Typical symptoms: Cylindrical batteries have large capacity but generate heat, square batteries are stable but have a large volume, and pouch batteries are lightweight but prone to being damaged.

Mystical moment: The same 18650 battery, why does some work for electric vehicles while others can only be used for flashlights?

Truth:

Cylindrical batteries: Model such as 18650 (diameter 18mm, height 65mm), Tesla Model 3 uses over 7000 sets of 21700 battery packs. The advantage is mature manufacturing process, but the disadvantage is poor heat dissipation.

Square batteries: Encased in aluminum, the blade battery used by BYD Han EV is square. The advantage is high space utilization, but the disadvantage is high customization cost.

Pouch batteries: Encased in aluminum plastic film, the one used by Apple MacBook is this. The advantage is high energy density, but the disadvantage is prone to being crushed.

Test case: One user disassembled a drone battery and found that the 21700 cylindrical battery had 30% longer battery life than the 18650, but its weight increased by 20%. Another user put the pouch battery in a jeans pocket and it leaked and broke after being bent. Solution:

For long battery life, choose cylindrical cells; for safety, select square cells; for lightness and thinness, opt for pouch cells.

Avoid squeezing or puncturing the pouch battery and stay away from high-temperature environments.