Battery diagnosis device, battery management system, battery pack, electric vehicle and battery diagnosis method

A battery diagnosis method for a battery including a parallel connection structure of unit cells, the battery diagnosis method comprising:

• receiving, by one or more processors, charge/discharge data including a voltage time series indicating a time-dependent change of a voltage across the battery and a current time series indicating a time-dependent change of a charge/discharge current flowing through the battery;
• determining, by the one or more processors, a first estimated capacity value of the battery at a first time, and a second estimated capacity value of the battery at a second time based on the charge/discharge data, the first estimated capacity value indicating a full charge capacity of the battery at the first time, and the second estimated capacity value indicating a full charge capacity of the battery at the second time after the first time;
• determining, by the one or more processors, a threshold capacity value at the second time based on (i) the first estimated capacity value of the battery at the first time and (ii) a reference capacity value;
• comparing, by the one or more processors, the second estimated capacity value of the battery at the second time with the threshold capacity value at the second time;
• diagnosing, —by the one or more processors, an abnormality indicating a cut-off fault in the parallel connection structure based on the comparison;
• and
• in response to diagnosing the abnormality, performing, by the one or more processors, a protection function by turning off a relay connecting the battery and a charging device.