Not enough power from USB ports


Mar 22, 2003
My desktop often doesn't seem to output enough power through the USB ports. I just purchased a USB enclosure and although the drive is rated at .55a all I get is a click click click like its trying to spin up but it cant.

Has anyone tried to add a capacitor to the power lines of a USB > SATA adapter to maybe get it spinning up?

Alternatively, my front USB ports are just connected to the headers, is it a decently wise idea to disconnect the two USB power cables and connect them direct to the PSU? One usb port that isn't always on but can spit out a solid 5v does seem to be appealing.
While trying to run a usb cable a decent distance, I resorted to wiring an internal usb connector (with pin sockets on one side, and a standard usb connector on the other) to both the motherboard and the 5v line of the power supply. It worked fine and didn't give me any problems.
Yes, you can hook up the appropriate lines on the USB connection to your PSU. Be forewarned, however, that if you short that connector out, bad things could happen. Your PSU ought to shut itself down on overcurrent, but don't count on it
:D ahhaha yes I almost forgot about that. Had some bad experiences shorting out the 5v line of a PSU before. Along the lines of watching the wire glow red, insulation melt, smoke, and sparks. It still works but that was not the best experience. Almost makes me consider putting in a 1amp fuse along the line. Ill think about it.

Thanks for the input though. I was concerned it might confuse the computer or something. Strange thought yes, but always good to ask first.
Once I shorted a 5 volt, 120 amp PSU with my wedding ring. Got a nice 3rd degree burn from it.
USB connectors have a 5V, Ground, and Data lines. The 5V is the standard old 5V, so it won't confused the computer at all. The wiring could be tricky if you don't have any previous exposure. There are powered USB hubs available, and that would probably be the route that I'd go for this one.
USB ports are limited to .5A and will shut down if you try to draw to much current. They are self protecting. If you are going to bypass this protection by drawing your power directly from the power supply I would recommend putting in an in-line fuse as a safety precaution. My father has a USB powered external drive enclosure. His has two USB cords on it, one is power and data and the other is a pass through power only. If your enclosure has two USB cables try using both of them to get more juice.
I forgot about trying it :eek:
Well, more gave up on the enclosure. Yeah, the enclosure does have 2 usb > one mini usb but its not enough. Funny that my laptop or ipod charger can easily power the drive with just 1 usb power connected. I presume I overloaded that 500ma limit a few too many times. :p
The spec is for 500 MA MAX but I don't know what the tolerance on that is. Maybe your desktop is on the low side say 490 MA and the laptop is on the high side say 510 MA. One is just enough to run the drive and the other just falls short. My fathers external drive has a power connector for an external power adapter, which he plans on buying.
It parallels up the 5v USB lines so it can supply enough power if your USB ports are weak or something. I had the same problem with my external drive.

If that isn't enough, there is a problem with the motherboard not supplying nearly enough power, or the controller in the hard drive enclosure is messed up.