Step / method
Method / Step 1:
National standard for lithium battery cycle life test conditions and requirements: at an ambient temperature of 20 ° C ± 5 ° C, 1 C charging, when the battery terminal voltage reaches the charging limitation of voltage 4.2V,
it changed to constant voltage charging, until the charging current is less than or equal to 1/20C, then stop charging, set aside for 0.5h~1h, then discharge with 1C current to the end voltage of 2.75V. After the end of discharge,
set aside for 0.5h~1h, and then proceed to the next charge and discharge cycle until the time of two consecutive discharge is less than 36 minutes, then we think it is the end of life of battery, the number of cycles must be more
than 300 times
Method / Step 2:
Interpretation of the national standard:
A. This definition stipulates that the test of cycle life is carried out in deep charge and deep release mode.
B. The national standard stipulates that according to this mode, the capacity is still more than 60% after ≥300 cycles.
However, the number of cycles obtained by different circulation systems is quite different. For example, the other conditions above are unchanged, only the constant voltage of 4.2V is changed to the constant voltage of 4.1V
to test the cycle life of the same type of battery. In this way, the battery is no longer a deep charge method, and the number of cycles life that can be improved in the final test can be increased by nearly 60%. Then if the cut-off voltage is increased to 3.9V for testing, the number of cycles should be increased several times.
Method / Step 3:
This statement about the cycle of charge and discharge once less life, we should pay attention to the definition of the lithium battery charge cycle: a charge cycle refers to the process of all the power of the lithium battery from full to empty, then from empty to full. And this is not the same as charging once. In addition, when you talk about the number of cycles, you can't ignore the condition of the cycle. It doesn't make sense to talk about the number of cycles without standards, because the number of cycles is a means of detecting battery life, not the purpose!