This I’ve noticed happened to my IPhone just after coming back from Holiday in another country. What I did while I was away is, I switched the Date and Time on the phone to set the Time Zone automatically. Soon after that I’ve noticed that the battery life drains quickly from 90% to 10% in just a couple of hours. A couple of Days ago I’ve updated to iOS 5.1 so I’m sure it’s a bug in iOS 5
After turning the feature off that automatically sets the Time Zone, my battery did not drain that quickly anymore although the entire draining issue is not solved it did help a bit.
To turn the feature off do the following
- Press Settings->General->Date & Time
- Flip Set Automatically from On to Off
Also do the following
- Press Settings->Location Services->System Services
- Flip the Setting Time Zone to off.
Once all is done drain your Battery up untill 3% and do a Full Cycle Recharge and turn the Phone off.