Comparison of Testing Standards for Power Lithium Batteries at Home and Abroad

Comparison of Testing Standards for Power Lithium Batteries at Home and Abroad

1、 Foreign standards for power lithium-ion batteries

Table 1 lists the commonly used testing standards for lithium-ion batteries abroad. The standard issuing bodies mainly include the International Electrotechnical Commission (IEC), the International Organization for Standardization (ISO), the Underwriters' Laboratories (UL) of the United States, the Society of Automotive Engineers (SAE) of the United States, and relevant institutions of the European Union.

1） International standards

The power lithium-ion battery standards released by IEC mainly include IEC 62660-1:2010 "Lithium ion power battery units for electric road vehicles - Part 1: Performance testing" and IEC 62660-2:2010 "Lithium ion power battery units for electric road vehicles - Part 2: Reliability and abuse testing". UN 38 issued by the United Nations Transport Commission The requirements for lithium battery testing in the "United Nations Recommendations, Standards and Test Manual on the Transport of Dangerous Goods" are aimed at the safety of batteries during transportation.

The standards developed by ISO in the field of power lithium-ion batteries include ISO 12405-1:2011 "Electric drive vehicles - Test procedures for lithium-ion power battery packs and systems - Part 1: High power applications" ISO 12405-2:2012 "Electric drive vehicles - Lithium ion power battery packs and systems testing procedures - Part 2: High energy applications" and ISO 12405-3:2014 "Electric drive vehicles - Lithium ion power battery packs and systems testing procedures - Part 3: Safety requirements" respectively target high-power batteries, high-energy batteries, and safety performance requirements, with the aim of providing vehicle manufacturers with optional testing items and methods.

2） American Standards

UL 2580:2011 "Batteries for Electric Vehicles" mainly evaluates the reliability of battery abuse and the ability to protect personnel in the event of harm caused by abuse. This standard was revised in 2013.

SAE has a vast and comprehensive standard system in the automotive industry. The SAE J2464: 2009 "Safety and Abuse Testing of Rechargeable Energy Storage Systems for Electric and Hybrid Electric Vehicles", issued in 2009, is an early batch of vehicle battery abuse testing manuals applied in North America and the world. It clearly specifies the scope of application and the data to be collected for each test item, and also provides recommendations for the number of samples required for the test item.

The SAE J2929: 2011 "Safety Standards for Electric and Hybrid Battery Systems" is a safety standard proposed by SAE in summarizing various power battery related standards previously issued, including two parts: routine testing and abnormal testing that may occur during electric vehicle operation.

SAE J2380: 2013 "Vibration Testing of Electric Vehicle Batteries" is a classic standard for vibration testing of electric vehicle batteries. Based on the collected statistical results of the vibration load spectrum of actual vehicle driving on the road, the testing method is more in line with the vibration situation of actual vehicles and has important reference value.

3 Other organizational standards

The US Department of Energy (DOE) is primarily responsible for energy policy formulation, energy industry management, and energy related technology research and development. In 2002, the US government established the "Freedom CAR" project and successively issued the Freedom CAR power assisted hybrid electric vehicle battery testing manual and the energy storage system abuse testing manual for electric and hybrid vehicles.

The German Automobile Industry Association (VDA) is an association formed in Germany to unify various standards for the domestic automotive industry. The standards issued are VDA 2007 "Battery System Testing for Hybrid Electric Vehicles", which mainly focuses on the performance and reliability testing of lithium-ion battery systems for hybrid electric vehicles.

2、 Domestic standard for power lithium-ion batteries

In 2001, the Automotive Standardization Committee issued the first guiding technical document for lithium-ion battery testing of electric vehicles in China, GB/Z 18333 1: 2011 "Lithium ion batteries for electric road vehicles". When formulating this standard, reference was made to IEC 61960-2:2000 "Portable lithium batteries and battery packs - Part 2: Lithium battery packs", which is used for lithium-ion batteries and battery packs in portable devices. The testing content includes performance and safety, but is only applicable to batteries of 21.6V and 14.4V.

In 2006, the Ministry of Industry and Information Technology issued QC/T 743 "Lithium ion Power Batteries for Electric Vehicles", which was widely used in the industry and revised in 2012. GB/Z 18333 1: 2001 and QC/T 743: 2006 are both standards for individual and module levels, with a narrow application range and testing content that no longer meets the needs of the rapidly developing electric vehicle industry.

In 2015, the National Standardization Administration issued a series of standards, including GB/T 31484-2015 "Cycle Life Requirements and Test Methods for Power Batteries for Electric Vehicles", GB/T 31485-2015 "Safety Requirements and Test Methods for Power Batteries for Electric Vehicles", GB/T 31486-2015 "Electrical Performance Requirements and Test Methods for Power Batteries for Electric Vehicles", and GB/T 31467 1-2015 "Lithium ion power battery packs and systems for electric vehicles - Part 1: High power application testing procedures, GB/T 31467 2-2015 "Lithium ion power battery packs and systems for electric vehicles - Part 2: High energy application testing procedures, GB/T 31467 3 "Test Procedures for Lithium Ion Power Battery Systems for Electric Vehicles - Part 3: Safety Requirements and Test Methods.

GB/T 31485-2015 and GB/T 31486-2015 respectively refer to the safety and electrical performance testing of individual units/modules. The GB/T 31467-2015 series refers to the ISO 12405 series and is suitable for testing battery packs or battery systems. GB/T 31484-2015 is a testing standard specifically designed for cycle life, with standard cycle life used for individual units and modules, and operating cycle life used for battery packs and systems.

Economic Commission for Europe (ECE) R100 The "Uniform Provisions on the Approval of Vehicles in Respect of Special Requirements for Electric Vehicles" is a specific requirement formulated by ECE for electric vehicles, which is divided into two parts: the first part regulates the motor protection, rechargeable energy storage systems, functional safety, and hydrogen emissions of the entire vehicle, and the second part adds specific requirements for the safety and reliability of rechargeable energy storage systems.

In 2016, the Ministry of Industry and Information Technology issued the "Safety Technical Conditions for Electric Bus", which comprehensively considered personnel electric shock, water dust protection, fire protection, charging safety, collision safety, remote monitoring, and other aspects. It fully drew on existing traditional bus and electric vehicle related standards and local standards such as Shanghai and Beijing, and put forward higher technical requirements for power batteries, adding two test items: thermal runaway and thermal runaway expansion, It was officially implemented on January 1, 2017.

3、 Analysis of domestic and international standards for power lithium-ion batteries

Most of the international standards for power lithium-ion batteries were issued around 2010, with many revisions and new standards being introduced one after another. GB/Z 18333 1: 2001 was issued in 2001, indicating that China's lithium-ion battery standards for electric vehicles did not start late in the world, but their development was relatively slow. Since the release of the QC/T 743 standard in 2006, there has been no standard update in China for a long time, and before the release of the new national standard in 2015, there were no standards for battery packs or systems. The above domestic and foreign standards differ in terms of scope of application, content of test items, severity of test items, and judgment criteria.

1） Scope of application

The IEC 62660 series, QC/T 743, GB/T 31486, and GB/T 31485 are tests for individual and module levels of batteries, while the UL2580, SAE J2929, ISO12405, and GB/T 31467 series are applicable for testing battery packs and battery systems. In addition to IEC 62660, other standards abroad generally involve battery pack or system level testing, such as SAE J2929 and ECE R100 2 even mentioned vehicle level testing. This indicates that the formulation of foreign standards takes more into account the application of batteries in the entire vehicle, which is more in line with the needs of practical applications.

2） Test item content

Overall, all test items can be divided into two categories: electrical performance and safety reliability, while safety reliability can be further divided into mechanical reliability, environmental reliability, abuse reliability, and electrical reliability.

Mechanical reliability simulates the mechanical stress that a vehicle experiences during driving, such as vibration simulating the bumpiness of the vehicle on the road surface; Environmental reliability simulates the endurance of vehicles in different climates, such as temperature cycling simulating the situation of vehicles driving back and forth in cold and hot areas with large temperature differences between day and night; Abuse of reliability, such as fire, to assess the safety of batteries in the event of improper use; Electrical reliability, such as protective testing items, mainly examines whether the battery management system (BMS) can play a protective role at critical times.

In terms of battery cells, IEC 62660 is divided into two independent standards, IEC 62660-1 and IEC 62660-2, which correspond to performance and reliability testing, respectively. GB/T 31485 and GB/T 31486 are evolved from QC/T 743, and vibration resistance is classified as a performance test in GB/T 31486, as this test item examines the impact of battery vibration on battery performance. Compared to IEC 62660-2, the testing items of GB/T 31485 are more stringent, such as adding acupuncture and seawater immersion.

In terms of battery pack and battery system testing, both electrical performance and reliability, the US standard covers the most testing items. In terms of performance testing, DOE/ID-11069 has more test items than other standards, such as hybrid pulse power characteristics (HPPC), stability of operating set points, calendar life, reference performance, impedance spectrum, module control inspection testing, thermal management load, and system level testing combined with life verification.

The analysis methods for electrical performance test results are detailed in the appendix of the standard. Among them, HPPC testing can be used to detect the peak power of power batteries, and the DC internal resistance testing method derived from this has been widely used in the study of battery internal resistance characteristics. In terms of reliability, UL2580 has more testing items than other standards, such as unbalanced battery pack charging, voltage resistance, insulation, continuity testing, and cooling/heating stability system fault testing. It also includes basic safety testing for battery pack components on the production line, and strengthens safety review requirements in BMS, cooling system, and protection circuit design. SAE J2929 proposes to conduct fault analysis on various parts of the battery system and save relevant documentation, including improvement measures that are easy to identify faults.

The ISO 12405 series of standards includes both the performance and safety aspects of batteries. ISO 12405-1 is a battery performance testing standard for high-power applications, while ISO 12405-2 is a battery performance testing standard for high-energy applications. The former includes two more contents: cold start and hot start. The GB/T 31467 series combines the development status of power batteries in China and is modified according to the content of the ISO 12405 series standard.

Different from other standards are SAE J 2929 and ECE R100 Both involve requirements for high-voltage protection and belong to the safety category of electric vehicles. The relevant test items in China are listed in GB/T 18384 and GB/T 31467 3 points out that the battery pack and battery system must meet the requirements of GB/T 18384 before conducting safety tests 1 and GB/T 18384 3. Relevant requirements.

3） Severity

For the same test item, the testing methods and judgment criteria specified in different standards are also different. For example, for the state of charge (SOC) of test samples, GB/T 31467 3 requires the sample to be fully charged; ISO 12405 requires a power type battery SOC of 50% and an energy type battery SOC of 100%; ECE R100 2. Require the SOC of the battery to be above 50%; UN38. 3 has different requirements for different test items, and some test items also require recycled batteries.

In addition, it is also required that high simulation, thermal testing, vibration, impact, and external short circuits must be tested using the same sample, which is relatively more stringent. For vibration testing, ISO 12405 requires samples to vibrate at different ambient temperatures, with recommended high and low temperatures of 75 ℃ and -40 ℃, respectively. Other standards do not have this requirement.

For the fire test, GB/T 31467 The experimental method and parameter settings in 3 are consistent with ISO 12405 The difference is not significant, both of which are preheated, directly burned, and indirectly burned by igniting fuel, but GB/T 31467 3. If there is a flame in the sample, it must be extinguished within 2 minutes. ISO 12405 does not require a time for the flame to extinguish. The fire test in SAE J2929 is different from the previous two. It requires the sample to be placed in a thermal radiation container, rapidly heated to 890 ℃ within 90 seconds and maintained for 10 minutes, and no components or substances must pass through the metal mesh cover placed outside the test sample.

4、 Shortcomings in existing domestic standards

Although the formulation and release of relevant national standards have filled the gap in China's power lithium-ion battery combination systems and have been widely adopted, there are still shortcomings.

In terms of test objects: All standards only specify the testing of new batteries, and there are no relevant regulations or requirements for used batteries. The batteries have no problems when leaving the factory, which does not mean that they are still safe after being used for a period of time. Therefore, it is necessary to conduct the same testing on batteries used for different times, which is equivalent to regular physical examinations.

In terms of result judgment: The current judgment basis is relatively broad and single, with only provisions for no leakage, no shell rupture, no fire, and no explosion, lacking a quantifiable evaluation system. The European Commission for Automotive Research and Technology Development (EUCAR) has divided the harm level of batteries into 8 levels, which has certain reference significance.

In terms of test items: GB/T31467 3. There is a lack of testing content for battery packs and battery systems in terms of thermal management and thermal runaway, and thermal safety performance is crucial for batteries. How to control the thermal runaway of individual batteries and prevent the spread of thermal runaway is of great significance, as evidenced by the mandatory implementation of the "Safety Technical Conditions for Electric Bus". In addition, from the perspective of vehicle application, for non-destructive reliability testing, such as environmental reliability, it is necessary to add electrical performance testing after the test is completed to simulate the impact of vehicle performance after experiencing environmental changes.

In terms of testing methods: The cycle life testing of battery packs and battery systems takes too long, which affects the product development cycle and is difficult to execute well. How to develop a reasonable accelerated cycle life testing is a challenge.

5、 Summary

In recent years, China has made great progress in the formulation and application of standards for power lithium-ion batteries, but there is still a certain gap compared to foreign standards. In addition to testing standards, the standard system for lithium-ion batteries in China is also gradually improving in other aspects. On November 9, 2016, the Ministry of Industry and Information Technology released the "Comprehensive Standardization Technical System for Lithium Ion Batteries", which pointed out that the future standard system includes five major parts: basic general use, materials and components, design and manufacturing processes, manufacturing and testing equipment, and battery products. Among them, safety standards are of great importance. With the update and development of power battery products, testing standards also need to improve corresponding testing technologies, Furthermore, it enhances the safety level of power batteries.