I can't answer your question about the power distribution of your car, but I wouldn't have thought that the car charger charges faster. I'm wondering, I have some wall chargers that I used to use to charge 12v mototcycle batteries. I'm wondering if I could hook up a car plug to one of those chargers and use my car adapter to charge one of my DJI M2 batteries?
Is a dedicated drone battery charger better/worse than having an 12v sine wave inverter that powers the DJI wall charger?