Lithium batteries have become an important part of modern life, powering everything from smartphones to electric vehicles. As their use proliferates, ensuring their safety and environmental sustainability is paramount. This article delves into the key aspects of lithium battery safety testing and how we do this testing, examining the necessary protocols to ensure both reliability and minimal environmental impact.
1.Battery Safety testing
1.1Overcharging testing
The testing process: the battery cell is fully charged in the standard charging mode, and then charged at 1 C until the voltage reaches 1.5 times the termination voltage or the charging time reaches 60 min, and then stopped charging. The testing process maybe a bit different due to different cell factory.They have their owm testing standards.But all of them will do this overcharge test in their R&D team.
Performance standards: no explosion and no fire
Explainations:
1C: This indicates that the battery is being charged or discharged at a rate equal to its full capacity in one hour. For example, if a battery has a capacity of 1000mAh, a 1C rate means charging or discharging at 1000mA.
Standard charge mode: At 25 ± 2°C,relative humidity ≤ 75% ,the battery is initially charged at a constant current (0.2C) until the battery voltage reaches the desired level (4.2V). Once the battery voltage reaches 4.2V, the charger switches to supplying a constant voltage while the current gradually decreases 0.01C.
Standard discharge mode: At 25 ± 2°C,relative humidity ≤ 75% ,the battery is initially discharged at a constant current (0.2C) until the battery voltage reaches the desired level (2.75V).
1.2.130°C hot oven testing
Testing process: after the cell is fully charged in accordance with the standard charging mode, the cell is put into the oven, and set the oven to warm up from 5 ℃/min to 130 ℃, when the temperature of the cell also reaches 130℃, keep the cell quietly for 30 min in the oven with130℃ or till the battery cell is caught fire or exploded.
Performance standards: no explosion and no fire
1.3.Crush testing
Testing process: after standard charging, the cell is placed inside two flat plates for crush, when the pressure reaches force of 13kN±1kN, end the testing.
Performance standards: no explosion and no fire.
1.4.Short circuit testing
Testing process: After the battery is fully charged in the standard charging mode, the positive and negative terminals of the battery cell should be connected to each other by a wire with an internal resistance of less than5 m Ω for 10 minutes and observe for 1 hours.
Performance standards: no explosion and no fire.
1.5.Overdischarging testing
Testing process: The cell is charged according to the standard discharging mode and then discharged the battery at 1C for 90 minutes observe for 1 hours.
Performance standards: no explosion and no fire.
1.6.Drop testing
Testing process: The battery is charged according to the standard mode and then freely dropped from a height of 1.5m in both positive and negative directions to floor.
Performance standards: no explosion and no fire.
1.7.Viberation Testing
Testing process: After the battery is fully charged according to standard charging mode, fasten it to the vibration test bench for vibration test.
The test requirements are as follows:
1) Scanning mode: Logarithmic sine wave scanning;
2) Frequency range: 7 Hz to 200 Hz;
3) Logarithmic sweeping mode: start from 7 Hz, keep the maximum acceleration 1 gn
increase the frequency to ~ 18 Hz, then keep the amplitude of 0.8 mm (total displacement
1.6mm) and increase the frequency to ~50Hz, then keep the peak acceleration at 8gn.
increase the frequency to 200Hz and return to 7Hz.
4) Single cycle frequency sweep time: 15min.
The vibration testing needs to be axial and radial (Lithium ion cells and li-polymer cells are tested at 3 perpendicular directions ) tested for 12 times for each direction,the testing time of each direction is 3hours.
Performance standards: no explosion,no leakage and no fire.
2.Environmental safety testing
2.1. Temperature Cycle testing
Testing process: the battery cell is fully charged according to standard charging mode and placed in the test chamber for the following tests:
1) Increase the temperature in the chamber to 72 ± 2°C and keep it for 6h;
2) Decrease the temperature in the chamber to -40 ± 2℃ and keep it for 6h;
3) Repeat the above steps for 10 consecutive cycles;
The transition time between each two temperatures during the test is ≤ 30min.
Performance standards: no explosion,no leakage and no fire.
2.2.Low Pressure testing
Testing process: After the core is fully charged according to standard charging mode, place it in a vacuum chamber at 20 ± 5°C and adjust the pressure in the vacuum chamber to 11.6kPa.
Adjust the pressure in the vacuum chamber to 11.6kPa, keep it for 6h and observe for 1h.
2.3. Thermal abuse testing
Testing process: The battery is fully charged in accordance with standard charging mode and placed in the test chamber, and the temperature is increased to 130 ± 2°C at a rate of (5 ± 2°C)/min and kept at a constant temperature for 30 min.
Prformance standards: no explosion,no leakage and no fire.
3.1 Warning:
3.1.1 During the use of the battery cell, please avoid over-charging (voltage > 4.2V), over-discharging (voltage < 2.5V), over-current charging and discharging (maximum current allowed by the current temperature) and other abnormal use conditions.
It is strictly prohibited to use the battery cell in environments that are prone to static electricity, poor sealing (water, dust entry) and so on.
3.2.2 Using the battery cell in the environment of charging current greater than 0.5C, high/low temperature environment, vibration environment, poor assembly environment, humid environment will reduce the service life of the battery cell.
3.3.3 Do not use the battery cell in high-frequency microwave and ultrasonic environments.
Electromagnetic insulation cover is recommended when the battery is used in series and parallel, to prevent electromagnetic wave from damaging the neighboring devices and human body;
3.3.4 Battery positive and negative connecting wires should not overlap, contact and others to reduce the risk of short circuit;
3.3.5 Batteries should be charged and discharged in strict accordance with the current specified in the specifications designed to ensure the normal service life and safety of the battery;
3.3.6 When batteries are used in multi-parallel battery packs, we should use cells with the same capacity, the same internal resistance, the same batch and the same state of charge, and the grouping standard should be carried out in strict accordance with the technical agreement.
The temperature difference inside the battery pack should be <5℃ when the battery pack is discharging or working.
3.3.7 When the external environment is lower than 0℃, it is recommended that the battery cells should be put aside for a period of time in the environment of ≥ 0℃ before charging, and then charging should be carried out when the internal and external temperatures of the battery cells are both ≥ 0℃.
The recommended shelf time is as follows: External temperature and setting aside time
3.2 Safety Precautions:
3.2.1 Batteries should be placed far away from the place where children and infants can reach,if accidentally swallowed by children in the process of playing, or burned by the heat of the battery, or damaged by explosion, etc., please seek medical treatment immediately.
3.2.2 When charging and discharging the battery, it is strictly prohibited to use non-specified equipment for charging, and it is strictly prohibited to use ordinary constant-current and constant-voltage sources that can’t limit the voltage and current to charge and discharge the battery, which may cause the battery function to be invalid or dangerous.
3.2.3 When charging and discharging the battery or loading the battery into the equipment, pay attention not to reverse the positive and negative poles of the battery, otherwise the battery will be overcharged and over-discharged, resulting in serious battery failure or even danger.
3.2.4 Do not solder the battery directly, and it is strictly prohibited to decompose the battery;
3.2.5 Do not put the battery with necklaces, hairpins, coins or screws and other metal products in the pocket or bag, and do not store the battery with the above items.
3.2.6 Prohibit knocking, throwing or stepping on the battery, and do not put the battery into the washing machine or high-pressure container;
3.2.7 Do not place the battery close to heat sources, such as fire, heaters, etc. Do not use or store the battery under the scorching sun or at temperatures exceeding 60°C. Otherwise, the battery may be triggered to develop.
3.2.8 Do not wet the battery or put the battery into water, when not in use, please place it in a low temperature and dry environment;
3.2.9 When using, testing or storing the battery, if you find that the battery has abnormal heat, odor, discoloration, deformation or other abnormalities, please Immediately stop using or testing, try to isolate and keep away from the battery;
3.2.10 If the battery leaks and the electrolyte is splashed into the eyes accidentally, do not rub it, wash it immediately with clean water and go to the hospital for medical treatment, if the skin or clothes are splashed with electrolyte, do not rub it.
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