This part of IEC 62973 applies to lead acid batteries for auxiliary power supply systems used on railway rolling stock. This document supplements IEC 62973-1 which specifies common requirements for all battery technologies. This document describes the design, operation parameters, safety recommendations, routine and type tests, as well as marking of the lead acid battery. Specific requirements on subcomponents within the battery systems are covered in this document. Battery systems described in this document are used in conjunction with onboard charging systems of rolling stock, as described in IEC 62973-1. Charging systems (e.g. LVPS, converters, etc.) are excluded from the scope of this document. This document is used in conjunction with IEC 60254-1, IEC 60896-11, IEC 60896-21 and IEC 60896-22.