JK BMS abnormal balance wires resistance

[nazcord]

Hello!

I've got a new JK BMS B2A8S20P to use with my 4 x EVE MB31 batts but now I have some issues with balancing wires. After first start of BMS everything looked fine and it showed 0.053-0.054 resistance for all 4 wires, also it started balancing after 0.01V diff as expected during the charge. After reaching OVP the charging was stopped so everything was flowing normal. Next time I switched on the BMS I noticed the alarm "Abnormal resistance of the balance wire" and the value 0 for all of them. I've tried to restart BMS few times, reconnected wires bar, fully disconnected BMS from batteries but no success so far. Any clue what could be the reason and how to fix it? The BMS is totally new.

 

[littleharbor2]

Were you ever able to work this out?

 

[yur43]

Any clue what could be the reason and how to fix it? The BMS is totally new.

Greetings.
These are the control parameters of the balancing wires. After all, with a broken wire, the BMS will not be able to protect the cell, because it cannot see its voltage.
Perhaps BMS falls into an error, from which it is necessary to exit manually. Holding the button for 3 seconds will turn off the BMS. Then turn it back on.
Check the balancing wires, the first time I had a bad clamp on several wires at once. After patching and restarting everything was fine.

 

[nazcord]

Were you ever able to work this out?

no, still having this issue. I guess something wrong on hardware level but I’m not an expert to check it

 

[upnorthandpersonal]

Most likely burnt resistors on the balancing inputs (they act as a fuse). Some others had this when they had balancing on all the time at high currents. It's easy to fix by changing those resistors, but you need to be able to solder SMD (not the hardest thing to do really). Still strange that all 4 would be broken, but it's possible. See if you can take a picture: open the BMS, take a close up of the PCB close to the balance connector.

 

[nazcord]

Most likely burnt resistors on the balancing inputs (they act as a fuse). Some others had this when they had balancing on all the time at high currents. It's easy to fix by changing those resistors, but you need to be able to solder SMD (not the hardest thing to do really). Still strange that all 4 would be broken, but it's possible. See if you can take a picture: open the BMS, take a close up of the PCB close to the balance connector.

I opened the BMS and visually there is no evidence of something burnt

 

[nazcord]

Greetings.
These are the control parameters of the balancing wires. After all, with a broken wire, the BMS will not be able to protect the cell, because it cannot see its voltage.
Perhaps BMS falls into an error, from which it is necessary to exit manually. Holding the button for 3 seconds will turn off the BMS. Then turn it back on.
Check the balancing wires, the first time I had a bad clamp on several wires at once. After patching and restarting everything was fine.

I guess you didn't read my post attentively. There are no issues with voltage but with resistance. I compared voltage with multimeter and the values are correct. BMS is working fine except balancing because of invalid resistance metrics. I've also restarted BMS many times and disconnected it from batteries. Bad crimping is not the case as well

 

[upnorthandpersonal]

I opened the BMS and visually there is no evidence of something burnt

Yeah, looks fine from the pictures. It's also odd that all those values are 0.
I need to find one and open it up to check what the problem could be...

 

[Brearz]

I had zero resistance on all wires and missing voltage readings when I failed to realise it is ok for JK to use red wires as a negative B0 terminal and connected this to sense wire 1 cable. I am amazed it even worked but gave this error. I also fell into the B8 B8 trap.

If you have not found the error might be worth checking B0 connection is OK

 

[nazcord]

I had zero resistance on all wires and missing voltage readings when I failed to realise it is ok for JK to use red wires as a negative B0 terminal and connected this to sense wire 1 cable. I am amazed it even worked but gave this error. I also fell into the B8 B8 trap.

If you have not found the error might be worth checking B0 connection is OK

I don’t have issues with voltage readings

 

[Hedges]

People have mentioned balance lead connectors not making contact. Might have been a pin not fully inserted in shell of plug, or bad crimp.

I'd like to check resistance from end of lead to pins of connector on PCB, but with conformal coat may be difficult to contact. Try with a sharp probe.

Also make sure connectors are fully inserted.

 

[wanek]

I don’t have issues with voltage readings

Hi!

I had the exact same problem what you described, correct voltage values but error for resistance of wires after a few months use.

I made several test, the misleading thing in the app, when this error occures is that it displays 0.000R resistance value (which of course in real life is impossible). But actually they want to say that the resistance of the wires are too big, (not 0.000R) this is why throws the error.

So, what happens, the bms CAN meausre the voltage (because high resistance does not influence the correct voltage reading), but CAN NOT initialise the balancing algorithm - where current has to flow on the wire, because of high resistance.

My sugestion is, redo the wireing without extending the original red wires, and without adding any extra connectors to the system. I have 2023 kia niro battery pack, and what mistake I did, to use the original factory connectors on the battery modules, which for some reason caused imperfect connection and too high resistance on some cells... After all, I give up using the original connectors, opened the plastic cap on the top and soldered each bms wire directly to the cells. It is not very elegant, but super efficient. This way from the initial 0.250~0.300R resistance it went down to 0.055-0.060R, and the bms can balance at 2.0A without any issues.
In my opinion, none of the bms wires should have more than 0.08R, if it is anything higher, then there is a bad connection somwhere.

 

[nazcord]

Hi!

I had the exact same problem what you described, correct voltage values but error for resistance of wires after a few months use.

I made several test, the misleading thing in the app, when this error occures is that it displays 0.000R resistance value (which of course in real life is impossible). But actually they want to say that the resistance of the wires are too big, (not 0.000R) this is why throws the error.

So, what happens, the bms CAN meausre the voltage (because high resistance does not influence the correct voltage reading), but CAN NOT initialise the balancing algorithm - where current has to flow on the wire, because of high resistance.

My sugestion is, redo the wireing without extending the original red wires, and without adding any extra connectors to the system. I have 2023 kia niro battery pack, and what mistake I did, to use the original factory connectors on the battery modules, which for some reason caused imperfect connection and too high resistance on some cells... After all, I give up using the original connectors, opened the plastic cap on the top and soldered each bms wire directly to the cells. It is not very elegant, but super efficient. This way from the initial 0.250~0.300R resistance it went down to 0.055-0.060R, and the bms can balance at 2.0A without any issues.
In my opinion, none of the bms wires should have more than 0.08R, if it is anything higher, then there is a bad connection somwhere.

Hi! Thanks for sharing your experience but not sure it is my case. At initial BMS start I had 0.053-0.054R on all wires so it is strange that resistance might go up without any further impact. Also I recrimped the wires once and have no effect. May be I will try to recrimp them with soldering but I'm pretty sure it is not the crimping issue because I used to do the same "cold" crimping with the same connectors for other JKBMS setups and everything is working perfectly. I would say it is rather this particular BMS hardware issue. For now I use external balancer as a workaround

 

[wanek]

If you have an extra bms at hand, you can try to swap with the "faulty" one, using the same wires, see if it makes any difference.

 

[Roman59]

Hi! Thanks for sharing your experience but not sure it is my case. At initial BMS start I had 0.053-0.054R on all wires so it is strange that resistance might go up without any further impact. Also I recrimped the wires once and have no effect. May be I will try to recrimp them with soldering but I'm pretty sure it is not the crimping issue because I used to do the same "cold" crimping with the same connectors for other JKBMS setups and everything is working perfectly. I would say it is rather this particular BMS hardware issue. For now I use external balancer as a workaround

I have the same problem that you have and I haven't found a solution...I ask you...what external balancer did you use? Could you be more specific?...thanks

 

[nazcord]

I have the same problem that you have and I haven't found a solution...I ask you...what external balancer did you use? Could you be more specific?...thanks

Daly 5A active balancer

 

[nazcord]

If you have an extra bms at hand, you can try to swap with the "faulty" one, using the same wires, see if it makes any difference.

just got one more BMS and swapped it so I can confirm it is BMS issue and not the wires. New BMS works fine with old wires and shows resistance values