The safety is ensured in such a manner that with an abnormality detection system of a secondary battery, abnormality of a secondary battery is detected, for example, a phenomenon that lowers the safety of the secondary battery is detected early, and a user is warned or the use of the secondary battery is stopped. The abnormality detection system of the secondary battery determines whether the temperature of the secondary battery is within a temperature range in which normal operation can be performed on the basis of temperature data obtained with a temperature sensor. In the case where the temperature of the secondary battery is high, a cooling device is driven by a control signal from the abnormality detection system of the secondary battery. The abnormality detection system of the secondary battery includes at least a memory means. The memory means has a function of holding an analog signal and includes a transistor using an oxide semiconductor for a semiconductor layer.