An electrical energy generator that converts kinetic energy harvested from voluntary motor activity of a human or animal to electrical energy. The electrical energy generator includes a housing, a coil of electrically conductive material, a reciprocally movable electromagnetically active mass, springs connecting the mass to either the housing or to adjustment means engaged with said housing, and, optionally, means for constraining non-linear motion of the electromagnetically active mass, and/or means of mitigating motion retardation of the electromagnetically active mass within any existing housing atmosphere. The electrical energy generator may be associated with a carried item, such as a backpack.