The four-stage charging principle and requirements of lithium-ion battery charging

When the lithium-ion battery is in use, as the power is released, the voltage drops, and the chemical activity of the battery also decreases. In order to better protect the performance of lithium-ion batteries, lithium-ion batteries generally require the charging process to be controlled in four stages: trickle charge (low-voltage precharge), constant current charge, constant voltage charge, and charge termination. Take a conventional ternary lithium-ion battery as an example. The nominal capacity of the INR26650-50A battery is 5000mAh, the nominal voltage is 3.6V (there is also a standard 3.7V on the market), the discharge end voltage is 2.75V, and the charge end voltage is 4.20V. The basic requirement of a lithium-ion 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 test, 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-ion battery is limited voltage and constant current, which is controlled by IC chip. The typical charging method is: first test 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 constant 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, and when the current drops to 1/10 of the set charging current, charging ends. Description of the four stages of lithium-ion battery charging: Stage 1: trickle charge-trickle charge is used to pre-charge the fully discharged battery cell (recovery charge). When the battery voltage is lower than about 3V, trickle charging is used. The trickle charging current is one-tenth of the constant charging current, which is 0.1c (for example, if the constant charging current is 1A, the trickle charging current is 100mA). Phase 2: Constant current charging-when the battery voltage rises above the trickle charge threshold, increase the charging current for constant current charging. The current for constant current charging is between 0.2C and 1.0C. The battery voltage gradually increases with the constant current charging process. Generally, the voltage set for a single battery is 3.0-4.2V. Stage 3: Constant voltage charging-when the battery voltage rises to 4.2V, the constant current charging ends and the constant voltage charging phase begins. The current depends on the saturation of the battery cell. As the charging process continues, the charging current gradually decreases from the maximum value. When it decreases to 0.01C, the charging is considered to be terminated. (C is a way to express the nominal capacity of the battery against the current. For example, if the battery has a capacity of 1000mAh, 1C is the charging current of 1000mA.) Stage 4: Charge termination There are two typical charging termination methods: use the minimum charging current to judge or Use a timer (or a combination of the two). The minimum current method monitors the charging current in the constant voltage charging stage, and terminates the charging when the charging current is less than 0.02C. The second method starts timing at the beginning of the constant voltage charging phase, and terminates the charging process after two hours of continued charging. The above-mentioned four-stage charging method takes about 2.5 to 3 hours to complete the charging of the fully discharged battery. Advanced chargers also adopt more safety measures. For example, if the battery temperature exceeds the specified window (usually 0°C to 45°C), then charging will be suspended. After charging, if the battery voltage is lower than 3.89V, it will be recharged. 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: What is the commonly used lithium-ion battery charging management chip?