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

Announcement - Help us fight the BOTS! Please report all spam including stuff in your inbox!

AngeleToR

New member
Joined
Nov 28, 2021
Messages
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

20211111_214430000_iOS.jpg20211105_114027000_iOS.png20211112_094055000_iOS.png
 

OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
1,863
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.
1638113653133.png
 

AngeleToR

New member
Joined
Nov 28, 2021
Messages
6
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!!!!
 

floydR

Member
Joined
Aug 23, 2017
Messages
1,358
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
 
Top