After updating my SONYXperia U to ICS, battery drain was a very big problem. I tried lot of applications for fixing this but nothing worked and many things made it worse.
While checking the battery usage, I could see android is in the top list consuming almost 60 to 70% of the battery. For getting more information about battery, I tried the better battery stats app and found kworker threads are main contributors.
After searching a lot, I read in some forum that the problem is caused due to some incompatible settings present which is carried over from gingerbread.
So I did a factory reset and found the problem still exists. Again I am disappointed.
After checking in the settings, I found option to backup app settings to Google account and restore it when app is installed again. So what was happening is after the factory reset, since I have selected the restore option, settings were restored from gingerbread version.
Now that I have found the real problem, I did the following steps to fix the issue.
Deselected the backup option, which erased the gingerbread settings stored with Google.
Did a factory reset and found battery life of my xperia u improved :-) and lasted for almost two days