Buying UPS for Backup : Need Suggestion

Even UPS goes down rarely but the problem caused when its on mechanic shop is more. Whole family is affected.
I wanted to know that is it possible that i buy a backup ups of some low power to be used if main ups is down.
I have some confusion: Is all ups are operated on 12V input from battery. Is there inside adjustment for Power of Battery like 120 or 190.
Means if today i am using 165 battery and later upgrade to 190 do i need to make some changes in ups or not.

no changes needed.. as long as your 165AH battery was working fine, 190 will be equally good if there is no manufacturing defect in battery itself.

u dont have to change anything ....