Battery pack

A battery pack comprises a battery and a flexible printed circuit board (FPC) utilized to detect a voltage and a temperature of the battery. The FPC comprises a substrate having a front surface and a back surface, a thermistor which detects a temperature of the battery, temperature detection lines and voltage detection lines. The temperature detection lines are electrically connected to a thermistor and arranged between the back surface and the battery. The voltage detection lines are arranged on the front surface so as to overlap the temperature detection lines in a case that the FPC is observed in a plane view in a transmissive manner from a back surface to a front surface.