Negative to Negative?

[Jonah]

Hi all,

A newbie question: why are the negative terminals of my two starter batteries connected? I remember discovering this on my previous boat too. I am not trying to run them in parallel or in series.

Is this required for when I set my either of my selector switches to “both”? Does it have any other consequences I should be aware of?

Similarly, I believe I’ve just discovered that my DC panel has two grounding wires—one to each battery. I think this is a result of different POs wiring the panel to different batteries over the years. Ok to have wo grounding wires going to two different batteries?

 

[SkunkBoat]

When you set your switch to both, you are putting them in parallel.

The negative terminals should be connected together. All negatives and bonding wires on the boat should be connected.
There is nothing wrong with two DC negative "grounding"wires from the panel so long as they are both going to the batteries and the batteries' negative terminals are tied together.

 

[Jonah]

Nice, thank you Skunkboat.