Anil Ghatikar avatar image
Anil Ghatikar asked

Under voltage alarm on only Quattro not on BYD


I had multiple Undervoltage alarms/warnings on L1 Quattro in 3 phase setup out of sudden.

The LOG file shows BYD reporting normal 54.7 V voltage There was a normal load on the system and no overload recorded. The alarms were getting triggered randomly and the log shows wildly fluctuating VE bus voltage

Does the Ve bus take the voltage only from L1 Quattro?

I checked cable tightness in Quattro ( all three phases ) as well as on the LYNX busbar.

Will check later today the breakers and the individual battery module tightness. What else should I check? The system worked for the last 1 year without any major issues.

The system is ONgrid /ESS with 10 KWH BYD pro and 3 ph 5 KVA Quattro with 6 KVA Fronius and 250/70 Smartsolar

The Log is attached - Relevant entries around 10.30 AM are marked in yellow battery alarm

MultiPlus Quattro Inverter ChargerBYDlow battery warning
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7 Answers
Anil Ghatikar avatar image
Anil Ghatikar answered ·

Hurray, it is solved. The issue was internal battery communication between the 2.5 KWH packs and BMU

I realized it after I checked BYD under Venus in parameters and it was reporting 42 V instead of 56.5 So Venus was sending a shutdown command

I got service manual and software from BYD as advised by Daniël -( I must say excellent service support from Victron and BYD )

I am yet to use the software but I used the BYD Service manual ( downloaded from service site ) and It had nice troubleshooting tips

It was BMU Green LED blinking thrice . and Venus was showing 42 V in Parameters ( see the video -

See the attached snip from the service manual

All I did was to clean the RJ45 cables with contact cleaner - swapped the cables around and reset all the address dip switches to 0000 and set them back

The system is working now for last 24 hours without any issue

Thank you everybody who helped. For other users information who might encounter this thread BYD support is available here -

green-blinks.jpg (485.3 KiB)
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@BYD_service - The problem still persists - I could further investigate and realized that battery BMU is reporting lower voltage ( 53.5) than what is seen by Charge controllers and Quattro 56.5 - see screenshots -interestingly the BMS readout of parameters shows correct 56.5 v limit and no communication error on BCU

My guess is when there is a communication loss ( intermittent ) the battery voltage reported and actual voltage on battery drift apart. The under-voltage trips are actually BMS switching off on overvoltage

A complete switch-off of Battery and restarting seems to correct this problem and the voltages sync up again.

Is it something others have observed? What can I do other than restarting the whole system daily?

I am sending a separate email on the RJ485 cable and pinouts

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from-quatttro.jpg (47.7 KiB)
from-byd.jpg (57.6 KiB)
battery-history.jpg (313.1 KiB)

Hello Anil,

First of all, it's important to note that those are 3 different issues:

-As you mentioned the problem you had before was a installation connection issue. And once sorted the system worked normally.

-The undervoltage warning is user defined so you can change the threshold on when to report it.

-What you are seeing now is the case of the MPPT trying to charge the batteries while they are refusing charge.

Therefore, the difference in voltage is correct. The battery voltage is 53.5 which matches what you would expect at that SOC. The increase to 56 is not inside the battery but outside. As the battery is refusing the charge (see battery current 0) the inverter keeps increasing the voltage to try to force it.

I'll reply to your email on how to read the history so you can see what alarm is making the battery refuse the charge.

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laurentiupitran avatar image
laurentiupitran answered ·

Hello Anil,

How you already know, my system is a ESS system , three phase, with 2 x BYD batteries 10 Kw each.

You will see attached picture , that it was investigate in the past by me also, with separate tools and software; my conclusion it was that for each time when the grid power is going down as value, in any of the input phase, my system is going in inverting mode.

What is important to know is that only UFR 1001 E is detecting that undervoltage of the grid ; MULTIPLUS don’t have time to detect/react to those under voltages of the grid input. Separate I can detect also those under voltages that make my system going in INVERTER mode.

Just return to your case, I don t understood for the moment very clear if undervoltage it was detected on DC or in AC ?


ex-1.png (304.8 KiB)
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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Anil Ghatikar

DC bus voltage being different than battery voltage does indeed usually mean a disconnect somewhere between battery and inverters.

with BYD batteries, it's probably the batteries disconnecting themselves for some reason. To find the reason, read out the batteries with the correct software.

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Anil Ghatikar avatar image
Anil Ghatikar answered ·

In my case the DC Bus ( VE bus is what reporting undervolatge) but See values which are excessive leading me to think may be fronius related as SOC was near to 100 % and voltage swings very very large ( the barrery current was fairly samll less than 50 amps DC)- It is stabel now again . There is a new tree bracnh shading fronius connected panels I will cut that first and then try to watch the system . The tighness and fuses were checked and all seem to be ok

1592830698638.png (240.7 KiB)
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Anil Ghatikar avatar image
Anil Ghatikar answered ·

@Daniël Boekel (Victron Energy Staff)

Do you mean BYD service software - to compare with the LOGS. I checked all tightness and visually inspected each joint for signs of loose /overheating All seem to be normal. Next long weekend I will shutdown the system fully and check the lugs for loose crimping .

Interestingly the issue happens on FULL SOC with small load ( less than 750 Watt) - I see voltage recorded as 64.07 V on Vebus followed by 47.1. While BYD keeps reporting same volatge 53.6

Maybe BYD is siwtching off for few milliseconds ? - I am inlcined to think fronius may be the culprit due to low load

also forgot to mention that system is Nigeria so Although there is Ziehl islanding installed and I am only 20 meters from a 500 KVA transformer with a fairly large cable ( designed for 50 KW connection) network disturbance can be also the culprit causing transient instability

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1 comment
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Yes BYD software.

also make sure the battery is on the latest firmware.

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Anil Ghatikar avatar image
Anil Ghatikar answered ·

I seem to have partially isolated the problem

When the cable between Venus GX and Quattro is removed the system works fine. if the cable from Venus to Quattro is connected the system shuts down on error DEVICE #1 Switched oFF and Phase L1 shows Undervolatge signal -

When the same inverter is configured as standalone ( no change of AC/DC wiring) it works without error .

USing BYD and ESS manuals I could locate the fault location to the battery BMS . The Battery BMS is blinking 3 times . ( as per BYD service manual means ) communication error between modules - Will try one pack of 2.5KWh at a time till I find the culprit

Interestingly the Venus indication f in BYD/Parameters/Charge voltage limit is showing 42 V Which used to be 56.5 V

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byd-service avatar image
byd-service answered ·

Dear @Anil Ghatikar I have just emailed you the link to the software so you can read the history. As @Daniël Boekel (Victron Energy Staff) mentioned the Low voltage alarm and Low voltage warning may be symptoms of the issue rather than the root cause. When the battery shuts down to protect itself, the inverter will detect a low voltage.

You have 4 batteries and you mentioned you have detected a communication issue looking at the BMU LED lights. Please check if any of the batteries has a scrolling side to side LED light, this would be the one not communicating. If this battery is suffering an alarm but it is not being able to communicate that alarm to the BMU (And through the BMU to the inverter) it is possible that it is making the system misbehave. Therefore, please help solve this point first. I will give you some recommendations.

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