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Tony Alba avatar image
Tony Alba asked

Installing a Waeco fridge with BMV -712 and Redarc BCD1220D.

1st of a big hello, guys just bought a BMV-712..

trying to install my BMV fridge and Redarc BCD, problem I'm having is voltage drop and fridge keeps turning off and back on on its own, I have the fridge cable pos going to a fuse box and neg going to a Earth point, also don't have any cables going to the outpost on Shunt , is this right?

or should I have the pos going to battery and neg to the outpost of the Shunt...if this is so will the voltage still have droppage?

(mod note: minor spelling stuff corrected)

BMV Battery Monitor
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4 Answers
JohnC avatar image
JohnC answered ·

Hi @Tony Alba

V-drop issues are most likely caused by wires that are too small. What size are they? For a '20A' system I'd be looking at 6mm2 at least, and then bigger again if over a metre or two long. https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

And if you're buying auto cable, make sure it doesn't include the plastic insulation in it's rating.

The BMV shunt won't influence you, it's resistance is insignificant. Making that work is another issue, and you really should study up on it to see satisfaction from useful figures. https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-712-EN-NL-FR-DE-ES-SE.pdf

It needs wiring correctly, then some tender-loving-care to calibrate it for best results.

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Tony Alba avatar image
Tony Alba answered ·

Today I made some changers, however noticed overnight my voltage has dropped without any devices on other than the led on the front of monitor, is this normal how much will it consume?

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JohnC avatar image JohnC ♦ commented ·

Not sure what you mean by 'led'. But the BMV712 (Smart) is listed as self-consuming "<1mA". That's tiny, almost immeasurable.

Maybe you have sick batteries? Or a phantom load (that the BMV can measure too).

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Tony Alba avatar image
Tony Alba answered ·

bump anyone?


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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
Maybe make some pictures of the installation and/or add a wiring diagram.

As John wrote above I also think there is something connected directly to the battery so the BMV can't "see" that current or the battery is almost dead.

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kevgermany avatar image
kevgermany answered ·

The earth point of the batteries should be the load side of the shunt. There should be no connection to the battery negative, except the battery side of the shunt.

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