Main content:
Lithium batteries are everywhere, from electric two-wheelers, RV to boats and other types of equipment are inseparable from it, in the process of use may encounter the problem of battery capacity decline. Therefore it is necessary to lithium battery test to understand the performance of the battery. This article will introduce the lithium battery capacity test method, to help you easily grasp the battery performance.
Definition of lithium battery capacity
Lithium battery capacity refers to the amount of energy that lithium batteries can store, usually expressed in units of ampere-hours (Ah).
The necessity of lithium battery capacity test
Lithium battery capacity is one of the important indicators to measure the performance of the battery, with the growth of the use of time, the chemical reaction inside the battery will cause the structure of the positive and negative materials to change, thus affecting the capacity of the battery.
Taking the lithium battery used in electric vehicles as an example, the lithium battery used in electric vehicles refers to the lithium-ion battery pack, which is made of a small lithium battery through a series and parallel. This is because limited to technical factors, the volume of the current mass production of relatively stable and reliable quality of storage power is relatively large single lithium batteries are limited. The more monomer lithium batteries that make up the lithium battery pack, the consistency is still better when leaving the factory, and with the increase of the number of uses, the capacity pressure difference of different monomer small cells will slowly become prominent, which leads to the lithium battery capacity loss and the performance of lithium battery pack declines. This is the reason why lithium batteries are not durable after a period of time.
Therefore, it is necessary to periodically have the lithium battery capacity test to know the remaining capacity of the battery in time to avoid device failures caused by lithium-ion battery degradation.
Methods of lithium battery capacity test
Accurately testing the capacity of a lithium battery is important for evaluating battery performance and determining whether the battery needs to be replaced. The following are several commonly used lithium battery capacity test methods:
Professional testing
Test by using on-line monitoring system
Many manufacturers are equipped with an online monitoring system for their own lithium batteries, which can monitor the battery's voltage, current and temperature and other parameters in real time. When the battery capacity drops, the system will issue a warning signal to facilitate users to deal with it in time.
Use special testing instruments
There are also some test instruments on the market specifically used in lithium battery capacity test, such as internal resistance tester, constant current charge and discharge tester, etc. These instruments can accurately measure the capacity of the battery, internal resistance and other parameters, to provide users with detailed battery performance reports.
The following are the common instrument detection methods.
Voltage method: Estimate the battery capacity by measuring the voltage at both ends of the battery. The method of constant discharge is usually used to discharge the battery to a certain extent, and then measure the voltage of the battery, and estimate the battery capacity according to the discharge curve. This method is simple and easy, but the accuracy is low, and it is greatly affected by environmental temperature, battery aging and other factors.
Discharge method: The capacity of the battery is calculated by measuring the waveform and size of the pulse through the short-term pulse discharge of the battery. This method can quickly and accurately measure battery discharge capacity, but requires specialized equipment and technical support.
Internal resistance test method: The internal resistance test method is to evaluate the capacity of the battery indirectly by measuring the internal resistance of the battery. The internal resistance of the battery refers to the resistance of the current flowing through the inside of the battery when the battery is working. As the battery capacity decreases, the internal resistance of the battery will gradually increase. Therefore, by measuring the internal resistance of the battery, the capacity of the battery can be indirectly assessed. The internal resistance testing method requires the use of professional internal resistance testing instruments, which is simple to operate but the accuracy may be affected.
Roughly test by yourself
Judging by observing the charging and discharging process
In the daily use of the process, users can observe the battery charging and discharging process to initially determine whether the capacity of the battery is reduced, if it is found that the charging speed is significantly accelerated, the discharge time is shortened, it may mean that the battery capacity is reduced, but this method can only be used as a preliminary judgment, can not replace professional lithium battery capacity test.
Information from the lithium battery capacity test
Positive and negative electrodes, electrolyte and diaphragm are important components of lithium-ion batteries. Lithium embedment and removal reactions occur respectively in the positive and negative electrodes of lithium-ion batteries, and the amount of lithium embedment in the positive and negative electrodes becomes the main factor affecting the capacity of lithium-ion batteries. Therefore, the balance of positive and negative capacity of lithium-ion batteries must be maintained to ensure the best performance of the battery.
The chemical reaction in lithium-ion batteries not only includes the REDOX reaction in the process of lithium ion embedding and removal, but also includes side reactions such as the production and destruction of the SEI film on the surface of the negative electrode, the decomposition of the electrolyte, and the structural change and dissolution of the active material, which are the reasons for the attenuation of the capacity of lithium-ion batteries.
Therefore, if the test results are not ideal after the lithium battery capacity, it can be known that the main factors are the formation of SEI passivation film on the positive and negative surfaces of the lithium battery, lithium metal deposition, the dissolution of the electrode active material, the occurrence of anode and cathode REDOX reaction or side reaction, structural changes and phase changes.
Measures to extend the lifespan of lithium battery
Avoid overcharging and over discharging, and follow the manufacturer's recommended charging and discharging curve;
Try to keep the battery power between 20% and 80%, avoid frequent full charge and empty discharge;
Minimize the use of batteries in high temperature environments to avoid excessive battery temperature damage to battery performance;
For lithium batteries that are not used for a long time, charge and discharge operations should be carried out regularly to maintain the activity of the battery.
Conclusion
In daily life, it is difficult to intuitively determine whether the capacity of the battery is accurate, and there are still some fake and shoddy batteries on the market, which brings great security risks to the users. Therefore, the lithium battery capacity test is particularly important.
This article introduces the definition of lithium battery capacity, the necessity of the lithium battery capacity test, and the methods of lithium battery capacity test , so as to help users maximize the battery performance and better use lithium battery.
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