| CPC G01R 31/3835 (2019.01) [H01M 10/425 (2013.01); H02J 7/0048 (2020.01); H01M 2010/4271 (2013.01)] | 10 Claims |

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1. A battery management device that manages a state of a battery, comprising:
a detector that acquires a detected value of a voltage outputted from the battery; and
a processor that estimates a state of the battery,
wherein the processor identifies a first period from a start time point at or after an end time point when the battery finishes charging or discharging to a first time point when a first duration has elapsed from the start time point,
wherein the processor identifies a second period that starts at a time point after the end time point and that ends at a second time point after an end time of the first period,
wherein the processor acquires, as a second period difference, a difference of an output voltage of the battery from start of the second period to end of the second period,
wherein the processor acquires a relationship between the second period difference and a state of the battery,
wherein the processor refers to the relationship using the second period difference, thereby estimating a state of the battery,
wherein the processor acquires, as a first period difference, a difference of the output voltage from start of the first period to end of the first period, and
wherein if a ratio of the first period difference to the second period difference is at or above a first threshold, the processor estimates that the battery is not in a normal state.
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