I don’t know if the OBDII port is really meant for power to be pushed into it. Not if this is feasible on other cars but I have battery tender ring leads bolted to my battery and run the line through the opening on the bumper (2010 ACR)
Just a heads up to Deltran Battery Tender users…..they make a charging cable that plugs into the OBDII port now. May or may not be useful to you but on some vehicles it will beat popping the hood all the time.