Power regenerators X Power Conditioners

[ hemigreg ]buy a used commercial UPS for 800 and have better power quality than any "regen" unit cause thats what they are without the battery.

https://www.ebay.com/itm/APC-Smart-UPS-XL-3000VA-RM-5U-SUA3000XL-New-Batteries-1Yr-Wrnty-FreeShip/11...''

I presume you're using the filter provided by the UPS, is that correct?
If so, why not just buy a power filter?

That is, my understanding is that the UPS generates AC from DC if/when: (1) there's a loss of power (from the wall) (2) there's a battery in the unit. Otherwise, the UPS simply filters the AC coming from the wall and keeps the batteries charged.

So, no battery equals no DC, hence no generation of AC from the UPS.
Is that not correct?

Actually,
I just spoke with the technical support folks at APC and learned that their SRT line (e.g, SRT 3000 XLA) will convert AC to DC, and regenerate AC (pure sinewave) from DC even without a battery.