There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.

  • WraithGear@lemmy.world
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    28 days ago

    So a standard cable needs to be chipped to show its rating to the device, its not that the device can pull what it wants or can get, but the cable itself tells it what it can supply. Extension cables can’t do that, because it doesn’t know what it’s plugged into, and that would be if they even bothered to put a chip in. They instead piggy back off the chip for the main cable. The problem comes when you you have a 240 watt cable hooked up to a cheap 120 watt cable, with the device being told it can push 240, and starts to super heat the extension cable

    • Mr_Blott@feddit.uk
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      27 days ago

      Brilliant thanks

      5 sentences that inexplicably need a 9 minute video to say

      Fuck YouTube

    • TheChargedCreeper864@lemmy.ml
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      28 days ago

      This sounds solvable, doesn’t it? Have the extension cable have a chip saying it can do X at maximum, then compare with whatever is to be extended and communicate the minimum of both upstream. Might not become a sleek cable-like design, but would extend the 240W cable with the extender safely staying at 120W

      • Petter1@lemm.ee
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        27 days ago

        Well, the source checks the cable using the CC line which doesn’t go through the cable (VCONN). So source only knows the cable directly plugged in. To make the extension cable visible, the sink would be required to check the cable plugged in using VCONN and then the tell max ampere to the source over the other CC that goes through the cable.

        2 Problems:

        1. Sink devices normally don’t read or can’t read VCONN as far as I know

        2. No way of detecting if a third cable (extension in the middle) is present and what specs it has

    • Anivia@feddit.org
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      27 days ago

      Correct, except for your example. Firstly, 120 watt USB c cables don’t exist, only 60w, 100w, 140w and 240w. And only plugging in a 100w or higher cable into a 60w extension would be dangerous, since it would allow drawing 5 amps on a cable over an extension only designed for 3 amps. However, as soon as your extension is rated for 100w it is completely safe to use with any USB c cable, even those rated for 240w, as those only operate at a higher voltage but still only allow 5 amps max.

      I have also never seen an USB C extension cable rated for less than 100w, so this is kind of a moot point. If 60w usb c extensions exist somewhere, they would indeed be dangerous, but I have never come across one

    • Obinice@lemmy.world
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      27 days ago

      Interesting, I’d never trust any USB cable to push anywhere near 100 watts anyway haha good god, the most I ever do is maybe 20w at 5v.

      I’ll keep that in mind when buying cables in the future though this is very useful info!