Follow up on battery balance

[BDofMSP]

I had an idea as I was staring at my problem of not having the neutral long enough to reach the farthest battery. I have also been desiring a battery monitoring solution for these banks. Researching the Victron BMV 712, it seems that I connect the neutral of the battery bank to the Shunt, and then from the Shunt to the house load. Maybe that solves my problem?

Today the battery negative post is connected directly to the engine. However, the house load is connected to a buss bar (right above the batteries) which is ALSO connected to the engine. A diagram and a photo are attached. Remember, my bank serves both house and starting.

My question is two parts:
a) could I install the Victron by simply making a new cable from the battery bank negative cable and the Shunt, and then connect the shunt to the neutral buss bar (for house load)
b) and if so, then what do I do with the cable that currently runs from the battery to the engine? Connect it to the load side of the shunt too? Or connect it to the neutral buss?

A diagram for that is also attached.

Thanks!
BD

 

[BDofMSP]

Also a schematic, although I have no idea why they use that blue font. Impossible to read.

 

[tiltrider1]

Are we talking the AC neutral buss or did we mean to say 12v negative buss?

 

[BDofMSP]

Negative buss, sorry. I'm not very precise with my terminology. Nothing AC involved here.

Question is really would the current negative go to the load side of the shunt? Or would it go to that negative buss? Or am I off base completely?

Thanks!
BD

 

[BDofMSP]

Two more pictures. Overall and the negative buss itself. The large lug is the cable to the engine.

 

[tiltrider1]

I had an idea as I was staring at my problem of not having the neutral long enough to reach the farthest battery. I have also been desiring a battery monitoring solution for these banks. Researching the Victron BMV 712, it seems that I connect the neutral of the battery bank to the Shunt, and then from the Shunt to the house load. Maybe that solves my problem?

Today the battery negative post is connected directly to the engine. However, the house load is connected to a buss bar (right above the batteries) which is ALSO connected to the engine. A diagram and a photo are attached. Remember, my bank serves both house and starting.

My question is two parts:
a) could I install the Victron by simply making a new cable from the battery bank negative cable and the Shunt, and then connect the shunt to the neutral buss bar (for house load)
b) and if so, then what do I do with the cable that currently runs from the battery to the engine? Connect it to the load side of the shunt too? Or connect it to the neutral buss?

A diagram for that is also attached.

Thanks!
BDView attachment 139583

View attachment 139584

Yes this will work

 

[BDofMSP]

Thank you, tiltrider1. As I think about it more, it shouldn't matter whether I connect the existing battery-to-engine negative cable to the shunt or the buss, or at all actually, because there will still be a path. But I'll probably connect it to the buss anyway.

Thanks!
BD

 

[Bacchus]

For the batty monitor to function properly, and include all loads & and charging the shunt has to connect to the Neg batty terminal and be the only connection directly to the battys. If you have any other parallel connections they will not be seen & measured by the batty monitoring system.
The buss bar then connects to the other side of the shunt and becomes the connection / collection point for all neg cables.
Above is for a single batty bank (as shown) that acts as a combined house & starting bank.
If there are separate house & starting banks it will require separation of pos loads as well as the corresponding neg cables as well as separate shunts / monitors assuming you desire to monitor both.
Any 1-2-all batty switch complicates monitoring.

 

[jbinbi]

If you have separate banks, e.g. house and start, you would only have the shunt on the house side. As stated, neg of shunt goes directly to neg terminal of house battery. Other side of shunt connects to negative bus bar, neg side of all loads.

 

[BDofMSP]

Right. It's clear that the only thing connected to the battery (negative) is the shunt. The question is "what is the path to the load?" In the original configuration it was a direct connection of the battery to the engine. Which THEN provided a path to the load via the buss.

So if I tie the load side of the shunt directly to the buss, which is in turn connected to the engine, what additional value do I get by having a second cable also connected to the load side of the shunt connected to the engine? (The current cable that connects the battery to the engine? It's basically (as shown in the diagram) a redundant connection. It seems like I've gone from having to replace the battery negative cable, to eliminating it entirely and replacing it with two short cables from the negative to the shunt and the shunt to the house buss.

I'm looking for what I'm missing there. I can reuse that battery to engine cable to make the battery to shunt and shunt to buss cables. Sounds like a win!

 

[Bacchus]

Just my opinion but here are my thoughts on routing...

The purpose of the Neg buss is a collection point for multi Neg cables so using it that way makes sense.
The engine Neg is one of those loads so connecting it to the buss makes sense.
Connecting other Neg cables to the engine doesn't make sense to me as it just adds additional connections and possible V drop to those other loads / cable connections.
No need for redundant cables as long as the primary one is sized properly and the buss bar is capable of handling the total load... if the buss is undersized or marginal then a separate shunt to engine cable might make sense or stacking the eng neg cable on the same buss lug as the main cable from the shunt to minimize V drop.

 

[BDofMSP]

I've learned a lot here, as always. Thanks for all the great input! I'll post a picture when I'm done.

BD