[Al Skierkiewicz]

Time to add a few things to the discussion.
Some inverters reach maximum efficiency only at full output.
Even at peak, there is a lot of loss, 83% at full output is likely less. Use 75% for your calculations.
The 17.2 AH rating is speced at a 1.8 amp load. If you draw more the rating goes down. You will get 17 hours of battery (until the terminal voltage falls to 8 volts) at a 1 amp draw. You will not get 1 hour of battery with a 17 amp draw. (curves say about 35 minutes) At 7 amps figure between 14 and 15 AH.
Batteries have a defined life of about 400 charge/discharge cycles. Less if the batteries are used hard in competition.