JK BMS problem, not balancing due to high resistance in balance cables

AngeleToR

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Joined
Nov 28, 2021
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6
Good evening!!!

I'm having a problem with the JK BMS's i've got for my batteries. As I told in my intro, I own several VW iD3/iD4 batteries to power my whole house even for weeks (as long as I don't charge the cars, of course).

These 12S Li-Ion batteries I have are the best thing I can think of, with no balancing and after 6 months working, the ones I have monitored are showing ONLY 0,010V of maximum voltage delta between cells, with 0,007 being the most common values found.

The balancing connector for the batteries uses a flat cable internally, with one small SMD fuse for each of the 13 wires. The batteries are very very well built and enclosed, and I don't want to open them to improve that flat cabling, as the charging currents I need are really low, and if that flat cable is enough for the batteries inside a car, for my home application where my batteries work almost idle compared to the demand of a car it should be more than enough,

The problem is that the BMS, a JK one 17S, 60A dis/charge and 0,6A balance current (BD6A17S6P) is showing an error indicating that the resistance in the balance wiring is too high and the balancing function is not usable. I've got values ranging from 0,45ohms up to 0,58ohms. I'm sure it is because of the flat wiring and the integrated fuse, but I've seen videos where other guys have similar impedances in their balance wiring and have not this error.

I've tried to contact the manufacturer to no avail, so I beg to the community knowledge to see if any of you has had this problem or any similar and has been able to solve it, or has any idea on how to deal with ir or what to try.

One thing I've tried is to manually enter the value showed in yellow in the advanced configuration page of the BMS, and then it starts acting weird, starting to balance but after a few seconds it fails, disconnecting even the battery completely for a second and the reconnecting in an endless loop. When I've done that the voltage offset inside of the battery also worsens, instead of improving, so I'm just scratching my head on this...

Attached you can see screenshots of what I'm telling and a little video showing that bizarre behavior when I manually set the impedance values...

Hope it helps

Regards

Angel

P.S: I don' see how to add a video, so here are some screenshots until I find out

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Resistance - to reduce resistance can you 1) shorten the balance wiring or 2) make it thicker wire? (I know - obvious suggestions but its all I've got)

I use Batrium w/longmons, the longmons (the actual balance hardware) are close to the packs and its the network loop that spans the distance from those to the WM4 controller - could you consider a different BMS?

I agree that healthy packs don't need much balance. I have 84 packs @ 260ah each and they've only diverged an extra 20mv since the last balance touch-up on March 2021 (8 months ago). See the pic below for this morning's view. However, balance capability is good to have when expanding a battery bank and for occasional touchups.
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Thanks for the tips and the info about your pack. It eases my mind to know it, as I have not yet been able to setup the BMS's in every battery module.

About the wiring, I'm using the wires that brought the BMS, shortened in half almost. Apart os that there is very little I can do without disassembling each and every battery module, and to do that I have to cut the top soldering with a very big risk of damaging the battery. I believe my problem is the internal wiring in the module, as I said it's a flat ribbon with one SMD fuse for every cable, that's the reason for the high resistance I'm afraid.

My only hope is being able to 'tell' the balancer to work with the 0,6 ohms maximum impedance I've found in my cables.

Oh, about using other BMS system, I've been looking into it for months, checked batrium of course but for the huge amount of batteries I have it was a HUGE investment, almost as expensive as the batteries I'm trying to protect, and the JK BMS are way more powerful and completely decentralized, but I have to tinker a little more to connect it to grafana or make it balance my batteries... But in terms of protection, whoa the setup is amazing!!!!
 
Looks like you have several problems, First image " cell count is not equal to settings", second and third image "sample wire resistance too large". double check the balance wire connections between the BD6A17S6P wire loom and the VW iD3/iD4 balance connectors. Loose connections equal increased resistance?
Later floyd
 
Hi did you find any solution ? I have same issue .. JK BMS and ID3/ID4 li-ion battery pack.

What's does not make sense to me why BMS is not balancing. I was trying to decrease balancing voltage but wasn't helpful.

What I found that resistance is there due to fuses which are installed in battery pack and those cannot be removed without damaging the battery pack.
 
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Let me say it the hard way.... I cannot think of A good solution for your Problem.
The list what you cannot do ist endless, and i say nothing about it.

Thats what i wanted to write. And Just when i wrote the above, i had one.

Dont Beat me... it is simple.

Build a 12s2p, as example, from good 18650 cells. Put it parallel to the id3. Make suitable wires from the JK to the pack, and from there to the id3 you can go lenient.
That should fix the problem and Work.
 
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No results ?
 
No results ?
Many thanks for your answer and help!

Not yet. I asked ali seller about support to change some threshold or something like that but no success.

And buy some 12s2p will cost me almost same then different BMS which does not have this issue :(
 
Hi guys!

I have the same issue with BMS (B1A20S15P) (I hope so it's a BMS issue and not a battery problem).
Yesterday I did a setup with PowMr hybrid solar inverter (POW-HPM5.6KW) and VW Module 12S - 6.85kWh / 156Ah / 44V (battery info).

So when I ran the BMS and got this message (check the screenshot please). The shop where I bought the battery said it's a 100% BMS issue. They don't know how to solve it with the affected BMS yet. But they had a similar situation and BMS replacement was an effective solution.

But I would love to ask you guys, maybe you can know how to solve this issue without BMS replacement? I ordered it from aliexpress and it's to long wait for it, and if buy it locally in Ukraine it cost x2 (200$).

Thanks for any help!
Much appreciate it
 

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Maybe look for a setting about wire resistance in the BMS?
Maybe look for a setting to reduce the balance current so it doesn't trigger the wire resistance issue?
(If any of these can be found?)
 
Hi all!

Already managed, cropped a wire, and did the soldering again. All issues were run away)
 

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Hi all!

Already managed, cropped a wire, and did the soldering again. All issues were run away)
can you please show me how ? Some pictures ?

I did also cropped a wire and no luck.. I mean no change on resistance.

thanks
 
can you please show me how ? Some pictures ?

I did also cropped a wire and no luck.. I mean no change on resistance.

thanks
Sure, I did it like this (check the image). I also added how to make a connection between the battery and BMS. Make sure you choose the proper cable connector to the battery (the black one) because the brown one is not good for BMS. The brown doesn't have enough connectors inside.

Be aware, it works for my setup, you can check it on the top message of which kind of battery and BMS I have.
 

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thanks for the pictures! You did shorter also cables from the connnector. I did shorter only cables from the bms.

Will try, thanks again.
 
I did shorter both cable as much as possible and still no luck :( No diference in resistance
 

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greetings to all!
thanks to those who participated in the search for a solution to the problem!
faced the same problem, my jk bms jk-bd6a20s10p showed high resistance and refused to balance cells on vw id3/id4 battery.
I tried all the options, shortened the wires, tried twisting, soldering, but the resistance remained almost unchanged. I took jk bms jk-b1a20s15p from friends for testing, connected it to the same wires and the original chip as my bms and voila, the resistance was normal and the balancer worked.
So the problem is in a specific bms model, screenshots with versions in the attachment.
When I connected my bms back, 1 pin flew out on the battery connector. There were no options left but to open the battery, so I opened it from the side where there are no + and - terminals. I used a manual hacksaw for metal, sawed along the seam between the lid and the body, 3-4 mm deep. I soldered 1 pin to the soldering point of the original cable to the copper bus and what I saw 1 and 2 cells on my bms began to show normal resistance. I soldered every odd pin, the resistance on it and every subsequent even pin became normal, my bms worked. I hope this information will help someone and save time, money, nerves.
 

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Hi All!

So, after my "success" post about cutting wires reduced the resistance, it became high again.

I really have no idea why it happened. Maybe someone from your team can help me with ideas on how to fix it?

I thinking of buying the new BMS, but I'm really not sure if it helped or if it was ok previously.

I don't want to cut and open the battery (and connect wires from BMS directly), but if there are no other options okay.

Thx a lot!

P.S.

@ziporah sorry I did not see your message, Is it still actual for you?
 

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You didn't actually fix the issue as the values were at the limit's high.

Are these the original wires? How did you make the end-connectors ? Normally you should use a crimping tool with 0.5 wire and 6mm hole connectors.

It does not look like a bad general connectivity since the values are too close unless you used some very poor quality connectors. Can you post a pic ?

I get 0.051 to 0.052 per wire for my 300Ah pack while using a junk crimping tool.

A common omission is not putting the red power wire at the end + where the last BMS red wire is, but I don't remember the exact effect of that.

I don't use intermediary connectors since many times they are of extremely poor quality.
 
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