hey i just got my pink ipod nano clone mp4 player off of ebay

i used it and the thing is amazing and love it so much except its battery finally ran out so i plug it into the computer to recharge and wait for hours and take it out and the battery is still low and will only play for 6 minutes

ive tried the wall charger and different usb cables

is it possible my battery is messed up and i need a new one? will i hav to return my mp4 player. i have been waiting for weeks for this thing and now im having problems this really sux.

please any advice would be greatly appreciate