victron ESS overcharging pylontech and ignoring 'do not charge' status

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jacola asked May 7, '22

victron ESS overcharging pylontech and ignoring 'do not charge' status

All, i am puzzled by a 'last problem' in my install.
My system has 28 pylontech US2000B/C batteries in a mixed config, a Venus and 7 Multiplus (6x 5000, 1x 3000).
The 3000 is only used to feed IT loads, it never connects to the grid.
I am usually off-grid (on-grid in emergency with depleted batteries only).
So, when i reach the point of 'full', the Pylons correctly report a max. charge current of 0Amps and report the 'charge disable' bit.
However, the Multipluses continue to charge the batteries under these conditions with approx.25 amps, driving the battery voltage above the max. allowed voltage by the battery, and then vitron seems to switch to inverter and takes around 10kw from the batteries until the voltage drops to about 51V.

I have explicitely programmed a max. charge voltage of 52.5 in DVCC which it usually seems to comply with, but not in those 'peaks'. it us clearly visible from those graphs that victron violates the battery reported max. voltage, the configured max. charge voltage and even the 'charge forbidden' flag from the batteries.
Multiplus firmware version 481.

Any idea what could cause this behavior ?

Thanks - Johannes

(the above data is directly taken from the pylontech canbus by sniffing, but vrm reports same data)

Multiplus-II Pylontech

screenshot-2022-05-08-at-003622.png (407.2 KiB)

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Answer 1 · 2022-05-08T04:39:52Z

Paul B answered · May 08, 2022 at 04:39 AM

Hi Johannes - what are you using for the Solar chargers. as you do not state this and its very important.

My reply is based on Grid Tie solar inverters being used on AC1 out. and thus Maybe the issue is caused because the grid ties derating command is not working and thus not working the power from the solar has to go somewhere so you end up overcharging the batteries. or Hi AC voltage

Just a area to look at

If grid tie are being used then these units are are maybe NOT de-rating correctly

1 there is NO pv assistant install on the Multi's- or incorrectly installed

2. the gride tie units are NOT responding to frequency shift commands or incorrect setup in the Grid Tie units

I

1

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Paul B commented · May 08, 2022 at 04:43 AM

If you Have victron MPPT VE.Direct or Canbus units then are these connect and if can is the can operational - they should be showing in the gx device List as well

So much more infor about your setup if the above is of no help is needed

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Answer 2 · 2022-05-08T07:52:04Z

nickdb answered · May 08, 2022 at 07:52 AM

How is all this connected up? A 3000 can’t be mixed with 5000’s. How are these “mixed” batteries connected and their BMS’s wired?

Complex setups create complicated problems, ones which are not easily triaged on an internet forum.

You really need to check you are following both victron and pylon’s install requirements.

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Answer 3 · 2022-05-08T10:36:11Z

jacola answered · May 08, 2022 at 10:36 AM

Hi Pau, Nick, thanks for the feedback ! I will check into the generation (PV) side of things, good hint.
I have massive PV overcapacity in summer, most is SMA (5 systems), grid tie with frequency derating, correctly configured (i double checked).
HOWEVER, there are few smaller microinverters and one 1kw Solis 4G system (these are distributed in various locations and places, and over the phases). I have individual metering with Shellies for those small systems and can switch them off via relay also, but i see from the metering that they shut down with the frequency shifting which is as expected and, in my view, ok.
So for now, i just shut the one system in doubt (Solis 1kw) manually off and will se if that one is the culprit.
What makes me scratch my head is that the ESS, after the overvoltage/charge happens, is able to discharge the batteries - to where, if frequency throttling would not work ?

On the 5000/3000 mixture, they are not really 'mixed' in that sense. the 3000 'just' draws on the batteries, it is in inverter only setup, working to provide a clean grid to my IT infrastructure. The battery BMS connection (Pylontech CAN) is going to one Venus which is not aware of the 3000. I eavesdrop on the CAN connection and control the Venus via Modbus/TCP (to decide when to go on grid for charging).

I will report back here if that was the reason - many thanks for the hint.

Johannes

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