battery pack core 10 inside the cavity 31 of the mold 30 and injecting molten synthetic resin into the mold cavity 31 to insert mold one part of the battery pack core 10 in the molded resin region 1 the battery pack core 10 is made up of a battery 2 an insulating cover 4 that is disposed in a position opposite the exhaust outlet 13 of the safety valve 12 established on the battery 2 and that also serves to insulate the lead plate 5 from the battery 2 a lead plate 5 disposed on the insulating cover 4 and a circuit board 3 disposed on the lead plates 5 and connected to the lead plates 5 the battery 2 is a lithium ion battery however the battery can be any rechargeable battery such as a nickel hydride battery or nickel cadmium battery instead of a lithium ion battery in the battery pack of the figures the battery is a thin outline battery a thin outline battery is shaped with curved surfaces on both sides and the four corner regions of the external case have rounded edges if a lithium ion battery is used as the thin outline battery charge capacity can be increased for a given battery pack volume as shown in fig2 and 3 this battery 2 is provided with a safety valve 12 on the sealing cap 11 which has the protruding electrode 2 b this battery 2 is provided with a protruding electrode 2 b in the center region of the sealing cap 11 and is provided with a safety.