Batter drain after 6.1.2 update

My 4s was the third replacement from apple in 2 months because of battery drain after 6.1.1 was released. This current phone did not have the 6.1.1 update installed on it and I did not install it. My battery would maybe get to 60% after being off the charge for 18 hours. Yesterday I p,urged it into iTunes for the first time and it did the 6.1.2 update AUTOMATICALLY and now the battery only lasted from 7 am to 11 am and it was at 20%. I did not change settings, I did not I stall any new apps, nothing changed except the apple software. I have reset the phone, turned off the cloud, set it up as new, and still have the same issue. When going and looking at the usage, before the update my usage time and stand by it ex would be what you would expect, usage 2 hours ans stand by 12 hours, or something close to that. Noe the usage and standby are only 9 minutes different. What in the software is causing it to run continuously and preventing it o go into standby???????????