For the first few weeks after getting my 4S my battery life was excellent, the suddenly it went bad... Originally: Charged to 100% at night, ~95% in the morning, and ~35% when I got home from work Now: Charged to 100% at night, ~80% in the morning, and ~20% when I got home from work Been trying everything, and doing some serious head scratching. Then I realized that the daytime usage was the same - ~60% - for both scenarios so the big drain was only overnight At home I have W-Fi, but during the day at work only 2G cellular. So, it seems to only be a problem when on Wi-Fi Finally, I worked out that I didn't enable iTunes Wi-Fi Sync until I'd had the phone a few weeks (it's disabled by default) although I can't be certain that the change in battery drain coincided with enabling iTunes WiFi sync, but it was certainly around that time. I'm now thinking that my phone is searching for my MBP (which is turned off) all night trying to sync to iTunes. This would explain the big overnight drain. Tonight I'm going to disable Wi-Fi Sync (has to be done from iTunes) and see if the battery drain rate goes back to how it was. Does anyone else with poor battery life have Wi-Fi Sync enabled? I would guess that if you have any Wi-Fi connection then it will try to sync, even if it's not your own home W-Fi - which may explain why some people have really massive battery drain as they may have a Wi-Fi connection at work etc.