using 400 watt solar kit w/ extra battery I already have....

400 watts of solar
400 watts is 3.5 amps at 120v output from the inverter
The a/c uses about 12 amps at 120v that's 1400 watts
Wire all the batteries together to the solar
Using DC into inverter to drive converter to make DC for the other battery is double conversion and a lot of wasted power, possibly 20% our more wasted in the process
There are one or two members that run a small 5 amp 600 watt, window a/c using a big battery bank and 900 watts or more of solar