Dell DJ Pocket DJ User Manual page 10

NOTE:
You can charge your device through the USB connector on your
computer only if the battery icon indicates your device has at least a 25 percent
charge remaining. If it is less than 25 percent, you must use the AC adapter to
charge your device. To charge your device from your computer's USB
connector, your computer must be turned on, and your device turned off.
10
About Yo ur Device