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texascharlie avatar image
texascharlie asked

BMV-712 - seems dead. Suggestions before I return it?

[Solved: Replacing the 1A inline fuse got the BMV working again. The fuse looked fine to my eye, but it clearly wasn't. I might have found the culprit, see picture.]


Today I tried to do a "pretty" install of my BMV-712 and it stopped working. Making it pretty meant cutting the cable that came with the BMV and crimping a new terminator, so I could route the cable out of sight.

On my first try the BMV worked fine, but I had to re-cut and re-crimp to get the cable through another small hole that I had overlooked.

At that point the BMV stopped working.

The cable is pinned out identically on both ends - blue/orange/green/gr-white/or-white/bl-white. I've re-crimped new terminators multiple times, same result. I've tested two different home-made cables, same result. Should there be a cross-over in the cable?

I've confirmed that the lead coming off the shunt has power, but was a little surprised that it showed 10.76V whereas testing the shunt directly shows 13.40. If I disconnect the UTP cable from the BMV, the lead off of the shunt reads 0.00.

Any thought before I get a replacement BMV?


BMV Battery Monitor
screen-shot-2020-10-07-at-70111-pm-collage.jpg (278.7 KiB)
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wkirby avatar image wkirby ♦♦ commented ·

Did you check the inline fuse in the red wire between the shunt and battery positive?

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texascharlie avatar image texascharlie wkirby ♦♦ commented ·

The inline fuse is good.

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wkirby avatar image wkirby ♦♦ texascharlie commented ·

The wiring order that you describe is correct.
I'm kind of out of ideas. Has the cable from shunt to BMV has not become damaged somewhere along the way.
It's difficult for me to imagine how the BMV could have got damaged, unless one of your previous terminations was bad.

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texascharlie avatar image texascharlie texascharlie commented ·

Turns out the fuse wasn't good. No visual sign of a problem, but a new fuse has the BMV working once again (using my shortened cable.) So perhaps I miswired the terminals on one of my many crimp attempts and that half-blew the fuse? Dunno since I discarded the one that started the problem.

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nigelfxs avatar image nigelfxs commented ·

I've confirmed that the lead coming off the shunt has power, but was a little surprised that it showed 10.76V whereas testing the shunt directly shows 13.40.

The "power" lead coming off the shunt should have the same voltage as measured between battery ground and the shunt. I would try replacing the fuse with a new 1A fuse.

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texascharlie avatar image texascharlie nigelfxs commented ·

My 13.40V measurement was taken from battery positive to shunt, and 10.76V from battery positive to the "power" lead off the shunt.

Does that affect the suggestion that replacing the 1A fuse might help? Visually, the fuse looks fine.

I'll note that it is *possible*, but I think unlikely, that the manually crimped terminator was mis-wired when the BMV stopped working, but I could not confirm because I could not find it in the trash afterward.

I'm certain that subsequent crimps were correct.

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ewalderasmus avatar image ewalderasmus texascharlie commented ·

https://community.victronenergy.com/answers/62100/view.html


Very interesting article regarding a half-blown fuse. Don't know much about the BMV, but reading such a low voltage is concerning.

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wkirby avatar image wkirby ♦♦ texascharlie commented ·

What do you measure between battery negative and the end of the red wire at the shunt. This should read battery Voltage otherwise the fuse is open.
It's be useful also perform a continuity check over the fuse in addition to a visual check.

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texascharlie avatar image texascharlie wkirby ♦♦ commented ·

I replaced the fuse today, assuming it wouldn't solve the problem but just to be thorough. It fixed the problem!

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2 Answers
michelg avatar image
michelg answered ·


mvader (Victron Energy) answered · May 06 at 11:15 AM EXPERT ANSWER


Hi @PMarine, we designed and tested for the cable length that comes with the BMV: 10 meters. Thats the official answer: max length 10 meter.

A longer cable might work, or might not. Or it can depend on the amount of interference, longer cable will have more interference. Another possible is issue is more voltage drop, so less accurate voltage reading.



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klim8skeptic avatar image
klim8skeptic answered ·

Myself, I would replace the cable,, before replacing the whole BMV unit.....

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