Knowledge related to battery life of 18650 lithium batteries and polymer lithium batteries.

Knowledge related to battery life of 18650 lithium batteries and polymer lithium batteries.

Can 18650 lithium batteries and polymer lithium batteries only be charged and discharged 500 times? 

I believe the vast majority of consumers have heard that the lifespan of 18650 lithium batteries and polymer lithium batteries is "500 times". After 500 charge and discharge cycles, the battery will "end its life". Many friends, in order to extend the battery's lifespan, only charge it when the battery is completely depleted. Does this really have an effect on extending the battery's lifespan? The answer is negative. The lifespan of a lithium battery is "500 times", which refers not to the number of times it is charged, but to one cycle of charging and discharging. 

A charging cycle means the process of the battery's entire charge from full to empty, and then from empty to full, which is not equivalent to charging once. For example, a lithium battery only uses half of its capacity on the first day and then fully charges it. If it continues like this the next day, charging half of it and charging twice in total, this can only be considered as one charging cycle, not two. Therefore, it may usually take several charges to complete a cycle. After completing each charging cycle, the battery capacity will decrease slightly. However, the decrease in battery capacity is very small. High quality batteries can still retain 80% of their original capacity after multiple cycles of charging, and many lithium powered products can still be used as usual after two to three years. Of course, lithium batteries still need to be replaced at the end of their lifespan. And the so-called 500 times refers to the manufacturer achieving about 625 rechargeable times at a constant discharge depth (such as 80%), reaching 500 charging cycles. (80% * 625=500) (ignoring factors such as reduced lithium battery capacity) However, due to various influences in real life, especially the non constant discharge depth during charging, the "500 charging cycles" can only be used as a reference battery life.