Please bear with me as I cannot post links or more than one image, I made an account to reply to this as I just went through the process of trying many ways to do this including a usb c QC 3.0 to cigar adapter and a power bank. as you know though the rock pi 4 can take 5-20v I had to do some research myself but I found a thread on here confirming that the usb-c port can take a direct 12v line and then the rest is history, I got to work sourcing parts and ended up with a very functional outcome.
what ended up being the best solution for me was a direct 12v (3.5a fuse) line to a programmable relay then to usb-c using a custom cable i made with some cat-5 (nothing excels like excess right?)
I now have it turn on when I start the car and run for an hour after it shuts down, and is working great!
let me know if you have any questions
