A quick and safe charging optimization method for nickel-hydrogen battery pack under wide temperature conditions

Abstract

A kind of nickel-metal hydride battery pack fast safe charging optimization method for wide temperature working condition, the charge transfer resistance and double-layer capacitance are calculated by obtaining impedance spectrum response data, then the lattice stress parameters are calculated by impedance-stress mapping model, the non-symmetrical pulse current waveform data containing amplitude, frequency and duty cycle are generated according to the parameters, and the above parameters are updated according to the feedback data of lattice stress parameters in the charging period.The impedance measurement results are converted into lattice stress evaluation basis in the present application, and the fast safe charging of nickel-metal hydride battery pack under wide temperature working condition is realized.

Description

Technical Field

[0001] This invention belongs to the field of battery testing technology, and in particular relates to an optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions. Background Technology

[0002] Nickel-metal hydride (NiMH) batteries are widely used in hybrid electric vehicles, rail transportation, backup power supplies, energy storage systems, and various special equipment due to their high safety, long cycle life, good rate performance, and environmental friendliness. In practical applications, NiMH batteries often operate in a wide temperature range, especially at low temperatures. Under these conditions, the viscosity of the electrolyte increases, and the diffusion rate of hydrogen ions in the negative electrode hydrogen storage alloy decreases significantly, leading to a sharp increase in internal resistance and a decrease in charging efficiency. Using conventional charging methods can easily trigger hydrogen evolution, thermal runaway, or even irreversible battery damage.

[0003] In the prior art, CN2014100932330 proposed an impedance measurement system and method for secondary batteries. The system includes a battery module, a charging and discharging module, an AC sweep frequency module, and a signal collection and processing module. It can perform multi-channel parallel impedance testing on secondary batteries and measure the ohmic internal resistance, electrochemical polarization impedance, and concentration polarization impedance of the secondary batteries for battery charge and discharge performance analysis and service life estimation.

[0004] However, the aforementioned invention only achieves basic detection and parameter analysis of the AC impedance of secondary batteries, belonging to a single testing technology with obvious application limitations and technical one-sidedness. Its core objective is only to obtain the battery's impedance parameters and draw impedance spectra, remaining at the level of "parameter measurement" and failing to provide accurate microscopic basis for optimizing nickel-metal hydride battery charging. Furthermore, the impedance measurement of this scheme is a static detection process, only completing impedance tests at different frequencies under constant charge and discharge conditions of the battery. It lacks real-time feedback and dynamic control mechanisms, and cannot adapt to dynamic changes such as battery heat generation, hydrogen atom absorption and diffusion, and the evolution of the lattice state of hydrogen storage alloys during charging, nor can it adjust the charging strategy in real time according to impedance changes. Summary of the Invention

[0005] To address the technical problem that existing technologies can only statically detect battery impedance parameters and cannot dynamically adjust the charging strategy in real time according to the internal lattice stress state of the battery under wide temperature conditions, resulting in low charging efficiency at low temperatures and easy irreversible damage to the battery, this invention provides a fast and safe charging optimization method for nickel-metal hydride battery packs under wide temperature conditions.

[0006] To achieve the above objectives, a first aspect of the present invention provides an optimized method for fast and safe charging of nickel-metal hydride battery packs under wide operating temperatures, comprising the following steps: S1. Obtain impedance spectrum response data after injecting a low-amplitude AC signal into a nickel-metal hydride battery, and calculate the charge transfer resistance and double-layer capacitance of the battery based on the impedance spectrum response data. S2. Based on the charge transfer resistance and the double-layer capacitance, calculate the lattice stress parameters using a preset impedance-stress mapping model. The impedance-stress mapping model is used to map the impedance data to the stress state inside the hydrogen storage alloy lattice of the battery negative electrode. S3. Generate asymmetric pulse current waveform data based on the lattice stress parameters. The asymmetric pulse current waveform data includes amplitude parameters, frequency parameters, and duty cycle parameters. S4. During the charging cycle, update the amplitude parameter, frequency parameter, and duty cycle parameter of the asymmetric pulse current waveform data according to the feedback data of the lattice stress parameter.

[0007] Furthermore, step S1 specifically includes: Before the battery charging process is started, a low-amplitude AC signal is injected into the nickel-metal hydride battery, which is in a low-temperature environment. The low-amplitude AC signal is used to actively detect the microscopic state of the internal materials of the battery. The impedance spectrum response data of the low amplitude AC signal is collected, and the charge transfer impedance and double layer capacitance of the battery electrode interface are obtained based on the impedance spectrum response data. The charge transfer impedance and double layer capacitance reflect the characteristics of the reaction between the battery negative electrode hydrogen storage alloy and the electrolyte interface. The charge transfer impedance and the double layer capacitance are fitted by the Nyquist plot of the impedance spectrum to obtain the charge transfer resistance and the double layer capacitance. The charge transfer resistance represents the ability of charge to be transferred from the electrode to the electrolyte, and the double layer capacitance represents the charge storage capacity of the electrode interface. The charge transfer resistance and the double-layer capacitance are output as intermediate parameters so that subsequent steps can quantify the characteristic value of the current stress level inside the hydrogen storage alloy lattice of the battery negative electrode based on the charge transfer resistance and the double-layer capacitance.

[0008] Furthermore, step S2 specifically includes: The impedance spectrum response data is analyzed to obtain complex impedance data, which includes real part parameters and imaginary part parameters; A coupling model between electrode interface reaction kinetics and material micro-deformation is established. This coupling model is used to describe the correspondence between complex impedance data and stress distribution within the lattice of the hydrogen storage alloy. Based on the coupling relationship model, the complex impedance data is mapped into a quantitative index reflecting the stress distribution inside the lattice of the negative electrode hydrogen storage alloy. The quantitative index is used to determine whether the lattice stress exceeds a preset threshold, and the result is output as a lattice stress parameter. The lattice stress parameter is used to characterize whether the lattice faces the risk of irreversible damage under the current working condition.

[0009] Furthermore, the establishment of the coupling relationship model between electrode interface reaction kinetics and material micro-deformation specifically includes: Charging tests were conducted in a low-temperature environment to measure the complex impedance data of the battery. The complex impedance data includes a real part and an imaginary part of the impedance, and the real part and the imaginary part of the impedance are related to the frequency of the signal. The charge transfer resistance and the double-layer capacitance are obtained by analyzing the complex impedance data. The charge transfer resistance and the double-layer capacitance are related to the stress state inside the material. The complex impedance data is correlated with the stress state. The series resistance of the battery, the double layer impedance reflecting the charge accumulation state at the electrode interface, and the charge transfer impedance reflecting the reduction of hydrogen ions to hydrogen atoms on the surface of the hydrogen storage alloy and the resistance to hydrogen absorption and dehydrogenation kinetics within the crystal lattice together constitute the components of the complex impedance data. A stress-impedance mapping function was established to characterize the relationship between charge transfer resistance and double-layer capacitance and lattice stress of hydrogen storage alloy using a mapping function obtained from experimental data, with temperature and lattice stress as variables. The calculated stress values ​​are used to assess in real time whether the lattice of the hydrogen storage alloy in the negative electrode of the battery is at risk of irreversible damage.

[0010] Furthermore, step S3 specifically includes: The lattice stress parameter is compared with a preset critical threshold. When it is determined that the lattice stress parameter is close to or reaches the preset critical threshold, the optimization algorithm is activated; The optimization algorithm aims to minimize the lattice strain energy and promote uniform hydrogen absorption and diffusion of hydrogen atoms, and determines the amplitude, frequency, and duty cycle parameters of the pulse current waveform. Based on the determined amplitude parameters, frequency parameters, and duty cycle parameters, at least one asymmetric pulse current waveform data is generated, wherein the asymmetric pulse current waveform data includes a positive pulse portion and a negative pulse portion; The asymmetric pulse current waveform data is output as a pulse current command sequence, so that subsequent steps can apply a composite energy field according to the pulse current command sequence.

[0011] Furthermore, it also includes: The preset critical threshold is determined through the following steps: For the nickel-metal hydride battery pack to be calibrated, a calibration experiment was performed under low-temperature conditions to collect performance data of the nickel-metal hydride battery pack under different stress states. During the calibration experiment, a gradually increasing charging current was applied to the nickel-metal hydride battery pack, and the lattice stress change of the hydrogen storage alloy of the negative electrode of the nickel-metal hydride battery pack was monitored in real time. The lattice stress value corresponding to the occurrence of irreversible damage to the nickel-metal hydride battery pack was recorded, and the lattice stress value was determined as the upper limit of stress. The upper limit of stress is multiplied by a preset safety factor to obtain the critical threshold of lattice stress of the nickel-metal hydride battery pack. The value of the safety factor is greater than 0 and less than 1. The critical threshold of lattice stress is stored in the battery management system, which is used to compare the lattice stress parameters calculated in real time with the critical threshold of lattice stress during the charging process.

[0012] Furthermore, step S4 specifically includes: It runs continuously from the start of the charging process until the end of the charging cycle, using the real-time monitored lattice stress parameters as the core feedback basis. The lattice stress parameters monitored in real time are continuously compared with the preset ideal stability range of lattice stress, and the deviation value between the lattice stress parameters and the ideal stability range is calculated. The adjustment direction of the pulse current waveform parameters is determined based on the deviation value, and the adjustment direction includes increasing the parameter, decreasing the parameter, or keeping the parameter unchanged; When the lattice stress parameter approaches the upper limit of the ideal stable range and shows a stress accumulation trend, the amplitude parameter is reduced, the frequency parameter is increased, or the duty cycle parameter is decreased to reduce the duration of a single pulse energization. When the lattice stress parameter is within the ideal stable range, the duty cycle parameter is adjusted to accelerate the hydrogen atom absorption and diffusion rate without increasing the lattice stress. The adjusted amplitude, frequency, and duty cycle parameters are output to continue generating updated asymmetric pulse current waveform data.

[0013] Furthermore, the step of continuously comparing the real-time monitored lattice stress parameters with a preset ideal lattice stress stability range, and calculating the deviation value between the lattice stress parameters and the ideal stability range, specifically includes: Obtain a preset ideal stability range of lattice stress, wherein the ideal stability range includes an upper limit value and a lower limit value; Obtain the values ​​of lattice stress parameters monitored in real time during the current charging cycle; The lattice stress parameter values ​​are compared with the upper limit of the interval and the lower limit of the interval, respectively. When the value of the lattice stress parameter is greater than the upper limit of the interval, a first difference between the value of the lattice stress parameter and the upper limit of the interval is calculated, and the first difference is determined as a first type of deviation value. The first type of deviation value is used to characterize the degree to which the current lattice stress exceeds the safe range. When the value of the lattice stress parameter is less than the lower limit of the interval, a second difference between the lower limit of the interval and the value of the lattice stress parameter is calculated, and the second difference is determined as a second type of deviation value. The second type of deviation value is used to characterize the degree to which the current lattice stress is lower than the ideal state. When the value of the lattice stress parameter is between the upper limit of the interval and the lower limit of the interval, the deviation value is determined to be zero; The calculated deviation value is output so that subsequent steps can determine the adjustment direction of the pulse current waveform parameters based on the deviation value.

[0014] Secondly, the present invention also provides a fast and safe charging optimization device for nickel-metal hydride battery packs under wide temperature operating conditions, comprising: Battery module, the battery module comprising a nickel-metal hydride battery pack; One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors execute any one of the described fast and safe charging optimization methods for nickel-metal hydride battery packs under wide temperature conditions, and output the execution results to the battery module.

[0015] Thirdly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements any of the above-described methods for optimizing fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions.

[0016] The beneficial technical effects of the present invention are at least as follows: This invention provides an optimized method for fast and safe charging of nickel-metal hydride (NiMH) battery packs under wide temperature conditions. Before charging begins, a low-amplitude AC signal is injected into the NiMH battery under low-temperature conditions. Impedance spectroscopy response is used to probe the microscopic stress state within the negative electrode hydrogen storage alloy lattice, obtaining charge transfer resistance and double-layer capacitance, which are then mapped to lattice stress parameters. This achieves a non-destructive conversion from macroscopic electrical measurements to microscopic material mechanical states. By constructing a coupling model between electrode interface reaction kinetics and material micro-deformation, complex impedance data is mapped to quantitative indicators reflecting the stress distribution within the hydrogen storage alloy lattice, thus incorporating the mechanical stress state of the battery's internal materials. The monitoring system provides a quantitative basis for determining whether the lattice faces irreversible damage risk. A composite energy field with both heating and material pretreatment functions is applied to the battery. At the macroscopic level, Joule heating is generated by the internal resistance of the pulse current to increase the battery temperature. At the microscopic level, the hydrogen concentration polarization effect during the pulse interval drives hydrogen atoms to diffuse into the hydrogen storage alloy lattice, simultaneously achieving temperature management optimization and material structure stability. Throughout the entire charging cycle, the lattice stress change is continuously monitored and the amplitude, frequency, or duty cycle of the pulse current is finely adjusted in real time to keep the lattice stability within the optimal range throughout the entire charging cycle, preventing stress accumulation from causing or propagating microcracks. Attached Figure Description

[0017] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0018] Figure 1 This is a flowchart of the steps of an optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions, according to one embodiment of the present invention. Figure 2 This is a diagram showing the mapping of impedance spectrum data to stress parameters according to one embodiment of the present invention; Figure 3 This is a logic diagram of the optimization algorithm for dynamically generating pulse waveforms disclosed in one embodiment of the present invention; Figure 4 This is a time-domain waveform diagram of an asymmetric continuous pulse current disclosed in one embodiment of the present invention; Figure 5 This is a schematic diagram of the mechanism of action of the composite energy field disclosed in one embodiment of the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] Currently, nickel-metal hydride (NiMH) batteries are widely used in hybrid electric vehicles, rail transportation, backup power supplies, energy storage systems, and various special equipment due to their high safety, long cycle life, good rate performance, and environmental friendliness. In practical applications, NiMH batteries often face a wide temperature range, especially at low temperatures. Under these conditions, the viscosity of the electrolyte increases, and the diffusion rate of hydrogen ions in the negative electrode hydrogen storage alloy decreases significantly, leading to a sharp increase in internal resistance and a decrease in charging efficiency. Using conventional charging methods can easily cause hydrogen evolution, thermal runaway, or even irreversible battery damage. In existing technology, CN2014100932330 proposes an impedance measurement system and method for secondary batteries. However, this scheme only achieves basic detection and parameter analysis of the AC impedance of secondary batteries, belonging to a single testing technology. Its core objective is only to obtain the battery's impedance parameters and draw impedance spectra, remaining at the level of "parameter measurement" and failing to provide accurate microscopic evidence for optimizing NiMH battery charging. Furthermore, the impedance measurement in this scheme is a static detection process, which only completes impedance testing at different frequencies under constant charge and discharge conditions of the battery. It lacks real-time feedback and dynamic control mechanisms, and cannot adapt to dynamic changes such as battery heat generation, hydrogen atom absorption and diffusion, and the evolution of the lattice state of hydrogen storage alloy during charging. It also cannot adjust the charging strategy in real time according to impedance changes.

[0021] To address the technical problems of existing technologies that can only statically detect battery impedance parameters and cannot dynamically adjust the charging strategy in real time based on the internal lattice stress state of the battery under wide temperature conditions, resulting in low charging efficiency at low temperatures and easy irreversible damage to the battery, this embodiment provides an optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions. This method calculates charge transfer resistance and double-layer capacitance by acquiring impedance spectrum response data, and then calculates lattice stress parameters through an impedance-stress mapping model. Based on these parameters, it generates asymmetric pulse current waveform data containing amplitude, frequency, and duty cycle. During the charging cycle, it updates these parameters based on feedback data of the lattice stress parameters, transforming the impedance measurement results into a basis for lattice stress evaluation, thus achieving fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions.

[0022] The fast and safe charging optimization method for nickel-metal hydride battery packs provided in this embodiment can be executed by a battery charging management device. This battery charging management device can be implemented through software and / or hardware. The device can consist of two or more physical entities, or it can be a single physical entity. For example, the battery charging management device can be a battery management system (BMS) or a charging controller for battery charging management.

[0023] The battery charging management device is equipped with at least one operating system, including but not limited to Android, Linux, and Windows. The device can install at least one application based on this operating system; this application can be a built-in application or an application downloaded from a third-party device or server. In this embodiment, the battery charging management device has at least one application capable of executing a fast and safe charging optimization method for nickel-metal hydride battery packs.

[0024] For ease of understanding, this embodiment uses the charging controller as the main body for implementing the fast and safe charging optimization method for nickel-metal hydride battery packs as an example for description.

[0025] Figure 1 A flowchart of an optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions, as provided in an embodiment of this application, is given. (Reference) Figure 1 The method specifically includes: S1. Obtain impedance spectrum response data after injecting a low-amplitude AC signal into the nickel-metal hydride battery, and calculate the charge transfer resistance and double-layer capacitance of the battery based on the impedance spectrum response data, so as to calculate the lattice stress parameters.

[0026] See Figure 2 In some embodiments, impedance spectral response data is acquired after a low-amplitude AC signal is injected into the nickel-metal hydride battery. The charge transfer resistance and double-layer capacitance of the battery are calculated based on this impedance spectral response data for subsequent calculation of lattice stress parameters. The low-amplitude AC signal is used to actively probe the microscopic state of the battery's internal materials. The impedance spectral response data contains information on the battery's electrochemical response at different frequencies. The charge transfer resistance represents the ability to transfer charge from the electrode to the electrolyte, and the double-layer capacitance represents the charge storage capacity at the electrode interface.

[0027] In one embodiment, before the battery charging process begins, a low-amplitude AC signal is injected into the nickel-metal hydride battery, which is in a low-temperature environment. This low-amplitude AC signal has a frequency range of 1 Hz to 1 kHz and an amplitude range of 1 mA to 10 mA. Impedance spectrum response data of the low-amplitude AC signal is collected to obtain the charge transfer impedance and double-layer capacitance at the battery electrode interface. The charge transfer resistance and double-layer capacitance are obtained by fitting the Nyquist plot of the impedance spectrum to the charge transfer impedance and double-layer capacitance. The charge transfer resistance and double-layer capacitance are output as intermediate parameters for subsequent steps to quantify the characteristic values ​​of the current stress level within the hydrogen storage alloy lattice of the battery's negative electrode.

[0028] When a low-amplitude AC signal is injected into the battery, the electrochemical impedance spectroscopy of the battery's negative electrode hydrogen storage alloy changes according to the battery's operating state and the microscopic deformation of the material. Parameters such as the charge transfer impedance at the battery electrode interface, the double-layer capacitance, and the conductivity of the electrode material are obtained; the battery's charge transfer resistance... and double-layer capacitor These two parameters reflect the characteristics of the interface reaction between the battery's negative electrode hydrogen storage alloy and the electrolyte. Charge transfer resistance. Obtained by fitting the Nyquist plot of the impedance spectrum, it represents the charge transfer capability from the electrode to the electrolyte; double-layer capacitance. This indicates the charge storage capacity at the electrode interface. Both are affected by the stress in the battery material. Combining the relationship model between electrochemical impedance and the internal stress of the hydrogen storage alloy lattice, the impedance data is mapped to a stress level parameter. This parameter is used to quantify the stress state of the hydrogen storage alloy lattice, and the unit is Pa. The intermediate parameters output by the system include: charge transfer resistance. Double-layer capacitor and stress level parameters ; S2. Based on the charge transfer resistor and the double-layer capacitance, calculate the lattice stress parameters using a preset impedance-stress mapping model to generate asymmetric pulse current waveform data.

[0029] See Figure 3 In some embodiments, lattice stress parameters are calculated based on charge transfer resistance and double-layer capacitance using a preset impedance-stress mapping model, wherein the impedance-stress mapping model is used to map impedance data to the stress state inside the hydrogen storage alloy lattice of the battery negative electrode.

[0030] In one embodiment, the obtained AC impedance spectrum signal is subjected to in-depth analysis and modeling calculation. By establishing a coupling relationship model between electrode interface reaction kinetics and material micro-deformation, the measured complex impedance data is mapped into a quantitative index reflecting the stress distribution inside the negative electrode hydrogen storage alloy lattice. This transforms the macroscopic electrical measurement signal into a real-time, non-destructive assessment of the micro-mechanical state inside the material, and outputs a dynamic stress parameter that can accurately characterize whether the lattice faces the risk of irreversible damage under the current operating conditions.

[0031] Assuming a charging test is conducted in a low-temperature environment, the complex impedance data of the battery is measured: , in and These are the real and imaginary parts of the impedance, respectively. It is the imaginary unit. This refers to the frequency of the signal. At this frequency, the electrode reactions of the battery mainly include: the transport of hydrogen ions (H+) from the electrolyte to the negative electrode, their reduction to hydrogen atoms (H) on the surface of the hydrogen storage alloy, and the subsequent hydrogen absorption and desorption processes within the hydrogen storage alloy lattice. This process is closely related to the microscopic stress within the hydrogen storage alloy lattice. To correlate these electrical data with the material stress state, a coupled model is established. This model maps the frequency response of the impedance to the stress distribution of the electrode through an impedance-stress relationship.

[0032] Charge transfer resistance was obtained by AC impedance spectroscopy. and double-layer capacitor These two parameters are related to the stress state within the material. Correlating complex impedance data with the stress state: , in, It is the series resistance of the battery. It reflects the charge accumulation state at the electrode interface. This reflects the kinetic resistance of hydrogen ions being reduced to hydrogen atoms on the surface of the hydrogen storage alloy, and the hydrogen absorption / desorption within the crystal lattice. and The changes reflect the stress distribution within the crystal lattice; Establish the stress-impedance mapping function. and Lattice stress of hydrogen storage alloys The relationship between them is represented as follows: The stress-impedance mapping function is a fitting function based on experimental data. In practical applications, the fitting coefficients need to be calibrated through a large number of low-temperature operating condition experiments for different models and specifications of nickel-metal hydride battery packs. in, It's temperature. It is a mapping function derived from experimental data, reflecting the stress distribution of the battery under specific operating conditions. The stress values ​​are obtained through calculation. Unit: Pa, to assess in real time whether the lattice of the hydrogen storage alloy in the battery negative electrode faces the risk of irreversible damage. If Exceeding the set critical threshold This indicates that the lattice structure of the battery may be at risk of irreversible damage. Charge transfer resistance This reflects the kinetic resistance of hydrogen ions being reduced to hydrogen atoms on the surface of the hydrogen storage alloy, as well as the kinetic resistance of hydrogen atoms absorbing / desorbing hydrogen within the crystal lattice.

[0033] Double-layer capacitor This reflects the state of charge accumulation at the electrode interface.

[0034] Stress parameters : Quantitatively represents the stress level of the hydrogen storage alloy lattice, with the unit being Pa, indicating the stress state of the material under the current operating conditions.

[0035] In another embodiment, establishing the coupling relationship model between electrode interface reaction kinetics and material micro-deformation specifically includes: conducting charging tests at low temperatures to measure complex impedance data of the battery, the complex impedance data including a real part and an imaginary part of impedance, the real part and the imaginary part of impedance being related to the frequency of the signal; analyzing the charge transfer resistance and double-layer capacitance from the complex impedance data, the charge transfer resistance and the double-layer capacitance being related to the stress state inside the material; correlating the complex impedance data with the stress state, wherein the series resistance of the battery, the double-layer impedance reflecting the charge accumulation state at the electrode interface, and the charge transfer impedance reflecting the reduction of hydrogen ions to hydrogen atoms on the surface of the hydrogen storage alloy and the resistance to hydrogen absorption and desorption kinetics within the lattice of hydrogen atoms together constitute the components of the complex impedance data; establishing a stress-impedance mapping function, characterizing the relationship between charge transfer resistance and double-layer capacitance and the lattice stress of the hydrogen storage alloy through a mapping function obtained based on experimental data, the mapping function using temperature and lattice stress as variables; and using the calculated stress value to assess in real time whether the lattice of the battery negative electrode hydrogen storage alloy faces the risk of irreversible damage.

[0036] S3. Generate asymmetric pulse current waveform data based on the lattice stress parameters. The asymmetric pulse current waveform data includes amplitude parameters, frequency parameters, and duty cycle parameters for updating the asymmetric pulse current waveform data.

[0037] In some embodiments, asymmetric pulsed current waveform data is generated based on lattice stress parameters. The asymmetric pulsed current waveform data includes amplitude parameters, frequency parameters, and duty cycle parameters, which are used to update the waveform data based on feedback data.

[0038] See Figure 5 In one embodiment, the calculated lattice stress parameters are obtained and compared with a preset critical threshold. When the lattice stress parameters are determined to be close to or reach the preset critical threshold, an optimization algorithm is initiated. The optimization algorithm aims to minimize the lattice strain energy and promote uniform hydrogen absorption and diffusion, and determines the amplitude, frequency, and duty cycle parameters of the pulse current waveform. Based on the determined amplitude, frequency, and duty cycle parameters, an asymmetric pulse current waveform data is generated, which includes a positive pulse portion and a negative pulse portion. The asymmetric pulse current waveform data is output as a pulse current command sequence for subsequent steps to apply a composite energy field according to the pulse current command sequence.

[0039] When the lattice stress is monitored in real time Approaching the preset critical threshold When the system is activated, the optimization algorithm will be started. The optimization goal is to minimize the strain energy of the lattice and promote the uniform absorption and diffusion of hydrogen atoms into the lattice structure of the negative electrode hydrogen storage alloy, so as to avoid local stress concentration and irreversible damage to the material.

[0040] To achieve this goal, the strain energy density of the hydrogen storage alloy lattice in the battery's negative electrode is first determined. Lattice strain energy : , in, Indicates the maximum stress in the crystal lattice. This represents the maximum strain corresponding to the maximum stress. It quantifies the material deformation energy caused by stress. During the charging process, the crystal lattice accumulates strain energy, and excessive accumulation of this strain energy can lead to irreversible damage to the material. Minimizing strain energy can reduce material deformation and prevent crack formation. Based on real-time stress parameters and strain energy The system then initiates a waveform optimization algorithm. The goal of this algorithm is to dynamically generate a pulse current waveform, whose characteristics include the current amplitude. ,frequency and duty cycle This pulsed current waveform can effectively disperse stress, reduce strain energy, and promote the uniform diffusion of hydrogen atoms into the crystal structure of the negative electrode hydrogen storage alloy. The generation of the pulsed current waveform is obtained by solving the following formula: , in, It is the strain energy of the current crystal lattice. This indicates the deviation of stress from the critical threshold. This is an adjustment coefficient used to balance the weights between strain energy and stress deviation. It is adapted to the hydrogen storage alloy material and the wide operating temperature range of the battery. The objective function aims to minimize lattice strain energy while minimizing lattice stress. Controlled to near the critical threshold Within a certain range, thus avoiding material damage caused by excessive stress accumulation; During the optimization process, the system will continuously adjust the amplitude of the pulse current. ,frequency and duty cycle This allows for the dynamic generation of the most suitable asymmetric pulse current waveform based on the battery's current stress state during each charging cycle. The amplitude, frequency, and duty cycle of the pulse current need to be optimized according to the battery's real-time operating conditions. For example, under high stress conditions, the system disperses stress and prevents localized stress concentration by reducing the amplitude or increasing the frequency; while under lower stress conditions, the system may increase the pulse amplitude to promote more uniform hydrogen atom absorption and diffusion into the lattice of the negative electrode hydrogen storage alloy.

[0041] In another embodiment, the preset critical threshold is determined through the following steps: For the nickel-metal hydride battery pack to be calibrated, a calibration experiment is performed under low-temperature conditions, and performance data of the nickel-metal hydride battery pack under different stress states are collected; during the calibration experiment, a gradually increasing charging current is applied to the nickel-metal hydride battery pack, and the lattice stress change of the hydrogen storage alloy at the negative electrode of the nickel-metal hydride battery pack is monitored in real time, and the lattice stress value corresponding to irreversible damage to the nickel-metal hydride battery pack is recorded, and the lattice stress value is determined as the upper limit of stress; the upper limit of stress is multiplied by a preset safety factor to obtain the critical threshold of lattice stress for the nickel-metal hydride battery pack, wherein the safety factor has a value greater than 0 and less than 1; the critical threshold of lattice stress is stored in a battery management system, which is used to compare the real-time calculated lattice stress parameters with the critical threshold of lattice stress during charging.

[0042] S4. During the charging cycle, update the amplitude parameter, frequency parameter, or duty cycle parameter of the asymmetric pulse current waveform data according to the feedback data of the lattice stress parameter.

[0043] In some embodiments, during a charging cycle, the amplitude parameter, frequency parameter, or duty cycle parameter of the asymmetric pulse current waveform data is updated based on feedback data of the lattice stress parameter.

[0044] In one embodiment, the system operates continuously from the start of the charging process until the end of the charging cycle, using the real-time monitored lattice stress parameters as the core feedback basis. The real-time monitored lattice stress parameters are continuously compared with a preset ideal stable range of lattice stress, and the deviation value between the lattice stress parameters and the ideal stable range is calculated. The adjustment direction of the pulse current waveform parameters is determined based on the deviation value; the adjustment direction includes increasing the parameters, decreasing the parameters, or keeping the parameters unchanged. When the lattice stress parameters approach the upper limit of the ideal stable range and show a stress accumulation trend, the amplitude parameter is reduced, the frequency parameter is increased, or the duty cycle parameter is decreased to reduce the duration of a single pulse. When the lattice stress parameters are within the ideal stable range, the duty cycle parameter is adjusted to accelerate the hydrogen atom absorption and diffusion rate without increasing the lattice stress. The adjusted amplitude parameter, frequency parameter, and duty cycle parameter are output for continued generation of updated asymmetric pulse current waveform data.

[0045] See Figure 4 The time-domain waveform of the asymmetric continuous pulse current for charging nickel-metal hydride battery packs under wide temperature conditions exhibits dynamic changes in the pulse current: a small negative pulse is applied first in the 0–3ms period, followed by a positive pulse with a peak value of 5A and a duration of 5–7ms, a positive pulse with a peak value of 3A, a negative pulse with an amplitude of -1A and a duration of 8–12ms, a positive pulse with a peak value approximately at the corresponding level and a duration of 15–16ms, and finally a negative pulse is applied in the 17–21ms period, ending at a stable plateau of 3.5Ams; the overall waveform has no fixed period or duty cycle, and the pulse amplitude, polarity, and duration are dynamically adjusted with the charging process. The battery temperature is raised through the Joule heating of the positive pulse, and the polarization and lattice stress are relieved by the negative pulse and the interval, ultimately forming a composite energy field that combines thermal management and material modification functions; The amplitude, frequency, and duty cycle of the pulse current control the local and overall temperature rise of the battery, as well as the temperature changes inside the battery. This is described by the relationship between current and battery thermal characteristics, taking into account the battery's heat capacity. Thermal conductivity and the effective heat exchange area of ​​the battery The temperature change can be approximated using the heat conduction equation: , This represents the battery during the charging process. The change in temperature over time. It is the effective heat exchange area of ​​the battery. yes The amplitude of the pulse current constantly applied to the battery, It is the specific heat capacity of the battery, reflecting the battery's ability to absorb heat and rise in temperature. Thermal conductivity is the conductivity of a battery, reflecting the rate at which heat is conducted inside the battery. It is a natural constant, first passed through The basic temperature rise capacity generated by the pulsed current through the battery's internal resistance to produce Joule heating is calculated, and then... This index, which combines the battery's thermal conductivity, effective heat exchange area, and specific heat capacity, corrects for the battery's heat conduction and dissipation at different times, thereby approximately estimating the actual temperature change of the battery due to the pulse current at any given moment. The intermittent periods of the pulsed current (i.e., the time periods when the current is zero) generate a hydrogen concentration polarization effect. This effect creates a local hydrogen concentration gradient on the surface of the negative electrode hydrogen storage alloy of the battery, driving hydrogen atoms to preferentially absorb and diffuse at specific active sites, resulting in concentration polarization. : ]in, It is a pulse current. It is the duration of the pulse. It is the Faraday constant. The hydrogen concentration polarization effect promotes hydrogen atom absorption and diffusion at the active sites of the hydrogen storage alloy, thereby avoiding stress accumulation caused by uneven hydrogen absorption; By precisely controlling the amplitude, frequency, and duty cycle of the pulse current, the system can regulate the overall heating rate of the battery and the local hydrogen atom absorption behavior. During charging, the temperature uniformity of the battery is guaranteed, and the hydrogen atoms inside the battery can absorb and diffuse hydrogen gently and uniformly at the active sites of the negative electrode hydrogen storage alloy. This effectively protects the active sites of the hydrogen storage alloy, delays the decay of hydrogen storage performance, stabilizes the crystal structure, and prevents stress accumulation and the generation of microcracks.

[0046] The pulsed current-controlled composite energy field can not only optimize battery temperature management, but also achieve microscopic modification of materials, ensuring that the battery's lattice structure remains stable throughout the entire charging cycle.

[0047] In another embodiment, the step of continuously comparing the real-time monitored lattice stress parameters with a preset ideal stability range of lattice stress and calculating the deviation value between the lattice stress parameters and the ideal stability range specifically includes: obtaining a preset ideal stability range of lattice stress, the ideal stability range including an upper limit value and a lower limit value; obtaining the real-time monitored lattice stress parameter values ​​during the current charging cycle; comparing the lattice stress parameter values ​​with the upper limit value and the lower limit value of the range respectively; when the lattice stress parameter value is greater than the upper limit value of the range, calculating a first difference between the lattice stress parameter value and the upper limit value of the range, and then... The first difference is determined as a first-type deviation value, which characterizes the degree to which the current lattice stress exceeds the safe range. When the lattice stress parameter value is less than the lower limit of the interval, a second difference is calculated between the lower limit of the interval and the lattice stress parameter value, and the second difference is determined as a second-type deviation value, which characterizes the degree to which the current lattice stress is lower than the ideal state. When the lattice stress parameter value is between the upper limit of the interval and the lower limit of the interval, the deviation value is determined to be zero. The calculated deviation value is output so that subsequent steps can determine the adjustment direction of the pulse current waveform parameters based on the deviation value.

[0048] Optionally, when the constant current charging phase ends and the battery is close to full charge, a low-amplitude restorative pulse current sequence is applied. By adjusting the relaxation time of the pulse, hydrogen atoms that are unevenly distributed in the shallow layer of the negative electrode hydrogen storage alloy lattice are encouraged to diffuse and rearrange to more stable lattice positions.

[0049] Figure 2 A structural block diagram of a fast and safe charging optimization device for nickel-metal hydride battery packs under wide temperature conditions, provided in an embodiment of this application, is given. (Reference) Figure 2 The device specifically includes: a battery module, one or more processors, and a memory.

[0050] The battery module includes a nickel-metal hydride battery pack; the memory is used to store one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors execute the fast and safe charging optimization method for nickel-metal hydride battery packs provided in the above embodiments, and output the execution result to the battery module.

[0051] This application also provides a storage medium containing computer-executable instructions, wherein when the computer program is executed by a processor, it implements the fast and safe charging optimization method for nickel-metal hydride battery packs provided in the above embodiments.

[0052] The nickel-metal hydride battery pack fast and safe charging optimization device, storage medium, and battery charging management device provided in the above embodiments can execute the nickel-metal hydride battery pack fast and safe charging optimization method provided in any embodiment of this application. For technical details not described in detail in the above embodiments, please refer to the nickel-metal hydride battery pack fast and safe charging optimization method provided in any embodiment of this application.

[0053] Of course, the computer-executable instructions provided in the embodiments of this application are not limited to the measurement methods described above, but can also perform related operations in the measurement methods provided in any embodiment of this application.

[0054] The above description is merely a preferred embodiment and the technical principles employed in this application. This application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions that can be made by those skilled in the art will not depart from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application. The scope of this application is determined by the scope of the claims.

Claims

1. An optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions, characterized in that, Includes the following steps: S1. Obtain impedance spectrum response data after injecting a low-amplitude AC signal into a nickel-metal hydride battery, and calculate the charge transfer resistance and double-layer capacitance of the battery based on the impedance spectrum response data. S2. Based on the charge transfer resistance and the double-layer capacitance, calculate the lattice stress parameters using a preset impedance-stress mapping model. The impedance-stress mapping model is used to map the impedance data to the stress state inside the hydrogen storage alloy lattice of the battery negative electrode. S3. Generate asymmetric pulse current waveform data based on the lattice stress parameters. The asymmetric pulse current waveform data includes amplitude parameters, frequency parameters, and duty cycle parameters. S4. During the charging cycle, update the amplitude parameter, frequency parameter, and duty cycle parameter of the asymmetric pulse current waveform data according to the feedback data of the lattice stress parameter.

2. The optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions according to claim 1, characterized in that, Step S1 specifically includes: Before the battery charging process is started, a low-amplitude AC signal is injected into the nickel-metal hydride battery, which is in a low-temperature environment. The low-amplitude AC signal is used to actively detect the microscopic state of the internal materials of the battery. The impedance spectrum response data of the low amplitude AC signal is collected, and the charge transfer impedance and double layer capacitance of the battery electrode interface are obtained based on the impedance spectrum response data. The charge transfer impedance and double layer capacitance reflect the characteristics of the reaction between the battery negative electrode hydrogen storage alloy and the electrolyte interface. The charge transfer impedance and the double layer capacitance are fitted by the Nyquist plot of the impedance spectrum to obtain the charge transfer resistance and the double layer capacitance. The charge transfer resistance represents the ability of charge to be transferred from the electrode to the electrolyte, and the double layer capacitance represents the charge storage capacity of the electrode interface. The charge transfer resistance and the double-layer capacitance are output as intermediate parameters so that subsequent steps can quantify the characteristic value of the current stress level inside the hydrogen storage alloy lattice of the battery negative electrode based on the charge transfer resistance and the double-layer capacitance.

3. The optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions according to claim 1, characterized in that, Step S2 specifically includes: The impedance spectrum response data is analyzed to obtain complex impedance data, which includes real part parameters and imaginary part parameters; A coupling model between electrode interface reaction kinetics and material micro-deformation is established. This coupling model is used to describe the correspondence between complex impedance data and stress distribution within the lattice of the hydrogen storage alloy. Based on the coupling relationship model, the complex impedance data is mapped into a quantitative index reflecting the stress distribution inside the lattice of the negative electrode hydrogen storage alloy. The quantitative index is used to determine whether the lattice stress exceeds a preset threshold, and the result is output as a lattice stress parameter. The lattice stress parameter is used to characterize whether the lattice faces the risk of irreversible damage under the current working condition.

4. The optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions according to claim 3, characterized in that, The specific steps involved in establishing the coupling relationship model between electrode interface reaction kinetics and material micro-deformation include: Charging tests were conducted in a low-temperature environment to measure the complex impedance data of the battery. The complex impedance data includes a real part and an imaginary part of the impedance, and the real part and the imaginary part of the impedance are related to the frequency of the signal. The charge transfer resistance and the double-layer capacitance are obtained by analyzing the complex impedance data. The charge transfer resistance and the double-layer capacitance are related to the stress state inside the material. The complex impedance data is correlated with the stress state. The series resistance of the battery, the double layer impedance reflecting the charge accumulation state at the electrode interface, and the charge transfer impedance reflecting the reduction of hydrogen ions to hydrogen atoms on the surface of the hydrogen storage alloy and the resistance to hydrogen absorption and dehydrogenation kinetics within the crystal lattice together constitute the components of the complex impedance data. A stress-impedance mapping function was established to characterize the relationship between charge transfer resistance and double-layer capacitance and lattice stress of hydrogen storage alloy using a mapping function obtained from experimental data, with temperature and lattice stress as variables. The calculated stress values ​​are used to assess in real time whether the lattice of the hydrogen storage alloy in the negative electrode of the battery is at risk of irreversible damage.

5. The optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions according to claim 1, characterized in that, Step S3 specifically includes: The lattice stress parameter is compared with a preset critical threshold. When it is determined that the lattice stress parameter is close to or reaches the preset critical threshold, the optimization algorithm is activated; The optimization algorithm aims to minimize the lattice strain energy and promote uniform hydrogen absorption and diffusion of hydrogen atoms, and determines the amplitude, frequency, and duty cycle parameters of the pulse current waveform. Based on the determined amplitude parameters, frequency parameters, and duty cycle parameters, at least one asymmetric pulse current waveform data is generated, wherein the asymmetric pulse current waveform data includes a positive pulse portion and a negative pulse portion; The asymmetric pulse current waveform data is output as a pulse current command sequence, so that subsequent steps can apply a composite energy field according to the pulse current command sequence.

6. The optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions according to claim 5, characterized in that, Also includes: The preset critical threshold is determined through the following steps: For the nickel-metal hydride battery pack to be calibrated, a calibration experiment was performed under low-temperature conditions to collect performance data of the nickel-metal hydride battery pack under different stress states. During the calibration experiment, a gradually increasing charging current was applied to the nickel-metal hydride battery pack, and the lattice stress change of the hydrogen storage alloy of the negative electrode of the nickel-metal hydride battery pack was monitored in real time. The lattice stress value corresponding to the occurrence of irreversible damage to the nickel-metal hydride battery pack was recorded, and the lattice stress value was determined as the upper limit of stress. The upper limit of stress is multiplied by a preset safety factor to obtain the critical threshold of lattice stress of the nickel-metal hydride battery pack. The value of the safety factor is greater than 0 and less than 1. The critical threshold of lattice stress is stored in the battery management system, which is used to compare the lattice stress parameters calculated in real time with the critical threshold of lattice stress during the charging process.

7. The optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions according to claim 1, characterized in that, Step S4 specifically includes: It runs continuously from the start of the charging process until the end of the charging cycle, using the real-time monitored lattice stress parameters as the core feedback basis. The lattice stress parameters monitored in real time are continuously compared with the preset ideal stability range of lattice stress, and the deviation value between the lattice stress parameters and the ideal stability range is calculated. The adjustment direction of the pulse current waveform parameters is determined based on the deviation value, and the adjustment direction includes increasing the parameter, decreasing the parameter, or keeping the parameter unchanged; When the lattice stress parameter approaches the upper limit of the ideal stable range and shows a stress accumulation trend, the amplitude parameter is reduced, the frequency parameter is increased, or the duty cycle parameter is decreased to reduce the duration of a single pulse energization. When the lattice stress parameter is within the ideal stable range, the duty cycle parameter is adjusted to accelerate the hydrogen atom absorption and diffusion rate without increasing the lattice stress. The adjusted amplitude, frequency, and duty cycle parameters are output to continue generating updated asymmetric pulse current waveform data.

8. The optimized method for fast and safe charging of nickel-metal hydride battery packs under wide temperature conditions according to claim 7, characterized in that, The step of continuously comparing the real-time monitored lattice stress parameters with a preset ideal stability range of lattice stress and calculating the deviation value between the lattice stress parameters and the ideal stability range specifically includes: Obtain a preset ideal stability range of lattice stress, wherein the ideal stability range includes an upper limit value and a lower limit value; Obtain the values ​​of lattice stress parameters monitored in real time during the current charging cycle; The lattice stress parameter values ​​are compared with the upper limit of the interval and the lower limit of the interval, respectively. When the value of the lattice stress parameter is greater than the upper limit of the interval, a first difference between the value of the lattice stress parameter and the upper limit of the interval is calculated, and the first difference is determined as a first type of deviation value. The first type of deviation value is used to characterize the degree to which the current lattice stress exceeds the safe range. When the value of the lattice stress parameter is less than the lower limit of the interval, a second difference between the lower limit of the interval and the value of the lattice stress parameter is calculated, and the second difference is determined as a second type of deviation value. The second type of deviation value is used to characterize the degree to which the current lattice stress is lower than the ideal state. When the value of the lattice stress parameter is between the upper limit of the interval and the lower limit of the interval, the deviation value is determined to be zero; The calculated deviation value is output so that subsequent steps can determine the adjustment direction of the pulse current waveform parameters based on the deviation value.

9. A fast and safe charging optimization device for nickel-metal hydride battery packs under wide temperature operating conditions, characterized in that, include: Battery module, the battery module comprising a nickel-metal hydride battery pack; One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors execute the fast and safe charging optimization method for nickel-metal hydride battery packs as described in any one of claims 1 to 8, and output the execution results to the battery module.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the fast and safe charging optimization method for nickel-metal hydride battery packs as described in any one of claims 1 to 8.

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