With this post I just wanted to report my recent finding.
I have had this problem for some time now. I am not too often off grid power, but when I am, it seemed that the laptop consistently crashed with a flickering screen around 50% battery power. I just upgraded to EC version 1.13_2023-03-22 today, and now the battery-meter have passed below 40% without crashing. It seems the problem has been solved. Does anyone else experience the same? Since the thread seems dead after the post by @Hologram on Jan 31, I guess the problem has been solved for everybody.