mark4 it always can happen that the power gets low
This requires the ASIAIR to execute an auto shutdown when voltages drop below 11V, like many computers do when the battery of an uninterruptible power supply gets depleted. Unfortunately, ZWO did not implement that precautionary measure into ASIAIR, even though it can read out the input voltage.
The way you can save yourself from grief is to actually place a 12V uninterruptible power supply (UPS) between your large battery and the ASIAIR. That way, when the battery gets depleted by higher power devices (like dew heaters, camera coolers and mounts), your ASIAIR remains powered. You will also need to remove all power hungry devices from your ASIAIR's power hub.
I actually do use a UPS myself, but to my mount instead of to the ASIAIR, because it is a harmonic drive without brakes, and I can't afford for the mount to lose power when there is a power outage. My UPS is a home constructed one using an SLA battery and a Epic PWRgate, but you can get turnkey DC UPS (12V in, 12V out) from Amazon if you don't mind using Lithium ion batteries.
Chen