Battery monitoring device and battery monitoring method

Abstract

A battery monitoring device (1) comprises n + 1 first terminals, two second terminals, a storage unit (12), and an impedance calculation unit (11), a multi-cell filter unit (100) is connected between n battery cells and the n + 1 first terminals, a single-cell filter unit (200) is connected between a shunt resistor (300) and the two second terminals, the storage unit (12) stores a multi-cell filter characteristic prepared in advance and a single-cell filter characteristic prepared in advance, and the impedance calculation unit (11) calculates an AC impedance in which components of the multi-cell filter characteristic and the single-cell filter characteristic are cancelled, on the basis of a voltage measured via the n + 1 first terminals, a current measured via the two second terminals, the multi-cell filter characteristic, and the single-cell filter characteristic.

Description

Battery Monitoring Device and Battery Monitoring Method

[0001] The present disclosure relates to a battery monitoring device and a battery monitoring method for monitoring states such as voltage, current, and temperature of a secondary battery such as a lithium-ion battery.

[0002] In Patent Document 1, an alternating current is supplied to a battery pack composed of a plurality of battery cells, and for the voltages and currents of the plurality of battery cells to which the alternating current is supplied, a sine wave and a cosine wave having a phase difference of 90° from each other are used for multiplication and integration processing to convert them into complex numbers, and complex voltage and complex current are measured, that is, a technique for measuring the AC impedance of battery cells is disclosed.

[0003] International Publication No. 2020 / 003841

[0004] When measuring the voltages and currents of a plurality of battery cells to which an alternating current is supplied, an RC filter for anti-aliasing may be connected between the battery pack and the battery monitoring device. When a primary RC filter is connected for each battery cell, one RC filter is required for each battery cell, and the number of RC filters increases. That is, the number of parts increases. Also, since a terminal of the battery monitoring device is required for each RC filter connected to the battery cell, the number of terminals of the battery monitoring device increases. Therefore, when a primary RC filter is connected for each battery cell, cost increase becomes a problem.

[0005] In contrast, it is conceivable to connect a multi-cell filter unit between the battery pack and the battery monitoring device so that the negative terminal and the positive terminal of adjacent battery cells are connected to one common terminal of the battery monitoring device. However, in this case, although details will be described later using FIG. 2, an error occurs in the measurement result of the AC impedance.

[0006] Therefore, the present disclosure provides a battery monitoring device and the like that can suppress the occurrence of an error in the measurement result of the AC impedance.

[0007] The battery monitoring device according to this disclosure is a battery monitoring device that monitors n (n is an integer of 2 or more) battery cells connected in series, comprising: n+1 first terminals for measuring the voltage of each of the n battery cells; two second terminals connected to a current measuring unit for measuring the current flowing through the n battery cells; a storage unit; and an impedance calculation unit for calculating the AC impedance of each of the n battery cells, wherein a multi-cell filter unit including a capacitive element is connected between the n battery cells and the n+1 first terminals, and the negative terminal of the k (k is an integer of 1 or more and n-1 or less)th battery cell and the positive terminal of the k+1th battery cell included in the n battery cells are The k+1th first terminal included in the +1 first terminal is connected via the multi-cell filter section, a single-cell filter section including a capacitive element is connected between the current measurement section and the two second terminals, the storage section stores the multi-cell filter characteristics of the multi-cell filter section and the single-cell filter characteristics of the single-cell filter section that have been prepared in advance, and the impedance calculation section calculates the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics and the single-cell filter characteristics.

[0008] The battery monitoring method according to this disclosure is a battery monitoring method performed by a battery monitoring device that monitors n battery cells connected in series, the battery monitoring device comprising: n+1 first terminals for measuring the voltage of each of the n battery cells; two second terminals connected to a current measuring unit for measuring the current flowing through the n battery cells; and a storage unit, wherein a multi-cell filter unit including a capacitive element is connected between the n battery cells and the n+1 first terminals, and the negative terminal of the k-th battery cell (where k is an integer between 1 and n-1) and the positive terminal of the k+1-th battery cell included in the n battery cells are connected to the k+1-th first terminal included in the n+1 first terminals, and the multi-cell filter unit A single-cell filter unit including a capacitive element is connected between the current measurement unit and the two second terminals via a cell filter unit, and the storage unit stores the multi-cell filter characteristics of the multi-cell filter unit and the single-cell filter characteristics of the single-cell filter unit that have been prepared in advance. The battery monitoring method includes the steps of: calculating an AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics and the single-cell filter characteristics; and outputting the calculated AC impedance.

[0009] These comprehensive or specific embodiments may be implemented as a system, method, integrated circuit, computer program, or recording medium such as a computer-readable CD-ROM, or as any combination of a system, method, integrated circuit, computer program, and recording medium.

[0010] According to one aspect of this disclosure, a battery monitoring device, etc., can suppress errors in the measurement results of AC impedance.

[0011] This is a circuit diagram showing an example of a battery monitoring device according to Comparative Example 1. This is a circuit diagram showing an example of a battery monitoring device according to Comparative Example 2. This is a circuit diagram showing an example of a battery monitoring device according to Embodiment 1. This is a diagram for explaining multi-cell filter characteristics according to the number of cells. This is a circuit diagram showing an example of a battery monitoring device according to Embodiment 2. This is a flowchart showing an example of the operation of a battery monitoring device according to Embodiment 2. This is a diagram showing an example of multiple multi-cell filter characteristics prepared in advance for each number of cells. This is a diagram for explaining multi-cell filter characteristics according to the ESR of a battery cell. This is a circuit diagram showing an example of a battery monitoring device according to Embodiment 3. This is a diagram showing an example of multiple multi-cell filter characteristics prepared in advance for each combination of ESR ratios. This is a diagram showing an example of multi-cell filter characteristics including the filter characteristics of the multi-cell filter section for the target battery cell and the filter characteristics for battery cells surrounding the target battery cell. This is a diagram for explaining a method for creating multi-cell filter characteristics when multiple battery cells have deteriorated. This is a flowchart showing an example of the operation of a battery monitoring device according to Embodiment 3. This is a flowchart showing an example of a battery monitoring method according to another embodiment.

[0012] (Background leading to one aspect of this disclosure) First, the background leading to one aspect of this disclosure will be explained using Figures 1 and 2.

[0013] Figure 1 is a circuit diagram showing an example of a battery monitoring device 1a according to Comparative Example 1.

[0014] The battery monitoring device 1a is a device that monitors n (where n is an integer of 2 or more) battery cells connected in series. Figure 1 shows battery cells Bat1 to Batn as n battery cells. The battery monitoring device 1a has the function of calculating the AC impedance of the n battery cells. For example, the n battery cells are rechargeable secondary batteries such as lithium-ion batteries.

[0015] The battery monitoring device 1a is equipped with n sets of terminal pairs for measuring the voltage of each of the n battery cells. Figure 1 shows the n sets of terminal pairs, which are terminals t1p and t1n for measuring the voltage of battery cell Bat1, terminals t2p and t2n (not shown) for measuring the voltage of battery cell Bat2 (not shown), ..., and terminals tnp and tnn for measuring the voltage of battery cell Batn.

[0016] The battery monitoring device 1a is equipped with two second terminals connected to a current measuring unit for measuring the current flowing through n battery cells. In Figure 1, a shunt resistor 300 is shown as the current measuring unit, and terminals ta and tb are shown as the two second terminals. The current flowing through the n battery cells is the current flowing through the load resistor R1, the transistor Tr1, and the shunt resistor 300. Since a voltage corresponding to the current flowing through the n battery cells is generated in the shunt resistor 300, the battery monitoring device 1a can obtain the current value of the current flowing through the n battery cells by acquiring the voltage generated in the shunt resistor 300 input to terminals ta and tb.

[0017] The battery monitoring device 1a is equipped with a terminal tc for controlling transistor Tr1. Transistor Tr1 is a transistor that allows current to flow from n battery cells to the shunt resistor 300. Transistor Tr1 is, for example, an FET (Field Effect Transistor), but may also be a bipolar transistor. The drain of transistor Tr1 is connected to the load resistor R1, the source of transistor Tr1 is connected to the shunt resistor 300, and the gate of transistor Tr1 is connected to terminal tc.

[0018] A single-cell filter section 200 containing a capacitive element is connected between each of the n battery cells and each of the n pairs of terminals. Additionally, a single-cell filter section 200 containing a capacitive element is connected between the shunt resistor 300 and the two second terminals. As shown in Figure 1, the single-cell filter section 200 is a first-order RC filter for anti-aliasing.

[0019] The battery monitoring device 1a comprises n A / D converters 30 and one A / D converter 40. Each of the n A / D converters 30 is connected one-to-one with each of the n terminal pairs and converts the voltage (analog value) of the corresponding battery cell to a digital value. As shown in Figure 1, the A / D converter 30 connected to terminals t1p and t1n converts the voltage of battery cell Bat1 to a digital value, and the A / D converter 30 connected to terminals tnp and tnn converts the voltage of battery cell Batn to a digital value. The A / D converter 40 is connected to two second terminals ta and tb and converts the current value (analog value) of the current flowing through the n battery cells to a digital value.

[0020] The signal generation unit 70 generates a sine wave signal of a predetermined frequency, a cosine wave signal of a predetermined frequency having a phase orthogonal to the sine wave signal, and a pulse signal of a predetermined frequency. The signal generation unit 70 applies the pulse signal of a predetermined frequency to the gate of transistor Tr1 via terminal tc. As a result, an alternating current of a predetermined frequency can be passed through n battery cells, and alternating voltages are input to n pairs of terminals. Since the alternating voltages corresponding to the alternating current flowing through the shunt resistor 300 are input to terminals ta and tb, the battery monitoring device 1a can calculate the alternating impedance of the n battery cells.

[0021] The battery monitoring device 1a has n multiplier pairs 31 for n A / D converters 30, and one multiplier pair 41 corresponding to one A / D converter 40. Each multiplier pair multiplies the digital value from each A / D converter by a sine wave signal and a cosine wave signal. As a result, each digital value is converted into the real and imaginary components of a complex voltage and a complex current, respectively. The result of multiplying the digital value output from the A / D converter with the sine wave signal shows the real component when the sampled voltage is expressed as a complex voltage and the sampled current is expressed as a complex current. The result of multiplying the digital value output from the A / D converter with the cosine wave signal shows the imaginary component when the sampled voltage is expressed as a complex voltage and the sampled current is expressed as a complex current.

[0022] The battery monitoring device 1a comprises n integrating units 50 and one integrating unit 60. The n integrating units 50 each have an equal number of averaging circuit pairs corresponding to the n multiplier pairs 31, and average the real and imaginary components of repeatedly measured complex voltages. The integrating unit 60 each has an averaging circuit pair corresponding to the multiplier pair 41, and averages the real and imaginary components of repeatedly measured complex currents. This averaging reduces measurement errors in complex voltages and complex currents, and oversampling improves the resolution (measurement accuracy). As a result, even with an A / D converter with a small number of bits (for example, around 16 bits), it becomes possible to obtain AC impedance calculation results with an accuracy of 20 to 24 bits. Figure 1 shows Vsumr + i × Vsumi as the averaged complex voltage value, and Isumr + i × Isumi as the averaged complex current value.

[0023] As shown in Figure 1, a single-cell filter section 200 is provided between the battery monitoring device 1a and the n battery cells, so the complex voltage value Vsumr + i × Vsumi includes a component of the single-cell filter characteristics. Also, since a single-cell filter section 200 is provided between the battery monitoring device 1a and the shunt resistor 300, the complex current value Isumr + i × Isumi includes a component of the single-cell filter characteristics.

[0024] The battery monitoring device 1a includes an impedance calculation unit 11 that calculates the AC impedance of each of the n battery cells. The impedance calculation unit 11 is a computer having a processor and memory, for example, an MCU (Micro Control Unit). The functions of the A / D converters 30 and 40, the multiplier pairs 31 and 41, the integrators 50 and 60, and the signal generation unit 70 may also be implemented by a computer such as an MCU.

[0025] The impedance calculation unit 11 calculates the AC impedance of each of the n battery cells by dividing the complex voltage value Vsumr + i × Vsumi of each of the n battery cells by the complex current value Isumr + i × Isumi. The complex voltage value Vsumr + i × Vsumi and the complex current value Isumr + i × Isumi each contain components of the single-cell filter characteristics, but these components are canceled out by the above division. Therefore, the impedance calculation unit 11 calculates the AC impedance with the single-cell filter characteristics canceled out.

[0026] In the battery monitoring device 1a according to Comparative Example 1, a single-cell filter unit 200 is connected to each battery cell, resulting in a large number of single-cell filter units 200. In other words, the number of components increases. Furthermore, a terminal of the battery monitoring device 1a is required for each single-cell filter unit 200 connected to a battery cell (specifically, twice the number of terminals as the number of n battery cells are required), resulting in a large number of terminals for the battery monitoring device 1a. For this reason, the battery monitoring device 1a according to Comparative Example 1 suffers from high costs.

[0027] In contrast, it is conceivable to connect a multi-cell filter unit between n battery cells and a battery monitoring device so that the negative and positive terminals of adjacent battery cells are connected to a single common terminal of the battery monitoring device. This will be explained using Figure 2.

[0028] Figure 2 is a circuit diagram showing an example of a battery monitoring device 1b according to Comparative Example 2.

[0029] The battery monitoring device 1b according to Comparative Example 2 differs from the battery monitoring device 1a according to Comparative Example 1 in that it has n+1 first terminals instead of n sets of terminal pairs. Other aspects are the same as those of the battery monitoring device 1a according to Comparative Example 1, so their explanation will be omitted. The following explanation will focus on the differences from Comparative Example 1.

[0030] The n+1 first terminals are terminals for measuring the voltage of each of the n battery cells. Figure 2 shows the n+1 first terminals, including terminals t1 and t2 for measuring the voltage of battery cell Bat1, terminals t2 and t3 (not shown) for measuring the voltage of battery cell Bat2 (not shown), ..., and terminals tn and tn+1 for measuring the voltage of battery cell Batn.

[0031] A multi-cell filter unit 100, including capacitive elements, is connected between n battery cells and n+1 first terminals. The negative terminal of the k-th battery cell (where k is an integer between 1 and n-1) and the positive terminal of the k+1th battery cell, both included in the n battery cells, are connected to the k+1th first terminal included in the n+1 first terminals via the multi-cell filter unit 100. For example, the negative terminal of the first battery cell Bat1 and the positive terminal of the second battery cell Bat2 (not shown), both included in the n battery cells, are connected to the second first terminal (i.e., terminal t2) included in the n+1 first terminals via the multi-cell filter unit 100. Also, for example, the negative terminal of the (n-1)th battery cell Batn-1 (not shown) and the positive terminal of the nth battery cell Batn, both included in the n battery cells, are connected to the nth first terminal (i.e., terminal tn) included in the n+1 first terminals via the multi-cell filter unit 100. In other words, the negative terminal of one adjacent battery cell and the positive terminal of the other battery cell are connected to a common first terminal via the multi-cell filter unit 100.

[0032] In the battery monitoring device 1a according to Comparative Example 1, twice the number of terminals as the number of n battery cells are required, but in the battery monitoring device 1b according to Comparative Example 2, the number of first terminals is only one more than the number of n battery cells.

[0033] As shown in Figure 2, a multi-cell filter section 100 is provided between the battery monitoring device 1b and the n battery cells, so the complex voltage value Vsumr + i × Vsumi includes a component of the multi-cell filter characteristics. Also, a single-cell filter section 200 is provided between the battery monitoring device 1b and the shunt resistor 300, so the complex current value Isumr + i × Isumi includes a component of the single-cell filter characteristics.

[0034] The impedance calculation unit 11 calculates the AC impedance of each of the n battery cells by dividing the complex voltage value Vsumr + i × Vsumi of each of the n battery cells by the complex current value Isumr + i × Isumi. However, the complex voltage value Vsumr + i × Vsumi contains a component of the multi-cell filter characteristics, and the complex current value Isumr + i × Isumi contains a component of the single-cell filter characteristics. Since these are different components, the above division does not cancel out the multi-cell filter characteristics and the single-cell filter characteristics. Therefore, an error occurs in the measurement result of the AC impedance.

[0035] Therefore, the following section will specifically describe a battery monitoring device and battery monitoring method that can suppress errors in the measurement results of AC impedance, with reference to the drawings.

[0036] The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure.

[0037] (Embodiment 1) The battery monitoring device according to Embodiment 1 will be described below.

[0038] Figure 3 is a circuit diagram showing an example of a battery monitoring device 1 according to Embodiment 1.

[0039] The battery monitoring device 1 according to Embodiment 1 differs from the battery monitoring device 1b according to Comparative Example 2 in that it comprises a storage unit 12, n dividers 51, and one divider 61. Other aspects are the same as those of the battery monitoring device 1b according to Comparative Example 2, so the following explanation will focus on the differences from Comparative Example 2.

[0040] The storage unit 12 is a memory such as ROM (Read Only Memory). The storage unit 12 stores the multi-cell filter characteristics (complex numbers) of the multi-cell filter unit 100 and the single-cell filter characteristics (complex numbers) of the single-cell filter unit 200 that have been prepared in advance. As will be described later, the multi-cell filter characteristics change depending on the number of cells in the battery cell connected to the battery monitoring device 1, so if the number of cells in the battery cell connected to the battery monitoring device 1 is known in advance, the multi-cell filter characteristics corresponding to that number of cells can be stored in the storage unit 12 in advance. The single-cell filter characteristics do not change depending on the number of cells in the battery cell connected to the battery monitoring device 1, so the single-cell filter characteristics can be stored in the storage unit 12 in advance.

[0041] n dividers 51 are provided corresponding to n integrators 50, and divider 61 is provided corresponding to one integrator 60. For example, n dividers 51 and divider 61 are provided in the impedance calculation unit 11. The functions of dividers 51 and 61 may be implemented by a computer such as an MCU. Each of the n dividers 51 divides the complex voltage value Vsumr + i × Vsumi output from the corresponding integrator 50 by the multi-cell filter characteristics stored in the memory unit 12. This cancels out the multi-cell filter characteristic component included in the complex voltage value Vsumr + i × Vsumi. Divider 61 divides the complex current value Isumr + i × Isumi output from the integrator 60 by the single-cell filter characteristics stored in the memory unit 12. This makes it possible to cancel out the single-cell filter characteristic component contained in the complex current value Isumr + i × Isumi.

[0042] The impedance calculation unit 11 then calculates the AC impedance of each of the n battery cells by dividing the complex voltage values ​​Vsumr + i × Vsumi of each of the n battery cells, which are output from each of the n dividers 51 and have the multi-cell filter characteristic components canceled out, by the complex current value Isumr + i × Isumi, which is output from the divider 61 and has the single-cell filter characteristic components canceled out.

[0043] In this way, the impedance calculation unit 11 calculates the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled based on the voltage measured via the n + 1 first terminals (specifically, the complex voltage values output from the n integrators 50), the current measured via the two second terminals (specifically, the complex current value output from the integrator 60), the multi-cell filter characteristics stored in the storage unit 12, and the single-cell filter characteristics stored in the storage unit 12.

[0044] As described above, by using the multi-cell filter characteristics prepared in advance, the components of the multi-cell filter characteristics included in the measured voltage can be canceled, and by using the single-cell filter characteristics prepared in advance, the components of the single-cell filter characteristics included in the measured current can be canceled. Therefore, since the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled can be calculated, it is possible to suppress the occurrence of errors in the measurement result of the AC impedance.

[0045] (Embodiment 2) The multi-cell filter characteristics of the multi-cell filter unit 100 vary depending on the number of battery cells connected to the battery monitoring device. This will be described with reference to FIG. 4.

[0046] FIG. 4 is a diagram for explaining the multi-cell filter characteristics according to the number of cells. On the left side of FIG. 4, from top to bottom, the multi-cell filter unit 100 in the case of one cell, the multi-cell filter unit 100 in the case of two cells, and the multi-cell filter unit 100 in the case of three cells are shown. The resistance values of the resistors and the capacitances of the capacitors constituting each multi-cell filter unit 100 are the same, and the ESRs of each battery cell are the same.

[0047] When the number of cells is one, let V1_1_cell be the voltage generated between the first terminals to which one battery cell is connected when an excitation current flows through the one battery cell. When the number of cells is two, when an excitation current flows through the two battery cells, let V1_2_cell be the voltage generated between the first terminals to which the lower battery cell is connected, and let V2_2_cell be the voltage generated between the first terminals to which the upper battery cell is connected. When the number of cells is three, when an excitation current flows through the three battery cells, let V1_3_cell be the voltage generated between the first terminals to which the lower battery cell is connected, let V2_3_cell be the voltage generated between the first terminals to which the middle battery cell is connected, and let V3_3_cell be the voltage generated between the first terminals to which the upper battery cell is connected.

[0048] On the right side of FIG. 4, the filter characteristics (specifically, the upper is the frequency characteristic of the gain and the lower is the frequency characteristic of the phase) for each battery cell of the multi-cell filter unit 100 are shown. It can be seen that the multi-cell filter characteristics differ depending on the number of cells. Therefore, when one multi-cell filter characteristic is stored in the storage unit 12, even if a battery pack with a number of cells different from the number of cells corresponding to the multi-cell filter characteristic stored in the storage unit 12 is connected to the battery monitoring device, the components of the multi-cell filter characteristic cannot be accurately canceled.

[0049] Therefore, in the second embodiment, a battery monitoring device that can be applied to various battery packs with different numbers of cells will be described.

[0050] FIG. 5 is a circuit configuration diagram showing an example of the battery monitoring device 2 according to the second embodiment.

[0051] The battery monitoring device 2 according to the second embodiment is different from the battery monitoring device 1 according to the first embodiment in that it includes a cell number determination unit 13 and a filter characteristic output unit 14. Since the other points are the same as those in the battery monitoring device 1 according to the first embodiment, the following description will focus on the differences from the first embodiment.

[0052] The cell count determination unit 13 determines the number of cells in the n battery cells based on the voltage measured via the n+1 first terminals. The details of the operation of the cell count determination unit 13 will be described later. Note that the function of the cell count determination unit 13 may be implemented by a computer such as an MCU.

[0053] The filter characteristic output unit 14 outputs the multi-cell filter characteristics and single-cell filter characteristics stored in the storage unit 12. Details of the operation of the filter characteristic output unit 14 will be described later. Note that the functions of the filter characteristic output unit 14 may be implemented by a computer such as an MCU.

[0054] Next, the operation of the battery monitoring device 2 will be explained in detail using Figure 6.

[0055] Figure 6 is a flowchart showing an example of the operation of the battery monitoring device 2 according to Embodiment 2.

[0056] First, (i) filter characteristics for each number of cells (multi-cell filter characteristics) are pre-databased as complex number data (step S101). Single-cell filter characteristics are also pre-databased as complex number data. Specifically, the storage unit 12 stores multiple multi-cell filter characteristics and pre-prepared single-cell filter characteristics for each number of cells in n battery cells. In other words, the storage unit 12 stores multiple multi-cell filter characteristics that correspond one-to-one with each of the total number of cells in all battery cells that can be connected to the battery monitoring device 2.

[0057] Figure 7 shows an example of multiple multi-cell filter characteristics prepared in advance for each number of cells. For example, if the number of battery cells that can be connected to the battery monitoring device 2 is one to five, five different multi-cell filter characteristics (e.g., complex number correction coefficients) are stored in the storage unit 12, as shown in Figure 7.

[0058] Next, (ii) the cell count determination unit 13 determines the number of cells from the complex voltage values ​​of each cell terminal (first terminal) (i.e., the outputs of the n integral units 50) (step S102). For example, the cell count determination unit 13 determines the number of cells in the n battery cells based on the number of first terminals from which signals are output among the n+1 first terminals. The number of first terminals from which signals are output corresponds to the number of cells in the battery cells connected to the battery monitoring device 2, so the number of cells can be determined from the number of first terminals from which signals are output.

[0059] Next, (iii) the filter characteristic output unit 14 selects a multi-cell filter characteristic from the database (i) that matches the number of cells determined by the cell count determination unit 13 (step S103). For example, the filter characteristic output unit 14 selects a multi-cell filter characteristic from among the multiple multi-cell filter characteristics stored in the storage unit 12 that corresponds to the number of cells determined by the cell count determination unit 13, and outputs the selected multi-cell filter characteristic to the divider 51. The filter characteristic output unit 14 also outputs a single-cell filter characteristic stored in the storage unit 12 to the divider 61.

[0060] Next, (iv) the impedance calculation unit 11 performs calculations using the multi-cell filter characteristics selected in (iii) and cancels the multi-cell filter characteristics (step S104). For example, each of the n dividers 51 divides the complex voltage value Vsumr + i × Vsumi output from the corresponding integral unit 50 by the multi-cell filter characteristics output from the filter characteristics output unit 14 (specifically, the multi-cell filter characteristics corresponding to the number of battery cells currently connected to the battery monitoring device 2). This cancels the multi-cell filter characteristic component included in the complex voltage value Vsumr + i × Vsumi. In addition, the divider 61 divides the complex current value Isumr + i × Isumi output from the integral unit 60 by the single-cell filter characteristics output from the filter characteristics output unit 14. This cancels the single-cell filter characteristic component included in the complex current value Isumr + i × Isumi. Therefore, the impedance calculation unit 11 can calculate the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out.

[0061] Then, (v) the impedance calculation unit 11 outputs the calculated AC impedance (step S105). For example, the impedance calculation unit 11 outputs the calculated AC impedance to a function block that determines the state of n battery cells.

[0062] In this way, the impedance calculation unit 11 calculates the AC impedance obtained by canceling out the components of the multi-cell filter characteristics and single-cell filter characteristics, based on the voltage measured through n+1 first terminals (specifically, the complex voltage values ​​output from the n integration units 50), the current measured through two second terminals (specifically, the complex current values ​​output from the integration unit 60), and the multi-cell filter characteristics and single-cell filter characteristics corresponding to the number of cells of the n battery cells determined by the cell number determination unit 13.

[0063] As explained above, since the multi-cell filter characteristics differ depending on the number of cells, the number of cells in the battery connected to the battery monitoring device 2 is determined, and by using the pre-prepared multi-cell filter characteristics corresponding to the determined number of cells, the multi-cell filter characteristics included in the measured voltage can be canceled. Therefore, the battery monitoring device 2 can be applied to various battery packs with different numbers of cells.

[0064] (Embodiment 3) The multi-cell filter characteristics of the multi-cell filter unit 100 change as the battery cells connected to the battery monitoring device deteriorate, specifically as the ESR (Equivalent Series Resistance) increases. This will be explained using Figure 8.

[0065] Figure 8 is a diagram illustrating the multi-cell filter characteristics according to the ESR of the battery cells. The upper left of Figure 8 shows the multi-cell filter section 100 when the ESRs of the two battery cells are the same, and the lower left of Figure 8 shows the multi-cell filter section 100 when the ESRs of the two battery cells are different. For example, the ESR of the upper battery cell is twice that of the lower battery cell. The resistance values ​​of the resistors and the capacitance of the capacitors constituting each multi-cell filter section 100 are assumed to be the same. When an excitation current flows through the two battery cells, the voltage generated between the first terminals to which the lower battery cell is connected is denoted as V1, and the voltage generated between the first terminals to which the upper battery cell is connected is denoted as V2.

[0066] The upper right side of Figure 8 shows the filter characteristics of the multi-cell filter unit 100 for each battery cell when the ESRs of the two battery cells are the same (specifically, the upper side shows the frequency characteristics of the gain, and the lower side shows the frequency characteristics of the phase). The lower right side of Figure 8 shows the filter characteristics of the multi-cell filter unit 100 for each battery cell when the ESRs of the two battery cells are different (specifically, the upper side shows the frequency characteristics of the gain, and the lower side shows the frequency characteristics of the phase).

[0067] When the ESRs of the two battery cells are the same, it can be seen that the filter characteristics of the multi-cell filter section 100 for battery cell V1 and the filter characteristics of the multi-cell filter section 100 for battery cell V2 are the same. On the other hand, when the ESRs of the two battery cells are different (for example, when the ESR of battery cell V2 is twice that of battery cell V1), the cutoff frequency of the filter characteristics of the multi-cell filter section 100 for battery cell V2 shifts to a lower frequency, and the cutoff frequency of the filter characteristics of the multi-cell filter section 100 for battery cell V1 shifts to a higher frequency. In other words, it can be seen that the filter characteristics of the multi-cell filter section 100 for battery cell V1 and the filter characteristics of the multi-cell filter section 100 for battery cell V2 are different.

[0068] Therefore, if the multi-cell filter characteristics without considering ESR are stored in the memory unit 12, the components of the multi-cell filter characteristics cannot be accurately canceled when the battery cells deteriorate.

[0069] Therefore, Embodiment 3 describes a battery monitoring device that can accurately cancel out the multi-cell filter characteristic component even when the battery cells have deteriorated.

[0070] Figure 9 is a circuit diagram showing an example of a battery monitoring device 3 according to Embodiment 3.

[0071] The battery monitoring device 3 according to Embodiment 3 differs from the battery monitoring device 2 according to Embodiment 2 in that it includes an ESR ratio calculation unit 15. Other aspects are the same as those of the battery monitoring device 2 according to Embodiment 2, so the following description will focus on the differences from Embodiment 2.

[0072] The ESR ratio calculation unit 15 estimates the ESR ratio of each of the n battery cells, which is the ratio of the current ESR to the ESR when the battery is undegraded, based on the voltages measured through the n+1 first terminals. For example, the ESR ratio calculation unit 15 estimates the ESR ratio from the ratio of the complex voltage value when the battery is undegraded to the current complex voltage value. The function of the ESR ratio calculation unit 15 may be implemented by a computer such as an MCU.

[0073] The memory unit 12 stores multiple multi-cell filter characteristics and single-cell filter characteristics, each prepared in advance for each combination of ESR ratios of the n battery cells. In the third embodiment, the memory unit 12 also stores multiple multi-cell filter characteristics, each prepared in advance for each number of cells, as shown in Figure 7.

[0074] Figure 10 shows an example of multiple multi-cell filter characteristics pre-prepared for each combination of ESR ratios. The ESR ratio of a non-degraded battery cell is assumed to be ±5%. Figure 10 shows multiple multi-cell filter characteristics for a case with three cells. Figure 10 also shows multi-cell filter characteristics when the ESR ratio of a degraded battery cell is between +5% and +10%. In addition to the multiple multi-cell filter characteristics shown in Figure 10, the storage unit 12 stores numerous multi-cell filter characteristics corresponding to various cell counts and various ESR ratios.

[0075] For example, if the cell count determination unit 13 determines that there are three battery cells connected to the battery monitoring device 3, and the ESR ratio calculation unit 15 estimates that the ESR ratio of cell 1 is between +5% and +10%, and that cells 2 and 3 are not degraded (i.e., their ESR ratio is ±5%), the filter characteristic output unit 14 outputs the correction coefficient shown in (A) of Figure 10. Then, the impedance calculation unit 11 uses the output correction coefficient to cancel out the multi-cell filter characteristic component and calculates the AC impedance with the multi-cell filter characteristic component canceled out.

[0076] In this way, the impedance calculation unit 11 calculates the AC impedance in which the components of the multi-cell filter characteristics and single-cell filter characteristics are canceled out, based on the voltage measured through n+1 first terminals (specifically, the complex voltage values ​​output from the n integration units 50), the current measured through two second terminals (specifically, the complex current values ​​output from the integration unit 60), and the multi-cell filter characteristics and single-cell filter characteristics corresponding to the combination of ESR ratios of the n battery cells estimated by the ESR ratio calculation unit 15.

[0077] As explained above, since the multi-cell filter characteristics differ depending on the ESR of each cell, the ESR ratio of each battery cell can be estimated, and by using pre-prepared multi-cell filter characteristics corresponding to the combination of ESR ratios of each battery cell, the multi-cell filter characteristics included in the measured voltage can be accurately canceled. Therefore, the battery monitoring device 3 can be applied to battery packs where the ESR of each battery cell is different.

[0078] However, this method requires pre-preparing multi-cell filter characteristics for each number of battery cells, each combination of ESR ratios for each battery cell, and each magnitude of the ESR ratio, thus requiring the storage of a vast number of multi-cell filter characteristics in the storage unit 12. In contrast, the inventors of the present invention have discovered that when the ESR of a certain battery cell increases, the filter characteristics of the multi-cell filter unit 100 for that battery cell are greatly affected, and furthermore, the filter characteristics for surrounding battery cells are also affected, and that there is a certain relationship between the filter characteristics of the multi-cell filter unit 100 for that battery cell and the filter characteristics for surrounding battery cells at that time.

[0079] Using this relationship, multi-cell filter characteristics can be pre-prepared, including the filter characteristics for the target battery cell of the multi-cell filter unit 100 and the filter characteristics for the battery cells surrounding the target battery cell. In other words, the storage unit 12 may store pre-prepared multi-cell filter characteristics, including the filter characteristics for the target battery cell among the n battery cells of the multi-cell filter unit 100 and the filter characteristics for the battery cells surrounding the target battery cell, as well as pre-prepared single-cell filter characteristics.

[0080] Figure 11 shows an example of multi-cell filter characteristics, including the filter characteristics of the multi-cell filter unit 100 for the target battery cell and the filter characteristics for surrounding battery cells. Figure 11 shows multiple multi-cell filter characteristics for the case of 9 cells. Also, Figure 11 shows six multi-cell filter characteristics for ESR ratios of 1, 1.01, 1.025, 1.05, 1.075, and 1.1. Furthermore, Figure 11 shows complex numbers as the filter characteristics of each battery cell of the multi-cell filter unit 100. For example, the filter characteristics of the multi-cell filter section 100 for a target battery cell with an ESR ratio of 1.1 have the following relationships with the adjacent, second, third, and fourth adjacent battery cells: -0.02793-0.01656i, 0.01596+0.00411i, -0.0001+0.00372i, 0.00002+0.00004i, and -0.00004-0.00016i.

[0081] For example, the impedance calculation unit 11 may calculate an AC impedance in which the components of the multi-cell filter characteristics and single-cell filter characteristics are canceled out, based on the voltage measured through n+1 first terminals, the current measured through two second terminals, the multi-cell filter characteristics obtained by applying battery cells from among the n battery cells whose ESR ratio estimated by the ESR ratio calculation unit 15 is equal to or greater than a predetermined value to the target battery cell, and the single-cell filter characteristics.

[0082] As shown in Figure 11, if cell 5 is a battery cell with an ESR ratio greater than or equal to a predetermined value, and its ESR ratio is 1.1, the impedance calculation unit 11 applies cell 5 to the target battery cell and determines the filter characteristics of the multi-cell filter unit 100 for cell 5 to be -0.02793 - 0.01656i. The impedance calculation unit 11 also determines the filter characteristics of the multi-cell filter unit 100 for cells 4 and 6 to be 0.01596 + 0.00411i, for cells 3 and 7 to be -0.0001 + 0.00372i, for cells 2 and 8 to be 0.00002 + 0.00004i, and for cells 1 and 9 to be -0.00004 - 0.00016i.

[0083] In this way, a battery cell with an ESR ratio of a predetermined value or higher is applied to the target battery cell in a pre-prepared multi-cell filter characteristic, and by using this multi-cell filter characteristic, the multi-cell filter characteristic included in the measured voltage can be canceled out. As a result, it is not necessary to prepare a multi-cell filter characteristic in advance for each combination of ESR ratios, and the number of multi-cell filter characteristics that need to be prepared in advance can be reduced.

[0084] Furthermore, if there are multiple degraded battery cells, a multi-cell filter characteristic may be created to represent the case where multiple battery cells have degraded.

[0085] Figure 12 is a diagram illustrating a method for creating multi-cell filter characteristics when multiple battery cells have degraded.

[0086] As shown in Figure 12, if cells 4 and 7 are degraded and their ESR ratios are each 1.1, the impedance calculation unit 11 creates a multi-cell filter characteristic for when cells 4 and 7 are degraded by superimposing the multi-cell filter characteristic obtained by applying cell 4 to the target battery cell with the multi-cell filter characteristic obtained by applying cell 7 to the target battery. In this case, the filter characteristic for cell 4 of the multi-cell filter unit 100 is the sum of the filter characteristic for cell 4 in the multi-cell filter characteristic obtained by applying cell 4 to the target battery cell, which is -0.02793 - 0.01656i, and the filter characteristic for cell 4 in the multi-cell filter characteristic obtained by applying cell 7 to the target battery cell, which is 0.00002 + 0.00004i, which is -0.02791 - 0.01652i. Furthermore, the filter characteristics of the multi-cell filter unit 100 for cell 7 are the sum of -0.02791 - 0.01652i, which is the filter characteristics for cell 7 in the multi-cell filter characteristics when cell 7 is applied to the target battery cell, and 0.00002 + 0.00004i, which is the filter characteristics for cell 7 in the multi-cell filter characteristics when cell 4 is applied to the target battery cell. The filter characteristics for surrounding battery cells can be calculated in the same manner.

[0087] Thus, if there are multiple degraded battery cells, the multi-cell filter characteristics for when multiple battery cells are degraded may be created by combining the multi-cell filter characteristics that each of the degraded battery cells is assigned to.

[0088] Furthermore, if the battery cells deteriorate, the filter characteristics of the multi-cell filter unit 100 for each battery cell will change. As a result, the accuracy of estimating the ESR ratio, which is measured through the changed filter characteristics, will deteriorate, and errors will occur in the measurement results of the AC impedance. Therefore, in order to improve the accuracy of estimating the ESR ratio, the battery monitoring device 3 may perform the processing shown in Figure 13.

[0089] Figure 13 is a flowchart showing an example of the operation of the battery monitoring device 3 according to Embodiment 3.

[0090] First, (i) filter characteristics for each number of cells and ESR ratio (multi-cell filter characteristics) are pre-databased as complex number data (step S201). Single-cell filter characteristics are also pre-databased as complex number data. Specifically, the storage unit 12 stores multiple multi-cell filter characteristics, which are prepared in advance for each number of cells in n battery cells and for each ESR ratio, as well as pre-prepared single-cell filter characteristics. In other words, the storage unit 12 stores multiple multi-cell filter characteristics that correspond one-to-one with each of the number of cells in all battery cells that can be connected to the battery monitoring device 2, and that also correspond one-to-one with each of the multiple ESR ratios.

[0091] Next, (ii) the cell count determination unit 13 determines the number of cells from the complex voltage value of each cell terminal (first terminal) (i.e., the output of the n integral units 50) (step S202). The process in step S202 is the same as the process in step S102 in Figure 6, so the explanation is omitted.

[0092] Next, (iii) the filter characteristic output unit 14 and the ESR ratio calculation unit 15 select a multi-cell filter characteristic from the database in (i) that matches the number of cells determined by the cell count determination unit 13 (step S203). Since multiple multi-cell filter characteristics are prepared in advance for each ESR ratio for a given number of cells, there are multiple multi-cell filter characteristics for each ESR ratio that match the number of cells determined by the cell count determination unit 13. For this reason, the filter characteristic output unit 14 selects multiple multi-cell filter characteristics for each cell count that match the number of cells determined by the cell count determination unit 13, and the ESR ratio calculation unit 15 selects one of the multiple multi-cell filter characteristics. In step S203, the ESR ratio calculation unit 15 selects any one of the multiple multi-cell filter characteristics.

[0093] Next, (iv) the impedance calculation unit 11 performs calculations using the multi-cell filter characteristics selected in (iii) and cancels the multi-cell filter characteristics (step S204). Specifically, the impedance calculation unit 11 calculates the input voltage (e.g., a complex voltage value) to be input to the multi-cell filter unit 100 based on the voltages measured through the n+1 first terminals (specifically, the complex voltage values ​​output from the n integration units 50) and one multi-cell filter characteristic selected in (iii) by the ESR ratio calculation unit 15 from among the multiple multi-cell filter characteristics. The input voltage to be input to the multi-cell filter unit 100 is a voltage that is not affected by the multi-cell filter characteristics, that is, a voltage in which the components of the multi-cell filter characteristics have been canceled out.

[0094] Next, (v) the ESR ratio calculation unit 15 estimates the ESR ratio based on the calculated input voltage, specifically, it estimates the ESR ratio from the complex voltage values ​​of each cell calculated by the impedance calculation unit 11 in (iv) (step S205).

[0095] Next, (vi) the ESR ratio calculation unit 15 selects one multi-cell filter characteristic from among a plurality of multi-cell filter characteristics that corresponds to the estimated ESR ratio. Specifically, it selects the multi-cell filter characteristics of (i) by cell number and ESR ratio according to the ESR ratio estimated in (v) (step S206).

[0096] Next, (vii) the impedance calculation unit 11 performs calculations using the multi-cell filter characteristics selected in (vi) and cancels the multi-cell filter characteristics (step S207). Specifically, the impedance calculation unit 11 calculates the input voltage (e.g., complex voltage value) input to the multi-cell filter unit 100 using one of the multi-cell filter characteristics selected in (vi), just as in (iv).

[0097] Next, the impedance calculation unit 11 determines whether the complex voltage values ​​of each cell in (vii) are within the acceptable range (step S208). Specifically, the impedance calculation unit 11 determines whether the difference between the input voltage calculated this time (the input voltage calculated in (vii)) and the input voltage calculated last time (the input voltage calculated in (iv)) is less than or equal to a predetermined value.

[0098] If it is determined that the complex voltage value of each cell is not within the acceptable range (No in step S208), the ESR ratio calculation unit 15 estimates the ESR ratio from the complex voltage value of each cell calculated in (vii), in the same way as in (v).

[0099] Then, in (vi), the ESR ratio calculation unit 15 selects multi-cell filter characteristics for each cell number and ESR ratio in (i) according to the ESR ratio estimated in (ix), in (vii), the impedance calculation unit 11 calculates the input voltage (for example, a complex voltage value) by performing calculations using the multi-cell filter characteristics selected in the current (vi), canceling the multi-cell filter characteristics, and in (viiii), the impedance calculation unit 11 determines whether the difference between the input voltage calculated in the current (vii) and the input voltage calculated in the previous (vii) is less than or equal to a predetermined value.

[0100] Then, if the impedance calculation unit 11 determines that the complex voltage value of each cell is within the acceptable range, that is, if the difference between the input voltage calculated this time and the input voltage calculated last time is less than or equal to a predetermined value (Yes in step S208), (x) calculates the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the input voltage calculated this time, the current measured through the two second terminals, and the single-cell filter characteristics, and outputs the calculated AC impedance (step S210).

[0101] Thus, the impedance calculation unit calculates the input voltage to be input to the multi-cell filter unit 100 based on (a) the voltage measured through n+1 first terminals and one selected multi-cell filter characteristic from among multiple multi-cell filter characteristics, and the ESR ratio calculation unit 15 estimates the ESR ratio based on the input voltage and selects one multi-cell filter characteristic from among multiple multi-cell filter characteristics that corresponds to the estimated ESR ratio. The impedance calculation unit 11 and the ESR ratio calculation unit 15 repeat the process in (a) and the process in (b) above. Then, when the difference between the input voltage calculated this time and the input voltage calculated last time becomes less than or equal to a predetermined value, the impedance calculation unit 11 calculates the AC impedance in which the components of the multi-cell filter characteristic and the single-cell filter characteristic are canceled out, based on the input voltage calculated this time, the current measured through the two second terminals, and the single-cell filter characteristic.

[0102] As explained above, first, the input voltage to the multi-cell filter unit 100 (i.e., the voltage with the multi-cell filter characteristics canceled) is calculated using an arbitrary multi-cell filter characteristic, and the ESR ratio is estimated using this input voltage. Then, the input voltage to the multi-cell filter unit 100 is calculated using the multi-cell filter characteristic corresponding to the estimated ESR ratio. By repeating this process until the input voltage is the same as the previous time, the accuracy of the ESR ratio estimation can be improved, and consequently, errors in the AC impedance measurement results can be suppressed.

[0103] For example, let n be the cell number, let Vout(n) be the output voltage of the multi-cell filter unit 100 (i.e., the voltage affected by the multi-cell filter characteristics), let Vin(n) be the input voltage of the multi-cell filter unit 100 (i.e., the voltage from which the multi-cell filter characteristic components have been canceled), and let C(n) be the multi-cell filter characteristic (also called the correction coefficient) selected from among a plurality of multi-cell filter characteristics (also called the correction coefficient table) stored in the memory unit 12 in order to cancel the multi-cell filter characteristic components included in the output voltage.

[0104] The following shows a method for calculating the input voltage Vin(n) from the output voltage Vout(n) of the multi-cell filter unit 100 using a correction coefficient table.

[0105] First, the input voltage is calculated as Vin'(n) = Vout(n) / C(n) using an arbitrary correction factor C(n) selected from the correction factor table. Since the correction factor depends on the input voltage (specifically, the ESR ratio estimated from the input voltage), the input voltage is calculated as Vin''(n) = Vout(n) / C'(n) using a correction factor C'(n) selected from the correction factor table that corresponds to the calculated input voltage Vin'(n) (in other words, the ESR ratio). This process is repeated until the input voltage converges.

[0106] For example, if the calculated Vin'(n) and Vin''(n) are compared and the difference exceeds a predetermined value, indicating insufficient calculation accuracy, the input voltage is calculated as Vin'''(n) = Vout(n) / C''(n) using a correction coefficient C''(n) selected from the correction coefficient table that corresponds to Vin''(n). If the difference between Vin''(n) and Vin'''(n) becomes less than or equal to the predetermined value, it is determined that the input voltage has converged, and the input voltage is set to Vin(n) = Vin'''(n).

[0107] Alternatively, the correction coefficient C(n) in the correction coefficient table may be taken as the reciprocal, and the input voltage may be calculated by multiplying it by Vin(n) = Vout(n) × C(n).

[0108] Furthermore, the correction coefficients in the correction coefficient table may be linearly interpolated. In other words, in the correction coefficient table, there is a correction coefficient for each discrete input voltage (ESR ratio), and the correction coefficient corresponding to an input voltage (ESR ratio) not present in the correction coefficient table may be calculated by linearly interpolating it to the actual input voltage.

[0109] Furthermore, since the complex impedance Z is calculated as Z = V / I, if a common current I flows through multiple battery cells, the correction factor table may include a correction factor for the complex impedance of each cell, rather than a correction factor for the voltage and current of each battery cell.

[0110] (Other Embodiments) Embodiments have been described above as examples of the technology relating to this disclosure. However, the technology relating to this disclosure is not limited thereto and can be applied to embodiments that are modified, replaced, added to, or omitted as appropriate. For example, the following modified examples are also included in one embodiment of this disclosure.

[0111] For example, in the above embodiment, an example was described in which the impedance calculation unit 11 calculates the AC impedance after removing the filter characteristics, but it is not limited to this. For example, the impedance calculation unit 11 may calculate the AC impedance and then remove the filter characteristics.

[0112] For example, in the above embodiment 3, an example was described in which the battery monitoring device 3 includes a cell count determination unit 13. However, if the number of cells in the battery connected to the battery monitoring device 3 is known in advance, the battery monitoring device 3 does not need to include a cell count determination unit 13. In this case, the storage unit 12 does not need to store a plurality of multi-cell filter characteristics prepared in advance for each number of cells, as shown in Figure 7.

[0113] For example, this disclosure can be implemented not only as a battery monitoring device, but also as a battery monitoring method that includes steps (processes) performed by the components constituting the battery monitoring device.

[0114] Figure 14 is a flowchart showing an example of a battery monitoring method according to another embodiment.

[0115] The battery monitoring method is performed by a battery monitoring device that monitors n battery cells connected in series, the battery monitoring device comprising n+1 first terminals for measuring the voltage of each of the n battery cells, two second terminals connected to a current measuring unit for measuring the current flowing through the n battery cells, and a storage unit, a multi-cell filter unit including a capacitive element connected between the n battery cells and the n+1 first terminals, the negative terminal of the k-th battery cell (where k is an integer between 1 and n-1) and the positive terminal of the k+1-th battery cell included in the n battery cells are connected to the k+1-th first terminal included in the n+1 first terminals via the multi-cell filter unit. A single-cell filter section including a capacitive element is connected between the current measurement section and the two second terminals, and the multi-cell filter characteristics of a pre-prepared multi-cell filter section and the single-cell filter characteristics of a pre-prepared single-cell filter section are stored in the storage section. The battery monitoring method, as shown in Figure 14, includes the steps of: calculating an AC impedance (step S11) in which the components of the multi-cell filter characteristics and single-cell filter characteristics are canceled out, based on the voltage measured via n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics, and the single-cell filter characteristics; and outputting the calculated AC impedance (step S12).

[0116] For example, this disclosure can be implemented as a program that causes a computer (processor) to execute the steps included in the battery monitoring method. Furthermore, this disclosure can be implemented as a non-temporary computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

[0117] For example, if this disclosure is implemented in a program (software), each step is executed by the program using hardware resources such as the computer's CPU, memory, and input / output circuits. In other words, each step is executed by the CPU obtaining data from memory or input / output circuits, performing calculations, and outputting the calculation results to memory or input / output circuits.

[0118] In the above embodiment, each component included in the battery monitoring device may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may also be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0119] Some or all of the functions of the battery monitoring device according to the above embodiment are typically implemented as an LSI, which is an integrated circuit. These may be individually integrated onto a single chip, or some or all of them may be integrated onto a single chip. Furthermore, the implementation is not limited to an LSI, but may also be implemented using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI may also be used.

[0120] Furthermore, if advances in semiconductor technology or other derived technologies lead to the emergence of integrated circuit technologies that can replace LSIs, then naturally, those technologies may be used to integrate each component included in the battery monitoring device into an integrated circuit.

[0121] Furthermore, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of this disclosure.

[0122] (Note) The above description of embodiments discloses the following technology.

[0123] (Technology 1) A battery monitoring device for monitoring n (n is an integer of 2 or more) battery cells connected in series, comprising: n+1 first terminals for measuring the voltage of each of the n battery cells; two second terminals connected to a current measuring unit for measuring the current flowing through the n battery cells; a storage unit; and an impedance calculation unit for calculating the AC impedance of each of the n battery cells, wherein a multi-cell filter unit including a capacitive element is connected between the n battery cells and the n+1 first terminals, and the negative terminal of the k (k is an integer of 1 or more and n-1 or less)th battery cell and the positive terminal of the k+1th battery cell are connected to the n+1 first terminals A battery monitoring device comprising: a k+1th first terminal included in the battery, connected via the multi-cell filter section; a single-cell filter section including a capacitive element connected between the current measurement section and the two second terminals; a storage section that stores pre-prepared multi-cell filter characteristics of the multi-cell filter section and pre-prepared single-cell filter characteristics of the single-cell filter section; and an impedance calculation section that calculates the AC impedance, in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics, and the single-cell filter characteristics.

[0124] According to this method, by using pre-prepared multi-cell filter characteristics, the multi-cell filter characteristic component included in the measured voltage can be canceled out, and by using pre-prepared single-cell filter characteristics, the single-cell filter characteristic component included in the measured current can be canceled out. Therefore, since the AC impedance with the multi-cell and single-cell filter characteristic components canceled out can be calculated, errors in the AC impedance measurement results can be suppressed.

[0125] (Technical 2) The battery monitoring device further comprises a cell number determination unit that determines the number of cells in the n battery cells based on the voltage measured via the n+1 first terminals, the storage unit stores a plurality of multi-cell filter characteristics and single-cell filter characteristics prepared in advance for each number of cells in the n battery cells, and the impedance calculation unit calculates the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics corresponding to the determined number of cells in the n battery cells, and the single-cell filter characteristics.

[0126] According to this, since the multi-cell filter characteristics differ depending on the number of cells, the number of cells in the battery connected to the battery monitoring device is determined, and by using a pre-prepared multi-cell filter characteristic corresponding to the determined number of cells, the multi-cell filter characteristics included in the measured voltage can be canceled. Therefore, the battery monitoring device can be applied to various battery packs with different numbers of cells.

[0127] (Technical 3) The battery monitoring device according to Technical 2, wherein the cell count determination unit determines the number of cells in the n battery cells based on the number of first terminals from which a signal is output among the n+1 first terminals.

[0128] According to this, the number of first terminals that output a signal corresponds to the number of cells in the battery connected to the battery monitoring device, so the number of cells can be determined from the number of first terminals that output a signal.

[0129] (Technical 4) The battery monitoring device further comprises an ESR ratio calculation unit that estimates the ESR ratio of each of the n battery cells, which is the ratio of the current ESR to the ESR when undegraded, based on the voltage measured via the n+1 first terminals, and the storage unit stores a plurality of multi-cell filter characteristics and single-cell filter characteristics prepared in advance for each combination of the ESR ratios of the n battery cells, and the impedance calculation unit calculates the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, and the multi-cell filter characteristics and single-cell filter characteristics corresponding to the estimated combination of the ESR ratios of the n battery cells.

[0130] According to this, the multi-cell filter characteristics differ depending on the ESR of each cell. Therefore, the ESR ratio of each battery cell is estimated, and by using pre-prepared multi-cell filter characteristics corresponding to the combination of ESR ratios of each battery cell, the multi-cell filter characteristics included in the measured voltage can be canceled out. Consequently, the battery monitoring device can be applied to battery packs where the ESR of each battery cell is different.

[0131] (Technical 5) The battery monitoring device further comprises an ESR ratio calculation unit that estimates the ESR ratio of each of the n battery cells, which is the ratio of the current ESR to the ESR when undegraded, based on the voltage measured via the n+1 first terminals, and the storage unit stores the multi-cell filter characteristics, which include the filter characteristics of the multi-cell filter unit for a target battery cell among the n battery cells and the filter characteristics for battery cells surrounding the target battery cell, and the single-cell filter characteristics, which have been prepared in advance, and the impedance calculation unit calculates the AC impedance, in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics obtained by applying the battery cells among the n battery cells whose estimated ESR ratio is equal to or greater than a predetermined value to the target battery cell, and the single-cell filter characteristics, the battery monitoring device according to any one of Technical 1 to 3.

[0132] When the ESR of a particular battery cell increases, the filtering characteristics of the multi-cell filter section for that battery cell are significantly affected, and furthermore, the filtering characteristics of the multi-cell filter section for surrounding battery cells are also affected. In this case, there is a certain relationship between the filtering characteristics of the multi-cell filter section for that battery cell and the filtering characteristics of surrounding battery cells. Therefore, using this relationship, a multi-cell filter characteristic including the filtering characteristics of the multi-cell filter section for the target battery cell and the filtering characteristics for surrounding battery cells can be prepared in advance. Then, the ESR ratio of each battery cell is estimated, and battery cells with an ESR ratio of a predetermined value or higher are applied to the target battery cell in the pre-prepared multi-cell filter characteristic. By using this multi-cell filter characteristic, the multi-cell filter characteristic included in the measured voltage can be canceled out. As a result, it is not necessary to prepare a multi-cell filter characteristic in advance for each combination of ESR ratios of each battery cell, and the number of multi-cell filter characteristics to be prepared in advance can be reduced.

[0133] (Technical 6) The battery monitoring device further includes an ESR ratio calculation unit that estimates the ESR ratio of each of the n battery cells, which is the ratio of the current ESR to the ESR when undegraded, based on the voltage measured via the n+1 first terminals, and the storage unit stores a plurality of multi-cell filter characteristics and a single-cell filter characteristic prepared in advance for each ESR ratio, and the ESR ratio calculation unit selects one of the plurality of multi-cell filter characteristics, and the impedance calculation unit calculates the input voltage to be input to the multi-cell filter unit based on (a) the voltage measured via the n+1 first terminals and the selected one of the plurality of multi-cell filter characteristics. A battery monitoring device according to any one of the technologies 1 to 5, wherein the ESR ratio calculation unit calculates (b) the ESR ratio based on the input voltage, selects one of the multi-cell filter characteristics from a plurality of multi-cell filter characteristics corresponding to the estimated ESR ratio, and the impedance calculation unit and the ESR ratio calculation unit repeat the process of (a) and the process of (b), and when the difference between the input voltage calculated this time and the input voltage calculated last time becomes less than or equal to a predetermined value, the impedance calculation unit calculates the AC impedance in which the components of the multi-cell filter characteristic and the single-cell filter characteristic are canceled out, based on the input voltage calculated this time, the current measured through the two second terminals, and the single-cell filter characteristic.

[0134] According to this method, first, the input voltage to the multi-cell filter section (i.e., the voltage with the multi-cell filter characteristics canceled out) is calculated using an arbitrary multi-cell filter characteristic, and the ESR ratio is estimated using this input voltage. Then, the input voltage to the multi-cell filter section is calculated using the multi-cell filter characteristic corresponding to the estimated ESR ratio. By repeating this process until the input voltage is the same as the previous time, the accuracy of the ESR ratio estimation can be improved, and consequently, errors in the AC impedance measurement results can be suppressed.

[0135] (Technical 7) A battery monitoring method performed by a battery monitoring device that monitors n battery cells connected in series, wherein the battery monitoring device comprises n+1 first terminals for measuring the voltage of each of the n battery cells, two second terminals connected to a current measuring unit for measuring the current flowing through the n battery cells, and a storage unit, wherein a multi-cell filter unit including a capacitive element is connected between the n battery cells and the n+1 first terminals, and the negative terminal of the k-th battery cell (where k is an integer between 1 and n-1) and the positive terminal of the k+1-th battery cell included in the n battery cells are connected to the k+1-th first terminal included in the n+1 first terminals and the multi-cell filter unit A battery monitoring method comprising the steps of: connecting via a current measuring unit and the two second terminals, a single-cell filter unit including a capacitive element connected between the current measuring unit and the two second terminals, storing the multi-cell filter characteristics of the multi-cell filter unit and the single-cell filter characteristics of the single-cell filter unit prepared in advance in the storage unit, and calculating an AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics and the single-cell filter characteristics, and outputting the calculated AC impedance.

[0136] This provides a battery monitoring method that can suppress errors in the measurement results of AC impedance.

[0137] This disclosure can be applied to battery packs and the like, which consist of multiple battery cells connected in series.

[0138] 1, 1a, 1b, 2, 3, Battery monitoring device 11 Impedance calculation unit 12 Memory unit 13 Cell count determination unit 14 Filter characteristic output unit 15 ESR ratio calculation unit 30, 40 A / D converter 31, 41 Multiplier pair 50, 60 Integrator unit 51, 61 Divider 70 Signal generation unit 100 Multi-cell filter unit 200 Single-cell filter unit 300 Shunt resistor Bat1, Batn Battery cell R1 Load resistor Tr1 Transistor t1, t2, tn, tn+1, t1p, t1n, t2p, tn-1n, tnp, tnn, ta, tb, tc Terminals

Claims

1. A battery monitoring device for monitoring n (n is an integer of 2 or more) battery cells connected in series, comprising: n+1 first terminals for measuring the voltage of each of the n battery cells; two second terminals connected to a current measuring unit for measuring the current flowing through the n battery cells; a storage unit; and an impedance calculation unit for calculating the AC impedance of each of the n battery cells, wherein a multi-cell filter unit including a capacitive element is connected between the n battery cells and the n+1 first terminals; the negative terminal of the k (k is an integer of 1 or more and n-1 or less)th battery cell and the positive terminal of the k+1th battery cell included in the n battery cells are connected to the k+1th first terminal included in the n+1 first terminals via the multi-cell filter unit; a single-cell filter unit including a capacitive element is connected between the current measuring unit and the two second terminals; and the storage unit stores the multi-cell filter characteristics of the multi-cell filter unit and the single-cell filter characteristics of the single-cell filter unit that have been prepared in advance. Battery monitoring device, wherein the impedance calculation unit calculates the AC impedance, in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured through the n+1 first terminals, the current measured through the two second terminals, the multi-cell filter characteristics, and the single-cell filter characteristics.

2. The battery monitoring device further comprises a cell number determination unit that determines the number of cells in the n battery cells based on the voltage measured via the n+1 first terminals, the storage unit stores a plurality of multi-cell filter characteristics and a single-cell filter characteristic prepared in advance for each number of cells in the n battery cells, and the impedance calculation unit calculates the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics corresponding to the determined number of cells in the n battery cells, and the single-cell filter characteristics.

3. The battery monitoring device according to claim 2, wherein the cell count determination unit determines the number of cells in the n battery cells based on the number of first terminals from which a signal is output among the n+1 first terminals.

4. The battery monitoring device further comprises an ESR ratio calculation unit that estimates the ESR ratio of each of the n battery cells, which is the ratio of the current ESR to the undegraded ESR (Equivalent Series Resistance), based on the voltage measured via the n+1 first terminals; the storage unit stores a plurality of multi-cell filter characteristics and single-cell filter characteristics prepared in advance for each combination of the ESR ratios of the n battery cells; and the impedance calculation unit calculates the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, and the multi-cell filter characteristics and single-cell filter characteristics corresponding to the estimated combination of the ESR ratios of the n battery cells. The battery monitoring device according to any one of claims 1 to 3.

5. The battery monitoring device further comprises an ESR ratio calculation unit that estimates the ESR ratio of each of the n battery cells, which is the ratio of the current ESR to the ESR when undegraded, based on the voltage measured via the n+1 first terminals, the storage unit stores the multi-cell filter characteristics, which include the filter characteristics of the multi-cell filter unit for a target battery cell among the n battery cells and the filter characteristics for battery cells surrounding the target battery cell, and the single-cell filter characteristics, which have been prepared in advance, and the impedance calculation unit calculates the AC impedance, in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured via the n+1 first terminals, the current measured via the two second terminals, the multi-cell filter characteristics obtained by applying the battery cells among the n battery cells whose estimated ESR ratio is equal to or greater than a predetermined value to the target battery cell, and the single-cell filter characteristics.

6. The battery monitoring device further includes an ESR ratio calculation unit that estimates the ESR ratio of each of the n battery cells, which is the ratio of the current ESR to the ESR when undegraded, based on the voltage measured via the n+1 first terminals; the storage unit stores a plurality of multi-cell filter characteristics and a single-cell filter characteristic prepared in advance for each ESR ratio; the ESR ratio calculation unit selects one of the plurality of multi-cell filter characteristics; the impedance calculation unit calculates the input voltage to be input to the multi-cell filter unit based on the voltage measured via the n+1 first terminals and the selected multi-cell filter characteristic from the plurality of multi-cell filter characteristics; the ESR ratio calculation unit estimates the ESR ratio based on the input voltage and selects one of the plurality of multi-cell filter characteristics corresponding to the estimated ESR ratio. The battery monitoring device according to any one of claims 1 to 5, wherein the impedance calculation unit and the ESR ratio calculation unit repeatedly perform the process of (a) and the process of (b), and when the difference between the input voltage calculated this time and the input voltage calculated last time becomes less than or equal to a predetermined value, the impedance calculation unit calculates the AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the input voltage calculated this time, the current measured through the two second terminals, and the single-cell filter characteristics.

7. A battery monitoring method performed by a battery monitoring device that monitors n battery cells connected in series, the battery monitoring device comprising: n+1 first terminals for measuring the voltage of each of the n battery cells; two second terminals connected to a current measuring unit for measuring the current flowing through the n battery cells; and a storage unit, a multi-cell filter unit including a capacitive element is connected between the n battery cells and the n+1 first terminals, the negative terminal of the k-th battery cell (where k is an integer between 1 and n-1) and the positive terminal of the k+1-th battery cell included in the n battery cells are connected to the k+1-th first terminal included in the n+1 first terminals via the multi-cell filter unit, a single-cell filter unit including a capacitive element is connected between the current measuring unit and the two second terminals, and the storage unit stores the multi-cell filter characteristics of the multi-cell filter unit and the single-cell filter characteristics of the single-cell filter unit prepared in advance, the battery monitoring method is: A battery monitoring method comprising the steps of: calculating an AC impedance in which the components of the multi-cell filter characteristics and the single-cell filter characteristics are canceled out, based on the voltage measured through the n+1 first terminals, the current measured through the two second terminals, the multi-cell filter characteristics and the single-cell filter characteristics; and outputting the calculated AC impedance.

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