An energy distribution system and methods for coupling a plurality of energy storage cells to an energy source or load by replaceable insertion of a segment within a magnetic circuit common to the cells. An energy storage cell interface couples each of the cells to the source or load, and a separate power converter is coupled through the interface to each one of the energy storage cells. The energy distribution system has a magnetic core containing a magnetic circuit shared among multiple windings, where the magnetic core includes a detachable segment replaceably insertable into the magnetic circuit.