Battery design
Battery design starts with the load.
A useful pack concept begins with the watts the system needs, the runtime target and the voltage range the electronics can accept.
Define the job
Start with peak load, continuous load, startup current and duty cycle before choosing cells.
Choose topology
Series groups set voltage. Parallel groups set capacity and current sharing.
Add protection
BMS current rating, fusing, temperature sensing and switching are part of the first concept, not an afterthought.