Charging voltage is a core control parameter in the charging process of lithium-ion batteries, which directly determines the charging efficiency, capacity performance, service life and safety performance of the battery. Reasonably controlling the charging voltage is a key prerequisite for ensuring the safe and stable operation of the battery and avoiding charging failures. The charging voltage of lithium-ion batteries is not a fixed value, but varies according to the battery type, number of cells, and application scenarios. In-depth understanding of their charging voltage characteristics and standardized control of the charging voltage range are of great significance for the daily use, maintenance and safety management of the battery, and are also core measures to avoid potential safety hazards such as battery bulging, leakage, and fire.

　　At present, the charging voltage of mainstream lithium-ion batteries has a clear standard range. Among them, the standard charging voltage of single-cell lithium-ion batteries is the most common. The standard charging voltage of a single ternary lithium battery cell is 4.2V, and the charging termination voltage should be controlled between 4.15-4.25V. If it exceeds 4.3V, it will cause decomposition of the electrolyte inside the battery, damage to the electrode materials, accelerate capacity attenuation, and even cause safety accidents; the standard charging voltage of a single lithium iron phosphate battery cell is 3.65V, and the charging termination voltage is controlled between 3.6-3.7V. Its overcharge resistance is better than that of ternary lithium batteries, but the voltage range still needs to be strictly controlled to avoid overcharge damage.

　　For lithium-ion battery packs with multiple cells connected in series, the charging voltage needs to be calculated by superimposing the number of series cells. For example, the commonly used 18650 ternary lithium battery pack has a standard charging voltage of 12.6V (4.2V×3) for 3-series combination and 16.8V (4.2V×4) for 4-series combination. When charging, a dedicated charger with corresponding voltage should be used to ensure the voltage balance of each cell, avoiding overcharging or undercharging of a single cell. Otherwise, it will lead to the overall performance attenuation and service life shortening of the battery pack, and even cause the battery pack to bulge or catch fire. In addition, the stability of the charging voltage is also crucial. Excessively fluctuating charging voltage will damage the internal structure of the battery. It is recommended to use a dedicated charger with constant voltage and constant current functions. The constant current mode is adopted in the initial stage of charging, and it switches to the constant voltage mode when the voltage is close to the termination voltage to ensure a stable charging process, which not only ensures that the battery is fully charged, but also avoids overcharge damage, and at the same time extends the battery cycle life, adapting to the use needs of various household, industrial and consumer lithium-ion batteries.