I have an X200 with a 9 cell battery, bought new a while ago, but I think 4h max is what I get, if I lower brightness and only run Emacs or so. How do you manage to run 10h? Does the X220 somehow use less?
Probably not a new oem battery? The OEM 9 Cell was really good. Also - definitely need to tune it down with powertop, you can suspend most of the stuff like usb only the fly, also using and ssd over hdd.
Though, to be fair, this one had an HDD originally and has an "HDAPS" system. It's a built in gyroscope that will park the head of the disk if it notices the laptop is in free fall. how silly and fantastic that is
