IMO trying to monitor a sleepy device’s battery drain is a losing battle. It never works out anything like what we’ve come to expect from the the rechargeable Li-ion batteries in our phones and laptops. My experience with my smartthings hub before I moved to Hubitat was the same.
Setting notifications based on x time since activity received by the hub has been more reliable for me. Plus that lets me know something might be wrong with a device that’s not specifically related to the battery, but still worth looking into.
I’m no expert in this area, but I think this is a misunderstanding of how the hub and battery powered devices communicate.
Re: why there is no built-in app for monitoring device health, I think this post explains the staff’s reasoning pretty succinctly:
