Slightly OT -- Power Supply for External USB HDD used with Portable Device

[GrayStrickland]

This query is not 100% on topic, but I think it fits here better than elsewhere.

Does anyone make, for lack of a better term, a powered usb cable?

Lots of usb host devices (pcs, portable dvd players, etc...) don't provide enough current over their usb bus to power some power-hungry "usb bus-powered" devices, such as external 2.5" hard drives. If you have two usb host ports available, you can use a usb Y cable which draws power from two host usb ports to supply a single usb mini port. It seems to me that since a usb (pre usb 3) consists of only four conductors, of which one pair is for data and one pair for power, that you could make a cable which carries the data between the host and device, supplies power over the other pair by mains of an AC-DC (home) or a DC-DC (car) transformer. It would be a little clunky, but it would work. I've searched, but can find nothing.

[minidv2dvd]

i use a powered usb hub. it has it's own ac-dc converter and provides power on the usb line even when the computer is off so you can recharge usb devices.

[Supreme2k]

This is probably not what you're asking, but here's my two cents:

I was trying to transfer data from a desktop to a laptop using and external 3.5" drive. The laptop only had one (working) usb port , which couldn't quite power the drive. Solution: The drive already had a y-cable, so I plugged the other cable into one of those usb-ac adapters and it worked fine

This kind of thing