Lithium battery capacity test: the simple understanding is capacity sorting, performance screening and grading. Battery capacity division, that is, by charging and discharging the battery, the capacity of the lithium battery is determined by detecting the discharge capacity when the battery is fully charged. How to do the capacity test of lithium battery and what are the test methods? Please keep looking down.
The first explanation:
The simple understanding of lithium battery capacity test is capacity sorting, performance screening and grading. During the lithium battery capacity test, the data of each detection point is obtained through computer management, so as to analyze the size and internal resistance of these batteries and determine the quality level of the lithium battery. This process is the capacity test. After the first capacity test of the lithium battery, it needs to stand for a period of time, generally not less than 15 days. During this period, some internal quality problems will appear.
The second explanation:
After a batch of lithium batteries are made, although the size is the same, the battery capacity will be different. Therefore, the equipment must be fully charged according to the specifications, and then discharged (discharged) according to the specified current. The time taken to discharge the battery multiplied by the discharge current is the capacity of the battery. Only when the tested capacity meets or is greater than the designed capacity, the lithium battery is qualified, while the battery less than the designed capacity is not qualified. This process of screening qualified batteries through capacity test is called capacity test.
The second explanation:
Generally, it refers to the implementation of a series of process measures to stabilize the performance of the initially charged battery, including small current charging and discharging, constant temperature standing, etc.
Lithium battery capacity test principle:
The capacity test of lithium battery is completed through the chemical conversion capacity test cabinet (because the basic principles of chemical conversion and capacity test are the same, the functions of chemical conversion and capacity test are integrated in the same cabinet, which is called chemical conversion capacity test cabinet). The function of the chemical conversion capacity cabinet is actually like a charger, but it can charge and discharge a large number of batteries at the same time.
During the lithium battery capacity test, the data of each detection point is obtained through computer management, so as to analyze the size and internal resistance of these batteries and determine the quality level of the battery. This process is the capacity test.
What is the function of lithium battery capacity test?
The produced lithium battery cells cannot be sold immediately, and should be stored for at least 15 days. During this period, some internal defects appear, such as excessive self discharge. After receiving the order, the battery cells that have reached the storage period in the warehouse will be taken out for re inspection and capacity test, that is to say, they will be charged and discharged again to eliminate those whose capacity fails to reach the grade or quality problems, Then, about 50% of the electricity is delivered to the sales department and finally to the mobile phone battery assembly factory.
The cells to be used for lithium battery assembly are converted into machine capacity test again. Through this process, some cells that do not meet the requirements can always be selected and returned to the cell factory. After the mechanical test of the lithium battery detection, it can be seen that the battery cell has been charged and discharged again and is “charged”. So it’s normal to get two grids of electricity when you get the battery.
Each channel of battery capacity test can be started and stopped at a single point, with fast reaction speed. Each channel has an independent constant current source and constant voltage source. The current and voltage are sampled in real time, and the constant current and constant voltage are switched continuously without disturbance. It can be used for cycle life test.
The classification and compilation of lithium batteries is to select and combine the monomers with the same internal resistance and capacity. When combined, only those with close performance can form a lithium battery pack. For example, in order to meet the energy demand of electric vehicles, the power battery pack often needs dozens to thousands of batteries. Affected by the complexity of the system, the behavior of the battery pack has its own uniqueness. It is not a simple addition and subtraction method of the single battery that can obtain the performance of the lithium battery pack.
Requirements for composition and capacity test accuracy of lithium battery:
In order to improve the cycle life, stability, self discharge, safety and other electrochemical performance of lithium batteries, the consistency of lithium batteries must be strictly controlled or the battery grade must be accurately assessed. Therefore, there are high requirements for the measurement accuracy of the current and voltage of the chemical composition and capacity test equipment, which is limited to the sensor collection accuracy. At present, the measurement accuracy of the current and voltage of the chemical composition and capacity test equipment in the market is generally about one thousandth. For the chemical process, the higher the control accuracy of current and voltage, the better the quality of lithium battery products. The accuracy of the current and voltage sensor is more than 1 / 10000, which is an ideal choice.
The batteries have been capacity tested before leaving the factory. The capacity test cabinet in the lithium battery factory is the capacity test. Lithium battery has been widely used in various fields such as electronic products because of its excellent performance such as high energy density, high voltage, high cycle, high safety and environmental protection. Therefore, it is very important to ensure the consistency and reliability of lithium battery products.
Attachment: Neware aging equipment test software interface.
Note: the protection voltage must be set at each work step.
1. Work step setting options
A. Standard work step settings: as the name implies, standard settings. Recording conditions and protection conditions are global.
B. Professional work step settings: different from standard work steps, the recording conditions and protection conditions are for each work step, that is, each work step can have its own recording conditions and protection conditions. In addition, in the multi range equipment, the range of the professional work step can be manually selected.
C. University professional work step setting: this item is specially designed for the laboratories of university research institutes. The interface is simple and hides some parameters of the production line setting, making it easier for the actual users of the laboratory to understand and operate.
2. Work step name
A variety of work steps can be selected, and the corresponding process command work steps can be selected according to the test principle and test method.
3. Initial work step
Set the number of work steps to start
4. Recording conditions
The recording condition is checked. As long as any condition is met during the test, data will be recorded once. Properly select the recording conditions (for example, if the time interval is set to be long, the data file
The piece shall be as small as possible, but the required data shall not be omitted). This is true for other items.
5. Delay protection
Delay protection means that when the protection conditions are met, the protection will be started by delaying the corresponding time. Because the test is abnormal due to unstable factors such as current and voltage at the beginning or during the test. “Work step delay” means that when a work step reaches the protection condition in the test, the protection is performed after the set time is delayed. “Connection protection” means that when the connection operation is carried out, the connection is carried out after the delay setting. “Primary and secondary delay” is not yet supported. If necessary, it needs to be developed later.
6. Conversion voltage change rate
Change rate of formation voltage: during battery formation, it can be protected by setting the change rate of voltage. Within the “detection time”, that is, from the start of channel startup to the detection time point, if the voltage change value is less than the set “voltage value”, the channel will automatically enter the “protection” state, otherwise, the channel will continue to perform the test steps.
7. Safety protection
Safety protection: provide hardware protection for channels with abnormal sampling of battery current and voltage during the test. Take lithium battery as an example. Generally, the discharge voltage of lithium battery is 2.75V, the charging voltage is 4.20V, and the upper and lower limit voltage of safety protection parameters can be set as 2.5 ~ 4.3v; Current upper and lower limit protection settings: the system defines charging current as “+” and discharge as “-“, that is, “current upper limit” is positive and “current lower limit” is negative. Set “delay time” to delay the effective time of protection conditions set in safety protection.
8. Platform voltage
Platform voltage: users can set three different values of platform voltage, which is an important parameter of battery capacity.
9. Auxiliary channel protection conditions
Auxiliary channel safety protection conditions: hardware protection for abnormal sampling of battery cell voltage and temperature during the test. As long as any auxiliary channel meets the upper and lower limit conditions, the main channel enters the protection state. This function can only be realized when there is an auxiliary channel, otherwise it is unavailable. “Voltage difference” refers to the voltage difference between the main channel and the auxiliary channel. When the voltage difference exceeds the set parameter, it will enter the protection state.
10. Temperature connection
This item must be used when the auxiliary channel is connected. It is defined as that when the temperature protection condition is reached and the monitoring temperature drops to the set range, the system will automatically continue to test.
11. Auxiliary channel recording conditions
Auxiliary channel recording conditions: including three options: time interval, voltage interval and temperature interval. It is equally effective when multiple options are selected. The relationship between various recording conditions is “logical or”. This function can only be realized when there is an auxiliary channel, otherwise it is unavailable.
12. Magnification parameter
According to the setting of the active substance and the nominal specific capacity, the current can be automatically converted into the current by inputting only several times of the value in the step setting column
13. Basic information
The content includes the creator, battery batch number and remarks. These information will be saved in the database together with the work step information to facilitate the user’s search and query of the test data.
14. Save step
You can save the currently set work step settings and protection conditions, and you can directly import the work step files next time, thus saving the time to reset the same parameters.
15. Open the work step
Import the previously saved step file (. End of XML format), saving the time for resetting.
SmartPropel Pay high attention on the lithium battery quality control, all battery cells pass the capacity testing. And battery packs are 100% tested before delivery.