What Is Cycle Life — ISO 12405?
The cycle life test is a life test in which the battery is repeatedly charged and discharged under defined conditions to track how its capacity decreases relative to the initial value. End of life is generally defined as a drop to a specified capacity ratio.
Purpose of Cycle Life — ISO 12405
The purpose is to verify the battery's declared cycle life and to predict capacity loss over its service life.
Which Products Is Cycle Life — ISO 12405 Applied To?
- Lithium-ion cells and modules
- Electric vehicle batteries
- Energy storage systems
- Portable device batteries
In Which Sectors Is Cycle Life — ISO 12405 Used?
Standards Related to Cycle Life — ISO 12405
- ISO 12405Test conditions for electric vehicle lithium battery packs test
Cycle Life — ISO 12405 Conditions
- Cycle profile
- Charge/discharge current and depth of discharge (DOD) defined in the specification
- Temperature
- Fixed reference temperature; a higher temperature may be used for acceleration
- Capacity check
- Reference capacity measurement at specified cycle intervals
- End of life
- Typically a drop to 80% of the initial capacity
Equipment for Cycle Life — ISO 12405
- Multi-channel battery cycler
- Temperature chambers
- Long-duration data logging system
- Safety enclosure
Sample Requirements for Cycle Life — ISO 12405
- The number of specimens must be suitable for statistical evaluation
- The initial capacity and internal resistance must be recorded
- The declared cycle life and DOD information must be provided
- Specimens remain in the chamber throughout the test
Duration of Cycle Life — ISO 12405
This is the longest-running battery test. Depending on the number of cycles and the profile, it can take from weeks to months; scheduling is clarified at the quote stage.
Cycle Life — ISO 12405 Procedure
- 1The initial capacity and internal resistance are measured.
- 2The cycle profile defined in the specification is applied.
- 3Reference capacity measurements are taken at specified intervals.
- 4A capacity-versus-cycle curve is produced.
- 5The test is stopped when the end-of-life criterion is reached or the target number of cycles is completed.
Cycle Life — ISO 12405 Acceptance Criteria
The acceptance criterion is a minimum capacity-retention ratio after a specified number of cycles, as given in the specification.
Evaluation of Results
The capacity-retention curve and the increase in internal resistance are evaluated together. Results accelerated at high temperature cannot be directly translated to real conditions.
Cycle Life — ISO 12405 Report
- Standard applied
- Cycle profile, DOD and temperature
- Reference capacity measurement intervals
- Capacity-retention curve and number of cycles
- Change in internal resistance
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
- EU Battery Regulation (durability declaration)
- UNECE R100
Batarya Testleri — What Does This Testing Field Cover?
The section below describes the field that the Cycle Life 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 Cycle Life — ISO 12405
Why does the cycle life test take so long?
Every cycle requires real-time charging and discharging. For example, a thousand cycles at 1C discharge, together with rest periods, can take months. A higher temperature is used for acceleration, but the results must be interpreted indirectly.