A pencil sharpener is a device for sharpening a pencil's writing point by shaving away its worn surface. Battery Powered Electric pencil sharpeners work on the same principle as mechanical ones, but the cylindrical cutters are rotated rapidly by an electric motor, speeding up the sharpening process. Battery Powered Electric Pencil Sharpeners are very popular because they are portable, where as with a traditional electric pencil sharpener you are limited to where there is an electrical outlet.