Cannot build ESS - setpoint is ignored

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question

xzv asked Dec 24, '23

Cannot build ESS - setpoint is ignored

My setup: I have a Multiplus 48/800/9 and a Cerbo GX, combined with a LiFePo4 Pylontech BMS (connected via CAN). I also own a MK3 for using the VE Config tool.

My goal is to build an ESS whose logic is programmed in Node-RED. An external device supplies all the measured values of the house. The setpoint is calculated from this and then set in Node-RED.

My problem: after I was initially able to discharge the battery from 50 % to approx. 15 %, I can no longer get the inverter to apply the setpoint.

The battery is often charged (very slowly), but the setpoint is ignored, regardless of whether charging or discharging. When I manually set the switch to "Inverter only" the green light goes on but no discharging happens. The batteries and the inverter have no alarm or warning and the allowed (dis)charging current of the battery pack is high enough to allow any operation.

I have tried pretty much every setting in the Remote Console and in VE Connect, but nothing has helped. I suspect that I have not understood something somewhere or that a setting is blocking the desired operation.

Here are a few screenshots. I think I have tried out almost all variants and settings but nothing helped so far.

Can someone please guide me what else I could try?

cerbo gx ESS Venus OS Pylontech

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Answer 1 · 2023-12-24T16:41:36Z

Alexandra answered · Dec 24, 2023 at 04:41 PM

@XZv

Start by programming according to the official guide.

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

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Answer 2 · 2023-12-25T08:02:17Z

xzv answered · Dec 25, 2023 at 08:02 AM

Thanks for your hint. I carefully read the guide for Pylontech and set all settings accordingly.

One thing I forgot to mention is: It's a 16 cell battery (not 15) with a Pylontech BMS, with 51.2 Volts of nominal voltage.

I scaled all voltage levels suggested in the guide accordingly by multiplying them by (16/15).

Unfortunately again, this is what happened: Starting at 16 % SoC, I set a setpoint of -600 Watts and the system started a discharge accordingly. After about 10 minutes and reaching a SoC of 14 % the inverting stopped and an immediate kind of a forced charging with ~500 Watts started that I could not stop. Now it's stuck at 18 % and any setpoint I give (charging/discharing) is ignored.

I don't understand what's going on, especially I don't understand why the system behaves initially like I expect it to work until it goes into that kind of forced mode that I cannot exit in either direction.

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Alexandra ♦ commented · Dec 25, 2023 at 09:21 AM

Does it feedback when you set feedback from DC from the actual ess feed -in menu? Instead of jimnying it with the grid set point? That is how it is designed to work. Keep battery life off.

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xzv Alexandra ♦ commented · Dec 25, 2023 at 09:49 AM

You mean changing the "AC-coupled PV" and "DC-coupled PV" setting? I tried all combinations, it didn't change the result.
In my setup, I don't have a PV connected on the Victron's DC or AC output side.

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Answer 3 · 2023-12-25T08:09:14Z

Alex Pescaru answered · Dec 25, 2023 at 08:09 AM

From what I am remembering, the Victron team modified / overridden some values given by the Pylontech BMS in order to prolong the battery life.

A Pylontech battery comes, generally, with a 15 cell layout and when you apply something for a 15 cell to a 16 cell... who knows...

Maybe it's something conflicting there... What it is, what they believe, etc... And the worlds are colliding... :-))

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Alexandra ♦ commented · Dec 26, 2023 at 07:28 AM

This was done in Venus OS ver 3.0.

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Alex Pescaru Alexandra ♦ commented · Dec 26, 2023 at 07:37 AM

I saw that later... Sorry.

Didn't got the chance to read all release notes... Yet. :-)))

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Answer 4 · 2023-12-25T09:51:24Z

xzv answered · Dec 25, 2023 at 09:51 AM

@Alex Pescaru I also read this but it was said that with GX firmware v3 it would work correctly also with 16-cell batteries. But I have no clue if or where I have to tell the GX that it's a 16 cell battery.

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Alexandra ♦ commented · Dec 25, 2023 at 01:15 PM

The GX should read whatever the battery is telling it. Make sure the firmware is up to date.

Under the battery in the devices menu you can see what information has been shared there. Including cell number and capacity.

And whether the batty is allowing the charge and discharge.

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Answer 5 · 2023-12-25T16:15:34Z

gerd-weiss answered · Dec 25, 2023 at 04:15 PM

Hello,

Check Battery>Parameter. There you find the limits the GX gets from the Battery dynamically, the maximum Voltage and Current the battery allows for the moment.

Regards,

Gerd

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xzv commented · Dec 25, 2023 at 05:39 PM

It's always 55.0 V (CVL), 50.0 A (CCL) and 50.0 A (DCL). So the BMS is always open to charge and discharge.

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gerd-weiss xzv commented · Dec 25, 2023 at 08:09 PM

Maybe you check the Advanced Page, Espresso. the System state widget and all the Battery Widgets. It might give you a hint in which state the ESS thinks it is - and the history.

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Alexandra ♦ gerd-weiss commented · Dec 26, 2023 at 07:29 AM

@XZv

A 0A DCL means the battery is not allowing discharge.

55v CCL means the absorption in the system is a little high for the battery. What does the manual say for these batteries?

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Alex Pescaru Alexandra ♦ commented · Dec 26, 2023 at 07:42 AM

He said dd.0 A. Maybe a typo or maybe, if it's real, some bug in sending or getting that value.

55v for a 16 pack means 3.43v per cell. On 15 pack is 3.54 (limited by Victron at 3.49) . So better anyway in the case of 16 pack.

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xzv Alex Pescaru commented · Dec 26, 2023 at 08:00 AM

Sorry, it was a typo. It's always 50 Amps in both directions, no limitations any time.

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Answer 6 · 2023-12-26T08:29:55Z

jeanmarie answered · Dec 26, 2023 at 08:29 AM

Hi

so far I remember, there is a limit at 52,4V for pylontech due to the 15S structure.

obviously you have reprogrammed the BMS as it is showing 55V but what if some setting (internal to Victron) force the voltage as your battery is well recognized as a Pylontech.

Have you try to force the CVL from the DVCC menu to any voltage like 55 or 56 like it should be for a 16S structure (for respectively 3.43V and 3.5V per cell)?

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Answer 7 · 2023-12-26T09:08:23Z

ejrossouw answered · Dec 26, 2023 at 09:08 AM

Not sure why you want to "reinvent" ESS. Maybe first get it working as Victron intended and then introduce the additional functions in node red. You state "An external device supplies all the measured values of the house." however, your grid metering is set to inverter/charger. Do you have loads on the ACOUT?

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xzv commented · Dec 26, 2023 at 10:35 PM

I also tried changing that setting to "external", but it didn't help to break through the 14 % SoC lower barrier with forced recharge.

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Answer 8 · 2023-12-26T09:43:02Z

thanar answered · Dec 26, 2023 at 09:43 AM

I would try with the BMS disconnected from the GX, just to make sure it's not some kind of BMS incompatibility.

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