In support of the Army’s Modernization Strategy focus on Next Generation Combat Vehicle (NGCV), GVSC with OSD partners (OECIF, NAVY) is developing a Joint Service High-Voltage (HV) Specification for Energy Storage Modules (ESMs), i.e. Li-ion batteries. Greater penetration of safe, low cost ESM in support of electrification will result in improved platform survivability, maneuverability and capability. It is anticipated that an HV ESM specification for an adaptable, scalable energy storage based on commercial practices, will benefit multiple DOD platforms resulting in an acquisition life cycle cost reduction and a reduced logistical burden. To support multiple platform requirements, the specification is being developed to allow for a modular electrical architecture from 50V to 1000V. Analysis is also presented on the ability to obtain an optimum solution using a combination of standard power and energy battery modules vs. a platform unique battery, demonstrating the viability of a modular battery specification effort. This work also reviews the development of the specification including module format, power and energy requirements, environmental, safety, control, shock and vibration requirements. Additionally a case study of Hybrid Electric Vehicle is also presented that illustrates the value of a specification.