I have a BattleBornBattery GC3 270 amp hour 12 V battery and a BMV 712. I recently disconnected everything to add some bus bars, and when I reconnected to BMV no longer showed any voltage but 0.03V. I have measured with a voltmeter and my battery levels are consistent with what my MPPT chargers say (13ish). My Victron connect app has the BMV and 2 MPPT chargers all connected through VE direct. I have fully charged it and reset the charge to 100 once using the app. I’ve also fully charged it to float level yesterday with a charger and the BMV showed 100% charge. The voltage on there did not chang however and remained at 0.03. The voltage measured coming from the tiny red wire is consistent with accurate or correct battery voltage and I’ve checked all my connections over and over. I have even got to the point of only having the battery and the BMV connected and nothing else and I cannot get this thing to change. I’m utterly baffled. This has been a week now and I’m not sure what to do. Do you have any insight?.
You have most likely reconnected something wrong or damaged the BMV in the process. Check the fuse in the holder and the springs. Check the red wire is in the correct input, not the aux input. Check the BMV is set up with aux function as none. I do not expect issues here as the unit is working. Check the cable between the BMV and the head unit, sometimes that causes comms issues, bent or dirty / oxidised pins. Is it reading 0.03V on both head unit and the app.
The app also shows 0.03. The small cable from battery w fuse shows 13.x at the point it enters the shunt and its correctly inserted in the primary input. All cables are clean and checked. I stripped all connections down to just ground from battery and tiny red from pos and no other wires so unlikely a wrong connection. At no point do I recall accidentally shorting things and I did not change the wiring once layed out. I rewired everything separate from battery then connected it. All seems to be charging ok etc. The only thing I can think of was that during disconnect I lost the fuse (from tiny red wire) which is a 1A it appears. I had a 4A sitting around that I used then found the correct one. I suppose a surge could have happened but seems unlikely and the wire would have showed.
I do see a replacement PCB for this on amazon. I assume that could be the culprit if it is a fried thing.