One automation for each battery was getting crazy. A temperature sensor in most rooms, motion detectors and a handful of door/window sensors. This blueprint creates an automation that manages all batteries dynamically. Really is amazing.
What blueprints do find useful?
https://community.home-assistant.io/t/low-battery-notifications-actions/653754
It scans the network and dynamically adds or removes batteries which it then reports on percentage level, or if the battery status is unavailable. Pretty ingenious actually.