Patent ID: 8150642

Claim:
A secondary battery deterioration judging device, comprising: an overdischarge detecting section for detecting a terminal voltage of a secondary battery of which a deterioration is to be judged, determining whether the detected terminal voltage is equal to or less than a predetermined voltage value, and detecting an overdischarge state of the secondary battery when the detected terminal voltage is equal to or less than the predetermined voltage value; a computing section for integrating a value indicating the deterioration of the secondary battery while the overdischarge state is detected by the overdischarge detecting section; and a judging section for judging a deterioration state of the secondary battery based on an integration value obtained by the computing section, wherein the overdischarge detecting section includes, as the predetermined voltage value, a first voltage value which is a positive value or zero and a second voltage value which is less than zero, and detects a first overdischarge state of the secondary battery when the detected terminal voltage is equal to or less than the first voltage value and equal to or more than the second voltage value, and detects a second overdischarge state of the secondary battery when the detected terminal voltage is less than the second voltage value.