JK BMS randomly stops charge & discharge? JK-B2A24S-20P

[hb48]

I'm a bit puzzled by this, I have 2 of JK-B2A24S-20P BMS in parallel, one on each 22s Battery pack.

They are about less then 2 years old, up to this point they function as expected but I just noticed one of the two just randomly stops charging and discharging. The LCD screen normally turns on by default when it discharges so that was the initial indicator. I used the JK app to connnect and confirmed the display is working properly b/c it was just not discharging to charging.

I go into the control of the BMS, cycle the charge and discharge buttons and it is working again. I went as far as just turning off the other BMS while this was happening and the suspect BMS started to charge and discharge. The two BMS don't talk to each other they just monitor their own pack so there is no communication and the parallel path connect to the main line.

I'm puzzled by this behavior and there is no hard reset option, turning it off and on or cycleing the Charge/Discharge in the app makes it work but than just randomly over sometimes from 15 mins to overnight it just stops charge/discharge again on the suspect JK BMS.

I'm thinking it is just time to replace it but was wondering if any one has any suggestions.

 

[Shawn Hayes]

Bump…. Following along to see/hear if anyone can share?
I just bought two of the same JK’s for two new 16s packs to come. So curious as to an answer myself in case I encounter this issues later on.

 

[GXMnow]

My JK-BMS shut down charge and discharge on me. What it turned out to be was a failing BMS cell sense lead. The plug at the BMS was not making a good connection and it would randomly report a very low cell voltage.

On the JK BMS ap, there is a menu and you can look at the history log. It should list what caused the charge and discharge disconnect events. What state of charge was it at when it happened? Are these LiFePO4 cells or Li Ion like NMC? Trying to get to full charge on LiFePO4 can be an issue as even closely balanced can have a runner hit cell over voltage protection very quickly. But if it is happening while in the middle of the charge curve, that won't be the issue.

 

[hb48]

I checked the logs, nothing unusual, even the detailed log only shows when I manually flip the buttons only at least at glance at the logs since it is intermittent. These are Li-ion packs.

I checked the connection, it is making good solid contact so i know that is not it, i had everything strain relieved with zip ties and mounts.

I'm thinking maybe this is just potentially a faulty BMS, no rhyme or reason since there isn't a lot of people responding. I already ordered a replacement, will monitor and see what happens.

 

[GXMnow]

How far back did you look in the log? Mine logs everything and it fills up a fe pages pretty quick. I had to scroll back a bit to find the faults. The time stamp on my unit is just the time since it was first powered up. I had to look at the current run time to get an idea how far back I had to go. If you are not seeing a shut down in the log, something is very odd.

Other than the sense lead failure my JK-BMS has been rock solid for almost 5 years. The balance lead connector as plugged in nice and tight and showed no signs of an issue at all. But it was reporting cells net to each other as going to a very low voltage. I think the wire may have been crimped mostly on the insulation. Since I am only running 14S on a 24S capable unit, i just ued one of the other pin and moved it over in the connector and it ha been working perfectly ever since.

 

[hb48]

The shutdown shows but nothing else is indicated as to why it is shutting down. There is not other errors or indicators of the fault. I'm again unsure of the behavior. There isn't a lot of data to gleen from the logs to point to a root cause.

Might be a fluke one off problem possibly with an intermittent internal IC causing an issue. Hard to say at this point.

I confirmed the cell reporting was perfectly normal when it was in this condition. It is not a case where the cells were out of whack or even miss-reporting the voltages. It was perfectly normal other than the fact it decided to just stop charging and discharging for what ever reason.