Battery pack

Abstract

The problem of the present invention is to provide a battery pack that improves the SOC estimation accuracy of battery cells. To solve the above problem, the battery pack includes a storage unit that stores the following (A1) and (A2) and a battery state estimation unit. (A1) OCV versus SOC characteristic diagram (A2) HF versus SOC initial characteristic The battery state estimation unit estimates the initial SOC corresponding to the detected OCV according to (A1) at the start of charging, measures the current HF versus SOC characteristic during charging, senses the peak value of the differential characteristic of the measured current HF versus SOC characteristic, calculates the sensed peak SOC as SOC(HF) according to (A2), calculates the charging capacity from the start of charging to the peak sensing time according to the detected charging current and charging time, calculates SOC(OCV) according to the calculated charging capacity and the estimated initial SOC at the start of charging, and corrects (A1) if SOC(OCV) deviates from SOC(HF) by a predetermined value or more.

Description

Technical Field

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

[0002] In recent years, with the widespread adoption of electrical and electronic devices of all sizes, such as automobiles, computers, and information terminals, battery packs have been widely used as the power source for these devices. Particularly in the automotive sector, in order to reduce negative impacts on the global environment and considering climate-related disasters and natural hazard mitigation, as well as to reduce CO2 emissions and improve the global environment, there is a growing interest in electric vehicles, and the use of battery packs for in-vehicle applications is being discussed.

[0003] For the efficient and safe use of electronic and electrical devices, techniques for estimating the state of charge (SOC) or state of health (SOH) of battery cells are crucial in battery packs. For example, it is known that the state of charge (SOC) or state of health (SOH) of a battery cell is related to the voltage of the battery cell. Therefore, techniques for estimating the state of charge (SOC) or state of health (SOH) of a battery cell based on the voltage of the battery cell are known (for example, see 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] G.Assat et al., "Probing the thermal effects of voltage hysteresis inanionic redox-based lithium-rich cathodes using isothermal calorimetry", Nature Energy, volume 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 Charge (SOC) of a battery cell. In SOC estimation, the open circuit voltage (OCV) characteristic of the battery cell is pre-stored as multiple tables according to temperature. For example, when no charging or discharging is performed, the SOC corresponding to the detected OCV is estimated as the battery cell SOC by referring to the table corresponding to the detected temperature.

[0012] Therefore, for battery cells where voltage changes relative to capacity, such as lithium-ion batteries using hard carbon as the negative electrode material, the state of charge (SOC) can be estimated with high accuracy based on the cell voltage.

[0013] In recent years, there have been battery cells with relatively small voltage changes compared to capacity changes, such as lithium-ion batteries that use graphite as the negative electrode material. In battery packs with such cells, the accuracy of SOC estimation is reduced if the voltage of the battery cells is used as the basis for estimation.

[0014] Furthermore, the OCV versus SOC characteristic gradually changes due to the degradation of the battery cells, thus deviating from the initial characteristics. Regarding this, the inventors of this application considered periodically measuring the Closed Circuit Voltage (CCV) versus SOC characteristic during charging in actual use of graphite-based lithium-ion batteries to correct for SOC estimation errors. Moreover, charging at a constant current and low rate allows the capacity (mAh) to be determined based on the charging current (mA) and charging time (h).

[0015] Specifically, in lithium-ion batteries using graphite, the differential characteristic of CCV versus SOC, i.e., the differential characteristic d(CCV) / d(SOC) of CCV = f(SOC) with respect to SOC, exhibits multiple peaks associated with phase transitions, corresponding to graphite. However, only two peaks are clearly visible. Therefore, the OCV versus SOC characteristic chart is corrected based on the offset of the SOC estimated from the CCV versus SOC differential characteristic relative to the peak SOC in the CCV versus SOC differential characteristic. Moreover, this characteristic of having peaks associated with phase transitions in the differential characteristic of CCV versus SOC is not present in lithium-ion batteries using hard carbon.

[0016] However, in the CCV versus SOC differential characteristics, the peak size is small, the spectrum is blunt, and the S / N ratio is low. This problem becomes particularly pronounced once degradation occurs. Therefore, even if the SOC estimate is corrected based on the CCV versus SOC differential characteristics, the correction accuracy is expected to be low, and the estimation accuracy will also be low.

[0017] The purpose of this invention is to provide a battery pack that improves the accuracy of SOC estimation for battery cells.

[0018] [Technical means to solve the problem]

[0019] The inventors of this application have also obtained the following insight: there is a correlation between the state of charge (SOC) of the battery cell and the heat flow (HF) of the battery cell caused by phase transitions of the active materials in the electrode materials. Furthermore, the inventors of this application have obtained the following insight: the differential characteristics of HF versus SOC are different from those of CCV versus SOC.

[0020] • It has large peak size, sharp spectrum, and large S / N ratio, and retains these characteristics even when it deteriorates;

[0021] In addition, there are many peaks and short peak intervals;

[0022] Furthermore, the specific patterns exhibiting both positive and negative peak values ​​remain consistent even with degradation; in other words, the peak values' positions relative to the State of Charge (SOC) are not easily shifted even with degradation. Therefore, the inventors devised a method to correct the SOC estimate of the battery cell based on the cell's heat distribution, in detail according to the HF versus SOC characteristics, and even more precisely, based on the HF versus SOC differential characteristics.

[0023] (1) Therefore, the battery pack of the present invention includes a battery module, the battery module having battery cells, and the battery pack includes: a voltage detection unit for detecting the open-circuit voltage or closed-circuit voltage of the aforementioned battery cells; a current detection unit for detecting the current of the aforementioned battery cells; a battery heat detection unit for detecting the heat of the aforementioned battery cells; and a storage unit for storing the following (A1) and (A2).

[0024] (A1) Table of Open Circuit Voltage (OCV) versus SOC characteristics of the aforementioned battery cell

[0025] (A2) The initial characteristics of the aforementioned battery cell's thermal HF versus SOC, and the SOC in the peak value of the differential characteristics of the aforementioned initial characteristics of HF versus SOC; and,

[0026] The battery state estimation unit estimates the state of the battery cell corresponding to the detected battery cell OCV according to (A1). The battery state estimation unit (i) at the start of charging of the battery cell, estimates the battery cell SOC corresponding to the battery cell OCV detected by the voltage detection unit as the initial SOC according to (A1); (ii) during charging of the battery cell, measures the current characteristic of the battery cell HF versus SOC based on the battery cell HF detected by the battery heat detection unit, senses the peak value of the differential characteristic of the measured current characteristic of HF versus SOC, and calculates the sensed peak SOC as SOC(HF) according to (A2); (iii) calculates the charging capacity from the start of charging to the peak sensing time based on the charging current and charging time detected by the current detection unit, and calculates SOC(OCV) based on the calculated charging capacity and the estimated initial SOC at the start of charging; if the SOC(OCV) deviates from the SOC(HF) by a predetermined value or more, the aforementioned (A1) is corrected according to the deviation.

[0027] (2) In the battery pack of the present invention, the aforementioned battery state estimation unit can (iv) estimate the SOH of the aforementioned battery cell based on the ratio of the measured peak-to-peak segment length mAh in the differential characteristic of the aforementioned HFversus SOC current characteristic to the peak-to-peak segment length mAh in the differential characteristic of the aforementioned HFversus SOC initial characteristic stored in the aforementioned storage unit; and (v) calculate the ΔSOC corresponding to the calculated charging capacity Q(t) according to the following formula.

[0028] ΔSOC=Q(t) / C0(t)…(Equation)

[0029] C0(t)=C0×SOH…(Equation)

[0030] C0(t): Current total capacity

[0031] C0: Initial total capacity

[0032] t: Time elapsed

[0033] (vi) Calculate the aforementioned SOC (OCV) based on the calculated ΔSOC and the estimated initial SOC at the start of charging.

[0034] (3) Furthermore, in the battery pack of the present invention, the aforementioned storage unit also stores the following (A11),

[0035] (A11) The aforementioned battery cell closed-circuit voltage (CCV) versus SOC characteristic table diagram

[0036] The aforementioned battery state estimation unit can (vii) calculate the SOC(CCV) corresponding to the CCV detected by the aforementioned voltage detection unit when sensing the peak value based on (A11) above; and (viii) if the aforementioned SOC(CCV) deviates by a predetermined value relative to the aforementioned SOC(HF), then correct the aforementioned (A11) based on the deviance amount.

[0037] Furthermore, the inventors of this application focus on the enthalpy potential (UH) calculated from the closed-circuit voltage CCV, heat HF, and current I using the following formula.

[0038] UH=CCV-HF / I…(Formula)

[0039] The inventors have obtained the following insights: the UH versus SOC differential characteristic, compared to the CCV versus SOC differential characteristic,

[0040] • It has large peak size, sharp spectrum, and large S / N ratio, and retains these characteristics even when it deteriorates;

[0041] In addition, there are many peaks and short peak intervals;

[0042] Furthermore, the specific patterns exhibiting both positive and negative peak values ​​maintain their shape even during degradation; in other words, the peak values' positions relative to the State of Charge (SOC) are less prone to shift even with degradation. Therefore, the inventors devised a method to correct the SOC estimate of the battery cell based on the enthalpy potential of the battery cell, specifically according to the UH versus SOC characteristics, and even more specifically according to the differential characteristics of UH versus SOC.

[0043] (4) Therefore, another battery pack of the present invention includes a battery module having battery cells, and the battery pack includes: a voltage detection unit for detecting the open-circuit voltage or closed-circuit voltage of the aforementioned battery cells; a current detection unit for detecting the current of the aforementioned battery cells; a battery heat detection unit for detecting the heat of the aforementioned battery cells; and a storage unit for storing the following (A1) and (A3).

[0044] (A1) Table showing the open-circuit voltage (OCV) versus SOC of the aforementioned battery cell.

[0045] (A3) The initial characteristics of the enthalpy potential UH versus SOC of the aforementioned battery cell, and the SOC in the peak value of the differential characteristics of the aforementioned initial characteristics of UH versus SOC;

[0046] UH is calculated based on the closed-circuit voltage CCV, heat HF, and current I using the following formula: UH=CCV-HF / I…(Equation)

[0047] The battery state estimation unit estimates the SOC of the battery cell corresponding to the detected battery cell OCV based on the aforementioned (A1). The aforementioned battery state estimation unit (i) at the start of charging of the aforementioned battery cell, according to (A1) above, estimates the SOC of the aforementioned battery cell corresponding to the OCV of the aforementioned battery cell detected by the aforementioned voltage detection unit as the initial SOC; (ii) during charging of the aforementioned battery cell, according to 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, measures the current characteristic of the aforementioned battery cell UH versus SOC, senses the peak value in the differential characteristic of the measured current characteristic of the aforementioned UH versus SOC, and calculates the sensed peak value SOC as SOC(UH) according to (A3) above; (iii) according to the charging current and charging time detected by the aforementioned current detection unit, calculates the charging capacity from the start of charging to the time of peak sensing, and calculates SOC(OCV) according to the calculated charging capacity and the aforementioned initial SOC estimated at the start of charging; if the aforementioned SOC(OCV) deviates from the aforementioned SOC(UH) by a predetermined value or more, then corrects the aforementioned (A1) according to the deviation amount.

[0048] (5) In another battery pack of the present invention, the aforementioned battery state estimation unit may (iv) estimate the SOH of the aforementioned battery cell based on the ratio of the measured peak-to-peak segment length mAh in the differential characteristic of the aforementioned UH versus SOC current characteristic to the peak-to-peak segment length mAh in the differential characteristic of the aforementioned UH versus SOC initial characteristic stored in the aforementioned storage unit; and (v) calculate the ΔSOC corresponding to the calculated charging capacity Q(t) according to the following formula.

[0049] ΔSOC=Q(t) / C0(t)…(Equation)

[0050] C0(t)=C0×SOH…(Equation)

[0051] C0(t): Current total capacity

[0052] C0: Initial total capacity

[0053] t: Time elapsed

[0054] (vi) Calculate the aforementioned SOC (OCV) based on the calculated ΔSOC and the estimated initial SOC at the start of charging.

[0055] (6) Furthermore, in another battery pack of the present invention, the aforementioned storage unit also stores the following (A11),

[0056] (A11) The aforementioned battery cell closed-circuit voltage (CCV) versus SOC characteristic table diagram

[0057] The aforementioned battery state estimation unit can (vii) calculate the SOC(CCV) corresponding to the CCV detected by the aforementioned voltage detection unit when sensing the peak value based on (A11) above; and (viii) if the aforementioned SOC(CCV) deviates by a predetermined value relative to the aforementioned SOC(UH), then correct the aforementioned (A11) based on the deviance amount.

[0058] (7) Furthermore, the battery pack of the present invention also includes a reference heat detection unit that detects the heat of the aforementioned battery pack as a reference heat. In the battery pack of the present invention, the aforementioned battery state estimation unit subtracts the reference heat detected by the aforementioned reference heat detection unit from the heat detected by the aforementioned battery heat detection unit, thereby using the heat that has been freed from the influence of the heat inside the aforementioned battery as the heat of the aforementioned battery cell.

[0059] (The effect of the invention)

[0060] According to the invention described in (1) to (2) and (4) to (5), compared with the correction of the battery cell SOC estimation based on the differential characteristics of CCV versus SOC, the correction accuracy of the battery cell SOC estimation can be improved, and the accuracy of the battery cell SOC estimation can be improved.

[0061] Furthermore, according to the invention described in (3) and (6), it is possible not only to use the deterioration correction OCV versus SOC characteristic chart, but also to use the deterioration correction CCV versus SOC characteristic chart.

[0062] Furthermore, according to the invention described in (7), based on the heat from removing noise within the battery pack, the correction accuracy of the battery cell SOC estimation can be improved, and the accuracy of the battery cell SOC estimation can be further improved. Attached Figure Description

[0063] Figure 1 This is an exploded perspective view illustrating the battery pack of this embodiment.

[0064] Figure 2A yes Figure 1 A side view of an example of a battery module in the battery pack shown.

[0065] Figure 2B yes Figure 1 A side view of another example of a battery module in the battery pack shown.

[0066] Figure 3A This is a diagram illustrating an example of the HF versus SOC characteristics and UH versus SOC characteristics in the initial state of this embodiment.

[0067] Figure 3BThis is a diagram illustrating an example of the HF versus SOC characteristics and UH versus SOC characteristics under the deterioration state of this embodiment.

[0068] Figure 3C This is a diagram illustrating an example of the HF versus SOC characteristics and UH versus SOC characteristics under deterioration conditions in this embodiment.

[0069] Figure 3D It is an overlay drawing Figure 3A The HF versus SOC characteristics in the initial state are shown. Figure 3B The HF versus SOC characteristics under the degraded small state are shown. Figure 3C The graph shows the HF versus SOC characteristics under deterioration conditions.

[0070] Figure 4 This is a diagram illustrating an example of the differential characteristics (degraded small state) of HF versus SOC in this embodiment.

[0071] Figure 5 This is a diagram illustrating an example of the UH versus SOC differential characteristics (degraded small state) of this embodiment.

[0072] Figure 6 This is a diagram illustrating an example of the differential characteristics (degraded small states) of CCV versus SOC in a comparative manner. Detailed Implementation

[0073] Hereinafter, an example of an embodiment of the present invention will be described with reference to the accompanying drawings. Furthermore, the same or equivalent parts will be given the same reference numerals in the drawings.

[0074] (Battery pack)

[0075] Figure 1 This is an exploded perspective view illustrating the battery pack of this embodiment. Figure 2A yes Figure 1 A side view of an example of a battery module in the battery pack shown. Figure 1 The battery pack 100 shown is an intelligent power unit (IPU) installed in electric vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), or battery electric vehicles (BEV).

[0076] like Figure 1 and Figure 2A As shown, the battery pack 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 1 In the example, the components of the battery pack 100 are housed within the housing 101 and covered by the outer casing 102.

[0077] Moreover, in Figure 1 In the example, the battery pack 100 includes a lower frame 103 and an upper frame 104. Furthermore, the battery pack 100 includes a lower cooling plate 105 for cooling the battery module 110. Additionally, the battery pack 100 includes a mechanism (e.g., a fan, air duct, and air intake duct) 106 for introducing air to cool the battery module 110.

[0078] like Figure 2A As shown, the battery module 110 mainly includes: a stacked body 112, formed by stacking multiple battery cells 111; a pair of end plates clamping the stacked body 112 in the stacking direction; and a unit busbar 114 connecting the multiple battery cells 111. Furthermore, as... Figure 1 As shown, multiple battery modules 110 can be connected via module bus 119.

[0079] There is no particular limitation on the battery cell 111; for example, a lithium-ion battery can be listed. Lithium-ion batteries preferably use graphite, a material that generates heat during phase transitions, as the negative electrode material, or lithium-ion batteries that use layered compounds such as lithium cobalt oxide (LCO) or lithium nickel oxide (LNO), a material that generates heat during phase transitions, as the positive electrode material.

[0080] The following describes a lithium-ion battery that uses graphite or other materials that generate heat during phase transitions as the negative electrode material and lithium nickel cobalt manganese oxide (NCM) as the positive electrode material (SOC 0% is mainly determined by the negative electrode potential: negative electrode cutoff). However, this invention is also applicable to lithium-ion batteries that use LCO or LNO, which generate heat during phase transitions, as the positive electrode material (SOC 0% is mainly determined by the positive electrode potential: positive electrode cutoff).

[0081] The battery heat detection unit 120 is a heat sensor that detects the heat of the battery cell 111 and the battery pack 100. That is, it not only detects the heat of the battery cell 111, but also detects the heat affected by various heat sources in the battery pack 100, such as noise.

[0082] There are no particular limitations on the type of heat sensor; examples include Peltier elements, thermopile elements, and thermocouples. Among these, Peltier elements, which have high heat flux sensitivity and can be used in temperature control 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 as a cooling element otherwise.

[0083] The battery heat detection unit 120 can be configured in at least one battery cell 111 in the battery module 110. Furthermore, as... Figure 2A As shown, the battery heat detection unit 120 can be respectively disposed on the two battery cells 111 adjacent to the end plate 113 in the battery cell 111. In addition, the battery heat detection unit 120 can also be disposed in the battery cell 111 located in the center in the battery cell 111 stacking direction, in addition to the two battery cells 111 adjacent to the end plate 113.

[0084] The reference heat detection unit 130 is a heat sensor that detects the heat of the battery pack 100, that is, various types of heat within the battery pack 100, and noise heat as a reference heat.

[0085] As mentioned above, there are no particular limitations on the heat sensor; for example, Peltier elements, thermopile, thermocouples, and other temperature sensors can be listed. Among these, Peltier elements are preferred. Thus, the Peltier element used for cooling the battery cell 111 can be used for both heat detection and cooling.

[0086] The reference heat detection unit 130 is disposed in a part of the battery pack 100 where the temperature change is small and the heat capacity is large. For example, any one of (A) to (F) below can be listed as the placement location of the reference heat detection unit 130.

[0087] (A) Cooling plate 105 for cooling battery module 110

[0088] For example, such as Figure 1 As shown, the cooling plate 105 is configured to contact the bottom surface of the battery module 110, and the reference heat detection unit 130 is disposed on the side of the cooling plate 105 that is not opposite to the bottom surface of the battery cell 111. There are no particular limitations on the configuration of the multiple battery cells 111; for example, they can be configured to correspond to the battery cell 111 located in the center of the stacking direction.

[0089] (B) End plate 113 in battery module 110

[0090] Figure 2Byes Figure 1 A side view of another example of a battery module in the battery pack shown. (As shown) Figure 2B As shown, for example, the reference heat detection unit 130 can be disposed on the surface side of the end plate 113 that is not opposite to the battery cell 111.

[0091] (C) Buses 114 and 119 in battery module 110

[0092] For example, the reference heat detection unit 130 can be disposed in the battery bus 114 that connects the battery cells 111 to each other (see reference). Figure 2A The surface side that is not opposite to the battery cell 111. Furthermore, for example, the reference heat detection unit 130 can be disposed in the module bus 119 that connects the battery modules 110 to each other (see reference). Figure 1 ), the surface side not opposite to the battery cell 111. There are no particular limitations on the configuration of the multiple battery cells 111, but for example, they can be configured to correspond to the battery cell 111 located in the center in the stacking direction.

[0093] (D) Flange within battery pack 100

[0094] like Figure 1 As shown, for example, the reference heat detection unit 130 can be configured on the flange (connector) of the battery module used to fix the battery module 110.

[0095] (E) Space within battery pack 100

[0096] like Figure 1 As shown, for example, the reference heat detection unit 130 can be disposed in a suspended state in the space within the battery pack 100.

[0097] (F) Conduit protecting high-voltage conductors

[0098] like Figure 1 As shown, for example, the reference heat detection unit 130 can be disposed inside or outside the conduit protecting the high-voltage conductor (e.g., disposed inside if exposed to outside air, and disposed outside if not exposed to outside air).

[0099] Furthermore, the battery heat detection unit 120 can be disposed on two battery cells 111 adjacent to the end plate 113 in the battery cell 111, and the reference heat detection unit 130 can be disposed on the battery cells 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 in the center in the stacking direction.

[0100] The voltage detection unit 141 is a voltage sensor that detects the open-circuit voltage or 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 be configured on battery module 110.

[0101] 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 be configured on battery module 110.

[0102] Temperature detection unit 143 is a temperature sensor that detects the temperature of various parts. There are no particular limitations on the temperature sensor; for example, a thermocouple can be used. Figure 2A As shown, a temperature detection unit 143 is disposed on each battery cell 111 and detects the temperature of each battery cell 111. Furthermore, the temperature detection unit 143 is disposed at the location where the battery heat detection unit 120 is located and detects the temperature at that heat detection location. Moreover, 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.

[0103] (Battery Management System: Battery State Estimation Department)

[0104] The Battery Management System (BMS) 200 provides overall control of the battery cells 111 (Electronic Control Unit; also known as ECU), including charge and discharge control, overcharge protection, over-discharge protection, and monitoring of battery states such as SOC (State of Charge) or SOH (State of Health). The Battery Management System 200 mainly comprises a battery state estimation unit 210 and a storage unit 220.

[0105] The battery state estimation unit 210 is configured, for example, by a computing processor such as a DSP (Digital Signal Processor) or an FPGA (Field-Programmable Gate Array). 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 through a combination of hardware and software, or solely by hardware (electronic circuitry).

[0106] The storage unit 220 is a rewritable memory such as an EEPROM. The storage unit 220 stores predetermined software (programs) for performing various functions of the battery state estimation unit 210 described above.

[0107] Furthermore, the storage unit 220 stores, in tabular form, characteristics of the correlation between the open-circuit voltage and the state of charge (OVC versus SOC) of the battery cell 111 in, for example, the initial state, i.e., multiple characteristics of the battery cell 111 at each temperature. Moreover, as... Figure 3A As shown, the storage unit 220 stores, in tabular form, characteristics of the correlation between the closed-circuit voltage and the state of charge (CCV versus SOC) of the battery cell 111 in, for example, the initial state; that is, multiple characteristics of the battery cell 111 at each temperature and each current (charging). Furthermore, as... Figure 3A As shown, the storage unit 220 stores, in tabular form, the characteristics of the correlation between the heat and SOC of the battery cell 111 in the initial state (HF versus SOC initial characteristics), that is, multiple characteristics of the battery cell 111 at each temperature and each current (charging). Furthermore, as... Figure 3A As shown, the storage unit 220 stores in tabular form the characteristics of the correlation between the enthalpy potential and SOC of the battery cell 111 in the initial state (UH versus SOC initial characteristics), that is, multiple characteristics of the battery cell 111 at each temperature and each current (charging).

[0108] The enthalpy potential UH is a parameter calculated from the heat HF ​​of the battery cell 111, the closed-circuit voltage CCV, and the current I using the following formula (refer to Non-Patent Literature 1).

[0109] UH=CCV-HF / I...(Equation)

[0110] The battery state estimation unit 210 estimates the SOC of the battery cell 111 corresponding to the OCV of the battery cell 111 detected by the voltage detection unit 141, for example, when the vehicle is parked and not being charged or discharged in actual use, by referring to the OCV versus SOC characteristic table stored in the storage unit 220.

[0111] Furthermore, when the battery state estimation unit 210 starts charging, for example when the vehicle is parked in actual use, it refers to the OCV versus SOC characteristic table stored in the storage unit 220 and estimates the SOC of the battery cell 111 corresponding to the OCV of the battery cell 111 detected by the voltage detection unit 141 as the initial SOC.

[0112] Moreover, such as Figure 3B and Figure 3C As shown, the battery state estimation unit 210, for example, when charging the vehicle while it is parked in actual use, measures the current HF versus SOC characteristic of the battery cell 111 and calculates the battery cell SOC (HF) based on the peak value of the differential characteristic of the measured current HF versus SOC characteristic.

[0113] Furthermore, at this time, the battery state estimation unit 210 calculates the battery cell SOC(OCV) corresponding to the SOC(HF) based on the initial SOC estimated from the OCV versus SOC characteristic table.

[0114] Furthermore, if the SOC(OCV) calculated from the OCV versus SOC characteristic chart deviates by a predetermined value relative to the SOC(HF) obtained from the differential characteristic peak of the current HF versus SOC characteristic chart, the battery state estimation unit 210 corrects the OCV versus SOC characteristic chart based on the deviation. Details will be described later (Correction of SOC Estimation 1).

[0115] Or, such as Figure 3B and Figure 3C As shown, the battery state estimation unit 210, for example, when charging the vehicle while it is parked in actual use, measures the current UH versus SOC characteristic of the battery cell 111 and calculates the battery cell SOC (UH) based on the peak value of the differential characteristic of the measured current UH versus SOC characteristic.

[0116] Furthermore, at this time, the battery state estimation unit 210 calculates the battery cell SOC(OCV) corresponding to the SOC(UH) based on the initial SOC estimated from the OCV versus SOC characteristic table.

[0117] Furthermore, if the SOC(OCV) calculated from the OCV versus SOC characteristic chart deviates by a predetermined value relative to the SOC(UH) obtained from the peak value of the differential characteristic of the current UH versus SOC characteristic chart, the battery state estimation unit 210 corrects the OCV versus SOC characteristic chart based on the deviation. Details will be described later (SOC estimation correction 2).

[0118] Furthermore, the heat detected by the battery heat detection unit 120 can be directly used as the heat HF ​​of the battery cell 111. Alternatively, the heat 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 can be used as the heat HF ​​of the battery cell 111. Thus, the heat of the battery cell 111, free from various heat-related effects, i.e., noise effects, within the battery pack 100, can be obtained. Moreover, the heat of the positive electrode side battery cell 111 and the heat of the negative electrode side battery cell 111 can be averaged to obtain the heat HF ​​of the battery cell 111.

[0119] In the SOC estimation, the battery cell OCV versus SOC characteristics are pre-stored as multiple tables according to temperature. For example, in actual use, when the vehicle is parked and not being charged or discharged, the SOC corresponding to the detected OCV is estimated as the battery cell SOC by referring to the table corresponding to the detected temperature.

[0120] Therefore, for battery cells where voltage changes relative to capacity, such as lithium-ion batteries using hard carbon as the negative electrode material, the state of charge (SOC) can be estimated with high accuracy based on the battery cell's voltage.

[0121] In recent years, battery cells with relatively small voltage changes compared to capacity changes have emerged, such as lithium-ion batteries using graphite as the negative electrode material. In battery packs with such cells, the accuracy of state-of-the-art (SOC) estimation based on cell voltage decreases.

[0122] Furthermore, battery cell degradation leads to a gradual change in the OCV versus SOC characteristic, causing it to deviate from its initial characteristics. To address this, the inventors of this application considered measuring the current CCV versus SOC characteristic in graphite-based lithium-ion batteries, for example, during charging while the vehicle is parked in real-world use, and correcting for errors in SOC estimation. Moreover, by charging at a constant current and low rate, the capacity (mAh) can be determined from the charging current (mA) and charging time (h).

[0123] Figure 6 This is a graph illustrating an example of the baseline characteristics and differential characteristics of CCV versus SOC, specifically the differential characteristic d(CCV) / d(SOC) of CCV = f(SOC). For example... Figure 6 As shown, in lithium-ion batteries using graphite as the negative electrode material and NCM as the positive electrode material, the differential characteristics of CCV versus SOC exhibit multiple peaks associated with phase transitions, as seen with graphite. However, only two peaks are clearly visible. Moreover, this characteristic of peaks associated with phase transitions in the differential characteristics of CCV versus SOC is not present in lithium-ion batteries using hard carbon.

[0124] Therefore, in the correction of the SOC estimation of the comparative scale, the OCV versus SOC characteristic chart is corrected according to the offset of the SOC estimated by the OCV versus SOC characteristic chart relative to the peak SOC in the differential characteristic of CCV versus SOC.

[0125] Specifically, for example, when a vehicle starts charging while parked in actual use, the SOC corresponding to the measured OCV is estimated as the initial SOC by referring to the OCV versus SOC characteristic table.

[0126] Furthermore, for example, when charging a vehicle while it is parked in actual use, the current characteristics of CCV versus SOC are measured, and the peak value of the measured differential characteristics of CCV versus SOC is sensed. For example, the peak value of the differential characteristics of CCV versus SOC is referenced to a pre-stored peak value of SOC, and the sensed peak value is used as the SOC (CCV) to calculate the SOC.

[0127] Furthermore, at this time, the charging capacity from the start of charging to the peak sensing time is calculated based on the charging current and charging time, and the SOC(OCV) is calculated based on the calculated charging capacity and the initial SOC estimated by the OCV versus SOC chart as described above at the start of charging.

[0128] Furthermore, if the SOC(OCV) calculated from the OCV versus SOC characteristic chart deviates by a predetermined value relative to the SOC(CCV) obtained from the peak value of the differential characteristic of CCV versus SOC, the OCV versus SOC characteristic chart is corrected based on the deviation.

[0129] However, in the CCV versus SOC differential characteristics, the peak size is small, the spectrum is blunt, and the S / N ratio is low. This problem becomes particularly pronounced once degradation occurs. Therefore, even if the initial SOC estimate is corrected based on the CCV versus SOC differential characteristics, the correction accuracy is expected to be low, and the estimation accuracy will also be low.

[0130] In this application, the inventors have gained insights into the relationship between the battery cell's state of charge (SOC) and the phase transition of the electrode material's active material, as well as the associated heat (HF) of the battery cell. Furthermore, the inventors have gained the following insights: the differential characteristics of HF versus SOC, compared to the differential characteristics of CCV versus SOC,

[0131] • It has large peak size, sharp spectrum, and large S / N ratio, and retains these characteristics even when it deteriorates;

[0132] In addition, there are many peaks and short peak intervals;

[0133] Furthermore, the specific pattern of positive and negative peak values ​​remains unchanged even with degradation; in other words, the position of the peak value relative to the SOC is not easily shifted even with degradation. Therefore, the inventors of this application have designed the following method: based on the heat of the battery cell, the SOC estimate of the battery cell is corrected in detail based on the HF versus SOC characteristics, and even more in detail based on the HF versus SOC differential characteristics (the correction of SOC estimate described below).

[0134] The inventors of this application have obtained the following insight: the UH versus SOC differential characteristic compared to the CCV versus SOC differential characteristic...

[0135] • It has large peak size, sharp spectrum, and large S / N ratio, and retains these characteristics even when it deteriorates;

[0136] In addition, there are many peaks and short peak intervals;

[0137] Furthermore, the specific pattern with both positive and negative peak values ​​remains consistent even after degradation; in other words, the position of the peak value relative to the State of Charge (SOC) is not easily shifted even after degradation. Therefore, the inventors of this application have designed the following method: based on the enthalpy potential of the battery cell, the SOC estimate of the battery cell is corrected in detail based on the UH versus SOC characteristic, and even more in detail based on the UH versus SOC differential characteristic (SOC estimate correction 2 described later).

[0138] (Correction to SOC estimation 1)

[0139] First, an example of the correction of the SOC estimate of battery cell 111 performed by battery state estimation unit 210 based on the heat of battery cell, in detail based on HF versus SOC characteristics, and more in detail based on HF versus SOC differential characteristics will be described.

[0140] For example, in actual use, when the vehicle is parked and not being charged or discharged, the battery state estimation unit 210 periodically refers to the OCV versus SOC characteristic chart to estimate the SOC of the battery cell 111 corresponding to the detected OCV of the battery cell 111.

[0141] Furthermore, for example, when the vehicle starts charging while parked in actual use, the battery state estimation unit 210 refers to the OCV versus SOC characteristic chart and estimates the SOC of the battery cell 111 corresponding to the detected OCV of the battery cell 111 as the initial SOC.

[0142] Then, for example, when charging the vehicle while it is parked in actual use, such as... Figure 3B and Figure 3C As shown, the battery state estimation unit 210 measures the current HF versus SOC characteristic of the battery cell 111 and senses the measured peak value of the HF versus SOC differential characteristic.

[0143] Figure 4 This is a diagram illustrating an example of the HF versus SOC characteristics and their differential characteristics in this embodiment, specifically the differential characteristic d(HF) / d(SOC) of the HF characteristic with respect to SOC, HF = f(SOC). Figure 4 As shown, in lithium-ion batteries using graphite as the negative electrode material and NCM as the positive electrode material, the HF versus SOC differential characteristics exhibit multiple peaks 1 to 7 associated with graphite phase transitions. Even with battery degradation, these peak positions (SOC) are not easily shifted. Moreover, they become even more difficult to shift in the order of peaks 7, 6, 5, 4, 3, 2, and 1.

[0144] Therefore, the battery state estimation unit 210 refers to the differential characteristic peak SOC of the HF versus SOC initial characteristic stored in the storage unit 220, and calculates the sensed peak SOC as SOC(HF).

[0145] Furthermore, at this time, the battery state estimation unit 210 calculates the charging capacity from the start of charging to the peak sensing time based on the charging current and charging time, and calculates the SOC(OCV) based on the calculated charging capacity and the initial SOC estimated at the start of charging based on the OCV versus SOC chart as described above.

[0146] For example, the battery state estimation unit 210 calculates the ΔSOC corresponding to the calculated charging capacity Q(t) according to the following formula, and calculates the SOC(OCV) based on the calculated ΔSOC and the initial SOC estimated at the start of charging according to the OCV versus SOC chart.

[0147] SOC(OCV) = Initial SOC + ΔSOC…(Equation)

[0148] ΔSOC=Q(t) / C0(t)…(Equation)

[0149] C0(t)=C0×SOH…(Equation)

[0150] C0(t): Current total capacity

[0151] C0: Initial total capacity

[0152] SOH: Deterioration state

[0153] t: Time elapsed

[0154] Among them, it is believed that as long as SOH can be accurately estimated, ΔSOC can also be accurately estimated. SOC(OCV) reflects the shift of the initial SOC estimated according to the OCV versus SOC table.

[0155] Furthermore, SOH can be determined, for example, by the following method.

[0156] For example, the battery state estimation unit 210, based on, as Figure 3B or Figure 3C The measured HF versus SOC current characteristics and as shown Figure 3A The pre-stored HF versus SOC initial characteristics are used to estimate the SOH of the battery cell.

[0157] and, Figure 3D Overlapping shown Figure 3A The initial characteristics of HF versus SOC shown Figure 3B The HF versus SOC characteristics under the degraded small state are shown, and Figure 3C The HF versus SOC characteristics under deterioration are shown.

[0158] In lithium-ion batteries where the negative electrode is cut, such as Figure 4 The peak-to-peak segment lengths of the HF versus SOC differential characteristic shown are related to the total battery cell capacity. Therefore, knowing these peak-to-peak segment lengths (mAh) allows us to determine the total battery cell capacity (mAh). For example, assuming an initial SOC of 0%-100% with a capacity of 100mAh, the peak-to-peak segment length is 20mAh. Furthermore, the peak-to-peak segment length (mAh) can be calculated based on the charging current and charging time. If the battery cell deteriorates significantly, and the peak-to-peak segment length is 10mAh, then the total battery cell capacity is 50mAh.

[0159] Therefore, the battery state estimation unit 210 pre-stores the length of the line segment between each peak in the differential characteristic of the initial HF versus SOC characteristic (mAh). Then, during charging, the battery state estimation unit 210 measures the length of the line segment between any two peaks in the differential characteristic of the current (degraded) HF versus SOC characteristic and performs SOH estimation according to the following formula.

[0160] SOH = {Length of the line segment between the two peaks in the differential characteristic of HF versus SOC (when deteriorating) in mAh} / {Length of the line segment between the corresponding two peaks in the differential characteristic of HF versus SOC in mAh} ... (Equation)

[0161] Furthermore, since charging in actual use is done with a constant current and a low rate, the length of the peak segment (mAh) can be calculated based on the charging current (mA) and the charging time (h).

[0162] Therefore, since it is not necessary to start charging from 0% SOC and it is not necessary to charge to 100% SOC, the SOH can be estimated during charging in actual use.

[0163] Then, if the SOC(OCV) calculated from the OCV versus SOC characteristic chart as described above deviates by a predetermined value from the SOC(HF) obtained from the peak value of the differential characteristic of HF versus SOC as described above, the battery state estimation unit 210 corrects the OCV versus SOC characteristic chart based on the deviation. As a correction method, the chart can be offset horizontally and vertically throughout (e.g., the degree of deviation (SOC%)).

[0164] As described above, in the correction of SOC estimation in this embodiment, the SOC estimation of the battery cell is corrected according to the HF versus SOC differential characteristic instead of the CCV versus SOC differential characteristic. As described above, the HF versus SOC differential characteristic, compared to the CCV versus SOC differential characteristic,

[0165] • It has large peak size, sharp spectrum, and large S / N ratio, and retains these characteristics even when it deteriorates;

[0166] In addition, there are many peaks and short peak intervals;

[0167] Furthermore, the specific patterns exhibiting both positive and negative peak values ​​maintain their shape even after degradation; in other words, the peak position relative to the State of Charge (SOC) is less prone to shift even with degradation. Therefore, this improves the correction accuracy of battery cell SOC estimation and enhances the estimation accuracy of the SOC estimate itself.

[0168] Especially in the differential characteristic of HF versus SOC, there are many peaks and the peak intervals are small. Therefore, in actual use, when charging according to various SOCs, the SOC estimate can be corrected, even when charging for a short time in actual use.

[0169] Furthermore, the HF versus SOC differential characteristic has a specific pattern of positive and negative peak values. Therefore, even when charging according to various SOCs in actual use, the peak position (SOC) in the HF versus SOC differential characteristic can be easily identified based on the pattern of the positive and negative values ​​and magnitude of the peak values, and the SOC estimate can be easily corrected.

[0170] In practical applications, sometimes an End-of-Life (EOL) chart is prepared as the OCV versus SOC characteristic chart. Alternatively, in practical applications, multiple charts are prepared as OCV versus SOC characteristic charts based on degradation states such as the Beginning-of-Life (BOL), End-of-Life (EOL), and intermediate degradation states. Regarding this, according to the correction of SOC estimation in this embodiment, the OCV versus SOC characteristic chart can be corrected according to degradation; therefore, for example, only the initial state chart may be prepared.

[0171] However, regarding SOC and SOH estimation, it is generally known to construct a mathematical model of the battery cell and use a state estimator created based on the model to estimate SOC and SOH. In this estimation, errors in the battery model lead to a fundamental problem of decreased accuracy. Furthermore, it is impossible to determine the accuracy of the estimated values ​​during battery use. Regarding this issue, according to the present invention, by measuring HF characteristics, even if errors occur in the battery mathematical model, they can be corrected during battery use.

[0172] (Correction to SOC estimation 2)

[0173] Next, an example of the correction of the SOC estimate of battery cell 111 performed by battery state estimation unit 210 based on the thermal enthalpy potential of battery cell, in detail based on UHversus SOC characteristics, and in more detail based on UH versus SOC differential characteristics will be described.

[0174] For example, in actual use, when the vehicle is parked and not being charged or discharged, the battery state estimation unit 210 periodically refers to the OCV versus SOC characteristic chart to estimate the SOC of the battery cell 111 corresponding to the detected OCV of the battery cell 111.

[0175] Furthermore, for example, when the vehicle starts charging while parked in actual use, the battery state estimation unit 210 refers to the OCV versus SOC characteristic chart and estimates the SOC of the battery cell 111 corresponding to the detected OCV of the battery cell 111 as the initial SOC.

[0176] Then, for example, when charging the vehicle while it is parked in actual use, such as... Figure 3B and Figure 3C As shown, the battery state estimation unit 210 measures the current UH versus SOC characteristic of the battery cell 111 and senses the measured peak value of the UH versus SOC differential characteristic.

[0177] Figure 5 This is a diagram illustrating an example of the UH versus SOC characteristic and its differential characteristic in this embodiment, that is, the differential characteristic of UH with respect to SOC, d(UH) / d(SOC), where UH = f(SOC). Figure 5 As shown, for example, in lithium-ion batteries using graphite as the negative electrode material and NCM as the positive electrode material, the UH versus SOC differential characteristics exhibit multiple peaks 1 to 7 associated with graphite phase transitions. Even with battery degradation, these peak positions (SOC) are not easily shifted. Moreover, they become even more difficult to shift in the order of peaks 7, 6, 5, 4, 3, 2, and 1.

[0178] Therefore, the battery state estimation unit 210 refers to the differential characteristic peak SOC of the initial characteristics of UH versus SOC stored in the storage unit 220, and calculates the sensed peak SOC as SOC(UH).

[0179] Furthermore, at this time, the battery state estimation unit 210 calculates the charging capacity from the start of charging to the peak sensing time based on the charging current and charging time, and calculates the SOC(OCV) based on the calculated charging capacity and the initial SOC estimated at the start of charging based on the OCV versus SOC chart as described above.

[0180] For example, the battery state estimation unit 210 calculates the ΔSOC corresponding to the calculated charging capacity Q(t) according to the following formula, and calculates the SOC(OCV) based on the calculated ΔSOC and the initial SOC estimated at the start of charging according to the OCV versus SOC chart.

[0181] SOC(OCV) = Initial SOC + ΔSOC…(Equation)

[0182] ΔSOC=Q(t) / C0(t)…(Equation)

[0183] C0(t)=C0×SOH…(Equation)

[0184] C0(t): Current total capacity

[0185] C0: Initial total capacity

[0186] SOH: Deterioration state

[0187] t: Time elapsed

[0188] Among them, it is believed that as long as SOH can be accurately estimated, ΔSOC can also be accurately estimated. SOC(OCV) reflects the shift of the initial SOC estimated according to the OCV versus SOC table.

[0189] Furthermore, SOH can be determined by methods such as those described below.

[0190] For example, the battery state estimation unit 210, based on, as Figure 3B or Figure 3C The measured UH versus SOC current characteristics are shown and as follows Figure 3A The pre-stored UH versus SOC initial characteristics are used to estimate the SOH of the battery cell.

[0191] In lithium-ion batteries where the negative electrode is cut, such as Figure 5 The length of the peak segments in the UH versus SOC differential characteristic shown is related to the total capacity of the battery cell. Therefore, knowing the lengths of these peak segments (mAh) allows us to determine the total 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 any two peaks is 20mAh. Furthermore, the length of the peak segments (mAh) can be calculated based on the charging current and charging time. If the battery cell deteriorates significantly, and the length of these two peak segments is 10mAh, then the total capacity of the battery cell is 50mAh.

[0192] Therefore, the battery state estimation unit 210 pre-stores the length of the line segment between each peak in the differential characteristic of the initial UH versus SOC characteristic (mAh). Then, during charging, the battery state estimation unit 210 measures the length of the line segment between any two peaks in the differential characteristic of the current (degraded) UH versus SOC characteristic and performs SOH estimation according to the following formula.

[0193] SOH = {Length of the line segment between the two peaks in the differential characteristic of UH versus SOC (when deteriorating) in mAh} / {Length of the line segment between the corresponding two peaks in the differential characteristic of UH versus SOC in mAh} ... (Equation)

[0194] Furthermore, since charging in actual use is done with a constant current and a low rate, the length of the peak segment (mAh) can be calculated based on the charging current (mA) and the charging time (h).

[0195] Therefore, since it is not necessary to start charging from 0% SOC and it is not necessary to charge to 100% SOC, the SOH can be estimated during charging in actual use.

[0196] Then, if the SOC(OCV) calculated from the OCV versus SOC characteristic chart as described above deviates by a predetermined value from the SOC(UH) obtained from the peak value of the differential characteristic of UH versus SOC as described above, the battery state estimation unit 210 corrects the OCV versus SOC characteristic chart based on the deviation. As a correction method, the chart can be offset horizontally and vertically throughout (e.g., the degree of deviation (SOC%)).

[0197] As described above, in the correction of SOC estimation in this embodiment, the SOC estimation of the battery cell is corrected according to the UH versus SOC differential characteristic instead of the CCV versus SOC differential characteristic. As described above, the UH versus SOC differential characteristic, compared to the CCV versus SOC differential characteristic,

[0198] • It has large peak size, sharp spectrum, and large S / N ratio, and retains these characteristics even when it deteriorates;

[0199] In addition, there are many peaks and short peak intervals;

[0200] Furthermore, the specific patterns exhibiting both positive and negative peak values ​​maintain their shape even during degradation; in other words, the position of the peak value relative to the State of Charge (SOC) is not easily shifted even with degradation. Therefore, the correction accuracy of battery cell SOC estimation can be improved, and the estimation accuracy of SOC estimation can also be enhanced.

[0201] Especially in the UH versus SOC differential characteristics, there are many peaks and the peak intervals are small. Therefore, in actual use, when charging according to various SOCs, the SOC estimate can also be corrected, even when charging for a short time in actual use.

[0202] Furthermore, the UH versus SOC differential characteristic has a specific pattern of positive and negative peak values. Therefore, even when charging according to various SOCs in actual use, the peak position (SOC) in the UH versus SOC differential characteristic can be easily identified based on the pattern of the positive and negative values ​​and magnitude of the peak values, and the SOC estimate can be easily corrected.

[0203] Furthermore, as mentioned above, in practical applications, sometimes an End-of-Life (EOL) chart is prepared as an OCV versus SOC characteristic chart. Alternatively, in practical applications, sometimes multiple charts are prepared as OCV versus SOC characteristic charts based on degradation states such as the Beginning-of-Life (BOL), the End-of-Life (EOL), and intermediate degradation states. Regarding this, according to the correction of SOC estimation in this embodiment, the OCV versus SOC characteristic chart can be corrected according to degradation; therefore, for example, only the initial state chart can be prepared.

[0204] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and various modifications and variations can be made. For example, in the above-described correction 1 for SOC estimation, the CCV versus SOC characteristic chart can be corrected based on the heat of the battery cell, in detail based on the HF versus SOC characteristics, and even more in detail based on the HF versus SOC differential characteristics.

[0205] Specifically, similar to the above, for example, when charging the vehicle while it is parked in actual use, such as... Figure 3B and Figure 3C As shown, the battery state estimation unit 210 measures the current HF versus SOC characteristic of the battery cell 111 and senses the measured HF versus SOC differential characteristic peak. The battery state estimation unit 210 refers to the differential characteristic peak SOC of the initial HF versus SOC characteristic stored in the storage unit 220 and calculates the SOC corresponding to the sensed peak as SOC(HF).

[0206] Furthermore, the battery state estimation unit 210 refers to the stored CCV versus SOC characteristic table, which is the CCV versus SOC characteristic table corresponding to the temperature and current detected during the peak sensing, and calculates the SOC corresponding to the CCV detected during the peak sensing as SOC(CCV).

[0207] Then, if the SOC(CCV) calculated from the CCV versus SOC characteristic chart as described above deviates by a predetermined value from the SOC(HF) obtained from the peak value of the differential characteristic of HF versus SOC as described above, the battery state estimation unit 210 corrects the CCV versus SOC characteristic chart based on the deviation. As a correction method, the chart can be offset horizontally and vertically throughout (e.g., the degree of deviation (SOC%)).

[0208] In practical applications, sometimes an End-of-Life (EOL) chart is prepared as the CCV versus SOC characteristic chart. Alternatively, in practical applications, multiple charts are sometimes prepared as CCV versus SOC characteristic charts based on degradation states such as the Beginning-of-Life (BOL), End-of-Life (EOL), and intermediate degradation states. Regarding this, based on the correction for SOC estimation in this variation, the CCV versus SOC characteristic chart can be corrected according to degradation; therefore, for example, only the initial state chart may be prepared.

[0209] Furthermore, in the above-mentioned correction 2 for SOC estimation, the CCV versus SOC characteristic chart can be corrected based on the enthalpy potential of the battery cell, in detail based on the UH versus SOC characteristic, and even more in detail based on the UH versus SOC differential characteristic.

[0210] Specifically, similar to the above, for example, when charging the vehicle while it is parked in actual use, such as... Figure 3B and Figure 3C As shown, the battery state estimation unit 210 measures the current UH versus SOC characteristic of the battery cell 111 and senses the measured UH versus SOC differential characteristic peak. The battery state estimation unit 210 refers to the differential characteristic peak SOC of the initial UH versus SOC characteristic stored in the storage unit 220 and calculates the SOC corresponding to the sensed peak as SOC(UH).

[0211] Furthermore, the battery state estimation unit 210 refers to the stored CCV versus SOC characteristic table, which is the CCV versus SOC characteristic table corresponding to the temperature and current detected during the peak sensing, and calculates the SOC corresponding to the CCV detected during the peak sensing as SOC(CCV).

[0212] Then, if the SOC(CCV) calculated from the CCV versus SOC characteristic chart as described above deviates by a predetermined value from the SOC(UH) obtained from the peak value of the UH versus SOC differential characteristic as described above, the battery state estimation unit 210 corrects the CCV versus SOC characteristic chart based on the deviation. As a correction method, the chart can be shifted left and right uniformly throughout (e.g., the degree of deviation (SOC%)).

[0213] As described above, in practical applications, sometimes an End-of-Life (EOL) chart is prepared as a CCV versus SOC characteristic chart. Alternatively, in practical applications, sometimes multiple charts are prepared as CCV versus SOC characteristic charts based on degradation states such as the Beginning-of-Life (BOL), the End-of-Life (EOL), and intermediate degradation states. Regarding this, according to the correction of SOC estimation in this embodiment, the CCV versus SOC characteristic chart can be corrected according to degradation; therefore, for example, only the initial state chart can be prepared.

[0214] Figure Labels

[0215] 100 battery pack

[0216] 101 Casing

[0217] 102 Outer shell

[0218] 103 Lower Frame

[0219] 104 Upper Frame

[0220] 105 Cooling Plate

[0221] 106 Air Inlet Mechanism

[0222] 110 Battery Module

[0223] 111 battery cell

[0224] 112-layered structure

[0225] 113 end plate

[0226] 114 Unit Busbar

[0227] 119 Module Bus

[0228] 120 Battery Thermal Detection Department

[0229] 130 Standard Heat Detection Department

[0230] 141 Voltage Detection Department

[0231] 142 Current Detection Unit

[0232] 143 Temperature Detection Department

[0233] 200 Battery Management System (BMS)

[0234] 210 Battery State Estimation Unit

[0235] 220 Storage Department

Claims

1. A battery pack comprising a battery module, the battery module having battery cells, the battery pack comprising: The voltage detection unit detects the open-circuit voltage or closed-circuit voltage of the aforementioned battery cell; The current detection unit detects the current of the aforementioned battery cell; The battery thermal detection unit detects the heat of the aforementioned battery cells; The storage unit stores the following (A1) and (A2). (A1) Table of Open Circuit Voltage (OCV) versus State of Charge (SOC) of the aforementioned battery cell (A2) The initial characteristics of the heat HF ​​versus SOC of the aforementioned battery cell, and the SOC in the peak value of the differential characteristics of the aforementioned initial characteristics of HF versus SOC; and, The battery state estimation unit estimates the state of charge (SOC) of the battery cell corresponding to the detected battery cell OCV, based on the aforementioned (A1); and... The aforementioned battery state estimation unit, When the charging of the aforementioned battery cell begins, according to (A1) above, the SOC of the aforementioned battery cell corresponding to the OCV of the aforementioned battery cell detected by the aforementioned voltage detection unit is estimated as the initial SOC; When the aforementioned battery cell is charging, the battery cell HF detected by the aforementioned battery heat detection unit is used to measure the current characteristic of the aforementioned battery cell HF versus SOC, and the peak value in the differential characteristic of the measured current characteristic of the aforementioned HF versus SOC is sensed. Based on the aforementioned (A2), the sensed peak value SOC is calculated as SOC(HF). Based on the charging current and charging time detected by the aforementioned current detection unit, the charging capacity from the start of charging to the peak sensing time is calculated, and the SOC (OCV) is calculated based on the calculated charging capacity and the aforementioned initial SOC estimated at the start of charging. If the aforementioned SOC(OCV) deviates by a predetermined value relative to the aforementioned SOC(HF), then the aforementioned (A1) is corrected according to the offset.

2. The battery pack according to claim 1, wherein, The aforementioned battery state estimation unit, The SOH of the battery cell is estimated based on the ratio of the peak-to-peak line length mAh in the differential characteristic of the current HF versus SOC characteristic measured above to the peak-to-peak line length mAh in the differential characteristic of the initial HF versus SOC characteristic stored in the aforementioned storage unit. The ΔSOC corresponding to the calculated charging capacity Q(t) is then calculated using the following formula. ΔSOC=Q(t) / C0(t) C0(t) = C0 × SOH C0(t): Current total capacity C0: Initial total capacity t: Time elapsed The aforementioned SOC (OCV) is calculated based on the calculated ΔSOC and the estimated initial SOC at the start of charging.

3. The battery pack according to claim 1 or 2, wherein, The aforementioned storage unit also stores the following (A11), (A11) The aforementioned battery cell closed-circuit voltage (CCV) versus SOC characteristic table. The aforementioned battery state estimation unit, Based on the aforementioned (A11), when sensing the peak value, the SOC(CCV) corresponding to the CCV detected by the aforementioned voltage detection unit is calculated; If the aforementioned SOC(CCV) deviates by a predetermined value relative to the aforementioned SOC(HF), then the aforementioned (A11) can be corrected based on the offset.

4. A battery pack comprising a battery module, the battery module having battery cells, the battery pack comprising: The voltage detection unit detects the open-circuit voltage or closed-circuit voltage of the aforementioned battery cell; The current detection unit detects the current of the aforementioned battery cell; The battery thermal detection unit detects the heat of the aforementioned battery cells; The storage unit stores the following (A1) and (A3). (A1) Table of Open Circuit Voltage (OCV) versus State of Charge (SOC) characteristics of the aforementioned battery cell (A3) The initial characteristics of the enthalpy potential UH versus SOC of the aforementioned battery cell, and the peak SOC in the differential characteristics of the initial characteristics of UH versus SOC; in, UH is calculated using the following formula based on the closed-circuit voltage CCV, heat HF, and current I. UH=CCV-HF / I The battery state estimation unit estimates the state of charge (SOC) of the battery cell corresponding to the detected battery cell OCV based on the aforementioned (A1). The aforementioned battery state estimation unit, When the charging of the aforementioned battery cell begins, according to (A1) above, the SOC of the aforementioned battery cell corresponding to the OCV of the aforementioned battery cell detected by the aforementioned voltage detection unit is estimated as the initial SOC; When the aforementioned battery cell is being charged, the battery cell's HF, CCV, and I are detected by the aforementioned battery heat detection unit, the aforementioned voltage detection unit, and the aforementioned current detection unit. The current characteristic of the aforementioned battery cell's UH versus SOC is measured, and the peak value in the differential characteristic of the measured current characteristic of the aforementioned UH versus SOC is sensed. Based on the aforementioned (A3), the sensed peak value SOC is calculated as SOC(UH). Based on the charging current and charging time detected by the aforementioned current detection unit, the charging capacity from the start of charging to the peak sensing time is calculated, and the SOC (OCV) is calculated based on the calculated charging capacity and the aforementioned initial SOC estimated at the start of charging. If the aforementioned SOC(OCV) deviates by a predetermined value relative to the aforementioned SOC(UH), then the aforementioned (A1) is corrected according to the offset.

5. The battery pack according to claim 4, wherein, The aforementioned battery state estimation unit, The SOH of the battery cell is estimated based on the ratio of the peak-to-peak segment length mAh in the differential characteristic of the current UH versus SOC measured to the peak-to-peak segment length mAh in the differential characteristic of the initial UH versus SOC stored in the storage unit. The ΔSOC corresponding to the calculated charging capacity Q(t) is then calculated using the following formula. ΔSOC=Q(t) / C0(t) C0(t) = C0 × SOH C0(t): Current total capacity C0: Initial total capacity t: Time elapsed The aforementioned SOC (OCV) is calculated based on the calculated ΔSOC and the estimated initial SOC at the start of charging.

6. The battery pack according to claim 4 or 5, wherein, The aforementioned storage unit also stores the following (A11), (A11) The aforementioned battery cell closed-circuit voltage (CCV) versus SOC characteristic table diagram The aforementioned battery state estimation unit, Based on the aforementioned (A11), when sensing the peak value, the SOC(CCV) corresponding to the CCV detected by the aforementioned voltage detection unit is calculated; If the aforementioned SOC(CCV) is offset by a predetermined value relative to the aforementioned SOC(UH), then the aforementioned (A11) can be corrected based on the offset.

7. The battery pack according to any one of claims 1, 2, 4 and 5, wherein, It also includes a reference heat detection unit that detects the heat of the aforementioned battery pack as a reference heat. The aforementioned battery state estimation unit subtracts the reference heat detected by the aforementioned reference heat detection unit from the heat detected by the aforementioned battery heat detection unit, thereby using the heat that has been freed from the influence of the aforementioned internal battery heat as the heat of the aforementioned battery cell.

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