JP2019106794A - Secondary battery system - Google Patents

Abstract

To sufficiently utilize a secondary battery while appropriately protecting the secondary battery.SOLUTION: An input map MP1A indicates a correspondence between the SOC of a battery pack 10 and an input control upper limit value Win when the SOC and OCV of the battery pack 10 are plotted on a charge curve CHG. An input correction map MP2A indicates a correspondence between an input correction coefficient kin for correcting the input control upper limit value Win and a voltage difference (input ΔV) between an OCV on the charge curve CHG and the measured value of the OCV of the battery pack 10. When the SOC and OCV of the battery pack 10 are plotted on the charge curve CHG, an ECU 100 calculates the input control upper limit value Win by referring to the input map MP1A. When the SOC and OCV of the battery pack 10 are not plotted on the charge curve CHG, the ECU 100 calculates the input correction coefficient kin by referring to the input correction map MP2A, and corrects the input control upper limit value Win on the basis of the input correction coefficient kin.SELECTED DRAWING: Figure 12

Description

  The present disclosure relates to a secondary battery system, and more particularly 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.

  In general, in a secondary battery system mounted on an electric vehicle or the like, a certain degree of restriction is provided to charging and 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 Win indicating the control upper limit, and the output power from the secondary battery indicates the control upper limit indicating the control upper limit The charge and discharge of the secondary battery are controlled so as not to exceed Wout.

  A technique has been proposed for calculating appropriate values for the input control upper limit Win and the output control upper limit Wout. For example, Japanese Patent Laid-Open No. 2000-030748 (Patent Document 1) accurately calculates input / output power of a secondary battery (that is, input control upper limit Win and output control upper limit Wout) whose open circuit voltage changes according to charge / discharge history. To disclose the method for

JP 2000-030748 A JP, 2015-038444, A JP, 2014-139521, A JP, 2015-166710, A

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

  If the input control upper limit value Win is not set appropriately, the secondary battery can be sufficiently protected because the voltage of the secondary battery becomes excessively high or the input current to the secondary battery becomes excessively large. It may not be possible. On the other hand, if the input control upper limit value Win is set too low, although the secondary battery can be protected, the charging to the secondary battery is excessively limited and the secondary battery can not 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-described problems, and an object of the present disclosure is to fully utilize a secondary battery while appropriately protecting the secondary battery.

  (1) A secondary battery system according to an aspect of the present disclosure includes a secondary battery and a calculation device that calculates a control upper limit value of input power to the secondary battery. The calculation device includes a memory in which first and second correspondences are stored. The first correspondence relationship is when the SOC and OCV of the secondary battery are represented on a charging curve that indicates the SOC-OCV characteristics of the secondary battery when the secondary battery is charged from the fully discharged state to the fully charged state. And the upper limit value of the control of the secondary battery. The second correspondence relationship is the voltage difference between the OCV on the charging curve and the measured value of the OCV of the secondary battery, and the point in time when the combination of the SOC and the OCV of the secondary battery deviates from the charging curve or the discharging curve. And a correction coefficient for correcting the control upper limit value. When the SOC and the OCV of the secondary battery are represented on the charging curve, the calculation device calculates the control upper limit value from the SOC of the secondary battery by referring to the first correspondence relationship. When the SOC and the 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 relationship, and The control upper limit value calculated by referring to the correspondence relationship 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 that calculates a control upper limit value of output power from the secondary battery. The calculation device includes a memory in which first and second correspondences are stored. The first correspondence relationship is that when the secondary battery's SOC and OCV 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. And the upper limit value of the control of the secondary battery. The second correspondence relationship 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 And a correction coefficient for correcting the control upper limit value. When the SOC and the 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 relationship. 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 relationship, and The control upper limit value calculated by referring to the correspondence relationship of 1 is corrected by the correction coefficient.

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

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

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

FIG. 1 schematically shows an overall configuration of a vehicle equipped with a secondary battery system according to an embodiment of the present invention. It is a figure for demonstrating the structure of each cell in more detail. It is a figure which shows typically an example of the change of surface stress (sigma) accompanying charging / discharging of a single cell. 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 arises in a single cell. It is a figure for demonstrating the input-output hysteresis (output hysteresis) which arises in a single cell. It is a figure for demonstrating input deltaV and output deltaV. It is a flowchart which shows calculation processing of OCV change amount (DELTA) OCV. It is a figure for demonstrating the content of a parameter. It is a flowchart which shows the procedure of the prior measurement in this Embodiment. It is a figure which shows an example of input map MP1A. It is a figure which shows an example of output map MP1B. It is a figure which shows an example of input correction | amendment map MP2A. It is a figure which shows an example of 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 showing an example of input amendment map MP4A in a modification. It is a figure showing an example of output amendment map MP4B in a modification. FIG. 6 is a diagram for illustrating an SOC change amount ΔSOC and a flag G. It is a flowchart for demonstrating the input upper limit calculation process in a 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. In the drawings, the same or corresponding portions are denoted by the same reference characters and 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 not limited to hybrid vehicles, and is applicable to all vehicles (electric vehicles, fuel cell vehicles, and the like) on which a traveling assembled battery is mounted. Furthermore, the application of the secondary battery system according to the present embodiment is not limited to vehicles, and may be stationary, for example.

Embodiment
<Overall Configuration of Vehicle>
FIG. 1 is a view schematically showing an overall configuration of a vehicle equipped with the secondary battery system according to the present embodiment. Referring to FIG. 1, vehicle 1 is a hybrid vehicle, and includes a secondary battery system 2, motor generators 41 and 42, an engine 43, a power split device 44, a drive shaft 45, and a drive wheel 46. Equipped with The secondary battery system 2 includes a battery assembly 10, a monitoring unit 20, a power control unit (PCU) 30, and an electronic control unit (ECU) 100.

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

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

  The engine 43 is an internal combustion engine that outputs motive power by converting combustion energy generated when a mixture of air and fuel is burned into kinetic energy of a moving element such as a piston or a rotor.

  Power split 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. Power split device 44 splits the power output from engine 43 into power for driving motor generator 41 and power for driving drive wheel 46.

  The battery assembly 10 includes a plurality of cells 11 (see FIG. 2). In the present embodiment, each cell is a lithium ion secondary battery. The battery assembly 10 stores electric power for driving the motor generators 41 and 42 and supplies the electric power to the motor generators 41 and 42 through the PCU 30. Further, the battery pack 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 battery pack 10. Current sensor 22 detects a current IB input / output to / from battery assembly 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 with, for example, a plurality of cells 11 connected in series as a monitoring unit. Also, the temperature sensor 23 may detect the temperature TB with the plurality of adjacent cells 11 as a monitoring unit. Thus, in the present embodiment, the monitoring unit is not particularly limited. Therefore, in the following, for simplification of the description, it is simply described as "detect the voltage VB of the battery pack 10" or "detect the temperature TB of the battery pack 10." Likewise, the battery pack 10 is described as an estimation unit for SOC and OCV.

  PCU 30 performs bi-directional power conversion between battery assembly 10 and motor generators 41 and 42 in accordance with a control signal from ECU 100. PCU 30 is configured to be capable of separately controlling the states of motor generators 41 and 42. For example, motor generator 42 can be brought into a power running state while motor generator 41 is brought into a regeneration state (power generation state). For example, PCU 30 includes two inverters provided corresponding to motor generators 41 and 42, and a converter (not shown) for boosting DC voltage supplied to each inverter to an output voltage of assembled battery 10 or more. It is comprised including.

  The ECU 100 includes a central processing unit (CPU) 100A, a memory (more specifically, a read only memory (ROM) and a random access memory (RAM)) 100B, and an input / output port (not shown) for inputting and outputting various signals. And is included. ECU 100 controls the upper limit value of power that can be input to battery assembly 10 (input control upper limit value Win based on the signals received from each sensor of monitoring unit 20 and the program and maps stored in memory 100B (each map described later)). And “output upper limit calculation processing” for calculating the control upper limit value (power control upper limit value Wout) of the electric power that can be output from the battery pack 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 its interior.

  Referring to FIG. 2, cell 11 has a rectangular (substantially rectangular) battery case 111. The top surface of the battery case 111 is sealed by a lid 112. One end of each of the positive electrode terminal 113 and the negative electrode terminal 114 protrudes from the lid 112 to the outside. 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 (both not shown) in the battery case 111. An electrode body 115 is accommodated in the battery case 111. The electrode body 115 is formed by laminating the positive electrode 116 and the negative electrode 117 with the separator 118 interposed therebetween, and winding the laminated body. The electrolytic solution is held by 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 constitutions and materials can be used as the positive electrode of the lithium ion secondary battery, the separator and the electrolytic solution. As an example, for the positive electrode 116, a ternary material in which a part of lithium cobaltate is substituted by nickel and manganese can be used. For the separator, polyolefin (for example, polyethylene or polypropylene) can be used. The electrolytic solution contains an organic solvent (for example, a mixed solvent of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and ethylene carbonate (EC)), a lithium salt (for example, LiPF ₆ ), an additive (for example, LiBOB (lithium bromide) (oxalate) borate) or Li [PF ₂ (C ₂ O ₄ ) ₂ ]). Instead of the electrolytic solution, a polymer electrolyte may be used, or an inorganic solid electrolyte such as an oxide type or a sulfide type may be used.

  The configuration 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 rectangular battery case but also a cylindrical or laminate battery case can be adopted.

<Evoked voltage hysteresis>
Conventionally, a typical negative electrode active material of a lithium ion secondary battery is a carbon material (for example, graphite (graphite)). On the other hand, in the present embodiment, a silicon compound (Si or SiO) is employed as the active material of the negative electrode 117. This is because the energy density and the like of the battery pack 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 be noticeable in the SOC-OCV characteristic (SOC-OCV curve). As the factor, as described below, the volume change of the negative electrode active material accompanying charge and discharge can be considered. In the following, this hysteresis is also referred to as “electromotive voltage hysteresis”.

  The negative electrode active material expands as lithium is inserted, and contracts as lithium is desorbed. 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 volume change of the silicon-based compound due to the insertion or removal of lithium is larger than the volume change of graphite. Specifically, when based on the minimum volume in the state where lithium is not inserted, the volume change amount (expansion coefficient) of graphite accompanying lithium insertion is about 1.1 times, The volume change of the silicon compound is about 4 times at the maximum. Therefore, when a silicon-based compound is employed as the negative electrode active material, stress generated on the surface of the negative electrode active material is greater than when a graphite is employed. Hereinafter, this stress is also referred to as "surface stress".

  In general, 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 that causes a large volume change, such as a silicon-based compound, is adopted, the amount of change in surface stress with an increase or decrease in the amount of lithium also becomes large. Here, hysteresis exists in the surface stress. Therefore, the negative electrode potential can be defined with high accuracy by considering the surface stress and the influence of the hysteresis. And when estimating SOC from OCV using the relationship between SOC and OCV, SOC can be estimated with high precision by assuming the negative electrode potential in which the surface stress was considered in this way.

  The OCV, as described above, means a voltage in a state in which the voltage of the battery pack 10 is sufficiently relaxed and the lithium concentration in the active material is relaxed, and is also referred to as an electromotive voltage. The stress remaining on the negative electrode surface in this relaxed state includes various forces including the stress generated inside the negative electrode active material and the reaction force acting from the surrounding material to the negative electrode active material along with the volume change of the negative electrode active material. Can be considered as the stress when the whole system is balanced. The peripheral materials are, for example, binders, conductive assistants, and other active materials present around the active material.

FIG. 3: is a figure which shows typically an example of the change of surface stress (sigma) accompanying charging / discharging of a single cell (cell 11). In FIG. 3, the horizontal axis indicates the SOC of single cell 0, and the vertical axis indicates surface stress σ. Regarding surface stress σ, tensile stress σ _ten generated at the time of contraction of negative electrode active material 71 (at the time of discharge of a single cell) is indicated in a positive direction, and generated at the time of expansion of negative electrode active material 71 (at the time of charge of single cell) The compressive stress σ _com is represented in the negative direction.

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

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

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

  When charging of a single cell is continued, compressive stress mainly acts on the surface of the negative electrode active material (surface stress σ becomes compressive stress), and the negative electrode potential decreases compared to the ideal state in which surface stress σ is not generated. As a result, the OCV of a single cell rises. On the other hand, when the discharge of the single cell is continued, a tensile stress mainly acts on the surface of the negative electrode active material (surface stress σ becomes a tensile stress), and the negative electrode potential rises compared to the ideal state. As a result, the OCV of a single cell is reduced. According to the above mechanism, hysteresis accompanying charge and 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 battery assembly 10 in the present embodiment. In FIG. 4, the horizontal axis represents the SOC of the battery pack 10, and the vertical axis represents the OCV of the battery pack 10.

  In FIG. 4, a curve (indicated by CHG) obtained by charging the battery assembly 10 and a curve (indicated by DCH) obtained by discharging the battery assembly 10 are shown. Hereinafter, the OCV on the former is referred to as "charge OCV", and the OCV on the latter is referred to as "discharge OCV". The difference between the charge OCV and the discharge OCV at the same SOC (for example, about 150 mV in the case of a silicon-based compound) represents an electromotive voltage hysteresis.

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

  Subsequently, charging of the amount of electricity corresponding to the next 5% SOC (charging from SOC = 5% to 10%) is started. When charging is completed, the OCV of a single cell is similarly measured after lapse of standing time. Then, the combination of SOC and OCV is plotted again from the measurement result of OCV. Thereafter, the same procedure is repeated until the single cell reaches a fully charged state. A charge OCV can be obtained by performing such a measurement.

  Next, from the fully charged state to the fully discharged state of the single cell, the OCV of the single cell at 5% SOC is measured, repeating the discharge and the discharge stop of the single cell this time. A discharge OCV can be obtained by performing 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 (state of σ ≒ 0) in which no stress remains on the surface in 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 a method of measuring the surface stress σ will be briefly described. First, the change in the curvature κ of the thin film negative electrode 117 deformed by stress is measured. The curvature κ can be measured optically, for example 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 (the negative electrode active material 71 and the peripheral member 72) into the Stoney equation , Surface stress σ can be calculated (for details of stress measurement, see, for example, Non-Patent Document 1).

Referring to FIG. 5, the surface stress σ on the charge OCV is almost constant at the compressive stress σ _com at yield, and the surface stress σ on the discharge OCV is almost constant at tensile stress σ _ten at yield . Therefore, a curve (D _com : the distance D _com between the ideal OCV and the charge OCV and the distance D _ten between the ideal OCV and the discharge OCV is equal to the ratio of the compressive stress σ _com and the tensile stress σ _ten The surface stress σ can be regarded as substantially zero on the curve (D _ten = σ _com : σ _ten ). By calculating such a curve, an ideal OCV can be set.

<Input and output hysteresis>
The inventor has found that input / output performance of the battery pack 10 (more specifically, charge / discharge voltage of the battery pack 10) when the charge / discharge history of the battery pack 10 is different due to the electromotive voltage hysteresis shown in FIG. We also found that hysteresis also 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) occurring in a single cell. In FIG. 6 and FIG. 7 described later, the horizontal axis indicates the elapsed time. The vertical axis represents the SOC of the battery assembly 10 and the voltage VB from the top.

  In FIG. 6, the single cell is charged from the fully discharged state (state of SOC = 0%) to adjust the SOC to 50%, and after pausing for a while in the adjusted state, the single cell is subjected to a constant current (for example, Changes in the SOC and the voltage VB when charging with a current of 3 C) are shown by solid lines. Below, such SOC adjustment is described as "charge adjustment." On the other hand, after the single cell is discharged from the fully charged state (state of SOC = 100%) and the SOC is adjusted to 50% by the alternate long and short dash line (after the suspension), the current equal to that for charging the single cell The changes in SOC and voltage VB are shown when charging at. This SOC adjustment is referred to as "discharge match".

  As shown in FIG. 6, the charging with the same current is started from the same SOC (= 50%) at the charge match time and the discharge match time (see time t12). (OCV)) is lower than the voltage VB at the time of charge combination. This indicates that the input performance of the single cell is higher at the discharge alignment than at the charge alignment. In other words, since the voltage VB is relatively lower at the time of discharge combination than at the time of charge combination, the voltage VB does not easily rise to a voltage at which the single cell may deteriorate, and the input control upper limit value Win (absolute value) is set large. It also shows that single cells can be protected.

  FIG. 7 is a diagram for explaining input / output hysteresis (more specifically, output hysteresis) occurring in a single cell. In FIG. 7, after charging a single cell from the fully discharged state, adjusting SOC to 50% and pausing, change in SOC and voltage VB when the single cell is discharged at a constant current (for example, 3 C current) Is indicated by a solid line (denoted as "charge match"). On the other hand, after discharging the single cell from the fully charged state and adjusting the SOC to 50% and pausing, changes in the SOC and the voltage VB when the single cell is discharged with the same current as the charge combination are shown by the alternate long and short dashed line. (Described as "discharge match").

  In FIG. 7, after the start of discharge at a constant current (see time t22), the voltage VB at the time of charge combination is higher than the voltage VB at the time of discharge combination. For this reason, the output performance of the single cell is higher at the time of charge combination than at the time of discharge combination. That is, since the voltage VB is less likely to be excessively low during charge matching than during discharge matching, the output control upper limit value Wout (absolute value thereof) can be set large.

  Although FIG. 6 and FIG. 7 show the time change of the voltage VB, the inventor also measured the potential change of the positive electrode and the negative electrode alone, and there is a difference between such charge combination and discharge combination. It is 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 combination and the voltage VB at the time of discharge combination decreases with time and when a predetermined time passes (see time t13), the voltage It turns out that the difference almost disappears. This is because, when charging of the battery pack 10 continues for a certain period of time, the OCV of the battery pack 10 becomes defined by the charging OCV regardless of the previous charge / discharge history (on the curve indicated by CHG Is to be plotted).

  In FIG. 7 as well as the result shown in FIG. 6, the voltage difference between the voltage VB at the time of charge combination and the voltage VB at the time of discharge combination becomes smaller with the passage of time, and the voltage difference eventually disappears substantially . This indicates that, when the discharge of the battery pack 10 is continued, the OCV of the battery pack 10 is defined by the discharge OCV regardless of the past charge and discharge history. In the present embodiment, “input ΔV” indicating the OCV change amount of the battery pack 10 based on the charge OCV and “output ΔV” indicating the OCV change amount of the battery pack 10 based on the discharge OCV are used. .

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

  In the SOC-OCV characteristic diagram, the OCV of the battery pack 10 is never plotted above the charging OCV (curve CHG) and is not plotted below the discharge OCV (curve DCH). Therefore, according to the above definition, the input ΔV and the output ΔV both have values 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, an ideal OCV (an OCV on a curve obtained in an ideal state where no stress remains on the surface in the negative electrode active material 71) described in FIG. 5 and an OCV (OCV _ES ) of the assembled battery 10 Is defined as "OCV variation .DELTA.OCV". The calculation method of this OCV change amount ΔOCV will be described.

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

  9 and 10, in S10, ECU 100 sets voltage VB, current IB and temperature TB of battery assembly 10 from each sensor (voltage sensor 21, current sensor 22 and temperature sensor 23) in monitoring unit 20. get.

In S20, the ECU 100 estimates the OCV of the battery pack 10 (obtains the OCV _ES ). OCV _ES can be calculated according to the following equation (1). In equation (1), the internal resistance of the battery pack 10 is represented by R. Further, a correction term for correcting the influence of polarization generated in the assembled battery 10 is represented by ΔΔV _i (i is a natural number). By this correction term ΔΔV _i , polarization generated due to lithium diffusion in the positive electrode active material and in the negative electrode active material and lithium salt diffusion in the electrolytic solution is corrected. When considering lithium diffusion in the negative electrode active material, it is desirable to consider the influence of both the lithium concentration difference and the internal stress in the negative electrode active material. It is assumed that the correction term ΔΔV _i is obtained in the preliminary experiment in advance and stored in the memory 100B. The correction term ΔΔV _{i is} also determined so that the value at the time of charging of the assembled battery 10 is positive.
OCV _ES = VB-IB × 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 previous calculation time. . SOC More specifically, ECU 100 is to correct the estimated OCV by OCV variation DerutaOCV calculated at the previous calculation (i.e., calculates the _{OCV ES} + ΔOCV), corresponding to the estimated OCV of the corrected _{(OCV ES} + ΔOCV) Is calculated by referring to the ideal OCV (curve indicated by 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 linearly approximateable 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 charge / discharge switching of the assembled battery 10.

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

On the other hand, when the battery pack 10 is discharged and the OCV of the battery pack 10 is represented on the discharged OCV (curve DCH), when the battery pack 10 is further discharged, the reference SOC _REF is on the curve DCH. It is updated to the SOC moved in the discharge direction (left direction on the SOC-OCV characteristic diagram). On the other hand, when the charge / discharge 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 switching (immediately before the start of charging). Note that the reference stress sigma _REF, a surface stress corresponding to the reference _{SOC REF} sigma (surface stress when SOC is the reference _{SOC REF).}

  Further, in Equation (2), a positive proportional constant (slope of a straight line) of a linear relationship established between the surface stress σ and the SOC difference is described as α. The proportional constant α is a parameter determined in accordance with the mechanical characteristics of the negative electrode active material 71 (and the peripheral member 72), and can be determined by experiment. More specifically, the proportional constant α changes according to 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). It can. Therefore, it is preferable to determine a proportional constant α for each of various combinations of the temperature TB and the 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 . If the surface stress σ when considering the sign of the surface stress σ is less than or equal to the compressive stress σ _com , that is, if 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 = _σcom , assuming that the surface stress σ _yields at the compression stress _σcom (S62). Then, the ECU 100 updates the reference SOC _REF calculated in S30. The current SOC is set to the reference SOC _REF (S64). Further, the ECU 100 sets the current surface stress σ (that is, the compressive stress σ _com ) calculated in S30 to the reference stress σ _REF (S66).

In the case where the surface stress σ is less than the compressive stress σ _com at S50, that is, when the magnitude of the surface stress σ when considering the sign of the surface stress σ is smaller than the magnitude of the compressive stress σ _com (NO in S50) The ECU 100 advances the process to S70, and compares the surface stress σ with the tensile stress σ _ten .

If the surface stress σ in consideration of the sign of the surface stress σ is equal to or greater than the tensile stress σ _ten , that is, if the magnitude of the surface stress σ is equal to or greater than the tensile stress σ _ten (YES in S70), the ECU 100 Is set as σ = σ _ten (S 82), assuming that the surface stress σ _yields at the tensile stress σ _ten (S 82). Then, the ECU 100 sets the current SOC calculated in S30 as the reference SOC _REF (S84). Further, the ECU 100 sets the present surface stress σ (that is, the tensile stress σ _ten ) calculated in S30 to the reference stress σ _REF (S86). The order of the processes of S84 and S86 may be reversed. The order of the processes of S64 and S66 can also be switched.

When the process of S66 or S86 ends, the ECU 100 calculates the OCV variation ΔOCV from the surface stress σ according to the linear relationship that is established between the OCV variation ΔOCV and the surface stress σ (S90). Specifically, this linear relationship is expressed as 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 a constant determined experimentally.

<Pre-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. May not be properly protected. On the other hand, if the input control upper limit value Win is set too low, although the battery pack 10 can be protected, charging of the battery pack 10 is excessively limited, and the battery pack 10 can not 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 prior measurement described below is performed. By using the result of this preliminary measurement, it is possible to reflect the influence of the electromotive voltage hysteresis on the input control upper limit Win and the output control upper limit Wout, and appropriately correct the input control upper limit Win and the output control upper limit Wout. become.

  FIG. 11 is a flow chart showing the procedure of prior measurement in the present embodiment. This flowchart is implemented by an experimenter (developer of the secondary battery system 2).

  Referring to FIG. 7, at S110, the experimenter obtains a charge OCV and a discharge OCV according to the method described in detail in FIG.

  In S120, the experimenter creates an “input map MP1A” for calculating the input control upper limit Win when the OCV of the battery pack 10 is plotted on the charging OCV (curve CHG). Also, the experimenter creates an “output map MP1B” for calculating the output control upper limit value Wout when the OCV of the battery assembly 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.

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

  In the SOC-OCV characteristic diagram, the OCV of the battery pack 10 is plotted on one of the charge OCV, the discharge OCV, and a region D (see FIG. 4) surrounded by the charge OCV and the discharge OCV. When the battery pack 10 is charged under the conditions where the OCV of the battery pack 10 is plotted on the charge OCV, the voltage VB of the battery pack 10 is the highest. The input control upper limit Win specified in the input map MP1A is used when the OCV of the battery pack 10 is plotted on the charge OCV, and therefore represents the strictest input restriction (charge power restriction).

  Similarly, in 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 defined in the output map MP1B is used when the OCV of the battery pack 10 is plotted on the discharge OCV, that is, when the voltage VB of the battery pack 10 is in the lowest state. As it is, it shows the strictest output limit (discharge power limit).

The input map MP1A and the output map MP1B correspond to the “first correspondence relationship” according to the present disclosure. In the example of the input map MP1A and output map MP1B, specific numerical values to the average temperature _{TB ave} and SOC are described. However, these numerical values are merely illustrative for facilitating the understanding of the respective maps MP1A and MP1B, and it will be stated with confirmation that the contents are not limited at all. The same applies to other maps (see FIGS. 14, 15, 17 and 19) described later.

  Returning to FIG. 11, in S140, the experimenter performs an input / output test for each of various SOC adjustment histories. More specifically, the experimenter prepares many conditions (or history) in which the SOC at the start of charge and discharge of the battery pack 10, the temperature TB, and the input ΔV differ, and sets the input control upper limit Win under each condition. calculate. The input control upper limit value Win is set to a power value that can appropriately protect the assembled battery 10 without the voltage of the assembled battery 10 exceeding a predetermined protection voltage, as described in FIG. 4. Although the detailed description is not repeated, the same applies to the output control upper limit value Wout.

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

  In S150, the experimenter creates an “input correction map MP2A” for correcting the input map MP1A created in S120. Furthermore, 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 procedures of the pre-measurement shown in FIG.

  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, by adding ave to the subscript of a parameter, it is indicated that the parameter indicates a time average within a certain period.

Referring to FIG. 14, in input correction map MP2A, an input correction coefficient kin is defined for each combination (SOC, TB _ave , input ΔV) of SOC of battery assembly 10, average temperature TB _ave , and input ΔV. ing. The input correction coefficient kin is based on the input control upper limit Win (input control upper limit Win defined by the input correction map MP2A) when the OCV of the battery pack 10 is on the charge OCV and the input ΔV = 0. The coefficient indicates the ratio of the input control upper limit Win (the input control upper limit Win calculated at S140) when the OCV of the battery pack 10 is not on the charge OCV (when the input ΔV> 0).

Also in the output correction map MP2B, as shown in FIG. 15, an 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 battery pack 10 is not on the discharge OCV based on the output control upper limit value Wout when the OCV of the battery pack 10 is on the discharge OCV (when the output ΔV = 0). It is a coefficient that indicates the ratio of the output control upper limit value Wout (when the output ΔV> 0). Each of the input correction coefficient kin and the output correction coefficient kout has a value of 1 or more (kink1, kout ≧ 1). The input correction map MP2A and the output correction map MP2B correspond to the “second correspondence relationship” according to the present disclosure.

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

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

  In S220, the ECU 100 calculates the SOC of the battery pack 10. The SOC can be calculated by a known method such as current integration. Further, as described in the processing of S20 and S30 in FIG. 9, the SOC may be calculated using an 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 factor, and adding those SOCs (ie, blending the two methods). May be

In S230, the ECU 100 calculates the average temperature TB _ave of the battery pack 10. As the average temperature _TBave, it is possible to use a time average value of the temperature TB of the assembled battery 10 in the latest predetermined period (for example, several minutes).

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

In S250, the ECU 100 determines whether the magnitude of the input ΔV is positive. At 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 variation ΔOCV, the ideal OCV, and the charging OCV.

  If the magnitude of input ΔV is not positive, that is, if input ΔV = 0 and the OCV of battery assembly 10 is plotted on the charge OCV (YES in S250), ECU 100 produces the input map shown in FIG. The input control upper limit value Win is calculated from (TB, SOC) by referring to MP1A (S260).

On the other hand, when the magnitude of input ΔV is positive, that is, when the OCV of assembled battery 10 is not plotted on the charge OCV (NO in S250), 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 using the input correction coefficient kin (S280). Specifically, the ECU 100 calculates the corrected input control upper limit Win 'by multiplying the input control upper limit Win specified in the input map MP1A (see FIG. 12) by the correction coefficient kin (Win' (Win '). = Kin x Win). Since the input correction coefficient kin is 1 or more, the input control upper limit Win 'after correction is a value larger than the input control upper limit Win before correction.

  FIG. 17 is a flowchart for describing the output upper limit calculation process in the present embodiment. 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 direction of the assembled battery 10 is different, so the detailed description will not be repeated here.

  As described above, according to the present embodiment, although charging of the battery pack 10 is performed within the range of the input control upper limit value Win, the input control upper limit value Win is the condition under which the input restriction is the strictest (OCV of the battery pack 10 Are defined under the condition that is plotted on the charge OCV. Similarly, regarding the discharge of the assembled battery 10, the output control upper limit value Wout is defined under the condition that the output limitation is the strictest (the condition that the OCV of the assembled battery 10 is plotted on the discharged OCV). Therefore, the battery assembly 10 can be properly protected.

  Furthermore, for example, when the silicon 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 charged OCV, 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 battery pack 10 is not plotted on the charging OCV, by multiplying the input correction coefficient kin () 1), as compared to when the OCV of the battery pack 10 is plotted on the charging OCV The input control upper limit Win (input control upper limit Win 'after correction) is increased. In other words, when the OCV of the battery pack 10 is not plotted on the charging OCV, the input control upper limit Win is expanded. Similarly, when the OCV of the battery pack 10 is not on the discharge OCV, the output control upper limit value Wout is expanded as compared to the case where the OCV of the battery pack 10 is not on the discharge OCV. By expanding the input control upper limit value Win and the output control upper limit value Wout in this manner, it is possible to fully utilize the battery pack 10.

[Modification]
In the modification of the present embodiment, it is determined whether or not OCV of assembled battery 10 is on curves CHG and DCH according to SOC change amount ΔSOC (described later) instead of input ΔV or output ΔV. 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 modification. FIG. 19 is a diagram showing an example of the output correction map MP4B in the modification.

Referring to FIG. 18, in input correction map MP4A, for example, for each combination of SOC of battery assembly 10, average temperature TB _{ave of} battery assembly 10, and SOC variation amount .DELTA.SOC (SOC, TB _ave , .DELTA.SOC) An input correction coefficient kin is specified. Similarly, in the output correction map MP4B shown in FIG. 19, an output correction coefficient kout is defined for each (SOC, TB _ave , ΔSOC).

  In the present modification, input upper limit calculation processing and output upper limit calculation processing are realized using SOC change amount ΔSOC and flag G stored in 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 white circles) and the charge OCV or the discharge OCV. As shown in FIG. 20A, when the reference point is on the charge OCV (charge curve CHG), the flag G is set to G = 1 by another flow not shown. On the other hand, as shown in FIG. 20B, when the reference point is on the discharge OCV (discharge curve DCH), the flag G is set to G = 2.

  Referring to FIG. 20A, when battery assembly 10 is charged with the reference point on charge OCV (G = 1), the state of battery assembly 10 (combination of SOC and OCV) is charge 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 battery pack 10 after charging.

  On the other hand, when the battery pack 10 is discharged in a state where the reference point is on the charge OCV, the state of the battery pack 10 deviates from the charge OCV and the charge OCV and the discharge OCV are shown as solid lines. Will be represented in the area between The reference point at this time is maintained at a point on the charge OCV before the start of discharge. The SOC change amount based on the reference point is described as ΔSOC (ΔSOC <0 in FIG. 20A).

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

  When the battery pack 10 is charged with the reference point on the discharge OCV, the state of the battery pack 10 is represented as indicated by a solid line deviating from the discharge OCV. The reference point is maintained at a point on the discharge OCV before charging starts. Further, the SOC change amount based on the reference point at this time is described as ΔSOC (in FIG. 20B, ΔSOC> 0). Thus, the SOC change amount ΔSOC indicates the SOC change amount from the time when the state of the battery pack 10 deviates from the charge OCV or the discharge OCV.

  FIG. 21 is a flowchart for explaining the input upper limit calculation process in the modification. 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 obtains the voltage VB, the current IB, and the temperature TB of the battery pack 10 from each sensor in the monitoring unit 20.

  In S422, the ECU 100 calculates the SOC of the battery pack 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 battery pack 10 based on 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 battery pack 10. The time for which the time average is to be made is also determined experimentally, but is preferably the same as the period used to calculate the SOC change amount ΔSOC in S424.

  Subsequently, in S450, it is determined whether the state of the assembled battery 10 (combination of SOC and OCV) is present on the charging OCV. More specifically, the ECU 100 determines whether the condition that the flag G is G = 1 and the SOC change amount ΔSOC is positive is satisfied (see FIG. 20A). If this condition is satisfied (YES in S450), the state of the battery pack 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, if the above condition is not satisfied (NO in S450), that is, if G = 2 or the SOC change amount ΔSOC is 0, the state of the battery pack 10 does not exist on the charging OCV. Therefore, the ECU 100 proceeds to step S470 and calculates the input correction coefficient kin from (SOC, TB _ave , ΔSOC) by referring to the input correction map MP4A shown in FIG. Furthermore, the ECU 100 corrects the input control upper limit value Win using the input correction coefficient kin (S480).

  In the process of S460 executed when the above condition is not satisfied, it is described that the input correction map MP4A is not referred to. However, the input correction map MP4A may be always referred to, and the input correction map MP4A to be referred to when the above condition is 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 modification. Since this output upper limit calculation process is basically equivalent to the input upper limit calculation process shown in FIG. 21, detailed description will not be repeated.

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

  Further, in the present modification, it is determined using SOC change amount ΔSOC whether or not the OCV of battery assembly 10 is plotted on the charge OCV (see S450 in FIG. 20). Thus, whether the OCV of the battery pack 10 is out of the charging OCV, or whether the OCV of the battery pack 10 may be plotted on the charging OCV, does not use the OCV change amount ΔOCV. Can also be determined. When it is determined that the OCV of the battery pack 10 is not on the charging OCV (YES in S450), the input control upper limit value Win is expanded (S470). Similar expansion is performed for the output control upper limit value Wout when it is determined that the OCV of the battery pack 10 is not on the discharge OCV (YES in S550 of FIG. 21) (S570). As a result, the battery assembly 10 can be fully utilized.

  In the embodiment and the modification, an example in which the silicon-based compound is used as the negative electrode active material having a large volume change due to charge and discharge has been described. However, the negative electrode active material having a large volume change due to charge and discharge is not limited to this. In the present specification, “a negative electrode active material having a large volume change” refers to a material having a large volume change as compared to a volume change (about 10%) of graphite accompanying charge and discharge. As a negative electrode material of such a lithium ion secondary battery, a tin type compound (Sn or SnO etc.), a germanium type compound, or a lead type compound is mentioned. The lithium ion secondary battery is not limited to a liquid type, and may be a polymer type or an all solid type.

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

  Furthermore, the secondary battery to which the input upper limit estimation processing and the output upper limit estimation processing can be applied is not limited to the lithium ion secondary battery, and may be another secondary battery (for example, a nickel hydrogen battery). 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.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present disclosure is indicated not by the description of the embodiments described above but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

  Reference Signs List 1 vehicle, 2 secondary battery system, 10 assembled 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 split devices, 45 Drive shaft, 46 drive wheels, 100 ECU, 100 A CPU, 100 B 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,
A calculation device that includes a memory in which first and second correspondence relationships are stored, and calculates a control upper limit value of input power to the secondary battery;
In the first correspondence relationship, the SOC and the OCV of the secondary battery are on a charge curve indicating the SOC-OCV characteristic of the secondary battery when the secondary battery is charged from the fully discharged state to the fully charged state. A correspondence relationship between the SOC of the secondary battery and the control upper limit value when
The second correspondence relationship 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 the OCV of the secondary battery are on the charge curve or the discharge. It is a correspondence relation between any one of the SOC change amounts of the secondary battery from the point of time when it deviates from the curve and the correction coefficient for correcting the control upper limit value,
The calculation device is
When SOC and OCV of the secondary battery are represented on the charging curve, the control upper limit value is calculated from the SOC of the secondary battery by referring to the first correspondence relationship,
If the SOC and OCV of the secondary battery are not represented on the charging curve, the correction coefficient is calculated from either the voltage difference or the SOC change amount by referring to the second correspondence relationship. A secondary battery system, wherein the control upper limit value calculated by referring to the first correspondence relationship is corrected by the correction coefficient. With a secondary battery,
A calculation device that includes a memory in which first and second correspondence relationships are stored, and calculates a control upper limit value of output power from the secondary battery;
The first correspondence relationship is that the SOC and OCV of the secondary battery are on a 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. A correspondence relationship between the SOC of the secondary battery and the control upper limit value when
The second correspondence relationship is that the voltage difference between the measured value of 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 relation between any one of the SOC change amounts of the secondary battery from the point of time when it deviates from the curve and the correction coefficient for correcting the control upper limit value,
The calculation device is
When the SOC and the 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 relationship,
If 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 relationship. A secondary battery system, wherein the control upper limit value calculated by referring to the first correspondence relationship is corrected by the correction coefficient.

Images