3.5" caviar green as external HDD USB-powered


I use almost exclusively WD Caviar green 3.5" disks as internal storage on my desktop mainly because of their cool&quiet operation.

I’d like to know if it is possible, or if anyone has done it, to put these HDD (3.5" caviar green) on an external case with the following two important conditions:

1/ ONLY USB-powered; that is no other additional powering for my external case

2/ NO fan on the external case; that is the case body should be enough to cool the drive without any fan

The reason I don’t consider 2.5" external disks which satisfy the above two conditions is simply because I want to reuse my internal disks that I already have as external additional disks.

If anyone has done it, I’d be interested to know since how long and on which case and if the case becomes hot or just warm.



Well, I can certainly answer #2.

All my USB MyBook Essential drives from WD appear to be Caviar Green drives inside the case, and they don’t have fans - just ventilation slots in the case… apparently WD doesn’t feel a Caviar Green should overheat in an external case as long as the case is well ventilated.

I personally would shy away from USB power, however.  It seems that these forums are full of people having issues with USB-powered drives (not that people aren’t having issues with powered drives as well, but those problems tend to not be power-related).  You “could” be getting enough power over USB to run the drive properly, but if there is a cabling issue or a port issue, or anything like that, and you start losing your data, you’ll end up quite upset… an external power source for the drive just seems better to me… but then on the other hand, there are seemingly tons of happy USB-powered users.

When I look at specs quickly, the Caviar Greens seem to say they need 5.5 watts… the Passports seem to say they need 1000mA of current to function properly, which actually exceeds the minimum USB specs (which I read as 500-900 mA @ 5V).  It’s quite possible, as with the Passports, that your USB port won’t output sufficient current to power the drive.

Thank you for your reply.

The fact that WD sells 3.5" FANLESS enclosures is a good thing to note. However, it is not always easy to find out what HDD model is inside the enclosure if it is sold together (sometimes no way to open it) and often the models are different from those sold without the enclosure.

As for the current delivered by the “standard” USB port, I agree with you that seems not enough to power on a HDD; however the max current needed for a HDD is usually only to get it running (starting to spin). After it is running, it consumes much less. More, (decent) USB ports usually deliver this high current (above the standard) for a short period of time letting the drive starts to spin, then the current consumption falls and the USB port can provide it in cruse regime. I mean often current consumption and delivery on the USB don’t match but the drive still works. Since the numbers are above the standard, you have to be lucky and have a decent USB port.

3.5" drives require +12V and +5V supplies. USB is 5V only.

are you sure this is not +5v OR +12v ? (one OR the other)

Every 3.5" that I’ve seen to date requires +12V for the motor, and +5V for the logic. You can see the power requirements on the label:


The product specification should also tell you the power requirements. However, the following spec sheet only mentions 12VDC (obviously an error):