JK BMS Cell Count Problem on B2A24S20P

dakamalu · Mar 13, 2023

I agree with you in general, but these are wires, and crimps - essentially, they are resistors. The interesting thing is that the common failure on both of them (cell 9) has the best connectivity. So I wondered if that was a problem if there was some kind of surge when the inverter shut down. Perhaps the active balancer isn't meant to deal with that.

Maybe I should reduce the balancing current?

timselectric · Mar 13, 2023

I run the same units.
And have pushed 150a charging through them. (Kids, don't try this at home)
I have charged and discharged enough to trip them off.
And they just keep running fine.
I understand that it's possible to get a faulty unit. But 3 in a row, tells me it's probably something else.

dakamalu · Mar 13, 2023

Yes, it seems so. I am thinking that it is the interaction with the inverter, but we'll see. I do like the unit when it works!

It is the inverter tripping that I think is the problem, not the BMS.

timselectric · Mar 13, 2023

Are you using BMS communications?

dakamalu · Mar 13, 2023

timselectric said:
Are you using BMS communications?

Not sure what you mean. But I do use an older android phone to monitor and adjust the settings using the built-in bluetooth capability of the BMS. The inverter is a standalone and I cannot change those settings.

I purchased the inverter because it can provide split-phase AC that is needed in the US.

timselectric · Mar 13, 2023

dakamalu said:
Not sure what you mean. But I do use an older android phone to monitor and adjust the settings using the built-in bluetooth capability of the BMS. The inverter is a standalone and I cannot change those settings.

I purchased the inverter because it can provide split-phase AC that is needed in the US.

BMS communications is a data connection between the BMS and inverter. I was thinking that it could be the problem. (Because you said interaction) it appears that you are not using it.

dakamalu · Mar 13, 2023

Thanks again, no, I am not using it. Perhaps I should go into my issues with the inverter or at least provide the info on it.

timselectric · Mar 13, 2023

That might help.

dakamalu · Mar 13, 2023

The inverter is a GS8K-48-60a-SP. I bought it because it does split phase and has massive copper wound coils.

It does provide power to the house pretty well. However, when you exceed the 8K for an extended time, it does trip, and those times are associated with the BMS failures.

timselectric · Mar 13, 2023

Interesting

timselectric · Mar 13, 2023

When it shuts down.
Is it the inverter shutting down?
Or the BMS? Which would also shut down the inverter.

dakamalu · Mar 13, 2023

The two times that the BMS failed, I believe the inverter shut down first (I wasn't at the house, my kids were taking care of it - supposedly).

timselectric · Mar 13, 2023

The coronation sounds right.
I'm just not sure how to verify or correct it.
How many batteries do you have?

dakamalu · Mar 13, 2023

timselectric said:
The coronation sounds right.
I'm just not sure how to verify or correct it.
How many batteries do you have?

Just one 280 AH LifePO4 with 16 cells in series.

dakamalu · Mar 13, 2023

If it is due to the inverter tripping first, perhaps I can adjust the discharge current on the BMS to make sure it trips first?

timselectric · Mar 13, 2023

You could try it. But, I don't think that's the problem.

dakamalu · Mar 20, 2023

timselectric said:
You could try it. But, I don't think that's the problem.

Seems to be working well so far.

I was interested in the pre-charge comment but that only works when I am turning on the inverter, not when it trips and turns on by itself again. Or am I wrong about that.

timselectric · Mar 20, 2023

dakamalu said:
Seems to be working well so far.

I was interested in the pre-charge comment but that only works when I am turning on the inverter, not when it trips and turns on by itself again. Or am I wrong about that.

If only off for a few seconds, the capacitors should still be charged.

upnorthandpersonal · Apr 1, 2023

Just a small update: the BMS @dakamalu sent me arrived. I will see if I can find time this weekend to have a preliminary look.

dakamalu · Apr 2, 2023

Just FYI since I am on my third and last JK BMS, I did reduce the balancing current from 2A to 1.5A. So far it is working, but who knows why?

I have a manual transfer switch from the grid to pure solar power. I have been careful to make sure that the inverter is up and running before making the manual transfer, but some of the family who made the transfer may not have been. Don't know if that's a problem.

JK BMS Cell Count Problem on B2A24S20P

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