[MetalMan]

A "P" cell can not go out of balance. Like Brian said, a low "P" cell would drag the others with it.

Going with "P" cells might be for several reasons:
-cheaper to go with more cells than a single cell (cost decreases when quantity increases)
-increased capacity where no larger cells have a form factor that will work
-form factor of smaller cells is good, but capacity/discharge rate isn't enough