Energy Storage Permitting Guidebook - Report - Page 18
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Energy Storage Guidebook
components must also comply with their respective safety standards. For example, lithium battery cells
must be certified to UL 1642; inverters and controllers must be certified to UL 1741. ESS can be configured
as AC ESS where the battery, battery management system (BMS), and inverter are housed within a single
manufactured package. It can also be configured as DC ESS where the battery and BMS are in a UL 9540
listed enclosure, but the inverter is a separate component. UL 9540 also requires large-scale fire testing for
specific installation locations and applications.
Although the standard itself is voluntary, both the National Electric Code and International Residential Code
require ESS to be UL 9540 listed. All residential battery energy storage systems installed in California since
January 1, 2020, must be permitted and certified to UL 9540.
UL9540A Test Method
UL 9540A, the Standard for Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy
Storage Systems, is the American and Canadian national standard for assessing fire propagation related
to thermal runaway events in battery energy storage systems (ESS). Testing to these national standard
requirements is an essential element of due diligence. UL 9540A provides a methodology for testing a
system’s safety-related behavior when the design or installation conditions of an ESS exceed the limits
set by the National Fire Protection Association (NFPA) 855, NFPA 1, the International Fire Code (IFC), or the
International Residential Code (IRC).
UL 9540A is the only consensus standard explicitly cited in NFPA 855 for large-scale fire testing and the only
national standard in the U.S. and Canada for fire safety testing methods for battery ESS.
NFPA 855 Standard
NFPA 855 Standard for the Installation of Stationary ESS “applies to the design, construction, installation,
commissioning, operation, maintenance, and decommissioning of ESS, including mobile and portable ESS
installed in a stationary situation and the storage of lithium metal or lithium-ion batteries.” NFPA 855
provides guidelines for the design, installation, operation, and maintenance of these systems to mitigate fire
hazards and ensure the safety of occupants and responders.
