question

Did you configured the PV-inverter assistent?

I did, but since it did not change the beavior I removed it again.

Hello Sebastian, @Sebastian Jaksch

Without knowing more details about your installation, it is difficult to narrow down such a problem.
In any case, for safety reasons alone, I would have the PV inverters curtailed when 100% SOC is reached. As far as I know, this only works when using the PV assistant.

Based on my experience, I have a similar setup as you, but with a Pylontech US2000, I know before a Pylontech battery reaches 100% SOC at 53.2V that the internal BMS reduces the current drawn and at 100% SOC the the battery even switches from "charging" to "idle" and back for balancing. From that point of view, I have now guessed that the problem you describe can only occur if either the Pylontech batteries are very different in each individual SOC level and/or the battery is from a specific Pylontech battery - the Cells within this battery are not sufficiently balanced in relation to one another.

If the system has not been in operation for long and the three batteries had and have very different SOC levels at the beginning, it will take some time for the three batterie units to balance each other out. As an example, if I add an additional Pylontech battery to a existing stack, I first pre-charge the battery externally with a battery charger to 100% SOC, wait until the existing stack also has 100% SOC through PV and then add the additional battery to the existing battery pack.

First I would monitor and log the batteries with the Batteryview software and a suitable USB-Pylontech communication cable.

In any case, you can first determine whether the three batteries match each other in terms of SOC level or whether they are far apart. If the three pieces in the SOC are very different, I would first align all three with each other.

You can then also determine whether it is always the identical battery pack that causes the HV alarm and track whether, for example, only a specific cell within the pack is affected.

In the latter case, I would contact the seller of the Pylontech battery.

Servus - DayAndNight

Possibly your 10Kw SMA inverter is too powerfull for the 3 phase Multiplus system in an island setup. Look up AC-coupling and the 1.0 rule.

https://www.victronenergy.com/live/ac_coupling:start

paragraph 2.2. :

• When batteries are (nearly) full, the battery voltage will spike, possibly causing the Multi to switch off in DC over-voltage alarm.

You can avoid this issue, if you have the possibility, if you convert the system to a grid coupled ESS and use the SMA on the AC-in side?

Also worth checking is if the battery bank is large enough for the system, see if 2 modules is maybe on the limit. (I did not check the US5000 values, so i might be wrong here)