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Comment by jacquesm | Hacker News Reader

Check the video. It starts off as a fire, then there is a significant bang and pieces spray all over the room.

That’s still deflagration and not detonation. Don’t get me wrong, understand that rapid thermal decomposition of a battery strongly resembles an explosion, but it isn’t one. Scary, dangerous, but only in terms of burns and shrapnel, no shockwave is produced.

I am fairly sure the distinction is lost on the general public, and I am also fairly sure that to all intents and purposes it will not make a difference. When people plug in a laptop and it goes bang and sprays burning pieces all over the room they will be more than happy to call it an explosion (see title of TFA) even if the scientist in you does not see one.

Also, I did not see a barometer in the footage and if expanding gas did not propel those pieces of shrapnel outwards I wonder what did. So maybe there was a shockwave, just not a very large one and that was probably mostly due to the confinement of the battery not being very strong.

If there is one way to turn a small bang into a bigger one it is by confining the gas a little longer by using a stronger package.

First I just want to say that I agree with you, that was an explosion; explosion and detonation aren’t necessarily the same thing. Loud noise and rapidly expanding gas = explosion. One correction though, which is that a shockwave is supersonic, and just judging by the fact that burning fragments were on the floor and not punching through the wall, I’ll guess it wasn’t supersonic.

Still an explosion!

Ah I wasn't aware of that distinction, I thought a shockwave was any sudden rise and subsequent fall in pressure. Learn a new thing every day, thank you!

My pleasure, and by the way, I really enjoy your blog. You have an interesting perspective and you write very well.

Indeed. These are very dangerous. The fire itself and the initial explosion if someone was in the room but not at proximity of the laptop. On the other hand, the spray could hurt and do incurable skin damage.

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