I'm about to install a voltage sensitive relay which will be in between my car battery and my auxiliary battery in my van. When doing research for this, I find diagrams like this:
What confuses me here, is ground, and if I should be grounding my aux battery to the chassis, and what would be the purpose of this?
In this schema, does ground just mean that the negative poles should be connected? I understood it like just a shortcut, instead of having to close the circuit in the schema, you can just use the ground symbol, which means the negative poles should be connected to each other. Or does it actually mean grounding to the chassis?
Sorry if this is a duplicate. I've done research for this but I haven't been able to grasp it yet…
Thank you.
Best Answer
The chassis, metal body on a monocoque car is used as the negative wire, or ground.
This saves on needing two cables (supply and return) to each device or light etc. The accountants save on the cost by reducing the number of cables and often by minimizing the cable size used to each device.
So each battery negative is connected to the chassis, you could control the negative instead of the positive but it does depend on the total of what you want to achieve and not with that particular relay which has an override function.
Just remember to ground or provide a return for devices or lights on cars that have fibreglass panels :)
Also take care as many cars before about 1965 were positive earth...