The short version is that you will get about an hour of AC from those two batteries. 45A actually seems pretty low to me, either your AC units are small, efficient or your battery monitor is out of calibration.

Ball park figures: you need one, 100AH battery for every hour you want to run the AC.

If you replace your AC units with something that uses less power you will get more. You just need to get good at doing the math so you can figure out what will work. John explained it one way, I'll do it again, you need to be able to do this in your head so practice.

Here are the numbers for a typical rooftop AC unit. Find the current spec for you units and you can adjust for them.

A 100AH battery will deliver 100A for one hour.

a 1500W Air Conditioner will draw 1500W / 120VAC = 12.5A (AC)

When converting 12VDC to 120VAC the inverter will use 125A DC to make 12.5A AC. It's a basic factor of 10.

Additionally the inverter is only 90% efficient so you lose 10% of your battery power in heat given off during the conversion.

125A DC / .9 = 138.8A DC

So you'll be drawing 138A out of your batteries 100/138.8 = 0.72 hours. (each)

A 3000W pure sine wave inverter is a good choice to run AC, it's about twice the power needed which may keep the inverter cool running.