What is the difference between the voltage for sorting indiv

What is the difference between the voltage for sorting individual cells and the internal resistance for sorting?

 

The voltage for sorting individual cells and the internal resistance for sorting are mainly different in the following aspects:

 

1. Different sorting basis

 

Sorting voltage:

The sorting operation is performed based on the terminal voltage of the cell. The cell will show different voltage values ​​under different charge and discharge states. By accurately measuring the voltage of the cell, the cells in a specific voltage range are classified into one category.

 

Sorting internal resistance:

Based on the internal resistance of the cell. The internal resistance of the cell refers to the ability of the cell to hinder the passage of current when it is working. It is the result of the combined effect of multiple factors such as the material properties, electrode structure, and manufacturing process of the cell itself. The internal resistance value of the cell is accurately measured by a professional internal resistance tester, and then the cell is classified according to the set internal resistance standard range.

 

2. Different cell characteristics reflected

 

Sorting voltage:

Mainly reflects the state of charge (SOC) of the cell. When the voltage is high, it usually means that the cell is in a higher state of charge, such as just fully charged; and when the voltage is low, it means that the cell power has been partially released and is in a lower state of charge. At the same time, the voltage situation can also reflect the health of the battery cell to a certain extent. If the voltage of a battery cell deviates abnormally from the standard voltage range of the same type of battery cell during normal use, it may indicate that there are some potential problems with the battery cell, such as internal short circuit of the battery may cause voltage drop.

Sorting internal resistance:

It reflects more the characteristics of the internal conductivity and energy conversion efficiency of the battery cell. The smaller the internal resistance, the smaller the internal energy loss of the battery cell during the charging and discharging process, and the higher the efficiency of converting electrical energy into chemical energy (when charging) and chemical energy into electrical energy (when discharging). Moreover, the size of the internal resistance is relatively stable, and it will not change rapidly and significantly with the charging and discharging state of the battery cell like the voltage (under normal working conditions), so it can reflect the consistency and quality of the battery cell from another perspective. If the internal resistance of the same batch of batteries is too different, it may cause uneven charging and discharging performance of each battery cell when used in groups.

3. Different impacts on subsequent applications

Sorting voltage:

For the subsequent grouping of batteries, the sorting voltage can ensure that the initial charge state of the batteries that make up the battery pack is relatively close. For example, in the power battery pack of an electric vehicle, if the cell sorting voltage is unreasonable and the initial power of each cell is very different, then in the subsequent charge and discharge cycle, it is easy for individual cells to be overcharged or over-discharged, thereby accelerating the aging of these cells or even damaging them, affecting the life and performance of the entire battery pack.

Sorting internal resistance:

Reasonable sorting of internal resistance is conducive to improving the overall charging and discharging efficiency of the battery pack. When cells with similar internal resistance form a battery pack, the energy loss inside each cell is relatively balanced during the charging and discharging process, and there will be no situation where the internal resistance of some cells is too large, causing serious heating and energy waste, thereby improving the working efficiency of the entire battery pack.

4. Different sorting equipment and test methods

Sorting voltage:

Usually a high-precision voltmeter or a battery test equipment with voltage measurement function is used for measurement. When measuring, the positive and negative poles of the cell need to be correctly connected to the corresponding interface of the measuring equipment to ensure a stable measurement environment and avoid external factors such as electromagnetic interference from affecting the measurement results. During large-scale production sorting, an automated sorting system will also be used. The voltage sorting standards are set through the program to automatically divide the cells into different categories.

Sorting internal resistance:

A special internal resistance tester is required to accurately measure the internal resistance of the cell. The internal resistance tester generally uses the AC four-probe method or AC voltammetry method to measure, which can effectively overcome the influence of factors such as internal polarization of the cell on the measurement results. Similarly, in industrial production, automated equipment will be combined to achieve efficient and accurate cell internal resistance sorting operations according to the set internal resistance sorting standards.

In summary, there are obvious differences between the cell sorting voltage and the sorting internal resistance in terms of sorting basis, cell characteristics reflected, impact on subsequent applications, sorting equipment and testing methods. They play an important role in the production and application of cells, and are key measures to ensure the performance and life of cells and battery packs.