iPhone 4 Bursts into Flames

[Joe Johaneman]

<div class='os_post_top_link'><a href='http://www.tuaw.com/2010/07/08/report-iphone-4-burst-into-flames-faulty-usb-port-blamed/' target='_blank'>http://www.tuaw.com/2010/07/08/repo...sb-port-blamed/</a><br /><br /></div><p><em>"The above picture is from from Boy Genius Report, who claim they received it from an AT&amp;T Store employee dealing with a customer who said their iPhone 4 had spontaneously burst into flames. As you can see above, the adapter cable is completely melted, and the iPhone's stainless steel antenna band is charred. The customer said his hand was burned, and the adapter cord itself burned up, too."</em></p><p><img src="http://images.thoughtsmedia.com/resizer/thumbs/size/600/at/auto/1278676730.usr105505.jpg" style="border: 1px solid #d2d2bb;" /></p><p>This seems to be a unique event. &nbsp;The problem wasn't with the iPhone or the sync cable. &nbsp;The USB port on the computer the phone was connected to was pushing too much power. &nbsp;Still, the phrase "spontaneously burst into flames" is enough to send shivers down the spine of any smartphone owner. &nbsp;I always worry about breaking the glass on my phone, but this is obviously much worse. &nbsp;What's your worst smartphone experience? &nbsp;</p>

[Brad Adrian]

I had something similar happen, only without quite as dramatic a meltdown. I had an IBM ThinkPad that had a special high-voltage USB port for powering its external DVD drive. It was supposed to be safe for all USB devices, but I made the mistake of connecting my Windows Mobile Phone via a third-party sync cable. I also made the mistake of doing so during an important staff meeting.

Up to that point, I had kinda been known as the group's technophile, the gadget geek. However, it was difficult to live up to that reputation once everybody in the group had seen pretty blue smoke suddenly poof from my beloved phone.:eek:

[Sven Johannsen]

OK, once again, power supplies don't push power, they deliver what is asked for. The high power port on your laptop (Brad) allows you to connect something that DRAWS more current than the normal .5 A, it does not push more current into device that requires less. The amount of current a device draws is governed by the device and the voltage behind the source of the current. Given everything is expecting 5 volts (USB norm) everything should work just fine. Consider your car battery, it has the ability to crank your engine, putting our several hundred Amps at 12 volts. When you turn on the accessory switch in the car, does your radio burst into flames? Does the dome light go off like an old time flash bulb? No? that's because they only draw the current they need from the battery.

So, why do things have problems? Most of the time it will be some breakdown in the electronics of the device, or just as often, a short, or partial short at the connector. The physical connectors at a mini-usb plug and socket are very close together. If you give a little voltage, with the ability to provide a bit of current the chance, they will go for the least resistance (which generates the maximum current)

So, plugging something that requires .5A at 5 volts, into a supply that can deliver 5 volts at 1, or 2.5 or 10 amps is not inherently going to harm it. Don't chew on your USB power cords or suck on the cables BTW. Saliva is fairly conductive, and even 5 volts at only .5 amps is enough to light you up. It the very least it'll tingle your tongue. Any of you test 9 volt batteries on your tongue?

[Brad Adrian]

Right. But does that mean that a faulty connector alone could have drawn too much power and passed it to the phone, or that the phone itself must have also been faulty and drawn too much power?

Just curious. My understanding of electronics ends at your example with the 9-volt battery.

And BTW, is sucking on connectors and cords a real problem these days? Are there, like, support groups popping up for it?

[Brad Adrian]

...and while I'm thinking about it...

What are the dangers of using an UNDERpowered charger? For example, if I have a notebook PC and use a charger that is in every way identical to the original but it delivers, say 0.5 or 1.0 volt LESS than the original, does that harm the battery or PC?

Thank you for the impromptu lessons in electronics, Dr. Sven!:D