We encounter this quite often in the National Guard. Trucks sit for a month without any loving and the batteries become run down. A quick jump start usually does the trick in this scenario. Leave the vehicles hooked together for a while. If the batteries are really low, the truck will do one of two things. It will either shut off if the batteries are really low, or it will stay running and the ¨Battery Disconnect¨ light will illuminate which means the truck has sensed the batteries are too low and it is only powered by the alternator for electrical power. I have run into an odd issue on my M1089A1P2 where it will illuminate that light under similar conditions only to extinguish as soon as put into gear. I have not noticed this behavior on the cargo variants. I will retire in a few years. I long for the days of the simpler trucks we used to have!!! Thanks EPA for the cool play toys as hobbiest but I enjoy mission capable vehicles as well.