Battery system

Abstract

To accurately estimate whether a secondary battery including a nonaqueous electrolyte solution deteriorates.SOLUTION: A battery system is to estimate whether a battery 20 deteriorates. The battery system includes a voltage sensor 21 and an ECU 40. The voltage sensor 21 detects a voltage value VV of the battery 20. The ECU 40 is configured to perform a determination process of determining a polarization resolution time, which is the time after charging and discharging of the battery 20 are stopped and before the polarization of the battery 20 is resolved, in accordance with the voltage value VV, and an estimation process of estimating whether the battery 20 deteriorates in accordance with the polarization resolution time. The estimation process includes a process of estimating that the deterioration has not occurred when the polarization resolution time is less than a threshold and a process of estimating that the deterioration has occurred when the polarization resolution time is more than or equal to the threshold.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a battery system, and more particularly to a battery system for estimating the presence or absence of deterioration of a secondary battery including a non-aqueous electrolyte.

Background Art

[0002] Secondary batteries having a non-aqueous electrolyte, such as lithium ion batteries, have attracted attention. When charging or discharging at a high rate (high current) of such a secondary battery is repeated, the ion concentration in the non-aqueous electrolyte becomes uneven. As a result, the resistance of the secondary battery increases and the secondary battery deteriorates. Such deterioration of the secondary battery is also called "high-rate deterioration".

[0003] Japanese Unexamined Patent Application Publication No. 2017-103080 (Patent Document 1) discloses a battery system. The battery system includes a secondary battery, a current sensor, and a control device. The current sensor detects a charging current or a discharging current of the secondary battery. The control device calculates an evaluation value for evaluating the high-rate deterioration of the secondary battery based on the detection value of the current sensor. The control device determines whether or not the integrated value of the evaluation value is higher than a threshold value. When the integrated value is higher than the threshold value, the control device limits the charging power or the discharging power of the battery in order to prevent excessive high-rate deterioration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the battery system described above, if the current sensor's detected value includes detection errors, these errors can accumulate in the integrated value. As a result, the accumulated errors in the integrated value may become too large to ignore. In this case, it may not be possible to accurately estimate the presence or absence of high-rate degradation based on the integrated value (making it impossible to limit charging or discharging power at the appropriate timing).

[0006] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a battery system that can accurately estimate whether or not a secondary battery containing a non-aqueous electrolyte has deteriorated. [Means for solving the problem]

[0007] The battery system of this disclosure is a battery system for estimating whether or not a secondary battery containing a non-aqueous electrolyte has deteriorated. This deterioration is a phenomenon in which the internal resistance of the secondary battery increases due to an imbalance in the ion concentration in the non-aqueous electrolyte. The battery system comprises a voltage sensor and a processing unit. The voltage sensor detects the voltage value of the secondary battery. The processing unit is configured to perform a determination process that determines the depolarization time, which is the time it takes for the polarization of the secondary battery to disappear after the charging and discharging of the secondary battery has stopped, according to the voltage value, and an estimation process that estimates whether or not the secondary battery has deteriorated according to the depolarization time. The estimation process includes a process that estimates that there is no deterioration if the depolarization time is less than a threshold, and a process that estimates that there is deterioration if the depolarization time is greater than or equal to the threshold.

[0008] Whether or not a secondary battery is degraded is related to whether or not the depolarization process is prolonged. Whether or not the depolarization process is prolonged is reflected in the depolarization time. With the above configuration, the presence or absence of secondary battery degradation can be estimated according to the depolarization time. The depolarization time is calculated according to the voltage value of the voltage sensor, and even if this voltage value contains errors, it can be accurately determined as long as the voltage value is stable. Therefore, the results of the estimation process are not fundamentally affected by the detection errors of the voltage sensor and many other sensors. As a result, the presence or absence of secondary battery degradation can be estimated with high accuracy.

[0009] The battery system may be mounted on the vehicle. The processing unit may perform determination and estimation processing after the vehicle's running system has stopped.

[0010] The battery system may be mounted on the vehicle. The processing unit may perform determination processing and estimation processing after the external charging, which charges the secondary battery with a charging current supplied from a charging facility located outside the vehicle, has been stopped.

[0011] If the charge / discharge current of the secondary battery during a predetermined period before the cessation of charging and discharging of the secondary battery is equal to or greater than the threshold current, the processing device may perform a determination process and an estimation process.

[0012] The larger the charge / discharge current, the longer the depolarization of a degraded battery tends to take. As a result, it becomes easier to distinguish whether a secondary battery is degraded or not based on the depolarization time. With the above configuration, the estimation process is executed when the charging current is large enough to exceed the threshold current, that is, when the presence or absence of degradation can be easily distinguished based on the depolarization time. This makes it possible to estimate whether a secondary battery is degraded more easily and accurately.

[0013] The battery system may further include a memory unit. The memory unit stores a first voltage value, which is the voltage value when charging and discharging stops; a second voltage value, which is the voltage value when the polarization of the secondary battery has been resolved after charging and discharging stops; and a third voltage value, which is predetermined as the voltage value between the first voltage value and the second voltage value. The processing unit may further be configured to perform an intermediate determination process to determine the time required until the voltage value reaches the third voltage value after charging and discharging stops, and an intermediate estimation process to estimate whether or not the secondary battery has deteriorated according to the time required. The intermediate estimation process includes a process to estimate that there is no deterioration if the time required is less than a reference time, and a process to estimate that there is deterioration if the time required is equal to or greater than the reference time.

[0014] With the above configuration, the intermediate estimation process is performed after the charging and discharging of the secondary battery has stopped and before polarization has been resolved. This means that the processing unit does not necessarily need to wait until polarization has been resolved in order to estimate whether or not the secondary battery has deteriorated. As a result, it is possible to estimate whether or not deterioration has occurred before polarization has been resolved, and if deterioration is present, the charging and discharging power can be limited early. Therefore, protection of the secondary battery can be initiated earlier. [Effects of the Invention]

[0015] According to this disclosure, it is possible to accurately estimate whether or not a secondary battery containing a non-aqueous electrolyte has deteriorated. [Brief explanation of the drawing]

[0016] [Figure 1] This diagram schematically shows the overall configuration of a charging system, including a vehicle equipped with a battery system according to an embodiment. [Figure 2] This diagram shows the hardware configuration of the vehicle and charging equipment in detail. [Figure 3] This diagram illustrates the change in voltage value during polarization relaxation after battery discharge, depending on whether or not high-rate degradation is present. [Figure 4] This diagram illustrates the voltage change during polarization relaxation after external charging of a battery, depending on whether or not high-rate degradation is present. [Figure 5] This is a flowchart showing an example of the processing executed by the ECU in the embodiment. [Figure 6] This is a flowchart showing another example of the processing executed by the ECU in the embodiment.

Embodiment for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and their description will not be repeated. Each of the embodiments and their modifications may be combined with each other as appropriate.

[0018] FIG. 1 is a diagram schematically showing the overall configuration of a charging system including a vehicle in which a battery system according to an embodiment is mounted. Referring to FIG. 1, the charging system 100 includes a vehicle 1 and a charging facility 5.

[0019] The vehicle 1 is an electric vehicle equipped with a battery 20, for example, a battery electric vehicle (BEV: Battery Electric Vehicle). The vehicle 1 may be other types of electric vehicles such as a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle). The vehicle 1 is electrically connected to the charging facility 5 via a charging cable 6 and is configured to execute external charging for charging the battery 20 with a charging current supplied from the charging facility 5.

[0020] The charging facility 5 is provided outside the vehicle 1. The charging facility 5 is configured to be able to supply high-current power supply (DC power) to the battery 20 via the charging cable 6 during external charging.

[0021] FIG. 2 is a diagram showing in detail the hardware configuration of the vehicle 1 and the charging facility 5. Referring to FIG. 2, the charging facility 5 includes an AC / DC converter 51, a HMI (Human Machine Interface) device 53, and a control circuit 55.

[0022] The AC / DC converter 51 converts AC power from the power grid (AC power source) 7 into DC power (charging power for the battery 20). The HMI device 53 receives user input to instruct the start of external charging of the vehicle 1. The control circuit 55 controls the AC / DC converter 51 and exchanges various information with the vehicle 1, for example, via CAN (Controller Area Network) communication.

[0023] Vehicle 1 comprises an inlet 11, charging relays 131 and 132, a PCU (Power Control Unit) 16, a motor generator 17, and drive wheels 19. Vehicle 1 further comprises a battery 20, system main relays (SMRs) 141 and 142, a voltage sensor 21, a current sensor 22, a temperature sensor 23, a start switch (ST-SW) 35, and an ECU 40.

[0024] The inlet 11 is configured to be connectable to the charging connector 61 of the charging cable 6. The charging relays 131 and 132 are connected to the charging lines PL1 and NL1, respectively. The PCU 16 is electrically connected between the power lines PL2 and NL2 and the motor generator 17. The PCU 16 is configured to drive the motor generator 17 by converting the output power of the battery 20 into AC power. When the output torque of the motor generator 17 is transmitted to the drive wheels 19, the vehicle 1 moves. The PCU 16 is configured to be able to charge the battery 20 by converting the AC power generated by the motor generator 17 into DC power.

[0025] Battery 20 is a secondary battery containing a non-aqueous electrolyte, and in this example, it is a lithium-ion battery. Battery 20 stores power to generate the driving force for vehicle 1. The positive electrode of battery 20 is electrically connected to the charging line PL1 and the power line PL2 via SMR141. The negative electrode of battery 20 is electrically connected to the charging line NL1 and the power line NL2 via SMR142.

[0026] Polarization in battery 20 is known as a phenomenon in which an electromotive force in the opposite direction to the current flows through battery 20 temporarily. For example, after charging battery 20, polarization is a phenomenon in which the voltage VB temporarily rises. After discharging battery 20, polarization is a phenomenon in which the voltage VB temporarily falls. Polarization eases over time and disappears after a sufficiently long period of time (the electromotive force becomes zero and the voltage of battery 20 stabilizes).

[0027] The voltage sensor 21, current sensor 22, and temperature sensor 23 detect the voltage VV, current CV, and temperature TV of the battery 20, respectively. The voltage VV, current CV, and temperature TV are the detected values ​​of the voltage VB, current IB, and temperature TB of the battery 20, respectively. The current CV (current IB) is assumed to be positive when the battery 20 is charging, and negative when it is discharging.

[0028] The start switch 35 receives user input to start or stop the vehicle 1's running system. Starting the running system corresponds to turning on the SMRs 141 and 142 (specifically, establishing electrical connections between the battery 20, PCU 16, and MG 17). Stopping the running system corresponds to turning off the SMRs 141 and 142. After stopping the running system (turning off the SMRs 141 and 142), the battery 20 is electrically disconnected from the PCU 16, and charging or discharging of the battery 20 stops.

[0029] The ECU 40 includes a CPU 41, memory 42, and timer 43. The CPU 41 performs various arithmetic operations. The memory 42 includes ROM 42A and RAM 42B. ROM 42A stores programs executed by the CPU 41 and various data. The memory 42 may be located outside the ECU 40. The measurement results of the timer 43 are provided to the CPU 41.

[0030] The ECU 40 controls various components of the vehicle 1, such as the charging relays 131 and 132, the SMRs 141 and 142, the PCU 16, and the motor generator 17. The ECU 40 controls the charging and discharging power of the battery 20 while the vehicle 1 is running by controlling the PCU 16. The ECU 40 can also limit the charging and discharging power while running (by setting the upper limit of charging power Win and the upper limit of discharging power Wout to a small value). The ECU 40 is configured to control the on / off switching of the charging relays 131 and 132 and the SMRs 141 and 142. The ECU 40 estimates the State of Charge (SOC) of the battery 20 based on the voltage value VV, current value CV, and temperature value TV. The ECU 40 sequentially stores the history of the voltage value VV and current value CV in the memory 42.

[0031] The ECU 40 can perform external charging control processing to control external charging. During this processing, the ECU 40 turns on the charging relays 131, 132 and SMRs 141, 142 and exchanges various information with the control circuit 55 via CAN communication. For example, the ECU 40 sends a control command to the control circuit 55 to instruct the supply of power from the charging equipment 5 to the inlet 11 (battery 20), thereby executing the external charging control processing. The external charging control processing includes external charging stop processing, which stops external charging when the State of Charge (SOC) of the battery 20 reaches the charging stop SOC (target SOC).

[0032] The battery 20, voltage sensor 21, charging relays 131, 132, SMRs 141, 142, PCU 16, and ECU 40 form an example of the “battery system” of this disclosure.

[0033] If the battery 20 is frequently charged and discharged at a high rate, for example, through external charging using the charging equipment 5, the ion concentration in the non-aqueous electrolyte of the battery 20 becomes uneven. As a result, the internal resistance of the battery 20 increases, causing degradation of the battery 20. Such degradation, that is, the phenomenon in which the internal resistance of the battery 20 increases due to an uneven distribution of ion concentration in the non-aqueous electrolyte of the battery 20, is also called "high-rate degradation" of the battery 20. If high-rate degradation of the battery 20 is present, it is preferable for the ECU 40 to limit the charging power and discharging power during driving in order to prevent further progression of high-rate degradation. In order to limit the charging power and discharging power in this way at the appropriate timing, it is necessary to accurately estimate whether or not high-rate degradation is present.

[0034] One method for estimating the presence or absence of high-rate degradation is to calculate the integrated value of the detected values ​​(current values ​​CV) from the current sensor 22 and estimate the presence or absence of high-rate degradation based on this integrated value. However, in this method, detection errors included in each current value CV can accumulate in the integrated value. This may lead to a decrease in the accuracy of the estimation result for the presence or absence of high-rate degradation.

[0035] The inventors focused on the fact that the presence or absence of high-rate degradation is reflected in the depolarization time, which is the time it takes for the polarization of the battery 20 to disappear after charging and discharging of the battery 20 stops. Specifically, they noted that if high-rate degradation is present, the depolarization time is prolonged (polarization disappears relatively slowly). The method for estimating the presence or absence of high-rate degradation will be described below in the embodiment.

[0036] The ECU40 is configured to perform a determination process to determine the depolarization time according to the voltage value VV, and an estimation process to estimate whether or not high-rate degradation is present according to the depolarization time. The estimation process includes a process to estimate that there is no high-rate degradation if the depolarization time is less than a threshold, and a process to estimate that there is high-rate degradation if the depolarization time is equal to or greater than the threshold.

[0037] With this configuration, the presence or absence of high-rate degradation is calculated according to the polarization depolarization time. The polarization depolarization time is calculated according to the voltage value VV of the voltage sensor 21, and even if the voltage value VV contains errors, it can be accurately determined as long as the voltage value VV is stable. Therefore, the results of the estimation process are not fundamentally affected by the detection errors of the voltage sensor 21 and other sensors. As a result, the presence or absence of high-rate degradation can be estimated with high accuracy.

[0038] Figure 3 is a diagram illustrating the change in voltage value VV during polarization relaxation after discharge of battery 20, depending on whether or not high-rate degradation occurs. Referring to Figure 3, lines 300 and 320 represent the change in voltage value VV in cases A and B, respectively. Case A is assumed to have high-rate degradation, and Case B is assumed to have no high-rate degradation.

[0039] At time t0, the discharge of battery 20 is stopped due to the stopping of the driving system by pressing the start switch 35. Assume that before time t0, vehicle 1 was running and battery 20 was discharging. The voltage value VV at time t0 is also represented as V0. In both cases A and B, polarization relaxation (increase in voltage value VV) begins after time t0 (lines 300, 320). V0 changes depending on the state of charge (SOC) when the driving system stops (discharge stop SOC) and the temperature TB and current IB immediately before vehicle 1 stops running (for example, a predetermined period before time t0). Time t0 and V0 are stored in memory 42.

[0040] Time t1 is later than time t0. The voltage values ​​VV at time t1 in cases A and B are also represented as V1a and V1b, respectively. In case A, polarization relaxation is not yet complete and is still ongoing. On the other hand, in case B, polarization has already been resolved (polarization relaxation is complete). The voltage value VV at the time of polarization resolution after the discharge has stopped is represented as the reference value RV. Polarization resolution refers to the time when polarization has already been resolved. In this example, V1a is lower than the reference value RV, and V1b is equal to the reference value RV.

[0041] Time t2 is later than time t1. In both cases A and B, at time t2, the voltage value VV is equal to the reference value RV, so polarization has been resolved. The reference value RV depends on the temperature TB. The polarization resolution time DT in case A (time from time t0 to time t2) is also denoted as DTa, and the polarization resolution time DT in case B (time from time t0 to time t1) is also denoted as DTb. The magnitude of the difference between DTa and DTb is also denoted as the difference Diff. The length of DTa is longer than the length of DTb (DTa > DTb). This means that if there is high-rate degradation, polarization relaxation is prolonged. Thus, the presence or absence of high-rate degradation is reflected in the polarization resolution time DT (whether polarization relaxation is early or late).

[0042] The ECU 40 determines that polarization has been resolved based on the voltage value VV becoming constant (in this example, the voltage value VV stopping rising). The ECU 40 may also determine that polarization has been resolved based on the voltage value VV entering a range near the reference value RV. The range near the reference value RV is a voltage range that includes the reference value RV, the lower limit of this range being a predetermined small value lower than the voltage value VV, and the upper limit of this range being a predetermined small value higher than the voltage value VV. The reference value RV and the small value are stored in memory 42.

[0043] In Case A, at time t2, ECU40 determines that polarization has been resolved according to the voltage value VV and determines DTa. In this example, since DTa is greater than or equal to the threshold TH, ECU40 determines that there is high-rate degradation. In Case B, at time t1, ECU40 determines that polarization has been resolved according to the voltage value VV and determines DTb. In this example, since DTb is less than the threshold TH, ECU40 determines that there is no high-rate degradation. The threshold TH is pre-stored in memory 42.

[0044] If ECU40 estimates that there is no high-rate degradation, it sets the upper limit value Win to its default value and the upper limit value Wout to its default value. On the other hand, if ECU40 estimates that there is high-rate degradation, it sets the upper limit value Win to a value smaller than its default value and the upper limit value Wout to a value smaller than its default value. This limits the charging or discharging power of battery 20. The default values ​​of upper limit value Win and upper limit value Wout are pre-stored in memory 42.

[0045] The ECU 40 may perform the aforementioned determination process and estimation process if the charge / discharge current of the battery 20 (specifically, its absolute value) during a predetermined period before the battery 20 stops charging and discharging (for example, before time t0) is greater than or equal to a threshold current. Information representing the length of the predetermined period and a value representing the threshold current (threshold current value) are stored in the memory 42.

[0046] The larger the charge / discharge current, the longer the depolarization of battery 20 tends to take during high-rate degradation. As a result, the depolarization time DT(DTa) of this battery also becomes longer, and the difference Diff becomes larger. Therefore, by setting the threshold TH appropriately (for example, to the average value of DTa and DTb) in the ECU 40, it becomes easier to distinguish whether or not high-rate degradation is present according to the depolarization time DT(DTa,DTb). According to the above estimation process, the estimation process is executed when the charging current is large enough to exceed the threshold current, that is, when the presence or absence of high-rate degradation can be easily distinguished according to the depolarization time DT. This makes it possible to estimate the presence or absence of high-rate degradation more easily and accurately.

[0047] Figure 4 is a diagram illustrating the change in voltage value VV during polarization relaxation after external charging of battery 20, depending on whether or not high-rate degradation is present. Referring to Figure 4, lines 350 and 370 represent the change in voltage value VV in cases A and B, respectively.

[0048] At time t0c, external charging is stopped due to the external charging stop process performed by ECU40. The voltage value VV at time t0c is also represented as V0c. In both cases A and B, polarization relaxation (decrease in voltage value VV) begins after time t0c (lines 350, 370). V0c changes depending on the state of charge (SOC) at the time external charging stops and the temperature TB and current IB immediately before the external charging stops (for example, a predetermined period before time t0c). Time t0c and V0c are stored in memory 42.

[0049] Time t1c is later than time t0c. The voltage values ​​VV at time t1c in cases A and B are also represented as V1ac and V1bc, respectively. In case A, polarization relaxation is not yet complete and is still ongoing. On the other hand, in case B, polarization has already been resolved (polarization relaxation is complete). The voltage value VV at the time of polarization resolution after external charging has stopped is represented as the reference value RVc. In this example, V1ac is higher than the reference value RVc, and V1bc is equal to the reference value RVc.

[0050] Time t2c is later than time t1c. In both cases A and B, at time t2c, the voltage value VV is equal to the reference value RVc, so polarization has been eliminated. The reference value RVc depends on the temperature TB. The polarization elimination time DT in case A is also expressed as DTac, and the polarization elimination time DT in case B is also expressed as DTbc (DTac > DTbc). The magnitude of the difference between DTac and DTbc is also expressed as the difference Diffc. In case A, since DTac is greater than or equal to the threshold TH, ECU40 determines that there is high-rate degradation. In case B, since DTbc is less than the threshold TH, ECU40 determines that there is no high-rate degradation.

[0051] The ECU 40 may perform the aforementioned determination process and estimation process if the charging current of the battery 20 (specifically, its absolute value) during a predetermined period before the external charging of the battery 20 is stopped (for example, before time t0c) is greater than or equal to a threshold current. When such a charging current is large enough to be greater than or equal to the threshold current, the depolarization time DT(DTac) of the battery 20 during high-rate degradation also becomes longer, and the difference Diffc becomes larger. As a result, by appropriately setting the threshold TH as described above, it becomes easier to distinguish whether or not high-rate degradation has occurred according to the depolarization time DT(DTac,DTbc). Furthermore, since the charging current is basically stable during external charging compared to when the vehicle 1 is running, the above estimation process can easily create a situation where the charging current is greater than or equal to the threshold current (a situation where it is easy to distinguish whether or not high-rate degradation has occurred).

[0052] Figure 5 is a flowchart showing an example of the process performed by the ECU 40 in this embodiment. This flowchart starts when the driving system stops due to the operation of the start switch 35. In this example, the ECU 40 performs the aforementioned determination process and estimation process after the driving system has stopped.

[0053] Referring to Figure 5, the ECU 40 reads the history of charge and discharge currents during a predetermined period before the driving system is stopped from the memory 42 (S102). The ECU 40 determines whether the charge and discharge currents during the predetermined period are equal to or greater than the threshold current (S104). If the charge and discharge currents are less than the threshold current (NO in S104), the process ends. If the charge and discharge currents are equal to or greater than the threshold current (YES in S104), the process proceeds to S105.

[0054] The ECU 40 obtains a voltage value VV from the voltage sensor 21 (S105) and determines whether or not polarization has been resolved according to the voltage value VV (S110). For example, the ECU 40 performs S110 by determining whether or not the voltage value VV has become constant. The ECU 40 may also perform S110 by determining whether or not the voltage value VV has entered a range near the reference value RV. If polarization has not yet been resolved (NO in S110), the process returns to S105. If polarization has been resolved (YES in S110), the ECU 40 performs a determination process to determine the polarization resolution time DT (S111), and then performs an estimation process (S112). S112 includes S115, S120, and S125, which are described below.

[0055] The ECU40 determines whether the depolarization time DT is less than the threshold TH (S115). If the depolarization time DT is less than the threshold TH (YES in S115), the ECU40 estimates that there is no high-rate degradation (S120). If the depolarization time DT is greater than or equal to the threshold TH (NO in S115), the ECU40 estimates that there is high-rate degradation (S125).

[0056] In the above, S102 and S104 are not necessarily required. In this case, S105 will be executed without S102 and S104 after the driving system has stopped.

[0057] Figure 6 is a flowchart showing another example of the processing performed by the ECU 40 in the embodiment. Referring to Figure 6, this flowchart differs from the flowchart in Figure 5 in that it starts when external charging stops due to the external charging stop processing, and S102A and S104A are executed in place of S102 and S104, but is otherwise the same as the flowchart in Figure 5. In this example, the ECU 40 performs the aforementioned determination processing and estimation processing after the external charging stops.

[0058] The ECU 40 reads the history of the charging current during a predetermined period before the external charging is stopped from the memory 42 (S102A). The ECU 40 determines whether the charging current during the predetermined period is greater than or equal to the threshold current (S104A). If the charge / discharge current is less than the threshold current (NO in S104A), the process ends. If the charge / discharge current is greater than or equal to the threshold current (YES in S104A), the process proceeds to S105. In this example as well, S102A and S104A are not necessarily required.

[0059] As described above, according to the embodiment, the ECU 40 performs an estimation process to estimate whether or not high-rate degradation is present after the charging and discharging of the battery 20 is stopped, according to the polarization depolarization time DT. As a result, the presence or absence of high-rate degradation can be estimated with high accuracy.

[0060] [Differentiation] In this embodiment, the memory 42 stores a first voltage value (e.g., V0 or V0c) which is the voltage value VV when charging and discharging of the battery 20 stops, and a second voltage value (e.g., RV or RVc) which is the voltage value VV when the polarization of the battery 20 is resolved after charging and discharging stops. In this modified example, the memory 42 further stores a third voltage value (not shown) which is predetermined as the voltage value VV between the first voltage value and the second voltage value. The third voltage value is predetermined by the ECU 40 according to the SOC when charging and discharging stops, and the temperature value TV (temperature TB) and current value CV (current IB) immediately before charging and discharging.

[0061] The ECU40 is further configured to perform an intermediate determination process to determine the time required for the voltage value VV to reach the third voltage value after the charging and discharging of the battery 20 has stopped, and an intermediate estimation process to estimate whether or not high-rate degradation has occurred according to this required time. The intermediate determination process and intermediate estimation process differ from the determination process and estimation process of the embodiment in that they are performed during the polarization relaxation (i.e., before polarization is resolved). The intermediate estimation process includes a process to estimate that there is no high-rate degradation if the required time is shorter than the reference time, and a process to estimate that there is high-rate degradation if the required time is longer than or equal to the reference time.

[0062] As mentioned above, the presence or absence of high-rate degradation is related to how quickly or slowly polarization depolarization (polarization relaxation) occurs. Whether polarization relaxation occurs quickly or slowly is reflected in the time required as described above. Specifically, if high-rate degradation is present, the time required is relatively long, while if high-rate degradation is absent, the time required is relatively short. According to this modification, the intermediate estimation process is executed according to the time required after charging and discharging of battery 20 stops and before polarization depolarization occurs. As a result, ECU 40 does not necessarily need to wait until polarization is resolved in order to estimate the presence or absence of high-rate degradation. Consequently, even if the user of vehicle 1 starts driving vehicle 1 without waiting for polarization to resolve, ECU 40 can appropriately estimate the presence or absence of high-rate degradation before polarization is resolved. Therefore, if high-rate degradation is present, the charging power and discharging power can be limited early (appropriate upper limits Win and Wout can be set early). Thus, battery 20 protection can be started early, and user convenience can be improved.

[0063] If intermediate determination and estimation processes are performed after the driving system has stopped, the first voltage value is V0 (Figure 3), the second voltage value is the reference value RV, and the third voltage value is higher than V0 and lower than the reference value RV. If intermediate determination and estimation processes are performed after external charging, the first voltage value is V0c (Figure 4), the second voltage value is the reference value RVc, and the third voltage value is lower than V0c and higher than the reference value RVc.

[0064] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0065] 1 vehicle, 5 charging equipment, 20 batteries, 21 voltage sensors, 35 start switches, 41 CPU, 42 memory, 100 charging system.

Claims

1. A battery system for estimating whether or not a secondary battery containing a non-aqueous electrolyte has deteriorated, wherein the deterioration is a phenomenon in which the internal resistance of the secondary battery increases due to an imbalance in the ion concentration in the non-aqueous electrolyte, and the battery system is mounted on a vehicle. A current sensor for detecting the current value of the secondary battery, A voltage sensor for detecting the voltage value of the secondary battery, The apparatus comprises a processing unit configured to perform a stop process for stopping external charging, which charges the secondary battery with a charging current supplied from a charging facility located outside the vehicle; a determination process for determining the depolarization time, which is the time until the polarization of the secondary battery is resolved after the stop process, according to the voltage value; and an estimation process for estimating whether or not degradation has occurred according to the depolarization time. The aforementioned estimation process is, If the polarization depolarization time is less than a threshold, a process is performed to estimate that there is no degradation. If the polarization depolarization time is greater than or equal to the threshold, the process includes a process for estimating that the degradation is present. The processing device is a battery system that performs the determination process and the estimation process when the current value during a predetermined period prior to the stop process within the external charging period is greater than or equal to a threshold current value.

2. The storage unit further stores a first voltage value which is the voltage value when the stop process is executed, a second voltage value which is the voltage value when the polarization of the secondary battery is resolved after the stop process, and a third voltage value which is predetermined as the voltage value between the first voltage value and the second voltage value. The processing device is further configured to perform an intermediate determination process to determine the time required for the voltage value to reach the third voltage value after the stop process, and an intermediate estimation process to estimate whether or not degradation has occurred according to the required time. The aforementioned intermediate estimation process is If the aforementioned required time is less than the standard time, the process of estimating that there is no deterioration is performed, The battery system according to claim 1, further comprising a process for estimating that deterioration has occurred if the required time is equal to or greater than the reference time.

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