Introduction to the test method for lithium battery safety

Lithium-ion battery, as well as an integral sample consisting of a non-user-replaceable battery/lithium-ion battery and its electronics, for non-user-replaceable batteries, they should be installed in electronic products as a whole sample for the lithium-ion battery environmental safety test in the standard; for non-user-replaceable lithium-ion batteries, they can be placed in electronic products as a whole sample. It is also possible to take out the lithium-ion battery separately and perform the environmental safety test of the lithium-ion battery in the standard. It is recommended to test it as a whole sample. Since air, smoke, fire, or even explosion may occur during the test, necessary protective measures must be taken, such as placing the sample in an explosion-proof ventilation unit.

1. Low pressure

Test Purpose: The low air pressure test is used to simulate the effect of low air pressure conditions on the safety of lithium-ion batteries during air transportation. After the test, the samples should not ignite, explode or leak. Equipment: such as vacuum box (or low-pressure test chamber), charge and discharge tester, etc.

2. Temperature cycle

Test Purpose: Lithium-ion battery temperature cycling test is used to simulate the safety of lithium-ion batteries during repeated transportation to low-temperature and high-temperature environments during lithium-ion battery transportation. The test is carried out using rapid and extreme temperature changes. . After the test, the sample should not ignite, explode, or leak. Equipment: such as temperature test chamber, charge and discharge tester, etc.

Constant temperature and humidity chamber test equipment

3. Vibration

Test Purpose: This test simulates the vibration during transportation and carrying, which should not cause safety problems such as liquid leakage, fire, and explosion of lithium-ion batteries. Equipment: such as vibration test bench, charge and discharge tester, etc.

Note: Lithium-ion battery vibration test needs to pay attention to the following points: (1) The way the sample is fixed, it is necessary to ensure that the vibration signal is accurately transmitted to the sample, and the sample cannot be deformed; (2) Each sample needs to be continuously continuous. Vibration test in different directions; (3) Regarding the test direction, since the shape of the lithium ion battery may be irregular, it is necessary to test three mutually perpendicular directions. In addition, it is necessary to pay attention to the discharge charging cycle after the lithium-ion battery vibration test. (It is recommended to use a special fixture for vibration to ensure that the G value does not change when the sample is displaced during the vibration process).

4. Acceleration shock

Test purpose: Lithium-ion battery acceleration shock test is a safety problem that should not cause fire, explosion or liquid leakage after simulating the acceleration shock during lithium-ion battery carrying or transportation. Equipment: such as acceleration impact test bench, charge and discharge tester, etc.

Note: Lithium-ion battery acceleration shock test needs to pay attention to the following points: (1) Lithium-ion battery acceleration shock test is similar to lithium-ion battery vibration test, need to pay attention to the sample fixing method, each sample multiple tests, test direction. (2) The precautions for the peak acceleration of the lithium-ion battery acceleration shock test are the same as the acceleration shock test of the battery. (3) In addition, it is necessary to pay attention to the discharge charging cycle after the lithium-ion battery acceleration test.

5. Fall

The cylindrical and button-type lithium-ion batteries were dropped once on both end faces, and the cylindrical surface fell twice, for a total of four drop tests; each side of the lithium-ion battery fell once for each test, a total of six tests; for non-users The replacement battery/lithium-ion battery is subjected to a drop test with the device, and the device is dropped once per side. The sample should not ignite, explode, or leak.

Test Purpose: This test simulates accidental drops during transportation, carrying and use (such as falling from benches, tables, and hands) and should not cause safety problems such as leakage, fire and explosion of lithium-ion batteries. This test simulates a reasonable and foreseeable accidental fall, regardless of the safety issues caused by artificial, deliberate, unreasonable and unpredictable falls. Equipment: such as multi-degree of freedom test bench, charge and discharge tester.

Drop test machine

Note: The lithium-ion battery drop test needs to pay attention to the following points: (1) Each sample needs to be subjected to multiple drop tests in different directions; (2) necessary measures must be taken to ensure the accuracy of the test direction, and the measure is also It should not affect the free fall movement; (3) The lithium ion battery drop test conditions also take into account the accidental fall during actual use, so for some lithium-ion batteries, a 1.5m drop test is required; in addition, it is necessary to pay attention to the lithium-ion battery drop. It is also necessary to perform a discharge charging cycle.

6. Stress relief

The molded or injection molded thermoplastic outer casing shall be constructed to ensure that any shrinkage or deformation of the outer casing material does not expose the internal components when the internal stress generated by the molding or injection molding is released. The sample casing should not undergo physical deformation that would result in the exposure of the internal components.

Test Purpose: The stress relief test simulates the ability of a lithium-ion battery to maintain its integrity after being subjected to an appropriate high temperature. Equipment: such as high-temperature test chamber.

Note: The stress relief test needs to pay attention to the following points: (1) This test is only performed on a molded or molded thermoplastic lithium ion battery; (2) The test chamber is heated to 70 °C ± 2 °C before the test. Place the sample in the test chamber instead of warming it up after the sample is placed. After the test, the sample is taken out and returned to room temperature instead of returning to room temperature in the test chamber. (3) If the sample is fired or exploded during the test, the shell was destroyed and was also found to be unqualified. (It is recommended to use tools such as clips when taking samples to avoid burns. The samples after the test should be placed in a dedicated explosion-proof box and left for more than two hours.)

7. High-temperature use

The sample should be sufficiently safe to use under high-temperature conditions. Compliance is checked by the following high-temperature use test: the full-charge sample is placed in a high-temperature test chamber, and the temperature in the test chamber is set to the maximum upper and lower discharge temperature of the lithium-ion battery specified by the manufacturer, the upper limit temperature of the battery, and The upper limit of discharge temperature and the maximum value at 80 °C. After the surface temperature of the sample is stable, it is kept for 7 hours.

The sample shall meet one of the following requirements: (1) cut off the circuit, and do not ignite, explode, or leak liquid; (2) the circuit is not cut off, and the charging and discharging method during the high-temperature test continue with a discharge charging cycle. No fire, no explosion, no leakage.

Test Purpose: This test simulates the safety of lithium-ion batteries when used in high-temperature environments. For example, a mobile phone that is in a standby or in-vehicle state of charge is forgotten in a car that is exposed to the sun for a long time. Equipment: such as high-temperature test chamber, charge and discharge tester, etc.

Note: Lithium-ion battery high-temperature test needs to pay attention to the following points: (1) High temperature holding time 7h to start timing after the surface temperature of the sample is balanced. If the time of one discharge charging cycle is more than 7h, the high-temperature test time can be extended to this time. The charge and discharge cycle ends; (2) The test temperature is selected by selecting the upper limit temperature of the lithium-ion battery (such as 40 ° C) and the upper limit of the discharge temperature (such as 55 ° C), the upper limit of the charge of the battery (such as 45 ° C) and the upper limit of the discharge temperature. (For example, the maximum value at 60 ° C and 80 ° C, in general: the upper limit of the charging temperature of the lithium-ion battery ≤ the upper limit temperature of the battery is <80 ° C, the upper limit temperature of the discharge of the lithium-ion battery ≤ the upper limit temperature of the battery is <80 ° C, Therefore, the test temperature is generally selected to be 80 ° C. (3) Since the air flow in the test chamber accelerates the heat transfer, causing heat loss on the surface of the battery during charging and discharging, it may be necessary to reduce the wind speed to minimize the influence on the sample.

8. The conclusion

Lithium-ion batteries are increasingly used in communications, transportation, lighting, and other fields. With their unique applicability and convenience, they are increasingly popular. However, the safety of lithium-ion batteries has been criticized in safety trials. The aspect has always been alert to us and must be treated seriously. The above are some of the aspects of safety testing for readers to discuss.

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