Battery information processing system, battery information processing method, and battery assembly and method of manufacturing battery assembly

A battery information processing system which processes information on a secondary battery representing a nickel metal hydride battery including a positive electrode, a negative electrode, and a safety valve, the battery information processing system comprising:

• an obtaining device configured to obtain a measurement value of an AC impedance of the secondary battery for creating a Nyquist plot;
• and
• an analysis device configured to determine, by a Maharanobis-Taguchi method using a plurality of explanatory variables, to which of a first group and a second group the secondary battery will belong when the secondary battery is subjected to capacity restoration processing, the first group being defined as a group of secondary batteries of which battery capacity is lower than a reference capacity, the second group being defined as a group of secondary batteries of which battery capacity is higher than the reference capacity,
• the plurality of explanatory variables including a plurality of feature values extracted from the Nyquist plot,
• the Nyquist plot including a semicircular portion which is a semicircular track of measurement values of the AC impedance and a linear portion which is a linear track of measurement values of the AC impedance,
• the plurality of feature values including
• at least two AC impedance real number components plotted in the semicircular portion,
• at least two AC impedance imaginary number components plotted in the semicircular portion, and
• at least one AC impedance imaginary number component plotted in the linear portion.