I have a huge battery drain (about 60%) by OS Android proccess even in the standby mode. I don't know what to do with this ****. From 100% to 0% it takes about 6 hours my phone dies in standby mode (with CM9 rom), with stock rom my phone lives in standby mode about 2-3 days.
Sounds like you have a rouge app(s). Download Better Battery Stats and CPU Spy. Read their respective threads to understand how to use them. There are threads where people will help you interpret the logs these provide.
Did you download better battery stats and CPU spy? Look in the ATT Galaxy S II thread. There's a pretty good known battery drain thread. My idle drain is less than 2% part hour. My deep sleep is over 95% when idle. Has to be a rogue app.
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