A method and system for identifying the capacity balance degree of each single battery in a battery system

Abstract

The present invention discloses a method and system for identifying the capacity balance of each battery cell in a battery system, relating to the field of new energy battery technology. The method comprises: calculating the dischargeable capacity difference between each battery cell based on battery discharge data; when the charging data meets the conditions for constant current charging, calculating the capacity charge balance of each battery cell using the charging data; when the maximum value of the capacity charge balance of each battery cell is less than a set threshold, calculating the available capacity difference between each battery cell based on the capacity charge balance of each battery cell and the dischargeable capacity difference between each battery cell; and calculating the capacity balance of each battery cell based on the available capacity difference between each battery cell and the dischargeable capacity difference between each battery cell. The present invention can solve the problem of over-balancing caused by the existing technical solutions that do not consider battery capacity consistency, avoid erroneous balancing, and improve the accuracy of balance identification.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy batteries, and in particular to a method and system for identifying the capacity balance degree of each single battery in a battery system. Background Art

[0002] Due to power or energy demands, battery systems often consist of a large number of battery cells connected in series and parallel. However, when the state of charge (SOC) of individual cells varies, the system's available charge and discharge capacity can be lower than the individual available capacity, leading to incomplete energy utilization. To address this issue, balancing functions within battery management systems have emerged. However, some battery systems are hampered by the difficulty in identifying balancing issues, and existing balancing systems offer less than ideal balancing results. This is particularly true for lithium iron phosphate battery systems. Because the battery voltage platform is relatively flat, relying on the voltage difference between cells at the end of charge to control balancing often results in insufficient balancing time, making it difficult to recover from severe balancing issues. Relying on the voltage difference at the low end of the SOC to identify balancing results often results in poor balancing results because cells rarely discharge into this region. Furthermore, when batteries age at different rates, resulting in significant discrepancies in available capacity between individual cells, balancing errors can often occur. Therefore, identifying the capacity balance (SOD) of each cell in the battery system is crucial for efficient balancing. Summary of the Invention

[0003] The purpose of the present invention is to provide a method and system for identifying the capacity balance of each single battery in a battery system, so as to solve the problem of over-balancing caused by the existing technical solutions not considering the consistency of battery capacity, avoid incorrect balancing and improve the accuracy of balance identification.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A method for identifying the capacity balance degree of each single battery in a battery system, comprising:

[0006] Calculate the discharge capacity difference between each battery cell based on the battery discharge data;

[0007] When the charging data meets the conditions for constant current charging, the charging data is used to calculate the charging balance of each battery cell capacity;

[0008] When the maximum value of the charge balance degree of each battery cell capacity is less than a set threshold, calculating the available capacity difference between each battery cell according to the charge balance degree of each battery cell capacity and the dischargeable capacity difference between each battery cell;

[0009] The capacity balance degree of each battery cell is calculated based on the difference in available capacity between each battery cell and the difference in dischargeable capacity between each battery cell.

[0010] To achieve the above object, the present invention also provides the following solution:

[0011] A system for identifying the capacity balance of each single battery in a battery system, comprising:

[0012] A discharge capacity difference calculation module is used to calculate the discharge capacity difference between each battery cell based on the battery discharge data;

[0013] A battery cell capacity charge balance calculation module is used to calculate the charge balance of each battery cell capacity using the charging data when the charging data meets the constant current charging conditions;

[0014] a module for calculating the difference in available capacity between battery cells, configured to calculate the difference in available capacity between the battery cells based on the charge balance degrees of the battery cells and the difference in dischargeable capacity between the battery cells when the maximum value among the charge balance degrees of the battery cells is less than a set threshold;

[0015] The battery cell capacity balance calculation module is used to calculate the capacity balance of each battery cell according to the difference in available capacity between each battery cell and the difference in dischargeable capacity between each battery cell.

[0016] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0017] This invention designs SODT to represent the sum of the available capacity difference (detaSOH) and the balance degree (SOD) between each battery cell in a battery system. This value is calculated using discharge data and represents the capacity difference between each battery cell until it is fully discharged. By leveraging the principle that SODT incorporates the combined influence of the balance degree (SOD) and the available capacity difference (detaSOH), SOD stripping estimation is achieved, resolving the issue of incorrect balance caused by inconsistent aging between battery cells. By combining the reliable SOD calculation capabilities of charging data with the limited versatility of charging data due to its difficulty maintaining constant current charging, a method for updating detaSOH using charging data was devised. Combined with the high versatility of discharge data, this method achieves both reliable and versatile balance quantification. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A flow chart of the method for identifying the capacity balance degree of each single battery in a battery system provided by the present invention;

[0020] Figure 2 Another flow chart of the method for identifying the capacity balance degree of each single battery in a battery system provided by the present invention;

[0021] Figure 3 Schematic diagram of the smoothing and differentiation processing of capacitance data and voltage data dQ / dV~V according to the present invention;

[0022] Figure 4 Schematic diagram of the present invention using the peak difference ΔV to calculate the balance degree. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] The purpose of the present invention is to provide a method and system for identifying the capacity balance of each single battery in a battery system, so as to solve the problem of over-balancing caused by the existing technical solutions not considering the consistency of battery capacity, avoid incorrect balancing and improve the accuracy of balance identification.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] like Figure 1 and Figure 2 As shown, the method for identifying the capacity balance degree of each single battery in a battery system provided by the present invention includes the following steps:

[0028] S1: Calculate the discharge capacity difference between each battery cell based on the battery discharge data.

[0029] SODT is defined as the difference in discharge capacity between individual battery cells. It represents the difference in discharge capacity between each cell when the battery system is fully charged (i.e., in the current unbalanced state). The cell with the largest discharge capacity is used as the benchmark discharge capacity. The SODT of other batteries is calculated by subtracting their own discharge capacity from the benchmark discharge capacity value and dividing the result by the rated capacity.

[0030] The calculation formula is: [Qd 基准电池 -Qd(i)] / Qn; wherein, Qdbase battery represents the discharge capacity of the base battery, Qd(i) represents the discharge capacity of the i-th battery cell, and Qn represents the rated capacity of the battery cell.

[0031] S2: When the charging data meets the conditions for constant current charging, the charging data is used to calculate the charging balance of each battery cell capacity.

[0032] By retrieving the charging data and searching for the appropriate charging data segment, when the charging data segment meets the conditions for constant current charging, the charging data can be used to more accurately determine the characteristics of the SOD and calculate the initial SOD (i.e., charging balance).

[0033] (1) Collect the highest single cell voltage V max , Minimum single cell voltage V min The time and current data of the charging process are converted into capacity Q data.

[0034] (2) The V collected in step (1) max 、V min The corresponding capacity Q data is smoothed and capacity differential is performed. At the same time, dQ / dV and V are plotted, as shown in the following example: Figure 3 shown.

[0035] (3) The complete charging capacity differential curve of the lithium iron phosphide battery contains three peaks, which are named P1, P2 and P3 in descending order according to the voltage. The peaks appearing in the dQ / dV~V diagram obtained in step (2) are classified as P1 to P3.

[0036] (4) According to the peak classification in step (3), calculate the peak position difference of similar peaks and calculate dQ / dV max and dQ / dV min The peak position difference ΔV.

[0037] (5) Figure 4 As shown, the peak difference ΔV value obtained in step (4) is used to calculate the balance degree:

[0038] SOD 充电 =ΔQ / Q 系统 (1)

[0039] ΔQ=Y C -Y B (2)

[0040] X B =X A +ΔV (3)

[0041] Among them, Y B 、Y C Represent the capacity values ​​of points B and C respectively, X A 、X B Represent the voltage values ​​of points A and B respectively, Q 系统represents the rated capacity of the battery system, and point A is the last point on the V min ~Q curve, and point C is the last point on the V max ~Q curve, and point B is the point on the V max ~Q (smoothed) curve where X B =X A +ΔV.

[0042] S3: When the maximum value in the charging balance degrees of the capacities of the individual battery cells is less than the set threshold, calculate the available capacity differences between the individual battery cells according to the charging balance degrees of the capacities of the individual battery cells and the dischargeable capacity differences between the battery cells.

[0043] When it is determined that the charging balance degree of the capacity of each battery cell is less than a%, it means that the balance degree of the entire battery system is good at this time. At this time, adjust SODT through formula (4) to obtain the accurate detaSOH.

[0044] detaSOH = SODT - SOD 充电 (4)

[0045] The condition of max(SOD 充电 ) < a% represents the constraint condition that can make the result accuracy higher when calculating SOD using charging data. a is preferably 5 - 10, and a can be changed to other thresholds according to different scenarios. When a is changed to 100, it means no constraint, indicating that all calculation results have high reliability.

[0046] S4: Calculate the capacity balance degrees of the individual battery cells according to the available capacity differences between the individual battery cells and the dischargeable capacity differences between the battery cells.

[0047] When the updated value of detaSOH is received, update the initial value and historical value, and perform SOD update in combination with formula (5): SOD = SODT - detaSOH (5).

[0048] [[ID=3I]]When the calculation of SOD ends, when its minimum value is non - 0, process SOD. The processing method is SOD' = SOD - min(SOD), where SOD' represents the updated array after processing, min(SOD) represents the minimum value in the SOD array, and the subtraction of the array and the value means subtracting min(SOD) from each value in the array.

[0049] The present invention designs SODT parameters, uses discharge data to solve them, and uses the principle that its value includes the combined influence of the balance degree SOD and the capacity inconsistency detaSOH to realize SOD stripping estimation, solving the problem of incorrect balance caused by inconsistent aging between battery cells. The present invention combines the characteristics of charging data that can reliably solve SOD, and the characteristics of charging data that are difficult to maintain constant current charging resulting in poor versatility, to design a method for updating detaSOH using charging data, and combines the characteristics of discharge data that are highly versatile to realize a quantitative analysis method for balance that is both reliable and versatile. The technical solution provided by the present invention can solve the problems of low balance estimation accuracy, low balance efficiency and energy waste caused by the existing technical solutions that do not consider the battery aging situation, and can improve the balance efficiency.

[0050] Example 2

[0051] In order to execute the method corresponding to the above-mentioned embodiment 1 and achieve the corresponding functions and technical effects, a system for identifying the capacity balance degree of each single battery in a battery system is provided below.

[0052] The system includes:

[0053] The discharge capacity difference calculation module is used to calculate the discharge capacity difference between each battery cell according to the battery discharge data.

[0054] The battery cell capacity charge balance calculation module is used to calculate the charge balance of each battery cell capacity using the charging data when the charging data meets the constant current charging conditions.

[0055] The module for calculating the difference in available capacity between battery cells is configured to calculate the difference in available capacity between the battery cells based on the charge balance degrees of the battery cells and the difference in dischargeable capacity between the battery cells when the maximum value among the charge balance degrees of the battery cells is less than a set threshold.

[0056] The battery cell capacity balance calculation module is used to calculate the capacity balance of each battery cell according to the difference in available capacity between each battery cell and the difference in dischargeable capacity between each battery cell.

[0057] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0058] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for identifying the capacity balance of each single battery in a battery system, characterized in that: include: Calculate the discharge capacity difference between each battery cell based on the battery discharge data; use the formula: [Qd 基准电池 -Qd(i)] / Qn, calculate the discharge capacity difference between each battery cell; where Qd 基准电池 represents the discharge capacity of the reference battery, Qd(i) represents the discharge capacity of the i-th battery cell, and Qn represents the rated capacity of the battery cell; When the charging data meets the conditions for constant current charging, the charging data is used to calculate the charging balance of each battery cell capacity; When the maximum value of the charge balance degree of each battery cell capacity is less than a set threshold, calculating the available capacity difference between each battery cell according to the charge balance degree of each battery cell capacity and the dischargeable capacity difference between each battery cell; The capacity balance degree of each battery cell is calculated based on the difference in available capacity between each battery cell and the difference in dischargeable capacity between each battery cell.

2. The method for identifying the capacity balance degree of each single battery in a battery system according to claim 1, characterized in that: When the charging data meets the conditions for constant current charging, the charging data is used to calculate the charging balance of each battery cell capacity, including: Collect the highest single cell voltage V max and the minimum cell voltage V min The time and current data of the charging process are converted into capacity Q data; V max 、V min The capacity Q data is smoothed and differentiated, and dQ / dV and V are plotted. Classify the peaks appearing in the obtained dQ / dV~V graph; According to the peak classification, the peak position difference of the same peak is calculated and the dQ / dV is obtained. max and dQ / dV min The peak position difference ΔV; The peak-to-peak difference ΔV value is used to calculate the charge balance degree of each battery cell capacity.

3. The method for identifying the capacity balance degree of each single battery in a battery system according to claim 1, characterized in that: The formula for calculating the difference in available capacity between individual battery cells is: detaSOH=SODT-SOD 充电 Among them, detaSOH represents the difference in available capacity between each battery cell, SODT represents the difference in discharge capacity between each battery cell, SOD 充电 Indicates the charge balance of each battery cell capacity.

4. The method for identifying the capacity balance degree of each single battery in a battery system according to claim 3, characterized in that: The calculation formula for the capacity balance of each battery cell is: SOD=SODT-detaSOH SOD indicates the capacity balance of each battery cell.

5. The method for identifying the capacity balance degree of each single battery in a battery system according to claim 1, characterized in that: When the minimum value of the capacity balance degree SOD of each battery cell is not 0, the SOD is processed using the formula SOD'=SOD-min(SOD), where min(SOD) represents the minimum value in the SOD array.

6. A system for identifying the capacity balance of each single cell in a battery system, characterized in that: include: The discharge capacity difference calculation module is used to calculate the discharge capacity difference between each battery cell according to the battery discharge data; the formula is: [Qd 基准电池 -Qd(i)] / Qn, calculate the discharge capacity difference between each battery cell; where Qd 基准电池 represents the discharge capacity of the reference battery, Qd(i) represents the discharge capacity of the i-th battery cell, and Qn represents the rated capacity of the battery cell; A battery cell capacity charge balance calculation module is used to calculate the charge balance of each battery cell capacity using the charging data when the charging data meets the constant current charging conditions; a module for calculating the difference in available capacity between battery cells, configured to calculate the difference in available capacity between the battery cells based on the charge balance degrees of the battery cells and the difference in dischargeable capacity between the battery cells when the maximum value among the charge balance degrees of the battery cells is less than a set threshold; The battery cell capacity balance calculation module is used to calculate the capacity balance of each battery cell according to the difference in available capacity between each battery cell and the difference in dischargeable capacity between each battery cell.

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