Help paralleling JBD-AP21S002 7-21S 300A BMS

[Aabshir]

quick over view of my system.

2 packs each contains 2p16s 280a LFP. Total of 62 cells.

Each set has brand new JBD JBD-AP21S002 7-21S 300A BMS. Individually they work like a charm.

I have two bus bars way too oversized for this but when I parallel these BMS one doesn’t get charged only one does. Eg. If I turn the first one off the second starts to get charged fine. Turn the first one back on. It senses the other BMS and it won’t get charged. It shows everything fine but won’t charge or discharge as long as the other BMS is doing something.

I can’t comprehend what is going on here. I am trying to balance and match the packs voltage one pack is 56.7 and the other is 56.8. Can that be the issue ?

Got these BMS from batteryhookup.

thank you so much for all the awesome things you guys do.

Ab.

 

[Aabshir]

Not a single response ? Where is Steve ? . Just emailed batteryhookup about this too. You’re suggestions are greatly appreciated

 

[ChrisG]

Are both packs at the same voltage? Could one overrun the other with current and it’s going into protection?

 

[42OhmsPA]

Something doesn't add up. Can you post more photos and screenshots of your settings?
I'm running 3 smart JBDs in parallel.
If I remember correctly I had to isolate each one with a charge to get them to work.

Edit Found post.

 

[MisterSandals]

I'd like to see a pic of how these are wired in parallel. The way they function should not change individual or parallel.

 

[thedodgersonline]

Hi
I have just discovered from LLT ( the manufacturers) that their BMS cannot be wired in parallel. I cannot get any sort of technical reason - just NO - sorry - not allowed etc.
THis might be your problem.
Just had a look at the technical spec sheet and parallel function is not allowed.

Looking ta the dates this is very old news but might help someone.

 

[42OhmsPA]

Hi
I have just discovered from LLT ( the manufacturers) that their BMS cannot be wired in parallel. I cannot get any sort of technical reason - just NO - sorry - not allowed etc.
THis might be your problem.
Just had a look at the technical spec sheet and parallel function is not allowed.

Looking ta the dates this is very old news but might help someone.

View attachment 200345

That's baloney. 3 in parallel here and I'll be adding more.

 

[MisterSandals]

I have just discovered from LLT ( the manufacturers) that their BMS cannot be wired in parallel.

So what exactly did you ask? Is it possible that they misunderstood your question?

That's baloney. 3 in parallel here and I'll be adding more.

Agreed, baloney. I have 2 working in parallel and never read or heard anything that paralleling was not allowed.

 

[upnorthandpersonal]

but when I parallel these BMS one doesn’t get charged only one does. Eg. If I turn the first one off the second starts to get charged fine. Turn the first one back on. It senses the other BMS and it won’t get charged. It shows everything fine but won’t charge or discharge as long as the other BMS is doing something.

That doesn't make sense. The BMS can't sense anything since they're separate packs for all intends and purposes, just happened to be connected to the same bus bars. There is nothing to sense.

Are you sure both packs are at the same state of charge though? Internal resistance can be different at different states of charge (and same voltage), meaning the one with the lower internal resistance will draw more current. If one pack is at 80%, and the other at 40%, the 40% one will pull most, if not all, of the current.