3-phase system: L2 and L3 do not invert when grid is connected (only L1)

[Netrange (Steffen)]

Last idea for today…

Are the current transformers CORRECTLY positioned on the line… Arrows … etc …

[ravo (Radim)]

Dear Steffen,

Nothing has been changed on the CTs — positions and arrows are exactly the same as when the system was working.

Just to be sure, yesterday I tested it by disconnecting the external CTs (so the system measured only the backup/critical-load part), and then I switched back to the external CTs again.
The readings were correct in both cases.

So the CT wiring/position shouldn’t be the reason.

I will update later when I got Mk3 and If I don’t see any “wrong” value in the CT readings or VE.Bus configuration, then my plan is to reconfigure the whole 3-phase system from scratch and set everything up again step by step.

Sometimes a full clean configuration is the only way to rule out hidden inconsistencies in the Assistants or VE.Bus settings.

Thanks again for your time and suggestions.

Radim

[ravo (Radim)]

Dear @Netrange

We have exhausted all options we could think of. Yesterday we completely removed the existing VE.Bus configuration and rebuilt the whole 3-phase system from scratch using Mk3 USB cable. After that, we re-applied all VEConfigure settings and manually added the ESS assistants with the original parameters.

Unfortunately, the behaviour is still exactly the same — nothing has changed. L2 and L3 do not export/invert under ESS control, even though the 3-phase setup and AC measurements are correct.

While checking through the forum, I found two or three other recent threads describing very similar symptoms when the inverter goes into pass-through.

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Multiplus II Low Battery and missing Dynamic Cut-Off page in assistant

Hello, I have a 3 phase ess system with one multiplus II 48/5000 GX and two multiplus II 48/5000, cerbo gx, Pylontech battery. Lately I got a low battery (Multiplus switches to pass-thru) warning on the multiplus but not on the cerbo, SoC is the same as on the cerbo (e.g. 85%). When I cut mains multiplus switches to discharging. When I restart the multiplus everything is working fine again. After some time the issue occurs. Yesterday it did not work, no power, I think it thinks it is completel…

This might indicate that the issue could be related to the latest 3.66 firmware, but I cannot confirm it. At this point, all hardware, wiring and measurements seem correct, and only the ESS logic is refusing to activate discharge on L2/L3. If needed, I can provide full logs (VRM diagnostics, gx-device logs, VE.Bus status, Modbus register snapshots, etc.).

Thank you in advance for any additional suggestions on what else we could try.

[Netrange (Steffen)]

… slipped way down

It’s a shame that the rebuild wasn’t successful. Strangely enough, many people in the forum, including in the German section, have a 3-phase system and it is running.
The only difference could really be the use of CT sensors. Many use an external meter… if it really is due to the firmware in connection with the CT sensors, the only solution would be to downgrade the firmware… You can find the old FW on the Victron Professional website.

[ravo (Radim)]

Dear Steffen,

Yes, I also noticed that most 3-phase installations in the forum run without issues, which is why this case is so unusual. There are, however, a few similar reports — maybe users have not updated to the latest firmware yet, or they simply did not report it. After we rebuilt the entire 3-phase system from scratch, re-applied all VEConfigure settings and manually added the ESS assistants, the behaviour is still exactly the same.

Regarding the CT sensors:
we also repeated the test with internal metering only, but there was no change — L2 and L3 still do not export/invert under ESS. I am also considering testing with an external meter as suggested in the documentation, but it is strange that identical configurations elsewhere work perfectly with CT clamps. This increasingly points to some behavioural change in the recent firmware.

One more thing I would like to add, because it might be relevant:

According to the official Victron documentation:
https://www.victronenergy.com/media/pg/Energy_Storage_System/en/multiphase-regulation—further-information.html

If I understood it correctly, in section 7.2 “Individual phase” it states:

“With ‘Individual phase’ option selected, the (single-phase) ESS uses the battery to balance only L1 to 0 W. L2 and L3 are visible on the CCGX, but not used by the ESS in any way.”

We discussed this internally, but in reality most 3-phase ESS systems on this forum do compensate L2 and L3 down to 0 W even with “Individual phase” enabled — including our other installations.

So the behaviour we are seeing here is inconsistent with both:

• the documentation, and

• other real-world 3-phase systems using CT sensors.

Of course, I also tested switching to 7.3 Three-phase ESS, but the result was the same — still only L1 is inverting. Unfortunately, we cannot use Three-phase ESS permanently because our grid operator bills per phase rather than by total export.

This makes the issue even more confusing, because under the same configuration other sites still export/invert correctly on all three phases — only this installation refuses to discharge on L2/L3.

Tomorrow we plan another full restart and completely wipe the VE.Bus configuration, and I am thinking to also try physically swapping the L1 and L2 inverters to see whether the behaviour follows the phase or the device.

Regards
Radim

[ravo (Radim)]

@Netrange

The only difference could really be the use of CT sensors. Many use an external meter… if it really is due to the firmware in connection with the CT sensors, the only solution would be to downgrade the firmware… You can find the old FW on the Victron Professional website.

I also tried to find older firmware, for example version 502. However, on Victron Professional I can only find the latest 558 release and the older 459. (files 2629558.vff, 2629459.vff). I tested 558 today as well, but the situation still persists.

Small update — I managed to find the 502 firmware in the public archive here:
https://updates.victronenergy.com/feeds/VEBus/firmware-archive/
File 2629502.vff is available.

When I get back home, I will try the downgrade and report the results here.

[Netrange (Steffen)]

Great… thanks for the info… it’s always nice to get feedback. That helps other users too… even if things don’t always work out… that’s part of it.
We all learn from the experiences of others… positive or negative.

I was also referring to the GX when I mentioned the downgrade…

[ravo (Radim)]

Thanks Steffen,

just to summarise our progress so far:

we already fully reset the entire 3-phase VE.Bus system configuration and rebuilt it from scratch, and today we downgraded all inverters to firmware 502. Some time ago we also tried running the Cerbo GX on version 3.51, but the behaviour was exactly the same. At this point I feel we have exhausted every technical possibility of what could be wrong on the configuration side.

I also considered completely wiping the Cerbo GX and installing a fresh Venus OS image, but that would most likely mean losing all history and dashboard data, so I will leave this as a last resort.

As the next step we plan to physically swap the L1 and L2 inverters. If the unit currently on L2 starts working normally when placed in the L1 (master) position, then we can rule out any hardware issue.