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thomas67 avatar image
thomas67 asked

BMV 700 displays wrong Voltage

Hi,

I have 4 Varta batterys dual purpose, (12v, 230Ah, 5 years old) connected serially to 48v, 230Ah Leadacid no AGM on my boat. They are used for an electric motor. The batteies are charged by a Zivan NG1. with shore power only. They are charged permanently 5 days the week.


Batteries are checked with a professional midronics tester and have very good „health“.

When I measure Voltage with my digital multimeter at the shunt (Battery +, shunt -) I have 53,7 Volt. BMV 700 shows 49,3V

(each battery measured seperatly show 13,4 V)

Do you have any idea? Thanks a lot in advance

Tom

BMV Battery Monitor
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4 Answers
Paul B avatar image
Paul B answered ·

Check the small fuse in the BMVs voltage sense wire it should be 1 amp in size.

also check the + voltage reading with your meter at the shunt connection

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thomas67 avatar image
thomas67 answered ·

Hi Paul,

thanks for your answer. I just checked:

Fuse quecked: fuse Ok

Plus voltage at voltage sense wire on the shunt 53,6 Volt (- measured at shunt, both sides: load and battery)

BMV shows 49,8 V

br Tom


2 comments
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klim8skeptic avatar image klim8skeptic ♦ commented ·

post a picture of your shunt.

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thomas67 avatar image thomas67 klim8skeptic ♦ commented ·

Picture of my shunt

PS: The shunt worked perfectly for 5 years...

After going with the motor for half an hour extracting some 10Ah the Bmv shows 48,3 V, my meter (measuring at the shunt) shows 52,9 V.


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88918bc0-d090-4615-850e-ca1c1a180d9d.jpeg (2.4 MiB)
thomas67 avatar image
thomas67 answered ·

For all who are interested:

As I could not find the cause for my shunt displaying a voltage that was approximattly 4 V Too low, i replaced the shunt with a new victron smart shunt 500A/50mV and everything was fine. Voltage is identical with the measured voltage with my multimeter.

53,8 V after fully loading.

So something in the old shunt 500A/50mV must be defekt, i will try to find out...

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thomas67 avatar image
thomas67 answered ·

For all how are interested: Problem is identified. I bought a new BMV 712 and installed the new shunt using the old CAT cable to connected the new Display. Voltage was correct as expected, some 53,8 V.

Than I pluged in the old Display of the BMV 700 to the new shunt I got the incorrect voltage showing app. 4 Volts too low (49,7V).

So, the Display of the 700 was defekt.

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