The UPS you described isn’t designed for continuous use, but will supply the rated wattage for about 10-15 minutes. Basically this is to give you time to save your work and shut down the equipment or bridge short power outages(brownouts).
To convert from CCA to AH:
(CCA/10)+16 = AH
So a 1000 CCA battery should = 116 AH
This will take over 16 times the amount of time to charge at the charge rate of your UPS. Theoretically, you should be able to get about 150 minutes of power out.
With your cooling fan it might do it, but my bet would be about 30 minutes and it will blow the fuses or the circuit breaker, particularly if you are driving it at or near the rated load.
Also, remember that your larger batteries will off gas as they are charged/discharged.
Thanks! Xlent info, just what I was looking for. Not the answer I wanted, but hey, gotta have a little whine with that cheese!
Looks like I will be searching for some bigger inverters. Maybe I can figure out a way to have the UPS trip the inverters.