question

drblind avatar image
drblind asked

To high current and watt reading on my BMV 712

Why does my BMV show almost 24amps when my solar shows that it's charging 12,3amps?


No other chargers connect, engine off.


I have 2* 100ah LiFePo4, 3*100w solar panels, a Victron smart solar MPPT 100/30 and a BMV712 monitor.

BMV Battery Monitorcharger
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4 Answers
Mark avatar image
Mark answered ·

When comparing charge currents you need to look at the MPPT output current (not the solar input current), as that is at the same voltage as the battery & should include losses in the MPPT.

But that still does not explain your issue. There is a significant disconnect that can't be logically explained (15A vs 24A).

As solar power can be constantly changing, sometimes the numbers momentarily won't add up/match due to a different refresh rate/timing, but again I don't think that explains your issue.

The BMV is also always considered as the master reference, since it is a calibrated measurment device & the MPPT is not.

I think that you either have a poor connection or a fault with the BMV. As a start, make sure that the shunt PCB is tight and also try to have a play with the UTP cable ends while watching the display, there have been a few recent cases where a faulty UTP cable end was the cause.

If you physically disconnect all loads & charge sources from that end of the BMV, what current does the BMV read in that state - 0A or something else?

If you can get a hold of a multimeter with a current clamp that would be very useful to verify the readings & diagnose your issue.

Also double check that the shunt settings are correctly calibrated in VictronConnect under 'Settings' > 'Misc'. If that's wrong it could also cause your issue.



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drblind avatar image
drblind answered ·

A photo of my BMV with solar shut off.

And here is simultaneously solar mppt and BMV display when turning it on.

my shunt:


Placed Abit further from the batteries than optimal, 1,5metres.



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boekel avatar image boekel ♦ commented ·

That's the cause..don't connect anything but the circuit-board itself to the small screws.
All connections should be made at the M10 bolts:

https://www.victronenergy.com/upload/documents/Quickinstallsheet_BMV70x_part1_2.pdf

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drblind avatar image drblind boekel ♦ commented ·

Aha thank you! I will try to make the change and hopfully this is the problem :)


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Mark avatar image Mark ♦♦ commented ·

I agree, having the connections on the small PCB screws is adding additional resistance. Move all terminal lugs to the M10 bolt & tighten the PCB screw.

The fact that it reads 0A with everything disconnected also indicates that the unit most probably has no issue.

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drblind avatar image
drblind answered ·

The shunt setting's is default from factory


500A

50mV

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fiaskogaul avatar image
fiaskogaul answered ·

Hi @Dr.blind,

I got a similar issue And wiring. Did you solve the problem by moving the lugs?


regards

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Do you have a picture of your shunt wiring?

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drblind avatar image drblind commented ·

Yes!


The connections on the print card made the fault.


The negative charger and solar have have to be moved to the big screw on the output side of the shunt, and not on top of the print card like you can see i had on my photo.



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fiaskogaul avatar image fiaskogaul drblind commented ·

Great thanks! I need new lugs then...

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