The BMS adapter from BigBattery consists of two parts. One is an adapter PCB which converts the socket from the battery pack to 9-pin 2.54mm JST male connector. The second part is the 8-wire cell balance lead cable, one end is 9-pin 2.54mm JST female connector and another end is a 8-pin 1.5mm JST female connector. Yes, the cable has only 8 wires from the positive of 8 cells. no the negative lead wire. I guess the BigBattery's 130A BMS don't need the it as it already has one from battery negative. The adapter PCB does expose the negative, so I made my own 9-wire balance lead wire cable with 9-pin 2.54mm JST female connectors both both end.
BTW, I use the overkill 24V 100A BMS.