BMV-712 installed in a small camper trailer. 12V 100Ah LiFePO4 battery with small loads and a solar panel MPPT (also Victron). Shunt is only thing connected to the battery negative terminal, and there is only one wire on the load side of the shunt. Chassis ground goes to a negative bus bar, which is connected to the load side of the shunt. Has worked well for 2+ years until recently.
Started seeing a current of 13A even with everything disconnected (including solar panel). Clamp-meter showed negligible current on both negative and positive cables from battery.
I disconnected the wire from the load side of the shunt and unit still reported 13A. Following instructions in the manual, I then performed a zero current calibration . . . and the current dropped to 9.2 amps (fluctuating slightly). Repeated zero current calibrations don’t reduce the current to zero!
I’m stumped. Can’t see any reason for the phantom current because NOTHING is passing through the shunt.
Sometimes the comms cable between the shunt and the display can get damp / corrosion in the contacts in boat / vehicle installs which affects the displayed values so check this. Additionally, have you installed anything new that could be a source of interference to the comms cable.
Thanks for the quick reply. The comms cable is actually new; I had to replace the original one because I accidentally nicked it and clipped the wire that transmitted voltage. So just 6 months ago I replaced it. Following replacement, everything was working perfectly until last week (voltage and current). i did install a small inverter just after I replaced the cable, but I have the option to completely disconnect this and the BMV-712 was reading phantom current with the inverter disconnected.
Quick followup question–if the BMV thinks it’s actually getting 10-13A all the time, could that explain why the SOC never drops below 100%, even when I know there have been loads running? In other words, is the calculation of SOC being misled by the phantom current? This is actually my immediate concern, because if I can’t trust the SOC then there’s no reason for the BMV in the first place.
If the cable’s the problem, maybe I’m better off just replacing the BMV-712 with a smartshunt and doing away with the cable altogether. I would miss the BMV-712 gauge inside the trailer though, and I wish it were possible to add a simple repeater display to the Smartshunt, though I don’t think this is possible.
The phantom current will be being used in the calculation of SOC, so if the current is in the direction of charging then the SOC will read higher than actual.