There is no current draw when the Montana is off or out of the cradle.
My Garmin rugged mount is wired directly to the battery. When my bike's ignition is switched off with the key, the rugged mount is still powered.
I measured 8 ma draw from the rugged mount when my Montana is in the rugged mount and is turned off and my bike's ignition is switched off.
I measured no draw from the rugged mount when my Montana was removed from the rugged mount.
I use non-rechargeable lithium AA batteries in my Montana for those rare instances when I want to use my Montana and it is not in the rugged mount nor connected to my iMac.