Why do lithium-ion batteries need to be precharged?

For many lithium battery counterparts, I don’t really understand why lithium batteries need to be precharged first. This is mainly because lithium-ion batteries have a higher energy ratio. If you enter the fast charging mode directly, it will cause damage to the battery and affect its use. Longevity and may therefore bring safety hazards. Although the current lithium-ion battery has a built-in circuit protection board in the design process, the chance of overcharging and overcharging is usually very small, but if the battery is not precharged at first, it will bring many hidden dangers, such as failure of the protection board, long The self-discharge rate of the battery is left over time, etc., when the battery is over-discharged, it will be difficult to recover the active material. It is necessary to charge it to 2.5V to 3.0V with a small current and then convert it to a fast charge. The pre-charged small battery can effectively solve the charging problem of the over-discharged battery. The voltage of the lithium battery is from 2.5V to 4.2V when it is working. When the voltage is less than 2.5V, the battery discharge is terminated. At the same time, the current loss of the internal protection circuit is also minimized because the discharge circuit is closed. Of course, in actual applications, due to different internal Material, the discharge termination voltage can be in the range of 2.5V-3.0V, when the voltage exceeds 4.2V, the charging circuit is terminated to protect the battery safety; and when the operating voltage of the single battery drops below 3.0V, we can consider the over-discharge state , The discharge circuit is terminated to protect battery safety. Some colleagues believe that: In order to fully charge quickly, use high current fast charging. This idea is a misunderstanding. The charging current is not the greater the better. Take the single lithium ion battery for example, its charging method includes constant current. , Constant voltage charging process, the constant voltage is usually 4.2V, and the constant current setting value is 0.1C～1C. Although high current charging will shorten the charging time, it will also shorten the battery life cycle and reduce the capacity, so correct understanding The importance of battery pre-charging is the reason why lithium batteries increase the pre-charging function during the design process. This is why the battery must be pre-charged, and an appropriate constant current value is selected to charge the battery. The charging process of lithium-ion batteries can be divided into four stages: trickle charge (low-voltage precharge), constant current charge, constant voltage charge, and charge termination. The basic requirement of a lithium battery charger is a specific charging current and charging voltage, so as to ensure the safe charging of the battery. Other charging auxiliary functions are added to improve battery life and simplify the operation of the charger, including trickle charging for over-discharged batteries, battery voltage detection, input current limit, turn off the charger after charging is complete, and automatic battery after partial discharge Start charging, etc. The charging method of lithium battery is limited voltage and constant current, which is controlled by IC chip. The typical charging method is: first detect the voltage of the battery to be charged, if the voltage is lower than 3V, pre-charge first, and the charging current is set 1/10 of the current, after the voltage rises to 3V, it enters the standard charging process. The standard charging process is: constant current charging with the set current, when the battery voltage rises to 4.20V, change to constant voltage charging, and keep the charging voltage at 4.20V. At this time, the charging current gradually decreases. When the current drops to 1/10 of the set charging current, the charging end statement: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete the previous article: Lithium The four-stage charging principle and requirements of ion battery charging