question

Paul B avatar image
Paul B asked

Lithium Battery overcharge of Battery Bank /Cells using ess

Hi all, I have come across a Issue in one of my customers system.

its a Quattro 24/5000 setup with ess and AC connect PV with a pv outpuut of 5000

Quattro on 508 fw

Cerbo on 3.22

BMS is 123 smart123

latest ess assistant installed

schedule charge set to 100%


Battery at 100%

Solar is exporting 4.57 KW

load is 780 watts'Grid Tie pv is producing 4.8kw

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1710918509952.png


NOW the issue

The battery voltage at times just keeps rising above its set absorption voltage setting of 28v and its BMS setting of 3.5 per cell -

However if I reduce the schedule charge level to 95% then the battery voltage drops back to its correct voltage also when the schedule charge goes inactive it also drops back


Notes

Cerbo is using GUIMods

Of course if you drop the SOC limit to 95% the issue also stops



ESS
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1 Answer
nickdb avatar image
nickdb answered ·

The limit very much works in that way, with a sub-limit for grid-exporting in the ESS feed-in menu.

I can recreate it myself, though it seems to behave for me.

Your system is custom/modified, so that may be contributing and I am not sure what help you may find.

Mine is very much on the supported list and not using AC PV, which can also contribute.

Ideally this would need to be reproduced in a tested config.

Hope you get to the bottom of it.


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Paul B avatar image Paul B commented ·
Hi Nick, I have updated the post somewhat , as I have isolated the issue to be with scheduled charge in the ESS and setting it to SOC 100, i fixed the issue by reducing the SOC back to 95% under scheduled charge (when its active that is)


anyway it should not happen at 100% as well


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matt1309 avatar image matt1309 Paul B commented ·
Does the behaviour occur when AC PV is disconnected as well? ie scheduled charging 100% but no PV coming in?


If it doesn't then suppose that proves Nick is right and it's the fact the AC PV is coming in elevating the voltage ever so slightly.


How high above absorption does it go? Is it just the 0.16v in the above picture? So 3.52v per cell?

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nickdb avatar image nickdb ♦♦ Paul B commented ·

Have you tried to slightly lower the CVL in DVCC instead of changing the schedule. It is more likely that the battery voltage really ramps in that top few percent, and will be prone to overvoltage, so I suspect that is just a symptom, not the cause.

Feeding in, iirc, like keep batteries charged, will push the voltage up a bit regardless.

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