Here are no problem it seems.
Soon, power consumption counted by Windows do not point actual state, because Windows is hungry and forced "to be a bit wrong" to user. It's my very subjective opinion.
Hovewer, it is very relativistic question due to very relative nature of an ACTUAL STATE term.
A very many ways exist to explain why for Windows 60% is actual but EQUAL for actuals Ubuntu 82%'s. Most simple is about differences between Windows and Ubuntu paradigms.
update 1
Try to test your environment with fwts :
sudo add-apt-repository ppa:firmware-testing-team/ppa-fwts-stable
sudo apt-get update
sudo apt-get install fwts
Read: wiki.ubuntu.com/Kernel/Reference/fwts
update 2
Thus battery.log shows that power ACPI interface disabled.
It means you have first solution for your problem by enabling power interface in BIOS.
Or if this behavior initiated by boot-parameter you need to find correct value.
update 3
Obviously booting parametrization have weight here.
New readings based on updates: UEFIBooting
Most actual parameters (WARNING! Use only correct parameters referred to your config) :
acpi
noefi
acpi_osi
apm
Kernel boot parameters Documentation
update 4
Also you can try to test output parameters with acpi program:
sudo apt-get install acpi
acpi -V
Finally all my web surf point to: ThinkPad ACPI Extras Driver
And: Lenovo Diagnostics (Linux Bootable CD).
Best Answer
This is not entirely mine, more like a mashup of several answers I've read all over the Internet.
Main source: https://wiki.archlinux.org/index.php/Wake-on-LAN#Battery_draining_problem
Aparently the "Wake On Lan" is the culprit of this drain issue.
Several ways of fixing this, my favorite would be creating a systemd service:
/lib/systemd/system/wolfix.serviceThen enable the service and good to go:
systemctl enable wolfixPD: This is assuming you are running 16.04 or newer, if not just add the
ethtoolline to/etc/rc.local, but keep in mind if some other program enable the wol feature before shutdown this fix will be useless.