question

ctownj30 avatar image
ctownj30 asked

BMV-700 Showing zero voltage

We purchased a boat that had a BMV-600S. It is displaying current fine, but voltage displays 0.00 (sometimes 0.01).

How could this be? Seems like if the unit is powering up and displaying current there must be no problem with any of the wiring to the shunt or +.

Could an errant setting cause this?

Thanks

BMV Battery Monitor
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10 Answers
kevgermany avatar image
kevgermany answered ·

Current and voltage don't share the same wiring. Current is from the shunt. Voltage has a wire to battery positive. Maybe check that leg.

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ctownj30 avatar image
ctownj30 answered ·

Thanks for getting back to me. Well, that was my point: the unit has a single RJ connector (6-pin) coming from the shunt assembly, and hot to the battery wires into that as well. I would assume that the unit would not power on unless the battery hot wire were connected.

Given it only has one 12V hot input, is it even possible that it could power on and run, but NOT read voltage?

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klim8skeptic avatar image klim8skeptic ♦ commented ·
There could be 2 hot wires running in the RJ12 cable. 1 to power the display, and 1 as a voltage sense wire, this is just conjecture tho.

Might be worth checking the cable/sockets for damage. Probably a good time to clean the black paint of the shunt/pcb.

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ctownj30 avatar image
ctownj30 answered ·

Anyone have any ideas? Still reading zero voltage although everything else worked. I crimped a new cable to run from the shunt to the gauge but still no joy. Don't understand how it could read zero volts, but still power up and run and happily measure current?


pxl-20220507-204046827mp.jpg

pxl-20220507-170657410.jpg



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bruces avatar image
bruces answered ·

Can't see enough detail but....

Is that red wire with the black fuse holder plugged into the correct hole? (2 of them there)

Is that fuse OK?

You say the 12v hot wire is in the network cable? You reckon?

What let the smoke out? Evidence of a bad short in that box or was that in a previous life?

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ctownj30 avatar image
ctownj30 answered ·

Red wire - yup, confirmed. Fuse checked.

The black is actually a conformal coating (anti-corrosive) that the PO sprayed over any exposed metal he could (bit annoying, that).

Basically, it was working fine with previous lead acid batteries when we bought the boat. We switched LifePO4 lithiums and re-ran the network cable at the same time so a lot of variables changed at once. The new cable was terminated exactly as the previous one was and tested for continuity on all pins.

Everything is wired exactly like this:

screenshot-2022-05-09-092412.png

There is no other way for Pos./+ into this system except for the single supply cable into the shunt - so I'm the fact the unit lights up and operates as proof that the Pos. supply is correctly hooked up and the fuse is fine.

Seems like zero voltage must mean either the unit has failed, or something is misconfigured (obviously hoping for the latter).


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ctownj30 avatar image
ctownj30 answered ·

If it matters, I just realized I have a BMV-700, NOT a 600s

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klim8skeptic avatar image klim8skeptic ♦ commented ·
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ebphinn avatar image
ebphinn answered ·

I have the same issue. When I commissioned the boat this year it started out showing the correct voltage but then it began to degrade within a week or so. Now it reads .01 to .02 of a volt. All the other values displayed are correct. When I view it on the BT dongle it gives also the .01 or .02 as well. This happened to another monitor before this. Is their a fault in the Display? Is there a way to reset? Won't be installing any more of these until this is resolved. Eric Renforth Boat Works, Marine Systems Specialist.

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piotr-nowinski avatar image
piotr-nowinski answered ·

Hello All.

I've BMV-700 and I've the same issue. At the beginning voltage start fluctuating randomly, now it shows 0.01V. Current is displayed correctly. I've check cable with ohmometer and all wires seems to be OK. I've sent monitor and shunt back to the seller, monitor has been replaced with no avail. It' still shows 0.01V. Did you resolve your issue ?

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johanndo avatar image
johanndo answered ·

Probably damaged ADC inside or bad connection. What Ve.Direct cables do you use, original or DIY USB adapters? You could power that thing via the ve.direct cable instead of the battery plus (for flashing firmware for instance).

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piotr-nowinski avatar image
piotr-nowinski answered ·

I don't use Ve.Direct cable, battery monitor is connected to shunt via RJ12 cable. I assume shunt doesn't provide Vcc+ value but provide power to monitor (I assume +Vcc for measurement and Vcc+ to power up monitor goes separatelly). I've measured voltage on each pin on shunt and there is only one pin with Vcc+.

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