question

leverg avatar image
leverg asked

Multiple BMV,s (2 ) and placing shunts to negative wiring and grounding earth to metal boat.

Hi all,

I,m trying to figure out how to use 2 bmv,s on my boat system.

I have 2 seperate circuits, one for start battery and one for accesoires.

I would like to know both soc,s so i have 2 bmv,s . The start battery gets default charged by the alternator, the accesoire battery gets loaded by the default solar panel. (default because in between is a cyrix.


Placing the shunts is troubling me, how do I place the shunt. The starter circuit has some devices which are grouded by the metallic shell of the boat, like starter engine, and dynamo, but of course also uses a negative cable. . The accesoire circuit does nog have this and therefore a minus cable is used only to power electronics inverters etc. However i,m confused If I connect both shunts of both bmv,s together to the metallic frame that the readings won`t be correct.


I,ve created a scheme, maybe that can clarify the situation.


electra-8-dec-2020.jpg


BMV Battery Monitor
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2 Answers
JohnC avatar image
JohnC answered ·

Hi @Leverg

In your diagram you've drawn in the earths on the wrong side of the shunts. Relocate them to the LOAD side of the shunts and you should be sweet.

Think of the Load side of the shunt as your battery earth terminal, as it's only really a 'calibrated' piece of wire.

Of course in a marine situation, only one single earth connection to the hull is good practice, but that's another subject..

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leverg avatar image
leverg answered ·

Thanks for your answer. @JohnC


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