Does this battery become useless after reaching the number of life cycles?
The number of life cycles in this standard does not mean that the battery can no longer be used, but that after many cycles, the storage capacity of the battery decreases to a certain extent.
No less than 75% of nominal capacity after 1000 cycles”
That is, after 1000 cycles, the maximum charge of the battery is only 70 percent of the new battery, and the performance drops to a certain point. We can also use this battery with lower performance. When its effective capacity has fallen to its unique limit, 60%,for example, the battery stop working.
If battery life cycle number will lose one time as well as we charge the battery?
Nope. A charge cycle refers to the process in which all the charge of a lithium battery goes from full to empty and then back to full. For example, if we discharge 25% energy and then we charge 25% energy again, this process is just a quarter of a life cycle. In other words, you have to repeat the same steps four time to equal one complete cycle.
How to estimate life span of a battery?
As consumers, we care about how long the battery we can use. We name it as battery calender life.
Combined battery cycle life,we can make reasonable guesses about how long it will last.
Determine how often your battery will get a complete charging-and-discharging cycle
Multiple by numbers of cycle life
For example, there is a battery gives a clear definition of 500 life cycles. And we do a complete charging-and-discharging cycle takes an average of 5 days.
Convert into years, we may totally use this battery for 6 to 7 years in ideal condition. But this is just an estimate, actual battery life span depends on how you use it.
Influencing factors of lithium battery capacity attenuation
The performance of the battery will deteriorate with the deepening of the degree of battery use, which is mainly reflected in the attenuation of the battery capacity. And lithium battery capacity is directly related to the battery cycle life.
The capacity attenuation is related to the following factors to varying degrees:
(1) the deposition of lithium ions;
(2) the decomposition of the electrolyte;
(3) the dissolution of the active substance;
(4) the phase transition of the electrode material;
(5) the continuous growth of the solid electrolyte interface membrane (SEI).
Among them, the metamorphosis of the cathode material is the main cause of the attenuation of the battery capacity.The thickening of the negative electrode surface film makes it difficult for lithium-ion diffusion and accelerates the capacity attenuation of lithium batteries.
In addition, unreasonable use will also exacerbate the attenuation of lithium battery capacity. Overcharging and over-discharging of the battery may cause electrolyte decomposition. Furthermore, negative lithium deposition, blockage of lithium ion migration channels, changes in electrode material structure, thermal runaway and other undesirable consequences will influence lithium battery life span as well.Too high or too low temperature may affect the lithium ion diffusion coefficient, electrolyte decomposition, reactivity, electrochemical impedance and other factors.
No matter if the battery is in charging cycle state or not, its capacity is gradually decreasing. All of us have mobile phones, no one knows this fact better than us.
Look at this “capacity-cycle times” curve chart, we can discover that the capacity of a cell decreases linearly with the increasing number of charging and discharging cycles, and the rate is related to the discharge current of a single battery.
The following is a chart describing the relation between internal resistance and cycle times of lithium ion cell. We can easily gain that: for several times of cycle, the internal resistance decreases slightly while after hundreds of cycle times, the internal resistance is on the rise with quiet fast speed.
Under a certain discharge system, before the capacity of the secondary battery drops to a specified value, the number of cycles that the battery can withstand is called the cycle life or service cycle of the battery. Cycle life is an important parameter to evaluate the practical technology economy of battery.Cycle life is affected by the maximum discharge depth of the battery, so the expression of cycle life should also indicate the discharge depth. For example, the battery cycle life is 400 cycles /100% DOD or 1000 cycles /50%DOD.