Core Viewpoint - The article discusses the recent updates to the UL 9540A standard for battery energy storage systems (BESS), emphasizing the importance of large-scale fire testing and system-level safety in the energy storage industry [3][4][6]. Summary by Sections Event Announcement - The 9th Frontier Technology Conference on Energy Storage will be held on April 1-2, 2026, during the 14th International Energy Storage Summit and Exhibition (ESIE 2026), featuring international experts discussing fire safety and regulatory frameworks in energy storage [3][19]. Standard Update - The sixth edition of the UL 9540A standard, titled "Test Methods for Evaluating Fire Propagation in Battery Energy Storage Systems," was officially released on March 13, 2026. This version sets a new precedent in testing and certification for energy storage systems, focusing on thermal runaway and fire propagation risks [3][4]. Testing Enhancements - The new version of UL 9540A expands the testing scope by including large-scale fire testing (LSFT), which evaluates system-level safety by igniting a storage unit and observing fire spread without fire suppression systems. This change addresses limitations of previous versions and emphasizes the importance of system-level safety [4][6]. Industry Trends - There is a growing industry focus on large-scale fire testing, with five leading domestic energy storage companies conducting such tests in early 2026. These tests are centered on ultra-large capacity battery systems, with some cells reaching capacities of 1,175Ah [4][5]. Performance Data - Key performance data from large-scale fire tests conducted by various companies in early 2026 show promising results, such as maintaining structural integrity and low temperatures in adjacent cells during fire events. For instance, Haibo's test showed a maximum temperature of only 56°C in neighboring cells [5]. Regulatory Compliance - The updated UL 9540A meets the safety testing requirements of the NFPA 855 standard, but regulatory bodies may still require additional performance data for site assessments. The new version incorporates spacing and propagation considerations into the certification framework, which were not included in previous versions [6][7]. Complementary Standards - The CSA/ANSI C800:25 standard, which assesses the reliability of energy storage systems, complements UL 9540A by providing additional performance metrics such as heat release rates and gas composition, aiding in site evaluations and regulatory reviews [6][7].