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JK BMS Cell Count Problem on B2A24S20P

dakamalu

dakamalu

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Joined
Mar 11, 2023
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36
Location
Waianae, Hawaii ~ 20 degrees North Latitude
I am on my third B2A24S20P. They seem to run great for a while, but the first two both failed with the error being "CELL COUNT DOES NOT MATCH SETTINGS"

I have a 16S 48V 280 AH battery. It is not the wiring, been all through that and besides, it runs fine for a while but once the error comes, the unit is toast. The first one stopped seeing cells 8, 9, and 16. The second one stopped seeing cells 9 and 10.

Any thoughts?
 
What version of the app are you running? I know there are some issues with some versions of the BMS (see here), but that's usually with an 4s/8s version - would be interesting to know if this was the same on yours. How handy are you with soldering SMD components?

Personally I've been running multiple of those for years without issues, so I'm very keen to know what causes this issue. On the ones that failed, do you happen to hear a hissing sound when they're in use?
 
One more thing: check the BMS leads contacts themselves. There have been instances of bad cabling/contact crimps with the connectors. See this post:

diysolarforum.com

New 2A Active Balancer with BMS Function won`t run

I Hi there I bought this ( https://de.aliexpress.com/item/4000529723243.html?spm=a2g0s.9042311.0.0.493e4c4d6I7yk6 ) Active Balance with BMS function. My existing Active Balancer works as it should. But the new one doesn't want to go on. The cables are the same for both.Both devices have the same...
diysolarforum.com diysolarforum.com
 
upnorthandpersonal said:
What version of the app are you running? I know there are some issues with some versions of the BMS (see here), but that's usually with an 4s/8s version - would be interesting to know if this was the same on yours. How handy are you with soldering SMD components?

Personally I've been running multiple of those for years without issues, so I'm very keen to know what causes this issue. On the ones that failed, do you happen to hear a hissing sound when they're in use?
Click to expand...
It is V 4.81. Here is the screenshot . . . from the working unit.

I am not the best at soldering, but hey, I've got two units to practice on.
 

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upnorthandpersonal said:
One more thing: check the BMS leads contacts themselves. There have been instances of bad cabling/contact crimps with the connectors. See this post:

diysolarforum.com

New 2A Active Balancer with BMS Function won`t run

I Hi there I bought this ( https://de.aliexpress.com/item/4000529723243.html?spm=a2g0s.9042311.0.0.493e4c4d6I7yk6 ) Active Balance with BMS function. My existing Active Balancer works as it should. But the new one doesn't want to go on. The cables are the same for both.Both devices have the same...
diysolarforum.com diysolarforum.com
Click to expand...
Thanks for that link. I did check the leads (or so I thought) because it seemed to be the reasonable thing to do. I will check them again but that still begs the question as to why a new unit works with no change to the leads at all.
 
Is it possible that the leads have to be within a certain tolerance of each other or some of the balance electronics gets fried?

It is a bit suspicious that cell 9 is on both failed units and the two cells on either side also failed on one and then the other.
 
Last edited:
Working on updating the app, but not sure why the app version matters if the settings are in the BMS itself.

I updated the app on the 3 devices I use. One of them (an older Android) had to use version 4.9 but the others (one is an iPad) are all updated.
 
Last edited:
I'm just making sure - there were issues with something similar on earlier app versions that were fixed later. Make absolutely sure the order of cells is correct. Go over everything again, just in case - and maybe replace the balance leads with another one. I know, but just in case...

If nothing works, and if you're willing to: see if you could ship one to Finland (I can pay for it, and can send it back). I'd like to know what the issue is exactly, and if it's related to the stuff I've been working on.
 
upnorthandpersonal said:
I'm just making sure - there were issues with something similar on earlier app versions that were fixed later. Make absolutely sure the order of cells is correct. Go over everything again, just in case - and maybe replace the balance leads with another one. I know, but just in case...

If nothing works, and if you're willing to: see if you could ship one to Finland (I can pay for it, and can send it back). I'd like to know what the issue is exactly, and if it's related to the stuff I've been working on.
Click to expand...
I have been over it many times. Many many times. The wiring is good. Checked the voltage reaching the pins and that is also good. Even opened up one and checked that the voltage from the cell passes through the pins to the circuit board. I wouldn't mind sending one to you. Sounds good.

I did have another thought. They both failed when I was out and my daughter was taking care of things. We have an 8K inverter and I think they turned on too many loads when I was gone because the inverter tripped on them both times. Would that somehow cause a feedback that might damage the BMS?

Let me know where to send it.

Mahalo (thanks) from Hawaii.
 
Last edited:
dakamalu said:
I did have another thought. They both failed when I was out and my daughter was taking care of things. We have an 8K inverter and I think they turned on too many loads when I was gone because the inverter tripped on them both times. Would that somehow cause a feedback that might damage the BMS?
Click to expand...

Ah, that's something. Yeah, what can happen is huge inrush currents thought the BMS when the inverter turns back on (without a precharge resistor), or a huge surge of power (back EMF) going to the BMS because of a sudden shutdown of the heavy load.

This could very well kill the BMS and other things connected on the DC bus...
 
upnorthandpersonal said:
Ah, that's something. Yeah, what can happen is huge inrush currents thought the BMS when the inverter turns back on (without a precharge resistor), or a huge surge of power (back EMF) going to the BMS because of a sudden shutdown of the heavy load.

This could very well kill the BMS and other things connected on the DC bus...
Click to expand...
Thanks for that. I'll still send you one if you want to see it. As I said, I am on my third one and need to figure out how to stop this from happening again.
 
One question.
When replacing them. Are you using the same harness? Or replacing it also?
It really seems like a connection issue.
 
upnorthandpersonal said:
Yes, I'll take it. If it's broken and I can fix it, you can have it back. I'll PM you the address.
Click to expand...
That's very kind, but if you do fix it, perhaps I'll send you the other broken one and you can keep it if you choose to return the one you fixed.

I am interested in how it failed and if you fix it, you can keep it or trade it for my other broken one.
 
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