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I'm trying to set up a notebook with 3 external monitors attached, trying to do it as clean as possible without wires sticking out everywhere so I want to velcro a hub on the back, etc.

The external monitors consume 7.5 watts each.

I have a usb c hub but I lost the dc, but I'd prefer not to be plugged into external power if I could and only use the notebook anyway.

I also lost one cable for one of the monitors, and a replacement is expensive but working on finding a cheaper one, but, I can't test, but 2 monitors on the hub work fine with their original cables and no dc, would a third?

edit: system port specs

acer aspire 5 a515-51g

USB 2.0 ports quantity *2

USB 3.2 Gen 1 (3.1 Gen 1) Type-A ports quantity *1

USB 3.2 Gen 1 (3.1 Gen 1) Type-C ports quantity *1

about the burnt out controller, are you saying I should get a powered hub?

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  • Are we talking USB 3.2 Gen 2 Type-C or USB 3.2 Gen 1? Please edit your question instead of submitting a comment.
    – Ramhound
    Commented Sep 29, 2020 at 22:44
  • @John, 3 x 7.5 = 22.5 W, or ~4.5 A. Also, when a device starts, it draws a surge as capacitors charge. A replacement powered hub is much cheaper than repairs for a burnt-out USB controller.
    – DrMoishe Pippik
    Commented Sep 29, 2020 at 22:55
  • Error in my answer: I read 0.75 A in error. My apologies
    – anon
    Commented Sep 29, 2020 at 22:57
  • @DrMoishe Pippek, I didn't see John's comment, are you saying it's a danger to my usb controller not using a powered hub? thanks.
    – Toddd
    Commented Sep 30, 2020 at 1:30
  • Yes, that is what I stated.
    – DrMoishe Pippik
    Commented Sep 30, 2020 at 4:02

1 Answer 1

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No.

USB hubs that are bus-powered themselves cannot pass bus power along to other devices.

Only self-powered hubs (i.e. ones with their own power supply, separate from their upstream USB connection) can provide bus power.

This has always been true of USB since the beginning, and remains true of the latest flavors of USB, even with Type-C connectors.

There have been some hub vendors that use proprietary tricks to break or bend those rules for various reasons, but it's not standard, so it generally doesn't interoperate between vendors.

By the way, USB 3.x bus power is only 5V x 0.9A = 4.5W, so a 7.5W display can't be powered via standard USB bus power anyway.

If your displays can be powered over USB, they're probably using USB-PD (Power Delivery), which is a new optional USB standard for delivering up to 100W of power. If your 7.5W display has the ability to be powered over standard USB at all, it probably uses USB-PD. So you would need to confirm that, and then look into USB hubs that can act as USB-PD power supplies. But I doubt you'll find a hub like that, that somehow passes through USB-PD from an upstream USB-PD power supply.

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  • the monitors are asus mb mb169b+ cnet.com/products/… that site says they consume 5 watts but I read 7.5 watts elsewhere,I couldn't find anything about usb-pd but I can confirm 2 work nicely with only usb 3 cables going into one unpowered usb c hub, but they have to be authentic cables, so I don't know what kind of power scheme they use. I may consider getting a powered hub but that kind of ruins the portability (although it's not used portably, but 2 acs going into the notebook I'd like to avoid).
    – Toddd
    Commented Sep 30, 2020 at 1:48
  • @GGarrett2 Hmm, something doesn't add up. I'd like to look up the specs of the bus-powered USB hub you're using. Can you give me the brand and model number?
    – Spiff
    Commented Sep 30, 2020 at 4:36
  • it's nothing fancy, actually I've since read bad things about the brand, amazon.ca/gp/product/B01MY397KG/…
    – Toddd
    Commented Sep 30, 2020 at 4:51
  • actually you guys were correct, usb c is nothing special, it worked well for about 10 minutes with 2 plugged into that hub and one into usb 2, then it started flickering out, not stable, I used a usb 2, usb 3, and usb c port to each power a monitor and it was stable, so I guess that's how it'll have to be, or I can play with a powered hub I have.
    – Toddd
    Commented Sep 30, 2020 at 5:14

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