+ 0 Votes Types of devices connected makes a difference. darinj March 16, 2013 at 10:24am PST Standard USB power output is 500mA, which handles most USB devices. With some types of scanners a power adapter must be connected in order for the device to work. Most devices with this type of need comes with the power adpater insert already on the cord. One instance I ran into was the cable I was using to power my phone appeared to be fine except were it had been pinched when I had closed my briefcase and internally it was shorting out causing a major power draw. What kind of devices are you attaching?