Inverter vs Battery

[Tinner12002]

Ok not sure how to ask this, but I have 3 SRM-24 batteries in my RV which have a CCA 550 and a MCA 690. At 15 amp load I have 4.9 hrs of use per battery, that's according to Interstate chart. Now my question is if I have 4.9 hrs for each battery x 3, I should have 14.7 hrs of use, but is that until batteries are dead or until I can't get 15 amps?
I have auto start on my gen but I don't want gen to have to start all the time. I was thinking of getting an inverter that I can use to just run a Samsung soundbar for outside music rather than running my gen or having to take my Honda 2000. We usually only run the soundbar for 4-6 hrs while were sitting around campfire.
I was thinking of getting a portable one that I can alligator clip on the batteries and plug an extension cord into of about a 1500-2000 watt variety inverter. I'm kinda inexperienced at working on the 12v/110v combination systems. I know as they say, just enough to be dangerous! Lol!
Any recommendations, thoughts or ideas?

[notanlines]

Steven, I'm posting a site that you can use to calculate the length of time your inverter will work with the battery bank you have. You will probably find that the time will be considerably shorter than you think.
https://www.donrowe.com/power-inverter-faq-a/258.htm#how_long

[Tinner12002]

Thanks for that info Jim, very informative site! Turns out I'd only be able to run it about 4.5 hrs so sounds like the Honda will be taking another trip south!