I already used a couple of GRUB boot parameters that help, at least with the heating. But I’d really like to get my battery back. From what I understand this is related to the power regression issues of the newer kernels, though I am not Sandybridge, but an Intel Atom.
seriously you had 6 working hours on battery shrinked to 2 ?
why not go back to 11.4 so 
(assuming you had 11.4 b4 )
Which desktop are you using? They each have their own power management utilities. Also how many times have you recharged the battery and is it in the machine permanently. If the former is over 300 you should expect it to decline; if the answer to the latter is Yes, then that is the problem.