Interesting, So, I had one of these and wanted to just test.. its a 12-5v converter. I didnt want to use this as I want to free up the usb port. powering it with car is working fine. no issues with screen. sleep wake up.. all working.
something wrong with 7809? but it works fine with no car circuits though... weird. will make a pcb circuit for 7809 and try next.. or maybe just use 7805.