Doing nothing special our iPhones drain their batteries at between 2% and 4% per hour so we usually charge them each night. However a couple of days ago they started eating battery at the rate of about 15% per hour which caused much distress in our household especially as it just so happened that I had upgraded the IOS to 4.02 around that time and also installed an update to the Bria iPhone VOIP client. I had broken the fundamental IT rule of change one thing at a time.
It seems from Mr Google that battery drain isn’t an uncommon problem on iPhones and there are multiple causes including dud batteries, errant applications not going to sleep properly with IOS 4, hungry VOIP applications and IOS 4 timeout too low talking to MS Exchange. One thing that did seem to fix a lot of the problems was restoring the iPhone to factory defaults and in the end I had to do this and it did fix the problem – until I configured the email that is and then it was deja vu all over again.
The problem it turned out was that I’d made a third change that day, I’d applied some Windows security patches the our Exchange server and one of them had crippled Activesync. I guess the phones were continually connecting to email to download mail. The fix here followed by a restart of the server fixed the problem.
From now on its strictly one change at a time.