Discharge characteristics and life of lithium iron phosphate batteries

Discharge characteristics and lifespan of lithium iron phosphate batteries Lithium iron phosphate batteries (hereinafter referred to as lithium iron batteries), as a kind of iron batteries, have always been widely valued by friends in the industry (some people say that lithium iron batteries are actually lithium batteries). As far as iron batteries are concerned, they can be divided into high-speed railway batteries and lithium iron batteries. Today, we take the STL18650 lithium-iron battery as an example to illustrate the discharge characteristics and lifespan of the lithium-iron battery. Under different discharge rates, the discharge characteristics of a STL18650 iron-lithium battery with a capacity of 1100mAh is shown in Figure 2. The minimum discharge rate is 0.5c, and the maximum discharge rate is 10C. Five different discharge rates form a set of discharge curves. From Figure 1, we can see that regardless of the discharge rate, the voltage during the discharge process is very flat (that is, the discharge voltage is stable and obeys the same), and only the discharge voltage is quickly stopped, and the curve is a downward zigzag ( After discharge, it reaches a downward saw-tooth shape of 800mah). In the discharge rate range of 0.5~10C, the largest change in output voltage is 2.7~3.2v. It shows that the battery has good discharge characteristics. The discharge curve of STL18650 with a capacity of 1000mAh at different temperatures (-20~+40℃) is shown in Figure 2. If the discharge capacity is 100% at 23°C, the discharge capacity drops to 78% at 0°C, to 65% at -20°C, and slightly more than 100% at +40°C. It can be seen from Figure 3 that the STL18650 lithium iron battery can work at -20°C, but the output energy should be reduced by about 35%. The charge-discharge cycle life curve of STL18650 is shown in Figure 4. The charging and discharging cycle conditions are: charging 1C rate, discharging 2C rate, after 570 times of charging and discharging. It can be seen from the characteristic curve in Figure 3 that after 570 charge-discharge cycles, the discharge capacity remains unchanged, indicating that the battery has a higher service life. The over-discharge to zero-voltage test uses STL18650 (1100mAh) lithium iron power lithium-ion battery for zero-voltage discharge test. Experimental conditions: Cover the 1100mAh STL18650 battery with a charge rate of 0.5c, and discharge to a battery voltage of 0C, with a discharge rate of 1.0c. Then divide the 0V battery into two groups: one group is stored for 7 days, and the other group is stored for 30 days. After the storage period expires, the charging rate is 0.5c and the discharge is 1.0c. After all, compare the differences between the two zero-voltage storage periods. The experimental results show that after 7 days of zero-voltage storage, the battery has no leakage, excellent performance, and 100% capacity. After 30 days of storage, there is no leakage, excellent performance, 98% capacity; after 30 days of storage, the battery has been charged and discharged three times, and the capacity has returned to 100%. 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 set up a safe lithium battery protection circuit?