Online identification method, system and medium for short-board single-cell battery based on ohmic characteristics

Abstract

The present application discloses an online identification method, system and medium for short-board single-cell batteries based on ohmic characteristics. The method includes the following steps: periodically collecting terminal voltage data of all cells, marking the maximum voltage and minimum voltage in the terminal voltage sequence of all cells collected each time; calculating the extreme difference voltage of each cell; normalizing the extreme difference voltage to obtain the discreteness of the cell extreme difference voltage; counting the frequency of high discreteness of cells within a period of time, marking the first several cells with larger size within the period of time as suspected short-board single-cell batteries. The present application can identify short-board or suspected short-board cells in a power battery pack online, thereby identifying single-cell batteries that are about to be retired, which is conducive to accurately replacing single-cell batteries that are about to be retired, and can effectively improve the range of electric vehicles, extend the retirement time of battery packs, and improve the utilization rate of battery packs.

Description

Technical Field

[0001] The present application relates to the technical field of power batteries, and in particular to an online identification method, system and medium for short-board single-cell batteries based on ohmic characteristics. Background Art

[0002] For automotive power batteries, as the number of charge and discharge cycles increases, the ohmic internal resistance of the single cell will slowly increase, and the nominal capacity of the single cell will gradually decay. Accurately replacing the single cell that is about to be retired can effectively increase the range of electric vehicles, extend the retirement time of the battery pack, and improve the utilization rate of the battery pack, thereby truly achieving the goal of reducing costs and increasing efficiency for customers, which has important theoretical research significance and engineering application value.

[0003] However, how to online identify the single cells that are about to be retired in the in-service battery pack is a very challenging task. Summary of the invention

[0004] The present application provides an online identification method, system and medium for short-board single-cell batteries based on ohmic characteristics, which has the advantage of being able to online identify short-board or suspected short-board single-cell batteries in a power battery pack, thereby identifying single-cell batteries that are about to be retired, which is conducive to accurately replacing single-cell batteries that are about to be retired, and can effectively improve the cruising range of electric vehicles, extend the retirement time of battery packs, and improve the utilization rate of battery packs.

[0005] The above-mentioned object of the present application is achieved through the following technical solutions:

[0006] On the one hand, the present application provides an online identification method for short-board single-cell batteries based on ohmic characteristics, comprising the following steps:

[0007] Step 1: Periodically collect terminal voltage data of all monomers, and mark the maximum voltage and minimum voltage in the terminal voltage sequence of all monomers collected each time;

[0008] Step 2: Calculate the extreme voltage difference of each monomer according to the data obtained in step 1;

[0009] Step 3: Normalize the extreme difference voltage to obtain the discreteness of the single extreme difference voltage;

[0010] Step 4: Count the frequency of high discreteness of cells within a period of time, and mark the first several cells with larger cells within the period as suspected short-board cells.

[0011] Furthermore, in step 1, the terminal voltages of all monomers are collected. ,in, L is the total number of monomers, k is the sampling time, i is the monomer number andi ∈[1, L ], in the terminal voltage sequence of all monomers collected each time, mark the maximum voltage and minimum voltage As an extreme feature.

[0012] Furthermore, step 2 includes the following steps:

[0013] Step 21: Traverse the extreme characteristic voltage sequence in the first time period of the day , find the maximum voltage With minimum voltage The sampling time k max and k min ;

[0014] Step 22: Record the first time period separately k max , k min The maximum voltage and minimum voltage of each monomer at the moment;

[0015] Step 23: According to step 21 and step 22, the maximum voltage and minimum voltage of each monomer in other time periods in one day are recorded, and then the maximum voltage set and minimum voltage set of each monomer in one day are obtained;

[0016] Step 24: Obtain the maximum value of the maximum voltage set and the minimum value of the minimum voltage set, respectively, and record them as ,in, d Indicates d A natural day, i is the monomer serial number;

[0017] Step 25: Calculate the voltage difference of each cell in one day .

[0018] Furthermore, in step 3, the extreme difference voltage is normalized

[0019]

[0020] In the formula, The monomer on day d i The normalized value of the extreme difference voltage is used to represent the monomer i The dispersion of the extreme voltage difference, They represent finding the maximum and minimum values ​​in a sequence respectively.

[0021] Furthermore, in step 4, the frequency of high dispersion of monomer i in a period of time is counted

[0022]

[0023] In the formula, is the design parameter, Indicates the statistical frequency, For a period of time i The number of times the discreteness of the i aging conditions;

[0024] Mark the time period Larger front m The single cell is suspected to be the short board single cell.

[0025] Furthermore, the method further comprises the steps of:

[0026] Draw a bar graph of the maximum and minimum voltages of each cell on a certain day, and Sort by size in descending order;

[0027] Draw over a period of time About Monomer i The bar graph of The sizes are sorted in descending order to obtain a bar graph of the relative changes of the ohmic characteristic parameters at the monomer level;

[0028] Statistics d Total number of monomers with high dispersion within a day

[0029]

[0030] In the formula, For the d The total number of monomers with high dispersion within a day, and ;

[0031] According to the statistical results of each natural day , fitting Regarding the relationship curve of natural day, the situation diagram of the ohmic characteristic parameters at the vehicle level is obtained.

[0032] Furthermore, step 1 also includes the step of: balancing the terminal voltages or SOCs of all the single cells, so that the terminal voltages or SOCs of all the single cells remain consistent or the difference is within a set range.

[0033] Furthermore, the method is applied to an electric bus and further comprises the steps of:

[0034] Collect the total current of the vehicle , vehicle speed data ;

[0035] According to the changes in vehicle speed and total current, it is possible to distinguish whether the vehicle is in operation or stopped, and identify the various shifts of electric buses:

[0036] (1) When the vehicle speed remains greater than 0 for a period of time, it is judged that the vehicle starts to move;

[0037] (2) During the operation of the vehicle, ① if the vehicle speed is 0 for a period of time and the total current is 0 for a period of time, it is judged that the vehicle has reached the terminal and is turned off; ② if the vehicle speed is 0 for a period of time and the total current jumps from 0 to a negative value, it is judged that the vehicle has reached the terminal and starts charging;

[0038] (3) When conditions ① or ② in (2) are met and the vehicle running time exceeds a certain threshold, a shift is judged to be over;

[0039] (4) Repeat (1), (2), and (3) to identify each shift in a day;

[0040] The first time period in step 2 is a shift of the electric bus.

[0041] On the other hand, the present application provides an online identification system for short-board single-cell batteries based on ohmic characteristics, including a processor and a memory, wherein the memory stores a computer program, and when the computer program is called and executed by the processor, the online identification method for short-board single-cell batteries based on ohmic characteristics as described above is implemented.

[0042] On the other hand, the present application provides a computer-readable medium storing a computer program, and when the computer program is called and executed by a computer, the online identification method of short-board single-cell batteries based on ohmic characteristics as described above is implemented.

[0043] To sum up, the beneficial effects of the present application are as follows: the present application can online identify the short board or suspected short board cells in the power battery pack, thereby identifying the single cells that are about to be retired, which is conducive to the accurate replacement of the single cells that are about to be retired, and can effectively improve the cruising range of electric vehicles, extend the retirement time of battery packs, and improve the utilization rate of battery packs. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the principle of this application;

[0045] Figure 2 This is the operating condition diagram of an electric bus on a certain day;

[0046] Figure 3 It is the operating condition diagram of a certain shift of an electric bus;

[0047] Figure 4It is a bar distribution diagram of the maximum voltage, minimum voltage, and extreme voltage difference of each cell of an electric bus on a certain day. DETAILED DESCRIPTION

[0048] The specific implementation of the present application is described in detail below with reference to the accompanying drawings.

[0049] Embodiment: A specific embodiment of the present application provides an online identification method of a short-board single cell based on ohmic characteristics, which is used for online identification of suspected "short-board" single cells in a power battery pack.

[0050] Before identification, the terminal voltage or SOC of all single cells is balanced to keep the terminal voltage or SOC of all single cells consistent or the difference is within a set range, so as to improve the accuracy and reliability of the identification of suspected "short board" single cells. Specifically, the method of balancing the terminal voltage or SOC of single cells can be implemented by using the method in invention patent 202410157345.1 or 202410157341.3, or by installing a system in invention patent 202410157345.1 or 202410157341.3 on the electric vehicle.

[0051] In this embodiment, if Figure 1 As shown, the method is implemented in the edge main control module and the power battery Internet of Things platform. The edge main control module is connected to the cloud platform for communication, and the identification object is the power battery pack in the electric bus. The edge main control module includes the following steps:

[0052] Step 1: Data Collection

[0053] Periodically collect the terminal voltage of all monomers , total current , vehicle speed data ,in, L is the total number of monomers, k is the sampling time, i is the monomer number and i ∈[1, L ].

[0054] like If the voltage at one end exceeds the threshold range, the re-collection logic is started to ensure All are normal data. Note: When the vehicle is in the discharging condition, the total current is greater than 0; when the vehicle is in the charging condition, the total current is less than 0.

[0055] Extreme value feature extraction

[0056] The terminal voltage sequence of all monomers collected at each time In the figure, mark the maximum voltage and minimum voltage As the extreme value feature, the average voltage is calculated and recorded as .

[0057] Coding and Framing

[0058] Considering factors such as the message length limit, the byte overhead of the string, the cost of wireless network traffic, and data security, the terminal voltage is first encoded, that is, , is the offset, For the resolution, then the terminal voltage , total current , vehicle speed , extreme characteristic voltage and other data are encoded in hexadecimal and decimal combinations as needed, and then the encoded data are framed according to the MQTT transmission protocol standard.

[0059] Task monitoring processing

[0060] The task monitoring mechanism is enabled on the edge side, and the encoded data acquisition messages are periodically uploaded to the platform through the wireless network. When the edge master receives the message sent by the platform, the serial port data reception interrupt is triggered, and the data is first saved to the buffer, and then the parsing task of the sent message is executed when idle.

[0061] The platform side includes the following steps:

[0062] Based on the reported data acquisition messages, draw the operating condition curve of an electric bus on a certain day, including the highest single cell voltage curve, the lowest single cell voltage curve, the average single cell voltage curve, and the vehicle speed curve.

[0063] Shift Identification

[0064] The changes in vehicle speed and total current in the data acquisition message can be used to distinguish whether the vehicle is in operation or in shutdown condition.

[0065] (1) When the vehicle speed continues for a period of time ( ) is greater than 0, the vehicle is considered to start running;

[0066] (2) During vehicle operation, ① if the vehicle speed continues for a period of time ( ) is 0, the total current continues for a period of time ( ) is 0, the vehicle is considered to have reached the terminal and turned off; ② If the vehicle speed continues for a period of time ( ) is 0, and the total current jumps from 0 to a negative value, it is considered that the vehicle has reached the terminal and starts charging;

[0067] (3) When conditions ① or ② in (2) are met and the vehicle operation time exceeds a certain threshold (to exclude the possibility that the driver temporarily moves the vehicle), a shift is considered to be over;

[0068] (4) Repeat (1), (2), and (3) to effectively identify each shift in a day.

[0069] Note: In traffic light conditions, traffic jams, etc., if the vehicle speed is 0 and the vehicle is not turned off (i.e., the total current is greater than 0), then a shift cannot be considered to have ended. In particular, if a short-term shutdown occurs during the shift, then a shift cannot be misjudged as over. Therefore, the threshold in (2) With threshold The design should avoid this problem.

[0070] Curve fitting (operating conditions of a certain shift)

[0071] According to the above steps, select and fit the curve of the operating condition of a certain shift of an electric bus, such as Figure 3 shown.

[0072] Step 2: Calculate the extreme voltage difference of each monomer according to the data obtained in step 1;

[0073] Step 21: Traverse the extreme characteristic voltage sequence in the first time period of the day , find the maximum voltage With minimum voltage The sampling time k max and k min ;

[0074] Step 22: Record the first time period separately k max , k min The maximum voltage and minimum voltage of each monomer at the moment;

[0075] Step 23: According to step 21 and step 22, the maximum voltage and minimum voltage of each monomer in other time periods in one day are recorded, and then the maximum voltage set and minimum voltage set of each monomer in one day are obtained;

[0076] Step 24: Obtain the maximum value of the maximum voltage set and the minimum value of the minimum voltage set, respectively, and record them as ,in, d Indicates d A natural day, i is the monomer serial number;

[0077] Step 25: Calculate the voltage difference of each cell in one day .

[0078] Extreme value characteristic histogram drawing

[0079] Draw a bar graph of the maximum and minimum voltages of each cell of an electric bus on a certain day, and Sort by size in descending order, such as Figure 4 As shown, it includes some cells in the battery pack. Among them, the horizontal axis represents the cell number, and the vertical axis represents the extreme voltage of the cell. The high part of the bar graph represents the maximum voltage of the cell, the high part of the lower part of the bar graph represents the minimum voltage of the cell, and the difference between the two represents the extreme voltage.

[0080] Step 3: Normalize the extreme difference voltage to obtain the discreteness of the single extreme difference voltage;

[0081] Normalize the extreme voltage difference

[0082]

[0083] In the formula, The monomer on day d i The normalized value of the extreme difference voltage is used to represent the monomer i The dispersion of the extreme voltage difference, They represent finding the maximum and minimum values ​​in a sequence respectively.

[0084] Step 4: Count the frequency of high discreteness of monomers within a period of time

[0085]

[0086] In the formula, is a design parameter close to 1, Indicates the statistical frequency, For a period of time i The number of times the discreteness of the i of aging.

[0087] Statistics d Total number of monomers with high dispersion within a day

[0088]

[0089] In the formula, For the d The total number of monomers with high dispersion within a day, and When the monomer consistency is high, The total number of monomers close to or equal to 1 is very small, that is, Very little; otherwise, more.

[0090] Single-unit level ohmic characteristic parameter evaluation

[0091] Draw over a period of time About Monomer i The bar graph of The size is sorted in descending order to obtain a bar graph of the relative changes in the monomer-level ohmic characteristic parameters. As the time span continues to increase, the bar graph can intuitively reflect the relative changes in the monomer-level ohmic characteristic parameters. i The relative degree of aging of the battery can be measured, thus providing a quantitative reference for the evaluation of the ohmic characteristic parameters at the monomer level.

[0092] In actual application, we found that the serial number of the "short board" battery is not always fixed, so we marked the larger front battery in this time period. m Single cells, that is, the cells closest to the left in the bar graph. m single cell and mark it as a suspected short-board single cell.

[0093] Vehicle-level ohmic characteristic parameter evaluation

[0094] According to the statistical results of each natural day , fitting The relationship curve of natural days is used to obtain the trend diagram of vehicle-level ohmic characteristic parameters. As time goes by, this curve diagram can intuitively reflect the evolution trend of the health status of the vehicle's power battery.

[0095] Ultimately, the bar distribution chart based on the relative changes in the ohmic characteristic parameters at the cell level and the situation chart of the ohmic characteristic parameters at the vehicle level can provide a visual reference for the accurate identification of cell batteries that are about to be retired in the in-service battery pack and the health assessment of the vehicle's power battery.

[0096] In another specific embodiment of the present application, a short-board single-cell battery online identification system based on ohmic characteristics is provided, including a processor and a memory, wherein the memory stores a computer program, and when the computer program is called and executed by the processor, the short-board single-cell battery online identification method based on ohmic characteristics as described above is implemented.

[0097] In another specific embodiment of the present application, a computer-readable medium is provided, wherein the computer-readable medium stores a computer program, and when the computer program is called and executed by a computer, the online identification method of a short-board single cell based on ohmic characteristics as described above is implemented.

[0098] The above is only a preferred implementation of the present application. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present application, and these all fall within the scope of protection of the present application.

Claims

1. An online identification method for short-board single-cell batteries based on ohmic characteristics, characterized in that: The steps include: Step 1: Periodically collect terminal voltage data of all monomers, and mark the maximum voltage and minimum voltage in the terminal voltage sequence of all monomers collected each time; Step 2: Calculate the extreme voltage difference of each monomer according to the data obtained in step 1; Step 3: Normalize the extreme difference voltage to obtain the discreteness of the single extreme difference voltage; Step 4: Count the frequency of high discreteness of cells within a period of time, and mark the first several cells with larger discreteness within the period of time as suspected short-board cells; In step 1, the terminal voltage of all monomers is collected ,in, L is the total number of monomers, k is the sampling time, i is the monomer number and i ∈[1, L ], in the terminal voltage sequence of all monomers collected each time, mark the maximum voltage and minimum voltage As extreme value features; Step 2 includes the following steps: Step 21: Traverse the extreme characteristic voltage sequence in the first time period of the day , find the maximum voltage With minimum voltage The sampling time k max and k min ; Step 22: Record the first time period separately k max , k min The maximum voltage and minimum voltage of each monomer at the moment; Step 23: According to step 21 and step 22, the maximum voltage and minimum voltage of each monomer in other time periods in one day are recorded, and then the maximum voltage set and minimum voltage set of each monomer in one day are obtained; Step 24: Obtain the maximum value of the maximum voltage set and the minimum value of the minimum voltage set, respectively, and record them as ,in, d Indicates d A natural day, i is the monomer serial number; Step 25: Calculate the voltage difference of each cell in one day ; In step 3, the extreme difference voltage is normalized ； In the formula, The monomer on day d i The normalized value of the extreme difference voltage is used to represent the monomer i The dispersion of the extreme voltage difference, They represent finding the maximum and minimum values ​​in a sequence respectively.

2. The online identification method of short-board single-cell battery based on ohmic characteristics according to claim 1 is characterized in that: In step 4, count the monomers within a period of time i The frequency of high dispersion ； In the formula, is the design parameter, Indicates the statistical frequency, For a period of time i The number of times the discreteness of the i aging conditions; Mark the time period Larger front m The single cell is suspected to be the short board single cell.

3. The online identification method of short-board single-cell battery based on ohmic characteristics according to claim 2 is characterized in that: Also includes the steps: Draw a bar graph of the maximum and minimum voltages of each cell on a certain day, and Sort by size in descending order; Draw over a period of time About Monomer i The bar graph of The sizes are sorted in descending order to obtain a bar graph of the relative changes of the ohmic characteristic parameters at the monomer level; Statistics d Total number of monomers with high dispersion within a day ； In the formula, For the d The total number of monomers with high dispersion within a day, and ; According to the statistical results of each natural day , fitting Regarding the relationship curve of natural day, the situation diagram of the ohmic characteristic parameters at the vehicle level is obtained.

4. The online identification method of short-board single-cell battery based on ohmic characteristics according to claim 1 is characterized in that: Step 1 also includes the step of: balancing the terminal voltages or SOCs of all the single cells, so that the terminal voltages or SOCs of all the single cells remain consistent or the difference is within a set range.

5. The online identification method of short-board single-cell battery based on ohmic characteristics according to claim 1 is characterized in that: The method is applied to an electric bus and further comprises the steps of: Collect the total current of the vehicle , vehicle speed data ; According to the changes in vehicle speed and total current, it is possible to distinguish whether the vehicle is in operation or stopped, and identify the various shifts of electric buses: (1) When the vehicle speed remains greater than 0 for a period of time, it is judged that the vehicle starts to move; (2) During the operation of the vehicle, ① if the vehicle speed is 0 for a period of time and the total current is 0 for a period of time, it is judged that the vehicle has reached the terminal and is turned off; ② if the vehicle speed is 0 for a period of time and the total current jumps from 0 to a negative value, it is judged that the vehicle has reached the terminal and starts charging; (3) When conditions ① or ② in (2) are met and the vehicle running time exceeds a certain threshold, a shift is judged to be over; (4) Repeat (1), (2), and (3) to identify each shift in a day; The first time period in step 2 is a shift of the electric bus.

6. An online identification system for short-board single-cell batteries based on ohmic characteristics, characterized in that: The method comprises a processor and a memory, wherein the memory stores a computer program, and when the computer program is called and executed by the processor, the online identification method for short-board single-cell batteries based on ohmic characteristics as described in any one of claims 1 to 5 is implemented.

7. A computer-readable medium, characterized in that The computer-readable medium stores a computer program, and when the computer program is called and executed by a computer, the online identification method for short-board single-cell batteries based on ohmic characteristics as described in any one of claims 1 to 5 is implemented.

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