As advanced battery systems become a standard choice for mainstream production vehicle portfolios, comprehensive battery system validation plans are essential to ensure that the battery performance, reliability, and durability targets are met prior to vehicle integration. (Note: Safety and Abuse testing are outside of the scope of this paper.)The validation plan for the Chevrolet Volt Rechargeable_Energy Storage System (RESS), the first lithium-ion battery pack designed and manufactured by General Motors (GM), was developed using a functional silo approach based on the battery design requirements documentation. While the Chevrolet Volt was the lead program at General Motors to use this validation plan development approach, other GM programs with different battery system mounting locations and cooling techniques are now using this method.Battery system design validation (DV) and product validation (PV) test flows are segmented into three main areas: environmental / durability, electrical performance / characterization, and warranty lifecycle.There are challenging considerations in test flow development. These considerations include testing to life targets for the entire battery pack (i.e. cells, pack thermal system, and enclosure), choosing battery duty cycles that represented the full distribution of projected customer drive cycle profiles, and configuring test hardware based on test method (i.e. battery modules, “dummy cell” packs, or cell load simulators for controllers.)This paper includes an overview of a comprehensive battery validation test plan. It also explores the methods for developing the test flows, including rationalizations for test scope (component versus battery pack versus vehicle), sample sizes and vintages, test duration, and test methods to introduce aging effects.