Apple iPod nano (7th generation) - Manual (Page 8)

Chapter 2 Getting Started 8
If iPod nano is connected to the USB port, the battery will not charge if the computer is turned
off or asleep.
You can disconnect iPod nano before the battery is fully charged, and you can sync while the
battery charges. For more information, see
About the battery on page 13.
5 Disconnect the cable from iPod nano when you finish.
Don’t disconnect iPod nano if you see the “Connected” or “Synchronizing” message. To avoid
damaging files on iPod nano, eject iPod nano before disconnecting the cable if you see one of
these messages.
For more information about safely disconnecting iPod nano, see
Disconnecting iPod nano from
your computer on page 13.