So much stuff gets turfed because of those stupid "No consumer serviceable parts inside" labels!! Those just plain need to be outlawed completely!!
How many times have I changed a blown fuse in something like a microwave that was totally dead and it worked like new! I would call a fuse "User Serviceable"!
Back to UPS.
What country is that UPS for?? Looks like a strange plug on the back, I am USA power here. Anyway to answer you question, NO you probably can not connect the 3 together for triple the power. Yes, if you connect the batteries correctly it should work as an inverter fine.
I have a 120V 600 watt output with 24Vdc input, I used 2 12V deepcycles for the 24vdc input and it worked fine, done it with others too.
How long they last may depend on various things, quality of the unit, how heavy you load it, if it runs contionous or just once in a while. These are really only inteneded to be used as backup power for electronics and such for short periods normally. Some will work great as a inverter for a long long time and cheapies may fry soon. Looks like you might have a good one from the pics. Nice big heat sinks and fans are a plus.
How heavy you load it of course makes a lot of difference. If yours are say 1kw and you try to run a 1kw electric heater for 10hrs a day I wouldn't expect it to last long.
On the other hand, it might run your frig and other stuff for months or years.
You should be able to connect all 3 to the same battery bank to power them and get 3kw total, 3X 1kw each, but you probably won't be able to connect them together on the output to run any 2kw or 3kw loads, just 3 1kw loads at the same time.
As for using them all on the same battery bank, I don't see any real problem with that off hand as long as they are all wired for the same DC input, but might want to check that out a bit more to be sure. If it weren't for needing so many batteries for each one I'd say run each on it's own bank. That way if one goes dead you still have power to the others instead of them all going dead at once and having no power at all.
I can't make out in the pic what it says for amps on the serail tag. 2 Places I see 250V at 10amp?? 2500 watts??? On the outlet I figure that's just the outlet rating if conected to regular lines, but printed on the case it says that too but I can't see why exactly from here. Is that Circuit protection, and if so is that for your house lines or the built in protection on the unit for over loads?
