North American Certification Guidelines for Battery Energy Storage Systems (BESS)

As the global energy transition accelerates, Battery Energy Storage Systems (BESS) are playing an increasingly important role in grid peak shaving, renewable energy integration, and emergency backup power. As a key export destination for energy storage products, the North American market imposes particularly stringent requirements on product safety, system reliability, and regulatory compliance.

To provide a clear and systematic understanding of these requirements, this article takes a typical battery energy storage cabinet as an example and summarizes the core certification standards, testing expectations, and cross-functional coordination points for exporting BESS products to North America.

I. Certification Framework Overview: A Complete Safety Chain from Cell to System

North American energy storage certification follows a bottom-up, step-by-step verification philosophy, forming a complete and traceable safety evidence chain from battery cells and modules to the fully integrated system:

• Basic battery safety certification – UL 1973: Evaluates electrical, mechanical, and environmental safety of batteries at the cell, module, and system levels.
• Thermal runaway and fire propagation assessment – UL 9540A: Assesses thermal runaway behavior and propagation risks through representative fire and abuse testing.
• System integration certification – UL 9540: Confirms that the complete energy storage system complies with North American safety requirements for installation and operation.
• Regulatory compliance documentation – NFPA 68 / 69 / 855: Fire protection and installation codes commonly used as the technical basis for approval by the Authority Having Jurisdiction (AHJ).

Together, these elements form the indispensable “safety triangle” for market access in North America.

II. Core Certification Standards Overview

The table below summarizes the main certification standards, their applicable scope, typical sample requirements, and practical interpretation.

Note: The NFPA standards are not certifications themselves, but conformity assessment documents. In most cases, they must be reviewed and endorsed by a U.S.-licensed fire protection engineer before being submitted for local installation permitting.

III. Certification Process and Practical Considerations

1. Definition of Certification Scope

• UL 1973: Focuses on the safety of a single cabinet or rack.
• UL 9540A: Focuses on a group of cabinets, emphasizing whether thermal runaway propagation may impact adjacent equipment or evacuation routes.

2. Pre-Certification Product Review

Before initiating formal certification, engineering teams should conduct an internal self-check:

• UL 1973: Thermal management design, number of modules per cabinet, suitability for coastal or high-salt environments, IP rating, altitude limits, grounding scheme, and number of BMS protection layers.
• FCC Part 15B: Maximum operating frequency; length of communication and power cables (especially those exceeding 3 meters).
• UL 9540A: Installation scenario (indoor/outdoor), rack-to-rack and rack-to-wall spacing, and fire suppression system configuration.

3. Test Sample Preparation

• UL 1973: One complete cabinet, representative modules and HV boxes, plus critical spare components (e.g., BMS, fuses).
• UL 9540A: One live rack and three racks filled with dummy modules, including all wiring harnesses. Racks must be pre-drilled for heat flux sensor installation.

Key reminder: Test samples must fully represent the final mass-production configuration. Design changes after testing may invalidate certification results.

4. Documentation Preparation

To streamline review and testing, the following materials should be prepared in advance:

• Battery cell specification sheets
• Existing UL 1973 cell test reports and certificates
• Electrical block diagrams
• Protection logic diagrams and functional descriptions
• Mechanical drawings, dimensions, and exploded views

5. Safety Design Review

During pilot production, safety engineers typically lead design reviews focusing on:

• Adequacy of protection mechanisms
• Compliance of creepage and clearance distances
• Rationality of mechanical and structural design
• Certification status of key components
• Compliance of product labels and markings

6. Baseline Testing Recommendations

R&D and safety teams should jointly define baseline validation tests, which typically include:

• Thermal runaway testing (single-cell per UL 1973 and system-level propagation per UL 9540A)
• Short-circuit testing
• Vibration testing

IV. Conclusion

North American certification is not merely about obtaining certificates—it represents a comprehensive and systematic validation of product safety and risk controllability. From battery cells to full system integration, the certification process serves as a rigorous safety refinement exercise.

By embedding safety considerations early in product design and aligning certification planning across teams, manufacturers can achieve smoother certification processes, faster project approvals, and sustainable success in the North American energy storage market.