In recent years, countries around the world have continuously increased policy support for new energy vehicles, and car companies such as Tesla have also launched new models. It has led to the rapid growth of the global electric vehicle market. However, the fire and explosion accidents of electric vehicles have occurred many times, making the safety issue the focus of consumers. In this context, countries and relevant international organizations have issued standards for the safety testing of power batteries to standardize the safe use of power batteries.

At present, the international technical standards/specifications related to the safety of power batteries are shown in the figure. Among them, the standards issued by ISO (International Organization for Standardization), IEC (International Electrotechnical Commission) and SAE International (Society of Automotive Engineers) are international standards, which have strong reference significance for national standards, As specified in JIS C8715-2-2012 Secondary lithium batteries for industrial applications – Part 2: Test and safety requirements of Japan, IEC 62660 series standards are preferred for batteries for road vehicles.

UL 2580 is a power lithium battery standard issued by the Underwriters Laboratories (UL) of the United States. It covers a comprehensive range of contents, including the electrical performance, environmental suitability and safety requirements of individual batteries, battery modules, battery stacks and battery systems, as well as the basic safety tests for battery components on the production line. At the same time, it strengthens the safety review requirements in battery management system, cooling system and protection circuit design. ECE R100 is the vehicle regulation of the United Nations Economic Commission for Europe. The standard is divided into two parts. Part 2 of the standard specifies the safety of the rechargeable energy storage system (REESS) for vehicles in detail. In addition to the above standards, FreedomCAR of the United States Department of Energy plans to launch a safety test manual for power batteries for electric vehicles in 2005, which provides comprehensive provisions for the safety test of power batteries.

According to the characteristics of the test items, the safety test can generally be divided into mechanical safety test (vibration, shock, drop, puncture, etc.), environmental safety test (thermal shock, thermal stability, fire, etc.), and electrical safety test (short circuit, overcharge, over-discharge, etc.). Among them, thermal shock cycle, short circuit, overcharge, over-discharge, vibration, mechanical shock, extrusion and other projects that are widely used will be described in detail below.

1.Mechanical Safety

1.1 Vibration

Vibration is inevitable in the driving process of electric vehicles. Therefore, almost all standards/specifications in this paper list it as a safety test item. The frequency, power spectral density and other parameters of vibration test vary greatly in different standards. Sinusoidal scanning test is usually used to identify product resonance, while random vibration usually simulates the daily life scene that the sample will experience.

The vibration parameters of ISO 12405-1 (2.3) and IEC 62660-2 (3) refer to IEC 60068-2-64. The former is the only standard (series) listed in Table 3 that requires vibration tests at different temperatures (- 40 ℃,+25 ℃,+75 ℃). The original vibration test of GB/T 31467.3-2015 refers to ISO 12405 series standards, and the vibration parameters are the same. In 2017, the standard changed the vibration test to sinusoidal vibration, and the specific test parameters are the same as ECE R100-02. The sinusoidal sweep of SAE J2929 2013 refers to UN 38.3-2015, and the random vibration refers to SAEJ2380. The sinusoidal sweep specifies that different test parameters are selected according to the quality of the sample. The vibration of single battery in UL 2580-2013 [16] indirectly refers to IEC 60068-2-64 through IEC 62660-2.

The vibration of battery module and battery stack refers to SAE J2380. Although the random vibration of FreedomCAR has not explicitly stated to refer to SAE J2380, its vibration parameters are the same as the latter. From the perspective of the duration of the vibration test, the longest is 92.6 h and the shortest is 3h. It can be seen that the vibration test is more representative of the short-term abuse of the battery than the long-term mechanical durability. IEC63660-2 (3) does not mention the vibration direction. ECE R100-02-2013 and GB/T 31487.3-2015 [11] only vibrate from the vertical direction. The other standards vibrate from three mutually perpendicular directions, which can comprehensively evaluate the vibration that the battery may suffer during use. For the state of charge (SOC) of test samples, the provisions of various standards vary from 20% to 100%.

1.2 Mechanical Shock

Mechanical shock aims to evaluate the impact of sudden acceleration/deceleration of electric vehicles on batteries. From the acceleration and deceleration in the normal driving process, the pressure on the curb when driving at high speed to the car accident, these scenarios can be simulated or partially simulated through mechanical impact. There are great differences in the provisions of various standards/specifications on the test conditions (peak acceleration, duration, etc.) of mechanical impact. In addition, ISO 12405-3-2014 also refers to ECE R100-02 in the entry of mechanical impact, but the mechanical impact test of the latter shall be impact test.

Both SAE J2464 2009 and SAE J2929 2013 refer to UN 38.3-2015. The test parameters are selected according to the mass of the sample. The peak acceleration with small mass is large and the duration is short. These two standards adopt much higher peak acceleration than other standards for single battery and battery module/battery system with smaller mass. Although the scope of application is different, the mechanical impact tests of six standards, such as ISO 12405-1 (2.3), IEC 62660-2 (3) and UL 2580-2013, have indirectly referenced IEC 60068-2-27 through ISO 16750-3. FreedomCAR divides the impact test into two levels: low level (the sample may not be damaged after the test) and medium level (the sample may not work normally after the test). In addition, FreedomCAR allows the use of other pulse waveforms in addition to half-sine wave, while other standards require the use of half-sine wave. The duration specified by FreedomCAR is longer than other standards, and the peak acceleration is lower than other standards.

1.3 Crash

The purpose of crash test day is to verify the safety performance of the sample under the inertial load brought by the vehicle crash, so it is also called inertial load at vehicle crash in ISO 12405-32014. This test item has certain similarity with mechanical impact. ECE R100-02-2013, although called mechanical shock, is actually a crash test. In addition, the two standards ISO 12405-3: 2014 and GB/T 31467.3-2015 also specify the test items. It is worth mentioning that the test parameters of the impact test of the three standards are identical. The acceleration value of impact test is much lower than that of mechanical impact test, and the pulse duration is longer than that of mechanical impact test.

1.4 Crush

The crush test is used to evaluate the impact of the continuous force on the battery shape and safety performance when the vehicle encounters an accident or other external force. This test is called contact force at vehicle crash in ISO 12405-3:2014 and battery enclosure integrity in SAE J2929 2013. The extrusion test usually applies a force to the battery through a steel plate with a specified shape until the specified pressure value is reached or a certain deformation or sudden voltage drop occurs.