I've been experiencing some trouble with fast battery drain since I have updated to iOS 4.3.5, never experienced it before. I've spent some time reading out through the web, including the Apple Discussion forums, and never found anything conclusive that could lead me to a solution. With some hints from many places and some particular obstination for fixing the problem, I've managed to find a solution. I was willing to share this here just to see if anyone else had the same problem and try to figure out wheter this is a bug or just an ignorant user like me
This is the configuration and symptoms I had for my iPhone 3GS with iOS 4.3.5 (didn' happen until 4.3.4):
Location services enabled, with several apps been allowed to use it;
Celular data (and 3G) turned off;
Usage and Stand by times reported always equal since last charge (really weird, although other have already reported this);
Cell phone overheated;
Battery drain really fast, dropping from 100% to 50% in about four to five hours with almost no use at all.
The following steps solved my problem:
Close all applications to make sure nothing is running in the background;
Reset statistics in order to observe correctly the celular data traffic;
Make sure you have access to the internet over Wifi;
Turn on Celular data and 3G for a short time (2 minutes should be enough). Observe celular data exchange stats: for me it was 3Kb download and 2Kb uploaded, although no application was running in the background (and there was also no need for celular data, since I was connected over Wifi);
Turn off Celular data and 3G.
Turn off (completelly!) Location services;
No more overheating, usage and stand by being reported equal nor battery fast drain noticed: everything was back to normal.
I have come to the following conclusions: it seems that Location services causes problems with Celular data turned off. I'm not sure whether Location services should work at all with Celular data turned off, but I also believe it doesn't give it the right to drain my battery so fast . I'd like to here from others just to see if anyone has experienced a similar thing and if the solution above helped fixed it. It would be interest if we could confirm this is indeed a bug in iOS 4.3.5.