Consumer "UPS" (Uninterruptible Power Supply) as an automatic transfer switch etc etc

[XERTYX]

I'm not aware of a more similar, yet safety-centric discussion on the safety of using a UPS (uninterruptible power supply) as an off grid power supply option.  

I have heard of AC voltage reading across DC terminals on an uninterruptible power supply but I didn't understand how. Here's how.

 

[bullfrog]

When I was researching using a Prius as a 3000 watt power supply with the main big battery as a supply I found some discussions on adapting UPS components to do so.