Better to remain silent and be thought a fool than to speak and to remove all doubt.
Some companies need to learn that silence on a matter is better than obviously contrived excuses.
A relay switch could work. You would put the car 12V and ground across the coil connections, the 12V on the NO connection, the panel on the NC connection, and the power pack on the C connection. Make sure you get a 12VDC relay.
Are you going to have the panel installed permanently on your car?
Definitely don't connect a 24V source directly to your cars 12V system. There's a good chance of frying something important. A fuse would not protect from overvoltage so don't rely on those to protect components.
I lived in an area that was going to start strip mining for sand that was the right consistency for fracking. Plenty of conservatives were amongst the loudest opponents. There's plenty of hypocracy, no need to exaggerate. Their reasons were not wanting to have so much heavy equipment on the roads and fear of silicosis, not opposing natural gas extraction.
"Don't breathe the fumes" seems like a bit of an understatement for a reaction that produces chlorine gas.