Hello Paul!
A schematic would be amazing! Im talking about driving a bare relay.
Ideally, for the schematic you'll draw tomorrow, the relay's coil would be 12V as this will go in a car, but If you decide to use any other relays (with different coil voltages like 5V or so...) I'll use a boost converter or similar!
So ideally 12V coil, if not its gonna be okay anyways!