3.Protection of hardware facilities
The elements of personnel protection have been listed above. It is not difficult to prepare these equipment. The important thing is to use appropriate equipment on appropriate occasions. Laboratory management should standardize this effective document, remove the paralytic thought of test operators and maintain preventive awareness. Regular drills may be as important as configuring these equipment.
The test process of rolling test and impact (impact) test in abnormal work (abuse) test may produce violent response. The former is rolled with a force equivalent to 1000 times the self weight of the sample: the impact test is to drop a 9.1kg weight freely from 610mm and impact the sample.
The relatively closed steel test chamber has good protective effect, but it will be inconvenient because the line of sight is blocked in the test. The observation window can be opened with explosion-proof glass and protective net. The protective net is applicable to the protection of rolling and impact test, and is also commonly used for the protection of normal temperature test and test in the test chamber. UL recommends 16 ~ 18 aluminum wires with a diameter of 0.25mm per inch to 20 steel wires with a diameter of 0.43mm per inch. Different protective nets can be selected for the protection of different estimated intensities and different scattering substances.
The climate test chamber is an independent climate space. Flowing air with circulation. In case of sample gas leakage or viscous substance injection, agitation and dispersion will increase. After suction into the air circulation system, foreign matters falling on the air duct, fan blade, heater, humidifier and temperature and humidity sensor are difficult to be cleaned. After the battery cell is dried, if it is suspended in the form of dust, it will also cause greater secondary disasters. Even if the spray is bonded to the box wall, it is not a small trouble. In this case, the test box with large working space should be selected first to facilitate protective measures and emergency operation; The test chamber shall have certain explosion-proof design, such as avoiding metal friction of electric sparks, electric contacts and moving parts; It is better to have exhaust emission channel. In addition, appropriate protective nets can be used. The setting of protective net shall also take into account the operability of emergency evacuation of samples.
The vibration test bench and impact test bench shall prevent foreign matters from entering the gap of the moving part of the test equipment. The basic protective measures are also protective nets, but the protective nets shall be set for the equipment. The setting of protective net on the sample will affect the dynamic response of the test.
Appropriate fire extinguishing measures shall be taken. According to different site conditions. Cover and spray fire extinguishing agent can be taken. The preservation of equipment shall be fully considered before the condition occurs. In case of condition, whether the fire extinguishing agent will affect the preservation of equipment shall not be considered.
Setting video probe to monitor and record the test is an effective method. It can not only improve the monitoring efficiency. You can also preserve the original image. In case of any situation, it also saves the process of collecting and recording evidence materials. The setting position of video probe shall be reasonable and appropriate.
Whether software technology or hardware facilities are used for laboratory safety protection, its coordination, integration, complementarity and effective implementation still depend on the management mechanism. Arrange or vacate enough space for possible conditions affecting safety; Discharge and ventilation facilities shall be designed or arranged; Standardize the order and trade-off principle of disposal status with documents; Specify the operation elements and steps with the implementation rules: organize personnel training and drill; Specific requirements for record, description and report of status process; And the basis for preserving insurance claims, and so on.
4.Summary
1) When the temperature of the tested battery cell unit and battery pack / battery system is higher than the pretreatment / recovery temperature during the temperature test, life cycle test and exit test, and after the short-circuit test, low air pressure test and vibration impact test, the internal activities and reactions of the sample have not actually stopped or subsided, and there is the possibility of lagging and unsafe state. The temperature measurement and appearance observation shall be continued, and the monitoring shall be withdrawn according to the lag reaction conditions required by the standard. These exit conditions can be continuous observation for 1h, 2h or 4H to provide a function (curve) of temperature with respect to time. The temperature here should gradually tend to RT; If the temperature change is less than IK within 1h, it is considered that the temperature tends to be stable.
2) According to different test basis standards. The parameter settings and criteria for test termination conditions are different. In some cases, the test termination temperature is given according to the “closed cell temperature”, “film breaking temperature” of the test sample or the relatively low temperature of about 5K; Some tests require a typical description of the test results, such as abnormal operation (abuse) test.
3) In temperature measurement, we will encounter battery cell monomer with different packaging. Different packaging styles, materials and thickness will form different temperature transfer efficiency, that is, gradient. These factors shall be reflected in the correction settings in the measurement, analysis and early warning system. Therefore, the termination conditions and criterion parameters of the test should be clearly specified in the test design or entrustment. This is usually associated with the nature of the experiment and mission objectives.
4) Although it seems insignificant to measure and record temperature parameters in abnormal operation (abuse) tests, it is extremely valuable to analyze the internal bearing capacity of samples in test items such as external short circuit, impact, vibration, high temperature and high humidity, overcharge and discharge.
5) The layout of the temperature sensor shall have a distribution list of corresponding sample location. This is the case for the sample test of the single battery cell. It is particularly necessary to locate the single battery cell in the battery pack / system. These temperature sensors can start from test preparation. Go through all test links until the sample exits the test, always accompanied by the battery cell sample.
6) The principle and intensity of protection against explosion and combustion shall be properly estimated. It is not appropriate to convert the chemical energy of the charging material in the battery cell into explosion energy or TNT equivalent. The explosion and combustion caused by the test are mostly due to the high temperature caused by the internal damage of the battery cell (short circuit or increased internal resistance), or the instantaneous release of high temperature and high pressure caused by the abnormal activity in the battery cell caused by external force and external temperature. The more violent is the explosion. This is different from the style and effect of TNT chemical reaction explosion. When the light metal powder or flammable substance in the battery cell overflows under high temperature conditions, it meets the combustion conditions. Cause combustion. The sustainable conditions of combustion are not sufficient, which is closely related to the combustion characteristics of components near the ignition point. The combustion performance of the wrapping material of the test sample should be known before the test. The combustion performance of materials can be measured first, especially for battery packs / systems with complex built-in components. For the samples of light metal castings or brittle plastic shell, the scale of fragment impact or scattering that may occur in explosion shall also be taken into account.
7) The use of protective net in the temperature test chamber will change the temperature distribution in the test chamber. The more effective method is to calibrate the small environment in the protective net. Correct the temperature control parameters.
8) The environmental test and performance test of automotive power lithium-ion battery are very expensive from the value of the tested sample to the implementation cost of the test. The whole set of test time experience is also very long. At the same time, essential safety protection measures must be taken, which inevitably leads to some additional losses, such as sensor loss and equipment damage. Therefore, before the test, the test should be carefully planned and designed, and the operation should be carried out carefully in the test to prevent trouble before it happens, so as to obtain complete test results.