For information, I used isolated plugs, to be able to easily separate the BLOCK BMS from the battery packs, but this is not mandatory.
The only focus of this step is at the switch.
Indeed in order to simplify the power as much as possible, this one is at 3 positions, the closed circuit is either the recharge or the power, but not both simultaneously. It should be noted that the circuit is interrupted by upstream of the control stepdown. The BMS will always be energized.
The consequence is that it is necessary to ensure that the wire from the BMS P is connected to the plug in the center of the switch. The wire that goes to the stepdown to the in-regulator since is connected to the plug located on the side of the number 1 of the switch button
The P- is connected directly to the in-entry of the regulator.
The BMS is attached to the block with hot glue.