When did the decline in production capacity mainly occur?
The secondary battery with good quality can be continuously charged and discharged for more than 500 times, and its capacity can reach more than 70% or even higher. However, the speed of battery capacity decay depends not only on the quality of batteries, but also on the matching of batteries, users' habits, storage temperature and brightness to prolong battery life.
In fact, although the secondary battery is marked as reusable, it still has a service life. Take the notebook battery as an example. Although the capacity is marked as 4000MAH, the capacity will gradually decrease after charging and discharging, and it is easier to drop below 3300MAH after one year of use, which is a normal phenomenon of secondary batteries. At the same time, it can be seen that the battery is actually in continuous use, and the use time can only be very short. When a battery pack is used,
▓ What is voltage difference?
The capacity reduction or failure of many lithium battery packs is caused by the voltage difference between a series of batteries, which is inevitable because the performance of each series of batteries in the battery pack cannot be exactly the same. After a long time, some batteries with poor characteristics will naturally age first, which will affect the overall discharge curve. It is the aging battery that is fully charged first and then discharged first, while the capacity of other batteries is not fully utilized at this time.
For example, when charging, other batteries begin to approach the full charging voltage of 4.2V, and the aging batteries may have reached the voltage of 4.3V or even higher, resulting in overcharge of the electrical string and dissatisfaction of others; When discharging, each string is still in a large working voltage range, but the aging string cell is lower than the normal working voltage of the battery, 3.0V, resulting in a single string under-voltage protection, forming a fast charge and discharge of the battery.
▓ What is "battery aging"
The so-called battery aging phenomenon is that the storage capacity of the battery gradually deteriorates with the increase of the number and time of use or long-term storage. When the battery pack has only a single battery, the capacity will decrease; However, when the battery pack has a plurality of battery cells connected in series and parallel, the voltage difference of each battery cell will be generated. At this time, users are most likely to notice that the battery clearly shows more than 50%, and how it suddenly drops below 10%, or even turns off abnormally, resulting in shortened service time. Simply put, "battery aging is the decline of battery capacity."
When the battery is aging, is there anything inside the battery that must be changed?
In aging batteries, the change of internal resistance is the most common and easy to detect. The internal resistance of the battery is very small when it leaves the factory. However, after long-term charge and discharge, the internal resistance increases due to the decrease of the activity of electrolyte and chemicals in the electronic watch pool. The electrolyte will gradually degenerate during repeated charging and discharging, and the internal resistance will continue to increase until the internal resistance is so large that the electricity in the battery cannot be released normally. A common phenomenon is battery heating. At this time, the battery is so-called aging, and the relative battery capacity will also decrease. Most aging batteries cannot be used because of excessive internal resistance.
The change of battery internal resistance includes the following points:
Change of cathode material
The molecular structure of the battery has a hole structure on the anode and cathode that can accommodate the precipitated chemical molecules. With the increase of charge and discharge times, it will gradually collapse and block, that is, the anode and cathode materials will be actively passivated, and even the anode and cathode materials will be polarized, which will reduce the number of ions that can move freely during charge and discharge in the battery.
Replacement of catalyst
Due to the storage time of environmental temperature and humidity, the structure and performance of catalysts with catalytic molecular structure gradually changed, and finally they could not catalyze.
Electrolyte deterioration
After the battery is repeatedly charged and discharged, the electrolyte will deteriorate or even lose. Poor quality batteries are more likely to deteriorate faster because of poor control of the components in the electrolyte.
Conclusion:
Thirdly, the battery itself is a kind of consumption port. With the increase of use times, the storage capacity of the battery will gradually decrease, and the charging cycle life will be more than 500 times. According to the time estimate, if it is used on the first day, it will take about 1-2 years to replace the battery.