New Energy Vehicle Battery Crush (Extrusion) Testing: Standards, Methods and Acceptance Criteria

Battery crush testing, also known as extrusion testing, is a mandatory mechanical abuse test that verifies whether the traction battery of a new energy vehicle can withstand severe deformation without catching fire or exploding. This article explains the technical principles, applicable standards, sample requirements, test procedures, and pass criteria for EV battery crush testing, providing a practical reference for battery designers, vehicle manufacturers, and quality engineers working with accredited third-party laboratories.

Technical Overview

Crush testing (extrusion testing) is one of the most important mechanical abuse evaluations for lithium-ion traction batteries used in new energy vehicles. The test simulates the severe deformation that a battery may experience during a vehicle collision, rollover, or object intrusion, in which the cell, module, or pack is compressed between rigid surfaces until structural failure or a defined force limit is reached.

The primary hazard being investigated is the internal short circuit. When mechanical deformation brings cathode and anode materials into direct contact, localized high-current discharge can trigger thermal runaway, which may propagate through the battery and result in fire or explosion. Crush testing therefore evaluates the combined effectiveness of cell design (electrode and separator robustness), housing strength, venting behavior, and pack-level crash protection.

Crush tests are typically performed as quasi-static compression, in which a rigid plate or a cylindrical indenting head presses into the specimen at a controlled low speed while force, displacement, voltage, and temperature are continuously recorded. The most commonly referenced standards and regulations include:

• GB 38031-2020 — mandatory safety standard for EV traction batteries in China (pack and system level)
• GB/T 31485-2015 — safety requirements and test methods for cells and modules
• GB/T 31467.3-2015 — safety requirements for battery packs and systems
• UN 38.3 (Test T.6) — crush test for transport safety of lithium cells
• IEC 62660-2 — safety testing of secondary lithium cells for EV applications
• ISO 12405-3 — safety performance requirements for lithium-ion battery packs and systems
• SAE J2464 — abuse testing of rechargeable energy storage systems for electric and hybrid vehicles
• UL 2580 and UL 1642 — battery safety standards referencing crush methods
• UN ECE R100 — regional homologation requirements including mechanical abuse assessment

Testing Samples

Cell-Level Samples

Cell samples include cylindrical, prismatic, and pouch formats in their final production configuration. Specimens are usually tested in a fully charged state (upper limit of charge voltage as specified by the manufacturer) after temperature conditioning, because a high state of charge represents the worst-case energy content. Cylindrical cells are typically crushed perpendicular to their longitudinal axis using a half-cylindrical indenter, while prismatic and pouch cells are compressed on their large faces with a flat plate.

Module-Level Samples

Module samples consist of multiple cells assembled with busbars, sensing harnesses, and mechanical frames in the configuration used in the pack. Module testing verifies that cell-to-cell spacing, compression pads, and module housings provide adequate protection under deformation. The number of samples is defined by the applicable standard, and fresh production samples without prior abuse are normally required.

Pack and System-Level Samples

Battery packs and complete battery systems, including the battery management unit, cooling circuit, and enclosure, are tested to satisfy pack-level requirements such as those in GB 38031-2020. The crush direction is typically aligned with the vehicle longitudinal (travel) direction and, where required, the lateral direction, reflecting the most probable intrusion paths during a crash. Samples must be complete, representative of series production, and instrumented where the standard permits.

Testing Items

During crush testing, the following items are evaluated and documented:

• Force–displacement response (stiffness, structural resistance, energy absorption)
• Deformation resistance and enclosure integrity under compression
• Occurrence and characteristics of internal short circuits (voltage drop behavior)
• Surface and internal temperature rise during and after compression
• Electrolyte leakage and casing rupture
• Gas venting, smoke release, and pressure-relief device activation
• Fire and explosion events within the specified observation period
• Thermal propagation behavior between cells after localized failure, where applicable
• Comparison of flat-plate crush versus cylindrical-head (rod) crush failure modes

Testing Methods

Equipment and Test Setup

Crush tests are performed with a servo-hydraulic or servo-electric compression machine installed inside a reinforced, ventilated explosion-proof chamber. Typical equipment features include force capacity from 200 kN up to 1000 kN for pack-level testing, programmable crosshead speed control, interchangeable indenters (flat plate or half-cylinder with a radius of approximately 75 mm), thermocouple and voltage monitoring channels, high-speed video recording, smoke and gas detection, and a fire suppression system.

Standard Test Conditions

Typical conditions specified by the major standards are as follows:

• Crush speed: generally not exceeding 2 mm/s for quasi-static extrusion
• Cell-level endpoint: surface pressure of approximately 17.2 MPa (GB/T 31485) or a force of 13 kN, or 1000 times the cell mass, whichever is smaller (UN 38.3); some frameworks terminate the test when the voltage falls to one third of its initial value
• Module and pack-level endpoint: the reaction force limit defined by the standard, commonly 100 kN or a specified multiple of the sample weight, or a defined deformation criterion
• State of charge: fully charged or as specified by the applicable standard or the manufacturer
• Environmental temperature: usually room temperature, unless otherwise specified

Test Procedure

• Charge the sample according to the manufacturer's specified procedure and allow it to rest and stabilize at the test temperature.
• Install instrumentation (voltage taps, thermocouples) and position the sample between the rigid platen and the indenter, aligning the crush direction with the electrode stack, cell axis, or vehicle axis as required.
• Apply compression at the controlled speed while recording force, displacement, voltage, and temperature continuously.
• Stop the test when the force, pressure, voltage, or deformation endpoint defined by the standard is reached, then hold or release as specified.
• Observe the sample throughout the test and for the post-test observation period defined by the standard, typically at least one hour.
• Photograph, document, and analyze the specimen; classify the result against the acceptance criteria.

Acceptance Criteria

The universal pass criterion for crush testing is no fire and no explosion during the test and the specified observation period. Depending on the standard and the test level, additional requirements may apply, such as no rupture of the enclosure, no exposure of hazardous components, and acceptable isolation resistance after the test. Elevated temperature, smoke, or leakage may be recorded as informative results but do not necessarily constitute failure unless the applicable standard states otherwise.

Safety Precautions

Because crush testing can trigger thermal runaway, tests must be conducted by trained personnel using remote operation, blast-resistant enclosures, exhaust gas scrubbing, and standby fire suppression. Damaged specimens must be quarantined and monitored after testing before disposal through certified hazardous waste channels.

Applications

Crush testing serves multiple purposes across the battery and vehicle development lifecycle:

• Mandatory type approval and market access for new energy vehicles in China under GB 38031-2020
• Transport safety classification of lithium cells under UN 38.3 for shipping and logistics
• Regional homologation and export certification, including mechanical abuse evidence for European and North American markets
• Research and development of cell formats, separator materials, casings, and venting designs
• Validation of pack enclosure design, crash structures, and anti-intrusion strategies
• Design change verification, supplier qualification, and incoming quality control for battery components
• Root cause analysis and forensic investigation after field incidents or failed mechanical abuse tests

FAQ

What is the difference between crush testing and nail penetration testing?

Both tests induce internal short circuits, but crush testing compresses the battery between rigid surfaces to simulate collision deformation, while nail penetration drives a conductive rod through the cell. Crush testing is a regulatory requirement under standards such as GB 38031, whereas nail penetration is more commonly used as a research and comparison tool.

At what state of charge is the sample tested?

Most standards require the sample to be fully charged to the upper limit voltage specified by the manufacturer, because a high state of charge represents the worst case for released energy. Some frameworks permit or require other defined states of charge, so the applicable standard must always be confirmed before testing.

What results constitute a failure?

Fire or explosion at any time during the test or the observation period is a failure under all major standards. Criteria such as voltage drop and temperature rise are used as termination conditions or diagnostic indicators rather than automatic failures, and leakage requirements depend on the specific standard and test level.

Which standard applies to market access in China?

GB 38031-2020 is the mandatory national standard for traction battery safety and applies to battery packs and systems installed in new energy vehicles. Cell and module level evidence under GB/T 31485 is frequently submitted alongside pack-level results as part of a complete compliance dossier.

Can crush testing be performed on all sample levels?

Yes. Cell-level tests characterize intrinsic safety of the electrode design, module-level tests verify group-level protection, and pack-level tests demonstrate system-level crashworthiness. Accredited third-party laboratories can advise on the appropriate test matrix for a given regulatory objective.

How long does a crush test take?

The active compression phase is usually short due to the low crush speed and limited stroke, but full cycle time includes conditioning, instrumentation, the post-test observation period, and safe handling of the damaged specimen, so a complete test session typically requires several hours per sample.