try change a SIM card
hi,
I was having the same problem of high battery drain by Android OS,
I have a Google Nexus S with 2.3.4 stock.
When I was in France, the phone can be used for 1,5 to 2 days if fully charged(with 3G, sync on),
but when I came back to china recently, the battery is used up in just 8 hours with my old Chinese GSM SIM card(bought in 2006) even though I turn off sync, data, etc. And i can see in the battery usage, Android OS with a bizarrely high percentage(~25%). I've tried to close or uninstall some apps or change wifi settings, but the problem persisted.
then i tried to put in my french SIM card just to test, only 10% battery drained in 10 hours standby, and Android OS with just 2% battery usage.
And I've just been to the service center of china mobile, and changed a new SIM card keeping my old phone number, the battery then went normal. In 1 hour standby, only 1% battery drained, and Android OS drop from 14% to 12%(because I didn't reset the stats).
So, if u guys have the same problem, I suggest u to change a new SIM card.