Box 2.5" powered by only 1 USB

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Is there an external box for 2.5" HD which can be powered on connecting
only 1 USB?

Re: Box 2.5" powered by only 1 USB

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Hi marco, go to and type in
external 2.5 HD case.
You`ll get loads of options

Re: Box 2.5" powered by only 1 USB

Marco wrote:
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They exist. Whether it works depends largely upon which HD you install and
how good your USB port is. I've got an old one from Apricorn which has an
equally old Toshiba MK4025GAS drive in it. It is on the ragged edge of
working/not working when powered from a USB port. Most of the time it does
spin up and work fine but this time when I plugged it in the light came on
but the drive didn't initialize (it did start up when the PS was plugged
in). I'd assume that if one had a very low current single-platter drive a
dependable unit might result.

BTW: just tried again and with the drive warmed up for a few minutes it
starts/reads/writes fine with just the single USB port for power.

John McGaw
[Knoxville, TN, USA]

Re: Box 2.5" powered by only 1 USB

John McGaw wrote:
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Expanding on what you've said.

The problem is not the box, it's the port and the drive.
A USB drive reports to the OS how much current it needs.
All the ones I've seen have reported the maximum USB rating
no matter what drive is installed.  And ALL of the drives
required more than the maximum current.  The chip can't
report more than the maximum available, or it wouldn't be
standards compliant, so they LIE.

My observation is that:
Desktop USB2 ports are more robust than laptop ports.
USB 2.0 laptop ports can sometimes work.
USB 1.1 laptop ports almost never work.

There's often overcurrent protection, but different strategies.
Some ports just limit the current and let the voltage drop.
This can send your drive into fits.
Some reach the limit, give an error message, but continue to work.
Some reach the limit and shutdown until the load is removed.
Some reach the limit and shutdown until the system is powered off/on

There's often a PTC resistor in the mix too.  Problem is that
once a PTC resistor gets hot enough to trip, it's structure
is changed so that it takes less current to trip it next time.
I've seen ports work initially, then start failing later.

The dual cable splits the power load randomly between the ports
and often works...often...

Another solution is to get a box that has an input port for
power...but these, too, have problems.
The cheapest thing to do is just put the power directly in parallel
with USB power.  That works fine until you turn off your computer
and the USB drive power tries to run your computer.  People have
reported dead laptop motherboards from this.  Ok, fix it with a pair
of isolating diodes.  Problem now is that the margnial voltage is
now marginaler.

Using a powered hub with a switch for internal/external power
solves both of these problems.

I finally got so fed up with it that I made a USB extender cable
where I cut the power wire and tapped in an AC supply for the drive.
I also rewired a laptop docking station by connecting a fuse from the
5V mouse power to the USB port.

The problem with all this is that it's almost impossible to learn
how a drive box will work.  They're no-name no-support no-vendor
devices.  Closest thing to a spec is, "works good, lasts a long time."

I have a pair of Western Digital 250GB drives
WD2500XMS-00.  Seems to work well in most cases.
Get overcurrent message on my laptop, but it works.


The good news is that flash thumb drives are now cheap enough that most
of hardly ever need a USB hard drive any more.

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