Users of Apple's new iPhone 4S have reported that the battery life is abysmal even when no apps are open. With battery life dropping by up to 10% an hour, with nothing open. This has also been noticed by a few users of other models of iPhones since upgrading to iOS5.
The problem was first brought to light by The Telegraph in England and apple had been unable to explain it.
The fix for this is quite simple - the battery life is being drained by location services. To stop this drain simply open your settings, go to location services, scroll down to the bottom where it says System Services and open this. Then disable every service except for Cell Network Search.
Battery life can also be effected by a bug in the iCloud Contact Sync coding, which causes the processor to work hard, causing the battery to drop 20-30% in 10-15 minutes while running warm. This can possibly be fixed by by disabling contacts in the iCloud or restarting the device.
But whatever happens expect the engineers at apple to find a solution to the issues and a fix to be issued with the next iOS update.