I'm a bit confused in the ground wiring of the BMV in a two battery setup. Where in the Victron diagram is the chassis ground of the starter battery. I have two options in mind but not sure which one to use. First one is just to run a negative cable from the starter to the shunt, no extra ground from the shunt to the chassis. Second one is to run the original starter battery negative to the shunt as a system ground and also connect the starter battery negative to the shunt. Any suggestions what to do?