Multiplus II GX / ESS mode 3 not inverting - how to troubleshoot/debug

Q&A and troubleshooting
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1

I’m a long time professional in the power and battery management field, but new to the Victron product line; I’m probably missing something trivial or doing something wrong, any insights appreciated:

TL;DR version:

Where does the multiplus report any reasons for not switching on the inverter, even though I ask it to?

Long version:

  • Multiplus II gx, connected to mains on the AC input, connected to a ‘dumb’ LiFePo4 battery (no connection with external BMS) on DC bus
  • Grid code is set to europe, tried with LOM both enabled and disabled
  • Control is done through modbus TCP, ESS is configured to mode 3 ‘External control’, Configuring the power set point through register 37 on ID 228; writes are accepted by the modbus server and the written value is properly read back.
  • Registers 38 and 39 are verified to be 0, meaning “charger enbled” and “inverter enabled”.
  • Battery ‘Mode’ switch is set to “on”, meaning “charge” and “discharge” is allowed.
  • Positive values allow the device to charge the battery with the requested power, all is good all is well. power ramping is a bit slow but I can live with that.
  • My problem: Negative values should allow the inverter to kick in and transfer energy from the DC to AC. However, reported power is somehow capped to a few watts, which I suspect to be the self-consumption of the victron. No power is ever delivered back to AC.

Obviously the Multiplus is limiting the inverter power for some reason, but after staring at this problem for way too many hours, I still can not tell why it is doing this - what are the authoritative sources (logs, status) I can look at to debug this issue? I am looking for a status overview or detailed log where the device is telling me “hey, I can not do this because of this and that reason”. Instead all I see from my end is the modbus server that happily accepts my requested power, and the inverter that simply does not start.

2

Right. I’m pretty mad right now - at myself but also at Victron for not representing the rocker switch state in any way in the diagnostics or user interface. Put the switch on ‘I’ to allow inverting and charging, and on ‘II’ for charging only. Very intuitive.

3

The Manual includes both On and I for the switch positions, but did putting it to On/I solve your issue?

4

Yes it was the switch. I was so buried in the ESS manuals, modbus protocol lists and getting acquainted with all the Victron lingo that I apparently failed to pick up fact that the power switch has more then two positions, one of is cripples the functionality of the devices without notifying the user in any way.

5

When I last checked, the status of the inverter in the VRM dash, as well as advanced widgets tend to be quite clear that it is in a different state.
Finger trouble happens, but Victron has done their part that anyone who follows the docs and training won’t get stuck like this.

6

I’d love to know where to look for that, do you happen to know where I can find this in the gui-v1 or gui-v2 overview?

7

You should be able to test this (I can’t at the moment).
Set it to charge only and see what is written in the text box under the inverter on VRM. iirc it should be passthrough or similar.
In advanced, look at the inverter state widget, it should also change.
I can’t recall if the software switch in the device entry in the console will change.