A battery pack comprising: a battery ; a switching element (Q22, Q26) that is provided in a discharge path from the battery to an external load and that is configured to complete or interrupt the discharge path; a control circuit that is configured to operate by receiving a supply of an electric power from the battery , that is configured to generate a control signal to turn on the switching element (Q22, Q26) to allow an electric current to flow through the switching element (Q22, Q26) so as to allow discharge from the battery to the external load, and that is configured to interrupt the switching element (Q22, Q26) upon occurrence of an abnormality in the battery or the external load during the discharge so as to inhibit the discharge from the battery to the external load; and a protection circuit (24; Q2, R7, R8; 29, D5) that is configured to monitor an operating condition of the control circuit and that is configured to interrupt the switching element (Q22, Q26) when the control circuit is inoperative, characterized in that the control circuit comprises a second output port (P3) that is configured to have a specified electric potential during operation of the control circuit and that is configured to be in a floating state when the operation of the control circuit is stopped, and wherein the battery pack comprises a second protection circuit (Q2, R7, R8; 29, D5) as the protection circuit (24; Q2, R7, R8; 29, D5), the protection circuit (24; Q2, R7, R8; 29, D5) being configured such that when the second output port (P3) of the control circuit is in the floating state, the second protection circuit (Q2, R7, R8; 29, D5) determines that the control circuit is inoperative and interrupts the switching element (Q22, Q26). a battery ; a switching element (Q22, Q26) that is provided in a discharge path from the battery to an external load and that is configured to complete or interrupt the discharge path; a control circuit that is configured to operate by receiving a supply of an electric power from the battery , that is configured to generate a control signal to turn on the switching element (Q22, Q26) to allow an electric current to flow through the switching element (Q22, Q26) so as to allow discharge from the battery to the external load, and that is configured to interrupt the switching element (Q22, Q26) upon occurrence of an abnormality in the battery or the external load during the discharge so as to inhibit the discharge from the battery to the external load; and a protection circuit (24; Q2, R7, R8; 29, D5) that is configured to monitor an operating condition of the control circuit and that is configured to interrupt the switching element (Q22, Q26) when the control circuit is inoperative, characterized in that the control circuit comprises a second output port (P3) that is configured to have a specified electric potential during operation of the control circuit and that is configured to be in a floating state when the operation of the control circuit is stopped, and wherein the battery pack comprises a second protection circuit (Q2, R7, R8; 29, D5) as the protection circuit (24; Q2, R7, R8; 29, D5), the protection circuit (24; Q2, R7, R8; 29, D5) being configured such that when the second output port (P3) of the control circuit is in the floating state, the second protection circuit (Q2, R7, R8; 29, D5) determines that the control circuit is inoperative and interrupts the switching element (Q22, Q26). <EOS>