Goodmorning fellow gurus. I have an older T400 which I use for linux. It got the 9-cell battery which is quite old aswell. It lasts for about 40 min. to 1½ hours which is good for a thing of this age. I'm going to try the freezer trick. Freeze it 3-4 times for 12 hours, charge it each time and discharge it ofc. I'll repport here if it blows up or succeeds. I'm currently having a T431s, but it's a work laptop so I can't really use it for linux.