iPod shuts down during itunes sync

Hi, i'm trying to sync my itunes and after a few minutes the ipod beeps twice over 3 times, I then get an error message on my imac saying "Attempting to copy to the disc "XXXX iPod" failed. The disc could not be read from or written to.

I look at the screen on the ipod and it shows a battery icon that appears 1/3 full, yet the screen is dark and if I touch the wheel the screen remains dark and nothing happens.

I left the ipod connected to the imac and after about 5 minutes it started to re-sync again, and again after a few minutes it beeped and disconnected.

Any ideas if this is a battery or hard drive issue?