Go to Settings/About Phone/Battery Use/Cell Standby and look at your time without signal percentage. If this is high, then that is the main culprit. During the workweek I sit where there is a poor signal and I am usually between 90-95% of time without signal and I usually have to charge again by 1:00-2:00 because I am down to less than 40%. I take it off the charger at 6:30 in the morning. On weekends at home I take it off by probably 9:00 and by evening I will still have 70%+ charge. BTW, time without signal means that you are not connected to at least three towers. It searches until it finds three. I never actually lose a signal at my work and can still use the phone normally. It just kills my battery.