Although I am not at the point of running an AC off the alternator, I was wondering about the wire size required from the alternator to the battery bank. I realize that you are running the AC off the battery bank and the alternator is recharging the batts, but since it seems that it would have to be recharging them at the rate of discharge, would it not need a cable capable of carrying the AC load? Further, I was also curious about whether one could run the AC directly from the alternator to an dedicated inverter without using a battery bank.
Wire size should be rated for maximum output of alternator (1 size bigger would probably be better).
If you try to run your AC off an inverter fed directly by the alternator, what happens when you slow down or stop at a light. At slower RPM, alternator is not producing as much power. I would consider the battery bank as a buffer: When alternator is not putting out enough, batteries make up the difference. If alternator is putting out more than required by AC, excess can recharge the batteries. Jack