SOC updating method and system, and medium

Abstract

The invention provides an SOC updating method and system and a medium, and the method comprises the steps: building an independent equivalent circuit model for each cell, precisely determining the internal resistance of the cell through combining the discharge parameter of each cell and the current environment temperature, and guaranteeing the individual pertinence and temperature adaptability of the internal resistance calculation. And then, on the basis of the current internal resistance and a preset internal resistance life mapping relation representing the SOH and temperature mapping relation, an SOH value obtained through a linear interpolation algorithm better fits the real-time aging state of the battery cell compared with a traditional durability cycle index estimation mode. According to the method, the current internal resistance and the SOH value are calculated, parameters of each equivalent circuit model are further updated according to the current internal resistance and the SOH value, a dynamically adaptive first calculation parameter set is formed, SOC updating is performed in combination with real-time state data of each battery cell and the parameter set, the influence of battery cell consistency difference, aging attenuation and temperature fluctuation on SOC calculation is effectively offset, and the accuracy of SOC updating calculation is greatly improved.

Description

A SOC update method, system, and medium Technical Field

[0001] This application relates to the field of vehicle networking technology, and in particular to a SOC update method, system and medium. Background Technology

[0002] Currently, in traditional battery management systems (BMS), the State of Charge (SOC) calculation and updates for ternary lithium batteries and lithium iron phosphate cells rely on pre-set fixed parameters. Furthermore, SOH (State of Health) assessments are primarily based on cycle life, failing to adequately adapt to the dynamic changes in cell condition during vehicle use. In practical applications, cell internal resistance gradually changes with aging, and fluctuations in ambient temperature and measurement deviations in current sensors continuously affect data accuracy. Traditional solutions lack real-time adaptation mechanisms to these dynamic factors, resulting in poor accuracy in current SOC update calculations for battery packs. Summary of the Invention

[0003] To address the aforementioned issues and improve the accuracy of SOC update calculations for battery packs, this application provides an SOC update method, system, and medium.

[0004] The embodiments of this application disclose the following technical solutions:

[0005] In a first aspect, embodiments of this application provide a SOC update method, including:

[0006] The target battery pack is controlled to discharge based on the target discharge value. The current internal resistance of each cell is determined according to the discharge parameters of each cell in the target battery pack and the current ambient temperature. Each cell has a separate equivalent circuit model.

[0007] Based on the current internal resistance of each cell and a preset internal resistance lifetime mapping relationship, the SOH value of each cell is determined by a linear interpolation algorithm; the preset internal resistance lifetime mapping relationship is used to characterize the mapping relationship between the SOH value of the cell and the current ambient temperature.

[0008] Based on the current internal resistance and the SOH value of each of the battery cells, the model parameters in each of the equivalent circuit models are updated to obtain a first set of calculation parameters; the first set of calculation parameters includes the updated model parameters of each of the equivalent circuit models.

[0009] The SOC is updated based on the cell state data of each cell and the first set of calculation parameters to obtain the updated SOC value.

[0010] In one possible implementation, the step of updating the SOC based on the cell state data of each cell and the first set of calculation parameters to obtain the updated SOC value includes:

[0011] Based on the state data of each cell, verify whether each cell is in a balanced state.

[0012] When it is determined that there is a first cell that is not in the balanced state, the first cell is adjusted for balanced state based on the cell state data of the first cell to obtain the adjusted cell state data of the first cell.

[0013] The SOC is updated based on the adjusted cell status data of the first cell, the cell status data of the other cells besides the first cell, and the first set of calculation parameters to obtain the updated SOC value.

[0014] In one possible implementation, the cell status data includes cell voltage and cell capacity;

[0015] The step of verifying whether each of the battery cells is in a balanced state based on the state data of each of the battery cells includes:

[0016] If the voltage difference between any two of the battery cells is greater than a preset voltage threshold, or the capacity difference between any two of the battery cells is greater than a preset capacity threshold, it is determined that neither of the two battery cells is in an balanced state.

[0017] If the voltage difference between any two cells is not greater than the preset voltage threshold and the capacity difference between any two cells is not greater than the preset capacity threshold, then all cells are determined to be in a balanced state.

[0018] In one possible implementation, adjusting the balancing state of the first battery cell based on its cell state data includes:

[0019] For the first cell whose cell capacity is greater than the average cell capacity, the onboard equalization resistor of the first cell is connected until the difference between the cell capacity and cell voltage of the first cell and the corresponding parameters of the second cell is less than a first threshold; the second cell is the cell with the smallest cell capacity among all the cells.

[0020] For the first cell whose cell capacity is less than the average cell capacity, the power in the third cell is transferred to the first cell through an equalization circuit until the difference between the cell capacity and cell voltage of the first cell and the corresponding parameters of the third cell is less than the first threshold; the third cell is the cell with the smallest cell capacity among all the cells.

[0021] In one possible implementation, after obtaining the first set of computational parameters, the method further includes:

[0022] Based on the current ambient temperature, determine the deviation correction data of the current sensor at the current ambient temperature;

[0023] Based on the deviation correction data of the current sensor, the first set of calculation parameters is corrected to obtain the second set of calculation parameters.

[0024] In one possible implementation, the method further includes:

[0025] Obtain the initial charge / discharge voltage protection threshold, rated current, and initial internal resistance of each of the battery cells;

[0026] The real-time charge / discharge voltage protection threshold of each cell is determined based on the initial charge / discharge voltage protection threshold, the rated current, the initial resistance, the SOH value, and the current internal resistance of each cell.

[0027] Based on the current ambient temperature, a temperature correction coefficient is determined using a linear interpolation algorithm, and the real-time charge / discharge voltage protection threshold is corrected using the temperature correction coefficient.

[0028] Secondly, embodiments of this application provide a SOC update system, including:

[0029] The internal resistance determination module is used to control the target battery pack to discharge based on the target discharge value. It determines the current internal resistance of each cell based on the discharge parameters of each cell in the target battery pack and the current ambient temperature. Each cell has a separate equivalent circuit model.

[0030] The SOH determination module is used to determine the SOH value of each of the battery cells based on the current internal resistance of each cell and a preset internal resistance lifetime mapping relationship, using a linear interpolation algorithm; the preset internal resistance lifetime mapping relationship is used to characterize the mapping relationship between the SOH value of the battery cell and the current ambient temperature.

[0031] The parameter update module is used to update the model parameters in each equivalent circuit model according to the current internal resistance and the SOH value of each of the battery cells to obtain a first calculation parameter set; the first calculation parameter set includes the model parameters of each equivalent circuit model after parameter update;

[0032] The SOC update module is used to update the SOC based on the cell status data of each cell and the first set of calculation parameters to obtain the updated SOC value.

[0033] In one possible implementation, the SOC update module is specifically used for:

[0034] Based on the state data of each cell, verify whether each cell is in a balanced state.

[0035] When it is determined that there is a first cell that is not in the balanced state, the first cell is adjusted for balanced state based on the cell state data of the first cell to obtain the adjusted cell state data of the first cell.

[0036] The SOC is updated based on the adjusted cell status data of the first cell, the cell status data of the other cells besides the first cell, and the first set of calculation parameters to obtain the updated SOC value.

[0037] In one possible implementation, the cell status data includes cell voltage and cell capacity; the SOC update module includes a verification unit.

[0038] The verification unit is specifically used for:

[0039] If the voltage difference between any two of the battery cells is greater than a preset voltage threshold, or the capacity difference between any two of the battery cells is greater than a preset capacity threshold, it is determined that neither of the two battery cells is in an balanced state.

[0040] If the voltage difference between any two cells is greater than the preset voltage threshold, and the capacity difference between any two cells is greater than the preset capacity threshold, then all cells are determined to be in a balanced state.

[0041] Thirdly, embodiments of this application provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the SOC update method described in any one of the first aspects.

[0042] Compared to existing technologies, this application offers the following advantages: This application provides a SOC update method, system, and medium. In this method, an independent equivalent circuit model is established for each battery cell. The internal resistance of each cell is accurately determined by combining its discharge parameters and the current ambient temperature, ensuring individual relevance and temperature adaptability in the internal resistance calculation. Subsequently, based on the current internal resistance and a preset internal resistance lifetime mapping relationship characterizing the SOH-temperature mapping relationship, the SOH value obtained through a linear interpolation algorithm is more consistent with the real-time aging state of the battery cell compared to traditional durability cycle estimation methods. Furthermore, the parameters of each equivalent circuit model are updated based on the current internal resistance and SOH value, forming a dynamically adapted first set of calculation parameters. The SOC is then updated by combining the real-time state data of each battery cell with this parameter set, effectively offsetting the impact of cell consistency differences, aging degradation, and temperature fluctuations on the SOC calculation. This significantly improves the matching degree between the SOC value and the actual remaining battery capacity, ensuring the accuracy of the SOC update calculation. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 is a flowchart illustrating a SOC update method provided in an embodiment of this application;

[0045] Figure 2 is a schematic diagram of the circuit structure of an equivalent circuit model corresponding to a battery cell provided in an embodiment of this application;

[0046] Figure 3 is a flowchart illustrating another SOC update method provided in an embodiment of this application;

[0047] Figure 4 is a schematic diagram of the curve relationship between OCV and SOC provided in an embodiment of this application;

[0048] Figure 5 is a schematic diagram of the structure of a SOC update system provided in an embodiment of this application. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and accompanying drawings. It should be particularly noted that the embodiments described in this application are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0050] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0051] As described earlier, in traditional battery management systems (BMS), the State of Charge (SOC) calculation and updates for ternary lithium batteries and lithium iron phosphate cells rely on pre-set fixed parameters. Furthermore, SOH assessments for batteries are primarily based on the number of cycle tests, failing to adequately adapt to the dynamic changes in cell condition during vehicle use. In practical applications, cell internal resistance gradually changes with aging, and fluctuations in ambient temperature and measurement deviations of current sensors continuously affect data accuracy. Traditional solutions lack real-time adaptation mechanisms to these dynamic factors, resulting in poor accuracy in current SOC update calculations for battery packs.

[0052] Based on this, embodiments of this application provide a SOC update method, system, and medium. In this method, an independent equivalent circuit model is established for each battery cell. The internal resistance of each cell is accurately determined by combining its discharge parameters and the current ambient temperature, ensuring the individual specificity and temperature adaptability of the internal resistance calculation. Subsequently, based on the current internal resistance and a preset internal resistance-lifetime mapping relationship characterizing the SOH-temperature mapping relationship, the SOH value obtained through a linear interpolation algorithm is more consistent with the real-time aging state of the battery cell compared to traditional durability cycle estimation methods. Furthermore, the parameters of each equivalent circuit model are updated based on the current internal resistance and SOH value, forming a dynamically adapted first calculation parameter set. The SOC is then updated by combining the real-time state data of each battery cell with this parameter set, effectively offsetting the impact of cell consistency differences, aging degradation, and temperature fluctuations on the SOC calculation. This significantly improves the matching degree between the SOC value and the actual remaining battery capacity, ensuring the accuracy of the SOC update calculation.

[0053] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0054] Referring to Figures 1 and 2, Figure 1 is a flowchart illustrating a SOC update method according to an embodiment of this application, and Figure 2 is a circuit structure diagram illustrating an equivalent circuit model of a battery cell according to an embodiment of this application. Referring to Figure 1, the specific steps include:

[0055] S101: Control the target battery pack to discharge based on the target discharge value, and determine the current internal resistance of each cell according to the discharge parameters of each cell in the target battery pack and the current ambient temperature; wherein each cell has a separate corresponding equivalent circuit model.

[0056] In this embodiment, each cell of the target battery pack is configured with a separate equivalent circuit model. If the target battery pack has a 1-parallel 96-series structure, the BMS will simultaneously build 96 independent equivalent circuit models in the software. Each equivalent circuit model fully includes parameters such as ideal voltage source, ohmic internal resistance R0, polarization internal resistance R1 / R2 and polarization capacitance C1 / C2, so as to replicate the electrochemical characteristics of the corresponding cell.

[0057] Specifically, during the control of the target battery, including discharging based on the target discharge value, it is necessary to ensure that the discharge data accurately reflects the current state of the battery cell. One possible implementation involves periodically waking up the BMS and the vehicle via an RTC (Remote Temperature Controller). Before initiating the discharge test, the ambient temperature and the current SOC (State of Charge) of the target battery pack must be assessed. For example, if the ambient temperature is below 15°C, the battery pack is heated to the target temperature via a thermal management system. If it is a lithium iron phosphate (LFP) cell, it is also necessary to ensure that it is not within the voltage plateau range to avoid voltage drop calculation errors caused by insignificant voltage changes in the plateau region. After meeting the test conditions, the vehicle is put in Park (P) and braked. The relay is closed, driving the battery pack to continuously discharge at the target discharge value (which can be set to 5A in this scenario). During the discharge process, key discharge parameters are collected for each cell: the static voltage U1 before discharge (the stable voltage after eliminating polarization effects) and the real-time dynamic voltage U2 during discharge. Simultaneously, the current ambient temperature is recorded to provide complete parameter input for internal resistance calculation.

[0058] In calculating the current internal resistance of each cell, the collected individual cell values ​​U1 and U2, along with the unified target discharge value I, are substituted into the formula R0=(U1-U2) / I to calculate the current ohmic internal resistance R0 of the cell. It is important to emphasize that the current ambient temperature data is correlated with pre-set multi-temperature-domain internal resistance data from the laboratory to support the validity verification of the internal resistance. The calculated cell internal resistance must fall within the parameter range of the laboratory-calibrated better and worse cells, and the calculation results are fine-tuned using a temperature correction coefficient to avoid measurement deviations caused by temperature changes. For example, the internal resistance calculated at 25℃ must refer to the standard range of cell internal resistance at that temperature; if it exceeds this range, it is considered abnormal, no update is reported, and a fault warning is triggered. This effectively ensures the accuracy of the internal resistance calculation for each cell, thereby improving the accuracy of subsequent SOC updates for the battery pack.

[0059] S102: Based on the current internal resistance of each cell and the preset internal resistance lifetime mapping relationship, the SOH value of each cell is determined by a linear interpolation algorithm; the preset internal resistance lifetime mapping relationship is used to characterize the mapping relationship between the SOH value of the cell and the current ambient temperature.

[0060] In this step, the preset internal resistance lifetime mapping relationship is the core benchmark. Its logic lies in storing the correlation between the state of harmonics (SOH) value, current internal resistance, and ambient temperature established in the laboratory, in the BMS as a set of multi-temperature domain SOH calibration curves or data tables. Specifically, establishing the preset internal resistance lifetime mapping relationship requires full-cycle aging tests. During the construction of this mapping relationship, for mass-produced cell samples with consistent performance, repeated charge-discharge aging experiments are conducted under different temperature conditions covering key ranges such as -20℃, 10℃, 15℃, and 30℃. The internal resistance data of the cells at different aging levels (i.e., different SOH values) is recorded in real time. Simultaneously, the internal resistance threshold ranges for better and worse cells are calibrated to ensure the coverage and reliability of the mapping relationship. Unlike the traditional single internal resistance-to-SOH correspondence, this mapping relationship incorporates the influence of ambient temperature. Since temperature significantly changes the electrochemical characteristics of the battery cell, the internal resistance of a battery cell with the same SOH value will be higher at low temperatures than at high temperatures. The same internal resistance value will also correspond to different SOH values ​​at different temperatures. Therefore, by temperature-zoned calibration, the mapping relationship forms a three-dimensional correlation between temperature, internal resistance, and SOH value.

[0061] Furthermore, the process of determining the SOH value of a battery cell based on the mapping relationship revolves around cell-by-cell adaptation, temperature range matching, interpolation calculation, and reliability verification. First, the internal resistance of each cell calculated in the previous step and the current ambient temperature are retrieved, and an independent calculation process is initiated for each cell. Next, based on the current ambient temperature, the corresponding temperature range is located from the preset internal resistance-lifetime mapping relationship. For example, when the current temperature is 22℃, the calibration curves or data tables corresponding to 20℃ and 25℃ are matched. Then, the current internal resistance of the cell is substituted into the mapping data for the corresponding temperature range, and a linear interpolation algorithm is used to calculate the SOH value. If the current internal resistance falls between the internal resistances corresponding to two known SOH values ​​at that temperature, the intermediate value is obtained through proportional calculation. For example, at 25℃, an SOH value of 90% corresponds to an internal resistance of 0.005 ohms; an SOH value of 80% corresponds to 0.006 ohms; and the current internal resistance is 0.0053 ohms, so the interpolated SOH value is 87%. Meanwhile, the calculation process verifies whether the current internal resistance is within the preset range of better and worse cell parameters. If it exceeds the range, a fault is immediately reported to prevent abnormal data from affecting subsequent calculations. Ultimately, each cell in the target battery pack will obtain an independent SOH value based on its current internal resistance and temperature conditions. This reflects the individual differences of the cells and ensures calculation accuracy through temperature adaptation and interpolation algorithms.

[0062] S103: Based on the current internal resistance of each battery cell and the SOH value, update the model parameters in each equivalent circuit model to obtain a first set of calculation parameters; the first set of calculation parameters includes the updated model parameters of each equivalent circuit model.

[0063] This step is implemented using a cell-by-cell adaptation logic. Based on the current internal resistance and SOH values ​​obtained in the previous step, the equivalent circuit model corresponding to each cell is dynamically updated. First, for each cell, the original parameter data from its dedicated equivalent circuit model is retrieved, including polarization internal resistances R1 and R2, and polarization time constants τ1 and τ2. These initial parameters are the baseline data of the worst-case cell calibrated when the battery pack was produced. Then, using the cell's current internal resistance and SOH value as input, combined with preset parameter ranges for better and worse cells, the model parameters are updated using corresponding algorithms. The current internal resistance directly replaces the original R0 value in the model, while R1, R2, and τ1 and τ2 are adjusted according to the aging degree reflected by the SOH value. For example, when cell aging causes a decrease in the SOH value, the polarization parameters are simultaneously corrected to match the actual electrochemical characteristics. For temperature ranges not directly tested, linear interpolation is used to derive the corresponding parameter values ​​to ensure parameter integrity under all operating conditions. During the update process, the system will simultaneously check whether the new parameters are within the preset reasonable range. If they exceed the range, it will be judged as abnormal, the update result of the parameter will not be reported, and a fault prompt will be triggered to ensure the reliability of the first set of calculated parameters.

[0064] The generated first set of calculation parameters serves as a digital mapping of the equivalent circuit model of each cell. This parameter set preserves the individual differences of each cell, avoiding the limitations of traditional fixed-parameter models that cannot adapt to cell aging and temperature changes. This allows subsequent calculations to accurately reflect the true state of each cell. Simultaneously, the first set of calculation parameters provides a unified input standard for subsequent SOC calculations, working in conjunction with temperature deviation correction data from the current sensor and dynamically adjusted charge / discharge voltage protection thresholds. This ensures that the calculation process considers both changes in the cell's own characteristics and offsets the impact of external measurement errors. Furthermore, the updated parameters accurately match the current health status of the cells, avoiding the risk of lithium plating due to parameter mismatch. This improves the accuracy of SOC calculations while effectively protecting the cells, ensuring the overall safety and stability of the battery pack.

[0065] S104: Update the SOC based on the cell status data of each cell and the first set of calculation parameters to obtain the updated SOC value.

[0066] In this step, cell status data reflects the actual physical state of the cells, including cell voltage and cell capacity. Cell voltage is collected in real-time by the BIC at fixed intervals. Whether through equalization adjustments or natural consistency requirements, the voltage difference between all cells is ensured to be within a preset threshold, avoiding calculation errors caused by voltage fluctuations. Cell capacity is the real-time usable capacity obtained by multiplying the initial capacity by the SOH value. The capacity data for each cell is precisely matched to its aging degree; for example, cells with significant aging will show a lower real-time capacity due to a decrease in SOH value, accurately reflecting their current charge / discharge capacity boundary. The first set of calculation parameters provides equivalent circuit model parameters adapted to each cell's state, including updated ohmic resistance, polarization resistance, and polarization time constant. These dynamically adjusted parameters simulate the electrochemical response of the cell in its current state, complementing the cell status data and jointly eliminating SOC calculation interference caused by individual cell differences and aging degradation. Meanwhile, the calculation process incorporates current sensor deviation correction data at different temperatures to further offset the impact of external measurement errors on the results, making the input data more consistent with actual working conditions.

[0067] Next, with reference to the accompanying drawings of specific embodiments, the process of updating the SOC in step S104 based on the cell status data and the first set of calculation parameters will be described in detail.

[0068] Referring to Figure 3, which is a flowchart illustrating another SOC update method provided in an embodiment of this application, the method specifically includes the following steps:

[0069] S1041: Based on the state data of each cell, verify whether each cell is in a balanced state.

[0070] In practical applications, voltage and capacity differences between cells directly lead to inconsistent remaining capacity percentages, thus affecting the accuracy of overall SOC calculation for the battery pack. Therefore, it is necessary to ensure that each cell is in a balanced state before calculating SOC. Specifically, determining whether a cell is in a balanced state relies on the voltage difference, capacitance difference, preset voltage threshold, and preset capacity threshold between any two cells. The preset voltage threshold is determined based on the self-discharge difference test results after high-temperature storage of cells. For example, the maximum voltage difference after 93 days of full-charge storage at 45℃ is 12mV. Combined with the SOC difference calculated from the OCV-SOC curve (see Figure 4 for a schematic diagram of the OCV-SOC curve relationship), 20mV is ultimately determined as the critical threshold. The preset capacity threshold is calculated based on the cell type, battery pack specifications, and worst-case self-discharge scenarios in mass production data. This ensures that the threshold covers the differences in actual use without causing frequent balancing due to an overly strict threshold or ignoring critical differences due to an overly broad threshold. Using both capacitance and voltage as indicators to verify whether a battery cell is in a balanced state can effectively avoid the one-sidedness of verification by a single indicator. For example, some battery cells may have a small voltage difference due to polarization effect, but a significant difference in capacity. Relying solely on the voltage indicator will miss such cases that require balancing. The dual-indicator judgment method in this embodiment can effectively cover such cases.

[0071] The specific verification logic for whether the battery cell is in an equalization state is implemented through the following two steps:

[0072] Step 1: If the voltage difference between any two cells is greater than a preset voltage threshold, or the capacity difference between any two cells is greater than a preset capacity threshold, then it is determined that neither of the two cells is in an balanced state.

[0073] When the voltage difference between any two battery cells exceeds a preset voltage threshold, or the capacity difference between any two battery cells exceeds a preset capacity threshold, it can be determined that these two battery cells are not in an balanced state. This ensures that all differences affecting the consistency of SOC calculation can be accurately identified. For example, if the voltage difference between battery cell A and battery cell B reaches 25mV, exceeding the preset 20mV voltage threshold, regardless of whether their capacity difference is within a reasonable range, these two battery cells will be determined to be unbalanced. This is because the voltage difference directly corresponds to the SOC difference in the OCV-SOC curve; failure to adjust will lead to deviations in the calculation of their remaining capacity percentage. Similarly, if the voltage difference between battery cell C and battery cell D is 18mV, not exceeding the preset voltage threshold, but the capacity difference reaches the preset capacitance threshold, it indicates a significant difference in their actual usable capacity. Even if the current voltages appear consistent, voltage divergence will occur during subsequent charging and discharging, thus affecting the accuracy of SOC updates. Therefore, it is also determined to be unbalanced.

[0074] Step 2: If the voltage difference between any two cells is not greater than the preset voltage threshold and the capacity difference between any two cells is not greater than the preset capacity threshold, then all cells are determined to be in a balanced state.

[0075] Conversely, the two cells are considered to be in a balanced state only when the voltage difference between any two cells does not exceed the preset voltage threshold and the capacity difference does not exceed the preset capacity threshold.

[0076] S1042: When it is determined that there is a first cell that is not in the balanced state, the first cell is adjusted for balanced state according to the cell state data of the first cell to obtain the adjusted cell state data of the first cell.

[0077] Furthermore, when it is determined that there is a first cell in the target battery pack that is not in an balanced state, it is necessary to adjust this first cell to a balanced state using either passive or active balancing methods, based on the relative relationship between the first cell and the average capacity. Specifically, this includes the following two execution steps:

[0078] Step 1: For the first cell whose cell capacity is greater than the average cell capacity, control the first cell to connect the onboard equalization resistor until the difference between the cell capacity and cell voltage of the first cell and the corresponding parameters of the second cell is less than the first threshold; the second cell is the cell with the smallest cell capacity among all the cells.

[0079] Specifically, when the capacity of the first cell is greater than the average capacity of all cells, it indicates that the first cell is a high-capacity cell, with its remaining capacity and usable capacity exceeding the overall average level. In this case, a passive balancing adjustment method is adopted. The BMS controls the first cell to connect to the onboard balancing resistor, using resistor discharge to dissipate its excess remaining capacity and return it to a balanced state. During the adjustment process, the BIC collects the voltage and capacity data of the cell in real time at a set period, continuously comparing it with the corresponding parameters of the second cell (i.e., the cell with the smallest capacity in the target battery pack), until the voltage difference and capacity difference between the two are both less than a first threshold. The first threshold references the calibrated voltage difference and the capacity difference standard adapted to the worst-case self-discharge situation in mass production, ensuring that the adjusted cell state meets the consistency requirements of SOC calculation.

[0080] Step 2: For the first cell whose cell capacity is less than the average cell capacity, the power in the third cell is transferred to the first cell through an equalization circuit until the difference between the cell capacity and cell voltage of the first cell and the corresponding parameters of the third cell is less than the first threshold; the third cell is the cell with the smallest cell capacity among all the cells.

[0081] When the capacity of the first cell is less than the average capacity of all cells, it indicates that the cell is a low-capacity cell, with its usable capacity and remaining capacity at a relative disadvantage. Active balancing is needed to replenish its capacity and narrow the gap. In this case, active balancing is initiated, using a balancing circuit to transfer some capacity from the third cell (the smallest capacity cell among all cells) to the first cell. In practical applications, the circuit can also allocate redundant capacity from high-capacity cells to supplement the low-capacity first cell, preventing a single low-capacity cell from becoming a bottleneck in overall performance. During the capacity transfer, the system monitors the voltage and capacity changes of the first cell in real time to ensure that the capacity replenishment rate matches the cell's electrochemical characteristics. This avoids the risk of lithium plating due to excessively rapid charging and accurately controls the replenishment amount. The stopping condition for adjustment is the same as for passive balancing: the difference between the voltage and capacity of the first cell and the corresponding parameters of the third cell is less than a first threshold. This balancing adjustment method brings the state of low-capacity cells closer to a unified benchmark, avoiding charge / discharge differentiation due to individual insufficient capacity and ensuring the overall energy utilization efficiency of the battery pack.

[0082] S1043: Based on the adjusted cell status data of the first cell, the cell status data of the other cells besides the first cell, and the first calculation parameter set, the SOC is updated to obtain the updated SOC value.

[0083] Finally, after equalization adjustments, the voltage and capacity of the first cell are consistent with those of the other cells. The state data of all cells meet the preset consistency threshold requirements, eliminating computational interference caused by individual differences while preserving the true usable capacity boundary of each cell based on its own SOH. The first calculation parameter set provides the core parameters of the equivalent circuit model updated cell by cell, including the ohmic internal resistance, polarization internal resistance, and polarization time constant adapted to the current internal resistance and SOH. During the calculation process, the BMS will substitute the state data of each cell into its dedicated equivalent circuit model one by one, and correct the influence of polarization voltage by combining the preset OCV-SOC correspondence. Finally, the actual usable total capacity of the battery pack is determined based on the shortest cell with the smallest real-time usable capacity among all cells. Then, the remaining total capacity of the battery pack is obtained by summing the remaining capacity of each cell. The ratio of the two is the updated SOC value, ensuring that the result can truly reflect the current remaining power supply capacity of the battery pack and providing a reliable basis for vehicle energy management.

[0084] In one possible implementation, after determining the first set of calculation parameters in step S103, the parameter set can be corrected based on the error present in the current sensor at different temperatures. This process is achieved through the following two steps:

[0085] Step 1: Determine the deviation correction data of the current sensor at the current ambient temperature.

[0086] The purpose of this step is to match the deviation correction data of the current sensor with the current ambient temperature, thereby providing a targeted basis for subsequent parameter adjustments. This deviation correction data is determined through specialized testing. After battery pack assembly, each current sensor undergoes discharge testing under specific temperature conditions, covering key temperature ranges such as 15℃, 20℃, 25℃, and 30℃. The discharge current is uniformly set to 5A, and the positive deflection deviation of the sensor is recorded; for example, the deviation is 0.01A at 25℃ and 0.008A at 20℃, forming a basic deviation database. When the SOC update process is initiated during vehicle operation, the system collects the current ambient temperature in real time. If the temperature falls within the preset test temperature point, the corresponding deviation value is directly retrieved. If it falls between two test temperatures, linear interpolation is used to calculate the deviation correction data corresponding to the current temperature, ensuring accurate deviation parameters matching actual operating conditions regardless of ambient temperature changes, effectively avoiding the impact of insufficient sensor accuracy and temperature variations on current acquisition.

[0087] Step 2: Based on the deviation correction data of the current sensor, correct the parameters of the first set of calculation parameters to obtain the second set of calculation parameters.

[0088] As mentioned earlier, the first set of calculation parameters has been updated using the cell's current internal resistance and SOH value to update the equivalent circuit model parameters. It covers core data such as ohmic internal resistance, polarization internal resistance, and polarization time constant, reflecting the cell's aging state and electrochemical characteristics. However, it does not consider the error interference from external measurement equipment. By incorporating the current sensor deviation correction data obtained in step one, the parameters related to current acquisition in the first set of calculation parameters are specifically corrected. This ensures that the model parameters not only adapt to the individual cell state but also compensate for the measurement deviation caused by the current sensor. Thus, the corrected second set of calculation parameters is realized, providing a more comprehensive and accurate input basis for subsequent SOC calculations. This ensures that the final SOC update result avoids the influence of individual cell differences and aging degradation, while eliminating calculation interference caused by sensor deviation and temperature fluctuations, further improving the matching degree between the SOC value and the actual remaining battery capacity.

[0089] In one possible implementation, the method of this embodiment can also update the charge and discharge protection threshold of the battery cell in real time to ensure that the real-time threshold accurately matches the actual health state of the battery cell. This is achieved through the following three steps:

[0090] Step 1: Obtain the initial charge / discharge voltage protection threshold, rated current, and initial internal resistance of each of the battery cells.

[0091] First, it is necessary to obtain the initial charge / discharge voltage protection threshold, rated current, and initial internal resistance of each battery cell. These parameters are derived from standardized testing during the cell's factory manufacturing process and are stored in the BMS database, bound to a unique identifier for each cell. The initial charge / discharge voltage protection threshold is a safety boundary determined based on the cell type through three-electrode experiments, ensuring that the cell will not suffer damage such as lithium plating during initial charging and discharging. The rated current is the standard operating current specified at the cell's factory, serving as a fixed benchmark for the current parameter in the threshold calculation. The initial internal resistance is the initial value calculated through voltage drop testing under factory testing conditions.

[0092] Step 2: Determine the real-time charge / discharge voltage protection threshold for each of the battery cells based on the initial charge / discharge voltage protection threshold, the rated current, the initial resistance, the SOH value, and the current internal resistance.

[0093] In calculating the real-time charge / discharge voltage protection threshold, the initial charge / discharge voltage protection threshold is the benchmark calibrated based on the safety boundary at the time of cell manufacturing. The rated current is a fixed operating current reference, and the initial internal resistance is the initial state parameter measured at the time of manufacturing. The SOH value and current internal resistance obtained through discharge testing and linear interpolation algorithm in the preceding steps directly reflect the aging degree of the cell after use. As the cell ages, the decrease in SOH value is accompanied by an increase in current internal resistance. At this time, the discharge threshold needs to be adjusted accordingly to avoid the terminal voltage from prematurely reaching the original threshold due to the increase in internal resistance, thus failing to fully release the power. The charging threshold is adjusted synchronously to ensure that the full charging requirement is met while avoiding the risk of lithium plating due to excessively low negative electrode potential. This adjustment logic is completely consistent with the cell safety boundary verified by the three-electrode experiment, ensuring the safety of the charging and discharging process from the root.

[0094] Each cell's real-time threshold is calculated independently. The initial charge / discharge voltage protection threshold, rated current, and initial internal resistance are all factory-specific data bound to each cell's unique identifier. The SOH value and current internal resistance are also real-time status indicators calculated individually for each cell. The combination of these two factors provides a stable initial benchmark for threshold calculation while dynamically responding to the unique aging changes of each cell. The SOH value, reflecting the cell's aging degree, indirectly affects the difference between the current and initial internal resistance, thus determining the threshold adjustment range. This threshold determination method effectively solves the problem of traditional uniform thresholds being difficult to adapt to cells in different aging states. It avoids insufficient charging and discharging of new cells due to overly strict thresholds, and also prevents overcharging and over-discharging risks faced by aged cells due to overly wide thresholds, providing a precise safety boundary for subsequent charge / discharge control.

[0095] Step 3: Based on the current ambient temperature, determine the temperature correction coefficient using a linear interpolation algorithm, and then correct the real-time charge / discharge voltage protection threshold using the temperature correction coefficient.

[0096] Finally, based on the current ambient temperature, a temperature correction coefficient is determined using a linear interpolation algorithm, and the real-time charge / discharge voltage protection threshold is corrected. Since temperature significantly affects the electrochemical characteristics of the battery cell, the safe voltage boundary differs at different temperatures for the same internal resistance and state of equilibrium (SOH). For example, in low-temperature environments, the internal resistance of the battery cell further increases, and failure to correct the threshold may lead to premature termination of discharge. In this embodiment, a temperature correction coefficient table covering key temperature ranges (such as -20℃, -10℃, 0℃, 15℃, 25℃, 30℃, etc.) is pre-set. These coefficients are calibrated through multi-temperature-range aging tests in the laboratory. When the current ambient temperature is obtained, if the temperature falls within the preset range, the corresponding correction coefficient is directly retrieved; if it falls between two preset temperatures, an accurate coefficient is calculated using a linear interpolation algorithm, ensuring that a suitable correction basis is obtained for any actual operating temperature. Substituting this coefficient into the real-time threshold can offset the impact of temperature fluctuations on the cell voltage characteristics, allowing the corrected threshold to both conform to the cell aging state and adapt to the current ambient temperature, ultimately forming a protection threshold that is both individualized and adaptable to operating conditions, providing a safe and accurate boundary basis for subsequent charge and discharge control and SOC calculation.

[0097] This application provides a SOC update method. In this method, an independent equivalent circuit model is established for each battery cell. The internal resistance of each cell is accurately determined by combining its discharge parameters and the current ambient temperature, ensuring the individual specificity and temperature adaptability of the internal resistance calculation. Subsequently, based on the current internal resistance and a preset internal resistance-lifetime mapping relationship characterizing the SOH (State of Harmony) versus temperature mapping, the SOH value obtained through a linear interpolation algorithm is more closely aligned with the real-time aging state of the battery cell compared to traditional durability cycle estimation methods. Furthermore, the parameters of each equivalent circuit model are updated based on the current internal resistance and SOH value, forming a dynamically adapted first calculation parameter set. The SOC is then updated by combining the real-time state data of each battery cell with this parameter set, effectively offsetting the impact of cell consistency differences, aging degradation, and temperature fluctuations on the SOC calculation. This significantly improves the matching degree between the SOC value and the actual remaining battery capacity, ensuring the accuracy of the SOC update calculation.

[0098] The following describes a SOC update system provided by an embodiment of this application. The SOC update system described below can be referred to in correspondence with the SOC update method described above.

[0099] Referring to Figure 5, which is a schematic diagram of the structure of a SOC update system provided in an embodiment of this application, the system specifically includes the following modules:

[0100] The internal resistance determination module 100 is used to control the target battery pack to discharge based on the target discharge value, and to determine the current internal resistance of each cell according to the discharge parameters of each cell in the target battery pack and the current ambient temperature; wherein each cell has a separate corresponding equivalent circuit model.

[0101] SOH determination module 200 is used to determine the SOH value of each of the battery cells based on the current internal resistance of each battery cell and a preset internal resistance lifetime mapping relationship through a linear interpolation algorithm; the preset internal resistance lifetime mapping relationship is used to characterize the mapping relationship between the SOH value of the battery cell and the current ambient temperature;

[0102] The parameter update module 300 is used to update the model parameters in each equivalent circuit model according to the current internal resistance and the SOH value of each of the battery cells to obtain a first calculation parameter set; the first calculation parameter set includes the model parameters of each equivalent circuit model after parameter update;

[0103] The SOC update module 400 is used to update the SOC based on the cell status data of each cell and the first set of calculation parameters to obtain the updated SOC value.

[0104] In one possible implementation, the SOC update module 400 is specifically used for:

[0105] Based on the state data of each cell, verify whether each cell is in a balanced state.

[0106] When it is determined that there is a first cell that is not in the balanced state, the first cell is adjusted for balanced state based on the cell state data of the first cell to obtain the adjusted cell state data of the first cell.

[0107] The SOC is updated based on the adjusted cell status data of the first cell, the cell status data of the other cells besides the first cell, and the first set of calculation parameters to obtain the updated SOC value.

[0108] In one possible implementation, the cell status data includes cell voltage and cell capacity; the SOC update module 400 includes a verification unit.

[0109] The verification unit is specifically used for:

[0110] If the voltage difference between any two of the battery cells is greater than a preset voltage threshold, or the capacity difference between any two of the battery cells is greater than a preset capacity threshold, it is determined that neither of the two battery cells is in an balanced state.

[0111] If the voltage difference between any two cells is greater than the preset voltage threshold, and the capacity difference between any two cells is greater than the preset capacity threshold, then all cells are determined to be in a balanced state.

[0112] Based on the same inventive concept, corresponding to the methods of any of the above embodiments, this application also provides a computer-readable storage medium storing computer instructions for causing the computer to execute the SOC update method as described in any of the above embodiments.

[0113] The computer-readable media in this application embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information accessible by a computing device.

[0114] The computer instructions stored in the storage medium of the above embodiments are used to cause the computer to execute the SOC update method as described in any of the above embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0115] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the system, method, and medium embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiments. The system, method, and medium embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components indicated as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0116] The above description is merely one specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A SOC update method, characterized in that, include: The target battery pack is controlled to discharge based on a target discharge value. The current internal resistance of each cell is determined according to its discharge parameters and the current ambient temperature. Each cell has a corresponding equivalent circuit model. The state of equilibrium (SOH) value of each cell is determined using a linear interpolation algorithm based on its current internal resistance and a preset internal resistance lifetime mapping relationship. The preset internal resistance lifetime mapping relationship characterizes the mapping relationship between the SOH value of the cell and the current ambient temperature. Based on the current internal resistance and SOH value of each cell, the model parameters within each equivalent circuit model are updated to obtain a first set of calculation parameters. This first set of calculation parameters includes the updated model parameters of each equivalent circuit model. Finally, the state of charge (SOC) is updated based on the cell state data of each cell and the first set of calculation parameters to obtain the updated SOC value.

2. The method according to claim 1, characterized in that, The step of updating the SOC based on the cell state data of each cell and the first calculation parameter set to obtain the updated SOC value includes: verifying whether each cell is in a balanced state based on the cell state data; when it is determined that there is a first cell that is not in the balanced state, adjusting the balance state of the first cell based on the cell state data of the first cell to obtain the adjusted cell state data of the first cell; and updating the SOC based on the adjusted cell state data of the first cell, the cell state data of the other cells besides the first cell, and the first calculation parameter set to obtain the updated SOC value.

3. The method according to claim 2, characterized in that, The cell status data includes cell voltage and cell capacity; the step of verifying whether each cell is in a balanced state based on the cell status data includes: determining that neither of the two cells is in a balanced state if the voltage difference between any two cells is greater than a preset voltage threshold or the capacity difference between any two cells is greater than a preset capacity threshold; and determining that all the cells are in a balanced state if the voltage difference between any two cells is not greater than the preset voltage threshold and the capacity difference between any two cells is not greater than the preset capacity threshold.

4. The method according to claim 3, characterized in that, The step of adjusting the balancing state of the first battery cell based on its cell state data includes: for a first battery cell whose cell capacity is greater than the average cell capacity, controlling the first battery cell to connect to the onboard balancing resistor until the difference between the cell capacity and cell voltage of the first battery cell and the corresponding parameters of the second battery cell is less than a first threshold; the second battery cell is the battery cell with the smallest cell capacity among all the battery cells; for a first battery cell whose cell capacity is less than the average cell capacity, transferring the charge in the third battery cell to the first battery cell through a balancing circuit until the difference between the cell capacity and cell voltage of the first battery cell and the corresponding parameters of the third battery cell is less than the first threshold; the third battery cell is the battery cell with the smallest cell capacity among all the battery cells.

5. The method according to claim 1, characterized in that, After obtaining the first set of calculation parameters, the method further includes: determining the deviation correction data of the current sensor at the current ambient temperature based on the current ambient temperature; and correcting the first set of calculation parameters based on the deviation correction data of the current sensor to obtain a second set of calculation parameters.

6. The method according to claim 1, characterized in that, The method further includes: obtaining the initial charge / discharge voltage protection threshold, rated current, and initial internal resistance of each of the battery cells; determining the real-time charge / discharge voltage protection threshold of each of the battery cells based on the initial charge / discharge voltage protection threshold, rated current, initial resistance, SOH value, and current internal resistance; determining a temperature correction coefficient based on the current ambient temperature using a linear interpolation algorithm, and correcting the real-time charge / discharge voltage protection threshold using the temperature correction coefficient.

7. A SOC update system, characterized in that, include: An internal resistance determination module is used to control the target battery pack to discharge based on a target discharge value. It determines the current internal resistance of each cell based on its discharge parameters and the current ambient temperature. Each cell has a corresponding equivalent circuit model. A state of equilibrium (SOH) determination module is used to determine the SOH value of each cell using a linear interpolation algorithm based on its current internal resistance and a preset internal resistance lifetime mapping relationship. The preset internal resistance lifetime mapping relationship characterizes the mapping relationship between the SOH value of the cell and the current ambient temperature. A parameter update module is used to update the model parameters in each equivalent circuit model based on the current internal resistance and the SOH value of each cell, obtaining a first set of calculation parameters. The first set of calculation parameters includes the updated model parameters of each equivalent circuit model. A state of charge (SOC) update module is used to update the SOC based on the cell state data of each cell and the first set of calculation parameters, obtaining an updated SOC value.

8. The system according to claim 7, characterized in that, The SOC update module is specifically used for: verifying whether each of the battery cells is in a balanced state based on the state data of each battery cell; when it is determined that there is a first battery cell that is not in the balanced state, adjusting the balance state of the first battery cell based on the cell state data of the first battery cell to obtain the adjusted cell state data of the first battery cell; updating the SOC based on the adjusted cell state data of the first battery cell, the cell state data of the other battery cells besides the first battery cell, and the first calculation parameter set to obtain the updated SOC value.

9. The system according to claim 8, characterized in that, The cell status data includes cell voltage and cell capacity; the SOC update module includes a verification unit; the verification unit is specifically used to: determine that neither of the two cells is in an balanced state when the voltage difference between any two cells is greater than a preset voltage threshold, or the capacity difference between any two cells is greater than a preset capacity threshold; and determine that all the cells are in a balanced state when the voltage difference between any two cells is greater than the preset voltage threshold and the capacity difference between any two cells is greater than the preset capacity threshold.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the SOC update method as described in any one of claims 1-6.

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