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I have a couple of questions on the grounding of the Shunt.

1) Instead of grounding to the starter battery terminal (which is grounded to the chassis) can I save some routing of very large wires and just ground to the chassis?

2) Does the shunt still sense the charging from the alternator when the Smart Isolator (S.I.) allows it to do that?

 

[RDinNHandAZ]

#1 yes
#2 yes, any current through the battery will be sensed.

 

[Streetdoctor]

I have a couple of questions on the grounding of the Shunt.

1) Instead of grounding to the starter battery terminal (which is grounded to the chassis) can I save some routing of very large wires and just ground to the chassis?

2) Does the shunt still sense the charging from the alternator when the Smart Isolator (S.I.) allows it to do that?

I'm trying to currently understand shunt wiring myself. In the manual for the Victron BMV-700 monitor it says,

"Connect the ‘- Load and Charger’ side of the shunt to all the Load and Chargers in the system.
Connect the negative pole of the battery directly to the ‘- Battery’ side of the shunt. Do not connect anything else to this side of the shunt."

This is where I'm confused. My system would have 4 inputs to the Load/Charge side of the shunt- B2B charger, Inverter/Charger, Solar, and the 12V Distribution block. Do all of these need to connect to one pole on the shunt? Is there anything wrong with doing that if they fit? The shunt is stamped 500A and my totals if everything were on and running equal 390A. Then the opposite pole connects to the battery and the battery connects to a chassis ground? Conversely I could purchase a Busbar that's rated to at least 390A and have just one wire going to the shunt correct? I guess I'm worried about the size of wire required from the battery to the chassis ground. The circuit wizard from Bluesea says 4/0 wire for a 1' run, is that really correct?

 

[RDinNHandAZ]

Bluesea is correct. Bigger wire is no harm. All your electricity needs to go through the shunt so connect only it to the negative side of the battery and then wire to the buss bar and connect all grounds to the buss bar.

 

[Streetdoctor]

Bluesea is correct. Bigger wire is no harm. All your electricity needs to go through the shunt so connect only it to the negative side of the battery and then wire to the buss bar and connect all grounds to the buss bar.

Thanks, what about actually grounding the system? I can chassis ground the battery correct? 4/0 wire is $100!

 

[tgregg]

I'm trying to currently understand shunt wiring myself. In the manual for the Victron BMV-700 monitor it says,

"Connect the ‘- Load and Charger’ side of the shunt to all the Load and Chargers in the system.
Connect the negative pole of the battery directly to the ‘- Battery’ side of the shunt. Do not connect anything else to this side of the shunt."

This is where I'm confused. My system would have 4 inputs to the Load/Charge side of the shunt- B2B charger, Inverter/Charger, Solar, and the 12V Distribution block. Do all of these need to connect to one pole on the shunt? Is there anything wrong with doing that if they fit? The shunt is stamped 500A and my totals if everything were on and running equal 390A. Then the opposite pole connects to the battery and the battery connects to a chassis ground?

No, the only connection on the battery negative post is the shunt. If you're going to connect to the chassis ground that's on the opposite pole of the shunt.

Conversely I could purchase a Busbar that's rated to at least 390A and have just one wire going to the shunt correct?

Correct.

I guess I'm worried about the size of wire required from the battery to the chassis ground. The circuit wizard from Bluesea says 4/0 wire for a 1' run, is that really correct?

Usually you only connect the negative to the chassis if you are using the alternator to charge the batteries or you're not running two wires to your loads and charging sources and using the chassis as the return path. Even then the wire only has to be sized to handle the amperage of the devices using the chassis ground as part of their circuit.

The wire from the shunt to the battery negative has to handle the maximum net current in or out of the battery.

 

[Streetdoctor]

No, the only connection on the battery negative post is the shunt. If you're going to connect to the chassis ground that's on the opposite pole of the shunt.


Correct.


Usually you only connect the negative to the chassis if you are using the alternator to charge the batteries or you're not running two wires to your loads and charging sources and using the chassis as the return path. Even then the wire only has to be sized to handle the amperage of the devices using the chassis ground as part of their circuit.

The wire from the shunt to the battery negative has to handle the maximum net current in or out of the battery.

Thank you, this is making more sense now. I am using a battery to battery charger in the system So I need a chassis ground I believe. Can you take a look at this diagram and tell me your opinion? Specifically the ground/negative busbar.

Or is a ground only required for the battery to battery charger in this case? Example being just running a ground from the battery to battery charger to the starter battery and eliminate the ground on the busbar?

 

[SteveSS]

The shunt wiring in Diagram2 looks good to me. It matches the clear instructions that came with our Bogart battery monitor and its shunt. I.e., only the battery bank on the one end, and nothing else.

Two other things for you to consider:
1) you should also have a fuse real close to each (+) battery terminal to protect each battery cable against accidental shorts (etc)

2) a circuit breaker and a switch (red boxes) on the same wire is redundant, i.e., your solar controller to +busbar. Those 2-in-1 circuit breakers also act as on-off switches (push the red button to trip). You might even consider replacing most of the other switches with 2-in-1 circuit breakers. The only actual switches I am using are 2-source selector switches for optional splitting of our large solar and battery banks, and you probably don't need or want that.

 

[Streetdoctor]

The shunt wiring in Diagram2 looks good to me. It matches the clear instructions that came with our Bogart battery monitor and its shunt. I.e., only the battery bank on the one end, and nothing else.

Two other things for you to consider:
1) you should also have a fuse real close to each (+) battery terminal to protect each battery cable against accidental shorts (etc)

2) a circuit breaker and a switch (red boxes) on the same wire is redundant, i.e., your solar controller to +busbar. Those 2-in-1 circuit breakers also act as on-off switches (push the red button to trip). You might even consider replacing most of the other switches with 2-in-1 circuit breakers. The only actual switches I am using are 2-source selector switches for optional splitting of our large solar and battery banks, and you probably don't need or want that.

Thanks for the response!

1) There is a fuse next to each battery, an 80A at the starter and a 200 at the house. The 80A will be attached to the starter battery, the 200A will be within 12" of the house battery.

2) I'll look into the 2 in 1 circuit breakers! The switch on the solar was recommended by some one here to be able to shut the system down for work during daylight. I guess I could throw the circuit... duuh.