I have a Samsung Galaxy lll. I have had it since May.Lately I have been having problems with the battery. (or something) I unplugged it this morning as it was fully charged at 100 % ..then put it in my purse for safekeeping..went to get it 30 minutes later and it was down to 39%. I did not turn iton . Its been doing weird things like that lately. I did take the battery out once and put it back in. Any suggestions ?