How can I find out what causes "Android OS" to consume battery? The issue is that I see a high percentage on the "Android OS" item in the Battery Usage, and I want to find out what is causing it. But let me say that I'm interested in diagnostics techniques and tools, rather than increasing the battery life, as you will see in the below figures that the battery isn't drained much faster than expected.

Here's the situation with the phone right now:


Last charged 13 hours ago
I restarted the phone after charging it
I have switched off everything (such as GPS, WiFi, Data network)
I was on a 2G network all the time
My only use from the phone during the day was a few minutes of WiFi, receiving two SMS messages, and a call that lasted less than a minute.
I have auto-sync turned off


And here's the battery usage stat:


Android OS: 67%
Display: 10%
Cell standby: 9%
Phone idle: 6%


The Android OS shows 1 hour and 30 minutes of CPU time, but the total time that the phone was turned on was less than 30 minutes, and I don't have anything active in the background.

The battery level isn't bad at all (80%), but considering that I haven't done anything with the phone (and that the phone has a 2500 mAh battery) I am curious to find out what is causing the battery usage.

Obviously, this should be caused by some background tasks that aren't listed in the battery usage. I am looking for ways, tools, and methods that enables me to diagnose this further and relate the 67% of the usage to actual applications.

Some additional information:

I have a Galaxy Note, with Gingerbread 2.3.6 installed. I have "Usage Timelines Free" installed (which wasn't running during the day), and it doesn't show any excessive CPU usage by any app that can lead me toward who's consuming the battery.

Related question (helpful, but didn't answer my question) :
What can cause &quot;Android OS&quot; process to use high percentage of battery?
Use an app such as "Better battery stats". This app provides detailed information about all the services running. This is way better than the stock app for diagnostics.

Additionally, a lot of the core services for the system are attributed as part of the "Android OS". There is a very particular bug in Samsung Galaxy S II devices relating to the TouchWiz calendar that keeps doing a lot of unnecessary checks which prevents the device from sleeping properly when the screen is turned off. This causes a huge drain in battery life. Since the TouchWiz on an S II is very similar to the one on a Galaxy Note, you might have the same inherent bug. 

These links might give you a better idea:


StartingAlertService Wakelock...
[FIX] StartingAlertService Wakelock (TouchWizCalendar.apk)