and batteries in a special box and not in the flashlight because they can leak and destroy the Mag
IMO, that defeats the purpose of carrying a flashlight in your car. What if you break down with a car battery or electrical problem, and you have no lights to look around for the batteries and flashlight and get them installed?
I keep one of my older flashlights in the car, loaded with Eneloops or (if I really hate the flashlight) alkalines. If it leaks, no big loss. I check it every couple of months to make sure the batteries are okay.