Methods, apparatus and battery management system for determining the state of harm (SOH) of power battery packs

Abstract

This invention discloses a method, apparatus, and battery management system for determining the State of Harm (SOH) of a power battery pack. The method includes: acquiring the initial State of Charge (SOC) value of each individual cell in the power battery pack; acquiring charging data for each individual cell, including the charging cutoff voltage and charging cutoff current at the charging cutoff moment; using the individual cell with the maximum charging cutoff voltage as the target cell, determining the actual capacity of the target cell based on its charging cutoff current and initial SOC value; based on the charging data of each individual cell, combined with the charging error of each individual cell, determining the actual capacity of the remaining individual cells according to the actual capacity of the target cell and the initial SOC value of each individual cell; and determining the SOH of each individual cell in the power battery pack based on its actual capacity. This solution helps improve the estimation accuracy of the SOH of individual cells.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, and in particular to a method, apparatus and battery management system for determining the state of harmonics (SOH) of a power battery pack. Background Technology

[0002] New energy vehicles are favored by the market due to their advantages in power and economy, with production and sales increasing year by year and penetration rate continuously rising. Lithium-ion power batteries are widely used in new energy vehicles, but lithium-ion batteries must be equipped with a Battery Management System (BMS) to ensure their safe and efficient use.

[0003] Battery State of Health (SOH) is a crucial indicator that directly impacts a vehicle's range and stability. Current technologies typically determine SOH through driving conditions or by fully charging and discharging the battery. However, driving conditions are difficult to guarantee with consistent performance, significantly affecting the accuracy of the SOH reading. Furthermore, the fully charging and discharging method is ineffective because a real powertrain system comprises numerous battery cells, each with its own inherent differences. It's impossible to fully charge and discharge all cells simultaneously, leading to inconsistencies and wasting energy. Summary of the Invention

[0004] This invention provides a method, apparatus, and battery management system for determining the state of harmonics (SOH) of a power battery pack, thereby improving the accuracy of SOH calculation.

[0005] According to one aspect of the present invention, a method for determining the state of harmonics (SOH) of a power battery pack is provided, comprising:

[0006] Obtain the initial SOC value of each individual cell in the power battery pack;

[0007] Obtain the charging data of each individual cell in the power battery pack, the charging data including the charging cut-off voltage and charging cut-off current of each individual cell at the charging cut-off time;

[0008] Using the single cell with the maximum charging cut-off voltage as the target cell, the actual capacity of the target cell is determined based on the charging cut-off current and the initial SOC value of the target cell.

[0009] Based on the charging data of each individual battery cell, combined with the charging error of each individual battery cell, the actual capacity of the remaining individual batteries cell is determined according to the actual capacity of the target battery and the initial SOC value of each individual battery cell.

[0010] The state of harmonics (SOH) of each individual cell in the power battery pack is determined based on the actual capacity of each individual cell.

[0011] Optionally, determining the actual capacity of the target battery based on the charging cut-off current and the initial SOC value, using the single cell with the maximum charging cut-off voltage as the target battery, includes:

[0012] Using a single cell with the maximum charging cutoff voltage as the target cell, the maximum stored capacity of the target cell at the charging cutoff time is calculated based on the charging cutoff current of the target cell.

[0013] The actual capacity of the target battery is determined based on the maximum storage capacity of the target battery and the initial SOC value;

[0014] The actual capacity of the target battery is expressed as follows:

[0015] CAPmax=Qmaxend / (1-SOCmax0);

[0016] CAPmax is the actual capacity of the target battery, Qmaxend is the maximum stored capacity of the target battery at the charging cutoff time, and SOCmax0 is the initial SOC value of the target battery.

[0017] Optionally, the charging data also includes the charging voltage of each individual battery during the charging process; the step of determining the actual capacity of the remaining individual batteries based on the charging data of each individual battery, combined with the charging error of each individual battery, and according to the actual capacity of the target battery and the initial SOC value of each individual battery includes:

[0018] Based on the charging current and the charging cutoff current of the target battery, the first stored capacity of the target battery at a preset time and the maximum stored capacity at the charging cutoff time are obtained respectively; wherein, the preset time is the time when the charging voltage of the target battery is equal to the charging cutoff voltage of the remaining individual cells;

[0019] Based on the charging cutoff current corresponding to the remaining individual cells, calculate the second stored capacity of each of the remaining individual cells at the charging cutoff time;

[0020] The actual capacity of each remaining individual battery is determined based on the difference between the maximum storage capacity and the first storage capacity, the second storage capacity, the actual capacity of the target battery, and the initial SOC value of each individual battery.

[0021] The difference between the maximum storage capacity and the first storage capacity is used to characterize the charging error of the single battery cell.

[0022] The actual capacity of the single battery cell is expressed as: CAPi = Qiend / (1-(Qmaxend-Qi) / CAPmax-SOCi), where CAPi is the actual capacity of the single battery cell, CAPmax is the actual capacity of the target battery, Qiend is the second stored capacity, Qi is the first stored capacity, Qmaxend is the maximum stored capacity of the target battery at the charging cutoff time, and SOCi is the initial SOC value of the single battery cell, where i is an integer greater than 1.

[0023] Optionally, the SOH of the single cell is equal to the ratio of the actual capacity of the single cell to the nominal capacity of the single cell.

[0024] Optionally, the charging cutoff time is the time when the target battery reaches the full charge condition; wherein, the full charge condition is that the charging cutoff current of the target battery is less than or equal to a preset current value.

[0025] Optionally, obtaining the initial SOC value of each individual cell in the power battery pack includes:

[0026] Based on the initial voltage of the individual battery cell, the SOC-OCV table is consulted to determine the initial SOC value.

[0027] Optionally, before obtaining the initial SOC value of each individual cell in the power battery pack, the method further includes:

[0028] Determine whether the initial voltage of each individual cell in the power battery pack after the settling time is less than a preset voltage value;

[0029] If the initial voltage is greater than or equal to the preset voltage value, the individual battery is discharged until the initial voltage is less than the preset voltage value;

[0030] If the initial voltage is less than the preset voltage value, then the initial SOC value of each individual cell in the power battery pack is obtained.

[0031] Optionally, before acquiring the charging data of each individual cell in the power battery pack, the method further includes:

[0032] Determine whether the error between the sum of currents on the power battery pack side and the sum of currents on the charging device side is less than a set threshold.

[0033] If the error is greater than or equal to the set threshold, then fault information is reported, the charging data is not acquired, and the determination of SOH is prohibited;

[0034] If the error is less than the set threshold, then the charging data is acquired.

[0035] According to another aspect of the present invention, a power battery pack SOH determination device is provided, comprising:

[0036] The parameter determination module is used to obtain the initial SOC value of each individual cell in the power battery pack, and to obtain the charging data of each individual cell in the power battery pack; the charging data includes the charging cutoff voltage and charging cutoff current of each individual cell at the charging cutoff time.

[0037] The first capacity determination module is used to determine the actual capacity of the target battery by taking the single cell with the maximum charging cut-off voltage as the target battery and the initial SOC value of the target battery.

[0038] The second capacity determination module is used to determine the actual capacity of the remaining individual cells based on the charging data of each individual cell, combined with the charging error of each individual cell, and according to the actual capacity of the target battery and the initial SOC value of each individual cell.

[0039] The SOH determination module is used to determine the SOH of each individual cell in the power battery pack based on the actual capacity of each individual cell.

[0040] According to another aspect of the present invention, a battery management system is provided for use in a vehicle, the battery management system being used to execute the SOH determination method for a power battery pack provided in any embodiment of the present invention.

[0041] The technical solution provided in this embodiment of the invention obtains the charging data of each individual cell in the power battery pack. The charging data includes the charging cut-off voltage and charging cut-off current of each individual cell at the charging cut-off moment. The individual cell with the maximum charging cut-off voltage is selected as the target cell. The actual capacity of the target cell is determined based on its charging cut-off current and initial SOC value. Then, considering the charging error of each individual cell, the actual capacity of the remaining individual cells is determined based on the actual capacity of the target cell and the initial SOC value of each individual cell. Finally, the SOH of each individual cell in the power battery pack is determined based on its actual capacity. Compared to related technologies, the technical solution provided in this embodiment can obtain the SOH of all individual cells based on only partial charging data, without requiring full charging and discharging of all cells, and is unaffected by driving conditions. This improves the convenience of calculating the SOH of individual cells. Furthermore, the calculation of SOH takes into account the charging error of different individual cells, and uses the actual capacity of the target cell with the maximum charging cut-off voltage and the initial SOC value of each individual cell to obtain the accurate actual capacity of each individual cell, thereby improving the estimation accuracy of the SOH of individual cells.

[0042] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

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

[0044] Figure 1 A flowchart of a method for determining the state of harmonics (SOH) of a power battery pack provided in an embodiment of the present invention;

[0045] Figure 2 A flowchart of another method for determining the state of harmonics (SOH) of a power battery pack provided in an embodiment of the present invention;

[0046] Figure 3 A flowchart of another method for determining the state of harmonics (SOH) of a power battery pack provided in an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of a charging curve of a single battery provided in an embodiment of the present invention;

[0048] Figure 5A flowchart of another method for determining the state of harmonics (SOH) of a power battery pack provided in an embodiment of the present invention;

[0049] Figure 6 This is a schematic diagram of a power battery pack SOH determination device provided in an embodiment of the present invention. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0052] Figure 1 A flowchart of a method for determining the state of harmonics (SOH) of a power battery pack is provided in an embodiment of the present invention, referred to in the following text. Figure 1 The method for determining the state of harmonics (SOH) of a power battery pack provided in this embodiment includes:

[0053] S110. Obtain the initial SOC value of each individual cell in the power battery pack.

[0054] Specifically, the power battery pack can be a lithium battery pack, which includes multiple individual cells and can be used to power new energy vehicles. The initial SOC (State of Charge) value of a single cell refers to the SOC value of the single cell in its initial state. The initial state of a single cell is the state when the initial voltage of the battery meets a certain voltage range, so as to better estimate the SOH.

[0055] Here, the initial SOC value can be calculated based on the initial voltage of the individual battery cell, or obtained directly from a table.

[0056] S120. Obtain the charging data of each individual cell in the power battery pack. The charging data includes the charging cut-off voltage and charging cut-off current of each individual cell at the charging cut-off time.

[0057] Specifically, after obtaining the initial SOC value of each individual battery cell, the charging process begins, which can be performed in a constant current / constant voltage mode or a multi-stage constant current mode. For example, the power battery pack can be charged through a charging pile. During the charging process, the BMS can collect charging data for each individual battery cell. Based on the charging data, the BMS can obtain the charging curve for each individual battery cell using a charging algorithm. The charging curve can at least reflect the relationship between the charging voltage and charging time of an individual battery cell. At the charging cutoff point, the charging voltage reached by the individual battery cell is called the charging cutoff voltage. Due to the differences between individual batteries, the charging cutoff voltage of each individual battery cell may be different. For example, at the charging cutoff point, some individual batteries cell have a charging cutoff voltage of 4V, while others have a charging cutoff voltage less than 4V, or some have a charging cutoff voltage greater than 4V. The charging cutoff current can be obtained by a current sensor.

[0058] S130. Using the single cell with the maximum charging cut-off voltage as the target cell, determine the actual capacity of the target cell based on the charging cut-off current and initial SOC value of the target cell.

[0059] Specifically, in conjunction with step S120, since the charging cut-off voltage of each individual battery cell is different, the individual battery cell with the maximum charging cut-off voltage is selected as the target battery. The actual capacity of the target battery can be calculated based on its charging cut-off current and initial SOC value. For example, the actual capacity can be calculated based on the relationship between the target battery's stored capacity and SOC, where the stored capacity can be calculated from the charging cut-off current.

[0060] S140. Based on the charging data of each individual battery cell, combined with the charging error of each individual battery cell, and according to the actual capacity of the target battery and the initial SOC value of each individual battery cell, determine the actual capacity of the remaining individual battery cells respectively.

[0061] Specifically, the charging curve shows the charging voltage at different times. At the charging cutoff point, due to the differences in the characteristics of each individual battery cell, there are differences in charging, and the stored capacity of different individual batteries is inconsistent. Since the target battery has the highest charging cutoff voltage, under the same charging conditions (charging current, charging rate, etc.), the target battery has the largest stored capacity, and its actual capacity is also the largest. The stored capacity of other individual batteries is less than that of the target battery.

[0062] In this embodiment, the charging differences of each individual battery cell are considered. For example, the difference in stored capacity between the remaining individual batteries (excluding the target battery) and the target battery is taken into account. The stored capacity of the remaining individual batteries can be obtained by combining the charging cut-off current of each individual battery. The remaining capacity of the remaining individual batteries is calculated by comparing the stored capacity of the target battery with the stored capacity of the remaining individual batteries. Furthermore, the remaining state of charge (SOC) value of the remaining individual battery can be determined based on the ratio of the difference in stored capacity to the actual capacity of the target battery. Finally, combined with the initial SOC value of the individual battery, the actual capacity of the remaining individual batteries is determined.

[0063] S150. Determine the SOH of each individual cell in the power battery pack based on the actual capacity of each individual cell.

[0064] Specifically, the State of Harmony (SOH) of a single cell is equal to the ratio of the actual capacity of the single cell to its nominal capacity. The nominal capacity can be obtained from the manufacturer's specifications.

[0065] The technical solution provided in this embodiment of the invention obtains the charging data of each individual cell in the power battery pack. The charging data includes the charging cut-off voltage and charging cut-off current of each individual cell at the charging cut-off moment. The individual cell with the maximum charging cut-off voltage is selected as the target cell. The actual capacity of the target cell is determined based on its charging cut-off current and initial SOC value. Then, considering the charging error of each individual cell, the actual capacity of the remaining individual cells is determined based on the actual capacity of the target cell and the initial SOC value of each individual cell. Finally, the SOH of each individual cell in the power battery pack is determined based on its actual capacity. Compared to related technologies, the technical solution provided in this embodiment can obtain the SOH of all individual cells based on only partial charging data, without requiring full charging and discharging of all cells, and is unaffected by driving conditions. This improves the convenience of calculating the SOH of individual cells. Furthermore, the calculation of SOH takes into account the charging error of different individual cells, and uses the actual capacity of the target cell with the maximum charging cut-off voltage and the initial SOC value of each individual cell to obtain the accurate actual capacity of each individual cell, thereby improving the estimation accuracy of the SOH of individual cells.

[0066] Figure 2 A flowchart of another method for determining the state of harmonics (SOH) of a power battery pack provided in an embodiment of the present invention is shown below. Figure 2 Based on the above embodiments, optionally, the method for determining the state of harmonics (SOH) of the power battery pack provided in this embodiment includes:

[0067] S110. Obtain the initial SOC value of each individual cell in the power battery pack.

[0068] S120. Obtain the charging data of each individual cell in the power battery pack. The charging data includes the charging cut-off voltage and charging cut-off current of each individual cell at the charging cut-off time.

[0069] S1301. Using the single cell with the maximum charging cutoff voltage as the target cell, calculate the maximum stored capacity of the target cell at the charging cutoff time based on the charging cutoff current of the target cell.

[0070] Specifically, the charging cutoff time is defined as the moment when the target battery reaches full charge. At the charging cutoff time, charging of the power battery pack is stopped. The full charge condition is defined as the charging cutoff current of the target battery being less than or equal to a preset current value.

[0071] The maximum stored capacity of the target battery at the charging cutoff time can be obtained by integrating the charging cutoff current of the branch containing the target battery in ampere-hours.

[0072] S1302. Determine the actual capacity of the target battery based on its maximum storage capacity and initial SOC value.

[0073] Specifically, in this embodiment, the actual capacity of the target battery can be expressed as: CAPmax = Qmaxend / (1 - SOCmax0); where CAPmax is the actual capacity of the target battery, Qmaxend is the maximum stored capacity of the target battery at the charging cutoff time, which is also the ampere-hour integral of the current in the branch where the target battery is located at the charging cutoff time, and SOCmax0 is the initial SOC value of the target battery.

[0074] S140. Based on the charging data of each individual battery cell, combined with the charging error of each individual battery cell, and according to the actual capacity of the target battery and the initial SOC value of each individual battery cell, determine the actual capacity of the remaining individual battery cells respectively.

[0075] S150. Determine the SOH of each individual cell in the power battery pack based on the actual capacity of each individual cell.

[0076] Figure 3 A flowchart of another method for determining the state of harmonics (SOH) of a power battery pack provided in an embodiment of the present invention is shown below. Figure 3 Based on the above embodiments, optionally, the method for determining the state of harmonics (SOH) of the power battery pack provided in this embodiment includes:

[0077] S110. Obtain the initial SOC value of each individual cell in the power battery pack.

[0078] S120. Obtain the charging data of each individual cell in the power battery pack. The charging data includes the charging cut-off voltage and charging cut-off current of each individual cell at the charging cut-off time.

[0079] S1301. Using the single cell with the maximum charging cutoff voltage as the target cell, calculate the maximum stored capacity of the target cell at the charging cutoff time based on the charging cutoff current of the target cell.

[0080] S1302. Determine the actual capacity of the target battery based on its maximum storage capacity and initial SOC value.

[0081] S1401. Based on the charging current and charging cutoff current of the target battery, obtain the first stored capacity of the target battery at a preset time and the maximum stored capacity at the charging cutoff time, respectively; wherein, the preset time is the time when the charging voltage of the target battery is equal to the charging cutoff voltage of the remaining individual cells.

[0082] Specifically, the charging data also includes the charging voltage of each individual battery cell during the charging process. Figure 4 This is a schematic diagram of the charging curve of a single battery cell provided in an embodiment of the present invention, wherein the thick solid line represents the charging curve of the target battery, and the thin solid line represents the charging curve of the remaining single battery cells. Figure 4 The second voltage V2 is used as the maximum charging cutoff voltage of the target battery, and the time tend is the charging cutoff time. The preset time is the time when the charging voltage of the target battery equals the charging cutoff voltage of the remaining individual cells. For example, at the charging cutoff time, the charging cutoff voltage of the target battery is the second voltage V2, and the charging cutoff voltage of a certain remaining cell is the first voltage V1. Since the charging curve of the target battery includes the entire charging voltage range from the charging start time to the charging cutoff time, there exists a voltage on the charging curve of the target battery that is the same as the charging cutoff voltage of the remaining cell. Therefore, the time ti when the target battery reaches the same voltage as the charging cutoff voltage of the remaining cell is the preset time.

[0083] It should be understood that different individual cells have different charging cut-off voltages at the charging cut-off time. Therefore, the preset time corresponding to the target cell is different. That is, ti is not a fixed value. ti changes with the charging cut-off voltage of the remaining individual cells.

[0084] The charging data also includes the charging current of each individual battery cell during the charging process. The first stored capacity is obtained by integrating the ampere-hours of the charging current of the branch where the target battery is located at a preset time ti, and the maximum stored capacity is obtained by integrating the ampere-hours of the charging cutoff current of the branch where the target battery is located at the charging cutoff time tend.

[0085] S1402. Calculate the second stored capacity of the remaining individual cells at the charging cutoff time based on the charging cutoff current corresponding to the remaining individual cells.

[0086] Specifically, at the charging cutoff time (tend), the ampere-hour integral of the charging cutoff current of each individual battery branch is calculated to obtain the second stored capacity corresponding to each individual battery.

[0087] S1403. Based on the difference between the maximum storage capacity and the first storage capacity, the second storage capacity, the actual capacity of the target battery, and the initial SOC value of each individual battery, determine the actual capacity of each remaining individual battery.

[0088] Specifically, the actual capacity of a single battery cell is expressed as:

[0089] CAPi=Qiend / (1-(Qmaxend-Qi) / CAPmax-SOCi);

[0090] CAPi represents the actual capacity of the individual battery, CAPmax represents the actual capacity of the target battery, Qiend represents the second stored capacity, Qi represents the first stored capacity, Qmaxend represents the maximum stored capacity of the target battery at the charging cutoff point, and SOCi represents the initial SOC value of the individual battery, where i is an integer greater than 1. The difference between the maximum stored capacity Qmaxend and the first stored capacity Qi characterizes the charging difference of the individual battery; that is, the difference between the stored capacity of the remaining individual battery and the stored capacity of the target battery at the charging cutoff point. Here, (Qmaxend - Qi) / CAPmax represents the SOC value required for the individual battery to be fully charged.

[0091] It should be noted that the above formula CAPi = Qiend / (1-(Qmaxend-Qi) / CAPmax-SOCi) also applies to the target battery. When the single cell is the target battery, the charging cutoff time tend is the preset time, the first stored capacity Qi is equal to the maximum stored capacity Qmaxend, therefore, (Qmaxend-Qi) / CAPmax = 0; and the second stored capacity Qiend is also equal to the maximum stored capacity Qmaxend. This formula is modified to be the same as the formula for calculating the actual capacity of the target battery.

[0092] In this embodiment, when calculating the actual capacity of each individual battery cell, by fully charging only the target battery and combining the charging differences caused by the characteristics of the individual battery cells themselves (i.e., the different stored charge at the charging cutoff time), the true capacity of all individual battery cells can be obtained, eliminating the error in the SOC value caused by the capacity error between individual battery cells, thereby improving the accuracy of SOH determination.

[0093] S150. Determine the SOH of each individual cell in the power battery pack based on the actual capacity of each individual cell.

[0094] Optionally, in the above embodiments, the SOC value can be obtained by looking up a table. Step S110 includes:

[0095] Based on the initial voltage of the individual cell, consult the SOC-OCV table to determine the initial SOC value.

[0096] Specifically, when acquiring charging data or charging curves for each individual battery cell, the charging voltage at each moment can be obtained based on the charging data or charging curve. Based on the charging voltage, the SOC value at the corresponding charging voltage can be obtained by looking up the SOC-OCV table. Here, OCV (Open circuit voltage) is the open circuit voltage, and in the branch where the individual battery cell is located, its charging voltage can be equivalent to the open circuit voltage.

[0097] Optionally, before step S110, the SOH determination method of the power battery pack further includes a step of determining the initial state of each individual cell. Figure 5 A flowchart of another method for determining the state of harmonics (SOH) of a power battery pack provided in an embodiment of the present invention is shown below. Figure 5 Based on the above embodiments, optionally, the SOH determination method for the power battery pack provided in this embodiment specifically includes the following steps before step S110:

[0098] S210. Determine whether the initial voltage of each individual cell in the power battery pack after the settling time is less than the preset voltage value.

[0099] S220. If the initial voltage is greater than or equal to the preset voltage value, the individual battery cell is discharged until the initial voltage is less than the preset voltage value.

[0100] If the initial voltage is less than the preset voltage value, then step S110 is executed, that is, the initial SOC value of each individual cell in the power battery pack is obtained.

[0101] Specifically, before charging the power battery pack, the initial voltage state of each individual battery cell after a resting period needs to be determined. If the initial voltage does not meet the preset voltage value, the individual battery cell needs to be discharged to ensure that the voltage of all individual batteries in the power battery pack is below the preset voltage value, thus guaranteeing the validity and accuracy of the SOH calculation. The resting period can be 12 hours or 24 hours, which can be set according to actual needs.

[0102] Optionally, the individual battery cells can be discharged using a braking resistor or the discharge function of a charging station.

[0103] Optionally, continue to refer to Figure 5 Before acquiring the charging data of each individual cell in the power battery pack, the following steps are also included:

[0104] S310. Determine whether the error between the total current on the power battery pack side and the total current on the charging device side is less than a set threshold.

[0105] S320. If the error is greater than or equal to the set threshold, report the fault information, do not acquire charging data, and prohibit the determination of SOH.

[0106] Specifically, if the error between the total current on the power battery pack side and the total current on the charging device side is greater than or equal to a set threshold, it indicates that the current sensor has malfunctioned. In this case, the fault information of the current sensor can be reported, and the SOH determination is not performed to avoid poor accuracy of the calculated SOH.

[0107] If the error is less than the set threshold, then step S120 is executed, that is, charging data is obtained.

[0108] refer to Figures 1-5 The following example, using a power battery pack comprising 10 individual cells, illustrates the specific working principle of the SOH determination method provided in this embodiment:

[0109] Assuming the first cell has the maximum initial voltage, and the initial voltages of the other nine cells are all less than the maximum initial voltage, and the maximum initial voltage is less than a preset voltage value (if the maximum initial voltage is not less than the preset voltage value, the first cell is discharged until it is less than the preset voltage value), then the initial voltages of the other nine cells are also less than the preset voltage value.

[0110] After determining the initial state of voltage of each individual battery cell, the initial state of voltage (SOC) is obtained by looking up the SOC-OCV table based on the initial voltage of each individual battery cell. The power battery pack is then charged in a constant current / constant voltage mode or a multi-stage constant current mode. The state of equilibrium (SOH) is only calculated when the error between the total current on the power battery pack side and the total current on the charging device side is less than a set threshold.

[0111] The charging curves of each individual battery cell are obtained during the charging process. The charging process is stopped when the individual battery cell with the maximum charging voltage reaches the full charge condition, and this moment is recorded as the charging cutoff moment. For example, if the first individual battery cell has the maximum charging voltage, charging of the power battery pack is stopped when the first individual battery cell reaches the full charge condition, and the charging cutoff voltage corresponding to the first individual battery cell at the charging cutoff moment is recorded as the maximum charging cutoff voltage.

[0112] Then, combining charging data and charging curves, the time when the charging voltage of the first individual cell (target cell) equals the charging cutoff voltage of the remaining nine individual cells is selected as the preset time *ti*. The ampere-hour integral of the charging current of the branch containing the first individual cell at time *ti* is calculated to obtain the first stored capacity, and the ampere-hour integral of the charging cutoff current of the branch containing the first individual cell at the charging cutoff time *tend* is calculated to obtain the maximum stored capacity. At the charging cutoff time *tend*, the ampere-hour integral of the charging cutoff current of the branches containing the remaining nine individual cells is calculated to obtain the second stored capacity for each individual cell. The maximum stored capacity of the first individual cell is its second stored capacity.

[0113] The actual capacity of the first single cell is calculated using the formula CAPmax = Qmaxend / (1 - SOCmax0). The actual capacities of the remaining nine single cells are calculated using the formula CAPi = Qiend / (1 - (Qmaxend - Qi) / CAPmax - SOCi), where i = 2, 3, ..., 9. Here, CAPmax is the actual capacity of the target cell (the first single cell), Qmaxend is the maximum stored capacity of the target cell at the charging cutoff point (i.e., the ampere-hour integral of the current in the branch where the target cell is located at the charging cutoff point), SOCmax0 is the initial SOC value of the target cell, CAPi is the actual capacity of the single cell, Qiend is the second stored capacity, Qi is the first stored capacity, and SOCi is the initial SOC value of the single cell.

[0114] The SOH of each individual cell is calculated based on the ratio of its actual capacity to its nominal capacity.

[0115] The technical solution provided in this embodiment uses the single cell with the maximum charging cut-off voltage as the target cell and, based on the maximum charging cut-off voltage of this target cell, calculates the actual capacity of each single cell by incorporating charging error. This eliminates capacity errors between single cells, thereby improving the accuracy of SOH calculation. This solution eliminates the need for full charging and discharging of all single cells, avoiding energy waste, and is unaffected by vehicle driving conditions, thus improving the convenience and flexibility of SOH calculation.

[0116] Optionally, embodiments of the present invention also provide a device for determining the state of harm (SOH) of a power battery pack. Figure 6 This is a schematic diagram of a power battery pack SOH determination device provided in an embodiment of the present invention, with reference to... Figure 6 The SOH determination device for this power battery pack includes:

[0117] The parameter determination module 11 is used to obtain the initial SOC value of each individual cell in the power battery pack, and to obtain the charging data of each individual cell in the power battery pack. The charging data includes the charging cutoff voltage and charging cutoff current of each individual cell at the charging cutoff time.

[0118] The first capacity determination module 12 is used to determine the actual capacity of the target battery by taking the single cell with the maximum charging cut-off voltage as the target battery and the charging cut-off current and initial SOC value of the target battery.

[0119] The second capacity determination module 13 is used to determine the actual capacity of the remaining individual cells based on the charging data of each individual cell, combined with the charging error of each individual cell, and according to the actual capacity of the target battery and the initial SOC value of each individual cell.

[0120] SOH determination module 14 is used to determine the SOH of each individual cell in the power battery pack based on the actual capacity of each individual cell.

[0121] The technical solution provided in this embodiment does not require fully charging and discharging all batteries and is unaffected by driving conditions. Based on partial charging data, it can obtain the SOH of all individual batteries. By combining the charging differences of each individual battery, the actual capacity of the target battery with the maximum charging cutoff voltage and the initial SOC value of each individual battery can be used to obtain the accurate actual capacity of each individual battery, thereby improving the estimation accuracy of the SOH of the individual batteries.

[0122] Optionally, embodiments of the present invention also provide a battery management system, which can be applied to vehicles, such as new energy vehicles. This battery management system is used to execute the SOH determination method for power battery packs provided in any embodiment of the present invention. Therefore, the battery management system provided in this embodiment also possesses the beneficial effects described in any of the above embodiments.

[0123] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0124] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for determining the state of harmonics (SOH) of a power battery pack, characterized in that, include: Obtain the initial SOC value of each individual cell in the power battery pack; Obtain the charging data of each individual cell in the power battery pack, the charging data including the charging cut-off voltage and charging cut-off current of each individual cell at the charging cut-off time; Using the single cell with the maximum charging cut-off voltage as the target cell, the actual capacity of the target cell is determined based on the charging cut-off current and the initial SOC value of the target cell. Based on the charging data of each individual battery cell, combined with the charging error of each individual battery cell, and according to the actual capacity of the target battery cell and the initial SOC value of each individual battery cell, the actual capacity of the remaining individual battery cells is determined respectively. The SOH of each individual cell in the power battery pack is determined based on the actual capacity of each individual cell. The charging data also includes the charging voltage and charging current of each individual battery cell during the charging process; The determination of the actual capacity of the remaining individual cells based on the charging data of each individual cell, combined with the charging error of each individual cell, and according to the actual capacity of the target battery and the initial SOC value of each individual cell, includes: Based on the charging current and the charging cutoff current of the target battery, the first stored capacity of the target battery at a preset time and the maximum stored capacity at the charging cutoff time are obtained respectively; wherein, the preset time is the time when the charging voltage of the target battery is equal to the charging cutoff voltage of the remaining individual cells; Based on the charging cutoff current corresponding to the remaining individual cells, calculate the second stored capacity of each of the remaining individual cells at the charging cutoff time; The actual capacity of each remaining individual battery is determined based on the difference between the maximum storage capacity and the first storage capacity, the second storage capacity, the actual capacity of the target battery, and the initial SOC value of each individual battery. The difference between the maximum storage capacity and the first storage capacity is used to characterize the charging error of the single battery cell. The actual capacity of the single battery cell is expressed as follows: CAPi=Qiend / (1-(Qmaxend-Qi) / CAPmax-SOCi); CAPi is the actual capacity of the single battery cell, CAPmax is the actual capacity of the target battery, Qiend is the second stored capacity, Qi is the first stored capacity, Qmaxend is the maximum stored capacity of the target battery at the charging cutoff time, SOCi is the initial SOC value of the single battery cell, and i is an integer greater than 1.

2. The method for determining the state of harmonics (SOH) of a power battery pack according to claim 1, characterized in that, The step of using the single cell with the maximum charging cut-off voltage as the target cell, and determining the actual capacity of the target cell based on the charging cut-off current and the initial SOC value of the target cell, includes: Using the single cell with the maximum charging cutoff voltage as the target cell, the maximum stored capacity of the target cell at the charging cutoff time is calculated based on the charging cutoff current of the target cell. The actual capacity of the target battery is determined based on the maximum storage capacity of the target battery and the initial SOC value; The actual capacity of the target battery is expressed as: CAPmax=Qmaxend / (1-SOCmax0); CAPmax is the actual capacity of the target battery, Qmaxend is the maximum stored capacity of the target battery at the charging cutoff time, and SOCmax0 is the initial SOC value of the target battery.

3. The method for determining the state of harmonics (SOH) of a power battery pack according to claim 1, characterized in that, The SOH of a single cell is equal to the ratio of the actual capacity of the single cell to the nominal capacity of the single cell.

4. The method for determining the state of harmonics (SOH) of a power battery pack according to claim 1, characterized in that, The charging cutoff time is the time when the target battery reaches the full charge condition; wherein, the full charge condition is that the charging cutoff current of the target battery is less than or equal to a preset current value.

5. The method for determining the state of harmonics (SOH) of a power battery pack according to claim 1, characterized in that, The process of obtaining the initial SOC value of each individual cell in the power battery pack includes: Based on the initial voltage of the individual battery cell, the SOC-OCV table is consulted to determine the initial SOC value.

6. The method for determining the state of harmonics (SOH) of a power battery pack according to claim 1, characterized in that, Before obtaining the initial SOC value of each individual cell in the power battery pack, the method further includes: Determine whether the initial voltage of each individual cell in the power battery pack after the settling time is less than a preset voltage value; If the initial voltage is greater than or equal to the preset voltage value, the individual battery is discharged until the initial voltage is less than the preset voltage value; If the initial voltage is less than the preset voltage value, then the initial SOC value of each individual cell in the power battery pack is obtained.

7. The method for determining the state of harmonics (SOH) of a power battery pack according to claim 1, characterized in that, Before acquiring the charging data of each individual cell in the power battery pack, the method further includes: Determine whether the error between the sum of currents on the power battery pack side and the sum of currents on the charging device side is less than a set threshold. If the error is greater than or equal to the set threshold, then fault information is reported, the charging data is not acquired, and the determination of SOH is prohibited; If the error is less than the set threshold, then the charging data is acquired.

8. A device for determining the state of harm (SOH) of a power battery pack, characterized in that, For performing the SOH determination method of the power battery pack according to any one of claims 1-7, the SOH determination device of the power battery pack includes: The parameter determination module is used to obtain the initial SOC value of each individual cell in the power battery pack, and to obtain the charging data of each individual cell in the power battery pack; the charging data includes the charging cutoff voltage and charging cutoff current of each individual cell at the charging cutoff time. The first capacity determination module is used to determine the actual capacity of the target battery based on the charging cut-off current and the initial SOC value of the target battery, using the single cell with the maximum charging cut-off voltage as the target battery. The second capacity determination module is used to determine the actual capacity of the remaining individual cells based on the charging data of each individual cell, combined with the charging error of each individual cell, and according to the actual capacity of the target battery and the initial SOC value of each individual cell. The SOH determination module is used to determine the SOH of each individual cell in the power battery pack based on the actual capacity of each individual cell.

9. A battery management system applied to a vehicle, characterized in that, The battery management system is used to perform the SOH determination method for the power battery pack according to any one of claims 1-7.

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