The critical performance and charge and discharge characteristics of lithium batteries

The critical performance of lithium batteries The rated voltage of lithium batteries is 3.6V (a few is 3.7V). The termination charging voltage during overflow is related to the anode material of the battery: 4.2V for graphite; 4.1V for coke. When charging, the accuracy of the termination charging voltage is required to be within ±1%. The final discharge voltage of the lithium battery is 2.4 ~ 2.7V (the battery manufacturer gives a slightly different parameter for the operating voltage range or the final discharge voltage). It will damage the battery when it is higher than the termination charge voltage and lower than the termination discharge voltage. There are certain requirements for its use: charging temperature: 0℃～45℃; storage temperature: -20℃～+60℃. Lithium batteries are not suitable for high current charging and discharging. Generally, the charging current is not more than 1C, and the discharging current is not more than 2C (C is the capacity of the battery, such as Cu003d950mAh, the charging rate of 1C means the charging current is 950mA). The charging and discharging effect is better at about 20℃, it cannot be charged under negative temperature, and the discharge effect is poor [4], (the discharge effect is the worst at -20℃, not only the discharge voltage is low, but the discharge time is half of that at 20℃. Still less). The charging and discharging characteristics of lithium batteries The nominal voltage of lithium batteries is 3.6V, and the overflow voltage is 4.2V, which is more sensitive to overcharge and overdischarge. In order to minimize the damage caused by overcharge, deep discharge, and short circuit that lithium batteries are vulnerable to, the charging voltage of single lithium batteries must be strictly limited. The charging and discharging characteristics are shown in Figure 2-3. The charging characteristics of lithium batteries. Lithium batteries have the following characteristics during charging: 1. During the first half of charging, the voltage gradually rises; 2. After the voltage reaches 4.2V, the internal resistance changes. The voltage remains the same; 3. During the whole process, the amount of electricity is constantly added; 4. When it is close to overflowing, the charging current will reach a very small value. After years of research, a better charging control method has been found: 1. Trickle charging reaches the end-of-discharge voltage of 2.7V; 2. Use constant current for charging, so that the voltage basically reaches 4.2V. The safety current is less than 0.8C; 3. The constant current stage can basically reach 80% of the power; 4. When the current is switched to constant voltage charging, the current gradually decreases; 5. When the current reaches a small value (such as 0.05C), the battery Reached a state of overflowing. This CC-CV charging method can reach the overflowing state of the battery well, and does not damage the battery, and has become an important charging method for lithium batteries. However, when the battery voltage is already very low, the lithium ion activity inside the battery is weakened. If a relatively large current is used to charge at this time, the battery may also be damaged. Just as a person has to perform necessary warm-up activities before strenuous exercise, the activity of lithium ions should also be gradually activated. The trickle method can be used in the low voltage section of the battery to effectively activate the battery voltage to above 2.7V, and then the CC-CV charging method can be used to effectively protect the battery. Discharge characteristics of lithium batteries In the process of online monitoring of lithium batteries, most of the battery parameters are obtained during the process of discharging the lithium battery. Therefore, discharging the battery is an indispensable link in battery monitoring. Since lithium batteries are very sensitive to overdischarge, deep discharge will seriously affect the quality of lithium batteries. Therefore, the discharge voltage of a single lithium battery must be accurately controlled. The test found that under the condition of the discharge termination voltage of 2.7V for lithium batteries, the greater the discharge current, the greater the polarization of the battery and the smaller the discharge capacity of the battery, but the relationship between the static voltage of the battery and the depth of discharge of the battery remains basically unchanged status. When the lithium battery is discharged with a large current (greater than 2C), the battery discharge curve appears the phenomenon that the voltage first decreases and then rises. Normally, when determining the discharge current of the lithium battery, the absolute value of the current cannot be used to weigh it. The ratio of the rated capacity C to the discharge time is expressed as the discharge rate or discharge rate. Regarding a 1700mAh battery, if it is discharged at a current of 0.1C, the discharge current is 170mA. Because the internal resistance of lithium batteries is generally between 30-100mm, high current discharge or charging will cause the battery to heat up. Therefore, during the monitoring process, lithium batteries are generally not allowed to discharge at a high rate. The general discharge rate should be less than 0.5C, and the maximum continues The discharge rate cannot exceed 1.5C, and the discharge should be terminated when the voltage is lower than 2.7V. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. 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