This is the second time to happen to me. My 4s is plugged in overnight, I take a look at some stage during the night and it is at 100%. I wake up in the morning and the battery is at 96%, even though the charge indicator is still on. This morning (second time to happen) I even chaecked my emails and played around with it still plugged in, and the charge went to to 95%. It's plugged into a wall charger, not a computer. I did search the forums and rebooted and now it is charging at 97% but why is it losing its charge while plugged in?