Is your Galaxy S2 driving battery like anything? Are you frustated with your Galaxy S2 battery backup? Here is a simple solution, as observed the battery life on Galaxy S2 with 3G on consistently is pretty bad. Perhaps the only way to minimize it, is using, GSM (2G) mode whenever 3G is not required.
To change the settings: Goto Settings->Wireless and Networks->Mobile Networks->Network Mode Select GSM only whenever you are not using 3G. It gives more than 1 day backup on a normal usage through out the day.