case fans that will start @ 5V ?

[knoober]

Im working on a modified laptop cooling pad for my modem (it cuts out when it gets warm) and I want it to run from a mobo USB port. USB can deliver 5V and my reading says that some fans will start at 5V while others will require 7V. I cant seem to find a list or even any mention of which fans will start @ 5V though. Does anyone know of one or 2 that will? 120mm is good 140mm is better. Thanks in advance

 

[Jeff G]

Ive done the 5v mod on a lot of fans (rosewill, corsair, scythe, bunch of no-namers) and I've never had one not run. My htpc and gaming rig both are currently running fans at 5v.

 

[trents]

It all depends on impedance (how much resistance there is to the start of the impeller turning). It will depend on the bearing design of the fan and the "umph" built into the hub windings. If you have two fans with identical construction except one draws more amps (and so will move more air) it will take more juice to overcome the impedance. So I would say stay away from ball bearing fans and high amp fans if you want it to be able to start turning on 5v.

 

[bob4933]

I've also had no trouble with several types of fans running at 5v. On my "deskputer" I ran several fans off a couple 5v wall warts.

 

[knoober]

Maybe I will make a long molex extension....

I've tried various fans that I have and none of them seem to want to run on 5v. I haven't tried them all, but enough to know I'll probably need to get one just for this project. I've got one running from a "wall wart" (that term is so funny BTW) right now so it isn't a big issue, I'd just love to have the outlet open and get rid of the wart