Dyness B3 modules: high charge/discharge current

Q&A and troubleshooting
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1

Dear community,

I have 6 Dyness B3 modules working in my solar installation for about four years.
I recently had to replace one of my Victron MPPTs due to a fault.
After the warranty replacement, I have started to receive messages from the batteries, from time to time, of high charge and/or discharge current. I attach an image.
I have gone through all the configuration parameters and cannot find what is causing this alarm. Can you help me?

My system is made up of:

  • a solar collector of about 10kWp,
  • two Victron Multiplus II 48/5000/70-48 inverters (master+slave)
  • two Victron 450/100 MPPT
  • a Cerbo GX
  • Dyness battery bank with 21.6kWh total capacity, 6 modules
    Captura de 2025-04-21 17-45-22
    Captura de 2025-04-21 17-45-22780×319 32.9 KB
2

Any ideas about where to start to look?

3

Is there anybody out there? :joy:

4

Uhm… Is my problem too obvious? Or maybe so complex that nobody feels like helping? I can provide more info if needed. I checked all config parameters to be equal to the previous situation, before replacement of the defective MPPT, but couldn’t find any difference… So I am a little lost here…
Any help would be REALLY appreciated :slight_smile:

5

Hi, I’d love to help you, but this might be out of my scope…

Could you please post the cerbo settings regarding the battery interface ?

Normally the BMS informs cerbo of the current limits, cerbo then distributes these to the inverters and chargers.

Maybe we can work something out with more data

6

But, just as a wild guess and looking at your configuration :

IF all 6 batteries are online you shouldn’t be able to have loads or charges over the limits.

So, it looks like several of your batteries are awol.

7

OH thanks Ludo for your answer, really appreciated!

I post some images with cerbo settings regarding the battery interface, if you wish to see any other config page let me know.

The data I see in the Cerbo monitor seems to give the idea that communication with battery is OK but it handles the battery bank as a whole and I don’t see any particular parameter making reference to the number of battery modules detected.

I have the impression that the communication between the 6 battery modules through the CAN bus is ok, because when I switch off the main battery (through the red pushbutton, not the main switch) the other five batteries switch off accordingly. However if I can make any test to assure that communication between modules is OK please instruct me on how to do so :smiley:

bms_can_port-status
bms_can_port-status519×315 20.4 KB

bms_can_port
bms_can_port520×309 11.2 KB

battery-device
battery-device524×318 15.7 KB

8

What you would need to investigate imusing the vrm is if there really is a high charge and discharge current there.

Is the charge going above what the battery is requesting the in the bms charge and discharge limits. (Those are found on the vrm in a widget and kn the GX usually under the dyness in device list)

9

Thanks LX! Charge and discharge current limit is reported under Dyness-L Batt/Parameters and it is 225.0A
These warnings occur daily (usually in sunny days) but spuriously, so I don’t know how to measure the current at the precise moment: it is difficult for me to be looking at the system right at the time when this is happening. How can I do?

10

In the first screenshot you have a charge and discharge overload in the same minute. I think this problem is in the bms, not on the victron side.

Ask your supplier if they have a newer firmware version to suppress these messages.

11

I have noticed this also, but these messages were not appearing before MPPT replacement, I am sure, so I think both things (replacement and warning) are related, somehow.

I have sent the inquiry to Dyness also, but for my past experience they are not much responsive… I don’t know if I will be able to get something from them.

12

Can you check the upper/lower cell voltages of all 6 battery packs ?

Is your system offgrid , or can the MP’s also charge ?

13

I can check voltages of batteries at a concrete time, but not monitor all day. Well, one sunny day I can try to catch the warning going on, but it can be tricky…

My system is connected to grid, with excedent injection.

14

You misunderstood, i just need a snapshot of your battery health.

15

I had a totally different brand do this (not after an mppt faliure)
Interesting it also then developed a high and low temperature warning. The bigger lol was high temperature -275° C… So yeah.

It is possible something sensitive on the bms board is not happy.

Have you tried switching your batteries over in terms of their stack and addressing positions. Are they daisy chained?

16

Oh! When batteries are charging the voltage is between 53.5-53.6V most of the time. Occasionally it can fluctuate a little bit and go up to 54.0V. This is what I can see with the response time of a tester, I am not able to see fast transients.

Things that I have observed:

  • From the 6 packs of batteries, only 3 give the warning. Not all 3 at the same time, sometimes one, sometimes a couple of them… I can see it because each pack has a red light that fires when the high charging/disch. current condition occurs.
  • high charging/disch. current warning always (or almost always, I am not sure 100%) fire in pairs: one charging current warning + one discharging current warning at the same time.

My six batteries are connected in two groups of 3+3 to distribute well current between these two branches, that are directly connected to bus bar.
Yes: The connection data is daisy chained.

I have not changed any connection since the warning started to appear. I have not tried to swap position of batteries in the stack because these are heavy and well mounted in the rack, and exchange their positions would be quite a hard job.