Battery Diagnosing Apparatus, Method and System

A battery diagnosis apparatus includes: an ohmic resistance determining unit configured to determine an ohmic resistance of a battery cell in each of a plurality of impedance profiles generated at different time points for the battery cell, a resistance change rate calculating unit configured to calculate a resistance change rate between the plurality of determined ohmic resistances, a gas generation level determining unit configured to determine an internal gas generation level of the battery cell based on the calculated resistance change rate, and a state diagnosing unit configured to diagnose a state of the battery cell according to the determined internal gas generation level.