question

Matthias Pallhuber avatar image
Matthias Pallhuber asked

Victron Multiplus on JK BMS - Balancing

I am using one of the new inverter JK BMS with 16 x EVE 280 Ah cells. Works fine also due to the support received from Andy@offgridgarage. My settings are as per recommendation of Andy.

One of the observations what I can see is that my cells seem to be drifting apart even that I have balancing activated starting at 3.45 V.


1708890957318.png


I seem to reach an optimum of balance after 15 minutes of 100% reached.. Its always the same 6 cells which are drifting down in the lower voltage block. Victron tries to stay on 55.2 V so we see one block moving up and one block moving down.

I am wondering why the active balancer is not able to mange that? Any ideas?


BMS
1708890957318.png (767.9 KiB)
4 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

k1rou avatar image k1rou commented ·

hello Matthias, could you tell me how you connected the new JK BMS to your cerbo GX.

thk You

0 Likes 0 ·
switchinggreen avatar image switchinggreen k1rou commented ·
Hi,


You need a special CAN cable.


Regards,

Jacco

0 Likes 0 ·
k1rou avatar image k1rou switchinggreen commented ·

Have you a link ?

or

tutorial

What is the configuration on Cergo GX and on JK BMS ?

On JKB BMS I have select CAN protocol N°4 = Victron_CANbus_protocol_20170717

What socket did you use on the JK BMS and the Cerbo GX?


0 Likes 0 ·
Matthias Pallhuber avatar image Matthias Pallhuber switchinggreen commented ·
I made the cable myself. There is a schema for that in the jk manuel. It was a bit of trial and error tough.
0 Likes 0 ·
6 Answers
Alex Pescaru avatar image
Alex Pescaru answered ·

Hi @Matthias Pallhuber

Probably a thing that has to do with internal balancing algorithm.

See if it's any change if you try to keep a pack voltage of 56V (3.5/cell) and start balancing from 3.36V per cell?

These voltages are from Pylontech experience/settings.

Alex

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

thanar avatar image
thanar answered ·

Most probably cell voltage measurement error. Every cell voltage is calculated by the BMS based on another voltage value in the battery, heck it could even be the BMS temperature that's playing a role here in deciphering the exact voltage of a cell. You're into too-much micro-management here, imho.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

klim8skeptic avatar image
klim8skeptic answered ·

@Matthias Pallhuber I seem to reach an optimum of balance after 15 minutes of 100% reached.. Its always the same 6 cells which are drifting down in the lower voltage block.

I have 4 winston cells and see the same thing when the charge current bottoms out. I never really looked into this and have just accepted that some cells have slightly different "full" charge voltage. Or perhaps more likely that the active balancer (deligreen) is a bit different at the top cells vs the bottom ones. Cells within 10mV at the start of absorp, going up to within 30mV at the end of absorp at 20 mins, 3% tail current.

Given you have noticed that optimal cell balance is about 15 mins into absorp, and around the same time the charge current bottoms out, it would be safe to suggest that the absorp period can be reduced down to 15-30 minutes.

Additional thoughts. Do check the cell voltages at both the cell and at the balance leads at the BMS.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

switchinggreen avatar image
switchinggreen answered ·

The can socket on both devices.

Kind regards,

Jacco

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

switchinggreen avatar image
switchinggreen answered ·

https://www.victronenergy.com/live/battery_compatibility:can-bus_bms-cable#introduction

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Alexandra avatar image
Alexandra answered ·

Did you top balance the cells?

If it is always the same six, open your pack swap some of them over in position and go again.

Torque and assembly are pretty important.

They show like a 0.02v difference in the beginning of the graph so not bad. The graph scaling makes it worse. Is probably related to the balance trigger between them assuming you have active balancing? (Also settable on JK.)

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.