BMS wiring mistake?

[Pat911]

Should be the same, but limited to 20 cells. The one I’m using can handle up to 24 cells.

[MDLNB]

Originally Posted by Pat911

Should be the same, but limited to 20 cells. The one I’m using can handle up to 24 cells.

Thanks.

[MDLNB]

Ok, so I ordered my JK BMS from AliExpress on 21 May and received it today! I had no idea that the shipping would be that fast; five days?
So, now I have to swap it out from the Daly BMS and test it out. Guess I will have to wait until next week, since we have family in for the holiday weekend.

[Pat911]

That was really fast!

[MDLNB]

One thing different between the Daly and the JK BMS is that the JK requires me to use the second ribbon type cable just for the extra data wire to the pack positive. Kind of strange. Or am I looking at it wrong? It doesn't make any sense to me, but I will just follow the diagram instructions. I also have to purchase four 7ga wire ring terminals for the P and B wires coming off the BMS. It would have been nice if they had thought to put those on the wire ends.
BTW, I used the golf cart yesterday with the DALY BMS and it did not act up. Of course, it was a short trip, with one stop (other than stop signs). I still get the feeling that it has something to do with the regen. I have to get used to the regen kicking in at about half pedal. My old Club Car did not have regen and ran great. My wife doesn't mind the regen so I am leaving it functioning.

[Pat911]

You’re reading the diagram correctly. The very last wire is used to power the BMS with the pack positive power. There’s a seperate wire to sense the highest cell voltage and will connect to pack positive. Join them at the cell terminal, don’t be tempted to combine them and use a single wire.

This seems like doubling up but there’s a reason for it. The sense wire is used to measure the cell voltage and to supply/draw up to 2A of active balance current. This could be done with one wire but the voltage drop caused during the 2A current movement could interfere with the supply voltage. Also, the current drawn in the power wire, although minimal, could interfere with the voltage sense.

Many BMS’s combine the two, but it’s better to keep them seperate.

[Volt_Ampere]

Separate wire for voltage sense is critical to get accurate cell readings. Yes - they draw current through it during balancing but good designs turn off the Balance current when measuring the cell voltages. (to avoid voltage drop on the sense wires) My design balances for 10 seconds, turns off the current, takes a voltage reading, turns balance current back on.

[MDLNB]

Glad you mentioned that, because I was getting ready to combine the two wires. Thanks.