Patent ID: 8685554

Claim:
A battery system comprising: a battery module that has a plurality of batteries which are provided with release portions each for releasing internal gas when an internal pressure is increased, and an exhaust portion which is provided with an opening portion and guides gas released from the release portions to the opening portion; a non-resettable switch element which is provided at a position where the guided gas passes in a vicinity of the opening portion, and is changed from a first state preset as one of an opened state and a closed state into a second state as the other one of the opened state and the closed state when a preset reference temperature or higher is reached; a high-temperature abnormality determination circuit which determines that the battery module has an abnormality when the switch element is in the second state; and a power supply which is provided separately from the battery module and outputs a voltage for causing the high-temperature abnormality determination circuit to operate, wherein: once the non-resettable switch element is brought into the second state, the non resettable switch element is not returned to the first state but maintained in the second state, irrespective of an operation state of the high-temperature abnormality determination circuit, and when the high-temperature abnormality determination circuit starts to operate by the voltage output from the power supply, the high-temperature abnormality determination circuit determines that the abnormality has occurred in the battery module before starting the operation of the high-temperature abnormality determination circuit, in a case where the non-resettable switch element is maintained in the second state.