Could be a specific app that hates the update. Widget Locker did this to me once after an update.

 

Battery is horrible after ICS!! ICS still cannot control the apps that decide to go wild!

 

Ok, i reset the phone and installed only vital apps, no games. All apps are from market place. Very basic. In about 8 hours (or a bit less), my wife Nexus S went from 98% to 49%...with two short phone calls and three texts. No surfing. Granted, this is with her at work where the Nexus has trouble holding onto Wifi signal. But since ICS, the battery life is worst than before!!

 

My battery life is ok after the update. The phone however runs sluggish if the Settings App is running. Kill that and everything goes back to decent.

 

My wife is getting really fed up with the Nexus. Battery life was poor before ICS...now, it is just embarrassing! Overnight, it goes from 96% (fully charged) to 46%...this is at home and while sleeping (8 hours)!! No active apps except The Weather Channel app.

We're done with Android. Google can't make an update without destroying the older phones. Wait till the GN folks get screwed on the 5.0 software!

 

You realize that weather app is constantly firing up to check the weather. Take a stock ICS install on the NS4G and don't add any 3rd party apps. I just finished doing this test with stock ICS and the OTA from 2.3.7. I don't have to use my NS4G for day to day use so I was able to not touch it for 4 days without the battery dying. Added 1 app that has ads and is free and it cuts down to 2. The problem is all of these free ad supported aps are constantly getting ads. A lot of them even get an ad if you only have the widget running because the applications are poorly written. This is not a Google problem but a app developer/end user problem. Reception is a big deal as well is the phone tower hopping or does it have full signal, do you have the 4G turned on, things like that? I wish Google would incorporate better profiles into the OS for things like turning off all data or only allowing background syncing at certain times. OEMs add this to Android but most of them are pretty bad except for the newer Motorola Smart Actions. Make sure the screen isn't coming on too for some reason at night. Any widget that can sync data is bad IMO. I try to keep my home screens to only icons if I can help it.

 

No 4G. The weather channel app is ICS compatible. And I have not changed any settings before or after ICS. It is on Wifi network at home.