The AA batteries are for powering the unit in a standalone or portable mode. I'm referring to a small (possibly button type or with solder leads) battery I suspect is mounted internally in the unit. I don't even know if the unit has one of these but it probably does and it would use it to maintain a low power memory device that remembers configuration data when the unit is powered off.
RV9A - 647JC - 300 hrs - SOLD 6/23/15
OneX - Under Construction - For Sale