Method and system for calibrating state of charge of battery and battery module
By detecting the battery ambient temperature and preload, collecting expansion force data and establishing a comparison database, the problem of low calibration accuracy of lithium batteries is solved, and higher calibration accuracy and battery safety performance are achieved.
Patent Information
- Application Number
- CN202311354684.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-18
- Publication Date
- 2025-04-18
AI Technical Summary
When calibrating lithium battery SOC, the prior art is susceptible to environmental factors such as charge and discharge intervals and temperature, resulting in low calibration accuracy. Especially during the use of lithium iron phosphate batteries, calibration accuracy is difficult to ensure.
By detecting the ambient temperature and preload of the battery, multiple expansion force data are collected, and a comparison database is established based on the relationship between the preset expansion force and the corresponding state of charge data, and then the corresponding SOC data is obtained to calibrate the state of charge of the battery.
Improves the calibration accuracy of SOC, enhances the safety performance of the battery, improves the user experience, and reduces costs.
Smart Images
Figure CN119846487A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of vehicles, and in particular to the field of battery systems for new energy vehicles. More specifically, it relates to a method and system for calibrating the state of charge of a battery and a battery module using the system. Background Art
[0002] In recent years, new energy vehicles have become more and more common in life. In new energy vehicles, lithium batteries are usually used as power sources. Due to the particularity of lithium batteries, it is necessary to avoid overcharging, over-discharging and overheating of the battery during use. For example, when the battery is over-discharged, it will cause serious damage to the battery, affecting the performance of the entire battery module, and even causing an explosion. Usually, a BMS (Battery Management System) is used to control the state of the battery, where the battery state includes SOC (State of Charge), SOH (State-of-Health), SOP (State-of-Power), etc. Since the SOH, SOP state calculation, and power balancing functions of the BMS are all based on the SOC value, the calibration accuracy of the SOC is particularly important.
[0003] SOC usually reflects the ratio of the current remaining power of the battery to the total available power under a certain discharge current, usually expressed as a percentage. SOC can directly affect the voltage and current of the battery. The value range of SOC is 0-1. Usually, when SOC=0, it means that the battery is fully discharged, and when SOC=1, it means that the battery is fully charged.
[0004] Currently, the open circuit voltage (OCV) method, ampere-hour integration method, Kalman filter method, neural network / deep learning method, etc. are mainly used to calibrate SOC. These methods are easily affected by the charge and discharge range, temperature, etc. during use. In particular, the accuracy of SOC calibration of lithium iron phosphate batteries is particularly affected by environmental factors. Therefore, it is necessary to improve the calibration accuracy of SOC. Summary of the invention
[0005] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and to provide a method for calibrating the state of charge of a battery, so as to improve the calibration accuracy of the SOC in a cost-effective and reliable manner.
[0006] To this end, according to one aspect of the present invention, a method for calibrating the state of charge of a battery is provided, the method comprising: detecting the ambient temperature and preload of the battery; collecting a plurality of first expansion forces of the battery at a first frequency; acquiring the state of charge data corresponding to each of the plurality of first expansion forces collected based on a comparison database storing the relationship between a plurality of preset expansion forces and corresponding state of charge data; and calibrating the state of charge of the battery based on the obtained state of charge data.
[0007] According to the above technical concept, the present invention may further include any one or more of the following optional forms.
[0008] In certain optional forms, collecting a plurality of first expansion forces of the battery at a first frequency includes: collecting the plurality of first expansion forces via a sensor disposed in the battery.
[0009] In certain optional forms, the plurality of first expansion forces include: one or more first expansion forces among the plurality of first expansion forces having a rate of change of zero relative to the state of charge data.
[0010] In certain optional forms, the method further includes: obtaining the multiple preset expansion forces of the battery at the second frequency under different ambient temperatures and preloads, and the charge state data corresponding to each of the multiple preset expansion forces; and generating the comparison database based on the relationship between each of the multiple preset expansion forces and the corresponding charge state data.
[0011] In certain optional forms, generating the comparison database further includes marking the following expansion forces: one or more preset expansion forces among the plurality of preset expansion forces having a rate of change of zero relative to the state of charge data.
[0012] In certain optional forms, the first frequency is greater than or equal to the second frequency.
[0013] According to another aspect of the present invention, a system for calibrating the state of charge of a battery is provided, the system comprising: a detection module, the detection module being configured to detect the ambient temperature and preload of the battery; an acquisition module, the acquisition module being configured to acquire a plurality of first expansion forces of the battery at a first frequency; a first acquisition module, the first acquisition module being configured to acquire the state of charge data corresponding to each of the plurality of first expansion forces acquired based on a comparison database storing the relationship between a plurality of preset expansion forces and the corresponding state of charge data; and a calibration module, the calibration module being configured to calibrate the state of charge of the battery based on the acquired state of charge data.
[0014] In some optional forms, the collection module includes a sensor disposed in the battery, and the sensor is configured to collect the plurality of first expansion forces.
[0015] In certain optional forms, the plurality of first expansion forces include: one or more first expansion forces among the plurality of first expansion forces having a rate of change of zero relative to the state of charge data.
[0016] In certain optional forms, the system also includes: a second acquisition module, the second acquisition module is configured to acquire the multiple preset expansion forces of the battery at a second frequency under different ambient temperatures and preloads, and the charge state data corresponding to each of the multiple preset expansion forces; a generation module, the generation module is configured to generate the comparison database based on the relationship between each of the multiple preset expansion forces and the corresponding charge state data.
[0017] In certain optional forms, the generating module further comprises a marking device configured to mark the following expansion forces: one or more preset expansion forces among the plurality of preset expansion forces whose rate of change relative to the state of charge data is zero.
[0018] In certain optional forms, the first frequency is greater than or equal to the second frequency.
[0019] According to another aspect of the present invention, a battery module is provided, comprising one or more batteries and the above-mentioned battery state of charge calibration system.
[0020] The present invention collects the expansion force and calibrates the state of charge of the battery according to the relationship between the preset expansion force and the corresponding state of charge data, thereby improving the calibration accuracy of the state of charge, making it possible to estimate the vehicle mileage more accurately, further improving the safety of the electric vehicle, and improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Other features and advantages of the present invention will be better understood through the following detailed description of the optional embodiments in conjunction with the accompanying drawings, in which the same reference numerals identify the same or similar components, wherein:
[0022] Figure 1 is a flow chart of a method for calibrating the state of charge of a battery according to an embodiment of the present invention;
[0023] Figure 2 is a flow chart of a method for calibrating a battery state of charge according to another embodiment of the present invention;
[0024] Figure 3is a schematic diagram of a system for calibrating the state of charge of a battery according to an embodiment of the present invention; and
[0025] Figure 4 is a graph showing the relationship between the SOC, OCV and expansion force of a battery at an ambient temperature of 25° C. and a preload of 20 kg according to an embodiment of the present invention. DETAILED DESCRIPTION
[0026] The implementation and use of the embodiments are discussed in detail below. However, it should be understood that the specific embodiments discussed are merely illustrative of specific ways to implement and use the invention, and are not intended to limit the scope of the invention.
[0027] New energy vehicles usually use lithium iron phosphate batteries as a power source. Compared with other lithium batteries such as ternary lithium batteries, lithium iron phosphate batteries have better material performance stability. During the charging and discharging process, the battery structure basically does not change, and has higher safety and service life. In addition, lithium iron phosphate batteries are less expensive due to their low content of heavy metals and rare metals. Therefore, lithium iron phosphate batteries are widely used in the field of new energy. The inventors found that lithium iron phosphate batteries have a plateau period during the process of SOC calibration using, for example, the open circuit voltage method. During this plateau period, the OCV of the battery basically does not change with the SOC, which may affect the calibration accuracy of the SOC and reduce the safety performance of the battery.
[0028] Reference Figure 1 , Figure 1 is a flow chart of a method for calibrating a battery state of charge according to an embodiment of the present invention.
[0029] A method for calibrating a battery state of charge according to an embodiment of the present invention may include the following steps.
[0030] Step S101: Detect the ambient temperature and preload of the battery.
[0031] In step S101, since the expansion force of the battery under different ambient temperatures and preloads is different, the ambient temperature and preload of the battery can be detected before the state of charge of the battery is calibrated to improve the calibration accuracy. In addition, a temperature sensor and a force sensor can be used to detect the ambient temperature and preload of the battery to be calibrated.
[0032] Step S102: collecting a plurality of first expansion forces of the battery at a first frequency.
[0033] In step S102, the first frequency may be greater than or equal to 1000 ms. It is understood that the first frequency is not limited thereto and may vary depending on different needs. After the first expansion force of the battery is collected, the collected data may be transmitted to a BMS or other processor disposed inside or outside the battery. In this embodiment, the BMS is taken as an example for description.
[0034] Step S103: acquiring the SOC corresponding to each of the collected first expansion forces according to a comparison database pre-stored in the BMS, wherein the comparison database stores a relationship between a preset expansion force and a corresponding SOC.
[0035] Step S104: Calibrate the state of charge of the battery based on the obtained state of charge data.
[0036] In step S104, based on the SOC obtained in step S103, the SOC may be updated in the BMS to complete the SOC calibration process, and the calibration result may be used as a calculation basis for the SOC before performing the SOC calibration process of the next cycle.
[0037] In this way, according to the SOC calibration method of the present invention, the calibration accuracy of the SOC, for example, during the plateau period of the open circuit voltage method, can be improved by using the expansion force of the battery. In addition, the inventors found that under different temperatures and preloads, the shape of the curve of the corresponding relationship between SOC and expansion force is almost unchanged, and only the position of the curve changes. Therefore, the present invention can further improve the calibration accuracy of the SOC, improve the safety of the vehicle and the user experience by pre-detecting the temperature and preload of the battery and finding the relationship curve between the SOC and the expansion force under the detected temperature and preload in the comparison database.
[0038] Specifically, refer to Figure 4 , Figure 4 It is a graph showing the relationship between SOC, OCV and expansion force of lithium iron phosphate battery at an ambient temperature of 25°C and a preload of 20kg. Figure 4 It can be seen that in the plateau period of OCV ( Figure 4 In the stage from point A to point B in the calibration, the SOC is in the range of about 28% to 94%), and the expansion force of the battery changes significantly relative to the SOC. Therefore, using the expansion force of the battery to calibrate the SOC can improve the accuracy of the calibration.
[0039] In addition, in step S102, the first expansion force can be collected by a sensor disposed in the battery, and the sensor can be a pressure sensor, such as a piezoresistive film. In addition, the sensor can be disposed between the end plate of the battery module and the battery of the battery module. In this way, real-time measurement of the battery expansion force can be achieved, and calibration accuracy can be improved.
[0040] In this embodiment, the collected multiple first expansion forces may include: one or more first expansion forces whose change rate relative to the state of charge data is 0 among the multiple first expansion forces. In other words, during the calibration of SOC, the first expansion force at the extreme point may be calibrated. Figure 4 In the curve diagram showing the relationship between SOC and expansion force, the SOC corresponding to the expansion force extreme points C and D can be calibrated. At points C and D, the rate of change of the expansion force relative to the SOC is 0.
[0041] Additionally, in some embodiments, after collecting a plurality of first expansion forces, the SOC may be calibrated by calculating the expansion force change rate between two adjacent first expansion forces among the collected plurality of first expansion forces. In this case, a comparison database pre-stored in the BMS may store a preset relationship between the expansion force change rate and the corresponding SOC, whereby the SOC corresponding to each of the calculated expansion force change rates may be obtained based on the comparison database. In this way, the SOC of the battery may be calibrated based on the obtained SOC.
[0042] Now refer to Figure 2 , Figure 2 is a flow chart of a method for calibrating a battery state of charge according to another embodiment of the present invention.
[0043] By comparison Figure 2 and Figure 1 It can be seen that, Figure 2 The method shown is similar to Figure 1 The method shown is different in that before calibrating the SOC, multiple preset expansion forces of the battery are obtained at different ambient temperatures and preloads and at a second frequency, and the SOC corresponding to each of the multiple preset expansion forces is obtained (step S201).
[0044] In step S201, the second frequency may be between 500ms and 1000ms. It is to be understood that the second frequency is not limited thereto and may vary depending on different needs. In addition, in step S201, the acquisition of the preset expansion force and the corresponding SOC is performed under different ambient temperatures and preloads. In this way, the comparison database may be made more complete, further improving the calibration accuracy of the SOC. For example, multiple preset expansion forces and corresponding SOCs may be acquired under conditions of an ambient temperature of 30°C and a preload of 25kg, an ambient temperature of 20°C and a preload of 10kg, and the like.
[0045] Step S202: Generate a comparison database based on the relationship between each of the preset expansion forces and the corresponding SOC.
[0046] In this way, before calibrating the SOC, the battery of the type to be calibrated can be tested to obtain the relationship between the expansion force under different temperatures and preloads and the corresponding SOC to generate the required comparison database, which can be used as a calibration database for the battery of this type. It is understandable that the comparison database can also be pre-stored in the battery system, for example, stored in the BMS in the form of chip burning.
[0047] In addition, in this embodiment, the first frequency may be greater than or equal to the second frequency. In this way, the generated comparison database has more sampling points than the collected data, thereby improving the calibration accuracy of the SOC.
[0048] In some embodiments, after the comparison database is generated, the following expansion forces in the comparison database may be marked: one or more of the preset expansion forces whose change rate relative to the state of charge data is 0 among the multiple preset expansion forces. In this way, it is helpful to calibrate the SOC corresponding to the expansion force at the extreme point and improve the calibration efficiency. It is understood that the marked expansion force is not limited thereto and may vary depending on different needs.
[0049] Reference Figure 3 , Figure 3 FIG. 4 is a schematic diagram of a system for calibrating the state of charge of a battery according to an embodiment of the present invention.
[0050] The embodiment of the present invention also provides a system 100 for calibrating the state of charge of a battery, and the system 100 can implement the above-mentioned state of charge calibration method. The system 100 according to this embodiment includes: a detection module 130, which is configured to detect the ambient temperature and preload of the battery to be calibrated; a collection module 140, which is configured to collect multiple first expansion forces of the battery at a first frequency; a first acquisition module 150, which is configured to obtain the SOC corresponding to each of the multiple first expansion forces collected according to a comparison database storing the relationship between the preset expansion force and the corresponding SOC; and a calibration module 160, which is configured to calibrate the SOC of the battery based on the obtained SOC.
[0051] In this way, the system 100 for calibrating SOC of the present invention can calibrate SOC by using the expansion force, thereby improving the accuracy of SOC calibration.
[0052] like Figure 3 As shown, the acquisition module 140 may include a sensor 141. The sensor 141 may be disposed in the battery, for example, between the end plate of the battery module and the battery of the battery module. The sensor 141 may be configured to acquire a plurality of first expansion forces.
[0053] Continue to refer to Figure 3 The system 100 of this embodiment may also include: a second acquisition module 110, which is configured to acquire multiple preset expansion forces of the battery at a second frequency under different ambient temperatures and preloads, and charge state data corresponding to each of the multiple preset expansion forces; and a generation module 120, which is configured to generate a comparison database based on the relationship between each of the preset expansion forces and the corresponding charge state data.
[0054] In some embodiments, the generation module 120 may include a marking device 121, which may be configured to mark the following expansion forces: one or more preset expansion forces among a plurality of preset expansion forces whose rate of change relative to the state of charge data is zero.
[0055] The battery state of charge calibration method of the present invention obtains the corresponding SOC through the expansion force of the battery, thereby calibrating the SOC of the battery, improving the calibration accuracy of the SOC, improving the safety performance of the battery, and being cost-effective and having high calibration efficiency. In addition, the calibration method of the present invention is not limited to use in new energy vehicles, but can also be applied to other types of vehicles such as hybrid vehicles according to needs, so as to calibrate the SOC of the battery of the vehicle and improve the safety performance of the vehicle. In addition, the calibration method of the present invention can also be conducive to the large-scale application of lithium iron phosphate batteries in the automotive industry.
[0056] It should be understood that the embodiments shown in the figure only show optional configurations of the system for calibrating the state of charge of the battery according to the present invention, but they are only illustrative and not restrictive, and other configurations may be adopted without departing from the spirit and scope of the present invention.
[0057] The technical content and technical features of the present invention have been disclosed above. However, it can be understood that under the creative ideas of the present invention, those skilled in the art can make various changes and improvements to the above disclosed concepts, but they all belong to the protection scope of the present invention. The description of the above embodiments is illustrative rather than restrictive, and the protection scope of the present invention is determined by the claims.
Claims
1. A method for calibrating the state of charge of a battery, characterized in that: The method comprises: Detecting the ambient temperature and preload of the battery (S101); collecting a plurality of first expansion forces of the battery at a first frequency (S102); Acquiring the state of charge data corresponding to each of the plurality of first expansion forces collected according to a comparison database storing the relationship between a plurality of preset expansion forces and corresponding state of charge data (S103); and Based on the obtained state-of-charge data, the state-of-charge of the battery is calibrated ( S104 ).
2. The method for calibrating the state of charge of a battery according to claim 1, characterized in that: Collecting a plurality of first expansion forces of the battery at a first frequency includes: collecting the plurality of first expansion forces by a sensor disposed in the battery.
3. The method for calibrating the state of charge of a battery according to claim 1, characterized in that: The plurality of first expansion forces include: one or more first expansion forces of the plurality of first expansion forces whose rate of change relative to the state of charge data is zero.
4. The method for calibrating the state of charge of a battery according to claim 1, characterized in that: The method further comprises: Acquiring the plurality of preset expansion forces of the battery at a second frequency under different ambient temperatures and preloads, and state of charge data corresponding to each of the plurality of preset expansion forces (S201); The comparison database is generated based on a relationship between each of the plurality of preset expansion forces and corresponding state of charge data (S202).
5. The method for calibrating the state of charge of a battery according to claim 4, characterized in that: Generating the comparison database further includes marking the following expansion forces: one or more preset expansion forces among the plurality of preset expansion forces whose rate of change relative to the state of charge data is zero.
6. The method for calibrating the state of charge of a battery according to claim 4, characterized in that: The first frequency is greater than or equal to the second frequency.
7. A system for calibrating the state of charge of a battery, characterized in that: The system (100) comprises: A detection module (130), the detection module (130) being configured to detect the ambient temperature and preload of the battery; A collection module (140), the collection module (140) being configured to collect a plurality of first expansion forces of the battery at a first frequency; a first acquisition module (150), the first acquisition module (150) being configured to acquire the state of charge data corresponding to each of the plurality of first expansion forces collected according to a comparison database storing the relationship between a plurality of preset expansion forces and corresponding state of charge data; and A calibration module (160) is configured to calibrate the state of charge of the battery based on the obtained state of charge data.
8. The system for calibrating the state of charge of a battery according to claim 7, characterized in that: The collection module (140) comprises a sensor (141) arranged in the battery, and the sensor (141) is configured to collect the plurality of first expansion forces.
9. The system for calibrating the state of charge of a battery according to claim 7, characterized in that: The plurality of first expansion forces include: one or more first expansion forces of the plurality of first expansion forces whose rate of change relative to the state of charge data is zero.
10. The system for calibrating the state of charge of a battery according to claim 7, characterized in that: The system (100) further comprises: a second acquisition module (110), the second acquisition module (110) being configured to acquire the plurality of preset expansion forces of the battery at a second frequency under different ambient temperatures and preloads, and state of charge data corresponding to each of the plurality of preset expansion forces; and A generation module (120) is configured to generate the comparison database based on a relationship between each preset expansion force of the plurality of preset expansion forces and corresponding state of charge data.
11. The system for calibrating the state of charge of a battery according to claim 10, characterized in that: The generating module (120) further comprises a marking device (121), wherein the marking device (121) is configured to mark the following expansion forces: one or more preset expansion forces among the plurality of preset expansion forces whose rate of change relative to the state of charge data is 0.
12. The system for calibrating the state of charge of a battery according to claim 10, characterized in that: The first frequency is greater than or equal to the second frequency.
13. A battery module, characterized in that: A system comprising one or more batteries and state of charge calibration of the battery according to any one of claims 7 to 12.