question

max-payne avatar image
max-payne asked

Undocumented 90% SOC behaviour


As seen below the charging power of the ESS drops at exactly 90% SOC to 1/3 of its nominal power. This is documented nowhere and I would like to continue 3KW charging at least to 5% more.

I checked VEConfigure as well as all the settings inside the Cerbo for the Multiplus.

1692191245287.png

My first guess was that 90% incidentally 51.5V and that the limit for absorption. That is not the case. The switch from absortion to float seems to be entirely unrelated to this 90% limit. The pylontech battery also supports more charge (big ESS bank of 6x US 5000). The charge current limit is also 60Amps under device limits of the pylontech bank.
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1692191599567.png

So my question is where does this 90% charge power limit come from and how can I change it?

(The limit neither comes from VE Configure Charge curve, nor pylontech charge current limit)





Multiplus-IIESSess settings
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3 Answers
evhaandel avatar image
evhaandel answered ·

The charging behaviour of my installation looks different.

  • 3 phase Victron multiplus 48/3000
  • 16 kWh Pylontech

View on 2 days

1692257619583.png


Zoom in on 90%

1692257969454.png


1692257619583.png (103.9 KiB)
1692257969454.png (81.1 KiB)
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max-payne avatar image max-payne commented ·

Thats insightful. This is solved now. My pylontech requests 20A charge current starting at 90% due to internal balancing. Seems like one of the pylontechs needs more time to balance than the others and slows down charing of the whole pack for around 1hr and resumes afterwards to 100%.


I could leave as is (probably).
If I wanted I could run the pylontech pack blind via a victron smart shunt and just rely on the multiplus charging algorithm to get the last 10% also. Since there is a cell issue I dont think this is recommended - so I will just live with it.

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nickdb avatar image
nickdb answered ·

What was battery voltage at the time? You have deviated from the recommended settings and shaved 0.5V off the charger settings.

Is there an indication of battery/ambient temp at that time?

Check if any packs are marked as blocking charge (GX - battery BMS details tab)

If charging is dropping it is either because that is all the battery pack wants, despite of CCL, derating or some other configuration.


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max-payne avatar image max-payne commented ·

Battery was at 50.75V

GX Battery Blocking: 0/0

This is behaviour I would expect at exactly 51.5V and not earlier. Seems to me a pylontech + Multiplus setup goes into float mode no matter what at 90% SOC.

Here is my data for a typlical day:
0-90% fast, then float mode.
1692196693779.png

This is documented nowhere and where can I change this. Maybe someone with a bigger ESS System can verify?

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1692196693779.png (49.7 KiB)
Alexandra avatar image Alexandra ♦ max-payne commented ·

90% is where Pylontec starts to balance its cells, usually that is where it tells the system to slow its roll.

Check CCL and DCL widget

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kevgermany avatar image kevgermany ♦♦ Alexandra ♦ commented ·
@Max Payne

To add, the charge current in your system is dictated by the BMSs in your Pylontechs. You cannot change it.

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max-payne avatar image max-payne kevgermany ♦♦ commented ·
Thats the answer! One of the Pylontechs inside the pack needs to balance more than the others at 90% and slows the pack down.
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nickdb avatar image nickdb ♦♦ max-payne commented ·

Start by using the exact victron settings that are documented. As stated, you have deviated from this.

Then use a meter to check you don’t have any voltage loss from one end to the other.

This isn’t a feature, it is unique to your installation, so use a standard configuration as documented and thoroughly check the wiring.

It is also noted here:

https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom

The battery won't charge to 100%

Also see the question above. The state of charge of the battery is estimated based on the overall voltage and on how well balanced the internal cells are. Because we cap the battery voltage at 52.4V, the state of charge will sometimes rise very slowly once it reaches the mid-90s. This is normal and usually resolves over time.

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Dean Perry avatar image
Dean Perry answered ·

@Max Payne see comments about Pylons controlling the charging (but I think you understand that).

Double-check that the reported DC bus voltages of everything (MP-II, MPPT, Pylons) involved are agreeing (+/- usual small cabling losses) and that they also agree with a multimeter. That can indicate other, non-ESS issues.

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