Control device of secondary battery

Abstract

To suppress deterioration of a secondary battery.SOLUTION: A control device 1 for a secondary battery 9 includes a status sensor 120 that detects at least one of the SOC and temperature of the secondary battery 9, and a controller 100 that determines whether a first condition is met, which is met when at least one of the SOC and temperature is continuously above a predetermined level, on the basis of the detection signal of the status sensor 120, and controls the charge / discharge current of the secondary battery 9 on the basis of the determination result. The controller 100 determines whether the first condition is met when the power supply to the drive source 3 is cut off, and when it is determined that the first condition is met, limits the magnitude of the charge / discharge current compared to when the first condition is not met.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a control device for a secondary battery. [Background technology]

[0002] For example, Patent Document 1 discloses a battery module that can be applied to electric vehicles (EVs), hybrid electric vehicles (HEVs), and the like.

[0003] Specifically, the battery module of Patent Document 1 includes a cell assembly, an upper plate, a lower plate, and a pair of side plates. Here, the cell assembly is composed of a plurality of pouch-type battery cells stacked in one direction. The upper and lower plates cover the upper and lower ends of the cell assembly, respectively. The pair of side plates are press-fitted or fitted into both ends of the upper and lower plates.

[0004] According to Patent Document 1, the provision of the side plates as described above forms a gas collection space. The gas collection space allows gas generated by decomposition of the internal electrolyte due to repeated charging and discharging to be collected. This prevents a sudden increase in pressure in the battery module and, ultimately, the resulting deformation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2020-517080 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, when a secondary battery for a vehicle is left outdoors or the like, there is a possibility that gas such as that described in Patent Document 1 may accumulate in the battery cells that make up the secondary battery. It is believed that such gas generation becomes more pronounced under conditions such as high temperatures and high SOC.

[0007] When gas accumulates inside a battery cell, it can interfere with the chemical reaction in each battery cell, reducing the reaction area of ​​each battery cell and potentially increasing its internal resistance, which can be detrimental from various perspectives, such as battery capacity.

[0008] The present disclosure has been made in view of the above points, and an object thereof is to suppress the deterioration of secondary batteries. [Means for solving the problem]

[0009] A first aspect of the present disclosure relates to a control device for a secondary battery that includes a plurality of battery cells and supplies power from the plurality of battery cells to a drive source of a vehicle. The control device includes a status sensor that detects at least one of a state of charge (SOC) and a temperature of the secondary battery, and a controller that determines whether a first condition is met based on a detection signal from the status sensor, the first condition being met when at least one of the SOC and the temperature is continuously equal to or higher than a predetermined value, and controls a charge / discharge current of the secondary battery based on the determination result. When power supply to the drive source is cut off, the controller determines whether the first condition is met, and if it is determined that the first condition is met, limits the magnitude of the charge / discharge current compared to when the first condition is not met.

[0010] The term "charge / discharge current" refers to at least one of a charge current and a discharge current.

[0011] The inventors attempted to release the gas accumulated in the battery cells to the outside through the electrodes of each battery cell by expanding and contracting each battery cell during charging and discharging. However, depending on the setting of the so-called "C rate," this can lead to electrodeposition of Li and other elements, which is inconvenient. In other words, it would be advantageous to have a mechanism for releasing gas from the battery cells without causing deposition.

[0012] In response to this, the inventors of the present invention have devised a method for limiting high-rate charging and discharging when the first condition, which indicates gas generation, is satisfied, as in the first aspect. This allows gas to be discharged from the battery cell without causing precipitation. As a result, it is possible to suppress deterioration of the secondary battery.

[0013] Furthermore, according to a second aspect of the present disclosure, the first condition is not satisfied when the internal resistance value of the secondary battery decreases continuously, and when the limitation on the magnitude of the charging / discharging current is initiated, the controller acquires the internal resistance value of the secondary battery after starting the driving source, updates the determination of the first condition based on the acquired internal resistance value, and if the first condition is not satisfied after the update, releases the limitation on the magnitude of the charging / discharging current.

[0014] When gas accumulates in a battery cell, the gas inhibits chemical reactions, which is thought to increase the internal resistance of the secondary battery. In other words, when gas is released from each battery cell, the internal resistance is thought to decrease. If the internal resistance continues to decrease, it is thought that there is no longer any need to limit the magnitude of the charge / discharge current.

[0015] Therefore, according to the second aspect, after starting the power source using electric power, the controller monitors the change in the internal resistance value and re-evaluates the first condition based on the change in the internal resistance value over time. This makes it possible to shorten the period during which the magnitude of the charge / discharge current is limited as much as possible. This makes it possible to both suppress deterioration of the secondary battery and shorten the charging period of the secondary battery.

[0016] Furthermore, according to a third aspect of the present disclosure, the drive source may be a motor capable of performing both powering operation and regenerative operation, and the controller may limit the magnitude of the charge / discharge current by limiting the regenerative current generated in association with the regenerative operation to a predetermined upper limit or less.

[0017] According to the third aspect, the controller limits the magnitude of the charge / discharge current (particularly the charge current) from a perspective different from that of power supply from the power supply facility to the vehicle, thereby suppressing deterioration of the secondary battery without interfering with the power supply from the outside.

[0018] Furthermore, according to a fourth aspect of the present disclosure, the vehicle may be capable of being powered at least by rapid charging, in which the secondary battery is charged by receiving a power supply of a predetermined power or more from a power supply facility, and normal charging, in which the secondary battery is charged by receiving a power supply of less than the predetermined power from a power supply facility, and the controller may limit the magnitude of the charge / discharge current by limiting the power supply by the rapid charging.

[0019] According to the fourth aspect, the controller limits the magnitude of the charging current (particularly the charging current) by limiting the rapid charging, thereby making it possible to suppress deterioration of the secondary battery while allowing normal charging.

[0020] Furthermore, according to a fifth aspect of the present disclosure, the control device may include a notification unit electrically connected to the controller and configured to notify an occupant of the vehicle of information, and the notification unit may determine whether there are signs that the first condition will be met based on the detection signal of the status sensor, and if it is determined that there are signs, notify the occupant of information indicating that the first condition is about to be met.

[0021] According to the fifth aspect, the occupant is notified of a warning before the magnitude of the charge / discharge current is actually limited due to the first condition being met. This reduces the frequency with which the magnitude of the charge / discharge current is limited, improving the usability of the vehicle. At the same time, by guiding the occupant to prevent the first condition from being met, it is also advantageous in preventing deterioration of the secondary battery.

[0022] Furthermore, according to a sixth aspect of the present disclosure, the plurality of battery cells each have a plate shape and are arranged in a line in the fore-and-aft direction of the vehicle while being constrained from both the front and back sides of the plate shape, the plurality of battery cells are arranged so that their longitudinal direction is along the vehicle width direction, their short side is along the vehicle height direction, and their thickness direction is along the fore-and-aft direction of the vehicle, the longitudinal dimension of each of the plurality of battery cells exceeds 50% of the width of the vehicle, and tabs corresponding to the positive and negative electrodes of the battery cell are arranged at both ends of each of the plurality of battery cells in the longitudinal direction.

[0023] Generally, gas accumulated inside a battery cell is released to the outside of the cell through tabs due to the restraining forces acting on both the front and back sides of each battery cell. However, in the case of a battery with a high aspect ratio, such as the sixth embodiment, the restraining force acting per unit area is weaker due to the increased surface area of ​​the front and back sides. On the other hand, while tabs are usually provided on both ends of a battery cell, the size of the tabs is not necessarily as large as the surface area of ​​each battery cell.

[0024] The weaker binding force per unit area, combined with the fact that the size of each tab is not significantly larger, makes it more difficult for gas that accumulates inside the battery cell to be released to the outside of the cell.

[0025] The first aspect is particularly effective for such high aspect ratio battery cells. [Effects of the Invention]

[0026] As described above, according to the present disclosure, deterioration of a secondary battery can be suppressed. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram illustrating a vehicle. [Figure 2] FIG. 2 is a perspective view illustrating the configuration of a secondary battery mounted on a vehicle. [Figure 3A] FIG. 3A is a perspective view illustrating the configuration of a battery cell. [Figure 3B] FIG. 3B is a cross-sectional view illustrating the configuration of a battery cell. [Figure 4] FIG. 4 is a block diagram illustrating the configuration of a control device for a secondary battery. [Figure 5] FIG. 5 is a functional block diagram illustrating the configuration of a control device for a secondary battery. [Figure 6] FIG. 6 is a diagram for explaining whether the second condition is met. [Figure 7] FIG. 7 is a diagram for explaining the transition of the evaluation value. [Figure 8] FIG. 8 is a flowchart illustrating a process related to low rate control. [Figure 9] FIG. 9 is a flowchart illustrating a process related to low rate control. [Figure 10] FIG. 10 is a diagram for explaining the relationship between the aspect ratio of a secondary battery and the amount of gas generated. [Figure 11] FIG. 11 is a diagram for explaining the relationship between the execution time of the low rate control and the amount of gas generated. [Figure 12] FIG. 12 is a diagram for explaining the relationship between the execution time of the low rate control and the transition of the internal resistance value. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following description is for illustrative purposes only.

[0029] <1. Overall structure> FIG. 1 is a schematic diagram illustrating a vehicle V. FIG. 2 is an exploded view illustrating the configuration of a secondary battery 9 mounted on the vehicle V. The vehicle V shown in each figure is equipped with a control device 1 for the secondary battery 9 according to this embodiment. The vehicle V is an automobile that can run using electric power.

[0030] Specifically, the vehicle V according to this embodiment is a so-called electric vehicle (EV). The vehicle V may also be a hybrid vehicle that uses electric power as a main energy source, such as a plug-in hybrid electric vehicle (PHEV).

[0031] Hereinafter, the fore-and-aft direction based on the body of the vehicle V will be referred to as the "vehicle fore-and-aft direction" or simply as the "fore-and-aft direction." As illustrated in Figures 1 and 2, "fore" here refers to the direction in which the vehicle V moves forward, and "rear" here refers to the direction in which the vehicle V moves backward.

[0032] Similarly, the left-right direction based on the body of the vehicle V is referred to as the "vehicle width direction" or simply the "left-right direction." As illustrated in Figures 1 and 2, "right" here refers to the right side as seen by an occupant of the vehicle V, and "left" here refers to the left side as seen by the occupant.

[0033] Similarly, the up-down direction based on the body of vehicle V is referred to as the "vehicle height direction" or simply the "up-down direction." As illustrated in FIG. 2, "up" here refers to a direction seen from the perspective of an occupant of vehicle V, which is perpendicular to the road surface of vehicle V and moves away from the road surface. On the other hand, "down" here refers to a direction seen from the perspective of an occupant of vehicle V, which is perpendicular to the road surface of vehicle V and moves closer to the road surface.

[0034] The secondary battery 9 in this embodiment is configured as a battery system including a plurality of battery cells 91. The control device 1 for the secondary battery 9 in this embodiment is a device that supplies power from the plurality of battery cells 91 to the drive source 3 of the vehicle V. In other words, this control device 1 can be referred to as a control device / control system that supplies power to the drive source 3 of the vehicle V, causing the drive source 3 to generate driving force for running the vehicle V.

[0035] Specifically, the vehicle V according to this embodiment includes a plurality of wheels 2, a motor 31 constituting a drive source 3, an inverter 5, a converter 6, a charging port 7, an on-board charger 8, a secondary battery 9, and a controller 100. All of these elements are mounted or disposed on the vehicle V.

[0036] The plurality of wheels 2 is composed of two front wheels 2F and two rear wheels 2R. That is, the vehicle V according to this embodiment is a four-wheeled vehicle. A drive source 3 is connected to all or some of the plurality of wheels 2 via a shaft or the like.

[0037] The drive source 3 is configured by a motor 31 capable of both power running and regenerative operations. The motor 31 is, for example, a permanent magnet synchronous motor driven by three-phase AC.

[0038] During power running, the motor 31 receives power from the secondary battery 9 and rotates. This rotation generates a driving force for the vehicle V to travel. When the motor 31 rotates during power running, the rotation is transmitted via a shaft (not shown). The rotation transmitted via the shaft rotates at least some of the wheels 2, such as the two front wheels 2F. The rotation of at least some of the wheels 2 causes the vehicle V to travel.

[0039] The motor 31 not only functions as a drive source in power running mode, but can also function as a generator in regenerative mode. The motor 31 is electrically connected to the secondary battery 9 via the inverter 5 and the converter 6. This connection is used in both power running mode and regenerative mode, as will be described in detail below.

[0040] During powering operation, the converter 6 steps down the high-voltage DC power supplied from the secondary battery 9 to DC power having a predetermined base voltage. The converter 6 inputs the stepped-down DC power to the inverter 5. The inverter 5 converts the DC power supplied from the secondary battery 9 via the converter 6 into three-phase AC having mutually different phases. The inverter 5 supplies the converted AC to the motor 31. Supplying the AC to the motor 31 causes the motor 31 to rotate as described above.

[0041] During regenerative operation, inverter 5 converts AC power generated by the rotation of motor 31 into DC power. Inverter 5 inputs the converted DC power to converter 6. Converter 6 boosts the DC power input from motor 31 via inverter 5. Converter 6 charges secondary battery 9 with the boosted DC power.

[0042] The secondary battery 9 includes one or more (multiple in this embodiment) battery modules 90. As shown in Figures 1 and 2, each battery module 90 is made up of a plurality of battery cells 91 described above.

[0043] For example, the secondary battery 9 according to this embodiment includes a first module 90A, a second module 90B, and a third module 90C as each of the plurality of battery modules 90.

[0044] Here, the multiple battery modules 90 according to this embodiment are arranged in the front-to-rear direction as shown in Fig. 1. Each battery module 90 arranged in the front-to-rear direction has a dimension in the vehicle width direction (longitudinal direction) that is, for example, three times or more larger than the dimension in the vehicle height direction (short direction). The dimension of each battery module 90 in the vehicle width direction is set to be 70% or more of the vehicle width Lw of the vehicle V.

[0045] Furthermore, the plurality of battery modules 90 are connected in parallel to one motor 31, for example. Each of the plurality of battery modules 90 may be connected to the motor 31 via the converter 6 individually.

[0046] Each battery module 90 is connected to a charging port 7 via an on-board charger 8. The charging port 7 can also be referred to as a charging inlet.

[0047] The vehicle V is configured to be able to receive power by at least rapid charging out of rapid charging and normal charging. In particular, the vehicle V according to this embodiment is configured to be able to receive power by both rapid charging and normal charging.

[0048] Here, quick charging is a charging standard in which the secondary battery 9 is charged by receiving a power supply of a predetermined power or more from a power supply facility. Quick charging includes CHAdeMO (registered trademark), CCS1, CCS2, GB / T, and Supercharger (TPC). The "predetermined power" here may be, for example, 10 kW. Charging with a C rate of 1.0 or more may also be classified as "quick charging" in this embodiment.

[0049] On the other hand, normal charging is a charging standard in which the secondary battery 9 is charged by receiving a power supply of less than a predetermined power from the power supply equipment. Normal charging includes J1772 (Type 1), J1772 (Type 2), and Mennekes (registered trademark). Charging with a C rate of less than 1.0 may also be classified as "normal charging" in this embodiment.

[0050] Although details are omitted, one or two charging ports 7 are provided for each vehicle V, and a connector of a power supply facility can be connected to each charging port 7. This connection allows power to be supplied from the power supply facility to the vehicle V via the charging port 7.

[0051] For example, when the power supplied to the vehicle V is AC, the power is converted to DC by the on-board charger 8 and then supplied to each battery module 90 of the secondary battery 9.

[0052] Furthermore, when the power supplied to the vehicle V is DC, the power is supplied to each battery module 90 of the secondary battery 9 without being converted at least between AC and DC.

[0053] The on-board charger 8 according to this embodiment is configured to limit power supply by rapid charging based on a control signal from the controller 100, which will be described later. The on-board charger 8 restricts power supply by prohibiting or cutting off power supply by rapid charging, or by reducing the magnitude of the current (charging current) that flows during power supply.

[0054] <3. Details of secondary batteries> Fig. 3A is a perspective view illustrating the configuration of a battery cell 91. Fig. 3B is a cross-sectional view illustrating the configuration of a battery cell 91. The cross section of Fig. 3B corresponds to a cross section along the front-rear and up-down directions.

[0055] 2, each battery module 90 is made up of a plurality of battery cells 91 each having a plate shape. The battery cells 91 are arranged in the front-rear direction and housed in a box-shaped module container 90a.

[0056] Specifically, in each battery module 90, the multiple battery cells 91 are arranged so that their longitudinal direction is aligned with the vehicle width direction, their lateral direction is aligned with the vehicle height direction, and their thickness direction is aligned with the vehicle front-rear direction. By arranging them in this manner, it is possible to make the dimension of each battery module 90 in the vehicle height direction as short as possible, while increasing the dimension in the vehicle width direction (longitudinal direction).

[0057] Furthermore, an external force acts on the multiple battery cells 91 housed in each module container 90a by the module container 90a or a separate member independent of the module container 90a, restraining them in the front-to-rear direction (see the black arrows in Figure 3B).

[0058] As shown in FIG. 3A, the longitudinal dimension La of each of the multiple battery cells 91 is longer than the lateral dimension Lb. In this embodiment, the longitudinal dimension La is three or more times the lateral dimension Lb. Each battery cell 91 is a high aspect ratio battery cell. Each battery cell 91 can be called a blade battery or blade cell.

[0059] Specifically, as shown in Fig. 1, the longitudinal dimension La of each of the multiple battery cells 91 exceeds 50% of the vehicle width Lw of the vehicle V. In other words, the multiple battery cells 91 extend so long in the vehicle width direction that they cannot be adjacent to each other in the vehicle width direction. The longitudinal dimension La of each of the multiple battery cells 91 preferably exceeds 70% of the vehicle width Lw.

[0060] Furthermore, tabs 91A and 91B corresponding to the positive and negative electrodes of each of the battery cells 91 are disposed at both ends in the longitudinal direction of each of the battery cells 91.

[0061] More specifically, each battery cell 91 is constructed by alternately stacking negative electrode sheets 92 and positive electrode sheets 93. The alternately stacked negative electrode sheets 92 and positive electrode sheets 93 are housed in a cell container 94 shown in Fig. 3A. Each battery cell 91 is a so-called lithium ion battery that utilizes the movement of lithium ions between the electrodes.

[0062] 3B, the negative electrode sheet 92 includes a current collector 92a, an active material 92b, and a separator 92c. The current collector 92a and the active material 92b form a so-called "negative electrode." The negative electrode sheet 92 extends longitudinally in the vehicle width direction.

[0063] The current collector 92a is a thin plate extending in a direction perpendicular to the stacking direction. One of both ends of the current collector 92a protrudes outside the cell container 94, for example, through an opening located on one longitudinal side of the cell container 94. This protruding portion forms the negative electrode tab 91A.

[0064] The active material 92b is applied to the surface of the current collector 92a. The negative electrode formed by the active material 92b and the current collector 92a faces the positive electrode sheet 93 with, for example, a separator 92c sandwiched therebetween.

[0065] 3B, the positive electrode sheet 93 includes a current collector 93a and an active material 93b. The current collector 93a and the active material 93b form a so-called "positive electrode." The positive electrode sheet 93 extends in the vehicle width direction.

[0066] The current collector 93a is a thin plate extending in a direction perpendicular to the stacking direction. One of both ends of the current collector 93a protrudes outside the cell container 94, for example, through an opening located on the other longitudinal side of the cell container 94. This protruding portion forms the positive electrode tab 91B.

[0067] The active material 93b is applied to the surface of the current collector 93a. The positive electrode formed by the active material 93b and the current collector 93a faces the active material 92b and the current collector 92a of the negative electrode sheet 92, for example, with a separator 92c sandwiched therebetween.

[0068] The cell container 94 also contains an electrolyte 95. Lithium ions move between the electrodes via this electrolyte 95. When an external current is applied to the battery cell 91, the lithium ions move to the negative electrode side. The movement of the lithium ions creates a potential difference between the negative electrode and the positive electrode. The creation of a potential difference by the external power supply is equivalent to the battery cell 91 being charged.

[0069] Furthermore, the migration of lithium ions from the negative electrode to the positive electrode eliminates the aforementioned potential difference. At that time, a current flows from the battery cell 91 to the outside. Eliminating the potential difference by supplying power to the outside is equivalent to discharging the battery cell 91.

[0070] <2. Control device configuration> 4 is a block diagram illustrating the configuration of a control device 1 for a secondary battery 9. The control device 1 includes switches such as an IG switch 111, status sensors 120 such as an SOC sensor 121, a notification unit 130, and a controller 100.

[0071] The IG switch 111 is a switch for energizing the drive source 3 of the vehicle V. The IG switch 111 is electrically connected to the controller 100. When the IG switch 111 is operated, an electrical signal for switching the operation mode of the vehicle V between "IG-ON" and "IG-OFF" is input to the controller 100. The IG switch 111 can also be called a power switch or an ignition switch.

[0072] "IG-OFF" is a mode used when the vehicle V is not running (particularly when the power supply to the driving source 3 is cut off), such as when the vehicle is parked or left unattended. In this mode, charging and discharging of the secondary battery 9 is restricted. In other words, in this mode, the secondary battery 9 and the driving source 3 are electrically disconnected (electrical connection is cut off). As a result, the power supply from the secondary battery 9 to the driving source 3 and the power supply from the driving source 3 to the secondary battery 9 are both cut off.

[0073] "IG-ON" is a mode that is mainly used when the vehicle V is running (especially when power is turned on to the driving source 3). In this mode, charging and discharging of the secondary battery 9 is permitted. In other words, in this mode, the secondary battery 9 and the driving source 3 are energized (electrically connected). As a result, power supply from the secondary battery 9 to the driving source 3 and power supply from the driving source 3 to the secondary battery 9 are both permitted.

[0074] The status sensor 120 is configured to detect at least one of the SOC (State Of Charge) and temperature of the secondary battery 9. The status sensor 120 is electrically connected to the controller 100. A detection signal from the status sensor 120 is input to the controller 100. In particular, in this embodiment, the status sensor 120 is configured to detect both the SOC and temperature of the secondary battery 9 individually.

[0075] More specifically, the status sensor 120 according to this embodiment includes at least an SOC sensor 121 and a temperature sensor 122. The SOC sensor 121 and the temperature sensor 122 are each electrically connected to the controller 100.

[0076] More specifically, the SOC sensor 121 detects the SOC of the secondary battery 9. The temperature sensor 122 detects the temperature of the secondary battery 9. The temperature sensor 122 may detect a physical quantity that has a correlation with the temperature of the secondary battery 9, such as the ambient temperature of the secondary battery 9 or the outside air temperature of the vehicle V. The SOC sensor 121 and the temperature sensor 122 input their detection signals to the controller 100.

[0077] Specifically, the SOC sensor 121 outputs a signal corresponding to the SOC based on a measured value of the open circuit voltage (OCV). The SOC sensor 121 may be configured by a voltage sensor capable of measuring the circuit voltage. The SOC sensor 121 is electrically connected to the controller 100. The SOC sensor 121 inputs its detection signal to the controller 100.

[0078] The state sensor 120 further includes a resistance sensor 123 that measures the internal resistance of the secondary battery 9. The resistance sensor 123 is electrically connected to the controller 100. A detection signal of the resistance sensor 123 is input to the controller 100.

[0079] The notification unit 130 is electrically connected to the controller 100. The notification unit 130 is configured to notify the occupant of the vehicle V of information related to processing by the controller 100, which will be described later.

[0080] More specifically, the notification unit 130 according to this embodiment is configured by a so-called DCM (Data Communication Module). The notification unit 130 can notify the occupant of information via the occupant's mobile device, such as a smartphone or tablet. The information notified to the occupant may be color vision information displayed on a screen, or audio information output from a speaker.

[0081] The controller 100 is composed of hardware such as a processor 100a, a memory 100b, and an input / output bus 100c, and software such as a database, a control program, etc. Please refer to Figure 5 for the functional elements related to the latter software.

[0082] Although the control device 1 in FIG. 4 shows one controller 100, this controller 100 may be configured by, for example, a module (PCM) for controlling the drive source 3 from among the various control modules installed in the vehicle V.

[0083] Based on signals input from the switches and sensors described above, the controller 100 executes processes related to charging and discharging the secondary battery 9. To execute such processes, the controller 100 includes multiple functional blocks shown in FIG.

[0084] <4. Controller details> As shown in Fig. 5, the controller 100 includes an evaluation value determination unit 101 and a charge / discharge control unit 102. The evaluation value determination unit 101 determines whether a first condition is met. The charge / discharge control unit 102 controls the charge / discharge current of the secondary battery 9 based on the determination result by the evaluation value determination unit 101. Here, the term "charge / discharge current" refers to at least one of a charge current and a discharge current. In this embodiment, the controller 100 controls at least the charge current as the charge / discharge current.

[0085] Here, the first condition is a condition that is met when at least one of the SOC and the temperature is continuously above a predetermined value. In particular, the first condition according to this embodiment is set to be met when both the SOC and the temperature are continuously above a predetermined value.

[0086] When the SOC and temperature of the secondary battery 9 are high, gas is more likely to be generated in the battery cells 91 than when they are low. Furthermore, if the SOC and temperature of the secondary battery 9 remain high for a long period of time, gas is likely to accumulate in the battery cells 91 depending on the duration of this state.

[0087] Therefore, by determining whether the first condition is met, it is possible to determine whether gas is being generated in the battery cell 91 and the amount of gas being generated.

[0088] The evaluation value determination unit 101 first determines whether the first condition is met when the ignition is turned off, such as when the vehicle V is left parked. In this embodiment, the determination of whether the first condition is met is made based on an evaluation value, which will be described in detail below.

[0089] Specifically, the evaluation value determining unit 101 monitors the transitions of the SOC and the temperature (particularly the transitions over time). The evaluation value determining unit 101 determines whether the second condition is met based on the values ​​of the SOC and the temperature.

[0090] Here, the second condition refers to a condition that is met when the SOC is equal to or greater than the first threshold T1 and the temperature is equal to or greater than the second threshold T2, as exemplified in region R1 of FIG.

[0091] When the second condition is satisfied, the evaluation value determination unit 101 calculates an evaluation value that increases according to the period during which the second condition is satisfied (satisfaction period). The longer the period during which the second condition is satisfied, the larger this evaluation value becomes. For example, as shown in FIG. 7, the evaluation value may be an integrated value that starts counting when the second condition is satisfied and counts up over time while the second condition is satisfied. As shown in the same figure, when the second condition is not satisfied, the evaluation value is not counted up. When the motor 31 is driven in response to IN-ON, the vehicle V is no longer left unattended, so counting of the evaluation value may be stopped.

[0092] A large evaluation value means that the second condition has been met continuously for a relatively long period of time. A small evaluation value means that the second condition has been met for only a relatively short period of time. The evaluation value is considered to have a positive correlation with the amount of gas accumulated in the battery cell 91.

[0093] When the evaluation value exceeds a predetermined third threshold T3, the evaluation value determination unit 101 determines that both the SOC and the temperature are continuously equal to or higher than a predetermined value. In other words, when the evaluation value exceeds the predetermined third threshold T3, the evaluation value determination unit 101 determines that the first condition is met.

[0094] When the evaluation value determination unit 101 determines that the first condition is met, the charge / discharge control unit 102 executes a predetermined low-rate control (see FIG. 7). Here, the low-rate control refers to a process of limiting the magnitude of the charge / discharge current compared to when the first condition is not met.

[0095] As described above, the charge / discharge control unit 102 according to this embodiment is configured to limit at least the magnitude of the charge current as the charge / discharge current. However, the present disclosure is not limited to such a configuration. The charge / discharge control unit 102 may limit at least the magnitude of the discharge current instead of the charge current. When limiting the magnitude of the discharge current, the charge / discharge control unit 102 may reduce the number of battery modules 90, and therefore the number of battery cells 91, connected to the converter 6 by switching the circuit structure of the electric circuit (the circuit through which the discharge current flows) connecting each battery module 90 and the converter 6. Alternatively, the charge / discharge control unit 102 may limit the magnitude of the discharge current by increasing the amount of voltage step-down in the converter 6.

[0096] Returning to the explanation of this embodiment, the charge / discharge control unit 102 according to this embodiment reduces the magnitude of the charge / discharge current when performing the low rate control compared to when the first condition is not satisfied. By reducing the magnitude of the charge / discharge current, at least the charge of the charge / discharge is performed at a relatively low C rate.

[0097] More specifically, the charge / discharge control unit 102 limits the C rate when executing the low rate control. When the C rate is limited, not only the charge current but also the discharge current is limited. In this case, by executing the low rate control, the C rate may be reduced to, for example, 0.1 C or less.

[0098] Specifically, the charge / discharge control unit 102 according to this embodiment limits the magnitude (C rate) of the charge / discharge current (particularly the charge current) by limiting power supply by rapid charging when executing the low rate control. In this case, power supply by rapid charging is prohibited, and only power supply by normal power supply is permitted.

[0099] Furthermore, instead of or in addition to limiting power supply by rapid charging, the charge / discharge control unit 102 according to this embodiment limits the magnitude of the charge / discharge current (particularly the charge current) by limiting the regenerative current generated by the regenerative operation of the motor 31 to a predetermined upper limit or less. In this case, the regenerative current may be limited to 0 by prohibiting the regenerative operation itself.

[0100] The evaluation value determination unit 101 also updates the determination of the first condition when the IG-ON state is reached, such as while the vehicle V is traveling. By updating the determination of the first condition, the controller 100 cancels the low rate control by the charge / discharge control unit 102.

[0101] Here, the first condition is set to be invalid if the internal resistance value of the secondary battery 9 decreases continuously. When gas is generated in the battery cell 91, the internal resistance value is thought to increase as the reaction area decreases. The internal resistance value of the secondary battery 9 has a positive correlation with the amount of gas accumulated in the battery cell 91. Therefore, by monitoring the change in the internal resistance value, it is possible to estimate the change in the amount of gas in the battery cell 91.

[0102] Furthermore, the evaluation value used to determine whether the first condition is met has a positive correlation with the gas amount, as described above, similar to the internal resistance value. Therefore, it is possible to associate the evaluation value with the internal resistance value.

[0103] For example, the controller 100 has a map that associates the amount of change in the internal resistance value with the evaluation value. As shown in Fig. 7, the controller 100 can update the evaluation value based on the transition of the internal resistance value after the IG-ON.

[0104] Therefore, when low rate control is initiated, the controller 100 according to this embodiment estimates the internal resistance value of the secondary battery 9 after starting (after IG-ON) the driving source 3. The controller 100 updates the evaluation value based on the estimated internal resistance value.

[0105] Thereafter, the controller 100 updates the determination of the first condition based on the updated evaluation value. As a result, if the first condition still holds, the controller 100 continues the low rate control. On the other hand, if the first condition no longer holds after the update, the controller 100 cancels the low rate control (cancels the limit on the magnitude of the charge / discharge current).

[0106] <5. Specific examples of processing by the controller> 8 and 9 are flowcharts showing specific examples of processing related to low rate control. The flow in FIG. 8 is processing that is mainly executed repeatedly before "IG-OFF" of vehicle V. The flow in FIG. 9 is processing that is repeatedly executed after "IG-ON" of vehicle V.

[0107] (5-1. Processing when IG-OFF) First, in step S101, the controller 100 reads the detection signal of the status sensor 120. The status sensor 120 used here includes an SOC sensor 121 and a temperature sensor 122.

[0108] In the following step S102, the controller 100 determines whether the second condition is met based on the detection signal of the status sensor 120. Specifically, the controller 100 determines whether the SOC of the secondary battery 9 is equal to or greater than a first threshold value (T1) and the temperature of the secondary battery 9 is equal to or greater than a second threshold value (T2) (SOC≧T1 and temperature≧T2?). The first threshold value and the second threshold value are set in advance and stored in the memory 100b of the controller 100, etc.

[0109] If the determination in step S102 is YES, the controller 100 advances the control process to step S3. If the determination in step S102 is NO, the controller 100 advances the control process to step S108.

[0110] In the latter step S108, the controller 100 changes the execution flag for the low-rate processing from ON to OFF, or keeps it OFF. If the execution flag is OFF, the controller 100 does not execute the low-rate processing. Thereafter, the controller 100 repeatedly executes the flow of FIG. 8, starting from step S101.

[0111] On the other hand, in the former step S103, the controller 100 counts up the evaluation value.

[0112] That is, as long as the second condition continues to be satisfied in step S102, the controller 100 counts up the evaluation value in step S103 so that the count increases in proportion to the period during which the second condition remains satisfied.

[0113] On the other hand, if the second condition is not met while the evaluation value is being counted up, the controller 100 suspends the counting up of the evaluation value, and turns off the execution flag for low-rate processing in step S108.

[0114] In step S104 following step S103, the controller 100 determines whether the third condition is met based on the counted-up evaluation value. Specifically, the controller 100 determines whether the evaluation value is equal to or greater than a fourth threshold (T4) (evaluation value≧T4?). The fourth threshold is a predetermined value that is at least less than the third threshold. The fourth threshold is set in advance and stored in the memory 100b or the like of the controller 100. Determining whether the third condition is met is equivalent to determining whether there is a sign that the first condition will be met.

[0115] If the determination in step S104 is YES (if the sign is present), the controller 100 advances the control process to step S105. If the determination in step S104 is NO, the controller 100 returns the control process to step S101.

[0116] In the next step S105, the controller 100 notifies the occupant of information via the notification unit 130. The notification unit 130 notifies the occupant of information indicating that the first condition is about to be fulfilled. This information may be information that suggests that the first condition is about to be fulfilled without explicitly stating that the first condition is about to be fulfilled, such as, for example, "the secondary battery has been left in a high temperature and high SOC state for a long period of time" or "the execution flag for low-rate processing will soon be turned ON."

[0117] The process of step S105 may be executed only when the third condition is met for the first time, or may be skipped when the execution flag for low-rate process is ON.

[0118] In the next step S106, the controller 100 determines whether the first condition is met based on the counted-up evaluation value. Specifically, the controller 100 determines whether the evaluation value is equal to or greater than a third threshold value (evaluation value≧T3?). The third threshold value is set in advance and stored in the memory 100b of the controller 100, etc.

[0119] If the determination in step S106 is YES, the controller 100 advances the control process to step S107. If the determination in step S106 is NO, the controller 100 returns the control process to step S101.

[0120] In step S107, the controller 100 changes the execution flag for the low-rate processing from OFF to ON, or keeps it ON. If the execution flag is ON, the controller 100 will execute the low-rate processing after IG-ON.

[0121] After step S107, the controller 100 repeatedly executes the flow of Fig. 8 until the IG switch 111 is operated to turn IG-ON. For example, if the determination in step S102 remains true even after the execution flag is turned ON, the controller 100 continues to count up the evaluation value.

[0122] (5-2. Processing after IG-ON) Thereafter, when the state is changed to "IG-ON", first, in step S201, the controller 100 reads the detection signal of the status sensor 120. The status sensor 120 used here includes a resistance sensor 123.

[0123] In the following step S202, the controller 100 determines whether or not the execution flag for low rate control is ON, and only if the determination is YES, executes the processing from step S203 onwards.

[0124] Specifically, in step S203, the controller 100 estimates the execution period of the low-rate control based on the internal resistance value. In the case of a typical secondary battery, the negative electrode of each battery cell 91 contracts when discharging and expands when charging. Furthermore, considering the regenerative operation of the motor 31, a charging current associated with the regenerative operation flows through the secondary battery 9. In other words, even when the vehicle V is running, each battery cell 91 repeatedly expands and contracts.

[0125] As a result, gas accumulated in each battery cell 91 (particularly gas resulting from decomposition of the electrolyte 95) is released from each tab 91A, 91B. This alleviates the inhibition of chemical reactions caused by the gas, and the internal resistance value of each battery cell 91 gradually decreases.

[0126] Based on the current internal resistance value, the controller 100 estimates the execution time required for the internal resistance value to decrease to an allowable value (a predetermined value at which low-rate control is no longer necessary). The controller 100 stores in advance a map or model that associates the detected values ​​of each status sensor 120, including the resistance sensor 123, with the execution period, and estimates the execution time based on the stored contents.

[0127] In the next step S204, the controller 100 notifies the occupant of the estimated execution period. This notification may be displayed, for example, on a display screen (display unit for a tachometer or the like) near the driver's seat.

[0128] In the next step S205, the controller 100 starts low-rate control. This limits the magnitude of various charging currents, such as the charging current during charging from the power supply facility and the charging current associated with regeneration. This allows each battery cell 91 to expand and contract without causing precipitation of Li or other elements due to high-rate charging.

[0129] In the following step S206, the controller 100 again reads the detection signal of the status sensor 120. The controller 100 acquires the internal resistance value after the motor 31 is driven after the IG-ON.

[0130] Here, when each battery cell 91 repeatedly expands and contracts, gas inside the cell is discharged, and this effect is reflected in the internal resistance value as described above.

[0131] Therefore, in the next step S207, the controller 100 updates the evaluation value used to determine whether the first condition is met, based on the acquired internal resistance value. The controller 100 stores in advance a map that associates the amount of decrease in the internal resistance value after the start of low-rate control with the evaluation value corresponding to that amount of decrease. This map is set so that the evaluation value decreases as the internal resistance value decreases. The controller 100 updates the evaluation value based on the amount of decrease in the internal resistance value.

[0132] In the next step S208, the controller 100 updates the determination of the first condition based on the updated evaluation value. If the first condition is no longer met after the update, the controller 100 proceeds to step S209 and cancels the low rate control. If the first condition is still met after the update, the controller 100 returns the control process to step S206.

[0133] When determining whether the first condition is not satisfied, a fifth threshold value set lower than the third threshold value may be used instead of the third threshold value.

[0134] <6. Gas generated inside the cell> When a secondary battery 9 for a vehicle V is left outdoors, gas due to decomposition of the electrolyte 95 may accumulate near the negative electrode of the battery cell 91 that constitutes the secondary battery 9. It is believed that such gas generation becomes more pronounced under conditions such as high temperatures and high SOC.

[0135] If gas accumulates inside the battery cells 91, the gas may interfere with the chemical reaction in each battery cell 91. This may reduce the reaction area of ​​each battery cell 91 and increase its internal resistance. This is disadvantageous from various perspectives, such as battery capacity.

[0136] Generally, gas accumulated inside the battery cells 91 is discharged to the outside of the cells 91 via tabs 91A and 91B due to the restraining forces acting on both the front and back sides of each battery cell 91, as indicated by the arrows in FIG. 3B.

[0137] However, in the case of a battery cell 91 with a high aspect ratio as in this embodiment, the surface areas of the front and back are increased, and the binding force acting per unit area is weakened accordingly. On the other hand, while tabs 91A, 91B are provided on both ends of the battery cell 91 as usual, the size of each tab 91A, 91B is not necessarily as large as the surface area of ​​each battery cell 91.

[0138] The reduced binding force per unit area, combined with the fact that the size of each of the tabs 91A, 91B is not significantly increased, makes it difficult for gas that has accumulated inside the battery cell to be discharged to the outside of the cell.

[0139] For example, the horizontal axis of FIG. 10 indicates the elapsed time when the secondary battery 9 is left at a high temperature so that the first condition is met. The vertical axis of the same figure indicates the cell reaction force of the secondary battery 9 by the load cell (reaction force against the constraint in the front-rear direction). The cell reaction force is considered to be proportional to the amount of gas inside the battery cell 91. As shown in FIG. 10, a battery cell 91 with a high aspect ratio has a higher cell reaction force than a battery cell 91 with a low aspect ratio.

[0140] In response to this problem, the inventors of the present application attempted to exhaust the gas accumulated in the battery cells to the outside through the electrodes of each battery cell 91 by expanding and contracting each battery cell 91 through charging and discharging. However, depending on the setting of the so-called C rate, this can lead to electrodeposition of Li and the like, which is inconvenient. In other words, it would be advantageous to have a mechanism for exhausting gas from the battery cells 91 without inducing deposition.

[0141] Therefore, as explained with reference to Figure 8, the inventors of the present application have devised a method for limiting high-rate charging by low-rate control when the first condition, which indicates gas generation, is satisfied. This allows gas to be discharged from the battery cell 91 without causing precipitation. As a result, it is possible to suppress deterioration of the secondary battery 9.

[0142] For example, the horizontal axis in Fig. 11 represents the elapsed time since the start of low-rate control. The vertical axis has the same meaning as in Fig. 10. As shown in Fig. 11, by performing low-rate control, the cell reaction force and, therefore, the amount of gas inside the battery cell 91 can be reduced.

[0143] Furthermore, if gas accumulates inside the battery cells 91, the gas will interfere with the chemical reaction, which is thought to result in an increase in the internal resistance of the secondary battery 9. In other words, if gas is discharged from each battery cell 91 by low-rate control, the internal resistance will likely gradually decrease, for example, as shown in Figure 12. If the internal resistance continues to decrease, it is thought that there is no longer any need to limit the magnitude of the charging current.

[0144] Therefore, as explained with reference to FIG. 9, after starting the driving source 3 by electric power, the controller 100 monitors the change in the internal resistance value and re-determines whether the first condition is met based on the change in the internal resistance value over time. This makes it possible to shorten the execution period of the low-rate control as much as possible. This makes it possible to both suppress deterioration of the secondary battery 9 and shorten the charging period of the secondary battery 9.

[0145] Furthermore, by limiting the magnitude of the charging current generated during regenerative operation and limiting rapid charging, low-rate control can be performed, thereby suppressing deterioration of the secondary battery 9 while allowing normal charging.

[0146] Furthermore, as explained with respect to step S105 in Fig. 8, before the magnitude of the charging current is actually limited due to the first condition being met, the occupant is notified of the prediction. This reduces the frequency with which the magnitude of the charging current is limited, improving the usability of the vehicle, while also guiding the occupant to prevent the first condition from being met, which is advantageous in preventing deterioration of the secondary battery. [Explanation of symbols]

[0147] 1. Control device 3. Drive source 31 Motor 9 Secondary battery 91 Battery Cells 100 Controllers 120 Status Sensor 121 SOC sensor 122 Temperature Sensor V vehicle

Claims

1. A control device for a secondary battery that includes a plurality of battery cells and supplies power from the plurality of battery cells to a drive source of a vehicle, a state sensor for detecting at least one of an SOC and a temperature of the secondary battery; a controller that determines whether a first condition is met, which is met when at least one of the SOC and the temperature is continuously equal to or higher than a predetermined value, based on a detection signal from the state sensor, and controls a charge / discharge current of the secondary battery based on the determination result; The controller determining whether the first condition is met when the power supply to the driving source is cut off; When it is determined that the first condition is satisfied, the magnitude of the charge / discharge current is limited compared to when the first condition is not satisfied. A control device for a secondary battery.

2. 2. The control device for a secondary battery according to claim 1, the first condition is not satisfied when the internal resistance value of the secondary battery is continuously decreasing, When the controller starts limiting the magnitude of the charging / discharging current, After the drive source is started, the internal resistance value is acquired; updating the determination of the first condition based on the estimated value of the internal resistance value; If the first condition is no longer satisfied after the update, the limit on the magnitude of the charge / discharge current is released. A control device for a secondary battery.

3. 2. The control device for a secondary battery according to claim 1, the drive source is a motor capable of performing both a power running operation and a regenerative operation, The controller limits the magnitude of the charge / discharge current by limiting the regenerative current generated by the regenerative operation to a predetermined upper limit or less. A control device for a secondary battery.

4. 2. The control device for a secondary battery according to claim 1, the vehicle is capable of being supplied with power by at least rapid charging, of rapid charging in which the secondary battery is charged by receiving a supply of power equal to or greater than a predetermined power from a power supply facility, and normal charging in which the secondary battery is charged by receiving a supply of power less than the predetermined power from the power supply facility, The controller limits the magnitude of the charge / discharge current by limiting the power supply by the fast charge. A control device for a secondary battery.

5. 2. The control device for a secondary battery according to claim 1, a notification unit electrically connected to the controller and configured to notify an occupant of the vehicle of information; The notification unit determining whether or not there is a sign that the first condition will be met based on the detection signal of the state sensor; If it is determined that the sign exists, the occupant is notified of information indicating that the first condition is about to be established. A control device for a secondary battery.

6. 2. The control device for a secondary battery according to claim 1, The plurality of battery cells each have a plate shape, and are arranged side by side in the front-to-rear direction of the vehicle while being constrained from both the front and rear sides of the plate shape, the plurality of battery cells are each arranged so that their longitudinal direction is aligned with the vehicle width direction, their lateral direction is aligned with the vehicle height direction, and their thickness direction is aligned with the vehicle front-rear direction, a longitudinal dimension of each of the plurality of battery cells exceeds 50% of a vehicle width of the vehicle; Tabs corresponding to the positive and negative electrodes of each of the plurality of battery cells are disposed at both ends in the longitudinal direction of the battery cells. A control device for a secondary battery.

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