I have previously had problems with my laptop freezing spontaneously when running on battery power.
Somewhat by chance I have discovered the reason, in the sense that if I disable laptop-mode the freezes don’t happen anymore.
For now I have simply uninstalled laptop-mode-tools.
I experienced the same behaviour with my Asus M2400N: Disabling / uninstalling laptop-mode disables the freezes.
If you find out, what exactly the problem with laptop-mode is. Please post it here