Battery :@:@

Hello,

I'm having trouble with my Ipod Nano battery not giving me the proper amount of playback time.I don't have any Eq's on and the backlight is only on for 2 seconds and the clicker sound is off. I use my nano while i'm at the gym for about 2 hours and this is after compeletly charging my battery and after the 2 hours I see that the battery indicator has lost about a quarter of its power.I got pretty annoyed because its happend more then once so I charged it again and yet again I get the same result. Anyone know whats going on??