Abstract: The present disclosure provides systems for storing electrical energy. A system for storing energy comprises a plurality of separable energy storage devices that are operatively connected in series or parallel. Each energy storage device of the plurality comprises a housing that includes a magnet that generates a magnetic field, an armature coil that rotates relative to the magnetic field upon user movement of the housing or the armature coil, and an energy storage unit electrically coupled to the armature coil and adapted to store electrical energy generated upon rotation of the armature coil in the magnetic field.