How long do i charge my mp4 player?
 

I have a Rockchip 2608a player and it is really weird as i can be charging it for 30 minutes only and the battery bar shows green(full) right away.Of cou,rse,when i used it,it lasted quite short.If this is the case,must i ''time'' the duration used to charge the player since it is not able to tell me accurately the battery level?Also,what is the reccomended time that i charge my mp4 player?