USB port powerful enough to power a external USB drive?

Discussion in 'MacBook Air' started by NRose8989, Feb 15, 2009.

  1. NRose8989 macrumors 6502a

    Feb 6, 2008
    I was wondering if the since the MBA's USB port has extra power running through it, if it is able to power a USB drive without a AC adapter.
  2. dborja macrumors 6502a

    Sep 13, 2007
    Northern California
    Yes. I've used it with a Seagate FreeAgent Go for backups and Time Machine with no problems.
  3. SFStateStudent macrumors 604


    Aug 28, 2007
    San Francisco California, USA
    +1 ^^^ No problem whatsoever. If it can handle your MBAir Superdrive, it can definitely handle the external USB drive...:cool:
  4. millar876 macrumors 6502a


    May 13, 2004
    Kilmarnock, Scotland UK
    only issue you might have is some 2.5" HDD cases require 2 USB Ports to power them, and cos the MBA only has 1, you'd need to use a hub, which might not pull through enough power from the port as its a non standard (as far as power output goes) USB port
  5. dborja macrumors 6502a

    Sep 13, 2007
    Northern California
    That's true. If you buy an external 2.5" drive, as opposed to building one, it usually is of the single port variety so I'd stick with those. Prices are better nowadays for external drives than for DIY external drives. So unless you absolutely want a specific drive or already have one...
  6. johnnj macrumors 6502a

    Dec 11, 2008
    Not here
    I'm using a WD 320 gb 7200rpm drive in a cheap NexStar enclosure. It came with one of those two port USB cables, but the drive works just fine on the MBA's port using a normal cable.
  7. hodgeheg macrumors regular

    Dec 7, 2008
    Basically, Yes.

    Many external drives come with a two port cable. This is for use on computers that don't supply quite enough power over a USB port. I've never needed to actually use the second one with any Mac (and I've had a lot, believe me), and the Air (which I now have) has a higher powered USB port than just about anything.

    I use an external case that contains my old MacBook's hard drive. For neatness I replaced the 2 plug cable with a single plug cable. It works fine.
  8. n8236 macrumors 65816

    Mar 1, 2006
    If memory serves me right, the total amount of power of all the USB ports on most laptops is 500mA. Do not confuse this as each USB port having 500mA. So, depending on the # of USB ports available, the 500mA gets distributed among them accordingly.

    Also, if you're plugging in an USB device that requires a substantial amount of power (ie. ext 2.5" hd), make sure you use the thicker cables. The thin ones only provide data transfer (for the most part).
  9. illegallydead macrumors 6502a


    Oct 22, 2007
    The USB port on the MBA is actually over-powered from the official USB spec. (more or less specifically because of the SuperDrive accessory)

    So yes, it will have plenty of power. If it has enough juice to spin a big 'ol CD around off of just USB, than it has plenty to power the little platters of an HDD (especially newer ones, as they are getting more and more power efficient).

    Those cables that have a split are only if you need the extra juice, which is really only a problem on older laptops and some un-powered USB hubs (I say some because I had a cheap-o one from Wal-Mart for YEARS that would power anything and everything I put in it, and that was w/o any form of extra power adapter :))

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