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jacola asked

ESS stuck and blocking PV inverters with frequency shift

I had my system (6x Multiplus 5000, 26x Pylontech US2000B/C) working well for some time. Venus with version 2.73, i control the system via modbus to go on/off grid as needed (to have frequency shift and avoid feed-in i go off grid normally during the day). Yesterday i updated the 'US2000C' Master batteries to the latest firmware version as i had some battery alarms before.

Now as of today, i noticed that first batteries got fully charged, freqency shift regulated down the inverters (several SMA plus some micro inverters). But then .. as i used some energy, the frequency shift got 'stuck' at 52.7Hz and the battery started to discharge, despite full sunshine and much more solar power available then needed.
I switched to on-grid (which means the frequency shift must stop) and 'charge' mode briefly, and that seems to hae 'unstuck' the system. Battery then charged up correctly and all is good now.

I have updated the software of the venus now to 2.84, but the weird taste stays - why would ESS get stuck, stop the panel production and not charge batteries ?

I have a can sniffer running on the pylontech connection and log all data to a victoriametrics/grafana instance. The pylontech bms protocol does not report anything unusual.

Venus reports a max charge voltage of 53.2V, BUT when reaching full it overshoots and reports 53.4V ..

ESS output voltage (all loads and inverters are here) is stable 230V +/-2V on all phases.

Any idea what could trigger that lock-down ?

Johannes


ESSfrequency
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shaneyake avatar image shaneyake commented ·
Can you post the VRM data for the BMS Charge and Discharge Limits? It is under battery Monitor on the advanced page.
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shaneyake avatar image
shaneyake answered ·

I don't think this is normal behavior.

It looks like the 53hz lockup problem.

https://www.victronenergy.com/live/assistants:pv-inverter-support#q1_the_system_is_locked_to_53_hz_and_does_not_resume

You might need to reconfigure your inverter.
What is the current inverter charger settings?

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jacola avatar image jacola commented ·
i will have to connect the configuration software to check the inverter charger settings. i think you are right with your assumption.

For now, this will be easy - i can quickly connect to the grid and then go off-grid again to reset this, according to the victron docs - and i do control many aspects via modbus/tcp anyways (including on/off grid) so that will be, for now, the quick fix.

Cheers

Johannes


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Phil Gavin avatar image
Phil Gavin answered ·

This is intended behaviour, it's in the Victron documentation. Essentially, it boils down to your battery voltage having to drop down a bit to indicate the batteries have discharged and it will reset again.

This provides a level of hysteresis. (But can be annoying in certain circumstances).

LA and Lithiums have different voltage turn-on thresholds. If memory serves Lithiums have to drop 0.7V and LA's are float voltage setting dependent.

But it is all described on the Victron site.


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jacola avatar image jacola commented ·
Hmm really ?

The voltage

it dropped to below 50V .. So from 53.2 to 50 is more than 3 Volts .., that is the usual level .. you can see that in the graphic. What reason would be there to not charge it if it is 50V and reported 95% ?


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