ESS assistant charges and discharges the battery continuously when there is not enugh PV, why?

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felix-vt asked Nov 8, '20

ESS assistant charges and discharges the battery continuously when there is not enugh PV, why?

I know that my question pretty much describes what the ESS Assistant should do.

But is there a way to prevent continuous charging and discharging?

My AC loads are mutch higher then what my PV is generating, this is why the ESS Assistant draws current from the battery until my desired SOC is reached but then it swiches of the inverter and is slowly charging the battery with PV and after charging 5% above minimum SOC the inverter turns on and quicky emtys the battery down to minimum SOC. Since my AC load is always greater than what I can generate with PV. It would make much more sense to feed the generated energy directly into the grid to help power AC loads. There is no ecess power, so why always charging 5% of the battery and then quickly emtiy the 5% at maximum current.

I would prefer a constant output power when the AC Loads are higher then what i can get from the PV and then only store excess power in the battery.

Thank you for your Help.

ESS SOC Assistants

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felix-vt commented · Nov 09, 2020 at 11:04 AM

i have found a similar topic here in the community but also no solution

https://community.victronenergy.com/questions/9567/ess-mode-cycle-battery.html

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felix-vt commented · Nov 09, 2020 at 11:42 AM

The ESS should stay at constat voltage mode instead swiching to charging when ac loads are higher than what is generated by the PV.

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Modifications Space

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Answer 1 · 2020-11-08T16:16:47Z

layesp answered · Nov 08, 2020 at 04:16 PM

Hello Felix,
you describe the problem very well, it is exactly the same for me. Together with my dealer we have been trying to change this behavior for weeks, but unfortunately without success. I'm very excited about the solution.
Greetings Richard

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Answer 2 · 2020-11-09T11:28:35Z

nickdb answered · Nov 09, 2020 at 11:28 AM

Short answer is no, That is how it works.

The DC bus is providing power and solar being variable, batteries have to buffer these changes.

Personally I think it is far too aggressive to use batteries, or rather too relaxed to use AC power, especially when inverter limits are set and there are bigger swings in power draw.

It does tend to slowly deplete the charge, but that is how it is designed to work.

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felix-vt commented · Nov 09, 2020 at 12:23 PM

The way it is designed is to cut all feed in from dc to ac, then charge the battery 5% over minimum SOC then power the loads till battery is empty again? For me a verry inefficient way to handle solar Power. And petty much the definition of an oscilating control loop.

when I swich to "keep batterys charged" it does exacly what I want. The battery is still uesd to buffer Power swings from PV. To stop the inverter to charge the battery wehn there is no ecess Power or not even enugh Power to Power the AC Loads makes no sense to me.

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nickdb ♦♦ felix-vt commented · Nov 10, 2020 at 05:32 AM

If you hit the minimum SOC limit it will revert to grid power. If your 2 SOC limits in ESS are quite close together, it will dedicate all PV (when it is generated) to charging the batteries until it gets near the stop on SOC schedule limit at which point PV is used to power loads again.

If there is a large gap between your ESS SOC limits, then it will also use grid to charge batteries so you can quickly get back to an acceptable limit.

Using batteries to buffer large loads isn't an issue in itself.

If you are trying to avoid using grid this is probably a good thing, if you are also wanting backup power then it isn't.

When PV become limited (or none) then the SOC will slowly leak.

It isn't a lot but you can lose a few percent, which is annoying when you want to preserve charge and there is grid available.

All in all it works, though it could be tuned to be more efficient, or to allow some user tuning to lean power usage towards grid without having to use "keep batteries charged",

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Answer 3 · 2020-11-13T16:18:02Z

felix-vt answered · Nov 13, 2020 at 04:18 PM

As nickdb in his comment says it is working and its doing its job, that is absolutely true but I want perfection, so i decided this to my new hobby project.

ESS Mode 2 is a good starting point for that. it gives you mutch more control over the system, without programming a new control loop from scratch.

I already use my Raspberry Pi to do some visualtsations via Grafana and sending data via modbus tcp is easy, so I started to do some experiments with node-red and looked how my system behaves.

I think im on a good way to tune my system.

I was also able to acesss my CerboGx device via SSH and run some Python scripts on the device witch is really cool. Maybe someday I will run some extra code on my CerboGX to tune the system.

But first I will do some more testing with node-red.

Regards Felix

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Answer 4 · 2020-11-13T18:05:42Z

layesp answered · Nov 13, 2020 at 06:05 PM

Hello Felix,
First of all I would like to apologize for the bad English, because I use Google Translate, so please don't be surprised.
My loading and unloading behavior is better now:
A new menu item was added at the last UP date, DC coupled mains supply in excess.
I have set this setting to "ON".
In addition, I activated the "only load" setting directly on the MPPT.
The system has been working much better for 2 days. However, I would also prefer the entire PV power to flow directly into my network.
greetings
LayesP

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felix-vt commented · Nov 13, 2020 at 07:52 PM

Ich kann auch nur auf mein Schulenglisch zurückgreifen:-).

Die Funktion kenn ich, prinzipiell macht sie auch das was ich gern hätte, lässt sich auch über modbus ansteuern, aber ich strebe hier dann doch ein etwas ausgefeilteres Konzept an. Die Steuerung ist drauf ausgelegt ihre sollwerte schnell und so gut wie möglich einzuhalten, was zu aller erst der Netzsollwert ist, darauf baut alles andere auf. Für meine Eigennutzung ist mir der Netzsollwert aber eigentlich egal, mir ist ein sinvoll gewählter Ladezustand und das vermeiden unnötiger Ladezüklen wichtiger, das stößt aber auf gegenwehr des ESS Assistenten, wenn ich dem mit Bordmitteln erklären will seinen Hauptregeparameter zu Ignoriern, deshalb kann ich an der Stelle fast nicht anders als meine eigene Regelung zu Programmiern, bisher versuche ich das zu vermeiden und greife nur teilweise in die Steuerung ein. Beispiel: Den Netzsollwert, den man im ESS Assistenen einstellen kann, kann man auch extern beschreiben, ich hab den jetzt automatisiert und immer den aktuellen der PV-Leistung vom aktuellen Verbrauch abgezochen (hab ein externen Netzzähler), total wierd den Wert im Display wild rumspringen zu sehn, aber der Effekt war, dass der Inverter ohne den Ladezustand zu verändern, einfach genau die erzeugte Energie ins netz gespeist hat. Ohne dieses ständige umschalten zwischen mal laden dann wieder von der Batterie usw.

Wenn die Leistung der PV den Verbrauch übersteigt, bin ich mir sicher würde die Sache anders aussehn, das ist bei mir jetzt ein sehr spezieller Fall, aber ich hab die Anlage auch erst seit Donnerstag letzte Woche.

Außerdem lässt mir das jetzt eh keine Ruhe mer bis es Perfekt ist.

Wenn ich was hab, werd ich es hier unter dem Thema posten

Gruß Felix

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Answer 5 · 2020-11-14T17:25:04Z

layesp answered · Nov 14, 2020 at 05:25 PM

Hallo Felix,

so ist es deulich besser, ich hab meine Anlage schon seit anfang Oktober und bin auch unzufrieden mit dem Lade und Entladeverhalten.In der BA steht das der Regelsollwert das Netz vorgibt, mir wäre allerdings lieber das der Sollwert von der zur verfügung-stehenden PV Leistung abhängig ist.Alles was die PV hergibt zum Netz ( bis zur 0-Einspeisung) dann erst Batterie laden.

Die Batterien sind mir eigentlich zu teuer und verbrauchte Batterien zu Entsorgen widerspricht dem Umweltgedanken, jeder Zyklus kostet im Prinzip Geld. Das möchte ich verhindern, eigentlich sollen die Batterien bei mir nur als Puffer dienen ( im Prinzip Kondensatoren ) für mich macht es keinen Sinn die Energie zuerst in die Batterie zu schieben um sie dann kurze Zeit später wieder aus der Batterie abzusaugen.

Problem 2 ist der hohe Entladestrom wenn das Netzt Energiehunger hat, leider kann ich den Entladestrom nicht begrenzen/reduzieren, hierzu finde ich auch keine Lösung.

Deshalb bin ich sehr gespannt auf deinen Lösungsansatz.

Grüße aus der Pfalz

Richard

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ESS assistant charges and discharges the battery continuously when there is not enugh PV, why?

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ESS assistant charges and discharges the battery continuously when there is not enugh PV, why?

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