Overcurrent protection element and battery system

A battery system comprising:

• a plurality of battery cells;
• metal plate bus bars fixed to electrode terminals of the plurality of battery cells and connecting the plurality of battery cells to one another;
• and
• a voltage detection circuit connected to the metal plate bus bars via voltage detection lines including overcurrent protection elements, wherein
• each of the overcurrent protection elements includes:
• a chip fuse;
• a printed circuit board on which the chip fuse is surface mounted;
• an external connection part coupled to the printed circuit board;
• and
• an insulating layer provided on the printed circuit board,
• the printed circuit board is provided with a conductive part on a surface of an insulating substrate,
• the external connection part is partially placed on and electrically connected to the conductive part of the printed circuit board,
• one end of the external connection part extends out of the printed circuit board
• the chip fuse is surface mounted on and electrically connected to the conductive part,
• the chip fuse is electrically connected to the external connection part via the conductive part, and
• the external connection part is connected to each respective voltage detection line;
• wherein the insulating layer is an insulating plastic molded body coupled to a surface of the printed circuit board;
• wherein the insulating plastic molded body includes an opening window that exposes the chip fuse, and the opening window is covered with an insulating material;
• wherein the insulating plastic molded body includes a holding portion of the external connection part;
• and
• wherein the holder portion of the external connection parts includes holding protrusions protruding toward each other.