I have a Thinkpad x220 (Debian Stretch) with a 6 cell battery which seems to be ok, according the the xfce4-power-manager. .
The odd thing is that the battery drains during hibernation (to disk) at a very high rate (30% in 10-12 hrs).
I've tried to determine the cause and fully charged the battery, went to hibernation, removed the battery, reattached after 12 hrs and checked the remaining charge. It lost just 0.4% of the charge, which was probably used during the boot process.
What may cause such an awful battery drainage and how may I fix it?
edit: I've just tried to completely shut down the system, waited for ~5 hrs and lost another 5%. (I've now disabled WOL and AlwaysOn USB). I will try to update my BIOS and check if that changes anything.