Excellent advice! Thanks. I do vaguely remember the topic about using one battery to jump start the other. It is great advice to figure that out in daylight and ahead of time!

It is fairly easy to run down a battery over 4-5 hours at a movie. I've done it three times over the years. The difference is always failing to remember to move the key to the "Accy" position. In Accy, only the radio is running and everything is fine. In the other position, the dash lights are on (plus other things that I am sure I don't notice) and you are likely to need a jump at the end of a night. So - the previous post did correctly identify that there is an Accy position for the key.

I guess my concern was that even to run the radio, the NAV panel is going to be on for the whole time. So - it is not just the radio, but a radio and a computer and maybe a GPS antenna.

Actually, what really sparked my interest is that just something like opening a door causes something to start happening in the back of the vehicle. (Maybe the battery vent opening or closing?)

Bottom line - I just give it a try and see how it works.

Thanks for your help!