I'm starting to layout the hardware for the phone client including power system. This is my first time at setting up a multi-cell LI ion, 4s, battery pack. The BMS has no documentation, so learning is slow. I'm debating weather to remove the per cell bms, since its duplicated on the 4s bms and one bms has failed during my troubleshooting.

Update: The wiring "instructions" for the BMS was practically non-existent, unclear and/ or wrong. Someone on the Amazon product page in the comments section kindly provided a screenshot of the correct wiring of the BMS and now I can move forward with powering things from the battery pack.