The battery of my Galaxy S 2 is draining very quickly...including on plane mode I just got a Galaxy S II which I upgraded to ICS.

I really struggle with the battery life. 

I have been looking around a lot on the forums explaining how to save my precious battery.

I have done quite a lot of testing, disabled all energy consuming widgets ... still I cannot get 10 hours of battery life (best case scenario without using the phone at all).

I have pushed the testing further by disabling WiFi, 3G and even switching to flight mode to reduce the consumption. I have also killed all apps (except Battery Monitor).

I haven't touched the phone for 4 hours (leaving it in sleep mode). During these 4 hours the phone has drained 40% of battery. The battery app didn't show anything suspicious.

When I do use the phone normaly (phone call, text, a bit of WiFi) the consumption is obviously a bit higher.

I am not quite sure what should be my next step:


factory reset ?
uninstall every single app to find out if one of them is faulty
Change the battery
The Android Authority has a great article on ways to extend your battery life on the S2.  

In my experience:


Live Wallpaper is a huge battery eater  
When I'm at work my 3G signal is very weak inside the building, which completely kills my battery in about 4 hours.  I've found that if I leave the Wi-Fi connected at work and at home, the phone won't constantly look for a 3G signal, thus saving my battery.
Turning down the screen brightness is also a big help


If you've tried all these suggestions with no improvement, you might consider trying  JuiceDefender.