Comment by delfinom

Comment by delfinom 10 months ago

37 replies

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I work in the battery space.

All you have to do is build replacement batteries without the pressure relief vents. You can easily get a Chinese manufacture to do this for a fee and properly some complaining about how stupid it is to do.

Then wrap it in some nichrome wire and have a micro run some power through it. The nichrome wire will overheat the cell really quickly causing the cell to rapidly over pressurize and boom.

Small pouch or prismatic cells that would be used at the size of a pager generally won't burn. And I speak from experience of doing stupid shit to them in the name of testing, nothing like using the nail puller side of a hammer to puncture them, or rigging up a fixture with 3 concrete nail guns to shoot it or well, fun stuff

jandrewrogers 10 months ago

This wasn't a battery, it doesn't match the damage seen. The evidence has all the hallmarks of a small charge of high-explosive.

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gizmo 10 months ago

Explosions are essentially about extremely rapid expansion of gasses. I don’t see how a battery, even one that is rigged to fail, can explode in an instant. Shorting out, overheating, and ultimately exploding because the battery compartment can no longer contain the expansion has got to be too slow by many orders of magnitude. Your theory makes no sense to me.

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  • Retr0id 10 months ago

    Pressure vessels without a pressure-relief system explode once sufficiently pressurized.

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    • kelnos 10 months ago

      Sure, but can you get 1,000 of them to explode simultaneously that way? You'd think there'd be some variation in the time of explosion, at least by tens of minutes or hours, maybe even by days.

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      • loodish 10 months ago

        Shorting the battery would probably cause an explosion in around one minute. That's close enough to simultaneous.

        From https://www.mdpi.com/2313-0105/8/11/201

        A puncture causes runaway/explosion in seconds. Overcharging takes 13 minutes. There's not good data on a dead short (because it's unlikely during normal operation), but it's going to be between those on the faster end. From personal experience a shorts cause things to get noticeably hot after about 10 seconds, the graphs show that once you hit 60C things rapidly get worse.

        A relay may have been required to hold the short as the battery stops supplying voltage.

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    • kergonath 10 months ago

      A battery pouch is a terrible pressure vessel under these conditions. It’s designed to bulge and deform to avoid catastrophic failure. It would need to be replaced with some very stiff material that can withstand the first step of thermal runaway. A battery not submitted to mechanical stress (e.g. by being punctured, hit very hard or shot at) is going to get quite hot before expanding.

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    • CydeWeys 10 months ago

      Batteries aren't pressure vessels though. Pressure vessels are generally decently large; how are you going to get one with significant capacity inside something as small and lightweight as a pager? Just putting in some plain explosives makes a lot more sense.

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      • Retr0id 10 months ago

        A battery without pressure relief is definitionally a pressure vessel. How much damage it actually does when it explodes is another question entirely.

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        • CydeWeys 10 months ago

          It's a very minimal amount of pressure it can withstand, is the point. Certainly nowhere close to lethal explosive pressure. It's not a pressure vessel in the sense of the kind of pressure vessel it takes to make an effective bomb.

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  • wizardforhire 10 months ago

    It’s the simultaneous timing thats a giveaway for me. Maybe you could have a few batteries explode but 2000 of them? It’s too clean to be just batteries imo.

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londons_explore 10 months ago

These pagers probably had puch cells - those catch fire violently, but don't explode because the film can't contain much pressure.

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dboreham 10 months ago

Ok well someone's on some TLA's list now.

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  • [removed] 10 months ago
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FergusArgyll 10 months ago

How do you ensure they all blow up at once?

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  • efitz 10 months ago

    Modified firmware that triggers on a receipt of a particular message and/or from a particular number?

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  • ocdtrekkie 10 months ago

    > Then wrap it in some nichrome wire and have a micro run some power through it.

    Presumably some software that triggers this?

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  • mrtksn 10 months ago

    I see some reports claiming that the trigger message was “07734 58008” but hard to tell if all these accounts are serious.

    My guess would be that not only the battery but also the main board was modified to initiate the action.

    edit: why do you think I'm not sure if they are serious? Calculator jokes are not a niche humor :)

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    • dllthomas 10 months ago

      > I see some reports claiming that the trigger message was “07734 58008” but hard to tell if all these accounts are serious.

      Clearly someone's not being serious.

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      • UberFly 10 months ago

        Good catch. Your 3rd grade, calculator-using self is serving you well.

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      • dogfighter75 10 months ago

        It's extremely hard to tell if these accounts are, in fact, serious

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davidw 10 months ago

I want to see a video of this compared to explosives.

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mrtksn 10 months ago

Very interesting, so the battery modification is plausible it seems.

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  • highcountess 10 months ago

    I agree with this theory even though I am not even sure it would require a specific modification like the mentioned heating wire, if you can simply use the existing circuit with some instruction to cause component overheating with the same effect.

    Another reason I do not believe it was an explosive is that a clandestine explosive installation would have resulted in far greater damage and included shrapnel. Because why would you not install very high explosives and shrapnel in a shape charge that directed the explosion into the likely body of the wearer if you are taking the risk of intercepting and making a physical modification.

    This is also less Stuxnet and more infiltrating insecure systems of vehicles to drive by wire accelerate cars into objects. There have been examples of this

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    • efitz 10 months ago

      > a clandestine explosive installation would have resulted in far greater damage and included shrapnel

      No and not much. The amount of explosion you get is proportional to the amount of explosives used. Small amount of explosives == small explosion.

      Shrapnel is specifically engineered into explosive military weapons - it is not an innate property of explosive reactions. If you want a lot of shrapnel you have to design the case to fragment (e.g. grenades) or pack the area around the explosive with the stuff you want to become shrapnel (as with many bombers packing nails and screws and bolts etc., around their bombs). A small explosion in a mostly plastic device will result in a small amount of small pieces of plastic being scattered, which might harm bystanders but is by no means guaranteed or even intended to do so.

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      • hindsightbias 10 months ago

        It would seem if they're going to all this trouble in the first place to design a substitute case of materials that had good shrapnel effects.

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    • zdragnar 10 months ago

      A shape charge would be pointless because you can't guarantee how the device is worn- one news article mentioned most people carry them in their pockets, so a shape charge would be blowing most of the energy away from the target in 50% of the cases.

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      • sandworm101 10 months ago

        A shaped charge need not be unidirectional. It could be focuses along an axis, resulting in a two-way explosion that would be more damaging than a symmetrical one. Two copper disks on either side of the charge would constitute a functional two-way shaped charged.

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        • fhub 10 months ago

          I think the grocery store security video supports the two directions idea. If you watch carefully it looks like a pressure wave away from the target and clearly something takes the target down. Perhaps a pressure wave in the opposite direction too.

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      • jcgrillo 10 months ago

        With a pager you can be pretty sure the target will be holding it with one hand and looking at the screen. Reports indicate the pagers beeped shortly before they went boom. So if the blast is focused in the plane normal to the screen that would focus it into the hand and face of the target. No idea whether that's actually a good idea or not.

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      • roywiggins 10 months ago

        Doing much more damage 50% of the time might be more effective, if an undirected explosion is too weak to kill anyone but a directed (and lucky) one could.

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        • ValentinA23 10 months ago

          I've seen some videos. Shattered hips, abdominal wounds, hands without fingers. I haven't seen any dead person, just maimed bodies. Mission successful I guess. Oh and one kid.

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