Keep CarPC running on Petrol Stations, etc
I've done some work on a wiring diagram how to keep the carpc running if you're on a petrol station, atm or something.
How it works:
Hold down Switch S1 and turn off ignition.
Relay K1 pulls and keeps itself alive - constant 12V on remote of M1/M2 or whatever.
If you turn on the ignition again K2 opens the circuit for K1 and the relay falls back to it's old state. The next time you just turn off the ignition without pushing S1 the powersupply (M1/M2) will shutdown like usuall.