Dead cell sample lines on JKBMS JK-B2A24S JK-BMS

[keepsake]

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 tot=49.87v low=0.0v high=3.326v delta=3.326v soc=None%
c1=0.0v c2=0.0v c3=3.325v c4=3.323v c5=3.323v c6=3.325v c7=3.325v c8=3.323v c9=3.325v
c10=3.325v c11=3.325v c12=3.325v c13=3.326v c14=3.325v c15=3.325v c16=3.325v c17=3.322v

below is when all was good ---
Wed, 29 Nov 2023 04:39:24 DEBUG JKBMS tot=56.78v low=3.336v high=3.348v delta=0.012v soc=85%
c1=3.348v c2=3.348v c3=3.347v c4=3.344v c5=3.338v c6=3.337v c7=3.338v c8=3.336v c9=3.338v
c10=3.338v c11=3.337v c12=3.336v c13=3.338v c14=3.338v c15=3.337v c16=3.337v c17=3.338v

Cannot find any way to get help or service.
It seems a firmware revision could allow this type of failure to workaround and use cells 3 and up in the process.

And yes my system has always had 17 cells in the bank.

 

[OffGridForGood]

Cell 1 and 2 both fail at the same time:
makes me wonder if one lead wire is no longer connected, messing up two calculations for cell 1 and cell 2
check the lead wire to pos end of cell 1/ neg end of cell 2 ?

 

[keepsake]

Voltages all there. I took a backup jkbms unit I have and it works fine and displays correctly with the existing harnesses.
So it's internal to the unit I pulled from service.

 

[OffGridForGood]

Voltages all there. I took a backup jkbms unit I have and it works fine and displays correctly with the existing harnesses.
So it's internal to the unit I pulled from service.

What would the cause be - that dropped out only two cells in a 16s ?

 

[keepsake]

These bms units pull and push up to 2 amps into a supercapacitor. Active balancing. That's their purpose in life. So the mosfets or other switching devices, failed. It's just a shame with the other 22 circuits apparently good, and I only need 17, there isn't a workaround to use the 'still good' remaining part of the device.

 

[keepsake]

Has anyone here had one of these fail and been able to get replaced or serviced ?

 

[keepsake]

JKBMS model JK-B2A24S
I am finding the seller 'useasy' on ebay WON'T HELP ME. I bought it from him six months ago, and it has the two broken inputs.
He claims to be acting as AGENT for the manufacturer and won't allow me to diagnose dead cell inputs with manuf.
Ebay itself blocks direct communications between buyer and seller and in the end, INHIBITS warranty activities.
HELLO EBAY -- you made your commission -- stop blocking direct communication.
Anybody with thoughts other than -- don't buy from China !

 

[ScrotusGobbleBottom]

I would look at the pins on the bad bms? I bent some of mine and then noticed and bent them back

 

[keepsake]

When I substitute another identical JKBMS unit it shows fine, just this one. It stopped correctly reporting while we were at sea, on a cruise for 9 days.

 

[ScrotusGobbleBottom]

When I substitute another identical JKBMS unit it shows fine

This would indicate a potential problem with the pins on the offending bms. The pins are on the BMS.

 

[kommando]

There is a resistor inline on the board sized to blow at a set amps, if you can solder smd components it can be fixed.

 

[ScrotusGobbleBottom]

There is a resistor inline on the board sized to blow at a set amps

This is great to know. Thank you.

 

[kommando]

Pic of the board I had fail on cells 8 and 9, you can see the capacitors and resistors in a row below the connectors. You will see one of the resistors is burnt out. I removed the resistor and on this board there was a spare next to it so I moved it across. For this board with 2A active balancing the resistor was a 1/16W 0.01 ohm resistor marked R01, this blows at 2.5A so for a board with no balancing, passive balancing or 1A active then it could be a different value.