Salvete! I recently purchased a USB 3.0 hub and, since it didn't come with a power adapter, I acquired one separately. I am attaching it to a computer with a low-output power supply, so it is necessary that the USB 3.0 hub provide its own power.

How can I know that the USB hub is drawing its power from the adapter and not the computer (without blowing the power supply on the computer)?

The adapter outputs 19v to the hub at 6.3 amps. The computer's power supply brings 500 watts.

How can I test this?

Is it possible to measure the power output and source with some sort of software? Really, I am at a loss here.

This thread is interesting, if anybody is following my question.

  • A 500 watt PSU is not really a "low-output power supply". A USB port has a maximum 4.5 watt capacity. The hub needs its own power supply because the hub cannot provide more power (through its ports) than its single USB connection to the PC. – sawdust Feb 11 '13 at 23:28
  • Ah, that make sense. So without the power supply, the hub cannot get power for 7 ports from its one-port connection; that is, it only sends 500MA power with 5V to the hub? – bgmCoder Feb 11 '13 at 23:30
  • 1
    USB 3.0 increased the current limit to 900 milliamps at the same 5 volts. – sawdust Feb 11 '13 at 23:44
  • Ah, yes. I knew that... – bgmCoder Feb 11 '13 at 23:44

You can try such third-party utility like USBDeview from Nirsoft

enter image description here

Although, it shows only negotiable power that device need from USB bus, it definitely works for USB 3.0.


The makers of that USB hub (StarTech) have a chat line, and this is what they told me. It IS an answer, so I am giving it here in case anyone finds this useful.

The easiest way of testing would be to use hard drive enclosures that require power to be provided by the hub, connected all these 1 by 1 with out the block being connected, to see how many the computer can handle on its own (when the hub is max'd out on the computers power supply) the last drive will not detect. then connect the power block and then reattach the drive it should then be detected, this will show that the power supply is being used and not the computer.

Here is a page where the user did just that (scroll toward the bottom).


This site has a way for you to see what power IS being used by your USB Hub.

So how do you check to see the amount of power being consumed by your current USB devices? Simple just follow these steps:

  1. Click Start
  2. Click Search bar (Click Run in Windows XP)
  3. Type Device manager
  4. Hit Enter
  5. Double Click one of the Root USB Hub options
  6. Click Power Tab

This will tell you about the particular hub and the amps required to power the hub and what is plugged into it. Here is another guide to the same method.

In this SuperUser posting, a fellow linked to a site where someone built their own tester, but I'd only do this if I were braver.

enter image description here

  • 1
    This does indeed work, however only for 2.0 USB and down - there's no power tab on USB 3.0 devices. – GodEater Jan 23 '15 at 7:54
  • This doesn't work for USB3.0 hub. – Suncatcher Jul 10 '17 at 12:38

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