source：Geerady       date： 2022-09-14
Rechargeable lithium-ion battery is the most widely used battery in mobile phones, but it is relatively "delicate", in use should not be overcharged, overdischarged (will damage the battery or make it scrapped). Therefore, there are protective components or protective circuits on the battery to prevent costly battery damage. Lithium-ion battery charging requirements are very high, to ensure that the termination voltage accuracy is within 1%, at present the major semiconductor device factories have developed a variety of lithium-ion battery charging IC, to ensure safe, reliable, fast charging.
Mobile phones are now ubiquitous. Some of them are nickel-metal hydride batteries, but the smart ones are lithium-ion batteries. Proper use of lithium-ion batteries is very important for prolonging battery life. Lithium-ion battery is the most widely used lithium battery, it can be made into flat rectangular, cylindrical, rectangular and button type according to the requirements of different electronic products, and there are several batteries connected in series together to form a battery pack. Lithium-ion batteries are rated at 3.6V(some products are 3.7V). The termination charging voltage is related to the anode material of the battery when fully charged: the anode material is 4.2V of graphite; The anode material is 4.1V of coke. The internal resistance of different anode materials is also different. The internal resistance of coke anode is slightly larger, and its discharge curve is also slightly different. Most of the batteries used now are 4.2V, and the termination discharge voltage of lithium ion batteries is 2.5V ~ 2.75V(the battery factory gives the working voltage range or the termination discharge voltage, each parameter is slightly different). Continued discharge below the termination discharge voltage is called over discharge, and over discharge will damage the battery.
Lithium-ion batteries are not suitable for large current discharges, as large current discharges will reduce the discharge time (higher internal temperature will be generated and energy loss). Therefore, the maximum discharge current given by the battery production plant should be less than the maximum discharge current in use. Lithium-ion batteries have certain requirements on temperature, and the factory provides the charging temperature range, discharge temperature range and storage temperature range. Lithium-ion batteries have very high requirements for charging, which require precise charging circuit to ensure the safety of charging. The accuracy allowance for the termination charging voltage is ±1% of the rated value (e.g., ±0.042V for a 4.2V lithium-ion battery). Overvoltage charging will cause permanent damage to the lithium-ion battery. The charging current of lithium-ion battery should be based on the recommendation of battery manufacturer, and the limited current circuit should be required to avoid overcurrent (overheating). Generally used charging rate is 0.25C ~ 1C(C is the capacity of the battery, such as C=800mAh, 1C charging rate is 800mA charging current). In the high current charging often to detect the battery temperature, to prevent overheating damage to the battery or produce an explosion.
Lithium-ion battery charging is divided into two stages: constant current charging, to near the end of the voltage to a constant voltage charging. Overcharge, overdischarge or overcurrent of lithium-ion battery in the process of charging or discharging will cause damage to the battery or reduce its service life.