Internal resistance determination method and related device

Abstract

The invention provides an internal resistance determination method and a related device, and relates to the field of energy storage. In the application, the current in the charging and discharging process of the battery pack is direct current, and when the target device outputs alternating current to the battery pack, the original charging and discharging process of the battery pack is not influenced, so that when the battery pack performs normal charging and discharging operation based on the target device, the voltage and current of the battery pack can be collected; and extracting the alternating current component of the voltage and the alternating current component of the current, and calculating the internal resistance of the battery pack by using the alternating current component of the voltage and the alternating current component of the current, thereby achieving the purpose of determining the internal resistance of the battery pack under the condition of not influencing the normal charging and discharging operation of the battery pack.

Description

Technical Field

[0001] This application relates to the field of energy storage, and more specifically, to a method for determining internal resistance and related devices. Background Art

[0002] A battery pack is configured in an energy storage system, and at least one battery cell is configured in the battery pack. The battery cells can be connected in series. The internal resistance is an important indicator for measuring the health of the battery pack. When the internal resistance is abnormal, the health of the battery pack is poor, and at this time, maintenance or replacement operations may be required for the battery pack.

[0003] Currently, when determining the internal resistance of a battery pack, the battery pack cannot be normally charged and discharged, reducing the reliability of the battery pack in use. Summary of the Invention

[0004] In view of this, this application provides a method for determining internal resistance and related devices to solve the problem that the battery pack cannot be normally charged and discharged when determining the internal resistance of the battery pack.

[0005] To solve the above technical problems, this application adopts the following technical solutions:

[0006] A method for determining internal resistance, where the battery pack is connected to a target device, and the battery pack performs charging and discharging operations based on the target device; the target device can output an alternating current to the battery pack, and the method for determining internal resistance includes:

[0007] When there is the alternating current in the battery pack, collect the voltage and current of the battery pack;

[0008] Extract the alternating current component of the voltage, and extract the alternating current component of the current;

[0009] Calculate the internal resistance of the battery pack by using the alternating current component of the voltage and the alternating current component of the current.

[0010] Optionally, extracting the alternating current component of the voltage and extracting the alternating current component of the current includes:

[0011] For a voltage, perform a filtering operation on the voltage by using the historical voltage and the alternating current component of the historical voltage to extract the alternating current component in the voltage; the historical voltage is the voltage collected before collecting the voltage;

[0012] For a current, perform a filtering operation on the current by using the historical current and the alternating current component of the historical current to extract the alternating current component in the current; the historical current is the current collected before collecting the current; the frequencies of the alternating current components in the voltage and the current are both greater than the same frequency threshold.

[0013] Optionally, extracting the AC component of the voltage and extracting the AC component of the current includes:

[0014] Calculating the average value of the voltage, calculating the first difference between each voltage and the average value, obtaining the sum of the first differences to get the total first difference, and determining the AC component of the voltage based on the number of voltages and the total first difference;

[0015] Calculating the average value of the current, calculating the second difference between each current and the average value, obtaining the sum of the second differences to get the total second difference, and determining the AC component of the current based on the number of currents and the total second difference.

[0016] Optionally, the voltage includes: the total voltage of the battery pack and the sub-voltages of each battery cell in the battery pack;

[0017] Using the AC component of the voltage and the AC component of the current to calculate the internal resistance of the battery pack includes:

[0018] Calculating the total internal resistance of the battery pack based on the AC component of the total voltage and the AC component of the current;

[0019] Calculating the internal resistance of the battery cells in the battery pack based on the AC component of the sub-voltages and the AC component of the current.

[0020] Optionally, the internal resistance determination method further includes:

[0021] Calculating the sum of the internal resistances of the battery cells in the battery pack to obtain the total internal resistance of the battery cells;

[0022] Obtaining the difference between the total internal resistance of the battery pack and the total internal resistance of the battery cells;

[0023] Using the difference to perform a verification operation on the total internal resistance of the battery pack to obtain a verification result.

[0024] Optionally, the internal resistance determination method further includes:

[0025] Determining the change trend of the internal resistance of the battery cells;

[0026] Using the change trend to determine the short-circuit analysis result of the battery pack.

[0027] Optionally, the internal resistance determination method further includes:

[0028] In the case where the short-circuit analysis result indicates a short-circuit risk, disconnecting the charge and discharge circuit of the battery pack.

[0029] An internal resistance determination device, where a battery pack is connected to a target device, and the battery pack performs charge and discharge operations based on the target device; the target device can output an alternating current to the battery pack, and the internal resistance determination device includes:

[0030] A collection module, configured to collect the voltage and current of the battery pack when there is the alternating current in the battery pack;

[0031] An extraction module, configured to extract the alternating current component of the voltage and extract the alternating current component of the current;

[0032] A calculation module, configured to calculate the internal resistance of the battery pack by using the alternating current component of the voltage and the alternating current component of the current.

[0033] An electronic device, including at least one processor and a memory connected to the processor, where:

[0034] The memory is used to store a computer program;

[0035] The processor is configured to execute the computer program so that the electronic device can implement the above internal resistance determination method.

[0036] A computer storage medium, where the storage medium carries one or more computer programs, and when the one or more computer programs are executed by an electronic device, the electronic device can implement the above internal resistance determination method.

[0037] This application provides an internal resistance determination method and related devices. In this application, the current during the charge and discharge process of the battery pack is a direct current. When the target device outputs an alternating current to the battery pack, it will not affect the original charge and discharge process of the battery pack. Therefore, the voltage and current of the battery pack can be collected when the battery pack performs normal charge and discharge operations based on the target device, the alternating current component of the voltage is extracted and the alternating current component of the current is extracted, and the internal resistance of the battery pack is calculated by using the alternating current component of the voltage and the alternating current component of the current, achieving the purpose of determining the internal resistance of the battery pack without affecting the normal charge and discharge operations of the battery pack. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the following will briefly introduce the drawings required to be used in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only the embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0039] Figure 1 A schematic structural diagram of a battery pack provided by an embodiment of this application;

[0040] Figure 2 It is a flowchart of a method for determining internal resistance provided by an embodiment of the present application;

[0041] Figure 3 It is a flowchart of a method for extracting the AC component of voltage provided by an embodiment of the present application;

[0042] Figure 4 It is a flowchart of a method for extracting the AC component of current provided by an embodiment of the present application;

[0043] Figure 5 It is a flowchart of a method for internal resistance verification provided by an embodiment of the present application;

[0044] Figure 6 It is a schematic structural diagram of a device for determining internal resistance provided by an embodiment of the present application. Specific embodiments

[0045] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0046] A battery pack is configured in the energy storage system, and at least one battery cell is configured in the battery pack, and the battery cells can be connected in series. The internal resistance is an important indicator for measuring the health of the battery pack. If the internal resistance of the battery pack is too large, it will cause the charge and discharge power of the battery pack to decrease and accelerate the aging of the battery. That is, when the internal resistance is abnormal, the health of the battery pack is poor, and at this time, maintenance or replacement operations may be required for the battery pack.

[0047] Currently, when determining the internal resistance of the battery pack, the high-frequency excitation signal injection method can be used. A high-frequency voltage and current are injected into the battery pack through a professional internal resistance detection device, and then the amplitude and phase relationship between the voltage and current are analyzed to calculate the internal resistance. In this way, the battery pack needs to be taken out of the energy storage system, and the internal resistance is measured by the internal resistance detection device when the battery pack is stationary in the environment. That is, this method cannot measure the internal resistance during the normal charge and discharge operation of the battery pack.

[0048] In one implementation, the internal resistance can also be measured by the pulse charge / discharge method. When charging the lithium battery, after the SOC (State of Charge) of the lithium battery changes to the specified SOC, a professional device generates a pulsed charge / discharge current and outputs the charge / discharge current to the battery pack. The internal resistance is calculated by detecting the change in the voltage and current of the battery pack. In this method, the charge / discharge current output to the battery pack is a direct current, and the charge / discharge current of the battery pack is also a direct current. Therefore, the current excitation delivered by the professional device to the battery pack will interfere with the normal charge / discharge process of the battery pack and reduce the user experience.

[0049] In addition, both of the above two solutions require the configuration of professional equipment, resulting in a relatively high cost.

[0050] In addition, for the first solution, the internal resistance detection can only be carried out after the battery pack is taken out. For the second solution, the SOC of the battery pack needs to be adjusted to the specified SOC. Both of the above two solutions require specific conditions to be met before the internal resistance can be detected, and it is impossible to perform real-time detection of the internal resistance of the battery pack. Therefore, when a fault occurs in the battery pack, the abnormal internal resistance cannot be detected in time.

[0051] Therefore, in the embodiments of the present application, the battery pack is connected to a target device, and the battery pack performs charge and discharge operations based on the target device. The target device can output an alternating current to the battery pack, and the alternating current will not affect the direct current in the original charge and discharge process of the battery pack. Therefore, the target device used in the embodiments of the present application will not affect the normal operation of the battery pack, and can measure the internal resistance during the normal charge and discharge process of the battery pack, achieving the purpose of real-time detection of the internal resistance of the battery pack, without the need to perform internal resistance detection when a certain specified condition is met. Furthermore, when a fault occurs in the battery pack, the abnormal internal resistance can be detected in time and a fault reporting operation can be performed.

[0052] In addition, the target device in the present application can be a device connected during the operation of the battery pack, such as a DCDC (DC-to-DC) voltage converter, an electrical device (such as a motor, etc.). These devices also need to be connected when the battery pack is operating normally. Therefore, in the embodiments of the present application, the internal resistance detection can be achieved by using the conventional devices connected to the battery pack, without the need to configure professional equipment, reducing the cost.

[0053] An embodiment of the present application provides a method for determining the internal resistance. The execution entity can be a control device (such as a control chip, etc.) in the battery pack, or a controller of the energy storage system where the battery pack is located, or a remote controller of the energy storage system, such as the cloud, etc. As long as it is a controller with logical processing capabilities, it can implement the method for determining the internal resistance in the present application.

[0054] In one implementation, the structure diagram of the battery pack refers to Figure 1, at least one battery cell is configured in the battery pack. In this embodiment, the number of battery cells is not limited. Figure 1 Taking five battery cells (BT1 - BT5) as an example for illustration in Figure 1 .

[0055] Multiple battery cells are connected in series. A switching element is connected in series with a certain battery cell. The switching element can be a switch such as a relay. If the switching element is turned on, the charge - discharge circuit of the battery pack is connected to an external device at this time, and the battery pack performs charge - discharge operations. If the switching element is turned off, the charge - discharge circuit of the battery pack is disconnected from the external device at this time, and the battery pack does not perform charge - discharge operations.

[0056] In order to be able to detect the voltage and current of the battery pack, a voltage sampling device and a current sampling device are configured in the battery pack. The voltage sampling device is provided with multiple sampling points. When specifically setting the sampling points, sampling points can be configured at both ends of each battery cell, so that the partial voltage of each battery cell and the total voltage of the battery pack can be detected.

[0057] The current sampling device is arranged in the charge - discharge circuit of the battery pack to detect the current of the battery pack. Since multiple battery cells in the battery pack are connected in series, the current of the battery pack is also the current of each battery cell.

[0058] The battery pack is connected to a target device. Among them, the target device can be a conversion device or an electrical device. The conversion device can be a switching power supply such as a charger or an electrical appliance. The switching power supply can specifically be a DCDC voltage converter, a DCDC current converter, etc. At this time, the battery pack can perform charge - discharge operations using the switching power supply. In an actual scenario, the battery pack is connected to the switching power supply during operation. Therefore, in this application, the internal resistance measurement operation is performed using the existing device connected to the battery pack. Due to the characteristics of the switching power supply, the switching power supply can output an alternating current to the battery pack, so that there are some high - frequency alternating current components in the charge - discharge current of the battery pack, and the internal resistance is determined using the high - frequency alternating current components subsequently.

[0059] The electrical device can be a device such as a motor or a charging pile. After connecting the battery pack to the electrical device, the battery pack can perform a discharge operation to output electrical energy to the electrical device and supply power to the electrical device. Due to the characteristics of the electrical device, the electrical device can output an alternating current to the battery pack, so that there are some high - frequency alternating current components in the charge - discharge current of the battery pack, and the internal resistance is determined using the high - frequency alternating current components subsequently.

[0060] In the embodiments of this application, the type of the target device is not limited, as long as it is a target device that can output an alternating current to the battery pack.

[0061] On the basis of Figure 1 , referring to Figure 2 , the internal resistance determination method in the embodiments of this application may include the following steps:

[0062] S11. When there is an alternating current in the battery pack, collect the voltage and current of the battery pack.

[0063] In this embodiment, after the battery pack is connected to the target device and during the normal charge and discharge process of the battery pack, due to the characteristics of the target device, the target device can output an alternating current to the battery pack, so that there are some high-frequency alternating current components in the charge and discharge current of the battery pack. At this time, the above voltage sampling device and current sampling device can be used to perform voltage and current collection operations.

[0064] When collecting voltage, the voltage sampling device can detect the partial voltage of each battery cell and the total voltage of the battery pack. When collecting current, the current sampling device can detect the current of the battery pack, and the current of the battery pack is also the current of each battery cell. In one implementation, a current detecting resistor can be configured in the current sampling device to detect the current flowing through the current detecting resistor, and this current is the current of the battery pack, and also the current of each battery cell.

[0065] In an actual scenario, the voltage sampling device and the current sampling device can continuously perform voltage and current collection operations. In one implementation, define the calculation period of the internal resistance as T. The shorter the calculation period of the internal resistance, the higher the real-time performance of the internal resistance detection. When setting the value of T, it should also be ensured that there are enough voltage and current sampling points within T. In one embodiment, if a set number (such as three, five, ten, etc.) or more values can be collected, it is considered that there are enough sampling points. In one implementation, T = 3s. In addition, the value of T can also be configured according to the actual situation.

[0066] Within the T time, the voltage sampling device and the current sampling device continuously perform collection operations, and within the T time, the following are sampled: , …… voltage sequence, and , …… current sequence. Among them, is a positive integer.

[0067] S12. Extract the alternating current component of the voltage, and extract the alternating current component of the current.

[0068] Specifically, in the collected voltage sequence and current sequence, there are both alternating current components provided by the target device and direct current components during the normal charge and discharge operation of the battery pack.

[0069] In this embodiment, the calculation operation of the internal resistance is performed using the alternating current component of the voltage and the alternating current component of the current. Therefore, in this embodiment, it is necessary to extract the alternating current component of the voltage and extract the alternating current component of the current.

[0070] Among them, since the voltage includes the partial voltage of each battery cell and the total voltage of the battery pack, and the number of partial voltages and total voltages is multiple, for each voltage value, an AC component extraction operation is performed to obtain the AC component of each voltage.

[0071] For the current, since multiple currents are acquired within one period T, for each current value, an AC component extraction operation is performed to obtain the AC component of each current.

[0072] S13. Calculate the internal resistance of the battery pack by using the AC component of the voltage and the AC component of the current.

[0073] After obtaining the AC component of the total voltage, calculate the total internal resistance of the battery pack based on the AC component of the total voltage and the AC component of the current.

[0074] In one implementation, the total internal resistance of the battery pack = the AC component of the total voltage / the AC component of the current.

[0075] After obtaining the AC component of the partial voltage, calculate the internal resistance of the battery cell in the battery pack based on the AC component of the partial voltage and the AC component of the current.

[0076] In one implementation, the internal resistance of the battery cell = the AC component of the partial voltage / the AC component of the current.

[0077] Among them, since at least one battery cell is configured in the battery pack, and the internal resistance of each battery cell is calculated according to the internal resistance calculation formula, and the types of the battery cells in the battery pack are generally the same, so the internal resistances of the battery cells are also close to each other.

[0078] In this embodiment, the current during the charge and discharge process of the battery pack is a direct current. When the target device outputs an alternating current to the battery pack, it will not affect the original charge and discharge process of the battery pack. Therefore, when the battery pack performs normal charge and discharge operations based on the target device, the voltage and current of the battery pack can be collected, the AC component of the voltage and the AC component of the current can be extracted, and the internal resistance of the battery pack can be calculated by using the AC component of the voltage and the AC component of the current, achieving the purpose of determining the internal resistance of the battery pack without affecting the normal charge and discharge operations of the battery pack.

[0079] In addition, the present application directly performs the internal resistance detection operation during the charge and discharge operation of the battery pack, does not affect the battery used by the user, and has high real-time performance, and can timely detect faults such as short circuits of the battery pack.

[0080] In addition, in the present application, the internal resistance is directly measured by using the target device connected to the battery pack, without additional cost. The internal resistance is directly calculated by using the alternating current provided by the target device, and no additional current excitation is required.

[0081] Based on any of the above embodiments, a filter can be used to extract the AC component of the voltage and, additionally, the AC component of the current. In one implementation, the filter is an IIR (Infinite Impulse Response) digital high-pass filter. This filter can be set in the control chip. ).

[0082] In one implementation, taking the IIR digital high-pass filter as a second-order Butterworth high-pass filter as an example for illustration. The general form of the system function H(z) of the second-order Butterworth high-pass filter is:

[0083]

[0084] where , , , , are the coefficients of the filter. In one embodiment, = -1.1716, = 0.4142, = 0.2929, = -0.5858, = 0.2929.

[0085] is the filter input, is the filter output, is a variable.

[0086] Performing an inverse transform on results in the difference equation:

[0087] .

[0088] where is the filter output at time , is the filter output at time , is the filter output at time , is the filter input at time , is the filter input at time , is the filter input at time .

[0089] In this embodiment, the partial voltage of the battery cells in the battery pack is collected in real time by the voltage sampling device, that is, the single-cell voltage is represented by , and the total voltage of the battery pack is represented by , the current of the battery pack collected in real time by the current sampling device is represented by .

[0090] Using the above differential equations for the single - cell voltage , the total voltage and the current respectively, we can obtain:

[0091] Among them, refers to the AC component of the sub - voltage output by the filter at time refers to the AC component of the sub - voltage output by the filter at time refers to the AC component of the sub - voltage output by the filter at time refers to the sub - voltage input to the filter at time refers to the sub - voltage input to the filter at time refers to the sub - voltage input to the filter at time

[0092]

[0093] Among them, refers to the total AC amount of the total voltage output by the filter at time refers to the total AC amount of the total voltage output by the filter at time refers to the total AC amount of the total voltage output by the filter at time refers to the total voltage input to the filter at time refers to the total voltage input to the filter at time refers to the total voltage input to the filter at time

[0094] Then, for a certain sub - voltage or total voltage, using the historical voltage and the AC component of the historical voltage, a voltage filtering operation is performed to extract the AC component in the voltage.

[0095] Among them, the historical voltage is the voltage collected before the voltage is collected.

[0096] Taking the total voltage input to the filter at time as an example to introduce the voltage filtering process. At this time, the historical voltages used are and , The corresponding AC component is , The corresponding AC component is , Substituting into the calculation formula of, we can obtain , That is the AC component of. For the partial voltage the processing logic is the same.

[0097]

[0098] Among them, refers to the total AC amount of the current output by the filter at time refers to the total AC amount of the current output by the filter at time refers to the total AC amount of the current output by the filter at time refers to the current input to the filter at time refers to the current input to the filter at time refers to the current input to the filter at time.

[0099] Then, for a current, using the historical current and the AC component of the historical current, filtering operation is performed on the current to extract the AC component in the current.

[0100] Among them, the historical current is the current collected before the current is collected.

[0101] Taking the current input to the filter at time as an example to introduce the voltage filtering process. At this time, the historical currents used are and , The corresponding AC component is , The corresponding AC component is , Substituting into the calculation formula of, we can obtain , That is the AC component of.

[0102] After obtaining , and , divide by , and then take the absolute value to obtain the internal resistance of the battery cell Divide the total voltage by , and then take the absolute value to obtain the total internal resistance of the battery pack , that is:

[0103]

[0104]

[0105] It should be noted that this filter can filter low-frequency signals and only retain high-frequency signals. Therefore, in this embodiment, the frequencies of the AC components in the voltage obtained through the filter and the AC components in the current are both greater than the same frequency threshold. The frequency threshold can be configured according to the actual situation.

[0106] In addition, in the embodiments of the present application, other types of filters can also be used for filtering operations. Specifically, the filtering process can be configured accordingly, which is not limited in this embodiment.

[0107] In this embodiment, the AC components of the voltage and current are extracted through the filter, so that the extracted components can be used for internal resistance calculation operations.

[0108] In the above embodiment, a filter is used to extract the AC components. In another embodiment, the AC components can also be extracted by using a numerical calculation method. Specifically, referring to Figure 3 , to extract the AC component of the voltage, it may include:

[0109] S21. Calculate the average value of the voltage.

[0110] In this embodiment, according to the above description, within the time T, the voltage sampling device and the current sampling device continuously perform sampling operations, and within the time T, the following are sampled: , …… a voltage sequence of, and , …… a current sequence of. Among them, is a positive integer.

[0111] Then the average value of the voltage The calculation formula is:

[0112]

[0113] That is, it represents the DC component of the voltage sequence, is a positive integer, specifically referring to the number of the sampled voltage sequence.

[0114] S22. Calculate the first difference between each voltage and the average value.

[0115] In this embodiment, for , ... the voltage sequence of..., calculate , ... and the differences from respectively. This difference is called the first difference, that is, calculate , ... . This first difference represents , ... the AC component in the voltage sequence.

[0116] S23. Obtain the sum of the first differences to get the total first difference.

[0117] In this embodiment, the total first difference = . The total first difference characterizes the sum of the AC components in the voltage sequence.

[0118] S24. Based on the number of voltages and the total first difference, determine the AC component of the voltage.

[0119] In this embodiment, the AC component of the voltage has the following calculation formula:

[0120]

[0121] That is, average the sum of the AC components to obtain the AC component of the voltage, and this AC component of the voltage is the average absolute deviation of the voltage sequence.

[0122] For the obtained , ... the current sequence is processed similarly to extract the AC component of the current. Specifically, referring to Figure 4 , to extract the AC component of the current, it may include:

[0123] S31. Calculate the average value of the current.

[0124] Specifically, within time T, the current sequence of , ... is collected. The calculation formula for the average value of the current is:

[0125] .

[0126] Among them, is a positive integer, specifically referring to the number of the sampled current sequences.

[0127] S32. Calculate the second difference between each current and the average value.

[0128] Among them, for , ... For the current sequence of , ... Calculate the differences from respectively. This difference is called the second difference, that is, calculate , ... . This second difference represents , ... The alternating current component in the current sequence.

[0129] S33. Obtain the sum of the second differences to get the total second difference.

[0130] In this embodiment, the total second difference = . The total second difference characterizes the sum of the alternating current components in the current sequence.

[0131] S34. Based on the number of currents and the total second difference, determine the alternating current component of the current.

[0132] In this embodiment, the alternating current component of the current has the following calculation formula:

[0133]

[0134] That is, average the sum of the alternating current components to obtain the alternating current component of the current, and this alternating current component is the average absolute deviation of the current sequence.

[0135] Subsequently, use and to calculate the internal resistance. The specific calculation formula is:

[0136]

[0137] In an actual scenario, the total internal resistance of the battery pack can be calculated using the alternating current component of the total voltage and . The internal resistance of the battery cells in the battery pack can be calculated using the alternating current component of the partial voltage and .

[0138] In this embodiment, during the normal use of the battery pack, the internal resistance of the battery cells is detected in real time using the average absolute deviation, without interfering with the normal use of the battery pack, and the faults of the battery pack can be detected in time, improving the safety of the battery pack during use.

[0139] Based on any of the above embodiments, after obtaining the total internal resistance of the battery pack and the internal resistance of the battery cells, the total internal resistance of the battery pack and the internal resistance of the battery cells can also be mutually verified. Specifically, referring to Figure 5 , the internal resistance determination method further includes:

[0140] S41. Calculate the sum of the internal resistances of the battery cells in the battery pack to obtain the total internal resistance of the battery cells.

[0141] In this embodiment, the internal resistances of the battery cells in the battery pack are added up to obtain the total internal resistance of the battery cells. That is:

[0142] Wherein, refers to the total internal resistance of the battery cells, , , ... refer to the internal resistances of the respective battery cells in the battery pack.

[0143] Taking Figure 1 as an example, Figure 1 the battery pack in

[0144] S42. Obtain the difference between the total internal resistance of the battery pack and the total internal resistance of the battery cells.

[0145] In this embodiment, in an ideal situation, the battery cells in the battery pack are in series, and the total resistance of the battery pack is equal to the sum of the internal resistances of the battery cells in the battery pack, that is is equal to .

[0146] Therefore, in this embodiment, the difference between and can be calculated to determine the mutual verification result between the total internal resistance of the battery pack and the total internal resistance of the battery cells based on the difference from zero.

[0147] S43. Use the difference to perform a verification operation on the total internal resistance of the battery pack to obtain a verification result.

[0148] Specifically, if the difference is close to zero, that is, the difference is within a preset range of zero, the preset range can be, for example, (-1, 1), etc., it means that the sum of the internal resistances of the battery cells is close to the total internal resistance of the battery pack directly calculated, and the verification result is that the verification passes, then save the internal resistance calculated in this calculation cycle.

[0149] If the difference is not close to zero, that is, the difference is not within the preset range of zero, it means that the sum of the internal resistances of the battery cells is not close to the total internal resistance of the battery pack directly calculated, and the verification result is that the verification fails. It can be judged that there is an error in the internal resistance calculation in this round, and then discard the internal resistance calculated in this calculation cycle.

[0150] In another implementation, the ratio of the difference to the total internal resistance of the battery pack can also be calculated to determine the proportion of the difference between the total internal resistance of the battery pack and the total internal resistance of the battery cells relative to the total internal resistance of the battery pack. .

[0151] If , it indicates that the difference between the total internal resistance of the battery pack and the total internal resistance of the battery cells is too large, and there is an error in the internal resistance calculation in this round. Then, discard the internal resistance calculated in this calculation cycle. If it is not greater than 10%, it means that the total internal resistance of the battery pack obtained by adding the internal resistances of the battery cells is close to the directly calculated total internal resistance of the battery pack, and the verification result is that the verification passes. Then, save the internal resistance calculated in this calculation cycle. Among them, 10% is only an example, and the specific scenario can configure the threshold according to the actual situation.

[0152] In this embodiment, the total internal resistance of the battery pack obtained by adding the internal resistances of the battery cells and the directly calculated total internal resistance of the battery pack are mutually verified, and unreliable data are discarded to ensure the reliability of the internal resistance data.

[0153] Based on any of the above embodiments, it is also possible to analyze whether there is an abnormality in the battery pack based on the change situation of the internal resistance of the battery cells. Specifically, the internal resistance determination method further includes:

[0154] Determine the change trend of the internal resistance of the battery cells, and use the change trend to determine the short - circuit analysis result of the battery pack.

[0155] Among them, in this embodiment, for a certain battery cell, the change trend of the internal resistance of the battery cell can be the change trend of the internal resistance value, or the change rate of the internal resistance calculated in adjacent periods, that is, the gradient , where the change region in this embodiment can be displayed in the form of curves, charts, etc.

[0156] In this embodiment, taking the change rate of the internal resistance as an example, the battery pack abnormality analysis operation is performed. If the change rate of at least one battery cell, where k is the change amount threshold (also called the gradient threshold), it indicates that the battery cell with a large change rate has a risk of short - circuit. When an internal short - circuit fault occurs in the battery cell, the internal separator of the battery cell is pierced by the precipitated lithium dendrites, which will cause the internal resistance of the lithium battery cell to suddenly decrease. At this time, the battery pack will short - circuit, and the short - circuit analysis result of the battery pack in this embodiment is that there is a short - circuit risk. If there is no change rate of the battery cell, it indicates that there is no short - circuit risk in the battery cells in the battery pack. At this time, the short - circuit analysis result of the battery pack is that there is no short - circuit risk.

[0157] Based on this embodiment, in one implementation, when the short - circuit analysis result is that there is a short - circuit risk, disconnect the charge - discharge circuit of the battery pack. Specifically, as Figure 1As shown, disconnecting the switching element provided in the battery pack can disconnect the charging and discharging circuit of the battery pack. By stopping the charging and discharging operation of the battery pack, it is possible to avoid abnormal charging and discharging currents of the battery pack due to abnormal battery cells, and further avoid the risk of burning the battery pack caused by abnormal currents.

[0158] In addition to disconnecting the switching element, it is also necessary to give an alarm to prompt the user that there is a short - circuit risk in the battery pack, so that the user can perform maintenance or replacement operations on the battery pack as soon as possible, improving the safety of the battery pack.

[0159] Based on the embodiments of the above - mentioned internal resistance determination method, another embodiment of the present application provides an internal resistance determination device. The battery pack is connected to a target device, and the battery pack performs charging and discharging operations based on the target device; the target device can output an alternating current to the battery pack. Referring to Figure 6 , the internal resistance determination device includes:

[0160] An acquisition module 11, configured to acquire the voltage and current of the battery pack when there is an alternating current in the battery pack;

[0161] An extraction module 12, configured to extract the alternating - current component of the voltage and the alternating - current component of the current;

[0162] A calculation module 13, configured to calculate the internal resistance of the battery pack by using the alternating - current component of the voltage and the alternating - current component of the current.

[0163] In one implementation, the extraction module 12 includes:

[0164] A first extraction sub - module, configured to perform a filtering operation on a voltage by using the historical voltage and the alternating - current component of the historical voltage to extract the alternating - current component in the voltage; the historical voltage is the voltage acquired before the voltage is acquired;

[0165] A second extraction sub - module, configured to perform a filtering operation on a current by using the historical current and the alternating - current component of the historical current to extract the alternating - current component in the current; the historical current is the current acquired before the current is acquired; the frequencies of the alternating - current components in the voltage and the current are both greater than the same frequency threshold.

[0166] In one implementation, the extraction module 12 includes:

[0167] A third extraction sub - module, configured to calculate the average value of the voltage, calculate the first difference between each voltage and the average value, obtain the sum of the first differences to get the total sum of the first differences, and determine the alternating - current component of the voltage based on the number of voltages and the total sum of the first differences;

[0168] The fourth extraction sub-module is used to calculate the average value of the current, calculate the second difference between each current and the average value, obtain the sum of the second differences, get the total sum of the second differences, and determine the AC component of the current based on the number of currents and the total sum of the second differences.

[0169] In one implementation, the voltage includes: the total voltage of the battery pack and the sub-voltages of each battery cell in the battery pack.

[0170] The calculation module 13 is specifically used for:

[0171] Based on the AC component of the total voltage and the AC component of the current, calculate the total internal resistance of the battery pack. Based on the AC component of the sub-voltage and the AC component of the current, calculate the internal resistance of the battery cells in the battery pack.

[0172] In one implementation, the internal resistance determination device further includes:

[0173] The summation module is used to calculate the sum of the internal resistances of the battery cells in the battery pack to obtain the total internal resistance of the battery cells.

[0174] The difference acquisition module is used to obtain the difference between the total internal resistance of the battery pack and the total internal resistance of the battery cells.

[0175] The verification module is used to perform a verification operation on the total internal resistance of the battery pack using the difference to obtain a verification result.

[0176] In one implementation, the internal resistance determination device further includes:

[0177] The short-circuit analysis module is used to determine the change trend of the internal resistance of the battery cells, and use the change trend to determine the short-circuit analysis result of the battery pack.

[0178] In one implementation, the internal resistance determination device further includes:

[0179] The circuit control module is used to disconnect the charge and discharge circuit of the battery pack when the short-circuit analysis result indicates a short-circuit risk.

[0180] In this embodiment, the current during the charge and discharge process of the battery pack is a direct current. When the target device outputs an alternating current to the battery pack, it will not affect the original charge and discharge process of the battery pack. Therefore, when the battery pack is performing normal charge and discharge operations based on the target device, the voltage and current of the battery pack can be collected, the AC component of the voltage and the AC component of the current can be extracted, and the internal resistance of the battery pack can be calculated using the AC component of the voltage and the AC component of the current, achieving the purpose of determining the internal resistance of the battery pack without affecting the normal charge and discharge operations of the battery pack.

[0181] It should be noted that for the working processes of each module and sub-module in this embodiment, please refer to the corresponding descriptions in the above embodiments, and will not be elaborated here.

[0182] In an embodiment of the present application, an electronic device is further provided, which includes at least one processor and a memory connected to the processor, where:

[0183] The memory is used to store a computer program;

[0184] The processor is used to execute the computer program so that the electronic device can implement the above-mentioned internal resistance determination method.

[0185] In an embodiment of the present application, a computer program product is further provided, which includes computer-readable instructions. When the computer-readable instructions run on an electronic device, the electronic device can implement any of the internal resistance determination methods provided by the embodiments of the present application.

[0186] In an embodiment of the present application, a computer-readable storage medium is further provided. The storage medium carries one or more computer programs. When the one or more computer programs are executed by an electronic device, the electronic device can implement any of the internal resistance determination methods provided by the embodiments of the present application.

[0187] 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 obvious to those skilled in the art. The general principles defined herein can 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 rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining internal resistance, characterized in that, The battery pack is connected to the target device, and the battery pack performs charge and discharge operations based on the target device; The target device is capable of outputting an alternating current to the battery pack, and the internal resistance determination method includes: When there is an alternating current in the battery pack, collect the voltage and current of the battery pack; Extract the alternating current component of the voltage and, extract the alternating current component of the current; Use the alternating current component of the voltage and the alternating current component of the current to calculate the internal resistance of the battery pack.

2. The internal resistance determination method according to claim 1, characterized in that Extracting the alternating current component of the voltage and, extracting the alternating current component of the current includes: For a voltage, perform a filtering operation on the voltage using the historical voltage and the alternating current component of the historical voltage to extract the alternating current component in the voltage; the historical voltage is the voltage collected before collecting the voltage; For a current, perform a filtering operation on the current using the historical current and the alternating current component of the historical current to extract the alternating current component in the current; the historical current is the current collected before collecting the current; the frequencies of the alternating current components in the voltage and the current are both greater than the same frequency threshold.

3. The internal resistance determination method according to claim 1, wherein Extracting the alternating current component of the voltage and, extracting the alternating current component of the current includes: Calculate the average value of the voltage, calculate the first difference between each voltage and the average value, obtain the sum of the first differences, get the total sum of the first differences, and determine the alternating current component of the voltage based on the number of voltages and the total sum of the first differences; Calculate the average value of the current, calculate the second difference between each current and the average value, obtain the sum of the second differences, get the total sum of the second differences, and determine the alternating current component of the current based on the number of currents and the total sum of the second differences.

4. The internal resistance determination method according to claim 1, wherein The voltage includes: the total voltage of the battery pack and, the partial voltage of each battery cell in the battery pack; Using the alternating current component of the voltage and the alternating current component of the current to calculate the internal resistance of the battery pack includes: Based on the alternating current component of the total voltage and the alternating current component of the current, calculate the total internal resistance of the battery pack; Based on the alternating current component of the partial voltage and the alternating current component of the current, calculate the internal resistance of the battery cells in the battery pack.

5. The internal resistance determination method according to claim 4, characterized in that, The internal resistance determination method further includes: Calculate the sum of the internal resistances of the battery cells in the battery pack to obtain the total internal resistance of the battery cells; Obtain the difference between the total internal resistance of the battery pack and the total internal resistance of the battery cells; Use the difference to perform a verification operation on the total internal resistance of the battery pack to obtain a verification result.

6. The internal resistance determination method according to claim 4, wherein The internal resistance determination method further includes: Determine the change trend of the internal resistance of the battery cells; Use the change trend to determine the short-circuit analysis result of the battery pack.

7. The internal resistance determination method according to claim 6, characterized in that, The internal resistance determination method further includes: When the short-circuit analysis result indicates a short-circuit risk, disconnect the charge and discharge circuit of the battery pack.

8. An internal resistance determination device, characterized in that, The battery pack is connected to the target device, and the battery pack performs charge and discharge operations based on the target device; The target device is capable of outputting an alternating current to the battery pack, and the internal resistance determination device includes: A collection module, configured to collect the voltage and current of the battery pack when there is alternating current in the battery pack; An extraction module, configured to extract the alternating current component of the voltage and the alternating current component of the current; A calculation module, configured to calculate the internal resistance of the battery pack by using the alternating current component of the voltage and the alternating current component of the current.

9. An electronic device, characterized in that, Comprising at least one processor and a memory connected to the processor, wherein: The memory is configured to store a computer program; The processor is configured to execute the computer program so that the electronic device can implement the internal resistance determination method according to any one of claims 1 to 7.

10. A computer storage medium, characterized in that, The storage medium carries one or more computer programs, and when the one or more computer programs are executed by an electronic device, the electronic device can implement the internal resistance determination method according to any one of claims 1 to 7.

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