I once heard a technology consultant say “You can do that?” when I said change the batteries in the ups. I think that is sort of sad. You do not take the car to the dump, landfill or crusher just because it has a dead battery.
That said I have a shelf full of dead ups’s that need new homes and new batteries. I replaced a few batteries in an APC 1400 ups. I looked on my shelf at 1100 ups. I thought I might test the 1100 with the new 1400 batteries but the 1100 had much smaller batteries and totaly different connections. I must have a half dozen different batteries for all the ups in the junk pile.
I had one go dead a few months ago. I removed the batteries and they looked like they had overheated. I had the same size ups at the office so I borrowed the batteries to test it. I hooked up the voltmeter to the batteries when the ups was turned on. The voltage was going all over the place instead of the usual steady slowly increasing voltage you see when you install fresh batteries. I guess a bridge rectifier or somethng was going bad. Electronics is not my thing but I do know fluctuating battery voltage with no load is a bad thing. The cooked batteries went to the battery store and the dead innards went into the scrap metal dumpster at the county recyling center.
Where to get batteries. I get them from the emergency lighting shop. They assembled a new battery pack for my Nitesun bicycle lights. They make batteries for those underwater photographers. They repair your cordless power tools battery packs. Most larger towns probably have at least one shop like that. The other place to get batteries is direct from the UPS maker. Well I know I have bought APC batteries via one of the big 4 distributors. I recall that in the US if you are dealing with software there are 3 or 4 major distibutors. Anyone down the food chain is getting stuff from the big 3 or 4 unless they are reselling cleanrance stuff. That sort of distribution makes a little sense. Could you imagine having to fill orders from tens of thousands of little shops. Well I guess Amazon does but I suspect selling stuff by the truckloads is easier.