|Hi Wilson, |
irrespective of how you power the pc, Stuart's comment regarding flat batteries needs considering.
With your intended installation power needs to be supplied after the car ignition is turned off. Eventually the pc is switched off, then (if remembered) the invertor or whatever supplies the pc's power turned off.
Perhaps an additional smaller battery, such as one from a motorcycle that charges when the car is running?
Please advise back on progress.
Good Luck - Keep us posted.