This is a well-known (and well-researched) issue.
Lumia 920 Cyan - ATT - Overheats, Battery Draining - Nokia Support Discussions
From my personal testing, this is limited to the Lumia 920, sad to say. I've performed similar testing on the Lumia 620, 720 and 820. None of those phones suffered from the same "battery drain" spiral that the 920 appears to have. My wife and I have (combined) had six Lumia 920 phones....all with the *exact* same problem.
Want to try and repro this problem yourself? Try this:
- Download 'Dredd vs Zombies' from the Windows Phone store
- Charge your phone to 100%
- Play 'Dredd vs Zombies' for 20 minutes (most any game will work, but this is a good one to get the phone warm)
- Exit the game, note the battery level %, and leave the phone alone -- this is best to do right before you go to bed
- Leave the phone unplugged overnight
- Note the battery level % again first thing in the morning
- Leave the phone unplugged, and note the battery level % every hour for the next few hours
In my case, my most recent Lumia 920 was down to 70% battery by morning, and then completely dead by 10PM. Nothing else was installed on the phone *except* for the 'Dredd vs Zombies' game (I had performed a factory reset). It essentially drained the remaining 70% of the course of 15 hours -- with me only taking a screenshot every hour.
A normal Lumia 920 -- even with email syncing, Facebook, etc. -- should only drain at a rate of 1% per hour if left alone. Usually even slower than that. After the (above) testing, I rebooted, charged to 100%, unplugged, and left it overnight again. In the morning, the battery was still at 100%, and only down to 98% by the end of the day.
Please note: The battery does not SUCK on these phones. It's actually
quite good under the right circumstance. That said, there is definitely an issue with "battery drain" that seems to occur after having warmed up, heavy data usage, and other things. Despite what others have said, it is NOT due to Facebook, Skype, the Drive app, and so on. They may trigger the issue, but they are not the cause.
Are you hacked about this? You probably should be. Please contact Nokia Support (as I have...on many occasions) and demand research and a fix.