Secondary battery control method and control device

Abstract

To provide a control method of a secondary battery and a control apparatus, in which an efficiency of a battery pack is increased.SOLUTION: A control method of a lithium ion secondary battery, comprises: a step (S1) of acquiring a battery temperature for acquiring a battery temperature T of a cell battery in a battery pack constructed by combining the plurality of cell batteries; a step (S2) of an input and output limit value calculation, for calculating an input and output limit value W that limit an input and output by a charging and discharging on the basis of the battery temperature T of the cell battery; and a step (S5) of an input and output limit value expansion for expanding the current input and output limit value W of the battery pack to an input and output limit value WLit in the case where it is the cell battery that is a first set temperature T1 or less (S3:YES), and the maximum temperature Tmax of the acquired battery temperature T is a second set temperature T2 or less (S4:YES).SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method and device for controlling a secondary battery, and more particularly to a method and device for controlling a secondary battery that allows efficient use of the battery. [Background technology]

[0002] In recent years, non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries and alkaline secondary batteries such as nickel-metal hydride batteries have come to be used as power sources for electric vehicles, etc. Since the voltage and current of such single secondary batteries are low, high voltage and current are supplied by battery packs, which are assembled secondary batteries consisting of multiple stacked cell batteries connected in series and parallel.

[0003] When secondary batteries are used as a battery pack, the center of the stacked battery pack is often harder to cool than the edges and therefore tends to be hotter. Furthermore, variations in the internal resistance and other inherent characteristics of individual battery cells can lead to differences in heat generation. The performance of secondary batteries changes depending on the temperature.

[0004] Therefore, in the power supply system disclosed in Patent Document 1, the power charged and discharged in each of the power storage units is managed by taking into consideration the temperature difference between the power storage units. As a result, it is possible to uniform the temperatures generated between the power storage units and efficiently manage the temperatures of all the power storage units while satisfying the power value required by the load device.

[0005] The invention disclosed in Patent Document 2 includes power storage devices used for driving a vehicle and arranged at different positions, a controller for controlling the drive of these devices, and temperature sensors for the power storage devices. The controller changes the drive ratio of each power storage device based on the relationship of the device temperature of each power storage device to the temperature range used for temperature control of the power storage devices and the magnitude relationship of the temperatures.

[0006] According to such an invention, control can be performed based on the temperature difference between the secondary batteries. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-154302 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-200140 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the temperature distribution within the battery pack is not taken into consideration. The problem to be solved by the secondary battery control method and control device of the present invention is to increase the efficiency of the battery pack. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the control method for a secondary battery of the present invention includes a battery temperature acquisition step for acquiring battery temperatures T [°C] of the plurality of unit batteries constituting the battery pack, the battery temperature T [°C] of the plurality of unit batteries constituting the battery pack acquired in the battery temperature acquisition step, an input / output limit value calculation step for calculating an input / output limit value W [W] for limiting input / output due to charging and discharging based on the battery temperatures T [°C] of each of the plurality of unit batteries constituting the battery pack acquired in the battery temperature acquisition step, and a step for calculating a maximum temperature T [W] of the unit battery temperatures T acquired in the battery temperature acquisition step if there is a unit battery that is equal to or lower than a set first temperature T1 [°C] and if the maximum temperature T [W] of the acquired unit battery temperatures T is equal to or lower than a set first temperature T2 [°C]. max When the temperature T2 [°C] is equal to or lower than the set second temperature T1 [°C], the current input / output limit value W [W] of the battery pack is set to the input / output limit value W Lit and a step of expanding the input / output limit value to [W].

[0010] In the step of increasing the input / output limit value, the input / output limit value W [W] is set to a value less than the maximum temperature T max [°C] and minimum temperature T min The larger the difference from [°C], the larger the value may be.

[0011] In the step of expanding the input / output limit value, the input / output limit is set to an average temperature T ave and maximum temperature T max The larger the difference between them, the larger the magnification may be.

[0012] The step of calculating the input / output limit value is performed by calculating the minimum temperature T min When the SOC of the unit battery at the lowest temperature is less than the minimum value of the set charge / discharge range, the limit value of the input / output limit value W [W] on the charge side may be increased; when the SOC of the unit battery at the lowest temperature exceeds the maximum value of the set charge / discharge range, the limit value of the input / output limit value W [W] on the discharge side may be increased; and when the SOC of the unit battery at the lowest temperature is equal to or greater than the minimum value and equal to or less than the maximum value, the limit values ​​of both the input / output limit values ​​W [W] on the charge side and the discharge side may be increased.

[0013] The step of calculating the input / output limit value is performed at an acquisition time interval T int [s] is the maximum temperature T max [°C] unit cell upper limit temperature T Lit [°C] Acquisition time interval T int The method may further comprise a step of calculating the application time [s].

[0014] The acquisition time interval T int [s] is the heat capacity of the unit cell in C [Cal] and the upper limit temperature in T Lit [°C], the maximum battery temperature is T max , input / output current is I [A], internal resistance is R [Ω], T int =C(T Lit -T) / I 2 It may be calculated based on R.

[0015] The step of expanding the input / output limit value is to set the recalculated input / output limit value to W Lit [W], current input / output limit value W[W], T max [°C] and T min The magnification (1.0x or more) determined from the difference in [°C] is M diff , Tmax [°C] and T ave The magnification (1.0x or more) determined from the difference in [°C] is M ave When the recalculated input / output limit value is set as W Lit [W] to W Lit =W×M diff ×M ave It may also be calculated by:

[0016] Environmental temperature T env [°C], T max [°C] and T env The magnification (1.0x or more) determined from the difference in [°C] is M env When the recalculated input / output limit value is set as W Lit [W] to W Lit =W×M diff ×M ave ×M env It may also be calculated by:

[0017] The present invention provides a secondary battery control device equipped with a computer, characterized in that, in an assembled battery formed by combining a plurality of unit batteries each consisting of a secondary battery, the device comprises: a battery temperature acquisition means for acquiring the battery temperatures of the plurality of unit batteries that constitute the assembled battery; an input / output limit value calculation means for calculating an input / output limit value W [W] that limits input / output due to charging and discharging based on the battery temperatures of each of the plurality of unit batteries that constitute the assembled battery acquired by the battery temperature acquisition means; and an input / output limit value expansion means for expanding the input / output limit value of the assembled battery when, among the unit battery temperatures acquired by the battery temperature acquisition means, there is a unit battery that is below a set first temperature and the acquired maximum temperature of the unit battery is below a set second temperature. [Effects of the Invention]

[0018] The control method and control device for a secondary battery of the present invention can improve the efficiency of the battery pack. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view showing a battery pack of a lithium ion secondary battery according to an embodiment of the present invention; [Figure 2] 1 is a perspective view of the appearance of a cell battery of a lithium ion secondary battery that is the subject of control in this embodiment. [Figure 3] 1 is a schematic diagram showing the configuration of an electrode body of a lithium ion secondary battery according to an embodiment of the present invention. [Figure 4] 1 is a diagram showing a schematic overall configuration of a vehicle equipped with a battery pack of lithium-ion secondary batteries according to an embodiment of the present invention; [Figure 5] FIG. 2 is a detailed block diagram of a monitoring unit of the control device. [Figure 6] 3 is a flowchart showing the steps of a control method for a lithium ion secondary battery according to the present embodiment. [Figure 7] 10 is a flowchart showing the procedure of a subroutine for recalculating the input / output limit value W (S5). [Figure 8] 10 is a graph showing the relationship between battery temperature and input / output limits. [Figure 9] 1 is a graph showing the relationship between battery temperature T [°C] and internal resistance R [Ω]. [Figure 10] This is a graph showing the temperature change when a current I [A] is applied to two cell batteries 1A and 1B, which have different battery temperatures T [°C], respectively designated as TA and TB [°C]. [Figure 11] 1 is a graph showing the relationship between battery temperature T and maximum temperature Tmax, minimum temperature Tmin, average temperature Tave, and environmental temperature Tenv. [Figure 12] 10 is a graph illustrating the relationship between the average temperature Tave and the maximum temperature Tmax when the average temperature Tave is high. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a method and a control device for a secondary battery according to the present invention will be described using an embodiment of a method and a control device for a lithium ion secondary battery for a vehicle. (Outline of this embodiment) <Principle of this embodiment> FIG. 1 is a perspective view showing a battery pack 4 of a lithium-ion secondary battery according to this embodiment. The method for controlling a secondary battery according to this embodiment is applied to a battery pack 4 used, for example, as a driving power source for a vehicle. The battery pack 4 is formed by stacking and restraining a plurality of (34 in FIG. 1) cell batteries 1 (see FIG. 2) one upon the other to form a battery stack 2. This battery stack 2 is housed in a battery case 3. The battery stacks housed in this battery case 3 are housed in a plurality of (two in this case) housing containers (not shown), electrically connected, and sealed with a control device, sensor, cooling device, external terminals, etc. attached. The battery pack 4 thus formed is charged and discharged as a driving power source for a vehicle. This battery pack 4 is charged and discharged by driving current and regenerative current during vehicle operation, and by internal and external charging.

[0021] In a battery pack 4 equipped with such multiple cell batteries 1, differences in battery temperature T [°C] may occur due to the cooling structure at the location where the cell batteries 1 are arranged, or the characteristics or deterioration of the cell batteries 1 themselves. For example, cell battery 1a shown in FIG. 1 is arranged at the end, while cell battery 1b is arranged in the center in the stacking direction. In such an arrangement, cell battery 1a at the end is generally more easily cooled than cell battery 1b in the center, and therefore often has a lower battery temperature T [°C].

[0022] <Battery temperature T and input / output limit value W> FIG. 8 is a graph showing the relationship between battery temperature T [°C] and input / output limit value W [W]. In FIG. 8, the horizontal axis represents battery temperature T [°C]. The vertical axis represents the charge / discharge capacity at that battery temperature T [°C] in terms of power [W]. Charging (+) is indicated above the horizontal axis, and discharging (-) is indicated below the horizontal axis. A characteristic of lithium-ion secondary batteries is that their charge / discharge capacity varies with battery temperature T. As shown in FIG. 8, when the battery temperature T is within a certain temperature range, the battery exhibits a predetermined charge / discharge capacity. However, at high and low temperatures, the input / output capacity decreases. Therefore, the control device 5 (see FIG. 4) of the battery pack 4 limits the input / output. For example, above a first temperature T1 [°C] and below a second temperature T2 [°C], the input / output limit value [W] remains almost constant for both charging and discharging. On the other hand, below the first temperature T1 [°C], the absolute value of the input / output limit value [W] decreases as the temperature decreases. Furthermore, when the temperature exceeds the second temperature T2 [°C], the absolute value of the input / output limit value W [W] rapidly decreases for both charging and discharging as the temperature drops. Therefore, it is preferable to use the battery pack 4 within the range of the first temperature T1 [°C] or higher and the second temperature T2 [°C] or lower.

[0023] Note that this control of the input / output limit value [W] is performed for the entire battery pack 4. Therefore, if there is variation in the battery temperature T [°C] of the cell batteries 1, it becomes difficult to perform appropriate control for all cell batteries 1. For this reason, the input / output limit value [W] is basically set to the input / output limit value [W] of the cell battery 1 with the greatest input / output limit, which results in a decrease in the efficiency of the battery pack 4.

[0024] <Battery temperature T and internal resistance R> Figure 9 is a graph showing the relationship between battery temperature T [°C] and internal resistance R [Ω]. The horizontal axis represents battery temperature T [°C]. The vertical axis represents internal resistance R [Ω] at that battery temperature T [°C]. Internal resistance R [Ω] is direct current resistance (DC-IR).

[0025] It is known that the internal resistance R of a battery changes exponentially depending on the battery temperature T [°C] according to the Arrhenius equation. As shown in Figure 9, in a lithium-ion secondary battery, as the battery temperature T [°C] rises, chemical reactions become more active, resulting in a decrease in the internal resistance R [Ω]. On the other hand, as the battery temperature T [°C] drops, the internal resistance R [Ω] rises sharply.

[0026] <Why this embodiment can achieve uniform temperature> Figure 10 shows the temperature of two cells in a battery with different T[°C]. A and cell battery 1 B The battery temperature T [°C] is T A , T B This is a graph showing the temperature change when a current I [A] is applied, where the temperature is [°C]. The horizontal axis shows the change in time t [s]. The vertical axis shows the change in the temperature of the two-cell battery 1 at that time. A and cell battery 1 B Battery temperature T A , T B [°C] is shown.

[0027] This embodiment is an invention for equalizing the battery temperatures T [°C] of the cell batteries 1 in the battery pack 4 when there is a temperature difference. In FIG. 10, at the start of the comparison, there are two cell batteries 1 with different battery temperatures T [°C]. A and cell battery 1 B The battery temperature T [°C] is T A , T B [°C] where T A >T B Also, T A -T B =T diff [°C].

[0028] Then, a current I [A] is applied. At this time, as explained in Figure 9, the higher the battery temperature T [°C], the smaller the internal resistance R [Ω]. Cell battery 1 when current I [A] is applied A The internal resistance R A and cell battery 1 B The internal resistance R BIn this case, cell battery 1 A Battery temperature T A 1 cell battery B Battery temperature T B is T A >T B Therefore, the higher the battery temperature T [°C], the smaller the internal resistance R [Ω]. A <R B The relationship is as follows.

[0029] Cell battery 1 A and cell battery 1 B The heat generation amounts of I 2 R A Δt, I 2 R B Δt where cell battery 1 A and cell battery 1 B Since the current is a common circuit, I = I. Also, the time during which the current I is applied is also common, Δt. Therefore, cell battery 1 A Calorific value I 2 R A Δt, cell battery 1 B Heat generation amount I 2 R B Δt ratio, I 2 R A Δt:I 2 R B Δt=R A :R B As mentioned above, the internal resistance [Ω] is R A <R B Therefore, cell battery 1 A Calorific value I 2 R A Δt, cell battery 1 B Heat generation amount I 2 R B At Δt, cell battery 1 B Heat generation amount I 2 R B Δt is larger.

[0030] That is, as shown in FIG. 10, when the input / output current I is applied for only Δt, the temperature difference within the battery pack 4 can be reduced. ATemperature and cell battery 1 B Temperature difference T' diff =T' A -T' B It is expressed as T before applying the input / output current I diff =T A -T B [°C] is T' diff <T diff Therefore, by applying an input / output current I [A] for Δt, the temperature difference within the battery pack 4 can be reduced.

[0031] (Configuration of this embodiment) Next, a specific configuration of this embodiment will be briefly described. <Configuration of lithium-ion secondary battery> FIG. 2 is a perspective view of the appearance of the cell battery 1 of the lithium ion secondary battery that is the subject of control in this embodiment.

[0032] First, a brief description will be given of the configuration of the lithium-ion secondary battery that is the premise of this embodiment. As shown in FIG. 2 , the lithium-ion secondary battery is configured as a cell battery 1. It includes a rectangular parallelepiped battery case 11 made of, for example, an aluminum alloy and having an opening on the upper side. The battery case 11 includes a lid 12 that seals the battery case 11. The lid 12 is provided with a vent valve 18 that discharges gas from the battery case 11 when the pressure inside the battery case 11 sealed by the lid 12 exceeds a certain pressure value. An electrode assembly 10 is housed inside the battery case 11. A nonaqueous electrolyte 17 is injected into the battery case 11 through a filler port 19 provided in the lid 12, and the filler port 19 is then sealed. The battery case 11 and the lid 12 are made of a metal such as an aluminum alloy and are sealed by laser welding or the like. Therefore, the lithium-ion secondary battery is configured as a sealed battery container by attaching the lid 12 to the battery case 11. The lithium ion secondary battery also includes, on the cover 12, a negative electrode current collector 13, a negative electrode external terminal 14, a positive electrode current collector 15, and a positive electrode external terminal 16, which are used for charging and discharging power.

[0033] <Electrode body 10> Fig. 3 is a schematic diagram showing a partially developed configuration of an electrode body 10 of a lithium ion secondary battery. As shown in Fig. 3, the electrode body 10 of the lithium ion secondary battery includes a negative electrode plate 100, a positive electrode plate 110, and a separator 120. The negative electrode plate 100 includes a negative electrode composite layer 102 on both sides of a negative electrode substrate 101. The positive electrode plate 110 includes a positive electrode composite layer 112 on both sides of a positive electrode substrate 111. The negative electrode plate 100 and the positive electrode plate 110 are stacked one on top of the other with the separator 120 interposed therebetween to form the electrode body 10. This laminate is wound in the longitudinal direction Z around a winding axis and shaped into a flat shape to form the electrode body 10.

[0034] Negative electrode connector 103 functions as a current collector that extracts electricity from negative electrode composite layer 102 of negative electrode plate 100. Positive electrode connector 113 functions as a current collector that extracts electricity from positive electrode composite layer 112 of positive electrode plate 110.

[0035] <Negative electrode plate 100> Negative electrode plate 100 is constructed by forming negative electrode composite layers 102 on both sides of negative electrode substrate 101. In this embodiment, negative electrode substrate 101 is made of Cu foil. Negative electrode substrate 101 serves as a base for the aggregate of negative electrode composite layer 102 and also functions as a current collecting member that collects electricity from negative electrode composite layer 102. In negative electrode plate 100, negative electrode composite layer 102 is formed on negative electrode substrate 101 made of metal. In this embodiment, the negative electrode active material is a material that can occlude and release lithium ions, and a powdered carbon material made of graphite or the like is used.

[0036] Negative electrode plate 100 is produced, for example, by kneading a negative electrode active material, a solvent, and a binder, and then applying the kneaded negative electrode mixture to negative electrode substrate 101 and drying it. <Positive electrode plate 110> Positive electrode plate 110 is configured by forming positive electrode composite layers 112 on both sides of positive electrode substrate 111. In this embodiment, positive electrode substrate 111 is configured from Al foil or Al alloy foil. Positive electrode substrate 111 serves as a base as an aggregate for positive electrode composite layer 112 and also functions as a current collecting member that collects electricity from positive electrode composite layer 112.

[0037] The positive electrode plate 110 has a positive electrode composite layer 112 formed on the surface of a positive electrode substrate 111. The positive electrode composite layer 112 contains a positive electrode active material. The positive electrode active material is a material capable of absorbing and releasing lithium, and examples of the positive electrode active material that can be used include lithium cobalt oxide (LiCoO), lithium manganese oxide (LiMnO), and lithium nickel oxide (LiNiO). Alternatively, a material in which LiCoO, LiMnO, and LiNiO are mixed in any ratio may be used.

[0038] Positive electrode mixture layer 112 also contains a conductive material, which may be, for example, carbon black such as acetylene black (AB) or ketjen black, or graphite.

[0039] The positive electrode plate 110 is produced, for example, by kneading a positive electrode active material, a conductive material, a solvent, and a binder, and then applying the kneaded positive electrode mixture to the positive electrode substrate 111 and drying it. <Separator 120> The separator 120 is a nonwoven fabric made of a porous resin such as polypropylene, which holds the nonaqueous electrolyte 17 between the negative electrode plate 100 and the positive electrode plate 110. Alternatively, the separator 120 may be made of a porous polymer membrane such as a porous polyethylene membrane, a porous polyolefin membrane, or a porous polyvinyl chloride membrane, or a lithium ion or ion conductive polymer electrolyte membrane, either singly or in combination. When the electrode assembly 10 is immersed in the nonaqueous electrolyte 17, the nonaqueous electrolyte permeates from the edges of the separator 120 toward the center.

[0040] <Nonaqueous electrolyte 17> The nonaqueous electrolyte is a composition in which a supporting salt is contained in a nonaqueous solvent. Ethylene carbonate (EC) can be used as the nonaqueous solvent. Alternatively, one or more materials selected from the group consisting of propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc. can be used. The supporting salt can be LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiI, etc. Alternatively, one or more lithium compounds (lithium salts) selected from these can be used.

[0041] <Heat generation in lithium-ion secondary batteries> In the cell battery 1 of the lithium ion secondary battery of this embodiment, a battery reaction occurs in the electrode body 10, generating heat, which is released to the outside through the battery case 11. The heat is released to the outside by a cooling system (not shown) of the battery pack 4, but uneven cooling for each cell battery 1 is unavoidable.

[0042] <Overall configuration of a vehicle equipped with a secondary battery> Next, a brief description will be given of a vehicle 200 on which the battery pack 4 of the lithium ion secondary battery of this embodiment is mounted.

[0043] Fig. 4 is a diagram showing a schematic overall configuration of a vehicle 200 equipped with a battery pack 4 of lithium-ion secondary batteries according to this embodiment. The vehicle 200 shown in Fig. 4 is a hybrid vehicle. The vehicle 200 includes a control device 5 for the lithium-ion secondary battery, a PCU (Power Control Unit) 30, motor generators 41 and 42, an engine 50, a power split device 60, a drive shaft 70, and drive wheels 80.

[0044] The control device 5 for the lithium ion secondary battery includes a monitoring unit 20 that monitors the cell voltage BV, current BI, and ambient temperature BT of each cell battery 1 in the battery pack 4, a CPU 25 that controls the monitoring unit 20, and an ECU (Electronic Control Unit) 24 that includes a memory 26 that stores time-lapse data TD and time-lapse data VD.

[0045] <Motor Generator 42> Motor generator 42 mainly operates as an electric motor, and during sudden acceleration, drives drive wheels 80 with a large current supplied from battery pack 4. On the other hand, during braking of the vehicle or on a downhill slope, motor generator 42 operates as a generator to generate a large regenerative current and supply the large current to battery pack 4.

[0046] In such an in-vehicle battery pack 4, the ambient temperature T env The battery temperature T [°C] can vary greatly depending on the usage environment, such as when the battery temperature [°C] changes from low to high, when high-rate charging and discharging is performed, and when the cell SOC changes from low to high depending on the charging and discharging conditions.

[0047] <Lithium-ion secondary battery monitoring unit 20> FIG. 5 is a detailed block diagram of the monitoring unit 20 of the control device 5. The monitoring unit 20 includes a voltage sensor 21, a current sensor 22, and a temperature sensor 23. The voltage sensor 21 detects the voltage VB of each cell battery 1 individually. The current sensor 22 detects the current IB input / output to / from the cell battery 1, i.e., the current I [W] flowing through the battery pack 4. The temperature sensor 23 detects the battery temperature T [°C] of each cell battery 1 individually. The temperature sensor 23 also detects the environmental temperature T outside the battery pack 4. env Each sensor outputs a signal indicating the detection result as a current IB, a voltage VB, and a temperature TB to the ECU 24. These temperatures TB, cell voltage VB, and current IB indicate the state of the cell battery 1 and are used to calculate the battery temperature T [°C] and the environmental temperature T envThe temperature [°C], input / output current I [A], and cell voltage V [V] are stored. The internal resistance R [Ω] is also calculated from the input / output current I [A] and cell voltage V [V].

[0048] (Action of this embodiment) The control device 5 of this embodiment having such a configuration provides the following effects. <Procedure for controlling lithium-ion secondary batteries> 6 is a flowchart showing the procedure of the control method for a lithium ion secondary battery according to this embodiment. The purpose of this procedure is to determine whether or not it is necessary to reset the input / output limit value W. The control method for a lithium ion secondary battery according to this embodiment is executed by the control device 5.

[0049] When the procedure of the control method for the lithium ion secondary battery of this embodiment is started, first, the battery temperature T of each cell battery 1 and the environmental temperature T env is measured by the temperature sensor 23 and stored in the memory 26 of the ECU 24. This procedure corresponds to the "battery temperature acquisition step" of the present invention.

[0050] Next, an input / output limit value W is calculated based on the battery temperature T of each cell battery 1 (S2). Here, the input / output limit value W for each cell battery 1 is calculated based on the measured battery temperature T of each cell battery 1 and the relationship shown in Figure 8. Then, the input / output limit value W for the battery pack 4 is determined by referencing the input / output limit value W with the strictest limit value W among them. If this is not done, an excessive burden will be placed on a specific cell battery 1, which will accelerate the deterioration of that cell battery 1. This procedure corresponds to the "input / output limit value calculation step" of the present invention.

[0051] Next, the control device 5 determines whether there are any cell batteries 1 whose temperature is below the first temperature T1 (S3). Here, the "first temperature T1 [°C]" is the temperature below which the input / output capacity of the cell battery 1 falls below a set range, as shown in Figure 8. Therefore, when the battery temperature T [°C] falls below the first temperature T1 [°C], raising the battery temperature improves the input / output capacity, and the control device 5 can widen the range of the input / output limit value W [W]. Therefore, if there are no cell batteries 1 whose temperature is below the first temperature T1 (S2: NO), there is no need to raise the temperature, and control is performed based on the input / output limit value W that was set (S7).

[0052] On the other hand, if there is a cell battery 1 whose temperature is below the first temperature T1 (S3: YES), the range of the input / output limit value W [W] can be widened by setting the cell battery 1 to a battery temperature T [°C] higher than the first temperature T1.

[0053] Next, the maximum temperature T max [°C] is determined to be equal to or lower than the second temperature T2 [°C] (S4). max If the maximum temperature T [°C] exceeds the second temperature T2 (S4: NO), as shown in FIG. 8, if the battery temperature T of the cell battery 1 that exceeds the second temperature T2 is further increased, the range of the input / output limit value W [W] will be narrowed. Therefore, the input / output limit value W for the battery pack 4 will be narrowed due to that cell battery 1. On the other hand, max If the battery temperature T [°C] is equal to or lower than the second temperature T2 [°C] (S4: YES), there is room for raising the battery temperature T of that cell battery 1.

[0054] In this way, in this embodiment, among the battery temperatures T of the cell batteries 1 acquired in the battery temperature acquisition step (S1), there is a cell battery 1 that is equal to or lower than the set first temperature T1 [°C]. max [°C] is equal to or lower than the set second temperature T2 [°C]. In this case, the step (S5) of increasing the input / output limit value is executed.

[0055] <Step for expanding input / output limits (S5)> In the step (S5) of expanding the input / output limit value, the current input / output limit value W[W] of the battery pack 4 is increased to the input / output limit value W Lit This is the procedure for recalculating the input / output limit value in order to enlarge it to [W]. The procedure from S3 to S5 corresponds to the "step of enlarging the input / output limit value" of the present invention.

[0056] 7 is a flowchart showing the steps of a subroutine for the step (S5) of recalculating the input / output limit value W. Next, the step (S5) of recalculating the input / output limit value W will be described with reference to FIG.

[0057] When the procedure for recalculating the input / output limit value W (S5) is started, the minimum temperature T min [°C] SOC [%] is the threshold Th H It is determined whether the threshold value Th is greater than or equal to the threshold value Th (S51). H " is, for example, SOC 60%. This is because, in the case of an in-vehicle battery pack 4, the remaining discharge capacity for driving is expected to have a margin that does not exceed SOC 60%. In the high SOC range exceeding SOC 60%, it becomes impossible to utilize large regenerative currents, and the efficiency of the vehicle decreases. The value of SOC [%] can be determined, for example, from the cell voltage [V].

[0058] The SOC [%] of the lowest temperature is the threshold value Th H In the above cases (S51: YES), the input / output limit value W [W] is set to the expanded value only on the discharge side (S52). Minimum temperature T min [°C] SOC [%] is the threshold Th H If the value is less than the limit value (S51: NO), it is determined that the limit value on the charge side can be increased, and it is determined whether the limit value on the discharge side can be increased. min [°C] SOC [%] is the threshold Th L It is determined whether the threshold value Th is less than or equal to the threshold value Th (S53). L" is, for example, SOC 40%. This is because, for an in-vehicle battery pack 4, it is preferable to allow for a margin of not falling below SOC 40% as the remaining discharge capacity for driving. If the SOC is in the low SOC range below SOC 40%, it will not be possible to respond to sudden requests for output from the prime mover, and the efficiency of the vehicle will decrease. The value of SOC [%] can be determined, for example, from the cell voltage [V].

[0059] Minimum temperature T min [°C] SOC [%] is the threshold Th L If it is less than the limit value (S53: YES), the limit value on the charging side only is set to the expanded input / output limit value W [W] (S54). Minimum temperature T min [°C] SOC [%] is the threshold Th L If the limit value exceeds the above (S53: NO), an input / output limit value W is set that expands both charging and discharging.

[0060] <Calculation of input / output limit value W> Figure 11 shows the battery temperature T and the maximum temperature T max , minimum temperature T min , average temperature T ave , environmental temperature T env 1 is a graph showing the relationship between the battery temperature T and the maximum temperature T. max is the highest temperature among these. The lowest temperature T min is the lowest temperature among these. The temperature distribution of the battery temperature T is generally such that the temperature of the cell batteries 1a at both ends of the battery stack 2 shown in FIG. 1 is low and the temperature of the cell battery 1b in the center is high. The average temperature T ave is the arithmetic mean value of these battery temperatures T. Note that the ambient temperature T env is the temperature of the air around the battery pack 4, and is a factor that affects the cooling of the battery pack 4. For example, in summer, when a load is applied to the internal combustion engine under the scorching sun, the value will be high, and in winter, when the battery pack is left unused, the value will be low.

[0061] Here, the steps of expanding the input / output limit values ​​(S52, S54, S55) in this embodiment are as follows: Lit Determine [W]. The recalculated input / output limit value is W Lit [W], current input / output limit value W[W], T max [°C] and T min The magnification (1.0x or more) determined from the difference in [°C] is M diff Also, T max [°C] and T ave The magnification (1.0x or more) determined from the difference in [°C] is M ave In this case, the recalculated input / output limit value is W Lit [W] is calculated using the following formula.

[0062] W Lit =W×M diff ×M ave These scaling factors are optimized by those skilled in the art based on measurements with similar cells. In this case, the ambient temperature is T env The ambient temperature is not considered [°C]. env If [°C] is further taken into consideration, the results are as follows:

[0063] Environmental temperature T env [°C], T max [°C] and T env The magnification (1.0 or more) determined from the difference in [°C] is M env When the recalculated input / output limit value is W Lit Calculate [W] using the following formula.

[0064] W Lit =W×M diff ×M ave ×M env When making adjustments, it is advisable to pay attention to the following points: "M diff " In T max [°C] and T min The larger the difference in [°C], the greater the T minThe limit value of [°C] makes performance useless. diff Increase the T max [°C] and T min Therefore, it is preferable to reduce the difference between the maximum temperature T max [°C] and minimum temperature T min The larger the difference from [°C], the larger the expansion.

[0065] <Maximum temperature T max [°C] and average temperature T ave [°C] Relationship "M ave " In T max [°C] and T ave The larger the difference in [°C], the more cells 1 there are on the low-temperature side. ave It is preferable to increase the average temperature T of the cells 1 in the battery pack 4 by increasing the input / output limit value W [W]. ave and maximum temperature T max The larger the difference, the larger the expansion.

[0066] Figure 12 shows the average temperature T ave The maximum temperature T when max 12 is a graph illustrating the relationship between the average temperature T ave High, maximum temperature T max When the difference between the battery temperature T and the cell battery temperature T is small, the battery temperature T is high and the temperature difference between the cell batteries 1 naturally decreases.

[0067] "M env " In T max [°C] and T env The smaller the difference in [°C], the greater the T env The effect of increasing the battery temperature T of the cell battery 1 due to the env It is preferable to increase the input / output limit value W [W] to reduce the temperature variation by increasing the heat generated by the increase in the input / output limit value W [W].

[0068] <Operation time calculation (S56)> Once the input / output limit value W [W] has been determined using the above procedure, the operation time calculation (S56) is performed. In the operation time calculation (S56), if the operation time for sampling the battery temperature T [°C] is too long, excessive temperature adjustment may occur. To prevent such excessive temperature adjustment, the heat generation amount is estimated in advance and the operation time is adjusted accordingly.

[0069] In the step of calculating the application time (S56), the acquisition time interval T int If [s] is longer than the set value, the maximum temperature T max [°C] unit cell upper limit temperature T Lit [°C] Acquisition time interval T int Determine [s].

[0070] Acquisition time interval T int [s] is the heat capacity of cell battery 1 in C [Cal] and the upper limit temperature in T Lit [°C], the maximum battery temperature is T max , input / output current is I [A], internal resistance is R [Ω], T int =C(T Lit -T max ) / I 2 Calculated based on R.

[0071] By setting it in this way, it is possible to prevent excessive temperature adjustment. This completes the steps S51 to S56, which are the subroutine of the step (S5) for increasing the input / output limit values.

[0072] Now, returning to the flowchart shown in Fig. 6, the explanation will be continued. After the procedure of recalculating the input / output limit value (S5) is completed, the recalculated input / output limit value W Lit [W] performs the input / output (S6) procedure. Here, the recalculated input / output limit value W Lit By inputting and outputting at [W], it is possible to promote the heat generation of the low-temperature cell batteries 1, thereby equalizing the battery temperature T among the cell batteries 1 and improving the efficiency of the battery pack 4.

[0073] Recalculated input / output limit value WLit After executing the input / output procedure (S6) in [W], the process returns to S1 and the control of this embodiment is performed. (Effects of this embodiment) The control method and control device for a lithium ion secondary battery according to the present embodiment as described above has the following advantages.

[0074] (1) The control method for a lithium ion secondary battery according to this embodiment has the effect of enabling efficient use by making the battery temperature T [°C] uniform. (2) Also, the input / output limit value W Lit [W] has the effect of reducing the temperature difference of the cell batteries 1, which have a temperature difference, simply by appropriately controlling the input and output of the entire battery pack 4.

[0075] (3) Input / output limit value W Lit [W] is the maximum temperature T of the unit battery 1 that is below the first temperature T1 [°C]. max [°C] is equal to or lower than the second temperature T2 [°C]. Lit This has the effect of making it possible to write [W].

[0076] (3) The input / output limit value calculation step (S5) is performed based on the minimum temperature T min If the SOC of the cell battery 1 at [°C] is less than the minimum value of the set charge / discharge range (for example, SOC 40 [%]), the limit value of the input / output limit value W [W] on the charge side is increased. min If the SOC of the cell battery 1 at [°C] exceeds the maximum value of the set charge / discharge range (for example, 60[%]), the limit value of the discharge side input / output limit value W [W] is increased. min If the SOC of the cell battery 1 in °C is equal to or greater than the minimum value and equal to or less than the maximum value, the limit values ​​of both the charge-side and discharge-side input / output limit values ​​W [W] are increased. This has the effect of avoiding control such as discharging in a low SOC region or charging in a high SOC region.

[0077] (4) The procedure for calculating the operating time (S56) can prevent excessive temperature adjustment caused by the operating time for sampling the battery temperature T [°C] being too long. To prevent such excessive temperature adjustment, the procedure for calculating the operating time (S56) estimates the amount of heat generated in advance and adjusts the operating time, which has the effect of enabling appropriate temperature management.

[0078] (5) Recalculated input / output limit value W Lit [W] to W Lit =W×M diff ×M ave Therefore, the optimum input / output limit value W Lit This has the effect of allowing you to determine [W].

[0079] (6) Furthermore, the ambient temperature is T env [°C], and set the input / output limit value to W. Lit [W] to W Lit =W×M diff ×M ave ×M env Therefore, a more appropriate input / output limit value W Lit This has the effect of allowing you to determine [W].

[0080] (Another example) The present invention is not limited to the above-described embodiment, and can be implemented, for example, as follows. The secondary battery of this embodiment has been described using an example in which the battery pack 4 is an in-vehicle lithium-ion secondary battery as the assembled battery, and the cell batteries 1 that make up the battery pack 4 are the unit batteries. The present invention is not limited to this example. For example, instead of a single lithium-ion secondary battery cell 1, a unit battery can be formed by assembling multiple cell batteries 1. The type of battery is not limited to a lithium-ion secondary battery, and can be a non-aqueous electrolyte secondary battery, an alkaline secondary battery, an all-solid-state battery, or the like. In addition, in batteries such as nickel-metal hydride batteries, a battery module including multiple single cells can be used as the unit battery. Furthermore, in a battery pack 4 including multiple battery stacks 2, the battery stacks 4 themselves can be used as the unit batteries.

[0081] In the present embodiment, the temperatures of all the cells included in the battery pack are measured as unit cells. However, it is also possible to measure the temperatures of only the cells at the end and center, for example. Examples of assembled batteries include a battery stack including a plurality of cell batteries 1 or battery modules, and a battery pack 4 including a plurality of battery stacks.

[0082] The shape of the secondary battery is not limited to a plate shape, but may be a cylindrical shape, and the assembled battery does not necessarily have to be the battery stack 2. In the present embodiment, the wound electrode body 10 as shown in FIGS. 2 and 3 has been described as an example. However, the present invention is not limited to the wound electrode body 10 and can also be applied to a laminated electrode body.

[0083] The battery case 11 of the cell battery 1 may be made of any material, including aluminum alloy, other metals such as stainless steel, or resin. The numerical values ​​and numerical ranges described in the present embodiment are merely examples for explaining one embodiment, and the present invention is not limited thereto. These can be optimized and implemented by those skilled in the art according to the configuration of the target secondary battery, etc.

[0084] The drawings and graphs are for the purpose of explaining the present embodiment, and the present invention is not limited thereto. Furthermore, the shapes, dimensions, balance, number of layers, etc. of the electrode body 10 of the lithium ion secondary battery shown in the drawings are schematically simplified or exaggerated, and other drawings and graphs do not limit the present invention.

[0085] The flowcharts shown in Figures 6 and 7 are examples, and steps can be added, deleted, changed, or implemented in a different order. In addition, it goes without saying that the present invention can be implemented by those skilled in the art by adding, deleting or modifying its configuration, provided that the addition, deletion or modification does not deviate from the scope of the claims. [Explanation of symbols]

[0086] 1...Cell battery (unit battery) 2...Battery stack 3. Battery case 4...Battery pack (battery assembly) 5...Control device 10...Electrode body 11...Battery case 12...lid body 13...Negative electrode current collector 14...Negative external terminal 15...Positive electrode current collector 16...Positive external terminal 17...Electrolyte 18...Discharge valve 19...Filling port 100...Negative electrode plate 101...Negative electrode substrate 102...Negative electrode composite layer 103...Negative electrode connection part 110...Positive electrode plate 111...Positive electrode substrate 112...Positive electrode mixture layer 113...Positive electrode connection part 120...Separator 200...vehicle 20...Monitoring unit 21...Voltage sensor 22...Current sensor 23...Temperature sensor 24...ECU (Electronic Control Unit) 25...CPU 26...Memory 30...PCU (Power Control Unit) 41, 42...Motor generator 50...Engine 60...Power split device 70...Drive shaft 80...Drive wheels TB…Temperature VB: Cell voltage IB…Current T[°C]…Battery temperature T1 [°C]...First temperature T2 [°C]: Second temperature T max [°C]…Maximum temperature T min [°C]…Minimum temperature T ave [°C]…Average temperature T env [°C]…Environmental temperature Th: Set threshold W[W]...Current input / output limit value W Lit [W]...Recalculated input / output limit value T int [s]...Acquisition time interval Δt...time C [Cal]...Heat capacity of unit battery T Lit [°C]…Upper temperature limit I [A]...Input / output current R[Ω]…Internal resistance M diff …T max [°C] and T min Magnification (1.0x or more) determined from the difference in [°C] M ave …T max [°C] and T ave Magnification (1.0x or more) determined from the difference in [°C] M env …T max [°C] and T env Magnification (1.0x or more) determined from the difference in [°C]

Claims

1. In a battery pack configured by combining a plurality of unit batteries each consisting of a secondary battery, a battery temperature acquisition step of acquiring battery temperatures T [°C] of the plurality of unit batteries constituting the battery pack; an input / output limit value calculation step of calculating an input / output limit value W [W] that limits input / output due to charging and discharging based on the battery temperatures T [°C] of each of the plurality of unit batteries constituting the battery pack, which are acquired in the battery temperature acquisition step; The battery temperature T [°C] of the unit battery acquired in the step of acquiring the battery temperature is the set first temperature T １ There are unit cells below [°C], The maximum temperature T of the acquired unit battery temperatures T [°C] ｍａｘ [°C] is the set second temperature T ２ [°C] or less, The current input / output limit value W [W] of the battery pack is set as the input / output limit value W Ｌｉｔ Steps for expanding the input / output limit value to [W] A method for controlling a secondary battery, comprising:

2. In the step of increasing the input / output limit value, the input / output limit value W [W] is set to a value less than the maximum temperature T ｍａｘ [°C] and minimum temperature T ｍｉｎ The larger the difference between [°C], the larger the 2. The method for controlling a secondary battery according to claim 1,

3. In the step of increasing the input / output limit value, the input / output limit value W [W] is set to an average temperature T ａｖｅ [°C] and maximum temperature T ｍａｘ The larger the difference between [°C], the larger the 2. The method for controlling a secondary battery according to claim 1,

4. The step of calculating the input / output limit values ​​includes: Minimum temperature T ｍｉｎ If the SOC of the unit battery [°C] is less than the minimum value of the set charge / discharge range, the limit value of the charge-side input / output limit value W [W] is increased, The minimum temperature T ｍｉｎ When the SOC of the unit battery [°C] exceeds the maximum value of the set charge / discharge range, the limit value of the discharge side input / output limit value W [W] is increased, The minimum temperature T ｍｉｎ When the SOC of the unit battery [°C] is equal to or greater than the minimum value and equal to or less than the maximum value, the limits of both the charge-side and discharge-side input / output limit values ​​W [W] are increased.

2. The method for controlling a secondary battery according to claim 1,

5. The step of calculating the input / output limit values ​​includes: The time interval T for acquiring the battery temperature T [°C] ｉｎｔ [s] is the maximum temperature T ｍａｘ The unit battery reaches the upper limit temperature T Ｌｉｔ [°C] so that the acquisition time interval T ｉｎｔ The step of calculating the application time [s] is provided.

2. The method for controlling a secondary battery according to claim 1,

6. The acquisition time interval T ｉｎｔ [s] is The heat capacity of the unit battery is C [Cal], and the upper limit temperature is T Ｌｉｔ [°C], the maximum battery temperature is T ｍａｘ [°C], input / output current is I [A], and internal resistance is R [Ω]. T ｉｎｔ =C(T Ｌｉｔ -T ｍａｘ ) / I ２ R Calculation based on 6. The method for controlling a secondary battery according to claim 5,

7. The step of expanding the input / output limit value includes: The recalculated input / output limit value is W Ｌｉｔ [W], the current input / output limit value is W[W], T ｍａｘ [°C] and T ｍｉｎ The magnification (1.0 or more) determined from the difference in [°C] is M ｄｉｆｆ , T ｍａｘ [°C] and T ａｖｅ The magnification (1.0 or more) determined from the difference in [°C] is M ａｖｅ When The recalculated input / output limit value is W Ｌｉｔ [W], W Ｌｉｔ =W×M ｄｉｆｆ ×M ａｖｅ 2. The method for controlling a secondary battery according to claim 1, wherein the calculation is performed by:

8. environmental temperature to T ｅｎｖ When expressed as [°C], T ｍａｘ When expressed as [°C], T ｍａｘ [°C] and T ｅｎｖ The magnification (1.0 or more) determined from the difference in [°C] is M ｅｎｖ When The recalculated input / output limit value is W Ｌｉｔ [W], W Ｌｉｔ =W×M ｄｉｆｆ ×M ａｖｅ ×M ｅｎｖ 8. The method for controlling a secondary battery according to claim 7, wherein the calculation is performed by:

9. A control device for a secondary battery equipped with a computer, In an assembled battery configured by combining a plurality of unit batteries each composed of a secondary battery, a battery temperature acquisition means for acquiring a battery temperature T [°C] of the plurality of unit batteries that constitute the assembled battery; an input / output limit value calculation means for calculating an input / output limit value W [W] that limits input / output due to charging and discharging based on the battery temperature T [°C] of each of the plurality of unit batteries constituting the battery pack acquired by the battery temperature acquisition means; The battery temperature T [°C] of the unit battery acquired by the battery temperature acquisition means is the set first temperature T １ There are unit cells below [°C], The maximum temperature T of the unit battery T obtained ｍａｘ [°C] is the set second temperature T ２ [°C] or less, The input / output limit value W [W] of the battery pack is set to the input / output limit value W Ｌｉｔ [W], and A control device for a secondary battery comprising:

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