I have two batteries in my Thinkpad T440s. Is there any way to switch between them, this is, to make it use BAT1 instead of BAT0? Even manually on the command line, but automated switching e.g. at 20% would be best.
I've installed TLP but it doesn't seem to help.

Solution so far: Physically pull out BAT0. Otherwise it'll discharge down to 5% before switching. :/
Any better ideas?