I. Introduction

The 18650 battery is a cylindrical, standardized lithium-ion battery named for its standardized size (18 mm in diameter and 65 mm in length). This battery has the characteristics of high energy density, rechargeability, and multiple chemical systems, and is widely used in consumer electronics, power tools, portable devices, electric vehicles, and other fields.
Because 18650 batteries are standard batteries and are used in large quantities, there are many manufacturers and models of 18650 batteries, ranging from a few cents to tens of yuan. Therefore, when selecting a battery, you need to consider multiple factors to ensure the safety, performance, and service life of the battery.

Ⅱ. Selection considerations

1. Brand selection
It is very important to choose 18650 batteries produced by well-known brands for safety. Well-known brands such as Panasonic, Samsung, LG, and Sony have been continuously improved for decades and have strict quality control systems and perfect after-sales services. The batteries of these brands are more guaranteed in terms of safety, performance and life.

2.Capacity

The capacity of 18650 batteries is an important criterion for selecting batteries and a key indicator for measuring their ability to store electrical energy. The unit is milliampere-hour (mAh, that is, 1mA discharge current can be continuously discharged for 1 hour). The common capacity range is 1000mAh to 3500mAh. The higher the capacity, the longer the battery life. However, there are a large number of batteries with false capacity on the market, and consumers should be cautious when purchasing. Generally speaking, the actual capacity of domestic 18650 batteries is between 800mAh and 3500mAh. In order to ensure the true capacity of the battery, it is recommended to purchase samples and use a discharge meter for testing.

3.Continuous discharge current

Continuous discharge current (CDR) refers to the maximum current that a battery can continuously output without damaging itself, usually expressed as a C number. For example, a 18650 battery with a capacity of 2800mAh has a continuous discharge capacity of 0.5C, and the continuous discharge current is 1.4A. If the device requires a higher discharge current, a battery with a higher C number should be selected.

4.Internal resistance

Internal resistance is the size of the battery's own resistance. The smaller the internal resistance, the stronger the battery's discharge capacity and the less its own energy loss. Generally speaking, the internal resistance of a high-quality 18650 battery should be less than 100mΩ. Excessive internal resistance will not only affect the performance of the battery, but may also cause the battery to overheat and even cause safety problems. Therefore, you should pay attention to the internal resistance parameters of the battery when purchasing.

5.Voltage

The standard voltage of 18650 batteries is usually 3.7V, and the charging cut-off voltage is 4.2V. However, some batteries may have different nominal voltages, such as the nominal voltage of lithium iron phosphate (LFP) 18650 batteries is 3.2V. When selecting, it is necessary to ensure that the voltage of the battery matches the requirements of the device, otherwise the device may not work properly or be damaged.

6.Safety performance

Safety performance is one of the most important factors in the selection of 18650 batteries. High-quality 18650 batteries should have good safety protection devices to prevent abnormal situations such as short circuit, overcharge, over discharge and high temperature. In addition, attention should also be paid to the safety certification of the battery, such as CE, UL, PSE, etc. These certification marks mean that the battery has passed international or national safety standard tests and is more assured to use.

7.Temperature adaptability

Temperature has a significant impact on the performance and life of 18650 batteries. Generally speaking, the operating temperature range of 18650 batteries is -20℃ to 60℃, but at extreme temperatures, the performance of the battery will decrease. For example, in a low temperature environment, the discharge capacity of the battery will be reduced; in a high temperature environment, the battery life will be shortened. Therefore, when selecting, the appropriate battery should be selected according to the use environment of the equipment.

8.Cycle life

Cycle life refers to the number of charge and discharge cycles that a battery can perform while maintaining a certain capacity. High cycle life means that the battery has a longer service life and can reduce the cost of long-term use. Generally speaking, the cycle life of high-quality 18650 batteries can reach hundreds to thousands of times. When selecting, you should try to choose batteries with a longer cycle life, and the service life of the whole product will be longer.

9.Battery shape

18650 batteries are divided into two types: flat head and pointed head. Flat head batteries do not have a protective cover, while pointed head batteries have a protective cover to prevent the battery from overcharging. When selecting, you should choose the appropriate battery shape according to the requirements of the device.

10.Other factors

In addition to the above factors, the weight, size, production date, etc. of the battery should also be considered. For example, the weight and size of the battery will affect the overall design and portability of the device. In addition, you should try to choose a battery with a recent production date to ensure its performance and life.

III. Application scenarios and selection recommendations

1.Consumer electronics

In the field of consumer electronics, such as laptops, digital cameras, etc., it is usually necessary to consider the energy density and cycle life of the battery. For example, laptops require 18650 batteries with large capacity and long cycle life to meet the needs of long-term use. It is recommended to choose a battery with a capacity between 2500mAh and 3000mAh and a cycle life of more than 500 times.

2.Power tools

Power tools have high requirements for the discharge capacity of the battery. For example, devices such as electric wrenches and electric scissors require batteries with high discharge current to ensure the efficient operation of the tools. Therefore, 18650 batteries with high discharge capacity (such as 3C or above) should be selected.

3.Electric vehicles

Electric vehicles have extremely high requirements for the energy density, cycle life and safety of batteries. For example, Tesla Model S and early X models used a large number of 18650 batteries to form battery packs. When selecting, batteries with high energy density, long cycle life and excellent safety performance should be selected.

4.Portable devices

In portable devices, such as power banks and high-intensity flashlights, the capacity and portability of the battery need to be considered. For example, power banks require large-capacity 18650 batteries to meet the needs of users for long-term use. It is recommended to choose a battery with a capacity between 2500mAh and 3000mAh.

IV. Summary

18650 battery has an important position in the market due to its excellent performance and wide range of applications. However, when selecting, it is necessary to comprehensively consider multiple factors such as brand, capacity, continuous discharge current, internal resistance, voltage, safety performance, temperature adaptability, cycle life, etc. Only by choosing the right 18650 battery can the safe, efficient operation and long-term use of the equipment be ensured.

V. Related products

EID031-1X03, using the high-quality lithium battery of Hengdian Dongci, a listed company, with a large capacity of 3300mAh (not false), reliable quality, low internal resistance, sufficient capacity, and long life.