Samsung galaxy s2 battery problem?

i have the galaxy s2 and wondering if i have a faulty unit, i remove my phone from 100% charge at 8am and by 8pm the battery is flat, rarely use it for games i have only the basic wallpapers, wifi is turned off as is auto sync, i have the display on the lowest brightness setting with auto time out set to 15 seconds, all widgets are removed from my home page except the weather widget and im not running any apps in the background or multi tasking. i only make a handfull of short phone calls and texts a day,sometimes i will play the odd game for half an hour (i usually dont) it says that display is using 55% of my battery life but i have it set on lowest setting, i love this phone and i want to keep it but im currently having to carry a charger around in my pocket as by 8pm it needs charging, is anyone else having this problem and can give me some advice on power saving, or confirm i have a faulty unit, any help is much appreciated.