A battery pack impedance detection method and device

Abstract

The embodiment of the present application discloses a battery pack impedance detection method and device, specifically, when the battery pack is in a static state, an AC signal is injected into the negative electrode of the battery pack, so as to obtain the voltage signal of each battery cell under the action of the AC signal. For any battery cell, the first resistance of the battery cell is determined according to the injected AC signal and the voltage signal corresponding to the battery cell. When the battery pack is in a dynamic state, the dynamic voltage and dynamic current of the battery cell in the dynamic state are obtained, and the second resistance of the battery cell is determined according to the dynamic voltage, dynamic current and static voltage. Then, the first resistance and the second resistance are filtered and fused, and the accurate resistance value of the battery cell is obtained through filtering iteration. That is, because the real-time performance is high when the battery pack is in a dynamic state, and the reliability is high when it is static. The two calculation results obtained in the two states are filtered and iterated at the same time to obtain the accurate resistance value of the battery cell, providing accurate calculation data for calculating the remaining battery capacity and health.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery pack impedance detection method and device. Background Art

[0002] With the development of new energy vehicles, the requirements for battery packs and battery management systems are getting higher and higher, especially the accuracy and safety of battery management. At present, the battery pack solutions are all implemented in the form of multiple strings of battery cells in series to form a battery pack, and the inconsistency of battery cell resistance is inevitable. Moreover, with the increase of usage time, this inconsistency will become more serious, which will increase the deviation of the battery pack's power and health estimation, and then cause improper control strategy of the battery management system BMS, resulting in a decrease in the battery pack's service life or inaccurate mileage estimation. Therefore, it is very necessary to obtain the resistance of the battery cell in order to accurately estimate the power and health based on the resistance of the battery cell. Summary of the invention

[0003] In view of this, an embodiment of the present application provides a battery pack impedance detection method and device to achieve more reasonable and effective processing of network requests.

[0004] To solve the above problems, the technical solutions provided in the embodiments of the present application are as follows:

[0005] In a first aspect of an embodiment of the present application, a method for detecting impedance of a battery pack is provided, wherein the battery pack includes a plurality of battery cells, and the method includes:

[0006] When the battery pack is in a static state, an AC signal is input to the battery pack; the battery pack is in a static state when the battery pack current is less than a first preset threshold;

[0007] For any of the battery cells, obtaining a voltage signal of the battery cell, and determining a first resistance of the battery cell according to the voltage signal and the AC signal;

[0008] When the battery pack is in a dynamic state, obtaining a dynamic voltage and a dynamic current of the battery cell; the battery pack is in a dynamic state when the current of the battery pack is greater than a second preset threshold;

[0009] Determine the second resistance of the battery cell according to the dynamic voltage, the dynamic current and the static voltage, wherein the static voltage is the voltage corresponding to the battery cell when the battery pack is in a static state;

[0010] The first resistor and the second resistor are filtered iteratively until the filtering converges to obtain the resistance of the battery cell.

[0011] In a possible implementation manner, determining the first resistance according to the voltage signal and the AC signal includes:

[0012] determining a phase difference according to the voltage signal and the AC signal;

[0013] A first resistance of the battery cell is determined according to the modulus of the voltage signal and the phase difference.

[0014] In a possible implementation, determining the second resistance of the battery cell according to the dynamic voltage, the dynamic current, and the static voltage includes:

[0015] The dynamic voltage is subtracted from the static voltage to obtain a first voltage;

[0016] The first voltage is divided by the dynamic current to obtain a second resistance of the battery cell.

[0017] In a possible implementation, the battery pack includes at least two battery modules, the battery module includes a plurality of battery cells, and the method further includes:

[0018] When the AC signal is input to the battery pack, for any high-voltage connection point, a voltage signal of the high-voltage connection point is obtained, and a third impedance is determined according to the voltage signal and the AC signal; the high-voltage connection point includes one or more of a connection point between modules, a connection point between a module and a high-voltage relay, or a connection point between a high-voltage relay and an output terminal;

[0019] When the battery pack is in a dynamic state, obtaining a dynamic voltage and a dynamic current of the high-voltage connection point;

[0020] Determine the fourth impedance of the high-voltage connection point according to the dynamic voltage, the dynamic current and the static voltage; the static voltage is the voltage corresponding to the high-voltage connection point when the battery pack is in a static state;

[0021] The third impedance and the fourth impedance are filtered iteratively until the filtering converges to obtain the impedance of the high-voltage connection point.

[0022] In a possible implementation, the method further includes:

[0023] When the resistance of any of the high-voltage connection points is greater than a third preset threshold, an early warning is issued.

[0024] In a possible implementation, a complementary filter or a Kalman filter is used to perform filtering iterations.

[0025] In a second aspect of an embodiment of the present application, a battery pack impedance detection device is provided, the device comprising:

[0026] An input unit, used for inputting an AC signal to the battery pack when the battery pack is in a static state; the battery pack is in a static state when the battery pack current is less than a first preset threshold;

[0027] A first acquisition unit, used for acquiring a voltage signal of any of the battery cells;

[0028] A first determining unit, configured to determine a first resistance of the battery cell according to the voltage signal and the AC signal;

[0029] A second acquisition unit is used to acquire the dynamic voltage and dynamic current of the battery cell when the battery pack is in a dynamic state; the battery pack is in a dynamic state when the current of the battery pack is greater than a second preset threshold;

[0030] A second determination unit, configured to determine a second resistance of the battery cell according to the dynamic voltage, the dynamic current, and a static voltage, wherein the static voltage is a voltage corresponding to the battery cell when the battery pack is in a static state;

[0031] The first iterative unit is used to perform filtering iteration on the first resistor and the second resistor until the filtering converges to obtain the resistance of the battery cell.

[0032] In a possible implementation manner, the first determining unit includes:

[0033] A first determining subunit, configured to determine a phase difference according to the voltage signal and the AC signal;

[0034] The second determining subunit is used to determine the first resistance of the battery cell according to the modulus of the voltage signal and the phase difference.

[0035] In a possible implementation manner, the second determining unit includes:

[0036] A first acquisition subunit, configured to subtract the dynamic voltage from the static voltage to obtain a first voltage;

[0037] The second acquisition subunit is used to obtain a second resistance of the battery cell by dividing the first voltage by the dynamic current.

[0038] In a possible implementation, the battery pack includes at least two battery modules, the battery module includes a plurality of battery cells, and the device further includes:

[0039] A third acquisition unit, configured to acquire a voltage signal of any high-voltage connection point when the AC signal is input to the battery pack;

[0040] A third determination unit is used to determine a third impedance according to the voltage signal and the AC signal; the high-voltage connection point includes one or more of a connection point between modules, a connection point between a module and a high-voltage relay, or a connection point between a high-voltage relay and an output terminal;

[0041] a fourth acquisition unit, configured to acquire a dynamic voltage and a dynamic current of the high-voltage connection point when the battery pack is in a dynamic state;

[0042] a fourth determining unit, configured to determine a fourth impedance of the high-voltage connection point according to the dynamic voltage, the dynamic current, and a static voltage; the static voltage being a voltage corresponding to the high-voltage connection point when the battery pack is in a static state;

[0043] The second iterative unit is used to perform filtering iteration on the third impedance and the fourth impedance until the filtering converges to obtain the impedance of the high-voltage connection point.

[0044] In a possible implementation manner, the device further includes:

[0045] The early warning unit is used to issue an early warning when the resistance of any of the high-voltage connection points is greater than a third preset threshold.

[0046] In a possible implementation, a complementary filter or a Kalman filter is used to perform filtering iterations.

[0047] It can be seen that the embodiments of the present application have the following beneficial effects:

[0048] In the embodiment of the present application, when the battery pack is in a static state, an AC signal is first injected into the negative electrode of the battery pack, so as to obtain the voltage signal of each battery cell under the action of the AC signal. For any battery cell, the first resistance of the battery cell is determined according to the injected AC signal and the voltage signal corresponding to the battery cell. Then, when the battery pack is in a dynamic state, the dynamic voltage and dynamic current of the battery cell in the dynamic state are obtained, and the second resistance of the battery cell is determined according to the dynamic voltage, dynamic current and static voltage. Then, the first resistance and the second resistance are filtered and fused, and the accurate resistance value of the battery cell is obtained through filtering iteration. That is, because the real-time performance is high when the battery pack is in a dynamic state, and the reliability is high when it is static. The two calculation results obtained by calculation in the two states are filtered and iterated at the same time to obtain the accurate resistance value of the battery cell, so as to provide accurate calculation data for the subsequent calculation of the remaining battery capacity and health. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1a A schematic diagram of a battery pack structure provided in an embodiment of the present application;

[0050] Figure 1b A schematic diagram of another battery pack structure provided in an embodiment of the present application;

[0051] Figure 2 A flow chart of a battery pack impedance detection method provided in an embodiment of the present application;

[0052] Figure 3 A flowchart of another battery pack impedance detection method provided in an embodiment of the present application;

[0053] Figure 4 A structural diagram of a battery pack impedance detection device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0054] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0055] The inventors found in their research on traditional BMS products that they did not calculate the internal resistance of the battery cells. In this case, the estimated battery pack life and mileage would be greatly deviated, causing improper BMS control strategy.

[0056] In addition, the reliability of the high-voltage copper connection in the battery pack gradually decreases with the increase of life. The existing monitoring means only monitor and judge based on the temperature sensor of the module tab, and take protection when overheating. However, this solution does not monitor the reliability of the high-voltage connection in the battery pack 100%. When these unreliable connections fail and the BMS has no relevant monitoring, the battery pack's external output is likely to be abnormally interrupted, causing an accident to the vehicle while driving.

[0057] Based on this, an embodiment of the present application provides a battery pack impedance detection method, which obtains the resistance of the battery cell in two different states when the battery pack is in different states, and then filters and calculates the two resistances to obtain a more accurate resistance. Specifically, when the battery pack is in a static state, an AC signal is input to the negative pole of the battery pack, and the voltage signal of the battery cell after the AC signal is injected is obtained. The first resistance of the battery cell is determined based on the voltage signal of the battery cell and the original AC signal. Then, when the battery pack is in a dynamic state, the dynamic voltage and dynamic current of each battery cell in this state are obtained, and the second resistance of the battery cell is determined based on the dynamic voltage, dynamic current and the static voltage of the battery cell when it is static. Finally, the first resistance and the second resistance are filtered iteratively until the filtering converges to obtain the resistance of the battery cell.

[0058] In addition, for the impedance of the high-voltage connection point of the battery pack, similarly, when the battery pack is in a static state and an AC signal is injected, the voltage signal of the high-voltage connection point at this moment is obtained, and the third impedance is determined based on the voltage signal and the AC signal. When the battery pack is in a dynamic state, the dynamic voltage and dynamic current of the high-voltage connection point are obtained. The fourth impedance of the high-voltage connection point is determined based on the dynamic voltage, dynamic current and the static voltage of the high-voltage connection point in a static state. Finally, the third impedance and the fourth impedance are filtered iteratively until the filtering converges to obtain the impedance of the high-voltage connection point, and then when the impedance of the high-voltage connection point is greater than the threshold, an early warning is issued to achieve safety monitoring.

[0059] For easier understanding of this application, see Figure 1a The schematic diagram of the battery pack structure is shown in FIG. Figure 1a As shown, the battery pack may include multiple battery modules. R0 is the effective resistance between the battery negative electrode sampling point and module 1, R1-Rk-1 is the effective resistance between modules, and Rk is the effective resistance between the battery positive electrode sampling point and module k. Each battery module may include multiple cells, such as Figure 1b As shown, the cn sampling point is the negative electrode sampling point of the n-th battery cell, and the cn+1 sampling point is the positive electrode sampling point of the n-th battery cell.

[0060] In a specific implementation, when the battery pack is in a static state, an AC signal is input to the negative electrode of the battery pack, and the voltage signal of the corresponding battery cell is obtained from each sampling point, so as to determine the first resistance of each battery cell according to the voltage signal and the AC signal. When the battery pack is in a dynamic state, the dynamic voltage and dynamic current of the corresponding battery cell are obtained from each sampling point, and the second resistance of the battery cell is obtained according to the dynamic voltage, dynamic current and static voltage of the battery cell. The first resistance and the second resistance are then used for filtering iteration to obtain the resistance of the battery cell.

[0061] It should be noted that the above method can be used to determine the resistance value of each battery cell in the battery pack.

[0062] See also Figure 2 , which is a flow chart of a battery pack impedance detection method provided in an embodiment of the present application, wherein the battery pack includes a plurality of cells, such as Figure 2 As shown, the method may include:

[0063] S201: When the battery pack is in a static state, an AC signal is input to the battery pack.

[0064] In this embodiment, when the battery pack is in a static state, an AC signal is input to the battery pack so as to use the AC signal to determine the resistance of the battery cell in a static state. The battery pack being in a static state means that the current current of the battery pack is less than a first preset threshold value, and the first preset threshold value can be set according to actual application conditions, for example, the first preset threshold value is 5A.

[0065] In a specific implementation, the current of the battery pack may be sampled first, and it may be determined whether the sampled current is less than a first preset threshold value. If so, it indicates that the battery pack is in a static state, and an AC signal is injected into the battery pack.

[0066] S202: For any battery cell, obtain a voltage signal of the battery cell, and determine a first resistance of the battery cell according to the voltage signal and the AC signal.

[0067] After the AC signal is injected into the battery pack, the voltage signal of each battery cell is acquired to determine the first resistance of the battery cell according to the voltage signal of the battery cell and the injected AC signal.

[0068] In specific implementation, this embodiment provides a specific implementation of determining the first resistance, and the first resistance is determined according to the voltage signal and the AC signal, including: determining the phase difference according to the voltage signal and the AC signal; determining the first resistance of the battery cell according to the modulus of the voltage signal and the phase difference.

[0069] That is, according to the input AC signal and the output voltage signal, the phase change of the AC signal passing through the battery cell is determined, and the first resistance of the battery cell is determined according to the modulus of the voltage signal and the phase change. For example, the phase difference is The modulus of the voltage signal is |Z|, so the first resistance of the cell is In practical applications, in order to reduce interference from other interfering signals, after the voltage signal is obtained, a Fourier transform is performed first, and then the signal component of a specific frequency (the frequency of the AC signal) is extracted, so as to calculate the first resistance of the battery cell based on the modulus value of the voltage signal of a specific frequency.

[0070] Specifically, Figure 1b As shown, the first resistance of each battery cell can be calculated using formula (1):

[0071]

[0072] Among them, R cn is the first resistance of the nth cell, is the effective value of the voltage across the cell n, and I is the current value of the injected AC signal

[0073] S203: When the battery pack is in a dynamic state, obtain the dynamic voltage and dynamic current of the battery cell.

[0074] In this embodiment, when the battery pack is in a dynamic state, the dynamic voltage and dynamic current of each battery cell in this state are obtained. The dynamic voltage can be the voltage of the battery pack during charging and discharging, and the dynamic current is the current of the battery pack during charging and discharging. The battery pack being in a dynamic state means that the current of the battery pack is greater than the second preset threshold value, and the second preset threshold value can be determined according to the actual application situation, for example, the second preset threshold value is 80A.

[0075] In practical applications, the battery pack may be sampled first, and it may be determined whether the sampled current is greater than a second preset threshold value. If the current is greater than the second preset threshold value, it is determined that the battery pack is in a dynamic state.

[0076] S204: Determine a second resistance of the battery cell according to the dynamic voltage, the dynamic current, and the static voltage.

[0077] After obtaining the dynamic voltage and dynamic current of the battery cell in the dynamic state, the second resistance of the battery cell is determined according to the dynamic voltage, dynamic current and the voltage corresponding to the battery cell in the static state, wherein the static voltage is the voltage corresponding to the battery cell when the battery pack is in the static state.

[0078] In a possible implementation, a specific implementation method for determining the second resistance is provided, wherein the second resistance of the battery cell is determined according to the dynamic voltage, the dynamic current and the static voltage, including: subtracting the dynamic voltage from the static voltage to obtain the first voltage; and dividing the first voltage by the dynamic current to obtain the second resistance of the battery cell. For example, when a battery cell is static, the static voltage V0, the dynamic current I and the dynamic voltage are V1, then the resistance R of the battery cell is (V1-V0) / I. Among them, V0 is the voltage just before the step current appears, V1 is the voltage when the step current appears, and I is the step current.

[0079] S205: Perform filtering iterations on the first resistor and the second resistor until the filtering converges to obtain the resistance of the battery cell.

[0080] After obtaining the first resistance and the second resistance corresponding to the battery cell in static and dynamic state respectively, the first resistance and the second resistance are filtered iteratively until the filtering converges to obtain the resistance of the battery cell, thereby estimating the remaining battery power and battery health of the battery pack according to the resistance of each battery cell, and providing a more accurate range estimation. Specifically, complementary filters and Kalman filters can be used for filtering iteration. That is, the first resistance and the second resistance are used as input parameters of the above filter, and the covariance of the resistance estimated by the filter based on the first resistance and the second resistance meets the preset conditions.

[0081] It can be seen from the above description that in this embodiment, when the battery pack is in a static state, an AC signal is first injected into the negative electrode of the battery pack, so as to obtain the voltage signal of each battery cell under the action of the AC signal. For any battery cell, the first resistance of the battery cell is determined according to the injected AC signal and the voltage signal corresponding to the battery cell. Then, when the battery pack is in a dynamic state, the dynamic voltage and dynamic current of the battery cell in the dynamic state are obtained, and the second resistance of the battery cell is determined according to the dynamic voltage, dynamic current and static voltage. Then, the first resistance and the second resistance are filtered and fused, and the accurate resistance value of the battery cell is obtained through filtering iteration. That is, because the real-time performance is high when the battery pack is in a dynamic state, and the reliability is high when it is static. The two calculation results obtained by calculation in the two states are filtered and iterated at the same time to obtain the accurate resistance value of the battery cell, so as to provide accurate calculation data for the subsequent calculation of the remaining battery capacity and health.

[0082] Based on the above method example, the impedance of the high-voltage connection point of the battery pack can also be detected, so that after obtaining the impedance of the high-voltage connection point, an early warning can be issued according to the impedance of the high-voltage connection point to achieve the purpose of safety monitoring. The detection of the impedance of the high-voltage connection point will be described below.

[0083] See also Figure 3 , which is a flow chart of another battery pack impedance detection method provided in an embodiment of the present application, wherein the battery pack includes at least two battery modules, each battery module includes a plurality of battery cells, and the method may include:

[0084] S301: When an AC signal is input to the battery pack, a voltage signal of any high-voltage connection point is obtained, and a third impedance is determined according to the voltage signal and the AC signal.

[0085] The high voltage connection point includes one or more of a connection point between modules, a connection point between a module and a high voltage relay, or a connection point between a high voltage relay and an output terminal. The high voltage relay may include a main negative relay and a main positive relay.

[0086] In a specific implementation, when the high-voltage connection point is the connection point between the negative electrode of the first battery cell and the main negative relay, the third impedance is determined according to the voltage signal of the high-voltage connection point and the AC signal as follows:

[0087]

[0088] Among them, R0 is the impedance between the negative electrode of the first battery cell and the main negative relay voltage, is the effective value of the voltage between the negative electrode of the first battery cell and the main negative relay, and I is the current value of the AC signal.

[0089] When the high-voltage connection point is a connection point between two adjacent modules, the third impedance is determined according to the voltage signal and the AC signal of the high-voltage connection point as follows:

[0090]

[0091] Among them, R k-1 is the third impedance between the k-1th battery module and the kth battery module, is the effective voltage value between the k-1th battery module and the kth battery module, and I is the current value of the AC signal.

[0092] When the high-voltage connection point is the connection point between the main positive relay and the highest positive electrode of the battery cell in the kth battery module, the third impedance is determined according to the voltage signal of the high-voltage connection point and the AC signal as follows:

[0093]

[0094] Among them, R k is the third impedance between the main positive relay and the highest positive electrode of the kth battery module, is the effective voltage value between the main positive relay and the positive electrode of the highest battery cell in the kth battery module, and I is the current value of the AC signal.

[0095] In specific implementation, the impedance across the main negative relay can be determined based on the effective value of the voltage across the main negative relay and the current value of the AC signal; the impedance across the main positive relay can be determined based on the effective value of the voltage across the main positive relay and the current value of the AC signal.

[0096] S302: When the battery pack is in a dynamic state, obtain a dynamic voltage and a dynamic current of the high-voltage connection point.

[0097] S303: Determine a fourth impedance of the high voltage connection point according to the dynamic voltage, the dynamic current, and the static voltage.

[0098] In specific implementation, R = (V1-V0) / I can be used. Among them, V0 is the voltage just before the step current appears, that is, the static voltage, V1 is the voltage when the step current appears, that is, the dynamic voltage, and I is the step current. Among them, the static voltage is the voltage corresponding to the high-voltage connection point when the battery pack is in a static state.

[0099] S304: Perform filtering iterations on the third impedance and the fourth impedance until the filtering converges to obtain the impedance of the high voltage connection point.

[0100] Specifically, a complementary filter or a Kalman filter may be used to perform filtering iteration to obtain the impedance of the high-voltage connection point. For the specific implementation, see S205.

[0101] Based on the above method embodiment, the present application embodiment provides a battery pack impedance detection device, see Figure 4, which is a schematic diagram of the structure of a battery pack impedance detection device provided in an embodiment of the present application, and the device includes:

[0102] An input unit 401 is used to input an AC signal to the battery pack when the battery pack is in a static state; the battery pack is in a static state when the battery pack current is less than a first preset threshold;

[0103] A first acquisition unit 402 is used to acquire a voltage signal of any of the battery cells;

[0104] A first determining unit 403, configured to determine a first resistance of the battery cell according to the voltage signal and the AC signal;

[0105] A second acquisition unit 404 is used to acquire the dynamic voltage and dynamic current of the battery cell when the battery pack is in a dynamic state; the battery pack is in a dynamic state when the current of the battery pack is greater than a second preset threshold;

[0106] A second determining unit 405, configured to determine a second resistance of the battery cell according to the dynamic voltage, the dynamic current and a static voltage, wherein the static voltage is a voltage corresponding to the battery cell when the battery pack is in a static state;

[0107] The first iterative unit 406 is used to perform filtering iteration on the first resistor and the second resistor until the filtering converges to obtain the resistance of the battery cell.

[0108] In a possible implementation manner, the first determining unit includes:

[0109] A first determining subunit, configured to determine a phase difference according to the voltage signal and the AC signal;

[0110] The second determining subunit is used to determine the first resistance of the battery cell according to the modulus of the voltage signal and the phase difference.

[0111] In a possible implementation manner, the second determining unit includes:

[0112] A first acquisition subunit, configured to subtract the dynamic voltage from the static voltage to obtain a first voltage;

[0113] The second acquisition subunit is used to obtain a second resistance of the battery cell by dividing the first voltage by the dynamic current.

[0114] In a possible implementation, the battery pack includes at least two battery modules, the battery module includes a plurality of battery cells, and the device further includes:

[0115] A third acquisition unit, configured to acquire a voltage signal of any high-voltage connection point when the AC signal is input to the battery pack;

[0116] A third determination unit is used to determine a third impedance according to the voltage signal and the AC signal; the high-voltage connection point includes one or more of a connection point between modules, a connection point between a module and a high-voltage relay, or a connection point between a high-voltage relay and an output terminal;

[0117] a fourth acquisition unit, configured to acquire a dynamic voltage and a dynamic current of the high-voltage connection point when the battery pack is in a dynamic state;

[0118] a fourth determining unit, configured to determine a fourth impedance of the high-voltage connection point according to the dynamic voltage, the dynamic current, and a static voltage; the static voltage being a voltage corresponding to the high-voltage connection point when the battery pack is in a static state;

[0119] The second iterative unit is used to perform filtering iteration on the third impedance and the fourth impedance until the filtering converges to obtain the impedance of the high-voltage connection point.

[0120] In a possible implementation manner, the device further includes:

[0121] The early warning unit is used to issue an early warning when the resistance of any of the high-voltage connection points is greater than a third preset threshold.

[0122] In a possible implementation, a complementary filter or a Kalman filter is used to perform filtering iterations.

[0123] It should be noted that the implementation of each unit in this embodiment can refer to the above method embodiment, and this embodiment will not be repeated here.

[0124] From the above, it can be seen that when the battery pack is in a static state, an AC signal is injected into the negative electrode of the battery pack to obtain the voltage signal of each battery cell under the action of the AC signal. For any battery cell, the first resistance of the battery cell is determined according to the injected AC signal and the voltage signal corresponding to the battery cell. Then, when the battery pack is in a dynamic state, the dynamic voltage and dynamic current of the battery cell in the dynamic state are obtained, and the second resistance of the battery cell is determined according to the dynamic voltage, dynamic current and static voltage. Then, the first resistance and the second resistance are filtered and fused, and the accurate resistance value of the battery cell is obtained through filtering iteration. That is, because the real-time performance is high when the battery pack is in a dynamic state, and the reliability is high when it is static. The two calculation results obtained in the two states are filtered and iterated at the same time to obtain the accurate resistance value of the battery cell, so as to provide accurate calculation data for the subsequent calculation of the remaining battery capacity and health.

[0125] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0126] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0127] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0128] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0129] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery pack impedance detection method, wherein the battery pack comprises a plurality of battery cells, characterized in that: The method comprises: When the battery pack is in a static state, an AC signal is input to the battery pack; the battery pack is in a static state when the battery pack current is less than a first preset threshold; For any of the battery cells, obtaining a voltage signal of the battery cell, and determining a first resistance of the battery cell according to the voltage signal and the AC signal; When the battery pack is in a dynamic state, obtaining a dynamic voltage and a dynamic current of the battery cell; the battery pack is in a dynamic state when the current of the battery pack is greater than a second preset threshold; Determine the second resistance of the battery cell according to the dynamic voltage, the dynamic current and the static voltage, wherein the static voltage is the voltage corresponding to the battery cell when the battery pack is in a static state; Performing filtering iterations on the first resistor and the second resistor until filtering converges to obtain the resistance of the battery cell; The battery pack includes at least two battery modules, and the battery module includes a plurality of battery cells. The method further includes: When the AC signal is input to the battery pack, for any high-voltage connection point, a voltage signal of the high-voltage connection point is obtained, and a third impedance is determined according to the voltage signal and the AC signal; the high-voltage connection point includes one or more of a connection point between modules, a connection point between a module and a high-voltage relay, or a connection point between a high-voltage relay and an output terminal; When the battery pack is in a dynamic state, obtaining a dynamic voltage and a dynamic current of the high-voltage connection point; Determine the fourth impedance of the high-voltage connection point according to the dynamic voltage, the dynamic current and the static voltage; the static voltage is the voltage corresponding to the high-voltage connection point when the battery pack is in a static state; The third impedance and the fourth impedance are filtered iteratively until the filtering converges to obtain the impedance of the high-voltage connection point.

2. The method according to claim 1, characterized in that The determining the first resistance according to the voltage signal and the AC signal comprises: determining a phase difference according to the voltage signal and the AC signal; A first resistance of the battery cell is determined according to the modulus of the voltage signal and the phase difference.

3. The method according to claim 1, characterized in that The determining the second resistance of the battery cell according to the dynamic voltage, the dynamic current and the static voltage includes: The dynamic voltage is subtracted from the static voltage to obtain a first voltage; The first voltage is divided by the dynamic current to obtain a second resistance of the battery cell.

4. The method according to claim 1, characterized in that The method further comprises: When the resistance of any of the high-voltage connection points is greater than a third preset threshold, an early warning is issued.

5. The method according to any one of claims 1 to 4, characterized in that: Filtering iterations are performed using complementary filters or Kalman filters.

6. A battery pack impedance detection device, characterized in that: The device comprises: An input unit, used for inputting an AC signal to the battery pack when the battery pack is in a static state; the battery pack is in a static state when the battery pack current is less than a first preset threshold; A first acquisition unit, used for acquiring a voltage signal of any battery cell; A first determining unit, configured to determine a first resistance of the battery cell according to the voltage signal and the AC signal; A second acquisition unit is used to acquire the dynamic voltage and dynamic current of the battery cell when the battery pack is in a dynamic state; the battery pack is in a dynamic state when the current of the battery pack is greater than a second preset threshold; A second determination unit, configured to determine a second resistance of the battery cell according to the dynamic voltage, the dynamic current, and a static voltage, wherein the static voltage is a voltage corresponding to the battery cell when the battery pack is in a static state; A first iterative unit, configured to perform filtering iteration on the first resistor and the second resistor until filtering converges to obtain the resistance of the battery cell; The battery pack includes at least two battery modules, each of which includes a plurality of battery cells. The device also includes: A third acquisition unit, configured to acquire a voltage signal of any high-voltage connection point when the AC signal is input to the battery pack; A third determination unit is used to determine a third impedance according to the voltage signal and the AC signal; the high-voltage connection point includes one or more of a connection point between modules, a connection point between a module and a high-voltage relay, or a connection point between a high-voltage relay and an output terminal; a fourth acquisition unit, configured to acquire a dynamic voltage and a dynamic current of the high-voltage connection point when the battery pack is in a dynamic state; a fourth determining unit, configured to determine a fourth impedance of the high-voltage connection point according to the dynamic voltage, the dynamic current, and a static voltage; the static voltage being a voltage corresponding to the high-voltage connection point when the battery pack is in a static state; The second iterative unit is used to perform filtering iteration on the third impedance and the fourth impedance until the filtering converges to obtain the impedance of the high-voltage connection point.

7. The device according to claim 6, characterized in that The first determining unit includes: A first determining subunit, configured to determine a phase difference according to the voltage signal and the AC signal; The second determining subunit is used to determine the first resistance of the battery cell according to the modulus of the voltage signal and the phase difference.

8. The device according to claim 6, characterized in that The second determining unit includes: A first acquisition subunit, configured to subtract the dynamic voltage from the static voltage to obtain a first voltage; The second acquisition subunit is used to obtain a second resistance of the battery cell by dividing the first voltage by the dynamic current.

9. The device according to claim 6, characterized in that The device also includes: The early warning unit is used to issue an early warning when the resistance of any of the high-voltage connection points is greater than a third preset threshold.

10. The device according to any one of claims 6 to 9, characterized in that: Filtering iterations are performed using complementary filters or Kalman filters.

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