Thinkpad X220 with battery problem

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https://bbs.archlinux.org – Hello everyone, I got some problem about my X220 battery after I reinstall it.I think this picture can show the problem I got......when The battery left around 40%, after a few minutes, it well drop to 6%....Is there any setting I forgot to use? Thanks for helping.*kernel version: Linux  3.5.5-1-ARCH x86_64 grd https://bbs.archlinux.org/profile.php?id=58157 2012-10-19T11:00:35Z (HowTos)