Oh I get it. But my problem is I've bought maybe 20 UPS systems (the majority were APC, so not junk) in teh last 20 years. Well, maybe 15 in the 10 years before 10 years ago. I stopped buying them. Each and every one of them, after two years of being plugged in and not used - will up and die on you. So when the power DOES go out, so does your device. I hate paying $75 for something that when I actually need it, won't work.
The boat is what I'm thinking of. If I think the main battery is going kaput, instead of trying to string a line out to it, just plug it into that for a bit and recharge it. (Boat stays in teh water from April 15-Sept 15 every year. 9.9hp motor. No alternator AFAIK.)