My ipod touch 32GB keeps clicking and won't turn on or charge even though power is getting to it. The screen shows a sad face ipod.

We have an ipod classic with wheel. It keeps saying low battery even though I have had it charging for ages. It also makes this clicking sound but refuses to do anything else. I can't get any screen to show except a sad face ipod and the "low battery" screen. I have tried to do the restart option but it makes no difference. Help!