ESS with Fronius and zero feedin is overcharging Pylontech Batteries

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Hugo Russouw asked Feb 2, '21

ESS with Fronius and zero feedin is overcharging Pylontech Batteries

I have a systems that is set to Zero feed in.

It is made up of a Multiplus-II 5kVA , Fronius Primo 5.0-1, MPPT-100 and 12kW Pylontech battery.

The Fronius is connected to Out-1 of MultiPlus.

The problem is that when the battery is 100% charged I start getting battery over voltage errors. 53.8V-54V and the Pylontech switches off when 54V is reached.

This started to happen after replacing one of the MPPT-100 with the Fronius.

The battery charge voltages are set correctly on the MultiPlus.

What else should I look at.

Fronius

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Answer 1 · 2021-02-02T23:04:18Z

Daniël Boekel (Victron Energy Staff) answered · Feb 02, 2021 at 11:04 PM

Hi @Hugo Russouw

I've moved your question to the regular section.

Is this a new installation? if so best to set to 'keep batteries charged' for a while, and maybe disconnect PV inverter. this way the battery can properly balance itself.

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Hugo Russouw commented · Feb 03, 2021 at 04:56 AM

Hi Daniël

No, this is not a new installation.

The installation had 2 MPPT-100 and I replaced one of them with a Fronius for the simple reason that the client wanted more peak power.

So the problem only started now.

I am thinking that because of the zero feed in, the power is dumped in the battery when there are a big change in power usage. So if the batteries are fully charge, this is a problem??

Thanks

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alan Hugo Russouw commented · Feb 03, 2021 at 07:10 AM

This is what it sounds like, Fronius zero feed in works via modbus-tcp, which is a "slower" than Frequency shift.

Unfortunately going by here, you can't use frequency shift.
https://www.victronenergy.com/media/pg/Energy_Storage_System/en/system-design.html

Try to lower the charge voltage and see if it fixes it. It won't hurt the lithium or cause a noticeable loss of capacity. However I believe the charge settings are controlled by the pylontech BMS.

Maybe try changing from zero feed in to limited feed in but set the gridpoint to 50w, I assume feed-in is not allowed by the power provider, but its only going to be an unnoticeable amount. Unless the grid meter will disconnect from the grid when they detect Feed-in.

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Hugo Russouw alan commented · Feb 07, 2021 at 02:47 PM

HI Daniël

I have tried everything I can think of, but the batteries are still charging to 54V and then switching off.

I also contacted Pylontech about this and they told me I should contact Victron.

I need to get the charge voltage lower.

Can Victron do a firmware change to overwrite the BMS charge voltage from 53.2V to 51-52 V?

Thanks Hugo

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alan Hugo Russouw commented · Feb 07, 2021 at 11:38 PM

What so you have charge current set to? Possibly reducing it will allow the battery voltage a little time for the fronius to ramp down.

Also tagged @Daniël Boekel (Victron Energy Staff) as you replied to me

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Hugo Russouw alan commented · Feb 08, 2021 at 09:56 AM

Hi

I currently have the Charge current set to 20A.

Absorption Voltage is 51V

Float Voltage is 50.50V

And I am still getting batteries charging to 54V.

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Answer 2 · 2021-02-02T23:25:11Z

seb71 answered · Feb 02, 2021 at 11:25 PM

54V is the maximum voltage for 15 LiFePO4 cells in series. For perfectly identical cells it would mean 3.6V per cell. Since the cells are not identical, for sure one cell is above 3.6V when the battery voltage is 54V.

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Hugo Russouw commented · Feb 03, 2021 at 04:55 AM

I know that 54V is the max and this is why the batteries are switching off.

I want to know how to set the hardware so that it does not happen.

Should I set the float voltage from 52V to 51V so when power is dumped in the batteries, it can still handle it?

Thanks

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seb71 Hugo Russouw commented · Feb 03, 2021 at 08:02 AM

I thought that's your setting.

You wrote that "The battery charge voltages are set correctly on the MultiPlus.", but you did not wrote the actual values you have there.

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Hugo Russouw seb71 commented · Feb 03, 2021 at 08:41 AM

I did set it to 51.5V .

I am thinking of dropping the Float Voltage to 50.5V and the Absorption Voltage to 51V.

Thanks Hugo

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alan Hugo Russouw commented · Feb 03, 2021 at 09:03 AM

Try to lower the charge voltage and see if it fixes it. It won't hurt the lithium or cause a noticeable loss of capacity. However I believe the charge settings are controlled by the pylontech BMS.

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Answer 3 · 2021-02-08T06:05:48Z

Hugo Russouw answered · Feb 08, 2021 at 06:05 AM

Hi @Daniël Boekel (Victron Energy Staff)

Yes, I have dropped the MultiPlus charge current down to 50A. So +/- 2500W

How low should I drop it to?

I was also thinking of moving the Fronius to the input side of the MultiPlus.

The problem is that it will switch off when the grid is lost and the client will not like this.

I might do it just as a test.

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dgnevans commented · Feb 08, 2021 at 06:36 AM

What is your bulk/absorption voltage set to on your Multiplus ?

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Hugo Russouw dgnevans commented · Feb 08, 2021 at 07:04 AM

Hi

See the current settings.

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dgnevans Hugo Russouw commented · Feb 08, 2021 at 10:38 AM

Can you confirm if DVCC is enabled and setup correctly.

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Hugo Russouw dgnevans commented · Feb 08, 2021 at 10:58 AM

Yes, See pic.

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dgnevans Hugo Russouw commented · Feb 08, 2021 at 12:25 PM

Can you share your ess that you have set so far?
Is the customer able to export to the grid excess power?

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Answer 4 · 2021-02-08T09:55:40Z

Hugo Russouw answered · Feb 08, 2021 at 09:55 AM

Hi

I currently have the Charge current set to 20A.

Absorption Voltage is 51V

Float Voltage is 50.50V

And I am still getting batteries charging to 54V.

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Ingo commented · Feb 08, 2021 at 10:10 AM

Correct me if I am wrong but isn't the Battery telling the Charger what voltage to use? Setting the voltage on the Charger will have no effect unless the CAN connection to the GX is broken (then it's ortoff a failsafe voltage setting of the Charger). See reference documentation below.

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

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Hugo Russouw Ingo commented · Feb 08, 2021 at 10:27 AM

Hi Ingo

Yes, I can change the settings all I want.

The BMS will control all changing Voltages and Current.

The Battery will protect itself.

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Ingo Hugo Russouw commented · Feb 08, 2021 at 12:34 PM

In that case you need to contact the Battery manufacturer, Seems your BMS is not doing what it's supposed to do - charge at the correct voltage.

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Hugo Russouw Ingo commented · Feb 08, 2021 at 01:06 PM

No, the battery BMS is working.

It is the MultiPlus that is charging the battery more then what it should.

I am busy with Level3support to see if we can find a work-a-round.

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Ingo Hugo Russouw commented · Feb 08, 2021 at 02:09 PM

Ok. This is an interesting fault.

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alan Hugo Russouw commented · Feb 08, 2021 at 11:00 PM

How is the fronius and ccgx networked? Via cable or wifi?

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Hugo Russouw alan commented · Feb 09, 2021 at 06:43 AM

WiFi

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alan Hugo Russouw commented · Feb 09, 2021 at 06:55 AM

Is it possible to hardwire them via ethernet? I wonder if its the wifi latency slowing down control. Even though wifi "only" adds 2ms, it's a lot of time in the control system world. If you add any packet loss then the delay is even worse.
The other thing against the timing is the upper voltage knee of Lithium. Voltage increases exponentially at the upper end.

You did enable Modbus control in the fronius as specified in section 4.3.11 of the ESS manual right?

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alan Hugo Russouw commented · Feb 09, 2021 at 01:01 AM

Can you share the site so we can look at the advanced tabs?

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Answer 5 · 2021-02-11T16:48:58Z

Hugo Russouw answered · Feb 11, 2021 at 04:48 PM

OK. So Daniël helped me and I think we have a solution.

First we turned ON the "DC-Coupled PV" and set the "Maximum feed-in" to 0W.

Second we turned ON the "Dynamic current limiter".

I am still testing, but it is looking good.

Thanks

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Answer 6 · 2021-06-01T20:53:14Z

josephm answered · Jun 01, 2021 at 08:53 PM

I have same issue, did you solve the problem ? My BMS did not disconnect and almost burned my house !

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Answer 7 · 2021-06-02T00:21:55Z

H.W.Oelofse answered · Jun 02, 2021 at 12:21 AM

We have seen some of these issues with ESS systems with fronius integration particularly when keeping the battery at a high state of charge with zero grid feed in, when you have significant loads in the system and the fronius is contributing a large proportion of this when the load is removed from the system there is no way for the system to sink the overshoot from the fronius it can't feed back to the grid so the overshoot has to be absorbed by the battery which if it is at 100 percent will in the pylontech batteries case will lead to the alarms that you are experiencing we have found it useful to run the battery charge percentage between 85 and 90 percent of full to have some capacity to handle this situation.

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Answer 8 · 2021-06-02T05:58:16Z

Daniël Boekel (Victron Energy Staff) answered · Jun 02, 2021 at 05:58 AM

Hi all,

A new solution for systems that are sensitive to overcharge is to use the 'reduce maximum charge voltage' setting in the DVCC menu:

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

This way systems with a sensitive (imbalanced) or small battery with a lot of AC coupled PV input can have a bit more headroom for absorbing peaks.

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