When a lithium battery is charged, the electric potential applied to the two poles of the battery forces the compound of the positive electrode to release lithium ions, which are embedded in the carbon in which the molecules of the negative electrode are arranged in a sheet structure. During discharge, lithium ions are precipitated from the carbon of the sheet structure and recombine with the compound of the positive electrode. The movement of lithium ions generates an electric current. Although the principle is very simple, in actual industrial production, there are many practical issues that need to be considered: the material of the positive electrode needs additives to maintain the activity of multiple charging and discharging, and the material of the negative electrode needs to be designed at the molecular structure level to accommodate more More lithium ions; the electrolyte filled between the positive and negative electrodes, in addition to maintaining stability, also needs to have good conductivity to reduce the internal resistance of the battery.

　　Although lithium-ion batteries have all the advantages mentioned above, they have relatively high requirements for protection circuits. Overcharge and overdischarge should be strictly avoided during use, and the discharge current should not be too large. Generally speaking, the discharge rate It should not be greater than 0.2C. The charging process of the lithium battery is shown in the figure. In a charging cycle, the lithium-ion battery needs to detect the battery's voltage and temperature before charging to determine whether it is rechargeable. If the battery voltage or temperature exceeds the manufacturer's allowable range, charging is prohibited. The allowable charging voltage range is: 2.5V~4.2V per battery.

　　When the battery is in deep discharge, the charger must be required to have a pre-charging process to make the battery meet the conditions for fast charging; then, according to the fast charging speed recommended by the battery manufacturer, which is generally 1C, the charger will charge the battery with constant current. The battery voltage rises slowly; once the battery voltage reaches the set termination voltage (generally 4.1V or 4.2V), the constant current charging is terminated, the charging current decays rapidly, and the charging enters the full charging process; during the full charging process, the charging current gradually Attenuate until the charging rate drops below C/10 or when the full charge time expires, it will switch to the top end of charging; when the top end of charging, the charger will replenish energy for the battery with a very small charging current. After charging for a while at the top end, turn off charging.