This document applies to onboard lithium-ion traction batteries for railway applications. This document specifies the design, operation parameters, safety recommendations, data exchange, routine and type tests, as well as marking and designation. Battery systems described in this document are used for the energy storage system (ESS) for the traction power of railway vehicles such as hybrid vehicles as defined in IEC62864‑1:2016 . Auxiliary batteries to supply power only to the auxiliary equipment are excluded. Subcomponents within the battery systems, e.g. battery management system (BMS) and battery thermal management system (BTMS), are also covered in this document. Power conversion equipment (e.g. chopper, converter, etc.), inductors, capacitors and switchgear are excluded from the scope of this document. General requirements for onboard ESS are described in IEC62864‑1:2016 . This document specifies the lithium-ion battery technology but does not prevent the use of battery technologies other than lithium-ion technology for application as traction batteries. A hybrid energy storage system, which uses two or more energy storage technologies combined, e.g. a traction battery and double layer capacitors, is not covered in this document. However, if different technologies of energy storage systems are used on the same railway vehicle and managed independently, each independent energy storage system is covered by its own document.