When my ipod battery dies, and shuts off, I plug the cord in to charged it and all of a sudden it pops up that the battery is half full... This happened on the first 4th gen ipod touch I bought. I returned it to futureshop thinking there was a battery problem. Even when I unplug it, the battery still says half full. Should I be concerned about this? Again, this is after the battery has been completely drained. Thanks!