Hi there,
I'm not sure if anyone out there has an answer to this insane question:
But is it possible to use my laptop only has power supply via usb for my
mobile phone. Yes you heard right: I don't want to boot an operating
system I only want to charge my battery of my mobile phone. No fan should
be powered on. I only need voltage on the USB ports.
Any suggestions? 
best regards,
FliTTi
Get a minty boost from LadyAda and use batteries. Much lighter than carrying a laptop as a big battery around. 
http://www.ladyada.net/make/mintyboost/
-Gabriel
Matthias Flittner wrote:
I think the last dell business notebook I had my hands on has a bios setting that enables usb power when the laptop is off and plugged into the AC adapter.
It's not on by default.
If you have one, you may want to check.
-Paul
Matthias Flittner wrote:
My last Lenovo laptop had a setting in the BIOS for exactly that. Worked
great for hotel rooms (which notoriously have very few power plugs) when I
wanted to charge my cell phone and other devices over night. No clue
about other vendors.
Hope that helps,
Adam
Every Mac laptop I have ever used has powered the USB ports whenever connected to AC or airline power, regardless of whether asleep or awake.
Not sure if it will power USB ports when powered, but, shut down or not. Have not tested that.
Owen
Why carry a laptop? Here are some examples
If you're looking at one of these, just be aware that they are 110 volts
only.
  Scott.
Roy wrote:
Why carry a laptop? Here are some examples
Belkin Mini Surge Protector with USB Charger - Walmart.com
131 0711 - MILI POCKETPAL USB CHARGER, BLACK/BLUE - is no longer available at Cyberguys.com
131 0704 - DUAL USB AC ADAPTER IPOD/IPHONE COMPATIBLE - is no longer available at Cyberguys.com
Toshiba netbooks also have a (bios-enabled) USB charging port (and a
netbook's something you might be lugging around anyway?)
I only need voltage on the USB ports.
Voltage won't be a problem .. current will be.
By default, USB supplies 100ma of power. To switch into "high-power"
mode (500ma) requires the device and the host agree on doing so.
If you're at all handy with a soldering iron, this is a fun project to
do what you need : Minty Boost! - USB charger for your gadgets
There are also any number of commercial devices that can do universal
voltage (100-250v 50/60hz) to 5v USB that are barely larger than a
matchbook.
Cheers,
Michael Holstein
Cleveland State University
Why carry a laptop? Here are some examples
Belkin Mini Surge Protector with USB Charger - Walmart.com
131 0711 - MILI POCKETPAL USB CHARGER, BLACK/BLUE - is no longer available at Cyberguys.com
131 0704 - DUAL USB AC ADAPTER IPOD/IPHONE COMPATIBLE - is no longer available at Cyberguys.com
I have two of these (bought from Fry's and Micro Center stores) and they
work well (charging my iphone and
headset as we speak :-). zip-linq also has a dual auto version that
works well (I actually have 3 of that one,
one for each of my and my wife's cars and another to leave in the
backpack). Neither terribly expensive.
You can also use a powered usb hub. Overkill unless you need the hub too...
-- Pete