I would like to know the answer to that one. I realized this was happening just after upgradeing my iOS to 6. Then when I looked up my purchase date, I was about 5 days past my one year warranty. So I'm dead in the water. Apple will replace the battery, but it will be about $80+. I took it to the Apple store, and they checked a bunch of stuff, but said that it seemed ok. I'm debating getting a battery for a more reasonable price off of ebay. But if it's the iOS thats draining the battery, then I'm not going to be able to help it. I wish I knew a better way to tell if its the battery, the phone, or the iOS.
Mohebbi, thanks for posting. It is no fun having battery issues! Are you still having issues with the device? How long does your battery last after it's completely charge? Have you tried using multiple chargers?^SP