Dongguan lithium battery manufacturer analysis: lithium battery charge and discharge life

August 17, 2021

Lithium battery life problem: Is the cycle charge and discharge once less life? Before answering this question, let us first talk about the test conditions of lithium battery cycle life.

The cycle is the use, we are using the battery, the concern is the time of use, in order to measure how long the rechargeable battery can be used for such a performance, the definition of the number of cycles is specified. The actual user usage is ever-changing, because the tests with different conditions are not comparable, and the definition of cycle life must be standardized for comparison.

National standard regulations 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 limit voltage 4.2V, changed to constant voltage charging, until the charging current is less than Or equal to 1/20C, 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, let go for 0.5h~1h, then proceed to the next charge and discharge cycle until two consecutive discharge times Less than 36min, the end of life is considered, the number of cycles must be greater than 300 times

Interpretation of the national standard:

A. This definition stipulates that the test of cycle life is carried out in deep charge and deep release.

B. The cycle life of the lithium battery is specified. 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. In the end, the cycle life 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.

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 all the power of the lithium battery from full to empty, then from empty to full the process of. This is not the same as charging once. In addition, when you talk about the number of loops, you can't ignore the condition of the loop. It doesn't make sense to talk about the number of loops, because the number of loops is a means of detecting battery life, not the purpose!

▲ Misunderstanding: Many people like to use the mobile phone lithium-ion battery to automatically shut down and recharge, this is completely unnecessary.

In fact, it is impossible for the user 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 a high current constant current discharge, but a GSM pulse discharge and a small current discharge mix. The way.

There is another measure of cycle life, which is time. Some experts have suggested that the life of a general-purpose lithium-ion battery is 2 to 3 years. In combination with actual conditions, such as the termination of life with 60% capacity, and the aging effect of lithium-ion batteries, it is time to express the cycle life. More reasonable.

Tip: For lithium-ion batteries, there is no need to use shutdown and recharge. Lithium-ion batteries are suitable for charging at any time. This is one of his biggest advantages for NiMH batteries. Please take advantage of this feature. The lithium battery is fully charged and discharged once (complete charge and discharge is not equivalent to one charge and discharge), and the cycle life is reduced once.

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Author:

Ms. LISA CHEN

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Lisa@ie-energy.com

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