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USB 3.0 external 3.5" drive without power adapter?

Is it possible to have an External USB 3.0 enclosure (for Sata 3.5" HDD) with no power adapter requirement??? Most of the External enclosures I've seen on Newegg have a power adapter. (I see some 2.5" models without them though.) Is this for backup/extra boost or is it needed?

I'm on my last decision before buying all the parts needed for my new system build. The last part: The desktop case.

The difference: The front port either has eSata or USB 3.0 connection. eSata is faster so if I need a power adapter anyway than who needs the USB 3.0?? Know what I mean? :)

3.5" USB 3.0 Enclosure
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  1. Best answer
    I don't think a USB port can provide enough power for a 3.5" drive, thus the need for a power supply.
  2. Hawkeye: Didn't USB 3.0 increase the available power? Yes, the OP should use a drive with a separate power supply, but...

    USB 3.0 increased the power from 0.5 watts to 0.9 watts at a nominal 5 volts. Still pretty tight for a 3.5" HDD, at under 5 watts.
  3. WyomingKnott said:
    Hawkeye: Didn't USB 3.0 increase the available power? Yes, the OP should use a drive with a separate power supply, but...

    USB 3.0 increased the power from 0.5 watts to 0.9 watts at a nominal 5 volts. Still pretty tight for a 3.5" HDD, at under 5 watts.


    Yes they did. I wish they had boosted it just a bit more. You might be able to get away with using USB power alone, but as you stated, it will be tight. If the manufacturer provides a power adapter, then I assume it won't be able to draw enough power from the USB port.

    If the OP is willing to trade off a 3.5" drive for a 2.5" drive, then he'll have more options available.
  4. I've got two 2.5" USB 2.0 drives that require that g*d-awful Y cable to draw power from two USB ports. I usually plug them into a powered USB hub that I have that's way out of spec - it provides massive amounts of power if the drive tries to pull it.
  5. Thank you all. This is what I thought.

    I hate hunting for an extra power outlet but I want to put my old 3.5" drives to use so no choice. I've decided to go with both types of front ports though, since I found one for $49.99.

    http://www.newegg.com/Product/Product.aspx?Item=11-147-159&SortField=0&SummaryType=0&Pagesize=10&PurchaseMark=&SelectedRating=3&VideoOnlyMark=False&VendorMark=&IsFeedbackTab=true&Keywords=%28keywords%29&Page=1#scrollFullInfo
  6. A USB port provides power at +5V.

    A 3.5" drive requires +5V and +12V power. I haven't heard of any external enclosure that steps up a +5V input to +12V. Plenty of +12V enclosures go the other way, though.
  7. Thanks guys.
  8. So many times I've wished that I had DC 5V and 12V outlets in my home office...
  9. Best answer selected by gggirlgeek.
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