A battery charger having fixed ends for winding and releasing wires includes a box; an immovable axis provided at an inner wall of the box; a large turning wheel having a larger diameter and a small turning wheel having a smaller diameter disposed next to the large turning wheel, wherein the large and small turning wheels have a same center orifice flexibly connected into the immovable axis; and a wire having one end thereof penetrated through a through hole provided at the inner wall and further connected to the circuit board and winded in the large and small wire storage grooves. A wire is efficiently collected in the box, and thus making the wire of the battery charger spaceless for ready storage.