Brief analysis of the charging and discharging principle of 18650 lithium battery

The charging and discharging principle of lithium batteries As far as lithium batteries are concerned, according to industry standards, the nominal capacity is generally the minimum capacity. This capacity is a batch of batteries, at room temperature 25 degrees, first charge cc/cv0.5c, and then stand for a period of time (usually 12 hours). Discharge at a constant current of 0.2c to 3.0v (there is also a standard of 2.75v, but the effect is not significant; 3v to 2.75v drops very fast, there is not much capacity), the capacity value is released, because a batch of batteries must have individual differences, and the practice release is the lowest The capacity value of the battery. In other words, the actual capacity of this batch of batteries should be greater than or equal to the nominal capacity. 1. The charging process of the 18650 lithium battery is ended by some chargers with cheap methods, and the control accuracy is not good enough. The simple form of battery charging is abnormal, and even the battery is damaged. When choosing a charger, try to choose a big brand of 18650 lithium battery charger, quality and after-sales guarantee to extend the battery life. The brand-guaranteed 18650 lithium battery charger has four maintenance functions: short-circuit maintenance, over-current maintenance, over-voltage maintenance, and battery reverse maintenance. Overcharge maintenance: When the charger overcharges the lithium battery, it is necessary to stop charging in order to prevent the temperature rise caused by the increase in internal pressure. Therefore, the maintenance device must monitor the battery voltage, and when the battery overcharge voltage is reached, the overcharge maintenance function is activated to continue charging. Over-discharge maintenance: In order to prevent the over-discharge state of the lithium battery, when the voltage of the lithium battery is lower than its over-discharge voltage detection point, the over-discharge maintenance is started, and the discharge is continued to keep the battery in a low quiescent current standby state. Over-current and short-circuit maintenance: When the lithium battery discharge current is too large or a short-circuit occurs, the maintenance device will start the over-current maintenance function. Lithium battery charge control is divided into two stages. The first stage is constant current charging. When the battery voltage is lower than 4.2v, the charger charges with constant current. The second stage is the constant voltage charging stage. When the battery voltage reaches 4.2V, because of the characteristics of lithium batteries, assuming that the voltage is high, it will be damaged. The charger will be fixed at 4.2V and the charging current will gradually decrease. Value (usually set the current 1/10), cut off the charging circuit, charging instructions, charging is over. Excessive charging and discharging of lithium batteries can cause permanent damage to the positive and negative electrodes. Excessive discharge will cause depressions in the structure of the negative carbon sheet, and the negative carbon sheet is formed by lithium ions that cannot penetrate during the charging process. Excessive charging will cause lithium ions to be embedded in the carbon structure of the cathode, some of which can no longer be released. 2. 18650 lithium battery charging principle The working principle of lithium battery is charging and discharging. When the battery is charged, lithium ions are formed at the positive electrode of the battery, and the resulting lithium ions pass through the electrolyte to the negative electrode. Carbon is the negative electrode and has a layered structure with many micropores. Lithium ions reaching the negative electrode are inserted into the micropores of the carbon layer. The more lithium ions are inserted, the greater the charging capacity. In the same way, when the battery is discharged (the process we use the battery), the lithium ions embedded in the negative electrode carbon will come out and return to the positive electrode. The more lithium ions return to the positive electrode, the greater the discharge capacity. When we talk about battery capacity, we are referring to discharge capacity. It is not difficult to see that during the charging and discharging process of lithium batteries, lithium ions are in a state of movement from the positive electrode to the negative electrode and then to the positive electrode. Let us compare the lithium battery to a rocking chair. The two ends of the rocking chair are the north and south poles of the battery, and the lithium ion is like an excellent athlete, moving back and forth on the two ends of the rocking chair. Therefore, the experts gave the lithium battery a lovely name: rocking chair battery. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to solve the problem of the short life of drone lithium battery in winter?