The battery unit ( 1 ) includes a flat battery ( 2 ) having a cylindrical positive electrode can ( 10 ) with a bottom and a cylindrical negative electrode can ( 20 ) with a bottom that covers an opening side of the positive electrode can and having a side wall of the positive electrode can on the opening side fitted to an outer circumferential surface of a side wall of the negative electrode can and a substrate ( 61 ) provided on a flat surface of one of the negative electrode can and the positive electrode can and mounted with circuit components ( 62 ) thereon. The other of the negative electrode can and the positive electrode can that has a flat surface on an opposite side to the substrate in a thickness-wise direction of the flat battery serves as an external terminal for one of a positive electrode and a negative electrode.
1. A battery unit used as a power source for a device comprising terminals, the battery unit comprising:
a coin shaped flat battery having a cylindrical positive electrode exterior can with a bottom and a cylindrical negative electrode sealing can with a bottom that covers an opening of the positive electrode exterior can, the open end of a side wall of the positive electrode exterior can being fitted on an outer circumferential surface of a side wall of the negative electrode sealing can; and
a single substrate layered above the flat battery and provided on a side of the negative electrode sealing can, the substrate having a circular disc shape,
the substrate having:
a circuit component mounted on an inner surface of the substrate facing to the negative electrode sealing can; and
a ground external terminal formed on an outer surface of the substrate opposite to the inner surface and electrically connected to the negative electrode sealing can, and
wherein the positive electrode exterior and the negative external terminal are adapted to respectively contact to the terminals of the device.
2. The battery unit according to claim 1 , wherein
the flat battery has a protrusion formed by the negative electrode sealing can that protrudes with respect to the positive electrode exterior can, and
the substrate is provided with a projection corresponding to the protrusion of the flat battery on the outer surface.
3. The battery unit according to claim 1 , further comprising an exterior member used to cover circumferences of the substrate and the negative electrode sealing can while a circumference of the positive electrode exterior can is exposed.
4. The battery unit according to claim 1 , further comprising a spacer provided between the substrate and the negative electrode sealing can,
at least a part of the spacer being made of an anisotropic conductive material that can electrically connect the substrate and the negative electrode sealing can and can electrically insulate the flat surface in planar direction.
5. The battery unit according to claim 1 , further comprising a tube used to cover circumferences of the substrate and the negative electrode sealing can while a circumference of the positive electrode exterior can is exposed.