MultiPlus Compact 12/1600/70-16 – Internal voltage misreading 9V, no inverter operation without shor

Q&A and troubleshooting
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1

Hi everyone,

I’m hoping to get some help diagnosing an issue with my MultiPlus Compact 12/1600/70-16 in a motorhome system.

System:

  • MultiPlus Compact 12/1600/70-16
  • 3x Victron Smart Lithium 100Ah (parallel)
  • VE.Bus BMS
  • Raspberry Pi with Venus OS
  • Orion XS DC-DC charger
  • 785Wp solar
  • BMV-712

How the fault occurred: While the air conditioning (1400W) was running on shore power, I disconnected shore power without first switching off the AC load. This caused an immediate voltage drop and the MultiPlus shut down. After reconnecting shore power and attempting multiple restarts, the unit entered Bulk Protection Mode.

Current symptoms:

  • VictronConnect shows internal battery voltage as ~9V despite actual voltage being 13.2-13.5V (confirmed by BMV-712 and external multimeter)
  • Bulk Protection Mode repeatedly triggered
  • Charging current only 10-20W instead of rated 70A
  • PowerAssist works normally with shore power connected
  • Pass-through up to 1000W works normally
  • Inverter mode without shore power: unit shuts down immediately upon shore power disconnection
  • Alarm LED active when switching to „On” mode without shore power

What I have tried:

  • Bulk Protection reset via MK3-USB and VictronConnect (disabling „Stop after excessive bulk”)
  • Adjusted DC input low restart from 12.9V to 12.5V
  • Full battery charge to 100% SOC before testing
  • Multiple power cycles

My suspicion: The internal voltage measurement circuit appears to be faulty – reading ~9V instead of actual ~13.5V. This would explain all symptoms: low charging current, immediate shutdown when inverting, repeated Bulk Protection triggering.

Question: Is there a way to diagnose or recalibrate the internal voltage measurement via VEConfigure or any other tool? Or is this a hardware fault requiring board replacement?

Thank you in advance.

René

2

It is not a calibration issue, i think you just triggered a protection in the battery.
Does the bms show any error codes? Is it the v1 or the v2 bms?

Did you try just setting the inverter into charger only mode and seeing if it wakes up again?

3

Thanks for the quick response.

The BMS is a VE.Bus BMS (the older version, no V1/V2 marking visible, part number 10R-05 4003).

I checked the BMS via VictronConnect – status shows „Funktionsbereit” (operational), no error codes, all cells balanced at 3.30-3.31V. The „Enabled” LED on the BMS is active.

Regarding Charger Only: yes, this was tried extensively. In Charger Only mode the unit charges normally and reaches Absorption and Float phases. Internal voltage reading in VictronConnect is correct (14.25V during charging).

When switching to „On” mode with shore power connected, PowerAssist works normally. However when shore power is disconnected the unit shuts down immediately and cannot restart in inverter mode. Charging current in Charger Only is also limited to 10-20W instead of rated 70A

4

That sounds like a blown fuse, you should check that.
The MultiPlus also has an internal fuse.

5

Internal fuse checked (MEGA fuse 250A 32V ZH274-1) – continuity confirmed, fuse is intact.

6

Did you take the fuse out to check it?

7

No, I checked it while it was installed.

8

@kettelinks our wise friend @M_Lange was giving you a big hint that you need to remove the fuse and test it out of the circuit.