High-Temperature Testing for New Energy Vehicle Batteries: Standards, Methods and Safety Evaluation

High-temperature testing is a critical safety and performance evaluation process for new energy vehicle (NEV) batteries, verifying that lithium-ion cells, modules, and packs can withstand extreme thermal stress without fire, explosion, or unacceptable degradation. This article explains the technical basis, sample requirements, test items, methodologies, applicable standards, and industrial applications of high-temperature battery testing for automotive manufacturers and battery developers.

Technical Overview

Lithium-ion power batteries used in new energy vehicles are highly sensitive to heat. Elevated temperatures accelerate side reactions inside the cell, including decomposition of the solid electrolyte interphase (SEI) layer, electrolyte oxidation, separator shrinkage, and cathode material instability. In severe cases, these mechanisms can progress into thermal runaway, an uncontrolled exothermic reaction that may result in fire or explosion. High-temperature testing therefore simulates worst-case thermal scenarios such as hot-climate operation, prolonged summer parking, heat generated during fast charging, and internal or external short circuits.

High-temperature testing is a mandatory part of battery safety homologation in most major markets. In China, GB 38031-2020 defines the compulsory safety requirements for traction batteries of electric vehicles, while GB/T 31486 and GB/T 31467.3 cover performance and system-level testing. International frameworks include IEC 62660-2 for cell-level reliability and abuse testing, IEC 62133-2, ISO 12405-3 for battery packs and systems, UL 2580 for EV battery modules and packs, and the UN 38.3 transport requirements. Accredited third-party laboratories perform these evaluations under controlled conditions to demonstrate that products meet regulatory and customer specifications.

Testing Samples

Battery Cells

Cell-level samples include cylindrical (such as 18650, 21700, and 46xx formats), prismatic, and pouch-type lithium-ion cells. Cells are typically tested at specified states of charge, most commonly 100% SOC for worst-case safety tests and 50% SOC for certain characterization tests. Both fresh cells and aged cells that have completed a defined number of charge-discharge cycles may be evaluated, because aging changes the thermal behavior of the cell.

Battery Modules and Packs

Module and pack samples include the cell assemblies, busbars, fuses, current sensors, thermal barriers, cooling interfaces, enclosures, and the battery management system (BMS). System-level high-temperature tests verify not only electrochemical safety but also the mechanical integrity of housings, connector retention, insulation coordination, and the accuracy of BMS temperature monitoring under sustained heat.

Components and Materials

Supporting materials such as separators, electrolytes, adhesives, thermal interface materials, insulation films, cables, and plastic enclosures can be tested separately for heat resistance, flammability, and dimensional stability at elevated temperatures, in line with standards such as IEC 60068-2 series environmental test methods and applicable UL material standards.

Testing Items

Typical high-temperature test items for NEV power batteries include:

• High-temperature storage test, evaluating capacity retention and internal resistance after prolonged hot storage.
• High-temperature discharge and operation test, verifying usable capacity and power capability at ambient temperatures of 55 °C to 60 °C.
• High-temperature charging test, assessing charge acceptance and safety during charging in hot conditions.
• Thermal abuse (hot oven) test, confirming that a fully charged cell does not catch fire or explode when heated to 130 °C and held.
• Thermal shock and temperature cycling test, subjecting samples to rapid transitions between extreme cold and heat, commonly between −40 °C and +85 °C.
• Heat resistance test of the pack enclosure and external circuits at elevated ambient temperature.
• Thermal runaway propagation test, verifying that failure of a single cell does not spread, or that occupants receive adequate warning time.
• Accelerated thermal aging tests, characterizing calendar life and degradation behavior during long-term storage at 45 °C to 60 °C.
• Insulation resistance and dielectric withstand tests performed at elevated temperature to confirm electrical safety.

Testing Methods

Thermal Abuse (Hot Oven) Test

In accordance with GB 38031-2020 and IEC 62660-2, a fully charged cell is placed in a temperature-controlled oven and heated at a defined ramp rate, commonly about 5 °C per minute, up to 130 °C, then held at that temperature for a specified period, typically 30 minutes. The sample passes if no fire and no explosion occur. Thermocouples attached to the cell surface and, where feasible, internal reference points record the temperature response throughout the test.

High-Temperature Storage Test

Samples are stored in climatic chambers at temperatures such as 72 °C (consistent with UN 38.3 thermal conditioning), 85 °C, or other agreed values for durations ranging from several hours to several weeks. After storage and recovery at room temperature, laboratories measure residual capacity, capacity recovery, internal resistance, thickness growth, mass loss, and gas generation. Acceptance criteria are defined by the applicable standard or by customer specification.

High-Temperature Operation Test

Cells, modules, or packs are conditioned at 55 °C to 60 °C and then subjected to standardized discharge and charge profiles. The test verifies capacity retention and energy efficiency at high ambient temperature, and at pack level it confirms that BMS temperature sensors report accurately, cooling systems respond correctly, and derating strategies behave as designed.

Thermal Cycling and Thermal Shock Test

Temperature cycling exposes samples to repeated excursions between low and high extremes, for example −40 °C to +85 °C with dwell times of several hours per plateau, following frameworks such as ISO 12405-3, UL 2580, and IEC 60068-2 change-of-temperature methods. This evaluation reveals fatigue of welds, busbars, seals, and interfaces caused by repeated thermal expansion and contraction.

Instrumentation and Evaluation

Testing is conducted in forced-air ovens or walk-in environmental chambers with multi-channel data acquisition systems, K-type thermocouples, and infrared thermography for surface temperature mapping. For research and characterization purposes, accelerating rate calorimetry (ARC) can determine the onset temperature of self-heating, the thermal runaway trigger temperature, and the maximum self-heating rate. Test reports document temperatures, voltages, visual observations, and pass or fail conclusions against the defined acceptance criteria.

Applications

High-temperature battery testing supports a wide range of engineering and commercial objectives:

• Regulatory compliance and market access, including mandatory homologation of traction batteries under GB 38031-2020 and alignment with IEC, ISO, EN, UL, and JIS frameworks for export products.
• Design validation and production validation during vehicle development programs, ensuring thermal management systems meet performance targets.
• Supplier quality control, comparing incoming battery lots against agreed thermal performance baselines.
• Research and development of cell chemistry, thermal barriers, immersion cooling, and cell-to-pack structures.
• Warranty analysis and failure investigation, reproducing heat-related field failures under laboratory conditions.
• Aging and lifecycle studies, using accelerated thermal stress to project long-term capacity fade and impedance growth.

FAQ

What temperature range is covered by high-temperature battery testing?

Most tests are performed between 55 °C and 130 °C, covering hot ambient operation, storage conditioning, and the thermal abuse threshold. Specialized studies, such as thermal stability characterization of cell materials, may extend to 200 °C or higher in calorimetric instruments.

Which standards are mandatory in China?

GB 38031-2020 is the compulsory national standard for traction battery safety, including the thermal abuse test at 130 °C. GB/T 31486 and GB/T 31467 series are widely applied for performance and system-level evaluation, and international standards such as IEC 62660-2, ISO 12405-3, and UL 2580 are used for global programs.

What are the typical pass criteria?

For safety tests, the standard criteria are no fire and no explosion, often accompanied by no rupture, no leakage, and maintained insulation resistance. For performance tests, acceptance is based on measurable thresholds such as minimum capacity retention, maximum internal resistance growth, and limited dimensional swelling.

How long does high-temperature testing take?

Single-event tests such as the oven test can be completed within one to two days including conditioning. Thermal cycling and accelerated aging programs may last from several weeks to several months depending on the number of cycles and the required storage duration.

Can aged or used batteries be tested?

Yes. Testing aged cells after defined cycling is increasingly important for evaluating end-of-life safety, second-life applications, and thermal runaway propagation behavior, since aged cells can exhibit different thermal characteristics compared with new cells.