Besides 18650 and 21700, what other common types are there? Which is cost-effective?

　　14500, 26650, 20700, etc. It is the same size as No. 5. Battery and commonly used flashlight. Since the voltage of the lithium-ion battery is 3.7v, it is under normal operation You may not see it on 14500 appliances. 5 Battery. The 26650 is also mostly used for flashlights. The 26650 is larger than the 18650. The capacity of 21700 is also larger. 20700 characters range from 18650 to 21700, with a capacity of more than 18650 and a volume of slightly less than 21700, and a narrow scope of application.

　　As for cost performance, it depends on whether you are useful. Take a bright flashlight compatible with 26650 and 18650 as an example. 18650 and 21700 are more widely applicable, so they may become more complex skills and crafts. 18650 may be the most used type now, but 21700 is the type in the future.

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