Battery monitoring device and battery monitoring method

Abstract

This battery monitoring device (1) comprises: a storage unit (24) in which relationship data is stored, the relationship data indicating the relationship between the battery state of a secondary battery (5) and a resistance component, which changes depending on the battery state of the secondary battery (5), among a plurality of resistance components that constitute the impedance of the secondary battery (5); an impedance acquisition unit (23a) that acquires the impedance of the secondary battery (5) being monitored; and an arithmetic processing unit (23) that, on the basis of the impedance acquired by the impedance acquisition unit (23a), calculates the value of a resistance component that changes depending on the battery state of the secondary battery (5) being monitored, and estimates the battery state of the secondary battery (5) being monitored on the basis of the value of the resistance component and the relationship data.

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 the battery state of a secondary battery.

[0002] In recent years, applications using secondary batteries have been rapidly increasing in battery-powered devices such as vehicles, power storage devices, stationary power supplies, automated guided vehicles (AGVs), robots, and drones. Secondary batteries such as lithium-ion batteries (LiBs) are often used in such applications due to their high energy density. Many automotive and storage batteries are configured as battery packs by arranging multiple batteries side by side and connecting them in series or parallel.

[0003] It is known that secondary batteries deteriorate due to overcharging, overdischarging, or temperature changes during use, and that secondary batteries also deteriorate due to changes in their internal state over long periods of use.

[0004] Patent Document 1 discloses a battery monitoring device that monitors the state of a secondary battery. This battery monitoring device measures the voltage, current, and temperature of all batteries in a battery pack made up of secondary batteries and monitors the state of each battery. Patent Document 2 discloses a method for measuring the AC impedance of a secondary battery and diagnosing the deterioration state of the secondary battery. Patent Document 3 discloses a method for measuring the internal resistance of a secondary battery and diagnosing the deterioration state of the secondary battery.

[0005] Japanese Patent No. 5403437 Japanese Patent No. 6842212 Japanese Patent Application Laid-Open No. 2009-288039

[0006] However, the methods disclosed in the above patent documents may not always provide accurate diagnosis results for the deterioration state of the secondary battery. Therefore, there is a need for a device that can monitor the battery state of the secondary battery based on reliable data.

[0007] The present disclosure provides a battery monitoring device and the like that can improve reliability when monitoring the battery state of a secondary battery.

[0008] A battery monitoring device according to one aspect of the present disclosure includes a memory unit that stores relationship data indicating the relationship between a resistance component that varies depending on the battery state of the secondary battery and the battery state of the secondary battery, among multiple resistance components that constitute the impedance of the secondary battery; an impedance acquisition unit that acquires the impedance of the secondary battery to be monitored; and an arithmetic processing unit that calculates the value of the resistance component that varies depending on the battery state of the secondary battery to be monitored based on the impedance acquired by the impedance acquisition unit, and estimates the battery state of the secondary battery to be monitored based on the value of the resistance component and the relationship data.

[0009] A battery monitoring method according to one aspect of the present disclosure includes a relational data acquisition step of acquiring relational data indicating the relationship between a resistance component that varies depending on the battery state of the secondary battery and the battery state of the secondary battery, among multiple resistance components that constitute the impedance of the secondary battery; an impedance acquisition step of acquiring the impedance of the secondary battery to be monitored; and a calculation step of calculating the value of the resistance component that varies depending on the battery state of the secondary battery to be monitored based on the impedance acquired in the impedance acquisition step, and estimating the battery state of the secondary battery to be monitored based on the value of the resistance component and the relational data.

[0010] According to the battery monitoring device and the like of the present disclosure, it is possible to improve the reliability when monitoring the battery state of a secondary battery.

[0011] FIG. 1 is a diagram showing the battery capacity of an initial battery and a capacity-degraded battery. FIG. 2 is a diagram showing a flow for quantifying the amount of lithium remaining in the negative electrode of a battery. FIG. 3 is a diagram showing an equivalent circuit model and impedance of a secondary battery. FIG. 4 is a diagram showing an example of a Nyquist plot. FIG. 5 is a Nyquist plot of a secondary battery. FIG. 6 is a diagram showing the resistance component of the wiring system among the multiple resistance components that make up the impedance of a secondary battery. FIG. 7 is a diagram showing the state after the resistance component of the wiring system has been removed from the multiple resistance components of a secondary battery. FIG. 8 is a diagram showing the state after the resistance component of the wiring system and the resistance component due to the electrolyte have been removed from the multiple resistance components of a secondary battery. FIG. 9 is a diagram showing the state after the resistance component of the wiring system, the resistance component due to the electrolyte, the resistance component of the negative electrode, and the resistance component of the positive electrode have been removed from the multiple resistance components of a secondary battery, and the resistance component due to deposits has been extracted. FIG. 10 is a diagram showing a flow for deriving the relationship between the resistance component due to deposits and the amount of capacity loss. FIG. 11 is a diagram showing relationship data between the resistance component due to deposits and the amount of capacity loss. FIG. 12 is a block diagram of a battery monitoring device according to embodiment 1. FIG. 13 is a perspective view of a battery monitoring device according to the first embodiment. FIG. 14 is a diagram showing an operation flow of the battery monitoring device according to the first embodiment. FIG. 15 is a diagram showing an operation flow of the battery monitoring device according to the first modification of the first embodiment. FIG. 16 is a diagram showing a flow for acquiring battery temperature. FIG. 17 is a diagram showing relationship data between the resistance component due to deposits and the battery temperature. FIG. 18 is a diagram showing the relationship between the resistance component due to deposits, the battery temperature, and the SOH. FIG. 19 is a block diagram of a battery monitoring device according to the second modification of the first embodiment. FIG. 20 is a diagram showing another example of measuring the impedance of a secondary battery using the battery monitoring device according to the third modification of the first embodiment. FIG. 21 is a diagram showing yet another example of measuring the impedance of a secondary battery using the battery monitoring device according to the third modification of the first embodiment. FIG. 22 is a block diagram of a battery monitoring device according to the second embodiment. FIG. 23 is a perspective view of a battery monitoring device according to the second embodiment. FIG. 24 is a diagram showing relationship data between the resistance component due to deposits and the SOH. FIG. 25 is a diagram showing relationship data between the resistance component due to the electrolyte and the battery temperature.FIG. 26 is a diagram showing a state in which the resistance components of the wiring system and the resistance components due to deposits are removed from the multiple resistance components of a secondary battery. FIG. 27 is a diagram showing a state in which the resistance components of the wiring system, the resistance components due to deposits, the resistance components of the negative electrode, and the resistance components of the positive electrode are removed from the multiple resistance components of a secondary battery, and the resistance component due to the electrolyte is extracted. FIG. 28 is a diagram showing an operation flow of a battery monitoring device according to a second embodiment. FIG. 29 is a diagram showing a method for correcting an estimated value of the internal temperature of a secondary battery, performed in a first modification of the second embodiment. FIG. 30 is a diagram showing the relationship between the resistance component due to deposits, battery temperature, and SOH. FIG. 31 is a diagram showing the relationship between the resistance component of the wiring system, battery temperature, and SOH. FIG. 32 is a diagram showing the relationship between the resistance component due to the electrolyte, battery temperature, and SOH. FIG. 33 is a block diagram of a battery monitoring device according to a second modification of the second embodiment. FIG. 34 is a block diagram of a battery monitoring device according to a third embodiment. FIG. 35 is a perspective view of a battery monitoring device according to the third embodiment. FIG. 36 is a diagram showing an example of temperature correction data. FIG. 37 is a flowchart showing the operation of a battery monitoring device according to the third embodiment. FIG. 38 is a flowchart showing the operation of a battery monitoring device according to Modification 1 of Embodiment 3. FIG. 39 is a perspective view of a battery monitoring device according to Modification 2 of Embodiment 3. FIG. 40 is a flowchart showing the operation of a battery monitoring device according to Modification 2 of Embodiment 3. FIG. 41 is a flowchart showing the operation of a battery monitoring device according to Modification 3 of Embodiment 3. FIG. 42 is a flowchart showing the operation of a battery monitoring device according to Modification 4 of Embodiment 3. FIG. 43 is a flowchart showing the operation of a battery monitoring device according to Modification 5 of Embodiment 3. FIG. 44 is a perspective view of a battery monitoring device according to Modification 6 of Embodiment 3. FIG. 45 is a diagram showing a resistor of a battery monitoring device according to Modification 6 of Embodiment 3. FIG. 46 is a perspective view of a battery monitoring device according to Modification 7 of Embodiment 3. FIG. 47 is a diagram showing an assembled battery connected to a battery monitoring device as seen from above. FIG. 48 is a diagram showing terminals of a secondary battery as seen from above. FIG. 49 is a perspective view showing another example of a secondary battery. FIG. 50 is a diagram showing an example of a secondary battery and a thermally conductive member. FIG. 51 is a diagram showing another example of a secondary battery and a thermally conductive member.

[0012] (Foundational Knowledge of the Present Disclosure) The fundamental knowledge of the present disclosure will be described below. In the present disclosure, a lithium ion battery, which is an example of a secondary battery, will be described as an example.

[0013] First, the decrease in battery capacity of a lithium ion battery and the deposits that occur on the negative electrode of the lithium ion battery will be described.

[0014] Below is an equation showing the chemical reactions that occur in a lithium-ion battery.

[0015]

[0016]

[0017]

[0018] The above formula (1) includes lithium cobalt oxide (LiCoO ２ The reaction of the graphite or carbon material at the negative electrode is shown in (Equation 2). The reaction of the entire battery is shown in (Equation 3).

[0019] In each equation, the charge reaction proceeds from left to right, and the discharge reaction proceeds in reverse. As shown in these equations, in lithium-ion batteries, lithium ions travel back and forth between the negative and positive electrodes, enabling reversible battery reactions.

[0020] In lithium-ion batteries, repeated charging and discharging or long-term storage can cause internal degradation reactions. For example, lithium ions that reversibly move between the positive and negative electrodes are consumed by reactions such as electrolyte decomposition at the active material interface, surface film formation (e.g., SEI growth), and lithium metal deposition (lithium plating).

[0021] FIG. 1 is a diagram showing the battery capacities of an initial battery product and a capacity-degraded battery product.

[0022] The figure shows the results of measuring the 0.2 C discharge capacity and capacity loss of an initial battery with a nominal capacity of 10 Ah and several capacity-degraded batteries. Note that the capacity loss of the initial battery shown in the figure is the capacity loss that occurs during charging and discharging during the production process.

[0023] In the figure, the more degraded the capacity of the battery, the further to the right it is on the horizontal axis. As shown in the figure, the more degraded the capacity of the battery, the smaller the discharge capacity, but the greater the capacity loss.

[0024] In lithium-ion batteries, deposits form on the surface of the negative electrode, which faces the positive electrode through the separator. Deposits form due to a variety of factors, including electrolyte reactions on the electrode surface, the deposition of metal components of the active material eluted from the positive electrode on the negative electrode, and lithium metal deposition due to concentrated current density. When deposits form, they block the pores between the active material particles, preventing lithium ions from passing through. This traps lithium in the negative electrode (inside the graphite), hindering reversible reactions and reducing battery capacity. Furthermore, physical structural changes in the electrode during charging and discharging can disrupt the conductive network between the active materials, isolating the active materials and trapping lithium in the negative electrode, reducing battery capacity.

[0025] Furthermore, the occurrence of deposits as described above increases the impedance of the battery, which in turn causes a corresponding voltage drop (during discharge) or voltage increase (during charge), leading to a decrease in battery capacity.

[0026] As described above, capacity loss occurs when a battery is repeatedly charged and discharged or when the battery is left for a long period of time. Furthermore, capacity loss occurs when lithium is trapped in the negative electrode. Since the amount of lithium trapped in the negative electrode increases, the capacity loss of the secondary battery also increases. Therefore, in this disclosure, the capacity loss is calculated based on the amount of lithium remaining in the negative electrode (the amount of irreversible lithium).

[0027] The amount of capacity loss is calculated by converting the amount of lithium remaining in the negative electrode into electrical capacity using the following (Equation 4).

[0028]

[0029] For example, the amount of electricity required for one mole of lithium ions to move is equivalent to 96,500 coulombs (C) according to Faraday's constant. Converting the amount of coulombs to electrical capacity A-hours gives 96,500 ÷ 3,600 = 26.8 (A-hours).

[0030] Therefore, the amount of lithium remaining in the negative electrode is converted into the number of moles and converted into electrical capacity using Equation 4. This converted electrical capacity is the amount of capacity loss in the battery.

[0031] The amount of lithium to be substituted into (Equation 4) can be obtained, for example, by dismantling an initial battery (an unused battery) and a capacity-degraded battery whose capacity has decreased, and quantitatively analyzing the amount of lithium remaining in the negative electrode.

[0032] Figure 2 shows a flow chart for quantifying the amount of lithium remaining in the negative electrode of a battery. The flow chart also includes a step for determining the impedance of the battery. The battery in Figure 2 is a data acquisition battery.

[0033] First, the SOC (State of Charge) of the target battery is adjusted to 0% using a charge / discharge device (step S10). Note that 0% SOC refers to a state in which the battery has been discharged at a constant current (CC) until it reaches the minimum operating voltage. For example, if the operating voltage is between 2.75V and 4.2V, the SOC is adjusted by CC discharging the battery to 2.75V at a current value of 0.2C.

[0034] Next, before disassembling the battery, the impedance of each of the initial battery and the multiple capacity-degraded batteries is measured (step S20). The impedance is measured in order to understand the relationship between the impedance of the initial battery and the multiple capacity-degraded batteries and the amount of capacity loss calculated from the amount of lithium remaining in the negative electrode. For example, if the correlation between the impedance and the amount of capacity loss of a battery can be understood, it is possible to determine the amount of capacity loss of the battery by measuring the impedance of the battery to be monitored. This will be described later.

[0035] To quantify the amount of lithium remaining in the negative electrode, the battery is disassembled in a facility where the dew point is controlled (step S31), and the negative electrode is removed (step S32). Next, the negative electrode is washed with a non-aqueous solvent (e.g., diethyl carbonate, ethyl methyl carbonate, etc.) (step S33), and vacuum dried (step S34) to remove the solvent component. The dew point is preferably −40° C. or lower.

[0036] After vacuum drying, the density and area of ​​the negative electrode are measured (step S35). Next, the active material layer (or slurry layer) is removed from the negative electrode using a spatula or the like (step S36). A sample to be subjected to ICP (inductively coupled plasma) emission spectroscopy (ICP measurement sample) is prepared, and the weight of the ICP measurement sample is measured (step S37). The active material layer is then extracted with an acid solvent (step S38) to obtain an extract containing the constituent elements. The extract is then subjected to ICP analysis (step S39), and the amount of lithium is quantified (step S40).

[0037] The capacity loss can be calculated using the above formula (4). Specifically, the amount of lithium obtained by ICP analysis is converted into moles, and the amount of lithium remaining in the negative electrode is converted to electrical capacity (step S41). The converted electrical capacity is the capacity loss of the battery. This allows the capacity loss of the battery to be obtained (step S42).

[0038] Next, a specific impedance related to the amount of capacity loss is extracted from the measured impedances of the initial product and the plurality of capacity-degraded products obtained in step S20.

[0039] 3A and 3B are diagrams showing an equivalent circuit model and impedance of a secondary battery, in which (a) shows the equivalent circuit model of the secondary battery, and (b) shows an equation expressing the relationship of the impedance of the secondary battery.

[0040] As shown in Fig. 3(a), the equivalent circuit of a secondary battery is a circuit including multiple resistance components. As shown in Fig. 3(b), the impedance of a secondary battery is composed of multiple resistance components. The multiple resistance components shown in Fig. 3 are a resistance component I of the wiring system, a resistance component II due to the electrolyte, a resistance component III due to deposits, a resistance component IV of the negative electrode, and a resistance component V of the positive electrode.

[0041] The resistance component I of the wiring system is the impedance of the wiring and the impedance between the wiring and the secondary battery. The resistance component I of the wiring system is a component that generates electrical resistance (including contact resistance and welding resistance) when electrons move, such as metals such as the wiring, battery terminals 31, bus bars 32 (see FIG. 13), and current collector foils in the secondary battery. Therefore, the resistance component I of the wiring system does not contribute to the electrochemical capacity loss of the secondary battery. The value of the resistance component I of the wiring system is observed on the high frequency side (e.g., 1 kHz or higher) and can be measured by AC impedance measurement or DC resistance measurement.

[0042] The resistance component II due to the electrolyte is the impedance resulting from the migration resistance in the electrolyte of the secondary battery. The resistance component II due to the electrolyte is caused by the physical resistance when lithium ions move. The resistance component II due to the electrolyte is affected by the electrolyte salt concentration of the electrolyte, the ionic conductivity of the non-aqueous electrolyte, the viscosity (specific gravity) of the electrolyte, the pore size of the separator (ease of lithium ion passage), etc.

[0043] The resistance component III due to deposits is the impedance resulting from the resistance of deposits on the electrode surface. Deposits are produced by by-products of electrochemical reactions, such as reactions of the electrolyte on the active material surface, deposition of metal components of the active material eluted from the positive electrode on the negative electrode, or lithium metal deposition due to current density concentration. The formation of these deposits increases the impedance of the secondary battery, while blocking pores between the negative electrode active material, preventing the passage of lithium ions and trapping lithium in the negative electrode (inside the graphite). These deposits increase when the secondary battery is repeatedly charged and discharged or when the secondary battery is left in storage for a long period of time.

[0044] The negative electrode resistance component IV represents the impedance of the negative electrode of the secondary battery. The positive electrode resistance component V represents the impedance of the positive electrode of the secondary battery. These resistance components IV and V represent the internal or surface impedance of the active material, conductive additive, etc. that constitute the electrode.

[0045] Among the multiple resistance components, the resistance component III due to deposits is involved in the capacity loss of the secondary battery, compared to the resistance component I due to the wiring system, the resistance component II due to the electrolyte, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode.

[0046] Since it is difficult to directly measure the impedance of the resistance component III due to deposits, in this example, the impedance of other resistance components is subtracted from the measured impedance of the secondary battery to obtain the impedance of the resistance component III due to deposits. Also, in this example, a Nyquist plot of the secondary battery is used to obtain the resistance component III due to deposits.

[0047] FIG. 4 is a diagram showing an example of a Nyquist plot.

[0048] The Nyquist plot is a diagram on a complex plane that depicts the change in impedance when the frequency of a secondary battery is swept. The horizontal axis of Fig. 4 represents the real part ReZ of the complex impedance Z, and the vertical axis represents the imaginary part ImZ of the complex impedance Z.

[0049] Region (i) is the region of the ohmic resistance of the secondary battery, which corresponds to the resistance component I of the wiring system, the resistance component II of the electrolyte, and the resistance component III of the deposits. Region (ii) is the region of the reaction resistance of the secondary battery, which corresponds to the resistance component IV of the negative electrode and the resistance component V of the positive electrode. Region (iii) is the region of the diffusion resistance of the secondary battery, which reflects the influence of the Warburg impedance of the secondary battery.

[0050] The following describes a procedure for extracting the resistance component III due to deposits using a Nyquist plot. This procedure is applicable to both extracting the resistance component III due to deposits from the measured impedance of an initial secondary battery and a deteriorated secondary battery, and extracting the resistance component III due to deposits from the measured impedance of a secondary battery to be monitored.

[0051] 5 is a Nyquist plot of a secondary battery, showing the impedance changes of an initial secondary battery and a deteriorated battery.

[0052] Fig. 6 shows the resistance component I of the wiring system among the multiple resistance components that make up the impedance of a secondary battery. Fig. 6(a) shows a Nyquist plot illustrating the change in impedance of the resistance component I of the wiring system. Fig. 6(b) shows an equivalent circuit of the secondary battery.

[0053] Fig. 7 is a diagram showing the state of a secondary battery after removing the resistance component I of the wiring system from the multiple resistance components. Fig. 7(a) shows a Nyquist plot illustrating the impedance changes of the resistance component II due to the electrolyte, the resistance component III due to deposits, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode. Fig. 7(b) shows an equivalent circuit of the resistance component II due to the electrolyte, the resistance component III due to deposits, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode.

[0054] Fig. 8 is a diagram showing the state of a secondary battery after removing the resistance component I of the wiring system and the resistance component II of the electrolyte from the multiple resistance components. Fig. 8(a) shows a Nyquist plot illustrating the impedance changes of the resistance component III of the deposits, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode. Fig. 8(b) shows an equivalent circuit of the resistance component III of the deposits, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode. The method for determining the resistance component II of the electrolyte will be described later.

[0055] 9 shows the state in which the resistance component III due to deposits is extracted from the multiple resistance components of a secondary battery, excluding the resistance component I of the wiring system, the resistance component II due to the electrolyte, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode. (a) of FIG. 9 shows a Nyquist plot illustrating the impedance change of the resistance component III due to deposits. As shown in the figure, the value of the resistance component III due to deposits is expressed only by the real part of the complex impedance Z. (b) of FIG. 9 shows an equivalent circuit of the resistance component III due to deposits.

[0056] In this way, the resistance component III due to deposits is extracted by subtracting the resistance component I of the wiring system, the resistance component II due to the electrolyte, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode from the impedance of the secondary battery.

[0057] The resistance component III due to deposits is a parameter related to the capacity loss of the secondary battery, and its value varies depending on the amount of capacity loss of the secondary battery. Therefore, if the relationship between the resistance component III due to deposits and the amount of capacity loss can be determined in advance, it is thought that the capacity loss of the secondary battery can be estimated based on the impedance of the secondary battery being monitored.

[0058] 10 is a diagram showing a flow for deriving the relationship between the resistance component III due to deposits and the amount of capacity loss. The secondary battery in FIG. 10 is a secondary battery for data collection.

[0059] Fig. 10 shows the process corresponding to step S20 in Fig. 2 and the subsequent process. Below, steps S21 to S24 are shown as the process corresponding to step S20 in Fig. 2, and step S25 is shown as the subsequent process.

[0060] First, the impedance of an initial secondary battery is measured (step S21). Then, the impedance obtained for the initial battery is subjected to curve fitting in a Nyquist plot to obtain the resistance component I of the wiring system (step S22). Note that the resistance component I of the wiring system differs for each secondary battery due to differences in the length and type of wiring, the length of the bus bar, the welding resistance of the connection points, etc., and therefore individual measurements and calculation of the impedance value are required.

[0061] Next, the impedance of each of the initial secondary battery and the plurality of capacity-degraded secondary batteries is measured (step S23). Note that step S23 may be performed before steps S21 and S22.

[0062] Next, the resistance component I of the wiring system, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode are subtracted from the measured impedance. The resistance component IV of the negative electrode and the resistance component V of the positive electrode are obtained by curve fitting in a Nyquist plot. The value obtained by subtracting these resistance components from the measured impedance is the combined value of the resistance component II due to the electrolyte and the resistance component III due to the deposits. This obtains the combined value of the resistance component II due to the electrolyte and the resistance component III due to the deposits (step S24).

[0063] 2 and the combined value of the resistance component II due to the electrolyte and the resistance component III due to the deposits obtained in step S24 are plotted on a graph, thereby obtaining the relationship between the capacity loss of the secondary battery and the resistance component II due to the electrolyte and the resistance component III due to the deposits (step S25).

[0064] 11 shows data relating to the resistance component III due to deposits and the amount of capacity loss. The horizontal axis of the figure represents the amount of capacity loss of the secondary battery, and the left vertical axis represents the combined value of the resistance component II due to the electrolyte and the resistance component III due to deposits. The right vertical axis represents the resistance component III due to deposits.

[0065] As shown in the figure, the capacity loss of a secondary battery is correlated with the resistance component II due to the electrolyte and the resistance component III due to deposits, as shown by the first relational expression E1. The first relational expression E1 can be obtained, for example, by the least squares method and expressed as a linear equation. In this example, the slope of the first relational expression E1 represents the relationship between the capacity loss and the resistance component III due to deposits. Furthermore, in the figure, the value at which the capacity loss is 0 (zero) when the straight line connecting each plot is extended is the resistance component II due to the electrolyte. In this example, the intercept of the first relational expression E1 is the value (fixed value) of the resistance component II due to the electrolyte.

[0066] When attention is focused only on the resistance component III due to the deposits and excluding the resistance component II due to the electrolyte, the first relational expression E1 becomes relational data represented by the horizontal axis and the right vertical axis in FIG.

[0067] These steps result in obtaining a first relational expression E1 that indicates the relationship between the resistance component III due to deposits and the amount of capacity loss of the secondary battery. This allows the amount of capacity loss of the secondary battery to be determined by measuring the impedance of the secondary battery to be monitored, extracting the resistance component III due to deposits that contributes to the amount of capacity loss from the impedance, and substituting the extracted resistance component III into the first relational expression E1.

[0068] Furthermore, the SOH (State of Health) can be calculated based on the following (Equation 5).

[0069]

[0070] The SOH of the secondary battery being monitored is calculated by subtracting the amount of capacity loss from the initial capacity (the capacity set when the battery was first used), as shown in Equation 5. Note that the SOH is the ratio of the full charge capacity (Ah) of the initial battery to the full charge capacity (Ah) of the deteriorated battery, assuming that the full charge capacity (Ah) of the initial battery is 100%.

[0071] It is believed that by undergoing these processes, it is possible to improve the reliability in monitoring the battery state of the secondary battery, specifically, the reliability in monitoring the amount of capacity loss and SOH.

[0072] Hereinafter, the embodiments will be described in detail with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims will be described as optional components.

[0073] It should be noted that the drawings are schematic diagrams and are not necessarily strict illustrations. In addition, in the drawings, substantially the same components are denoted by the same reference numerals, and overlapping descriptions may be omitted or simplified.

[0074] (Embodiment 1) [Configuration of Battery Monitoring Device] A description will be given of a schematic configuration of a battery monitoring device according to embodiment 1. The following describes an example in which the battery monitoring device is applied to a power supply system of a vehicle (for example, a hybrid vehicle or an electric vehicle).

[0075] Hereinafter, the resistance component III due to the deposits may be referred to as a first resistance component. The resistance component III due to the deposits is an example of the first resistance component.

[0076] Fig. 12 is a schematic configuration diagram showing an example of a battery monitoring device 1 according to embodiment 1. Fig. 13 is a perspective view of the battery monitoring device 1 according to embodiment 1. In addition to the battery monitoring device 1, Fig. 12 also shows a host control unit 2, a load 3, and a relay 4. In addition to the battery monitoring device 1, Fig. 13 also shows a battery pack 6, a thermistor 16, a current application line 11, a voltage detection line 12, and the like.

[0077] 12, the battery monitoring device 1 is connected to a battery pack 6 that is a combination of a plurality of secondary batteries 5 (for example, batteries C0 to C7). The secondary batteries 5 are, for example, lithium ion batteries, but are not limited to this and may be other batteries such as nickel-metal hydride batteries.

[0078] A relay 4 is provided between the battery pack 6 and a load 3 (e.g., a motor, an inverter, or an accelerator) to turn on / off the connection between the battery pack 6 and the load 3. In the vehicle, an application is operated in response to the on / off of the connection between the battery pack 6 and the load 3 by the relay 4. Note that if the multiple secondary batteries 5 are storage batteries, the load 3 may be a charger.

[0079] The battery monitoring device 1 is a device that acquires the internal impedance of multiple secondary batteries 5 and monitors the battery states of the secondary batteries 5. For example, the battery monitoring device 1 measures and acquires the internal AC impedance of the multiple secondary batteries 5. Also, for example, the battery monitoring device 1 measures and acquires the internal impedance (e.g., internal AC impedance) of each of the multiple secondary batteries 5.

[0080] The battery monitoring device 1 includes a measurement unit 7 , a battery monitoring unit 8 , a control unit 9 , and a communication unit 10 .

[0081] The battery monitoring device 1 measures the internal AC impedance of the plurality of secondary batteries 5 (e.g., the internal AC impedance of each of the plurality of secondary batteries 5) based on the AC current applied to the battery pack 6 and the voltages of the plurality of secondary batteries 5 (e.g., the voltages of each of the plurality of secondary batteries 5) that make up the battery pack 6. For example, the battery monitoring device 1 measures the internal AC impedance characteristics of the secondary batteries 5 using EIS (electro-chemical impedance spectroscopy) and monitors the battery state of the secondary batteries 5 in real time.

[0082] The battery pack 6 and the battery monitoring device 1 are connected by a current application line 11 and a plurality of voltage detection lines 12 .

[0083] The battery pack 6 functions as a power source for the upper control unit 2 and the load 3 (or charging unit), and supplies power to the upper control unit 2 and the load 3 (or charging unit).

[0084] The measurement unit 7 is an example of a CMU (Cell Management Unit). The measurement unit 7 includes a voltage measurement unit 13 that measures the voltage of the battery pack 6, a current measurement unit 14 that measures the current, and an external temperature acquisition unit 15 that measures the external temperature of the secondary battery 5. The measurement unit 7 also includes a reference resistor 14a, a thermistor 16 that measures the external temperature of the battery, a load resistor 17, a switching element 18, a shunt resistor (AC superposition) 19, a signal generation unit 20, an AC superposition measurement unit (voltage conversion) 21, and a timing generation unit 22.

[0085] The control unit 9, the voltage measurement unit 13, the signal generation unit 20, the AC superposition measurement unit 21, and the timing generation unit 22 are functional components for measuring the internal AC impedance of the battery pack 6 (specifically, the multiple secondary batteries 5 that make up the battery pack 6).

[0086] The load resistor 17 , the switching element 18 and the shunt resistor 19 form a circuit for measuring the internal AC impedance of the battery pack 6 .

[0087] The control unit 9 controls the signal generating unit 20 that sweeps the AC signal, thereby turning the switching element 18 on and off at a specific frequency, thereby causing the battery pack 6 to output an AC current at a specific frequency.

[0088] The AC superposition measuring unit 21 measures the voltage generated across the shunt resistor 19 (i.e., the voltage converted from the AC current output from the battery pack 6).

[0089] The load resistor 17 and the battery pack 6, and the shunt resistor 19 and the battery pack 6 are each connected via a current application line 11. The load resistor 17 and the shunt resistor 19 are included in the battery monitoring device 1, and the battery monitoring device 1 and the battery pack 6 are connected via the current application line 11. The current application line 11 is a wiring, such as a conductor, for applying an AC current to the battery pack 6.

[0090] The voltage measurement unit 13 measures the voltages of the multiple secondary batteries 5 that make up the assembled battery 6. The voltage measurement unit 13 may measure the voltages of all of the secondary batteries 5 that make up the assembled battery 6. Alternatively, the voltage measurement unit 13 may measure the voltages of some (for example, at least two) of the secondary batteries 5 that make up the assembled battery 6. In other words, the assembled battery 6 may include secondary batteries 5 whose voltages are not measured by the voltage measurement unit 13.

[0091] The voltage measurement unit 13 measures the voltages of the multiple secondary batteries 5 that make up the battery pack 6 at the same timing, at the measurement timing set by the timing generation unit 22 .

[0092] The voltage measurement unit 13 is connected to the plurality of secondary batteries 5 via the plurality of voltage detection lines 12, and measures the voltages of the plurality of secondary batteries 5 (for example, the voltages of the respective secondary batteries 5).

[0093] The plurality of voltage detection lines 12 are wirings for detecting the voltages of the plurality of secondary batteries 5 (for example, the voltages of the respective secondary batteries 5).

[0094] As shown in Fig. 13, the voltage detection wires 12 are connected to the positive battery terminal 31a and negative battery terminal 31b of each of the multiple secondary batteries 5. In the example shown in Fig. 13, 16 voltage detection wires 12 are provided for the eight batteries C0 to C7. The voltage detection wires 12 are, for example, conductive wires.

[0095] The external temperature acquisition unit 15 measures and acquires the external temperature of the secondary battery 5 using a thermistor 16. The thermistor 16 is disposed, for example, on a side surface of the battery pack 6, on a terminal portion of the battery pack 6, or on a part of a bus bar 32 that connects the secondary batteries in series or parallel (see FIG. 13 ). The thermistor 16 may be a temperature sensor using other elements such as a thermocouple.

[0096] The battery monitoring unit 8 shown in FIG. 12 is a BMU (Battery Management Unit), and includes an arithmetic processing unit 23 and a storage unit 24 .

[0097] The memory unit 24 stores in advance relational data indicating the relationship between a resistance component that changes depending on the battery state of the secondary battery 5 and the battery state of the secondary battery 5. Specifically, the memory unit 24 stores a first relational formula E1 that indicates the relationship between a first resistance component that changes depending on the amount of capacity loss of the secondary battery 5 and the amount of capacity loss of the secondary battery 5. In this example, the first resistance component is a resistance component III due to deposits accumulated on the surface of the negative electrode of the secondary battery 5. Note that the first relational formula E1 is an example of relational data.

[0098] The first relational equation E1 stored in the memory unit 24 is derived based on the amount of capacity loss of the plurality of secondary batteries 5 whose battery capacity is equal to or less than that of the initial product, as described above, and the plurality of first resistance components obtained by measuring the impedance of the plurality of secondary batteries 5 in advance.

[0099] The capacity loss amount of the secondary battery 5 in the first relational expression E1 is calculated based on the amount of irreversible lithium remaining in the negative electrode of the secondary battery 5. Furthermore, the first resistance component in the first relational expression E1 is obtained by subtracting from the impedance of the secondary battery 5 whose battery capacity is equal to or less than that of the initial product: a resistance component I of the wiring system, which is the resistance component between the wiring connected to the secondary battery 5 and the secondary battery 5; a resistance component II based on the migration resistance in the electrolyte of the secondary battery 5; and a resistance component IV of the negative electrode and a resistance component V of the positive electrode of the secondary battery 5.

[0100] The storage unit 24 also stores the value of the resistance component II due to the electrolyte solution obtained in the process of deriving the first relational expression E1, and the value of the resistance component I of the wiring system obtained in step S22 of Fig. 10. The value of the resistance component II due to the electrolyte solution and the value of the resistance component I of the wiring system are fixed values ​​that do not fluctuate due to deterioration of the secondary battery 5.

[0101] The calculation processing unit 23 performs calculation processing on the information output from the measurement unit 7 and the information stored in the storage unit 24 to obtain information on the battery state (amount of capacity loss, SOH) of the secondary battery 5. Note that the battery state may include battery abnormalities (failure, degradation).

[0102] The calculation processing unit 23 of this embodiment calculates the value of the resistance component that changes depending on the battery state of the secondary battery 5 to be monitored, based on the impedance measured by the measurement unit 7, and estimates the battery state of the secondary battery 5 based on the value of the resistance component and the relationship data stored in the memory unit 24.

[0103] To perform the above processing, the calculation processing unit 23 includes an impedance acquisition unit 23a, a capacity loss factor extraction unit 23b, a temperature correction unit 23c, a capacity loss estimation unit 23d, and an SOH calculation unit 23e.

[0104] The impedance acquisition unit 23a, capacity loss factor extraction unit 23b, temperature correction unit 23c, capacity loss estimation unit 23d, and SOH calculation unit 23e are functional components for estimating the amount of capacity loss and SOH of batteries C0 to C7.

[0105] The impedance acquisition unit 23a acquires the impedances Z0 to Z7 of the batteries C0 to C7 based on the voltages V0 to V7 of the batteries C0 to C7 measured by the voltage measurement unit 13 and the current value Iac measured and converted to voltage by the AC superposition measurement unit 21. Each of the impedances Z0 to Z7 is a complex number, and a real part ReZ and an imaginary part ImZ are calculated for each of the batteries C0 to C7. The calculated complex impedance is the ratio of the voltage measured by the voltage measurement unit 13 to the current measured by the AC superposition measurement unit 21 at each frequency when the signal generation unit 20 outputs AC current from the battery pack 6 at each frequency. By plotting the complex impedances on a complex plane, Nyquist plots such as those shown in FIGS. 5 to 9 can be obtained. The impedance acquisition unit 23a outputs the calculated complex impedance values ​​Z0 to Z7 of the batteries C0 to C7 to the capacity loss factor extraction unit 23b.

[0106] The capacity loss factor extracting unit 23b extracts the resistance component III due to deposits, which is a capacity loss factor of the secondary battery 5, based on the complex impedance values ​​Z0 to Z7 of the batteries C0 to C7.

[0107] The calculation processing unit 23 performs the following process to estimate the amount of capacity loss of the secondary battery 5 based on the resistance component III due to deposits, which is the first resistance component.

[0108] For example, the capacity loss factor extraction unit 23b calculates the value of the first resistance component of the secondary battery 5 to be monitored based on the impedance acquired by the impedance acquisition unit 23a. When calculating the value of the first resistance component, the calculation processing unit 23 calculates the value of the first resistance component by subtracting from the impedance acquired by the impedance acquisition unit 23a a resistance component I of the wiring system, which is the resistance component of the wiring connected to the secondary battery 5 and between the wiring and the secondary battery 5, a resistance component II based on the transfer resistance in the electrolyte of the secondary battery 5, and a resistance component IV of the negative electrode and a resistance component V of the positive electrode of the secondary battery 5.

[0109] The resistance component I of the wiring system is a value obtained in step S22 of FIG. 10 and is stored in advance in the memory unit 24. The resistance component II due to the electrolyte solution is a value derived from the first relational expression E1 of FIG. 11 and is stored in advance in the memory unit 24. The resistance component IV of the negative electrode and the resistance component V of the positive electrode are values ​​obtained by curve fitting in a Nyquist plot showing the impedance change of the secondary battery 5. Note that, although the above example illustrates the case where the impedance of the resistance component II due to the electrolyte solution is derived from the first relational expression E1, this is not limiting. For example, the resistance component II due to the electrolyte solution can also be calculated from the ionic conductivity of the electrolyte solution used in the secondary battery. In other words, the resistance component II due to the electrolyte solution stored in the memory unit 24 may be a value calculated from the ionic conductivity.

[0110] Information about the first resistance component (resistance component III due to deposits) extracted by the capacity loss factor extraction unit 23b is output to the temperature correction unit 23c or the capacity loss estimation unit 23d.

[0111] The capacity loss estimation unit 23d estimates the amount of capacity loss of the secondary battery 5 based on the value of the first resistance component and the first relational expression E1 stored in the storage unit 24. Specifically, the capacity loss estimation unit 23d derives the amount of capacity loss of the secondary battery 5 by substituting the value of the first resistance component into the first relational expression E1. The derived amount of capacity loss is output to the SOH calculation unit 23e.

[0112] The capacity loss estimation unit 23 d may estimate the capacity loss amount based on the relationship data between the value of the first resistance component and the capacity loss amount after the temperature correction is performed by the temperature correction unit 23 c. The temperature correction will be described later in Modification 1.

[0113] The SOH calculation unit 23e estimates the current capacity of the secondary battery 5 by subtracting the amount of capacity loss estimated by the calculation processing unit 23 from the initial capacity of the secondary battery 5. For example, the SOH calculation unit 23e calculates the SOH from the difference between the initial capacity (the capacity set when the battery started to be used) and the amount of capacity loss using the above (Equation 5). Information about the SOH calculated by the SOH calculation unit 23e is stored in the storage unit 24.

[0114] Furthermore, information relating to the amount of capacity loss, SOH, and abnormality of batteries C0 to C7 obtained by arithmetic processing unit 23 is notified to host control unit 2 via storage unit 24, control unit 9, and communication unit 10. Communication unit 10 is a communication module that transmits the above information wirelessly or via a wire to host control unit 2. Host control unit 2 executes control in the vehicle according to the notified amount of capacity loss, SOH, abnormality, etc. of secondary battery 5.

[0115] The battery monitoring device 1 of this embodiment calculates the value of the resistance component III due to deposits based on the impedance acquired by the impedance acquisition unit 23a. Then, the battery state of the secondary battery 5 is estimated based on the value of the resistance component III due to deposits and the first relational expression E1. By monitoring the battery state of the secondary battery 5 based on reliable data in this manner, the reliability of monitoring the battery state of the secondary battery 5 can be improved.

[0116] [Operation of Battery Monitoring Device] The operation of the battery monitoring device 1 according to the first embodiment will be described.

[0117] FIG. 14 is a diagram showing an operation flow of the battery monitoring device 1 according to the first embodiment.

[0118] The battery monitoring device 1 stores initial information required for monitoring the secondary battery 5 in the storage unit 24 (step S110). The initial information includes, for example, a first relational expression E1 that indicates the relationship between a first resistance component that varies depending on the amount of capacity loss of the secondary battery 5 and the amount of capacity loss of the secondary battery 5. The first relational expression E1 is expressed, for example, as a linear expression, but is not limited to this and may be expressed as a gentle quadratic curve. The initial information also includes the value of the resistance component I of the wiring system and the value of the resistance component II due to the electrolyte.

[0119] Next, the battery monitoring device 1 acquires the impedance of the secondary battery 5 to be monitored (step S120).

[0120] Next, the battery monitoring device 1 calculates the value of the first resistance component of the secondary battery 5 to be monitored (step S130). Specifically, the battery monitoring device 1 calculates the value of the resistance component III due to deposits of the secondary battery 5 to be monitored based on the impedance acquired in step S120. The resistance component III due to deposits, i.e., the value of the first resistance component, is derived by the process shown in FIGS. 5 to 9.

[0121] Next, the battery monitoring device 1 estimates the amount of capacity loss of the secondary battery 5 to be monitored based on the value of the first resistance component obtained in step S130 and the first relational expression E1 stored in the memory unit 24 (step S140).

[0122] Next, the battery monitoring device 1 estimates the current capacity of the secondary battery 5 to be monitored by subtracting the amount of capacity loss from the initial capacity of the secondary battery 5 (step S150).

[0123] By carrying out these steps, it is possible to improve the reliability of monitoring the amount of capacity loss and the current capacity of the secondary battery 5.

[0124] [First Modification of First Embodiment] A battery monitoring device 1 according to a first modification of the first embodiment will be described. In the first modification, an example will be described in which temperature correction is performed on the resistance component III due to deposits calculated by the arithmetic processing unit 23.

[0125] The battery monitoring device 1 of the first modification includes a measurement unit 7, a battery monitoring unit 8, a control unit 9, and a communication unit 10. The battery monitoring unit 8 includes an arithmetic processing unit 23 and a storage unit 24. The configurations of the measurement unit 7, battery monitoring unit 8, control unit 9, and communication unit 10 of the first modification are the same as those of the first embodiment.

[0126] In the first modification, the temperature corrector 23c of the arithmetic processor 23 performs temperature correction on the resistance component III due to deposits. The temperature correction is performed because the internal resistance of the secondary battery 5 changes exponentially with temperature.

[0127] The temperature corrector 23c receives temperature information of the secondary battery 5 measured by the external temperature acquirer 15, and performs temperature correction of the resistance component III due to deposits based on the received temperature information.

[0128] FIG. 15 is a diagram showing an operation flow of the battery monitoring device 1 according to the first modification of the first embodiment.

[0129] The operational flow of Modification 1 is a flow in which steps S131 and S132 are added between steps S130 and S140 shown in Fig. 14 of Embodiment 1. Note that the added step S131 includes steps S210 to S240 shown below.

[0130] As shown in the figure, the battery monitoring device 1 acquires the battery temperature of the secondary battery being monitored after or immediately before acquiring the resistance component III due to the deposit (step S131 in FIG. 15). The battery monitoring device 1 of the first modification executes the following process to acquire the battery temperature.

[0131] FIG. 16 is a diagram showing a flow for acquiring the battery temperature.

[0132] When the application is stopped, the battery monitoring device 1 outputs an instruction signal from the control unit 9 to perform temperature measurement. Based on this instruction signal, the external temperature acquisition unit 15 measures the temperature of the secondary battery 5 using the thermistor 16 set at an arbitrary location (step S210). For example, this temperature measurement is performed twice, with the interval between the first and second measurements being 10 minutes according to the setting value at the time of manufacture. Note that the number of measurements is not limited to two, and may be one or three or more times.

[0133] The external temperature acquisition unit 15 determines whether the temperature difference between the first measurement and the second measurement is within a preset range (step S220). If the temperature difference exceeds the preset range (No in S220), the external temperature acquisition unit 15 returns to step S210 and measures the temperature of the secondary battery 5 again.

[0134] On the other hand, if the temperature difference is within the predetermined range (Yes in S220), the external temperature acquisition unit 15 calculates the average value of the first measured temperature and the second measured temperature (step S230), and outputs the average measured temperature to the temperature correction unit 23c (step S240).

[0135] The temperature corrector 23c performs temperature correction on the resistance component III due to deposits based on the average value of the measured temperatures (step S132 in FIG. 15). For example, the temperature corrector 23c performs temperature correction on the resistance component III based on relationship data between the battery temperature and the resistance component III due to deposits, which is stored in advance in the memory 24.

[0136] 17 is a graph showing data relating to the resistance component III due to deposits and battery temperature, and shows data for initial products and products that have been used for a specified number of years.

[0137] The temperature corrector 23c corrects the value of the resistance component III due to deposits based on the relationship data between the resistance component III due to deposits and the battery temperature shown in Fig. 17. The temperature corrector 23c outputs the corrected value of the resistance component III due to deposits to the capacity loss estimator 23d.

[0138] The capacity loss estimating unit 23d estimates the amount of capacity loss of the secondary battery 5 based on the corrected resistance component III due to deposits (step S140).

[0139] Furthermore, the capacity loss estimation unit 23d outputs the corrected amount of capacity loss to the SOH calculation unit 23e, etc. The SOH calculation unit 23e calculates the SOH based on the corrected amount of capacity loss. Information about the SOH calculated by the SOH calculation unit 23e is output to the upper control unit 2 via the storage unit 24, the control unit 9, and the communication unit 10.

[0140] 18A and 18B are diagrams showing the relationship between the resistance component III due to deposits, the battery temperature, and the SOH. (a) of Fig. 18 shows a graph showing the relationship between the resistance component III due to deposits, the temperature, and the SOH, and (b) shows the data on which (a) is based.

[0141] The parameters in the figure are correlated, and it is desirable to manage them using a map that summarizes the correlation data. This allows the host control unit 2 to manage the power that can be charged and discharged, preventing the secondary battery 5 from being overcharged or overdischarged, and enabling the secondary battery 5 to be used efficiently for a long period of time.

[0142] [Second Modification of First Embodiment] A battery monitoring device 1A according to a second modification of the first embodiment will be described. In the second modification, an example in which the battery monitoring device 1A includes an external storage device 25 will be described.

[0143] FIG. 19 is a block diagram of a battery monitoring device 1A according to a second modification of the first embodiment.

[0144] The battery monitoring device 1A of the second modification includes a measurement unit 7, a battery monitoring unit 8, a control unit 9, and a communication unit 10. The battery monitoring unit 8 includes an arithmetic processing unit 23 and a storage unit 24. The configurations of the measurement unit 7, battery monitoring unit 8, control unit 9, and communication unit 10 of the second modification are the same as those of the first embodiment.

[0145] As shown in the figure, the battery monitoring device 1A of the second modification includes an external storage device 25. The external storage device 25 is provided, for example, in a computer (server) connected via a network such as the Internet, or in a server in a cloud environment. In this case, the battery monitoring device 1A downloads a program required to estimate the battery state of the secondary battery 5 via the network.

[0146] According to this battery monitoring device 1A, the data stored in the memory unit 24 of the battery monitoring device 1A can be updated to the latest data corresponding to the battery type via the external storage device 25. This makes it possible to estimate the battery state with high accuracy.

[0147] [Third Modification of First Embodiment] A battery monitoring device 1 according to a third modification of the first embodiment will be described. In the third modification, a method for calculating a specific impedance component from the impedance component in a pulse current will be described.

[0148] The battery monitoring device 1 of the third modification includes a measurement section 7, a battery monitoring unit 8, a control section 9, and a communication section 10. The battery monitoring unit 8 includes an arithmetic processing section 23 and a storage section 24.

[0149] FIG. 20 is a diagram showing another example of measuring the impedance of the secondary battery 5 by the battery monitoring device 1 according to the third modification of the first embodiment.

[0150] 20 shows the waveforms of the voltage and current of the secondary battery 5 when a discharge pulse is applied to the battery pack 6. In this example, the current OCV (voltage V ０ ) and the voltage VB at the start of the charge / discharge section, the difference voltage value ΔV ０ (=V ０ -VB) is the current I at the start of the charge / discharge section ０ By dividing by , the ohmic resistance (= ΔV ０ / I ０ ) is calculated. By subtracting the resistance component I of the wiring system and the resistance component II of the electrolyte from the ohmic resistance, the resistance component III of the deposits can be obtained. According to this calculation method, the resistance component III of the deposits can be obtained without using a Nyquist plot.

[0151] FIG. 21 is a diagram showing yet another example of measuring the impedance of the secondary battery 5 by the battery monitoring device 1 according to the third modification of the first embodiment.

[0152] 21 shows the waveforms of the voltage and current of the secondary battery 5 when a charging pulse is applied to the battery pack 6. In this example, the current OCV (voltage V ０ ) and the voltage VB at the start of the charge / discharge section, the difference voltage value ΔV ０ (= VB-V ０ ) is the current I at the start of the charge / discharge section ０ By dividing by , the ohmic resistance (= ΔV ０ / I ０) is calculated. By subtracting the resistance component I of the wiring system and the resistance component II of the electrolyte from the ohmic resistance, the resistance component III of the deposits can be obtained. According to this calculation method, the resistance component III of the deposits can be obtained without using a Nyquist plot.

[0153] In addition, in the third modification, the resistance component III is calculated by subtracting the resistance components I and II from the ohmic resistance, which is the resistance from which the resistance components IV and V have been previously subtracted. However, this calculation method is essentially the same as calculating the resistance component III by subtracting the resistance components I, II, IV, and V from the impedance measured for the secondary battery 5.

[0154] (Embodiment 2) [Background to the present disclosure] In an EV (electric vehicle), the performance of the battery (lithium ion battery) is directly linked to the vehicle's performance, such as mileage. Generally, a battery has a characteristic that its lifespan is short in a high-temperature environment and its charging capacity is low in a low-temperature environment, and the battery cannot perform optimally unless it is in an appropriate temperature environment.

[0155] Therefore, temperature management of the battery is important, and it is necessary to operate the battery within an appropriate temperature range. It is also desirable to monitor the battery condition, detect factors that may cause battery malfunction in advance, and send a warning message to the application user or the control unit.

[0156] For example, when the temperature drops, the battery impedance increases, and rapid charging of a lithium-ion battery may not be possible at temperatures below 0°C. On the other hand, when the temperature rises to, for example, 70°C to 100°C, thermal runaway may occur.

[0157] Furthermore, when a battery is used in an EV, it is composed of many cells connected in series. This makes it difficult to measure the temperature of each cell. Generally, the most deteriorated cell determines the capacity and current driving capability of the battery pack, but the most deteriorated cell may be different depending on the temperature. Therefore, it is necessary to properly monitor the temperature of many batteries.

[0158] The battery monitoring device according to the second embodiment has the following configuration in order to improve reliability when monitoring the temperature of the secondary battery 5 .

[0159] [Configuration of Battery Monitoring Device] A battery monitoring device 1B according to a second embodiment will be described. In the second embodiment, an example will be described in which the temperature of a secondary battery 5 is estimated using a resistance component II due to the electrolytic solution. Note that, hereinafter, the resistance component II due to the electrolytic solution may be referred to as a second resistance component. The resistance component II due to the electrolytic solution is an example of the second resistance component.

[0160] Fig. 22 is a schematic configuration diagram showing an example of a battery monitoring device 1B according to embodiment 2. Fig. 23 is a perspective view of the battery monitoring device 1B according to embodiment 2. In addition to the battery monitoring device 1B, Fig. 22 also shows a host control unit 2, a load 3, and a relay 4. Fig. 22 also shows a timer 27 provided between the storage unit 24 and the communication unit 10. The perspective view of the battery monitoring device 1B is the same as that of embodiment 1.

[0161] The battery monitoring device 1B is connected to an assembled battery 6 which is a combination of a plurality of secondary batteries 5. The battery monitoring device 1B is a device which measures the internal impedance of the plurality of secondary batteries 5 and monitors the battery states of the plurality of secondary batteries 5.

[0162] 22, the battery monitoring device 1B includes a measurement unit 7, a battery monitoring unit 8B, a control unit 9, and a communication unit 10. The configurations of the measurement unit 7, the control unit 9, and the communication unit 10 are the same as those in the first embodiment.

[0163] 22 is a BMU, and includes a processing unit 23B and a storage unit 24. Furthermore, the battery monitoring unit 8B of the second embodiment includes a SOH acquisition unit 26.

[0164] The storage unit 24 stores in advance relational data indicating the relationship between the resistance component that changes depending on the battery state of the secondary battery 5 and the battery state of the secondary battery 5. For example, the storage unit 24 stores a relational expression similar to the first relational expression E1 shown in the first embodiment and a second relational expression E2 described below. The storage unit 24 also stores the value of the resistance component I of the wiring system. Note that the first relational expression E1 and the second relational expression E2 are examples of relational data.

[0165] The first relational expression E1 is an expression that shows the relationship between the first resistance component that changes depending on the amount of capacity loss of the secondary battery 5 and the amount of capacity loss of the secondary battery 5. In this example, the first resistance component is a resistance component III due to deposits deposited on the surface of the negative electrode of the secondary battery 5.

[0166] FIG. 24 is a diagram showing data relating to the resistive component III due to deposits and SOH.

[0167] The vertical axis of the figure represents the resistance component III due to deposits, and the horizontal axis represents SOH (%). In the figure, the horizontal axis represents SOH, but this is achieved by replacing the capacity loss on the horizontal axis of FIG. 11 with SOH based on Equation 5, "SOH = (initial capacity) - (capacity loss)." Therefore, the relational data shown in FIG. 24 is substantially the same as the first relational expression E1. In this embodiment, the relationship between the resistance component III due to deposits and SOH shown in FIG. 24 will be described assuming that it also follows the relationship defined by the first relational expression E1.

[0168] The second relational expression E2 is an expression that shows the relationship between the second resistance component that changes depending on the internal temperature of the secondary battery 5 and the internal temperature of the secondary battery 5. In this example, the second resistance component is a resistance component based on the migration resistance in the electrolyte of the secondary battery 5, i.e., a resistance component II due to the electrolyte.

[0169] FIG. 25 is a diagram showing the relationship data between the resistance component II due to the electrolyte and the battery temperature.

[0170] The horizontal axis of the figure represents battery temperature, and the vertical axis represents resistance component II due to the electrolyte. As shown in the figure, there is a correlation between battery temperature and resistance component II due to the electrolyte. The relationship between battery temperature and resistance component II due to the electrolyte is expressed by a curve-approximated second relational expression E2. The second relational expression E2 shown in the figure is obtained by prior data collection and stored in the memory unit 24. Note that the relationship between battery temperature and resistance component II due to the electrolyte is independent of changes in SOH (see FIG. 32). Therefore, it is possible to estimate battery temperature using resistance component II due to the electrolyte.

[0171] The calculation processing unit 23B calculates the value of the resistance component that changes depending on the battery state of the secondary battery 5 being monitored, based on the impedance measured by the measurement unit 7, and estimates the battery state of the secondary battery 5 based on the value of the resistance component and the relationship data stored in the memory unit 24.

[0172] To perform the above processing, the calculation processing unit 23B includes an impedance acquisition unit 23a, an SOH correction unit 23h, an internal temperature estimation factor extraction unit 23i, an internal temperature estimation unit 23j, and an internal temperature correction unit 23k.

[0173] The impedance acquisition unit 23a, the SOH correction unit 23h, the internal temperature estimation factor extraction unit 23i, the internal temperature estimation unit 23j, and the internal temperature correction unit 23k are functional components for estimating the internal temperatures of the batteries C0 to C7.

[0174] The impedance acquisition unit 23a acquires impedances Z0 to Z7 of batteries C0 to C7 based on the voltages V0 to V7 of batteries C0 to C7 measured by the voltage measurement unit 13 and the current value Iac measured and converted to voltage by the AC superposition measurement unit 21. Each of the impedances Z0 to Z7 is a complex number, and a real part ReZ and an imaginary part ImZ are calculated for each of batteries C0 to C7. The calculated complex impedance is the ratio between the voltage measured by the voltage measurement unit 13 and the current measured by the AC superposition measurement unit 21 at each frequency when AC current is output from the battery pack 6 at each frequency by the signal generation unit 20. The impedance acquisition unit 23a outputs the calculated complex impedance values ​​Z0 to Z7 of batteries C0 to C7 to the internal temperature estimation factor extraction unit 23i.

[0175] As described above, the battery monitoring unit 8B includes the SOH acquisition unit 26. The SOH acquisition unit 26 calculates and acquires the SOH based on the integrated amount of current measured by the current measurement unit 14, and outputs the acquired SOH to the SOH correction unit 23h via the storage unit 24. The SOH correction unit 23h outputs the acquired SOH to the internal temperature estimation factor extraction unit 23i.

[0176] The internal temperature estimation factor extraction unit 23i extracts the resistance component II due to the electrolyte of the secondary battery 5 by performing a predetermined processing using the complex impedance values ​​Z0 to Z7 output from the impedance acquisition unit 23a and the SOH output from the SOH correction unit 23h.

[0177] The calculation processing unit 23B performs the following process to estimate the internal temperature of the secondary battery 5 using the resistance component II due to the electrolyte, which is the second resistance component.

[0178] For example, the internal temperature estimation factor extraction unit 23i calculates the value of a first resistance component of the secondary battery 5 to be monitored based on the SOH acquired by the SOH acquisition unit 26 and the first relational expression E1 stored in the memory unit 24, and acquires the value of a second resistance component based on the value of the first resistance component. The internal temperature estimation unit 23j estimates the internal temperature of the secondary battery 5 based on the value of the second resistance component and the second relational expression E2.

[0179] The first resistance component is a resistance component III due to deposits, and is derived from the first relational expression E1 shown in Fig. 24. That is, the first resistance component is calculated and acquired by the SOH acquisition unit 26, and is derived by applying the SOH output from the SOH correction unit 23h to the first relational expression E1.

[0180] When calculating the value of the second resistance component, the internal temperature estimation factor extraction unit 23i calculates the value of the second resistance component by subtracting from the impedance acquired by the impedance acquisition unit 23a the resistance component I of the wiring system, which is the resistance component of the wiring connected to the secondary battery 5 and the resistance component between the wiring and the secondary battery 5, the resistance component III due to deposits, which is the first resistance component, and the resistance component IV of the negative electrode of the secondary battery 5 and the resistance component V of the positive electrode.

[0181] The value of the second resistance component is calculated using the Nyquist plot described above. Note that the Nyquist plot of the secondary battery 5, the diagram showing the resistance component I of the wiring system, and the diagram showing the state in which the resistance component I of the wiring system is removed from the multiple resistance components of the secondary battery 5 are the same as those in Figures 5, 6, and 7, respectively, and therefore only the following explanations will be given below.

[0182] Fig. 26 is a diagram showing the state of a secondary battery 5 after removing the resistance component I of the wiring system and the resistance component III due to deposits from the multiple resistance components. Fig. 26(a) shows a Nyquist plot illustrating the impedance changes of the resistance component II due to the electrolyte, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode. Fig. 26(b) shows an equivalent circuit of the resistance component II due to the electrolyte, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode.

[0183] Figure 27 shows the state in which the resistance component II due to the electrolyte solution is extracted from the multiple resistance components of a secondary battery 5, excluding the resistance component I due to the wiring system, the resistance component III due to deposits, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode. Figure 27(a) shows a Nyquist plot illustrating the impedance change of the resistance component II due to the electrolyte solution. As shown in the figure, the value of the resistance component II due to the electrolyte solution is expressed only by the real part of the complex impedance Z. Figure 27(b) shows an equivalent circuit of the resistance component II due to the electrolyte solution.

[0184] The resistance component I of the wiring system is a value obtained in accordance with the first embodiment and is stored in advance in the storage unit 24. The resistance component III due to deposits, which is the first resistance component, is derived from the SOH output from the SOH correction unit 23h and the first relational expression E1 shown in Fig. 24. The resistance component IV of the negative electrode and the resistance component V of the positive electrode are values ​​obtained by curve fitting in a Nyquist plot showing the impedance change of the secondary battery 5.

[0185] The resistance component II due to the electrolytic solution may be calculated from the impedance component of the pulse current, as shown in FIGS. 20 and 21.

[0186] In this way, the resistance component II due to the electrolyte is extracted by subtracting the resistance component I of the wiring system, the resistance component III due to deposits, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode from the impedance of the secondary battery 5.

[0187] Information relating to the second resistance component (resistance component II due to the electrolyte) extracted by the internal temperature estimation factor extraction unit 23i is output to the internal temperature estimation unit 23j.

[0188] The internal temperature estimator 23j estimates the internal temperature of the secondary battery 5 based on the value of the second resistance component and the second relational expression E2 stored in the memory 24. Specifically, the internal temperature estimator 23j derives the internal temperature of the secondary battery 5 by substituting the value of the second resistance component into the second relational expression E2.

[0189] Information relating to the internal temperature of the secondary battery 5 obtained by the internal temperature estimation unit 23j is notified to the upper control unit 2 via the storage unit 24, the control unit 9, and the communication unit 10. The communication unit 10 is a communication module, and transmits the above information to the upper control unit 2 wirelessly or via a wired connection. The upper control unit 2 executes control in the vehicle according to the notified internal temperature of the secondary battery 5.

[0190] The battery monitoring device 1B of this embodiment calculates the value of the resistance component II due to the electrolyte based on the impedance acquired by the impedance acquisition unit 23a. Then, the battery state of the secondary battery 5 is estimated based on the value of the resistance component II due to the electrolyte and the second relational expression E2. By monitoring the battery state of the secondary battery 5 based on reliable data in this manner, the reliability of monitoring the battery state of the secondary battery 5 can be improved.

[0191] [Operation of Battery Monitoring Device] The operation of the battery monitoring device 1B according to the second embodiment will be described.

[0192] FIG. 28 is a diagram showing the operation flow of the battery monitoring device 1B according to the second embodiment.

[0193] The battery monitoring device 1B stores initial information required for monitoring the secondary battery 5 in the storage unit 24 (step S310). The initial information includes, for example, a second relational expression E2 that indicates the relationship between a second resistance component that varies depending on the internal temperature of the secondary battery 5 and the internal temperature of the secondary battery 5. The initial information also includes a first relational expression E1 that indicates the relationship between a first resistance component that varies depending on the amount of capacity loss of the secondary battery 5 and the amount of capacity loss of the secondary battery 5. Note that the horizontal axis of the first relational expression E1 may represent the amount of capacity loss as described above, or may represent the SOH (%). The initial information also includes the value of the resistance component I of the wiring system.

[0194] Next, the battery monitoring device 1B acquires the impedance of the secondary battery 5 to be monitored (step S320).

[0195] Next, the battery monitoring device 1B acquires the SOH of the secondary battery to be monitored (step S330). For example, the SOH acquisition unit 26 acquires the SOH by integrating the data measured by the current measurement unit 14.

[0196] Next, the battery monitoring device 1B calculates the value of the first resistance component (resistance component III due to deposits) of the secondary battery 5 to be monitored (step S340). Specifically, the battery monitoring device 1B derives the value of the resistance component III due to deposits of the secondary battery 5 based on the SOH acquired in step S330 and the first relational expression E1 stored in the storage unit 24. Note that steps S320 and S330 may be executed between steps S310 and S320, or may be executed simultaneously with step S320.

[0197] Next, the battery monitoring device 1B calculates the value of the resistance component II due to the electrolyte, which is the second resistance component, based on the value of the resistance component III due to the deposits (step S350). For example, the battery monitoring device 1B calculates the value of the second resistance component by subtracting the resistance component I of the wiring system, the resistance component III due to the deposits, which is the first resistance component, the resistance component IV of the negative electrode, and the resistance component V of the positive electrode from the impedance obtained in step S320.

[0198] Next, the battery monitoring device 1B acquires the internal temperature of the secondary battery 5 to be monitored based on the second resistance component obtained in step S350 and the second relational expression E2 stored in the memory unit 24 (step S360).

[0199] By carrying out these steps, the reliability of monitoring the internal temperature of the secondary battery 5 can be improved.

[0200] [First Modification of Second Embodiment] A battery monitoring device 1B according to a first modification of the second embodiment will be described. In this first modification, an example in which correction is made to the internal temperature estimated by the calculation processing unit 23 will be described.

[0201] The battery monitoring device 1B of this example includes a measurement unit 7, a battery monitoring unit 8B, a control unit 9, and a communication unit 10. The battery monitoring unit 8B includes an arithmetic processing unit 23B and a storage unit 24. The configurations of the measurement unit 7, battery monitoring unit 8B, control unit 9, and communication unit 10 of this example are the same as those of the second embodiment.

[0202] The internal temperature correction unit 23 k of the calculation processing unit 23 B corrects the estimated value of the internal temperature of the secondary battery 5 based on the external temperature acquired by the external temperature acquisition unit 15 .

[0203] FIG. 29 is a diagram showing a method of correcting the estimated value of the internal temperature of the secondary battery 5, which is performed in the first modification of the second embodiment.

[0204] For example, it would be sufficient if the second relational expression E2, which shows the relationship between the resistance component II of the electrolyte and the battery temperature, could be prepared for each battery, but in practice, a statistical average value for a certain population is adopted. Therefore, a correlation is taken between the internal temperature calculated from the measured impedance and the external temperature acquired by the external temperature acquisition unit 15, and temperature correction is performed based on the temperature when the battery pack 6 reaches the equilibrium temperature.

[0205] First, the battery monitoring device 1B estimates the internal temperature before manufacturing and shipping, preferably in an environment adjusted to a temperature of 15° C. or higher and 30° C. or lower (step S410).

[0206] The battery monitoring device 1B also measures the external temperature (step S420).

[0207] Next, the battery monitoring device 1B calculates the correlation between the estimated value of the internal temperature and the external temperature (step S430).

[0208] The battery monitoring device 1B stores the relative relationship calculated in step S430 in the storage unit 24 as a relative temperature correction value (step S440).

[0209] The internal temperature correction unit 23k of the battery monitoring device 1B corrects the estimated value of the internal temperature to match the equilibrium temperature value of the battery pack 6 using the correlation value stored in the storage unit 24 (step S450).

[0210] The battery monitoring device 1B outputs information regarding the corrected battery temperature, the resistance components that constitute the impedance of the secondary battery 5, information regarding the SOH, etc. to the upper control unit 2 via the memory unit 24, the control unit 9 and the communication unit 10.

[0211] An example of information relating to each resistance component, battery temperature, and SOH is shown below.

[0212] FIG. 30 is a diagram showing the relationship between the resistance component III due to deposits, the battery temperature, and the SOH.

[0213] As shown in Figure 30, the relationship between the resistance component III due to deposits and the battery temperature shows a completely different trend when the SOH changes. Therefore, it is not easy to use the resistance component III due to deposits when estimating the battery temperature.

[0214] 31A and 31B are diagrams showing the relationship between the resistance component I of the wiring system, the battery temperature, and the SOH, where (a) and (b) show diagrams with different scales on the vertical axis.

[0215] 31, the relationship between the resistance component I of the wiring system and the battery temperature shows different trends when the SOH changes. Therefore, it is difficult to use the resistance component I of the wiring system when estimating the battery temperature.

[0216] 32A and 32B are diagrams showing the relationship between the resistance component II due to the electrolyte, the battery temperature, and the SOH, where (a) and (b) show diagrams with different scales on the vertical axis.

[0217] As shown in Figure 32, the relationship between the resistance component II due to the electrolyte and the battery temperature shows the same tendency even when the SOH changes, and is a relationship independent of the SOH. Therefore, by using the resistance component II due to the electrolyte when estimating the battery temperature, the battery temperature can be easily estimated.

[0218] It is desirable that each parameter shown in Fig. 32 be managed by a map, whereby the upper control unit 2 manages the temperature and the like of the secondary battery 5, preventing the secondary battery 5 from being overcharged or overdischarged, and enabling the secondary battery 5 to be used efficiently for a long period of time.

[0219] [Second Modification of Second Embodiment] A battery monitoring device 1C according to a second modification of the second embodiment will be described. In this second modification, an example in which the battery monitoring device 1C includes an external storage device 25 will be described.

[0220] FIG. 33 is a block configuration diagram of a battery monitoring device 1C according to a second modification of the second embodiment.

[0221] The battery monitoring device 1C of the first modification includes a measurement unit 7, a battery monitoring unit 8B, a control unit 9, and a communication unit 10. The battery monitoring unit 8B includes an arithmetic processing unit 23 and a storage unit 24. The configurations of the measurement unit 7, battery monitoring unit 8B, control unit 9, and communication unit 10 of the second modification are the same as those of the second embodiment.

[0222] As shown in the figure, the battery monitoring device 1C of the second modification includes an external storage device 25. The external storage device 25 is provided, for example, in a computer (server) connected via a network such as the Internet, or in a server in a cloud environment. In this case, the battery monitoring device 1C downloads a program required to estimate the battery state of the secondary battery 5 via the network.

[0223] According to this battery monitoring device 1C, the data stored in the memory unit 24 of the battery monitoring device 1C can be updated to the latest data corresponding to the battery type via the external storage device 25. This makes it possible to estimate the battery state with high accuracy.

[0224] (Summary of First and Second Embodiments) Battery monitoring devices according to the first and second embodiments will be illustrated.

[0225] The battery monitoring device of Example 1 includes a memory unit 24 that stores relationship data indicating the relationship between the resistance component that varies depending on the battery state of the secondary battery 5, among the multiple resistance components that make up the impedance of the secondary battery 5, and the battery state of the secondary battery 5; an impedance acquisition unit 23a that acquires the impedance of the secondary battery 5 to be monitored; and an arithmetic processing unit 23 that calculates the value of the resistance component that varies depending on the battery state of the secondary battery 5 to be monitored based on the impedance acquired by the impedance acquisition unit 23a, and estimates the battery state of the secondary battery 5 to be monitored based on the value of the resistance component and the above-mentioned relationship data.

[0226] In this way, by estimating the battery state of the secondary battery 5 based on the value of the resistance component that changes depending on the battery state and the above-mentioned relationship data, it is possible to monitor the battery state of the secondary battery 5 based on reliable data, etc. This makes it possible to increase the reliability of monitoring the battery state of the secondary battery 5.

[0227] The battery monitoring device 1 of Example 2 is the battery monitoring device described in Example 1, and the storage unit 24 stores, as relational data, a first relational expression E1 that indicates the relationship between a first resistance component that varies depending on the amount of capacity loss of the secondary battery 5 and the amount of capacity loss of the secondary battery 5. The calculation processing unit 23 may calculate the value of the first resistance component of the secondary battery 5 to be monitored based on the impedance acquired by the impedance acquisition unit 23a, and estimate the amount of capacity loss of the secondary battery 5 to be monitored based on the value of the first resistance component and the first relational expression E1.

[0228] In this way, by estimating the amount of capacity loss of the secondary battery 5 based on the value of the first resistance component that changes depending on the battery state and the first relational expression E1, it is possible to monitor the amount of capacity loss of the secondary battery 5 based on reliable data, etc. This makes it possible to improve the reliability of monitoring the battery state of the secondary battery 5.

[0229] The battery monitoring device 1 of Example 3 is the battery monitoring device described in Example 2, and the first relational expression E1 may be derived based on the amount of capacity loss of multiple secondary batteries 5 whose battery capacity is equal to or less than that of the initial product, and multiple first resistance components obtained by measuring the impedance of the multiple secondary batteries 5.

[0230] In this way, by deriving the first relational expression E1 based on performance data, the reliability of the first relational expression E1 can be improved. Therefore, the amount of capacity loss of the secondary battery 5 can be monitored based on reliable data, etc. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0231] The battery monitoring device 1 of Example 4 is the battery monitoring device described in Example 2 or 3, and the amount of capacity loss of the secondary battery 5 in the first relational expression E1 may be calculated based on the amount of irreversible lithium remaining in the negative electrode of the secondary battery 5.

[0232] In this way, by calculating the amount of capacity loss based on the amount of irreversible lithium, the reliability of the first relational expression E1 can be improved. Therefore, the amount of capacity loss of the secondary battery 5 can be monitored based on reliable data, etc. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0233] The battery monitoring device 1 of Example 5 is the battery monitoring device described in any of Examples 2 to 4, and the first resistance component in the first relational expression E1 may be obtained by subtracting, from the impedance of the secondary battery 5 whose battery capacity is equal to or less than that of the initial product, a resistance component I of the wiring connected to the secondary battery 5 and between the wiring and the secondary battery, a resistance component II based on the transfer resistance in the electrolyte of the secondary battery 5, and a resistance component IV of the negative electrode and a resistance component V of the positive electrode of the secondary battery 5.

[0234] By acquiring the first resistance component as described above, the reliability of the first relational expression E1 can be improved. Therefore, the amount of capacity loss of the secondary battery 5 can be monitored based on reliable data, etc. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0235] The battery monitoring device 1 of Example 6 is the battery monitoring device described in any one of Examples 2 to 5, and the calculation processing unit 23 may calculate the value of the first resistance component by subtracting from the impedance acquired by the impedance acquisition unit 23a a resistance component I of the wiring connected to the secondary battery 5 to be monitored and between the wiring and the secondary battery, a resistance component II based on the transfer resistance in the electrolyte of the secondary battery 5, and a resistance component IV of the negative electrode and a resistance component V of the positive electrode of the secondary battery 5.

[0236] This makes it possible to obtain a highly reliable first resistance component by calculation, thereby improving the reliability of monitoring the battery state of the secondary battery 5.

[0237] The battery monitoring device 1 of Example 7 is the battery monitoring device according to any one of Examples 2 to 6, and the first resistance component may be a resistance component III due to deposits deposited on the surface of the negative electrode of the secondary battery 5.

[0238] This allows the first resistance component to be obtained by calculation, thereby improving the reliability of monitoring the battery state of the secondary battery 5.

[0239] The battery monitoring device 1 of Example 8 is a battery monitoring device described in any of Examples 2 to 7, and the calculation processing unit 23 may estimate the current capacity of the secondary battery 5 to be monitored by subtracting the amount of capacity loss estimated by the calculation processing unit 23 from the initial capacity of the secondary battery 5 to be monitored.

[0240] This makes it possible to estimate the current capacity of the secondary battery 5 based on a reliable amount of capacity loss, thereby improving the reliability of monitoring the battery state of the secondary battery 5.

[0241] A battery monitoring device 1B of Example 9 is the battery monitoring device described in Example 1, and the memory unit 24 stores, as relational data, a second relational expression E2 that indicates the relationship between a second resistance component that varies depending on the internal temperature of the secondary battery 5 and the internal temperature of the secondary battery 5. The calculation processing unit 23B may calculate the value of the second resistance component of the secondary battery 5 to be monitored based on the impedance acquired by the impedance acquisition unit 23a, and estimate the internal temperature of the secondary battery 5 to be monitored based on the value of the second resistance component and the second relational expression E2.

[0242] In this way, by estimating the internal temperature of the secondary battery 5 based on the value of the second resistance component that changes depending on the battery state and the second relational expression E2, it is possible to monitor the internal capacity of the secondary battery 5 based on reliable data, etc. This makes it possible to improve the reliability of monitoring the battery state of the secondary battery 5.

[0243] A battery monitoring device 1B of Example 10 is the battery monitoring device described in Example 9, and further includes an SOH acquisition unit 26 that acquires the SOH of a secondary battery 5 that is a monitoring target. The storage unit 24 further stores a first relational expression E1 that indicates the relationship between a first resistance component that varies depending on the amount of capacity loss of the secondary battery 5 and the amount of capacity loss of the secondary battery 5. The calculation processing unit 23B may calculate the value of the first resistance component of the secondary battery 5 that is a monitoring target based on the SOH acquired by the SOH acquisition unit 26 and the first relational expression E1, and acquire the value of a second resistance component based on the value of the first resistance component.

[0244] In this way, by obtaining the first resistance component based on the SOH and the first relational expression E1, and then obtaining the second resistance component based on the first resistance component, the reliability of the value of the second resistance component can be improved. Therefore, the internal temperature of the secondary battery 5 can be estimated based on a reliable value. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0245] The battery monitoring device 1B of Example 11 is the battery monitoring device described in Example 10, and the calculation processing unit 23B may calculate the value of the second resistance component by subtracting from the impedance acquired by the impedance acquisition unit 23a the resistance component I of the wiring connected to the secondary battery 5 to be monitored and the resistance component between the wiring and the secondary battery 5, the first resistance component, and the resistance component IV of the negative electrode of the secondary battery 5 and the resistance component V of the positive electrode.

[0246] By calculating the value of the second resistance component as described above, a highly reliable second resistance component can be obtained by calculation, thereby improving the reliability of monitoring the battery state of the secondary battery 5.

[0247] A battery monitoring device 1B of Example 12 is the battery monitoring device according to any one of Examples 9 to 11, and the second resistance component may be a resistance component II based on a migration resistance in the electrolyte of the secondary battery 5.

[0248] This allows the second resistance component to be obtained by calculation, thereby improving the reliability of monitoring the battery state of the secondary battery 5.

[0249] The battery monitoring device of Example 13 is the battery monitoring device according to any one of Examples 1 to 12, further comprising an external temperature acquisition unit 15 that acquires the external temperature of the secondary battery 5 to be monitored, and a temperature correction unit 23c that corrects a resistance component that varies depending on the battery state based on the external temperature. The calculation processing unit 23 may estimate the battery state of the secondary battery 5 to be monitored based on the resistance component corrected by the temperature correction unit 23c.

[0250] This makes it possible to obtain the resistance component based on the external temperature, thereby improving the reliability of monitoring the battery state of the secondary battery 5.

[0251] The battery monitoring device of Example 14 is the battery monitoring device according to any one of Examples 1 to 12, and may further include a communication unit 10 that transmits data stored in the storage unit 24 to an external device.

[0252] This allows the upper control unit 2 to manage the temperature of the secondary battery 5, preventing the secondary battery 5 from being overcharged or overdischarged, and allowing the secondary battery 5 to be used efficiently for a long period of time.

[0253] The battery monitoring method of Example 15 includes a relational data acquisition step of acquiring relational data indicating the relationship between the resistance component that varies depending on the battery state of the secondary battery 5, among the multiple resistance components that make up the impedance of the secondary battery 5, and the battery state of the secondary battery 5; an impedance acquisition step of acquiring the impedance of the secondary battery 5 to be monitored; and a calculation step of calculating the value of the resistance component that varies depending on the battery state of the secondary battery 5 to be monitored based on the impedance acquired in the impedance acquisition step, and estimating the battery state of the secondary battery 5 to be monitored based on the value of the resistance component and the relational data.

[0254] In this way, by estimating the battery state of the secondary battery 5 based on the value of the resistance component that changes depending on the battery state and the above-mentioned relationship data, it is possible to monitor the battery state of the secondary battery 5 based on reliable data, etc. This makes it possible to increase the reliability of monitoring the battery state of the secondary battery 5.

[0255] A battery monitoring method of Example 16 is the battery monitoring method described in Example 15, and in the relational data acquisition step, a first relational formula E1 indicating the relationship between a first resistance component that changes depending on the amount of capacity loss of the secondary battery 5 and the amount of capacity loss of the secondary battery 5 is acquired as relational data, and in the calculation step, the value of the first resistance component of the secondary battery 5 to be monitored is calculated based on the impedance acquired in the impedance acquisition step, and the amount of capacity loss of the secondary battery 5 to be monitored may be estimated based on the value of the first resistance component and the first relational formula E1.

[0256] In this way, by estimating the amount of capacity loss of the secondary battery 5 based on the value of the first resistance component that changes depending on the battery state and the first relational expression E1, it is possible to monitor the amount of capacity loss of the secondary battery 5 based on reliable data, etc. This makes it possible to improve the reliability of monitoring the battery state of the secondary battery 5.

[0257] The battery monitoring method of Example 17 is the battery monitoring method described in Example 15, and in the relationship data acquisition step, a second relational equation E2 indicating the relationship between a second resistance component that changes depending on the internal temperature of the secondary battery 5 and the internal temperature of the secondary battery 5 is acquired as relationship data, and in the calculation step, the value of the second resistance component of the secondary battery 5 to be monitored is calculated based on the impedance acquired in the impedance acquisition step, and the internal temperature of the secondary battery 5 to be monitored may be estimated based on the value of the second resistance component and the second relational equation E2.

[0258] In this way, by estimating the internal temperature of the secondary battery 5 based on the value of the second resistance component that changes depending on the battery state and the second relational expression E2, it is possible to monitor the internal capacity of the secondary battery 5 based on reliable data, etc. This makes it possible to improve the reliability of monitoring the battery state of the secondary battery 5.

[0259] (Embodiment 3) [Background to the present disclosure] It is possible to estimate the internal temperature of the secondary battery 5 based on the relationship between the internal temperature of the secondary battery 5 and the internal impedance of the secondary battery 5. However, the internal impedance of the secondary battery 5 varies from battery to battery depending on the material and structure of the secondary battery 5. Furthermore, the internal impedance of the secondary battery 5 varies with changes in the ambient environment in which the secondary battery 5 is used and with deterioration of the secondary battery 5 (cycle deterioration or calendar deterioration). Therefore, simply estimating the internal temperature of the secondary battery 5 based on the impedance of the secondary battery 5 may result in an error in the estimated internal temperature of the secondary battery 5.

[0260] In the present disclosure, the internal temperature of the secondary battery 5 is corrected based on the external temperature (surface temperature) of the secondary battery 5. This correction makes it possible to accurately obtain the internal temperature of the secondary battery 5. Furthermore, by periodically repeating the correction of the internal temperature, it is possible to perform temperature correction that corresponds to individual differences in the secondary battery 5, differences in the ambient environment such as day and night or seasons, and deterioration of the secondary battery 5.

[0261] [Configuration of Battery Monitoring Device] A battery monitoring device 1D according to embodiment 3 will be described. In embodiment 3, an example in which the internal temperature estimated by the internal temperature estimator 23j is corrected will be described.

[0262] Fig. 34 is a block diagram of a battery monitoring device 1D according to embodiment 3. Fig. 35 is a perspective view of the battery monitoring device 1D. In addition to the battery monitoring device 1D, Fig. 35 also shows a battery pack 6, a thermistor 16, a current application line 11, a voltage detection line 12, and the like.

[0263] 34 , a battery monitoring device 1D includes a measurement unit 7, a battery monitoring unit 8D, a control unit 9, and a communication unit 10. The battery monitoring unit 8D includes an arithmetic processing unit 23D, a storage unit 24, and an SOH acquisition unit 26. The configurations of the measurement unit 7, the control unit 9, and the communication unit 10, and the configuration of the SOH acquisition unit 26 are the same as those in the second embodiment.

[0264] The internal temperature estimator 23j of the calculation processor 23D estimates the internal temperature of the secondary battery 5 based on the impedance of the secondary battery 5 acquired by the impedance acquirer 23a. For example, the internal temperature estimator 23j estimates the internal temperature of the secondary battery 5 by the calculation process described in the second embodiment.

[0265] The calculation processing unit 23D may estimate the internal temperature of the secondary battery 5 by substituting the impedance acquired by the impedance acquisition unit 23a into a conversion table showing the relationship between the internal temperature and impedance of the secondary battery 5. This conversion table is expressed, for example, by a relational expression with the internal temperature on the horizontal axis and the impedance on the vertical axis, and shows a tendency for the impedance value to decrease as the internal temperature of the secondary battery 5 increases. The relationship between the internal temperature and the impedance is based on the Arrhenius law, and estimating the internal temperature based on the Arrhenius law allows for accurate estimation of the internal temperature.

[0266] Furthermore, the calculation processing unit 23D corrects the estimated internal temperature when the secondary battery 5 reaches a predetermined state. The predetermined state is, for example, a state in which the external temperature or estimated internal temperature of the secondary battery 5 falls within a certain range, i.e., when the secondary battery 5 reaches a thermal equilibrium state. Note that the certain range of temperatures is assumed to be a normal outside air temperature (e.g., between -10°C and 40°C), and the temperature is within this range at this outside air temperature. For example, the thermal equilibrium state of a secondary battery 5 mounted on a vehicle is achieved when the vehicle power supply (or ignition switch) is turned off so that the secondary batteries 5 constituting the battery pack 6 are neither charged nor discharged.

[0267] The calculation processing unit 23D estimates the internal temperature of the secondary battery 5 at predetermined time intervals, and determines that the secondary battery 5 is in a thermal equilibrium state when the change in the internal temperature is within a first range.

[0268] The predetermined time is, for example, 3 minutes, but is not limited to this and may be appropriately selected from a time of 5 minutes or less. The first range is, for example, a temperature of ±2°C, but is not limited to this and may be a temperature of ±1°C or a temperature of ±0.5°C. The first range may be appropriately selected from a temperature of ±3°C or less. The internal temperature may be estimated once every predetermined time, or multiple times (for example, three times) every predetermined time.

[0269] In the third embodiment, when the secondary battery 5 reaches a thermal equilibrium state and the temperature is stabilized, the internal temperature is corrected by executing the following process.

[0270] When the change in the internal temperature of the secondary battery 5 falls within the first range, the calculation processing unit 23D causes the impedance acquisition unit 23a to again acquire the impedance of the secondary battery 5. The internal temperature estimation unit 23j again estimates the internal temperature of the secondary battery 5 based on the again acquired impedance.

[0271] The battery monitoring device 1D also acquires the external temperature of the secondary battery 5 using an external temperature acquisition unit 15. The external temperature of the secondary battery 5 is the temperature at the outer portion of the secondary battery 5, including the surface temperature of the secondary battery 5. As shown in Fig. 35 , the battery monitoring device 1D acquires the external temperature of the battery pack 6 using one thermistor 16. Note that the battery monitoring device 1D may acquire the external temperature of each secondary battery 5 using multiple thermistors 16 attached to multiple secondary batteries 5.

[0272] The calculation processing unit 23D corrects the re-estimated internal temperature of the secondary battery 5 based on the external temperature of the secondary battery 5 acquired by the external temperature acquisition unit 15 and the internal temperature of the secondary battery 5 re-estimated by the internal temperature estimation unit 23j. When correcting the internal temperature of the secondary battery 5, the calculation processing unit 23D corrects the internal temperature using the temperature correction data shown below.

[0273] FIG. 36 is a diagram showing an example of the temperature correction data Dt.

[0274] The first axis of the coordinate system of the graph in Figure 36 represents the internal temperature of the secondary battery 5 estimated by the internal temperature estimator 23j, the second axis represents the external temperature of the secondary battery 5, and the third axis represents correction data for the internal temperature. The coordinates on the three axes may be expressed as an addition or subtraction value to the internal temperature, or as a multiplication factor with the internal temperature as a reference value. The correction graph shown in Figure 36 may be a relational expression expressed by curve approximation. The temperature correction data Dt may be updated daily based on actual data on the external and internal temperatures to address deterioration of the secondary battery 5, etc. This temperature correction data Dt is stored in the memory unit 24 of the battery monitoring device 1D.

[0275] The calculation processing unit 23D corrects the internal temperature of the secondary battery 5 estimated by the internal temperature estimating unit 23j based on the temperature correction data Dt stored in the memory unit 24. For example, the calculation processing unit 23D obtains correction data for the internal temperature based on the temperature correction data Dt, and uses this correction data to correct the internal temperature estimated by the internal temperature estimating unit 23j. This makes it possible to accurately obtain the internal temperature of the secondary battery 5.

[0276] Although the above example illustrates the use of the thermistor 16 to acquire the external temperature, this is not limiting. The battery monitoring device 1D may acquire the external temperature using an optical fiber temperature sensor or infrared thermography instead of the thermistor 16. The optical fiber temperature sensor can measure a wider temperature distribution than the thermistor 16. Furthermore, because optical fibers are very thin, they can be easily placed inside the battery pack 6, allowing temperature monitoring without affecting the operation of the battery pack 6. Infrared thermography measures temperature by detecting infrared rays emitted from an object, allowing the surface temperature of the battery pack 6 to be measured quickly and without contact. Infrared thermography is effective for detecting the temperature distribution on the surface of the battery pack 6 using an infrared camera.

[0277] Furthermore, an increase in impedance due to deterioration of the secondary battery 5 may cause an error in estimating the internal temperature of the secondary battery 5. In this case, the SOH correction unit 23h (see FIG. 34) may obtain SOH data from an SOH diagnosis (such as a history memory and a capacity measurement function) of the BMS (a management system for the secondary battery 5) and correct the impedance value based on a correlation table between impedance and SOH created in advance. The internal temperature estimator 23j may estimate the internal temperature based on the corrected impedance. This allows the internal temperature of the secondary battery 5 to be accurately estimated even if the secondary battery 5 has deteriorated.

[0278] [Operation of Battery Monitoring Device] The following describes the operation of the battery monitoring device 1D according to embodiment 3. In this embodiment, an example will be described in which the internal temperature is corrected when the estimated change in the internal temperature of the secondary battery 5 falls within a first range.

[0279] FIG. 37 is a flowchart showing the operation of the battery monitoring device 1D according to the third embodiment.

[0280] The battery monitoring device 1D measures the impedance of the secondary batteries 5 that make up the battery pack 6 (step S510). The number of secondary batteries 5 to be measured may be one, two or more, or all of the multiple secondary batteries 5. The battery monitoring device 1D measures the impedance of the secondary batteries 5, for example, three times every three minutes.

[0281] The battery monitoring device 1D estimates the internal temperature of the secondary battery 5 based on the impedance measured in step S510 (step S511).

[0282] The battery monitoring device 1D determines whether the change in the internal temperature of the secondary battery 5 is within a first range (step S512). The first range is, for example, a temperature of ±2°C.

[0283] If the change in internal temperature is not within the first range (No in S512), the process returns to step S510 and waits until the change in internal temperature falls within the first range. Note that if multiple thermistors 16 are attached to multiple secondary batteries 5, the battery monitoring device 1D may not execute steps S510 and S511 again for secondary batteries 5 whose internal temperature change falls within the first range, but may execute steps S510 and S511 again only for secondary batteries 5 whose internal temperature change falls within the first range.

[0284] If the change in the internal temperature is within the first range (Yes in S512), the battery monitoring device 1D acquires the external temperature of the secondary battery 5 (step S561). The battery monitoring device 1D acquires the external temperature based on the output signal of the thermistor 16 that is in contact with the surface of the secondary battery 5.

[0285] The battery monitoring device 1D also measures the impedance of the secondary battery 5 again (step S562). It is preferable that steps S561 and S562 are executed simultaneously.

[0286] The battery monitoring device 1D again estimates the internal temperature of the secondary battery 5 from the impedance measured in step S562 (step S563). The battery monitoring device 1D stores information about the internal temperature estimated in step S563 and the external temperature acquired in step S561 in the storage unit 24.

[0287] The battery monitoring device 1D derives correction data for the internal temperature based on the external temperature acquired in step S561 and the internal temperature estimated in step S563 (step S564). For example, the battery monitoring device 1D derives the correction data for the internal temperature by substituting the above-described external temperature and internal temperature into the relational expression for the temperature correction data Dt.

[0288] The battery monitoring device 1D corrects the internal temperature of the secondary battery 5 estimated in step S563 based on the derived correction data (step S565). The battery monitoring device 1D stores the derived correction data and information related to the corrected internal temperature in the storage unit 24.

[0289] By carrying out these steps to correct the internal temperature of the secondary battery 5, the internal temperature of the secondary battery 5 can be accurately obtained.

[0290] [Variation 1 of Embodiment 3] A battery monitoring device 1D according to Variation 1 of Embodiment 3 will be described. Variation 1 describes an example in which the internal temperature is corrected when the change in external temperature is within a second range.

[0291] FIG. 38 is a flowchart showing the operation of the battery monitoring device 1D according to the first modification of the third embodiment.

[0292] The battery monitoring device 1D acquires the external temperature of the secondary battery 5 that constitutes the battery pack 6 (step S520). The battery monitoring device 1D acquires the external temperature based on the output signal of the thermistor 16 that is in contact with the surface of the secondary battery 5. The battery monitoring device 1D acquires the external temperature of the secondary battery 5, for example, three times every five minutes.

[0293] The battery monitoring device 1D determines whether the temperature rise of the external temperature of the secondary battery 5 is equal to or greater than a first threshold (step S521). For example, the first threshold for the temperature rise over a five-minute period is set to 5°C. If the temperature rise over a five-minute period is equal to or greater than 5°C, an internal short circuit may have occurred in the secondary battery 5, causing abnormal heat generation in the secondary battery 5. An internal short circuit may be caused by contact between the positive and negative electrodes due to lithium deposition, metallic foreign matter, or physical damage. Furthermore, if the temperature rise over a five-minute period is equal to or greater than 5°C, the thermistor 16 may be malfunctioning.

[0294] If the temperature rise in the external temperature is equal to or greater than the first threshold (Yes in S521), the battery monitoring device 1D determines that there is an abnormality in the state of the secondary battery 5 or in the measurement of the external temperature (step S522) and outputs an abnormality occurrence signal to the upper control unit 2.

[0295] If the temperature rise of the external temperature is not equal to or greater than the first threshold (No in S521), the battery monitoring device 1D next determines whether the change in the external temperature of the secondary battery 5 is within a second range (step S523). The second range is, for example, a temperature of ±2°C, but is not limited to this and may be a temperature of ±1°C or a temperature of ±0.5°C. The second range may be appropriately selected from temperatures of ±3°C or less.

[0296] If the change in the external temperature is not within the second range (No in S523), the battery monitoring device 1D waits for 30 minutes (step S524), and then executes the process of step S520 again.

[0297] If the change in the external temperature is within the second range (Yes in S523), the battery monitoring device 1D again acquires the external temperature of the secondary battery 5 (step S561). Note that if the external temperature acquired in step S520 is used as the external temperature of the secondary battery 5, the processing of step S561 may be omitted. The external temperature of the secondary battery 5 may be the average value of the multiple external temperatures acquired in step S520.

[0298] The battery monitoring device 1D also measures the impedance of the secondary battery 5 (S562). It is preferable that steps S561 and S562 are executed simultaneously.

[0299] Next, the battery monitoring device 1D estimates the internal temperature of the secondary battery 5 from the impedance measured in step S562 (S563). The battery monitoring device 1D derives correction data for the internal temperature based on the external temperature acquired in step S561 and the internal temperature estimated in step S563 (S564). For example, the battery monitoring device 1D derives the correction data for the internal temperature by substituting the above external temperature and internal temperature into the relational expression of the temperature correction data Dt. The battery monitoring device 1D corrects the internal temperature of the secondary battery 5 estimated in step S563 based on this correction data (S565). By performing these steps to correct the internal temperature of the secondary battery 5, the internal temperature of the secondary battery 5 can be accurately obtained.

[0300] [Second Modification of Third Embodiment] A battery monitoring device 1D according to a second modification of the third embodiment will be described. In the second modification, an example will be described in which a plurality of thermistors 16 are used to acquire the external temperatures at a plurality of locations on the battery pack 6.

[0301] FIG. 39 is a perspective view of a battery monitoring device 1D according to a second modification of the third embodiment.

[0302] In the second modification, a plurality of thermistors 16 are arranged in a plurality of secondary batteries 5 that constitute a battery pack 6 .

[0303] The locations of the multiple thermistors 16 are determined based on the uneven heat distribution within the battery pack 6, the outside temperature, and the influence of the cooling system. The number of thermistors 16 arranged in the battery pack 6 may be two or more, or may be fewer than the number of secondary batteries 5 constituting the battery pack 6. In this example, three thermistors 16 are arranged at both end portions 5a and a central portion 5b of the battery pack 6. As shown in FIG. 39 , by monitoring the temperature of the end portions 5a of the battery pack 6, which are susceptible to the outside air, and the temperature of the central portion 5b of the battery pack 6, which is less susceptible to the outside air, it is possible to accurately determine whether a state of thermal equilibrium has been achieved. The battery monitoring device 1D acquires the external temperature of the battery pack 6 based on the output signals from the multiple thermistors 16.

[0304] The battery monitoring device 1D may determine whether or not a thermal equilibrium state has been achieved based on the average or median temperature value obtained using the multiple thermistors 16. In this case, the thermal equilibrium state can be determined appropriately without taking into account the online / offline state of the vehicle system.

[0305] FIG. 40 is a flowchart showing the operation of the battery monitoring device 1D according to the second modification of the third embodiment.

[0306] The battery monitoring device 1D acquires multiple external temperatures of the battery pack 6 (step S530). The battery monitoring device 1D acquires external temperatures at two or more locations on the battery pack 6. The battery monitoring device 1D also acquires the external temperature of the secondary battery 5, for example, three times every five minutes.

[0307] The battery monitoring device 1D determines whether the difference in external temperature between two or more locations on the battery pack 6 is within a third range (step S533). The third range is, for example, a temperature difference of 4°C, but is not limited to this and may be a temperature difference of 2°C or a temperature difference of 1°C. The third range may be appropriately selected from temperature differences of 6°C or less.

[0308] If the change in the external temperature is not within the third range (No in S533), the battery monitoring device 1D waits for 30 minutes (step S534), and then executes the process of step S530 again.

[0309] If the change in the external temperature is within the third range (Yes in S533), the battery monitoring device 1D again acquires the external temperature of the secondary battery 5 (step S561). Note that if the external temperature acquired in step S530 is used as the external temperature of the secondary battery 5, the processing of step S561 may be omitted. The external temperature of the secondary battery 5 may be the average value of the multiple external temperatures acquired in step S530.

[0310] The battery monitoring device 1D also measures the impedance of the secondary battery 5 (step S562). It is preferable that steps S561 and S562 are executed simultaneously.

[0311] Steps S563 to S565 are the same as those in Modification 1. By executing these steps and correcting the internal temperature of the secondary battery 5, the internal temperature of the secondary battery 5 can be obtained accurately.

[0312] If the heat distribution of the battery pack 6 varies depending on the location where the external temperature is measured and the cooling system of the battery pack 6, the difference in heat distribution of the battery pack 6 may be obtained by measuring the difference in heat distribution depending on the location where the external temperature is measured or by performing a thermal analysis (thermal simulation) of the battery pack 6 using the cooling system. This difference in heat distribution may then be assigned to the measurement location of the battery pack 6 and corrected. Also, if the heat distribution varies depending on the material (e.g., a member having a heat-retaining effect) that makes up the battery pack 6, the difference due to material factors taking into account the thermal conductivity of the material may be assigned to the measurement location of the battery pack 6 and corrected. By performing correction depending on the location where the external temperature is measured in this way, it is possible to accurately determine whether thermal equilibrium has been reached.

[0313] [Third Modification of Third Embodiment] A battery monitoring device 1D according to a third modification of the third embodiment will be described. In the third modification, correction of the internal temperature in an offline state (a state in which the current or voltage does not change, the vehicle is stopped, and the relay 4 is cut) will be described. In the third modification, the offline state is determined based on the time measured by a timer.

[0314] FIG. 41 is a flowchart showing the operation of the battery monitoring device 1D according to the third modification of the third embodiment.

[0315] After the vehicle engine is stopped, the battery monitoring device 1D starts a one-hour timer measurement (step S540). The timer measurement time is set in advance based on the time from when the engine is stopped until the current or voltage of the secondary battery 5 reaches a state where it does not change. Because the time it takes for the current or voltage to reach a state where it does not change differs between summer and winter, the timer measurement time may be changed depending on the season.

[0316] The timer measurement time is, for example, one hour, but is not limited to this and may be three hours. If the second resistance component (impedance) of the secondary battery 5 is on the high frequency side, the timer measurement time may be shorter than one hour. If the second resistance component is on the low frequency side, it takes a long time for the impedance to reach thermal equilibrium, so the timer measurement time may be longer than one hour, for example, three hours.

[0317] After the measurement time has elapsed, the battery monitoring device 1D executes steps S561 to S565, as in embodiment 3. By executing these steps to correct the internal temperature of the secondary battery 5, the internal temperature of the secondary battery 5 can be accurately obtained.

[0318] In the above description, the offline state is determined by timer measurement, but this is not limiting. For example, the voltage measurement unit 13 or the current measurement unit 14 may measure a state in which the voltage or current of each secondary battery 5 remains unchanged, and the state in which the voltage or current remains unchanged may be determined as the offline state. For example, the state in which the voltage remains unchanged may be set to ±20 mV, and when the voltage remains within this range, the offline state may be determined, and correction of the internal temperature may be initiated.

[0319] [Fourth Modification of Third Embodiment] A battery monitoring device 1D according to a fourth modification of the third embodiment will be described. In the fourth modification, an example will be described in which the offline state is determined based on the time measured by a timer, and the internal temperature is corrected when the change in the external temperature falls within a second range.

[0320] FIG. 42 is a flowchart showing the operation of the battery monitoring device 1D according to the fourth modification of the third embodiment.

[0321] After the vehicle engine is stopped, the battery monitoring device 1D starts a one-hour timer measurement (step S540). After the measurement time has elapsed, the battery monitoring device 1D executes steps S520 to S565, similar to the first modification of the third embodiment. By executing these steps to correct the internal temperature of the secondary battery 5, the internal temperature of the secondary battery 5 can be accurately obtained.

[0322] [Fifth Modification of Third Embodiment] The following describes the operation of a battery monitoring device 1D according to a fifth modification of the third embodiment. In the fifth modification, an example will be described in which the offline state is determined based on the time measured by a timer, and the internal temperature is corrected when the change in impedance of the secondary battery 5 falls within a fourth range.

[0323] FIG. 43 is a flowchart showing the operation of the battery monitoring device 1D according to the fifth modification of the third embodiment.

[0324] After the vehicle engine is stopped, the battery monitoring device 1D starts a timer measurement for one hour (step S540).

[0325] After the measurement time has elapsed, the battery monitoring device 1D measures the impedance of the secondary battery 5 that constitutes the battery pack 6 (step S510). The battery monitoring device 1D measures the impedance of the secondary battery 5, for example, three times every five minutes.

[0326] The battery monitoring device 1D estimates the internal temperature of the secondary battery 5 based on the impedance measured in step S510 (step S511).

[0327] The battery monitoring device 1D determines whether the internal temperature rise of the secondary battery 5 is equal to or greater than a second threshold (step S521A). For example, the second threshold for the temperature rise over a five-minute period is set to 5°C. If the temperature rise over a five-minute period is equal to or greater than 5°C, an internal short circuit may have occurred in the secondary battery 5, causing abnormal heat generation. An internal short circuit may be caused by contact between the positive and negative electrodes due to lithium deposition, metallic foreign matter, or physical damage. Furthermore, if the temperature rise over a five-minute period is equal to or greater than 5°C, the thermistor 16 may be faulty.

[0328] If the temperature rise in the internal temperature is equal to or greater than the second threshold (Yes in S521A), the battery monitoring device 1D determines that there is an abnormality in the state of the secondary battery 5 or in the measurement of the internal temperature (step S522A) and outputs an abnormality occurrence signal to the upper control unit 2.

[0329] If the internal temperature rise is not equal to or greater than the second threshold (No in S521A), the battery monitoring device 1D next determines whether the change in impedance of the secondary battery 5 is within a fourth range (step S523A).

[0330] If the change in impedance is not within the fourth range (No in S523A), the battery monitoring device 1D waits for 30 minutes (step S524A), and then executes the process of step S510 again.

[0331] If the change in impedance is within the fourth range (Yes in S523A), the battery monitoring device 1D acquires the external temperature of the secondary battery 5 (step S561).

[0332] The battery monitoring device 1D then again measures the impedance of the secondary battery 5 (S562). It is preferable that steps S561 and S562 are executed simultaneously.

[0333] Next, the battery monitoring device 1D estimates the internal temperature of the secondary battery 5 from the impedance measured in step S562 (S563). The battery monitoring device 1D derives correction data for the internal temperature based on the external temperature acquired in step S561 and the internal temperature estimated in step S563 (S564). For example, the battery monitoring device 1D derives the correction data for the internal temperature by substituting the above external temperature and internal temperature into the relational expression of the temperature correction data Dt. The battery monitoring device 1D corrects the internal temperature of the secondary battery 5 estimated in step S563 based on this correction data (S565). By performing these steps to correct the internal temperature of the secondary battery 5, the internal temperature of the secondary battery 5 can be accurately obtained.

[0334] [Sixth Modification of Third Embodiment] A battery monitoring device 1D according to a sixth modification of the third embodiment will be described. In the sixth modification, an example will be described in which the internal temperature is corrected when the change in the temperature of the resistor falls within a fifth range.

[0335] Fig. 44 is a perspective view of a battery monitoring device 1D according to a sixth modification of embodiment 3. Fig. 45 is a diagram showing a resistor 40 of a battery monitoring device 1D according to the sixth modification of embodiment 3.

[0336] 44, a resistor 40 and a thermistor 41 are arranged around the battery monitoring device 1D. The thermistor 41 is arranged so as to be in contact with the resistor 40.

[0337] A current and a voltage are applied to the resistor 40 under the same measurement conditions as those of the secondary battery 5. For example, a high-frequency signal having the same measurement frequency as that input to the secondary battery 5 when measuring the impedance of the secondary battery 5 is input to the resistor 40. The resistor 40 preferably has characteristics that indicate a conversion table similar to that used when estimating the internal temperature of the secondary battery 5. In other words, the resistor 40 preferably has a resistance value equivalent to that of the secondary battery 5. Note that if the resistance value of the resistor 40 is not equivalent to that of the secondary battery 5, a correlation table between the impedance of the resistor 40, the measurement frequency, and the internal temperature may be created in advance, and the thermal equilibrium state may be determined using this correlation table. Alternatively, a correlation table between the resistor 40 and the secondary battery 5 may be created in advance, and the thermal equilibrium state may be determined using this correlation table.

[0338] When the temperature change of the resistor 40 is within a fifth range, the battery monitoring device 1D corrects the internal temperature of the secondary battery 5 based on the external temperature of the secondary battery 5 acquired by the external temperature acquisition unit 15 and the internal temperature of the secondary battery 5 estimated by the internal temperature estimation unit 23j. For example, the battery monitoring device 1D derives correction data for the internal temperature by substituting the above-mentioned external temperature and internal temperature into the relational expression of the temperature correction data Dt, and corrects the estimated internal temperature of the secondary battery 5 based on the correction data. By correcting the internal temperature of the secondary battery 5 in this manner, the internal temperature of the secondary battery 5 can be accurately obtained.

[0339] Although the above description has been given using a resistor as an example, a capacitor or a small secondary battery 5 (e.g., a coin-type battery) may be used instead of the resistor. In particular, the secondary battery 5 may be an all-solid-state battery. An all-solid-state battery has the advantage of deteriorating at a slower rate than a secondary battery 5 that uses an electrolyte. An all-solid-state battery can be easily mounted on a substrate if it is small in size (e.g., 10 mm long x 10 mm wide x 5 mm thick). Another advantage of an all-solid-state battery is that it is free from metal corrosion due to leakage of the electrolyte.

[0340] [Seventh Modification of Third Embodiment] A battery monitoring device 1D according to a seventh modification of the third embodiment will be described. In the seventh modification, an example in which the secondary batteries 5 constituting the battery pack 6 are surrounded by a thermally conductive member 50 will be described.

[0341] Fig. 46 is a perspective view of a battery monitoring device 1D according to a seventh modification of embodiment 3. Fig. 47 is a top view of a battery pack 6 connected to the battery monitoring device 1D.

[0342] As shown in Figures 46 and 47, a portion of the secondary batteries 5 constituting the battery pack 6 is surrounded by a heat conduction member 50. The heat conduction member 50 is disposed in contact with or close to the side surface of the secondary batteries 5 so as to cover at least a portion of the secondary batteries 5. The heat conduction member 50 is made of a metal material with high thermal conductivity. The thermistor 16 is connected to the heat conduction member 50 by being fastened or welded.

[0343] The external temperature acquisition unit 15 acquires the external temperature based on the output signal of the thermistor 16 connected to the heat conduction member 50. In this way, by acquiring the temperature of the secondary batteries 5 via the heat conduction member 50 provided in the battery pack 6, the average temperature of the multiple secondary batteries 5 can be acquired.

[0344] Eighth Modification of Third Embodiment An eighth modification of the third embodiment will be described. In the eighth modification, the thermistor 16 is attached to the terminal 5c of the secondary battery 5.

[0345] FIG. 48 is a top view of the terminal portion 5c of the secondary battery 5.

[0346] 48, the thermistor 16 is connected to the terminal 5c (either the positive battery terminal 31a or the negative battery terminal 31b) of the secondary battery 5. The external temperature acquisition unit 15 of Modification 8 acquires the external temperature based on the output signal of the thermistor 16 connected to the terminal 5c of the secondary battery 5. The temperature of the terminal 5c of the secondary battery 5 is considered to be closer to the internal temperature of the secondary battery 5 than the temperature of the casing that forms the exterior of the secondary battery 5. Therefore, by using the external temperature of the secondary battery 5 obtained from the thermistor 16 of the terminal 5c, the internal temperature of the secondary battery 5 can be appropriately corrected.

[0347] [Ninth Modification of Third Embodiment] A ninth modification of the third embodiment will be described.

[0348] Fig. 49 is a perspective view showing another example of the secondary battery 5. Fig. 50 is a diagram showing an example of the secondary battery 5 and the heat conduction member 50. Fig. 51 is a diagram showing another example of the secondary battery 5 and the heat conduction member 50.

[0349] Figure 49 shows a cylindrical secondary battery 5. As shown in Figures 50 and 51, heat conduction members 50 are arranged between four secondary batteries 5. The heat conduction members 50 are arranged so as to contact part of the side surfaces of the four secondary batteries 5 or to enclose part of the side surfaces. The thermistor 16 is connected to the heat conduction members 50 by being fastened or welded.

[0350] The external temperature acquisition unit 15 acquires the external temperature based on the output signal of the thermistor 16 connected to the thermally conductive member 50. By acquiring the temperature of the secondary batteries 5 via the thermally conductive member 50 in contact with the secondary batteries 5, it is possible to acquire the average temperature of the secondary batteries 5.

[0351] (Summary of Third Embodiment) A description will be given of a battery monitoring device 1D according to the third embodiment. The battery monitoring device 1D according to the third embodiment has the basic configuration of the battery monitoring devices according to the first and second embodiments.

[0352] The battery monitoring device 1D of embodiment 3 includes a memory unit 24 that stores relationship data indicating the relationship between the battery state of the secondary battery 5 and a resistance component that varies depending on the battery state of the secondary battery 5, among multiple resistance components that make up the impedance of the secondary battery 5; an impedance acquisition unit 23a that acquires the impedance of the secondary battery 5 to be monitored; and an arithmetic processing unit 23D that calculates the value of the resistance component that varies depending on the battery state of the secondary battery 5 to be monitored based on the impedance acquired by the impedance acquisition unit 23a, and estimates the battery state of the secondary battery 5 to be monitored based on the value of the resistance component and the above-mentioned relationship data.

[0353] The battery monitoring device 1D of aspect 1 further includes an external temperature acquisition unit 15 that acquires the external temperature of the secondary battery 5 to be monitored. The calculation processing unit 23D estimates the internal temperature of the secondary battery 5 based on the impedance acquired by the impedance acquisition unit 23a, and corrects the estimated internal temperature of the secondary battery 5 based on the external temperature acquired by the external temperature acquisition unit 15.

[0354] In this way, by correcting the internal temperature of the secondary battery 5 based on the external temperature, it is possible to accurately obtain the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0355] The battery monitoring device 1D of aspect 2 is the battery monitoring device described in aspect 1, and the calculation processing unit 23D (1) estimates the internal temperature of the secondary battery 5 based on the impedance acquired by the impedance acquisition unit 23a, and if the change in the internal temperature is within a first range, re-estimates the internal temperature of the secondary battery 5 based on the impedance acquired again by the impedance acquisition unit 23a, and (2) may correct the re-estimated internal temperature of the secondary battery 5 based on the external temperature acquired by the external temperature acquisition unit 15.

[0356] In this way, by correcting the internal temperature of the secondary battery 5 when the change in the internal temperature is within the first range, it is possible to accurately obtain the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0357] The battery monitoring device 1D of aspect 3 is the battery monitoring device described in aspect 1, and the calculation processing unit 23D may (1) estimate the internal temperature of the secondary battery 5 based on the impedance acquired by the impedance acquisition unit 23a when the change in external temperature is within a second range, and (2) correct the estimated internal temperature of the secondary battery 5 based on the external temperature acquired by the external temperature acquisition unit 15.

[0358] In this way, by correcting the internal temperature of the secondary battery 5 when the change in external temperature is within the second range, it is possible to accurately obtain the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0359] The battery monitoring device 1D of aspect 4 is the battery monitoring device described in aspect 1, in which the external temperature acquisition unit 15 acquires external temperatures at two or more locations of a battery pack 6 having a plurality of secondary batteries 5 to be monitored, and the calculation processing unit 23D (1) estimates the internal temperature of the secondary batteries 5 based on the impedance acquired by the impedance acquisition unit 23a when the difference between the external temperatures at two or more locations is within a third range, and (2) corrects the estimated internal temperature of the secondary batteries 5 based on the external temperatures at two or more locations acquired by the external temperature acquisition unit 15.

[0360] In this way, when the difference between the external temperatures at two or more locations is within the third range, the internal temperature of the secondary battery 5 is corrected, thereby making it possible to accurately obtain the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0361] The battery monitoring device 1D of aspect 5 is the battery monitoring device described in aspect 4, and the external temperature acquisition unit 15 may acquire the external temperature at two or more locations based on the output signals of two or more thermistors 16 provided in the central portion 5b and the end portion 5a of the battery pack 6.

[0362] In this way, by acquiring the temperature of the end portion 5a of the battery pack 6, which is susceptible to the influence of the outside air, and the temperature of the central portion 5b of the battery pack 6, which is less susceptible to the influence of the outside air, it is possible to correct the internal temperature of the secondary battery 5 when a thermal equilibrium state is reached. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0363] The battery monitoring device 1D of aspect 6 is the battery monitoring device described in aspect 1, and the calculation processing unit 23D may (1) estimate the internal temperature of the secondary battery 5 based on the impedance acquired again by the impedance acquisition unit 23a when the change in impedance acquired by the impedance acquisition unit 23a is within a fourth range, and (2) correct the estimated internal temperature of the secondary battery 5 based on the external temperature acquired by the external temperature acquisition unit 15.

[0364] In this way, by correcting the internal temperature of the secondary battery 5 when the change in impedance is within the fourth range, it is possible to accurately obtain the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0365] A battery monitoring device 1D of aspect 7 is the battery monitoring device according to aspect 1, further including a resistor 40 to which a current and a voltage are applied under the same measurement conditions as those of the secondary battery 5. The calculation processing unit 23D may (1) estimate the internal temperature of the secondary battery 5 based on the impedance acquired by the impedance acquisition unit 23a when the temperature change of the resistor 40 is within a fifth range, and (2) correct the estimated internal temperature of the secondary battery 5 based on the external temperature acquired by the external temperature acquisition unit 15.

[0366] In this way, by correcting the internal temperature of the secondary battery 5 when the temperature change of the resistor 40 is within the fifth range, it is possible to accurately obtain the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0367] The battery monitoring device 1D of aspect 8 is a battery monitoring device described in any of aspects 1 to 7, and the calculation processing unit 23D may derive correction data based on temperature correction data Dt indicating the relationship between the external temperature, the internal temperature of the secondary battery 5, and correction data for the internal temperature, which is pre-stored in the memory unit 24, and correct the internal temperature of the secondary battery 5 based on the correction data.

[0368] In this way, by correcting the internal temperature of the secondary battery 5 based on the temperature correction data Dt, it is possible to accurately obtain the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0369] The battery monitoring device 1D of aspect 9 is a battery monitoring device described in any of aspects 1 to 8, and the external temperature acquisition unit 15 may acquire the external temperature based on the output signal of a thermistor 16 connected to a thermal conductive member 50 covering at least a portion of the secondary battery 5.

[0370] In this way, by obtaining the temperature of the secondary batteries 5 via the thermally conductive member 50, it is possible to obtain the average temperature of the plurality of secondary batteries 5. This improves the reliability of monitoring the battery states of the secondary batteries 5.

[0371] The battery monitoring device 1D of aspect 10 is a battery monitoring device described in any of aspects 1 to 8, and the external temperature acquisition unit 15 may acquire the external temperature based on the output signal of a thermistor 16 connected to the terminal portion 5c of the secondary battery 5.

[0372] In this way, by using the external temperature of the secondary battery 5 obtained from the thermistor 16 of the terminal portion 5c, it is possible to appropriately correct the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0373] The battery monitoring method of embodiment 3 includes a relational data acquisition step of acquiring relational data indicating the relationship between the battery state of the secondary battery 5 and a resistance component that varies depending on the battery state of the secondary battery 5, among multiple resistance components that make up the impedance of the secondary battery 5; an impedance acquisition step of acquiring the impedance of the secondary battery 5 to be monitored; and a calculation step of calculating the value of the resistance component that varies depending on the battery state of the secondary battery 5 to be monitored based on the impedance acquired in the impedance acquisition step, and estimating the battery state of the secondary battery 5 to be monitored based on the value of the resistance component and the relational data.

[0374] The battery monitoring method of aspect 11 further includes an external temperature acquisition step of acquiring the external temperature of the secondary battery 5 to be monitored, and a calculation step of estimating the internal temperature of the secondary battery 5 based on the impedance acquired in the impedance acquisition step, and correcting the estimated internal temperature of the secondary battery based on the external temperature acquired in the external temperature acquisition step.

[0375] In this way, by correcting the internal temperature of the secondary battery 5 based on the external temperature, it is possible to accurately obtain the internal temperature of the secondary battery 5. This improves the reliability of monitoring the battery state of the secondary battery 5.

[0376] (Other Embodiments) Although the first, second, and third embodiments have been described above, the present disclosure is not limited to the above-described embodiments.

[0377] For example, in the first embodiment, the resistance component III due to deposits is defined as the first resistance component, but this is not limiting. For example, if the resistance component II due to the electrolyte and the resistance component III due to deposits are defined as the first resistance components, the first relational expression E1 may be a relational expression represented by the horizontal axis and the left vertical axis in FIG.

[0378] For example, in the equivalent circuit shown in Figure 3, CPE (Constant Phase Element) is used to represent the electric double layer capacitance (capacitor) of the impedance value (R4C4) and the impedance value (R5C5). The CPE impedance is composed of the CPE constant T and the CPE index, and is used as a parameter for convenience in fitting the shape in curve fitting when the capacitive semicircle in the Nyquist plot of actual measurement does not become a perfect circle. However, this is not limited to the above method. In order to give chemical meaning to the electric double layer capacitance (capacitor) of the impedance value (R4C4) and the impedance value (R5C5), the number of stages of the RC arc may be increased.

[0379] In the above example, the impedance value (R4C4) and the impedance value (R5C5) were calculated by curve fitting in the equivalent circuit model. However, the impedance may be obtained by calculating the overvoltages at the negative and positive electrodes using the Butler-Volmer equation. Alternatively, the impedance may be obtained by simulating the electrochemical behavior of the battery using software (pseudo two-dimensional (P2D) electrochemical model).

[0380] In the summary of the third embodiment above, it has been stated that the battery monitoring device 1D according to the third embodiment has the basic configuration of the battery monitoring devices according to the first and second embodiments, but this is not limited thereto. For example, the battery monitoring device 1D according to the third embodiment may have the following configuration.

[0381] The battery monitoring device 1D of embodiment 3 includes an impedance acquisition unit 23a that acquires the impedance of the secondary battery 5 to be monitored, an arithmetic processing unit 23D that estimates the battery state of the secondary battery 5 to be monitored based on the impedance acquired by the impedance acquisition unit 23a, and an external temperature acquisition unit 15 that acquires the external temperature of the secondary battery 5 to be monitored, and the arithmetic processing unit 23D may estimate the internal temperature of the secondary battery 5 based on the impedance acquired by the impedance acquisition unit 23a, and correct the estimated internal temperature of the secondary battery 5 based on the external temperature acquired by the external temperature acquisition unit 15.

[0382] The circuit configurations described in the above embodiments are merely examples, and the present disclosure is not limited to the above circuit configurations. In other words, circuits that can achieve the characteristic functions of the present disclosure, similar to the above circuit configurations, are also included in the present disclosure. For example, the present disclosure also includes a circuit in which an element, such as a switching element (transistor), a resistive element, or a capacitive element, is connected in series or parallel to a certain element, as long as the circuit configuration can achieve the same functions.

[0383] In the above embodiments, the components included in the integrated circuit are implemented by hardware. However, some of the components included in the integrated circuit may be implemented by executing a software program suitable for the component. Some of the components included in the integrated circuit may be implemented by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0384] In the above-described embodiments, the processing performed by a specific processing unit may be performed by another processing unit. In the operations described in the above-described embodiments, the order of multiple processing operations may be changed, or multiple processing operations may be performed in parallel.

[0385] In addition, this disclosure also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art would think of, or forms realized by arbitrarily combining the components and functions of each embodiment within the scope that does not deviate from the intent of this disclosure.

[0386] The present disclosure is useful as a battery monitoring device that monitors the battery state of a secondary battery.

[0387] REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1D Battery monitoring device 2 Upper control unit 3 Load 4 Relay 5 Secondary battery 5a End 5b Center 5c Terminal 6 Assembled battery 7 Measurement unit 8, 8B, 8D Battery monitoring unit 9 Control unit 10 Communication unit 11 Current application line 12 Voltage detection line 13 Voltage measurement unit 14 Current measurement unit 14a Reference resistor 15 External temperature acquisition unit 16 Thermistor 17 Load resistor 18 Switching element 19 Shunt resistor 20 Signal generation unit 21 AC superposition measurement unit 22 Timing generation unit 23, 23B, 23D Calculation processing unit 23a Impedance acquisition unit 23b Capacity loss factor extraction unit 23c Temperature correction unit 23d Capacity loss estimation unit 23e SOH calculation unit 23h SOH correction unit 23i Internal temperature estimation factor extraction unit 23j Internal temperature estimation unit 23k Internal temperature correction unit 24 Memory unit 25 External storage device 26 SOH acquisition unit 27 Timer 31 Battery terminal 31a Positive battery terminal 31b Negative battery terminal 32 Bus bar 40 Resistor 41 Thermistor 50 Heat conduction member Dt Temperature correction data E1, E2 Relational formula I Resistance component of wiring system II Resistance component due to electrolyte III Resistance component due to deposits IV Resistance component of negative electrode V Resistance component of positive electrode

Claims

1. A battery monitoring device comprising: a memory unit that stores relationship data indicating the relationship between a resistance component that varies depending on the battery state of the secondary battery, among multiple resistance components that constitute the impedance of the secondary battery, and the battery state of the secondary battery; an impedance acquisition unit that acquires the impedance of the secondary battery to be monitored; and an arithmetic processing unit that calculates a value of the resistance component that varies depending on the battery state of the secondary battery to be monitored based on the impedance acquired by the impedance acquisition unit, and estimates the battery state of the secondary battery to be monitored based on the value of the resistance component and the relationship data.

2. The battery monitoring device of claim 1, wherein the memory unit stores, as the relationship data, a first relational equation indicating the relationship between a first resistance component that changes depending on the amount of capacity loss of the secondary battery and the amount of capacity loss of the secondary battery, and the arithmetic processing unit calculates the value of the first resistance component of the secondary battery to be monitored based on the impedance acquired by the impedance acquisition unit, and estimates the amount of capacity loss of the secondary battery to be monitored based on the value of the first resistance component and the first relational equation.

3. The battery monitoring device according to claim 2, wherein the first relational equation is derived based on the amount of capacity loss of a plurality of the secondary batteries whose battery capacity is equal to or less than that of the initial product, and a plurality of the first resistance components obtained by measuring the impedance of a plurality of the secondary batteries.

4. The battery monitoring device according to claim 3, wherein the amount of capacity loss of the secondary battery in the first relational expression is calculated based on the amount of irreversible lithium remaining in the negative electrode of the secondary battery.

5. The battery monitoring device of claim 3, wherein the first resistance component in the first relational expression is obtained by subtracting from the impedance of the secondary battery whose battery capacity is equal to or less than that of an initial product, the resistance components of the wiring connected to the secondary battery and between the wiring and the secondary battery, the resistance component based on the mobile resistance in the electrolyte of the secondary battery, and the resistance component of the negative electrode and the resistance component of the positive electrode of the secondary battery.

6. The battery monitoring device of claim 2, wherein the arithmetic processing unit calculates the value of the first resistance component by subtracting from the impedance acquired by the impedance acquisition unit the resistance components of the wiring connected to the secondary battery to be monitored and between the wiring and the secondary battery, the resistance component based on the mobile resistance in the electrolyte of the secondary battery, and the resistance component of the negative electrode and the resistance component of the positive electrode of the secondary battery.

7. The battery monitoring device according to claim 2, wherein the first resistance component is a resistance component due to deposits deposited on the surface of the negative electrode of the secondary battery.

8. The battery monitoring device of claim 2, wherein the calculation processing unit estimates the current capacity of the secondary battery being monitored by subtracting the amount of capacity loss estimated by the calculation processing unit from the initial capacity of the secondary battery being monitored.

9. The battery monitoring device of claim 1, wherein the memory unit stores, as the relationship data, a second relational equation indicating the relationship between a second resistance component that changes depending on the internal temperature of the secondary battery and the internal temperature of the secondary battery, and the arithmetic processing unit calculates the value of the second resistance component of the secondary battery to be monitored based on the impedance acquired by the impedance acquisition unit, and estimates the internal temperature of the secondary battery to be monitored based on the value of the second resistance component and the second relational equation.

10. The battery monitoring device of claim 9, further comprising a SOH acquisition unit that acquires the SOH (State of Health) of the secondary battery to be monitored, wherein the memory unit further stores a first relational equation indicating the relationship between a first resistance component that varies depending on the amount of capacity loss of the secondary battery and the amount of capacity loss of the secondary battery, and the arithmetic processing unit calculates the value of the first resistance component of the secondary battery to be monitored based on the SOH acquired by the SOH acquisition unit and the first relational equation, and acquires the value of the second resistance component based on the value of the first resistance component.

11. The battery monitoring device of claim 10, wherein the calculation processing unit calculates the value of the second resistance component by subtracting from the impedance acquired by the impedance acquisition unit the resistance components of the wiring connected to the secondary battery to be monitored and between the wiring and the secondary battery, the first resistance component, and the resistance components of the negative electrode and positive electrode of the secondary battery.

12. The battery monitoring device according to claim 9, wherein the second resistance component is a resistance component based on a migration resistance in an electrolyte of the secondary battery.

13. A battery monitoring device as described in any one of claims 1 to 12, further comprising an external temperature acquisition unit that acquires the external temperature of the secondary battery to be monitored, and a temperature correction unit that corrects a resistance component that varies depending on the battery state based on the external temperature, wherein the calculation processing unit estimates the battery state of the secondary battery to be monitored based on the resistance component after correction by the temperature correction unit.

14. A battery monitoring device according to any one of claims 1 to 12, further comprising a communication unit that transmits the data stored in the memory unit to an external device.

15. The battery monitoring device of claim 1, further comprising an external temperature acquisition unit that acquires the external temperature of the secondary battery to be monitored, wherein the calculation processing unit estimates the internal temperature of the secondary battery based on the impedance acquired by the impedance acquisition unit, and corrects the estimated internal temperature of the secondary battery based on the external temperature acquired by the external temperature acquisition unit.

16. The battery monitoring device of claim 15, wherein the calculation processing unit: (1) estimates an internal temperature of the secondary battery based on the impedance acquired by the impedance acquisition unit, and when a change in the internal temperature is within a first range, re-estimates the internal temperature of the secondary battery based on the impedance acquired again by the impedance acquisition unit; and (2) corrects the re-estimated internal temperature of the secondary battery based on the external temperature acquired by the external temperature acquisition unit.

17. The battery monitoring device of claim 15, wherein the calculation processing unit: (1) estimates an internal temperature of the secondary battery based on the impedance acquired by the impedance acquisition unit when the change in the external temperature is within a second range; and (2) corrects the estimated internal temperature of the secondary battery based on the external temperature acquired by the external temperature acquisition unit.

18. The battery monitoring device of claim 15, wherein the external temperature acquisition unit acquires the external temperatures at two or more locations of a battery pack having a plurality of the secondary batteries to be monitored, and the calculation processing unit: (1) estimates the internal temperature of the secondary battery based on the impedance acquired by the impedance acquisition unit when a difference between the external temperatures at the two or more locations is within a third range; and (2) corrects the estimated internal temperature of the secondary battery based on the external temperatures at the two or more locations acquired by the external temperature acquisition unit.

19. The battery monitoring device as described in claim 18, wherein the external temperature acquisition unit acquires the external temperatures at two or more locations based on output signals from two or more thermistors provided at the center and ends of the battery pack.

20. The battery monitoring device of claim 15, wherein the calculation processing unit: (1) estimates an internal temperature of the secondary battery based on the impedance acquired again by the impedance acquisition unit when the change in the impedance acquired by the impedance acquisition unit is within a fourth range; and (2) corrects the estimated internal temperature of the secondary battery based on the external temperature acquired by the external temperature acquisition unit.

21. The battery monitoring device of claim 15, further comprising a resistor to which a current and voltage having the same measurement conditions as those of the secondary battery can be applied, wherein the calculation processing unit: (1) estimates an internal temperature of the secondary battery based on the impedance acquired by the impedance acquisition unit when the change in temperature of the resistor is within a fifth range; and (2) corrects the estimated internal temperature of the secondary battery based on the external temperature acquired by the external temperature acquisition unit.

22. A battery monitoring device as described in any one of claims 15 to 21, wherein the calculation processing unit derives the correction data based on temperature correction data indicating the relationship between the external temperature, the internal temperature of the secondary battery, and correction data for the internal temperature, which is stored in advance in the memory unit, and corrects the internal temperature of the secondary battery based on the correction data.

23. A battery monitoring device as described in any one of claims 15 to 21, wherein the external temperature acquisition unit acquires the external temperature based on an output signal of a thermistor connected to a thermally conductive member covering at least a portion of the secondary battery.

24. A battery monitoring device according to any one of claims 15 to 21, wherein the external temperature acquisition unit acquires the external temperature based on an output signal of a thermistor connected to a terminal portion of the secondary battery.

25. A battery monitoring method including: a relationship data acquisition step of acquiring relationship data indicating the relationship between a resistance component that varies depending on the battery state of the secondary battery, among multiple resistance components that constitute the impedance of the secondary battery, and the battery state of the secondary battery; an impedance acquisition step of acquiring the impedance of the secondary battery to be monitored; and a calculation step of calculating a value of the resistance component that varies depending on the battery state of the secondary battery to be monitored based on the impedance acquired in the impedance acquisition step, and estimating the battery state of the secondary battery to be monitored based on the value of the resistance component and the relationship data.

26. A battery monitoring method as described in claim 25, wherein in the relationship data acquisition step, a first relational equation indicating a relationship between a first resistance component that varies depending on the amount of capacity loss of the secondary battery and the amount of capacity loss of the secondary battery is acquired as the relationship data, and in the calculation step, a value of the first resistance component of the secondary battery to be monitored is calculated based on the impedance acquired in the impedance acquisition step, and the amount of capacity loss of the secondary battery to be monitored is estimated based on the value of the first resistance component and the first relational equation.

27. A battery monitoring method as described in claim 25, wherein in the relationship data acquisition step, a second relational equation indicating the relationship between a second resistance component that changes depending on the internal temperature of the secondary battery and the internal temperature of the secondary battery is acquired as the relationship data, and in the calculation step, a value of the second resistance component of the secondary battery to be monitored is calculated based on the impedance acquired in the impedance acquisition step, and the internal temperature of the secondary battery to be monitored is estimated based on the value of the second resistance component and the second relational equation.

28. A battery monitoring method as described in claim 25, further comprising an external temperature acquisition step of acquiring the external temperature of the secondary battery to be monitored, wherein the calculation step estimates an internal temperature of the secondary battery based on the impedance acquired in the impedance acquisition step, and corrects the estimated internal temperature of the secondary battery based on the external temperature acquired in the external temperature acquisition step.

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