Having searched about for almost an hour and testing a few AC/DC converters, I'm coming here hoping to bump into someone with electrical expertise.

I'm looking for an AC/DC converter that I can use for my CoolMax HD-211-eSATA 2.5" HDD enclosure. I have to take this on site when analyzing / repairing computers. Recently, I've bumped into computers with USB ports that do not provide power. This would force me to bring my heavy 3.5" enclosure which I'd like to avoid.

I have a few AC/DC converters and most provide too much current (15V, 6V, etc.). I do have one that provides 5.41V but is this too much?

Having used a multimeter on a USB to DC plug (on a couple of USB ports), I get a DC measure of about 5.14V (+/- 0.03). Can I get away with using an AC/DC converter like the one mentioned above rated at 5.41V (approximately .3V too high)? Do I have to consider the amperage? On the converter, it has the following specifications:

Input: 100-240V 350mA 50/60Hz
Output: 5V ख़ 2A

I have seen AC/DC converters generally rated at 5V ख़ 2A Output, would I be safe with a reading of 5.41V?

Those numbers relate to voltage not current, and those adapters are definitely not compatible with an external device expecting to be USB-powered.


Typical 2.5" disk drives have a power spec of 5V +/- 5% (i.e. a maximum of 5.25V), so yes, 5.41V is too much. I don't know how accurate your voltage readings are, and I guess that measurement was taken with no load (and hence may be different with the load of the disk drive), but on balance, I wouldn't use that PSU.

Furthermore there are requirements regarding ripple, and some PSUs may also be outside the spec on the required load regulation, due to the changes in current requirements during power-on, for example.

CoolMax claim to offer an optional PSU for that enclosure. We could reasonably expect them to have tested that PSU for suitability, so IMHO the safe option would be for you to get their one (or another PSU specifically designed for 2.5" disk drive enclosures). Other PSUs might be OK, but there is more to testing for suitability than just measuring the off-load voltage, even though that is one important value.