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21s BMS?

wbwoodward

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Joined
Nov 30, 2020
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I ordered an 8s 120 amp JBD BMS from Aliexpress for a 24v battery build. What I received was a BMS that said 21s(?) 120 amp and had a 15-wire balance lead connector. Will this work with with an 8s configuration? Pardon my ignorance if this is an elementary question. I started a dispute to get a return and refund and the seller refused and replied "The label describes a fixed attribute, and the version purchased by the buyer is only one of the various attributes, which is the relationship between inclusion and inclusion, and the order is sent according to the buyer's purchase requirements." I think something is lost in translation. I have yet to reply but I wanted to make sure if I was correct in my thinking.

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Did you get the manual? It should show how to wire it. The store page shows it supports 6S to 21S. You do not need to have the number of wires match the number of cells you are using. With other BMS's the extra wires are simply left unconnected except for very last one which in your case would be connected to the 8th cell as well but would double check in manual and/or wait for someone with one to reply.. but at least you shouldn't worry about "getting the wrong one" since that one should work.
 
Did you get the manual? It should show how to wire it. The store page shows it supports 6S to 21S. You do not need to have the number of wires match the number of cells you are using. With other BMS's the extra wires are simply left unconnected except for very last one which in your case would be connected to the 8th cell as well but would double check in manual and/or wait for someone with one to reply.. but at least you shouldn't worry about "getting the wrong one" since that one should work.
There was no manual or instructions of any kind. I'm worried that if some wires are not connected they may be read as 0 voltage and that would mess up the charging(?).
 
I just recently the same 21s BMS but only need 18s. What did you do with the extra balance leads?
 
I just recently the same 21s BMS but only need 18s. What did you do with the extra balance leads?

See this thread. Looks like they all get tied to the negative of the last # cell of the pack.

 
I finally was able to open the wiring diagram file from JBD website, it shows it a little different and now showing all 18 cells correctly.
 
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