Typical dual battery wiring set up

[pstephens46]

I was researching diagrams online for wiring and noticed something different about my set up. I have two batteries, a cranking and a DEEP CYCLE for house. The cranking battery negative 4 guage wire is attached to the bus bar where all the grounds from various electronics are attached. The couple diagrams I have seen are showing the house negative attached to the bus with a 10 guage wire. In the scheme of things, does it matter that the cranking negative is attached to the bus on my boat? It may be doing the same thing with a different path but wanted any opinions on the matter.

[99yam40]

all of the negatives can be hooked to the same neg buss, but current will flow only from each battery pos back to that battery..

I look at more connections in a circuit being more places for a bad connection

[fairdeal]

There are only two rules;
- all the negatives ("grounds") should be connected "in common"
- the return path to the battery (ground) of any circuit
should use at least the same gauge wire as the supply.

Exactly how you work that out is your's to decide,
so long as you are not being hindered by voltage drop.

Personally I prefer to have the main engine ground cable
go direct to the cranking battery negative post;
since that is the absolute minimum pathway,
I feel good about that.

As to 10 gauge wire for the house negative,
FWIW that seems small to me -
is the house positive feed also 10 gauge?

[pstephens46]

As to 10 gauge wire for the house negative,
FWIW that seems small to me -
is the house positive feed also 10 gauge?

The set up I viewed online had the two battery negatives connected as mine. All battery red/black cables described as 2 guage. A separate 10 guage black cable from house negative to bus. So I assume the connection of the grounds from the two batteries completes the "charging" circuit? Or would the 10 guage wire have to endure the same load as the 2 guage, regardless? Hopefully this isn't a senseless mess.

[99yam40]

As to 10 gauge wire for the house negative,
FWIW that seems small to me -
is the house positive feed also 10 gauge?

The set up I viewed online had the two battery negatives connected as mine. All battery red/black cables described as 2 guage. A separate 10 guage black cable from house negative to bus. So I assume the connection of the grounds from the two batteries completes the "charging" circuit? Or would the 10 guage wire have to endure the same load as the 2 guage, regardless? Hopefully this isn't a senseless mess.

If all red & black wires at the batteries are #2, where does the house battery #2 neg land

[pstephens46]

If all red & black wires at the batteries are #2, where does the house battery #2 neg land

Sorry, the Blue Sea diagram shows 4 guage, not 2 guage battery mains.

[pstephens46]

If all red & black wires at the batteries are #2, where does the house battery #2 neg land

Let me try the link as the above is too small. My set up is different than this diagram.

https://www.pinterest.com/pin/347832771218655478/

[99yam40]

so the negs are jumped together on the batteries terminals I see or maybe your set up is not like that?

do you have the house battery hooked to the auxiliary charging wire on you motor?

if the neg bus is just for the gauges and lights, I do not thing 10 gauge is too small as long as it is not a very long run

I am not sure were you are trying to go with this post if your set up is not like this

[pstephens46]

so the negs are jumped together on the batteries terminals I see or maybe your set up is not like that?

do you have the house battery hooked to the auxiliary charging wire on you motor?

if the neg bus is just for the gauges and lights, I do not thing 10 gauge is too small as long as it is not a very long run

I am not sure were you are trying to go with this post if your set up is not like this

My start battery 4 guage wire ran to bus bar. I changed it tonite to follow the diagram. Everything seems to function fine. I used a 25 amp fuse in the bus 10guage run from house #2 battery. I think diagram suggested 30 amp. As Fairdeal, I thought it makes more sense for starting battery negative to run directly to motor. Who knows?

and yes, the aux charging wire runs to house.