Guys, this issue seems to be caused by the "Auto-Rotate screen" setting being enabled under the Display settings.
Some proof of this is by viewing CPU usage using OS Monitor. With "Auto-Rotate screen" enabled and the phone idle, CPU usage of "Android System" will remain anywhere between 25% to 30% (while the phone is idle) and apparently prevents the Nexus S from going into a deep sleep, which of course will be draining the battery faster. By disabling "Auto-Rotate screen", the CPU usage of "Android System" drops to between 0% and 4%. Re-enabling "Auto-Rotate screen" caused "Android System" to consistently jump between 25% and 30%. So I keep "Auto-Rotate screen" disabled now. Try this out as I had the same issue and my battery now lasts longer with it disabled. Download "OS Monitor" and see for yourselves. It MUST be a bug that is hopefully fixed in 4.1.1.
And it is definitely 100% the "Android System" process consistently running between 25% to 30% even when idle, but ONLY when "Auto-Rotate screen" is enabled. With it disabled, it goes straight down to between 0% and 4%.
People say the ram is there to be used but this will surely use more battery. I find uccw will sometimes be a hogger so dont know why some apps seem to randomly have been using battery in standby or how accurate a stock battery monitor is .Anyway, i have same problem as After ICS update with phone taking 55 seconds to shutdown. This cant be good - what is running that cant stop on shutdown?
I think cache cleaner messed things up some how.
I have heard of others complaining about battery drain with ICS, others that have the same hardware I do (Samsung Galaxy Tab 8.9). I find that the app I am running has more effect on battery usage than any sort of system housekeeping. After nearly 12 hours since I last charged my device, I still have 87% of the battery capacity. The screen has been the heavy user with 64% usage.
When I play a graphic intensive game like Bubble Shoot, I'll see my battery power go fairly quickly but that is more a factor of my playing the game for an extended period of time, I find it very addictive.