Ok well ive had the 4s for about a year, and its always been great on battery, i have ALWAYS unplugged it at about 95-100% so it doesnt overcharge and then i always make sure apps are closed and the brightness is down, but just recently (starting about 3 or 4 days ago) it is losing battery power so fast! I have to charge it from about 5% up to 100% almost 3 or 4 times a day, when before i could charge it once and be fine for a few days
Iphone 4s losing battery power?
Any new apps you have been using etc?
WiFi, Bluetooth, GPS etc etc KILL a battery.
Make sure you close your display (so the screen turns dark). Even if your brightness is low, if it still is displaying everything all the time, then it kills your battery quicker.
Other causes - animated or live/active desktops (wallpapers that are animated etc) also kill batteries crazy fast.
It's the operating system the iPhone is on.
iOS 5? I have the same problem with my 4s, it's a bug in ios 5 that eats battery life:(