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mike-b avatar image
mike-b asked

BMV712 connection for midpoint voltage

I have 6 Firefly L15 (4V) batteries. I would like to wire these in series(3x4V) /parallel to have 12V/ 900Ah. I am installing a BMV712, and would like to have Midpoint voltage monitoring. Please show a diagram of how to wire this configuration. The "Quick Start" guide does not show a diagram which seems to match.

Thank you

BMV Battery Monitor
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3 Answers
Mark avatar image
Mark answered ·

Hi Mike,

Sorry but with those particular batteries in a 12v setup you physically can't access the midpoint (6v), so midpoint monitoring is not posible The voltage at the link terminals/cables would be 4v & 8v.


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vineyardgray avatar image
vineyardgray answered ·

Each Firefly 4v battery are actually two 2v cells externally connected with a series busbar. It should be possible to get to the 6v midpoint.

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mike-b avatar image
mike-b answered ·

OK, 2 opposite answers, can we get some further clarification from Victron?

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klim8skeptic avatar image klim8skeptic ♦ commented ·

These batteries? https://coastalclimatecontrol.com/images/Firefly/Firefly-Users-Manual-G31-L15.pdf


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vineyardgray avatar image vineyardgray klim8skeptic ♦ commented ·

The OP is contemplating the L15 type, yes.

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Mark avatar image Mark ♦♦ commented ·

The answer has nothing to do with Victron - Victron do not make the batteries being discussed.

But this is not a complex matter...

If the link between the 2 cells can somehow be physically accessed to attach a wire for the mid point monitor (ie. if they are external), then yes it will work. But if you can't then it won't...

Basically all batteries are internally made up of separate 2v cells, but you typically can't access the links

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mike-b avatar image mike-b Mark ♦♦ commented ·

Hi Mark, looks like a midpoint reading is possible. The Firefly 4v batteries consist of 2 /2v cells connected externally with a connecting bar. Should allow the midpoint monitoring, correct?


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Mark avatar image Mark ♦♦ mike-b commented ·

In that case yes - it should work fine.

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