battery cell

Abstract

To solve the above problem, the battery unit of the present application, which includes a battery module having a battery cell, includes: a battery heat detection section that detects heat of the battery cell; a storage section that stores an initial characteristic of the heat HF of the battery cell with respect to a state of charge SOC; and a battery state estimation section that estimates a state of health SOH of the battery cell. The battery state estimation section measures a current characteristic of the HF of the battery cell with respect to the SOC based on the heat of the battery cell detected by the battery heat detection section when the battery cell is charged, and estimates the state of health SOH of the battery cell based on a ratio of a length mAh of a line segment between peaks in a differential characteristic of the current characteristic of the HF with respect to the SOC to a length mAh of a line segment between peaks in a differential characteristic of the initial characteristic of the HF with respect to the SOC stored in the storage section.

Description

Technical Field

[0001] This invention relates to a storage battery unit. Background Technology

[0002] In recent years, with the widespread use of electrical and electronic devices of various sizes, such as automobiles, personal computers, and information terminals, battery cells have been widely used as the power source for these devices. In particular, in the automotive sector, in order to mitigate the adverse impacts on the Earth's environment, and from the perspective of climate-related disasters and natural disasters, in order to reduce CO2 and improve the Earth's environment, there has been increased attention on electric vehicles, and the use of battery cells in vehicle applications is being explored.

[0003] In order to use electronic and electrical equipment efficiently and safely, it is crucial to have techniques for estimating the state of charge (SOC) or state of health (SOH) of individual battery cells. For example, it is known that the state of a battery cell, such as SOC or SOH, is correlated with its voltage. Therefore, techniques for estimating the state of a battery cell, such as SOC or SOH, based on its voltage are known (see, for example, Patent Documents 1 and 2).

[0004] [Previous Technical Documents]

[0005] (Patent Documents)

[0006] Patent Document 1: Japanese Patent No. 5287844

[0007] Patent Document 2: Japanese Patent No. 5044511

[0008] (Non-patent literature)

[0009] Non-patent literature 1: G. Assat et al., “Probing the thermal effects of voltage hysteresis in anionic redox-based lithium-rich cathodes using isothermal calorimetry”, Nature Energy, Vol. 4, August 2019, pp. 647-656. Summary of the Invention

[0010] [The problem the invention aims to solve]

[0011] This invention relates to a technique for estimating the State of Health (SOH) of a single battery cell. SOH is defined by the following formula.

[0012] SOH = {Current (at degradation) full charge capacity (SOC 0% - 100%)} / {Initial full charge capacity (SOC 0% - 100%)} ... (Equation)

[0013] Therefore, the simplest known method for SOH estimation is as follows: pre-store the initial full charge capacity (SOC 0%-100%), measure the current (degraded) full charge capacity (SOC 0%-100%) during actual use, and use the above formula to estimate SOH.

[0014] However, in actual use, charging does not start from 0% SOC. Furthermore, in actual use, charging is not limited to reaching 100% SOC. Therefore, to determine the current (in deterioration) fully charged capacity (0%-100% SOC), for example, it is necessary to stop using the battery cell and discharge it to 0% SOC, then charge it from 0% to 100% SOC. Moreover, by charging with a constant current and a low rate, the capacity (mAh) can be calculated from the charging current (mA) and charging time (h).

[0015] Regarding this aspect, the inventors of this application propose to estimate SOH based on a portion of the closed-circuit voltage (CCV) characteristic relative to SOC. For example, in lithium-ion batteries using graphite as the negative electrode material, peaks associated with phase transitions exist in the differential characteristic of CCV relative to SOC, i.e., the differential characteristic of CCV = f(SOC) d(CCV) / d(SOC) with respect to SOC. In lithium-ion batteries where SOC 0% is mainly determined by the potential of the negative electrode, the length (mAh) of the segment between these peaks is related to the overall capacity (mAh) of the battery cell.

[0016] Therefore, in the proposed SOH estimation, the length of the line segment between the peaks in the differential characteristic of the initial characteristic of CCV relative to SOC (mAh) is stored in advance. During actual use and charging, the length of the line segment between the peaks in the differential characteristic of the current (degraded) characteristic of CCV relative to SOC (mAh) is measured, and the SOH is estimated using the following formula.

[0017] SOH = {the length of the line segment between the peaks in the differential characteristic of CCV relative to SOC (when it is deteriorated), in mAh} / {the length of the line segment between the peaks in the differential characteristic of CCV relative to SOC, in mAh} ... (Equation)

[0018] Furthermore, in actual use, charging is constant current and at a low rate, so the length of the segment between the peaks (mAh) can be calculated based on the charging current (mA) and the charging time (h). According to the proposed SOH estimate, since charging does not need to start from SOC 0%, and furthermore, since charging to SOC 100% is not required, it can be performed during actual use.

[0019] However, in the differential characteristics of CCV relative to SOC, the peak size is relatively small, the spectrum is relatively flat, and the signal-to-noise (S / N) ratio is relatively low. Therefore, it can be expected that the SOH estimation accuracy of the proposal based on the differential characteristics of CCV relative to SOC for estimating the SOH of a battery cell will be relatively low.

[0020] The purpose of this invention is to provide a battery unit that improves the estimation accuracy of the state of harmonics (SOH) of a single battery cell.

[0021] [Technical means to solve the problem]

[0022] The inventors of this application have obtained the following insights: the State of Charge (SOC) of a battery cell is correlated with the heat flow (HF) of the battery cell generated by phase changes in the active materials of the electrode materials. Furthermore, the inventors of this application have obtained the following insights: the length (mAh) of the line segment between the peaks in the differential characteristic of HF relative to SOC is related to the overall capacity (mAh) of the battery cell. In the differential characteristic of HF relative to SOC, compared with the differential characteristic of CCV relative to SOC,

[0023] • The peaks are relatively large, the spectrum is sharp, and the S / N ratio is large;

[0024] Furthermore, there are many peaks and the intervals between peaks are small;

[0025] Furthermore, the specific pattern between positive and negative peaks remains unchanged even with degradation; in other words, even with degradation, the position of the peaks for SOC is not easily shifted.

[0026] Therefore, the inventors of this application propose a method for estimating the SOH of a battery cell based on the heat of the battery cell, specifically the HF characteristics relative to SOC, and more specifically the differential characteristics of HF relative to SOC.

[0027] (1) Therefore, the battery unit of the present invention includes a battery module having battery cells, the battery unit including: a battery heat detection unit for detecting the heat HF ​​of the aforementioned battery cell; a storage unit for storing the initial characteristics of the HF of the aforementioned battery cell relative to SOC; and a battery state estimation unit for estimating the degradation state SOH of the aforementioned battery cell. When the aforementioned battery cell is charging, the aforementioned battery state estimation unit measures the current characteristics of the HF of the aforementioned battery cell relative to SOC based on the HF of the aforementioned battery cell detected by the aforementioned battery heat detection unit, and estimates the first degradation state SOH (Real, R) of the aforementioned battery cell based on the ratio of the length mAh of the line segment between the peaks in the differential characteristic of the current characteristic of the aforementioned HF relative to SOC to the length mAh of the line segment between the peaks in the differential characteristic of the aforementioned initial characteristic of the aforementioned HF relative to SOC stored in the aforementioned storage unit.

[0028] In addition, the inventors of this application focus on the enthalpy potential (UH) calculated using the following formula based on the closed-circuit voltage CCV, heat HF ​​and current I.

[0029] UH = CCV - HF / I···(Equation)

[0030] The inventors of this application have obtained the following insight: the length of the line segment between the peaks in the differential characteristic of UH relative to SOC (mAh) is also related to the overall capacity (mAh) of the battery cell. Even in the differential characteristic of UH relative to SOC, compared with the differential characteristic of CCV relative to SOC, the following will occur:

[0031] • The peaks are relatively large, the spectrum is sharp, and the S / N ratio is large;

[0032] Furthermore, there are many peaks and the intervals between peaks are small;

[0033] Furthermore, the specific pattern between positive and negative peaks remains unchanged even with degradation; in other words, even with degradation, the position of the peaks for SOC is not easily shifted.

[0034] Therefore, the inventors of this application propose a method for estimating the SOH of a battery cell based on the enthalpy potential UH of the battery cell, specifically the characteristics of UH relative to SOC, and more specifically the differential characteristics of UH relative to SOC.

[0035] (2) Therefore, another battery unit of the present invention includes a battery module having battery cells, the battery unit including: a battery heat detection unit for detecting the heat of the aforementioned battery cells; a voltage detection unit for detecting the closed-circuit voltage of the aforementioned battery cells; a current detection unit for detecting the current of the aforementioned battery cells; a storage unit for storing the initial characteristics of the aforementioned battery cells UH relative to SOC, wherein the enthalpy potential UH is calculated using the following formula based on the closed-circuit voltage CCV, heat HF ​​and current I; and a battery state estimation unit for estimating the degradation state SOH of the aforementioned battery cells.

[0036] UH = CCV - HF / I···(Equation)

[0037] When the aforementioned battery cell is charging, the aforementioned battery state estimation unit measures the current characteristics of the battery cell's UH relative to SOC based on the heat HF, closed-circuit voltage CCV, and current I detected by the aforementioned battery heat detection unit, the aforementioned voltage detection unit, and the aforementioned current detection unit. It then estimates the second degradation state SOH (Ideal, I) of the aforementioned battery cell based on the ratio of the length mAh of the line segment between the peaks in the differential characteristic of the current UH relative to SOC to the length mAh of the line segment between the peaks in the differential characteristic of the initial UH relative to SOC stored in the aforementioned storage unit.

[0038] Furthermore, the inventors of this application focus on the differential enthalpy potential ΔUH obtained by subtracting the initial characteristics of the enthalpy potential from the current characteristics of the enthalpy potential. The inventors of this application have gained the following insight: the magnitude of the peak in the differential characteristic of ΔUH relative to SOC is related to the overall capacity (mAh) of the battery cell. In the differential characteristic of ΔUH relative to SOC, compared to the differential characteristic of CCV relative to SOC,

[0039] • The peaks are relatively large, the spectrum is sharp, and the S / N ratio is large;

[0040] Furthermore, there are many peaks and the intervals between peaks are small;

[0041] Furthermore, the specific pattern between positive and negative peaks remains unchanged even with degradation; in other words, even with degradation, the position of the peaks for SOC is not easily shifted.

[0042] Therefore, the inventors of this application propose a method for estimating the SOH of a battery cell based on the differential enthalpy potential of the battery cell, specifically the characteristic of ΔUH relative to SOC, and more specifically the differential characteristic of ΔUH relative to SOC.

[0043] (3) Therefore, another battery unit of the present invention includes a battery module having battery cells, the battery unit including: a battery heat detection unit for detecting the heat of the aforementioned battery cells; a voltage detection unit for detecting the closed-circuit voltage of the aforementioned battery cells; a current detection unit for detecting the current of the aforementioned battery cells; a storage unit for storing the initial characteristics of the UH of the aforementioned battery cells relative to the SOC, wherein the enthalpy potential UH is calculated using the following formula based on the closed-circuit voltage CCV, the heat HF ​​and the current I; and a battery state estimation unit for estimating the deterioration state SOH of the aforementioned battery cells.

[0044] UH = CCV - HF / I···(Equation)

[0045] When the aforementioned battery cell is charging, the aforementioned battery state estimation unit measures the current characteristics of the battery cell's UH relative to SOC based on the HF, CCV, and I of the aforementioned battery cell detected by the aforementioned battery heat detection unit, the aforementioned voltage detection unit, and the aforementioned current detection unit. It calculates the ΔUH relative to SOC characteristic obtained by subtracting the initial characteristics of the aforementioned UH relative to SOC stored in the aforementioned storage unit from the measured current characteristics of the aforementioned UH relative to SOC. Based on the magnitude of the peak in the calculated differential characteristics of the aforementioned ΔUH relative to SOC, it estimates the second degradation state SOH(I) of the aforementioned battery cell.

[0046] Here, since the closed-circuit voltage CCV or heat HF ​​mentioned above individually includes resistance loss (insulation resistance (IR) loss), the SOH estimated based on the characteristics of CCV relative to SOC or HF relative to SOC also includes the increase in resistance loss caused by the increase in internal resistance R resulting from accompanying degradation. On the other hand, since the resistance loss included in CCV and the resistance loss included in HF are eliminated in the above UH, the SOH estimated based on the characteristics of UH relative to SOC is an ideal capacity that eliminates the increase in resistance loss caused by the increase in internal resistance resulting from accompanying degradation. Therefore, the inventors of this application propose to estimate the increase in resistance loss caused by the increase in internal resistance resulting from accompanying degradation based on the first degradation state SOH(R) estimated by the SOH estimation of this invention (1) and the second degradation state SOH(I) estimated by the SOH estimation of this invention (3).

[0047] (4) Therefore, optionally, the battery cell of the present invention (1) further includes: a voltage detection unit for detecting the closed-circuit voltage of the aforementioned battery cell; and a current detection unit for detecting the current of the aforementioned battery cell; in the battery cell of the present invention (1), the aforementioned storage unit also stores the initial characteristics of the UH of the aforementioned battery cell relative to the SOC, wherein the enthalpy potential UH is calculated using the following formula based on the closed-circuit voltage CCV, the heat HF ​​and the current I.

[0048] UH = CCV - HF / I···(Equation)

[0049] The aforementioned battery state estimation unit further measures the current characteristics of the battery cell's UH relative to SOC during battery cell charging based on the HF, CCV, and I of the battery cell detected by the aforementioned battery heat detection unit, the aforementioned voltage detection unit, and the aforementioned current detection unit. It then calculates the differential enthalpy potential ΔUH relative to SOC characteristic obtained by subtracting the initial characteristics of the UH relative to SOC stored in the aforementioned storage unit from the measured current characteristics of the UH relative to SOC. Based on the magnitude of the peak in the calculated differential characteristics of the ΔUH relative to SOC, it estimates the second degradation state SOH(I) of the battery cell. Based on the difference between the first degradation state SOH(R) and the second degradation state SOH(I), it estimates the increase in resistance loss (IR loss) that accompanies the degradation of the battery cell.

[0050] (5) In the battery cell of the present invention (3) or (4), optionally, the aforementioned storage unit pre-stores the differential characteristic of the aforementioned ΔUH relative to SOC under the specified second deterioration state SOH(I) of the aforementioned battery cell, and the aforementioned battery state estimation unit assumes that there is a proportional relationship between the aforementioned second deterioration state SOH(I) and the size of the aforementioned peak based on the size of the peak in the differential characteristic of the aforementioned ΔUH relative to SOC under the specified second deterioration state SOH(I) stored in the aforementioned storage unit, and estimates the second deterioration state SOH(I) of the aforementioned battery cell based on the aforementioned proportional relationship and the calculated size of the peak in the differential characteristic of the aforementioned ΔUH relative to SOC.

[0051] (6) Optionally, the battery cell of the present invention further includes a reference heat detection unit, which detects the heat of the aforementioned battery cell as a reference heat. In the battery cell of the present invention, the aforementioned battery state estimation unit uses the heat that has been removed from the heat of the aforementioned battery cell by subtracting the reference heat detected by the aforementioned reference heat detection unit from the heat detected by the aforementioned battery heat detection unit as the heat of the aforementioned battery cell.

[0052] (The effect of the invention)

[0053] According to the invention described in (1) to (3) and (5), the SOH estimation accuracy of a battery cell can be improved compared with the SOH estimation of a battery cell based on the differential characteristics of CCV relative to SOC.

[0054] Furthermore, according to the invention described in (2) to (3), SOH estimation can be performed using only an ideal capacitance degradation component that does not contain resistance degradation components.

[0055] In addition, according to the invention described in (4), the increase in resistance loss (IR loss) caused by the increase in internal resistance R that accompanies degradation can be estimated.

[0056] Furthermore, according to the invention described in (6), since it is based on the heat after removing the noise in the battery cell, the estimation accuracy of the SOH of the battery cell can be further improved. Attached Figure Description

[0057] Figure 1 This is an exploded perspective view illustrating the battery unit of this embodiment.

[0058] Figure 2A yes Figure 1 The image shows a side view of an example of a battery module in a battery cell.

[0059] Figure 2B yes Figure 1 The image shows a side view of another example of a battery module in a battery cell.

[0060] Figure 3A This is a diagram illustrating an example of the characteristics of HF relative to SOC and UH relative to SOC in the initial state of this embodiment.

[0061] Figure 3B This is a diagram illustrating an example of the HF characteristics relative to SOC and the UH characteristics relative to SOC under a slightly degraded state according to this embodiment.

[0062] Figure 3C This is a diagram illustrating an example of the characteristics of HF relative to SOC and UH relative to SOC under the deteriorated state in this embodiment.

[0063] Figure 3D It is an overlay drawing Figure 3A The initial state HF characteristics relative to SOC are illustrated in the figure. Figure 3B The small degradation state of HF relative to SOC characteristics is illustrated in the figure. Figure 3C The figure shows the characteristics of HF versus SOC in a moderately degraded state.

[0064] Figure 4This is a diagram illustrating an example of the differential characteristics (small degradation state) of HF relative to SOC in this embodiment.

[0065] Figure 5 This is a diagram illustrating an example of the differential characteristics (small degradation state) of UH relative to SOC in this embodiment.

[0066] Figure 6A This is a diagram illustrating an example of the ΔUH characteristic relative to SOC in this embodiment.

[0067] Figure 6B This is a diagram illustrating an example of the differential characteristics of ΔUH relative to SOC in this embodiment.

[0068] Figure 7 This is a diagram illustrating an example of the differential characteristics (small degradation state) of CCV relative to SOC for a comparative example. Detailed Implementation

[0069] Hereinafter, an example of an embodiment of the present invention will be described with reference to the accompanying drawings. Furthermore, in each drawing, the same or equivalent parts are labeled with the same symbols.

[0070] (Battery unit)

[0071] Figure 1 This is an exploded perspective view illustrating the battery unit of this embodiment. Figure 2A yes Figure 1 The image shows a side view of an example of a battery module in a battery cell. Figure 1 The battery unit 100 shown is a battery pack (also known as an intelligent power unit) installed in electric vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), or battery electric vehicles (BEV).

[0072] like Figure 1 and Figure 2A As shown, the battery unit 100 mainly includes a battery module 110, a battery heat detection unit 120, a reference heat detection unit 130, a voltage detection unit 141, a current detection unit 142, a temperature detection unit 143, and a battery management system (BMS) 200. Figure 1In this example, the components of the battery unit 100 are housed in a housing 101 and covered by a cover 102.

[0073] In addition, Figure 1 In this example, the battery unit 100 includes a lower frame 103 and an upper frame 104. Additionally, the battery unit 100 includes a lower cooling plate 105 for cooling the battery module 110. Furthermore, the battery unit 100 includes a mechanism (e.g., a fan, air duct, and intake duct) 106 for introducing air to cool the battery module 110.

[0074] like Figure 2A As shown, the battery module 110 mainly includes: a laminate 112 on which multiple battery cells 111 are stacked; a pair of end plates 113 clamping the laminate 112 in the stacking direction; and a cell busbar 114 connecting the multiple battery cells 111. Furthermore, as... Figure 1 As shown, it can also be configured as multiple battery modules 110 connected by module bus 119.

[0075] As for the battery cell 111, there is no particular limitation; for example, a lithium-ion battery can be listed. Among lithium-ion batteries, it is preferable to use a lithium-ion battery that uses a material such as graphite, which generates heat during phase transitions, as the negative electrode material, or a lithium-ion battery that uses a material such as layered compound lithium cobalt oxide (LCO) or lithium nickel oxide (LNO), which generates heat during phase transitions, as the positive electrode material.

[0076] The following description pertains to lithium-ion batteries that use graphite, a material that generates heat during phase transitions, as the negative electrode, and lithium nickel cobalt manganese oxide (NCM), a layered compound, as the positive electrode (SOC 0% is primarily determined by the potential of the negative electrode: negative electrode cut-off). However, the present invention can also be applied to lithium-ion batteries that use materials such as LCO or LNO, which generate heat during phase transitions, as the positive electrode (SOC 0% is primarily determined by the potential of the positive electrode: positive electrode cut-off).

[0077] The battery heat detection unit 120 is a heat sensor that not only detects the heat of the battery cell 111 and the battery unit 100, i.e. the heat of the battery cell 111, but also detects the influence of various heats within the battery unit 100, i.e. the heat caused by noise.

[0078] As a heat sensor, there are no particular limitations; examples include Peltier elements, thermopile devices, and thermocouples. Among these, Peltier elements, which have high heat flux sensitivity and can also be used as temperature regulating devices, are preferred. Figure 2A As shown, a Peltier element is sometimes placed between the battery cell 111 and the cooling plate 105 to cool the battery cell 111. In this case, the Peltier element can be used for both heat detection and cooling. For example, the Peltier element can be used as a heat sensor for heat detection, and also for cooling.

[0079] The battery thermal detection unit 120 can be disposed on at least one of the battery cells 111 in the battery module 110. Furthermore, as... Figure 2A As shown, the battery heat detection unit 120 can also be disposed on two battery cells 111 adjacent to the end plate 113. Alternatively, the battery heat detection unit 120 can be disposed not only on the two battery cells 111 adjacent to the end plate 113, but also on the battery cell 111 located at the center in the stacking direction of the battery cells 111.

[0080] The reference heat detection unit 130 is a heat sensor that detects the heat of the battery unit 100, that is, the various types of heat within the battery unit 100, such as the heat from noise, as the reference heat.

[0081] Similarly, as described above, there are no particular limitations on the heat sensor; examples include Peltier elements, thermopile devices, and thermocouples. Among these, Peltier elements are preferred. Therefore, the Peltier element used for cooling the battery cell 111 can also be used for heat detection and cooling.

[0082] The reference heat detection unit 130 is disposed in the battery unit 100 in a location where the temperature fluctuation is small and the heat capacity is large. For example, any of the following (A) to (F) can be listed as the location of the reference heat detection unit 130.

[0083] (A) Cooling plate 105 for cooling battery module 110

[0084] For example, such as Figure 1 As shown, the cooling plate 105 is arranged in contact with the bottom surface of the battery module 110, and the reference heat detection unit 130 is disposed in the cooling plate 105 on a side that does not face the bottom surface of the battery cell 111. The arrangement relative to the plurality of battery cells 111 is not particularly limited, for example, it may be arranged corresponding to the battery cell 111 located in the center of the stacking direction of the battery cells 111.

[0085] (B) End plate 113 in battery module 110

[0086] Figure 2B yes Figure 1 The image shows a side view of another example of a battery module in a battery cell. (See image for reference.) Figure 2B As shown, for example, the reference heat detection unit 130 in the end plate 113 may also be configured on a side that is not opposite to the battery cell 111.

[0087] (C) Busbars 114 and 119 in battery module 110

[0088] For example, the reference heat detection unit 130 is located in the cell bus 114 that connects the battery cells 111 to each other (see reference). Figure 2A Alternatively, it can be configured on a side that does not face the battery cell 111. Additionally, for example, the reference heat detection unit 130 is located in the module bus 119 connecting the battery modules 110 to each other (see reference). Figure 1 Alternatively, it can be configured on a side that is not opposite to the battery cell 111. There are no particular limitations on the configuration of multiple battery cells 111; for example, it can be configured to correspond to the battery cell 111 located in the center of the stacking direction of the battery cells 111.

[0089] (D) Flange within battery cell 100

[0090] like Figure 1 As shown, for example, the reference heat detection unit 130 can also be configured on the flange (connector) of the battery module within the fixed battery unit 100.

[0091] (E) Space within the battery unit 100

[0092] like Figure 1 As shown, for example, the reference heat detection unit 130 can also be configured in a floating state within the space of the battery unit 100.

[0093] (F) Conduit protecting high-voltage conductors

[0094] like Figure 1 As shown, for example, the reference heat detection unit 130 can also be configured in or outside the conduit protecting the high-voltage conductor (for example, in the conduit if exposed to the outside air, and outside the conduit if not exposed to the outside air).

[0095] Alternatively, the battery heat detection unit 120 may be disposed on two battery cells 111 adjacent to the end plate 113, while the reference heat detection unit 130 may be disposed on a battery cell 111 other than the battery cell 111 in which the battery heat detection unit 120 is disposed, for example, on the battery cell 111 located at the center in the stacking direction of the battery cells 111.

[0096] The voltage detection unit 141 is a voltage sensor that detects the closed-circuit voltage of the battery cell 111. The configuration of the voltage detection unit 141 is not particularly limited; for example, ... Figure 2A As shown, it can also be configured on the battery module 110.

[0097] The current detection unit 142 is a current sensor that detects the current of the battery cell 111. The configuration of the current detection unit 142 is not particularly limited; for example, ... Figure 2A As shown, it can also be configured on the battery module 110.

[0098] Temperature detection unit 143 is a temperature sensor that detects the temperature of various parts. There are no particular limitations on the type of temperature sensor; for example, a thermocouple can be used. Figure 2A As shown, the temperature detection unit 143 is disposed on each battery cell 111 to detect the temperature of each battery cell 111. Additionally, the temperature detection unit 143 is disposed at the location where the battery heat detection unit 120 is located to detect the temperature at the heat detection location. Furthermore, as... Figure 1 and Figure 2B As shown, the temperature detection unit 143 is disposed at the position where the reference heat detection unit 130 is disposed, and detects the temperature at the heat detection position.

[0099] (Battery Management System: Battery Status Estimation Department)

[0100] The battery management system (BMS) 200 performs overall control of the battery cells 111, including charge and discharge control, overcharge protection, over-discharge protection, and monitoring of the battery's state of charge (SOC) or state of health (SOH). The battery management system 200 mainly includes a battery state estimation unit 210 and a storage unit 220.

[0101] The battery state estimation unit 210 is configured, for example, by a digital signal processor (DSP) or a field-programmable gate array (FPGA). The various functions of the battery state estimation unit 210 are implemented, for example, by executing predetermined software (programs) stored in the storage unit 220. The various functions of the battery state estimation unit 210 can be implemented either through a combination of hardware and software, or solely through hardware (electronic circuitry).

[0102] Storage unit 220 is a rewritable memory such as electrically erasable programmable read-only memory (EEPROM). Storage unit 220 stores the software (program) specified for performing the various functions of battery state estimation unit 210.

[0103] In addition, such as Figure 3A As shown, the storage unit 220 stores, in a table-mapped format, characteristics related to the correlation between the heat HF ​​and SOC of the battery cell 111 in its initial state (initial characteristics of HF relative to SOC), that is, multiple characteristics of the battery cell 111 at various temperatures and currents (charging). Additionally, as... Figure 3A As shown, the storage unit 220 stores, in a table-mapped format, characteristics related to the correlation between the enthalpy potential UH and the state of charge (SOC) of the battery cell 111 in its initial state (the initial characteristics of UH relative to SOC), that is, multiple characteristics of the battery cell 111 at various temperatures and currents (charging). Furthermore, as... Figure 3A As shown, the storage unit 220 can also store, in a table-mapped format, the characteristics related to the correlation between the closed-circuit voltage CCV and the state of charge (the initial characteristics of CCV relative to the state of charge), that is, the multiple characteristics of the battery cell 111 at various temperatures and currents (charging).

[0104] Here, enthalpy potential UH refers to the parameter calculated using the following formula based on the heat HF, closed-circuit voltage CCV, and current I of the battery cell 111 (refer to Non-Patent Literature 1).

[0105] UH = CCV - HF / I···(Equation)

[0106] The battery state estimation unit 210, for example, during charging in actual use, such as... Figure 3B and Figure 3CAs shown, the actual characteristics of the heat HF ​​of the battery cell 111 relative to the state of charge (SOC) are measured. Based on the measured actual characteristics of HF relative to SOC and the initial characteristics of HF relative to SOC stored in the storage unit 220, the battery state of charge (SOH) estimation unit 210 estimates the state of degradation (SOH) of the battery cell. Details will be described below (SOH estimation 1).

[0107] Additionally, the battery state estimation unit 210, for example, during charging in actual use, such as... Figure 3B and Figure 3C As shown, the actual characteristics of the enthalpy potential UH of the battery cell 111 relative to the state of charge (SOC) are measured. Based on the measured actual characteristics of UH relative to SOC and the initial characteristics of UH relative to SOC stored in the storage unit 220, the battery state estimation unit 210 estimates the degradation state (SOH) of the battery cell. Details will be described below (SOH estimation 2).

[0108] Furthermore, the heat HF ​​of the battery cell 111 can be directly obtained from the heat detected by the battery heat detection unit 120. Alternatively, the heat HF ​​of the battery cell 111 can be obtained by subtracting the reference heat detected by the reference heat detection unit 130 from the heat detected by the battery heat detection unit 120. This allows for the acquisition of heat from the battery cell 111 that eliminates the influence of various heat sources within the battery unit 100, i.e., the influence of noise. Alternatively, the heat HF ​​of the battery cell 111 can be obtained by averaging the heat from the positive terminal side of the battery cell 111 with the heat from the negative terminal side.

[0109] Here, SOH is defined by the following formula.

[0110] SOH = {Current (at degradation) full charge capacity (SOC 0% - 100%)} / {Initial full charge capacity (SOC 0% - 100%)} ... (Equation)

[0111] Therefore, the simplest known method for SOH estimation is as follows: pre-store the initial full charge capacity (SOC 0%-100%), measure the current (degraded) full charge capacity (SOC 0%-100%) during actual use, and use the above formula to estimate SOH.

[0112] However, in actual use, charging does not start from 0% SOC. Furthermore, in actual use, charging is not limited to reaching 100% SOC. Therefore, to determine the current (in deterioration) fully charged capacity (0%-100% SOC), for example, it is necessary to stop using the battery cell and discharge it to 0% SOC, then charge it from 0% to 100% SOC. Moreover, by charging with a constant current and a low rate, the capacity (mAh) can be calculated from the charging current (mA) and charging time (h).

[0113] In this regard, the inventors of this application propose to estimate SOH based on a portion of the CCV characteristics relative to SOC. Figure 7 This is a graph illustrating the CCV characteristic relative to SOC and its differential characteristic, specifically the differential characteristic of CCV = f(SOC) d(CCV) / d(SOC) with respect to SOC. For example... Figure 7 As shown, for example, in a lithium-ion battery using graphite as the negative electrode and NCM as the positive electrode, the differential characteristic of CCV relative to SOC exhibits multiple peaks, including those associated with the phase transition corresponding to graphite. However, only two peaks are clearly visible.

[0114] In lithium-ion batteries with the negative electrode cutoff, the length of the segment between these peaks is related to the overall capacity of the battery cell. Therefore, knowing the length of the segment between the peaks (mAh) allows us to determine the overall capacity of the battery cell (mAh). For example, assuming an initial capacity of 100mAh from 0% to 100% SOC, the length of the segment between the peaks is 40mAh. Furthermore, the length of the segment between the peaks (mAh) can be calculated based on the charging current and charging time. As the battery cell deteriorates further, and the length of the segment between the peaks becomes 20mAh, the overall capacity of the battery cell becomes 50mAh.

[0115] Therefore, in the SOH estimation of the comparative example, the length of the line segment between the peaks in the differential characteristic of the initial characteristic of CCV relative to SOC (mAh) is stored in advance. During actual use and charging, the length of the line segment between the peaks in the differential characteristic of the current (degraded) characteristic of CCV relative to SOC (mAh) is measured, and the SOH is estimated using the following formula.

[0116] SOH = {the length of the line segment between the peaks in the differential characteristic of CCV relative to SOC (when it is deteriorated), in mAh} / {the length of the line segment between the peaks in the differential characteristic of CCV relative to SOC, in mAh} ... (Equation)

[0117] Furthermore, in actual use, charging is constant current and at a low rate, so the length of the segment between the peaks (mAh) can be calculated based on the charging current (mA) and the charging time (h). Based on the SOH estimation of this comparative example, since charging does not need to start from SOC 0%, and furthermore, since charging to SOC 100% is not required, it can be performed during actual use.

[0118] However, in the differential characteristics of CCV relative to SOC, the peak size is relatively small, the spectrum is relatively flat, and the S / N ratio is relatively small. Therefore, it can be expected that the SOH estimation accuracy of the proposal based on the differential characteristics of CCV relative to SOC for estimating the SOH of a battery cell will be relatively low.

[0119] Here, the inventors of this application have obtained the following insight: the State of Charge (SOC) of a battery cell is also correlated with the heat (HF) generated by the phase transition of the active material in the electrode material. Furthermore, the inventors of this application have obtained the following insight: the length (mAh) of the line segment between the peaks in the differential characteristic of HF relative to SOC is related to the overall capacity (mAh) of the battery cell. In the differential characteristic of HF relative to SOC, compared with the differential characteristic of CCV relative to SOC,

[0120] • The peaks are relatively large, the spectrum is sharp, and the S / N ratio is large;

[0121] Furthermore, there are many peaks and the intervals between peaks are small;

[0122] Furthermore, the specific pattern between positive and negative peaks remains unchanged even with degradation; in other words, even with degradation, the position of the peaks for SOC is not easily shifted.

[0123] Therefore, the inventors of this application propose a method for estimating the SOH of a battery cell based on the heat of the battery cell, specifically the HF characteristics relative to SOC, and more specifically the differential characteristics of HF relative to SOC (hereinafter referred to as SOH estimation 1).

[0124] Furthermore, the inventors of this application have obtained the following insight: the length of the line segment between the peaks in the differential characteristic of UH relative to SOC (mAh) is also related to the overall capacity (mAh) of the battery cell. This is also relevant when comparing the differential characteristic of UH relative to SOC with that of CCV (CCV) relative to SOC.

[0125] • The peaks are relatively large, the spectrum is sharp, and the S / N ratio is large;

[0126] Furthermore, there are many peaks and the intervals between peaks are small;

[0127] Furthermore, the specific pattern between positive and negative peaks remains unchanged even with degradation; in other words, even with degradation, the position of the peaks for SOC is not easily shifted.

[0128] Therefore, the inventors of this application propose a method for estimating the SOH of a battery cell based on the enthalpy potential of the battery cell, specifically the characteristics of UH relative to SOC, and more specifically the differential characteristics of UH relative to SOC (SOH estimation 2 described below).

[0129] Here, the actual measured capacity shown below includes resistive losses (IR losses) caused by the internal resistance R of the battery cells.

[0130] Actual capacity = Ideal capacity + Resistance loss... (Equation)

[0131] The internal resistance of a battery cell increases with degradation, resulting in increased resistance loss.

[0132] Since the closed-circuit voltage CCV or heat HF ​​mentioned above individually includes resistive losses (IR losses), the SOH estimated based on the characteristics of CCV relative to SOC or HF relative to SOC also includes the increase in resistive losses caused by the increase in internal resistance R due to accompanying degradation. On the other hand, since the resistive losses included in CCV and HF are eliminated in the enthalpy potential UH mentioned above, the SOH estimated based on the characteristics of UH relative to SOC is an ideal capacity that eliminates the increase in resistive losses caused by the increase in internal resistance due to accompanying degradation.

[0133] Therefore, in the following, the SOH estimated based on HF will sometimes be set as SOH(R), and the SOH estimated based on UH will be set as SOH(I) to distinguish the SOH estimated separately.

[0134] (SOH estimate 1)

[0135] First, an example will be explained regarding how the state of battery estimation unit 210 estimates the state of battery cell 111's state of ohm (SOH) based on the heat HF ​​of the battery cell 111, specifically the characteristics of HF relative to SOC, and more specifically the differential characteristics of HF relative to SOC.

[0136] During actual use and charging, the battery state estimation unit 210 periodically measures the current characteristics of HF relative to SOC. The battery state estimation unit 210 is based on... Figure 3B or Figure 3C The measured current characteristics of HF relative to SOC are illustrated in the figure. Figure 3AThe pre-stored HF relative to the initial characteristics of SOC is illustrated in the figure to estimate the degradation state SOH(R) of a battery cell.

[0137] also, Figure 3D Overlapping drawing Figure 3A The initial characteristics of HF relative to SOC are shown in the figure. Figure 3B The small degradation state of HF relative to SOC characteristics is illustrated in the figure. Figure 3C The diagram illustrates the characteristics of HF relative to SOC in a moderately degraded state.

[0138] Here, Figure 4 This is a diagram illustrating an example of the HF characteristic relative to SOC and its differential characteristic, specifically the differential characteristic d(HF) / d(SOC) of the HF characteristic HF = f(SOC) with respect to SOC. Figure 4 As shown, for example, in a lithium-ion battery that uses graphite as the negative electrode material and NCM as the positive electrode material, there are multiple peaks 1 to 7 in the differential characteristics of HF relative to SOC, which are accompanied by the phase transition of graphite.

[0139] In lithium-ion batteries with the negative electrode cutoff, the length of the segment between these peaks is related to the overall capacity of the battery cell. Therefore, knowing the length of this segment (mAh) allows us to determine the overall capacity (mAh) of the battery cell. For example, assuming an initial capacity of 100mAh from 0% to 100% SOC, the length of the segment between any two peaks is 20mAh. Furthermore, the length of this segment (mAh) can be calculated based on the charging current and charging time. As the battery cell deteriorates further, and the length of this segment between the two peaks becomes 10mAh, the overall capacity of the battery cell becomes 50mAh.

[0140] Therefore, in the SOH estimation of this embodiment, the battery state estimation unit 210 pre-stores the length mAh of the line segment between each peak in the differential characteristic of the initial characteristic of HF with respect to SOC. Then, during charging in actual use, the battery state estimation unit 210 measures the length mAh of the line segment between any two peaks in the differential characteristic of the current (deteriorated) characteristic of HF with respect to SOC, and performs SOH estimation using the following formula.

[0141] SOH = {the length of the line segment between two peaks in the differential characteristic of HF relative to the current (degraded) characteristic of SOC (mAh)} / {the length of the line segment between two corresponding peaks in the differential characteristic of HF relative to the initial characteristic of SOC (mAh)} ... (Equation)

[0142] Furthermore, in actual use, charging is constant current and low rate, so the length of the line segment between the peaks (mAh) can be calculated based on the charging current (mA) and the charging time (h).

[0143] The SOH estimation according to this embodiment is the same as the SOH estimation in the comparative example above, which is based on the length of the line segment between the peaks of the differential characteristic of CCV relative to SOC in mAh. Since it is not necessary to start charging from SOC 0%, and since it is not necessary to charge to SOC 100%, it can be performed during actual use.

[0144] Furthermore, in the SOH estimation of this embodiment, the SOH of a single battery cell is estimated based on the differential characteristics of HF relative to SOC, instead of the differential characteristics of CCV relative to SOC. As described above, in the differential characteristics of HF relative to SOC, compared with the differential characteristics of CCV relative to SOC,

[0145] • The peaks are relatively large, the spectrum is sharp, and the S / N ratio is large;

[0146] Furthermore, there are many peaks and the intervals between peaks are small;

[0147] Furthermore, the specific pattern between positive and negative peaks remains unchanged even with degradation; in other words, even with degradation, the position of the peaks for SOC is not easily shifted.

[0148] Therefore, the estimation accuracy of the SOH of a single battery cell can be improved.

[0149] In particular, due to the large number of peaks and the small interval between them, SOH estimation can be performed even when charging from various SOCs in actual use, and even when charging for a short time in actual use.

[0150] However, regarding the estimation of SOC and SOH, the known techniques generally involve constructing a mathematical model of a single battery cell and using a state estimator based on that model to estimate SOC and SOH. In this estimation, a fundamental problem arises when errors exist in the battery model, leading to reduced accuracy. Furthermore, it is impossible to determine the accuracy of the estimated values ​​during battery use. Regarding this aspect, according to the present invention, by measuring the characteristics of HF, even if errors exist in the battery's mathematical model, they can be corrected during battery use.

[0151] (SOH estimate 2)

[0152] Next, an example will be described regarding how the battery state estimation unit 210 estimates the state of energy (SOH) of the battery cell 111 based on the enthalpy potential of the battery cell 111, specifically the characteristics of UH relative to SOC, and more specifically the differential characteristics of UH relative to SOC.

[0153] During actual use and charging, the battery state estimation unit 210 periodically measures the current characteristics of UH relative to SOC. The battery state estimation unit 210 is based on... Figure 3B or Figure 3C The measured current characteristics of UH relative to SOC are shown in the figure. Figure 3A The pre-stored UH relative to the initial characteristics of SOC is illustrated in the figure to estimate the degradation state SOH(I) of a battery cell.

[0154] Here, Figure 5 This is a diagram illustrating an example of the UH characteristic relative to SOC and its differential characteristic, specifically the differential characteristic d(UH) / d(SOC) of the UH characteristic UH = f(SOC) with respect to SOC. Figure 5 As shown, for example, in lithium-ion batteries that use graphite as the negative electrode material and NCM as the positive electrode material, there are multiple peaks (1-7) in the differential characteristics of UH relative to SOC, which are accompanied by the phase transition of graphite.

[0155] The length of the line segments between these peaks is related to the overall capacity of the battery cell. Therefore, knowing the length of these line segments (mAh) allows us to determine the overall capacity (mAh) of the battery cell. For example, assuming an initial capacity of 100mAh from 0% to 100% SOC, the length of the line segment between any two peaks is 20mAh. Furthermore, the length of the line segments between the peaks (mAh) can be calculated based on the charging current and charging time. As the battery cell deteriorates further, and the length of the line segment between these two peaks becomes 10mAh, the overall capacity of the battery cell becomes 50mAh.

[0156] Therefore, in the SOH estimation of this embodiment, the battery state estimation unit 210 pre-stores the length mAh of the line segment between each peak in the differential characteristic of the initial characteristic of UH relative to SOC. Then, during charging in actual use, the battery state estimation unit 210 measures the length mAh of the line segment between any two peaks in the differential characteristic of the current (deteriorated) characteristic of UH relative to SOC, and performs SOH estimation using the following formula.

[0157] SOH = {the length of the line segment between two peaks in the differential characteristic of UH relative to the current (degraded) characteristic of SOC, in mAh} / {the length of the line segment between the corresponding two peaks in the differential characteristic of UH relative to the initial characteristic of SOC, in mAh} ... (Equation)

[0158] Furthermore, in actual use, charging is constant current and low rate, so the length of the line segment between the peaks (mAh) can be calculated based on the charging current (mA) and the charging time (h).

[0159] The SOH estimation according to this embodiment is the same as the SOH estimation in the comparative example above, which is based on the length of the line segment between the peaks of the differential characteristic of CCV relative to SOC in mAh. Since it is not necessary to start charging from SOC 0%, and since it is not necessary to charge to SOC 100%, it can be performed during actual use.

[0160] Furthermore, in the SOH estimation of this embodiment, the SOH of a single battery cell is estimated based on the differential characteristic of UH relative to SOC, instead of the differential characteristic of CCV relative to SOC. As mentioned above, in the differential characteristic of UH relative to SOC, compared with the differential characteristic of CCV relative to SOC, the following also occurs:

[0161] • The peaks are relatively large, the spectrum is sharp, and the S / N ratio is large;

[0162] Furthermore, there are many peaks and the intervals between peaks are small;

[0163] Furthermore, the specific pattern between positive and negative peaks remains unchanged even with degradation; in other words, even with degradation, the position of the peaks for SOC is not easily shifted.

[0164] Therefore, the estimation accuracy of the SOH of a single battery cell can be improved.

[0165] In particular, due to the large number of peaks and the small interval between them, SOH estimation can be performed even when charging from various SOCs in actual use, and even when charging for a short time in actual use.

[0166] Furthermore, as mentioned above, in the enthalpy potential UH, the resistive loss (IR loss) contained in the closed-circuit voltage CCV and the resistive loss contained in the heat HF ​​are eliminated. Therefore, the SOH estimated based on the UH relative to the SOC characteristic is an ideal capacity that eliminates the increase in resistive loss caused by the increase in internal resistance R accompanying degradation. Thus, the actual capacity under degradation can be determined.

[0167] (A variation of SOH estimation 2)

[0168] Regarding the enthalpy potential used in the SOH estimation 2 above, the inventors of this application focus on the differential enthalpy potential ΔUH obtained by subtracting the initial characteristics of the enthalpy potential from the current (degraded) characteristics of the enthalpy potential. The inventors of this application have obtained the following insight: the magnitude of the peak in the differential characteristic of ΔUH relative to SOC is related to the overall capacity (mAh) of the battery cell. In the differential characteristic of ΔUH relative to SOC, compared to the differential characteristic of CCV relative to SOC,

[0169] • The peaks are relatively large, the spectrum is sharp, and the S / N ratio is large;

[0170] Furthermore, there are many peaks and the intervals between peaks are small;

[0171] Furthermore, even with degradation, the specific pattern between positive and negative peaks maintains a certain pattern.

[0172] Therefore, the inventors of this application propose a method for estimating the SOH of a battery cell based on the differential enthalpy potential of the battery cell, specifically the characteristic of ΔUH relative to SOC, and more specifically the differential characteristic of ΔUH relative to SOC.

[0173] As described above, in the enthalpy potential UH, the resistive losses (IR losses) contained in the closed-circuit voltage CCV and the resistive losses contained in the heat HF ​​are eliminated. Therefore, the SOH estimated based on the ΔUH relative to the SOC characteristic is an ideal capacity that eliminates the increase in resistive losses caused by the increase in internal resistance R accompanying degradation. Thus, the actual capacity under degradation can be determined.

[0174] During actual use and charging, the battery state estimation unit 210 periodically measures the current characteristics of UH relative to SOC and calculates the remaining UH value. Figure 3B or Figure 3C The measured UH relative to the current characteristics of SOC shown in the figure is subtracted Figure 3A The ΔUH characteristic relative to SOC is obtained from the pre-stored initial characteristics of UH relative to SOC. The battery state estimation unit 210 estimates the degradation state SOH(I) of the battery cell based on the calculated differential characteristics of ΔUH relative to SOC and the pre-stored differential characteristics of ΔUH relative to SOC under a specified SOH.

[0175] Here, Figure 6A This is a diagram illustrating an example of the ΔUH versus SOC characteristics in this embodiment. Figure 6B This is a diagram illustrating an example of the differential characteristic of ΔUH with respect to SOC in this embodiment, specifically the differential characteristic of ΔUH = f(SOC) as d(ΔUH) / d(SOC). Figure 6BAs shown, for example, in a lithium-ion battery that uses graphite as the negative electrode material and NCM as the positive electrode material, there are also multiple peaks in the differential characteristic of ΔUH relative to SOC.

[0176] The size (height) of these peaks is related to the overall capacity of the battery cell. Specifically, as the battery cell deteriorates, its overall capacity decreases, and the size of these peaks increases. Furthermore, as mentioned above, positive and negative peaks exhibit specific patterns. Therefore, knowing the size and sign of these peaks allows us to determine the overall capacity (mAh) and state of charge (SOH) of the battery cell.

[0177] Therefore, in the SOH estimation of this embodiment, the storage unit 220 pre-stores the differential characteristic of ΔUH relative to SOC under a specified SOH, and the battery state estimation unit 210 assumes that SOH is proportional to the size of the peak of the differential characteristic of ΔUH relative to SOC under the initial state (SOH 100%) and the size of the peak of the differential characteristic of ΔUH relative to SOC under the specified SOH.

[0178] Then, during actual charging, the battery state estimation unit 210 calculates the differential enthalpy potential ΔUH relative to SOC characteristic, obtained by subtracting the initial characteristic of UH relative to SOC from the current (deteriorated) characteristic of UH relative to SOC. The battery state estimation unit 210 estimates the SOH corresponding to the magnitude of any peak of the calculated differential characteristic of ΔUH relative to SOC by referring to a pre-stored proportional relationship of the differential characteristic of ΔUH relative to SOC under a predetermined SOH.

[0179] As explained above, the same advantages as the SOH estimation 2 of this embodiment can be obtained in the SOH estimation of this modified example.

[0180] (A variation of SOH estimation 1)

[0181] As mentioned above, according to Figure 6B The magnitude (height) of the peak in the differential characteristic of ΔUH relative to SOC is estimated by SOH and Figure 4 The length of the line segment between the peaks in the differential characteristic of HF relative to SOC is related to mAh. Therefore, the inventors of this application propose to estimate the increase in resistance loss caused by the increase in internal resistance due to degradation based on SOH(R) estimated by SOH estimation 1 above, which includes the increase in resistance loss caused by the increase in internal resistance due to degradation, and SOH(I) estimated by SOH estimation 2 above, which eliminates the increase in resistance loss caused by the increase in internal resistance due to degradation.

[0182] Specifically, the battery state estimation unit 210 estimates the increase in resistance loss caused by the increase in internal resistance accompanying deterioration based on the difference between the SOH(R) estimated by the SOH estimation 1 and the SOH(I) estimated by the SOH estimation 2.

[0183] The estimated increase in resistive loss caused by the increase in internal resistance can be used in the following control.

[0184] • Control of the output voltage, i.e., discharge current of individual battery cells

[0185] • Control of cooling, i.e., heat dissipation, during battery cell charging

[0186] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and various changes and modifications can be made.

[0187] Figure Labels

[0188] 100 battery units

[0189] 101 Casing

[0190] 102 Cover

[0191] 103 Lower Frame

[0192] 104 Upper Frame

[0193] 105 Cooling Plate

[0194] 106 Air Inlet Mechanism

[0195] 110 Battery Module

[0196] 111 Battery cell

[0197] 112-layered structure

[0198] 113 end plate

[0199] 114 Single busbar

[0200] 119 Module Busbar

[0201] 120 Battery Thermal Detection Department

[0202] 130 Standard Heat Detection Department

[0203] 141 Voltage Detection Department

[0204] 142 Current Detection Unit

[0205] 143 Temperature Detection Department

[0206] 200 Battery Management System (BMS)

[0207] 210 Battery Status Estimation Unit

[0208] 220 Storage Department

Claims

1. A battery unit including a battery module having a battery cell, the battery unit comprising: a battery heat detection section that detects heat of the battery cell; a storage section that stores an initial characteristic of the heat HF of the battery cell with respect to a state of charge SOC; and a battery state estimation section that estimates a state of health SOH of the battery cell; and wherein the battery state estimation section, upon charging of the battery cell, determines a current characteristic of the HF of the battery cell with respect to the SOC from the HF of the battery cell detected by the battery heat detection section, estimates a first state of health SOH(R) of the battery cell from a ratio of a capacity mAh of a line segment between peaks on an SOC axis in a differential characteristic of the determined current characteristic of the HF with respect to the SOC to a capacity mAh of the line segment between the peaks on the SOC axis in a differential characteristic of the initial characteristic of the HF with respect to the SOC stored in the storage section, and estimates an increase in a resistance loss R accompanying degradation of the battery cell from a difference between the first state of health SOH(R) and a second state of health SOH(I) of the battery cell estimated by the battery state estimation section. Further comprising: a voltage detection section that detects a closed circuit voltage CCV of the battery cell; and a current detection section that detects a current I of the battery cell; wherein the storage section further stores an initial characteristic of an enthalpy potential UH of the battery cell with respect to the SOC, the UH being calculated using the following equation based on the CCV, the HF, and the I, UH = CCV - HF / I (Equation) and wherein the battery state estimation section, upon charging of the battery cell, determines a current characteristic of the UH of the battery cell with respect to the SOC from the HF, the CCV, and the I of the battery cell detected by the battery heat detection section, the voltage detection section, and the current detection section, calculates a differential enthalpy potential ΔUH with respect to the SOC characteristic from the determined current characteristic of the UH with respect to the SOC minus the initial characteristic of the UH with respect to the SOC stored in the storage section, estimates a second state of health SOH(I) of the battery cell from a size of a peak in a differential characteristic of the ΔUH with respect to the SOC calculated from the calculated current characteristic of the UH with respect to the SOC, and estimates an increase in the resistance loss R accompanying degradation of the battery cell from a difference between the first state of health SOH(R) and the second state of health SOH(I) of the battery cell. The storage section stores in advance a differential characteristic of the ΔUH with respect to the SOC at a prescribed second state of health SOH(I) of the battery cell, the battery state estimation section assumes that there is a proportional relationship between the second state of health SOH(I) and the size of the peak in the differential characteristic of the ΔUH with respect to the SOC at the prescribed second state of health SOH(I) stored in the storage section, and estimates the second state of health SOH(I) of the battery cell from the size of the peak in the differential characteristic of the ΔUH with respect to the SOC calculated from the calculated current characteristic of the ΔUH with respect to the SOC based on the proportional relationship. ​ ​ ​ ​ ​ 2. The battery cell of claim 1, wherein, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 3. The battery cell of claim 2, wherein, ​ ​ ​ ​ 4. The battery cell of claim 1 or 2, wherein, Further comprising a reference heat detection section that detects heat of the battery cell as a reference heat, The battery state estimation section uses, as the heat of the battery cell, heat from which the influence of heat in the battery cell has been removed by subtracting the reference heat detected by the reference heat detection section from the heat detected by the battery heat detection section.

5. A battery unit including a battery module having a battery cell, the battery unit comprising: a battery heat detection section that detects heat of the battery cell; a voltage detection section that detects a closed-circuit voltage of the battery cell; a current detection section that detects a current of the battery cell; a storage section that stores an initial characteristic of enthalpy potential UH of the battery cell with respect to a state of charge SOC, wherein UH is calculated using the following equation based on a closed-circuit voltage CCV, heat HF, and current I, UH = CCV - HF / I ··· (Equation); and a battery state estimation section that estimates a deterioration state SOH of the battery cell; and The battery state estimation section, when the battery cell is charged, determines a current characteristic of UH of the battery cell with respect to SOC from HF, CCV, and I of the battery cell detected by the battery heat detection section, the voltage detection section, and the current detection section, and estimates a second deterioration state SOH(I) of the battery cell from a ratio of a capacity mAh of a length of a line segment between peaks on a SOC axis in a differential characteristic of the determined current characteristic of UH with respect to SOC to a capacity mAh of the length of the line segment between the peaks on the SOC axis in a differential characteristic of the initial characteristic of UH with respect to SOC stored in the storage section.

6. The battery cell of claim 5, wherein, Further comprising a reference heat detection section that detects heat of the battery cell as a reference heat, The battery state estimation section uses, as the heat of the battery cell, heat from which the influence of heat in the battery cell has been removed by subtracting the reference heat detected by the reference heat detection section from the heat detected by the battery heat detection section.

7. A battery unit including a battery module having a battery cell, the battery unit comprising: a battery heat detection section that detects heat of the battery cell; a voltage detection section that detects a closed-circuit voltage of the battery cell; a current detection section that detects a current of the battery cell; a storage section that stores an initial characteristic of enthalpy potential UH of the battery cell with respect to a state of charge SOC, wherein UH is calculated using the following equation based on a closed-circuit voltage CCV, heat HF, and current I, UH = CCV - HF / I ··· (Equation); and a battery state estimation section that estimates a deterioration state SOH of the battery cell; and The battery state estimation section, In charging the aforementioned battery cell, a current characteristic of UH with respect to SOC of the aforementioned battery cell is determined from HF, CCV, and I of the aforementioned battery cell detected by the aforementioned battery heat detection section, the aforementioned voltage detection section, and the aforementioned current detection section, a differential enthalpy potential ΔUH with respect to SOC characteristic is calculated from the determined current characteristic of UH with respect to SOC, and the initial characteristic of UH with respect to SOC stored in the aforementioned storage section is subtracted therefrom, and a second deterioration state SOH(I) of the aforementioned battery cell is estimated from the magnitude of a peak in the calculated differential characteristic of ΔUH with respect to SOC.

8. The battery cell of claim 7, wherein, the aforementioned storage section stores in advance a differential characteristic of ΔUH with respect to SOC at a prescribed second deterioration state SOH(I) of the aforementioned battery cell, the aforementioned battery state estimation section, the aforementioned battery state estimation section assumes that there is a proportional relationship between the aforementioned second deterioration state SOH(I) and the magnitude of the peak in the differential characteristic of ΔUH with respect to SOC at the aforementioned prescribed second deterioration state SOH(I) stored in the aforementioned storage section, and estimates the second deterioration state SOH(I) of the aforementioned battery cell from the magnitude of the peak in the calculated differential characteristic of ΔUH with respect to SOC on the basis of the aforementioned proportional relationship.

9. The battery cell of claim 7, wherein, a reference heat detection section that detects heat of the aforementioned battery cell as a reference heat, the aforementioned battery state estimation section uses heat from which the influence of heat within the aforementioned battery cell has been removed by subtracting the reference heat detected by the aforementioned reference heat detection section from the heat detected by the aforementioned battery heat detection section as the heat of the aforementioned battery cell.

Images