ESS with Pylontech feeding in from battery when disabled

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Graham Walmsley asked Dec 31, '23

ESS with Pylontech feeding in from battery when disabled

Hi,

I have a strange issue with feeding to the grid when disabled.

Multiplus-ii 230v 8000va on 481 with internal grid monitor
3 x MPPT 250/85 on 3.13
Cerbo GX on 3.12 (also tried 3.13)
12 x Pylontech US3000C (6 x 2 in parallel)
3 Lynx Distributor

I have configured ESS with BatteryLife (self-consumption) and a grid set point of the default 50w. Grid feed-in is disabled for both AC and DC PV. Setup is as per the ESS and Victron with Pylontech manuals

The system has been running for a few weeks and the Active SoC has been slowly climbing due to low PV and reached 80% a few days ago.

On a previous sunny day the MP2 swapped to using the battery rather than the grid (maintaining around the set point) until it dropped back to the Active SoC and started supplying all the loads from the grid again.

Today we had a good morning on the solar (over 2.5Kw at some points) before it clouded over and PV dropped to around 100w. SoC got to 84% and loads started to be supported off the batteries rather then grid the same as it did 5 days ago… but this time the AC in was varying wildly and on occasions feeding back to the grid. Also the AC out loads were reporting as higher than they actually are.

When I physically disconnect the grid the AC load returns to what is expected, but when I turn the grid back on the AC loads go up again for no visible reason.

Grid Off

Grid On (same AC load)

Even though the AC load is varying by only a few watts +-10) the Grid In number is changing wildly from -60 to +150 and settling on a negative ’feed in’ number for seconds at a time.

The only recent changes was adding the third MPPT and the Active SoC reaching 80% (now dropped to 75% due to good solar this morning and this seems to line up with when the issue started)

Things I have tried:

Disconnecting the new MPPT from the GX as this was the last change
Total power down and up including battery modules
With the MP2 powered down, putting a 3.5mm Jack in and out of the external current sensor port.

None of the above has made any difference. It feels like the AC current out isn’t working correctly and the inverter is over producing and then over correcting, but it is working fine when the grid is disconnected.

Any suggestions gratefully received.

Thanks

Graham

AC in for the last week

Multiplus-II ESS Pylontech feed-in limit

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Alexandra answered · Dec 31, 2023 at 06:25 PM

Update your MP2. I see everything else is up to date.

That is the first step in troubleshooting and also a step when adding to the system.

On a side note wattage going up or down can also be related to voltage. When connected to grid you are receiving 247v and inverting it will be 230v. With loads such as heaters/elements and loads like that, it does affect wattage.

Also check your ac wiring torque and connections. And neutral in the DB board, sometimes that can also be the cause of instability.

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Graham Walmsley commented · Dec 31, 2023 at 07:14 PM

Thanks for the reply. All the Torque and wiring checks out, both in the board and on the MP2.

I will look at running VictronConnect tomorrow and doing a firmware update.

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Graham Walmsley commented · Jan 01 at 02:14 PM

Firmware on the MP2 upgraded to 508 and all settings restored. Batteries need to get back over the active SoC to see if it has made any difference.

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Graham Walmsley commented · Jan 06 at 03:10 PM

This did the trick. After the MP2 firmware update it has been through multiple cycles of charge and discharge and the MP2 is now behaving as expected and maintaining the set point as expected.

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Alexandra ♦ Graham Walmsley commented · Jan 06 at 03:50 PM

Neat.

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Answer 1 · 2024-01-02T10:23:55Z

Alex Pescaru answered · Jan 02 at 10:23 AM

Use Remote console to monitor instant values, as the VRM dashboard is very inaccurate at instant values and updates only at 1 minute at best.

On the other hand, Remote Console values change at each second with the real values.

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Graham Walmsley commented · Jan 02 at 10:35 AM

Thanks for your reply. I did exactly that once I saw the "To Grid" number going to 0.1Kwh (it shouldn't have been exporting at all) and that is where I saw the Grid numbers bouncing around wildly and going negative for prolonged periods. I used the VRM data in my post because they were easy to screenshot and show the sudden difference in behaviour.

I have followed Alexandra's suggested and done the firmware upgrade on the MP2 from 481 to 508 to see if that resolves the issue. Just waiting for the SoC on the batteries to get to the same level and see if the problem reoccurs.

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