Electric bicycle potential safety hazard assessment method

Abstract

The invention discloses a potential safety hazard assessment method for an electric bicycle. The method comprises the following steps: performing appearance inspection on a battery pack of the electric bicycle; scanning a battery pack label of the electric bicycle to obtain model information, and calling an OCV-SOC mapping relation of a corresponding model; collecting the voltage and temperature of the current battery pack, and calculating the SOC of the current battery pack in combination with the OCV-SOC mapping relation; measuring electrochemical impedance spectroscopy data of the battery pack, constructing a fractional-order impedance model according to the electrochemical impedance spectroscopy data, extracting health state key parameters in the fractional-order impedance model, and inputting the health state key parameters into the key parameter-SOC-SOH mapping model to calculate SOH to obtain SOH; bMS information of the electric bicycle is obtained, a low-temperature and high-SOC charging behavior is extracted from the BMS information, relaxation voltage differential after the charging behavior is calculated, the lithium precipitation possibility of the battery pack is judged, and a lithium precipitation judgment result is obtained; and generating a comprehensive safety evaluation conclusion of the electric bicycle according to the result.

Description

Technical Field

[0001] The present invention belongs to the field of battery safety detection and relates to a method for evaluating potential safety hazards of electric bicycles. Background Art

[0002] Electric bicycles powered by lithium-ion batteries have advantages such as long cycle life, high cruising range, and lightweight. The trend of "lithium-ionization" of electric bicycles has gradually emerged. However, with the development of lithium-battery electric bicycles, fire accidents occur frequently. The quality of battery products for electric bicycles varies. Some merchants and consumers, in order to reduce costs and investment, illegally modify electric bicycles, use second-life batteries, batteries without safety certification, or even scrapped batteries from electric vehicles. The battery management system has incomplete or missing functions. In addition, electric bicycles are relatively cheaper than other means of transportation, and consumers have low enthusiasm for maintenance. The battery usage environment is poor, which may increase the probability of the battery being exposed to rain, immersed in water, vibrated, or collided, affecting the charging and usage safety of electric bicycles.

[0003] For in-service electric bicycles, the previous supervision measures are insufficient, the battery safety is poor, and the management level is low. There is an urgent need to evaluate and investigate potential safety hazards of in-service batteries.

[0004] Currently, the methods for battery safety monitoring and evaluation mainly include the evaluation of charging temperature, state of health, and state of safety. Chinese invention patent CN116080472B discloses a comprehensive monitoring method for electric bicycle batteries based on fire safety, which determines the highest charging temperature through the apparent information of the battery and evaluates the temperature rise safety of the battery. Chinese patent application CN115389949A discloses a method for evaluating and warning the safety of electric bicycle batteries based on vehicle-cloud collaboration. The high-frequency acquisition data of the electric bicycle BMS is aggregated to the cloud via Bluetooth, and a battery safety risk assessment model is established in the cloud to achieve the early perception of battery failure risks. Chinese invention patent CN102520366B discloses an electric vehicle battery safety and health assessment system and its method. By performing rapid charge and discharge tests on the electric vehicle battery, voltage, current, and temperature information is collected and input into an algorithm model to evaluate the state of safety, state of health, and remaining battery capacity.

[0005] However, the above methods only detect and evaluate single problems of the battery and cannot comprehensively judge the safety of the battery. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for evaluating potential safety hazards of electric bicycles, which can comprehensively judge the safety of the battery and achieve a comprehensive investigation of potential safety hazards of lithium-ion batteries in in-service electric bicycles.

[0007] To achieve the above object, the present invention is implemented by the following technical solutions: A method for evaluating potential safety hazards of an electric bicycle, comprising the following processes: Perform an appearance inspection on the battery pack of the electric bicycle to detect whether there is any deformation of the housing and leakage of the electrolyte, and obtain the appearance inspection result; Scan the battery pack label of the electric bicycle to obtain the model information, and retrieve the OCV-SOC mapping relationship corresponding to the model in the electric bicycle database; Collect the voltage and temperature of the current battery pack, and calculate the current battery pack SOC in combination with the OCV-SOC mapping relationship; Measure the electrochemical impedance spectroscopy data of the battery pack, construct a fractional-order impedance model based on the electrochemical impedance spectroscopy data, extract the key parameters of the health state in the fractional-order impedance model, and input them into the key parameter-SOC-SOH mapping model to calculate the SOH, and obtain the SOH; Obtain the BMS information of the electric bicycle, extract the charging behavior at low temperature and high SOC from the BMS information, calculate the relaxation voltage differential after this charging behavior, and judge the possibility of lithium plating of the battery pack to obtain the lithium plating determination result; Integrate the appearance inspection result, SOH and lithium plating determination result to generate a comprehensive safety assessment conclusion of the electric bicycle.

[0008] Preferably, the electric bicycle database includes the nominal capacity, the upper limit of the battery pack voltage, the lower limit of the battery pack voltage, the highest operating temperature, the lowest operating temperature, the OCV-SOC mapping relationship and the key parameter-SOC-SOH mapping model corresponding to the lithium-ion batteries of different models of electric bicycles.

[0009] Preferably, measure the electrochemical impedance spectroscopy data of the battery pack in the frequency range of 0.1 Hz - 1 kHz.

[0010] Preferably, the fractional-order impedance model includes an inductor, an ohmic internal resistance, a charge transfer impedance with a distributed time constant and a diffusion impedance.

[0011] Preferably, the process of extracting the key parameters of the health state in the fractional-order impedance model is: using the nonlinear least squares method for parameter identification of the fractional-order impedance model to extract the key parameters of the health state.

[0012] Preferably, judge whether it is over-service life through the SOH, and the judgment standard for over-service life is that the SOH capacity is less than 80% or the SOH internal resistance is greater than 200%.

[0013] Preferably, the BMS information includes historical SOC, current, voltage, temperature and absolute time.

[0014] Preferably, the process of obtaining the BMS information of an electric bicycle and extracting the charging behavior at low temperature and high SOC from the BMS information is as follows: wirelessly transmit the BMS stored information to the platform by Bluetooth, and intelligently determine whether there is battery temperature information. If there is temperature information, extract the charging behavior at low temperature and high SOC. If there is no temperature information, query the ambient temperature of the area corresponding to the absolute time of the BMS through the network to obtain historical temperature information.

[0015] Preferably, the process of determining whether lithium plating occurs in the battery pack is as follows: extract the charging behavior with SOC≥90% and temperature<0℃ at the end of charging. If there is no such behavior, it is determined that no lithium plating occurs. Furthermore, extract the lithium plating voltage platform signal according to the relaxation voltage curve. If a relaxation voltage platform appears, it is determined that lithium plating occurs. If there is no relaxation voltage platform, it is determined that there is a probability of lithium plating.

[0016] Preferably, in the comprehensive safety assessment conclusion of an electric bicycle, if there are appearance problems or SOH<80% or certain lithium plating, it is evaluated as the scrapped level; if there are no appearance problems and SOH≥80% and no lithium plating occurs, it is evaluated as the safe level, and in other cases, it is determined as the warning level.

[0017] Compared with the prior art, the present invention has the following beneficial effects: Through appearance scanning, electrochemical impedance spectroscopy testing, and lithium plating detection and calculation, the present invention can comprehensively judge the safety of the battery, realize a comprehensive safety hazard investigation of the lithium-ion battery of in-service electric bicycles, and without wasting manpower, with a small test power and cost savings. Combining the appearance scanning and the internal frequency sweeping based on electrochemical impedance spectroscopy for the grasping ability of the battery appearance and internal safety characteristics, it improves the accuracy of safety hazard investigation, can be applied to all categories of lithium-ion batteries of electric bicycles, and solves the problem of difficult self-safety hazard assessment caused by problems such as the lack of BMS acquisition ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flowchart of the method for assessing safety hazards of an electric bicycle according to the present invention; Figure 2 is a schematic diagram of the fractional-order impedance model for extracting key parameters of the health state according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms "mounted", "connected" and "coupled" should be interpreted broadly. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection, an electrical connection or a connection capable of mutual communication; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0022] In the present invention, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include direct contact between the first and second features, or may include the first and second features not being in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "beneath" and "under" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0023] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. This repetition is for the purpose of simplification and clarity and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0024] As Figure 1 shown, the following is the method for evaluating potential safety hazards of an electric bicycle according to this embodiment. The investigation of potential battery safety hazards is based on external scanning, internal frequency sweeping using electrochemical impedance spectroscopy, and lithium plating judgment based on BMS data, and includes the following steps: Step 1), scan the appearance of the electric bicycle battery pack 360° to determine whether there are problems such as deformation and leakage, and obtain the appearance detection result. If there are appearance problems, stop the current test and prompt to further check at a professional inspection point; if there are no appearance problems, go to Step 2).

[0025] Step 2), scan the label of the electric bicycle battery pack, obtain the battery model, query the electric bicycle database, and extract the battery information.

[0026] Step 3), collect the voltage and temperature of the battery pack, and extract the current SOC (state of charge) of the battery pack according to the OCV-SOC mapping relationship of this type of battery.

[0027] Step 4), use electrochemical impedance spectroscopy to scan the battery pack at different frequencies and extract the AC impedance of the battery pack.

[0028] Step 5), adopt a fractional-order impedance model to extract the key parameters of the health state. After temperature correction, use the key parameter-SOC-SOH mapping model to calculate the SOH, obtain the SOH, and judge whether it is overdue for service.

[0029] The SOH is the battery health state, which is defined as the ratio of the actual value to the initial nominal value of the battery performance parameters under standard conditions (room temperature) * 100%, and is characterized by capacity or internal resistance.

[0030] Step 6), upload the BMS information of this vehicle, including historical SOC, current, voltage, temperature, and absolute time.

[0031] Step 7), according to the data of SOC, voltage, temperature, and absolute time during charging, extract the charging behavior at low temperature and high SOC, calculate the differential of the relaxation voltage after this charging behavior. The relaxation voltage differential is obtained by differentiating the battery terminal voltage with respect to time during the rest time after charging ends. Determine the possibility of lithium plating in the battery based on the relaxation voltage differential result, and obtain the lithium plating determination result.

[0032] Step 8), based on the battery appearance inspection result, SOH, and lithium plating determination result, give a comprehensive safety evaluation of the electric bicycle battery. If there is any abnormality, report it to the superior department at the same time.

[0033] Specifically in this embodiment, in step 1), the evaluator uses a high-definition camera to perform a 360° scan on the electric bicycle battery pack, and uses image recognition technology to analyze the collected images. In this example, the image analysis result shows that there are no obvious deformations, cracks, bulges, or leakage traces on the surface of the battery pack. The battery pack shell is intact, and the fixing screws are not loose. Therefore, it is determined that the appearance of the battery pack is normal, and the next test is continued.

[0034] Specifically in this embodiment, the electric bicycle database information in step 2) includes information such as the nominal capacity corresponding to the lithium-ion battery of different models of electric bicycles, the upper limit of the battery pack voltage, the lower limit of the battery pack voltage, the highest operating temperature, the lowest operating temperature, the OCV-SOC mapping relationship, the key parameter-SOC-SOH mapping model, etc.

[0035] Specifically in this embodiment, for the electrochemical impedance spectroscopy test in step 4), the scanning frequency range is preferably 0.1 Hz - 1 kHz, with 41 frequency points. Considering the following two aspects: First, this frequency band can cover the entire frequency band reaction processes of electron and ion movement, interfacial electrochemical reaction, and diffusion in the battery; Second, the detection speed time of the AC internal resistance within this frequency band can be controlled within 5 minutes, and the evaluation duration is relatively short.

[0036] Specifically in this embodiment, the fractional-order impedance model in step 5) is as Figure 2 , the fractional-order impedance model includes an inductor L , ohmic internal resistance R 0, a charge transfer impedance with a distributed time constant (charge transfer resistance R ct and double-layer interfacial capacitance C dl in parallel) and a Warburg impedance element C w . The battery frequency-domain impedance formula is , and then the nonlinear least squares method is used for fractional-order impedance model parameter identification, and key health state parameters such as R 0, R ct ,C dl and C w 。

[0037] Specifically in this embodiment, the judgment criterion for over-service in step 5) is that SOH (capacity) is less than 80% or SOH (internal resistance) is greater than 200%.

[0038] Specifically in this embodiment, in step 6), the BMS stored information is wirelessly transmitted to the platform by Bluetooth, and it is intelligently judged whether there is battery temperature information. If there is temperature information, it can jump to step 7); if there is no temperature information, it is necessary to query the ambient temperature of this area corresponding to the BMS absolute time through the network to obtain historical temperature information.

[0039] Specifically in this embodiment, the lithium plating determination idea in step 7) is as follows: First, according to the BMS data, extract the charging behavior at low temperature and high SOC. Preferably, extract the charging behavior with SOC≥90% and temperature<0℃ at the end of charging. If there is no such behavior, it is determined that no lithium plating occurs; furthermore, extract the lithium plating voltage platform signal according to the relaxation voltage curve. If a relaxation voltage platform appears, it is considered that lithium plating must occur. If there is no relaxation voltage platform, it is considered that lithium plating may occur.

[0040] Specifically in this embodiment, the comprehensive evaluation results of the electric bicycle battery safety in step 8) include three levels: safe, warning, and scrapped. The comprehensive evaluation method is as follows: If there are appearance problems, or SOH<80%, or definite lithium plating, it is evaluated as the scrapped level; if there are no appearance problems, SOH≥80%, and no lithium plating occurs, it is evaluated as the safe level; in other cases, it is determined as the warning level.

[0041] The following is an evaluation and analysis using an actual electric bicycle: Step 1: Appearance scanning The evaluator uses a high-definition camera to perform a 360° scan on the electric bicycle battery pack, and uses image recognition technology to analyze the collected images. In this example, the image analysis result shows that there are no obvious deformations, cracks, bulges, or leakage traces on the surface of the battery pack. The battery pack shell is intact, and the fixing screws are not loose. Therefore, it is determined that the appearance of the battery pack is normal, and the next test is continued.

[0042] Step 2: Information extraction Scan the label on the battery pack to identify the battery model as "ABC-123". By querying the electric bicycle database, obtain information such as the nominal capacity of this model battery is 10Ah, the upper limit of the battery pack voltage is 42V, the lower limit of the battery pack voltage is 28V, the highest operating temperature is 55℃, the lowest operating temperature is -10℃, as well as the OCV-SOC mapping relationship and the key parameter-SOC-SOH mapping model, etc.

[0043] Step 3: SOC Estimation Use a multimeter to measure the voltage and temperature of the battery pack. The measured voltage is 36.5V and the temperature is 25°C. According to the OCV-SOC mapping relationship of the "ABC-123" battery (for example, by looking up a table or fitting a formula), estimate the current SOC of the battery pack to be 70%.

[0044] Step 4: Impedance Spectroscopy Test Use an electrochemical workstation to perform an impedance spectroscopy test on the battery pack. The scanning frequency range is from 0.1Hz to 1kHz, with a total of 41 frequency points. During the test, inject a small-amplitude AC signal into the battery pack and measure the voltage and current responses of the battery pack. Convert the measured voltage and current data into complex form to obtain the impedance values of the battery pack at different frequencies.

[0045] Step 5: SOH Calculation Fit the measured impedance spectroscopy data into a fractional-order impedance model. This model includes inductance L, ohmic internal resistance R0, charge transfer resistance R ct , double-layer capacitance C dl and Warburg impedance element C w . Use the nonlinear least squares method for parameter identification to extract the key parameters of the health state R 0, R ct , C dl and C w . Assume that the identified parameters are R0 = 0.05Ω, R ct = 0.02Ω, C dl = 1000F, C w = 0.01S.

[0046] Substitute the extracted key parameters, the current SOC (70%) and temperature (25°C) into the key parameter-SOC-SOH mapping model of the "ABC-123" battery. The calculated SOH is less than 80%, and it is preliminarily judged that the battery has exceeded its service life.

[0047] Step 6: BMS Data Upload Upload the historical data of the electric bicycle BMS to the platform through Bluetooth connection. Assume that the BMS records information such as historical SOC, current, voltage, temperature, and absolute time.

[0048] Step 7: Lithium Deposition Judgment Analyze the uploaded BMS data to find out if there is a charging behavior with low temperature and high SOC. For example, search for records where SOC ≥ 90% and temperature < 0°C at the end of charging. Assume that such a record is found: during a certain charging process, the SOC at the end of charging is 95% and the temperature is -5°C.

[0049] Calculate the differential of the relaxation voltage after this charging behavior. The relaxation voltage refers to the voltage change curve of the battery during a period of static rest after charging is completed. Differentiating the relaxation voltage curve can obtain the voltage change rate. If there is an obvious voltage plateau, it is considered that lithium plating must have occurred; if there is no obvious voltage plateau, it is considered that lithium plating may have occurred. In this example, it is assumed that the calculated differential curve of the relaxation voltage has an obvious voltage plateau, so it is determined that the battery has a lithium plating phenomenon.

[0050] Step 8: Comprehensive evaluation Based on the appearance scan, SOH calculation, and lithium plating determination results, conduct a comprehensive evaluation of the electric bicycle battery. Since the battery SOH is less than 80% and there is a lithium plating phenomenon, the safety level of this battery is rated as "scrapped" and reported to the relevant departments. At the same time, it is recommended that the user stop using this battery and replace it with a new one.

[0051] The serial numbers of the above embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0052] In the above embodiments of the present application, the descriptions of each embodiment have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0053] In the several embodiments provided by the present application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only illustrative. For example, the division of the units can be a logical function division. In actual implementation, there can be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the units or modules can be in electrical or other forms.

[0054] The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they can be located in one place or distributed to multiple units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0055] The above is only the preferred embodiment of the present application. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present application.

[0056] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Accordingly, the scope of this patent should not be determined with reference to the above description, but should be determined with reference to the full scope of the foregoing claims and their equivalents. For the sake of completeness, all articles and references, including patent applications and published disclosures, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein from the foregoing claims is not intended to abandon such subject matter, nor should it be considered that the applicant has not considered such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A method for assessing safety hazards of electric bicycles, characterized in that: The process includes: Perform appearance inspection on the battery pack of the electric bicycle to check whether there is shell deformation and electrolyte leakage, and obtain appearance inspection results; Scan the battery pack label of the electric bicycle to obtain the model information, and retrieve the OCV-SOC mapping relationship of the corresponding model in the electric bicycle database; Collect the voltage and temperature of the current battery pack, and calculate the current battery pack SOC based on the OCV-SOC mapping relationship; Measure the electrochemical impedance spectroscopy data of the battery pack, build a fractional impedance model based on the electrochemical impedance spectroscopy data, extract the key parameters of the health status in the fractional impedance model, and input them into the key parameter-SOC-SOH mapping model to calculate SOH and obtain SOH; Obtain the BMS information of the electric bicycle, extract the low-temperature and high SOC charging behavior from the BMS information, calculate the relaxation voltage differential after the charging behavior, determine the possibility of lithium deposition in the battery pack, and obtain the lithium deposition determination result; Based on the appearance inspection results, SOH and lithium plating determination results, a comprehensive safety assessment conclusion of the electric bicycle is generated.

2. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: The electric bicycle database includes the nominal capacity, battery pack voltage upper limit, battery pack voltage lower limit, maximum operating temperature, minimum operating temperature, OCV-SOC mapping relationship and key parameter-SOC-SOH mapping model corresponding to the lithium-ion batteries of different models of electric bicycles.

3. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: The electrochemical impedance spectroscopy data of the battery pack was measured in the frequency range of 0.1 Hz-1 kHz.

4. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: The fractional impedance model includes inductance, ohmic internal resistance, charge transfer impedance with distributed time constant and diffusion impedance.

5. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: The process of extracting the key parameters of the health state in the fractional-order impedance model is as follows: using the nonlinear least squares method to identify the parameters of the fractional-order impedance model and extracting the key parameters of the health state.

6. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: SOH is used to determine whether the battery has exceeded its service life. The criteria for exceeding service life are that the SOH capacity is less than 80% or the SOH internal resistance is greater than 200%.

7. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: BMS information includes historical SOC, current, voltage, temperature and absolute time.

8. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: The process of obtaining the BMS information of the electric bicycle and extracting the low-temperature and high-SOC charging behavior from the BMS information is as follows: the BMS storage information is wirelessly transmitted to the platform via Bluetooth, and the presence or absence of battery temperature information is intelligently determined. If there is temperature information, the low-temperature and high-SOC charging behavior is extracted; if there is no temperature information, the ambient temperature of the area corresponding to the BMS absolute time is queried online to obtain historical temperature information.

9. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: The process of judging whether lithium deposition has occurred in the battery pack is as follows: extracting the charging behavior when SOC ≥ 90% and temperature < 0°C at the end of charging. If there is no such behavior, it is judged that lithium deposition has not occurred. Then, extracting the lithium deposition voltage platform signal according to the relaxation voltage curve. If a relaxation voltage platform appears, it is judged that lithium deposition has occurred. If there is no relaxation voltage platform, it is judged that there is a probability of lithium deposition occurring.

10. The electric bicycle safety hazard assessment method according to claim 1, characterized in that: In the comprehensive safety assessment conclusion of electric bicycles, if there are appearance problems or SOH is less than 80% or there is a certain amount of lithium deposition, it is evaluated as a scrap level; if there are no appearance problems and SOH is ≥80% and there is no lithium deposition, it is evaluated as a safe level; all other situations are judged as warning levels.

Images