Comment by delfinom

Comment by delfinom 3 days 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 3 days 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 3 days 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 3 days ago

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

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    • kelnos 3 days 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 3 days 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 2 days 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 3 days 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 3 days 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 3 days 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 3 days 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 3 days 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 3 days ago

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

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  • [removed] 3 days ago
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FergusArgyll 3 days ago

How do you ensure they all blow up at once?

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  • efitz 3 days ago

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

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  • ocdtrekkie 3 days 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 3 days 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 3 days 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 3 days ago

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

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      • dogfighter75 3 days ago

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

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davidw 3 days ago

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

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mrtksn 3 days ago

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

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  • highcountess 3 days 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 3 days 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 3 days 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 3 days 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 3 days 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 3 days 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 3 days 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 3 days 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 3 days 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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