UL battery safety standard updated for new storage chemistries

US-based safety certification body UL has updated its test method for evaluating the risk of thermal runaway in battery energy storage systems (BESS).

Updates to the fifth edition of UL’s ANSI/CAN/UL 9540A standard include clearer criteria for determining cell-to-cell propagation of thermal runaway, a chemical reaction which causes rapid temperature and pressure rises in battery cells, leading to the risk of fire and explosion.

Other testing updates – determined by UL after consultation with the energy storage industry, regulatory authorities, members of UL’s technical committee, and the fire safety community – include new high-temperature testing methods for various battery chemistries, such as sodium-ion sites; and new testing protocols for emerging BESS applications such as rooftop and open-garage installation.

The ANSI/CAN/UL 9540A standard, used in the United States and Canada, determines the thermal runaway susceptibility of a BESS technology, evaluates the hazards present in fires and explosions caused by thermal runaway, and produces a report detailing relevant fire and explosion protection systems at BESS sites. Data generated by testing also informs North American public and first-responder safety codes.

“We are committed to working with industry to bring safer products to market and empower the safe and sustainable growth of the energy storage market,” said Wesley Kwok, vice president and general manager of the Energy and Industrial Automation group at UL Solutions, quoted in a UL press release announcing the updated standard yesterday. “These collaborative efforts with industry stakeholders and the fire safety community ultimately enhance the resilience of our energy infrastructure and protect communities worldwide.”

UL said its original BESS thermal runaway propagation testing methods were published in 2017 and were revised “multiple times” in 2018 before being published as the fourth edition of ANSI/CAN/UL 9540A in 2019.

The updated ANSI/CAN/UL 9540A standard dovetails with the safety body’s UL 9540 standard for entire BESS sites, including battery cells, modules, and racks; site power conversion equipment; and battery management, energy management, communication, and safety systems.