I was thinking, since my RPi 3B+ is powered by a USB cable, maybe someone sells a UPS I can put in-line between the wall transformer and the Pi.
Anyone do something like this? I tried searching various combinations of USB, UPS and Raspberry but the results are all over the place. I guess these are pretty common terms.
I don’t want a hat, I already have my Pi in a case. Something like this on Amazon seems about right. I don’t even care if it communicates with HA or not; just keep the Pi running long enough to survive a few hours. By then the power will be back or I’ll have fired up the generator.
I have one of these, not using it for my Pi but for the alarm panel itself, but it has a USB out (even shows how it powers Pi in one of the pictures): Backup Battery – Konnected Inc.
And with 2.1A I think your Pi3 should be fine.
Raspberry PI UPS does sort of exist: UPS HAT - Waveshare Wiki I have no experiance with this.
I have a APC UPS and that one shuts down when there is a very light load on it during an outage. so that woudn’t work for my pi’s