To provide an abnormality warning device in a lithium ion secondary battery for detecting abnormality with a sensor before the lithium ion secondary battery becomes an unusable state when the abnormality is produced in the lithium secondary battery, and capable of warning the abnormality to the outside.

This device has an abnormality detecting sensor for detecting abnormality when the abnormality is produced in a lithium ion secondary battery 4a, a warning device for sending out a warning, and a control means which receives a signal from the abnormality detecting sensor when the abnormality detecting sensor detects the abnormality and sends out a warning to the warning device before a specified time the lithium ion secondary battery 4a reaches a state not capable of supplying power. A plurality of lithium ion secondary batteries 4a are used. As the abnormality detecting sensor, a temperature sensor 5a, a pressure sensor 8, an organic substance sensor, an odor sensor, or a conductivity sensor is suitably used according to application. As the warning device, an alarm 3 is preferable. As an electric appliance, medical equipment is suitable.