August 16, 2023

What’s New in UL 9540 Energy Storage Safety Standard, 3rd Edition

The third edition of the UL 9540 Standard for Safety for Energy Storage Systems and Equipment, published in April 2023, introduces replacements, revisions and additions to the requirements for system deployment.
SEAC member LaTanya Schwalb presenting at the July 2023 general meeting

At SEAC’s July 2023 general meeting, LaTanya Schwalb, principal engineer at UL Solutions, presented key changes introduced for the third edition of the UL 9540 Standard for Safety for Energy Storage Systems and Equipment.

Schwalb, with over 20 years of product safety certification experience, is responsible for the development of technical requirements and the interpretation of UL standard requirements for Energy Storage Systems (ESS), stationary batteries, fuel cells and hydrogen generators. 

UL 9540 changes include:

  1. New provisions for lead acid and nickel cadmium systems
  2. New noise requirements for ESS
  3. Updates for information technology equipment

In this article, we briefly discuss each of the 20 proposals adopted in the third edition of UL 9540.

Basics of UL 9540

UL 9540 is a safety standard for the construction, manufacturing, performance testing and marking of grid-tied ESS. This includes electrochemical, chemical, mechanical, and thermal storage systems. It also covers systems operating in standalone mode.

UL 9540 defines electrical, mechanical, fluid containment, and environmental performance tests, along with system safety tests.

First introduced in 2016 by UL Solutions, a testing, inspection and certification body, UL 9540 has undergone subsequent updates with the third and most recent edition being published in April 2023.

Updates in UL 9540 Third Edition

1. New definitions, marking and instruction requirements

Revision of scope to add new definitions, marking and instruction requirements for AC ESS and DC ESS. A new diagram shows the components of a DC ESS. Definitions were added to align with terms used in the National Fire Protection Association standard NFPA 70, also known as the National Electrical Code, and International Code Council’s International Residential Code, and define a multipart ESS. 

Revisions align with the NFPA 855 ESS installation standard’s criteria for large-scale fire testing in the UL 9540A fire safety standard. Revisions for residential ESS meet unit-level performance criteria, rather than cell-level performance, for UL 9540A, to align with code requirements. Revisions were made to safety marking transitions for residential ESS in habitable and non-habitable spaces.

2. Removal of “wall-mounted applications” from existing ESS descriptions

The term “wall-mounted applications” was removed as it is covered in existing ESS descriptions. Additional revisions clarify the maximum amount of energy allowed for an ESS that meets performance criteria of UL 9540A testing.

3. Addition of NFPA 68 and NFPA 69 as reference standards

NFPA 68, Explosion Protection by Deflagration Venting, and NFPA 69, Explosion Prevention Systems, were added as reference standards. There was also an addition of a requirement for deflagration or explosion protection to be provided for ESS that have a flammable gas concentration within the enclosure.

4. New requirements for ESS that produce noise

UL 9540 3rd edition adds Occupational Safety and Health Administration (OSHA) regulation 1910.95, Occupational Noise Exposure, as a reference standard, plus requirements for noise levels and how to measure them. 

5. Addition of IEC 60060-1

IEC 60060-1, High-Voltage Test Techniques – Part 1: General Definitions and Test Requirements was added as a reference standard. 

Table 33.1 Correction to Impulse Table as columns for Circuits connected to mains and Circuits not connected to mains were reversed in original Table 29.1.

6. Revision of Tables E1 and E2

Tables E1 and E2 were revised to align with current NFPA 855 requirements for ESS energy capacity and separation distances.

7. Addition of NFPA 484, NFPA 704 and UL 1004-4 as reference standards for thermal ESS 

NFPA 484 Standard for Combustible Metals, NFPA 704 Standard System for the Identification of the Hazards of Materials for Emergency Response, Canadian Electrical Code’s CSA C22.2 No. 286, and UL 1004-4 Standard for Electric Generators were added as reference standards related to thermal ESS. Thermal ESS was also added as an ESS technology as well as requirements and tests specific to thermal ESS.

8. Addition of requirements for lead acid and nickel cadmium ESS

With the UL 1973 Standard for Batteries for Use in Stationary, Vehicle Auxiliary Power and Light Electric Rail Applications, Annex H provided a path for lead acid and nickel cadmium manufacturers to have their battery systems listed. Annex D adds new requirements for those systems to be evaluated under UL 9540.

9. Replacement of UL 508C 

Removal of the UL 508C Standard for Power Conversion Equipment and addition of the UL 61800-5-1 Standard for Adjustable Speed Electrical Power Drive Systems and CSA C22.2 No. 61800-5-1, replacing UL 508C, which has been withdrawn.

10. Replacement of UL 60950-1

Removal of the UL 60950-1/CSA C22.2 No. 60950-1 Standard for Safety Information Technology Equipment and addition of the UL 62368-1/CAN/CSA C22.2 No. 62388-1 Safety Standard For Audio/Video (AV) And Information and Communication Technology Equipment due to replacement of UL 60950-1.

11. Addition of UL 1778 for Uninterruptible Power Systems

Addition of the UL 1778 and CSA C22.2 No. 107.3 Standard for Safety Uninterruptible Power Systems for power conversion/battery chargers. Provides additional options for ESS manufacturers.

12. Clarification of material and enclosure tests

Clarification of material and enclosure tests for ESS allowance of thermoplastic materials and mechanical abuse tests (impact, steady force, mold stress) for ESS enclosures addition of flammability requirements for nonmetallic parts forming part of an enclosure.

13. Testing of representative subassemblies

Allowance of testing of representative subassemblies. This is to accommodate large systems as more are being submitted for testing.

14. Addition of standard references for compliance materials

Addition of standard references for compliance of materials used in ESS.

15. Requirements and production tests for flywheel ESS

Revisions to requirements for flywheel (mechanical) ESS. Revision of production tests for flywheel (mechanical) ESS.

16. Addition of communication system requirements

Addition of early-warning communication system requirements

17. Requirements for ESS containing hazardous fluids

Refinement of requirements for ESS containing hazardous fluids

18. Revisions to standard references in UL 9540 

Corrections to standard references throughout UL 9540

19. Addition of requirements for direct injection clean agent cooling systems 

Aimed at ways of slowing down the spread of fire, this covers new technology being introduced, such as systems where cooling agents are introduced directly into the battery packs of an ESS versus traditional overhead sprinkler systems.

20. Revision of requirements for remote software update For ESS 

This includes specific requirements to be met for the UL 5500 Standard for Safety for Remote Software Updates.

Published but not yet required

The third edition of UL 9540 is published but not effective. You can start using it, but it is not required. The third edition comes into effect on September 30, 2024. After the effective date, you will not be able to list to earlier versions.

There is further clarification to come on which version to use. If in doubt, defer to the latest version.

Contribute to future UL 9540 updates

The UL Energy Storage Systems and Equipment Standards Technical Panel invites participating industry stakeholders to comment on UL 9540 as it develops new editions of the standard.

For the third edition of UL 9540, SEAC’s ESS Standards working group reviewed stakeholder comments and issued eight modified revisions to address marking criteria, capacity limits, explosion protection, and noise levels.
Anyone can be a part of shaping future energy storage-related codes and standards.

Join a SEAC working group to get involved.