UPS, and i don't mean shipping

Hi folks! i got my hands on an old big UPS that was used for a computer server. It's the old kind that had batteries on line full time. If i'm not mistaking it first converts AC to DC, feeds it to the batteries and the output of the batteries is converted to AC again. Wouldn't this unit make a great power supply noise filter?

Has anybody tried it? The batteries in it are dead and i'm wondering if it's worth replacing them. The damn thing is quite noisy but i plan to install it in the garage and run a cable to my living room.

Thanks for any advice!