JP2023167560A - Control method of secondary battery and control apparatus - Google Patents

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

The present invention relates to a secondary battery control method and control device, and more particularly to a secondary battery control method and control device that allow efficient use of the battery.

BACKGROUND ART In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries and alkaline secondary batteries such as nickel-hydrogen storage batteries have been used as power sources for electric vehicles and the like. Since the voltage and current of these secondary battery cells are low, high voltage and high current can be carried out using a battery pack, which is an assembled battery of secondary batteries in which many cell batteries are stacked and connected in series and parallel. supply.

When a secondary battery is used as an assembled battery, for example, the center portion of the stacked assembled battery is less likely to be cooled than the end portions and often has a higher temperature. Furthermore, heat generation may vary due to variations in inherent characteristics such as internal resistance of individual cell batteries. The performance of secondary batteries changes depending on the temperature.

Therefore, in the invention of the power supply system disclosed in Patent Document 1, the electric power charged and discharged in each of the power storage units is managed in consideration of the temperature difference between the power storage units. Therefore, it is possible to equalize the temperature generated between the power storage units and efficiently manage the temperature of the entire power storage unit while satisfying the power request value from the load device.

Further, the invention disclosed in Patent Document 2 includes power storage devices that are used for driving a vehicle and are arranged at different positions, a controller that controls the drive of these power storage devices, and a temperature sensor for the power storage devices. The controller changes the drive ratio based on the relationship of the device temperature of each power storage device with respect to the temperature range used for temperature control of the power storage device, and the magnitude relationship of the temperatures.

With inventions such as these, control can be performed based on the temperature difference between each secondary battery.

Japanese Patent Application Publication No. 2008-154302 Japanese Patent Application Publication No. 2012-200140

However, the temperature distribution within the assembled battery is not taken into account.
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 assembled battery.

In order to solve the above problems, in the secondary battery control method of the present invention, in an assembled battery configured by combining a plurality of unit batteries made of secondary batteries, the battery temperature T[° C], and input/output due to charging and discharging based on the battery temperature T [°C] of each of the plurality of unit batteries constituting the assembled battery obtained in the step of obtaining the battery temperature. The set first temperature T ₁ [°C ] If there are the following unit batteries, and the maximum temperature T _max [°C] of the temperature T of the obtained unit battery is equal to or lower than the set second temperature T ₂ [°C], the temperature of the assembled battery is The present invention is characterized by comprising an input/output limit value expansion step of expanding the current input/output limit value W[W] to the input/output limit value W _Lit [W].

In the step of expanding the input/output limit value, the input/output limit value W [W] increases as the difference between the maximum temperature T _max [°C] and the minimum temperature T _min [°C] of the unit battery increases. You can do it like this.

In the step of expanding the input/output limit value, the input/output limit may be increased as the difference between the average temperature T _ave and the maximum temperature T _max of the unit cells in the assembled battery becomes larger.

In the input/output limit value calculation step, if the SOC of the unit battery at the minimum temperature T _min is less than the minimum value of the set charge/discharge range, the input/output limit value W [W] on the charging side is expanded. However, if the SOC of the unit battery with 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 is expanded, and the SOC of the unit battery with the lowest temperature exceeds the maximum value of the set charge/discharge range. When the SOC is equal to or greater than the minimum value and equal to or less than the maximum value, both the input/output limit values W [W] on the charging side and the discharging side may be expanded.

In the step of calculating the input/output limit value, the acquisition time interval T _int [s] of the battery temperature [°C] is such that the unit battery at the maximum temperature T _max [°C] reaches the upper limit temperature T _Lit [°C]. It may also include a step of calculating the application time to determine the acquisition time interval T int [s] so that the acquisition time interval T _int [s] does not occur.

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

The step of expanding the input/output limit value is to set the input/output limit value after recalculation as W _Lit [W], the current input/output limit value as W [W], T _max [°C] and T _min [°C] When M _{diff is} the magnification determined from the difference between T _max [°C] and T _ave [°C] (1.0 times or more), The calculated input/output limit value W _Lit [W] may be calculated by W _Lit = W x M _diff x M _ave .

When the environmental temperature is T _env [°C], and when the magnification (1.0 times or more) determined from the difference between T _max [°C] and T _env [°C] is M _env , the input after recalculation is The output limit value W _Lit [W] may be calculated by W _Lit = W x M _diff x M _ave x M _env .

A control device for a secondary battery equipped with a computer according to the present invention, in a battery assembly configured by combining a plurality of unit batteries made of secondary batteries, obtains battery temperatures of a plurality of unit batteries constituting the battery assembly. Calculating an input/output limit value W [W] that limits input/output due to charging and discharging based on a battery temperature acquisition means and each battery temperature of a plurality of unit batteries forming the assembled battery acquired by the battery temperature acquisition means. Among the unit battery temperatures acquired by the input/output limit value calculation means and the battery temperature acquisition means, there is a unit battery whose temperature is equal to or lower than the set first temperature, and the highest temperature of the acquired unit battery is the set temperature. The battery pack is characterized by further comprising input/output limit value expanding means for expanding the input/output limit value of the assembled battery when the temperature is below a second temperature.

The secondary battery control method and control device of the present invention can improve the efficiency of the assembled battery.

It is a perspective view showing a battery pack of a lithium ion secondary battery of this embodiment. FIG. 1 is a perspective view of the external appearance of a cell battery of a lithium ion secondary battery to be controlled in this embodiment. FIG. 1 is a schematic diagram showing the configuration of an electrode body of a lithium ion secondary battery according to the present embodiment. 1 is a diagram schematically showing the overall configuration of a vehicle equipped with a battery pack of lithium ion secondary batteries according to the present embodiment. FIG. 3 is a detailed block diagram of a monitoring unit of the control device; 3 is a flowchart showing the procedure of a method for controlling a lithium ion secondary battery according to the present embodiment. 3 is a flowchart showing the procedure of a subroutine for recalculating the input/output limit value W (S5). It is a graph showing the relationship between battery temperature and input/output limitations. It is a graph showing the relationship between battery temperature T [°C] and internal resistance R [Ω]. When the battery temperatures T [°C] of two cell batteries 1 _A and 1 _B with different battery temperatures T [°C] are T _A and T _B [°C], respectively, the current I [A] is It is a graph showing the temperature change when the voltage is applied. It is a graph showing the relationship between battery temperature T, maximum temperature T _max , minimum temperature T _min , average temperature T _ave , and environmental temperature T _env . It is a graph explaining the relationship with the maximum temperature T _max when the average temperature T _ave is high.

EMBODIMENT OF THE INVENTION Hereinafter, the control method and control apparatus of the secondary battery of this invention are demonstrated using one embodiment of the control method and control apparatus of the lithium ion secondary battery for vehicles.
(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 secondary battery control method of this embodiment is performed on a battery pack 4 that is used as an on-vehicle drive power source, for example. In the battery pack 4, a plurality of cell batteries 1 (see FIG. 2) are stacked and restrained (34 cells in FIG. 1) to form a battery stack 2. Such a battery stack 2 is housed in a battery case 3. A plurality of battery stacks (two in this case) housed in such a battery case 3 are housed in a housing container (not shown) and electrically connected to each other, and a control device, sensor, cooling device, external terminal, etc. Installed and sealed. The battery pack 4 formed in this manner is charged and discharged as a driving power source for a vehicle. In such a battery pack 4, charging and discharging are performed by driving when the vehicle is running, regenerative current, and internal and external charging.

In a battery pack 4 equipped with such a plurality of cell batteries 1, the battery temperature T [°C] may vary 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. Disparities may arise. For example, the cell battery 1a shown in FIG. 1 is placed at the end. Further, the cell battery 1b is arranged at the center in the stacking direction. In such an arrangement, the cell batteries 1a at the ends are generally more easily cooled than the cell batteries 1b at the center, so the battery temperature T [°C] is often lower.

<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 indicates the battery temperature T [°C]. The vertical axis indicates the charging/discharging capacity in power [W] when the battery temperature is T [°C]. Above the horizontal axis indicates charging (+), and below the horizontal axis indicates discharging (-). As a characteristic of a lithium ion secondary battery, the charging/discharging ability changes depending on the battery temperature T. As shown in FIG. 8, when the battery temperature T is within a constant temperature range, it exhibits a predetermined charging/discharging ability, but in a high temperature range or a low temperature range, the input/output ability decreases, so the control device 5 of the battery pack 4 (See FIG. 4), input/output is restricted. For example, at the first temperature T ₁ [°C] or higher and the second temperature T ₂ [°C] or lower, the input/output limit value [W] is approximately constant for both charging and discharging. Demonstrate ability. On the other hand, below the first temperature T ₁ [°C], the absolute value of the input/output limit value [W] becomes smaller for both charging and discharging as the temperature decreases. Further, when the second temperature T ₂ [°C] is exceeded, the absolute value of the input/output limit value W [W] rapidly decreases in both charging and discharging as the temperature decreases. Therefore, it can be seen that when using the battery pack 4, it is preferable to use the battery pack 4 within a range of not less than the first temperature T ₁ [°C] and not more than the second temperature T ₂ [°C].

Note that such control of the input/output limit value [W] is performed on the entire battery pack 4. Therefore, if there are variations in battery temperature T [°C] of the cell batteries 1, it becomes difficult to appropriately control all the cell batteries 1. For this reason, basically, the input/output limit value [W] of the cell battery 1 that has the largest input/output limit has to be matched, resulting in a decrease in the efficiency of the battery pack 4.

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

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 FIG. 9, in the lithium ion secondary battery, when the battery temperature T [°C] increases, the chemical reaction becomes active, and as a result, the internal resistance R [Ω] decreases. On the other hand, when the battery temperature T [°C] decreases, the internal resistance R [Ω] rapidly increases.

<Reason why this embodiment can equalize temperature>
FIG. 10 shows the current I when the battery temperatures T [°C] of two cell batteries 1 _A and 1 _B , which have different battery temperatures T [°C], are T _A and T _B [°C], respectively. It is a graph showing a temperature change when [A] is applied. The horizontal axis shows changes in time t [s]. The vertical axis indicates the battery temperatures T _A and T _B [°C] of the two-cell battery 1 _A and the cell battery 1 _B at that time.

This embodiment is an invention that homogenizes the difference in battery temperature T [°C] of the cell battery 1 in the battery pack 4 when there is a temperature difference. In FIG. 10, at the start of comparison, the battery temperatures T [°C] of two cell batteries 1 _A and 1 _B with different battery temperatures T [°C] are T _A and T _B [°C], respectively. . Here, T _A > T _B. Further, it is assumed that T _A −T _B =T _diff [°C].

After that, a current I [A] is applied. At this time, as explained in FIG. 9, the higher the battery temperature T [°C] is, the smaller the internal resistance R [Ω] is.
The internal resistance R _A of the cell battery 1 _A and the internal resistance R _B of the cell battery 1 _B when a current I [A] is applied are compared. In this case, the battery temperature T _A of the cell battery 1 _A and the battery temperature T _B of the cell battery 1 _B are such that T _A >T _B. Therefore, the higher the battery temperature T [°C] is, the smaller the internal resistance R [Ω] is, so that the internal resistance [Ω] has the relationship R _A <R _B.

The calorific value of the cell battery _1A and the cell battery _1B can be expressed as I ² _RA Δt and I ² _RB Δt, respectively. Here, since the current of cell battery _1A and cell battery _1B is a common circuit, I=I. Further, the time period during which the current I is applied is also common to Δt. Therefore, the ratio of the calorific value I ² _RA Δt of the cell battery 1 _A to the calorific value I ² _RB Δt of the cell battery 1 _B is I ² RA Δt:I ² _{RB Δt} =R _A : _RB . As mentioned above, the internal resistance [Ω] satisfies R _A < R _B , so if the calorific value I ² R _A Δt of cell battery 1 _A and the calorific value I ² R _B Δt of cell battery 1 _B , cell battery 1 The calorific value I ² R _B Δt of _B is larger.

That is, as shown in FIG. 10, when the input/output current I is applied by Δt, the difference in temperature within the battery pack 4 can be reduced. Here, the temperature difference between the temperature of the cell battery _1A and the temperature of the cell battery _1B is expressed as T' _diff =T' _A - T' _B. T _diff = _TA - T _B [°C] before applying the input/output current I has the relationship T' _diff <T _diff . Therefore, by applying the input/output current I[A] of Δt, the difference in temperature within the battery pack 4 can be reduced.

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

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

<Electrode body 10>
FIG. 3 is a schematic diagram illustrating a partially developed configuration of the stacked body of the 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 negative electrode composite material layers 102 on both sides of a negative electrode base material 101 . The positive electrode plate 110 includes positive electrode composite layers 112 on both sides of a positive electrode base material 111 . The negative electrode plate 100 and the positive electrode plate 110 are stacked on top of each other with a separator 120 in between to form an electrode body 10 . This laminated body is wound in the longitudinal direction Z around the winding axis and formed into a flat shape to constitute the electrode body 10.

The negative electrode connection portion 103 functions as a current collector that extracts electricity from the negative electrode composite material layer 102 of the negative electrode plate 100. The positive electrode connection portion 113 functions as a current collector that extracts electricity from the positive electrode composite material layer 112 of the positive electrode plate 110.

<Negative electrode plate 100>
A negative electrode plate 100 is constructed by forming negative electrode composite material layers 102 on both sides of a negative electrode base material 101. In the embodiment, the negative electrode base material 101 is made of Cu foil. The negative electrode base material 101 serves as a base for the negative electrode composite material layer 102 as an aggregate, and has the function of a current collecting member that collects electricity from the negative electrode composite material layer 102. In the negative electrode plate 100, a negative electrode composite layer 102 is formed on a negative electrode base material 101 made of metal. In the embodiment, the negative electrode active material is a material capable of intercalating and deintercalating lithium ions, and is a powdery carbon material made of graphite or the like.

The negative electrode plate 100 is produced, for example, by kneading a negative electrode active material, a solvent, and a binder, and applying the kneaded negative electrode mixture onto the negative electrode base material 101 and drying it.
<Positive electrode plate 110>
A positive electrode plate 110 is configured by forming positive electrode composite material layers 112 on both sides of a positive electrode base material 111. In the embodiment, the positive electrode base material 111 is made of Al foil or Al alloy foil. The positive electrode base material 111 serves as a base for the positive electrode composite material layer 112 as an aggregate, and has the function of a current collecting member that collects electricity from the positive electrode composite material layer 112.

In the positive electrode plate 110, a positive electrode composite layer 112 is formed on the surface of a positive electrode base material 111. The positive electrode composite material layer 112 includes a positive electrode active material. The positive electrode active material is a material that can insert and release lithium, and for example, lithium cobalt oxide (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium nickel oxide (LiNiO ₂ ), etc. can be used. Alternatively, a material in which LiCoO ₂ , LiMn ₂ O ₄ , and LiNiO ₂ are mixed in an arbitrary ratio may be used.

Further, the positive electrode composite material layer 112 includes a conductive material. As the conductive material, for example, carbon black such as acetylene black (AB) or Ketjen black, or graphite can be used.

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 applying the kneaded positive electrode mixture onto the positive electrode base material 111 and drying it. be done.
<Separator 120>
The separator 120 is a nonwoven fabric made of polypropylene or the like which is a porous resin for holding the non-aqueous electrolyte 17 between the negative electrode plate 100 and the positive electrode plate 110. As the separator 120, porous polymer membranes such as porous polyethylene membranes, porous polyolefin membranes, and porous polyvinyl chloride membranes, or lithium ion or ion conductive polymer electrolyte membranes may be used alone or in combination. You can also. When the electrode body 10 is immersed in the non-aqueous electrolyte 17, the non-aqueous electrolyte permeates from the ends of the separator 120 toward the center.

<Nonaqueous electrolyte 17>
A non-aqueous electrolyte is a composition containing a supporting salt in a non-aqueous solvent. Here, 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), ethylmethyl carbonate (EMC), etc. may be used. Supporting salts include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiC(CF ₃ SO ₂ ) ₃ , LiI etc. can be used. Moreover, one or more kinds of lithium compounds (lithium salts) selected from these can be used.

<Heat generation from 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 to generate heat, and the heat is released to the outside via 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 of each cell battery 1 is unavoidable.

<Overall configuration of vehicle equipped with secondary battery>
Next, the vehicle 200 in which the battery pack 4 of the lithium ion secondary battery of this embodiment is mounted will be briefly described.

FIG. 4 is a diagram schematically showing the overall configuration of a vehicle 200 in which a battery pack 4 of a lithium ion secondary battery according to the present embodiment is mounted. Vehicle 200 illustrated in FIG. 4 is a hybrid vehicle. Vehicle 200 includes a lithium ion secondary battery control device 5, a PCU (Power Control Unit) 30, motor generators 41 and 42, an engine 50, a power split device 60, a drive shaft 70, A driving wheel 80 is provided.

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

<Motor generator 42>
The motor generator 42 mainly operates as an electric motor, and drives the drive wheels 80 with a large current supplied from the battery pack 4 during sudden acceleration. On the other hand, when the vehicle is braking or on a downhill slope, the motor generator 42 operates as a generator to perform regenerative power generation with a large current, and supplies a large current to the battery pack 4.

In such an automotive battery pack 4, the environmental temperature T _env [°C] changes from low to high temperature, high-rate charging and discharging is performed, and the cell SOC changes from low to high due to the charging and discharging conditions. The battery temperature T [°C] changes greatly depending on the usage environment.

<Lithium ion secondary battery monitoring unit 20>
FIG. 5 is a detailed block diagram of the monitoring unit 20 of the control device 5. As shown in FIG. Monitoring unit 20 includes a voltage sensor 21, a current sensor 22, and a temperature sensor 23. Voltage sensor 21 detects voltage VB of each cell battery 1 individually. The current sensor 22 detects the current IB input/output to the cell battery 1, that is, the current I [W] flowing to the battery pack 4. The temperature sensor 23 individually detects the battery temperature T [°C] of each cell battery 1. The temperature sensor 23 also detects the environmental temperature T _env [°C] outside the battery pack 4 . Each sensor outputs a signal indicating its detection result to the ECU 24 as a current IB, a voltage VB, and a temperature TB. These temperature TB, cell voltage VB, and current IB indicate the state of these cell batteries 1. At each time Δt, the battery temperature T [°C], the environmental temperature T _env [°C], and the input/output current I [A] and the cell voltage V [V]. Furthermore, the internal resistance R [Ω] is calculated from the input/output current I [A] and the cell voltage V [V].

(Action of this embodiment)
The control device 5 of this embodiment having such a configuration has the following effects.
<Steps for controlling lithium ion secondary battery>
FIG. 6 is a flowchart showing the procedure of the lithium ion secondary battery control method of this embodiment. The purpose of this procedure is to determine whether the input/output limit value W needs to be reset. The lithium ion secondary battery control method of this embodiment is executed by the control device 5.

When the procedure of the lithium ion secondary battery control method of the present embodiment is started, the temperature sensor 23 first measures the battery temperature T of each cell battery 1 and the environmental temperature T _env by temperature measurement (S1). , are stored in the memory 26 of the ECU 24. This procedure corresponds to the "battery temperature acquisition step" of the present invention.

Next, an input/output limit value W is calculated based on the battery temperature T for 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 for each cell battery 1 and based on the relationship shown in FIG. Then, the input/output limit value W for the battery pack 4 is determined by referring to the one with the strictest input/output limit value W among them. This is because if this is not done, an excessive load will be placed on a particular cell battery 1, which will lead to further deterioration of that cell battery 1. This procedure corresponds to the "input/output limit value calculation step" of the present invention.

Next, the control device 5 determines whether there is any cell battery 1 whose temperature is less than the first temperature _T1 (S3). Here, the "first temperature T ₁ [°C]" is a temperature below which the input/output capacity becomes smaller than the set range in the cell battery 1, as shown in FIG. 8. Therefore, when the battery temperature T [°C] becomes less than the first temperature T ₁ [°C], the input/output capacity is improved by increasing the battery temperature, and the control device 5 sets the input/output limit value W It becomes possible to widen the width of [W]. Therefore, if there is no cell battery 1 whose temperature is less than the first temperature T ₁ (S2: NO), there is no need to increase the temperature, so control is performed based on the set input/output limit value W (S7). .

On the other hand, if there is a cell battery 1 whose first temperature T _is less than ₁ (S3: YES), the input/output It becomes possible to widen the width of the limit value W[W].

Next, it is determined whether the maximum temperature T _max [°C] is equal to or lower than the second temperature T ₂ [°C] (S4). Here _, if the maximum temperature T _max [°C] exceeds the second temperature T ₂ (S4: NO), as shown in FIG. If the temperature T is further increased, the width of the input/output limit value W [W] will become smaller. Therefore, the input/output limit value W of the battery pack 4 is narrowed due to the cell battery 1. On the other hand, if the maximum temperature T _max [°C] is equal to or lower than the second temperature T ₂ [°C] (S4: YES), there is room to increase the battery temperature T of the cell battery 1.

As described above, 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 T ₁ [°C]. In addition, the maximum temperature T _max [°C] of the acquired battery temperatures T is equal to or lower than the set second temperature T ₂ [°C]. In that case, a step (S5) of expanding the input/output limit value is executed.

<Step of expanding input/output limit value (S5)>
The input/output limit value expansion step (S5) is a procedure for recalculating the current input/output limit value W[W] of the battery pack 4 in order to expand it to the input/output limit value W _Lit [W]. The steps S3 to S5 correspond to the "input/output limit value expansion step" of the present invention.

FIG. 7 is a flowchart showing the subroutine procedure for recalculating the input/output limit value W (S5). Next, the procedure for recalculating the input/output limit value W (S5) will be explained with reference to FIG.

When the procedure for recalculating the input/output limit value W (S5) is started, it is determined whether the SOC [%] of the minimum temperature T _min [°C] is equal to or higher than the threshold Th _H (S51). Here, the "threshold value Th _H " is, for example, SOC 60%. This is because, in the case of the vehicle-mounted battery pack 4, the remaining discharge amount for driving is expected to have a margin that does not exceed the SOC of 60%. If the SOC is in a high SOC region exceeding 60%, it becomes impossible to utilize a large regenerative current, and the efficiency of the vehicle decreases. The value of SOC [%] can be determined based on, for example, the cell voltage [V].

If the lowest temperature SOC [%] is equal to or higher than the threshold value Th _H (S51: YES), the input/output limit value W [W] is set with only the discharge side expanded (S52).
If the SOC [%] of the minimum temperature T _min [°C] is less than the threshold Th _H (S51: NO), it is determined that the limit value on the charging side can be expanded, and it is determined whether the limit value on the discharging side can be expanded. to judge. Here, it is determined whether the SOC [%] of T _min [°C] is equal to or less than the threshold Th _L (S53). Here, the "threshold Th _L " is, for example, SOC 40%. This is because, in the case of the vehicle-mounted battery pack 4, it is preferable to allow a margin that does not fall below the SOC of 40% as the remaining discharge amount for driving. If the SOC is in a low SOC region below 40%, the efficiency of the vehicle will decrease because it will not be possible to respond to a sudden demand for output from the prime mover. The value of SOC [%] can be determined based on, for example, the cell voltage [V].

If the SOC [%] of the minimum temperature T _min [°C] is less than the threshold Th _L (S53: YES), set the input/output limit value W [W] which is an expanded limit value only on the charging side (S54). .
If the SOC [%] of the minimum temperature T _min [°C] exceeds the threshold Th _L or more (S53: NO), an input/output limit value W that expands both charging and discharging is set.

<Calculation of input/output limit value W>
FIG. 11 is a graph showing the relationship between battery temperature T, maximum temperature T _max , minimum temperature T _min , average temperature T _ave , and environmental temperature T _env . The battery temperature T is the battery temperature measured for each cell battery 1. The maximum temperature T _max is the highest temperature among these. The minimum temperature T _min is the lowest temperature among these. Generally, in the battery stack 2, the temperature distribution of the battery temperature T is such that the temperature of the cell batteries 1a at both ends shown in FIG. 1 is low, and the temperature of the cell battery 1b at the center is high. The average temperature T _ave is the arithmetic mean value of these battery temperatures T. Note that the environmental temperature T _env is the temperature of the atmosphere around the battery pack 4, and is a factor that affects cooling of the battery pack 4. For example, in the summer, when a load is applied to an internal combustion engine under the scorching sun, the value will be high, and if it has been left unused in the winter, the value will be low.

Here, in the step of expanding the input/output limit value (S52, S54, S55) of the present embodiment, the input/output limit value W _Lit [W] after recalculation is determined by the following procedure.
The input/output limit value after recalculation is W _Lit [W], the current _input /output limit value is W [W], and the _{magnification} (1.0 (more than twice) is defined as M _diff . Further, the magnification (1.0 times or more) determined from the difference between T _max [°C] and T _ave [°C] is defined as M _ave . At this time, the recalculated input/output limit value W _Lit [W] is calculated using the following formula.

W _Lit = W x M _diff x M _ave
These scaling factors are optimized by those skilled in the art based on measurements with similar cells.
Note that in this case, the environmental temperature T _env [°C] is not taken into account. When the environmental temperature T _env [°C] is further considered, the equation is as follows.

When the environmental temperature is T _env [°C], and when the magnification (1.0 times or more) determined from the difference between T _max [°C] and T _env [°C] is M _env , after recalculation The input/output limit value W _Lit [W] is calculated using the following formula.

W _Lit = W x M _diff x M _ave x M _env
Here, it is desirable to pay attention to the following points when making adjustments.
In "M _diff ", the larger the difference between T _max [°C] and T _min [°C], the more the performance is wasted due to the limit value of T _min [°C]. Therefore, it is preferable to increase M _diff to reduce the difference between T _max [°C] and T _min [°C]. Therefore, the input/output limit value W [W] increases as the difference between the maximum temperature T _max [°C] and the minimum temperature T _min [°C] of the cell battery 1 increases.

<Relationship between maximum temperature T _max [°C] and average temperature T _ave [°C]>
In "M _ave ", the larger the difference between T _max [°C] and T _ave [°C], the more cell batteries 1 are on the low temperature side. Therefore, it is preferable to increase M _ave to raise the battery temperature T of the cell batteries 1 in the battery pack 4 as a whole. Therefore, the input/output limit value W[W] increases as the difference between the average temperature T _ave and the maximum temperature T _max of the cell batteries 1 in the battery pack 4 increases.

FIG. 12 is a graph illustrating the relationship between a high average temperature T _ave and a maximum temperature T _max . As shown in FIG. 12, when the average temperature T _ave is high and the difference from the maximum temperature T _max is small, the battery temperature T is high and the temperature difference between each cell battery 1 is naturally reduced. .

In “M _env ”, the smaller the difference between T _max [°C] and T _env [°C], the smaller the effect of increasing the battery temperature T of the cell battery 1 due to T _env . Therefore, it is preferable to increase M _env and aim at alleviating temperature variations by generating heat by expanding the input/output limit value W [W].

<Operation time calculation (S56)>
After the input/output limit value W[W] is determined through the above-described procedure, the operating time is calculated (S56). In the operation time calculation procedure (S56), if the operation time for sampling the battery temperature T [°C] is too long, excessive temperature adjustment may occur. In order to avoid such excessive temperature adjustment, the amount of heat generated is estimated in advance and the operating time is adjusted.

In the step of calculating the application time (S56), if the acquisition time interval T _int [s] of the battery temperature T [°C] is longer than the set value, the unit battery at the maximum temperature T _max [°C] reaches the upper limit temperature T _Lit [ The acquisition time interval T _int [s] is determined so as not to reach [°C].

The acquisition time interval T _int [s] is the heat capacity of the cell battery 1 in C [Cal], the upper limit temperature in T _Lit [°C], the maximum battery temperature in T _max , the input/output current in I [A], and the internal When the resistance is R [Ω], it is calculated based on T _int =C(T _Lit -T _max )/I ² R.

By setting in this way, it is possible to prevent excessive temperature adjustment.
This completes the steps S51 to S56, which are the subroutines of the input/output limit value expansion step (S5).

Here, we return to the flowchart shown in FIG. 6 and continue the explanation. When the procedure of recalculating the input/output limit value (S5) is completed, the procedure of input/output (S6) is performed using the recalculated input/output limit value W _Lit [W]. Here, by performing input/output using the recalculated input/output limit value W _Lit [W], heat generation of the cell battery 1 with a low temperature is promoted, and the battery temperature T between the cell batteries 1 is made uniform, The efficiency of the battery pack 4 can be improved.

After executing the input/output (S6) procedure using the recalculated input/output limit value W _Lit [W], the process returns to S1 and the control of this embodiment is performed.
(Effects of this embodiment)
The lithium ion secondary battery control method and control device of this embodiment as described above has the following effects.

(1) The lithium ion secondary battery control method of the present embodiment has the effect that it can be used efficiently by making the battery temperature T [°C] uniform.
(2) In addition, the input/output limit value W _Lit [W] has the effect that temperature differences between the cell batteries 1 with temperature differences can be reduced simply by appropriately controlling the input/output of the entire battery pack 4. There is.

(3) The input/output limit value W _Lit [W] is equal to or lower than the first temperature T ₁ [°C] of the cell battery 1 . Further, when the maximum temperature T _max [°C] of the obtained temperature T of the unit battery is equal to or lower than the set second temperature T ₂ [°C], it is expanded. Therefore, there is an effect that the most appropriate input/output limit value W _Lit [W] can be set.

(3) In the input/output limit value calculation step (S5), if the SOC of the cell battery 1 at the minimum temperature T _min [°C] is less than the minimum value of the set charge/discharge range (for example, SOC40 [%]), , the limit value of the input/output limit value W [W] on the charging side is expanded. In addition, if the SOC of the cell battery 1 at the minimum temperature T _min [°C] exceeds the maximum value of the set charge/discharge range (for example, 60 [%]), the discharge side input/output limit value W [W] Expand the limit value. If the SOC of the cell battery 1 at the minimum temperature T _min [°C] is greater than or equal to the minimum value and less than or equal to the maximum value, both the input and output limit values W [W] on the charging side and the discharging side are limited. Expand the value. Therefore, there is an effect that control such as discharging in a low SOC region or charging in a high SOC region can be avoided.

(4) By the procedure of operation time calculation (S56), it is possible to avoid excessive temperature adjustment due to the operation time of sampling the battery temperature T [°C] being too long. In order to prevent such excessive temperature adjustment, the operating time calculation (S56) procedure estimates the amount of heat generated in advance and adjusts the operating time, which has the effect of enabling appropriate temperature control.

(5) Calculate the recalculated input/output limit value W _Lit [W] by W _Lit = W x M _diff x M _ave . Therefore, there is an effect that the optimum input/output limit value W _Lit [W] can be determined.

(6) Furthermore, since the environmental temperature T _env [°C] is taken into account and the input/output limit value W _Lit [W] is calculated by W _Lit = W x M _diff x M _ave x M _env , a more appropriate This has the effect that the input/output limit value W _Lit [W] can be determined.

(Another example)
The present invention is not limited to the above embodiments, and can be implemented, for example, as follows.
The secondary battery of this embodiment has been described using, as an example, a battery pack 4 of a lithium ion secondary battery for vehicle use as an assembled battery, and a cell battery 1 constituting the battery pack 4 as a unit battery. The invention is not limited to this example. For example, as a unit battery, instead of using a single cell battery 1 of a lithium ion secondary battery, a plurality of cell batteries 1 can be collectively used as a unit battery. Further, the type of battery is not limited to a lithium ion secondary battery, but may be a non-aqueous electrolyte secondary battery, an alkaline secondary battery, an all-solid-state battery, or the like. Further, in a battery such as a nickel-metal hydride storage battery, a battery module including a plurality of single cells can be used as a unit battery. Furthermore, in a battery pack 4 including a plurality of battery stacks 2, the battery stack 4 itself can be used as a unit battery.

In addition, in this embodiment, the temperature was measured using all the batteries included in the assembled battery as unit batteries, but it is also possible to measure the temperature of only the batteries at the ends and the center, for example.
○ Examples of the assembled battery include a battery stack including a plurality of cell batteries 1 and battery modules, and a battery pack 4 including a plurality of battery stacks.

In addition, the shape of the secondary battery is not limited to a plate-like one, but may be a cylindrical one, and the assembled battery does not necessarily have to be the battery stack 2.
○ In this embodiment, the wound type electrode body 10 as shown in FIG. 2 and FIG. be able to.

The battery case 11 of the cell battery 1 can be made of any material, including aluminum alloy, other metals such as stainless steel, and resin.
The numerical values, numerical ranges, etc. described in this embodiment are illustrative for explaining one example, and the present invention is not limited thereto. These can be optimized and implemented by those skilled in the art in accordance with the configuration of the target secondary battery, etc.

The drawings and graphs are for illustrating the present embodiment, and the present invention is not limited thereto. In addition, the shape, dimensions, balance, number of laminated layers, etc. of the electrode body 10 of the illustrated lithium ion secondary battery are schematically simplified or exaggerated, and other drawings and graphs are also included in the present invention. It is not limited to.

The flowcharts shown in FIGS. 6 and 7 are examples, and the procedures can be added, deleted, changed, and the order changed.
It goes without saying that the present invention can be implemented by adding, deleting, or changing other configurations by those skilled in the art without departing from the scope of the claims.

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 electrode external terminal 15... Positive electrode current collector 16... Positive electrode external terminal 17... Electrolyte solution 18... Discharge valve 19... Liquid injection Port 100... Negative electrode plate 101... Negative electrode base material 102... Negative electrode composite layer 103... Negative electrode connection part 110... Positive electrode plate 111... Positive electrode base material 112... Positive electrode composite material 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 wheel TB...Temperature VB...Cell voltage IB...Current T [°C]...Battery temperature T ₁ [°C]...First Temperature T ₂ [°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 value W [W]... Current input/output limit value W _Lit [W]... Input/output limit value after recalculation T _int [s]... Acquisition time interval Δt... Time C [Cal]... Heat capacity of unit battery T _Lit [°C]... Upper limit temperature I [A]... Input/output current R [Ω]... Internal resistance M _diff ... Magnification determined from the difference between T _max [°C] and T _min [°C] (1.0 times that's all)
M _ave ...Magnification determined from the difference between T _max [°C] and T _ave [°C] (1.0 times or more)
M _env ...Magnification determined from the difference between T _max [°C] and T _env [°C] (1.0 times or more)

Claims (9)

In an assembled battery configured by combining a plurality of unit batteries consisting of secondary batteries,
a step of obtaining a battery temperature T [°C] of a plurality of unit batteries constituting the assembled battery;
Calculate 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 forming the assembled battery obtained in the step of obtaining the battery temperature. a step of calculating input/output limit values;
Among the battery temperatures T [°C] of the unit batteries obtained in the step of obtaining the battery temperature, there is a unit battery whose temperature is equal to or lower than the set first temperature T ₁ [°C],
And when the maximum temperature T _max [°C] of the obtained battery temperature T [°C] of the unit battery is equal to or lower than the set second temperature T ₂ [°C],
A method for controlling a secondary battery, comprising: expanding the current input/output limit value W [W] of the assembled battery to an input/output limit value W _Lit [W]. . In the step of expanding the input/output limit value, the input/output limit value W [W] increases as the difference between the maximum temperature T _max [°C] and the minimum temperature T _min [°C] of the unit battery increases. The method for controlling a secondary battery according to claim 1, characterized in that: In the step of expanding the input/output limit value, the input/output limit value W [W] is the difference between the average temperature T _ave [°C] and the maximum temperature T _max [°C] of the unit cells in the assembled battery. 2. The method for controlling a secondary battery according to claim 1, wherein the larger the value, the larger the size. The step of calculating the input/output limit value is as follows:
If the SOC of the unit battery at the minimum temperature T _min [°C] is less than the minimum value of the set charge/discharge range, expand the limit value of the input/output limit value W [W] on the charging side,
If the SOC of the unit battery at the minimum temperature T _min [°C] exceeds the maximum value of the set charge/discharge range, expand the limit value of the input/output limit value W [W] on the discharge side,
If the SOC of the unit battery at the minimum temperature T _min [°C] is greater than or equal to the minimum value and less than or equal to the maximum value, both the input and output limit values W [W] on the charging side and discharging side are expanded. The method for controlling a secondary battery according to claim 1, characterized in that: The step of calculating the input/output limit value is as follows:
The acquisition time interval T _int [s] of the battery temperature T [°C] is set such that the unit battery _with the maximum temperature T _max [°C] does not reach the upper limit temperature T _Lit [°C]. 2. The method of controlling a secondary battery according to claim 1, further comprising the step of calculating an application time to determine the time period. The acquisition time interval T _int [s] is
The heat capacity of the unit battery is C [Cal], the upper limit temperature is T _Lit [°C], the maximum battery temperature is T _max [°C], the input/output current is I [A], and the internal resistance is R [Ω]. When I did,
T _int = C(T _Lit - T _max )/I ² R
6. The secondary battery control method according to claim 5, wherein the calculation is performed based on . The step of expanding the input/output limit value is as follows:
The input/output limit value after recalculation is W _Lit [W], the current _input /output limit value is W [W], and the _{magnification} (1.0 When M _diff is the magnification (1.0 times or more) determined from the difference between T _max [°C] and T _ave [°C], the input/output limit value after recalculation is _{W Lit} [W],
W _Lit = W x M _diff x M _ave
2. The method for controlling a secondary battery according to claim 1, wherein the calculation is performed by: When the environmental temperature is T _env [°C] and T _max [°C], the magnification (1.0 times or more) determined from the difference between T _max [°C] and T _env [°C] is When M _env is input/output limit value after recalculation, W _Lit [W] is
W _Lit = W x M _diff x M _ave x M _env
8. The method for controlling a secondary battery according to claim 7, wherein the calculation is performed by: A secondary battery control device equipped with a computer,
In an assembled battery configured by combining a plurality of unit batteries made of secondary batteries, a battery temperature acquisition means for acquiring the battery temperature T [°C] of the plurality of unit batteries making up the assembled battery;
Calculate 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 assembled battery acquired by the battery temperature acquisition means. Input/output limit value calculation means;
Among the battery temperatures T [°C] of the unit batteries acquired by the battery temperature acquisition means, there is a unit battery whose temperature is equal to or lower than the set first temperature T ₁ [°C],
And when the obtained maximum temperature T _max [°C] of the unit battery T is equal to or lower than the set second temperature T ₂ [°C],
A control device for a secondary battery, comprising: input/output limit value expanding means for expanding the input/output limit value W [W] of the assembled battery to the input/output limit value W _Lit [W].

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