Charging current value estimation system and charging current value estimation method

Abstract

A charging current value estimation system according to one aspect of the present technology is a system capable of estimating the charging current value of each secondary battery cell when n (where n is a natural number of 2 or higher) secondary battery cells are connected together in parallel. This system is capable of calculating the charging current value of each secondary battery cell on the basis of open-circuit voltage data for the integrated charge amount of each secondary battery cell and cell resistance data for the integrated charge amount of each secondary battery cell.

Description

Charging current value estimation system and charging current value estimation method

[0001] The present technology relates to a charging current value estimation system and a charging current value estimation method.

[0002] In recent years, the use of lithium-ion secondary batteries has expanded to larger devices such as electric vehicles (EVs) and stationary battery storage systems (ESSs). Rare metals such as lithium and cobalt are used as raw materials for lithium-ion secondary batteries. Therefore, from the perspective of effective resource utilization, repurposing and reusing used battery packs is being considered, particularly for lithium-ion secondary batteries used in large-scale devices.

[0003] Repurposing refers to reusing a used battery pack for a purpose other than its original purpose, while reuse refers to reusing a used battery pack for the same purpose. For example, when repurposing a used EV battery pack to build an ESS, or other use with a larger capacity, multiple used battery packs with different degrees of deterioration may be used in combination.

[0004] However, when multiple used battery packs with different degrees of degradation are connected in parallel and charged, the current distribution ratio for each used battery pack is different, which may cause current concentration in a specific used battery pack. Therefore, for example, it is conceivable to determine whether or not current concentration occurs in a specific used battery pack by estimating the charging current value of each used battery pack connected in parallel through a simulation. Methods for estimating the charging current value are disclosed in, for example, Patent Documents 1 and 2 listed below.

[0005] JP 2011-258337 A JP 2020-161422 A

[0006] It is desirable that the behavior of each used battery pack connected in parallel obtained by simulation (calculation results) closely matches the behavior of each used battery pack connected in parallel obtained by actual measurement (measurement results). Therefore, it is desirable to provide a charging current value estimation system and a charging current value estimation method that can achieve a good agreement between the calculation results and the actual measurement results.

[0007] A charging current value estimation system according to a first aspect of the present technology is a system capable of estimating a charging current value of each secondary battery cell when n (n is a natural number equal to or greater than 2) secondary battery cells are connected in parallel. The system includes a memory and a processing circuit. The memory stores open-circuit voltage data corresponding to the integrated charge amount of each secondary battery cell and cell resistance data corresponding to the integrated charge amount of each secondary battery cell. The processing circuit is capable of calculating a charging current value of each secondary battery cell based on the open-circuit voltage data and cell resistance data acquired from the memory. The processing circuit is capable of performing the following two operations: (A1) deriving an open-circuit voltage value corresponding to an initial charge amount of each secondary battery cell from the open-circuit voltage data, and deriving a resistance value corresponding to the initial charge amount of each secondary battery cell from the cell resistance data; and (A2) calculating a charging current value of each secondary battery cell when the charge amount of each secondary battery cell is the initial charge amount, based on the open-circuit voltage value and the resistance value.

[0008] A charging current value estimation method according to a second aspect of the present technology is a method capable of estimating a charging current value of each secondary battery cell when n (n is a natural number of 2 or more) secondary battery cells are connected in parallel with each other. This method includes the following three steps: (B1) acquiring open-circuit voltage data for an integrated charge amount of each secondary battery cell and cell resistance data for the integrated charge amount of each secondary battery cell; (B2) deriving an open-circuit voltage value for an initial charge amount of each secondary battery cell from the acquired open-circuit voltage data, and deriving a resistance value for the initial charge amount of each secondary battery cell from the acquired cell resistance data; and (B3) calculating a charging current value of each secondary battery cell when the charge amount of each secondary battery cell is the initial charge amount, based on the open-circuit voltage value and the resistance value.

[0009] In the charging current value estimation system according to the first aspect of the present technology and the charging current value estimation method according to the second aspect of the present technology, the charging current value of each secondary battery cell is calculated based on open circuit voltage data for the integrated charge amount of each secondary battery cell and cell resistance data for the integrated charge amount of each secondary battery cell. This makes it possible to achieve good agreement between the calculated result and the actual measurement result.

[0010] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below.

[0011] FIG. 1A is a diagram showing an example of a conventional battery cell model. FIG. 1B is a diagram showing a battery cell model used in the present technology. FIG. 2 is a diagram showing an example of a battery module used in the present technology. FIG. 3 is a diagram showing an example of an open circuit voltage and an overvoltage in the battery module of FIG. 2. FIG. 4 is a diagram showing an example of functional blocks of a charging current value estimation system according to a first embodiment of the present technology. FIG. 5 is a diagram showing a procedure for estimating charging current values ​​of two battery cells constituting the battery module of FIG. 2 in the charging current value estimation system of FIG. 1. FIG. 6 is a diagram showing a procedure following "A" in FIG. 5. FIG. 7 is a diagram showing a procedure following "B" in FIG. 5. FIG. 8 is a diagram showing an example of measured values ​​(OCV value, resistance value) of one battery cell alone of two battery cells connected in parallel. FIG. 9 is a diagram showing an example of measured values ​​(OCV value, resistance value) of the other battery cell alone of two battery cells connected in parallel. FIG. 10 is a diagram showing an example of simulation results (current values, voltage values) of a battery module (two-parallel module) in which two battery cells are connected in parallel. FIG. 11 is a diagram showing an example of actual measurement values ​​(current values, voltage values) of a battery module (two-parallel module) in which two battery cells are connected in parallel. FIG. 12 is a diagram showing an example of simulation results (OCV value, initial resistance value) of a battery module (two-parallel module) in which two battery cells are connected in parallel. FIG. 13 is a diagram showing an example of simulation results (ODD term and RBD term) of a battery module (two-parallel module) in which two battery cells are connected in parallel. FIG. 14 is a diagram showing an example of a battery module (three-parallel module) in which three battery cells are connected in parallel. FIG. 15 is a diagram showing a two-parallel module in which the second and third battery cells in the battery module of FIG. 14 are considered as one battery cell. FIG. 16 is a diagram showing a two-parallel module in which the first and third battery cells in the battery module of FIG. 14 are considered as one battery cell. Fig. 17 is a diagram showing a two-parallel module in which the first and second battery cells in the battery module of Fig. 13 are considered as one battery cell. Fig. 18 is a diagram showing the procedure for estimating the charging current values ​​of the three battery cells that make up the battery module of Fig. 14 in the charging current value estimation system of Fig. 1. Fig. 19 is a diagram showing the procedure following "D" in Fig. 18.FIG. 10 is a diagram illustrating an example of functional blocks of a charging current value estimation system according to a second embodiment of the present technology.

[0012] Hereinafter, embodiments of the present technology will be described in detail with reference to the drawings. The description will be given in the following order: 1. Battery cell model (FIG. 1) 2. Battery module (FIGS. 2 and 3) 3. Current distribution without considering the passage of time 4. Current distribution with considering the passage of time 5. First embodiment (FIGS. 4 to 13) Example of estimating a charging current value in a two-parallel module using measured values ​​acquired via a server 6. Modifications (FIGS. 14 to 19) Example of estimating a charging current value in a three-parallel module 7. Second embodiment (FIG. 20) Example of performing measurement and estimating a charging current value using a power supply device alone

[0013] <1. Battery Cell Model> First, we will explain the battery cell model used in this technology. FIG. 1(A) shows an example of a conventional battery cell model. FIG. 1(B) shows the battery cell model used in this technology. When discussing the electrical behavior of a battery cell, the battery cell is sometimes described using two elements: an internal resistance R and a voltage source E (FIG. 1(A)). However, because the voltage source E, which represents the electromotive force component, can input and output charge without limit, this model cannot reproduce how the open-circuit voltage changes with charging and discharging. In this technology, to address the concept of charging and discharging, we use the model shown in FIG. 1(B), which uses a capacitor C instead of the voltage source E.

[0014] In an ideal capacitor, the stored charge Q is described as the product of capacitance Ca and voltage V (Q = Ca x V). Because the capacitance of an ideal capacitor is constant regardless of the stored charge Q, the dQ / dV value, which is the voltage derivative of the charge, is also constant and equal to the capacitance Ca. On the other hand, it is known that the dQ / dV value of a battery depends on the stored charge Q. In other words, if we were to plot the dQ / dV value on the vertical axis and the stored charge Q on the horizontal axis, the resulting shape would be complex. Whether this dQ / dV value is constant or not is the difference between a capacitor and a battery from an electrical perspective.

[0015] <2. Battery Module> Next, a battery module M in which n (n is a natural number of 2 or more) battery cells are connected in parallel will be described. Fig. 2 shows an example of a battery module M used in the present technology. Fig. 3 shows an example of voltages generated in each of the battery cells E1, E2, ..., En of the battery module M shown in Fig. 2. Each of the battery cells E1, E2, ..., En is represented by the model shown in Fig. 1(B).

[0016] Each of the battery cells E1, E2, ..., En is a lithium-ion secondary battery. The battery cells shown in Figures 1(A) and 1(B) may be a unit cell, a battery block in which a plurality of unit cells are connected, or an assembled battery in which a battery block and accessories are integrally packed. In an assembled battery, a plurality of lithium-ion secondary batteries are connected in series. The assembled battery may also include a plurality of lithium-ion secondary batteries electrically connected in parallel.

[0017] 2, the open circuit voltage of each battery cell E1, E2, ..., En is Vi (1≦i≦n), the internal resistance of each battery cell E1, E2, ..., En is Ri, and the dQ / dV value (hereinafter referred to as "differential capacity") of each battery cell E1, E2, ..., En is Ci. If the current distribution ratio to each battery cell E1, E2, ..., En when a current I flows through this battery module M is αi, the overvoltage ηi of each battery cell E1, E2, ..., En is expressed by equation (1): ηi=Ri×αi×I... (1)

[0018] The sum of the current distribution ratios αi (α1+α2+...αn) is 1 (equation (2)), and all battery cells E1, E2,..., En are connected in parallel. Therefore, the value of the terminal voltage V obtained by adding the overvoltage ηi to the open circuit voltage Vn is equal for each battery cell E1, E2,..., En, and the following equation (3) holds true: α1+α2+...αn=1...(2) V1+η1=V2+η2=...=Vn+ηn=V...(3)

[0019] Next, to simplify the explanation, the block in which the second to n-th battery cells E2, ..., En are connected in parallel is considered as one large battery cell Eo, and two battery cells E1, Eo are considered as a battery module M connected in parallel (Fig. 2). In the second large battery cell Eo, the open circuit voltage is Vo, the internal resistance is Ro, and the differential capacity is Co. In this case, the sum of the current distribution ratios αi (α1 + αo) is 1 (Equation (4)), and the following Equation (5) holds: α1 + αo = 1... (4) V1 + η1 = Vo + ηo = V... (5)

[0020] The arithmetic sum Ra of the internal resistances and the arithmetic sum Ca of the differential capacitances are expressed by the following equations (6) and (7): Ra=R1+R2+...+Rn=R1+Ro...(6) Ca=C1+C2+...+Cn=C1+Co...(7)

[0021] <3. Current distribution when the passage of time is not taken into consideration> The open circuit voltages V1 and Vo change due to charging and discharging, but first we will explain the current distribution at the moment when the elapsed time t = 0. By substituting equation (1) into equation (5), we obtain the following equation (8): V1 + R1 × α1 × I = Vo + Ro × αo × I (8)

[0022] Here, rearranging equation (8) using the open circuit voltage difference ΔV=V1-Vo gives the following equation (9): Furthermore, using equation (4), eliminating αo and summarizing for α1 gives equation (10): ΔV=(Ro×αo-R1×α1)×I (9) α1=(Ro / Ra)-(ΔV / (Ra×I)) (10)

[0023] The first term on the right side of equation (10) is called the RBD term (Resistance Balance Dependent Term) because it is a component determined by the balance of resistance values ​​in the current distribution ratio. The second term on the right side of equation (10) is called the ODD term (OCV Difference Dependent Term) because it is a component determined by the difference in open circuit voltage.

[0024] The first term on the right-hand side of equation (10) indicates that the current distribution ratio depends on the balance of internal resistances. The second term on the right-hand side of equation (10) indicates that the current distribution ratio is proportional to the difference ΔV in open-circuit voltages. For example, if the internal resistances are the same (R1 = Ro, i.e., Ra = 2R1 = 2Ro) and the open-circuit voltages are also the same (ΔV = 0), substituting these equations into equation (10) results in α1 = 1 / 2. In other words, the current is distributed equally to the two battery cells E1 and Eo.

[0025] <4. Current distribution taking the passage of time into consideration> Next, we will explain the case where the open circuit voltages V1 and Vo change due to charging and discharging for t seconds. For simplicity's sake, we will first assume that the current distribution ratios α1 and αo do not change over time, and further assume that the differential capacities C1 and Co do not change even if the open circuit voltage changes. Since the differential capacities of battery cell A and battery cell B are C1 and Co, respectively, the changes in open circuit voltage δV1 and δVo can be expressed by the following equations (11) and (12): δV1 = (αi × I × t) / C1 (11) δVo = (αo × I × t) / Co (12)

[0026] The amount of change δΔV in the difference in open circuit voltage after t seconds has elapsed is expressed by equation (13). Therefore, the current distribution αi to battery cell A after t seconds can be expressed as equation (14) by replacing ΔV in equation (10) with ΔV + δΔV. δΔV = δV1 - δVo = ((αi / C1) - (αo / Co)) × I × t (13) α1 = (Ro / Ra) - ((ΔV + δΔV) / (Ra × I)) (14)

[0027] Substituting equation (13) into equation (14) gives equation (15). Eliminating αo in equation (15) using equation (4) gives equation (16). α1=(Ro / Ra)-(1 / (Ra×I))×{ΔV+((α1 / C1)-(αo / Co))×I×t}...(15) α1=(Ro / Ra)-(1 / (Ra×I))×{ΔV+((α1 / C1)-((1-α1) / Co))×I×t}...(16)

[0028] Solving equation (16) for α1 gives equation (17): α1=((Ra×C1×Co) / (Ra×C1×Co+Ca×t))×((Ro / Ra)-(ΔV / (Ra×I))+(t / (Ra×Co)))...(17)

[0029] Equation (17) is an analytical solution for the current distribution ratio that takes the passage of time into consideration. When the value of t is sufficiently large, equations (18) and (19) hold true. |Ra×C1×Co|<<|Ca×t| ... (18) |(Ro / Ra)-(ΔV / (Ra×I)|<<|t / (Ra×Co)| ... (19)

[0030] By substituting the left-hand sides of equations (18) and (19) into equation (17) with zero, the current distribution ratio α1 of battery cell A is expressed by equation (20). In other words, if the elapsed time is sufficiently long, it can be seen that the current distribution ratio becomes the current distribution ratio of that battery cell for the capacity of the entire battery module M. α1=C1 / Ca (20)

[0031] In equations (4) to (20), battery cell Eo can be replaced with the same type of battery cell as battery cell E1. That is, equations (4) to (20) also hold for a two-parallel battery module in which two battery cells E1 and E2 are connected in parallel. In this case, in equations (4) to (20), αo should be replaced with α2, Vo with V2, ηo with η2, Ro with R2, Co with C2, and δVo with δV2.

[0032] 5. Embodiments [Configuration] Next, a charging current value estimation system will be described that estimates charging current values ​​I1 and I2 of each battery cell E1, E2 in a battery module (two-parallel module) in which battery cells E1, E2 shown in FIG. 2 are connected in parallel. FIG. 4 shows an example of a schematic configuration of the charging current value estimation system. As shown in FIG. 4, the charging current value estimation system includes, for example, a charging current value estimation device 100, a server device 200, and a power supply device 300. The charging current value estimation device 100, the server device 200, and the power supply device 300 are capable of communicating with each other via a communication network 400. The communication network 400 includes, for example, the Internet, a cloud network, or a network specific to a business operator.

[0033] A battery cell E1 or E2 is connected to the power supply device 300. The power supply device 300 charges and discharges the battery cell E1 or E2, and is a network communication type device that has the function of communicating with external devices. The power supply device 200 has, for example, a charge / discharge circuit 310, an IV measurement circuit 320, and a communication unit 330.

[0034] The charge / discharge circuit 310 charges or discharges the battery cell E1 or E2. The charge / discharge circuit 310 charges or discharges in an OCV (Open Circuit Voltage) measurement mode or a CCV (Closed Circuit Voltage) measurement mode. In the OCV measurement mode, the charge / discharge circuit 310 performs, for example, intermittent charging after completely discharging the battery cell E1 or E2. In the OCV measurement mode, the charge / discharge circuit 310 performs, for example, intermittent charging by repeating 0.5 C charging for 6 minutes followed by a 30-minute break. In the CCV measurement mode, the charge / discharge circuit 310 performs, for example, 1 C constant current charging after completely discharging the battery cell E1 or E2.

[0035] The IV measurement circuit 320 measures the voltage and current of battery cell E1 or battery cell E2. The IV measurement circuit 320 acquires a measurement value D1 by measuring the voltage and current of battery cell E1 in the OCV measurement mode. The IV measurement circuit 320 acquires a measurement value D2 by measuring the voltage and current of battery cell E1 in the CCV measurement mode. The IV measurement circuit 320 acquires a measurement value D3 by measuring the voltage and current of battery cell E2 in the OCV measurement mode. The IV measurement circuit 320 acquires a measurement value D4 by measuring the voltage and current of battery cell E2 in the CCV measurement mode. The IV measurement circuit 320 outputs the measurement values ​​D1, D2, D3, and D4 obtained by the measurements to the server device 200 via the communication unit 330.

[0036] The communication unit 330 is a communication interface that communicates with the server device 200 via the communication network 400. The communication unit 330 transmits the measurement values ​​D1, D2, D3, and D4 obtained by the IV measurement circuit 320 to the server device 200 via the communication network 400.

[0037] Server device 200 has, for example, a communication unit 210, a control unit 220, and a storage unit 230. Communication unit 210 is a communication interface that communicates with power supply device 300 or charging current value estimation device 100 via communication network 400. Communication unit 210 receives measurement values ​​D1, D2, D3, and D4 from power supply device 300 via communication network 400 and outputs them to control unit 220. Communication unit 210 transmits measurement values ​​D1, D2, D3, and D4 input from control unit 220 to charging current value estimation device 100 via communication network 400.

[0038] The control unit 220 is configured to include, for example, a central processing unit (CPU). The control unit 220 stores the measurement values ​​D1, D2, D3, and D4 acquired from the power supply device 300 via the communication unit 210 in the storage unit 230. The storage unit 230 is configured, for example, with a non-volatile memory such as a flash memory. The measurement values ​​D1, D2, D3, and D4 acquired from the power supply device 300 are stored in the storage unit 230. For example, in response to a request from the charging current value estimation device 100, the control unit 220 reads the measurement values ​​D1, D2, D3, and D4 from the storage unit 230 and outputs them to the charging current value estimation device 100 via the communication unit 210.

[0039] Charging current value estimation device 100 includes, for example, a communication unit 110, a data processing unit 120, a storage unit 130, and a display unit 140. Communication unit 110 is a communication interface that communicates with server device 200 via communication network 400. Communication unit 110 receives measurement values ​​D1, D2, D3, and D4 from server device 200 via communication network 400, and outputs them to data processing unit 120.

[0040] The data processing unit 120 includes, for example, a central processing unit (CPU). The data processing unit 120 estimates the charging current values ​​I1 and I2 of the battery cells E1 and E2 in a battery module (two-parallel module) in which the battery cells E1 and E2 are connected in parallel, based on the measurement values ​​D1, D2, D3, and D4 acquired from the server device 200. The data processing unit 120 generates a video signal for displaying an image including the estimated charging current values ​​I1 and I2 of the battery cells E1 and E2, and outputs the video signal to the display unit 140. The display unit 140 includes, for example, a liquid crystal panel or an organic EL panel. The display unit 140 displays an image based on the video signal input from the data processing unit 120. The storage unit 130 includes, for example, a central processing unit (CPU). The storage unit 130 stores various data generated by the data processing unit 120.

[0041] [Calculation Procedure] Next, the procedure for calculating the charging current values ​​I1 and I2 of the battery cells E1 and E2 will be described. Fig. 5 shows an example of the procedure for calculating the charging current values ​​I1 and I2 of the battery cells E1 and E2. Fig. 6 shows an example of the procedure following "A" in Fig. 5. Fig. 7 shows an example of the procedure following "B" in Fig. 5.

[0042] The data processing unit 120 first acquires the measurement values ​​D1, D2, D3, and D4 of the battery cells E1 and E2 from the server device 200 (step S101). The data processing unit 120 generates data on the OCV of the battery cell E1 (OCV data Da) based on the acquired measurement value D1 and stores the data in the storage unit 130 (step S102). For example, the data processing unit 120 generates the OCV data Da by using the measurement value D1 to associate the final voltage V of each pause period of the intermittent charging with the integrated charge amount Q up to the final timing of each pause period of the intermittent charging. The OCV data Da is data indicating the relationship between the OCV of the battery cell E1 and the integrated charge amount Q.

[0043] The data processing unit 120 generates data on the CCV of the battery cell E1 (CCV data Db) based on the acquired measurement value D2 and stores the data in the storage unit 130 (step S102). The data processing unit 120 generates the CCV data Db by, for example, using the measurement value D2 to associate the voltage V at each predetermined timing with the accumulated charge amount Q up to the predetermined timing. The CCV data Db is data that indicates the relationship between the CCV and the accumulated charge amount Q of the battery cell E1.

[0044] The data processing unit 120 generates data on the OCV of the battery cell E2 (OCV data Dc) based on the acquired measurement value D3 and stores the data in the storage unit 130 (step S102). The data processing unit 120 generates the OCV data Dc by, for example, using the measurement value D3, associating the final voltage V of each pause period of the intermittent charging with the integrated charge amount Q up to the final timing of each pause period of the intermittent charging. The OCV data Dc is data that indicates the relationship between the OCV of the battery cell E2 and the integrated charge amount Q.

[0045] The data processing unit 120 generates data on the CCV of the battery cell E2 (CCV data Dd) based on the acquired measurement value D4 and stores the data in the storage unit 130 (step S102). The data processing unit 120 generates the CCV data Dd, for example, by using the measurement value D4 to associate the voltage V at each predetermined timing with the integrated charge amount Q up to the predetermined timing. The CCV data Dd is data that indicates the relationship between the CCV and the integrated charge amount Q of the battery cell E2.

[0046] The data processing unit 120 generates data (resistance data De) on the resistance value R1 of the battery cell E1 based on the OCV data Da and CCV data Db of the battery cell E1, and stores the data in the storage unit 130 (step S103). For example, for each integrated charge amount Q, the data processing unit 120 generates the resistance data De by subtracting the OCV value of the OCV data Da from the CCV value of the CCV data Db and dividing the resulting value (CCV value - OCV value) by the current value at the time the CCV data was acquired. The resistance data De is data indicating the relationship between the resistance value R1 of the battery cell E1 and the integrated charge amount Q. If the OCV data Da and the CCV data Db do not contain values ​​at the same integrated charge amount Q, the data processing unit 120 may appropriately perform data interpolation using an interpolation algorithm such as the B-Spline method.

[0047] The data processing unit 120 generates data (resistance data Df) on the resistance value R2 of the battery cell E2 based on the OCV data Dc and CCV data Dd of the battery cell E2, and stores the data in the storage unit 130 (step S103). For example, for each integrated charge amount Q, the data processing unit 120 generates the resistance data Df by subtracting the OCV value of the OCV data Dc from the CCV value of the CCV data Dd and dividing the resulting value (CCV value - OCV value) by the current value at the time the CCV data was acquired. The resistance data Df is data indicating the relationship between the resistance value R2 of the battery cell E2 and the integrated charge amount Q. If the OCV data Dc and the CCV data Dd do not contain values ​​at the same integrated charge amount Q, the data processing unit 120 may appropriately perform data interpolation using an interpolation algorithm such as the B-Spline method.

[0048] The data processing unit 120 generates capacitance data (capacity data Dg) for the capacitance value C1 of the battery cell E1 based on the OCV data Da and stores the capacitance data Dg in the storage unit 130 (step S104). The data processing unit 120 generates the capacitance data Dg by numerically differentiating the OCV data Da. For example, the data processing unit 120 extracts from the OCV data Da an OCV value at a certain integrated charge amount Qk and an OCV value at an integrated charge amount Qk+ΔQ, calculates the difference between the two extracted values, and divides ΔQ by the obtained value to obtain the capacitance value C1 at the certain integrated charge amount Qk. For example, the data processing unit 120 calculates the capacitance value C1 for each integrated charge amount Q included in the OCV data Da. When calculating the capacitance value C1, the data processing unit 120 may perform data interpolation using an interpolation algorithm such as the B-Spline method, as appropriate.

[0049] The data processing unit 120 generates data (capacity data Dh) on the capacity value C2 of the battery cell E2 based on the OCV data Dc and stores the data in the storage unit 130 (step S104). The data processing unit 120 generates the capacity data Dh by numerically differentiating the OCV data Dc. For example, the data processing unit 120 extracts from the OCV data Dc an OCV value at a certain integrated charge amount Qk and an OCV value at an integrated charge amount Qk+ΔQ, calculates the difference between the two extracted values, and divides ΔQ by the obtained value to obtain the capacity value C2 at the certain integrated charge amount Qk. For example, the data processing unit 120 calculates the capacity value C2 for each integrated charge amount Q included in the OCV data Dc. When calculating the capacity value C2, the data processing unit 120 may perform data interpolation using an interpolation algorithm such as the B-Spline method, as appropriate.

[0050] The data processing unit 120 obtains an OCV value V1 for a certain integrated charge amount Q1 of the battery cell E1 from the OCV data Da (step S105). The data processing unit 120 obtains an OCV value V1 for a certain integrated charge amount Q2 of the battery cell E2 from the OCV data Dc (step S105). The data processing unit 120 obtains a resistance value R1 for a certain integrated charge amount Q1 of the battery cell E1 from the resistance data De (step S105). The data processing unit 120 obtains a resistance value R2 for a certain integrated charge amount Q2 of the battery cell E2 from the resistance data Df (step S105). The data processing unit 120 obtains a capacitance value C1 for a certain integrated charge amount Q1 of the battery cell E1 from the numerical differentiation of the OCV data Da (step S106). The data processing unit 120 obtains a capacity value C2 for a certain integrated charge amount Q2 of the battery cell E2 from the numerical differentiation of the OCV data Dc (step S106).

[0051] The data processing unit 120 determines whether the difference ΔC between the capacity value C1 of the battery cell E1 and the capacity value C2 of the battery cell E1 for a certain integrated charge amount Q1, Q2 is greater than a predetermined threshold (step S107). If the difference ΔC is greater than the predetermined threshold (step S107; Y), the process proceeds to step S108. If the difference ΔC is equal to or less than the predetermined threshold (step S107; N), the process proceeds to step S112.

[0052] When the data processing unit 120 executes steps S105, S106, and S107 for the first time, it sets the initial charge amounts Q1 and Q2 (e.g., Q1=0, Q2=0) as "certain integrated charge amounts Q1 and Q2." When the data processing unit 120 executes steps S105, S106, and S107 for the second or subsequent time, it sets the integrated charge amounts Q1 and Q2 calculated in step S109 or step S113, which will be described later, as "certain integrated charge amounts Q1 and Q2." Note that the data processing unit 120 may set any charge amounts as the initial charge amounts Q1 and Q2.

[0053] In step S108, the data processing unit 120 calculates a current distribution ratio α1 for the integrated charge amount Q1 of the battery cell E1 by substituting the values ​​acquired in steps S105 and S106 (OCV values ​​V1 and V2, resistance values ​​R and R2, and capacitance values ​​C1 and C2 for the integrated charge amounts Q1 and Q2 of the battery cells E1 and E2) into equation (17) (step S108). The data processing unit 120 further calculates a current distribution ratio α2 for the integrated charge amount Q2 of the battery cell E2 by substituting the calculated current distribution ratio α1 into the following equation (21) (step S108). The data processing unit 120 calculates the current values ​​(charging current values ​​I1 and I2) flowing through each of the battery cells E1 and E2 (step S108). The data processing unit 120 calculates the charging current values ​​I1 and I2 flowing through each of the battery cells E1 and E2, for example, using the following equations (22) and (23). In equations (22) and (23), I is the current value under standard charging conditions for the battery module. For example, if two 3 Ah battery cells are connected in parallel and the standard charging conditions are 0.8 C, the current I flowing through the battery module is I = 3 × 2 × 0.8 = 4.8. α2 = 1 - α1 (21) I1 = I × α1 (22) I2 = I × α2 (23)

[0054] The data processing unit 120 calculates increments ΔQ1 and ΔQ2 in the integrated charge amounts Q1 and Q2 of the battery cells E1 and E2 after charging for a time Δt (step S109). The data processing unit 120 calculates the increment ΔQ1 in the integrated charge amount Q1 of the battery cell E1, for example, by substituting the charging current value I1 and the time Δt into the following equation (24). The data processing unit 120 calculates the increment ΔQ2 in the integrated charge amount Q2 of the battery cell E2, for example, by substituting the charging current value I2 and the time Δt into the following equation (25). ΔQ1=I1×Δt (24) ΔQ2=I2×Δt (25)

[0055] The data processing unit 120 calculates the voltage Va of the entire battery module M in which the battery cells E1 and E2 are connected in parallel (step S110). The data processing unit 120 calculates the open circuit voltage Vx of the battery cell E1 at the integrated charge amount Q1 by adding the product of the resistance R1 of the battery cell E1 at the integrated charge amount Q1 and the current I1 to the OCV value V1 of the battery cell E1 at the integrated charge amount Q1. The data processing unit 120 calculates the voltage Vy of the battery cell E2 at the integrated charge amount Q2 by adding the product of the resistance R2 of the battery cell E2 at the integrated charge amount Q2 and the current I2 to the OCV value V2 of the battery cell E2 at the integrated charge amount Q2. The data processing unit 120 estimates the voltage value of the entire battery module M to be, for example, the average value ((Vx+Vy) / 2) of the voltage value Vx of the battery cell E1 and the voltage value Vy of the battery cell E2.

[0056] The data processing unit 120 may calculate the internal resistance of the entire battery module M in which the battery cells E1 and E2 are connected in parallel, as necessary. The data processing unit 120 may calculate the internal resistance of the entire battery module M in which the battery cells E1 and E2 are connected in parallel, for example, by using the following equation (26): R=1 / ((1 / R1)+(1 / R2))...(26)

[0057] The data processing unit 120 determines whether charging of the battery modules M is complete (step S111). If the voltage value of the entire battery modules M is equal to or greater than a predetermined threshold (step S111; Y), the data processing unit 120 determines that charging of the battery modules M is complete and ends the process. If the voltage value of the entire battery modules M is less than the predetermined threshold (step S111; N), the data processing unit 120 determines that charging of the battery modules M is not complete and returns to step S105.

[0058] If the data processing unit 120 determines in step S107 that the difference ΔC is equal to or smaller than the predetermined threshold value (step S107; N), the process proceeds to step S112.

[0059] In step S112, the data processing unit 120 calculates a current distribution ratio α1 for the integrated charge amount Q1 of the battery cell E1 by substituting the numerical values ​​acquired in steps S105 and S106 (OCV values ​​V1 and V2 and resistance values ​​R and R2 for the integrated charge amounts Q1 and Q2 of the battery cells E1 and E2) into equation (10) (step S112). The data processing unit 120 further calculates a current distribution ratio α2 for the integrated charge amount Q2 of the battery cell E2 by substituting the calculated current distribution ratio α1 into equation (21) (step S112).

[0060] The data processing unit 120 calculates increments ΔQ1 and ΔQ2 in the integrated charge amounts Q1 and Q2 of the battery cells E1 and E2 after charging for a time period Δt (step S113). The data processing unit 120 calculates the increment ΔQ1 in the integrated charge amount Q1 of the battery cell E1, for example, by substituting the charging current value I1 and the time period Δt into the following equation (27). The data processing unit 120 calculates the increment ΔQ2 in the integrated charge amount Q2 of the battery cell E2, for example, by substituting the charging current value I2 and the time period Δt into the following equation (28). ΔQ1=I1×Δt (27) ΔQ2=I2×Δt (28)

[0061] The data processing unit 120 calculates the voltage Va of the entire battery module M in which the battery cells E1 and E2 are connected in parallel (step S114). The data processing unit 120 calculates the voltage Vx of the battery cell E1 at the integrated charge amount Q1 by adding a value obtained by multiplying the resistance value R1, the current I, and the current distribution ratio α1 of the battery cell E1 at the integrated charge amount Q1 to the OCV value V1 of the battery cell E1 at the integrated charge amount Q1 (equation (29)). The data processing unit 120 calculates the voltage Vy of the battery cell E2 at the integrated charge amount Q2 by adding a value obtained by multiplying the resistance value R2, the current I, and the current distribution ratio α2 of the battery cell E2 at the integrated charge amount Q2 to the OCV value V2 of the battery cell E2 at the integrated charge amount Q2 (equation (30)). The data processing unit 120 estimates, for example, the average value ((Vx+Vy) / 2) of the voltage value Vx of the battery cell E1 and the voltage value Vy of the battery cell E2 as the voltage Va of the entire battery module M (Equation (31)): Vx=V1+R1×I×α1 (29) Vy=V2+R2×I×α2 (30) Va=(Vx+Vy) / 2 (31)

[0062] The data processing unit 120 may calculate the internal resistance Ra of the entire battery module M in which the battery cells E1 and E2 are connected in parallel, as necessary. The data processing unit 120 may calculate the internal resistance Ra of the entire battery module M in which the battery cells E1 and E2 are connected in parallel, for example, by using the following equation (32): Ra=1 / ((1 / R1)+(1 / R2))...(32)

[0063] The data processing unit 120 determines whether charging of the battery module M is complete (step S115). If the voltage value Va of the entire battery module M is equal to or greater than a predetermined threshold (step S115; Y), the data processing unit 120 determines that charging of the battery module M is complete and ends the process. If the voltage value Va of the entire battery module M is less than the predetermined threshold (step S115; N), the data processing unit 120 determines that charging of the battery module M is not complete and returns to step S105.

[0064] [Example] A new (unused) cell was prepared as battery cell E1. The measurement values ​​(OCV data Da and resistance data De) obtained for this battery cell E1 are shown in Figure 8. A battery cell of the same type as battery cell E1 was prepared as battery cell E2, which was stored in a fully charged state at high temperature (90°C for 25 days) and allowed to deteriorate. The measurement values ​​(OCV data Dc and resistance data Df) obtained for this battery cell E2 are shown in Figure 9.

[0065] Furthermore, in the charging current value estimation system according to this embodiment, simulation results (current values ​​and voltage values) of each battery cell E1, E2 obtained using the data (OCV data Da, Dc and resistance data De, Df) shown in Figures 8 and 9 are shown in Figure 10. Also, actual measured current values ​​and voltage values ​​in a battery module (two-parallel module) in which battery cells E1, E2 having the characteristics (OCV data Da, Dc and resistance data De, Df) shown in Figures 8 and 9 are connected in parallel are shown in Figure 11.

[0066] Furthermore, in the charging current value estimation system according to the present embodiment, simulation results (OCV values, initial resistance values) of each battery cell E1, E2 obtained using the data (OCV data Da, Dc and resistance data De, Df) shown in Figures 8 and 9 are shown in Figure 12. Furthermore, in the charging current value estimation system according to the present embodiment, simulation results (ODD terms, RBD terms) of battery cell E1 obtained using the data (OCV data Da, Dc and resistance data De, Df) shown in Figures 8 and 9 are shown in Figure 13.

[0067] 8 and 9 confirm that the capacities of battery cell E1 and battery cell E2 are different from each other. Also, from FIG. 8, it was confirmed that a step occurs in the OCV of battery cell E1 at the end of charging. Also, from FIG. 8 and 9, it was confirmed that the resistance values ​​(internal resistance values) of battery cell E1 and battery cell E2 fluctuate, rising and falling as the cumulative charge amount increases. Also, from FIG. 8 and 9, it was confirmed that the resistance value (internal resistance value) of battery cell E2 tends to be higher overall than the resistance value (internal resistance value) of battery cell E1.

[0068] It was confirmed from Fig. 10 that the current value of battery cell E1 fluctuated, rising and falling, as the charging time increased. That is, as the charging time increased, a curve plotting the current value of battery cell E1 against the charging time had minimum value A, maximum value B, minimum value C, and maximum value D. It was also confirmed from Fig. 10 that the current of battery cell E1 began to decrease toward the end of charging and then monotonically decreased. On the other hand, it was confirmed from Fig. 10 that the current value of battery cell E2 changed in a manner opposite to the change in the current value of battery cell E1. That is, as the charging time increased, it was confirmed that when battery cell E1 was at minimum value A, battery cell E2 was at its maximum value; when battery cell E1 was at maximum value B, battery cell E2 was at its minimum value; when battery cell E1 was at minimum value C, battery cell E2 was at its maximum value; and when battery cell E1 was at maximum value D, battery cell E2 was at its minimum value. It was confirmed that the current value of battery cell E2 tended to be smaller overall than the current value of battery cell E1, but at the end of charging (point E), it was confirmed that the magnitude of the current value of battery cell E2 was reversed to the magnitude of the current value of battery cell E1.

[0069] 10 and 11, it was confirmed that the trends in both figures matched well. However, it was confirmed that the simulation results shown in Fig. 10 (curves plotting current and voltage values ​​against charging time) were generally elongated in the time axis direction compared to the actual measurements shown in Fig. 11 (curves plotting current and voltage values ​​against charging time). This is thought to be due in part to the accumulation of errors in the simulation.

[0070] 12, the OCV of battery cell E2 is elongated overall in the time axis direction compared to the OCV of battery cell E1, and as a result, it was confirmed that there were locations where the OCV of battery cell E2 differed from the OCV of battery cell E1. Also, from FIG. 12, it was confirmed that near the end of charging (point E), a step observed in the OCV of battery cell E1 caused a difference between the OCV of battery cell E2 and the OCV of battery cell E1. Also, from FIG. 12, it was confirmed that the difference in initial resistance between battery cell E1 and battery cell E2 was roughly constant regardless of charging time, but that it changed in a complex manner between the beginning and end of charging time.

[0071] In Figure 13, the sum of the ODD value and the RBD value corresponds to the current distribution ratio of battery cell E1, and the value obtained by multiplying the current distribution ratio of battery cell E1 by the value of the current flowing through the entire two-parallel module is the current value distributed to battery cell E1. From Figure 13, it was confirmed that the timing of the minimum point of the RBD value at the beginning of charging coincides with the timing of the minimum point of the initial resistance value in Figure 12. From this, it is presumed that the cause of the minimum value of the RBD value at the beginning of charging is the balance of the internal resistance of battery cell E1.

[0072] 13, P1 is located near the maximum value of the ODD value and the maximum value of the RBD value, and it was confirmed that the current value distributed to battery cell E1 reached a maximum value at P1. It is estimated that the current value distributed to battery cell E1 reached a maximum value at P1 due to the influence of both ODD and RBD.

[0073] 13, P2 is located near the minimum value of the ODD value and the minimum value of the RBD value, and it was confirmed that the current value distributed to battery cell E1 at P2 was the minimum value. It is presumed that the reason the current value distributed to battery cell E1 at P2 was the large difference between ODD and RBD was the cause.

[0074] 13, P3 is located near the maximum value of the ODD value and the maximum value of the RBD value, and it was confirmed that the current value distributed to battery cell E1 at P3 was the maximum value. It is estimated that the current value distributed to battery cell E1 at P3 was the maximum value due to the influence of both ODD and RBD.

[0075] 13, it was confirmed that the current value distributed to battery cell E1 monotonically decreased as the charging approached the end. At this time, ODD monotonically decreased, but RBD monotonically increased. In other words, the effect of resistance balance was to increase the current distributed to battery cell E1, but the effect of reducing the current due to the OCV difference was greater than the effect of resistance balance, and as a result, it is estimated that the current value distributed to battery cell E1 monotonically decreased.

[0076] [Effects] Next, the effects of the charging current value estimation system according to this embodiment will be described.

[0077] In this embodiment, the charging current value of each battery cell E1, E2 is calculated based on the open circuit voltage data for the integrated charge amount Q1, Q2 of each battery cell E1, E2 and the cell resistance data for the integrated charge amount Q1, Q2 of each battery cell E1, E2. This allows the calculated results to closely match the actual measurement results.

[0078] In this embodiment, the integrated charge amount (charge amount after Δt) of each battery cell E1, E2 after a time Δt has elapsed is calculated based on the charge current value of each battery cell E1, E2 at its initial charge amount. The open-circuit voltage value for the integrated charge amount (charge amount after Δt) of each battery cell E1, E2 is calculated from the open-circuit voltage data. The resistance value for the integrated charge amount (charge amount after Δt) of each battery cell E1, E2 is calculated from the cell resistance data. Furthermore, the capacitance value for the integrated charge amount (charge amount after Δt) of each battery cell E1, E2 is calculated from the capacitance data. Furthermore, the charge current value of each battery cell E1, E2 when the charge amount of each battery cell E1, E2 is the integrated charge amount (charge amount after Δt) is calculated based on the open-circuit voltage value, resistance value, and capacitance value at the initial charge amount and the integrated charge amount (charge amount after Δt). This allows for even more accurate agreement between the calculated results and the measured results.

[0079] In this embodiment, the integrated charge amount (charge amount after Δt), open circuit voltage, resistance, capacitance, and charge current of each battery cell E1, E2 are calculated every time Δt passes, which allows the calculated results to match the actual measurement results with even greater accuracy.

[0080] In this embodiment, the charge current value of each battery cell E1, E2 when the charge amount of each battery cell E1, E2 is the integrated charge amount (charge amount after Δt has elapsed) is calculated based on the open circuit voltage value, resistance value, and capacity value of the initial charge amount and the integrated charge amount (charge amount after Δt has elapsed), and the calculation formula for the charge current value of each battery cell E1, E2 is obtained by regarding each battery cell E1, E2 as an equivalent circuit including a series-connected capacitance Ca and internal resistance R. This makes it possible to more accurately match the calculated result with the actual measurement result.

[0081] 6. Modifications Next, modifications of the charging current value estimation system according to the present embodiment will be described.

[0082] In the above embodiment, the charging current values ​​of the two battery cells E1 and E2 included in the two-parallel module are calculated. However, in the above embodiment, for example, the charging current values ​​of the three battery cells E1, E2, and E3 included in a battery module in which three battery cells E1, E2, and E3 are connected in parallel (a three-parallel module) as shown in FIG. 14 may be calculated.

[0083] In this modification, for example, as shown in Figures 15, 16, and 17, two of the three battery cells E1, E2, and E3 are combined into one larger battery cell Eo1, Eo2, and Eo3, and the three-parallel module is converted into the following three types of two-parallel modules. Then, the charging current value I1 (= α1 × I) of the battery cell E1 is derived using a first two-parallel module, the charging current value I2 (= α2 × I) of the battery cell E2 is derived using a second two-parallel module, and the charging current value I3 (= α3 × I) of the battery cell E3 is derived using a third two-parallel module. - A first two-parallel module in which two battery cells E1 and Eo1 are connected in parallel (Figure 15) - A second two-parallel module in which two battery cells E2 and Eo2 are connected in parallel (Figure 16) - A third two-parallel module in which two battery cells E3 and Eo3 are connected in parallel (Figure 17)

[0084] [Calculation Procedure] Next, the procedure for calculating the charging current values ​​I1, I2, and I3 of the three battery cells E1, E2, and E3 will be described. Fig. 18 shows an example of the procedure for calculating the charging current values ​​I1, I2, and I3 of the three battery cells E1, E2, and E3. Fig. 19 shows an example of the procedure following "D" in Fig. 18.

[0085] First, the data processing unit 120 acquires the measurement values ​​D1, D2, D3, D4, D5, and D6 of the battery cells E1, E2, and E3 from the server device 200 (step S201).

[0086] The measured value D1 is a measured value obtained by the IV measurement circuit 320 by measuring the voltage and current of battery cell E1 in the OCV measurement mode. The measured value D2 is a measured value obtained by the IV measurement circuit 320 by measuring the voltage and current of battery cell E1 in the CCV measurement mode. The measured value D3 is a measured value obtained by the IV measurement circuit 320 by measuring the voltage and current of battery cell E2 in the OCV measurement mode. The measured value D4 is a measured value obtained by the IV measurement circuit 320 by measuring the voltage and current of battery cell E2 in the CCV measurement mode. The measured value D5 is a measured value obtained by the IV measurement circuit 320 by measuring the voltage and current of battery cell E3 in the OCV measurement mode. The measured value D6 is a measured value obtained by the IV measurement circuit 320 by measuring the voltage and current of battery cell E3 in the CCV measurement mode.

[0087] The data processing unit 120 generates data on the OCV of the battery cell E1 (OCV data Da) based on the acquired measurement value D1 and stores the data in the storage unit 130 (step S202). The data processing unit 120 generates the OCV data Da by, for example, using the measurement value D1 to associate the final voltage V of each pause period of the intermittent charging with the integrated charge amount Q up to the final timing of each pause period of the intermittent charging. The OCV data Da is data that indicates the relationship between the OCV of the battery cell E1 and the integrated charge amount Q.

[0088] The data processing unit 120 generates data on the CCV of the battery cell E1 (CCV data Db) based on the acquired measurement value D2 and stores the data in the storage unit 130 (step S202). The data processing unit 120 generates the CCV data Db by, for example, using the measurement value D2 to associate the voltage V at each predetermined timing with the integrated charge amount Q up to the predetermined timing. The CCV data Db is data that indicates the relationship between the CCV and the integrated charge amount Q of the battery cell E1.

[0089] The data processing unit 120 generates data on the OCV of the battery cell E2 (OCV data Dc) based on the acquired measurement value D3 and stores the data in the storage unit 130 (step S202). The data processing unit 120 generates the OCV data Dc by, for example, using the measurement value D3, associating the final voltage V of each pause period of the intermittent charging with the integrated charge amount Q up to the final timing of each pause period of the intermittent charging. The OCV data Dc is data that indicates the relationship between the OCV and the integrated charge amount Q of the battery cell E2.

[0090] The data processing unit 120 generates data on the CCV of the battery cell E2 (CCV data Dd) based on the acquired measurement value D4 and stores the data in the storage unit 130 (step S202). The data processing unit 120 generates the CCV data Dd, for example, by using the measurement value D4 to associate the voltage V at each predetermined timing with the integrated charge amount Q up to the predetermined timing. The CCV data Dd is data that indicates the relationship between the CCV and the integrated charge amount Q of the battery cell E2.

[0091] The data processing unit 120 generates data on the OCV of the battery cell E3 (OCV data Di) based on the acquired measurement value D5 and stores the data in the storage unit 130 (step S202). The data processing unit 120 generates the OCV data Di by, for example, using the measurement value D5, associating the final voltage V of each pause period of the intermittent charging with the integrated charge amount Q up to the final timing of each pause period of the intermittent charging. The OCV data Di is data that indicates the relationship between the OCV and the integrated charge amount Q of the battery cell E3.

[0092] The data processing unit 120 generates data on the CCV of the battery cell E3 (CCV data Dj) based on the acquired measurement value D6 and stores the data in the storage unit 130 (step S202). The data processing unit 120 generates the CCV data Dj, for example, by using the measurement value D6 to associate the voltage V at each predetermined timing with the integrated charge amount Q up to the predetermined timing. The CCV data Dj is data that indicates the relationship between the CCV and the integrated charge amount Q of the battery cell E3.

[0093] The data processing unit 120 generates data (resistance data De) on the resistance value R1 of the battery cell E1 based on the OCV data Da and CCV data Db of the battery cell E1, and stores the data in the storage unit 130 (step S203). For example, for each integrated charge amount Q, the data processing unit 120 generates the resistance data De by subtracting the OCV value of the OCV data Da from the CCV value of the CCV data Db and dividing the resulting value (CCV value - OCV value) by the current value at the time the CCV data was acquired. The resistance data De is data indicating the relationship between the resistance value R1 of the battery cell E1 and the integrated charge amount Q. If the OCV data Da and the CCV data Db do not contain values ​​at the same integrated charge amount Q, the data processing unit 120 may appropriately perform data interpolation using an interpolation algorithm such as the B-Spline method.

[0094] The data processing unit 120 generates data (resistance data Df) on the resistance value R2 of the battery cell E2 based on the OCV data Dc and CCV data Dd of the battery cell E2, and stores the data in the storage unit 130 (step S203). For example, for each integrated charge amount Q, the data processing unit 120 subtracts the OCV value of the OCV data Dc from the CCV value of the CCV data Dd, and divides the resulting value (CCV value - OCV value) by the current value at the time the CCV data was acquired, thereby generating the resistance data Df. The resistance data Df is data indicating the relationship between the resistance value R2 of the battery cell E2 and the integrated charge amount Q. If the OCV data Dc and the CCV data Dd do not contain values ​​at the same integrated charge amount Q, the data processing unit 120 may appropriately perform data interpolation using an interpolation algorithm such as the B-Spline method.

[0095] The data processing unit 120 generates data (resistance data Dk) on the resistance value R3 of the battery cell E3 based on the OCV data Di and CCV data Dj of the battery cell E3, and stores the data in the storage unit 130 (step S203). For example, for each integrated charge amount Q, the data processing unit 120 generates the resistance data Dk by subtracting the OCV value of the OCV data Dj from the CCV value of the CCV data Di and dividing the resulting value (CCV value - OCV value) by the current value at the time the CCV data was acquired. The resistance data Dk is data indicating the relationship between the resistance value R3 of the battery cell E3 and the integrated charge amount Q. If the OCV data Di and the CCV data Dj do not contain values ​​at the same integrated charge amount Q, the data processing unit 120 may appropriately perform data interpolation using an interpolation algorithm such as the B-Spline method.

[0096] The data processing unit 120 generates capacitance data (capacity data Dg) for the capacitance value C1 of the battery cell E1 based on the OCV data Da and stores the capacitance data Dg in the storage unit 130 (step S204). The data processing unit 120 generates the capacitance data Dg by numerically differentiating the OCV data Da. For example, the data processing unit 120 extracts from the OCV data Da an OCV value at a certain integrated charge amount Qk and an OCV value at an integrated charge amount Qk+ΔQ, calculates the difference between the two extracted values, and divides ΔQ by the obtained value to obtain the capacitance value C1 at the certain integrated charge amount Qk. For example, the data processing unit 120 calculates the capacitance value C1 for each integrated charge amount Q included in the OCV data Da. When calculating the capacitance value C1, the data processing unit 120 may perform data interpolation using an interpolation algorithm such as the B-Spline method, as appropriate.

[0097] The data processing unit 120 generates data (capacity data Dh) on the capacity value C2 of the battery cell E2 based on the OCV data Dc and stores the data in the storage unit 130 (step S204). The data processing unit 120 generates the capacity data Dh by numerically differentiating the OCV data Dc. For example, the data processing unit 120 extracts from the OCV data Dc an OCV value at a certain integrated charge amount Qk and an OCV value at an integrated charge amount Qk+ΔQ, calculates the difference between the two extracted values, and divides ΔQ by the obtained value to obtain the capacity value C2 at the certain integrated charge amount Qk. For example, the data processing unit 120 calculates the capacity value C2 for each integrated charge amount Q included in the OCV data Dc. When calculating the capacity value C2, the data processing unit 120 may perform data interpolation using an interpolation algorithm such as the B-Spline method, as appropriate.

[0098] The data processing unit 120 generates data (capacity data Dm) on the capacity value C3 of the battery cell E3 based on the OCV data Di and stores the data in the storage unit 130 (step S204). The data processing unit 120 generates the capacity data Dm by numerically differentiating the OCV data Di. For example, the data processing unit 120 extracts from the OCV data Di an OCV value at a certain integrated charge amount Qk and an OCV value at an integrated charge amount Qk+ΔQ, calculates the difference between the two extracted values, and divides ΔQ by the obtained value to obtain the capacity value C3 at the certain integrated charge amount Qk. For example, the data processing unit 120 calculates the capacity value C3 for each integrated charge amount Q included in the OCV data Di. When calculating the capacity value C3, the data processing unit 120 may perform data interpolation using an interpolation algorithm such as the B-Spline method, as appropriate.

[0099] The data processing unit 120 sets three two-parallel modules (a first two-parallel module ( FIG. 15 ), a second two-parallel module ( FIG. 16 ), and a third two-parallel module ( FIG. 17 )). The data processing unit 120 generates OCV data Dx1 and CCV data Dx2 for the battery cell Eo1 included in the first two-parallel module and stores them in the storage unit 130 (step S205). The data processing unit 120 multiplies the current I flowing through the entire first two-parallel module by the internal resistance Rx of the battery cell Eo1 to calculate the overvoltage ηx (= I × Rx) of the battery cell Eo1, and obtains the OCV data Dx1 of the battery cell Eo1 by subtracting the overvoltage ηx from the CCV data Dx2 of the battery cell Eo1.

[0100] The data processing unit 120 generates OCV data Dy1 and CCV data Dy2 for the battery cell Eo2 included in the second two-parallel module and stores them in the storage unit 130 (step S205). The data processing unit 120 calculates the overvoltage ηy (=I×Ry) of the battery cell Eo2 by multiplying the current I flowing through the entire second two-parallel module by the internal resistance Ry of the battery cell Eo2, and obtains the OCV data Dy1 of the battery cell Eo2 by subtracting the overvoltage ηy from the CCV data Dy2 of the battery cell Eo2.

[0101] The data processing unit 120 generates OCV data Dz1 and CCV data Dz2 for the battery cell Eo3 included in the third two-parallel module and stores them in the storage unit 130 (step S205). The data processing unit 120 calculates the overvoltage ηz (= I × Rz) of the battery cell Eo3 by multiplying the current I flowing through the entire third two-parallel module by the internal resistance Rz of the battery cell Eo3, and obtains the OCV data Dz1 for the battery cell Eo3 by subtracting the overvoltage ηz from the CCV data Dz2 for the battery cell Eo3.

[0102] The data processing unit 120 generates resistance data Dn for battery cell Eo1 based on the OCV data Dx1 and CCV data Dx2 for battery cell Eo1 and stores the data in the storage unit 130 (step S206). The data processing unit 120 generates resistance data Dp for battery cell Eo2 based on the OCV data Dy1 and CCV data Dy2 for battery cell Eo2 and stores the data in the storage unit 130 (step S206). The data processing unit 120 generates resistance data Dq for battery cell Eo3 based on the OCV data Dz1 and CCV data Dz2 for battery cell Eo3 and stores the data in the storage unit 130 (step S206).

[0103] The data processing unit 120 generates capacity data Dr for battery cell Eo1 based on the OCV data Dx1 for battery cell Eo1 and stores the data in the storage unit 130 (step S207). The data processing unit 120 acquires the capacity data Dr by numerically differentiating the OCV data Dx1. The data processing unit 120 generates capacity data Ds for battery cell Eo2 based on the OCV data Dy1 for battery cell Eo2 and stores the capacity data Ds in the storage unit 130 (step S207). The data processing unit 120 acquires the capacity data Ds by numerically differentiating the OCV data Dy1. The data processing unit 120 generates capacity data Dt for battery cell Eo3 based on the OCV data Dz1 for battery cell Eo3 and stores the capacity data Dt in the storage unit 130 (step S207). The data processing unit 120 acquires the capacity data Dt by numerically differentiating the OCV data Dz1.

[0104] The data processing unit 120 executes the above-described steps S105 to S108 and S112 for each of the two-parallel modules (the first two-parallel module (FIG. 15), the second two-parallel module (FIG. 16), and the third two-parallel module (FIG. 17)), and calculates the current distribution ratios α1, α2, α3 and the charging current values ​​I1, I2, I3 of the three battery cells E1, E2, E3 (step S208).

[0105] The data processing unit 120 calculates increments ΔQ1, ΔQ2, and ΔQ3 of the integrated charge amounts Q1, Q2, and Q3 of the battery cells E1, E2, and E3 after charging for a time period Δt (step S209). The data processing unit 120 calculates the increment ΔQ1 of the integrated charge amount Q1 of the battery cell E1, for example, by substituting the charging current value I1 and the time period Δt into equation (24). The data processing unit 120 calculates the increment ΔQ2 of the integrated charge amount Q2 of the battery cell E2, for example, by substituting the charging current value I2 and the time period Δt into equation (25). The data processing unit 120 calculates the increment ΔQ3 of the integrated charge amount Q3 of the battery cell E3, for example, by substituting the charging current value I3 and the time period Δt into equation (33) below. ΔQ3=I3×Δt (33)

[0106] The data processing unit 120 calculates the voltage Va of the entire battery module M in which the battery cells E1, E2, and E3 are connected in parallel (step S210). The data processing unit 120 calculates the voltage Vx of the battery cell E1 at the integrated charge amount Q1 by adding a value obtained by multiplying the resistance R1, current I1, and current distribution ratio α1 of the battery cell E1 at the integrated charge amount Q1 to the OCV V1 of the battery cell E1 at the integrated charge amount Q1 (equation (29)). The data processing unit 120 calculates the voltage Vy of the battery cell E2 at the integrated charge amount Q2 by adding a value obtained by multiplying the resistance R2, current I, and current distribution ratio α2 of the battery cell E2 at the integrated charge amount Q2 to the OCV V2 of the battery cell E2 at the integrated charge amount Q2 (equation (30)). For example, the data processing unit 120 calculates the voltage value Vz of the battery cell E3 at the integrated charge amount Q3 by adding the product of the resistance value R3 of the battery cell E3 at the integrated charge amount Q3, the current I, and the current distribution ratio α3 to the OCV value V3 of the battery cell E3 at the integrated charge amount Q3 (Equation (34)). The data processing unit 120 estimates the voltage Va of the entire battery module M as the average value ((Vx+Vy+Vz) / 3) of the voltage value Vx of the battery cell E1, the voltage value Vy of the battery cell E2, and the voltage value Vz of the battery cell E3 (Equation (35)). Vz=V3+R3×I×α3 (34) Va=(Vx+Vy+Vz) / 3 (35)

[0107] The data processing unit 120 determines whether charging of the battery module M is complete (step S211). If the voltage value Va of the entire battery module M is equal to or greater than a predetermined threshold (step S211; Y), the data processing unit 120 determines that charging of the battery module M is complete and ends the process. If the voltage value Va of the entire battery module M is less than the predetermined threshold (step S211; N), the data processing unit 120 determines that charging of the battery module M is not complete and returns to step S208.

[0108] In this modification, charging current values ​​I1, I2, and I3 of three battery cells E1, E2, and E3 included in a battery module (three-parallel module) in which three battery cells E1, E2, and E3 are connected in parallel are calculated. This makes it possible to achieve good agreement between the calculation results and the actual measurement results. Note that by applying the method described in this modification to n battery cells E1, E2, ..., En, it is possible to achieve good agreement between the calculation results and the actual measurement results for the n battery cells E1, E2, ..., En.

[0109] 7. Second Embodiment A charging current value estimation system according to a second embodiment of the present technology will be described. Fig. 20 illustrates an example of functional blocks of the charging current value estimation system according to the second embodiment of the present technology. The charging current value estimation system includes, for example, a power supply device 500 as shown in Fig. 20. The power supply device 500 is a device that charges and discharges a battery cell E1 or a battery cell E2, and is a standalone device that does not have a function of communicating with an external device.

[0110] 20, the power supply device 500 includes a charge / discharge circuit 310, an IV measurement circuit 320, a data processing unit 120, a storage unit 150, and a display unit 140. The power supply device 500 (charge / discharge circuit 310) is connected to a battery cell E1 or a battery cell E2.

[0111] The storage unit 150 is configured with a non-volatile memory such as a flash memory, etc. The storage unit 150 stores the measurement values ​​D1, D2, D3, and D4 acquired by the IV measurement circuit 320 and various data generated by the data processing unit 120.

[0112] In this embodiment, the power supply device 500 is provided with the data processing unit 120 together with the charge / discharge circuit 310 and the IV measurement circuit 320. As a result, simply by providing the power supply device 500, the charging current value of each of the battery cells E1 and E2 can be calculated.

[0113] In this embodiment, the data processing unit 120 may be configured to calculate charging current values ​​of three battery cells E1, E2, E3 included in a battery module in which three battery cells E1, E2, E3 are connected in parallel (a three-parallel module) by using the method described in the modified example of the first embodiment. Also, in this embodiment, the data processing unit 120 may be configured to calculate charging current values ​​of n battery cells E1, E2, ..., En included in a battery module in which n battery cells E1, E2, ..., En are connected in parallel (an n-parallel module) by applying the method described in the modified example of the first embodiment.

[0114] Note that the present technology may also be configured as follows: <1> A charging current value estimation system capable of estimating a charging current value of each of n (n is a natural number of 2 or more) secondary battery cells when the cells are connected in parallel, the charging current value estimation system comprising: a memory that stores open circuit voltage data for an integrated charge amount of each of the secondary battery cells and cell resistance data for the integrated charge amount of each of the secondary battery cells, and a processing circuit that calculates a charging current value of each of the secondary battery cells based on the open circuit voltage data and the cell resistance data acquired from the memory, wherein the processing circuit is capable of: deriving an open circuit voltage value for an initial charge amount of each of the secondary battery cells from the open circuit voltage data, and deriving a resistance value for an initial charge amount of each of the secondary battery cells from the cell resistance data, and calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the initial charge amount, based on the open circuit voltage value and the resistance value. <2> The memory further stores capacitance data for an integrated charge amount of each of the secondary battery cells, and the processing circuit is capable of executing the following: deriving a charge amount after Δt, which is the charge amount of each of the secondary battery cells after a time Δt has elapsed, based on a charge current value at the initial charge amount of each of the secondary battery cells; deriving an open circuit voltage value for the charge amount after Δt of each of the secondary battery cells from the open circuit voltage data, deriving a resistance value for the charge amount after Δt of each of the secondary battery cells from the cell resistance data, and further deriving a capacitance value for the charge amount after Δt of each of the secondary battery cells from the capacitance data; and calculating a charge current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the charge amount after Δt, based on the open circuit voltage value, the resistance value, and the capacitance value at the initial charge amount and the charge amount after Δt.<3> The charging current value estimation system according to <2>, wherein the processing circuit is capable of calculating the amount of charge after Δt has elapsed, the open-circuit voltage value, the resistance value, the capacitance value, and the charging current value of each of the secondary battery cells each time the time Δt has elapsed. <4> The charging current value estimation system according to <2> or <3>, further comprising: a power supply circuit capable of applying a current and a voltage to each of the secondary battery cells without connecting the secondary battery cells in parallel; and a measurement circuit that measures the open-circuit voltage and the voltage at a constant current of each of the secondary battery cells by controlling the power supply circuit, wherein the processing circuit is capable of generating the open-circuit voltage data, the cell resistance data, and the capacitance data based on the measurement results of the measurement circuit, and storing them in the memory. <5> The charging current value estimation system according to any one of <2> to <4>, wherein the processing circuit is capable of calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the charge amount after Δt has elapsed, based on a calculation formula for a charging current value of each of the secondary battery cells, which is obtained by regarding each of the secondary battery cells as an equivalent circuit including a capacity and an internal resistance connected in series, and the open circuit voltage value, the resistance value, and the capacitance value at the initial charge amount and the charge amount after Δt has elapsed. <6> A charging current value estimation method capable of estimating a charging current value of each of n secondary battery cells (where n is a natural number of 2 or more) when the secondary battery cells are connected in parallel to each other, the charging current value estimation method comprising: acquiring open circuit voltage data for an integrated charge amount of each of the secondary battery cells and cell resistance data for the integrated charge amount of each of the secondary battery cells; deriving an open circuit voltage value for an initial charge amount of each of the secondary battery cells from the acquired open circuit voltage data, and deriving a resistance value for an initial charge amount of each of the secondary battery cells from the acquired cell resistance data; and calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the initial charge amount, based on the open circuit voltage value and the resistance value.<7> The charging current value estimation method according to <6>, further comprising: acquiring capacitance data for an integrated charge amount of each of the secondary battery cells; deriving a charge amount after Δt, which is the charge amount of each of the secondary battery cells after a time Δt has elapsed, based on a charge current value at the initial charge amount of each of the secondary battery cells; deriving an open circuit voltage value for the charge amount after Δt of each of the secondary battery cells from the open circuit voltage data, deriving a resistance value for the charge amount after Δt of each of the secondary battery cells from the cell resistance data, and further deriving a capacitance value for the charge amount after Δt of each of the secondary battery cells from the capacitance data; and calculating a charge current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the charge amount after Δt, based on the open circuit voltage value, the resistance value, and the capacitance value at the initial charge amount and the charge amount after Δt. <8> The charging current value estimation method according to <7>, further comprising: calculating the charge amount after Δt has elapsed, the open circuit voltage value, the resistance value, the capacitance value, and the charging current value of each of the secondary battery cells each time the time Δt has elapsed. <9> The charging current value estimation method according to <7> or <8>, further comprising: measuring the open circuit voltage and the voltage at a constant current of each of the secondary battery cells by applying a current and a voltage to each of the secondary battery cells without connecting the secondary battery cells in parallel; and generating the open circuit voltage data, the cell resistance data, and the capacitance data based on the measurement results. <10> The charging current value estimation method according to any one of <7> to <9>, further comprising: calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the charge amount after Δt has elapsed, based on a calculation formula for a charging current value of each of the secondary battery cells, obtained by regarding each of the secondary battery cells as an equivalent circuit including a capacity and an internal resistance connected in series, and the open circuit voltage value, the resistance value, and the capacitance value at the initial charge amount and the charge amount after Δt has elapsed.

Claims

1. A charging current value estimation system capable of estimating a charging current value of each of n (n is a natural number of 2 or greater) secondary battery cells when the cells are connected in parallel, comprising: a memory that stores open circuit voltage data for an integrated charge amount of each of the secondary battery cells and cell resistance data for the integrated charge amount of each of the secondary battery cells; and a processing circuit that is capable of calculating a charging current value of each of the secondary battery cells based on the open circuit voltage data and the cell resistance data acquired from the memory, wherein the processing circuit is capable of: deriving an open circuit voltage value for an initial charge amount of each of the secondary battery cells from the open circuit voltage data, and deriving a resistance value for an initial charge amount of each of the secondary battery cells from the cell resistance data; and calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the initial charge amount based on the open circuit voltage value and the resistance value.

2. The charging current value estimation system according to claim 1, wherein the memory further stores capacitance data for an integrated charge amount of each of the secondary battery cells, and the processing circuit is capable of executing the following: deriving a charge amount after Δt, which is the charge amount of each of the secondary battery cells after a time Δt has elapsed, based on a charging current value of each of the secondary battery cells at the initial charge amount; deriving an open circuit voltage value for the charge amount after Δt of each of the secondary battery cells from the open circuit voltage data, deriving a resistance value for the charge amount after Δt of each of the secondary battery cells from the cell resistance data, and further deriving a capacitance value for the charge amount after Δt of each of the secondary battery cells from the capacitance data; and calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the charge amount after Δt, based on the open circuit voltage value, the resistance value, and the capacitance value at the initial charge amount and the charge amount after Δt.

3. The charging current value estimation system according to claim 2, wherein the processing circuit is capable of calculating the charge amount, the open circuit voltage value, the resistance value, the capacitance value and the charging current value of each of the secondary battery cells after the time Δt has elapsed.

4. A charging current value estimation system as described in claim 2 or 3, further comprising: a power supply circuit capable of applying a current and a voltage to each of the secondary battery cells without connecting the secondary battery cells in parallel; and a measurement circuit that measures an open circuit voltage and a constant current voltage of each of the secondary battery cells by controlling the power supply circuit, wherein the processing circuit is capable of generating the open circuit voltage data, the cell resistance data and the capacitance data based on the measurement results of the measurement circuit and storing them in the memory.

5. The charging current value estimation system according to any one of claims 2 to 4, wherein the processing circuit is capable of calculating the charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the charge amount after Δt has elapsed, based on a calculation formula for the charging current value of each of the secondary battery cells, obtained by regarding each of the secondary battery cells as an equivalent circuit including a capacity and internal resistance connected in series, and on the open circuit voltage value, the resistance value, and the capacitance value at the initial charge amount and the charge amount after Δt has elapsed.

6. A charging current value estimation method capable of estimating a charging current value of each of n (n is a natural number of 2 or greater) secondary battery cells when the cells are connected in parallel, comprising: acquiring open circuit voltage data for an integrated charge amount of each of the secondary battery cells and cell resistance data for the integrated charge amount of each of the secondary battery cells; deriving an open circuit voltage value for an initial charge amount of each of the secondary battery cells from the acquired open circuit voltage data, and deriving a resistance value for an initial charge amount of each of the secondary battery cells from the acquired cell resistance data; and calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the initial charge amount based on the open circuit voltage value and the resistance value.

7. The charging current value estimation method according to claim 6, further comprising: acquiring capacitance data for an integrated charge amount of each of the secondary battery cells; deriving a charge amount after Δt, which is the charge amount of each of the secondary battery cells after a time Δt has elapsed, based on a charging current value of each of the secondary battery cells at the initial charge amount; deriving an open circuit voltage value for the charge amount after Δt of each of the secondary battery cells from the open circuit voltage data, deriving a resistance value for the charge amount after Δt of each of the secondary battery cells from the cell resistance data, and further deriving a capacitance value for the charge amount after Δt of each of the secondary battery cells from the capacitance data; and calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the charge amount after Δt, based on the open circuit voltage value, the resistance value, and the capacitance value at the initial charge amount and the charge amount after Δt.

8. The charging current value estimation method according to claim 7, further comprising: calculating the charge amount, the open circuit voltage value, the resistance value, the capacitance value and the charging current value of each of the secondary battery cells after the time Δt has elapsed each time the time Δt has elapsed.

9. The charging current value estimation method according to claim 7 or 8, further comprising: measuring an open circuit voltage and a constant current voltage of each of the secondary battery cells by applying a current and a voltage to each of the secondary battery cells without connecting the secondary battery cells in parallel; and generating the open circuit voltage data, the cell resistance data, and the capacitance data based on the measurement results.

10. The method for estimating a charging current value according to any one of claims 7 to 9, further comprising: calculating a charging current value of each of the secondary battery cells when the charge amount of each of the secondary battery cells is the charge amount after Δt has elapsed, based on a calculation formula for the charging current value of each of the secondary battery cells, obtained by regarding each of the secondary battery cells as an equivalent circuit including a capacity and an internal resistance connected in series, and on the open circuit voltage value, the resistance value, and the capacitance value at the initial charge amount and the charge amount after Δt has elapsed.

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