18650 battery is the originator of lithium-ion batteries - a standard lithium-ion battery model set by Japan's SONY company in order to save costs. 18 means a diameter of 18mm, 65 means a length of 65mm, and 0 means a cylindrical battery. 18650 means that the diameter is 18 mm and the length is 65 mm.

Common 18650 batteries are divided into lithium-ion batteries and lithium iron phosphate batteries(lifepo4 battery). The nominal voltage of lithium-ion battery is 3.7v, the charge cut-off voltage is 4.2v, the nominal voltage of lithium iron phosphate battery is 3.2V, the charge cut-off voltage is 3.6v, the capacity is usually 1200mAh-3350mAh, and the common capacity is 2200mAh-2600mAh . The theoretical life of the 18650 lithium battery is 1000 cycles of charging.

18650 lithium batteries are mostly used for laptop batteries due to their large capacity per unit density. In addition, 18650 is widely used in various electronic fields because of its excellent stability in work: often used in high-end strong light Flashlights, portable power supplies, wireless data transmitters, electric thermal clothing, shoes, portable instruments, portable lighting equipment, portable printers, industrial instruments, medical instruments, etc.

Lithium batteries are labeled as either 3.7V or 4.2V. It's just that the manufacturer's labeling is different. 3.7V refers to the platform voltage (i.e. typical voltage) at which the battery is discharged during use, while 4.2V refers to the voltage at full charge. The common rechargeable 18650 lithium batteries have a voltage range of 3.6 or 3.7V, and when fully charged, it is 4.2V, which has little to do with battery capacity. The mainstream capacity of 18650 batteries ranges from 1800mAh to 2600mAh (most 18650 power batteries have capacities ranging from 2200 to 2600mAh), and the mainstream capacity even ranges from 3500 or 4000mAh or above.

It is generally believed that if the no-load voltage of a lithium battery is below 3.0V, it is considered exhausted (the specific value depends on the threshold value of the battery protection board, such as low as 2.8V and also 3.2V). Most lithium batteries cannot be discharged with an unloaded voltage below 3.2V, otherwise excessive discharge will damage the battery (generally, lithium batteries in the market are only used with protective plates, so excessive discharge can also cause the protective plates to not detect the battery and cannot charge the battery). 4.2V is the maximum limiting voltage for battery charging. It is generally believed that charging the no-load voltage of a lithium battery to 4.2V is considered fully charged. During the battery charging process, the voltage of the battery gradually increases from 3.7V to 4.2V. Lithium battery charging cannot charge the no-load voltage above 4.2V, otherwise it will also damage the battery. This is the special feature of lithium batteries.

Advantage:

1. The capacity of a large 18650 lithium battery is generally between 1200mah and 3600mah, while the general battery capacity is only around 800mah. If combined into an 18650 lithium battery pack, the 18650 lithium battery pack can easily exceed 5000mah.

2. Long lifespan 18650 lithium batteries have a long lifespan, with a cycle life of over 500 times during normal use, which is more than twice that of regular batteries.

3. High safety performance 18650 lithium battery has high safety performance. To prevent battery short circuits, the positive and negative poles of the 18650 lithium battery are separated. So the possibility of a short circuit occurring in it has been reduced to the extreme. A protective board can be installed to prevent overcharging and discharging of the battery, which can also extend its service life.

4. The voltage of 18650 lithium batteries is generally 3.6V, 3.8V, and 4.2V, which is much higher than the 1.2V voltage of nickel cadmium and nickel hydrogen batteries.

5. Without memory effect, it is not necessary to empty the remaining power before charging, so it is convenient to use.

6. The internal resistance of polymer cells with small internal resistance is smaller than that of general liquid cells. The internal resistance of domestic polymer cells can even reach below 35m Ω, greatly reducing the self consumption of the battery.