IEC 62391-1:2022 applies to fixed electric double-layer capacitors (hereafter referred to as capacitors) mainly used in DC circuits of electric and electronic equipment. This part of IEC 62391 establishes standard terms, inspection procedures and methods of test for use in sectional and detail specifications of electronic components for quality assessment or any other purpose. This edition includes the following significant technical changes with respect to the previous edition: The document has been completely restructured to comply with the ISO/IEC Directives, Part 2; a new technical categorization of test methods has been introduced and the test methods have been reorganized according to these new categories; tables, figures and references have been revised accordingly. Calculation formula of charging/discharging efficiency in Annex D were divided into two cases: \'Calculation assuming full charge and discharge\' and \'Calculation assuming incomplete charging and discharging due to internal resistance\'.