Question concerning the output voltage of a USB port...

The charger for my cellphone works two ways: I can plug it into a USB port on my computer, or I can plug the USB cord into a wall outlet adapter. I'm assuming the wall adaptor steps the voltage down to match the USB port voltage on a computer.

Now, my mp3 player can only be charged with the USB cord plugged into my computer, but I don't always have access to a computer to charge it. Since I don't always have access to a computer to charge my mp3 player, I'm considering plugging its cord into the same wall adaptor my cellphone uses.

Think this'll work, or am I gonna fry my mp3 player?

depends.



what does the label say on the phone charger?  does the phone charge have a usb compliant logo?



usb 1 and 2 are at  5 vdc, but the phone and its changer might be designed to run hotter .. at say 12v.

The phone charger says 5.0v - 0.7a

it will work fine.

I figured as much...thanks for the reply!

I would say that it won't break anything.  It might not work since some companies (Motorola and RIM) require that you either use their power supplies or a computer running the correct drivers.

Most USB ports are 5v and about 500mA.  Most phones with USB connectors should charge from this, but it will charge slower than the AC adapter charger.