JK Inverter BMS, short? No longer detects cell 8 & 9...

[Martijn]

Well then... I was assembling my 16S battery and as per instructions (also see here), I left cell 8 on the 3rd plug disconnected and rolled up the wire, zip-tied it into a bundle. It did have a ring terminal crimped to it.

Test start: the battery worked, yay!

Shortly thereafter, I turned the battery OFF and starting clearing up the balance-wire mess mess and put them into the ducts. So I started pulling a wire here and there and suddenly, I saw a small "zapp!" at the BMS connectors for the balance wires.

Crap.

Turned on the BMS and ... cell 8 & 9 are no longer detected.

I think the exposed ring terminal for 3rd plug cell 8 touched something, possible the BMS minus, and that caused the spark. I'm not sure. If that was the case, the lesson is to cut off that wire if you don't use it.

Removed the side covers of the BMS to see if I could see something burned, checked both sides, nothing to see...

Anyone got a clue?

Is there continuity from this ring connector to the corresponding pin on the connector?

Yes.

 

[MisterSandals]

for 3rd plug cell 8 touched something,

Is there continuity from this ring connector to the corresponding pin on the connector?

 

[kommando]

Likely you have blown the resistor in the balance wire circuit on the board in the BMS.

A long read including the linked threads in the thread.

Thread 'JK BMS Cell Count Problem on B2A24S20P'

Mar 11, 2023

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?

• dakamalu
• Replies: 99
• Forum: BMS (Battery Managment Systems)

It is also a common issue on the JK PB BMS which uses the same resistor that acts like a fuse, one resistor takes out 2 cells.

Another thread with less reading required

K

Thread 'Dead cell sample lines on JKBMS JK-B2A24S JK-BMS >> FIXED'

Mar 14, 2024

I have bought 5 of these JK-B2A24S active balancers over the past 3 years. JKBMS. Rather happy until one just broke itself.
It shows me '--' for the cell voltage on cell 1 and cell 2, the rest are all fine.
This condition triggers the CELL COUNT IS NOT EQUAL message and so the balancer has disabled itself.
There is no way to workaround 0.00 at cell 1 or 2.
There are correct voltage right down the pins on the module, cells are fine, just erroneous sample inside black module.
When I fetch data on bluetooth it shows all good except 1 and 2.

JK bad --
Fri, 08 Mar 2024 04:58:25 DEBUG JKBMS...

• keepsake
• Replies: 28
• Forum: BMS (Battery Managment Systems)

 

[Martijn]

Is there continuity from this ring connector to the corresponding pin on the connector?

Yes.

 

[Martijn]

Likely you have blown the resistor in the balance wire circuit on the board in the BMS.

A long read including the linked threads in the thread.

Thread 'JK BMS Cell Count Problem on B2A24S20P'

Mar 11, 2023

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?

• dakamalu
• Replies: 99
• Forum: BMS (Battery Managment Systems)

It is also a common issue on the JK PB BMS which uses the same resistor that acts like a fuse, one resistor takes out 2 cells.

I read through this thread and noticed a photo by @upnorthandpersonal --

Here's a photo I took after taking another good look. Looks awfully similar... but dang, these things are soooooooo small.

 

[upnorthandpersonal]

Yep, those are definitely bad. A fine tipped soldering iron and some flux and copper desolder braid should do to replace them if you don't have access to an SMD rework station.

 

[Martijn]

Yep, those are definitely bad. A fine tipped soldering iron and some flux should do to replace them.

I have some experience in soldering, but these are way too small for me...

 

[upnorthandpersonal]

I have some experience in soldering, but these are way too small for me...

I could replace them - mind sending it to Finland?

 

[Martijn]

I could replace them - mind sending it to Finland?

I'm sure that will cost me less than getting a new unit (Euro 120 or so). Let me know what you want me to do!

 

[upnorthandpersonal]

I'll send you a PM.

 

[Martijn]

Installed the fixed BMS Yesterday, all cells appear in the app again and it appears to work fine!

Many thanks to @upnorthandpersonal