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