Large 1000Watt fluctuations when charging my Victron / Pylontech system

[MarcKeulers]

Dear all, appreciate some help with large fluctuations in power readings in my grid meter when loading my Pylontech batteries.

My current system setup:

3 phase grid tied with 3 Multiplus 5000/48 inverters (one each phase)

Energy Meter VM-3P75CT between grid and three Multiplusses.

All loads on the AC-Out

SolarEdge 10kW inverter on the AC-Out, integrated through modbus (working)

6 Pylontech US5000 batteries (27.6 kWh in total)

All batteries connected individually to 3 Lynx Distributors (3 x 2) and each Lynx distributor connected to one Multiplus 5000/48 (Parallel operations with two batteries per Lynx per inverter)

Cerbo GX to control the system.

Settings inside the GX

ESS with no battery life chosen

In case of negative grid prices, the SolarEdge is limited

Gridsetpoint at -280 Watt (or -480 in case of night).

No alarms on the batteries, health status 99% system up for ¾ of a year in 3 phase mode.

Behaviour noted.

In case of battery full or low discharge power, the power reading on the Energy meter are smooth and do not fluctuate that much ( a few 10’s of watts maximum).

I discharge the battery for about 10 kWh every evening (19:30-22:30) with at grid setpoint of ~-3000 Watt for 3 hours. Then the settings is returned to -480 Watt Gridsetpoint.

Depending on the SoC at 19:30 the SoC at 08:00 in the morning is ~40 % and normally charging commences.

If i charge rapidly (charge current not limited) with solar energy (if available) there are fluctuations visible on the grid power setpoint but within limits, they are larger than the ones when fully charged.

If i charge slowly (allowing some solar energy to flow back to the grid and charge current around 3000 Watt) and charge later on rapidly i start to see large fluctuations on the grid power from -1000 to +1000.

What i notice is that the higher the charge current the larger the fluctuations and the longer i charge the larger and longer the fluctuations

When the battery is full the fluctuations reduce and after a while they go the minor ones noted at the beginning.

What i have tried to do so far with no result:

• If i do not discharge the 10kWh in the evening the batteries are at 70% in the morning and the fluctuations are within limits when chargng the batteries.

• Make sure the batteries are charged for 100% for a 4 hours they day before

• Check the Voltage of my batteries, they are between 3.371 and 3.376 (5 mV)

• Use a different Grid Setpoint (+100 Watt)

• Limit the max current to the batteries (5000 Watt)

Any suggestions on what i can do next or pointers to where the system needs a check ?

[alexpescaru]

Did you noticed those fluctuation when the SOC is about 95-100%?
Or they are all the time from 40% to 100%?

[DirkW]

Did I understand that correctly?

Each Multiplus is connected directly to two Pylontech batteries without being connected to the other two systems?

[MarcKeulers]

Daar Alex, thanks for the clarifying question. I notice these during the whole range from 15 to 100 SoC.

[MarcKeulers]

Dirk, no sorry I did not explain that correctly. I have three interconnected lynx distributors to which each one inverter and two pylontech accu’s are connected. The current can flow from one to the other lynx distributors. Sorry for my bad explaination …

[Netrange (Steffen)]

Why not have a look at your VRM log… or create a widget for your battery readings… and check the CCL or CVL values… perhaps these are fluctuating significantly and your system has to feed the surplus back into the grid… so it’s going back and forth…
You could post the screenshot… It might be coming from the BMS of the Pylontech

[MarcKeulers]

Thanks for the pointer Steffen, widgets are indeed meaningfull. Here is the requested one.

[Netrange (Steffen)]

It looks perfect … what sort of loads do you have running that might be causing this change …

[MarcKeulers]

The loads are a fridge, frezer and me or my wife cooking but even without the cooking these fluctuations occurr … Seems not related. I have once disconnected as much as possible and the fluctuations where still there … thanks for that pointer, forgot to mention! The basic loads are around 300 watt, a lot less then the 1000 watt swings …

[DuivertNL (Marc)]

Are your current clamps from the victron energy meter tight enough?

Possibly tighten them with a tyrap, seen this happen before with not tight enough or loose current clamps

[MarcKeulers]

Hi Marc, thanks for that pointer and honestly I have no clue! Will check tomorrow as of now I have just finished dinner with drinks, not a good combination with electricity …. Better safe then sorry …

[MarcKeulers]

Hi Marc, I have tighten the three ct-clamps with tyraps, white ones so visible in the picture. I will observe the fluctuations and report back. I did one check with disabling the grid meter and use the internal multiplus II meters, the fluctuations still occurred, that was in May. Picture is a bit messy with all the wiring.. sorry! I had the feeling that the ct-clamps were tightened correctly, but that is a hunch, feeling nothing scientifically…

[MarcKeulers]

Hi Marc, even with the tightened ct-clamps the fluctuations occurr, unfortunately. Thanks for your pointer!

Today made a recording, the voltages are quite stable but the current are also changing … through not as fast as the power … video’s 10 seconds.

[Philippoo]

voltage is stable, current is stable (more or less), power factor is stable, but the power is changing like hell - there must be something wrong with you energy meter?!?

[dognose]

@Philippoo

current is stable (more or less)

But currents are flipping their sign quite frequently.

Do you have any loads connected on acin, between the multis and the meter?

Either case, would be interesting to see what the inverters AC-IN values do, when this happens. Are they showing the same behaviour, or are they “stable”?

[MarcKeulers]

Hi dognose, thanks for your pointer, one question, how do i measure the AC in, is that per fase or per multiplus unit (last I have no clue how) ?

For your reference we have decoupled the grid meter, the fluctuations remained, so i trust they will be on ac in phase 1,2 and 3. I will measure tomorrow and show.

I decharge the batteries with 3000 watt for 3 hours every night, the fluctuations are bigger compared to my preset of -480 watt. I will decharge the next two nights with 5000 watt for two hours and 10.000 watt for one hour and show the graphs.

on your question on loads on the ac in, no there are no loads as far as I know … just my Victron meter and the energy company smartmeter that everyone has in the Netherlands …

I am starting to believe somethings wrong with one of the Victron multiplus units ( or with more) …

[Philippoo]

@MarcKeulers

how do i measure the AC in, is that per fase or per multiplus unit (last I have no clue how) ?

you may at least take a look using the d-bus spy. Certainly you only see what the Multis measure, if there is a failure in measurement, it will not be too helpfully. But I think not all 3 Multis will be faulty…

Connect to your GX device, open a ssh session:
ssh root@192.168.1.123 [enter]

(use the right IP address). Then enter your root password [enter]. Then type
dbus-spy [enter]

go to the line showing you (first) MultiPlus / vebus using the arrow keys and hit [enter] (probably the vebus in your system is not connected via USB, just look for MultiPlus and vebus)

you should see the d-bus live values of all 3 phases (I have only one Multi) and also the sum.

Recording the values to get grafix is not that easy. I’m not familiar with VRM, perhaps there is a way. I think on MQTT the values do not get updated that frequently

[dognose]

Yes, VRM logs all this values as well - but the best resolution you can get is a 1 minute log interval in VRM settings. That may be to slow if the peaks are “faster” than that.

For a momentary view, you also can view it in the UI, by clicking on the Inverter/Charger Box:

[nickdb (Nick)]

Victron also have a grafana build:

GitHub - victronenergy/venus-grafana: Default Grafana dashboards, for docker solution...

[Craigy]

Do you know anything about the grid supply resistance to your street transformer? This includes your own grid components and wiring, breakers, and the street wiring up to the transformer itself.

If it is high resistance, grid feeding (sell) will raise the grid voltage, and grid loading (buy) will lower the voltage. A good connection will barely change in voltage as the current (negative or positive) rises.

The theory here is that the SolarEdge and/or the Victron inverter is starting to pump power, the voltage changes, it changes mode to prevent the excessive change.

It is just a theory.