A Comprehensive Guide to Power Battery Leak Testing: National Standard Updates, Testing Methods, and Selection Guidelines

On July 1, 2026, GB 38031-2025 officially took effect, fully replacing the 2020 version. 

What does this mean for power battery manufacturers? How have the type test requirements changed? How should you choose an air leak tester for your production line? This article provides direct answers.

I. Several National Standards You Need to Know

(an official) standard	Main Functions	Relationship to Leak Testing
GB 38031-2025	Safety Requirements for Power Batteries Used in Electric Vehicles (Current Version)	Safety tests, including water immersion and wet-heat cycling, are core safety benchmarks.
GB/T 4208-2017	Enclosure Protection Rating (IP Code)	Basic Standards for Understanding and Verifying the Dust and Water Resistance Ratings of Enclosures
GB/T 30038-2013	Protection Ratings for Electrical and Electronic Equipment in Road Vehicles	IP Rating Evaluation for In-Vehicle Electrical Equipment
GB/T 31467-2023	Test Methods for the Electrical Performance of Lithium-Ion Battery Packs	Primarily focuses on electrical performance; not a general standard for airtightness leakage rates

One thing must be made clear:The type test requirements of GB 38031-2025 cannot be directly applied to production lines.airtightness meterPressure values and leakage rate limits. Production line parameters must be established separately in accordance with the product technical agreement, the automaker’s acceptance criteria, and the specific IP rating targets.

In addition, GB/T 30038-2026 has been published and will take effect on March 1, 2027. When developing new projects, assess in advance how the revision of this standard will affect the validation plan.

II. If the type test has been passed, why does the production line still need to be equipped with...airtightness meter?

The answer is simple:Type testing proves that “this product is safe by design,” while production line leak testing proves that “this product is actually leak-free.” These are two completely different things.

The sealing structure of a power battery pack is extremely complex—including the sealing gaskets between the top cover and bottom housing, the locations where high- and low-voltage connectors pass through the compartment, the cooling line connections and weld seams, the installation areas for the waterproof and breathable membrane, and the mating surfaces of die-cast parts and bolts. If a sealing defect occurs at any one of these points, the protection rating of the entire pack will be compromised. Yet visual inspections cannot detect even the slightest leak.

Replace subjective judgments like “it looks fine” with quantifiable data...This is the fundamental reason for conducting airtightness testing on production lines.

III. Four Testing Methods: Which One Should You Choose?

The key to selecting the right model lies not only in the instrument’s accuracy, but also in a comprehensive evaluation of the product’s volume, structural rigidity, target leak rate, production cycle time, and cost.

Direct-Pressure Leak Test

Apply a set pressure to the workpiece and monitor pressure changes after a stabilization period. This method has the simplest structure and is suitable for battery casings, sealing covers, various fasteners, and workpieces with larger volumes.Key Considerations for Selection: Test volume, elastic deformation of the workpiece, equilibration time, and allowable leakage rate.

Differential Pressure Leak Testing

The test piece and the reference chamber are pressurized simultaneously, and leaks are detected by comparing the pressure difference between the two sides. This effectively compensates for common-mode fluctuations caused by factors such as temperature,Higher repeatability, suitable for precision components with strict sealing requirements.Key Considerations for Selection: Reference chamber matching, temperature stabilization time, and sensor performance.

Flow-Based Detection

This method quantitatively evaluates leaks by measuring the gas flow rate passing through the leak point per unit of time, making it suitable for scenarios where product standards need to be established in units of mL/min or sccm.Key Considerations for Selection: Flow range, test pressure, unit conversion method.

Helium Mass Spectrometry Leak Detection

Using helium as a tracer gas provides significantly higher sensitivity than air detection and is suitable for R&D validation or specific high-reliability applications.Due to high consumable costs and slow inspection cycles, this approach is not typically the first choice for mass production scenarios.

These four methods are not ranked in order of increasing accuracy; rather, they each have their own specific focus depending on the product and application. For mass-production leak screening, an appropriate air-tightness solution is easier to integrate into the production line; helium testing is only necessary for verifying extreme micro-leaks. Both methods can be used in conjunction within the same quality system.

IV. Which Equipment Should You Choose for Different Components?

target of detection	Focus on Defects	Equipment Selection Recommendations
Battery Pack Top Cover, Lower Housing	Failed sealing strips, cracks in the housing, and leaks at welds	Direct-Pressure or Differential-Pressure
Battery Pack Assembly	Leaks across multiple sealing surfaces, connectors, and interfaces	Select between direct-pressure and differential-pressure types based on volume and target leak rate
Liquid-cooled plates, cooling lines, quick-connect fittings	Welding sand holes, poor joint sealing, and pipeline leaks	Differential-pressure, direct-pressure, or flow-based
waterproof and breathable membrane	Abnormal air permeability, insufficient water-blocking capacity	Combined Air Permeability and Water Pressure Resistance Testing Equipment
High-Reliability Seals and R&D Prototypes	Extremely low leakage rates or specific failure mechanisms	Methods Such as Helium Mass Spectrometry Based on Target Leak Rate Assessment

Large Thin-Walled ShellsThere is one pitfall that’s easy to overlook:Elastic deformation during inflation introduces noise into the pressure data. Not enough time to balance things out,Material ExpansionThe resulting pressure fluctuations could be mistaken for a leak. When selecting equipment, one should not rely solely on sensor resolution; it is essential to run the entire process using actual workpieces and conduct continuous, repeatable tests.

V. What Does Jingcheng Engineering Offer?

Jingcheng Engineering (JCGK) isShenzhen Jingchenggongke Technology Co., Ltd.A proprietary brand specializing in airtightness testing, coveringAirtightness Tester,Waterproof Tester,Non-standard automation equipment, supporting tooling and automation integration.

The logic behind the JCGK solution is as follows:First, confirm the product requirements; then, select the testing method and fixtures; finally, use actual samples to verify whether the requirements can be met for mass production. We don’t just sell equipment; we provide practical, end-to-end solutions tailored to product structure, production line rhythms, and data traceability requirements.

Dual-station or multi-channel inspection: For similar structural components such as top covers and bottom housings, we design dedicated workstations and matching fixtures; the use of multiple parallel channels significantly reduces wait times.

Battery Bottom CoverDual-channel airtightness meter

Precision Differential Pressure Measurement: For products with high sealing requirements and strict repeatability standards, establish a stable and traceable evaluation method by combining temperature stabilization time with standard leak hole calibration.

Integration of automated production lines: For high-volume projects, the system can integrate with PLCs, robotic arms, barcode readers, and MES systems to enable automatic start/stop, pass/fail determination, anomaly alerts, and traceability through individual inspection records.

VI. How do I set the test parameters?

There are no uniform pressure and leakage rate limits that apply to all battery packs.. The correct sequence is: product drawings and technical agreements take precedence, followed by the vehicle manufacturer’s acceptance criteria, and then confirmation of the equipment’s capabilities through prototype testing and repeatability verification.

Before the official implementation, the following five items must be verified one by one:

Checklist Items	The Core Issue
Pressure and Safety	Is the test pressure within the allowable range for the workpiece and fixture?
Test Cycle	Will the total time required for inflation, balancing, testing, and deflation meet the cycle time requirements?
repeatable	Verify using stable samples and standard leak holes to determine whether the measurement variations are acceptable.
Risk of Misjudgment	Have you checked for interference such as fixture leaks, temperature fluctuations, and elastic deformation of the workpiece?
Data traceability	Are the procedures for barcode linking, result storage, exception alerts, and MES integration clearly defined?

VII. What is most easily overlooked during the procurement process?

The unit price of the equipment is merely a one-time investment. What truly affects the overall cost is whether tooling and pneumatic components need to be purchased separately; whether changeovers are convenient and compatible with multiple product specifications; whether the system can be integrated with existing PLCs and MES; whether it can export per-unit data to support quality traceability; and whether sample verification, parameter debugging, and full-lifecycle after-sales support are provided.

JCGK Jingcheng Engineering has just one piece of advice:Use prototype verification, repeatability comparisons, and production line acceptance testing to objectively assess whether the equipment meets project requirements, rather than basing the decision on brand or price. The gap between domestically produced solutions and imported equipment should be demonstrated with data.

Conclusion

Quality control for the sealing of power batteries is a systematic engineering process that integrates standard requirements, product risks, and mass production processes. There is no single, universal testing parameter, nor is there a single method suitable for all scenarios.

If you are planning airtightness testing for battery housings, liquid-cooling plates, cooling lines, or battery pack assemblies, we recommend bringing your product drawings, target test pressure, allowable leak rate, and cycle time requirements to conduct a tailored solution validation.

Jingcheng Engineering (JCGK) is a leading company in the field of airtightness testing in China We offer comprehensive evaluations of direct-pressure, differential-pressure, multi-channel, and custom automated testing solutions. Please feel free to contact us for further discussion.

Original Statement: This article was written by ShenShenzhen Jingcheng Engineering Technology Co., Ltd.Written by the technical team, reproduced with attribution.Data sources: Precision Engineering internal test data and customer cases.