Lithium iron phosphate battery SOC calibration method and system, electronic device, and storage medium

Abstract

The present disclosure provides a lithium iron phosphate battery SOC calibration method and system, an electronic device, and a storage medium. The method comprises: acquiring a charge-discharge curve and a first pressure change curve of a sampled energy storage battery at a preset temperature and a preset charge and discharge power, wherein the model of the sampled energy storage battery is consistent with that of a lithium iron phosphate battery to be verified; on the basis of the charge-discharge curve and the first pressure change curve, determining the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve; acquiring a second pressure change curve of said lithium iron phosphate battery at the preset temperature and the preset charge and discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve; and verifying the SOC of said lithium iron phosphate battery on the basis of the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve.

Description

Lithium iron phosphate battery SOC calibration method, system, electronic device and storage medium

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure is based on and claims the priority of Chinese patent application with application number 202410108486.4 and application date January 25, 2024. The entire content of the Chinese patent application is hereby incorporated into this disclosure by reference. Technical Field

[0003] The present disclosure relates to the field of energy storage technology, and in particular to a method, system, electronic device, and storage medium for calibrating the SOC of a lithium iron phosphate battery. Background Art

[0004] Energy storage technology is a key supporting technology for solving energy consumption problems, building a new power system based on new energy, and achieving the strategic goals of "dual carbonization." Lithium battery energy storage has the advantages of fast response, short construction period, and small footprint. It can improve the peak-shaving and frequency regulation capabilities and stability of the power grid, and is currently experiencing large-scale and explosive growth. The battery management system (BMS) is a key device for realizing the functions of energy storage systems and ensuring system safety. Among them, the state of charge (SOC) is the most important parameter in the BMS. Its accuracy and error correction capabilities are crucial. Without an accurate SOC, the BMS cannot function properly. The higher the BMS accuracy, the more accurate the charge and discharge status of the energy storage power station, which can improve the safety, charge and discharge capacity, and cycle life of the power station.

[0005] Currently, the main SOC calibration methods include discharge test method, ampere-hour method, open circuit voltage method, internal resistance method, Kalman filter method, and linear model method. However, each method has certain defects. For example, the discharge test method requires the battery to be in a constant current discharge state, which takes a lot of testing time. The ampere-hour method is affected by the current measurement accuracy and has poor accuracy under high temperature or current fluctuations. The open circuit voltage method requires the battery to be stationary for a long time and is only applicable to battery systems with large voltage changes. The internal resistance method requires precise measurement of the battery internal resistance, which places very high demands on the measuring instrument and is difficult to apply in practice. The Kalman filter method is highly dependent on the battery model and requires the establishment of an accurate battery model. The accuracy and complexity of the battery model are proportional. The linear model method is divided into equivalent circuit model and simplified electrochemical model. If a complex model is used, the identification of parameters and the establishment of the state equation will be very challenging. If a simple model is used, it will cause large errors.

[0006] Currently, energy storage power stations mainly use the open-circuit voltage method to correct SOC. However, the charge and discharge characteristics of lithium iron phosphate batteries are that, except for large voltage changes at the two ends, the middle part is basically a horizontal line. This makes the voltage correction SOC function ineffective in the horizontal area, resulting in battery SOC errors and unable to meet the needs of engineering applications. Summary of the Invention

[0007] The present disclosure provides a lithium iron phosphate battery SOC calibration method, system, electronic device and storage medium to at least solve the technical problem of inaccurate calibration of energy storage batteries.

[0008] A first embodiment of the present disclosure provides a method for calibrating the SOC of a lithium iron phosphate battery, the method comprising:

[0009] Obtaining a charge-discharge curve and a first pressure change curve of a sampled energy storage battery at a preset temperature and a preset charge-discharge power; wherein the sampled energy storage battery is consistent with the model of the lithium iron phosphate battery to be verified;

[0010] Determine the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve according to the charge and discharge curve and the first pressure change curve;

[0011] Obtaining a second pressure change curve of the lithium iron phosphate battery to be verified at a preset temperature and a preset charge and discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve;

[0012] The SOC of the lithium iron phosphate battery to be verified is verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve.

[0013] Preferably, the step of obtaining a charge-discharge curve and a first pressure change curve of the sampled energy storage battery at a preset temperature and a preset charge-discharge power includes:

[0014] Performing a charge and discharge test on the sampled energy storage battery at a preset temperature and a preset charge and discharge power to obtain a charge and discharge curve of the sampled energy storage battery at the preset temperature and the preset charge and discharge power;

[0015] The sampled energy storage battery undergoing charge and discharge test is placed in a constant gap fixture and a preset initial pressure is applied. A planar pressure sensor is used to record the pressure changes in the center area of ​​the battery at different moments during the charge and discharge process to obtain the first pressure change curve of the sampled energy storage battery at a preset temperature and preset charge and discharge power.

[0016] Furthermore, the determining, based on the charge-discharge curve and the first pressure change curve, the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve includes:

[0017] Acquiring charge and discharge data corresponding to the sampled energy storage battery during the charge and discharge test, and calibrating the charge of the sampled energy storage battery based on the charge and discharge data;

[0018] Determining the SOC state of the sampling energy storage battery at each moment based on the calibrated charge of the sampling energy storage battery;

[0019] Dividing the charging and discharging process of the sampled energy storage battery into an early charging and discharging stage, a middle charging and discharging stage, and a late charging and discharging stage according to the rising and falling trends of the first pressure change curve, and establishing a mapping relationship between the pressure change and the corresponding SOC in each charging and discharging stage;

[0020] The SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve is determined based on the mapping relationship.

[0021] Furthermore, the step of obtaining a second pressure change curve of the lithium iron phosphate battery to be verified at a preset temperature and a preset charge and discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve includes:

[0022] Obtaining a pressure change curve of the lithium iron phosphate battery to be verified from the start time to the end time of discharge and from the start time to the end time of charge at a preset temperature and a preset charge and discharge power, and using the pressure change curve as the second pressure change curve;

[0023] Determine each turning point of the second pressure change curve and the SOC of the energy storage battery corresponding to each turning point.

[0024] Furthermore, the SOC of the lithium iron phosphate battery to be verified is verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve, including:

[0025] It is determined whether the SOC of the energy storage battery corresponding to each turning point of the second pressure change curve is the same as the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve. If they are the same, no verification is performed. Otherwise, the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve is used as the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve to complete the verification.

[0026] A second embodiment of the present disclosure provides a lithium iron phosphate battery SOC calibration system, comprising:

[0027] A first acquisition module is configured to acquire a charge-discharge curve and a first pressure change curve of a sampled energy storage battery at a preset temperature and a preset charge-discharge power; wherein the sampled energy storage battery is consistent with the model of the lithium iron phosphate battery to be verified;

[0028] a determination module, configured to determine, based on the charge-discharge curve and the first pressure change curve, the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve;

[0029] A second acquisition module is used to obtain a second pressure change curve of the lithium iron phosphate battery to be tested at a preset temperature and a preset charge and discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve;

[0030] A verification module is used to verify the SOC of the lithium iron phosphate battery to be verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve.

[0031] Preferably, the first acquisition module includes:

[0032] A first testing unit is configured to perform a charge and discharge test on the sampled energy storage battery at a preset temperature and a preset charge and discharge power to obtain a charge and discharge curve of the sampled energy storage battery at the preset temperature and the preset charge and discharge power;

[0033] The second testing unit is used to place the sampled energy storage battery undergoing charge and discharge testing in a constant gap fixture and apply a preset initial pressure, and use a planar pressure sensor to record the pressure changes in the central area of ​​the battery at different moments during the charge and discharge process to obtain a first pressure change curve of the sampled energy storage battery under a preset temperature and preset charge and discharge power.

[0034] Furthermore, the determining module includes:

[0035] a first acquiring unit, configured to acquire charge and discharge data corresponding to the sampled energy storage battery during a charge and discharge test, and calibrate the charge of the sampled energy storage battery based on the charge and discharge data;

[0036] a first determining unit, configured to determine the SOC state of the sampling energy storage battery at each moment based on the calibrated charge of the sampling energy storage battery;

[0037] a first establishing unit, configured to divide the charging and discharging process of the sampled energy storage battery into an early charging and discharging stage, a middle charging and discharging stage, and a late charging and discharging stage according to the rising and falling trends of the first pressure change curve, and establish a mapping relationship between the pressure change and the corresponding SOC in each charging and discharging stage;

[0038] The second determining unit is configured to determine the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve based on the mapping relationship.

[0039] The third aspect of the present disclosure provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method described in the first aspect is implemented.

[0040] A fourth aspect of the present disclosure provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method described in the first aspect of the disclosure is implemented.

[0041] The technical solutions provided by the embodiments of the present disclosure bring at least the following beneficial effects:

[0042] The present disclosure proposes a method, system, electronic device, and storage medium for calibrating the SOC of a lithium iron phosphate battery. The method includes: obtaining a charge-discharge curve and a first pressure change curve of a sampled energy storage battery at a preset temperature and a preset charge-discharge power; wherein the sampled energy storage battery is of the same model as the lithium iron phosphate battery to be verified; determining the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve based on the charge-discharge curve and the first pressure change curve; obtaining a second pressure change curve of the lithium iron phosphate battery to be verified at a preset temperature and a preset charge-discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve; and verifying the SOC of the lithium iron phosphate battery to be verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve. The technical solution proposed in the present disclosure has extremely high reliability and improves verification accuracy.

[0043] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and / or additional aspects and advantages of the present disclosure will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0045] FIG1 is a flow chart of a method for calibrating the SOC of a lithium iron phosphate battery according to an embodiment of the present disclosure;

[0046] FIG2 is a schematic diagram of a charge-discharge curve and a pressure change curve of a sample energy storage battery provided according to an embodiment of the present disclosure;

[0047] FIG3 is a structural diagram of a lithium iron phosphate battery SOC calibration system provided according to one embodiment of the present disclosure;

[0048] FIG4 is a structural diagram of a first acquisition module provided according to an embodiment of the present disclosure;

[0049] FIG5 is a structural diagram of a determination module provided according to an embodiment of the present disclosure;

[0050] FIG6 is a structural diagram of a second acquisition module provided according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0051] The following describes in detail embodiments of the present disclosure, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present disclosure, and should not be construed as limiting the present disclosure.

[0052] The present disclosure proposes a lithium iron phosphate battery SOC calibration method, system, electronic device, and storage medium. The method includes: obtaining a charge-discharge curve and a first pressure change curve of a sampled energy storage battery at a preset temperature and a preset charge-discharge power; wherein the sampled energy storage battery is of the same model as the lithium iron phosphate battery to be verified; determining the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve based on the charge-discharge curve and the first pressure change curve; obtaining a second pressure change curve of the lithium iron phosphate battery to be verified at a preset temperature and a preset charge-discharge power, and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve; and verifying the SOC of the lithium iron phosphate battery to be verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve. The technical solution proposed in the present disclosure has extremely high reliability and improves verification accuracy.

[0053] The following describes a lithium iron phosphate battery SOC calibration method, system, electronic device, and storage medium according to embodiments of the present disclosure with reference to the accompanying drawings.

[0054] Example 1

[0055] FIG1 is a flow chart of a method for calibrating the SOC of a lithium iron phosphate battery according to an embodiment of the present disclosure. As shown in FIG1 , the method includes:

[0056] Step 1: Obtain a charge and discharge curve and a first pressure change curve of a sampled energy storage battery at a preset temperature and a preset charge and discharge power; wherein the sampled energy storage battery is of the same model as the lithium iron phosphate battery to be verified.

[0057] In the embodiment of the present disclosure, step 1 specifically includes:

[0058] Step 1-1: performing a charge and discharge test on the sample energy storage battery at a preset temperature and a preset charge and discharge power to obtain a charge and discharge curve of the sample energy storage battery at the preset temperature and the preset charge and discharge power;

[0059] For example, at room temperature (25±2°C), a 280Ah lithium iron phosphate energy storage sampling battery is charged and discharged at a power of 0.5P to obtain the charge and discharge curve data of one cycle, including parameters such as voltage, current, and time, and then obtain the charge and discharge curve.

[0060] Step 1-2: Place the sampled energy storage battery undergoing charge and discharge test in a constant gap fixture and apply a preset initial pressure. Use a planar pressure sensor to record the pressure changes in the center area of ​​the battery at different moments during the charge and discharge process to obtain the first pressure change curve of the sampled energy storage battery at a preset temperature and preset charge and discharge power.

[0061] For example, a 280Ah lithium iron phosphate sample battery is placed in a constant gap fixture during the charge and discharge process, and a suitable initial pressure, such as 2000N, is set. A plane pressure sensor is placed to record the pressure (kPa) changes in the center area of ​​the battery (the appropriate area can be selected according to the specific battery size) at different moments during the charge and discharge process. For example, during the charging process of the 280Ah lithium iron phosphate sample battery at room temperature at 0.5P, after charging for 1h, the pressure in the center area 1cm 2 The pressure at is recorded as 135.808 kPa, thereby obtaining the first pressure change curve.

[0062] Step 2: Determine the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve according to the charge-discharge curve and the first pressure change curve.

[0063] In the embodiment of the present disclosure, step 2 specifically includes:

[0064] Step 2-1: Obtaining charge and discharge data corresponding to the sampled energy storage battery during the charge and discharge test, and calibrating the charge of the sampled energy storage battery based on the charge and discharge data;

[0065] Step 2-2: determining the SOC state of the sampling energy storage battery at each moment based on the calibrated charge of the sampling energy storage battery;

[0066] It should be noted that steps 2-1 and 2-2 may be used to calibrate the charge of the sampled energy storage battery based on its charge and discharge data, while simultaneously recording the charge and discharge charge (Qt) of the sampled energy storage battery at different times. The calibrated charge (Qn) refers to the total charge released or charged by the sampled energy storage battery from a fully charged state to a depleted state, or vice versa. The battery's state of charge (SOC) at different times is calculated: SOC = Qt / Qn × 100% for charging and SOC = 1-Qt / Qn × 100% for discharging.

[0067] For example, a 280Ah lithium iron phosphate energy storage sample battery is charged and discharged at a power of 0.5P at room temperature (25±2°C). The charge and discharge curve data of one cycle are obtained, including parameters such as voltage, current, and time. The charge capacity is calibrated based on the charge and discharge data, and the charge and discharge capacity of the battery at different times is calculated. For example, the charge calibration charge of the 280Ah lithium iron phosphate sample battery at room temperature and 0.5P is 1.027×10 6 C, the charge capacity after charging for 1 hour is 4.855×10 5 C, then at this moment of 1 hour the SOC of the battery is 47%.

[0068] Step 2-3: Dividing the charge and discharge process of the sampled energy storage battery into an early charge and discharge period, a middle charge and discharge period, and a late charge and discharge period according to the rising and falling trends of the first pressure change curve, and establishing a mapping relationship between the pressure change and the corresponding SOC in each charge and discharge process;

[0069] Step 2-4: Determine the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve based on the mapping relationship.

[0070] It should be noted that steps 2-3 and 2-4 may be performed by segmenting the data of the energy storage battery to establish a mapping relationship between the corresponding pressure change curve and the SOC state of the energy storage battery. The charge and discharge process can be divided into three stages based on the rising and falling trends of the pressure change curve: the early charge and discharge stage, the middle charge and discharge stage, and the late charge and discharge stage. The relative pressure change and the corresponding SOC are then associated with each stage of the charge and discharge process. The SOC corresponding to the turning point of the pressure change in the pressure change curve of the sampled energy storage battery during the charge and discharge process is also obtained to facilitate accurate SOC calibration at specific points.

[0071] For example, a mapping relationship between the pressure change curve and the SOC state corresponding to the 280Ah lithium iron phosphate energy storage sampling battery is established. Since the pressure of the battery will increase with the increase in the number of cycles, the pressure curve is first normalized and divided into the early charging period (pressure curve rising period), mid-charging period (pressure curve falling period), late charging period (pressure curve rising period), early discharge period (pressure curve falling period), mid-discharge period (pressure curve rising period), and late discharge period (pressure curve falling period) according to the rising and falling trends of the pressure change curve. The pressure data and SOC state of each charging and discharging process are fitted separately to establish a mapping relationship. The mapping formula is as follows: SOC = ax 3 +bx 2 +cx+d, x is the relative pressure value after normalization of the pressure curve, the value range of x is 0-1, a, b, c, d are the parameters to be fitted, which are obtained by fitting according to the numerical results. After the parameters to be fitted are determined, the mapping relationship between the pressure change curve and the SOC state can be obtained.

[0072] For example, a 280Ah lithium iron phosphate battery reaches its first pressure inflection point after 2670 seconds of charging, with an SOC value of 35.23%; reaches its second pressure inflection point after 4910 seconds of charging, with an SOC value of 64.13%; reaches its first pressure inflection point after 2500 seconds of discharge, with an SOC value of 66.43%; and reaches its second pressure inflection point after 5110 seconds of discharge, with an SOC value of 31.05%. Since the SOC values ​​corresponding to the pressure inflection points remain constant for the same battery model, accurate SOC calibration can be performed at specific points after obtaining these values.

[0073] Step 3: Obtain a second pressure change curve of the lithium iron phosphate battery to be verified at a preset temperature and a preset charge and discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve.

[0074] In the embodiment of the present disclosure, step 3 specifically includes:

[0075] Step 3-1: Obtaining a pressure change curve of the lithium iron phosphate battery to be tested from the start time to the end time of discharge and from the start time to the end time of charge at a preset temperature and a preset charge and discharge power, and using the pressure change curve as the second pressure change curve;

[0076] Step 3-2: Determine each turning point of the second pressure change curve and the SOC of the energy storage battery corresponding to each turning point.

[0077] It should be noted that during the charge and discharge process of the lithium iron phosphate battery to be verified at a specific temperature and a specific power, a second pressure change curve is obtained from the start of discharge to the end of discharge and from the start of charge to the end of charge. The current charge and discharge state of the lithium iron phosphate battery to be verified is obtained to determine whether it is in the early charge and discharge stage, the middle charge and discharge stage, and the late charge and discharge stage. At the same time, the current pressure state of the lithium iron phosphate battery to be verified is obtained. Based on the mapping relationship between the pressure change curve and the SOC state, combined with the current charge and discharge state and pressure state of the lithium iron phosphate battery to be verified, the current SOC of the lithium iron phosphate battery to be verified is obtained.

[0078] For example, during the 0.5P charge and discharge process at room temperature for a lithium iron phosphate battery of the same model to be verified, a pressure change curve is obtained during one of the charge and discharge cycles. The current charge and discharge state and pressure state of the lithium iron phosphate battery to be verified are also obtained. For example, if the lithium iron phosphate battery to be verified is in the early stage of charging and the pressure state is 124.937 kPa, normalization is performed using the second pressure change curve. Combined with the mapping relationship between the sampled battery pressure change curve, i.e., the first pressure change curve, and the SOC state, the current SOC of the lithium iron phosphate battery to be verified is obtained to be 20.06%. The SOC of the energy storage battery corresponding to the turning point can then be obtained.

[0079] Step 4: Verify the SOC of the lithium iron phosphate battery to be verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve.

[0080] In the embodiment of the present disclosure, step 4 specifically includes:

[0081] It is determined whether the SOC of the energy storage battery corresponding to each turning point of the second pressure change curve is the same as the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve. If they are the same, no verification is performed. Otherwise, the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve is used as the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve to complete the verification.

[0082] It should be noted that when the pressure state of the lithium iron phosphate battery to be verified reaches a turning point during the charge and discharge process, the current SOC of the lithium iron phosphate battery to be verified is obtained, and the SOC of the lithium iron phosphate battery to be verified is corrected by comparing the corresponding SOC when the pressure state of the sampled energy storage battery reaches the turning point to achieve SOC calibration.

[0083] For example, during the charge and discharge process of a lithium iron phosphate battery of the same model to be verified at room temperature and 0.5P, when the pressure state of the lithium iron phosphate battery to be verified reaches a turning point, the current SOC of the energy storage battery is obtained, and the SOC is corrected by comparing it with the sampled energy storage battery. For example, when the lithium iron phosphate battery to be verified reaches the first pressure turning point during the charging process, the SOC value at that point is obtained as 37.85%; while when the energy storage battery reaches the first pressure turning point during the charging process, the SOC value at that point is recorded as 35.23%. Therefore, the current SOC of the lithium iron phosphate battery to be verified is corrected by sampling the energy storage battery data, and the current SOC value of the lithium iron phosphate battery to be verified is corrected to 35.23%, achieving SOC calibration.

[0084] In an embodiment of the present disclosure, an SOC calibration example of a certain model 280Ah lithium iron phosphate energy storage battery is provided, including the following contents:

[0085] For example, a model 280Ah energy storage battery is placed in a constant gap fixture and a suitable initial pressure of 2000N is set. At the same time, a pressure sensing device is placed to record the pressure changes during the charging and discharging process, and the charge and discharge curves and pressure change curves of the sampled energy storage battery are obtained, as shown in Figure 2, where A, B, C, D, E, F, G, and H are all pressure turning points.

[0086] Figure 2 shows that the pressure changes during the charging process in a cycle of increase, decrease, and increase. Firstly, during charging, the delithiation product of lithium iron phosphate is iron phosphate, which has a very similar structure and volume to lithium iron phosphate. Furthermore, in the early stages of charging, the lithium iron phosphate shrinks little, while the graphite expands, causing the pressure to rise. In the middle stages of charging, the lithium iron phosphate contracts, partially offsetting the graphite expansion, causing the expansion force to decrease. In the later stages of charging, the lithium iron phosphate no longer shrinks, while the graphite continues to expand, causing the expansion force to increase again. The discharge process exhibits the opposite trend. Compared to the flat voltage curve of lithium iron phosphate during charge and discharge, its pressure curve exhibits significant fluctuations. This fluctuation can be used to correlate battery pressure with SOC, accurately determining the battery's SOC. Furthermore, the electrochemical state corresponding to the turning point of the battery's expansion force is fixed and does not change with declining battery capacity or changes in the expansion force. Therefore, the turning point of the expansion force can be used to calibrate the battery's SOC.

[0087] It should be noted that the solution provided in this embodiment is not only applicable to lithium iron phosphate batteries with a wide platform area, but can also be applied to other types of batteries.

[0088] In summary, the SOC calibration method for lithium iron phosphate batteries proposed in this embodiment achieves 1) high reliability by utilizing the physical property of pressure to calibrate the battery's SOC. Although the battery's capacity gradually declines and the pressure level fluctuates during cycling, the SOC values ​​corresponding to pressure peaks and troughs remain fixed, avoiding calibration errors and ensuring high technical controllability and accuracy. 2) SOC calibration can be performed solely using a pressure sensor, making it easy to operate. 3) This method has a wide range of applications, applicable not only to lithium iron phosphate batteries with a wide platform range, but also to other types of batteries.

[0089] Example 2

[0090] FIG3 is a structural diagram of a lithium iron phosphate battery SOC calibration system provided according to one embodiment of the present disclosure. As shown in FIG3 , the system includes:

[0091] A first acquisition module 100 is configured to acquire a charge-discharge curve and a first pressure change curve of a sampled energy storage battery at a preset temperature and a preset charge-discharge power; wherein the sampled energy storage battery is of the same model as the lithium iron phosphate battery to be verified;

[0092] a determination module 200 for determining the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve according to the charge-discharge curve and the first pressure change curve;

[0093] The second acquisition module 300 is used to obtain a second pressure change curve of the lithium iron phosphate battery to be tested at a preset temperature and a preset charge and discharge power, and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve;

[0094] The verification module 400 is configured to verify the SOC of the lithium iron phosphate battery to be verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve.

[0095] In the embodiment of the present disclosure, as shown in FIG4 , the first acquisition module 100 includes:

[0096] The first testing unit 101 is configured to perform a charge and discharge test on the sampled energy storage battery at a preset temperature and a preset charge and discharge power, and obtain a charge and discharge curve of the sampled energy storage battery at the preset temperature and the preset charge and discharge power;

[0097] The second testing unit 102 is used to place the sampled energy storage battery undergoing charge and discharge testing in a constant gap fixture and apply a preset initial pressure, and use a planar pressure sensor to record the pressure changes in the central area of ​​the battery at different moments during the charge and discharge process to obtain a first pressure change curve of the sampled energy storage battery under a preset temperature and preset charge and discharge power.

[0098] In the embodiment of the present disclosure, as shown in FIG5 , the determining module 200 includes:

[0099] The first acquisition unit 201 is configured to acquire charge and discharge data corresponding to the sampled energy storage battery during a charge and discharge test, and to calibrate the charge of the sampled energy storage battery based on the charge and discharge data;

[0100] A first determining unit 202 is configured to determine the SOC state of the sampled energy storage battery at each moment based on the calibrated charge of the sampled energy storage battery;

[0101] a first establishing unit 203, configured to divide the charging and discharging process of the sampled energy storage battery into an early charging and discharging stage, a middle charging and discharging stage, and a late charging and discharging stage according to the rising and falling trends of the first pressure change curve, and establish a mapping relationship between the pressure change and the corresponding SOC in each charging and discharging stage;

[0102] The second determining unit 204 is configured to determine the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve based on the mapping relationship.

[0103] In the embodiment of the present disclosure, as shown in FIG6 , the second acquisition module 300 includes:

[0104] The second acquiring unit 301 is configured to acquire a pressure change curve of the lithium iron phosphate battery to be tested from the start time to the end time of discharge and from the start time to the end time of charge at a preset temperature and a preset charge and discharge power, and use the pressure change curve as the second pressure change curve;

[0105] The third determining unit 302 is configured to determine the turning points of the second pressure variation curve and the SOC of the energy storage battery corresponding to the turning points.

[0106] In the embodiment of the present disclosure, the verification module 400 is specifically used to:

[0107] It is determined whether the SOC of the energy storage battery corresponding to each turning point of the second pressure change curve is the same as the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve. If they are the same, no verification is performed. Otherwise, the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve is used as the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve to complete the verification.

[0108] In summary, the lithium iron phosphate battery SOC calibration system proposed in this embodiment has the following advantages: 1) It utilizes the physical property of pressure to calibrate the battery's SOC, achieving extremely high reliability. Although the battery's capacity gradually declines and the pressure level fluctuates during cycling, the SOC values ​​corresponding to pressure peaks and troughs remain fixed, avoiding calibration errors and ensuring high technical controllability and accuracy. 2) SOC calibration can be performed solely through a pressure sensor, making operation simple. 3) This method has a wide range of applications, applicable not only to lithium iron phosphate batteries with a wide platform range, but also to other types of batteries.

[0109] Example 3

[0110] To implement the above embodiments, the present disclosure further proposes an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described in the first embodiment is implemented.

[0111] Example 4

[0112] In order to implement the above embodiments, the present disclosure further proposes a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method described in the first embodiment is implemented.

[0113] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0114] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present disclosure includes additional implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present disclosure belong.

[0115] Although the embodiments of the present disclosure have been shown and described above, it is understood that the above embodiments are illustrative and are not to be construed as limitations on the present disclosure. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present disclosure.

Claims

1. A method for calibrating the SOC of a lithium iron phosphate battery, the method comprising: Obtaining a charge-discharge curve and a first pressure change curve of a sampled energy storage battery at a preset temperature and a preset charge-discharge power; wherein, the sampled energy storage battery has the same model as the lithium iron phosphate battery to be calibrated; Determining the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve according to the charge-discharge curve and the first pressure change curve; Obtaining a second pressure change curve of the lithium iron phosphate battery to be calibrated at a preset temperature and a preset charge-discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve; Calibrating the SOC of the lithium iron phosphate battery to be calibrated based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve.

2. The method according to claim 1, wherein The obtaining of the charge-discharge curve and the first pressure change curve of the sampled energy storage battery at a preset temperature and a preset charge-discharge power includes: Performing a charge-discharge test on the sampled energy storage battery at a preset temperature and a preset charge-discharge power to obtain the charge-discharge curve of the sampled energy storage battery at the preset temperature and the preset charge-discharge power; Placing the sampled energy storage battery undergoing the charge-discharge test in a fixture with a constant gap and applying a preset initial pressure, and using a planar pressure sensor to record the pressure change situation in the central area of the battery at different moments during the charge-discharge process to obtain the first pressure change curve of the sampled energy storage battery at the preset temperature and the preset charge-discharge power.

3. The method according to claim 2, wherein, The determining of the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve according to the charge-discharge curve and the first pressure change curve includes: Obtaining the charge-discharge data corresponding to the sampled energy storage battery during the charge-discharge test, and calibrating the charge quantity of the sampled energy storage battery based on the charge-discharge data; Determining the SOC state of the sampled energy storage battery at each moment based on the calibrated charge quantity of the sampled energy storage battery; Dividing the charge-discharge process of the sampled energy storage battery into a pre-charge-discharge period, a mid-charge-discharge period, and a post-charge-discharge period according to the rising and falling trends of the first pressure change curve, and establishing a mapping relationship between the pressure change in each period of the charge-discharge process and the corresponding SOC; Determining the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve based on the mapping relationship.

4. The method according to claim 3, wherein, The obtaining of the second pressure change curve of the lithium iron phosphate battery to be calibrated at a preset temperature and a preset charge-discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve includes: Obtaining the pressure change curve of the lithium iron phosphate battery to be calibrated from the discharge start moment to the discharge end moment and from the charge start moment to the charge end moment at a preset temperature and a preset charge-discharge power, and using the pressure change curve as the second pressure change curve; Determining each turning point of the second pressure change curve and the SOC of the energy storage battery corresponding to each turning point.

5. The method according to claim 4, wherein, Calibrating the SOC of the lithium iron phosphate battery to be verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve includes: Judging whether the SOC of the energy storage battery corresponding to each turning point of the second pressure change curve is the same as the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve. If they are the same, no calibration is performed. Otherwise, the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve is used as the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve to complete the calibration.

6. A lithium iron phosphate battery SOC calibration system, the system includes: A first acquisition module, configured to acquire the charge-discharge curve and the first pressure change curve of the sampled energy storage battery at a preset temperature and a preset charge-discharge power; wherein, the sampled energy storage battery has the same model as the lithium iron phosphate battery to be verified; A determination module, configured to determine the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve according to the charge-discharge curve and the first pressure change curve; A second acquisition module, configured to acquire the second pressure change curve of the lithium iron phosphate battery to be verified at a preset temperature and a preset charge-discharge power and the SOC of the energy storage battery corresponding to each pressure change turning point in the second pressure change curve; A calibration module, configured to calibrate the SOC of the lithium iron phosphate battery to be verified based on the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve.

7. The system according to claim 6, wherein, The first acquisition module includes: A first test unit, configured to perform charge-discharge tests on the sampled energy storage battery at a preset temperature and a preset charge-discharge power to obtain the charge-discharge curve of the sampled energy storage battery at the preset temperature and the preset charge-discharge power; A second test unit, configured to place the sampled energy storage battery undergoing charge-discharge tests in a fixture with a constant gap and apply a preset initial pressure, and use a planar pressure sensor to record the pressure change conditions in the central area of the battery at different moments during the charge-discharge process to obtain the first pressure change curve of the sampled energy storage battery at the preset temperature and the preset charge-discharge power.

8. The system according to claim 6, wherein, The determination module includes: A first acquisition unit, configured to acquire the charge-discharge data corresponding to the sampled energy storage battery during the charge-discharge test and calibrate the charge quantity of the sampled energy storage battery based on the charge-discharge data; A first determination unit, configured to determine the SOC state of the sampled energy storage battery at each moment based on the calibrated charge quantity of the sampled energy storage battery; A first establishment unit, configured to divide the charge-discharge process of the sampled energy storage battery into the early stage of charge-discharge, the middle stage of charge-discharge, and the late stage of charge-discharge according to the rising and falling trends of the first pressure change curve, and establish a mapping relationship between the pressure change in each stage of the charge-discharge process and the corresponding SOC; A second determination unit, configured to determine the SOC of the energy storage battery corresponding to each pressure change turning point in the first pressure change curve based on the mapping relationship.

9. An electronic device, comprising: A memory, a processor, and a computer program stored on the memory and executable on the processor, wherein when the processor executes the computer program, the method according to any one of claims 1-5 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method according to any one of claims 1-5 is implemented.

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