Introduce the charging and discharging knowledge of 18650 lithium ion battery

Charging and discharging of 18650 lithium-ion batteries Regarding lithium-ion batteries, according to industry standards, the nominal capacity is generally the lowest capacity, that is, a batch of batteries are charged into cc/cv0.5c at room temperature at 25 degrees, and then allowed to rest for a period of time (usually For 12 hours). Discharge to 3.0v, constant discharge 0.2c current (there is also a standard of 2.75v, but the effect is not significant; 3v to 2.75v drops fast, the capacity is not large), the released capacity value is actually the capacity value of the battery with the lowest capacity, because There must be individual differences in a batch of batteries. 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 18650 lithium-ion battery Some chargers adopt cheap solutions to achieve, the control accuracy is not good enough, it is easy to cause abnormal battery charging, or even damage the battery. When choosing a charger, try to choose a big brand of 18650 lithium-ion battery charger, quality and after-sales guarantee, in order to extend the life of the battery. The brand guarantees that the 18650 lithium-ion battery charger has four protections: short-circuit protection, over-current protection, over-voltage protection, and battery reverse connection protection. Overcharge protection: When the charger overcharges the lithium-ion battery, the charging state should be terminated to prevent the internal pressure from rising due to temperature rise. For this reason, the protection device should monitor the battery voltage, and when the battery overcharge voltage is reached, the overcharge protection function is activated to stop charging. Over-discharge protection: In order to prevent the lithium-ion battery from being in the over-discharge state, when the lithium-ion battery voltage is lower than its over-discharge voltage detection point, the over-discharge protection is activated and the discharge is stopped, so that the battery is in a low quiescent current standby state. Over-current and short-circuit protection: When the discharge current of the lithium-ion battery is too large or a short-circuit occurs, the protection device will activate the over-current protection function. Li-ion 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 is 4.2V, due to the characteristics of lithium-ion batteries, if the voltage is high, it will be damaged. The charger voltage will be fixed at 4.2V, and the charging current will gradually decrease. If it is small to a certain value (usually set the current 1/10), cut off the charging circuit, a complete charging instruction, charging is completed. Excessive charging and discharging of lithium-ion batteries can cause permanent damage to the positive and negative electrodes. Excessive discharge will cause the collapse of the negative carbon sheet structure, and the collapse will cause the lithium ions to be unable to be inserted during the charging process. Overcharging will cause too many lithium ions to sink into the carbon structure, some of which can no longer be released. 2. The charging principle of 18650 lithium ion battery The working principle of lithium ion battery is charging and discharging. When the battery is charged, lithium ions are formed at the positive electrode of the battery, and the lithium ions reach the negative electrode through the electrolyte. Negative carbon 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. The battery capacity we usually call refers to the discharge capacity. It is not difficult to see that during the charging and discharging process of lithium-ion batteries, lithium ions are in a state of movement from the positive electrode to the negative electrode and then to the positive electrode. If we compare a lithium-ion battery to a rocking chair, the two ends of the rocking chair are the two poles of the battery, and the lithium ion is like an excellent athlete, moving back and forth on both ends of the rocking chair. Therefore, experts gave lithium-ion batteries a lovely name: rocking chair batteries. 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: Manganese-based cathode materials are expected to be widely used in energy storage batteries