JP7020095B2 - Rechargeable battery system - Google Patents

Description

The present disclosure relates to a secondary battery system, and more specifically, to a technique for calculating a control upper limit value of input power to a secondary battery or a control upper limit value of output power from a secondary battery.

Generally, in a secondary battery system mounted on an electric vehicle or the like, a certain degree of limitation is provided on the charging / discharging of the secondary battery for the purpose of protecting the secondary battery. More specifically, the input power to the secondary battery does not exceed the input control upper limit value Win indicating the control upper limit value, and the output power from the secondary battery is the output control upper limit value indicating the control upper limit value. The charge / discharge of the secondary battery is controlled so as not to exceed Wout.

A technique for calculating an appropriate value for the input control upper limit value Win and the output control upper limit value Wout has been proposed. For example, Japanese Patent Application Laid-Open No. 2000-030748 (Patent Document 1) accurately calculates the input / output power (that is, the input control upper limit value Win and the output control upper limit value Wout) of the secondary battery whose open circuit voltage changes depending on the charge / discharge history. Disclose the method for doing so.

Japanese Unexamined Patent Publication No. 2000-030748 Japanese Unexamined Patent Publication No. 2015-08444 Japanese Unexamined Patent Publication No. 2014-139521 JP-A-2015-166710

"In Situ Measurements of Stress-Potential Coupling in Lithiated Silicon", V. A. Sethuraman et al., Journal of The Electrochemical Society, 157 (11) A1253-A1261 (2010)

If the input control upper limit Win is not set properly, the voltage of the secondary battery may become excessively high or the input current to the secondary battery may become excessively large, which may sufficiently protect the secondary battery. It may not be possible. On the other hand, if the input control upper limit Win is set too low, the secondary battery can be protected, but the charging to the secondary battery is excessively restricted and the secondary battery cannot be fully utilized. there is a possibility. Although the detailed description is not repeated, the same applies to the output control upper limit value Wout.

The present disclosure has been made to solve the above problems, and an object thereof is to make full use of the secondary battery while appropriately protecting the secondary battery.

(1) The secondary battery system according to a certain aspect of the present disclosure includes a secondary battery and a calculation device for calculating the control upper limit value of the input power to the secondary battery. The calculator includes a memory in which the first and second correspondences are stored. The first correspondence is when the SOC and OCV of the secondary battery are represented on the charge curve showing the SOC-OCV characteristics of the secondary battery when the secondary battery is charged from the fully discharged state to the fully charged state. This is the correspondence between the SOC of the secondary battery and the control upper limit value. The second correspondence is the voltage difference between the OCV on the charge curve and the measured value of the OCV of the secondary battery, and the time when the combination of the SOC and OCV of the secondary battery deviates from the charge curve or the discharge curve. It is a correspondence relationship between one of the SOC change amounts of the secondary battery from the above and the correction coefficient for correcting the control upper limit value. When the SOC and OCV of the secondary battery are represented on the charge curve, the calculation device calculates the control upper limit value from the SOC of the secondary battery by referring to the first correspondence. When the SOC and OCV of the secondary battery are not represented on the charge curve, the calculation device calculates the correction coefficient from either the voltage difference or the SOC change amount by referring to the second correspondence, and the second The control upper limit value calculated by referring to the correspondence of 1 is corrected by the correction coefficient.

(2) A secondary battery system according to another aspect of the present disclosure includes a secondary battery and a calculation device for calculating a control upper limit value of output power from the secondary battery. The calculator includes a memory in which the first and second correspondences are stored. The first correspondence is when the SOC and OCV of the secondary battery are represented on the discharge curve showing the SOC-OCV characteristics of the secondary battery when the secondary battery is discharged from the fully charged state to the fully discharged state. This is the correspondence between the SOC of the secondary battery and the control upper limit value. The second correspondence is the voltage difference between the measured value of the OCV of the secondary battery and the OCV on the discharge curve, and the time when the combination of the SOC and the OCV of the secondary battery deviates from the charge curve or the discharge curve. It is a correspondence relationship between one of the SOC change amounts of the secondary battery from the above and the correction coefficient for correcting the control upper limit value. When the SOC and OCV of the secondary battery are represented on the discharge curve, the calculation device calculates the control upper limit value from the SOC of the secondary battery by referring to the first correspondence. When the SOC and OCV of the secondary battery are not represented on the discharge curve, the calculation device calculates the correction coefficient from either the voltage difference or the SOC change amount by referring to the second correspondence, and the second The control upper limit value calculated by referring to the correspondence of 1 is corrected by the correction coefficient.

Details will be described later, but according to the configuration of (1) above, when the SOC and OCV of the secondary battery are represented on the charge curve, the control upper limit value is calculated with reference to the first correspondence. To. In this case, the secondary battery can be appropriately protected by imposing the strictest input restriction. On the other hand, when the SOC and OCV of the secondary battery are not represented on the charge curve (when the influence of hysteresis described later becomes apparent), the control upper limit value calculated with reference to the first correspondence is the second. It is corrected using the correction coefficient calculated by referring to the correspondence of. In this case, the secondary battery can be fully utilized by relaxing the input restriction by the correction.

Similarly, depending on the configuration of (2) above, the value calculated with reference to the first correspondence is used as the control upper limit value of the output power from the secondary battery, or the value is used as the correction coefficient. Further correction is switched depending on whether the SOC and OCV of the secondary battery are on the discharge curve. As a result, the secondary battery can be fully utilized while appropriately protecting the secondary battery.

According to the present disclosure, the secondary battery can be fully utilized while appropriately protecting the secondary battery.

It is a figure which shows schematic the whole structure of the vehicle which mounted the secondary battery system which concerns on this embodiment. It is a figure for demonstrating the structure of each cell in more detail. It is a figure which shows an example of the change of the surface stress σ accompanying charge / discharge of a single cell schematically. It is a figure which shows an example of the electromotive voltage hysteresis of the assembled battery in this embodiment. It is a figure for demonstrating an example of the setting method of an ideal OCV. It is a figure for demonstrating the input / output hysteresis (input hysteresis) which occurs in a single cell. It is a figure for demonstrating the input / output hysteresis (output hysteresis) which occurs in a single cell. It is a figure for demonstrating an input ΔV and an output ΔV. It is a flowchart which shows the calculation process of OCV change amount ΔOCV. It is a figure for demonstrating the content of a parameter. It is a flowchart which shows the procedure of the pre-measurement in this embodiment. It is a figure which shows an example of the input map MP1A. It is a figure which shows an example of an output map MP1B. It is a figure which shows an example of the input correction map MP2A. It is a figure which shows an example of an output correction map MP2B. It is a flowchart for demonstrating the input upper limit calculation process in this embodiment. It is a flowchart for demonstrating the output upper limit calculation process in this embodiment. It is a figure which shows an example of the input correction map MP4A in the modification. It is a figure which shows an example of the output correction map MP4B in the modification. It is a figure for demonstrating the SOC change amount ΔSOC and the flag G. It is a flowchart for demonstrating the input upper limit calculation process in the modification. It is a flowchart for demonstrating the output upper limit calculation process in a modification.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

Hereinafter, a configuration in which the secondary battery system according to the present embodiment is mounted on a hybrid vehicle (more specifically, a plug-in hybrid vehicle) will be described as an example. However, the secondary battery system according to the present embodiment is applicable not only to hybrid vehicles but also to all vehicles (electric vehicles, fuel cell vehicles, etc.) equipped with a battery for traveling. Further, the application of the secondary battery system according to the present embodiment is not limited to the vehicle, and may be, for example, stationary.

[Embodiment]
<Overall configuration of the vehicle>
FIG. 1 is a diagram schematically showing an overall configuration of a vehicle equipped with a secondary battery system according to the present embodiment. Referring to FIG. 1, the vehicle 1 is a hybrid vehicle, which includes a secondary battery system 2, motor generators 41 and 42, an engine 43, a power splitting device 44, a drive shaft 45, and a drive wheel 46. To prepare for. The secondary battery system 2 includes an assembled battery 10, a monitoring unit 20, a power control unit (PCU: Power Control Unit) 30, and an electronic control unit (ECU: Electronic Control Unit) 100.

Each of the motor generators 41 and 42 is an AC rotary electric machine, for example, a three-phase AC synchronous electric machine in which a permanent magnet is embedded in a rotor. The motor generator 41 is mainly used as a generator driven by the engine 43 via the power dividing device 44. The electric power generated by the motor generator 41 is supplied to the motor generator 42 or the assembled battery 10 via the PCU 30.

The motor generator 42 mainly operates as an electric motor and drives the drive wheels 46. The motor generator 42 is driven by receiving at least one of the electric power from the assembled battery 10 and the electric power generated by the motor generator 41, and the driving force of the motor generator 42 is transmitted to the drive shaft 45. On the other hand, when the vehicle is braking or the acceleration is reduced on a downhill slope, the motor generator 42 operates as a generator to generate regenerative power generation. The electric power generated by the motor generator 42 is supplied to the assembled battery 10 via the PCU 30.

The engine 43 is an internal combustion engine that outputs power by converting the combustion energy generated when the air-fuel mixture is burned into the kinetic energy of movers such as pistons and rotors.

The power splitting device 44 includes, for example, a planetary gear mechanism (not shown) having three rotation axes of a sun gear, a carrier, and a ring gear. The power splitting device 44 divides the power output from the engine 43 into a power for driving the motor generator 41 and a power for driving the drive wheels 46.

The assembled battery 10 includes a plurality of cells 11 (see FIG. 2). In this embodiment, each cell is a lithium ion secondary battery. The assembled battery 10 stores electric power for driving the motor generators 41 and 42, and supplies electric power to the motor generators 41 and 42 through the PCU 30. Further, the assembled battery 10 is charged by receiving the generated power through the PCU 30 when the motor generators 41 and 42 generate power.

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 of each cell 11 included in the assembled battery 10. The current sensor 22 detects the current IB input / output to / from the assembled battery 10. The current IB during charging is positive, and the current IB during discharging is negative. The temperature sensor 23 detects the temperature of each cell 11. Each sensor outputs the detection result to the ECU 100.

The voltage sensor 21 may detect the voltage VB using, for example, a plurality of cells 11 connected in series as a monitoring unit. Further, the temperature sensor 23 may detect the temperature TB with a plurality of adjacent cells 11 as monitoring units. As described above, in the present embodiment, the monitoring unit is not particularly limited. Therefore, in the following, for the sake of simplification of the description, it is simply described as "detecting the voltage VB of the assembled battery 10" or "detecting the temperature TB of the assembled battery 10." Similarly, for SOC and OCV, the assembled battery 10 is described as an estimation unit.

The PCU 30 executes bidirectional power conversion between the assembled battery 10 and the motor generators 41 and 42 according to the control signal from the ECU 100. The PCU 30 is configured to be able to control the states of the motor generators 41 and 42 separately. For example, the motor generator 42 can be put into a power running state while the motor generator 41 is in a regenerative state (power generation state). The PCU 30 includes, for example, two inverters provided corresponding to the motor generators 41 and 42, and a converter (neither shown) that boosts the DC voltage supplied to each inverter to a voltage higher than the output voltage of the assembled battery 10. It is configured to include.

The ECU 100 includes a CPU (Central Processing Unit) 100A, a memory (more specifically, a ROM (Read Only Memory) and a RAM (Random Access Memory)) 100B, and an input / output port for inputting / outputting various signals (shown in the figure). It is configured to include (1) and. The ECU 100 has a control upper limit value (input control upper limit value Win) of electric power that can be input to the assembled battery 10 based on a signal received from each sensor of the monitoring unit 20 and a program and a map (each map described later) stored in the memory 100B. ), And the "output upper limit calculation process" for calculating the control upper limit value (output control upper limit value Wout) of the power that can be output from the assembled battery 10. The ECU 100 corresponds to the "calculation device" according to the present disclosure.

FIG. 2 is a diagram for explaining the configuration of each cell 11 in more detail. The cell 11 in FIG. 2 is shown through the inside thereof.

With reference to FIG. 2, cell 11 has a square (substantially rectangular parallelepiped) battery case 111. The upper surface of the battery case 111 is sealed by the lid 112. One end of each of the positive electrode terminal 113 and the negative electrode terminal 114 protrudes outward from the lid 112. The other ends of the positive electrode terminal 113 and the negative electrode terminal 114 are connected to the internal positive electrode terminal and the internal negative electrode terminal (neither of them is shown) inside the battery case 111, respectively. The electrode body 115 is housed inside the battery case 111. The electrode body 115 is formed by laminating a positive electrode 116 and a negative electrode 117 via a separator 118 and winding the laminated body. The electrolytic solution is held in the positive electrode 116, the negative electrode 117, the separator 118 and the like.

For the positive electrode 116, the separator 118, and the electrolytic solution, conventionally known configurations and materials as the positive electrode, the separator, and the electrolytic solution of the lithium ion secondary battery can be used, respectively. As an example, a ternary material in which a part of lithium cobalt oxide is replaced with nickel and manganese can be used for the positive electrode 116. Polyolefin (for example, polyethylene or polypropylene) can be used as the separator. The electrolytic solution includes an organic solvent (for example, a mixed solvent of DMC (dimethyl carbonate), EMC (ethyl methyl carbonate) and EC (ethylene carbonate)), a lithium salt (for example, LiPF ₆ ), and an additive (for example, LiBOB (lithium bis)). (oxalate) boron) or Li [PF ₂ (C ₂ O ₄ ) ₂ ]). A polymer-based electrolyte may be used instead of the electrolytic solution, or an oxide-based or sulfide-based inorganic solid electrolyte may be used.

The structure of the cell is not particularly limited, and the electrode body may have a laminated structure instead of a wound structure. Further, not only the square battery case but also the cylindrical or laminated battery case can be adopted.

<Electromotive force hysteresis>
Conventionally, a typical negative electrode active material of a lithium ion secondary battery has been a carbon material (for example, graphite). On the other hand, in the present embodiment, a silicon-based compound (Si or SiO) is adopted as the active material of the negative electrode 117. This is because the energy density and the like of the assembled battery 10 can be increased by adopting a silicon-based compound. On the other hand, in a system in which a silicon-based compound is adopted, hysteresis may remarkably appear in the SOC-OCV characteristics (SOC-OCV curve). As the cause, as described below, the volume change of the negative electrode active material due to charging / discharging can be considered. In the following, this hysteresis will also be referred to as "electromotive voltage hysteresis".

The negative electrode active material expands with the insertion of lithium and contracts with the desorption of lithium. With such a volume change of the negative electrode active material, stress is generated on the surface and the inside of the negative electrode active material. The amount of change in volume of the silicon-based compound due to the insertion or desorption of lithium is larger than the amount of change in volume of graphite. Specifically, the amount of change in the volume (expansion rate) of graphite due to the insertion of lithium is about 1.1 times the minimum volume when lithium is not inserted, whereas it is about 1.1 times. The amount of change in volume of the silicon-based compound is about four times at the maximum. Therefore, when a silicon-based compound is used as the negative electrode active material, the stress generated on the surface of the negative electrode active material becomes larger than when graphite is used. Hereinafter, this stress is also referred to as “surface stress”.

Generally, the unipolar potential (positive electrode potential or negative electrode potential) is determined by the state of the surface of the active material, more specifically, the amount of lithium on the surface of the active material and the surface stress. For example, it is known that the negative electrode potential decreases as the amount of lithium on the surface of the negative electrode active material increases. When a material such as a silicon-based compound that causes a large volume change is adopted, the amount of change in surface stress due to an increase or decrease in the amount of lithium also becomes large. Here, there is hysteresis in the surface stress. Therefore, the negative electrode potential can be defined with high accuracy by considering the influence of the surface stress and its hysteresis. Then, when estimating the SOC from the OCV using the relationship between the SOC and the OCV, the SOC can be estimated with high accuracy by assuming the negative electrode potential in which the surface stress is taken into consideration.

As described above, the OCV means a voltage in a state where the voltage of the assembled battery 10 is sufficiently relaxed and the lithium concentration in the active material is relaxed, and is also referred to as an electromotive force. The stress remaining on the surface of the negative electrode in this relaxed state includes various forces including the stress generated inside the negative electrode active material and the reaction force acting on the negative electrode active material from the peripheral material as the volume of the negative electrode active material changes. Can be thought of as the stress when the whole system is balanced. The peripheral material includes a binder, a conductive auxiliary agent, and other active materials existing around the active material.

FIG. 3 is a diagram schematically showing an example of a change in surface stress σ accompanying charge / discharge of a single cell (cell 11). In FIG. 3, the horizontal axis represents the SOC of the single cell 0, and the vertical axis represents the surface stress σ. Regarding the surface stress σ, the tensile stress σ _ten generated when the negative electrode active material 71 contracts (when the single cell is discharged) is expressed in the positive direction, and is generated when the negative electrode active material 71 expands (when the single cell is charged). The compressive stress σ _com is expressed in the negative direction.

In FIG. 3, first, a single cell is charged at a constant charging rate from a fully discharged state (SOC = 0% state) to a fully charged state (SOC = 100% state), and then from a fully charged state to a fully discharged state. An example of the change in surface stress σ when a single cell is discharged at a constant discharge rate up to the state is schematically shown.

Immediately after the start of charging from the completely discharged state, the surface stress σ (absolute value) increases linearly. It is considered that the surface of the negative electrode active material 71 is elastically deformed in the SOC region (region from SOC = 0% to SOC = Sa) during charging. On the other hand, in the region after that (the region from SOC = X to SOC = 100%), it is considered that the surface of the negative electrode active material 71 exceeds the elastic deformation and reaches the plastic deformation. On the other hand, when the single cell is discharged, elastic deformation occurs on the surface of the negative electrode active material 71 in the region immediately after the start of discharge from the fully charged state (the region from SOC = 100% to SOC = Sb), and the region thereafter. In (the region from SOC = Sb to SOC = 0%), it is considered that plastic deformation of the surface of the negative electrode active material 71 occurs.

In FIG. 3, all changes in the surface stress σ are shown by a straight line, but this is merely a schematic representation of the changes in the surface stress σ, and in reality, the plastic region after yielding (plastic deformation is Non-linear changes also occur in the SOC region where they occur (see, for example, FIG. 2 of Non-Patent Document 1). Further, FIG. 3 shows an example in which the SOC is changed from 0% to 100%, but the SOC region is not limited to this. Although not shown here, when the OCV of the assembled battery deviates from the charging OCV or the discharging OCV (described later), an elastic change occurs on the surface of the negative electrode active material 71.

When charging the single cell is continued, compressive stress mainly acts on the surface of the negative electrode active material (the surface stress σ becomes the compressive stress), and the negative electrode potential is lowered as compared with the ideal state in which the surface stress σ is not generated. As a result, the OCV of a single cell increases. On the other hand, when the discharge of the single cell is continued, the tensile stress mainly acts on the surface of the negative electrode active material (the surface stress σ becomes the tensile stress), and the negative electrode potential rises as compared with the ideal state. As a result, the OCV of a single cell decreases. According to the above mechanism, hysteresis due to charge / discharge appears in the SOC-OCV curve of the assembled battery 10.

FIG. 4 is a diagram showing an example of the electromotive voltage hysteresis of the assembled battery 10 in the present embodiment. In FIG. 4, the horizontal axis shows the SOC of the assembled battery 10, and the vertical axis shows the OCV of the assembled battery 10.

FIG. 4 shows a curve (indicated by CHG) acquired by charging the assembled battery 10 and a curve (indicated by DCH) acquired by discharging the assembled battery 10. In the following, the OCV on the former will be referred to as "charging OCV", and the OCV on the latter will be referred to as "discharging OCV". The dissociation between the charging OCV and the discharging OCV at the same SOC (for silicon-based compounds, for example, about 150 mV) represents the electromotive voltage hysteresis.

The charging OCV can be obtained as follows. First, a single cell in a completely discharged state is prepared and charged with an amount of electricity corresponding to, for example, 5% SOC. After charging the amount of electricity, charging is stopped, and the single cell is left for a time (for example, 30 minutes) until the polarization caused by the charging is eliminated. After the elapse of the leaving time, the OCV of a single cell is measured. Then, the combination (SOC, OCV) of the SOC (= 5%) after charging and the measured OCV is plotted in the figure.

Subsequently, charging of the amount of electricity corresponding to the next 5% SOC (SOC = charging from 5% to 10%) is started. When charging is completed, the OCV of a single cell is similarly measured after the elapse of the leaving time. Then, the combination of SOC and OCV is plotted again from the measurement result of OCV. After that, the same procedure is repeated until the single cell is fully charged. By carrying out such a measurement, the charging OCV can be obtained.

Next, from the fully charged state to the fully discharged state of the single cell, the OCV of the single cell at the SOC in 5% increments is measured while repeating the discharge and the discharge stop of the single cell. The discharge OCV can be obtained by carrying out such a measurement. The acquired charge OCV and discharge OCV are stored in the memory 100B of the ECU 100.

By the way, a curve obtained in an ideal (virtual) state (a state of σ≈0) in which no stress remains on the surface of the negative electrode active material 71 can be used as a reference. Hereinafter, the OCV on this curve is also referred to as "ideal OCV".

FIG. 5 is a diagram for explaining an example of an ideal OCV setting method. The surface stress σ (compressive stress σc and tensile stress σt) when plastic deformation of the negative electrode active material 71 occurs can be measured (estimated) through thin film evaluation. An example of the method for measuring the surface stress σ will be briefly described. First, the change in the curvature κ of the negative electrode 117 of the thin film deformed by stress is measured. For example, the curvature κ can be measured optically by using a commercially available radius of curvature measurement system. Then, by substituting the measured curvature κ and constants (Young's modulus, Poisson's ratio, thickness, etc.) determined according to the material and shape of the negative electrode 117 (negative electrode active material 71 and peripheral member 72) into Stoney's equation. , The surface stress σ can be calculated (see, for example, Non-Patent Document 1 for details of stress measurement).

With reference to FIG. 5, the surface stress σ on the charged OCV is substantially constant at the compressive stress σ _com during yield, and the surface stress σ on the discharged OCV is substantially constant at the tensile stress σ _ten during yielding. .. Therefore, the distance D _com between the ideal OCV and the charging OCV and the distance D _ten between the ideal OCV and the discharging OCV are curves equal to the ratio of the compressive stress σ _com and the tensile stress σ _ten (D _com :. On the curve where D _ten = σ _com : σ _ten ), the surface stress σ can be regarded as substantially 0. By calculating such a curve, the ideal OCV can be set.

<I / O hysteresis>
The present inventor presents the input / output performance of the assembled battery 10 (more specifically, the charge / discharge voltage of the assembled battery 10) when the charge / discharge history of the assembled battery 10 is different due to the electromotive voltage hysteresis shown in FIG. It was also found that hysteresis occurs. Hereinafter, this hysteresis is also referred to as “input / output hysteresis”.

FIG. 6 is a diagram for explaining input / output hysteresis (more specifically, input hysteresis) that occurs in a single cell. In FIG. 6 and FIG. 7 described later, the horizontal axis indicates the elapsed time. The vertical axis shows the SOC and the voltage VB of the assembled battery 10 from the top.

In FIG. 6, a single cell is charged from a completely discharged state (SOC = 0% state), the SOC is adjusted to 50%, and after resting for a while in the adjusted state, the single cell is charged with a constant current (for example,). The changes in SOC and voltage VB when charged with a current of 3C) are shown by solid lines. In the following, such SOC adjustment will be referred to as “charge adjustment”. On the other hand, after the single cell is discharged from the fully charged state (SOC = 100% state) and the SOC is adjusted to 50% by the alternate long and short dash line (after further pause), the current equal to that at the time of charging the single cell is the same. The changes in SOC and voltage VB when charged with are shown. This SOC adjustment is referred to as "discharge adjustment".

As shown in FIG. 6, charging with the same current is started from the same SOC (= 50%) at the time of charge adjustment and discharge adjustment (see time t12), but the voltage VB (electromotive voltage) at the time of discharge adjustment is started. (OCV)) is lower than the voltage VB at the time of charge adjustment. This indicates that the input performance of the single cell is higher when the discharge is adjusted than when the charge is adjusted. In other words, since the voltage VB is relatively low at the time of discharge adjustment as compared with the charge adjustment, it is difficult for the voltage VB to rise to the voltage at which the single cell can deteriorate, and the input control upper limit value Win (absolute value) is set large. However, it shows that a single cell can be protected.

FIG. 7 is a diagram for explaining input / output hysteresis (more specifically, output hysteresis) that occurs in a single cell. In FIG. 7, changes in SOC and voltage VB when a single cell is charged from a completely discharged state, the SOC is adjusted to 50%, and then the single cell is discharged with a constant current (for example, a current of 3C). Is indicated by a solid line (denoted as "charge matching"). On the other hand, the change in SOC and voltage VB when the single cell is discharged from the fully charged state, the SOC is adjusted to 50%, and then the single cell is discharged with the same current as when the charge is adjusted is shown by the alternate long and short dash line. (Described as "discharge adjustment").

In FIG. 7, after the start of discharge at a constant current (see time t22), the voltage VB at the time of charge adjustment is higher than the voltage VB at the time of discharge adjustment. Therefore, the output performance of the single cell is higher when the charge is adjusted than when the discharge is adjusted. That is, since the voltage VB is unlikely to be excessively low at the time of charge adjustment as compared with the discharge adjustment, the output control upper limit value Wout (absolute value) can be set large.

Although the time change of the voltage VB is shown in FIGS. 6 and 7, the present inventor also measures the potential change of the positive electrode and the negative electrode alone, and there is such a difference between the time of charge adjustment and the time of discharge adjustment. It has been confirmed that it is derived from the negative electrode.

<Input ΔV and output ΔV>
In FIG. 6, after the start of charging at a constant current, the voltage difference between the voltage VB at the time of charge adjustment and the voltage VB at the time of discharge adjustment becomes smaller with the passage of time, and when a predetermined time elapses (see time t13), the voltage is concerned. It can be seen that the difference is almost eliminated. This is because when the charging of the assembled battery 10 is continued for a certain period of time, the OCV of the assembled battery 10 is defined by the charging OCV regardless of the charge / discharge history before that (on the curve shown by CHG). It will be plotted).

Similar to the result shown in FIG. 6, in FIG. 7, the voltage difference between the voltage VB at the time of charge adjustment and the voltage VB at the time of discharge adjustment becomes smaller with the passage of time, and the voltage difference finally disappears. .. This indicates that when the discharge of the assembled battery 10 is continued, the OCV of the assembled battery 10 is defined by the discharge OCV regardless of the past charge / discharge history. In the present embodiment, "input ΔV" indicating the OCV change amount of the assembled battery 10 based on the charged OCV and "output ΔV" indicating the OCV change amount of the assembled battery 10 based on the discharged OCV are used. ..

FIG. 8 is a diagram for explaining an input ΔV and an output ΔV. As shown in FIG. 8A, the difference between the charged OCV and the estimated (or measured) OCV (OCV _ES described later) of the assembled battery 10 in the same SOC is defined as “input ΔV”. Further, as shown in FIG. 8B, the difference between the OCV (OCV _ES ) of the assembled battery 10 at the start of discharging and the discharging OCV in the same SOC is defined as “output ΔV”.

In the SOC-OCV characteristic diagram, the OCV of the assembled battery 10 is not plotted above the charging OCV (curve CHG) and is not plotted below the discharging OCV (curve DCH). Therefore, according to the above definition, both the input ΔV and the output ΔV have a value of 0 or more (0 or a positive value). However, the above definition is an example, and the definition method of the input ΔV or the output ΔV is not limited to this.

<Calculation of OCV change amount ΔOCV>
Subsequently, the ideal OCV (OCV on the curve obtained in an ideal state where no stress remains on the surface in the negative electrode active material 71) described with reference to FIG. 5 and the OCV (OCV _ES ) of the assembled battery 10 are used. The difference between the two is defined as "OCV change amount ΔOCV". The calculation method of this OCV change amount ΔOCV will be described.

FIG. 9 is a flowchart showing a calculation process of the OCV change amount ΔOCV. FIG. 10 is a diagram for explaining the contents of the parameters. The flowchart shown in FIG. 9 is called from a main routine (not shown) and executed by the ECU 100, for example, when a predetermined condition is satisfied. Further, each step (hereinafter abbreviated as "S") included in FIG. 12 and the flowchart described later is basically realized by software processing by the ECU 100, but dedicated hardware (electric circuit) manufactured in the ECU 100 is provided. ) May be realized.

With reference to FIGS. 9 and 10, in S10, the ECU 100 obtains the voltage VB, current IB and temperature TB of the assembled battery 10 from each sensor (voltage sensor 21, current sensor 22 and temperature sensor 23) in the monitoring unit 20. get.

In S20, the ECU 100 estimates the OCV of the assembled battery 10 (acquires the OCV _ES ). OCV _ES can be calculated according to the following equation (1). In the formula (1), the internal resistance of the assembled battery 10 is represented by R. Further, the correction term for correcting the influence of the polarization generated in the assembled battery 10 is represented by ΣΔV _i (i is a natural number). This correction term ΣΔV _i corrects the polarization caused by the lithium diffusion in the positive electrode active material and the negative electrode active material and the lithium salt diffusion in the electrolytic solution. When considering the lithium diffusion in the negative electrode active material, it is desirable to consider the effects of both the lithium concentration difference in the negative electrode active material and the internal stress. It is assumed that the correction term ΣΔV _i is obtained in the preliminary experiment in advance and is stored in the memory 100B. The correction term ΣΔV _i is also determined so that the value of the assembled battery 10 when charged is positive.
OCV _ES = VB-IB x R-ΣΔV _i ... (1)

In S30, the ECU 100 calculates the current OCV change amount ΔOCV from the ideal OCV (see FIG. 5), the estimated OCV (OCV _ES ) calculated in S20, and the OCV change amount ΔOCV calculated at the time of the previous calculation. .. More specifically, the ECU 100 corrects the estimated OCV by the OCV change amount ΔOCV calculated at the time of the previous calculation (that is, calculates OCV _ES + ΔOCV), and the SOC corresponding to the corrected estimated OCV (OCV _ES + ΔOCV). Is calculated by referring to the ideal OCV (curve indicated by the ID in FIG. 5).

In S40, the ECU 100 calculates the surface stress σ. The surface stress σ can be calculated according to the following equation (2).
σ = -α (SOC-SOC _REF ) + σ _REF ... (2)

According to the experimental results of the present inventor, there is a linear approximate relationship between the surface stress σ and the difference between the current SOC and the reference SOC _REF (SOC-SOC _REF ). Here, the reference SOC _REF is the SOC at the time of charging / discharging switching of the assembled battery 10.

More specifically, when the assembled battery 10 is overcharged and the OCV of the assembled battery 10 is represented on the charging OCV (curve CHG), when the assembled battery 10 is further charged, the reference SOC _REF becomes a curve. It is updated to the SOC that has moved in the charging direction (to the right on the SOC-OCV characteristic diagram) on the CHG. On the other hand, when the charging / discharging direction of the assembled battery 10 is switched from charging to discharging, the reference SOC _REF is set to the SOC at the time of the switching (immediately before the start of discharging).

On the other hand, when the assembled battery 10 is excessively discharged and the OCV of the assembled battery 10 is represented on the discharged OCV (curve DCH) and the assembled battery 10 is further discharged, the reference SOC _REF is on the curved DCH. It is updated to the SOC that has moved in the discharge direction (to the left on the SOC-OCV characteristic diagram). On the other hand, when the charging / discharging direction of the assembled battery 10 is switched from discharging to charging, the reference SOC _REF is set to the SOC at the time of the switching (immediately before the start of charging). The reference stress σ _REF is a surface stress σ corresponding to the reference SOC _REF (surface stress when the SOC is the reference SOC _REF ).

Further, in the equation (2), the positive proportionality constant (slope of a straight line) of the linear relationship established between the surface stress σ and the SOC difference is described as α. The proportionality constant α is a parameter determined according to the mechanical properties of the negative electrode active material 71 (and the peripheral member 72), and is obtained by an experiment. More specifically, the proportionality constant α changes depending on the temperature of the negative electrode active material 71 (≈ temperature TB of the assembled battery 10) and the lithium content in the negative electrode active material 71 (in other words, the SOC of the assembled battery 10). Can be. Therefore, it is preferable to obtain the proportionality constant α for each various combination of the temperature TB and SOC of the assembled battery 10 and prepare a map (not shown).

In S50, the ECU 100 compares the surface stress σ calculated in S40 with the compressive stress σ _com . When the surface stress σ when the sign of the surface stress σ is taken into consideration is less than or equal to the compressive stress σ _com , that is, when the magnitude of the surface stress σ is greater than or equal to the magnitude of the compressive stress σ _com (YES in S50), the ECU 100 Is set to σ = σ _com , assuming that the surface stress σ yields at the compressive stress σ _com (S62). Then, the ECU 100 updates the reference SOC _REF calculated in S30. This SOC is set as the reference SOC _REF (S64). Further, the ECU 100 sets the current surface stress σ (that is, compressive stress σ _com ) calculated in S30 as the reference stress σ _REF (S66).

When the surface stress σ is less than the compressive stress σ _com in S50, that is, when the magnitude of the surface stress σ when the sign of the surface stress σ is taken into consideration is smaller than the magnitude of the compressive stress σ _com (NO in S50). , ECU 100 advances the process to S70 and compares the surface stress σ and the tensile stress σ _ten .

When the surface stress σ when the sign of the surface stress σ is taken into consideration is equal to or greater than the tensile stress σ _ten , that is, when the magnitude of the surface stress σ is equal to or greater than the magnitude of the tensile stress σ _ten (YES in S70), the ECU 100 Is set to σ = σ _ten , assuming that the surface stress σ yields at the tensile stress σ _ten (S82). Then, the ECU 100 sets the current SOC calculated in S30 as the reference SOC _REF (S84). Further, the ECU 100 sets the current surface stress σ (that is, tensile stress σ _ten ) calculated in S30 to the reference stress σ _REF (S86). The order of processing of S84 and S86 may be changed. The order of processing of S64 and S66 can also be changed.

When the processing of S66 or S86 is completed, the ECU 100 calculates the OCV change amount ΔOCV from the surface stress σ according to the linear relationship established between the OCV change amount ΔOCV and the surface stress σ (S90). Specifically, this linear relationship is expressed by the following equation (3).
ΔOCV = k × Ω × σ / F ・ ・ ・ (3)

In formula (3), the volume increase of the negative electrode active material 71 when 1 mol of lithium is inserted is represented by Ω (unit: m ³ / mol), and the Faraday constant is F (unit: C / mol). It is shown. k is an experimentally determined constant.

<Preliminary measurement>
Here, if the input control upper limit value Win is not set to a sufficiently low value, the voltage VB of the assembled battery 10 becomes excessively high or the input current to the assembled battery 10 becomes excessively large, so that the assembled battery 10 becomes excessively large. May not be properly protected. On the other hand, if the input control upper limit value Win is set too low, the assembled battery 10 can be protected, but the charging of the assembled battery 10 is excessively restricted and the assembled battery 10 cannot be fully utilized. there is a possibility. The same applies to the output control upper limit value Wout of the assembled battery 10.

Therefore, in the present embodiment, the preliminary measurement described below is carried out. By using the result of this pre-measurement, the influence of the electromotive voltage hysteresis can be reflected in the input control upper limit value Win and the output control upper limit value Wout, and the input control upper limit value Win and the output control upper limit value Wout can be appropriately corrected. become.

FIG. 11 is a flowchart showing the procedure of pre-measurement in the present embodiment. This flowchart is carried out by an experimenter (developer of the secondary battery system 2).

With reference to FIG. 7, in S110, the experimenter acquires the charged OCV and the discharged OCV according to the technique described in detail in FIG.

In S120, the experimenter creates an "input map MP1A" for calculating the input control upper limit value Win when the OCV of the assembled battery 10 is plotted on the charging OCV (curve CHG). Further, the experimenter creates an "output map MP1B" for calculating the output control upper limit value Wout when the OCV of the assembled battery 10 is plotted on the discharge OCV (curve DCH) (S130).

FIG. 12 is a diagram showing an example of the input map MP1A. FIG. 13 is a diagram showing an example of the output map MP1B.

With reference to FIG. 12, in the input map MP1A, for example, the input control upper limit value Win is defined for each combination (TB, SOC) of the temperature TB of the assembled battery 10 and the SOC of the assembled battery 10. However, it is not essential to use the temperature TB of the assembled battery 10. The input map MP1A may simply define the correspondence between the SOC of the assembled battery 10 and the input control upper limit value Win.

In the SOC-OCV characteristic diagram, the OCV of the assembled battery 10 is plotted on the charging OCV, the discharging OCV, and the region D (see FIG. 4) surrounded by the charging OCV and the discharging OCV. When the OCV of the assembled battery 10 is charged under the condition plotted on the charged OCV, the voltage VB of the assembled battery 10 becomes the highest. The input control upper limit value Win defined in the input map MP1A indicates the strictest input limit (charge power limit) because it is used when the OCV of the assembled battery 10 is plotted on the charging OCV.

Similarly, for the output map MP1B shown in FIG. 13, the output control upper limit value Wout is defined for each (TB, SOC). The output control upper limit value Wout specified in the output map MP1B is used when the OCV of the assembled battery 10 is plotted on the discharged OCV, that is, when the voltage VB of the assembled battery 10 is likely to be the lowest. Therefore, the strictest output limit (discharge power limit) is shown.

The input map MP1A and the output map MP1B correspond to the "first correspondence" according to the present disclosure. Further, in the examples of the input map MP1A and the output map MP1B, specific numerical values are described in the average temperature TB _ave and SOC. However, it should be confirmed that these numerical values are merely examples for facilitating the understanding of each map MP1A and MP1B, and do not limit the contents in any way. The same applies to other maps described later (see FIGS. 14, 15, 17, and 19).

Returning to FIG. 11, in S140, the experimenter performs an input / output test for each various SOC adjustment history. More specifically, the experimenter prepares many conditions (or histories) in which the SOC, temperature TB, and input ΔV at the start of charging / discharging of the assembled battery 10 are different, and sets the input control upper limit value Win in each condition. calculate. As described with reference to FIG. 4, the input control upper limit value Win is set to a power value at which the voltage of the assembled battery 10 does not exceed a predetermined protection voltage and the assembled battery 10 can be appropriately protected. Although the detailed description is not repeated, the same applies to the output control upper limit value Wout.

It is not essential to use the three parameters (SOC, TB _ave , input ΔV) as the parameters for obtaining the correspondence with the input control upper limit value Win. The SOC dependence and TB dependence of the input control upper limit value Win may not be obtained, and the correspondence between the input control upper limit value Win and the input ΔV may be obtained. Similarly, for the output control upper limit value Wout, it may be sufficient to simply obtain the correspondence between the output control upper limit value Wout and the output ΔV.

In S150, the experimenter creates an "input correction map MP2A" for correcting the input map MP1A created in S120. Further, in S160, the experimenter creates an "output correction map MP2B" for correcting the output map MP1B created in S130. When the creation of the input correction map MP2A and the output correction map MP2B is completed, the series of pre-measurement procedures shown in FIG. 11 is completed.

FIG. 14 is a diagram showing an example of the input correction map MP2A. FIG. 15 is a diagram showing an example of the output correction map MP2B. In the following, it is indicated that the parameter indicates the time average within a certain period by adding ave to the subscript of the parameter.

With reference to FIG. 14, in the input correction map MP2A, the input correction coefficient kin is defined for each combination (SOC, TB _ave , input ΔV) of the SOC of the assembled battery 10, the average temperature TB _ave , and the input ΔV. ing. The input correction coefficient kin is based on the input control upper limit value Win (input control upper limit value Win defined by the input correction map MP2A) when the OCV of the assembled battery 10 is on the charging OCV and the input ΔV = 0. , Is a coefficient indicating the ratio of the input control upper limit value Win (input control upper limit value Win calculated in S140) when the OCV of the assembled battery 10 is not on the charging OCV (when the input ΔV> 0).

As shown in FIG. 15, in the output correction map MP2B, the output correction coefficient kout is defined for each combination of (SOC, TB _ave , output ΔV). The output correction coefficient kout is when the OCV of the assembled battery 10 is not on the discharged OCV based on the output control upper limit value Wout when the OCV of the assembled battery 10 is on the discharged OCV (when the output ΔV = 0). It is a coefficient indicating the ratio of the output control upper limit value Wout (when the output ΔV> 0). The input correction coefficient kin and the output correction coefficient kout are both values of 1 or more (kin ≧ 1, kout ≧ 1). The input correction map MP2A and the output correction map MP2B correspond to the "second correspondence" according to the present disclosure.

<Processing flow>
FIG. 16 is a flowchart for explaining the input upper limit calculation process in the present embodiment. The flowcharts shown in FIG. 16 and FIGS. 17, 20, and 21 described later are, for example, called from a main routine (not shown) every time a predetermined calculation cycle elapses, and are repeatedly executed by the ECU 100.

In S210, the ECU 100 acquires the voltage VB, the current IB, and the temperature TB of the assembled battery 10 from each sensor in the monitoring unit 20.

In S220, the ECU 100 calculates the SOC of the assembled battery 10. The SOC can be calculated by a known method such as current integration. Further, as described in the processes of S20 and S30 in FIG. 9, the SOC may be calculated using the ideal OCV. Alternatively, the SOC is calculated by multiplying each of the SOC calculated by current integration and the SOC calculated using the ideal OCV by a weighting coefficient and adding the SOCs (so to speak, blending the two methods). You may.

In S230, the ECU 100 calculates the average temperature TB _ave of the assembled battery 10. As the average temperature TB _ave , the time average value of the temperature TB of the assembled battery 10 in the latest predetermined period (for example, several minutes) can be used.

In S240, the ECU 100 calculates the OCV change amount ΔOCV. Since the OCV change amount ΔOCV can be calculated by the method described in the processes of S40, S50, S62 to S66, and S90 in FIG. 9, detailed description will not be repeated here.

In S250, the ECU 100 determines whether or not the magnitude of the input ΔV is positive. In S240, the OCV change amount ΔOCV, that is, the difference between the ideal OCV and the OCV _ES is calculated. The ideal OCV is known, and the charging OCV is also known. Therefore, the input ΔV (= charging OCV-OCV _ES ) can be calculated from the OCV change amount ΔOCV, the ideal OCV, and the charging OCV.

When the magnitude of the input ΔV is not positive, that is, when the input ΔV = 0 and the OCV of the assembled battery 10 is plotted on the charging OCV (YES in S250), the ECU 100 has the input map shown in FIG. By referring to MP1A, the input control upper limit value Win is calculated from (TB, SOC) (S260).

On the other hand, when the magnitude of the input ΔV is positive, that is, when the OCV of the assembled battery 10 is not plotted on the charging OCV (NO in S250), the ECU 100 advances the process to S270 and is shown in FIG. The input correction coefficient kin is calculated from (SOC, TB _ave , ΔOCV) by referring to the input correction map MP2A. Then, the ECU 100 corrects the input control upper limit value Win by using the input correction coefficient kin (S280). Specifically, the ECU 100 calculates the corrected input control upper limit value Win'by multiplying the input control upper limit value Win defined in the input map MP1A (see FIG. 12) by the correction coefficient kin (Win'). = Kin × Win). Since the input correction coefficient kin is 1 or more, the input control upper limit value Win'after correction is larger than the input control upper limit value Win'before correction.

FIG. 17 is a flowchart for explaining the output upper limit calculation process in the present embodiment. Although the output upper limit calculation process is basically the same as the input upper limit calculation process shown in FIG. 16, although the charge / discharge directions of the assembled battery 10 are different, the detailed description is not repeated here.

As described above, according to the present embodiment, when the assembled battery 10 is charged within the range of the input control upper limit value Win, the input control upper limit value Win is the condition where the input restriction is the strictest (OCV of the assembled battery 10). Is specified in the conditions plotted on the charging OCV). Similarly, for the discharge of the assembled battery 10, the output control upper limit value Wout is defined by the condition where the output limit is the strictest (the condition in which the OCV of the assembled battery 10 is plotted on the discharged OCV). Therefore, the assembled battery 10 can be appropriately protected.

Further, for example, when a silicon-based compound is adopted for the negative electrode 117 and the influence of the electromotive voltage hysteresis appears, when the OCV of the assembled battery 10 is not plotted on the charging OCV, it is caused by the electromotive voltage hysteresis of the assembled battery 10 and the electromotive voltage hysteresis. The input control upper limit value Win is corrected in consideration of the input / output hysteresis. More specifically, when the OCV of the assembled battery 10 is not plotted on the charged OCV, the input correction coefficient kin (≧ 1) is multiplied as compared with the case where the OCV of the assembled battery 10 is plotted on the charged OCV. The input control upper limit value Win (corrected input control upper limit value Win') is increased. In other words, when the OCV of the assembled battery 10 is not plotted on the charging OCV, the input control upper limit value Win is expanded. Similarly, when the OCV of the assembled battery 10 is not on the discharged OCV, the output control upper limit value Wout is expanded as compared with the case where the OCV of the assembled battery 10 is not on the discharged OCV. By expanding the input control upper limit value Win and the output control upper limit value Wout in this way, the assembled battery 10 can be fully utilized.

[Modification example]
In the modified example of the present embodiment, instead of the input ΔV or the output ΔV, the OCV of the assembled battery 10 determines whether or not it is on the curves CHG and DCH according to the SOC change amount ΔSOC (described later). Will be explained. In this modification, the parameters used for the input correction map and the output correction map are different from the parameters in the embodiment.

FIG. 18 is a diagram showing an example of the input correction map MP4A in the modified example. FIG. 19 is a diagram showing an example of the output correction map MP4B in the modified example.

With reference to FIG. 18, in the input correction map MP4A, for example, for each combination (SOC, TB _ave , ΔSOC) of the SOC of the assembled battery 10, the average temperature TB _ave of the assembled battery 10, and the SOC change amount ΔSOC. The input correction coefficient kin is specified. Similarly, for the output correction map MP4B shown in FIG. 19, the output correction coefficient kout is defined for each (SOC, TB _ave , ΔSOC).

In this modification, the input upper limit calculation process and the output upper limit calculation process are realized by using the SOC change amount ΔSOC and the flag G stored in the memory 100B.

FIG. 20 is a diagram for explaining the SOC change amount ΔSOC and the flag G. The flag G is used to manage the relationship between the combination of the reference SOC _REF and the reference OCV _REF (reference point indicated by a white circle) and the charging OCV or the discharging OCV. When the reference point is on the charging OCV (charging curve CHG) as shown in FIG. 20A, the flag G is set to G = 1 by another flow (not shown). On the other hand, when the reference point is on the discharge OCV (discharge curve DCH) as shown in FIG. 20B, the flag G is set to G = 2.

With reference to FIG. 20A, when the assembled battery 10 is charged while the reference point is on the charging OCV (G = 1 state), the state of the assembled battery 10 (combination of SOC and OCV) is the charging OCV. Move up in the charging direction (positive direction, right direction in the figure). At this time, the reference point is updated to a point indicating the state of the assembled battery 10 after charging.

On the other hand, when the assembled battery 10 is discharged while the reference point is on the charging OCV, the state of the assembled battery 10 deviates from the charging OCV and the charging OCV and the discharging OCV are shown by the solid line. It will be represented in the area between. The reference point at this time is maintained at a point on the charging OCV before the start of discharge. The amount of change in SOC with respect to the reference point is described as ΔSOC (ΔSOC <0 in FIG. 20A).

With reference to FIG. 20B, when the assembled battery 10 is discharged while the reference point is on the discharged OCV (G = 2 state), the state of the assembled battery 10 is in the discharge direction (negative direction, on the discharged OCV). Move to the left in the figure). The reference point is updated to a point indicating the state of the assembled battery 10 after discharging.

When the assembled battery 10 is charged while the reference point is on the discharged OCV, the state of the assembled battery 10 deviates from the discharged OCV and is represented by a solid line. The reference point is maintained at a point on the discharge OCV before the start of charging. Further, the amount of change in SOC with respect to the reference point at this time is described as ΔSOC (ΔSOC> 0 in FIG. 20B). As described above, the SOC change amount ΔSOC indicates the SOC change amount from the time when the state of the assembled battery 10 deviates from the charging OCV or the discharging OCV.

FIG. 21 is a flowchart for explaining the input upper limit calculation process in the modified example. This flowchart differs from the input upper limit calculation process (see FIG. 16) in the embodiment in that the process of S470 is included instead of the process of S240.

In S410, the ECU 100 acquires the voltage VB, the current IB, and the temperature TB of the assembled battery 10 from each sensor in the monitoring unit 20.

In S422, the ECU 100 calculates the SOC of the assembled battery 10. The SOC may be calculated from the OCV change amount ΔOCV by referring to the curve ID shown in FIG. Alternatively, the SOC may be calculated by a known method such as current integration.

In S424, the ECU 100 calculates the SOC change amount ΔSOC of the assembled battery 10 with reference to the SOC of the reference point.

In S426, the ECU 100 calculates TB _ave , which is the latest time average of the temperature TB of the assembled battery 10. The time to be the target of this time average is also determined experimentally, but it is preferably the same as the period used for calculating the SOC change amount ΔSOC in S424.

Subsequently, in S450, it is determined whether or not the state of the assembled battery 10 (combination of SOC and OCV) exists on the charged OCV. More specifically, the ECU 100 determines whether or not the condition that the flag G is G = 1 and the SOC change amount ΔSOC is positive is satisfied (see FIG. 20A). When this condition is satisfied (YES in S450), the state of the assembled battery 10 exists on the charging OCV. Therefore, the ECU 100 calculates the input control upper limit value Win from (TB, SOC) by referring to the input map MP1A shown in FIG. 12 (S460).

On the other hand, when the above condition is not satisfied (NO in S450), that is, when G = 2 or the SOC change amount ΔSOC is 0, the state of the assembled battery 10 does not exist on the charging OCV. Therefore, the ECU 100 advances the processing to S470 and calculates the input correction coefficient kin from (SOC, TB _ave , ΔSOC) by referring to the input correction map MP4A shown in FIG. Further, the ECU 100 corrects the input control upper limit value Win by using the input correction coefficient kin (S480).

It was explained that the input correction map MP4A is not referred to in the processing of S460 executed when the above condition is not satisfied. However, the input correction map MP4A may be always referred to, and the input correction map MP4A to be referred to when the above conditions are not satisfied may be prepared. In this input correction map MP4A, the input correction coefficient kin = 1 is set.

FIG. 22 is a flowchart for explaining the output upper limit calculation process in the modified example. Since this output upper limit calculation process is basically the same as the input upper limit calculation process shown in FIG. 21, detailed description will not be repeated.

As described above, in the modified example of the embodiment, the input control upper limit value Win is defined under the strictest input restriction condition as in the embodiment, so that the assembled battery 10 can be appropriately protected. .. The same applies to the output control upper limit value Wout when the assembled battery 10 is discharged.

Further, in this modification, whether or not the OCV of the assembled battery 10 is plotted on the charged OCV is determined by using the SOC change amount ΔSOC (see S450 in FIG. 20). In this way, whether or not the OCV of the assembled battery 10 is out of the charged OCV, or whether or not the OCV of the assembled battery 10 may be plotted on the charged OCV does not use the OCV change amount ΔOCV. Can also be determined. Then, when it is determined that the OCV of the assembled battery 10 is not on the charging OCV (YES in S450), the input control upper limit value Win is expanded (S470). When it is determined that the OCV of the assembled battery 10 is not on the discharged OCV (YES in S550 of FIG. 21), the output control upper limit value Wout is similarly expanded (S570). This makes it possible to fully utilize the assembled battery 10.

In the embodiments and modifications, an example in which a silicon compound is used as the negative electrode active material having a large volume change due to charging / discharging has been described. However, the negative electrode active material having a large volume change due to charging / discharging is not limited to this. In the present specification, the “negative electrode active material having a large volume change” means a material having a large volume change as compared with the volume change (about 10%) of graphite due to charge / discharge. Examples of the negative electrode material of such a lithium ion secondary battery include tin-based compounds (such as Sn or SnO), germanium-based compounds, and lead-based compounds. The lithium ion secondary battery is not limited to the liquid type, but may be a polymer type or an all-solid type.

Further, although the silicon-based compound is mentioned as an example of the negative electrode active material 71, a composite material of the silicon-based compound and another material may be used. Examples of the composite material include a composite material containing a silicon-based compound and graphite, a composite material containing a silicon-based compound and lithium titanate, and the like. When such a composite material is used, input / output hysteresis occurs only in a part of the SOC region (for example, when a mixed negative electrode of SOC and graphite is used, only a low SOC region). Therefore, the input upper limit calculation process and the output upper limit calculation process may be executed only in a part of the SOC area. Further, when the volume change amount of the positive electrode active material is large, the hysteresis derived from the positive electrode may be taken into consideration.

Further, the secondary battery to which the input upper limit estimation process and the output upper limit estimation process can be applied is not limited to the lithium ion secondary battery, and may be another secondary battery (for example, a nickel hydrogen battery). In addition, stress can also be generated on the positive electrode side of the secondary battery. Therefore, the input upper limit estimation process and the output upper limit estimation process may be executed in consideration of the stress on the positive electrode side of the secondary battery.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present disclosure is set forth by the claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims.

1 vehicle, 2 secondary battery system, 10 sets of batteries, 11 cells, 20 monitoring units, 21 voltage sensors, 22 current sensors, 23 temperature sensors, 30 PCUs, 41, 42 motor generators, 43 engines, 44 power dividers, 45 Drive shaft, 46 drive wheels, 100 ECU, 100A CPU, 100B memory, 111 battery case, 112 lid, 113 positive electrode terminal, 114 negative electrode terminal, 115 electrode body, 116 positive electrode, 117 negative electrode, 118 separator.

Claims (2)

With a secondary battery,
It includes a memory in which the first and second correspondences are stored, and includes a calculation device for calculating the control upper limit value of the input power to the secondary battery.
The first correspondence is a correspondence between the SOC of the secondary battery and the control upper limit value when the SOC and OCV of the secondary battery are represented on the charge curve.
The second correspondence is that the voltage difference between the OCV on the charge curve and the measured value of the OCV of the secondary battery, and the combination of the SOC and OCV of the secondary battery are on the charge curve or released . It is a correspondence relationship between one of the SOC change amounts of the secondary battery from the time when it deviates from the electric curve and the correction coefficient for correcting the control upper limit value.
The charging curve shows the SOC-OCV characteristics of the secondary battery when the secondary battery is charged from a fully discharged state to a fully charged state.
The discharge curve shows the SOC-OCV characteristics of the secondary battery when the secondary battery is discharged from a fully charged state to a fully discharged state.
The calculation device is
When the SOC and OCV of the secondary battery are represented on the charge curve, the control upper limit value is calculated from the SOC of the secondary battery by referring to the first correspondence.
When the SOC and OCV of the secondary battery are not represented on the charge curve, the correction coefficient is calculated from either the voltage difference or the SOC change amount by referring to the second correspondence. , The secondary battery system that corrects the control upper limit value calculated by referring to the first correspondence relationship by the correction coefficient. With a secondary battery,
It includes a memory in which the first and second correspondences are stored, and includes a calculation device for calculating the control upper limit value of the output power from the secondary battery.
The first correspondence is a correspondence between the SOC of the secondary battery and the control upper limit value when the SOC and OCV of the secondary battery are represented on the discharge curve.
The second correspondence is that the voltage difference between the measured value of the OCV of the secondary battery and the OCV on the discharge curve, and the combination of the SOC and the OCV of the secondary battery are on the charge curve or the discharge. It is a correspondence relationship between one of the SOC changes of the secondary battery from the time when the curve deviates from the curve and the correction coefficient for correcting the control upper limit value.
The charging curve shows the SOC-OCV characteristics of the secondary battery when the secondary battery is charged from a fully discharged state to a fully charged state.
The discharge curve shows the SOC-OCV characteristics of the secondary battery when the secondary battery is discharged from a fully charged state to a fully discharged state.
The calculation device is
When the SOC and OCV of the secondary battery are represented on the discharge curve, the control upper limit value is calculated from the SOC of the secondary battery by referring to the first correspondence.
When the SOC and OCV of the secondary battery are not represented on the discharge curve, the correction coefficient is calculated from either the voltage difference or the SOC change amount by referring to the second correspondence. , The secondary battery system that corrects the control upper limit value calculated by referring to the first correspondence relationship by the correction coefficient.

Images