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I occasionally get gibberish data on my BMV-712 display, e.g. the attached pic showing a Mid point battery discrepancy of 43,039% with the alarm indicator (!) on. When this happens the display generally rapidly changes with garbage data. Unplugging and replugging the device seems to clear it up.
I haven't yet mounted the display unit properly, I'm guessing this is from a bad connection between the shunt and BMV, or could the unit be faulty?
https://photos.app.goo.gl/md92R7px8GGAdiki8
Just to confirm - have you properly wired up the mid-point wiring to the mid point of your battery bank and does it have a fuse installed?
Maybe also test all the wiring direct from the shunt B2 terminal to the battery bank mid point terminal for continuity with a multi-meter.
Also what is the mid-point voltage reading that the BMV it is giving you - is that also unreasonable? is it 0v? Is it the full voltage?
If all this checks out OK then I would refer to your dealer/place of purchase for further advice - particularly if the unit is brand new.
I had a customer yesterday who reported a similar problem on his roughly 2-year old BMV-700; after an hour or so of troubleshooting we discovered that a thin layer of rust had built up on the ends of the inline glass fuse of the shunt PCB power wire. This was enough to cause a voltage drop to the PCB that would result in sporadic gibberish readings at the display head. He cleaned up the fuse, reinstalled it, and the system worked perfectly again.
Being that yours is (I presume) relatively new, rust in particular shouldn't be a particular issue, but I think it's worth checking both the fuse holder contacts to make sure they're clean on the inside; also check to be sure that you have a 1A fuse in there instead of the old 100mA fuses.
...also possible that the RJ11 cable has a defect or has taken some damage to the pins during installation, but I don't have a good way to test that without having a known good display head to check it with, so I'd suggest ruling out a fuse/holder issue first and going from there.
