No negative for bms to connect too? 60V lifepo4 from Jag35

[Quinc]

Hey all, I bought this battery from Jag for a Razor mx build. Wiring in the bms and I found there is no negative. The black wires all show 1v and are POS. red wires are what you would expect. Any ideas? Is the bms neg wire meant to be connected to main NEG connection coming out of the battery?

*Picture from jag website:

 

[fechter]

What do the black wires connect to inside the pack?
Typical BMS would have a B- connection that goes to the main negative wire from the cells.

 

[floydr]

I suspect the black wires are temperature sensors.The red wires are your balance leads with the two black wires in the red wires is the most negative. least all the battery packs I have seen use that color code. See the single black wire exiting the pack that is your most negative.
Further down the battery page you will see the pin out of the red wires and black wires
Later floyd

 

[docw009]

Here is what Lloyd is talking about. The connector picture suggests that the two end pins are NU, not used. That would leave the 19 red wires and one black wire, although the picture shows 2 blacks. Could be that the harness is wired different from this side.

They better not be "POS 1V" You will start at one end and find the first one at 3V referenced to ground (Black). Every succeeding wire will go up 3V until you get close to 60V.

 

[floydr]

I would first use the main negative (the single black large Gauge wire) to find the voltages of the red wires ~3.2| 6.4| 9.6|12.8|16|19.2| 22.4| 25.6| 28.8| 32| 35.2| 38.4| 41.6| 44.8| 48| 51.2| 54.4| 57.6| 60.8 Volts then one of the remaining wire has to be the most negative. To test which wire of the remaining wires is the negative check each wire with the negative lead and positive lead on ~3.2V wire.
Later Floyd

 

[Quinc]

Thank you all for the help! I took the battery apart and the black wires had pulled out of the connector on the board.. Shoved them back in and now the two little black wires work.. Not sure how this happened. They are all twisted together, zip tied and glued..