OK, the title is a "joke" but the rest of this post is not. Here's what happened.
I'm sitting in the house one evening and started hearing an occasional faint sound I hadn't heard before. It would last maybe 30 seconds then repeat a half hour or so later. After about the third time, I start walking around and note it gets louder near the garage. I open the door and there's The Enterprise purring along like a nice little kitty! Good grief! I know it never totally "goes to sleep", but starting up the engine? What new failure mode is this? I go get a key (thinking I'll have to cycle power), hit the garage door button and head for the car while trying to remember the symptoms of CO poisoning. Getting in, I find the other key already in the ignition and the green "ready to drive" light on! So that was it. Car left "ON" after parking in spite of the warning chime. It may have sat for an hour or more before starting the first time. It would run a bit to charge the HVB and shut off. I bet it could do this for months, left unattended! I doubt there was much CO with all the air leakage around our garage doors (and short run time) but I'm still thinking of putting a CO monitor out there.
But that 12 volt battery would sure stay charged!