CPAPtalk.com

I think Sleepy-eyes may be correct. Your link states that that it is a 17 AH battery and not 22 AH. It does not state if it is a "deep cycle" battery w/ regard to Sleepy-eyes comment.

You best try it out while you have power available rather than when the power goes off to see what exactly you can get out of it.

The link is for a 17AH, not the exact one I have, I could not find the link for the one I have. Mine is rated at 22AH and is a deep cycle battery. Still at 8 hours usage a night 2 or 3 nights should not be a problem at all. Especually with an auto which will run at the lower pressure most of the night. For a more acurate estimate you can always setup a meter and run the numbers for your specific case. These are my estimates for my setup. If I need more capacity after this I'll just pull one of my optima batteries out of my jeep, they are both deep cycle.