Battery not charging?

I'm trying to load music onto an iPod that hasn't been used for about a year. It's a 20Gb model.

The battery seems to be flat, and I don't seem to be able to charge it. I've got it plugged into an iPad charger, and the following cycle keeps repeating:

- An Apple logo appears on the screen, with the backlight flashing on and off a few times

- The iPod Menu appears for about 5 seconds (the battery icon on the top right flashes white and green, and has a lightning flash through it)

- There is a noise which sounds like a hard disk trying to spin up, then a click, then it spins down again

- This message is displayed: "no battery power remains please connect ipod to power"

Is there a problem with the hard disk and/or the battery?