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Joined 1 year ago
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Cake day: February 1st, 2024

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  • Is that true though? As in, is it really that dangerous? It seems that you’ll dissipate power equal to the inefficiency times the nominal charging power, so something like 5V x 2A x inefficiency (inefficiency being 1-efficiency), which will probably be of order a watt.

    I can use my car battery to charge itself without any issues — I just plug the red terminal to itself, and same with the black, which is to say, a battery is always connected in a way that “charges itself.”

    I think the key is that the battery probably isn’t really playing a big role in OOP’s setup — electricity doesn’t “go through the battery,” it just goes from the charging input to the power output circuits, with the additional power (due to inefficiency) being provided by the battery.


  • I’m not sure though — the power output and the charging input are both regulated and (almost certainly) current limited. So I think (not positive…) that you’re basically dissipating your power in the inefficiency the charging and output circuits, with this power coming from the battery.

    The inefficiency should (I think…) just be the round-trip inefficiency of the charging/discharging of your power bank — this should be way, way less than the short-circuit power dissipation.

    The simplest toy model is to take a battery and try to charge itself. So you put jumpers on the + terminal and you connect those to the + terminal, and same for - (charging is + to +, NOT + to -). But this is silly because you’ve just attached a loop of wire to your terminals, which is equivalent to doing nothing. With charging circuits in between things get much more complicated, but I’m not sure if it goes full catastrophic short…


  • For 75kg (roughly average South Korean male weight) and 7" step height (standard in the US I think, not sure about Korea), this is about 0.13kJ/step.

    By coincidence, the human metabolic efficiency is (roughly) the same as the conversion between kJ and food (kilo)calories, meaning this would be (very roughly) 0.1 calories/step.

    Not much, given a single French fry is maybe 5-10 calories. But it’s better than nothing!



  • Pick your favorite tech company, pick a small team with a “nerdy” engineering mandate, and I’m confident you’ll find the academic, geeky science and engineering types you’re talking about.

    They probably aren’t very vocal though, because 1) there’s a huge PR/marketing budget which is responsible for being the face of the company, and 2) well…these are nerdy STEM folks who probably like their job because they get very well compensated to be nerdy STEM types, and not because they’re fanboys/girls.




  • qjkxbmwvz@startrek.websitetoFunny@sh.itjust.worksVroom vroom!
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    2 months ago

    Hmmm, I’m not sure I understand…

    A large explosion every second has units of power, not energy. So to me this is suggesting that the train is putting out power equal to its kinetic energy per second. That’s certainly not the case — it implies that the train is powerful enough to accelerate to the speed in 1s, which is definitely not true.

    But that’s just my interpretation.





  • I think there’s a bias in the US against this sort of thing that doesn’t exist (or not to the same extent) in Europe due to the age of the cities/buildings.

    In the US, a building from the 1700s is a historic artifact to be cherished, while in parts of Europe a building from the 1500s is just the local pub.

    So, the US is often hesitant to modify these old buildings, but Europe seems to have more of a perspective of “it’s a building, not a museum, let’s give it new life by modifying it.”

    This is just from the perspective of me, from the US — and I think these old/new buildings are really neat!