taking advantage of the opportunity to scare people into paying the Apple Tax.
... and while it does a good job of charging, it does have a "sparking" habit whenever I plug it in to a wall outlet. Honestly, if this was truly a concern for Apple, they should make their chargers cheaper, or license aftermarket production to the spec of originals. I saved a bundle (about 50%) by going with a Chinese knock-off.
.. pa-ra-bo-la, pa-ra-bo-la, 2 pi R, 2 pi R, where's your latus rectum, where's your latus rectum, 2 pi R
A single AAA battery can be lethal, if you connect each end with something sharp directly inside your veins on each arm, bridging the 1.5v DC (or less) circuit across your heart.
Morphing Software
When I finally dumped my iPhone 3G, it was because it kept shocking me every time it rang. I don't know about the iPhone 5, but I think blaming the charger might be a little simplistic given that experience.
In SOVIET RUSSIA... erm...NSA AMERICA, the Internet logs onto YOU!
Those wires can easily carry 1A which at 220V is more than enough to kill you. The exposed metal bits of a device are often connected to a shield ground, and if that "ground" is actually at 220V line potential then it would be easy to kill someone.
No one is being killed by the 5v on the USB bus. The problem is the counterfeit chargers are often poorly designed and can fail in a way that shorts the USB cable to the AC power.
There was an excellent teardown & analysis of a cheap charger last year that pointed out serious safety issues.
Comment forecast: Bits of genius surrounded by a sea of mediocrity.
The cable certainly is thick enough for a lethal current at 220V, provided it's applied in the right place. It's easy to conceive of a badly made charger which produces 5.5V between two of its conductors, but at 220V from earth, due to poor isolation. Then all the victim needs to do is earth another part of his or her body and away you go.
Take a look at a teardown of a fake charger and you'll understand why it can be lethal. The creepage distances in particular are atrocious.
No one is going to die by having 5volts applied to their face.
But they do die from having 220 volts applied to their face.
The issue is that the counterfeit chargers short and deliver the mains directly to the head. It doesn't matter what electronic device is involved. hell, doesn't matter if any electronic device is connected to the end of the other side of the USB cable when the circuit is completed.
See the commentary at the top of the page from this link:
http://www.righto.com/2012/03/inside-cheap-phone-charger-and-why-you.html
--Paul
I'm not buying it, how could you possibly screwup a USB charger to the point where it would be lethal? I mean the cables aren't generally thick enough to carry enough 220V current to kill someone before they melt and 5.5V DC certainly isn't going to kill someone.
It only takes 100mA - 200mA of current to kill someone, and every USB cable is designed to carry at least 500mA since the USB spec says that USB hosts can supply up to 500mA of current (and many plug-in chargers exceed that). So it's certainly feasible that a USB cable can carry enough current to kill someone. It's not the voltage the determines the size of the conductor, it's the current.
The USB cable wires may not have sufficient insulation to protect against 220VAC (peak voltage is higher, around 310V if I remember correctly), but that's the point -- 220VAC is not supposed to be supplied to a USB device. But even if it's not certified for the voltage it seems that the individual conductor insulation combined with the plastic outer sleeve of the USB cable would seem to provide at least enough isolation, I think most plastics used for insulation have around 500 - 1000V/mil (1/1000th of an inch) of breakdown voltage.
I'm surprised that a phone doesn't have at least 220VAC of isolation between the USB power and the phone case. Is this typical in phones?
Especially in China.
Are you saying that China has counterfeit electronics? And that they don't meet safety standards? This simply must be a joke.
Copper (steel?) wires do not melt easily. If current @ 220V flows through your skull the brain is guaranteed to melt much sooner. Do not count on wires to be a life-saving insulator!
According to a US NAVY story about and electrician who pierced his skin with a volmeter, 5.5V can kill you, but it is more likely that the charger shorted 220 to the metal antennae bezel.
I'm not buying it, how could you possibly screwup a USB charger to the point where it would be lethal? I mean the cables aren't generally thick enough to carry enough 220V current to kill someone before they melt and 5.5V DC certainly isn't going to kill someone.
I suspect it wasn't the connecting cable where the fire occurred, but the small box that plugs into the electrical outlet. This box presumably contains components to convert AC to DC power, and if it was made very cheaply and in disregard of safety standards, it could easily cause a fire.
Current shmurrent. She died because she wasn't holding it right.
simple, they did not put in route features on the ac part of the board, these are grooves milled into the PCB so that high voltage wont flash over to other parts of the board. They also put their traces way too close so you might have 0.254mm isolating AC from DC
and it only takes a few 10's of millamps to kill you, and these cables are more than capible of handling 500 -1000 millamps ... usually the low voltage doesnt have enough punch to break the resistance of your skin, but 220 sure as fuck does
one hand on a hot line, other on ground, your toast
It's possible by having the charger fail in such a way that it's not 5 volts any more -- or that the 5-volt pair is at a substantial voltage relative to earth ground.
Although we don't have detailed reports, there isn't anything on the newswires to indicate that the victim was trying to defibrillate herself with the charger.
Perhaps she was channeling an old episode of McGyver?
Faster! Faster! Faster would be better!
I'm not buying it, how could you possibly screwup a USB charger to the point where it would be lethal? I mean the cables aren't generally thick enough to carry enough 220V current to kill someone before they melt and 5.5V DC certainly isn't going to kill someone.
Well, having it designed by someone like you should make it a killer.
http://www.righto.com/2012/03/inside-cheap-phone-charger-and-why-you.html
According to reports, a woman in China was tragically electrocuted using her iPhone while it was charging. This seems technically plausible to me if she were using a cheap or counterfeit charger like I describe below. There's 340 volts DC inside the charger, which is enough to kill. In a cheap charger, there can be less than a millimeter separating this voltage from the output, a fraction of the recommended safe distance. These charger sometimes short out (picture), which could send lethal voltage through the USB cable. If the user closes the circuit by standing on a damp floor or touching a grounded metal surface, electrocution is a possibility. If moisture condenses in the charger (e.g. in a humid bathroom), shorting becomes even more likely. Genuine Apple chargers (and other brand-name chargers) follow strict safety regulations (teardown) so I would be surprised if this electrocution happened with a name-brand charger. Since counterfeits look just like real chargers, I'll wait for an expert to determine if a genuine Apple charger was involved or not. I've read suggestions that the house wiring might have been to blame, but since chargers are typically ungrounded I don't see how faulty house wiring would play a role. I should point out that since there are few details at this point, this is all speculation; it's possible the phone and charger weren't involved at all.
Of course news about a fake are Fake News.
Most Android phones are plastic, a material which doesn't conduct electricity very well.
There are a lot of teardowns of cheap chargers on youtube It's practically a meme at this point.
Many of them are shockingly awful and have very dangerous designs. Not adequately isolating the mains lines from the output voltage can easily lead to killing someone. They almost all have completely inadequate performance characteristics on the output. Noise, ripple, voltage drop that produces nowhere near 5 volts at any significant load.
Official, legit ones are usually very good. Apple and Blackberry are noted to have particularly well built and well designed chargers.
But a cheap USB cable is not going to carry 220v very far. The cable will likely burnup first.
A fake one could be made any number of ways that could be potentially dangerous, If it's made with an autotransformer, it would be possible to have the "hot" side of the AC line connected directly to one or the other output contact. A slightly more sophisticated system has the AC line isolated only by a single capacitor, if the capacitor shorts or becomes leaky, some fraction of line voltage appears on the output. Many old tube radios were made with similar design, and if you touch any metal including the mounting screws holding it in the case, it can shock you, and if well-grounded, kill you. Millions of them were made this way, only a few people were ever hurt/killed.
If it's a "chopper" style power supply, a failure could put anything up to 311 volts on the output.
The wire is plenty adequate to pass lethal current, that's as little as 20 ma. Whether it is actually fatal depends on how well-grounded you are when you touch it.
Wouldn't the USB cable catch fire first?
Relying on vague memory of EE classes of 15 years ago: A badly built power transformer wouldn't shock someone with the transform voltage but the direct line. Poorly constructed circuits short from melting stuff contacting metal they shouldn't. If the circuit shorts and there are no GFI or fuses or other safety features, the power lines instead of being 12V DC or 5V DC or whatever are now 120V AC.
Safety features like fuses and GFI cost money where if one is seeking to make a fast buck on knock offs throwing out a few of them will make it even more profitable.
To me this is one of those forehead slappers. If you want to minimize cheap knockoffs, make your certification process cheaper and more straightforward.
Obviously Apple is going the other way, trying to use technology/encryption to force vendors into their certification and licensing process with the idea that they can control this market and make money off it, too.
Of course this has failed, and knock-offs are starting to proliferate, and it's hard to know if what Apple really cares about is the rare and unlikely chance of serious shock or if it wants to curtail products from unlicensed vendors.
its a step down transformer and a voltage regulator. 5vdc and 1 amp. 1 amp is what killed not a non branded charger. I mean yes stuff needs to be safe and up to code but what a bunch of tripe that article is spouting.
This is what's known as "spin" in non-apple ecosystems. I know Apple would never lie to you though, so let's just call it "iSpin"
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You will be electrocuted before the cable fails. It's likely that only a single leg of the 220V outlet will be forwarded to the phone therefore we are really talking about 110V. You holding the other end of the cable completes the circuit to ground. You will probably die or have serious injury before the load that you introduced melts the cable.
I wouldn't count on the cable acting as a fuse.
These comments are my own and do not necessarily reflect the views or opinions of my employer or colleagues...
Makes little difference if you burnup firstist.
100-220 V at 60 Hz can be lethal fairly quickly. You don''t need a hell of a lot of amperage, so a thin wire can handle it briefly.
Faster! Faster! Faster would be better!
The new "lighting" connector is very solid and handy, contrary to micro USB.
Its designed that way for obvious reasons.
http://en.wikipedia.org/wiki/USB#Mini_and_Micro_connectors
"The Micro plug design is rated for at least 10,000 connect-disconnect cycles—significantly more than the Mini plug design.[38] It is also designed to reduce the mechanical wear on the device; instead the easier-to-replace cable is designed to bear the mechanical wear of connection and disconnection"
So... take the advice from us here at Apple, and pay us $79 for a $5 charger.
Signature intentionally left blank.
Cue the Apple haters claiming that Apple engaged in a conspiracy to manufacture and distribute lethally-flawed apparently-counterfeit chargers in order to destroy the market for 3rd-party chargers and lock up all the profits...
No. the cables aren't built so cheaply that they would melt enough to break a circuit when a little heat is created. That's what fuses are for and USB cables aren't fuses.
It's this drivel again. Voltage and current are not independent. It's like saying that it isn't the height of the fall that kills you, but rather the speed at impact. Thanks, Einstein, but you know what determines the speed at impact (c.f. current)? That's right: height of fall (respectively voltage). The "amount of current the device is designed to carry" is at the design voltage. Which is a nonlethal voltage. USB 5V will not hurt. It's like being afraid of a 9V battery. The problem is, as you correctly noticed, line voltage somehow getting onto into the USB connection. 8/10 (2 points off for the first paragraph).
I've had several iDevices and have to say that apple branded cables suck. I've had to replace every apple branded cable with a generic because the sheath is thin & there's no support near the connectors, so the sheath cracks and wires are exposed. ( I've had 2 iPods and currently have an iPad ) I had the apple branded cable for less than 6 months and wires were visible at the connector... I've had the same iPod and cheap chinese cable from a no-name chinese company for well over 3 years now. It gets the same abuse that it did before & isn't even starting to show age. The new "lightning" connector doesn't seem to be as bad, but only because of the design of the connector as a whole. I wouldn't be too surprised if it was an apple cable...
Holy shit. This is the dumbest, most ignorant post I've read all day. And from a 4 digit UID. You will really do anything to badmouth apple, won't you?
Apple chargers are generally considered to be the best available for that type of device. The people that take these things apart and examine their designs for fun all agree that the apple devices are the best they've ever seen. (Small, USB chargers for smart phones and tablets) The designed aren't "overly complex" they're just not cheap pieces of garbage.
But don't take my word for it. There are hundreds of videos on you tube, by electrical engineers, that say exactly what I'm telling you right now.
It doesn't carry the current until the current has somewhere to flow. Namely, through you. Sure, the cable will melt in a matter of seconds, but that's a few seconds of electric shock, which is plenty.
I would think that metal cased phones only exasperate the issue of allowing that voltage to get to the person holding that phone in a most efficent manner too.
Um.. Easy. If you "Plug into the wall" and then don't do the right things in your power supply design, then it is possible to put full AC voltage on things the customer might touch. This is even more true for modern "switching" supply designs which don't make use of a transformer to step down the voltage. It would be extremely easy to connect the phone's "ground" (i.e. the case) to an input power lead and kill a customer who tries to handle the charging phone while otherwise grounded (In the tub, Bare feet in a puddle, touching some plumbing fixture etc.) . Such faults would not keep the charger from working.
A further complicating factor is that your charger made for the US market, may also work (with the proper adapters) in other places. This means that a specific design may be totally safe in the US, but be a death trap elsewhere, or be totally safe overseas but totally unsafe in North America.
Because of this, it's usually best to play it safe and use only power adapters designed and sold by companies in your own country. The cheap knockoffs you can get on E-Bay can be dangerous, and you would not know it until it was too late.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
The issue is that the counterfeit chargers short and deliver the mains directly to the head. It doesn't matter what electronic device is involved. hell, doesn't matter if any electronic device is connected to the end of the other side of the USB cable when the circuit is completed.
In the case of the woman who died, it was reported that her iPhone was still fine. So it seems 220 Volt was delivered only to her, and not to the phone at all (I doubt an iPhone or any other phone would survive being hit by 220 Volt).
But even if it's not certified for the voltage it seems that the individual conductor insulation combined with the plastic outer sleeve of the USB cable would seem to provide at least enough isolation...
The OP's point was even stupider than you gave him credit for. 1) Your heart would be stopped before the insulation melted. 2) Uninsulated wires are perfectly capable of carrying lethal current.
The cheap adapter may have sent big voltage to the phone connecteor... But IT'S THE APPLE DESIGN that bring that voltage outside the phone...
If the two leads of the charger are (relative to ground) 220V and (220+5)V, the phone should charge just fine and the user would still be fine...
If the charger send a rogue voltage (like 0V and 220V), the phone internals should get fried... but the user should still be fine...
But some retard thought it'd be cool to use the metal frame of the phone as an antenna... This lead to the "antenna-gate" with people losing their phone signal when holding the phone the wrong way, but that part is more funny than other. But this also mean that any invalid voltage sent to the phone connector may also reach that metallic frame and the user... With the sad consequences that you've seen here !!!
When you see electrical recommendation for electric appliances, you see that the box of an electric device should be grounded or completely insulated... Apple failed that basic recommendation... and THEY are responsible for that part.
Any phone charger can go rogue... this is even true for Apple's "official" chargers (even if risks are lower).
No, the truth is that it is exceptionally easy, when trying to be cheap, to not engineer the proper safety into your power supply design and manufacturing process. If a hot lead from the power plug finds itself connected to the device ground (i.e. the case) then any grounded person that touches the phone will be in trouble. So this is not a function of Apple's design.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
Wouldn't the USB cable catch fire first?
No, of course not. By the time you've run enough current to melt/ignite the insulation, you've run enough current to kill. It's not as though the insulation melts as the first electron passes by.
And, oh, by the way, since you seem to be unaware, an uninsulated cable can deliver enough current to kill you, even one covered in flaming insulation ;-)
Now if you're talking about the conductor melting instead of just the insulation, oh good lord, of course that does not happen before dangerous current has flowed. Good grief.
No
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
It's this drivel again. Voltage and current are not independent. It's like saying that it isn't the height of the fall that kills you, but rather the speed at impact. Thanks, Einstein, but you know what determines the speed at impact (c.f. current)? That's right: height of fall (respectively voltage). The "amount of current the device is designed to carry" is at the design voltage. Which is a nonlethal voltage. USB 5V will not hurt. It's like being afraid of a 9V battery. The problem is, as you correctly noticed, line voltage somehow getting onto into the USB connection. 8/10 (2 points off for the first paragraph).
Which part is drivel? The USB cable will happily carry enough current to kill you, and 220VAC is enough voltage to kill you (since people have died from 110VAC electrocution) so if your charger is designed poorly and exposes you to the 220VAC mains voltage, it can easily kill you. You could power a 100W 220VAC lightbulb (less than 500mA) with a USB cable if you wanted to (well probably....subject to breakdown voltage of the conductors).
So tell me again which part you didn't understand? My point was that a USB cable can easily carry a lethal amount of current, since the conductors are sized appropriately to carry that much current (which has nothing to do with the voltage they are designed to carry - that's determined by the insulation of the wires). You'd use the same size conductors to carry 500mA at 220VAC as you would to carry 500mA at 5VDC.
Speed and height seem like awfully poor metaphors for current and voltage... what would resistance be in this case? Frictional forces in the air? How do you account for terminal velocity in that speed and height metaphor? I like the pressure and volume of water flowing through a hose metaphor myself.
I am shocked!
At least this one makes some attempt, if incompetent, to isolate the AC. Some years ago I bought a battery charger (from a shabby convenience store while traveling) that had exactly 3 components: a capacitor in series with the AC, a rectifier diode, and a zener.
That's one way to force the use of proprietary hardware. Such a benevolent company. Use Official Apple Product or DIE!
It's not just Apple suggesting a counterfeit:
http://news.cnet.com/8301-13579_3-57594449-37/iphone-related-death-in-china-could-be-linked-to-fake-charger/
Granted, a guy listed as "phone expert" on Chinese media isn't exactly conclusive, but given that China actually had fake Apple stores for awhile I would not be surprised if some idiot who didn't know what he was doing made deadly chargers and slapped an Apple logo on them.
OTOH iPhone 4 has been out for three years. And it didn't kill anyone until Ma Ailun.
"After a User Dies, Apple Warns Against Counterfeit Chargers" Why would I be careful with counterfit charges only after I, a user, die?
Crap switching power supplies from China are a huge problem. You not only have to look for a UL logo, but check the logo in the UL database. UL even has special rules for China about where the UL stickers come from.
Tests of computer power supplies have shown that the UL-certified ones will consistently deliver their rated current. That makes sense, because that's how UL tests them. Others, loaded up to their rated load, overheat, shut down, burn out, or in a few cases, catch fire. The really bad ones lack key safety components, like a fuse.
I bought some laptop-type switching power supplies on Amazon which showed a UL logo in the picture, but the delivered power supply looked different and lacked a UL logo. I raised hell with Amazon over that, and they kicked that seller off.
No one is being killed by the 5v on the USB bus. The problem is the counterfeit chargers are often poorly designed and can fail in a way that shorts the USB cable to the AC power.
Righto. And it would seem there must have been something else contributing, path-to-ground-wise.
, and they contain a bit more than a simple transformer and regulator.
They take the AC line voltage, rectify it to high voltage DC, chop the DC up into high frequency pulses with a MOSFET, step the pulsed voltage down with a specially designed transformer, then rectify the output to low voltage DC. A sample of the output DC is then fed back to the primary side circuitry to achieve closed loop regulation.
Because the primary side of the system is at line potential, the insulation in the switching transformer (and the optocoupler used in the feedback loop) is all that prevents the output side from presenting a shock hazard with respect to earth ground. The quality of construction of many of the Chinese knockoff chargers is downright terrible, and I could easily believe that an insulation breakdown. Dave Jones "EEVBlog" did a teardown of one of these a while back. Scary stuff if you know what you are looking at:
http://www.youtube.com/watch?v=wi-b9k-0KfE
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It's current that kills you, not voltage, and it doesn't take much. Even a cheap USB cable will transfer more than enough power to kill you if you're unlucky.
If it's thick enough for 500mA(minimum USB standard), it's enough to kill you, as it only takes 100-200mA. Matter of fact, it says that 100-200mA is actually more dangerous than above 200mA if the victim can get prompt attention.
I don't read AC A human right
the part that plugs into the wall is mostly USB, with notable quirks so they can support high amperage modes.
Non impediti ratione cogitationus.
Better: don't buy at all.
I have an excess of Nokia, Samsung and HTC chargers, all compatible. I just pick the nearest one..
it isn't actually clear if it WAS a counterfit charger.... Apple wants you to believe it is, but maybe it isn't...
Pardon me for interrupting the usual /. dialogue with something relevant to the original topic, but Ken Shirriff did a couple of teardowns a year ago that point out exactly why the counterfeit chargers are Not Safe. The safety issues revolve around poor isolation practices between the line and USB sides of some USB chargers.
Major items include
1) lack of "double insulated" construction in the internal transformer.
2) parts placement of line and USB side components on a single circuit board such that paths may be readily formed between line and USB sides from moisture, construction errors, or component failure.
3) inadequate margins between line side and USB side in overall layout of the charger internal components.
http://www.righto.com/2012/05/apple-iphone-charger-teardown-quality.html
http://www.righto.com/2012/03/inside-cheap-phone-charger-and-why-you.html
It's absolutely possible to screw up that badly. All you'd need to do to electrocute someone through a USB charger would be short the wires that go from mains power to the 5V lead. And that's really easy to accomplish by accident if you're using a linear voltage regulator (wasteful - which means lots of HEAT) and you're not getting the required clearances between your high-voltage and low-voltage traces. Heat melts the solder, which shorts the connection, which gives you the shock. It doesn't matter in the slightest that "the cables aren't generally thick enough to carry enough 220V current". For one thing, there ain't no such thing as 220V current. 220V is voltage. Current is measured in amps. Secondly, the rating on the cable simply means they'll get hot and melt. But if the phone was on the woman's ear the moment the short occurred, there's plenty of time to electrocute her before the cables degraded. Shortly thereafter I'm sure the charging cable got hot and melted, breaking the circuit. Which would have been cold comfort to the woman's corpse.
This is what the teardown of a genuine Apple charger looks like. http://www.righto.com/2012/05/apple-iphone-charger-teardown-quality.html Say what you will about Apple - They made a really really nice product here. It ain't easy engineering 110VAC to 5VDC in 2 cubic inches...
Essentially all of the "universal" chargers (those designed to work worldwide on anything from 110 to 240 V) are indeed switching regulators and it's all too easy to have a failure that puts full line voltage on the output. Save a little money on the otherwise massive redundancy used to make them relatively safe, and boom, hot on the output stage.
As an aside, these type of wall warts are notorious generators of RF interference which in addition to merely noisy reception on AM radio, can play hob with many other devices. I was having all sorts of trouble with my digital voltmeter, which I eventually traced to a cell phone charger.
Maybe Siri just didn't like her?
What? Any USB charger will charge an iPhone/iPad just not as fast as one made for the it. The 30 pin cable is the only thing that is proprietary and even then you can get them cheaply. The problem here is that someone made a counterfeit one which was shoddy and killed someone.
Well, there's spam egg sausage and spam, that's not got much spam in it.
Anyone looking to buy anything should avoid China. There, that's much more realistic.
Voltage matters. The voltage needs to be high enough to overcome the natural resistance of your skin, otherwise, the current won't make it up to 200mA.
"First they came for the slanderers and i said nothing."
First? Remember, no current is flowing until the circuit is completed. The amount of current required to flash-ignite the charging wire is quite high compared to the amount necessary to cook human nervous tissue. Even if the wire burned through its insulation almost immediately, it could already be too late.
Also, remember that USB cables actually have moderately high current tolerances. Carrying any meaningful amount of power at 5V requires a relatively high amperage rating. 1A at 220V is quite a lot of power when applied to the human body, and that's merely what these charging cables are expected to carry in normal operation. In practice, they can probably manage several times that without anything worse than becoming a bit warm will occur. At 2.3A, that's over half a kilowatt (minus minor resistive losses in the wire, which will heat it but probably not melt/ignite it) being delivered to the head...
There's no place I could be, since I've found Serenity...
Ah yes. Apple's "You're holding it wrong" defense.
Have gnu, will travel.
This is a solid explanation of how the phone could be safely plugged in, but very dangerous once it's brought to your head. A cable with a resistance of 0.1 Ohms carrying a current of 1 Amp will experience a voltage drop of 0.1V, which means it will dissipate 0.1 Watts (I * dV) - a meager amount that the wire can maintain indefinitely (and indeed, is designed to). This happens regardless of whether the wire is carrying 5V or 225V; all that matters is the voltage drop *along* the wire (and the current on the wire, which is partially a function of that voltage drop).
Now, if you shorted the wire itself (rather than shorting the mains to one side of the wire), then (under normal circumstances) your wire is now dropping the full 5V that is the difference between its positive and ground terminals. To get a voltage drop of 5V with only 0.1 Ohms of resistance, you need 50 Amps (dV = I * R -> dV/R = I). 50A current times 5V potential drop is 250 Watts of dissipated heat, which would destroy your wire if the USB port could supply anywhere near that much current. The numbers for 220V are even more frightening (P = dV^2/R, so that would be 484000W). But, that won't happen unless the wire is shorted to itself. If the wire (at 220V) is instead connected to ground through a human being (with a resistance between that person's head and ground of, say, 49.9 Ohms) then you've got (220)^2 / 50, which is a mere 0.2% of the number given above. That's still about a kilowatt, enough to kill you very quickly.
As for the wire, it's now carrying 4.4A (220V/50 Ohm), but it still only has 0.1 Ohm of resistance and is therefore dissipating a mere 1.936W across a voltage drop of .44V. That's many times its normal dissipation, but still it might not even be enough to melt the plastic coating.
There's no place I could be, since I've found Serenity...
Nope. You can run as many volts as you like over a thin cable; it's amps that would cause it to heat up and fail.
I mean the cables aren't generally thick enough to carry enough 220V current to kill someone before they melt
BS it only takes relatively tiny ammounts of current (iirc tens to hundreds of milliamps depending on route through the body) to kill someone, far less than the currents used to charge a phone (~1A). The insulation may or may not hold out at 240V (I bet in most cases it would) but it doesn't really matter since the most plausable electrocution scenario is not current flowing down one charger wire and back through the other, it's current flowing through one charger wire, then through the persons body, then through some other return path (grounded metalwork of some sort).
So if the isolation barriers inside the charger (transformer, RFI suppression capacitors, general layout of stuff in the case) fail then it is very plausable to get an electric shock. Properly designed chargers are very carefully designed to minimise this risk. Counterfiets and cheap tat not so much.
5.5V DC certainly isn't going to kill someone.
Mostly true. The skin resistance is too high to let a dangerous current flow at such low voltages. With sub-skin electrodes though even voltages normally regarded as safe can become leathal.
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register
This is even more true for modern "switching" supply designs which don't make use of a transformer to step down the voltage.
Actually they do. While you can design switchers without a transformer they provide basically no isolation at all and afaict are not used in mains power supply applications. Your typical switched mode mains power supply uses a high frequency transformer both as the reactive component in the switcher and an isolation device.
Still there are cetainly more components crossing the "safety boundary" than in a traditional transformer based power supply. If any of those components are skimped on you have a potentially dangerous device.
This means that a specific design may be totally safe in the US, but be a death trap elsewhere, or be totally safe overseas but totally unsafe in North America.
I don't really buy your argument there.
In the case of phone chargers, their mains connections are generally ungrounded (supposedly class 2 though the knockoffs certainly don't meet class 2 requirements) and unpolarised anyway so there is little the supply system can do to make them less safe. In the case of larger power supplies that are class 1 then you need to make sure there is a good ground but agin that applies wherever the power supply was originally sold. They still sell class 1 appliances in places that don't have proper grounding :(
The biggest issue is probablly that sometimes people fail to use the proper adaptor and hence that doesn't actually connect the earth even though one is available and required by the appliance.
I guess the higher voltage in some parts of the world may make a bit of a difference but I doubt it's significant overall with PSUs sold by a reputable vendor as universal voltage input.
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register
Every USB power brick i've seen has a floating output. That is in normal operation neither side of the output is connected to "mains ground".
So it's quite feasible in a failure scenario for one side of the output to be connected to mains live while the two sides of the output remain at 5V relative to each other. The phone would probablly be fine with this, someone holding the phone not so much.
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register
It greatly contributes to the danger that iPhone's cover material is aluminum rather than plastic.
I came here to say exactly this. Apple is the one who ensured that the only manufacturers selling chargers for their products were those with no accountability.
If they did not use absurd proprietary designs, then most consumers would buy chargers from companies which have such qualifications as "an address" and "a name".
-- 'The' Lord and Master Bitman On High, Master Of All
This is even more true for modern "switching" supply designs which don't make use of a transformer to step down the voltage.
Actually they do. While you can design switchers without a transformer they provide basically no isolation at all and afaict are not used in mains power supply applications. Your typical switched mode mains power supply uses a high frequency transformer both as the reactive component in the switcher and an isolation device.
Still there are cetainly more components crossing the "safety boundary" than in a traditional transformer based power supply. If any of those components are skimped on you have a potentially dangerous device.
My point was that the mains isolation afforded by a step down transformer is no longer a given fact. In fact, it's unlikely. Large inductors are expensive, inefficient and heavy so they do not get used. Gone is the standard "wall wart" transformer and the safety it provided. I am aware of how some switchers work and know that there are high frequency transformers in some designs, but as you indicate, they no longer isolate the device from the power connections.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
Or maybe not charge a ridiculous amount of money for a proprietary charger so people wouldn't be forced into buying a much less expensive 3rd party one? Nah... why do that?
Apple chargers are nothing special. Much of what Apple does is nothing special.
Your attempt to help perpetuate the mindless hype is not convincing.
A Pirate and a Puritan look the same on a balance sheet.
FWIW, the shoddy quality of knock-off chargers is well-documented. Bottom line: stay away from them.
http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html
yeah. My generic drugstore checkout car counter won't even register a blink on the Iphone's led.
Star Trek transporters are just 3d printers.