You didnt just draw that did you
Anyway, I had thought about this setup before, it will work very well infact as long as your backup battery is big. The problem I thought I might have is when someone put the key on "ignition" position. The PC is now running off the backup battery, if the car is not started within a few minutes in my case (0.8Ah battery) the backup would have drained then. On cranking Ill get a reboot
Yes relay is good but its also bad. Ill try to get away from relay if I can help it.
What make your setup good is theres no voltage loss
