grizzly660fan avatar image
grizzly660fan asked

BMV-712 problems

Installed BMV-712 last night and all was working, first step in the app was a firmware update which seemed to work fine. I then set the 712 up via the app and watched everything for a while then off to bed, went to work, came home and wanted to see state of batteries and the 712 is now unresponsive from the unit (screen is blank) or via the app.

I disconnected the control cable (I think it’s rj11?) at the shunt and get no response. I disconnected the red power cable at the shunt and re-seated it no response. I checked the fuse on the red cable that connects to the shunt and the fuse is good, reconnect the fuse no response.

What else can I check? Could the unit go defective overnight? My RV has full power for all devices

Any help you can offer is greatly appreciated


BMV Battery MonitorinstallationHelp
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daniel1957 avatar image daniel1957 commented ·

Are you using the connection cable that came with the BMV712?

And have you connected the + battery voltage cable and tested that it is still connected properly?

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3 Answers
geomz avatar image
geomz answered ·

Sounds like a dead unit.

Are there any lights on it at all? Backlight, etc.

Try switching the RJ11 cable -technically I think it's RJ12 with 6p6c ends. Same plugs, more connectors. And I think it uses all 6 pins, so you need to have one that is straight-through 6-pin.

I'd pull out the display unit and use a short run, next to the shunt, just to test it.

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Paul B avatar image
Paul B answered ·

Check the fuse and make sure you have + 12 volts or battery voltage at the shunt USE A VOLT METER a visual look is not good enough.

the other suggestions above are also applicable, look for the basics bad connection or a broken wire

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grizzly660fan avatar image grizzly660fan commented ·

I will check with volt meter at the fuse as suggested.

Is there anything in the shunt electronics that could fail? trying to determine if the problem is at the shunt end or the display end?

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daniel1957 avatar image daniel1957 grizzly660fan commented ·

nothing to check other than the basics - + battery cable correctly connected and the Victron comms cable correctly plugged in.

Use a multimeter or test lamp to check that you have +/- at the shunt.

If it doesn't work then return for replacement.

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grizzly660fan avatar image
grizzly660fan answered ·

No lights on the Victron at all, no response from any of the buttons at all. Any idea where I can obtain such a cable as you describe?

While its good to rule out the RJ12 (thanks for the correction as I was guessing what it was called) I doubt that is the problem. I had a really nice low friction area of the trailer to pass through so I am confident nothing is pinched, cut, or otherwise would compromise the cable. Also the trailer didn't move from one day to the next where I now have the problem.

I also didn't plug shore power or anything into the trailer, my goal was to monitor the trailer and try to determine how much phantom loads exist with everything powered off that I can turn off.

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geomz avatar image geomz commented ·

I've had my BMV act "squirrelly" with the original RJ12, then by simply connecting it with a short RJ12-run it magically started working correctly, even with the original cable. It sounds ridiculous, believe me, I know :)

But it did happen. And the only thing changed was plugging the short cable, having it "magically" work correctly, and then simply plugging it back where it was. That was, of course, after several bouts of plugging, unplugging, replugging, end-to-end and interference testing; not to mention a lot of cussing :)

But in my case, the unit was "working" just giving me complete nonsense readings.

In your case, however, I think the unit is toast. If you've checked the fuse (electrically) and are certain of end-to-end continuity, there's really not much left. I will add an overtly over-simplistic suggestion, check the red wire (directly at the tip) and a multimeter directly against the negative lug on the shunt (both sides). You should see battery voltage. You've probably already done it, but...

FYI, the shunt-board is pretty much the electrical brains and heart of the whole operation. The little display-doodad is pretty much just that -the display/config/Bluetooth interface.

And you can get an RJ12 from a Wally World or even radio shack (do they even have those any more :) ). There's nothing fancy about it and it's the same as an RJ11, but it has all 6 pins wired (vs the inner 4). Often times it's called a "multi-line" or PBX phone cable.

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