I know that this thread is a bit old, and I'm not sure if this will help anyone else, but I figured I would pass on what I went through just in case. I've had my 13" Macbook Pro for about 2 and a half years now, and a few days ago, I upgraded from Lion to Mountain Lion via the App Store. I've never had battery issues before, but I immediately noticed a significant drop in my battery's life (it lost 1% every 2 minutes or less.) I scoured through forums and articles trying everything I could think of to fix the issue. I even tried reverting back to Lion (which unfortunately doesn't work.) I spoke to Apple Care, and made an appointment with the Genius Bar, and when they ran diagnostics, they said that my battery was perfectly normal, and suggested a fresh install. So I made sure that I had backed up all of my personal files and third-party apps to an external HD (manually, NOT via Time Machine), and then they completely erased my mac's hard drive and reinstalled Mountain Lion from scratch. As soon as I took it home, I followed their advice and calibrated the battery as well. I don't know whether the issue was a corrupt installation (which seems likely, given that the installation time began to count negative minutes) or whether my mac was trying to run both Lion and Mountain Lion systems at the same time (also likely, given the weird glitches I experienced), and as much of a pain in the *** it was to erase my HD and start over, having to recopy and reorganize all of my files, app icons, and bookmarks, it was kind of worth it in the end, because now everything is working as it should be. As of last night, I am now getting over five hours of battery life (and that was with constant file copying and organizing, running several apps at once, internet browsing, and movie streaming.) So, I hope my situation can help someone else experiencing similar issues. Maybe a fresh installation and a battery calibration is all that's needed in certain cases.