What Is Thermal Cycling — ISO 12405?
The thermal cycling test is a test in which the specimen is cycled a defined number of times between high and low temperature, evaluating damage arising from differences in material expansion.
Purpose of Thermal Cycling — ISO 12405
The purpose is to reveal, in an accelerated manner, the fatigue that temperature changes cause in structural joints, solder connections and sealing elements.
Which Products Is Thermal Cycling — ISO 12405 Applied To?
- Battery cells, modules and packages
- Electronic boards and solder joints
- Automotive and aerospace components
- Sealing elements
In Which Sectors Is Thermal Cycling — ISO 12405 Used?
Standards Related to Thermal Cycling — ISO 12405
- ISO 12405Test conditions for electric vehicle lithium battery packs test
Thermal Cycling — ISO 12405 Conditions
- UN 38.3 T.2 temperatures
- 72 °C ± 2 °C and −40 °C ± 2 °C
- UN 38.3 T.2 dwell time
- At least six hours at each temperature
- UN 38.3 T.2 number of cycles
- Ten cycles, followed by 24 hours of rest
- Transfer time
- Maximum transition time defined in the standard
Equipment for Thermal Cycling — ISO 12405
- Two-zone or programmable temperature chamber
- Multi-channel temperature recording
- Voltage and mass measurement (battery)
- Function-monitoring rig
Sample Requirements for Thermal Cycling — ISO 12405
- The specimen must be fully charged in battery tests
- Initial mass and voltage must be recorded
- The number of specimens is defined in the standard
- The specimen must be placed in the chamber with free air circulation
Duration of Thermal Cycling — ISO 12405
For UN 38.3 T.2, together with the ten cycles and rest period, it takes approximately six days.
Thermal Cycling — ISO 12405 Procedure
- 1The specimen is identified, and its mass and voltage are recorded.
- 2The specimen is placed in the chamber.
- 3It is held at the high temperature for the defined duration.
- 4It is transitioned to the low temperature and held for the defined duration.
- 5The cycle is repeated the defined number of times.
- 6Mass, voltage and physical condition are assessed after the rest period.
Thermal Cycling — ISO 12405 Acceptance Criteria
The acceptance criterion is defined in the applied standard. In UN 38.3 T.2, a mass-loss limit, the absence of leakage, fire and explosion, and a voltage condition are required.
Evaluation of Results
Mass loss, voltage change and visual inspection are evaluated together. Solder and gasket joints are checked for cracks.
Thermal Cycling — ISO 12405 Report
- Applied standard and test number
- Temperature levels, dwell times and number of cycles
- Initial and final mass and voltage
- temperature records
- Observations and photographs
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- UN 38.3 (battery transport)
- Automotive and aerospace component specifications
Batarya Testleri — What Does This Testing Field Cover?
The section below describes the field that the Thermal Cycling test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Battery testing answers three separate questions, each with its own body of standards: can the battery be transported, is it safe in use, does it deliver the declared performance? These three questions are often confused with one another, and the confusion has commercial consequences — a market cannot be entered with a transport report, and a shipment cannot be made with a product safety report.
On the transport side, UN 38.3 is a mandatory gate; a battery without that evidence cannot be shipped. On the safety side the application determines what applies: IEC 62133-2 for portable products, IEC 62619 and IEC 63056 for industrial and energy storage applications, UNECE R100, UL 2580 and ISO 6469 for electric vehicles. On the performance side, capacity, internal resistance, cycle life, self-discharge, charge acceptance and temperature-dependent behaviour are measured.
The distinction of LEVEL is essential in this family and is the subject that causes the most argument in the supply chain. Cell, module and pack are assessed separately; a certificate obtained for a cell does not demonstrate the conformity of the pack. Alongside the cells, the behaviour of the pack is determined by the battery management system, the cooling design, the mechanical structure, the interconnection arrangement and insulation coordination. Putting the cell supplier's report into the pack file is a common but inadequate approach.
Thermal runaway and its propagation are the most critical subject in the field. A lithium cell may enter a self-sustaining chemical reaction when damaged or overheated; at that point removing the heat from outside is usually not possible. Modern standards therefore treat thermal runaway of a single cell as an UNAVOIDABLE fault scenario and change the question: does the event propagate to neighbouring cells, what does it release outside the pack, and how much time is left for the user to escape?
In this field the battery management system is assessed not as an electronic board but as a SAFETY FUNCTION. It is shown that overcharge, overdischarge, overcurrent and overtemperature protections actually operate, that the system falls to the safe side in a fault, and that its software has been verified. In industrial and vehicle applications this assessment is tied to functional safety frameworks.
The regulatory side is becoming rapidly more demanding. Battery Regulation (EU) 2023/1542 goes beyond safety and introduces obligations for carbon footprint declaration, recovered content ratio, durability and capacity declaration, the battery passport, and removability for portable batteries. This takes the scope of testing beyond classical safety tests.
Method groups in this field
Electrical abuse
Overcharge, overdischarge, external short circuit, forced discharge and unbalanced charging. This is where it is seen whether the protection circuits actually work.
Mechanical abuse
Vibration, shock, crush, penetration, free fall and tipping. It is monitored whether internal short circuit conditions arise.
Thermal tests
Temperature cycling, thermal shock, high temperature storage, fire exposure and thermal runaway propagation.
Environmental tests
Humidity, low pressure, salt spray and, where required, immersion; these come to the fore in vehicle and outdoor applications.
Performance measurements
Capacity, energy and power, internal resistance, efficiency, cycle life, calendar life and temperature-dependent behaviour.
BMS verification
Verification of protection thresholds, the cell balancing function, communications and fault response.
Commonly confused in this field
- UN 38.3 is not a product safety certificate; it only demonstrates transport conformity.
- A cell certificate does not demonstrate pack conformity. The pack is assessed separately with its own architecture.
- Two packs built from the same cell give different results; cooling, interconnection and mechanical structure are decisive.
- A performance test is not a safety test. A cycle life report does not satisfy safety requirements.
- For an electric vehicle battery, a UL 2580 report and UNECE R100 approval are not the same thing; one is a standards assessment, the other a type approval regime.
- A vehicle battery moved into a second-life application enters a new usage profile; the earlier assessment does not carry over directly.
Which decisions these results support
- Transport conformity and the test summary for shipment
- Product safety declaration and market access
- Performance, durability and carbon footprint declarations under the Battery Regulation
- Assessing the impact of a cell supplier or BMS change
- Site acceptance processes for an energy storage system
Related Tests
Frequently Asked Questions About Thermal Cycling — ISO 12405
According to which standard is Thermal Cycling made?
Thermal Cycling is executed in scope UN 38.3 T.2, IEC 60068-2-14, IEC 62133-2, ISO 16750-4, MIL-STD-810 Method 503 and ISO 12405. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.
Which products does Thermal Cycling apply to?
Mainly applied to Battery cells, modules and packages, Electronic boards and solder joints, Automotive and aerospace components and Sealing elements. Whether your product is included in the scope is determined by examining its technical specifications and intended use.
Under what conditions is Thermal Cycling done?
The determining parameters are: UN 38.3 T.2 temperatures — 72 °C ± 2 °C and −40 °C ± 2 °C, UN 38.3 T.2 dwell time — At least six hours at each temperature and UN 38.3 T.2 number of cycles — Ten cycles, followed by 24 hours of rest. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.
What kind of sample is needed for Thermal Cycling?
The specimen must be fully charged in battery tests, Initial mass and voltage must be recorded and The number of specimens is defined in the standard. The number of samples is determined according to the product standard and the scope to be reported.
How long does Thermal Cycling take?
For UN 38.3 T.2, together with the ten cycles and rest period, it takes approximately six days. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.
What is the Thermal Cycling result called "appropriate"?
The acceptance criterion is defined in the applied standard. In UN 38.3 T.2, a mass-loss limit, the absence of leakage, fire and explosion, and a voltage condition are required.