I'm an Italian engineer and iOS developer, who recently bought the brand new iPhone 4S .
As most of you who have bought such device , I'm experiencing poor battery performances , even after the latest 5.0.1 iOS update from Apple.
Therefore I wanted to try to understand what was the real cause of such bad performances and - moreover - why does it seems that only certain iPhone 4S are affected from such battery inefficiency behaviour.
By looking at the Internet, most of the hints lead to the conclusion that a particular mix of Apps - or even just one App ( you may find many pointing at Facebook or Fousquare Apps as culprits for the bad battery performances) may cause this huge power drain.
The only way to match such apparently contrasting reports from users all over the world with the fact that at least one certain cause shall explain the power drainage exeperiencied by us all was - in my mind - to find a solution in what the Apps could do to make things go wrong.
By using the Apple Instruments tool from Apple Developer suite (shipped with XCode) , I found this interesting thing :
it seems that the very cause of battery drainage is a bug in the video card driver , which could be triggered by applications making use of certain iOS APIs.
I found this by looking at the energy consumption graphs extracted from my iPhone 4S and comparing them with other information taken from the device.
It seems that - even in sleep state - and when nothing should use the GPU, there is recorded video card activity. But the most interesting thing is that it seems the device does not recognizes this activity as a power draining activity, therefore my theory is that iOS can't trigger power saving algorithms to shut down the video card since it can't detect the fact it is consuming battery power.
I will attach here a screenshot taken from Apple Instruments tool which shows a 17% video card activity while energy usage is recorded as to be zero, and even when the Display Brightness is exactly zero, there's still video card activity ( near 1%) , but still no energy consumption is recorded by the iPhone.
I'm writing all this here hoping that Apple will examinate my theory and - if confirmed - will soon release a fix for this annoying issue.