NOVELTY - The battery pack (100a) has a protective circuit module that is provided with a thermistor. A case (130a) is provided to accommodate bare cells and protective circuit module. The case is included with a mounting portion mounted with thermistor and rib portion. A separate space is formed between the mounting portion and bare cells. The rib portion is positioned in the separate space. A head portion is provided to sense temperature of bare cells. A connection portion is provided to transmit sensed temperature to protective circuit module.    USE - Battery pack used as power source in mobile electronic device such as cellular phone and notebook computer and medium- and large-sized apparatus such as electric motor tool, electric bicycle and automobile.    ADVANTAGE - The rib portion is mounted in separate space between mounting portion and bare cell, so as to prevent the thermistor from damaging by inserting head portion of thermistor into separate space. Thus, the mounting position of the thermistor is easily guided to manufacture battery pack more conveniently. The position of thermistor is exactly set, so that the head portion of the thermistor can measure the temperature of the bare cells more accurately and/or precisely. The circuit board is configured to block overcharging, overdischarging, short circuit and reverse voltage of the battery pack, so that the explosion, overheat and leakage of the battery pack are prevented and deterioration of charging/discharging characteristics is prevented. Thus, the degradation of electrical performance and abnormal operation are prevented. Hence the dangerous factors are eliminated and lifespan of the battery pack is prolonged efficiently. Thus, damage to the thermistor is prevented and the position of the thermistor is exactly set, so that the head portion of the thermistor can more accurately and/or precisely measure the temperature of the bare cells.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of the battery pack.    Battery pack (100a)    Separator connector (121)    Case (130a)