To ensure the safety of battery products during air transport, the 3m Stacking Test has become a critical requirement in international air shipping. It is specifically designed to verify the stability and reliability of packaging under pressure conditions.

As global trade volumes of battery products continue to grow, air transport safety faces new challenges. The 3m Stacking Test requirement introduced by the International Air Transport Association (IATA) for battery products has become a key focus for battery enterprises engaged in exports.

By simulating the stacking pressure that packages may endure during air transport, this test evaluates the compressive strength and overall protective performance of packaging, ensuring the safety of battery products in transit. As early as the IATA DGR (Dangerous Goods Regulations) Version 64, the 3m Stacking Test requirement was added for PI 965 IB and PI 968 IB packaging. Under the new provisions of IATA DGR Version 66, this test requirement has been extended to additional packaging instruction chapters, including PI 966-II, PI 967-I/II, PI 969-II, and PI 970-I/II.

01. What Is the 3m Stacking Test?

The 3m Stacking Test is a standardized method to simulate the compressive capacity of packages in transport environments. It assesses the protective performance of a packaging system under stacking conditions through static pressure.

The test requires that a package withstands pressure equivalent to the total weight of identical packages stacked to a height of 3 meters on its top surface, for a continuous period of 24 hours—without sustaining damage or deformation. The goal is to ensure that battery packaging can bear the pressure from upper cargo during air transport, preventing packaging failure that could lead to battery short circuits, damage, or even thermal runaway.

02. Why Do Battery Products Require the 3m Stacking Test?

Lithium-ion batteries pose inherent safety risks during air transport; they are prone to combustion or explosion when exposed to heat, impact, or extrusion. The 3m Stacking Test is a critical means of evaluating the safety performance of battery packaging:

1. Safety Requirements: By testing the physical properties of battery packaging, the test can assess whether the packaging may cause hazards such as leakage, explosion, or self-ignition during transport. This enables airlines to formulate preventive measures and emergency response plans in advance.
2. Regulatory Compliance: IATA has strict regulations for the air transport of lithium-ion batteries. Providing proof of passing the 3m Stacking Test is key evidence of compliance with these regulations, helping goods pass inspections smoothly and avoiding transport refusal or penalties due to non-compliance.
3. Basis for Liability Division: In the event of a transport accident, the test report can serve as an important basis for liability division, proving that the enterprise has fulfilled its reasonable safety obligations.

03. Which Battery Products Require the 3m Stacking Test?

Under IATA DGR rules, the following types of battery packaging require the 3m Stacking Test:

Additionally, in accordance with the earlier IATA DGR Version 64, PI 965 IB (lithium-ion batteries shipped independently) and PI 968 IB (lithium-metal batteries shipped independently) have long been required to meet the 3m Stacking Test standard.

04. Specific Requirements and Process of the 3m Stacking Test

Number of Test Samples

3 test samples are required for each packaging design type and each manufacturer.

Test Method

1. Apply a specific force to the top surface of the test package.
2. This force equals the total weight of the same number of identical packages that would be stacked on top of it during transport.
3. The minimum stacking height (including the test sample) must be 3 meters.
4. The test duration is 24 consecutive hours.

Stacking Load Calculation Formula

The stacking load (P) is calculated using the formula:
P = (H/h) × m
Where:

• P: Applied load (unit: kilogram/kg)
• H: Stacking height (no less than 3 meters, unit: meter/m)
• h: Height of a single package (unit: meter/m)
• m: Gross weight of a single package (unit: kilogram/kg)

Pass Criteria

• No leakage from the test sample.
• For composite or combination containers, no leakage of contents from inner receptacles or containers.
• No damage to the test sample that could adversely affect transport safety.
• No deformation of the package that could reduce its strength or cause stacking instability.

05. Equipment Parameter Requirements for the 3m Stacking Test

Professional testing equipment is required for the 3m Stacking Test, with key parameters including:

• Pressure Plate Size: 1000 × 1000 mm
• Force Range: 0 ~ 2000 kgf
• Force Resolution: 0.001 kgf
• Equipment Height Adjustment Range: 0 ~ 800 mm
• Force Holding Time: 0 ~ 10000 hours

06. How to Prepare for the 3m Stacking Test?

To ensure successful completion of the 3m Stacking Test, battery manufacturers should complete the following preparation work:

Packaging Design Optimization

• Select High-Strength Packaging Materials: Choose packaging materials suitable for the battery’s weight and size to ensure sufficient compressive strength.
• Optimize Packaging Structure: Adopt reinforced designs (e.g., strengthened corner supports, internal cushioning structures) to improve overall compressive capacity.
• Ensure Adequate Internal Cushioning: Use appropriate cushioning materials to fill the package interior, preventing battery movement inside the package and enabling even pressure distribution.

Pre-Test Preparation

• Prepare Fully Packaged Samples Reflecting Actual Transport Conditions: Test samples should represent real transport states, including internal battery products, cushioning materials, and outer packaging.
• Accurately Measure and Record Package Dimensions and Weight: Precisely measure the package’s height and weight to calculate the stacking load correctly.
• Ensure Samples Represent Mass Production Standards: Test samples must be manufactured using the same materials, design, and processes as mass-produced packages.

Test Precautions

• Ensure the test environment meets standard requirements.
• Use calibrated testing equipment.
• Maintain detailed records of the test process and results.
• After the test, carefully inspect the packaging and battery condition to confirm compliance with all pass criteria.

07. How to Choose a 3m Stacking Test Service Provider?

Selecting a professional and reliable testing service provider is critical to ensuring the accuracy and international recognition of test results. A high-quality service provider should meet the following criteria:

• Relevant Qualifications and Accreditations: Possess laboratory accreditations such as CNAS (China National Accreditation Service for Conformity Assessment) or CMA (China Inspection Body and Laboratory Mandatory Approval), ensuring international credibility of test results.
• Rich Testing Experience: Familiar with the characteristics of battery products and test requirements, capable of providing professional test advice and problem-solving solutions.
• Advanced Testing Equipment: Equipped with test equipment that meets standard requirements, with regular calibration and maintenance.
• Global Recognition: Test results are widely accepted internationally to avoid duplicate testing.
• One-Stop Service Capability: Offer end-to-end services from testing to certification, including UN38.3 testing and transport identification reports.

Conclusion

The 3m Stacking Test is a key safeguard for the air transport safety of batteries. With the implementation of IATA DGR Version 66, its scope of application has expanded from the original PI 965 IB and PI 968 IB to more packaging types, including PI 966-II, PI 967-I/II, PI 969-II, and PI 970-I/II.

For battery manufacturers, equipment producers, and traders, fully recognizing the importance of the 3m Stacking Test and conducting tests and preparations in strict accordance with requirements is a critical step to ensure smooth product exports and promote the smooth progress of international trade. Planning test strategies in advance and selecting a professional, reliable testing partner are key to ensuring products comply with international transport regulations.