i have owned my SGS2 for 2 months. battery life has been ok, depending on usage. suddenly, from one day to another my batteries don't last anymore at all. go from 100% TO 0 in less than 4 hours. i at first thought the battery was defective, but my spare battery has the same problem! It's crazy! there's no background apps, the display brightness is turned down, i checked everything i can think of. once i just had the fully charged phone sitting there, at work. send 2 text messages and 4 hours later it was drained! without using it!!!! Help!?