Battery monitoring device, battery monitoring method, battery pack, and electric vehicle

A battery monitoring apparatus for a battery assembly having an internal space for accommodating at least one battery cell, the battery monitoring apparatus comprising:

• a first air quality sensor configured to generate a first detection signal indicating a first concentration of a first material in the internal space;
• a second air quality sensor configured to generate a second detection signal indicating a second concentration of a second material in the internal space;
• and
• a controller configured to execute a first monitoring mode for collecting the first detection signal in first time series in response to an operation start command,
• wherein the controller is configured to execute a second monitoring mode for collecting the second detection signal in second time series in response to the concentration of the first material indicated by the first detection signal exceeding a first threshold during the execution of the first monitoring mode,
• wherein the first material is produced by evaporation of a reactant required for a charge/discharge reaction of the battery cell, and
• the second material is produced as a by-product of the charge/discharge reaction of the battery cell.