A lithium ion battery voltage temperature compensation method and system based on SOC segmentation

Abstract

The application discloses a lithium ion battery voltage temperature compensation method and system based on SOC segmentation. The method establishes a linear relationship model of voltage and temperature by carrying out static experiments on lithium ion batteries in multiple SOC states at different temperatures, and identifies the characteristics that the voltage of the lithium ion battery rises with the increase of temperature when the SOC is above 65%, and the voltage of the lithium ion battery decreases with the increase of temperature when the SOC is below 52%. By introducing a self-discharge rate compensation mechanism of self-discharge influence, and adopting a 'nearest principle' to segment different SOC and temperature intervals, the corresponding temperature compensation coefficient alpha is calculated to dynamically compensate the voltage test value. The application effectively solves the problems of inaccurate self-discharge rate test, high defective rate and the like of the lithium ion battery caused by the change of the environmental temperature, and improves the consistency and production efficiency of the lithium ion battery sorting.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery testing and sorting technology, and in particular to a method and system for voltage and temperature compensation of lithium-ion batteries based on SOC segmentation. Background Technology

[0002] In the lithium-ion battery production process, self-discharge rate is typically used for consistent sorting of lithium-ion batteries. However, changes in ambient temperature in the workshop can significantly affect the test results of lithium-ion battery voltage, leading to inaccurate self-discharge rate calculations, which in turn affects sorting accuracy and yield. While existing technologies have attempted to compensate for voltage at temperature, they do not consider the differences in voltage response to temperature at different SOCs (State of Charge, i.e., percentage of charge), nor do they systematically address the interference of self-discharge on the testing process, resulting in limited compensation effectiveness. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for voltage and temperature compensation of lithium-ion batteries based on SOC segmentation, so as to solve the problem of inaccurate self-discharge rate testing caused by temperature changes in the prior art.

[0004] This invention is achieved through the following technical solution: a lithium-ion battery voltage and temperature compensation method based on SOC segmentation, comprising the following steps: Obtain voltage data of lithium-ion batteries under different temperature conditions and multiple SOC states, and establish the correspondence between voltage and temperature; Based on the voltage-temperature relationship, the characteristic of the lithium-ion battery is identified that the voltage increases with increasing temperature when the SOC is above 65% and decreases with increasing temperature when the SOC is below 52%. Based on the identification results, the temperature compensation coefficients corresponding to different SOC ranges are determined; Based on the current SOC and current temperature of the lithium-ion battery, a corresponding temperature compensation coefficient is selected to compensate the voltage test value.

[0005] Furthermore, the acquisition of voltage data of the lithium-ion battery under different temperature conditions and multiple SOC states, and the establishment of the correspondence between voltage and temperature, specifically includes: Multiple SOC points were selected, and the lithium-ion battery was subjected to a temperature change experiment within a temperature range of 18℃ to 30℃. The battery was left to stand for 1 hour for each 1℃ change, and the voltage value corresponding to each temperature point was recorded. A linear relationship model between voltage and temperature under various SOCs was established using linear regression.

[0006] Furthermore, determining the temperature compensation coefficients corresponding to different SOC ranges specifically includes: Calculate the slope of voltage change with temperature at each SOC, and use it as the temperature compensation coefficient α; Among them, the temperature compensation coefficient α corresponding to SOC above 65% is positive, and the temperature compensation coefficient α corresponding to SOC below 52% is negative.

[0007] Furthermore, in determining the temperature compensation coefficient, a self-discharge rate compensation mechanism is introduced, whereby the self-discharge rate is the rate of change of the lithium-ion battery voltage over time, used to eliminate the interference of the lithium-ion battery's self-discharge on the voltage measurement during the variable temperature experiment.

[0008] Furthermore, the self-discharge rate compensation adopts the proximity principle, specifically including: During the temperature rise phase from 18℃ to 30℃, the self-discharge rate measured at a preset time under the condition of standing at 23℃ before the temperature change is used as a benchmark for compensation. During the cooling phase from 30℃ to 18℃, compensation was performed based on the self-discharge rate measured after a preset time of standing at 23℃ following the temperature change.

[0009] Furthermore, the compensation based on the self-discharge rate measured at a preset time under conditions of 23°C before the temperature change specifically includes: For a temperature range of 18℃ to 22℃, the voltage after compensation equals the voltage before compensation. Time difference × self-discharge rate; For a temperature range of 24℃ to 30℃, the compensated voltage = the voltage before compensation + the time difference × the self-discharge rate.

[0010] Furthermore, the method for determining the temperature compensation coefficients corresponding to the different SOC ranges includes: For SOC of 30% and below, the temperature compensation coefficient α2 is obtained from the cooling experiment; For SOC of 35% and above, the average value of the temperature compensation coefficient α1 obtained by heating experiment and the temperature compensation coefficient α2 obtained by cooling experiment is α3.

[0011] Furthermore, it also includes identifying critical values ​​for the SOC range of 52% to 65% in order to optimize the temperature compensation coefficient corresponding to this range.

[0012] Furthermore, the temperature variation experiment includes a heating experiment and a cooling experiment. The temperature compensation coefficient at each SOC is calculated through the heating experiment and the cooling experiment, respectively. The temperature compensation coefficient calculated by the heating experiment is compared and verified with the temperature compensation coefficient calculated by the cooling experiment to confirm the reliability of the compensation coefficient.

[0013] A lithium-ion battery voltage and temperature compensation system, comprising: Temperature control module, used to control the ambient temperature of the lithium-ion battery testing environment; The data acquisition module is used to acquire the voltage and temperature data of the lithium-ion battery; The compensation calculation module is used to execute the above method, select the corresponding temperature compensation coefficient according to the current SOC and current temperature of the lithium-ion battery, compensate the voltage test value collected by the data acquisition module, and output the compensated voltage value.

[0014] Compared with the prior art, the present invention has the following significant advantages: First, it accurately identified the SOC-dependent voltage-temperature response law. Through systematic temperature variation experiments, this invention is the first to identify the characteristic that the voltage of a lithium-ion battery increases with increasing temperature when the SOC is above 65%, and decreases with increasing temperature when the SOC is below 52%. This reveals the essential difference in the voltage response to temperature in different SOC ranges, fundamentally solving the systematic error problem of traditional unified temperature compensation models.

[0015] Second, it eliminates the interference of self-discharge on temperature compensation. This invention introduces a self-discharge rate compensation mechanism, which dynamically selects the self-discharge rate compensation benchmark using the "proximity principle," effectively eliminating the interference of battery self-discharge on voltage measurement during temperature variation experiments and significantly improving the calculation accuracy of the temperature compensation coefficient α.

[0016] Third, it achieves high consistency compensation across the entire SOC range. This invention employs differentiated compensation strategies for different SOC ranges (α2 for 30% and below, α3 for 35% and above, and critical value identification and optimization for the 52%-65% range), ensuring accurate matching and smooth transition of the temperature compensation coefficient across the entire SOC range, and significantly improving the consistency and accuracy of lithium-ion battery self-discharge rate testing.

[0017] Fourth, the reliability of the compensation model is ensured through two-way verification. This invention effectively eliminates systematic errors that may exist in one-way experiments by comparing and verifying heating and cooling experiments, thus ensuring the reliability and repeatability of the compensation coefficients.

[0018] Fifth, it enables industrial automation applications. This invention integrates the above methods into a lithium-ion battery testing system, achieving real-time, automated, and precise voltage and temperature compensation. It effectively solves problems such as inaccurate self-discharge rate testing and high defect rates of lithium-ion batteries caused by changes in workshop ambient temperature, significantly improving the consistency and production efficiency of lithium-ion battery sorting. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the experimental process of the method of the present invention.

[0020] Figure 2This is a graph showing the voltage variation under different SOCs in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the self-discharge rate compensation logic in an embodiment of the present invention.

[0022] Figure 4 This is a graph showing the variation trend of the measured constant α and the calculated constant α at 23℃ under different SOCs in this embodiment of the invention.

[0023] Figure 5 This is a graph showing the variation trend of the constant α calculated during the heating and cooling processes under different SOCs in embodiments of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] This invention provides a method for voltage and temperature compensation of lithium-ion batteries based on SOC segmentation, comprising the following steps: First, voltage data of lithium-ion batteries under different temperature conditions and multiple State of Charge (SOC) states are obtained to establish the correlation between voltage and temperature. Specifically, multiple SOC states are selected, and static tests are performed on lithium-ion batteries at multiple temperature points. The open-circuit voltage value corresponding to each temperature point is recorded, and the correlation between voltage and temperature at each SOC state is established through data fitting.

[0026] Secondly, based on the voltage-temperature relationship and by eliminating the interference of self-discharge on temperature compensation, the characteristics of the lithium-ion battery were identified: the voltage increases with temperature when the SOC is above 65%, and decreases with temperature when the SOC is below 52%. This characteristic indicates that the response of lithium-ion batteries to temperature differs significantly in different SOC ranges: the high SOC range (above 65%) exhibits a positive temperature coefficient characteristic, while the low SOC range (below 52%) exhibits a negative temperature coefficient characteristic.

[0027] Next, based on the identification results, the temperature compensation coefficients corresponding to different SOC ranges are determined. For the SOC range above 65%, the temperature compensation coefficient α is positive; for the SOC range below 52%, the temperature compensation coefficient α is negative; for the SOC range between 52% and 65%, the compensation coefficient can be further optimized through critical value identification.

[0028] Finally, based on the current SOC and temperature of the lithium-ion battery, a corresponding temperature compensation coefficient is selected to dynamically compensate the voltage test value, and the compensated voltage value is output for self-discharge rate calculation. This invention, by pre-identifying the differential voltage response to temperature in different SOC ranges (increasing above 65% and decreasing below 52%), and accordingly configuring corresponding temperature compensation coefficients for different SOC ranges, can accurately select the compensation coefficient based on the battery's current SOC state and temperature. This effectively solves the problem of inconsistent compensation accuracy in different SOC ranges using traditional unified temperature compensation models, significantly improving the accuracy and consistency of voltage-temperature compensation across the entire SOC range.

[0029] Step 1: Experimental Modeling Multiple SOC points (e.g., 5%, 10%, 45%, 65%, 75%, 90%, 100%) were selected, and the voltage was recorded for 1 hour at each degree Celsius within the range of 18℃ to 30℃. The α value at each SOC was obtained through linear regression.

[0030] The acquisition of voltage data of lithium-ion batteries under different temperature conditions and multiple SOC states, and the establishment of the correspondence between voltage and temperature, specifically includes: Multiple State of Charge (SOC) points were selected, including but not limited to 5%, 10%, 45%, 65%, 75%, 90%, and 100%. A temperature variation experiment was conducted on the lithium-ion battery within a temperature range of 18°C ​​to 30°C. For each 1°C change, the battery was left to stand for 1 hour, and the voltage value corresponding to each temperature point was recorded. A linear regression model was used to establish a linear relationship between voltage and temperature at each SOC. In one specific embodiment, the self-discharge rate of the lithium-ion battery was calculated after standing at 23°C for 24 hours. Subsequently, the ambient temperature was gradually increased from 18°C ​​to 30°C, with each 1°C increase followed by 1 hour of standing. The voltage before reaching the next degree Celsius was selected as the voltage value at that temperature, and the voltage data corresponding to 13 temperature points from 18°C ​​to 30°C were recorded. For each State of Charge (SOC), a line graph is plotted with temperature on the x-axis and voltage on the y-axis. A linear regression is used to obtain the linear relationship between voltage and temperature at that SOC: V0 = V(T) - α·(T-T0), where V0 is the voltage value at the reference temperature T0 (23℃), and α is the temperature compensation coefficient. This invention, through refined temperature-varying experiments (one test point per 1℃) over a wide temperature range of 18℃ to 30℃, combined with linear regression modeling, can accurately establish the quantitative relationship between voltage and temperature at each SOC, providing a reliable data foundation for subsequent segmented compensation. Sufficient settling for one hour per degree ensures the stability and repeatability of the voltage measurements. Furthermore, determining the temperature compensation coefficients corresponding to different SOC intervals specifically includes: The slope value of voltage change with temperature under each SOC is calculated and used as the temperature compensation coefficient α. Specifically, the slope value α corresponding to each SOC is obtained by linear regression calculation using the linear relationship model V0=V(T)-α·(T-T0) established in claim 2 for each SOC.

[0031] Among them, the temperature compensation coefficient α corresponding to 65% SOC and 75% SOC is a positive number, while the temperature compensation coefficient α corresponding to the other SOCs is a negative number. For example, according to experimental measurements, α is approximately +0.05mV / ℃ at 75% SOC (voltage increases with increasing temperature), and approximately -0.15mV / ℃ at 10% SOC (voltage decreases with increasing temperature). Moreover, the higher the electrical state, the smaller the magnitude of voltage change with temperature.

[0032] Figure 2 Voltage variation under different SOCs A line graph was plotted for the voltage of each state of charge (SOC) at different temperatures, with temperature on the horizontal axis and voltage on the vertical axis. The total voltage range for each state was 15mV. The graph shows that: (1) The voltage and temperature of lithium-ion batteries in different states of charge show a linear relationship; (2) The voltage increases with increasing temperature at 65% and 75% SOC, while the voltage decreases with increasing temperature at other conditions.

[0033] (3) The higher the electrical state, the smaller the voltage changes with temperature.

[0034] In this embodiment, the slope of the voltage-temperature curve at each SOC is calculated as the temperature compensation coefficient α, which quantifies the influence of temperature on voltage into specific numerical parameters, facilitating subsequent compensation calculations.

[0035] Furthermore, a self-discharge rate compensation mechanism is introduced in the process of determining the temperature compensation coefficient. The self-discharge rate is the rate of change of the lithium-ion battery voltage over time, used to eliminate the interference of the lithium-ion battery's own self-discharge on the voltage measurement during the temperature variation experiment.

[0036] Specifically, before and after the temperature variation experiment, the lithium-ion batteries were subjected to a static test at 23°C, and the self-discharge rate K of each battery was calculated. The formula for calculating the self-discharge rate K is: K=(V1-V2) / Δt, where V1 is the initial static voltage, V2 is the final static voltage, and Δt is the static time.

[0037] In one specific embodiment, the lithium-ion battery is subjected to high-temperature aging at 45°C for 48 hours and then at room temperature (23°C) for 168 hours to ensure sufficient aging. Afterward, it is placed at 23°C for 24 hours, and the self-discharge rate under different SOC states is calculated to compensate for the self-discharge of the lithium-ion battery itself during the heating phase of the temperature-changing experiment. After stabilizing the battery at 30°C for an additional 6 hours, a cooling experiment is conducted from 30°C to 18°C. The battery is then placed at 23°C for 24 hours again, and the self-discharge rate under different SOC states is calculated to compensate for the self-discharge of the lithium-ion battery itself during the cooling phase.

[0038] Figure 1 To ensure sufficient aging of lithium-ion batteries, they were subjected to high-temperature aging at 45℃ for 48 hours and room-temperature aging at 23℃ for 168 hours. Then, after aging at 23℃ for 24 hours, the self-discharge rate under different SOC states was calculated to compensate for the self-discharge of the lithium-ion battery itself during the temperature rise phase of the variable-temperature experiment. Next, a temperature rise experiment was conducted from 18℃ to 30℃, with a 1-hour aging period for each 1℃ increase. The voltage before the temperature rise was used as the voltage at that temperature. An additional 6 hours of aging was performed at 30℃ to stabilize the lithium-ion battery. A cooling experiment from 30℃ to 18℃ was then conducted to verify the accuracy of the temperature rise experiment. Finally, a 24-hour aging period at 23℃ was performed to calculate the self-discharge rate under different SOC states to compensate for the self-discharge during the cooling phase of the variable-temperature experiment.

[0039] Step 2: Self-discharge rate compensation Based on the voltage data calculated after 24 hours of rest at 23℃, the self-discharge rate of lithium-ion batteries at each SOC state was calculated. In the temperature range of 18℃ to 22℃, the K value at 23℃ before temperature change was selected as the benchmark for self-discharge rate compensation. The product of the self-discharge rate and the time difference between the current temperature and 23℃ during the temperature rise phase was used as the voltage compensation value: Compensated voltage = Pre-compensation voltage - Time difference * Self-discharge rate; In the temperature range of 24℃ to 30℃: Compensated voltage = Pre-compensation voltage + Time difference * Self-discharge rate.

[0040] This embodiment introduces a self-discharge rate compensation mechanism in the temperature compensation coefficient calculation process, effectively eliminating the interference of battery self-discharge on voltage measurement during variable temperature experiments, and avoiding the voltage drop caused by self-discharge being misjudged as a temperature effect, thereby significantly improving the accuracy and reliability of the temperature compensation coefficient α calculation.

[0041] Furthermore, the self-discharge rate compensation adopts the proximity principle, specifically including: During the heating phase from 18°C ​​to 30°C, compensation is based on the self-discharge rate measured after a preset resting time (preferably 24 hours) at 23°C before the temperature change. Considering that lithium-ion batteries with similar resting times have similar self-discharge rates, the self-discharge rate measured after a 24-hour resting period at 23°C before the temperature change is selected as the compensation value for each temperature point during the heating phase, following the principle of proximity. During the cooling phase from 30°C to 18°C, compensation is based on the self-discharge rate measured after a preset resting time (preferably 24 hours) at 23°C after the temperature change. Again, the self-discharge rate measured after a 24-hour resting period at 23°C after the temperature change is selected as the compensation value for each temperature point during the cooling phase, following the principle of proximity.

[0042] This embodiment uses the "proximity principle" to dynamically select the self-discharge rate compensation benchmark at different temperature stages—the self-discharge rate at 23°C before the temperature change is used as the benchmark during the heating stage, and the self-discharge rate at 23°C after the temperature change is used as the benchmark during the cooling stage—effectively eliminating the time accumulation effect of the battery's self-discharge throughout the temperature change experiment, leveling the self-discharge error caused by the difference in test time at different temperatures to the same benchmark, and greatly reducing the time error of the compensation value.

[0043] Furthermore, the compensation based on the self-discharge rate measured at a preset time under conditions of 23°C before the temperature change specifically includes: For a temperature range of 18℃ to 22℃, the voltage after compensation equals the voltage before compensation. Time difference × self-discharge rate; For a temperature range of 24℃ to 30℃, the compensated voltage = the voltage before compensation + the time difference × the self-discharge rate.

[0044] Among them, "time difference" refers to the time interval between the time at that temperature (e.g., 22℃) and the time at 23℃ during the temperature change process, and "self-discharge rate" is the rate of change of voltage over time measured under the condition of standing at 23℃ for 24 hours before the temperature change (unit: mV / h).

[0045] Taking the 18℃ to 22℃ range as an example, since the temperature in this range is earlier than the 23℃ reference temperature in the experimental process, it takes a certain amount of time to reach 23℃. During this time, the battery itself undergoes self-discharge, causing a voltage drop. Therefore, the product of the time difference and the self-discharge rate needs to be subtracted from the voltage before compensation. For the 24℃ to 30℃ range, the temperature rises from 23℃ to this range. Self-discharge during the temperature rise also causes a voltage drop. The compensation direction is opposite, so the product of the time difference and the self-discharge rate needs to be added to the voltage before compensation.

[0046] Table 1. Examples of voltage compensation during the heating phase, adjusting the temperature to 23℃ (K value compensation at different times).

[0047] This embodiment uses the product of self-discharge rate and time difference as the voltage compensation value, and applies opposite compensation directions (subtracting in the low-temperature range and adding in the high-temperature range) for the temperature ranges below 23°C and above 23°C, respectively. This achieves accurate compensation for the battery's self-discharge throughout the variable temperature experiment and effectively eliminates the influence of time factor on the calculation of temperature compensation coefficient.

[0048] Figure 4 The graph shows the trend of the measured constant α under different SOCs and the calculated constant α at 23℃. The trend of the constant α under different SOCs at 18℃-30℃ is plotted as a line graph (the horizontal axis is different SOCs and the vertical axis is the constant α value). The measured constant and the constant after compensation using the self-discharge rate compensation formula show similar trends (the constant α value gradually increases as the SOC increases).

[0049] Furthermore, the method for determining the temperature compensation coefficients corresponding to the different SOC ranges includes: For SOC of 30% and below, the temperature compensation coefficient α2 is obtained from the cooling experiment; For SOC of 35% and above, the average value of the temperature compensation coefficient α1 obtained from the heating experiment and the temperature compensation coefficient α2 obtained from the cooling experiment is α3, i.e., α3=(α1+α2) / 2.

[0050] Step 3: Calculation and verification of α during the heating and cooling stages By integrating the data from step 2 and comparing the constants α calculated during the heating and cooling processes, it was confirmed that the electrical state compensation value α is positive for SOC above 65% and negative for SOC below 52%.

[0051] In this embodiment, the temperature compensation coefficient α1 for each SOC is calculated through a heating experiment (18℃→30℃), and the temperature compensation coefficient α2 for each SOC is calculated through a cooling experiment (30℃→18℃). The constant α calculated from the heating and cooling experiments is compared, and the trends are similar (the constant α value gradually increases with increasing electrical state), verifying the experimental results. Based on this, for the low SOC range of 30% and below, the α2 value from the cooling experiment is directly used for compensation; for the SOC range of 35% and above, the average α value of the heating and cooling experiments, α3, is used for compensation.

[0052] Figure 5 The graph shows the trend of the calculated constant α during the heating and cooling processes under different SOCs.

[0053] according to Figure 3 Figure 4The logic was used to calculate the cooling constant α2 at different SOCs from 30℃ to 18℃ in the cooling experiment, and the calculated constant was confirmed. The calculated constant α trends of the heating experiment and the cooling experiment were similar (the value of constant α gradually increases with the increase of the electric state). The experimental results were verified.

[0054] Step 4: Phased Compensation (1) For SOC of 30% and below, the α2 value based on the cooling experiment is adopted; (2) For SOC of 35% and above, the average value of α1 based on the heating experiment and α2 based on the cooling experiment is used as α3; (3) Identify the critical value in the 52%-65% range and further optimize the α value.

[0055] This embodiment adopts a differentiated compensation coefficient determination strategy for different SOC ranges—for the low SOC range (30% and below), the α2 value from the cooling experiment is directly used, while for the high SOC range (35% and above), the average value of heating and cooling α3 is used—fully taking into account the differences in voltage-temperature response characteristics in different SOC ranges, further improving the consistency and accuracy of voltage and temperature compensation across the entire SOC range.

[0056] Furthermore, it also includes identifying critical values ​​for the SOC range of 52% to 65% in order to optimize the temperature compensation coefficient corresponding to this range.

[0057] Specifically, within the SOC range of 52% to 65%, the voltage-temperature response characteristics of lithium-ion batteries are in a transitional region from a "negative temperature coefficient" (below 52%, voltage decreases with increasing temperature) to a "positive temperature coefficient" (above 65%, voltage increases with increasing temperature). Within this range, there exists a critical SOC point where the voltage is essentially unaffected by temperature, and the temperature compensation coefficient α≈0.

[0058] By increasing the density of SOC sampling points within this range (e.g., at intervals of 1% or 2%), conducting refined temperature variation experiments and linear regression analysis, the critical SOC point with α≈0 is identified. Based on this, the temperature compensation coefficient of each SOC point within this range is interpolated and optimized to ensure a smooth transition of the compensation coefficient between 52% and 65%.

[0059] This embodiment ensures a smooth transition of the temperature compensation coefficient across the entire SOC range (from negative values ​​below 52% to positive values ​​above 65%) by identifying critical values ​​and optimizing the compensation coefficient in the 52% to 65% transition range. This avoids compensation jumps caused by abrupt changes in the compensation coefficient and further improves the continuity and accuracy of voltage and temperature compensation.

[0060] Furthermore, the temperature variation experiment includes a heating experiment and a cooling experiment. The temperature compensation coefficient at each SOC is calculated through both the heating and cooling experiments, and the calculated temperature compensation coefficients are compared and verified with those calculated through the cooling experiment to confirm the reliability of the compensation coefficients.

[0061] Temperature rise experiment: After the lithium-ion battery was left to stand at 23℃ for 24 hours, the self-discharge rate of each SOC state was measured. Then, a temperature rise experiment was conducted within the range of 18℃ to 30℃, with a standing period of 1 hour for each 1℃ increase, and the voltage value at each temperature point was recorded. The temperature compensation coefficient α1 for each SOC under the temperature rise experiment was obtained by linear regression.

[0062] Cooling experiment: After reaching 30℃ in the heating experiment, the battery was allowed to stand for an additional 6 hours to stabilize its state. Then, a cooling experiment was conducted within the range of 30℃ to 18℃, with a 1-hour stand time for each 1℃ decrease, and the voltage value at each temperature point was recorded. The temperature compensation coefficient α2 for each SOC under the cooling experiment was obtained through linear regression.

[0063] Comparative Verification: The α1 calculated from the heating experiment and the α2 calculated from the cooling experiment were compared, and the trend of α value under different SOCs was plotted. The experimental results show that the calculated constant α from the heating experiment and the cooling experiment have similar trends—both gradually increase with increasing SOC, verifying the reliability of the experimental results and the accuracy of the compensation coefficient.

[0064] This embodiment effectively eliminates systematic and random errors that may exist in unidirectional experiments through bidirectional heating and cooling verification, ensuring the reliability and repeatability of the temperature compensation coefficient α. Successful bidirectional verification indicates that the compensation model has good stability and generalization ability.

[0065] Step 5: System Implementation The above algorithm is integrated into a lithium-ion battery testing system. The compensation logic is executed in real time through a temperature sensor, voltage acquisition module and processor, and the compensated voltage value is output for self-discharge rate calculation.

[0066] The present invention also provides a lithium-ion battery voltage and temperature compensation system, comprising: The temperature control module 100 is used to control the test environment temperature of lithium-ion batteries. It can perform precise temperature control within the range of 18℃ to 30℃, with a temperature control accuracy of ±0.5℃.

[0067] The data acquisition module 200 is used to acquire voltage and temperature data of the lithium-ion battery. The voltage acquisition accuracy is not less than 0.1mV, and the temperature acquisition accuracy is not less than 0.1℃.

[0068] The compensation calculation module 300 is used to execute the method as described in any one of claims 1 to 9, select a corresponding temperature compensation coefficient according to the current SOC and current temperature of the lithium-ion battery, compensate the voltage test value collected by the data acquisition module, and output the compensated voltage value.

[0069] Specifically, the compensation calculation module 300 has a built-in database of temperature compensation coefficients for each SOC range (including α1, α2, α3 and optimized values ​​for the 52%-65% range). It receives the current SOC and temperature values ​​from the data acquisition module 200 in real time, looks up the corresponding temperature compensation coefficient α in the table, and calculates the compensation coefficient according to the compensation formula V. comp =V meas +α·(T-T0) (T0=23℃) calculates the compensated voltage value and outputs it to the display or storage unit.

[0070] This embodiment integrates the above-mentioned temperature compensation method into an automated testing system, realizing real-time, automated, and precise voltage and temperature compensation. It can be widely applied to the self-discharge rate testing and consistency sorting stages in the lithium-ion battery production process, effectively improving production efficiency and product yield.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for voltage and temperature compensation of lithium-ion batteries based on SOC segmentation, characterized in that, Includes the following steps: Obtain voltage data of lithium-ion batteries under different temperature conditions and multiple SOC states, and establish the correspondence between voltage and temperature; Based on the voltage-temperature relationship, the characteristic of the lithium-ion battery is identified that the voltage increases with increasing temperature when the SOC is above 65% and decreases with increasing temperature when the SOC is below 52%. Based on the identification results, the temperature compensation coefficients corresponding to different SOC ranges are determined; Based on the current SOC and current temperature of the lithium-ion battery, a corresponding temperature compensation coefficient is selected to compensate the voltage test value.

2. The method according to claim 1, characterized in that, The acquisition of voltage data of lithium-ion batteries under different temperature conditions and multiple SOC states, and the establishment of the correspondence between voltage and temperature, specifically includes: Multiple SOC points were selected, and the lithium-ion battery was subjected to a temperature change experiment within a temperature range of 18℃ to 30℃. The battery was left to stand for 1 hour for each 1℃ change, and the voltage value corresponding to each temperature point was recorded. A linear relationship model between voltage and temperature under various SOCs was established using linear regression.

3. The method according to claim 1, characterized in that, The determination of the temperature compensation coefficients corresponding to different SOC ranges specifically includes: Calculate the slope of voltage change with temperature at each SOC, and use it as the temperature compensation coefficient α; Among them, the temperature compensation coefficient α corresponding to SOC above 65% is positive, and the temperature compensation coefficient α corresponding to SOC below 52% is negative.

4. The method according to claim 1, characterized in that, In determining the temperature compensation coefficient, a self-discharge rate compensation mechanism is also introduced. The self-discharge rate is the rate of change of the lithium-ion battery voltage over time, which is used to eliminate the interference of the lithium-ion battery's self-discharge on the voltage measurement during the variable temperature experiment.

5. The method according to claim 4, characterized in that, The self-discharge rate compensation adopts the nearest principle, specifically including: During the temperature rise phase from 18℃ to 30℃, the self-discharge rate measured at a preset time under the condition of standing at 23℃ before the temperature change is used as a benchmark for compensation. During the cooling phase from 30℃ to 18℃, compensation was performed based on the self-discharge rate measured after a preset time of standing at 23℃ following the temperature change.

6. The method according to claim 5, characterized in that, The compensation is based on the self-discharge rate measured at a preset time under conditions of 23°C before the temperature change, specifically including: For a temperature range of 18℃ to 22℃, the voltage after compensation equals the voltage before compensation. Time difference × self-discharge rate; For a temperature range of 24℃ to 30℃, the compensated voltage = the voltage before compensation + the time difference × the self-discharge rate.

7. The method according to claim 1, characterized in that, The methods for determining the temperature compensation coefficients corresponding to the different SOC ranges include: For SOC of 30% and below, the temperature compensation coefficient α2 is obtained from the cooling experiment; For SOC of 35% and above, the average value of the temperature compensation coefficient α1 obtained by heating experiment and the temperature compensation coefficient α2 obtained by cooling experiment is α3.

8. The method according to claim 1, characterized in that, It also includes identifying critical values ​​for the SOC range of 52% to 65% in order to optimize the temperature compensation coefficient for that range.

9. The method according to claim 2, characterized in that, The variable temperature experiment includes a heating experiment and a cooling experiment. The temperature compensation coefficient at each SOC is calculated through the heating experiment and the cooling experiment, respectively. The temperature compensation coefficient calculated by the heating experiment is compared and verified with the temperature compensation coefficient calculated by the cooling experiment to confirm the reliability of the compensation coefficient.

10. A lithium-ion battery voltage and temperature compensation system, characterized in that, include: Temperature control module, used to control the test environment temperature of lithium-ion batteries; The data acquisition module is used to acquire the voltage and temperature data of the lithium-ion battery; The compensation calculation module is used to execute the method as described in any one of claims 1-9, select the corresponding temperature compensation coefficient according to the current SOC and current temperature of the lithium-ion battery, compensate the voltage test value collected by the data acquisition module, and output the compensated voltage value.

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