2.5" harddisk with variable voltage

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I bought a Compactdrive PDX7 portable harddisk (see
http://www.eastgear.com/ ).

It appears that the 2.5" HDD is powered directly by the four NiMH cells,
and there is no voltage regulator. This means that voltage can vary
between 5.5 and 4.5 V depending on load and battery charge.

Most of the time the voltage is around at least 5V. NiMH cells are
pretty stable at 1.2-1.4V until shortly before they are completely

My question is, can the variable voltage affect negatively the write
process, i.e. could it happen that data on the disk becomes corrupted
because the voltage is not stable enough.

Has anybody tried operating a 2.5" HDD at less than 5V, i.e. 4.5V ? What
happens to the data and the drive ?

Alfred Molon
Olympus 4040, 5050, 5060, 7070, 8080, E300 forum at
http://groups.yahoo.com/group/MyOlympus /
Olympus 8080 resource - http://myolympus.org/8080 /

Re: 2.5" harddisk with variable voltage

On Wed, 11 May 2005 23:40:48 +0200, Alfred Molon

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What about on the drive itself?
Many do use regulators onboard so even at the lowest battery
voltage sustainable for more than a few moments, the drive
would still have enough power.  It'd be that last bit of
battery capacity that is the problem assuming the drive is
stable below ~4.4V.

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A bit lowe than 1.4, closer to 1.15 but yes that's true in
the general sense.

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Yes if there are no provisions to prevent operation during
that last rapid decline in voltage... though it would seem
likely that such provision was made because of this

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Why don't you try it and tell us?  Seems a  very useful test
as even though someone else may have tried it, that may not
be directly applicable to your specific drive.

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