I was doing some researches about this very topic a couple of weeks ago and saw a post on Speciesworks (still trying to find the post). In that post, one Eaton

I was doing some researches about this very topic a couple of weeks ago and saw a post on Speciesworks (still trying to find the post). In that post, one Eaton rep replied that the ups device would shut down once the battery died to protect the devices connected to it. Teah, it's just this simple. This is just a byproduct so all those companies can boast their insurance coverage on damaged equipment you connected to their UPS. And guess what, most of the time you won't be able to get this insurance even if your stuff got fried, saw a few stories like these from recent Slickdelas posts of UPS.