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manfred-1 asked

ESS flapping between absorption and discharging

In the ESS System, when there is a stable situation with enogh exceeding energy - Bulk Charging is working well – but as soon as the batteries are sufficiently charged to switch to absorption, the Multiplus is flapping between absorption and inverter (discharge) mode in changing intervals of 10sec to 1 minute and with changing amplitudes up to +/- 10 Amps. I would expect a stable absorption mode with constant voltage and decreasing current for the configured absorption time of 2 hours – but no negative current at all.
I already have posted the problem in german language "ESS springt zwischen Absorption und Discharge alle paar Sekunden" but unfortunately no solution yet and therefore i repost in english language and with extended documentation.
I have done a lot of measurements and tests - see attached documentation also including configuration parameters. 2022 01 14 Absorbtion Problem Doku.pdf

Looking forward to your recommendations - Manfred

Multiplus-IIESSFronius
2022-01-14-absorbtion-problem-doku.pdf (1.5 MiB)
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Alexandra answered ·

@manfred@pumberger.at

Just a thought. It may be your bms dictating to the system what it should be doing, maybe with cell balancing, since that is what is ultimately happening in absorption state. I have seen one or two brands of batteries do this. Just a guess though.

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manfred-1 avatar image manfred-1 commented ·

BMS is not communicating in my configuration It’s only disconnecting the battery in case of wrong voltage. In a test I have bridged the BMS and same problem. Therefore BMS is Not expected as root cause.

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