A method and system for assessing battery safety status

Abstract

This invention relates to the field of battery monitoring technology, and provides a method and system for assessing the safety status of a battery. The method includes: acquiring the State of Charge (SOC) of the battery under test before charging, as the initial SOC; acquiring the SOC interval including the initial SOC; and the initial and final charging temperatures of a standard battery within the SOC interval, and calculating the standard temperature rise of the battery under test; acquiring the ambient temperature, the ratio of the internal resistance of the battery under test, the ratio of the internal resistance of the standard battery, and the final charging temperature of the battery under test, and combining these with the standard temperature rise of the battery under test to calculate the safety status of the battery under test. This method has good generalization ability and can be directly applied to all types of batteries.

Description

Technical Field

[0001] This invention belongs to the field of battery monitoring technology, and in particular relates to a method and system for assessing battery safety status. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] With the accelerated global energy transition, electric vehicles will replace traditional gasoline-powered vehicles as the dominant force in the automotive market. Electric vehicles, using batteries as their energy storage medium, possess advantages that gasoline-powered vehicles cannot match, such as rapid acceleration, superior handling, and lower emissions. However, due to the immaturity of battery technology, battery operation is highly susceptible to uncontrollable phenomena. Fires, explosions, and thermal runaway significantly reduce the safety and reliability of electric vehicles. Therefore, accurately assessing the State of Safety (SOS) of electric batteries is of significant practical importance.

[0004] However, the safety mechanisms of large-scale batteries are unclear. They are dynamically coupled with multiple factors such as battery aging, operating conditions, environment, and regulatory control, making them highly complex, highly integrated, and strongly nonlinear systems. Safety risks are often hidden and gradual, and the mechanical and electrical connections between battery cells are highly coupled, meaning a fault in one cell can propagate to others (i.e., propagation). Therefore, quantitative assessment of power battery safety has become a technological bottleneck restricting the development of electric vehicles.

[0005] However, existing battery safety status evaluation standards only qualitatively analyze the impact of single factors such as aging, temperature, and operating conditions on battery safety in isolation. For example, the European Automotive Research and Development Council (EUCAR) has established an 8-level standard for qualitative battery safety assessment: "No impact," "Passive protection activated," "Defect present," "Minor venting or leakage," "Severe venting or leakage," "Rupture," "Fire," and "Explosion." But in practical applications, the safety differences between batteries of the same level are significant, lacking quantitative analysis and hindering proactive safety management.

[0006] With further exploration of battery mechanisms and safety risk characteristics, a number of novel SOS quantitative assessment methods have been proposed. However, these methods all suffer from shortcomings in accuracy or feasibility, making them difficult to apply in practice. Patent application number CN201810693627.8 establishes different evaluation indicators for different battery electrode materials and electrolyte compositions. This evaluation method results in different safety evaluation standards being used for different batteries, thus lacking generalizability. With the rapid development of new batteries, a quantitative SOS assessment standard should be applicable to all types of batteries.

[0007] Patents with application numbers CN202210934890.8, CN202210212963.2, and CN201610891196.7 all propose using battery voltage or battery capacity as important standards for quantitatively assessing safety status. However, these indicators only reflect the aging state of the battery, and battery aging does not necessarily mean a decline in safety. On the contrary, new batteries can also malfunction from time to time. Summary of the Invention

[0008] To address the technical problems mentioned above, this invention provides a battery safety status assessment method and system. Based on the constant current charging temperature rise starting from random SOC and combined with the battery aging state, the battery safety status is assessed. It has good generalization and can be directly applied to all types of batteries.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention provides a battery safety status assessment method, comprising:

[0011] The SOC of the battery under test before charging is obtained as the initial SOC. The SOC interval including the initial SOC is also obtained, as well as the initial and final charging temperatures of the standard battery under the SOC interval. The standard temperature rise of the battery under test is then calculated.

[0012] The ambient temperature, the ratio of the internal resistance of the battery under test, the ratio of the internal resistance of the standard battery, and the final charging temperature of the battery under test are obtained. Combined with the standard temperature rise of the battery under test, the safety status of the battery under test is calculated.

[0013] Furthermore, the safety status of the battery under test is as follows:

[0014]

[0015] in, T represents the standard temperature rise of the battery under test. ENV For ambient temperature, T end R is the final charging temperature of the battery under test. r and R c These are the ratios of the internal resistances of the battery under test and the standard battery, respectively, where n is an adjustable parameter, and SOH is the SOH value. t It is the ratio of the battery's full charge capacity to its rated capacity.

[0016] Furthermore, the standard temperature rise of the battery under test is:

[0017]

[0018] Among them, SOC b and SOC aT represents the two endpoints of the SOC interval, including the initial SOC. b and T a The initial charging temperature and final charging temperature of a standard battery at the SOC interval. t This is the initial SOC.

[0019] 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 a set SOC and at set intervals.

[0020] A second aspect of the present invention provides a battery safety status assessment system, comprising:

[0021] The first calculation module is configured to: obtain the SOC of the battery under test before charging as the initial SOC, and obtain the SOC interval including the initial SOC, as well as the initial charging temperature and final charging temperature of the standard battery under the SOC interval, and calculate the standard temperature rise of the battery under test.

[0022] The second calculation module is configured to: acquire the ambient temperature, the ratio of the internal resistance of the battery under test, the ratio of the internal resistance of the standard battery, and the final charging temperature of the battery under test; and calculate the safety status of the battery under test by combining the standard temperature rise of the battery under test.

[0023] Furthermore, the safety status of the battery under test is as follows:

[0024]

[0025] in, T represents the standard temperature rise of the battery under test. ENV For ambient temperature, T end R is the final charging temperature of the battery under test. t and R c These are the ratios of the internal resistances of the battery under test and the standard battery, respectively, where n is an adjustable parameter, and SOH is the SOH value. t It is the ratio of the battery's full charge capacity to its rated capacity.

[0026] Furthermore, the standard temperature rise of the battery under test is:

[0027]

[0028] Among them, SOC b and SOC a T represents the two endpoints of the SOC interval, including the initial SOC. b and T a The initial charging temperature and final charging temperature of a standard battery at the SOC interval. t This is the initial SOC.

[0029] 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 a set SOC and at set intervals.

[0030] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a battery safety status assessment method as described above.

[0031] A fourth aspect of the present invention provides a computer device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of a battery safety status assessment method as described above.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention provides a battery safety status assessment method, which uses constant current charging temperature rise starting from random SOC as the basis and combines it with battery aging status to assess battery safety status. It has good generalization and can be directly applied to all types of batteries.

[0034] This invention provides a battery safety status assessment method that decouples the effects of multiple states such as aging and temperature, resulting in accurate and objective evaluation results. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0036] Figure 1 This is a schematic diagram of the equivalent thermal model of Embodiment 1 of the present invention;

[0037] Figure 2 This is a schematic diagram of the open-circuit heat generation model according to Embodiment 1 of the present invention;

[0038] Figure 3 This is a schematic diagram of the short-circuit heat generation model according to Embodiment 1 of the present invention;

[0039] Figure 4 This is a graph showing the temperature change during 1C charging according to Embodiment 1 of the present invention.

[0040] Figure 5 This is a 1C charging temperature curve under the initial SOC = 0% condition of Embodiment 1 of the present invention;

[0041] Figure 6 This is a 1C charging temperature curve under the initial SOC = 60% condition of Embodiment 1 of the present invention. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0044] Example 1

[0045] This embodiment provides a battery safety status assessment method, based on the thermodynamic theory of power batteries and the fault evolution mechanism, taking the constant current charging temperature rise starting from the random state of charge (SOC) as the basis, and combining the battery aging status.

[0046] like Figure 1 The figure shown is an equivalent thermal model of a lithium-ion battery, the principle of which is as follows:

[0047]

[0048]

[0049] Where c1 represents the internal heat capacity of the lithium-ion battery, c2 represents the surface heat capacity, T1 represents the internal temperature, T2 represents the surface temperature, T3 represents the ambient temperature, Q represents the internal heat source, R1 represents the internal thermal resistance, and R2 represents the surface thermal resistance.

[0050] Combining equations (1) and (2), it can be seen that 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, under the same ambient temperature, the surface temperature of the battery can directly reflect the internal heat generation.

[0051] According to battery failure theory and with reference to various battery failure models, it can be known that a faulty battery will generate another heat source at the cell during charging. Figure 2 This is an open-circuit model of the battery's internal structure. A large amount of heat is accumulated on the open-circuit resistor, causing the surface temperature to rise rapidly. Figure 3 In the internal short-circuit model of the battery, the short-circuit resistance shunting current leads to an increase in total current, resulting in increased heat generation and a faster rate of surface temperature rise. Other fault models, such as excessive lithium plating and severe side reactions, produce similar effects. Therefore, battery surface temperature can serve as a decisive indicator for evaluating the battery's safety status.

[0052] Assuming the initial SOC of the battery is 0, the SOS is defined in this invention as follows:

[0053]

[0054] Among them, T end The final charging temperature of the battery under test; T ENDThe standard battery charging temperature for good safety; T ENV R represents ambient temperature. t and R c These are the ratios of the internal resistances of the battery under test and the standard battery, respectively; n is an adjustable parameter, which takes a positive value and can be adjusted appropriately according to the usage scenario. When the battery has good safety, the final charging temperature should be close to that of the standard battery. At this time, the SOS value is close to 100%, indicating that the battery has good safety. When a battery has a safety problem, due to the introduction of an additional heat source, the final charging temperature will be higher than that of the standard battery. At this time, the SOS value is lower than 100%, indicating that the battery has some safety problems. The severity of the safety problem can be defined by the degree to which the SOS value deviates from 100%. The smaller the SOS value, the worse the battery safety, as shown in Table 1. For the aging correction project, the impact of increased internal resistance and ohmic heat caused by battery aging on performance indicators is decoupled. At the same final temperature, a lower ohmic internal resistance indicates more additional heat generation and poorer battery safety.

[0055] Table 1. SOS Assessment Levels for Power Batteries

[0056] grade SOS Safety level 1 80％-100％ good 2 60％-80％ generally 3 0％-60％ Danger

[0057] In practical applications, the initial SOC is uncertain. Therefore, this invention generalizes the above formula to make it applicable to testing batteries with all initial SOCs. To this end, it is necessary to ensure that the final temperature of the battery is thermally consistent at any initial SOC, i.e., the temperature at which thermal equilibrium is reached or not reached.

[0058] Figure 4 The curves showing the surface temperature change over time when a battery is charged at 1C constant current from an initial state of 0% SOC are presented. It can be seen that the battery surface temperature has not yet reached thermal equilibrium at the end of charging. This indicates that the surface temperature of a battery starting charging at any SOC will not reach thermal equilibrium. Therefore, the final temperature of constant current charging at different initial SOCs exhibits formal consistency.

[0059] Under this premise, the SOS formula is defined as follows:

[0060]

[0061]

[0062] A standard battery was charged at its initial State of Charge (SOC) (set SOC), with 5% intervals between each set value, using a 1C constant current charge test at 20%–80% SOC. This resulted in 13 sets of final charging temperatures (e.g., charging tests at 1C current were performed at SOCs of 20%, 25%, 30%,…80% for the standard battery), thus obtaining 13 SOC intervals. These were used as a standard for comparing and evaluating the temperature rise of the battery under test. Where T… b and T a This refers to the final charging temperature of a standard battery within different SOC ranges, specifically the initial and final charging temperatures of the standard battery within the SOC interval, including the initial SOC of the battery under test. b and SOC a This refers to the right endpoint of different SOC ranges for a standard battery, i.e., SOC. b and SOC a T represents the two endpoints of the SOC interval, including the initial SOC. ENV , The meaning is the same as above; SOC t The initial SOC of the battery under test; The standard temperature rise of the battery under test at its initial state of charge (SOC); SOH t This is the battery health status defined by capacity. Its value is the ratio of the battery's full charge capacity to its rated capacity, used to eliminate temperature rise errors caused by differences in charging capacity.

[0063] The control conditions are: ① Ambient temperature T ENV =25℃; ②Initial battery temperature T b =25℃; ③ Constant charging current.

[0064] Figure 5 This section presents the simulated charging temperature rise curves for the standard battery and the battery under test, both under initial state of charge (SOC) of 0%. The battery under test has an SOH of 100% and an internal resistance equal to that of the standard battery, i.e., R. t = c According to the evaluation method proposed in this invention, the SOS of the battery under test can be calculated by the following formula:

[0065]

[0066] As shown in Table 1, the battery is in good safety condition and can be used normally.

[0067] Figure 6 Simulated charging temperature rise curves for the standard battery and the battery under test under an initial SOC of 60%. The battery under test has a SOH of 90% and an internal resistance equal to that of the standard battery. According to the evaluation method proposed in this invention, the SOS of the battery under test can be calculated using the following formula:

[0068]

[0069] As shown in Table 1, the battery's safety level is in a normal state. It is necessary to check for potential faults to prevent safety accidents.

[0070] This embodiment provides a battery safety status assessment method that quantifies the assessment results with high resolution; it has good generalization and can be directly applied to all types of batteries; it decouples the effects of multiple states such as aging and temperature, resulting in accurate and objective evaluation results.

[0071] Example 2

[0072] This embodiment provides a battery safety status assessment system, which specifically includes:

[0073] The first calculation module is configured to: obtain the SOC of the battery under test before charging as the initial SOC, and obtain the SOC interval including the initial SOC, as well as the initial charging temperature and final charging temperature of the standard battery under the SOC interval, and calculate the standard temperature rise of the battery under test.

[0074] The second calculation module is configured to: acquire the ambient temperature, the ratio of the internal resistance of the battery under test, the ratio of the internal resistance of the standard battery, and the final charging temperature of the battery under test; and calculate the safety status of the battery under test by combining the standard temperature rise of the battery under test.

[0075] It should be noted that each module in this embodiment corresponds one-to-one with each step in Embodiment 1, and their specific implementation processes are the same, so they will not be repeated here.

[0076] Example 3

[0077] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of a battery safety status assessment method as described in Embodiment 1 above.

[0078] Example 4

[0079] This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the battery safety status assessment method described in Embodiment 1 above.

[0080] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of hardware embodiments, software embodiments, or embodiments combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage) containing computer-usable program code.

[0081] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0082] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0083] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0084] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for assessing the safety status of a battery, characterized in that, include: The SOC of the battery under test before charging is obtained as the initial SOC. The SOC interval including the initial SOC is also obtained, as well as the initial and final charging temperatures of the standard battery under the SOC interval. The standard temperature rise of the battery under test is then calculated. The ambient temperature, the ratio of the internal resistance of the battery under test, the ratio of the internal resistance of the standard battery, and the final charging temperature of the battery under test are obtained. Combined with the standard temperature rise of the battery under test, the safety status of the battery under test is calculated. The safety status of the battery under test is: ;in, This represents the standard temperature rise of the battery under test. For ambient temperature, The final charging temperature of the battery under test. and These are the ratios of the internal resistance of the battery under test and the standard battery, respectively. It is an adjustable parameter. This is the ratio of the battery's full charge capacity to its rated capacity. The standard temperature rise of the battery under test is: ;in, The two endpoints of the SOC interval, including the initial SOC. The initial charging temperature and final charging temperature of a standard battery at the SOC interval. This is the initial SOC.

2. The battery safety status assessment method as described in claim 1, characterized in that, 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 a set SOC and at set intervals.

3. A battery safety status assessment system, characterized in that, include: The first calculation module is configured to: obtain the SOC of the battery under test before charging as the initial SOC, and obtain the SOC interval including the initial SOC, as well as the initial charging temperature and final charging temperature of the standard battery under the SOC interval, and calculate the standard temperature rise of the battery under test. The second calculation module is configured to: acquire the ambient temperature, the ratio of the internal resistance of the battery under test, the ratio of the internal resistance of the standard battery, and the final charging temperature of the battery under test; and calculate the safety status of the battery under test by combining the standard temperature rise of the battery under test. The safety status of the battery under test is: ;in, This represents the standard temperature rise of the battery under test. For ambient temperature, The final charging temperature of the battery under test. and These are the ratios of the internal resistance of the battery under test and the standard battery, respectively. It is an adjustable parameter. This is the ratio of the battery's full charge capacity to its rated capacity. The standard temperature rise of the battery under test is: ;in, The two endpoints of the SOC interval, including the initial SOC. The initial charging temperature and final charging temperature of a standard battery at the SOC interval. This is the initial SOC.

4. The battery safety status assessment system as described in claim 3, characterized in that, The initial and final charging temperatures of the standard battery were obtained by performing a 1C constant current charging test on the standard battery at a set SOC and at set intervals.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the battery safety status assessment method as described in any one of claims 1-2.

6. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the battery safety status assessment method as described in any one of claims 1-2.

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