Wiring one of my case fans as an external fan via USB

[Foolios]

I have a 12v fan wired with a usb end. USB will output 5v. Fan works on USB but it's rather slow of course.

More info:
I have the reds together and the blacks together from the fan wires to the usb wires. The - and the +'s...

My question is:
Can I take another red and black from another usb cord so that I can power my fan with 2(5v) USB ports to total 10v?
I am curious whether the usb ports would buck each other and fry themselves out if I combine their reds together even though their blacks will also be together.
Can anyone explain whether this would work or not?

THanks!

 

[johan851]

If the USB ports were on independent supplies (and they're not) then the correct way to get them to "stack" to 10V would be to wire the 5V output of one port to the ground of the second port, and then power the fan from the first one's ground and the second one's 5V output.

The problem is that they're going to share a ground, so that configuration effectively shorts the 5V of one port to ground, resulting in an unpleasant blowout.

In short - no, it can't be done.

 

[Foolios]

If the USB ports were on independent supplies (and they're not) then the correct way to get them to "stack" to 10V would be to wire the 5V output of one port to the ground of the second port, and then power the fan from the first one's ground and the second one's 5V output.

The problem is that they're going to share a ground, so that configuration effectively shorts the 5V of one port to ground, resulting in an unpleasant blowout.

In short - no, it can't be done.

Thank you for the information. Glad I didn't try it. I guess I will just drill a hole out the back and run a 12v molex out.

Thanks!