Well I got my iPhone 4 about a week ago. When I got it I did several full charging cycles, 3-5 if I remember correctly. And these days an iPhone battery really seemed "unkillable". It was really hard to drain about 50% with wifi and 3g internet, games, photos and videos, music, and several different apps.
But now I experience something strange: my battery drops 30% by night (just locked screen), and when I use my iPhone not so hard as first days (just music and Safari), battery has only 30% remaining (out of 100%) in 5 hrs.
Well, it's very bad. I don't want to charge my iPhone twice a day.
Also, when I leave my iPhone charging for night (I know it can fully charge in 1 hr), I see 93% in the morning. And it doesn't increase.
So, as I said I calibrated my battery several times when got an iPhone, and now battery drains super-fast. Can anybody tell me what's wrong and what should I do to make my battery work as expected (at least 10-15 hrs on hard usage, but 20+ hrs will be welcome :D)?
Hope to hear the solution. I tried setting it up as new already :/
(The original question is on Apple Disscussion Forum https://discussions.apple.com/message/16420171)
Best Answer
Since you've tagged your question with iOS 5, I'm assuming you've updated. Take a look at this question and see if anything there helps: Why is iOS 5 draining my battery so fast?
I had the same issue after updating, and deactivating syncing of Reminders with my work's Exchange server did the trick.