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　　Specifications of Cylindrical Lithium Batteries

　　Cylindrical lithium batteries come in a wide range of specifications, which are crucial for their applications in various industries. These specifications determine the physical dimensions, electrical characteristics, and performance capabilities of the batteries.

　　Physical Dimensions

　　The most common cylindrical lithium - ion battery sizes are based on the 18650 format. The "18" in 18650 represents the diameter of the battery, which is 18 mm, and the "650" represents the height, which is 65.0 mm. This size has become extremely popular due to its versatility. It is widely used in portable electronics such as laptops, power banks, and electric toothbrushes. Another well - known size is the 21700. With a diameter of 21 mm and a height of 70 mm, the 21700 battery offers a larger volume, which can potentially accommodate more active material, leading to higher energy capacity. It has found applications in high - performance electric vehicles and advanced energy storage systems. There are also smaller sizes like the 14500, with a diameter of 14 mm and a height of 50 mm, which are often used in small - scale devices such as digital cameras and some types of flashlights. These different physical dimensions allow manufacturers to choose the most suitable battery size for their specific product designs, whether it's for a compact, handheld device or a larger - scale energy - consuming application.

　　Electrical Specifications

　　In terms of electrical specifications, cylindrical lithium batteries have a nominal voltage. For most common lithium - ion chemistries, the nominal voltage is around 3.6 V or 3.7 V. However, during charging and discharging, the voltage varies. The upper cutoff voltage during charging is typically around 4.2 V, and the lower cutoff voltage during discharging is usually around 2.5 V to 3.0 V, depending on the specific battery chemistry and manufacturer's recommendations. The internal resistance of the battery is also an important electrical parameter. A lower internal resistance is desirable as it reduces power losses during charge and discharge processes. High - performance cylindrical lithium batteries, such as those used in electric vehicles, are designed to have very low internal resistance to enable high - current charging and discharging, which is essential for quick acceleration and efficient operation.

　　Safety - Related Specifications

　　Safety is a critical aspect of cylindrical lithium - battery design, and there are specific safety - related specifications. Many cylindrical lithium batteries are equipped with a built - in protection circuit module (PCM). The PCM is designed to prevent over - charging, over - discharging, and over - current conditions. For example, if the battery voltage reaches the upper cutoff voltage during charging, the PCM will cut off the charging current to prevent over - charging, which could lead to thermal runaway and potential fire hazards. In terms of temperature specifications, most cylindrical lithium batteries are designed to operate within a certain temperature range. The typical operating temperature range is from - 20 °C to 60 °C. Outside this range, the battery's performance, such as its capacity and cycle life, can be significantly affected. Some advanced cylindrical lithium - ion batteries are also designed to be resistant to vibration and shock, which is important for applications in vehicles and other mobile devices that may experience mechanical stress.

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