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Joop Weenk avatar image
Joop Weenk asked

Dynamic ESS slow discharge

Hello,

I have setup A Dynamic ESS system with 3 MultiPlus (3-phase). It seems to work alright except that during the periode between the end of the charge period and the start of the discharge periode the system is slowly discharging the battery.

It stopped around 06:00. Until now the battery is discharged till 93% (time now is 15:51)

slow-discharge.png

I can see that the target SOC is going down in the settings. Is this a know problem or a different setting somewhere? I use the standard D-ESS implementation.

Best regards,
Joop

dynamic ess
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3 Answers
dirk-s avatar image
dirk-s answered ·

What’s the size of the battery?

Could it be the self discharging of the batteries? During DESS idle the standby losses will be taken from the batteries . You have 3 MP with around 60W standby losses. In case your battery is small it could be the reason.

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Joop Weenk avatar image Joop Weenk commented ·
My battery is 20kW and the current is 2-way, in and out the battery.
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Dirk-Jan Faber (Victron Energy) avatar image
Dirk-Jan Faber (Victron Energy) answered ·

I took a look at the logging of your site and can only conclude that it works as intended, with the scheduled target SOC slowly going down from 99% to 92% and the battery following that plan.

It does raise the question though why the system planned to do so, instead of just keeping the battery charged until the prices where highest. My theory is that it has to do with the forecasted consumption mismatching the actual usage. But I am not 100% sure about that.


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Joop Weenk avatar image Joop Weenk commented ·
I think that the system is indeed following the target SOC. So the question remains why it is lowering the SOC while there is no need to?

Another question remains why the battery is charging and discharging all the time when the SOC is slowly going down. Is there an answer to that question?

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Joop Weenk avatar image
Joop Weenk answered ·

soc.png

This is today SOC


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