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Is it possible to convert a regular (normal size) hard drive in an enclosure run off USB power like a laptop hard drive? Answered


Newegg makes a nifty little adapter for this purpose - runs about $30. It comes with the ribbon cable to USB connection and has its own power supply. Wicked cool and it works.

I assume regular size means the hard drives typically used inside a desktop. These drives are 3.5". Hard drives used in notebook computers are 2.5" with some special drives smaller yet at 1.8".

For the desktop size, they require too much power to be powered via USB. USB provides 5V at a current of 0.5A. Newer ports can provide up to 1A. That means a newer port can provide up to 5 watts. Power is volts * current.

Assuming a 3.5" drive I have is typical, it requires: 0.46A at 5V and 0.56A at 12V. So it needs 2.3W from the 5V supply and 6.72W from the 12V supply for a total of about 9W. So, a USB port cannot supply this much power.

Even if you could combine 2 USB ports to supply this much power, the USB's 5V would still need to be converted to 12V. So, the short answer is that USB cannot power a 3.5" hard drive.

It all depends on which enclosure you use for the hard disk as most 5½ hard disks (Normal sized) need 12v which can't be powered by usb (5v)