ANSI/CAN/UL 9540A Latest Version: Core Updates & Industry Value for Energy Storage Systems

With the rapid development of the renewable energy industry, the safety of Battery Energy Storage Systems (BESS) has attracted growing global attention. As the core standard for evaluating thermal runaway fire propagation in energy storage systems, each update of ANSI/CAN/UL 9540A marks a milestone in the safe development of the industry. Combining the latest standard dynamics, Guangdong Energy Storage Testing Technology Co., Ltd. provides an in-depth analysis of the core content and industry value of the latest version of UL 9540A, helping energy storage enterprises accurately grasp the compliance direction.

Note: The latest version of ANSI/CAN/UL 9540A is the 5th edition, released on March 12, 2025. Its core content and industry value are detailed below.

Core Content of the Latest UL 9540A

1. Optimization of Testing Methods

• Gas Detection: For total hydrocarbon detection at the module and unit levels, flame ionization detectors are preferred, while Fourier transform infrared spectrometers are made optional. Additionally, electrochemical or thermal conductivity detectors are allowed for hydrogen measurement.
• Heating Methods: An optional method of continuous heating until the cell undergoes thermal runaway is added, eliminating the mandatory requirement of "holding at diaphragm melting point + 5°C for 4 hours".
• New Equipment: The use of Gardon-type heat flux meters is permitted, and it is specified that wall temperature and heat flux meter temperature shall be recorded as 60-second averages.

2. New Test Objects and Scenarios

• Test Objects: For the first time, testing methods for lead-acid batteries, flow batteries, and high-temperature sodium batteries are included, covering more energy storage technology routes.
• Test Scenarios: For residential energy storage unit testing, test walls are used instead of NFPA 286 test chambers to simplify the test environment setup. Heat flux measurement for exit paths of non-residential outdoor wall-mounted energy storage systems is added to enhance safety assessment in complex scenarios.

3. Upgrade of Safety Criteria

• Thermocouple Arrangement: Specifications for thermocouple placement at the cell level are clarified, including vent points and thermal runaway temperature monitoring points.
• Module-Level Criteria: The definition of "thermal runaway propagation between cells" is added, and module-level criteria are improved, requiring that the module case temperature shall not exceed the cell venting temperature.
• Installation Scenario Requirements: Testing requirements for roof and open garage installations are refined, with strict control over fire risks in outdoor residential energy storage installation scenarios.

4. Improvement of Reports and Appendices

• Report Content: Test reports at the module, unit, and installation levels must integrate test summaries from previous levels to ensure full-chain data traceability.
• Appendix Content: Appendix A adds recommendations for deflagration risk prevention and control, providing additional technical guidance for high-risk scenarios.

Industry Value of the Latest UL 9540A

1. Enhancing Safety Assurance

Through stricter and more precise testing methods and criteria, the standard can comprehensively evaluate the thermal runaway fire propagation risks of BESS. It provides more scientific data support for the fire and explosion protection design of energy storage systems, effectively reducing the probability of safety accidents such as fires and explosions, and safeguarding personnel and property safety.

2. Promoting Technological Development

The addition of testing methods for various non-lithium-ion battery chemical systems and testing processes for emerging application scenarios encourages energy storage enterprises to continuously develop and improve technologies to meet standard requirements, driving the diversification and innovative development of energy storage technologies.

3. Regulating Market Order

As a national standard jointly recognized by the United States and Canada, and the only U.S.-Canada consensus standard explicitly cited in NFPA 855 for large-scale fire testing, UL 9540A sets a unified safety access threshold for the energy storage market. It helps regulate market order and prevent low-quality, unsafe products from entering the market.

4. Facilitating International Cooperation

The update of this standard reflects global attention to energy storage system safety. Its wide application helps promote exchanges and cooperation in energy storage safety among different countries and regions, jointly driving the safe and sustainable development of the energy storage industry.

Synergistic Application Logic Between UL 9540A and UL 9540

In the energy storage system safety certification system, UL 9540A and UL 9540 form a complementary and synergistic relationship. UL 9540A focuses on the standardization of testing methods, while UL 9540 "Standard for Energy Storage Systems and Equipment" provides comprehensive product safety assessment requirements. It covers safety specifications for all system components, including battery cells, modules, racks, power conversion, and battery management, serving as the basic framework for BESS to obtain UL certification.

The synergistic application of the two standards, combined with strict compliance with NFPA series codes and international fire codes, can build a full-chain safety assurance system from product R&D to installation and deployment. It provides core technical support for the compliant and safe promotion of energy storage systems. Currently, UL Solutions is collaborating with the National Fire Protection Association (NFPA) Technical Committee to improve guidelines for Large-Scale Fire Testing (LSFT), further enhancing the synergistic implementation effect of the two standards.

Compliance Testing Service Advantages of Guangdong Energy Storage Testing

Facing the update and upgrading of UL 9540A and the continuous improvement of industry safety demands, Guangdong Energy Storage Testing Technology Co., Ltd. provides full-process compliance solutions for enterprises with professional capabilities. We accurately grasp the testing details of the new standard, are equipped with testing equipment adapted to multiple battery chemical systems, and can develop customized testing plans for different application scenarios to ensure the accuracy and authority of test results.

Based on our in-depth understanding of international standards and domestic regulations, our testing services can not only help enterprises meet the access requirements of the U.S. and Canadian markets but also provide data support for product optimization and upgrading. This helps enterprises establish safety and compliance advantages in the fierce market competition. From standard interpretation to test implementation, from report issuance to compliance consulting, we fully support energy storage enterprises throughout the process.

Energy storage safety is the lifeline of industrial development, and standard compliance is the core prerequisite for safety assurance. Guangdong Energy Storage Testing Technology Co., Ltd. will continue to track international standard dynamics, continuously improve testing technology capabilities, and contribute professional strength to promoting the safe and sustainable development of the energy storage industry.