Welcome to eastarbattery!

86-18664968482

info@eastarco.com sales6@eastarbattery.com

RM 905,Hongchang Plaza,Shennan Road East, luohu District, Shenzhen

Home > News > What is the consistency of a battery?

What is the consistency of a battery?

2018-06-15

What is the consistency of a battery?


Inconsistency between lithium cells can cause rapid capacity degradation and a reduction in battery life in lithium - battery packs.

It is important to select cells with the same capacity, voltage, and internal resistance to form a battery pack, which is crucial for the capacity and life of lithium - ion batteries.


Why Inconsistency? (Cask Effect)

Just as there are no two identical leaves in the world, cells from the same batch have some differences after production.

After being combined into a battery pack and cycled for a period of time, these differences continue to grow.

With the use of the battery, these performance differences accumulate, leading to a gradual increase in the inconsistency among the cells,

just like the barrel effect, where the capacity of the battery pack depends on the capacity of the smallest cell, causing the battery - pack performance and capacity to decay. Li - ion - battery inconsistency mainly refers to the inconsistency of Li - ion - cell parameters (mainly cell capacity,

internal resistance, voltage, and self - discharge) and the difference in battery SOC.


What Are the Causes of Inconsistency?


There are many reasons for the inconsistency of Li - ion - battery cells. Each step in the production process, such as the uniformity of the slurry during batching, the control of surface density and surface tension during coating, etc., can cause differences in the performance of single cells. In the battery - combination process, the spot - welding method and structure and the use of the environment will have an impact on the consistency of the battery pack. Because the energy consumed by each connection point is inconsistent, the performance of each component or structural part and the aging rate are also inconsistent, so the impact on the battery is also inconsistent. In addition, due to the different locations of each individual cell in the battery, the temperature is different, and the performance degradation is also different, which will amplify the inconsistency of the single cell.


How to Improve the Consistency of the Battery Cell? There are three main ways.


Production - Process Control

The control of the production process mainly focuses on raw materials and the production process. In terms of raw materials, try to select the same batch of raw materials to ensure the consistency of raw - material particle size and performance. The production process should be strictly controlled throughout. For example, ensure that the slurry is mixed uniformly and not left for a long time, control the speed of the coating machine to ensure the thickness and uniformity of the coating, check the appearance of the pole piece, weigh and grade it, control the amount of liquid injection, and also control chemical formation, capacity, storage conditions, and so on.


Selection - Process Control

Selection - process refers to the sorting of battery cells. Select cells of the same grade for the combination of battery packs (measure the capacity/voltage/internal resistance of the cells and select cells of the same grade for assembly) to ensure the consistency of the battery's initial performance. The voltage difference of a single cell is an important factor affecting the consistency of each single cell in the battery pack. Meanwhile, the difference in internal resistance of a single cell causes a significant difference in the voltage plateau of each single cell during the charging and discharging process of the battery pack. Moreover, as the discharge rate increases, the battery's inconsistency will be greater.


Maintenance - Process Control

Real - time monitoring of lithium - battery cells during the charging and discharging process can detect the consistency of the usage process in real time. Through real - time monitoring of faulty cells for timely adjustment or replacement, ensure that the inconsistency of the battery pack does not expand over time. Alternatively, a balancing management system (BMS) can be used, and common balancing methods can be divided into passive balancing and active balancing.

To meet the usage requirements, try to reduce the depth of battery discharge and, at the same time, avoid overcharging the battery to extend the cycle life of the battery pack.


Lithium - Ion - Battery Matching Method:


Considering a comprehensive evaluation of the battery's capacity, internal resistance, voltage, self - discharge rate, and other external conditions, you can sort out cells with closer capacity, internal resistance, and voltage. Measures to improve the consistency of the battery are mainly in the following three areas: strictly control the production process in terms of raw materials and the production process; use a more scientific approach to sorting and, as far as possible, select batteries with the same initial performance for grouping;

Previous article：无

Next article：Cylindrical batteries, pouch batteries, prismatic batteries, how to choose?