Yes, it is a UPS. I saw a few similar to that pulled out of service from a hospital. It is a good haul. I had to pass on some a few weeks ago as I had no way to move them.
Batteries are likely junk; even if they have "some" life- they were designed to remain on a float charge until needed, where they would be subjected to heavy current draw, and then replaced after the event, or replaced after a fixed period of time on float. They have less flexibility in charge and discharge than regular car batteries. If they do hold a charge for extended periods you might try them at least for a little while, but don't expect too much from them. they will likely not desulphate as they are of a design that notoriously does not desulphate well in the smaller packages.
Heavy and expensive best describe the batteries.
You might want to search for a manual for it before you dismantle further, you may find easily adaptable inverters, and system monitor circuits, and left intact, you can trace the installation to easier adapt it to your use. That transformer alone looks like it could be the basis for a decent inverter project in itself.
30 KiloWatt Brats anyone?
