Today I need to replace the gel cell battery in an old uninterruptible power supply (UPS). These are used on computers, sump pumps, and other equipment that can not tolerate a loss of electrical power. This particular model makes it very easy.
Replacing batteries is a big part of "right to repair."
Warning: There is always risk in dealing with electricity of shock, burns, fire, electrocution, etc. There are extra risks in working on uninterruptible power supplies: they can store dangerous voltages, and turn on unexpectedly. Opening the high voltage section of a UPS is not recommended. If you do not know, learn first or do not do this!