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Old 29-04-2018, 06:36   #1
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Aternative Shunt for Victron Bat Mon 712?

Victron says that you can use an existing or alternative shunt with their Battery Monitor, you just take off their shunt of their their circuit card and put their circuit card across your shunt.

1. My boat is 100 mi away, I do have a picture, but can't find dimensions of the circuit card for their circuit card. They have size of the whole product, but not the size from terminal to terminal. Was hoping someone might have done this and would know if all marine shunts have similiar dimensions?

2. My thought , see pic with wires attached, is that I could either take off the wires that lead to my control panel and just hopefully screw on the victron control board and hope that it makes proper contact at the right connections?

Was also wondering if it fit, if I could leave both systems attached to the same shunt. My system is the OEM system on a 2015 Lagoon 380, it just leads to the control panel that has a lcd display of battery V, and shows A draw. V is accurate, A is not much, but a good indicator (will show 6 say when electronics are on.) The victron BM can be programmed for pretty much any shunt, so I should be able to use mine. I don't know if connection to my panel and victrons will change readings as panel must have some draw.

3. If I wanted both systems, I guess I could take off lead coming from battery switch to bottom of my shunt, put in victron shunt, get a new very short cable from other side of victron shunt back to bottom of old shunt and have both meters working. Not sure what size cable I would need for a 2 or 3" run.

4. Or I could simply not have my meter read on the main panel, and just put in the victron shunt and take battery wires off mine and put on victron's.
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Old 30-04-2018, 16:42   #2
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Re: Aternative Shunt for Victron Bat Mon 712?

I have never tried to take one apart. I would just put the victron one in.

the volt meter will still work. that has nothing to do with the old shunt. if you put those 2 small wires onto the victron shunt, both amp meters will likly work.

that wire between the shunt and switch is too small looking. it should be the same size as the other others.

it also looks like you have 4 wires on each side of that neg swtich. so likely it won't do anything but cause a lot of weird things if you turn if off.
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Old 30-04-2018, 17:06   #3
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Re: Aternative Shunt for Victron Bat Mon 712?

The shunt is just a resistor with a very low, but very precise, resistance. The meter works by measuring the very small voltage drop across this resistor. Having multiple instruments measuring this voltage drop will work just fine.

Just be sure that the connections are very clean and well made, you are measuring tiny little voltages, on the order of 0.05 Volts
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Old 30-04-2018, 17:30   #4
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Re: Aternative Shunt for Victron Bat Mon 712?

Thanks guys. The LCD display that is there currently has some very large impedance. Was worried that having 2 meters reading inparallel would potentially change the reading. If you have say 2 multimeters reading in parallel, even if they have 10 M Ohm each, you have changed the reading from 10M to 5M ohm. Potentially chnages the reading as the shunt as you say is reading very small A.

Don't know why the wire from switch to shunt is smaller than others. This is the way Lagoon sold me the boat, new.

Lagoon / Beneteau/ Juneau all switch neg as well as pos.
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Old 30-04-2018, 17:44   #5
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Re: Aternative Shunt for Victron Bat Mon 712?

The effect on the voltage from multiple meters reading a single shunt will be astonishingly small. A 100 amp 50mV shunt (which is typical for these applications) has a resistance of 0.0005 ohms. To affect the reading by 1% you would need to have about two hundred million voltmeters measuring at once. They might weigh enough to sink your boat first.
The shunts have a very low resistance so they do not overheat at full load. That 0.0005 ohms with 100 amps is dissipating 5 Watts. It will be quite warm.
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Old 30-04-2018, 23:16   #6
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Re: Aternative Shunt for Victron Bat Mon 712?

Quote:
Originally Posted by jbinbi View Post

Lagoon / Beneteau/ Juneau all switch neg as well as pos.
yes but then you'd only have 2 wires on one side. the engine battery and the house battery. someone has likely added more wires.
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Old 01-05-2018, 02:13   #7
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Re: Aternative Shunt for Victron Bat Mon 712?

I have one and I am on the boat almost daily. What exactly do you want to know in terms of measurements and I will try and help.
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Old 01-05-2018, 17:27   #8
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Re: Aternative Shunt for Victron Bat Mon 712?

the holes for mounting are 200mm apart. Can measure anything else tomorrow.
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Old 09-05-2018, 07:43   #9
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Re: Aternative Shunt for Victron Bat Mon 712?

FYI, I was told by Lagoon that this shunt is a 100A 50mv shunt. I do NOT have an inverter on the boat, so I believe this to be sufficient. I had looked at adding a 2000W (really 1600W Victron) which would pull about 150 peak amps, so I guess this shunt would not be applicable anymore.
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Old 09-05-2018, 14:29   #10
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Re: Aternative Shunt for Victron Bat Mon 712?

Again, the size of your shunt depends how you want to use it.

If your goal is to measure **all** current flows in and out of a given bank, then it must be sized large enough to handle the maximum concurrent amps at a given time for the loads going through that bank.

Plus IMO 20-30% of headroom if that largest total current will last more than few seconds. Some sources are more conservative, but many users cut it finer.

It really is exactly the same process as sizing a fuse to handle its expected currents.
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Old 09-05-2018, 14:45   #11
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Re: Aternative Shunt for Victron Bat Mon 712?

Yup. But now I am looking at going Balmar Smart rather than Victron. Just finished reading Mainesails review, and the Balmar seems like it gives a much more accurate SOC reading. I figure with that, having the victron solar controller that has bluetooth that will let me know at least amps in (not sure if it shows amps out) and just reading volts, I kind of know what is going on. But I think that is for a different thread!
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Old 09-05-2018, 15:06   #12
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Re: Aternative Shunt for Victron Bat Mon 712?

Well it's your thread 8-)

I am a big fan of Merlin's SG myself, yes more accurate than anything else **when resting**, and for lead banks only

but I still recommend a good AH counter for the additional current information they provide.

Also as a secondary cross-reference for SoC, in case your SG gets out of whack, which has occasionally happened.

And I recommend people support MS by buying from him - he can get most anything - or at least by making the occasional donation.
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