18650 lithium battery, polymer lithium battery can only charge and discharge 500 times?　　

    I believe that most consumers have heard that the life of 18650 lithium batteries and polymer lithium batteries is "500 times", 500 charge and discharge times, beyond this number of times, the battery will "end of life", many friends in order to be able to extend the battery life Lifespan, each time the battery is fully depleted before charging, does this really extend the life of the battery? the answer is negative. The lifespan of a lithium battery is "500 times", which does not refer to the number of times of charging, but a cycle of charging and discharging.　

    A charging cycle means the process of using all the power of the battery from full to empty, and then from empty to full. This is not the same as charging once. For example, a lithium battery used only half of its power on the first day, and then it was fully charged. If it is still the case the next day, that is, use half of the charge and charge it twice in total. This can only be counted as one charging cycle, not two. Therefore, it may usually take several times to complete a cycle. Every time a charging cycle is completed, the battery capacity will decrease a bit. However, this reduction in power consumption is very small. A high-quality battery will still retain 80% of its original capacity after being charged for multiple cycles. Many lithium-powered products will still be used as usual after two or three years. Of course, the lithium battery still needs to be replaced after the end of its life. The so-called 500 times means that the manufacturer has achieved about 625 charging cycles at a constant depth of discharge (such as 80%), reaching 500 charging cycles. (80%*625=500) (Ignore factors such as the reduction of lithium battery capacity) 　　 Due to various effects of real life, especially the depth of discharge during charging is not constant, so "500 charging cycles" can only be used as a reference battery life .