Battery System

Abstract

To provide a battery system with a battery pack capable of improving the accuracy of diagnosis while labor-saving for the diagnosis by diagnosing the battery pack at the right time.SOLUTION: A restraint load estimation unit 55b estimates an estimated restraint load Le by a battery pack restraint band. When the estimated restraint load Le is greater than or equal to a predetermined value X, the diagnostic mode processing unit 55c performs a diagnosis of a restraint load Ls of the restraint band. The restraint load Ls is calculated based on a first battery voltage V1 when charging / discharging is not made for a first predetermined time T1 with SOC of a first predetermined value α or lower, a second battery voltage V2 when charge / discharge is not made for a second predetermined time T2 with the SOC at or above a second predetermined value β, and charge current integrated value ΣI when charging from the first predetermined value α to the second predetermined value β.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a battery system, and more particularly to a battery system including a battery pack. [Background technology]

[0002] In JP 2020-119820 A (Patent Document 1), in an assembled battery in which multiple stacked cells (single batteries) are restrained by a restraining member, fatigue failure of the restraining member is determined by estimating the restraining load of the restraining member using the deterioration level, temperature, and SOC (State Of Charge) of the assembled battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-119820 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this patent document 1, the fatigue failure of the restraining member is diagnosed by estimating the restraining load of the restraining member. The restraining load is estimated using the deterioration degree, temperature, and SOC estimated from the capacity retention rate. Therefore, in order to accurately estimate the restraining load, it is necessary to calculate the capacity retention rate with high accuracy.

[0005] In order to obtain a highly accurate capacity maintenance ratio, it is preferable to perform charge / discharge control suitable for calculating the capacity maintenance ratio (hereinafter, also referred to as diagnosis mode charge / discharge control). However, the diagnosis mode charge / discharge control is different from the charge / discharge control when the battery pack is in use. For this reason, frequently performing the diagnosis mode charge / discharge control results in a waste of power and time.

[0006] An object of the present disclosure is to improve the accuracy of diagnosis while reducing the labor required for diagnosis by diagnosing the battery pack at appropriate times in a battery system including a battery pack. [Means for solving the problem]

[0007] The battery system of the present disclosure includes a battery pack in which a plurality of stacked single cells are restrained by restraining members, and a control device that controls the battery pack. The control device includes a restraint load estimation unit that estimates a restraint load caused by the restraint members, and a diagnosis mode processing unit that executes a diagnosis of the battery pack when the restraint load estimated by the restraint load estimation unit is equal to or greater than a predetermined value.

[0008] When a cell is used for a long period of time, the electrodes expand and gas is generated inside the battery, causing the cell to expand. In addition, when the SOC of a cell is high, the electrodes expand, causing the cell to expand. When a cell expands, the restraining load of the restraining members increases, and the mechanical load (load, pressure, stress, etc.) applied to the restraining members and the cell is large, creating a harsh environment, which is likely to cause various malfunctions in the battery pack.

[0009] According to this configuration, when the restraint load estimated by the restraint load estimation unit of the control device is equal to or greater than a predetermined value, the diagnosis mode processing unit of the control device executes diagnosis of the battery pack. Therefore, when the restraint load of the restraining member is large and there is a high possibility that various malfunctions of the battery pack will occur, diagnosis of the battery pack is executed at an appropriate timing, and labor saving of diagnosis is achieved. In addition, since diagnosis of the battery pack is executed under a severe environment, improvement of accuracy of diagnosis can be expected.

[0010] Preferably, the diagnosis performed by the diagnostic mode processing unit is a diagnosis of a restraint load, and the diagnostic mode processing unit may include a first voltage acquisition unit that discharges the battery pack so that the SOC of the battery pack becomes equal to or less than a first predetermined value, and acquires a first battery voltage that is the voltage of the battery pack when charging and discharging of the battery pack is suspended for a first predetermined time while the SOC is equal to or less than the first predetermined value, a charging current accumulation unit that charges the battery pack after acquiring the first battery voltage and accumulates the charging current, a second voltage acquisition unit that stops charging when the SOC becomes equal to or greater than a second predetermined value, and acquires a second battery voltage that is the voltage of the battery pack when charging and discharging of the battery pack is suspended for a second predetermined time, and a restraint load calculation unit that calculates the restraint load based on the charging current accumulation value calculated by the charging current accumulation unit, the first battery voltage, and the second battery voltage.

[0011] According to this configuration, the diagnostic mode processing unit executes diagnosis of the restraint load. The first voltage acquisition unit of the diagnostic mode processing unit executes discharge of the battery pack so that the SOC of the battery pack becomes equal to or less than a first predetermined value, and acquires a first battery voltage which is a voltage when charging and discharging of the battery pack is suspended for a first predetermined time while the SOC is equal to or less than the first predetermined value. The charging current integrating unit executes charging of the battery pack after acquiring the first battery voltage, and integrates the charging current. When the SOC becomes equal to or greater than a second predetermined value, the second voltage acquiring unit stops charging and acquires a second battery voltage which is a voltage when charging and discharging of the battery pack is suspended for a second predetermined time. The restraint load calculation unit calculates the restraint load based on the charging current integrated value, the first battery voltage, and the second battery voltage.

[0012] The diagnostic mode processing unit performs charge and discharge control for the diagnostic mode in order to calculate the restraint load. Then, the diagnostic mode processing unit calculates the restraint load from the charge current integrated value, the first battery voltage, and the second battery voltage during the charge and discharge control for the diagnostic mode. The first battery voltage is the voltage when the charge and discharge of the battery pack is suspended for a first predetermined time, and the second battery voltage is the voltage when the charge and discharge of the battery pack is suspended for a second predetermined time, and is the voltage after the polarization is eliminated. Therefore, the restraint load can be calculated with high accuracy. Furthermore, when the restraint load estimated by the restraint load estimation unit becomes equal to or greater than a predetermined value and a highly accurate restraint load is required, such as for predicting the breakage of the restraint member, the diagnostic mode processing unit performs charge and discharge control for the diagnostic mode and calculates the restraint load, thereby reducing waste of power and time.

[0013] Preferably, the first battery voltage and the second battery voltage are voltages of the single cells, and the constraint load calculation unit may estimate a full charge capacity of the single cell based on the integrated charging current value, the first battery voltage, and the second battery voltage, and calculate the constraint load using the smallest value of the estimated full charge capacities.

[0014] According to this configuration, the full charge capacity of the cells is estimated, and the smallest value of the estimated full charge capacities is used to calculate the restraint load, so that the restraint load is calculated based on the state of the most deteriorated cell. The restraint load calculated for predicting breakage of the restraint member is preferably the restraint load under the most severe conditions, and this is expected to improve the accuracy of diagnosis of the battery pack.

[0015] Preferably, the diagnosis performed by the diagnostic mode processing unit is a diagnosis of a micro-short circuit in the battery pack, and the diagnostic mode processing unit may include a threshold setting unit that sets a smaller threshold value when the restraint load is large compared to when the restraint load is small, and a micro-short circuit detection unit that determines that a micro-short circuit has occurred when a parameter indicating a micro-short circuit in the battery pack is equal to or greater than the threshold value.

[0016] According to this configuration, the diagnostic mode processing unit diagnoses a micro-short circuit in the battery pack. The micro-short circuit detection unit of the diagnostic mode processing unit determines that a micro-short circuit has occurred when a parameter indicating a micro-short circuit in the battery pack is equal to or greater than a threshold value. The threshold setting unit sets a smaller threshold value when the binding load is large compared to when the binding load is small, so that the detection sensitivity of the micro-short circuit is high when the binding load is large. This makes it possible to detect a micro-short circuit with high accuracy. Furthermore, since the diagnostic mode processing unit diagnoses a micro-short circuit in a situation where the binding load estimated by the binding load estimation unit is equal to or greater than a predetermined value and a micro-short circuit is likely to occur, it is possible to diagnose a micro-short circuit in the battery pack at an appropriate time, thereby reducing the labor required for diagnosis. Effect of the Invention

[0017] According to the present disclosure, in a battery system including a battery pack, by diagnosing the battery pack at appropriate timing, it is possible to expect improvement in diagnostic accuracy while reducing the labor required for diagnosis. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a schematic configuration of a power system including a battery system according to an embodiment of the present invention. [Diagram 2] 1 is a perspective view showing a schematic structure of a battery pack according to an embodiment of the present invention; [Diagram 3] FIG. 2 is a diagram illustrating functional blocks configured in a control device in the present embodiment. [Figure 4] 4 is a flowchart showing an example of a process executed by a control device in the present embodiment. [Diagram 5] FIG. 11 is a diagram for explaining functional blocks configured in a control device in the second embodiment. [Figure 6] 11 is a flowchart showing an example of a process executed by a control device in the second embodiment. [Figure 7] FIG. 13 is a diagram showing the configuration of an electric vehicle equipped with a battery system according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments described below, the same or common parts are denoted by the same reference characters in the drawings, and the description thereof will not be repeated.

[0020] (Embodiment 1) Fig. 1 is a diagram showing a schematic configuration of a power system including a battery system according to the present embodiment. As shown in Fig. 1, the power system 1 includes a house 10, a power grid (power system) 20, a distribution transformer (pole transformer) 30, a smart meter 40, and a battery system 50.

[0021] The power grid 20 is a power system consisting of power plants, transmission lines, high-voltage substations, etc., and is a power grid managed by a power retailer or the like. The power of the power grid 20, which is stepped down to a voltage of, for example, 6.6 kV by a distribution substation, is stepped down to, for example, a single-phase three-wire 100 V / 200 V by a pole transformer 30, and is connected to a home power line 4 via a smart meter 40. The smart meter 40 is an electronic watt-hour meter with a communication function, which measures the amount of power exchanged between the power grid 20 and the house 10 during a predetermined measurement period (for example, 30 minutes), and transmits the measured amount of power to a server under the jurisdiction of the power retailer at predetermined intervals (for example, every 60 minutes).

[0022] In a house 10 connected to a power grid 20 via a smart meter 40, various electrical appliances (household loads) such as a power conditioner (PCS) 12, a photovoltaic power generation device 13, a heat pump water heater 14, a refrigerator 15, and an air conditioner (heating and cooling device) 16 are connected by using a home power line via a distribution board 11 compatible with a HEMS (Home Energy Management Service). A battery system 50 is also connected to the distribution board 11 via the home power line. This makes it possible to consume power supplied from the power grid 20, and to supply (reverse flow) power generated by the photovoltaic power generation device 13 and power discharged from the battery system 50 to the power grid 20. The power generated by the photovoltaic power generation device 13 is consumed by the home loads and stored in the battery system 50. The power discharged from the battery system 50 is also consumed by the home loads.

[0023] The house 10 is provided with a HEMS controller 60. The HEMS controller 60 is configured to be able to communicate with each electrical appliance, such as a HEMS-compatible distribution board 11, a PCS 12, a refrigerator 15, a cooling and heating device 16, and a battery system 50. The HEMS controller 60 acquires information about each electrical appliance and controls the operation of each electrical appliance.

[0024] The battery system 50 includes a battery 51, a monitoring unit 52, a charger / discharger 53, and a control device 55. The battery 51 is composed of a battery pack in which a plurality of single cells are stacked.

[0025] 2 is a perspective view showing a schematic structure of a battery pack according to the present embodiment. Battery pack 510 includes a plurality of cells (single cells) 81, a plurality of resin frames 82, a pair of end plates 83, and a pair of restraining bands 84. In battery pack 510, the cells 81 and the resin frames 82 are stacked to form a stacked body.

[0026] Each of the multiple cells 81 is a secondary battery such as a lithium ion battery or a nickel metal hydride battery. There is no particular limit to the number of cells included in the battery pack 510. Each cell 81 has a common configuration, and the stacked cells 81 are electrically connected in series.

[0027] Each of the multiple resin frames 82 is disposed between two adjacent cells 81 in the stacking direction. A pair of end plates 83 is disposed at one end and the other end of the stack in the stacking direction. The end plates 83 are disposed so as to sandwich the stack from both sides in the stacking direction.

[0028] A plurality of restraining bands (restraining members) 84 are disposed on the upper and lower surfaces of the resin frame 82. The restraining bands 84 restrain the pair of end plates 83 that sandwich the laminate between them.

[0029] The battery 51 may be a battery pack in which a plurality of assembled batteries 510 are connected in series or in parallel, or may be a battery module made up of one assembled battery 510.

[0030] 1, the monitoring unit 52 includes a voltage sensor, a current sensor, and a temperature sensor, which are not shown. The voltage sensor detects the voltage Vb of the assembled battery 510 (more specifically, the voltage of each cell 81). The current sensor detects the current Ib input to and output from the assembled battery 510. The temperature sensor detects the temperature Tb of the assembled battery 510. Each sensor outputs a signal indicating the detection result or measurement result to the control device 55.

[0031] The charger / discharger 53 charges and discharges the battery 51 (battery pack 510). The charger / discharger 53 is connected to the distribution board 11 and the PCS 12 via the in-house power line, and includes a relay that switches between connection and disconnection of the power path, and a power conversion circuit (e.g., a bidirectional converter). The charger / discharger 53 charges the battery pack 510 using power from the power grid 20 and power generated by the solar power generation device 13 (charging mode). The charger / discharger 53 supplies power to the household load or the power grid 20 by discharging the power stored in the battery pack 510 (discharging mode). The charger / discharger 53 is controlled by the control device 55.

[0032] The control device 55 is configured by, for example, an electronic control unit (ECU), and is capable of communicating with the HEMS controller 60. The control device 55 controls the charger / discharger 53 to control charging and discharging of the assembled battery 510, and also diagnoses the assembled battery 510.

[0033] 2, the battery pack 510 is restrained by restraining bands (restraining members) 84. When a cell (single cell) 81 is used for a long period of time, the electrodes expand and gas is generated in the cell 81, causing the cell 81 to expand. Furthermore, when the SOC of the cell 81 is high, the electrodes expand and the cell 81 expands. When the cell 81 expands, the restraining load of the restraining bands 84 increases, and the mechanical load (load, pressure, stress, etc.) applied to the restraining bands 84 and the cell 81 increases, which may result in, for example, the breakage of the restraining bands 84.

[0034] In this embodiment, by diagnosing the restraining load of the restraining band 84, it is possible to predict breakage of the restraining band 84, etc.

[0035] 3 is a diagram illustrating functional blocks configured in the control device 55 in this embodiment. The SOC calculation unit 55a calculates the SOC of the battery pack 510. The SOC may be calculated by a known coulomb counting method that integrates charge / discharge current, or may be calculated from SOC-OCV (Open Circuit Voltage) characteristics. Alternatively, the SOC-OCV characteristics and the coulomb counting method may be combined.

[0036] The restraint load estimation unit 55b estimates the restraint load (estimated restraint load Le) of the restraint band 84. In this embodiment, the estimation is based on the usage period of the battery pack 510. As the battery pack 510 is used and the cells (single cells) 81 deteriorate, the electrodes expand and gas is generated in the cells 81, causing the cells 81 to expand and increasing the restraint load. The relationship between the usage period of the battery pack 510 and the restraint load is obtained in advance by experiments, simulations, etc. When the battery pack 510 is new, an initial restraint load (design restraint load) is set in the restraint load estimation unit 55b. Then, the restraint load estimation unit 55b estimates the estimated restraint load Le so that the restraint load increases as the usage period of the battery pack 510 progresses.

[0037] When the estimated restraint load Le becomes equal to or greater than the predetermined value X, the diagnosis mode processing unit 55c executes diagnosis of the restraint load (restraint load Ls) of the restraint bands 84. The diagnosis mode processing unit 55c performs charge / discharge control for the diagnosis mode and calculates the restraint load Ls of the restraint bands 84.

[0038] The diagnosis mode processing unit 55c includes a first voltage acquisition unit 551, a charging current integrator 552, a second voltage acquisition unit 553, and a restraint load calculator 554. The first voltage acquisition unit 551 discharges the battery pack 510 until the SOC of the battery pack 510 becomes equal to or less than a first predetermined value α. The first predetermined value α may be, for example, 5%. The charger / discharger 53 is set to a discharge mode to discharge the battery pack 510. The power discharged from the battery pack 510 is consumed, for example, by a household load. When the SOC of the battery pack 510 drops to the first predetermined value α, the first voltage acquisition unit 551 stops discharging the battery pack 510 and suspends charging and discharging. Then, the first voltage acquisition unit 551 acquires a first battery voltage V1, which is a voltage Vb when a first predetermined time T1 has elapsed since the state in which discharging of the battery pack 510 has been suspended (a state in which charging and discharging are suspended). In this embodiment, the first battery voltage V1 is the voltage of each cell 81. The first predetermined time T1 may be, for example, one hour, and the first battery voltage V1 is the voltage Vb when polarization is eliminated.

[0039] After the first voltage acquisition unit 551 acquires the first battery voltage V1, the charging current accumulation unit 552 charges the assembled battery 510 and accumulates the current Ib (charging current) to calculate an accumulated charging current value ΣI. The charging current accumulation unit 552 sets the charger / discharger 53 to a charging mode and charges the assembled battery 510. The charging power may be power from the power grid 20, or may be power generated by the solar power generation device 13. The charging current accumulation unit 552 accumulates the current Ib output from the monitoring unit 52 to calculate the accumulated charging current value ΣI. The accumulated charging current value ΣI is a time integral value of the current Ib, and corresponds to the amount of change in the capacity [Ah] of the assembled battery 510 (cell 81).

[0040] The second voltage acquisition unit 553 stops charging and suspends charging and discharging when the SOC of the assembled battery 510 increases to a second predetermined value β by charging and the SOC becomes equal to or greater than the second predetermined value β. The second predetermined value β may be, for example, 85%. The second voltage acquisition unit 553 acquires a second battery voltage V2, which is a voltage Vb when the state in which charging of the assembled battery 510 is stopped (a state in which charging and discharging are suspended) has elapsed for a second predetermined time T2. In this embodiment, the second battery voltage V2 is a voltage for each cell 81. Note that the second predetermined time T2 may be, for example, one hour, and the second battery voltage V2 is the voltage Vb when polarization is eliminated. When charging is suspended, the charging current integration unit 552 stops integrating the current Ib (charging current).

[0041] The constraint load calculation unit 554 calculates the constraint load Ls based on the integrated current value ΣI, the first battery voltage V1, and the second battery voltage V2. In this embodiment, the full charge capacity FC of each cell 81 is estimated from the integrated current value ΣI, the first battery voltage V1, and the second battery voltage V2. Then, the constraint load Ls is calculated using the minimum value FCmin of the estimated full charge capacities FC. For example, the SOC change amount ΔS (=SOC2-SOC1) is calculated, which is the difference between SOC1, which is the SOC of the cell 81 calculated from the first battery voltage V1, and SOC2, which is the SOC of the cell 81 calculated from the second battery voltage V2. Then, the full charge capacity FC of the cell 81 is estimated as FC=ΣI / (ΔS / 100).

[0042] The restraint load calculation unit 554 estimates the full charge capacity FC for each cell 81, and calculates the restraint load Ls using the minimum value FCmin of the estimated full charge capacity FC. For example, the relationship between the full charge capacity FC and the restraint load Ls is calculated in advance by an experiment or the like, and this relationship is mapped and stored in the memory unit of the control device 55. Then, the minimum value FCmin is used to search the map to calculate the restraint load Ls.

[0043] The control device 55 may predict breakage of the restraint bands 84 using the restraint load Ls calculated by the restraint load calculation unit 554. For example, when the restraint load Ls exceeds a preset allowable value, it may determine that there is a possibility of breakage of the restraint bands 84 and turn on a Malfunction Indication Lamp (MIL), not shown.

[0044] FIG. 4 is a flowchart showing an example of processing executed by the control device 55 in this embodiment. This flowchart is repeatedly processed at predetermined intervals. In step (hereinafter, step is abbreviated as "S") 10, the estimated restraint load Le is calculated. The estimated restraint load Le is calculated by the restraint load estimating unit 55b so that the restraint load increases with the lapse of the usage period of the battery pack 510. In the following S11, it is checked whether the estimated restraint load Le is equal to or greater than a predetermined value X. If the estimated restraint load Le is less than the predetermined value X, a negative determination is made and the current routine is terminated. If the estimated restraint load Le is equal to or greater than the predetermined value X, an affirmative determination is made and the routine proceeds to S12.

[0045] In S12, battery pack 510 is discharged, and the process proceeds to S13. In S13, it is determined whether or not the SOC of battery pack 510 is equal to or lower than predetermined value α. If the SOC is greater than predetermined value α, a negative determination is made, and the process returns to S12 to continue discharging battery pack 510. When the SOC falls to predetermined value α due to discharging battery pack 510, the SOC becomes equal to or lower than predetermined value α, an affirmative determination is made in S13, and the process proceeds to S14.

[0046] In S14, discharging of battery pack 510 is stopped, charging and discharging are suspended, and then the process proceeds to S15. In S15, it is determined whether or not a first predetermined time T1 has elapsed since discharging of battery pack 510 was stopped (charging and discharging are suspended). If the first predetermined time T1 has elapsed since charging and discharging of battery pack 510 was suspended, a positive determination is made in S15 and the process proceeds to S16.

[0047] In S16, the voltage Vb is acquired as the first battery voltage V1, and the process proceeds to S17. In S17, the battery pack 510 is charged, and the current Ib is integrated to calculate an integrated charging current value ΣI.

[0048] In the next S18, it is determined whether the SOC of the battery pack 510 is equal to or greater than a predetermined value β. If the SOC is less than the predetermined value β, a negative determination is made and the process returns to S17, where the charging of the battery pack 510 continues and the calculation of the charging current integrated value ΣI continues. When the SOC increases to the predetermined value β due to the charging of the battery pack 510, the SOC becomes equal to or greater than the predetermined value β, an affirmative determination is made in S18, and the process proceeds to S19.

[0049] In S19, charging of the battery pack 510 is stopped, charging and discharging are suspended, and then the process proceeds to S20. In S20, it is determined whether or not a second predetermined time T2 has elapsed since charging of the battery pack 510 was stopped (charging and discharging are suspended). If the second predetermined time T2 has elapsed since charging and discharging of the battery pack 510 was suspended, a positive determination is made in S20 and the process proceeds to S21.

[0050] In S21, the voltage Vb is acquired as the second battery voltage V2, and the process proceeds to S22. In S22, as described above, the full charge capacity FC of each cell 81 is estimated using the charging current integrated value ΣI, the first battery voltage V1, and the second battery voltage V2.

[0051] In the next step S23, a map search is performed using the minimum value FCmin of the full charge capacity FC of each cell 81, and the restraining load Ls is calculated, after which the current routine is terminated.

[0052] According to the present embodiment, when the estimated restraint load Le estimated by the restraint load estimation unit 55b is equal to or greater than the predetermined value X, the diagnosis mode processing unit 55c executes diagnosis of the battery pack 510. Therefore, when the restraint load of the restraint bands 84 is large and there is a high possibility that various malfunctions may occur in the battery pack 510, the diagnosis of the battery pack 510 is executed, so that the diagnosis of the battery pack 510 is performed at an appropriate timing, thereby reducing the labor required for diagnosis.

[0053] According to this embodiment, the diagnosis mode processing unit 55c performs charge and discharge control for the diagnosis mode by the first voltage acquisition unit 551, the charge current integration unit 552, and the second voltage acquisition unit 553 in order to calculate the restraint load Ls. Then, the restraint load Ls is calculated from the charge current integration value ΣI, the first battery voltage V1, and the second battery voltage V2 during the charge and discharge control for the diagnosis mode. The first battery voltage V1 is the voltage when the charge and discharge of the battery pack 510 is suspended for a first predetermined time T1, and the second battery voltage V2 is the voltage when the charge and discharge of the battery pack 510 is suspended for a second predetermined time T2, and is the voltage after the polarization is eliminated. Therefore, the restraint load Ls can be calculated with high accuracy. In addition, when the estimated restraint load Le estimated by the restraint load estimation unit 55b becomes equal to or exceeds a predetermined value X and it becomes necessary to calculate the restraint load Ls with high accuracy, such as to predict breakage of the restraint band 84, the diagnosis mode processing unit 55c performs charge / discharge control for the diagnosis mode and calculates the restraint load Ls, thereby eliminating waste of power and time.

[0054] In the above embodiment, the constraint load estimation unit 55b estimates the estimated constraint load Le based on the period of use of the battery pack 510. However, the constraint load estimation unit 55b may calculate the estimated constraint load Le by the method described in the above Patent Document 1. For example, the capacity maintenance rate of the battery pack 510 is calculated by dividing a current integration value between two appropriate points when the battery pack 510 is being charged and discharged by the SOC difference between the two points. Then, the deterioration degree of the battery pack 510 is calculated from the capacity maintenance rate, and the estimated constraint load Le may be calculated from the deterioration degree, the SOC, and the temperature Tb of the battery pack 510. The constraint load estimation unit 55b may also calculate the estimated constraint load Le by using an output signal (output voltage) of a strain gauge provided in the battery pack 510.

[0055] (Embodiment 2) In the second embodiment, diagnosis mode processing unit 55c of control device 55 diagnoses a micro-short circuit in battery pack 510. The configurations of the battery system and power system in the second embodiment are similar to those of the battery system and power system in the first embodiment, and therefore, differences from the first embodiment will be described below.

[0056] 5 is a diagram illustrating functional blocks configured in the control device in the embodiment 2. The control device 55 in the embodiment 2 includes a restraint load estimation unit 55b and a diagnosis mode processing unit 55c. The restraint load estimation unit 55b is the same as that in the above embodiment 1.

[0057] When the estimated restraining load Le becomes equal to or greater than a predetermined value Y, the diagnosis mode processing unit 55c of the second embodiment executes a diagnosis of a micro short circuit of the battery pack 510. The diagnosis mode processing unit 55c includes a threshold setting unit 561, a cell voltage obtaining unit 562, a voltage difference calculating unit 563, and a micro short circuit detecting unit 564.

[0058] The threshold setting unit 561 uses the estimated restraint load Le estimated by the restraint load estimation unit 55b to set the threshold S. The threshold S is set to a smaller value as the estimated restraint load Le is larger.

[0059] The cell voltage acquisition unit 562 acquires the voltage of each cell 81 (cell voltage) by using the voltage Vb output from the monitoring unit 52. The cell voltage acquisition unit 562 acquires the voltage of each cell 81 from the voltage Vb when the battery pack 510 is being charged, for example.

[0060] The voltage difference calculation unit 563 calculates a voltage difference ΔVb, which is the difference between the maximum value and the minimum value of the voltage of each cell 81 acquired by the cell voltage acquisition unit 562 .

[0061] The micro short circuit detection unit 564 detects a micro short circuit in the battery pack 510 (cell 81) by comparing the voltage difference ΔVb with the threshold value S. When the voltage difference ΔVb is equal to or greater than the threshold value S (ΔVb≧S), the micro short circuit detection unit 564 determines that a micro short circuit has occurred and detects a micro short circuit. A micro short circuit may be a micro short circuit between terminals of the cell 81 (within the circuit of the battery pack 510) or a micro short circuit inside the cell 81. When the micro short circuit detection unit 564 detects a micro short circuit in the battery pack 510, the diagnosis mode processing unit 55c turns on the MIL 57.

[0062] FIG. 6 is a flowchart showing an example of the processing executed by the control device 55 in Embodiment 2. This flowchart is repeatedly processed at predetermined intervals. In S40, an estimated restraint load Le is calculated. The estimated restraint load Le is calculated by the restraint load estimation unit 55b so that the restraint load increases as the usage period of the assembled battery 510 elapses. In the subsequent S41, it is determined whether or not the estimated restraint load Le is equal to or greater than a predetermined value Y. If the estimated restraint load Le is less than the predetermined value Y, a negative determination is made and the current routine ends. If the estimated restraint load Le is equal to or greater than the predetermined value Y, an affirmative determination is made and the process proceeds to S42.

[0063] In S42, a threshold value S is set. The threshold value S is set to a smaller value as the estimated restraint load Le is larger. When the threshold value S is set, the process proceeds to S43, and it is determined whether or not the assembled battery 510 is being charged. If the assembled battery 510 is not being charged, the process waits until the assembled battery 510 starts charging. When the assembled battery 510 starts charging, an affirmative determination is made in S43 and the process proceeds to S44.

[0064] In S44, the voltage (cell voltage) of each cell 81 is acquired using the voltage Vb output from the monitoring unit 52. Note that the voltage of the cell 81 is acquired during charging of the assembled battery 510 because CC (Constant Current) charging or CCCV (Constant Current, Constant Voltage) charging is performed during charging of the assembled battery 510, and the voltage of the cell 81 does not change suddenly.

[0065] In the subsequent S45, after calculating a voltage difference ΔVb, which is the difference between the maximum value and the minimum value of the voltages of the cells 81 acquired in S44, the process proceeds to S46. In S46, it is determined whether or not the voltage difference ΔVb is equal to or greater than the threshold value S. When the voltage difference ΔVb is smaller than the threshold value S (ΔVb < S), a negative determination is made in S46 and the current routine ends. When the voltage difference ΔVb is equal to or greater than the threshold value S (ΔVb ≧ S), it is determined that a micro short circuit has occurred in the assembled battery 510. The process then proceeds to S47, where the MIL is turned on and the current routine ends.

[0066] According to the second embodiment, when the estimated restraint load Le estimated by the restraint load estimation unit 55b is equal to or greater than the predetermined value Y, the diagnosis mode processing unit 55c executes diagnosis of the battery pack 510. Therefore, when the restraint load of the restraint bands 84 is large and there is a high possibility that various malfunctions will occur in the battery pack 510, the diagnosis of the battery pack 510 is executed, so that the diagnosis of the battery pack 510 is performed at an appropriate timing, thereby reducing the labor required for diagnosis.

[0067] According to the second embodiment, the diagnostic mode processing unit 55c executes a diagnosis of a micro-short circuit of the battery pack 510. The micro-short circuit detection unit 564 of the diagnostic mode processing unit 55c determines that a micro-short circuit has occurred when a parameter indicating a micro-short circuit of the battery pack 510 (the voltage difference ΔVb calculated by the voltage difference calculation unit 563) is equal to or greater than the threshold value S. The threshold value setting unit 561 sets the threshold value S to a smaller value as the estimated restraint load Le increases, so that the threshold value S becomes smaller when the estimated restraint load Le is large than when the estimated restraint load Le is small. Therefore, when the restraint load of the restraint band 84 is large, the detection sensitivity of a micro-short circuit is increased, and a micro-short circuit can be detected with high accuracy. In addition, when the estimated restraint load Le estimated by the restraint load estimation unit 55b becomes equal to or greater than the predetermined value Y and a micro-short circuit is likely to occur, the diagnostic mode processing unit 55c diagnoses a micro-short circuit. Therefore, the diagnosis of a micro-short circuit of the battery pack 510 can be performed at an appropriate timing, and the labor required for diagnosis can be reduced.

[0068] In this second embodiment, the voltage difference ΔVb is used to detect a micro-short circuit. However, it is also possible to monitor the voltage drop of the cells 81 when the battery pack 510 is not charging or discharging, and determine that a micro-short circuit has occurred if there is a cell 81 whose voltage drop is equal to or greater than a threshold. It is also possible to calculate the resistance value of each cell 81 from the current and voltage when the battery pack 510 is charging or discharging, and determine that a micro-short circuit has occurred if there is a cell 81 whose resistance value is equal to or greater than a threshold.

[0069] In this second embodiment, detection (diagnosis) of a micro-short circuit in the battery pack 510 is performed when the estimated constraint load Le is equal to or greater than a predetermined value Y. However, a micro-short circuit in the battery pack 510 may be detected when the estimated constraint load Le is smaller than the predetermined value Y. In this case, the magnitude of the threshold value to be compared with the voltage difference ΔVb is set to a value that is a certain amount larger than the maximum value of the threshold value S set by the threshold setting unit 561 to detect a micro-short circuit in the battery pack 510. This makes it possible to appropriately set the detection sensitivity of a micro-short circuit and suppress erroneous detection.

[0070] The control device 55 may perform the diagnosis of the restraint load in the first embodiment and the diagnosis of a micro-short circuit in the second embodiment. In this case, the predetermined value Y may be set to be greater than the predetermined value X. According to this configuration, the threshold value setting unit 561 can set the threshold value S using the restraint load Ls calculated by the restraint load calculation unit 554 (FIG. 3: first embodiment), and it becomes possible to set the threshold value S based on the restraint load with high accuracy.

[0071] (Modification) In each of the above embodiments, the battery system 50 (battery assembly 510) is a stationary battery installed in the house 10. However, the battery system (battery assembly) may be mounted on a vehicle.

[0072] 7 is a diagram showing a schematic configuration of an electric vehicle equipped with a battery system according to a modified example. In this modified example, an example will be described in which the electric vehicle 100 is an electric vehicle (BEV: Battery Electric Vehicle), but the electric vehicle 100 is not limited to being a BEV and may be, for example, a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle) or an externally chargeable fuel cell electric vehicle (FCEV: Fuel Cell Electric Vehicle).

[0073] The electric vehicle 100 includes a battery pack 101 , a boost converter 102 , an inverter 103 , a motor generator 104 , a transmission gear 105 , driving wheels 106 , and a control device 200 .

[0074] The battery pack 101 is mounted on the electric vehicle 100 as a driving power source (i.e., a power source) of the electric vehicle 100. The battery pack 101 is a battery pack in which assembled batteries similar to the assembled battery 510 in the above embodiment are connected in series or in parallel. A monitoring unit 107 is disposed in the battery pack 101, and detects the voltage Vb of the assembled battery (the voltage of each cell), the current Ib input / output to / from the assembled battery, and the temperature Tb.

[0075] The battery pack 101 is connected to a boost converter 102 via system main relays 108a and 108b. The boost converter 102 is connected to an inverter 103, and the inverter 103 converts the DC power from the boost converter 102 into AC power.

[0076] The motor generator (three-phase AC motor) 104 receives AC power from the inverter 103 and generates kinetic energy for propelling the electric vehicle 100. The kinetic energy generated by the motor generator 104 is transmitted to drive wheels 106. On the other hand, when the electric vehicle 100 is to be decelerated or stopped, the motor generator 104 converts the kinetic energy of the electric vehicle 100 into electrical energy. The AC power generated by the motor generator 104 is converted into DC power by the inverter 103 and supplied to the battery pack 101 via the boost converter 102. This allows regenerative power to be stored in the battery pack 101.

[0077] The electric vehicle 100 is configured to have an external charging function for charging the battery pack 101 with an external power source 90. The electric vehicle 100 includes a charger 109 and charging relays 110a and 110b. The external power source 90 is a power source provided outside the vehicle, and an example of the external power source 90 is a commercial power source. The charger 109 converts power from the external power source 90 into charging power for the battery pack 101. The charger 109 is connected to the battery pack 101 via the charging relays 110a and 110b. When the charging relays 110a and 110b are on, the battery pack 101 can be charged with power from the external power source 90.

[0078] The battery pack 101 is connected to an auxiliary battery 112 and an auxiliary load 113 via a DC / DC converter 111. The power stored in the battery pack 101 is stepped down by the DC / DC converter 111 to charge the auxiliary battery 112 and drive the auxiliary load 113.

[0079] The control device 200 includes a battery ECU 201 and a vehicle ECU 202. Either the battery ECU 201 or the vehicle ECU 202 includes functional blocks similar to those included in the control device 55 of the above embodiment. For example, the SOC calculation unit 55a and the restraint load estimation unit 55b may be included in the battery ECU 201, and the diagnosis mode processing unit 55c may be included in the vehicle ECU 202.

[0080] In the modified example, when the estimated restraining load Le estimated by the restraining load estimation unit 55b configured in the control device 200 is equal to or greater than the predetermined value X, the diagnosis mode processing unit 55c configured in the control device 200 diagnoses the restraining load Ls of the restraining member (restraining band). In this case, it is preferable that the processing from S12 (FIG. 4) onwards is executed when the electric vehicle 100 is stopped (parked). For example, when the electric vehicle 100 is stopped (parked) and the external power supply 90 is connected, charging is performed to the auxiliary battery 112 and discharging is performed by driving the auxiliary load 113, and the processing from S12 to S16 is executed. Thereafter, charging is performed by the external power supply 90, and the processing from S17 to S23 is executed. Note that a charger / discharger may be provided instead of the charger 109, and power supply (discharge) to the outside of the electric vehicle 100 is enabled, discharging is performed by the external power supply, and the processing from S12 to S16 may be executed.

[0081] In the modified example, when the estimated restraint load Le estimated by the restraint load estimation unit 55b configured in the control device 200 is equal to or greater than a predetermined value Y, a diagnosis mode processing unit 55c configured in the control device 200 diagnoses a micro-short circuit in the battery pack. In this case, the processing from S42 (FIG. 6) onwards is preferably executed when external charging is being performed by the external power supply 90. This is because, although there is a possibility that the voltage fluctuation of the battery pack 101 (battery pack) will be large when charging while the electric vehicle 100 is traveling (for example, when charging using regenerative power), external charging of the electric vehicle 100 is performed by CC charging or CCCV charging, and the voltage of the battery pack does not change suddenly.

[0082] The embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, and includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0083] 1 Power system, 4 In-house power line, 10 House, 11 Distribution board, 12 Power conditioner, 13 Photovoltaic power generation device, 14 Heat pump water heater, 15 Refrigerator, 16 Air conditioner, 20 Power grid, 30 Pole transformer, 40 Smart meter, 50 Battery system, 51 Battery, 52 Monitoring unit, 53 Charger / discharger, 55 Control device, 55a SOC calculation unit, 55b Constraint load estimation unit, 55c Diagnostic mode processing unit, 60 HEMS controller, 57 MIL, 81 Cell (single cell), 82 Resin frame, 83 End plate, 84 Constraint band, 90 External power source, 100 Electric vehicle, 101 Battery pack, 102 Boost converter, 103 Inverter, 104 Motor generator, 105 Transmission gear, 106 Drive wheel, 107 Monitoring unit, 108a, 108b system main relay, 109 charger, 110a, 110b charging relay, 111 DC / DC converter, 112 auxiliary battery, 113 auxiliary load, 200 control device, 201 battery ECU, 202 vehicle ECU, 510 assembled battery, 551 first voltage acquisition unit, 552 charging current integration unit, 553 second voltage acquisition unit, 554 restraint load calculation unit, 561 threshold setting unit, 562 cell voltage acquisition unit, 563 voltage difference calculation unit, 564 micro-short circuit detection unit.

Claims

1. A battery pack in which a plurality of stacked single cells are restrained by a restraining member; A control device for controlling the battery pack, The control device includes: a restraint load estimation unit that estimates a restraint load caused by the restraint member; a diagnosis mode processing unit that executes a diagnosis of the battery pack when the restraint load estimated by the restraint load estimation unit is equal to or greater than a predetermined value, the diagnosis executed by the diagnosis mode processing unit is a diagnosis of the restraining load, The diagnostic mode processing unit: a first voltage acquisition unit that executes discharging of the battery pack so that an SOC of the battery pack becomes equal to or less than a first predetermined value, and acquires a first battery voltage that is a voltage when charging and discharging of the battery pack is suspended for a first predetermined time in a state in which the SOC is equal to or less than the first predetermined value; a charging current integrating unit that, after acquiring the first battery voltage, charges the battery pack and integrates a charging current; a second voltage acquisition unit that stops the charging when the SOC becomes equal to or greater than a second predetermined value and acquires a second battery voltage that is a voltage when charging and discharging of the battery pack is suspended for a second predetermined time; a restraint load calculation unit that calculates the restraint load based on the charging current integrated value calculated by the charging current integration unit, the first battery voltage, and the second battery voltage.

2. the first battery voltage and the second battery voltage are voltages of the single cells, 2. The battery system according to claim 1, wherein the restraint load calculation unit estimates a full charge capacity of the single battery based on the charging current integrated value, the first battery voltage, and the second battery voltage, and calculates the restraint load using the smallest value among the estimated full charge capacities.

3. A battery pack in which a plurality of stacked single cells are restrained by a restraining member; A control device for controlling the battery pack, The control device includes: a restraint load estimation unit that estimates a restraint load caused by the restraint member; a diagnosis mode processing unit that executes a diagnosis of the battery pack when the restraint load estimated by the restraint load estimation unit is equal to or greater than a predetermined value, the diagnosis executed by the diagnosis mode processing unit is a diagnosis of a micro-short circuit of the battery pack, The diagnostic mode processing unit: a threshold setting unit that sets a smaller threshold when the restraint load is large compared to when the restraint load is small; a micro-short circuit detection unit that determines that the micro-short circuit has occurred when a parameter indicating a micro-short circuit of the battery pack is equal to or greater than the threshold value.

4. The battery system according to claim 3 , wherein the parameter indicative of a micro-short circuit in the battery pack is a voltage difference between the cells.

Images