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UL Certifications for Battery Systems
Rahul Jalthar

UL Certifications for Battery Systems: A Complete Guide

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Battery Energy Storage Systems (BESS) are becoming essential in today’s energy landscape. Whether for renewable integration, grid stability, or backup power, ensuring the safety and reliability of these systems is critical. This is where UL certifications for battery systems play a crucial role.

UL (Underwriters Laboratories) is one of the most trusted global safety certification organizations. Its standards verify that battery energy storage systems meet strict safety, fire prevention, and performance requirements. For project developers, manufacturers, and operators, understanding these certifications is not optional—it’s necessary.

In this guide, we’ll explore key UL standards such as UL 9540, UL 9540A, UL 1973, and others. You’ll also learn how these certifications impact compliance, insurance, and deployment.

At Sunlith Energy, we help businesses navigate energy storage safety and compliance while building reliable battery solutions.

Why UL Certifications Matter for Battery Energy Storage

1. Safety and Risk Mitigation

Battery systems, if not designed properly, can pose fire hazards or thermal runaway risks. UL standards ensure that systems undergo rigorous testing to minimize these risks.

2. Regulatory Approval

Most jurisdictions require UL-certified equipment for permitting. Without it, projects can face delays, redesigns, or rejection.

3. Market Trust and Bankability

Investors, insurers, and end-users trust certified systems. A BESS with UL certifications demonstrates credibility and long-term reliability.

👉 Related Read: Complete Guide to Battery Energy Storage Certification

Key UL Certifications for Battery Systems

UL Certifications for Battery Systems

UL 9540 – Standard for Energy Storage Systems and Equipment

UL 9540 is the primary certification for energy storage systems. It evaluates the safety, performance, and construction of complete systems, not just individual components.

  • Covers batteries, Power Conversion Systems (PCS), control systems, and enclosures.
  • Required for grid-scale, commercial, and residential BESS installations.
  • Ensures systems meet fire safety and electrical safety standards.

Why it matters: Without UL 9540, your BESS may not receive local authority approval.

👉 Learn more about Energy Storage PCS and how it integrates into certified systems.

UL 9540A – Test Method for Evaluating Thermal Runaway Fire Propagation

UL 9540A is not a certification itself but a test method. It assesses how thermal runaway in one cell can propagate through modules, units, and installations.

  • Provides data on fire propagation and suppression.
  • Often required by fire marshals and building authorities.
  • Supports UL 9540 certification by demonstrating safe design.

👉 Explore our article: UL 9540A Test Method Explained

UL 1973 – Batteries for Use in Stationary and Vehicle Auxiliary Power Applications

UL 1973 focuses on individual battery modules and packs used in stationary systems.

  • Tests electrical, mechanical, and environmental safety.
  • Covers BESS, telecom backup, and EV auxiliary batteries.
  • Often a prerequisite before seeking UL 9540 certification.

Example: A lithium-ion module must first pass UL 1973 before being integrated into a UL 9540-certified system.

UL 1741 – Inverters, Converters, Controllers

Since BESS includes PCS (Power Conversion Systems), UL 1741 applies to inverters and related power electronics.

  • Validates PCS for interconnection safety with the grid.
  • Ensures compatibility with renewable energy and microgrids.
  • Critical for hybrid solar + storage projects.

👉 Read our guide: PCS vs Inverter – Key Differences

UL 1974 – Evaluation for Repurposing Batteries

As second-life batteries become more common, UL 1974 helps ensure repurposed cells are safe for reuse.

  • Evaluates used EV or industrial batteries for BESS applications.
  • Supports sustainability by extending battery life.
  • Ensures recycled batteries meet minimum safety standards.

Benefits of UL-Certified Battery Systems

  1. Regulatory Compliance – Smooth project approvals and grid interconnection.
  2. Enhanced Safety – Reduced risk of fire, explosion, and system failure.
  3. Market Acceptance – Easier financing and insurance.
  4. Long-Term Reliability – Certified systems undergo rigorous life-cycle testing.
  5. Future-Proofing – UL standards evolve with technology, ensuring systems stay relevant.

Challenges in Achieving UL Certification

  • Cost and Time: Certification requires extensive testing, which can delay projects.
  • Design Changes: If a component fails testing, redesign may be necessary.
  • Complex Standards: Navigating multiple UL standards can overwhelm new manufacturers.

This is where industry partners like Sunlith Energy provide support—helping companies design systems aligned with certification requirements from day one.

UL Certifications for Battery Systems

How Sunlith Energy Helps with UL-Compliant Solutions

At Sunlith Energy, we ensure that every battery system we design aligns with UL safety and certification standards. Our approach includes:

  • Design Consulting: Guiding OEMs and EPCs on compliance from the design phase.
  • Testing Support: Preparing systems for UL 9540, UL 9540A, and UL 1973 evaluations.
  • End-to-End Solutions: Delivering certified-ready BESS with integrated PCS, battery modules, and fire safety systems.

Whether you’re deploying grid-scale storage, C&I projects, or hybrid solar + storage, our certified solutions meet the highest safety benchmarks.

👉 Learn more about our Battery Energy Storage Systems

FAQs on UL Certifications for Battery Systems

1. What is UL certification for battery systems?

It is a safety and performance evaluation that ensures battery energy storage systems meet global standards for fire safety, electrical reliability, and environmental resilience.

2. Do all BESS need UL 9540 certification?

Yes. For commercial and residential deployment in most regions, UL 9540 is mandatory.

3. What’s the difference between UL 9540 and UL 9540A?

UL 9540 certifies the system, while UL 9540A is a test method used to analyze thermal runaway propagation.

4. How long does certification take?

Depending on system complexity, UL certification can take 6–12 months.

5. Can second-life batteries be certified?

Yes, through UL 1974, which evaluates repurposed batteries for safe use in stationary storage.

Conclusion

UL certifications for battery systems are the foundation of safe, compliant, and bankable energy storage projects. From UL 9540 system-level approvals to UL 9540A fire safety testing and UL 1973 battery-level compliance, these standards ensure that energy storage systems perform reliably under real-world conditions.

As energy storage adoption accelerates, ensuring compliance with UL standards will not just be a regulatory requirement—it will be a competitive advantage.

At Sunlith Energy, we’re committed to helping businesses deploy safe, certified, and future-ready energy storage systems.

UL 9540A Test Method: Complete Guide for Battery Energy Storage Safety
Rahul Jalthar

UL 9540A Test Method: The Ultimate Guide for Battery Energy Storage Safety

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UL 9540A Test Method: Battery Energy Storage Systems (BESS) are growing rapidly as renewable energy, electric vehicles, and grid-scale projects expand worldwide. While storage technology brings efficiency and sustainability, it also raises safety challenges—especially related to thermal runaway and fire propagation.

This is where the UL 9540A Test Method plays a vital role. It is the most widely accepted safety test for energy storage systems, referenced by codes such as NFPA 855 and the International Fire Code.

In this guide, we’ll explain:

  • What UL 9540A is
  • The four levels of testing
  • How it relates to UL 9540 and UL 9540B
  • The major 2025 updates
  • Why manufacturers and project developers should care
UL 9540A Test Method: Complete Guide for Battery Energy Storage Safety

What is the UL 9540A Test Method?

The UL 9540A Test Method for Evaluating Thermal Runaway Fire Propagation in BESS is the only national standard designed to measure how battery systems react under thermal runaway conditions.

It answers critical safety questions such as:

  • Will a single cell failure spread to neighboring cells?
  • How will a battery module or system behave in case of fire?
  • Can suppression systems prevent explosions, flames, or reignition?

Unlike general safety certifications, UL 9540A focuses only on fire propagation risks, making it the go-to test for engineers, installers, and regulators.

👉 Related: UL Certifications for Battery Systems

Why is UL 9540A Important for BESS?

Battery systems are often installed in homes, businesses, and utility-scale projects. If a fire starts and spreads, it can have devastating consequences. UL 9540A ensures that:

  • Manufacturers can prove their systems are safe.
  • Installers get clear installation requirements, such as spacing and suppression.
  • Authorities have a reliable, consensus-based safety test.

It is directly referenced in NFPA 855, which governs the installation of stationary energy storage systems, making it essential for compliance.

👉 Explore more: CE for BESS: Complete Guide

The Four Levels of UL 9540A Testing

UL 9540A follows a hierarchical four-level structure. Testing may stop early if performance criteria are met.

UL 9540A Test Method: Complete Guide for Battery Energy Storage Safety

1. Cell-Level Testing

The test begins with individual cells. The goal is to induce thermal runaway and analyze gas emissions, flames, and heat release.

  • If cells show no propagation risk, testing can stop here.

2. Module-Level Testing

If cell risks exist, groups of cells (modules) are tested. This step checks whether failures propagate across the module, creating larger hazards.

3. Unit-Level Testing

The full battery system (ESS unit) is tested. Suppression systems are often disabled unless they are built-in. Engineers assess:

  • Flame spread
  • Explosion risk
  • Gas emissions

4. Installation-Level Testing

The final stage evaluates the system in real-world conditions with fire suppression included. It ensures:

  • No detonation or deflagration
  • Effective fire suppression
  • No reignition after the event

👉 Related: What is BESS?

UL 9540A vs. UL 9540 and UL 9540B

It’s easy to confuse these standards, but they serve different purposes:

UL 9540A Test Method: Complete Guide for Battery Energy Storage Safety
  • UL 9540: Certification standard for energy storage equipment. Covers overall safety, performance, and compliance.
  • UL 9540A: Test method for fire propagation in thermal runaway scenarios. Supports UL 9540 certification.
  • UL 9540B: Designed specifically for residential-scale BESS, focusing on large-scale fire tests and vent gas ignition.

Together, these standards provide a complete safety framework for energy storage systems.

2025 Updates: What Changed in UL 9540A Fifth Edition?

UL 9540A Test Method: Complete Guide for Battery Energy Storage Safety

The fifth edition of UL 9540A, released on March 12, 2025, brings significant improvements to reflect evolving technology and chemistries.

Key Updates:

  • Optional hydrogen detection and heat flux measurements.
  • Clarified rest times after conditioning/charging.
  • Replacement of NFPA 286 fire room with an instrumented wall for residential testing.
  • More precise thermocouple placement and continuous ramping in cell tests.
  • Specific temperature limits for module casings.
  • Extended protocols for new chemistries like lead-acid, NiCd, and flow batteries.
  • Added requirements for rooftop and open garage installations.

These updates make UL 9540A more adaptable, helping manufacturers meet stricter fire codes and regulators enforce safer installations.

👉 Related: Green Hydrogen Storage

Who Needs UL 9540A Testing?

UL 9540A applies to:

  • Battery manufacturers – proving technology safety.
  • BESS integrators – ensuring compliance with NFPA 855 and local fire codes.
  • Developers and EPCs – gaining project approvals faster.
  • Home and commercial installers – understanding spacing and suppression requirements.

Without UL 9540A testing, it becomes nearly impossible to get approval for large BESS installations in the U.S.

Benefits of UL 9540A Testing

  • Compliance: Meets NFPA 855 and IFC requirements.
  • Design Optimization: Provides data for safe spacing and fire suppression.
  • Market Access: Required for many U.S. and Canadian projects.
  • Risk Reduction: Lowers fire and explosion risks in installations.

Conclusion

The UL 9540A Test Method is the backbone of energy storage safety in 2025. With its updated fifth edition, it provides a clear, science-based framework to evaluate thermal runaway risks at cell, module, unit, and installation levels.

For manufacturers, passing UL9540A testing means faster certifications, safer designs, and wider market acceptance. For regulators and installers, it provides confidence that battery energy storage systems meet the highest safety standards.

As BESS technology evolves, UL 9540A will continue to be the key standard shaping how we store renewable energy safely and effectively.

👉 Learn more: UL Certifications for Battery Systems

FAQs: UL 9540A Test Method

Q1. What is the UL 9540A Test Method?

The UL 9540A Test Method is a fire safety test designed to evaluate the thermal runaway characteristics of battery energy storage systems (BESS). It helps manufacturers and system designers understand how a battery reacts under stress, including fire, gas release, and propagation risks.

Q3. How does UL 9540A differ from UL 9540 certification?

UL 9540 is a system-level certification for battery energy storage systems, while UL 9540A is a fire test method. UL 9540A is often used to provide supporting safety data required to achieve UL 9540 certification or to meet local fire codes.

Q2. Why is UL 9540A testing important for energy storage systems?

UL 9540A testing provides critical data for fire safety, helping system integrators, regulators, and building authorities approve energy storage projects. It ensures that batteries are safe for use in residential, commercial, and grid-scale installations.

Q4. What are the levels of UL 9540A testing?

UL 9540A includes four test levels:

  1. Cell level – Tests how a single cell behaves in thermal runaway.
  2. Module level – Examines propagation within a battery module.
  3. Unit level – Assesses fire and gas risks in the entire system.
  4. Installation level – Evaluates safety in a real-world installed environment.

For more details on BESS safety, see our guide on energy storage PCS.

Q5. Who requires UL 9540A testing?

UL 9540A testing is often required by:

  • Battery manufacturers seeking UL 9540 certification.
  • System integrators installing BESS in commercial or residential sites.
  • Authorities Having Jurisdiction (AHJs) and fire marshals reviewing projects.

Learn more about BESS certifications required glo

Q6. What are the latest updates in UL 9540A (Fifth Edition, 2025)?

The March 2025 update to UL 9540A (5th Edition) added requirements for:

  • Hydrogen detection sensors.
  • Module casing integrity.
  • Testing for rooftop energy storage systems.

Check our post on battery regulations in the EU for related compliance u

Q7. Does passing UL 9540A mean a battery is certified?

No, UL 9540A is not a certification. It is a test method that provides data used to achieve UL 9540 certification or to comply with fire codes. Certification comes from successfully meeting UL 9540 requirements.

Q8. How long does UL 9540A testing take?

The duration depends on system size and complexity. A full series of tests (cell, module, unit, installation) can take several weeks to months, depending on scheduling and regulatory requirements.

Q9. Can UL 9540A testing be skipped if a battery is already safe?

No. Even if a system has proven safety records, AHJs and certification bodies often require UL 9540A data as part of the approval process, especially for large-scale installations.

Q10. How does UL 9540A testing impact project approval timelines?

Providing UL 9540A data often accelerates permitting and approval by demonstrating compliance with NFPA 855, IFC, and local fire codes. Without it, projects may face delays or additional scrutiny.

Bess Certifications Guide
Rahul Jalthar

BESS Certifications Explained: What You Need to Know Before You Buy or Sell

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BESS Certifications: Battery Energy Storage Systems (BESS) are becoming a critical part of our renewable energy future. Whether you’re buying, selling, installing, or manufacturing BESS units, understanding the required certifications is crucial. Without proper certifications, your product may not be legally sold, safely operated, or even insured in many regions.

In this blog, we’ll break down the most important certifications for BESS and explain what they mean, why they matter, and how to ensure your system is compliant.

1. Why Are BESS Certifications Important?

Certifications are like a stamp of approval from trusted organizations. They prove that a BESS unit has passed safety, performance, and environmental tests. Without them:

  • You risk safety issues like fires or system failure.
  • Your product might be blocked from certain markets.
  • Insurance claims can be denied after accidents.
  • You might face legal problems or product recalls.

2. BESS Certifications Common Global Standards

Different countries and regions have different certification requirements. Here are some of the most common ones globally:

A. UL Standards (Mainly for North America)for BESS Certifications


UL (Underwriters Laboratories) is a leading safety organization in the U.S. These are some key UL standards for BESS:

Why it matters: UL certifications are essential for selling in the U.S. and Canada. Without these, your product won’t be accepted in most residential or commercial projects.

B. IEC Standards (International) for BESS


The International Electrotechnical Commission (IEC) sets safety and performance standards recognized worldwide.

  • IEC 62619 – Safety for Secondary Lithium Cells and Batteries
  • IEC 62933 – Series of standards for energy storage systems
  • IEC 62133 – Safety for portable sealed secondary cells
  • IEC 61427 – Performance of batteries used in renewable energy systems

Why it matters: Many countries outside North America refer to IEC standards for regulatory compliance, especially in Europe, Asia, and the Middle East.

C. CE Marking (Europe)


Products sold in the European Union must meet CE requirements. For BESS, this includes:

  • EMC (Electromagnetic Compatibility)
  • LVD (Low Voltage Directive)
  • RoHS (Restriction of Hazardous Substances)
  • Safety & Fire Protection

Why it matters: Without CE marking, you can’t legally sell your BESS product in the European Economic Area (EEA).

D. BIS (India)


In India, the Bureau of Indian Standards (BIS) regulates battery and BESS imports and production.

Why it matters: India is a growing BESS market, and local certifications are mandatory for government tenders and utility-scale projects.

E. CEC (Australia)


The Clean Energy Council (CEC) governs renewable energy products in Australia.

  • Products must be on the CEC approved list
  • Certifications must include both product testing and installer compliance

Why it matters: BESS products not listed with the CEC are ineligible for rebates or connection to the grid.

3. Certification for the Entire System, Not Just the Cell

One major mistake people make is assuming that a certified cell means the entire battery system is certified. That’s not true.

A complete BESS includes:

  • Battery cells or packs
  • Battery Management System (BMS)
  • Power Conversion System (PCS)
  • Cooling systems, enclosures, cables, and connectors

Each component AND the fully assembled system must meet certification standards.

4. Factory-Level Certifications

Besides product certifications, the factory that makes your BESS should also be certified:

  • ISO 9001 – Quality Management
  • ISO 14001 – Environmental Management
  • ISO 45001 – Occupational Health & Safety
  • IATF 16949 – (If automotive-related BESS)

Why it matters: Certified factories reduce the risk of defects, improve traceability, and meet import regulations more smoothly.

5. Who Issues These Certifications?

  • UL – Underwriters Laboratories (USA)
  • TÜV – Germany-based, issues CE and IEC certifications
  • Intertek – Testing and certification services globally
  • SGS – Certification body with international presence
  • CSA – Canadian Standards Association

Always work with internationally recognized certification bodies for credibility and global market acceptance.

6. Red Flags to Watch Out For

  • Only cell report is shown – This is not enough! Ask for system-level reports.
  • No thermal runaway test (UL 9540A) – Risk of fire is very high without this.
  • Non-recognized lab – Some factories use fake or local-only reports.
  • Outdated reports – Certification validity matters. Check the dates.
  • No factory audit certificates – Poor factory management = higher product risk.

7. Tips for Buyers & Project Developers

  • Always request full certification reports, not just summaries.
  • Ask for the name of the lab and the full system test, not just component tests.
  • Make sure the certification is valid for the target market (UL for USA, CE for Europe, etc.)
  • Work with verified sourcing or consulting agents who understand the compliance rules.

Conclusion


BESS certifications are not just paperwork—they’re your protection against risk, rejection, and regulatory trouble. Whether you’re importing, installing, or investing in energy storage systems, certification is your first line of defense.

Make sure your BESS is properly tested, certified, and factory-audited to avoid future headaches. If you’re not sure, work with local experts who can help verify everything before the deal is done.

Need Help?

If you’re buying BESS from China or anywhere else, and you want to make sure the product is safe and certified, I can help. I do:

  • Factory checks
  • Certification report verification
  • BESS system inspections
  • Compliance guidance for your target market

Let’s make your BESS project safer, faster, and fully compliant.