To measure how long the performance of lithium-ion batteries can be used, the industry stipulates the meaning of the lifespan of lithium battery. But in fact, the user’s usage is ever-changing, because the tests under different conditions are not comparable, and the meaning of the cycle life must be standardized if there is a comparison.
The national standard stipulates the cycle life test conditions and requirements of lithium-ion batteries: at 25 degrees at room temperature, charge for 150 minutes with a constant current and constant voltage method of 1C charging system, and discharge with a constant current 1C discharge system to 2.75V cut-off as one cycle. The test ends when one discharge time is less than 36 minutes, and the number of cycles must be greater than 300.
In fact, the number of cycles of lithium-ion batteries is not only affected by the different ways of users, but also related to the production technology level and material formula of lithium-ion battery manufacturers.
Lithium-ion battery pack: This meaning stipulates that the test of cycle life is carried out by deep charge and deep discharge, and stipulates that after the cycle life is executed in this mode, the capacity must still be more than 60% after 300 times.
In fact, the number of cycles obtained by different cycle systems is completely different. For example, the above other conditions remain unchanged. Only change the constant voltage of 4.2V to the constant voltage of 4.1V to test the cycle life of the same type of battery. , so that this battery is no longer a deep charge method, and the final test results show that the cycle life can be increased by nearly 60%. If the cut-off voltage is increased to 3.9V for testing, the number of cycles should be increased by several times.
It doesn’t make any sense to talk about the number of cycles aside from the rules, because the number of cycles is a means to detect battery life, not an end!
Myth: Many people like to use the lithium-ion battery of their mobile phone to automatically shut down and recharge. This is totally unnecessary.
In fact, it is impossible for users to use the battery according to the national standard test mode. No mobile phone will be turned off at 2.75V, and its discharge mode is not high-current constant-current discharge, but a mixture of GSM pulse discharge and normal low-current discharge. The way.
Another measure of cycle life is time. Some experts propose that the life of general civilian lithium-ion batteries is 2 to 3 years. Combined with the actual situation, such as the end of life with 60% capacity, plus the aging use of lithium-ion batteries, the cycle life expressed by time is longer. to be reasonable.