What is UN 38.3 T6 Test ? – Part 1

1.Lithium Battery Transportation Safety

As a new type of clean energy, lithium battery has been supporting the products that are essential and accessible to people at any time. Therefore, its safety is related to all consumers, manufacturers and transport departments, which has aroused concern from all parties.


Lithium batteries are mainly divided into lithium metal batteries and lithium ion batteries. The cathode of lithium metal battery is lithium metal, and the positive and negative poles of lithium ion battery are compounds embedded with lithium ion. Since Sony Corporation of Japan successfully developed lithium-ion batteries in 1992 and commercialized them, they have been widely used as power supplies for mobile phones, portable computers, cameras, cameras, etc. due to their unique advantages such as high working voltage, high energy flow density, long cycle life, low self discharge and no pollution. Similarly, it is also gradually developed into a mainstream energy battery in aerospace, navigation, artificial satellites, small medical instruments, transportation and military communication equipment.


However, since the birth of lithium battery, its manufacturing, storage, transportation and use have been accompanied by various safety accidents, especially in the transportation process, accidents occur frequently. So far, many aircraft fires caused by lithium batteries have occurred, causing considerable economic losses and potential safety hazards. Therefore, the transportation safety of lithium battery has been paid more and more attention by governments and transportation industry all over the world. The transportation departments in China and even around the world have vigorously strengthened the supervision of lithium battery transportation.


Why are lithium batteries so dangerous? One of the reasons is that lithium metal is a very active substance with chemical properties. When exposed to the air, it will react with the oxygen in the air in a very intense way and burn. Lithium metal batteries, which use lithium metal as the anode material, are naturally dangerous.


For lithium-ion batteries, if the product quality is not up to standard or the use is improper, combustion or even explosion may occur. For example, when a short circuit occurs outside the lithium battery and the electronic components fail to cut off the circuit, high heat will be generated inside the battery cell, which will cause part of the electrolyte to vaporize and expand the battery shell. If the quality of the battery material is not up to standard, the battery temperature will continue to rise, which will vaporize more electrolyte and finally break the battery shell. Some even raise the battery temperature to the point where the material burns and explodes.


In addition, due to external mechanical reasons or overcharging and other factors, lithium metal dendrites may be formed inside the battery cell, causing internal short circuit, which will increase the internal temperature of the battery, leading to the vaporization of electrolyte, which also results in combustion or even explosion. It can be seen that external short circuit, internal short circuit, overcharging, etc. are important reasons for the danger of lithium batteries, and we should pay more attention to them in the process of production, storage, detection, transportation and use.


2.Transportation Safety Test and Existing Problems 

According to the United Nations Model Regulations on the Transport of Dangerous Goods, lithium batteries need to be tested according to paragraph 3 of Chapter 38 of the United Nations Manual of Tests and Standards on the Transport of Dangerous Goods (hereinafter referred to as UN38.3) before transport.

The test includes 8 items in total. Only lithium batteries passing the test can be transported according to the corresponding conditions. Therefore, strengthening the safety of batteries and passing the UN38.3 test to meet the requirements of transportation have also become the top priority for all lithium battery manufacturers.


This test standard for lithium battery has not changed substantially for a long time in the past, but during this period, the technology and application of lithium battery have made rapid development and progress. The types of lithium batteries have also been greatly updated. Now, there are many types of lithium batteries, ranging from button type batteries weighing a few grams to large batteries weighing dozens of kilograms or even more. The current standards can no longer be fully applicable to all types of lithium batteries.


In addition, because some of the standard test methods are not detailed and accurate enough, the test results of different laboratories may be inconsistent, which may lead to various contradictions or disputes. Therefore, the United Nations Transport Expert Committee established a lithium battery working group to evaluate and revise UN38.3 standard.

This paper will study and discuss the sixth test (hereinafter referred to as T6) in UN38.3 standard. This test has caused many controversies, and its purpose is to simulate the possible impact process of heavy objects during transportation. The industry also believes that this should be a test method for simulating internal short circuit.


The test object is lithium battery cell. The test method is to place a bar with a diameter of 15.8 mm horizontally on the lithium battery cell, and use a 9.1 kg hammer to drop on the sample from a height of (61 ± 2.5) cm to complete the impact of the weight. If the internal and external temperature of the sample during the test and observation time does not exceed 170 ℃, and there is no disintegration and ignition, the test is passed. According to this test method, the impact force borne by large battery cells or small battery cells is the same.

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