Hi fellow Nexus one users. I have story to share that may help others with a similar problem. For the last few weeks I had been experiencing extremely high battery drain, approx 3-4% an hour when idle, versus the 1% or less per hour that I was used to. Usually 70% of the usage was being logged as "Cell Standby". This would happen at the same 3-4% per hour with full signal or even with only 1 bar. I have an AT&T Nexus One on Bell in Canada. When this all started I was running Cyanogen 7.0.3 and the Clockwoork 188.8.131.52 recovery. Suspecting some rogue software/process, I spent some time running system monitor applications to try and find any clue that would lead me to the culprit but came up empty. I tried swapping to my spare battery, same issue. Tried some newer cyanogen nightlies, same issue. Tried wiping my phone completely and flashing back to the stock HTC 2.3.3 ROM with NO APPS or customization, same issue. Tried flashing to an older Radio version and to the newer 5.12.00.08 radio, everything still worked fine but the extra battery drain was still present. Wifi, Bluetooth and GPS, Data sync and Screen would always be disabled/off for an hour whenever I wanted to test a fix. If the battery dropped by 3-4% over the hour I new the problem still existed. I tried disabling Data (no 3g or 2g), same issue. I tried using Wifi instead of 3g, same issue. Only when I placed the phone into Airplane mode would the battery usage return to normal (better than normal actually but obviously that is to be expected if the phone is not talking with a cell tower) I suspected a possible problem with my SIM card. I ran the "Sim Toolkit" application and the app would freeze when I tried to use any of the options (Phone number, Special Numbers or Self Serve). Other friends with android phones had no problems reading their SIM cards with this app. The last fix I tired was pulling the SIM Card. FYI your phone will still communicate with the cell towers and report a cell signal without a SIM card. This is to allow for emergency calls (eg. 911) . And what do you know, NORMAL BATTERY USAGE with no SIM card! I stopped by my provider (Bell) and had them program me a brand new SIM Card. Swapped out the old one for the new one and I have been back to normal battery usage ever since. I'm not sure what could have caused my SIM to go bad in the first place. I got this SIM the same week I purchase my Nexus One (March 2010). It has never left my Nexus One until my last attempt to trouble shoot the problem. I guess It may be possible that I ran some sort of utility that tried to write to the SIM card without my knowledge. Perhaps one of the root utilities that comes with Cyanogen? Also, I don't think this problem could be limited to the Nexus One. Others with similar battery issues may find that changing their SIM card will help solve the problem. TL;DR Faulty SIM Card was causing huge amounts of battery usage (Cell Standby in battery stats). Bought a new SIM card and battery is back to normal.