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Explain the discharge characteristics and life of lithium iron phosphate batteries in detail

by:Vglory      2021-04-24
The discharge characteristics of the STL18650 lithium iron battery (with a capacity of 1100mAh) at different discharge rates. The minimum discharge rate is 0.5C, and the maximum discharge rate is 10C. Five different discharge rates form a set of discharge curves. It can be seen from Figure 1 that no matter what kind of discharge rate, the voltage during the discharge process is very flat (that is, the discharge voltage is stable and remains unchanged at all), and the curve only winds down when the discharge voltage stops. Serpentine (the discharge volume reaches 800mAh and then it appears to be winding downwards). In the discharge rate range of 0.5 to 10C, the output voltage is mostly changed in the range of 2.7 to 3.2V. This shows that the battery has good discharge characteristics. The discharge characteristic capacity of STL18650 is 1000mAh. The discharge curve of STL18650 under different temperature conditions (from -20~+40℃) is shown in Figure 2. If the discharge capacity is 100% at 23°C, the discharge capacity at 0°C will drop to 78%, and at -20°C it will drop to 65%, and the discharge capacity at +40°C will be slightly greater than 100%. It can be seen from Figure 3 that the STL18650 lithium iron battery can be operated at -20°C, but the output energy is reduced by about 35%. The charge-discharge cycle life curve of STL18650 is shown in Figure 4. The conditions of the charge-discharge cycle are: charge at 1C charge rate, discharge at 2C discharge rate, and go through 570 charge-discharge cycles. It can be seen from the characteristic curve of Fig. 3 that after 570 charge-discharge cycles, the discharge capacity remains unchanged, indicating that the battery has a very high life span. STL18650 (1100mAh) lithium iron power lithium-ion battery is selected for the over-discharge to zero voltage test for the over-discharge to zero voltage test. Test condition: Fully charge the 1100mAh STL18650 battery with a 0.5C charge rate, and then discharge the battery with a 1.0C discharge rate until the battery voltage is 0C. The batteries placed at 0V are divided into two groups: one group is stored for 7 days, the other group is stored for 30 days; after the storage expires, it is filled with a 0.5C charge rate, and then discharged with 1.0C. After all, compare the differences between the two zero-voltage register periods. The result of the test is that the battery has no leakage after 7 days of storage at zero voltage, with excellent function, and the capacity is 100%; after storage for 30 days, there is no leakage and excellent function, with a capacity of 98%; the battery after 30 days of storage is subjected to 3 charge and discharge cycles The capacity has recovered to 100% again. This test clarifies that even if the battery is over-discharged (even to 0V), and it must be stored for time, the battery will not leak or be damaged. This is a feature that other types of lithium batteries do not have. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to choose a suitable AFE for BMS lithium battery management system
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