Laptop Explodes at Japanese Conference

An anonymous reader writes "A laptop reported to be a Dell burst into flame and was caught on camera during a recent Japanese conference. Guess this laptop could be a poster child to prove that laptops really can cause sterility if they are on your lap."

Comments

Feeling hot, hot, hot...

[EnderGT]

While it's never caught fire, my Latitude D600 can get quite hot after several hours of World of Warcraft/Call of Duty/etc.

The hard drive is right under the left palm-rest area, and it has quite literally burned my hand several times. It's not suprising to me to see one on fire.

This is a common occurence

[Psykechan]

I was going to make a joke linking this story and a recent story about an iBook catching fire (on video as well) with Dell now listing Apple Mac OS X as a choice on their driver download page. This is serious though.

People, do not use your laptop on carpet or in situations where it may not get ample ventilation. It can burst into flames and harm people or property... well definitely the laptop at least. Read your manuals and follow the disclaimers.

Warning: Do not place your iBook G4 on a pillow or other soft material when it is on,
as the material may block the airflow vents, in particular the rear vents, and cause the
computer to overheat. -Apple iBook manual (Page 70)

Re:When will those idiots at Dell learn?

[dawnzer]

Agreed. My boyfriend's notebook gets so hot, that he puts it on a pillow if he wants to use it sitting in the recliner. I finally bought him a "chill pad" from Target that plugs into a USB port to power a couple of fans that draw the heat away. He loves it. =)

Re:When will those idiots at Dell learn?

[dawnzer]

It is made by Targus. They make a lot of notebook accessories.

http://www.amazon.com/gp/product/B0000AKA8Y/104-16 03678-2242319?v=glance&n=172282

Oh... and the boyfriend says to use a FIRM pillow to prevent blocking the chillpad vents in the back (he still uses a pillow sometimes to prop it up. ;)

Re:Battery explosion...

[NotQuiteInsane]

Must have been a pretty catastrophic failure. There are usually at least three levels of protection on any lithium-ion battery:

• PTC cutoff switch - there's an overtemperature cutoff switch inside each Li-ion cell. If the cell gets too hot, the resettable cutoff switch disconnects the battery from the others. If it gets really, REALLY hot, then that cutoff becomes permanent. This is a last resort protection device, and should NOT be relied on to work. It's there to try and limit damage if everything else fails.
• Protection circuit - monitors state-of-charge, voltage, temperature and input/output current of the battery. If the battery voltage is too low or too high, or if you try to overcharge or over discharge the pack, the circuit disconnects the battery pack from everything else until the voltage, etc. returns to its normal 'safe' range. If you REALLY piss off the protection circuit, it will literally blow a fuse - most packs are fitted with an "SC-Protector", which is basically a fuse that can be blown by an electrical signal (a "self destruct input" if you will). Not only do you get the overcurrent characteristics of a fuse, you also get to blow it if something bad happens. SC-Protectors are not readily available in quantities less than a thousand or so, so once it's blown your battery pack becomes a brick.
• Charge controller - the charging circuit should continuously monitor its output, and shut down if it goes out of range. Not all of them do...

The problem with Li-ion (and to a greater degree, Lithium Polymer) cells is that they're so sensitive - charge them over 4.2V or discharge them below 3.2V and the cell will be damaged. Abuse it a lot and it will blow up. To get that to happen in a properly designed circuit, you'd need a chain of failures:

• First, the protection circuit would have to fail in some way that would prevent it from protecting the battery pack. A shorted switching transistor (usually a MOSFET) and a dead SC-Protector drive transistor would do that nicely. The protection IC can see something's really, really wrong, but it won't be able to do anything about it. Bear in mind the switching transistor has to handle the power of charging and discharging - it takes quite a beating. Shorted MOSFETs really aren't that rare.
• Next you'd have to have a failure in the charge circuit that causes the battery to be overcharged. For the sake of argument, let's say the charge IC has latched up. It no longer regulates its output voltage properly and - again, for the sake of argument - we'll say that there's 5V over each cell instead of 4.2V.
• Now that fault condition has to exist for long enough that the cell electrolyte will break down (usually into hydrogen and other miscellaneous nasties). When that happens, the safety vent will fire and the battery ejects a hot stream of gas.
• Now the final act. A little spark (say, from the PTC switch) and that hydrogen catches fire. That flame heats up another cell to the point where the vent fires, and you have a second cell joining in the explosive fun. In a few seconds, that cell will set fire to another, and the process will keep on repeating until the cells burn each other out, and the fire runs out of fuel.

The big problem with Li-ions is that they're inherently unstable. The nickel-based batteries tend to be much more forgiving of abuse. They usually don't blow up unless you really, really abuse them. You might damage them and reduce their capacity a bit, but you usually won't be able to make them explode or spontaneously combust without some serious work. They do have a lower energy density and terminal voltage than Li-ion and Li-Polymer, though, which might partially explain why they're more stable.