APC has the biggest market share. They are pricey.
Battery replacement is absurdly expensive. Cheaper to buy a Costco car battery and wire it up!
You can replace the batteries (only) in an APC UPS, rather than buying their overpriced RBC packs. I cover this in detail in 2 of my blog posts:
New Year, new UPS batteries…
[Another] New Year, new UPS batteries…
APC units have a disturbing tendancy to drift out of calibration over time. This causes the float voltage to rise above the limit the batteries can take. Some newer units can calibrate this via the serial port. Of course, APC considers all information, even about long-discontinued product lines, as proprietary info and won't sell / give you any information.
Without calibrating the float, one battery pack replacement (normally when the first set fails, at 2-3 years) is all you'll get and that one won't last as long as the original ones. That is the reason APC no longer offers their "Charge-UPS" program, whih extended the warranty on the UPS when you bought replacement batteries and paid the Charge-UPS fee. That's because they know they've "price engineered" their products to last as long as the warranty, bot not much longer.
Also, APC required
repeated clubbing with clue-by-fours by a large mob for over FOUR YEARS before they made changes to let free software like
apcupsd and
NUTS work with their [now not-so-recent] new models. If you required that support, you should check with APC to make sure it is available in whatever product you plan on purchasing.
If it were me, I'd buy a later-build "legacy" unit used and replace the batteries, and calibrate the float voltage. Just make sure you get the rackmount hardware for it - APC is also notoriously bad at selling replacement parts like that.