Battery safety state evaluation method and system

Abstract

The present invention relates to the technical field of battery monitoring, and provides a battery safety state evaluation method and system, which includes the steps of: obtaining the SOC of a test battery before charging as an initial SOC; obtaining an SOC interval including the initial SOC, as well as the initial charging temperature and final charging temperature of a standard battery during the SOC interval, and calculating a standard temperature rise of the test battery; and obtaining an environmental temperature, an internal resistance ratio of the test battery, an internal resistance ratio of the standard battery, and the final charging temperature of the test battery, and using these, together with the standard temperature rise of the test battery, to calculate the safety state of the test battery. The present invention has good versatility and can be directly applied to all kinds of batteries.

Description

[Technical Field]

[0001] This invention claims priority to a Chinese patent application filed with the China Patent Office on January 29, 2023, bearing application number 202310076672.X and entitled "Battery Safety State Assessment Method and System," the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the technical field of battery monitoring, and in particular to a method and system for evaluating the safety state of a battery. [Background technology]

[0003] The discussion in this section merely provides background information related to the present invention and does not necessarily constitute prior art.

[0004] As the global energy transition accelerates, electric vehicles are replacing traditional fuel-powered vehicles and dominating the automotive market. Electric vehicles that use power batteries as their energy storage medium offer unparalleled advantages over fuel-powered vehicles, including rapid acceleration, good maneuverability, and low pollutant emissions. However, power battery technology is still immature, making battery operation prone to uncontrollable events. Phenomena such as fire, explosion, and thermal runaway can significantly reduce the safety and reliability of electric vehicles. Therefore, accurately assessing the state of safety (SOS) of power batteries is of great practical significance.

[0005] However, the safety mechanisms of large-scale batteries are unknown because they are affected by multiple dynamically intertwined factors, including battery aging, operating conditions, the environment, and management. They are highly complex, highly integrated, and strongly nonlinear systems. Safety risk factors are often hidden and change gradually, and the high degree of coupling between the mechanical and electrical connections between battery cells means that a failure in one cell can propagate to other cells (i.e., propagation). Therefore, quantitative evaluation of the safety of power batteries has become a technological bottleneck that limits the development of electric vehicles.

[0006] However, conventional battery safety assessment criteria are limited to individual qualitative analysis of the impact of single factors such as aging, temperature, and operating conditions on battery safety. For example, the European Council for Automotive Research and Development (EUCAR) has established eight qualitative assessment criteria for battery safety: "no impact," "passive protection activated," "defective," "minor ventilation or leakage," "severe ventilation or leakage," "rupture," "fire," and "explosion." However, in actual applications, there is a large variation in battery safety even within the same level, making active safety management impossible without quantitative analysis.

[0007] With further exploration of battery mechanisms and safety risk characteristics, a series of new SOS quantitative evaluation methods have been proposed. However, these methods all suffer from deficiencies in accuracy and feasibility, making them difficult to put into practical use. Patent application number CN201810693627.8 formulates different evaluation indices for different battery electrode materials and electrolyte components. This evaluation method lacks versatility because different safety evaluation standards are used for different batteries. Due to the rapid production of new batteries, SOS quantitative evaluation standards must be applicable to all types of batteries.

[0008] Patents with application numbers CN202210934890.8, CN202210212963.2, and CN201610891196.7 all propose using battery voltage or battery capacity as an important criterion for quantitatively assessing safety. However, these indicators only reflect the aging state of the battery, and aging does not necessarily mean a decrease in safety. On the other hand, even new batteries can fail. Summary of the Invention

[0009] In order to solve the technical problems existing in the background art described above, the present invention provides a method and system for evaluating the safety state of a battery, which is versatile and directly applicable to all kinds of batteries, by evaluating the safety state of a battery based on the temperature rise during constant current charging starting from a random SOC as well as the aging state of the battery.

[0010] To achieve the above objectives, the present invention adopts the following technical solutions.

[0011] A first aspect of the present invention is obtaining the SOC of the test battery before charging as an initial SOC, obtaining an SOC interval including the initial SOC, and the initial charging temperature and final charging temperature of the standard battery during the SOC interval, and calculating the standard temperature rise of the test battery; obtaining the environmental temperature, the internal resistance ratio of the battery under test, the internal resistance ratio of the standard battery, and the final charge temperature of the battery under test, and using these together with the standard temperature rise of the battery under test to calculate the safe state of the battery under test; The present invention provides a battery safety state evaluation method, including:

[0012] Furthermore, the safety status of the test battery is

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[0013] Furthermore, the standard temperature rise of the test battery is

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[0014] Furthermore, the initial charging temperature and final charging temperature of the standard battery are obtained by performing a 1C constant current charging test on the standard battery at set intervals according to a set SOC.

[0015] A second aspect of the present invention is a first calculation module configured to obtain an SOC of the test battery before charging as an initial SOC, obtain an SOC interval including the initial SOC, and an initial charging temperature and a final charging temperature of a standard battery during the SOC interval, and calculate a standard temperature rise of the test battery; a second calculation module configured to obtain the environmental temperature, the internal resistance ratio of the battery under test, the internal resistance ratio of the standard battery, and the end-of-charge temperature of the battery under test, and use the obtained temperature together with the standard temperature rise of the battery under test to calculate a safe state of the battery under test; A battery safety state assessment system is provided.

[0016] Furthermore, the safety status of the test battery is

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[0017] Furthermore, the standard temperature rise of the test battery is

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[0018] Furthermore, the initial charging temperature and final charging temperature of the standard battery are obtained by performing a 1C constant current charging test on the standard battery at set intervals according to a set SOC.

[0019] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored therein, the computer-readable storage medium enabling the steps of the battery safety state evaluation method described above to be realized when the program is executed by a processor.

[0020] A fourth aspect of the present invention provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor, wherein when the program is executed by the processor, the computer device realizes the steps of the battery safety state evaluation method described above.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a battery safety state evaluation method that is versatile and directly applicable to all types of batteries by evaluating the battery safety state based on the temperature rise during constant current charging starting from a random SOC as well as the aging state of the battery.

[0022] The present invention provides a battery safety state assessment method that separates the effects of multiple conditions such as aging and temperature, making the assessment results accurate and objective.

[0023] The accompanying drawings of the specification, which form a part of the present invention, are used to further understand the present invention, and the exemplary embodiments of the present invention and their descriptions are for interpreting the present invention and are not intended to unduly limit the present invention. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 2 is a schematic diagram of an equivalent thermal model according to the first embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram of an open-circuit heat generation model according to a first embodiment of the present invention. [Figure 3] FIG. 1 is a schematic diagram of a short-circuit heat generation model according to a first embodiment of the present invention. [Figure 4] 1 is a graph showing a change in temperature during 1C charging in Example 1 of the present invention. [Figure 5] 1 is a graph showing the 1C charging temperature under the condition of initial SOC=0% in Example 1 of the present invention. [Figure 6] 1 is a graph showing the 1C charging temperature under the condition of initial SOC=60% in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will now be further described with reference to the accompanying drawings and examples.

[0026] It should be pointed out that the following detailed description is all exemplary to further explain the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art.

[0027] Example 1 This embodiment provides a battery safety state assessment method based on the thermodynamic theory and failure progression mechanism of power batteries, which is based on the temperature rise during constant current charging starting from a random state of charge (SOC) as well as the aging state of the battery.

[0028] Figure 1 shows the equivalent thermal model of a lithium-ion battery, and its principle is as follows.

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[0029] As can be seen from the simultaneous equations (1) and (2), the surface temperature of the battery is mainly determined by the diffusion of internal heat to the surface and the dissipation of surface heat to the environment. Therefore, when the environmental temperature is the same, the surface temperature of the battery can directly reflect the state of internal heat generation.

[0030] Based on battery failure theory, and considering various types of battery failure models, we can see that a failed battery generates additional heat sources in the cell during charging. Figure 2 shows a battery's internal open circuit model, in which a large amount of thermal energy is stored in the open circuit resistor, causing a rapid rise in the surface temperature. Figure 3 shows a battery's internal short circuit model, in which the shunting of the short circuit resistor increases the total current, increasing the amount of heat generated and accelerating the rise in surface temperature. Similar effects occur in other failure models, such as massive lithium deposition and serious side reactions. Therefore, the battery's surface temperature can be used as a decisive indicator for evaluating the battery's safety status.

[0031] In the present invention, assuming that the initial SOC of the battery is 0, the SOS is defined as follows:

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[0032] [Table 1] In practical applications, the initial SOC is uncertain. Therefore, in this invention, the above formula is generalized so that it can be used to test batteries with any initial SOC. To do this, it is necessary to ensure that the final temperature of the battery is thermally consistent, i.e., the temperature is in a state where thermal equilibrium is reached or not reached, regardless of the initial SOC.

[0033] Figure 4 shows the time-dependent change in the battery surface temperature during 1C constant current charging from an initial state of 0% SOC. It can be seen that the battery surface temperature has not yet reached thermal equilibrium at the end of charging. This indicates that regardless of the SOC at which charging begins, the battery surface temperature will not reach thermal equilibrium. Therefore, when the initial SOC is different, the final temperature during constant current charging is formally consistent.

[0034] Under these assumptions, in the present invention, the SOS formula is defined as follows:

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[0035] The control conditions are: (1) ambient temperature T ENV =25℃, (2) Battery initial temperature T b = 25°C, (3) constant charging current.

[0036] Figure 5 shows the simulated temperature rise curves of the standard battery and the test battery under the condition that the initial SOH is 0%. The test battery has SOH=100% and the same internal resistance as the standard battery, i.e., R t =R c According to the evaluation method proposed in the present invention, the SOS of the test battery can be calculated using the following formula:

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[0037] Figure 6 shows the simulated charging temperature rise curves for a standard battery and a test battery under the condition that the initial SOC is 60%. The test battery has an SOH of 90% and is known to have the same internal resistance as the standard battery. According to the evaluation method proposed in this invention, the SOS of the test battery can be calculated using the following formula:

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[0038] The battery safety state assessment method provided in this embodiment quantifies the assessment results, has high resolution, is versatile, and can be directly applied to all kinds of batteries. It separates the influences of multiple conditions such as aging and temperature, and the assessment results are accurate and objective.

[0039] Example 2 In this embodiment, a first calculation module configured to obtain an SOC of the test battery before charging as an initial SOC, obtain an SOC interval including the initial SOC, and an initial charging temperature and a final charging temperature of a standard battery during the SOC interval, and calculate a standard temperature rise of the test battery; and a second calculation module configured to obtain the environmental temperature, the internal resistance ratio of the battery under test, the internal resistance ratio of the standard battery, and the final charge temperature of the battery under test, and use them together with the standard temperature rise of the battery under test to calculate the safety state of the battery under test.

[0040] It should be noted here that each module in this embodiment corresponds one-to-one to each step in the first embodiment, and the specific implementation process is similar, so it will not be described again here.

[0041] Example 3 This embodiment provides a computer-readable storage medium storing a computer program, which, when executed by a processor, realizes the steps of the battery safety state evaluation method described in the above-described first embodiment.

[0042] Example 4 This embodiment provides a computer device including a memory, a processor, and a computer program stored in the memory and executable by the processor, whereby, when the program is executed by the processor, the steps of the battery safety state evaluation method described in the above-mentioned embodiment 1 are realized.

[0043] Those skilled in the art will appreciate that embodiments of the present invention may be provided as a method, a system, or a computer program product. Accordingly, the present invention may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product embodied in one or more computer-usable storage media (including, but not limited to, magnetic disk memory, optical memory, etc.) containing computer-usable program code.

[0044] The present invention has been described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program commands. These computer program commands can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to form an apparatus, whereby the commands executed by the processor of the computer or other programmable data processing device form an apparatus for implementing the functions specified in one or more flows in the flowcharts and / or one or more blocks in the block diagrams.

[0045] These computer program instructions may be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, thereby forming an article of manufacture that includes a command apparatus that implements the functions specified in one or more flows of the flowcharts and / or one or more blocks of the block diagrams by the commands stored in the computer-readable memory.

[0046] These computer program instructions may be loaded into a computer or other programmable data processing device, causing the computer or other programmable device to perform a series of operational steps to generate a computer-implemented process, the commands executed by the computer or other programmable device providing steps for implementing the functions specified in one or more flows of the flowcharts and / or one or more blocks of the block diagrams.

[0047] As will be understood by those skilled in the art, all or part of the steps in the above-described method embodiments can be realized by instructing relevant hardware using a computer program, and the program may be stored in a computer-readable storage medium, which, when executed, may include the steps of the above-described method embodiments. Here, the storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), etc.

[0048] The above description is merely a preferred embodiment of the present invention, and is not intended to limit the present invention. Those skilled in the art can make various modifications and variations to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. acquiring the SOC of the test battery before charging as an initial SOC, acquiring an SOC interval including the initial SOC, and the initial charge temperature and final charge temperature of the standard battery in the SOC interval, and calculating a standard temperature rise of the test battery; obtaining the environmental temperature, the internal resistance ratio of the battery under test, the internal resistance ratio of the standard battery, and the final charge temperature of the battery under test, and using these together with the standard temperature rise of the battery under test to calculate the safe state of the battery under test; A battery safety state evaluation method comprising:

2. The safety status of the test battery is [0013] is the standard temperature rise of the battery under test, and T ＥＮＶ is the ambient temperature, and T ｅｎｄ is the final charging temperature of the battery under test, and R ｔ and R ｃ are the internal resistance ratios of the test battery and the standard battery, respectively, n is an adjustable parameter, and SOH ｔ 2. The method for evaluating the safety state of a battery according to claim 1, wherein the ratio of the fully charged capacity of the battery to the rated capacity is

3. The standard temperature rise of the test battery is: [0014] and However, SOC ｂ and SOC ａ are the two endpoints of the SOC interval that includes the initial SOC, and T ｂ and T ａ are the initial and final charging temperatures of a standard battery in the SOC interval, and SOC ｔ 2. The method for evaluating a battery safety state according to claim 1, wherein: is an initial SOC.

4. 2. The battery safety state evaluation method according to claim 1, wherein the initial charging temperature and the final charging temperature of the standard battery are obtained by performing a 1 C constant current charging test on the standard battery at set intervals in accordance with a set SOC.

5. a first calculation module configured to obtain an SOC of the test battery before charging as an initial SOC, obtain an SOC interval including the initial SOC, and an initial charge temperature and a final charge temperature of a standard battery in the SOC interval, and calculate a standard temperature rise of the test battery; a second calculation module configured to obtain the environmental temperature, the internal resistance ratio of the battery under test, the internal resistance ratio of the standard battery, and the end-of-charge temperature of the battery under test, and use the obtained temperature together with the standard temperature rise of the battery under test to calculate a safe state of the battery under test; A battery safety state evaluation system comprising:

6. The safety status of the test battery is [Equation 15] is the standard temperature rise of the battery under test, and T ＥＮＶ is the ambient temperature, and T ｅｎｄ is the final charging temperature of the battery under test, and R ｔ and R ｃ are the internal resistance ratios of the test battery and the standard battery, respectively, n is an adjustable parameter, and OH ｔ 6. The battery safety state evaluation system according to claim 5, wherein the ratio of the fully charged capacity of the battery to the rated capacity is .

7. The standard temperature rise of the test battery is: [0016] and However, SOC ｂ and SOC ａ are the two endpoints of the SOC interval that includes the initial SOC, and T ｂ and T ａ are the initial and final charging temperatures of a standard battery in the SOC interval, and SOC ｔ 6. The battery safety state evaluation system according to claim 5, wherein: is an initial SOC.

8. 6. The battery safety state evaluation system according to claim 5, wherein the initial charging temperature and the final charging temperature of the standard battery are obtained by performing a 1 C constant current charging test on the standard battery at set intervals in accordance with a set SOC.

9. A computer-readable storage medium having a computer program stored therein, the computer-readable storage medium being characterized in that, when the program is executed by a processor, the steps of the battery safety state evaluation method according to any one of claims 1 to 4 are realized.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor, wherein when the program is executed by the processor, the steps of the battery safety state evaluation method according to any one of claims 1 to 4 are realized.

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