Method of Power Lithium-ion Battery Cell Assembly
Battery Assembly is a complex task involving various methods, and it holds significant importance for the widespread application of lithium-ion batteries in power systems.
In this article, we will introduce five assembly methods for power lithium-ion batteries to improve the overall consistency of battery packs.
Method of Power Lithium-ion Battery Cell Assembly
1. Voltage Matching Method
The voltage matching method can be divided into static voltage matching and dynamic voltage matching.
- Static voltage matching, also known as open-circuit matching, is performed without a load, focusing solely on the battery itself. It measures the self-discharge rate of the selected individual battery in a fully charged state after several tens of days of static storage and the open-circuit voltage of the battery at different storage periods under full charge. While this method is operationally simple, it lacks accuracy.
- Dynamic voltage matchingexamines the voltage conditions with a load. But it does not consider factors such as load variations, making it less accurate.
2. Static Capacity Sorting Method
This method involves charging and discharging the batteries under specified conditions. The capacity is calculated based on the discharge current and discharge time, and the batteries are then sorted according to their capacity.
This method is simple and practical but can only reflect that batteries have the same capacity under specific conditions. It cannot illustrate the complete working characteristics of the batteries and has certain limitations.
3. Internal Resistance Sorting Method
This method primarily considers the internal resistance of individual batteries and allows for fast measurement.
However, since the internal resistance of batteries changes during the discharge process, accurately determining the internal resistance presents some difficulties.
4. Multi-Parameter Sorting Method
This method considers multiple external conditions such as capacity, internal resistance, voltage, self-discharge rate, etc., for the comprehensive assessment of batteries.
It can select batteries with better consistency. However, the prerequisite for this method is that accurate single-parameter sorting is necessary, and it may be time-consuming.
5. Dynamic Characteristics Sorting Method
The dynamic characteristics sorting method utilizes the charge and discharge characteristic curves of batteries to sort and group them. Charge and discharge curves can reflect most of the battery’s characteristics. Using the dynamic characteristics sorting method ensures the consistency of various performance indicators of batteries.
This method involves a lot of data and is usually implemented with the assistance of computer programs.
Additionally, the utilization rate of battery grouping is reduced, which is not conducive to reducing the cost of the battery pack.
Determining standard curves or benchmark curves is also a challenging aspect in the implementation process.
Summary
In battery grouping, the single-parameter sorting method, due to considering too few factors, lacks practical application value.
Multi-parameter sorting methods and dynamic characteristics sorting methods are relatively comprehensive.
Additionally, methods like electrochemical impedance spectroscopy have also made some progress.