How to set up a safe lithium battery protection circuit

    Firstly, let‘s understand the material composition of lithium-ion batteries. The performance of lithium-ion batteries mainly depends on the structure and performance of the internal materials used in the batteries. These internal materials of batteries include negative electrode materials, electrolytes, separators, and positive electrode materials. The selection and quality of positive and negative electrode materials directly determine the performance and price of lithium-ion batteries. Therefore, the research on cheap and high-performance positive and negative electrode materials has always been a focus of the development of the lithium-ion battery industry.

    Carbon materials are generally used as negative electrode materials, and their current development is relatively mature. The development of positive electrode materials has become an important factor restricting the further improvement of lithium-ion battery performance and price reduction. In the current commercial production of lithium-ion batteries, the cost of positive electrode materials accounts for about 40% of the entire battery cost, and the decrease in the price of positive electrode materials directly determines the decrease in the price of lithium-ion batteries. This is especially true for lithium-ion power batteries. For example, a small lithium-ion battery used for a mobile phone only requires about 5 grams of positive electrode material, while a lithium-ion power battery used to drive a bus may require up to 500 kilograms of positive electrode material.

    Although theoretically there are many types of positive electrode materials that can be used for lithium-ion batteries, the common positive electrode material is mainly composed of LiCoO2. During charging, the potential applied to the two poles of the battery forces the positive electrode compound to release lithium ions, which are embedded in the carbon with a layered structure of negative electrode molecules. During discharge, lithium ions precipitate from the layered carbon and recombine with the positive electrode compound. The movement of lithium ions generates an electric current. This is the principle of lithium battery operation. 2. Design of lithium battery charging and discharging management

    Although theoretically there are many types of positive electrode materials that can be used for lithium-ion batteries, the common positive electrode material is mainly composed of LiCoO2. During charging, the potential applied to the two poles of the battery forces the positive electrode compound to release lithium ions, which are embedded in the carbon with a layered structure of negative electrode molecules. During discharge, lithium ions precipitate from the layered carbon and recombine with the positive electrode compound. The movement of lithium ions generates an electric current. This is the principle of lithium battery operation. 2. Design of lithium battery charging and discharging management

    When charging a lithium battery, the electric potential applied to the two poles of the battery forces the positive electrode compound to release lithium ions, which are embedded in the carbon with a layered arrangement of negative electrode molecules. During discharge, lithium ions precipitate from the layered carbon and recombine with the positive electrode compound. The movement of lithium ions generates an electric current. Although lithium-ion batteries have various advantages mentioned above, they have high requirements for protective circuits. During use, overcharging and over discharge phenomena should be strictly avoided, and the discharge current should not be too large. Generally speaking, the discharge rate should not exceed 0.2C. The charging process of the lithium battery is shown in the figure. During a charging cycle, lithium-ion batteries need to be tested for voltage and temperature before charging to determine whether they can be charged. If the battery voltage or temperature exceeds the manufacturer‘s allowed range, charging is prohibited. The allowable charging voltage range is: 2.5V~4.2V per battery.

    In the case of deep discharge of the battery, it is necessary to require the charger to have a pre charging process to ensure that the battery meets the conditions for rapid charging; Then, according to the fast charging speed recommended by the battery manufacturer, usually 1C, the charger charges the battery with constant current, and the battery voltage slowly increases; Once the battery voltage reaches the set termination voltage (usually 4.1V or 4.2V), constant current charging is terminated, and the charging current rapidly decays, entering the full charging process; During the full charging process, the charging current gradually decays until the charging rate drops below C/10 or when the full charging time expires, it switches to the top to stop charging; When the top is cut off for charging, the charger replenishes the battery with minimal charging current. Turn off the charging after a period of time when the top end stops charging.