Battery system

Abstract

To estimate a battery capacity (fully charged capacity) accurately.SOLUTION: A fully charged capacity X is calculated by adding to a reference capacity C2 in which ΔVBSav which is an amount of change of an average value VBSav of a second correction voltage VBS is a maximum value, a current integrated quantity ΣQa from detection of the maximum value to full charge (or, current integrated quantity ΣQa from the full charge to detection of the maximum value). A first correction voltage VB1 is calculated by subtracting a density over-voltage dV_ce from a voltage VB of a cell (S21), and from a relation between the first correction voltage VB1 and charge / discharge current in a prescribed period, a second correction voltage VBS which is first correction voltage when a charge / discharge current is zero is calculated by extrapolation or interpolation (S22). An average value VBSav of the second correction voltage VBS is calculated (S23), and an amount of change ΔVBSav of the average value ΔVBSav is acquired. The maximum value of the amount of change ΔVBSav is detected and the fully charged capacity X is calculated.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a battery system. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2014-167457 (Patent Document 1) describes detecting a singular point, which is a maximum value of the amount of voltage change of a secondary battery during charging and discharging, and estimating the capacity of the secondary battery based on this singular point. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-167457 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the voltage across the secondary battery included in the battery pack is detected using a voltage measurement circuit. Polarization occurs when the secondary battery is charged or discharged. Therefore, the voltage detected by the voltage measurement circuit includes a deviation due to polarization. In particular, polarization caused by concentration overvoltage occurs with a delay relative to the increase or decrease in charge or discharge current, which may reduce the accuracy of the singular point determined using the battery voltage detected by the voltage measurement circuit. This raises concerns about a deterioration in the accuracy of estimating the capacity of the secondary battery.

[0005] An object of the present disclosure is to accurately estimate the capacity (full charge capacity) of a battery. [Means for solving the problem]

[0006] 1) A charging system according to the present disclosure is a battery system including a battery, a voltage sensor for detecting the battery voltage, a current sensor for detecting the battery's charge / discharge current, and a control device. The control device includes a current integrator for calculating a discharge current integrated value, which is an integrated value of the battery's discharge current, a concentration overvoltage calculator for acquiring the battery's concentration overvoltage, a first correction voltage calculator for calculating a first correction voltage by subtracting the concentration overvoltage from the battery voltage detected by the voltage sensor, and a maximum value detector for detecting a maximum value of the voltage change amount based on the first correction voltage. The control device estimates the full charge capacity of the battery based on a first current integrated value, which is an integrated value of the discharge current from when the battery is fully charged until the maximum value is detected.

[0007] According to this configuration, the maximum value detection unit detects the maximum value of the voltage change amount based on the first correction voltage. The full charge capacity of the battery is then estimated based on the first integrated current value, which is the integrated value of the discharge current from when the battery is fully charged until the maximum value is detected. The first correction voltage is the voltage obtained by subtracting the concentration overpotential from the battery voltage detected by the voltage sensor, so the maximum value is detected while eliminating the influence of polarization due to salt concentration overpotential, and the full charge capacity can be accurately estimated.

[0008] 2) A charging system according to the present disclosure is a battery system including a battery, a voltage sensor for detecting the battery voltage, a current sensor for detecting the battery's charge / discharge current, and a control device. The control device includes a current integration unit for calculating an integrated charging current value, which is an integrated value of the battery's charging current, a concentration overvoltage calculation unit for acquiring the battery's concentration overvoltage, a first correction voltage calculation unit for calculating a first correction voltage by subtracting the concentration overvoltage from the battery voltage detected by the voltage sensor, and a maximum value detection unit for detecting a maximum value of voltage change based on the first correction voltage. The control device estimates the full charge capacity of the battery based on a second integrated current value, which is an integrated charging current value from when the maximum value is detected until the battery is fully charged.

[0009] According to this configuration, the maximum value detection unit detects the maximum value of the voltage change amount based on the first correction voltage. The full charge capacity of the battery is then estimated based on the second integrated current value, which is the integrated value of the charging current from when the maximum value is detected until the battery is fully charged. The first correction voltage is the voltage obtained by subtracting the concentration overpotential from the battery voltage detected by the voltage sensor, so the maximum value is detected while eliminating the influence of polarization due to salt concentration overpotential, and the full charge capacity can be accurately estimated.

[0010] In the above 1 or 2, the control device may further include a second correction voltage estimation unit that estimates a second correction voltage, which is a value of the first correction voltage when the charging / discharging current is zero, based on the first correction voltage for a predetermined period. The maximum value detection unit detects the maximum value based on the second correction voltage.

[0011] According to this configuration, the second correction voltage estimation unit estimates the second correction voltage, which is the value of the first correction voltage when the charge / discharge current is zero, based on the first correction voltage over a predetermined period. Because the second correction voltage is the voltage when the battery's charge / discharge current is zero, its value excludes the effects of reaction resistance of the positive and negative electrodes, electrolyte resistance, and polarization due to overvoltage in the resistance system, such as IR loss. The maximum value detection unit detects the maximum value based on the second correction voltage. This allows the detection of the maximum value to take into account polarization in the resistance system, further enabling the full charge capacity to be estimated with high accuracy.

[0012] Preferably, the full charge capacity may be calculated based on a reference capacity, which is the capacity of the battery at its maximum value.

[0013] The maximum value occurs when the remaining capacity of the battery remains approximately the same, regardless of the state of deterioration of the battery. The remaining capacity when the maximum value occurs is set as the reference capacity. By adding the first or second integrated current value to this reference capacity, the full charge capacity can be accurately estimated.

[0014] Preferably, the battery has a characteristic in which there are a plurality of maximum values, and the reference capacity may be the capacity of the battery at a maximum value where the voltage of the battery is on the high-voltage side.

[0015] The longer the integration time (the larger the integration amount), the more the current sensor detection errors and other factors are integrated, deteriorating the accuracy of the integrated value of the charge / discharge current.With this configuration, the capacity at the maximum value where the battery voltage is on the high-voltage side is set as the reference capacity, so the integration time (integration amount) of the first current integrated value or the second current integrated value can be made relatively short, improving the accuracy of estimating the full charge capacity. [Effects of the Invention]

[0016] According to the present disclosure, the capacity (fully charged capacity) of a battery can be accurately estimated. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing the overall configuration of an electric vehicle equipped with a battery system according to an embodiment of the present invention; [Figure 2] 1A and 1B are diagrams showing the relationship between OCV and remaining capacity in a single cell (LFP battery) according to the present embodiment. [Figure 3] 4 is a flowchart showing an example of a full charge capacity estimation process during charging executed by the ECU. [Figure 4] 10 is a flowchart showing an example of a routine for calculating a change amount ΔVBSav executed by the ECU. [Figure 5] 10 is a flowchart of a charge / discharge current integration routine executed by the ECU. [Figure 6] 4 is a flowchart showing an example of a discharge-time full charge capacity estimation process executed by the ECU. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0019] 1 is an overall configuration diagram of an electric vehicle 1 equipped with a battery system S according to this embodiment. In this embodiment, the electric vehicle 1 is, for example, an electric car. The electric vehicle 1 includes a motor generator (MG) 10, which is a rotating electric machine, a power transmission gear 20, drive wheels 30, a power control unit (PCU) 40, a system main relay (SMR) 50, a battery 100, a monitoring unit 200, and an electronic control unit (ECU) 300, which is an example of a control device.

[0020] The MG 10 is, for example, an interior permanent magnet synchronous motor (IPM motor) that functions as both an electric motor and a generator. The output torque of the MG 10 is transmitted to the drive wheels 30 via a power transmission gear 20 that includes a reducer, a differential gear, and the like.

[0021] When braking the electric vehicle 1, the MG 10 is driven by the drive wheels 30 and operates as a generator. As a result, the MG 10 also functions as a braking device that performs regenerative braking to convert the kinetic energy of the electric vehicle 1 into electric power. The regenerative power generated by the regenerative braking force of the MG 10 is stored in the battery 100.

[0022] PCU 40 is a power conversion device that converts power bidirectionally between MG 10 and battery 100. PCU 40 includes an inverter and a converter that operate based on a control signal from ECU 300, for example.

[0023] The converter boosts the voltage supplied from the battery 100 and supplies it to the inverter when the battery 100 is discharging. The inverter converts the DC power supplied from the converter into AC power to drive the MG 10.

[0024] The inverter converts AC power generated by MG10 into DC power and supplies it to the converter when charging the battery 100. The converter steps down the voltage supplied from the inverter to a voltage suitable for charging the battery 100 and supplies it to the battery 100.

[0025] The SMR 50 is electrically connected to a power line connecting the battery 100 and the PCU 40. When the SMR 50 is closed (ON) in response to a control signal from the ECU 300, power can be exchanged between the battery 100 and the PCU 40. On the other hand, when the SMR 50 is opened (OFF) in response to a control signal from the ECU 300, the electrical connection between the battery 100 and the PCU 40 is cut off.

[0026] The battery 100 stores power for driving the MG 10. The battery 100 is a rechargeable DC power supply (secondary battery) and is configured by stacking a plurality of electric cells (battery cells) 100a and electrically connecting them in series, for example. The battery 100 and the electric cells 100a correspond to the "battery" in the present disclosure. The electric cells 100a may be configured as, for example, lithium ion batteries. In this embodiment, lithium iron phosphate ion batteries (LFP batteries) that use lithium iron phosphate as the positive electrode active material are used as the electric cells 100a.

[0027] The monitoring unit 200 includes a voltage sensor 210, a current sensor 220, and a temperature sensor 230. The voltage sensor 210 detects the voltage VB of the cell 100a (the voltage VB between each terminal of the cell 100a). The current sensor 220 detects the current IB input to and output from the battery 100 (cell 100a). The current IB may be positive (+) when charging the battery 100 and negative (-) when discharging from the battery 100. The temperature sensor 230 detects the temperature TB of each cell 100a. Each detection unit outputs its detection result to the ECU 300.

[0028] The electric vehicle 1 is equipped with a DC inlet 60, and the battery 100 can be rapidly charged from an external direct current (DC) power source, which is a charging facility. The DC inlet 60 is configured to be connectable to a connector 420 provided at the tip of a charging cable 410 of the external DC power source (charging facility) 400. The charging relay 70 is electrically connected to a power line connecting the DC inlet 60 and the battery 100. The charging relay 70 switches between supplying and cutting off power between the DC inlet 60 and the battery 100 in response to a control signal from the ECU 300. When the charging relay 70 is closed, external charging (rapid charging) of the battery 100 is performed.

[0029] The electric vehicle 1 is equipped with an AC inlet 80, and the battery 100 can be normally charged from an external alternating current (AC) power source, which is a charging facility. The AC inlet 80 is configured to allow connection to a connector 520 provided at the tip of a charging cable 510 of an external AC power source (charging facility) 500. An on-board charger 130 is provided in the power line between the AC inlet 80 and the battery 100, and converts AC power supplied from the external AC power source into DC power and also converts it into a voltage that can charge the battery 100. A charging relay 90 is electrically connected to the power line connecting the on-board charger 130 and the battery 100. The charging relay 90 switches between supplying and cutting off power between the on-board charger 130 and the battery 100 in response to a control signal from the ECU 300. When the charging relay 90 is closed, external charging (normal) of the battery 100 is performed.

[0030] The ECU 300 includes a CPU (Central Processing Unit) 301 and a memory (including, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory)) 302. The ECU 300 controls each device so that the electric vehicle 1 is in a desired state based on signals received from the monitoring unit 200, signals from various sensors (not shown) (for example, an accelerator position signal, a vehicle speed signal, etc.), and information such as maps and programs stored in the memory 302. The ECU 300 also executes a process for estimating a full charge capacity during charging, etc. The battery system S is made up of the battery 100 (cell 100a), the monitoring unit 200, the ECU 300, etc.

[0031] FIG. 2 is a diagram showing the relationship between OCV (Open Circuit Voltage) and remaining capacity in a cell 100a (LFP battery) according to the present embodiment. In FIG. 2(A), the vertical axis represents the OCV [V] of the cell 100a, and the horizontal axis represents the remaining capacity (charge capacity) [Ah] of the cell 100a. As shown in FIG. 2(A), the relationship between OCV and remaining capacity (hereinafter, this relationship will also be referred to as the OCV curve) has a wide region (a voltage plateau region) where the OCV curve changes very little. If the point where the OCV curve increases from the voltage plateau region and then returns to the voltage plateau region is referred to as a "step," then two steps P1 and P2 exist in the cell 100a according to the present embodiment.

[0032] The first step P1 (OCV is on the low-voltage side) occurs when the SOC (State of Charge) of the new cell 100a is approximately 30%. The second step P2 (OCV is on the high-voltage side) occurs when the SOC of the new cell 100a is approximately 60%. As shown by the dashed lines in Figure 2(A), the positions of these steps do not change even if the cell 100a deteriorates and the full charge capacity of the cell 100a decreases (if the capacity maintenance rate of the cell 100a decreases). Even if the cell 100a deteriorates, the remaining capacity value at which the steps appear does not change.

[0033] FIG. 2B shows the relationship between the voltage change ΔVB of the voltage VB and the remaining capacity when the battery 100 is charged or discharged at a constant current. The voltage change ΔVB is the change in voltage VB with respect to the remaining capacity (charge capacity) [V / Ah] or the change in voltage VB with respect to time (charge time or discharge time) [V / s]. As shown in FIG. 2B, the voltage change ΔVB reaches a maximum value M1 at the remaining capacity corresponding to a step P1, and reaches a maximum value M2 at the remaining capacity corresponding to a step P2. Therefore, the remaining capacity at which the voltage change ΔVB reaches the maximum value M1 is stored as a reference capacity C1, and the charging current is integrated from when the voltage change ΔVB reaches the maximum value M1 until the battery 100 is fully charged. The integrated value is then added to the reference capacity C1 to estimate the full charge capacity of the battery 100 (single cell 100a). Alternatively, the discharge current from when the battery 100 (single cell 100a) is fully charged until the voltage change ΔVB reaches the maximum value M1 can be integrated, and this integrated value can be added to the reference capacity C1 to estimate the full charge capacity of the battery 100 (single cell 100a).

[0034] Furthermore, the remaining capacity at which the voltage change amount ΔVB reaches the maximum value M2 is stored as the reference capacity C2, and the charging current is integrated from when the voltage change amount ΔVB reaches the maximum value M2 until the battery 100 is fully charged. This integrated value is then added to the reference capacity C2, thereby estimating the full charge capacity of the battery 100 (cell 100a). Alternatively, the full charge capacity of the battery 100 (cell 100a) can be estimated by integrating the discharging current from when the battery 100 (cell 100a) is fully charged until when the voltage change amount ΔVB reaches the maximum value M2. This integrated value is then added to the reference capacity C2.

[0035] The accuracy of the integrated value of the charge / discharge current deteriorates as the integration time increases (the integration amount increases) because detection errors of the current sensor 220 are also integrated. In this embodiment, to improve the accuracy of estimating the full charge capacity, the maximum value M2 corresponding to the step P2 of the second step (OCV on the high-voltage side) is detected, and the charge current from the maximum value M2 until full charge is achieved is integrated, and / or the discharge current from full charge until the maximum value M2 is detected is integrated to estimate the full charge capacity.

[0036] Polarization occurs during charging and discharging of the battery 100 (cell 100a). Therefore, during charging and discharging, the voltage VB detected by the voltage sensor 210 decreases by an amount corresponding to the overvoltage. Polarization includes overvoltages due to resistance systems, such as the reaction resistance of the positive and negative electrodes of the cell 100a, electrolyte resistance, and IR loss, as well as overvoltages due to electromotive forces, such as positive electrode diffusion, negative electrode diffusion, and concentration overvoltage (salt concentration overvoltage). In particular, polarization due to concentration overvoltage occurs with a delay relative to the increase or decrease in charge / discharge current. Therefore, when calculating the voltage change ΔVB using the voltage VB to determine the maximum value M2, there is a concern that the detection accuracy may decrease. A decrease in the detection accuracy of the maximum value M2 reduces the calculation accuracy of the “integrated value of the charging current from the maximum value M2 until full charge” and the “integrated value of the discharging current from full charge until the maximum value M2” and thus the estimation accuracy of the full charge capacity.

[0037] In this embodiment, by subtracting the concentration overpotential from the voltage VB detected by the voltage sensor 210, it is possible to suppress a decrease in the detection accuracy of the maximum value M2 and to accurately estimate the full charge capacity.

[0038] 3 is a flowchart showing an example of a charging-time full charge capacity estimation process executed by the ECU 300. This flowchart is executed when external charging of the battery 100 is started, and is executed for each cell 100a. When the connector 420 is connected to the DC inlet 60 or the connector 520 is connected to the AC inlet 80 and external charging of the battery 100 is started, the ECU 300 acquires various parameters in step (hereinafter, step will be abbreviated as "S") 10. The various parameters may be, for example, the voltage BV, the current IB, the temperature TB, etc. detected by the monitoring unit 200.

[0039] In the next step S11, a change amount ΔVBSav in the average value VBSav of the second correction voltage VBS is calculated. The change amount ΔVBSav is calculated by a change amount ΔVBSav calculation routine. Fig. 4 is a flowchart showing an example of the change amount ΔVBSav calculation routine executed by the ECU 300. This flowchart is repeatedly executed at set timing simultaneously with the start of the full-charge estimation process during charging.

[0040] Referring to Fig. 4, in S20, the concentration overvoltage (salt concentration overvoltage) dV_ce of the cell 100a is calculated. The concentration overvoltage dV_ce may be calculated, for example, from a first-order lag equation of "dV_ce = (1 - α) × dV_ce (previous value) - β × IB (where α and β are adaptive values)." The initial value of the concentration overvoltage dV_ce may be 0 (zero). The concentration overvoltage dV_ce may also be calculated from a known diffusion equation.

[0041] In the next S21, the first correction voltage VB1 is calculated by subtracting the concentration overpotential dV_ce from the voltage VB (VB1=VB-dV_ce). In S22, the second correction voltage VBS is calculated. The second correction voltage VBS is a value obtained by estimating the first correction voltage VB1 when the current IB (the charge / discharge current of the cell 100a) is 0 (zero) from the first correction voltage VB1 over a predetermined period (e.g., 30 seconds). For example, as shown in the VBS explanatory diagram in FIG. 4, data on the first correction voltage VB1 and the current IB over a predetermined period is plotted, and the first correction voltage VB1 when the current IB is 0 (zero) is determined by interpolation or extrapolation using a linear function (straight line), and the second correction voltage VBS is calculated.

[0042] In S23, an average value VBSav of the second correction voltage VBS is calculated. In this embodiment, the average value VBSav is a simple moving average of the second correction voltage VBS, and may be a simple moving average of n second correction voltages VBS including the current second correction voltage VBS (VBSav=VBSav(previous value)-VBS(n+1) / n+VBS / n: where VBS(n+1) is the value of VBS (n+1) times before). For example, n may be 10.

[0043] In the next S24, a change ΔVBSav in the average value VBSav of the second correction voltage VBS is calculated. The change ΔVBSav may be the change [V / Ah] in the average value VBSav of the second correction voltage VBS with respect to the remaining capacity (charge capacity), or may be the change [V / s] in the average value VBSav with respect to time (charging time). Once the change ΔVBSav is calculated, the current routine is terminated, and processing starts again from S20 to begin calculating the next change ΔVBSav.

[0044] 3, in S12, it is determined whether or not a maximum value of the change amount ΔVBSav has been detected. The maximum value may be detected when the current change amount ΔVBSav is smaller than the previous change amount ΔVBSav. Alternatively, the maximum value may be detected when the sign of the derivative of the change amount ΔVBSav changes from positive to negative. If a maximum value of the change amount ΔVBSav is not detected in S13, the process proceeds to S13. If a maximum value of the change amount ΔVBSav is detected, the process proceeds to S14.

[0045] In S13, it is determined whether the battery 100 (cells 100a) is fully charged. For example, if the battery 100 is being charged using CCCV (Constant Current-Constant Voltage) charging, it may be determined that the battery is fully charged when the charging current falls below a set value. Alternatively, it may be determined that the battery 100 is fully charged when the voltage VB of any of the cells 100a reaches a charging end voltage. If it is determined that the battery 100 is fully charged, the process proceeds to S18. If it is not fully charged, the process returns to S10.

[0046] In S14, it is determined whether the SOC of the cell 100a is greater than a predetermined value α. The predetermined value α is a value set to determine whether the maximum value detected in S12 corresponds to the maximum value M2 (see FIG. 2B), and may be, for example, 50(%). The SOC is the SOC of the cell 100a when it is new, and may be measured, for example, by a coulomb counting method. If the SOC is equal to or less than the predetermined value α, the maximum value detected in S12 corresponds to the maximum value M1 (see FIG. 2B), so a negative determination is made and the process returns to S10. If the SOC is greater than the predetermined value α (SOC>α), the maximum value detected in S12 corresponds to the maximum value M2, so a positive determination is made and the process proceeds to S15.

[0047] In S15, flag F1 is set to 1, and then the process proceeds to S16. The initial value of flag F is set to 0. In S16, it is determined whether or not the battery 100 (cells 100a) is fully charged. S16 is repeated until the battery 100 is fully charged, and when the battery 100 is fully charged, a positive determination is made and the process proceeds to S17.

[0048] In S17, the fully charged capacity X of the cell 100a is calculated by adding the integrated current amount ΣQa to the reference capacity C2 (X=C2+ΣQa).

[0049] 5 is a flowchart of a charge / discharge current integration routine executed by ECU 300. This flowchart is executed when external charging of battery 100 is started, and is repeatedly processed at predetermined intervals when the power switch of electric vehicle 1 is turned on and electric vehicle 1 becomes capable of running (when battery system S becomes capable of operation). First, in S30, it is determined whether flag F is 1. If flag F is 0, a negative determination is made, and the process proceeds to S31, where the current integrated value ΣQa is reset (the current integrated value ΣQa is set to 0). If flag F is 1, a positive determination is made, and the process proceeds to S32, where the charge / discharge current is integrated to calculate the current integrated value ΣQa. For example, the current integrated value ΣQa is calculated by integrating the current IB detected by current sensor 220, and the current integrated value ΣQa is calculated as an absolute value (positive value). When the battery 100 is externally charged, the charging current is integrated, and therefore the current integration value ΣQa is the integrated value of the charging current.

[0050] As shown in FIGS. 2A and 2B, the reference capacity C2 is the remaining capacity (charge capacity) of the cell 100a at the maximum value M2 (step P2), and is set in advance by experimentation or the like. The integrated current value Qa used in calculating the full charge capacity X in S17 is the integrated current value from when the maximum value corresponding to the polar body value M2 of the change amount ΔVBSav is detected until the cell 100a is fully charged. Therefore, the full charge capacity X of the cell 100a can be calculated by adding the integrated current value Qa to the reference capacity C2. The integrated current value Qa used in S17 corresponds to an example of the "second integrated current value" in the present disclosure.

[0051] After calculating the full charge capacity X in S17, the process proceeds to S 18. In S18, the flag F is set to 0, and the current charging full charge capacity estimation process is terminated.

[0052] 6 is a flowchart showing an example of a discharge-time full charge capacity estimation process executed by ECU 300. This flowchart is executed for each cell 100a when the power switch of the electric vehicle 1 is turned on and the electric vehicle 1 becomes capable of running. In S40, it is determined whether the battery 100 (cell 100a) is fully charged. For example, it may be determined that the battery 100 is fully charged when the voltage VB is equal to or higher than a predetermined voltage corresponding to full charge. If the battery is fully charged when the power switch is turned on, a positive determination is made and the process proceeds to S40, and if the battery is not fully charged, a negative determination is made and the process proceeds to S47.

[0053] In S41, flag F is set to 1, and then the process proceeds to S42 to acquire various parameters. S42 and S43 are similar processes to S10 and S11 in FIG. 3. However, the change amount ΔVBSav in S43 is calculated by the change amount ΔVBSav calculation routine in FIG. 4, which is started simultaneously with the power switch being turned on. Furthermore, the concentration overvoltage (salt concentration overvoltage) concentration overvoltage dV_ce calculated in S21 in FIG. 4 is calculated from the first-order lag formula "dV_ce = (1 - α) × dV_ce (previous value) + β × IB." Furthermore, the change amount ΔVBSav calculated in S24 (FIG. 4) is the change amount [V / Ah] of the average value VBSav of the second correction voltage VBS relative to the remaining capacity.

[0054] In S44, it is determined whether or not a maximum value of the amount of change ΔVBSav has been detected. In S44, the same process as in S12 (FIG. 3) is performed, and if a maximum value of the amount of change ΔVBSav has not been detected, the process returns to S42, and if a maximum value of the amount of change ΔVBSav has been detected, the process proceeds to S45.

[0055] In S45, it is determined whether the SOC of the cell 100a is greater than a predetermined value β. The predetermined value β is a value set to determine whether the maximum value detected in S12 corresponds to the maximum value M2 (see FIG. 2(B)), and may be the same value as the predetermined value α in S14 (FIG. 3). If the SOC is equal to or less than the predetermined value β, a negative determination is made and the process proceeds to S47. If the SOC is greater than the predetermined value β, an affirmative determination is made and the process proceeds to S46.

[0056] In S46, the full charge capacity X of the cell 100a is calculated. As in S17, the full charge capacity X is calculated by adding the reference capacity C2 to the accumulated current ΣQa (X=C2+ΣQa). In the discharge full charge capacity estimation process, when the battery 100 (cell 100a) is fully charged, the flag F is set to 1 (S41). Therefore, the accumulated current value Qa used in calculating the full charge capacity X in S46 is the accumulated current value from the fully charged state to the detection of the maximum value corresponding to the polar body value M2 of the change amount ΔVBSav. Therefore, the full charge capacity X of the cell 100a can be calculated by adding the accumulated current value Qa to the reference capacity C2. The accumulated current value Qa used in S46 corresponds to an example of the "first accumulated current value" in the present disclosure.

[0057] After the full charge capacity X is calculated in S46, the process proceeds to S47, where the flag F is set to 0, and the current discharge full charge capacity estimation process is terminated.

[0058] In the above embodiment, the process of FIG. 5 (charge / discharge current integration routine) corresponds to an example of a "current integration unit" of the present disclosure, and the process of S20 (FIG. 4) corresponds to an example of a "concentration overvoltage calculation unit" of the present disclosure. The process of S21 corresponds to an example of a "first correction voltage calculation unit" of the present disclosure, and the process of S22 corresponds to an example of a "second correction voltage estimation unit" of the present disclosure. Furthermore, the processes of S12 (FIG. 3) and S44 (FIG. 6) correspond to an example of a "maximum value detection unit" of the present disclosure.

[0059] In the above embodiment, the maximum value of the voltage change amount is detected using the change amount ΔVBSav of the average value VBSav of the second correction voltage VBS. However, the maximum value of the voltage change amount may be detected using the change amount ΔVB1 [V / Ah] of the first correction voltage VB1. Alternatively, the maximum value of the voltage change amount may be detected using the change amount ΔVBS [V / Ah] of the second correction voltage VBS.

[0060] According to this embodiment, the first correction voltage VB1 is a voltage obtained by subtracting the concentration overvoltage dV_ce from the voltage VB detected by the voltage sensor 210, and the maximum value M2 can be detected relatively accurately. Furthermore, the second correction voltage VBS is the first correction voltage VB1 when the charging / discharging current is zero, and therefore the maximum value M2 can be detected accurately while eliminating the influence of overvoltage (polarization) in the resistance system. Furthermore, the maximum value M2 is detected using the change amount ΔVBSav in VBSav, which is the moving average of the second correction voltage VBS. Therefore, the influence of noise and the like when detecting the voltage VB can be eliminated, and the maximum value M2 can be detected accurately.

[0061] In the above embodiment, a lithium iron phosphate battery (LFP battery) was used as the cell 100a. However, the cell 100a may be any other type of battery as long as it has a region where the OCV curve changes very little (a flat voltage region) and can detect a maximum value of the voltage change. Alternatively, the maximum value M1 may be detected and the full charge capacity may be calculated using the reference capacity C1.

[0062] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0063] 1 Electric vehicle, 10 Motor generator (MG), 20 Drive transmission gear, 30 Drive wheel, 40 PCU, 50 SMR, 60 DC inlet, 80 AC inlet 100 Battery, 100a single cell, 200 Monitoring unit, 210 Voltage sensor, 220 Current sensor, 230 Temperature sensor, 300 ECU, 400 DC power supply, 420 Connector, 500 AC power supply, 520 Connector, S Battery system.

Claims

1. A battery system including a battery, a voltage sensor that detects a battery voltage, which is a voltage of the battery, a current sensor that detects a charge / discharge current of the battery, and a control device, The control device a current integrating unit that calculates an integrated discharge current value that is an integrated value of the discharge current of the battery; a concentration overvoltage calculation unit for acquiring a concentration overvoltage of the battery; a first correction voltage calculation unit that calculates a first correction voltage by subtracting the concentration overvoltage from the battery voltage detected by the voltage sensor; a maximum value detection unit that detects a maximum value of a voltage change amount based on the first correction voltage, a first integrated current value that is the integrated value of the discharge current from when the battery is fully charged until the maximum value is detected, and a full charge capacity of the battery is estimated based on the first integrated current value.

2. A battery system including a battery, a voltage sensor that detects a battery voltage, which is a voltage of the battery, a current sensor that detects a charge / discharge current of the battery, and a control device, The control device a current integrating unit that calculates an integrated charging current value that is an integrated value of the charging current of the battery; a concentration overvoltage calculation unit for acquiring a concentration overvoltage of the battery; a first correction voltage calculation unit that calculates a first correction voltage by subtracting the concentration overvoltage from the battery voltage detected by the voltage sensor; a maximum value detection unit that detects a maximum value of a voltage change amount based on the first correction voltage, The battery system estimates a full charge capacity of the battery based on a second integrated current value, which is the integrated charging current value from when the maximum value is detected until the battery is fully charged.

3. The control device a second correction voltage estimation unit that estimates a second correction voltage, which is a value of the first correction voltage when the charging / discharging current is zero, based on the first correction voltage for a predetermined period of time; 3. The battery system according to claim 1, wherein the local maximum value detector detects the local maximum value based on the second correction voltage.

4. The battery system according to claim 3 , wherein the full charge capacity is calculated based on a reference capacity that is the capacity of the battery at the maximum value.

5. the battery has a characteristic in which a plurality of maximum values ​​exist, The battery system according to claim 4 , wherein the reference capacity is a capacity of the battery at a maximum value where the voltage of the battery is on a high voltage side, among the plurality of maximum values.

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