The answer is what else is on/running in the ACC mode. The Passport has multiple computers. How many of those are up and ready in the ACC mode.
The true answer could be found for your vehicle by connecting a VOM in series with the positive lead of the battery and measure DC amps. Measure with everything OFF. Then measure to your heart's content in the ACC mode.
There will be a point where one or more of the computers will cry uncle and issue alarms because of low battery voltage. Consult with your local Honda engineer.
Stuck,
The true answer could be found for your vehicle by connecting a VOM in series with the positive lead of the battery and measure DC amps. Measure with everything OFF. Then measure to your heart's content in the ACC mode.
There will be a point where one or more of the computers will cry uncle and issue alarms because of low battery voltage. Consult with your local Honda engineer.
Stuck,