How about including some PV cells in the pano roof to cover the battery maintenance electrical draw? That would keep the pack from ever reaching low volt damage. It would also look cool to see the PV cells through the sun roof. PV cells are getting so cheap and their efficency climbing every year. You could leave your car in long term parking for ever and that battery level would never drop. I don't know what the battery climate control draw is, but you might even have a little left over to charge the pack. What do you think?