18650 Test Method for Low Temperature Performance of Lithium Battery
18650 lithium battery low temperature performance safety characteristics including low temperature storage environment temperature with cover, - 40 ℃ storage environment temperature, low pressure working environment adaptability, etc., 18650 lithium battery low temperature performance test method also includes pulse, impact, temperature impact, vibration, low temperature monomer lithium battery safety characteristics, this paper found some of the low temperature performance of the battery in the production and research by low temperature lithium battery manufacturers Secret. Let's discuss with you. The related low-temperature safety analysis of lithium battery is as follows.
1. Storage ambient temperature.
When the ambient temperature is 70 ℃± 2 ℃, the storage time is 48 hours, and the lithium battery pack will not swell, deform or damage; when it is restored to normal temperature, the lithium battery core can meet the specified charging and discharging requirements. When the ambient temperature is - 55 ℃± 2 ℃, the lithium battery pack will not be deformed or damaged after 48 hours of storage; when it is restored to normal temperature, the lithium battery can meet the specified charging and discharging requirements.
2. Operating ambient temperature.
18650 low temperature performance of lithium battery requires charging temperature: 0 ℃ ~ + 40 ℃; discharge temperature: - 40 ℃ ~ + 55 ℃ (above 0 ℃, it is required to be able to discharge according to the specified requirements; when - 40 ℃ ~ 0 ℃, the lithium battery pack can be heated to above 0 ℃ with the aid of external heating unit (heating film), so that the single lithium battery can reach the discharge temperature requirements).
3. High altitude (low pressure).
The low-temperature performance of 18650 lithium battery must be able to meet the normal charging at an altitude of more than 5000 meters, and can discharge according to the specified discharge requirements. During the charging and discharging period, the lithium battery cell shall be free from gas, deformation and damage. This test also lays a solid foundation for the wide application of 18650 lithium battery.
4. Impact analysis of safety characteristics of low temperature lithium battery.
The fully charged 18650 lithium battery was rigidly fixed on the impact test-bed with an impact acceleration of 392m / s.
Second: 18650 test method for low temperature performance pulse of lithium battery.
The impact test was carried out on 18650 lithium battery at low temperature for 6ms. On three mutually perpendicular shafts, each shaft shall be impacted twice in the positive and negative directions respectively. The lithium battery pack shall be free from leakage, fire and explosion, and its overall dimension shall be kept the original size with an error of less than 2mm. The open circuit voltage range of the lithium battery pack is 43.2v-50.4v, and the lithium battery pack can discharge according to the specified discharge requirements.
Third、 18650 lithium battery low temperature performance test vibration method.
1. The fully charged lithium battery pack is fixed on the vibration table with a clamp, and a sinusoidal vibration with an amplitude of 0.76mm (double amplitude of 1.52mm) is applied. The vibration frequency range is 10Hz ~ 55Hz, and the frequency can be changed uniformly or logarithmically in this frequency range. From 10Hz to 55Hz and back to 10Hz, the scanning time is about 1 minute. The lithium battery pack shall be vibration tested in three directions.
2. The vibration time in each direction shall be 90-100 minutes, and the whole test time shall be 270-300 minutes. The lithium battery pack shall be free from leakage, fire and explosion, and its overall dimension shall be kept the original size with an error of less than 2mm. The open circuit voltage range of the lithium battery pack is 43.2v-50.4v. The lithium battery pack vibrates in each direction. After the vibration, the lithium battery pack can discharge according to the specified discharge requirements.
Fourth、 18650 lithium battery low temperature performance temperature shock method.
Place the low-temperature lithium battery pack in the - 40 ℃± 2 ℃ (or 70 ℃± 2 ℃) test chamber, keep the temperature constant for 2 hours at this temperature, then move it to the 70 ℃± 2 ℃ (or - 40 ℃± 2 ℃) test chamber quickly (time not more than 1 minute), and keep the temperature constant for 2 hours at this temperature, count one cycle. After 4 cycles, take out the lithium battery pack and keep it at 25 ℃ for at least 2 hours to make the lithium battery pack reach room temperature. The lithium battery pack shall not be deformed, cracked or leaked. The lithium battery pack can discharge according to the specified discharge requirements.
Fifth、 Comprehensive analysis of 18650 lithium battery's low temperature performance:
1. Overcharge: single lithium battery is overcharged with 0.2C current and 1C current respectively until the voltage rises to 4.6V, and the lithium battery shall not be ignited or exploded. As shown in the figure below, how to use the low-temperature 18650 lithium battery with good safety performance mainly depends on the electrical performance characteristics. In the technical description of the whole process of 18650 lithium battery production process It only requires manufacturers to keep testing. The most important thing is that as long as the safety test is OK, it is a good battery, which is the precondition.
2. Extrusion: after the single lithium battery is charged according to the battery standard, the battery is placed in two planes, which are perpendicular to the discharge of the electrode plate for extrusion (only extrusion test is conducted on the wide surface of the lithium battery), and 13.0kn ± 0.75kn extrusion pressure is applied between the two plates. Once the pressure reaches the maximum value, the extrusion test can be stopped. During the test, the single lithium battery shall not have external short circuit, and the lithium battery shall not fire or explode.