Multiplus II measures 6V higher than Pylontech BMS

Interesting one this — I've been half-following a similar situation on my narrowboat setup and wondered if anyone else here has run into it.

I've got a small stack of Pylontech US2000C batteries paired with a Victron Multiplus II, and I've noticed the voltage readings between the Victron and the Pylontech BMS (via VRM) can drift apart, sometimes by a couple of volts. Not 6V like some folk have reported elsewhere, but enough to make me scratch my head.

A few questions I keep coming back to:

• Is the discrepancy purely down to cable voltage drop between the battery terminals and the inverter's sense point?
• Could it be a calibration issue on the Multiplus II itself, or is it more likely the BMS reporting differently?
• Has anyone actually used remote voltage sensing wires on their Multiplus II to correct for this, and did it genuinely resolve the gap?

The reason I'm fussing over it is that if the Multiplus thinks the pack voltage is higher than it actually is, I'm worried it might cut out prematurely on charge cycles, or worse — if it's reading lower than reality, push the cells too hard.

I'm using the Victron VE.Can connection to allow proper DVCC communication, which is supposedly meant to let the BMS take control of charge parameters. But I'm still seeing this creep.

Would love to know if anyone's pulled a battery from their stack for similar reasons and whether it resolved the voltage measurement confusion on the remaining cells. Does isolating a rogue cell actually tighten up the BMS reporting on the others?

@LindaClark90 — had something eerily similar when I first wired up the Pylontech stack in my shepherd's hut. The Multiplus II was consistently reading higher than the BMS reported.

Turned out to be a measurement point problem — the Victron was measuring voltage at its own terminals rather than at the battery. Under load, voltage drop across the cable run was masking the true picture.

Worth checking:

• Cable length and cross-section between inverter and battery
• Whether your DVCC is properly enabled via VenusOS (forces the system to trust the BMS figures)
• Shared voltage sense wiring

Once DVCC was correctly configured, the Multiplus deferred to the Pylontech BMS entirely and the discrepancy vanished. The Pylontech comms via the Victron GX device essentially take over — which is exactly what you want with a managed battery.

Classic Victron/Pylontech voltage reporting quirk — the Multiplus II measures at its own terminals including any cable voltage drop in reverse when charging, so you're essentially seeing the charger's output voltage rather than the battery's resting voltage, which the BMS reports internally. Check your DC cable gauge and connection quality first; undersized cable on a motorhome or narrowboat install is the usual culprit making the discrepancy worse. Enable the DVCC setting in VenusOS if you're running a Cerbo/CCGX — that hands voltage/current control to the Pylontech BMS via CAN-bus and the two systems then play nicely together. Had exactly this sorted on my van conversion once DVCC was switched on; the 6V gap basically collapsed overnight.

@MarineGeoff has nailed the cable drop angle, but worth adding: check your cable cross-section too. Even 35mm² cable carrying 50A+ will show meaningful drop over a few metres.

The other thing I'd verify — are you using the Victron VE.Can or RS485 comms cable to let the Multiplus II actually talk to the Pylontech BMS? Without that link properly configured in Venus OS, the inverter is essentially flying blind on battery state and will prioritise its own terminal measurements.

On my cabin setup I had a 4V discrepancy until I sorted the comms and tightened a slightly dodgy lug on the positive busbar. Embarrassingly simple fix after two days of head-scratching! 😅

Also worth running BatteryView software on the Pylontech side to see what individual cell voltages look like — rules out a drifting cell skewing the BMS reading.

@MarineGeoff and @DailySolar have covered the cable drop side well enough.

One thing nobody's mentioned yet — make sure your Pylontech BMS data is actually reaching the Multiplus II correctly via CAN. If the DVCC settings in VenusOS aren't pulling SOC and voltage from the BMS properly, the Multiplus just falls back to its own internal voltage sensing, which compounds any cable drop discrepancy.

Check Device List → Pylontech on your GX device and confirm it's showing as the controlling BMS. If it's not listed or showing errors, that 6V gap will never resolve itself regardless of how well you've crimped your lugs.

Seen this exact scenario on my static caravan setup — turned out a dodgy RJ45 in the CAN cable was the culprit the whole time. Voltage readings were all over the place until I replaced it.