I asked a question a few months ago about what I thought was possibly a failing external USB HDD. I have disconnected that HDD and the powered USB 2.0 hub has worked better. But I noticed that the USB thumb drives would sometimes fail to be recognized by the computer and the hub. So my reasoning is that the hub cannot handle 3 external USB drives. It just dawned on me that the My Passport is powered through the USB interface not an external wall wart.

My hub now is only in the 10 watt range(5v@2A). Could I solve this by getting a powered USB 3.0 hub that has a higher wattage capacity, e.g., 36 W range?


The answer depends on two factors:

  1. What is the power capability of ports on your hub. Some hubs have built-in power switches with certain pre-set limits (which are subject to manufacturing variations), some have no control or protection other that "resettable polyfuses" that may have marginal threshold. You can do some experiments with your hub by momentarily shorting VBUS to GND (red wire with black wire in USB cable with, say, 5-Ohm resistor, to determine the port capability.

  2. The hard drive of 3TB size is definitely not a SSD. Mechanical drives have a spin-up current which can significantly exceed the USB port power capability. I have seen older drives that would normally consume 700-800mA during intensive RW operation, so USB3.0 ports should be fine. However, the spin-up current was in excess of 2 (!) Amps for a good portion of a second, which would cause port overcurrent and failure to connect.

The "WD My Passport" 3TB(TB?, or USB3.0?) drive does not publish any specifications about the spin-up current, which is a suspect in my books. If you could measure this in-rush/spin-up current, it will help you to determine if it can "overpower" your hub port.

EDIT: SUMMARY. A USB3 HDD has all rights to consume up to 900mA from the cable, per specifications. A USB2 hub must cut-off VBUS power if the connected device tries to consume more than 500mA. Therefore these two devices are not compatible and are not guaranteed to work together.

COMMENT: In theory, a HDD can determine if the connection is USB2 or USB3, and scale its consumption accordingly. Unfortunately, inexpensive USB-SATA bridges do not have this intelligence yet.

  • No the WD Passport is a usb factor 3.00 drive rated capacity of 2Tb but factoring in overhead comes to 1.8TB. – Rusty Russell Jul 26 '16 at 14:30
  • Your question is ill-defined. You didn't specify which particular hub do you have. "A hub" is not enough. There are different USB 2.0 hubs. Some hubs have individual port power controllers, some hubs gang all ports together and have only one common 2-3A polyswitch (resettable fuse). In the latter case this hub can source up to the entire wall AC adapter capacity into one port, and therefore this hub would be able to handle one USB3 device, maybe two. There are hubs with individual polyswitches per port. These switches might go off depending on hub temperature. – Ale..chenski Jul 26 '16 at 17:39

A little confused on exactly what you are asking, since your title and question seem to be two different questions, but here goes....

For your title question "Would a 3.0 WD My passport HD overpower a powered 2.0 hub" --> I have never seen any USB 2.0 port that could not power a USB 3.0 device. The only difference would be since it is a USB 2.0 port you would get 2.0 speeds NOT 3.0. Hence the name Universal Serial Bus.

For the question in your question (or the body rather) "Could I get a powered 3.00 hub in the $ 30.00 range as long as it had a higher wattage capacity, etc 36 W range" --> A quick google search will return endless hits on a USB 3.0 Hub, now to meet the specific wattage request you may have to drill down a bit on it. However, I googled and found multiple results so I am sure you can do the same for that.

  • Sorry I meant that the WD My Passport was a usb 3.0 device. Sorry for the confusion. Not that it is here nor there. Stomach issues can affect brain at times. TG that is finally over. – Rusty Russell Jul 26 '16 at 14:32
  • Thanks for the comments. I was told by a individual at InTrex computers that a 2.0 rated hub is not hardy enough to support a 3.0 rated HDD. I have noted in previous post that my computer at random times would not recognize the a third USB External HDD. Therefore I took that HDD out of the loop. But since then my computer at times fails to recognize a thumb drive which IMHO should be minimal power draw. But when you factor in one of the HDD is a 3.0 rated HDD that has no other means of being powered but through the usb port than it must be drawing a lot of amperage – Rusty Russell Jul 26 '16 at 14:39
  • Not sure I'm following "I have never seen any USB 2.0 port that could not power a USB 3.0 device". Many USB drives require a "Y" cable and two ports to get enough power from USB 2.0 but run from a single USB 3.0 port. – fixer1234 Jul 26 '16 at 19:11

A powered hub should provide the USB standard power to each of its ports. That will be 500mA (for 2.5W per port) for USB 2.0, or 900mA (for 4.5W per port for USB 3.0). The rating of the hub should match the total power of the ports (the number of ports will drive the hub's power, so you can't go by just the total power figure).

Multiple thumb drives shouldn't have a power issue on a USB 2.0 hub, although the hub could be a bottleneck in terms of data bandwidth. That said, USB hubs have notoriously high failure rates, so that could be an explanation if you're having problems with thumb drives. If the hub's ports work fine with other devices, and the thumb drives work fine if you plug them directly into the computer's USB ports, then there's a different issue that should be the subject of another question.

Hard drives can be a different matter because they need more power. Small drives can often be powered by a single USB 2.0 port. Larger drives often need to be powered by a "Y" cable and two USB 2.0 ports (technically a violation of USB standards), or a USB 3.0 port.

But you also need to consider the USB class of what the hub is connected to. If the devices you're plugging into a USB 3.0 hub are USB 3.0, they can draw USB 3.0 power levels from the hub. If they are USB 2.0 devices, they might be limited to USB 2.0 power levels (a USB 2.0 device should never try to draw more power than that, regardless, although the rules are violated for drives or enclosures using a "Y" cable).

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