Vangelis Beligiannis avatar image

BYD battery not charged by the Quattro


I have recently purchased a BYD LVS 20.0 battery and a Quattro 48/8000

My system is off-grid and has a Quattro 48/8000 with a FRONIUS PRIMO 3.0 on AC out, an MPPT 150/70 and a CCGX .

All setting are done according to your guidelines :

Victron & BYD [Victron Energy]

Here is the problem :

After the battery is fully charged TO 100% (around 13:00-14:00) the battery starts to discharge although there is plenty of sun to keep it charged. The MPPT keeps giving power but the Quattro shuts down the FRONIUS to 0W!!!

I can understand this happening if the battery voltage is above 55 V but this goes on even if the battery voltage goes down to 53V.

I am positive that this is not a BYD BMS issue. I tried connecting the AC GRID that I have as a back up and then the quattro started charging the battery as well immediately because it dropped the frequency back down.

I believe that the quattro should keep the fronius awake as long as the voltage is 55V or lower. Even if it has the frequency locked probably because of an overcharge insident (no error appeared) it should unlock after the voltage drops under the rebulk value. This value is 54.2V for my system but the frequency is still locked even reaching 53 V.

Why does it not unlock the frequency?

I am loosing power and the battery starts to discharge from 14:00 for no reason.

MultiPlus Quattro Inverter ChargerBYD
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Hi @Vangelis Beligiannis

I'm suspecting your system locks to 53Hz due to the battery lowering the CVL when fully charged.

Can you try raising the charge voltages slightly in ve.configure? this won't actually create a higher charging current (as the batteries BMS controls charging), but it does affect the PV inverter assistant (included in ESS assistant) and should prevent a 'frequency lock'

Vangelis Beligiannis avatar image Vangelis Beligiannis Daniël Boekel (Victron Energy Staff) ♦♦ ·

Hi! I am not Using ESS. My system is almost totally offgrid. Using the Ac in is extremely rare. I Will try your solution but the inverter does not start even if the voltage drops to 53V with the float voltage set at 55V

Hi @Vangelis Beligiannis

yes in your case it is the "pv inverter assistant" that controls this.
Please let us know what settings work best for you.

Also: check what parameters the battery is sending, if the battery lowers it's CVL (Charge Voltage Limit), PV will be shut down. Please also check the AC output frequency to know what is going on with your system.

3 Answers
thomasw-1 avatar image
thomasw-1 answered ·

Hi Vangelis,
I can confirm your observation. In my 3-phase system I have the identical behaviour. In island-mode instead of using primarily the AC-OUT-connected inverter power gets converted from MPPT and if that is not sufficent battery gets discharged.

@Izak (Victron Energy Staff) and @mvader (Victron Energy): I would also appreciate, if ESS would be modified in that way, so that AC-connected inverter is used before MPPT and before battery gets discharged.

In my case the MultiPluses even go in overload instead of activating the AC-OUT connected inverter. In 1 case system even switched off because of current overload!

According to a recommendation from @Guy Stewart (Victron Community Manager)

you should make your Victron dealer aware about that contraint, so importance gets raised on such requirement. I am going to forward that link to mine as well.

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Hi @ThomasW.

ESS has nothing to do with islanding / off grid mode.

thomasw-1 avatar image thomasw-1 Daniël Boekel (Victron Energy Staff) ♦♦ ·

Thanks for jumping on that topic, Daniel.
I have no insight about Victron's delelopment terminology. As you confirmed yourself the functionality is at least included in ESS-assisitant. Anyhow independent where the reason is caused, it is limiting the overall efficiency.

An increase of the battery voltage limit would be most likely not able to discover the current power requirements. It takes a while until voltage would be decreased to a level, where MultiPluses would initiate frequency decrease to wake up the inverter. During that phase battery is unnecessarily discharged (oberserved situations, where battery went down to 90% before AC-inverter was restarted) and especially not full PV-capacity is available to internal grid (leads to potential overloads of MultiPlus). From my point of view AC-inverters should have not the purpose to charge battery only.
I am looking forward seeing news from Vangelis.,

In a complex setup I am asking myself, why in island mode AC-OUT connected inverters are not also controlled by GX via modbus-TCP-based limits, when "Victron MPPT charge characteristics are automatically configured & governed by the GX device." (see BYD references on Victron webside). GX would be capable to detect power requirements much more efficient than a battery voltage based detection by MuliPlus.

Hi @ThomasW.

The problem is that BYD batteries lower CVL from about 55 volt to 51 volt, this is not needed and creates unwanted effects. (in ESS mode the system will actually discharge to grid)

We hope a feature update of BYD's firmware will improve this behavior, in the mean time it seems that tweaking the Victron inverter's charge voltage settings is a work-around to prevent the 'frequency lock'

please try raising voltages with 0,5V and report back.

Vangelis Beligiannis avatar image Vangelis Beligiannis Daniël Boekel (Victron Energy Staff) ♦♦ ·


Same thing today. I have not changed the charging voltage yet.

But here it is clear that the CVL is high and not causing the problem.

Finally the reason of locking the frequency is clear. It is because the Fronius inverter does not react quickly enough to prevent the overgharge that triggers the frequency lock.

The question is :


I will change the charger voltage tomorrow and keep you posted.

Vangelis Beligiannis avatar image Vangelis Beligiannis Daniël Boekel (Victron Energy Staff) ♦♦ ·

Hello! I changed the absorption voltage to 55.7V (55.2+0.50) as you mentioned.

It looks ok up to know. The fronius switched to 0W when the voltage of the battery reached 57.1V and came back on when the float voltage was reached (55V). I will check it out the following days to make sure it is ok.

There is another problem now. When battery is at 100% and 55V float volatge, the MPPT is almost closed (5W) and the fronius is giving the loads. This is correct and wanted, but the measurement of the AC LOADS on the CCGX has gone crazy. It is constantly jumping up and down for no reason. The frequency of the AC out is 51HZ which means that the fronius power reduction is active. But the AC load has gone crazy. If the ac load increases a lot and the frequency gets back to 50 HZ the problem stops.

Any hints?

Is it necessary to instal an energy meter on the AC load cables?

thomasw-1 avatar image thomasw-1 Vangelis Beligiannis ·

Hi Vangelis,

have you changed absorption voltage only or also the float voltage?
With that setting, I haven't discovered any change on island mode.


This afternoon I performed an additional test with 55,7 absorption and 55,0V float voltage.
I have observed following behaviour:

  • Voltage increased up to 57,1V before inverter and MPPT switch off.
    It seems that the voltages defined on MultiPlus are completely ignored and only DVCC is active.
  • Below At 54,8V MPPT returned and Fronius inverter was on idle (frequency at 52,8Hz.

What GX-release are you running? In case it is lower than 2.65 do you have DVCC activated?

Update after 1 hour:

Interestingly the behaviour changed now. In the moment main energy is provided by Fronius, Slightly throtteled at 51,4Hz, Battery remains at 100%

1617796464450.png (4.1 KiB)

Gx release is the latest. DVCC is on (forced). I am not sure if I have to activate the "limit managed battery charge voltage" tab.

thomasw-1 avatar image thomasw-1 Vangelis Beligiannis ·

We seem to be on the same OS level.

My "limit managed battery charge voltage" ist also deactivated.
In the moment it seems to run quite smooth (55,7V absorption and 55,0V float). Contrary to you I don't have any bouncing AC-loads being indicated. The only limiting factor is, when load deviates activation of inverter and MPTT capacity is quite slowly adapting.

However compared to before the behaviour is much better ;-)

One Last question thomasw-1. What GX device are you Using?

thomasw-1 avatar image thomasw-1 Vangelis Beligiannis ·

Hi Vangelis,
I use a Venus GX with version 2.65 currently.

are the ac loads appearing correctly when Fronius is regulated by the frequency?

thomasw-1 avatar image thomasw-1 Vangelis Beligiannis ·

Hi Vangelis,
I have not observed strange deviations during frequency regulation so far.
Since Fronius uses different thresholds than recommended in "AC-coupled PV with Fronius PV Inverters" for frequency regulation, I use 51,0Hz for start, 52,7Hz for minimum and 52,80Hz for disconnect.
Maybe that changes scenario for you.

In a different forum I recognized that weird power measurements can occur, when you have a thyristor based full wave power modulation (e.g. to control a heater).
Do you have any thyristor modulation in your network attached?

Thanks for the reply. I have a CCGX and was wondering if a cErbo GX woild solve the problem because it has a faster processor. I Will try it. I have no thyristor installed

thomasw-1 avatar image thomasw-1 Vangelis Beligiannis ·

Hi Vangelis,
I don't think so. Have a look to my latest post (see below).
Save the money.

Vangelis Beligiannis avatar image Vangelis Beligiannis Daniël Boekel (Victron Energy Staff) ♦♦ ·

@Daniël Boekel (Victron Energy Staff) Please follow up with the situation.

Vangelis Beligiannis avatar image Vangelis Beligiannis Daniël Boekel (Victron Energy Staff) ♦♦ ·

Ηello Daneil. Unfortunately the problem appeared again. The Quattro locks the frequency above 52.7 Hz and the Fronius stays out even if the voltage drops under 53V. So my system is not working.

Your PV Assistant manual clearly discribes that the Quattro Will enter rebulk phase at 54V. This Never happens. The machine us probably faulty and I Will have to return it.

thomasw-1 avatar image thomasw-1 Daniël Boekel (Victron Energy Staff) ♦♦ ·

Hi Daniel,

My euphoria was a bit early.
After 2 days expected behaviour the system unfortunately returned to standard behaviour. AC-OUT attached inverter is ignored after battery charging has been completed.

Snce the the modification of the absorption voltage definition does not substantially solve the problem, I would appreciate, if you could address the topic with your support department.



1617970794293.png (27.6 KiB)

Hi again! I think you have to wait a bit for the Fronius to get in.

If not and the frequency stays locked at above 52,6 Hz send me a message.

I found a solution for the problem and it is already working for me for 3 days.

it is a modification on the Fronius inverter that does not allow the Victron inverter to lock it out.

Let me know if you need the information.

thomasw-1 avatar image
thomasw-1 answered ·

@Daniël Boekel (Victron Energy Staff),

Interestingly the Fronius inverter for Vangelis' and my invironment went ok for a certain short time, in general however it is not a solution. I don't like to philosophize and take more assumptions on potential reasons.

Fact is that reasonable support of AC-OUT connected inverters is not given in island mode!
From my point of view there is no alternative thank fixing the issue.

@Vangelis Beligiannis: Yes, I agree with your proposal. It could raise a certain pressure, if you confront your dealer with returning the device complaining a defect.

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thomasw-1 avatar image
thomasw-1 answered ·

Hi Daniel,
I performed some tests this morning. Increasing the charging parameters on MulitPlus by 0,5V does not change any behaviour. The mentioned CVL is defined at 57,2V by BYD. Contrary to your statement it is definitely not the limiting factor. Maybe the described value of 51V was used in previous firmware versions, but not in recent or current versions of LVL BMS.

I made following observations.

  • Charging curve and AC-OUT inverter limit seems not directly controlled by MultiPlus. Defined charging current limits throttled my frequency shift follow directly the parameters of BYD CCL setting, even if voltages defined in MultiPlus are still not reached.
  • Frequency shift tested with Victron recommended voltage values and Fronius defined thresholds > no difference.
  • CVL is always higher than current battery voltage. Charging current adaptation and A-OUT inverter is only limited by CCL.
  • Even with 0,5V higher charging voltage definitions on Multiplus, the PV does not return, even if loads are >5.500W and battery voltage falls down below 54V.
  • Even if BYD provides information with CCL of 243A and CVL is above current voltage the AC-OUT inverter does not start-up immediately. It takes at least until battery is discharged below 95% SOC, sometimes even below 90%.

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