question

Are the 2 multies the ONLY items charging the batteries and could you please post the ve config settings that are applied ie a screen picture would help.

also are the units on the latest firmware if not please upgrade and retest.

Also have you checked BOTH multiplus units that they both have the same settings

Hi Paul,

thanks for your reply.

Indeed, the multies are the only items charging the batteries.

Both units have the latest firmware and the same settings.

We use one single config file for all our systems. See screenshots for inverter and charger settings.

Victron Multiplus 48/5000/70.

I have this same unit my firmware version is 459 please confirm that you are on 459 as you have not said the version

suggested things to check

1. Maybe the BMS you are using is disconnecting the batteries ???

2. what voltage sensing connections are you using, ie are they connected directly to the batteries and NOT to the inverter battery connections.

3. is the voltage high at low or high amps

4. could you send a detailed wiring diagram

5. also try reducing you float voltage by 1 volt as it seems very close to the absorption voltage ( this is a test suggestion ONLY to see if as they are so close that this somehow is causing a issue )

6. another thing you have not mentioned have you PV grid tie connect, if so are they shutting down on freq shift as if they are NOT and are still producing and the power used is less than there output then the inverters have no ware to put it so they dump it to the batteries (also presuming no grid connected here).

7. Again a FULL detailed system diagram, helps as the above are only guesses

8. ****Added this part this morning ****This is a try only if you have dvcc enabled in the Venus GX Disable it and see if this stops the issue.

Yesterday I had a simillar issue on a site and am still trying to find out why but the only change on the site before this was to add a BMV700 and then to turn ON DVCC then I seemed to have a high battery voltage when the batteries were full and my alarms went off as well.

I have so far NOT isolated the issue. but will be doing so over the weekend.

the VRM graph below for referance only ,The red one is the one of concern as the BMS would have given a shutdown to the VE BMS unit that would have then shut the charge down in the Inverter but the volts crept rising as per the graph. the one in blue is also of interest but this was before Iput the BMV in and it was also when I physically disconected the batteries as well, anyway more testing this weekend .

Hi Paul,

thanks again for following up. Regarding your queries:

Version: we have 2624433 installed (so not the last one, as i thought previously :/ ).

1. About BMS disconnecting the batteries . Don't know how we can check this - we do not experience communication errors, neither on BMU nor on batteries.

2. Voltage sensing - we use the standard BYD 2.5 batteries + BMU, which have no additional/exterior voltage sensing.

3. See diagrams below:
4. See diagram below

5. We can indeed try. However, we're using the settings as advised by Victron, float 55.V vs absorption 55.2V (see https://www.victronenergy.com/live/battery_compatibility:byd_b-box)

Also good to mention that the systems never get out of absorption mode, even once fully charged they stay in absorption.

6. PV - we do not have a PV inverter connected on the output of the battery.
The battery can be charged from either the grid or PV. See diagram. In case of any surplus PV power this can be fed to the grid.


Hope this helps to be more specific.

Thanks Peter

Hi Peter, I cant see any reason jumping out at me.

however the system in my opinion is missing some installed items as the Victron inverter is not getting info or being told stop charging or to stop loads in a battery fault occurs.

again in preferance you should be on 459 firmware, but I dont think that will make much diferance

I notice in your drawing that there is no VE.BMS that controls the inverter connected.

IE if some cells in the battery go high when balancing this may trigger the battery or batteries BMS to disconnect them,

thus the inverter is then open circit and thus showing a spick in its voltage as there are NO batteries connected.

you should have a VE bms connected so that charging from the inverter is TURNED off before the batteries disconect.

currently your diagram shows that only a venus is connected for monitoring but there is NO control of the multi at all.

and thus the batteris are being turned on and off during cell balancing or for some other reason

Hi Peter, Have done some more testing today and found the below on my system

TRY this if you are still having your issue, and see if it gets you back and going, yes its work around , and NOT a full solution, but it worked for me for the time being.

if you are using a VE BMS and it has got a High voltage trigger and the red light is on on the unit, this also maybe occurring with other BMS triggers as well but I cant test for that.

then

1. the Venus device may/will loose its Ethernet connection. only way to connect is with the inbuilt wifi

2. the General Flag control will not work, ie you cant turn it of or off

3. the Inverter will not reconnect to the mains until the over voltage trigger on the VE BMS is removed or the gen Flag is removed

So try REMOVING the General flag assistant for the time being or remove the high voltage stop charging trigger

Hello, I see the batteries are BYD. Sorry I had not caught this case before.

If the communication is correct the BMU will make sure the voltage range is respected and if due to an anomaly this is not respected, the batteries will shut down once the maximum cell voltage is reached. Therefore, could you first help confirm you are seeing the BBox in the device list and that the BMU LED is solid green?

Please note that if the BMU is bypassed or DVCC deactivated, this would void the warranty.