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mikeb avatar image
mikeb asked

Victron BYD with BMV?

Hi


Setting up a Victron 8kva Quattro with 5 byd units


Took note of your work around for the reporting of accurate soc for the unit and have a bmv700 in place


Just wondering what the best settings where for the auto sync to 100% in relation to this set up?


Have only ever used lead acid batterys before and have the auto sync setting mastered.


Also what would you recommend as settings for the auto genny start in relation to voltage and soc?


Also I notice on the mocked up set up I have running at the moment before it is taken to site for full installation the mppt are running in ess mode wanted to check this is normal?


Regards

Mike

BYD
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mikeb avatar image mikeb commented ·

Hi thanks for the reply guy


I have them running on a mocked up off grid system before it is due to be installed in october

I set the precautionary setting on them 48v battery 56.5v absorption. And the battery type trust this is ok?


Also I have the bmv for the soc work around


Notice a bit difference in the soc of each

I trust this is expected and that there won’t be any issues of over charging as I believe the byd bmu will tell the colour gx to back off the mppt’s or inverter charger?


Is there anything else I should be aware of? As this is the first install using the byd?


Regards

Mike

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mikeb avatar image mikeb commented ·

Should have said the mppt have the battery type lithium and the Quattro has been set as per the victron byd guide


The bmv has been set using the Bluetooth smart at a charge efficiency of 99% and the peukert at 1.05


Still wondering how the auto sync is going to work


Regard mike



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6 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

It is normal for the MPPT to report its STATE as ESS in a managed situation where it is not controlling its own charge state, but being directed by the CCGX/BYD battery.

This is a hold over from when this control system was first developed, it may be changed but for now ( MPPT Firmware v1.30), it is expected.

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Charging is based off battery voltage, not state of charge. So there is no issues with charging caused by the incorrect state of charge reading as reported by BYD, or any differential when there are two devices monitoring state of charge.

The issues arise with customer confusion, as there is now two states of charge.

I want to be clear, I personally DO NOT recommend using a BMV with a BYD for this reason.

If a more precise state of charge is REQUIRED for some reason, that is the solution. But I do not think that it is necessary in most cases.

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mikeb avatar image mikeb commented ·

Hi guy


So would say you are suggesting to use the byd to report the soc. and use this report to start a back up generator?

So what would your setting for starting a back up generator be?

Voltage? Soc?

Regards

Mike


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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

I am not comfortable recommending generator settings, as that depends on so many factors.

What I can tell you is some key points.


Automatic BYD battery shutdown voltage for under voltage self protection is ~43V

Inverter Cutoff is usually 47V.

Automatic BYD battery shutdown voltage for over voltage self protection is ~57V (reported as overcurrent)

BYD SOC Self correction thresholds at 15% & 100%




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mikeb avatar image mikeb commented ·

Thanks for the reply guy


From the details you gave in the last post I can sum up the setting to look at for auto starting and stopping the genny


I am just really trying to gain as much information as I can on the byd performance etc as it’s the first time of using


Only ever used rolls deep cycle batterys before and still have installs going strong with them as I have the experience of how they perform in the situation they are in ie winter with lower temperatures and lower solar


And summer higher temperature s and the solar working well


Regards

Mike

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mikeb avatar image mikeb commented ·

Just wanted to clarify 53v is roughly 50%?


Have full charged the battery’s had minimal load and a hour later the battery’s at 53v?

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ mikeb commented ·
I have now deleted that estimate. It was too rough, and undermined the other accurate information.
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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ mikeb commented ·

While I won't make any claims as to the interpretation, here is a charge cycle, with a 50% recharge mid-way through for a single BYD 2.5 kWh battery module.

It is important to be aware that these are not 'resting' voltages, there is charge and load acting on this battery during these cycles (as shown), and that will effect the readings.

At no-load, 50% settles at 53V at 3 am.

Even an 8A (400W) load will draw down battery voltage from a 100% full battery from 55.5V to 53.2V.


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gregn avatar image gregn commented ·

Hello

Why sometimes the Automatic BYD battery shutdown voltage for under voltage self protection is or Battery Low voltage ~43V and sometimes 48V on the parameters of the BYD battery on a ESS system?

Firmware problem? SOCadapted?

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mariowagner avatar image mariowagner commented ·

Hi guy,

in my expereince inverter cut off is not around 47V. It can be. but i've seen cutoffs at 49.5, some at 48.5. It seems to more depend on what SoC the BYD BMS beliefs to have.

we run off-grid systems by the way.


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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Both state of charge readings from BMV and BYD have limitations.

The BMV is an amp hour counter divided by a set Ah capacity, so if any of the BYD module cells shuts down (unlikely) its state of charge readings will be out.


The BYD counter (currently), doesn’t start counting until 50W per cell, which can lead to an artificially high reported state of charge.

It will correct before module shutdown.

A firmware fix will be released, but will require a site visit for installed systems.


Ideally you can have the system connected to the VRM and then Monitor if the system is suffering from the underreporting issue.

If it is, change the SOC priority to the BMV remotely via the Remote Console.

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gregn avatar image gregn commented ·

Hello

Do you know when the firmware relaese is available for lowering the 50 W per cell limit?

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Anil Ghatikar avatar image
Anil Ghatikar answered ·

Hello


for BMV sync settings on lithium see this (BMV Lithium settings)by victron

https://youtu.be/yMJ_vzB2avE


For SOC settings based on my personal use experience


Start SOC - keep enough SOC in reserve for emergency loads in case Genny fails to start otherwise any SOC is fine


STOP SOC- I would recommend to keep at 95% as in my case the Batteries tend to go into high voltage near the end of charge cycle or oscillate


this is adressed partially in Venus RC 2.20~23


DVCC: Improve BYD operation when the battery is full (CCL=0); by using a lower float voltage, 55V, and a 40A limit in that situation; DVCC only. This fixes a slow charge-idle-charge-idle cycle.



If you have ESS assistant loaded in Quattro then MPPT running in ESS is normal.


if you are running off grid then you will have to reset MPPT to factory default and set them again

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gregn avatar image
gregn answered ·

Hello

I have a big 20 kWh BYD battery with 3 Quattros and 4 MPPT's.

We get the inaccurate current reading problem and it is not nice for the customer to read a sudden SOC drop...

Instead of installing a BMV and having other problems,
Has anyone experienced the SOC reading from Ve.bus with the "Use solar charger current to improve VE.Bus SOC " function on? I did it with Victron Lithium and it works good, but with BYD I ask myself? It should work.

Thank you for a feedback.


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