Proposal to establish a new Amendment to UN Global Technical Regulation No. 25 on in-vehicle battery durability for electrified heavy-duty vehicles. The GTR provides harmonized methods to determine battery durability performance of HD-PEVs and HD-OVC-HEVs, including requirements for State of Certified Energy (SOCE) monitors, minimum performance requirements expressed as SOCE values at specific vehicle lifetime points, and in-use verification procedures with Parts A and B to verify monitor accuracy and battery durability compliance respectively. The document includes test procedures for usable battery energy determination via driving on test tracks, road driving, bidirectional power supply systems, or chassis dynamometer testing, family definitions for monitor and battery durability verification, vehicle survey requirements, and data collection specifications.