Advice for no bootable device found?

I've had this problem for a long while, my unreliable battery run out and when I try booting the system it give 'no bootable device found' . I can access the hd (ssd really) using a bootable usb but the computer stay unbootable. Since I will eventually face this problem again I'm looking for solutions now. I learn today about timeshift, but don't know if it would work if I can't boot the system, so any advices of what I can't do?