S.J. Jordan
Jensen Hughes,
United States
Keywords: Battery, BESS, LSFT, Fire Testing, UL9540A, C800, NFPA855, Standards
Summary:
In 2025, safety and fire protection initiatives involving the installation of battery energy storage systems have pivoted rapidly towards requiring large scale fire testing of systems prior to installation permitting. Testing at this scale is expensive, hazardous, and not guaranteed to provide the information required to justify the proposed installation configuration. The upcoming 2026 revision of NFPA 855: Standard for the Installation of Stationary Energy Storage Systems requires that a large scale fire test (LSFT) be conducted in which battery vent gases are intentionally ignited, and a fully developed fire event occurs within the system. The intent of this testing is to quantify the thermal exposure to adjacent units or exposures under a specific fire condition. While NFPA 855 requires LSFT to evaluate systems, a detailed methodology is not provided since NFPA 855 is not intended to be a testing standard . Instead, manufacturers are left to decide between testing that complies with a portion of C800, published in 2025 by CSA Group, or a current draft revision of the UL9540A testing framework that addresses LSFT, expected to be published in early 2026. Since both are American National Standards Institute (ANSI) recognized testing methodologies, manufacturers must navigate the nuances of the test procedures applied by each testing lab to ensure that their results satisfy the requirements of test standards, the changes in the 2026 revision of NFPA 855, and any additional information that the local authority having jurisdiction may require for final permit approvals. The prepared poster highlights the key differences between the three guiding documents and provides best practices to help manufacturers and testing agencies optimize BESS LSFT initiatives and align test procedures with the three governing documents discussed.