I received my nano 4th generation with what was supposed to be a non working battery. I could connect the ipod to a power source and it worked fine until I disconnected it and then it said battery too low so I replaced with a brand new battery. But I still have the same problem. I can connect ipod to a power source (outlet, computer, dock) and it works fine until I disconnect it and it shuts down. What can this be from? The battery I replaced with was brand new in the package. Ipod will read that the battery is fully charged.