Battery information processing system, battery assembly, method of calculating capacity of battery module, and method of manufacturing battery assembly

A battery module capacity calculation method of calculating a full charge capacity of a battery module including a plurality of nickel metal hydride batteries, there being a flat region and a steep region in an open circuit voltage (OCV)-state of charge (SOC) curve of the battery module, a ratio of variation representing an amount of increase in OCV with respect to an amount of increase in SOC of the battery module, the ratio in the flat region being lower than a reference value, the ratio in the steep region being higher than the reference value, the battery module capacity calculation method comprising:

• estimating an OCV of the battery module from a result of detection by a voltage sensor;
• obtaining a Nyquist plot representing a result of measurement of an alternating current (AC);
• and
• calculating the full charge capacity of the battery module based on a fitting curve calculated by fitting processing of the Nyquist plot when the OCV of the battery module estimated in the estimating an OCV is in the flat region.

A method of manufacturing a battery assembly, there being a flat region and a steep region in an open circuit voltage (OCV)-state of charge (SOC) curve of a battery module including a plurality of nickel metal hydride batteries, a ratio of variation representing an amount of increase in OCV with respect to an amount of increase in SOC of the battery module, the ratio in the flat region being lower than a reference value, the ratio in the steep region being higher than the reference value, the method comprising:

• estimating an OCV of the battery module from a result of detection by a voltage sensor;
• obtaining a Nyquist plot representing a result of measurement of an alternating current (AC) impedance of the battery module;
• calculating a full charge capacity of the battery module based on a fitting curve calculated by fitting processing of the Nyquist plot when the OCV of the battery module estimated in the estimating an OCV is in the flat region;
• and
• manufacturing a battery assembly from a plurality of battery modules of which full charge capacity has been calculated in the calculating the full charge capacity.