Analysis of constant current charging end
Release time：2017-6-7 14:41:50 Click on the number of times：1501
Fig. 2 to Fig. 4 can be seen, when battery discharge depth is about 1, the change rate of battery voltage is smaller in the constant current charging late. According to analysis of electrochemical reaction of the battery,at this point, there is a stable chemical reaction inside the battery, the battery temperature rises slowly, and the battery voltage rises slowly. When charging cut-off voltage set to 3.70 V, the battery charge into energy is about 11 Ah during battery voltage from 3.50 V up to 3.70 V. When battery discharge depth is about 0.2, the change rate of battery voltage is bigger in the constant current charging late. According to analysis of electrochemical reaction of the battery, at this point, there is an unstable chemical reaction inside the battery,the polarization intensified, the battery temperature and voltage rise rapidly. When charging cut-off voltage set to 3.70 V, the battery charge into energy is about 2 Ah during battery voltage from 3.50 V up to 3.70 V. When battery discharge depth is about 0, the rise rate of battery voltage rises rapidly in charging process.According to analysis of electrochemical reaction of the battery, at this point, there are fewer lithium ion in the cathode, the polarization resistance is large, temperature and voltage of the battery rise rapidly. When charging cut-off voltage set to 3.70 V, the battery hardly charges into energy during battery voltage from 3.50 V up to 3.70 V. If do not limit the battery charging cut-off voltage, battery voltage and temperature will rise rapidly in constant current charging process, which will affect cycle life of the battery, or even damage the battery. Therefore, the judgment of constant current charging end and the selection of constant voltage value are very important for the effective use of battery, which can extend cycle life of the battery.According to analysis of battery charge process under different discharge depth. When battery discharge depth is deeper, the battery voltage rises lowly in the constant current charging late, chemical reaction is stable inside the battery, the temperature increased slowly, can consider the battery charging cut-off voltage is set higher in current charging process, for example, set 3.70 V, this is less damage to battery, and allows more energy charge into the battery. When battery discharge depth is shallower, the battery voltage rises rapidly in the constant current charging late, chemical reaction is unstable inside the battery, the temperature increased rapidly, can consider the battery charging cut-off voltage is set lower in current charging process, for example,set 3.60 V. There is less damage to the battery. Therefore, a new charging method of LiFePO 4 battery has been proposed. In this way, at the end of the constant current charging, the battery can charge into more than 90% of capacity. The battery can be charged into 100% of capacity at the end of charging, and extend cycle life of the battery; this method is easily.
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