MultiplusII Mk3 will not switch ON (230/12/3000Va)

LATEST UPDATE : 2025/09/25

Following all the comments I took the following actions:

  • Disconnected AC supply

    Switched off DC supply (Fogstar Drift Pro 460AH)

    Inspected Distributors, wiring and connections

    Independently charged the DriftPro

    Checked firmware versions

    Brought system up in a controlled manner 1) DC battery On followed by 2)AC input on … tripped out!!

No obvious errors other than “Low Battery Voltage”

Following a hunch I replaced the “Mega” fuse in the distributor noting the incumbent one felt loose. Brought the system up again in the same controlled manner and noted everything is fully functional!!! I did not have a fuse blown error reported! Also noted my VRM no longer tells me the type of charge i.e. Float, Absorb or Bulk instead it now shows “external control” - not as helpful

My MP2 is protected by a 16amp B16 RCBO which it keeps tripping. The CERBO informs it is restricted to 16AMP and before it trips it goes to a state of “inverting”. In the time between resetting the RCBO and the multiplusII tripping I can set the soft state to “OFF” which then prevents the MP2 from tripping but there are no lights…nothing. L1 AC Out goes to a power panel on the boat with its own RCD which I have switched off essentially removing any AC draw from the MP2 and I have switched of the LifePO4 battery essentially nulling any DC charge output. When the soft switch is set to ON there is a time gap of approx 30 secs before it trips… any ideas

Further to what i have written I should say this behaviour is a recent event as the setup has been working flawlessly since April. This problem was triggered with an airfryer not able to draw enough and shutdown whilst the MP2 was in inverter mode. The shore power was connected and everything seemed to work as it should. Next I found it was trying to power assist the shore before switching to float (SOC 41%) on restart (multiple times) it keeps tripping after 30 secs with no LEDs or apparent errors. It didn’t help that shore power on/off and monitoring was all remote …

The MultiPlus always needs a battery.

The input breaker is tripping because of the huge inrush current of the MultiPlus to charge up the capacitors.

Connecting the battery first will charge the capacitors from DC.

Hi Matthias, thanks for your response. I have tried with the lifepo4 battery connected with the same results. This might be a red herring but the remote console briefly reports it is inverting just before it trips.

I also received low battery warnings even though the battery is 41%SOC (i have previously run down to 36%). I’m guessing this low battery warning stops the MP2 from sourcing its capacitor charge. Given the MP2 is not allowing pass through I can’t independently charge the battery.

is your battery big enough?

Hi Marc, it’s 460Ah and it’s been running since April without issue.

Hi @Darin
Show screenshots of the telemetry data from the following widgets from VRM with the timeline fully zoomed in at the moment of the issue.

VE.Bus Summary
Battery Summary
MultiPlus AC Input Voltage And Current
MultiPlus AC Output Voltage And Current
VE.Bus DC Voltage And Current
Battery Voltage and Current
BMS Charge and Discharge Limits

UPD: Also, a screenshot of the summary ESS Assistant settings from Configure3, if it’s being used.

Hi Diessel, I have taken snap shots from the VRM and I have downloaded the data in spreadsheet form if that is useful

Battery summary…

You’ve done something different from what I asked.
Please read the telemetry widget titles again, if they’re not added, add them from the available list.
Also, make sure to zoom in on the issue moment. I need the detail curve, but you’ve got a compressed timeline.

Hi Diessel, it took me while to digest the difference between what you asked for and what I gave since these widgets are a new experience to me. I was unable to “zoom” in on the device I was using but have since found a way on another device and I’ll post accordingly. The problem I have is placing the time of failure since the multiplus seemed to play up after the event so I’ll pull together more info. I have since fully charged the battery and tried to resynch but the multiplus still trips out even with no dc or ac draw. I will try and get the curves for then.

Hi Matthias, further to my initial response I have now fully charged the lifep04 battery independently of the multiplus 2 but still it trips. Maybe I need to do a full reset to manufacturer settings the reconfigure since nothing else seems to be working

It’s now working - thank you to all who took time out to assist