JP2014003826A - Cell system and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit increase in resistance associated with a bias in ion concentration.SOLUTION: A cell system comprises: secondary cells (10, 11) in which resistance increases depending on a bias in ion concentration associated with charge and discharge; and a controller (30) for controlling charge and discharge of the secondary cells. The controller restricts either one of charge or discharge of the secondary cells when a deterioration value (resistance increasing rate dR) defined by resistance is greater than a threshold value (dRth_on). As a result, when an amount of change (dR/dt) of the deterioration value after restriction is greater than an amount of change (dR/dt) of the deterioration value before restriction, the controller releases restriction of the either one of charge or discharge and restricts the other.

Description

  The present invention relates to a technique for controlling charging / discharging of a secondary battery based on an ion concentration bias in the secondary battery.

  In the technique described in Patent Document 1, the charge history value and the discharge history value are calculated. When the charge history value is larger than the discharge history value, the charging current is limited. When the discharge history value is larger than the charge history value, The discharge current is limited. Here, the charging history value indicates a charging history at a current exceeding the charging threshold current, and the discharging history value indicates a discharging history at a current exceeding the discharge threshold current.

  According to the technique described in Patent Document 1, even when charging / discharging at a high rate, by restricting the charging current or discharging current, the ion concentration distribution in the electrolyte is suppressed from becoming non-uniform. Can do. And the rise in internal resistance accompanying the nonuniformity of ion concentration distribution can be suppressed.

International Publication No. 2010/079595 Pamphlet JP 2010-060406 A JP 2011-257314 A

  Based on the technique of Patent Document 1, when comparing the charge history value and the discharge history value, it is determined which of the charge history value and the discharge history value is greater by an error of a current sensor that detects the charge current or the discharge current. It may be difficult. In this case, where the charging current should be limited, the discharging current may be limited, and the ion concentration distribution may remain uneven. In addition, where the discharge current should be limited, the charge current may be limited, and the ion concentration distribution may remain uneven.

  The battery system according to the first invention of the present application includes a secondary battery whose resistance increases in accordance with an uneven ion concentration associated with charging and discharging, and a controller that controls charging and discharging of the secondary battery. The controller limits one of charging and discharging of the secondary battery when the deterioration value defined by the resistance is larger than the threshold value. Here, when the change amount of the deterioration value after the restriction is larger than the change amount of the deterioration value before the restriction, the controller releases one restriction and restricts the other of the charging and discharging.

  When the resistance of the secondary battery is increased due to the bias of the ion concentration, by restricting the charging or discharging of the secondary battery, the bias of the ion concentration can be suppressed and the increase of the resistance can be suppressed. Here, in 1st invention of this application, after restrict | limiting charge or discharge of a secondary battery, the variation | change_quantity of the degradation value after a restriction | limiting is compared with the variation | change_quantity of the degradation value before a restriction | limiting.

  Here, if the bias of the ion concentration is suppressed by restricting charging or discharging, the amount of change in the deterioration value after the restriction is smaller than the amount of change in the deterioration value before the restriction. In this case, it is sufficient to continue limiting charging or discharging.

  On the other hand, if the bias of the ion concentration is not suppressed by limiting the charging or discharging, the amount of change in the deterioration value after the restriction is larger than the amount of change in the deterioration value before the restriction. Thus, by comparing the amount of change in the deterioration value before and after the restriction, it can be confirmed whether or not the restriction on charging or discharging contributes to the decrease in resistance.

  By confirming whether the limitation of charging or discharging contributes to the decrease in resistance, it is possible to suppress the bias of the ion concentration from being promoted. That is, if the resistance accompanying the bias of the ion concentration is reduced by limiting charging or discharging, the limitation can be continued as it is. On the other hand, if the resistance due to the bias of the ion concentration is not reduced due to the restriction of charging or discharging, the bias of the ion concentration can be suppressed from being promoted by changing the limit. For example, if the resistance cannot be lowered due to the restriction of charging, the resistance can be lowered by restricting discharging.

  When the deterioration value is larger than the threshold value, charging or discharging can be limited according to the deviation of the ion concentration. That is, when the ion concentration distribution is biased toward the discharge side, the secondary battery can be discharged. When the ion concentration distribution is biased toward the charge side, the secondary battery can be charged. it can. Thereby, it can suppress that the bias | inclination of ion concentration will be accelerated | stimulated, and the raise of the resistance accompanying the bias | inclination of ion concentration can be suppressed.

  It is possible to discriminate the ion concentration bias by using an evaluation value for evaluating a degradation component that degrades the input / output performance of the secondary battery with the ion concentration bias. Here, the evaluation value can be calculated from the history of current when the secondary battery is charged and discharged. When the integrated value obtained by integrating the evaluation values exceeding the target value exceeds the discharge threshold, it can be determined that the ion concentration distribution is biased toward the discharge side. Further, when the integrated value exceeds the charging threshold value, it can be determined that the ion concentration distribution is biased toward the charging side.

  Since the evaluation value includes the evaluation value on the discharge side and the charge side, the target value can be set on each of the discharge side and the charge side. The discharge threshold value and the charge threshold value may be equal to each other, but are preferably different from each other in order to suppress control hunting. By setting different discharge thresholds and charge thresholds, it is easy to distinguish the discharge-side bias and the charge-side bias.

  When restricting one of charging and discharging, it is possible not to restrict the other of charging and discharging. Since the ion concentration bias occurs on either the discharge side or the charge side, only one of charging and discharging needs to be limited in order to suppress an increase in resistance due to the ion concentration bias. And if the other of charge and discharge is not restrict | limited, the performance of the secondary battery in the other can be ensured. For example, if the discharge of the secondary battery is not limited, power can be easily supplied from the secondary battery to the load. Further, if the charging of the secondary battery is not limited, more electric energy can be stored in the secondary battery.

  As the deterioration value, a ratio (Rc / Rini) between the resistance (Rini) of the secondary battery in the initial state and the resistance (Rc) of the current secondary battery can be used. Further, the resistance of the secondary battery can be used as the deterioration value. Here, since the deterioration state of the secondary battery can be specified by the relationship between the resistance of the secondary battery in the initial state and the resistance of the current secondary battery, the ratio (Rc / Rini) described above is used as the deterioration value. If it uses, it will become easy to specify the deterioration state of a secondary battery.

  The energy output from the secondary battery can be used as energy for mounting the secondary battery on the vehicle and running the vehicle. As the secondary battery, for example, a lithium ion battery can be used.

  2nd invention of this application is a control method which controls charging / discharging of the secondary battery from which resistance rises according to the bias | inclination of the ion concentration accompanying charging / discharging. First, when the deterioration value defined by the resistance is larger than the threshold value, one of charging and discharging of the secondary battery is limited. When the change amount of the deterioration value after the restriction is larger than the change amount of the deterioration value before the restriction, one restriction is released and the other of the charging and discharging is restricted. Also in the second invention of the present application, the same effect as that of the first invention of the present application can be obtained.

It is a figure which shows the structure of a battery system. It is a flowchart which shows the process which controls charging / discharging of an assembled battery. It is explanatory drawing when calculating the change rate of resistance increase rate. It is a figure which shows the change of the resistance increase rate in the charging / discharging control of a present Example. It is a figure which shows the change of the resistance increase rate in the charging / discharging control of a present Example. It is a figure which shows the change of the resistance increase rate when charging / discharging control of a present Example is not performed. It is a flowchart which shows the process which discriminate | determines excessive charge and discharge of an assembled battery. It is a flowchart which shows the process which discriminate | determines excessive charge and discharge of an assembled battery. It is a figure which shows the relationship between temperature and a forgetting factor. It is a figure which shows the relationship between temperature and a limit value. It is a figure explaining change of an evaluation value (an example), and explaining accumulation of evaluation values.

  Examples of the present invention will be described below.

  The battery system which is Example 1 will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of a battery system.

  The battery system shown in FIG. 1 can be mounted on a vehicle, for example. Vehicles include hybrid cars and electric cars. A hybrid vehicle is a vehicle provided with a fuel cell, an internal combustion engine, etc. in addition to the assembled battery as a power source for running the vehicle. An electric vehicle is a vehicle that includes only an assembled battery as a power source for the vehicle.

  The assembled battery 10 includes a plurality of single cells 11 that are electrically connected in series. The number of unit cells 11 constituting the assembled battery 10 can be appropriately set based on the required output of the assembled battery 10 and the like. In the present embodiment, the assembled battery 10 is configured by electrically connecting a plurality of unit cells 11 in series. However, the assembled battery 10 includes a plurality of unit cells 11 electrically connected in parallel. May be included. As the cell 11, a secondary battery such as a lithium ion secondary battery can be used.

  The positive electrode of the unit cell 11 is formed of a material that can occlude and release ions (for example, lithium ions). As a positive electrode material, for example, lithium cobaltate or lithium manganate can be used. The negative electrode of the unit cell 11 is formed of a material that can occlude and release ions (for example, lithium ions). As the negative electrode material, for example, carbon can be used. When charging the unit cell 11, the positive electrode releases ions into the electrolytic solution, and the negative electrode occludes ions in the electrolytic solution. Further, when discharging the unit cell 11, the positive electrode occludes ions in the electrolytic solution, and the negative electrode releases ions into the electrolytic solution.

  The assembled battery 10 is connected to the booster circuit 22 via the system main relays 21a and 21b, and the booster circuit 22 boosts the output voltage of the assembled battery 10. The booster circuit 22 is connected to an inverter 23, and the inverter 23 converts the DC power output from the booster circuit 22 into AC power.

  The motor / generator 24 receives AC power from the inverter 23 to generate kinetic energy for running the vehicle. By transmitting the kinetic energy generated by the motor / generator 24 to the wheels, the vehicle can be driven. A three-phase AC motor can be used as the motor / generator 24. In this embodiment, the booster circuit 22 is used, but the booster circuit 22 may be omitted.

  When the vehicle is decelerated or the vehicle is stopped, the motor / generator 24 converts kinetic energy generated during braking of the vehicle into electric energy (AC power). The AC power generated by the motor / generator 24 is converted into DC power by the inverter 23. The step-up circuit 22 steps down the output voltage of the inverter 23 and supplies the lowered power to the assembled battery 10. Thereby, regenerative electric power can be stored in the assembled battery 10.

  The current sensor 25 detects the current flowing through the assembled battery 10 and outputs the detection result to the controller 30. Regarding the current detected by the current sensor 25, the discharge current is a positive value and the charging current is a negative value.

  The temperature sensor 26 detects the temperature of the assembled battery 10 or the single battery 11 and outputs the detection result to the controller 30. The number of temperature sensors 26 can be set as appropriate. When using a plurality of temperature sensors 26, the average value of the temperatures detected by the plurality of temperature sensors 26 is used as the temperature of the assembled battery 10 or the single battery 11, or the temperature detected by a specific temperature sensor 26 is used. Or as the temperature of the unit cell 11.

  The monitoring unit 27 detects the voltage of the assembled battery 10 or the voltage of the unit cell 11 and outputs the detection result to the controller 30. Here, when the plurality of single cells 11 constituting the assembled battery 10 are divided into a plurality of battery blocks, the monitoring unit 27 can detect the voltage of each battery block. Each battery block is configured by a plurality of single cells 11 electrically connected in series, and the assembled battery 10 is configured by connecting the plurality of battery blocks electrically in series.

  The controller 30 controls the operations of the system main relays 21a and 21b, the booster circuit 22 and the inverter 23. The controller 30 includes a memory 31 that stores various types of information. The memory 31 also stores a program for operating the controller 30. In this embodiment, the memory 31 is built in the controller 30, but the memory 31 can be provided outside the controller 30.

  Information related to the ignition switch of the vehicle is input to the controller 30. When the ignition switch is switched from OFF to ON, the controller 30 switches the system main relays 21a and 21b from OFF to ON, or operates the booster circuit 22 and the inverter 23. Further, when the ignition switch is switched from on to off, the controller 30 switches the system main relays 21a and 21b from on to off, or stops the operation of the booster circuit 22 and the inverter 23.

  The unit cell 11 deteriorates due to charging / discharging, or deteriorates over time. Here, when the deterioration of the unit cell 11 proceeds, the resistance value of the unit cell 11 increases, so that the deterioration state of the unit cell 11 can be grasped based on the resistance value of the unit cell 11. The deterioration of the battery cell 11 includes deterioration caused by wear of materials (positive electrode, negative electrode, etc.) constituting the battery cell 11 (referred to as wear deterioration), and deterioration components caused by uneven ion concentration inside the battery cell 11. (High rate degradation).

  If the cell 11 is continuously charged or discharged at a high rate, the internal resistance of the cell 11 may increase, and a phenomenon may occur in which the input / output performance of the cell 11 begins to deteriorate sharply. If this phenomenon occurs continuously, the unit cell 11 may deteriorate. Such deterioration is called high-rate deterioration. As one of the causes of high rate deterioration, it is conceivable that the ion concentration in the electrolytic solution of the unit cell 11 is biased by continuous charging or discharging at a high rate. In high-rate charging and high-rate discharging, the ion concentration bias states are in conflict.

  When the wear deterioration occurs, only the resistance value of the unit cell 11 increases. However, when the high rate deterioration occurs, the resistance value of the unit cell 11 may decrease. That is, the high rate deterioration occurs due to the deviation of the ion concentration. Therefore, if the deviation of the ion concentration is eliminated, the resistance value associated with the high rate deterioration decreases.

  If the discharge of the unit cell 11 is restricted when the ion concentration distribution is biased toward the discharge side, the ion concentration distribution can be suppressed from being biased toward the discharge side, and high-rate deterioration associated with discharge can be suppressed. Moreover, when the distribution of the ion concentration is biased toward the charging side, if the charging of the unit cell 11 is restricted, it is possible to suppress the bias of the ion concentration distribution toward the charging side, and it is possible to suppress the high rate deterioration accompanying the charging. .

  For this reason, if charging / discharging of the cell 11 (assembled battery 10) is controlled based on the deviation of the ion concentration, high-rate deterioration can be suppressed, and an increase in resistance value accompanying high-rate deterioration can be suppressed.

  Here, a method for controlling charging / discharging of the assembled battery 10 will be described with reference to a flowchart shown in FIG. The process shown in FIG. 2 is executed by the controller 30 and is repeatedly performed at a predetermined cycle.

  In step S <b> 101, the controller 30 calculates a resistance increase rate (corresponding to a deterioration value) of the assembled battery 10. The resistance increase rate dR can be calculated based on the following formula (1).

  In the above formula (1), Rc is the current resistance value of the assembled battery 10, and Rini is the resistance value of the assembled battery 10 in the initial state. The initial state is a state where the assembled battery 10 is not deteriorated. As an initial state, the state immediately after manufacturing the assembled battery 10 is mentioned, for example.

  The resistance values Rc and Rini can be calculated by measuring the current and voltage of the assembled battery 10. As a current flowing through the assembled battery 10, the detection result of the current sensor 25 can be used. As the voltage of the assembled battery 10, the detection result of the monitoring unit 27 can be used. When the current and voltage of the battery pack 10 are measured, the relationship between the measured current and voltage is plotted in a coordinate system having the current and voltage as coordinate axes. If a plurality of current and voltage relationships are plotted and a straight line approximated to the plurality of plots is obtained, the slope of the approximate straight line becomes the resistance values Rc and Rini.

  If the assembled battery 10 is not deteriorated, the assembled battery 10 remains in the initial state, and the resistance value Rc becomes equal to the resistance value Rini. For this reason, the resistance increase rate dR is 1. On the other hand, as the deterioration of the assembled battery 10 progresses, the resistance value Rc increases and becomes higher than the resistance value Rini. For this reason, the resistance increase rate dR is larger than 1. Thus, the deterioration state of the assembled battery 10 can be evaluated by using the resistance increase rate dR.

  In this embodiment, the resistance increase rate dR of the assembled battery 10 is calculated, but is not limited to this. Specifically, the resistance increase rate dR can be calculated for the single battery 11 and the battery block described above. In the following processing, the resistance increase rate dR of the assembled battery 10 is used, but the resistance increase rate dR of the unit cell 11 or the battery block can also be used.

  When the resistance increase rate dR of the unit cell 11 or the battery block is used, the resistance increase rate dR in the plurality of unit cells 11 may be different from each other, or the resistance increase rate dR in the plurality of battery blocks may be different from each other. In this case, for example, the highest resistance increase rate dR among the plurality of resistance increase rates dR can be used, or the median value of the plurality of resistance increase rates dR can be used.

  In step S102, the controller 30 determines whether or not the resistance increase rate dR calculated in step S101 is larger than the first threshold value dRth_on. The first threshold value dRth_on is a condition for starting a process for restricting charging / discharging of the assembled battery 10. When the resistance increase rate dR is larger than the first threshold value dRth_on, a process for restricting charging / discharging of the assembled battery 10 is started. The The first threshold value dRth_on is a value corresponding to the resistance increase rate dR of the battery pack 10 and can be set as appropriate. Information regarding the first threshold value dRth_on can be stored in the memory 31.

  When the resistance increase rate dR is smaller than the first threshold value dRth_on, the controller 30 ends the process shown in FIG. On the other hand, when the resistance increase rate dR is larger than the first threshold value dRth_on, the controller 30 performs the process of step S103.

  In this embodiment, the resistance increase rate dR is calculated, and the resistance increase rate dR and the first threshold value dRth_on are compared. However, the present invention is not limited to this. Specifically, the resistance value of the assembled battery 10 (or the single battery 11 or the battery block) can be calculated, and the resistance value can be compared with a threshold value corresponding to the first threshold value dRth_on. In this case, the calculated resistance value corresponds to the deterioration value in the present invention.

  Here, since the resistance increase rate dR is defined by the relationship between the resistance value Rini of the assembled battery 10 in the initial state and the current resistance value Rc of the assembled battery 10, it is easy to grasp the deterioration state of the assembled battery 10. . That is, it is easier to grasp the deterioration state of the assembled battery 10 by monitoring the resistance increase rate dR than by monitoring the resistance value of the assembled battery 10 itself.

  In step S103, the controller 30 determines whether or not the assembled battery 10 is in an excessively discharged state. The excessive discharge state is a state in which the ion concentration distribution inside the unit cell 11 is biased toward the discharge side rather than the charge side. A method for determining the state of excessive discharge will be described later. When the assembled battery 10 is in an excessively discharged state, the controller 30 performs the process of step S104. When the assembled battery 10 is not in an excessively discharged state, the controller 30 performs the process of step S105.

  In step S <b> 104, the controller 30 performs a process of limiting the output (discharge) of the assembled battery 10. Specifically, the controller 30 reduces the upper limit power that allows the output of the assembled battery 10. The upper limit power is used in the discharge control of the assembled battery 10, and the discharge of the assembled battery 10 is controlled so that the discharged power of the assembled battery 10 does not become higher than the upper limit power. For this reason, the output of the assembled battery 10 is limited by reducing the upper limit power.

  Here, lowering the upper limit power includes not only bringing the upper limit power close to 0 [kW] but also setting the upper limit power to 0 [kW]. When the upper limit power is set to 0 [kW], the assembled battery 10 is not discharged. The amount by which the upper limit power is reduced may be a fixed amount or may be changed according to the state of excessive discharge. Here, the amount by which the upper limit power is reduced can be increased as the state of excessive discharge progresses. If the correspondence between the reduction amount of the upper limit power and the excessive discharge state is determined in advance, the reduction amount corresponding to the excessive discharge state can be set.

  By restricting the output of the assembled battery 10, it is possible to suppress the excessive discharge state from progressing. That is, it is possible to suppress an increase in resistance value due to the ion concentration distribution being biased toward the discharge side. In the process of step S104, only the output of the assembled battery 10 is restricted, and the input of the assembled battery 10 is not restricted. In addition, although the input of the assembled battery 10 can also be restrict | limited, it is preferable that the limitation amount of an input is smaller than the limitation amount of an output.

  By not limiting the input of the assembled battery 10, the input of the assembled battery 10 can be ensured. When the assembled battery 10 is in a state of excessive discharge, securing the input of the assembled battery 10 can easily bias the ion concentration distribution toward the charging side, and as a result, the ion concentration distribution can be made uniform. it can. By making the ion concentration distribution uniform, it is possible to reduce the resistance value accompanying the bias of the ion concentration distribution, and to reduce the resistance increase rate dR. Moreover, it can suppress that the performance of the assembled battery 10 regarding charge falls by ensuring the input of the assembled battery 10. FIG.

  In step S105, the controller 30 determines whether or not the assembled battery 10 is in an overcharged state. The overcharged state is a state in which the ion concentration distribution inside the unit cell 11 is biased toward the charging side rather than the discharging side. A method for determining an overcharged state will be described later. When the assembled battery 10 is in an overcharged state, the controller 30 performs the process of step S106. When the assembled battery 10 is not in an overcharged state, the controller 30 ends the process shown in FIG.

  In step S <b> 106, the controller 30 performs a process of limiting input (charging) of the assembled battery 10. Specifically, the controller 30 reduces the upper limit power that allows the input of the assembled battery 10. This upper limit power is used in charging control of the assembled battery 10, and charging of the assembled battery 10 is controlled so that the charging power of the assembled battery 10 does not become higher than the upper limit power. For this reason, the input of the assembled battery 10 is restricted by lowering the upper limit power.

  Here, lowering the upper limit power includes not only bringing the upper limit power close to 0 [kW] but also setting the upper limit power to 0 [kW]. When the upper limit power is set to 0 [kW], the assembled battery 10 is not charged. The amount by which the upper limit power is reduced may be a fixed amount or may be changed according to the state of excessive charging. Here, the amount by which the upper limit power is reduced can be increased as the state of excessive charging progresses. If the correspondence between the amount of decrease in the upper limit power and the overcharged state is determined in advance, the amount of decrease corresponding to the overcharged state can be set.

  By restricting the input of the assembled battery 10, it is possible to suppress an excessively charged state from progressing. That is, it is possible to suppress an increase in resistance value due to the ion concentration distribution being biased toward the charging side. In the process of step S106, only the input of the assembled battery 10 is restricted, and the output of the assembled battery 10 is not restricted. In addition, although the output of the assembled battery 10 can also be restrict | limited, it is preferable that the limitation amount of an output is smaller than the limitation amount of an input.

  By not limiting the output of the assembled battery 10, the output of the assembled battery 10 can be ensured. When the assembled battery 10 is in an overcharged state, by securing the output of the assembled battery 10, the ion concentration distribution can be easily biased toward the discharge side, and as a result, the ion concentration distribution can be made uniform. it can. By making the ion concentration distribution uniform, it is possible to reduce the resistance value accompanying the bias of the ion concentration distribution, and to reduce the resistance increase rate dR. Moreover, it can suppress that the performance of the assembled battery 10 regarding discharge falls by ensuring the output of the assembled battery 10. FIG.

  In step S107, the controller 30 waits for a predetermined time t0. Specifically, the controller 30 starts measuring time using a timer when starting the process of limiting the output or input of the assembled battery 10 (the process of step S104 or step S106). Then, the controller 30 waits until the measurement time of the timer reaches the predetermined time t0.

  Immediately after starting the process of limiting the output or input of the assembled battery 10, it is difficult to grasp the change in the resistance value (specifically, the resistance increase rate dR) associated with the limiting process. Therefore, in the process of step S107, in order to make it easier to grasp the change in the resistance value (specifically, the resistance increase rate dR) associated with the limiting process, after the limiting process is started, a predetermined time t0 is waited. Yes. The specific value of the predetermined time t0 can be set as appropriate in consideration of the above points.

  In step S108, the controller 30 determines whether or not a condition represented by the following formula (2) is satisfied.

  DR / dt shown in the above equation (2) indicates a change in the resistance increase rate dR in a predetermined time, in other words, a change rate of the resistance increase rate dR. Here, the change rate of the resistance increase rate dR shown on both sides of the above formula (2) will be described with reference to FIG. As shown in FIG. 3, the right side of the above equation (2) indicates the change in the resistance increase rate dR from the timing before time 0 to time 0 as shown in FIG. At time 0, the output or input restriction of the battery pack 10 (the process of step S104 or step S106) is started. For this reason, the right side of the above formula (2) indicates the rate of change of the resistance increase rate dR before the output or input of the battery pack 10 is limited.

  As shown in FIG. 3, the left side of the above equation (2) indicates the change in the resistance increase rate dR from the timing t1 before the time t0 to the time t0. Time t0 corresponds to the predetermined time t0 described in the processing of step S107. Between time 0 and time t0, the output or input of the battery pack 10 is limited, and the left side of the above equation (2) indicates the resistance increase rate dR after the output or input of the battery pack 10 is limited. Indicates the rate of change. Since the time interval (time t1) on both sides of the above formula (2) is the same, the above formula (2) also compares the amount of change in the resistance increase rate dR.

  In step S108, when the change rate (dR / dt) after the limit process is lower than the change rate (dR / dt) before the limit process, the controller 30 performs the process of step S110. When excessive discharge or excessive charge is reduced by limiting the output or input of the assembled battery 10, the resistance value (resistance increase rate dR) of the assembled battery 10 is reduced. Thereby, the change rate (dR / dt) after the limit process is lower than the change rate (dR / dt) before the limit process.

  On the other hand, when the change rate (dR / dt) after the limit process is higher than the change rate (dR / dt) before the limit process, the controller 30 performs the process of step S109. In step S <b> 109, the controller 30 switches between a process for limiting the output of the assembled battery 10 and a process for limiting the input of the assembled battery 10.

  Specifically, when the output of the assembled battery 10 is restricted by the process of step S104, the controller 30 releases the restriction on the output and restricts the input of the assembled battery 10 in the process of step S109. Here, when canceling the output restriction, the controller 30 returns the upper limit power corresponding to the output to the state before the output restriction (the process of step S104). Thereby, the output of the assembled battery 10 is ensured.

  On the other hand, when the input of the assembled battery 10 is restricted by the process of step S106, the controller 30 releases the restriction of the input and restricts the output of the assembled battery 10 in the process of step S109. Here, when canceling the input restriction, the controller 30 returns the upper limit power corresponding to the input to the state before the input restriction (the process of step S106). Thereby, the input of the assembled battery 10 is ensured.

  After performing the process of step S109, the controller 30 performs the process of step S107 and waits for a predetermined time t0. In the process of step S108, it is determined whether or not the change rate (dR / dt) has decreased after switching between the output restriction process and the input restriction process.

  In step S110, the controller 30 determines whether or not a condition of the following formula (3) is satisfied.

  The change rate (dR / dt) of the resistance increase rate shown in the above equation (3) is the change in the resistance increase rate dR from the timing just before the time t0 by the time t2 to the time t0. Here, the time t2 may be the same as the time t1, or may be different from the time t1.

  When the change rate (dR / dt) of the resistance increase rate is 0 or less, the controller 30 performs the process of step S112. When the change rate (dR / dt) is higher than 0, the controller 30 performs the process of step S111. Process.

  In step S111, the controller 30 increases the amount for limiting the output or input. Specifically, when the output of the assembled battery 10 is limited, the controller 30 can increase the output limit amount by bringing the upper limit power corresponding to the output closer to 0 [kW]. Further, when the input of the assembled battery 10 is limited, the controller 30 can increase the input limit amount by further bringing the upper limit power corresponding to the input closer to 0 [kW].

  By increasing the output or input limit amount, an increase in the resistance increase rate dR in the battery pack 10 can be suppressed, and the rate of change in the resistance increase rate (dR / dt) can be reduced. After increasing the output or input limit amount in the process of step S111, the process shown in FIG.

  In step S112, the controller 30 calculates the resistance increase rate dR of the battery pack 10, and determines whether the calculated resistance increase rate dR is smaller than the second threshold value dRth_off. The second threshold value dRth_off is a condition for releasing the input / output restriction of the battery pack 10 and can be set as appropriate. Specifically, the second threshold value dRth_off can be made smaller than the first threshold value dRth_on. Information regarding the second threshold value dRth_off can be stored in the memory 31.

  When the resistance increase rate dR is smaller than the second threshold value dRth_off, the controller 30 performs the process of step S114. When the resistance increase rate dR is greater than the second threshold value dRth_off, the controller 30 performs the process of step S113. In step S113, the controller 30 waits for a predetermined time t2. Specifically, the controller 30 stands by until the measured time of the timer reaches a predetermined time t2.

  After waiting for the predetermined time t2, the process returns to step S110. In the process of step S110, the controller 30 calculates the rate of change in resistance increase rate (dR / dt) from the time t0 until the time t2 elapses, and the rate of change (dR / dt) is 0 or less. It is determined whether or not.

  In step S <b> 114, the controller 30 cancels the process of restricting the input / output of the assembled battery 10. Specifically, when the output of the assembled battery 10 is limited, the controller 30 returns the upper limit power corresponding to the output to the state before the limit process is performed. Moreover, when the input of the assembled battery 10 is restricted, the controller 30 returns the upper limit power corresponding to the input to the state before the restriction process is performed.

  When the resistance increase rate dR is smaller than the second threshold value dRth_off, it is not necessary to restrict the input / output of the assembled battery 10, and therefore the process of restricting the input / output of the assembled battery 10 is released. Thereby, charging / discharging of the assembled battery 10 can be performed without restrict | limiting the input / output of the assembled battery 10, and the input / output performance of the assembled battery 10 can fully be exhibited.

  Note that the second threshold value dRth_off may be equal to the first threshold value dRth_on, but in this case, control hunting may occur in which input / output restriction and restriction release may be frequently repeated. Resulting in. For this reason, it is preferable to use different values for the first threshold dRth_on and the second threshold dRth_off. Further, considering the behavior of the resistance increase rate dR after starting the input / output restriction, as described above, the second threshold value dRth_off is preferably smaller than the first threshold value dRth_on.

  According to the present embodiment, as shown in FIGS. 4 and 5, when the resistance increase rate dR of the assembled battery 10 increases with an uneven ion concentration, the resistance increase rate dR can be decreased. As shown in FIGS. 4 and 5, when the resistance increase rate dR reaches the first threshold value dRth_on, processing for limiting the output or input of the assembled battery 10 is started.

  FIG. 4 shows a change in the resistance increase rate dR when the input / output restriction of the battery pack 10 corresponds to an excessive charge / discharge state. Specifically, when the assembled battery 10 is in an overdischarged state, the output of the assembled battery 10 is restricted, and when the assembled battery 10 is in an overcharged state, the input of the assembled battery 10 is restricted. .

  In FIG. 4, the dotted line indicates the change in the resistance increase rate dR when the input / output of the assembled battery 10 is not limited, and the solid line indicates the change in the resistance increase rate dR when the processing shown in FIG. 2 is performed. ing. When the process shown in FIG. 2 is not performed, the resistance increase rate dR continues to increase and reaches the upper limit value dRlim according to the deviation of the ion concentration, as indicated by the dotted line.

  The upper limit value dRlim is an upper limit value that can allow an increase in the resistance increase rate dR, and can be appropriately set in consideration of the life of the assembled battery 10 and the like. When the resistance increase rate dR reaches the upper limit value dRlim, the assembled battery 10 is not charged or discharged. That is, it is necessary to replace the assembled battery 10. Information about the upper limit value dRlim can be stored in the memory 31.

  In the case illustrated in FIG. 4, the resistance increase rate dR is primarily larger than the first threshold value dRth_on, but the resistance increase rate dR can be reduced by limiting the output or input of the assembled battery 10. Here, when the resistance increase rate dR becomes smaller than the second threshold value dRth_off, the restriction on the output or input of the assembled battery 10 is released.

  FIG. 5 shows a change in the resistance increase rate dR when the input / output restriction of the battery pack 10 does not correspond to the excessive charge / discharge state. Specifically, when the assembled battery 10 is in an excessively discharged state, the change in the resistance increase rate dR when the input of the assembled battery 10 is restricted and the output of the assembled battery 10 is not restricted is shown. Further, when the assembled battery 10 is in an overcharged state, the output of the assembled battery 10 is restricted, and the change in the resistance increase rate dR when the input of the assembled battery 10 is not restricted is shown.

  In FIG. 5, the dotted line indicates the change in the resistance increase rate dR when the input / output of the battery pack 10 is not limited, and the solid line indicates the change in the resistance increase rate dR when the processing shown in FIG. 2 is performed. Yes.

  When the input / output of the battery pack 10 is limited in a state where the input / output limitation does not correspond to the excessive charge / discharge state, the resistance increase rate dR is likely to increase as shown in FIG. That is, the resistance increase rate dR (solid line) after limiting the input or output of the assembled battery 10 is higher than the resistance increase rate dR (dotted line) when the input / output of the assembled battery 10 is not limited.

  Here, in this embodiment, in the process of step S108, the change rate (dR / dt) before and after the limit process is compared, and the change rate after the limit process (dR / dt) is the change rate before the limit process. When higher than (dR / dt), the output restriction process and the input restriction process are switched. Thereby, the input / output restriction can be made to correspond to an excessive charge / discharge state, and the resistance increase rate dR can be lowered as shown in FIG.

  Here, unless the output restriction process and the input restriction process are switched as in the present embodiment, the increase in the resistance increase rate dR is promoted as shown in FIG. Further, as shown in FIG. 5, the time t0 used in the process of step S107 needs to be shorter than the time until the resistance increase rate dR indicated by the dotted line reaches the upper limit value dRlim. Furthermore, it is necessary to set the time t0 in consideration of the change in the resistance increase rate dR shown by the solid line in FIG. If the behavior of the resistance increase rate dR indicated by the dotted line in FIG. 5 and the behavior of the resistance increase rate dR indicated by the solid line in FIG. 6 are specified in advance, the time t0 can be specified.

  According to the present embodiment, when the output or input of the battery pack 10 is limited, an increase in the resistance increase rate dR can be suppressed by comparing the change rate (dR / dt) of the resistance increase rate before and after the limitation. It can be confirmed whether or not. Then, based on the confirmed result, it is possible to determine which of output and input should be restricted. Thereby, resistance increase rate dR can be reduced reliably.

  In this embodiment, the output or input of the assembled battery 10 is limited after determining whether the assembled battery 10 is excessively discharged or excessively charged. However, the present invention is not limited to this. Specifically, one of the output and the input of the assembled battery 10 is limited when the resistance increase rate dR becomes higher than the first threshold value dRth_on without determining whether the assembled battery 10 is overdischarged or overcharged. Can do.

  Here, it is possible to set in advance whether to perform output restriction or input restriction. When the vehicle is driven using the output of the assembled battery 10, the ion concentration distribution may be easily biased toward the discharge side. In this case, when the resistance increase rate dR becomes higher than the first threshold value dRth_on, first, the output of the assembled battery 10 can be limited.

  On the other hand, when the battery pack 10 is charged by supplying power from an external power source to the battery pack 10, the ion concentration distribution is likely to be biased toward the charge side. In this case, when the resistance increase rate dR becomes higher than the first threshold value dRth_on, first, the input of the assembled battery 10 can be limited. Here, the external power source is a power source provided separately from the battery system shown in FIG. 1, and examples of the external power source include a commercial power source.

  When the external power supply supplies AC power, a charger that converts AC power from the external power supply into DC power and supplies the DC power to the assembled battery 10 may be provided. The charger may be added to the battery system shown in FIG. 1 or may be provided separately from the battery system shown in FIG.

  In step S108, it is determined whether or not the rate of change in resistance increase rate (dR / dt) is decreasing. If the rate of change (dR / dt) is decreasing, input or output restriction is performed. Will continue. On the other hand, when the change speed (dR / dt) is increasing, the output restriction and the input restriction are switched in the process of step S109. Even in this case, the increase in the resistance increase rate dR can be suppressed as in the present embodiment.

  Next, processing for determining whether the assembled battery 10 is excessively discharged or excessively charged will be described. Here, although two methods are demonstrated, it is not restricted to this, What kind of method may be used if the bias of the ion concentration in the cell 11 can be estimated.

  As a first method, first, using the current sensor 25, a current when the assembled battery 10 is charged and a current when the assembled battery 10 is discharged are acquired. Then, the ratio k is calculated as shown in the following formula (4).

  In the above formula (4), Ic is a current value when the assembled battery 10 is being charged, and Id is a current value when the assembled battery 10 is being discharged. As shown in the above formula (4), by calculating the ratio of the charging current Ic and the discharging current Id, it can be determined whether the ion concentration distribution is biased toward the discharging side or the charging side. That is, if the charging current Ic is larger than the discharging current Id, it can be determined that the ion concentration distribution is biased toward the charging side. If the discharge current Id is larger than the charge current Ic, it can be determined that the ion concentration distribution is biased toward the discharge side.

  In the above formula (4), the ratio k between the value obtained by squaring the charging current Ic and the value obtained by squaring the discharging current Id is calculated, but the present invention is not limited to this, and the ratio of the charging current Ic and the discharging current Id is calculated. It is only necessary to calculate. However, by using the value obtained by squaring the charge current Ic and the discharge current Id, the difference between the value obtained by squaring the charge current Ic and the value obtained by squaring the discharge current Id can be widened, and the deviation of the ion concentration distribution can be confirmed. It becomes easy to do.

  A second method for determining excessive discharge and excessive charge will be described with reference to the flowcharts shown in FIGS. 7A and 7B. In the second method, as will be described later, an evaluation value for evaluating the bias of the ion concentration is defined, and based on this evaluation value, it is determined whether the assembled battery 10 is excessively discharged or excessively charged. I am doing so.

  The processing shown in FIGS. 7A and 7B is repeatedly performed at a preset time interval (cycle time). 7A and 7B is executed by the controller 30.

  In step S <b> 201, the controller 30 acquires a discharge current based on the output of the current sensor 25. When the battery pack 10 is being discharged, the discharge current has a positive value, and when the battery pack 10 is being charged, the discharge current has a negative value.

  In step S202, the controller 30 calculates (estimates) the SOC (State Of Charge) of the assembled battery 10, the single battery 11, or the battery block described above based on the discharge current obtained in the process of step S201. The SOC is the ratio of the current charge capacity to the full charge capacity. The controller 30 can calculate the SOC of the assembled battery 10, the single battery 11, or the battery block by accumulating the current when the assembled battery 10 is charged / discharged. The current when the assembled battery 10 is charged and discharged can be obtained from the output of the current sensor 25.

  On the other hand, from the detected voltage of the monitoring unit 27, the SOC of the assembled battery 10, the single battery 11, or the battery block can be estimated. Since the SOC has a correspondence with OCV (Open Circuit Voltage), the SOC can be specified from the OCV if the correspondence between the SOC and the OCV is obtained in advance. The OCV can be obtained from the detected voltage (CCV: Closed Circuit Voltage) of the monitoring unit 27 and the voltage drop amount due to the internal resistance of the assembled battery 10, the single battery 11 or the battery block. The SOC calculation method is not limited to the method described in this embodiment, and a known method can be selected as appropriate.

  In step S <b> 203, the controller 30 acquires the temperature of the assembled battery 10, the single battery 11, or the battery block based on the output signal of the temperature sensor 26. In step S204, the controller 30 calculates a forgetting factor based on the SOC calculated in step S202 and the temperature acquired in step S203. The forgetting factor is a factor relating to the diffusion rate of ions in the electrolytic solution of the unit cell 11. The forgetting factor is set within a range that satisfies the condition of the following formula (5).

  In the above equation (5), A represents a forgetting factor, and Δt represents a cycle time when the processes shown in FIGS. 7A and 7B are repeated. As the forgetting factor A, a value corresponding to the assembled battery 10, the single battery 11, or the battery block can be used.

  For example, the controller 30 can specify the forgetting factor A using the map shown in FIG. In FIG. 8, the vertical axis is the forgetting factor A, and the horizontal axis is the temperature. The map shown in FIG. 8 can be acquired in advance by an experiment or the like and can be stored in the memory 31.

  In the map shown in FIG. 8, the forgetting factor A can be specified by specifying the SOC acquired in the process of step S202 and the temperature acquired in the process of step S203. The forgetting factor A increases as the ion diffusion rate increases. In the map shown in FIG. 8, if the temperature is the same, the forgetting factor A increases as the SOC increases. For the same SOC, the forgetting factor A increases as the temperature increases.

  In step S205, the controller 30 calculates an evaluation value decrease amount D (-). The evaluation value D (N) is a value for evaluating the deterioration state (high-rate deterioration described later) of the assembled battery 10, the single battery 11, or the battery block.

  When the high-rate deterioration of the unit cell 11 proceeds, it is necessary to suppress charging / discharging of the unit cell 11 (the assembled battery 10). That is, unless charging / discharging of the cell 11 (the assembled battery 10) is not suppressed, the high rate deterioration of the cell 11 proceeds. In this embodiment, an evaluation value D (N) is set as a value for evaluating high-rate deterioration. A method for calculating the evaluation value D (N) will be described later.

  The amount of decrease D (−) in the evaluation value is the number of ions accompanying ion diffusion from the time when the previous (immediately) evaluation value D (N−1) is calculated until one cycle time Δt elapses. It is calculated according to the decrease in density deviation. For example, the controller 30 can calculate the evaluation value decrease amount D (−) based on the following equation (6).

  In the above formula (6), A and Δt are the same as in the above formula (5). D (N-1) represents the evaluation value calculated last time (immediately before). D (0) as an initial value can be set to 0, for example.

  As shown in the above equation (5), the value of “A × Δt” is a value from 0 to 1. Therefore, as the value of “A × Δt” approaches 1, the amount of decrease D (−) in the evaluation value increases. In other words, the greater the forgetting factor A or the longer the cycle time Δt, the greater the evaluation value reduction amount D (−). Note that the method of calculating the decrease amount D (−) is not limited to the method described in the present embodiment, and any method can be used as long as it can identify the decrease in the ion concentration bias.

  In step S <b> 206, the controller 30 reads the current coefficient stored in advance in the memory 31. In step S207, the controller 30 calculates a limit value based on the SOC calculated in the process of step S202 and the temperature acquired in the process of step S203.

  For example, the controller 30 can calculate the limit value using the map shown in FIG. The map shown in FIG. 9 can be acquired in advance by an experiment or the like, and can be stored in the memory 31. In FIG. 9, the vertical axis is the limit value, and the horizontal axis is the temperature. In the map shown in FIG. 9, the limit value can be specified by specifying the SOC acquired in the process of step S202 and the temperature acquired in the process of step S203.

  In the map shown in FIG. 9, if the temperature is the same, the limit value increases as the SOC increases. Moreover, if SOC is the same, a limit value will become large, so that temperature is high.

  In step S208, the controller 30 calculates the increase amount D (+) of the evaluation value. The amount of increase D (+) in the evaluation value is the ion concentration associated with the discharge from the time when the previous (immediately) evaluation value D (N−1) is calculated until one cycle time Δt elapses. Calculated according to the increase in bias. For example, the controller 30 can calculate the increase amount D (+) of the evaluation value based on the following formula (7).

  In the above equation (7), B represents a current coefficient, and the value acquired in the process of step S206 is used. C indicates a limit value, and the value acquired in the process of step S207 is used. As the current coefficient B and the limit value C, values corresponding to the assembled battery 10 or the single battery 11 are used. I represents the discharge current, and the value acquired in the process of step S201 is used. Δt is the cycle time.

  As can be seen from the above equation (7), the larger the discharge current I or the longer the cycle time Δt, the larger the evaluation value increase D (+). Note that the calculation method of the increase amount D (+) is not limited to the calculation method described in this embodiment, and any method that can identify an increase in the bias of the ion concentration may be used.

  In step S209, the controller 30 calculates an evaluation value D (N) at the current cycle time Δt. The evaluation value D (N) can be calculated based on the following formula (8).

  In the above equation (8), D (N) is an evaluation value at the current cycle time Δt, and D (N−1) is an evaluation value at the previous (immediately) cycle time Δt. D (0) as an initial value can be set to 0, for example. D (−) and D (+) indicate a decrease amount and an increase amount of the evaluation value D, respectively, and the values calculated in the processes of steps S205 and S208 are used.

  When the evaluation value D (N) is calculated, the controller 30 stores the calculated evaluation value D (N) in the memory 31. By storing the evaluation value D (N) in the memory 31, a change in the evaluation value D (N) can be monitored.

  In this embodiment, as shown in the above formula (8), an increase in the ion concentration bias (increase D (+)) and a decrease in the ion concentration bias (decrease D (−)) are taken into consideration. The evaluation value D (N) can be calculated. Thereby, the change (increase / decrease) in the ion concentration bias considered to be the cause of the high rate deterioration can be appropriately reflected in the evaluation value D (N). Therefore, it can be grasped based on the evaluation value D (N) how close to the state where the high rate deterioration occurs. Here, as the evaluation value D (N), the evaluation value D (N) corresponding to any of the assembled battery 10, the single battery 11, and the battery block can be used.

  In step S210, the controller 30 determines whether or not the evaluation value D (N) calculated in the process of step S209 is smaller than a predetermined target value Dtar (−), or the evaluation value D (N) is It is determined whether or not the target value is larger than a predetermined target value Dtar (+). That is, the controller 30 determines whether or not the absolute value of the evaluation value D (N) is larger than the absolute values of the target values Dtar (−) and Dtar (+).

  The target value Dtar (−) is set to a value smaller than the evaluation value D (N) at which high-rate deterioration due to charging starts to occur, and can be set in advance. Further, the target value Dtar (+) is set to a value smaller than the evaluation value D (N) at which high rate deterioration due to discharge starts to occur, and can be set in advance. If the absolute value of the evaluation value D (N) is larger than the absolute values of the target values Dtar (−) and Dtar (+), the process proceeds to step S211; otherwise, the process shown in FIGS. 7A and 7B. Exit.

  In the present embodiment, as shown in FIG. 10, the target value Dtar (−) is set on the minus side of the evaluation value D (N), and the target value Dtar (+) is equal to the evaluation value D (N). It is set on the plus side. FIG. 10 is a diagram illustrating a change (an example) in the evaluation value D (N).

  In step S211, the controller 30 integrates the evaluation values D (N). Specifically, as shown in FIG. 10, when the evaluation value D (N) is smaller than the target value Dtar (−), a portion of the evaluation value D (N) that is smaller than the target value Dtar (−) ( Integration is performed for the hatched area in FIG. Every time the evaluation value D (N) becomes smaller than the target value Dtar (−), integration processing is performed. When the evaluation value D (N) is smaller than the target value Dtar (−), the difference between the evaluation value D (N) and the target value Dtar (−) is integrated. Since the evaluation value D (N) here is a negative value, the integrated value is also a negative value.

  On the other hand, when the evaluation value D (N) is larger than the target value Dtar (+), integration is performed for a portion (hatched area in FIG. 10) of the evaluation value D (N) that is larger than the target value Dtar (+). Do. Every time the evaluation value D (N) becomes larger than the target value Dtar (+), integration processing is performed. When the evaluation value D (N) is larger than the target value Dtar (+), the difference between the evaluation value D (N) and the target value Dtar (+) is integrated. Since the evaluation value D (N) here is a positive value, the integrated value is also a positive value.

  In the present embodiment, the integrated value ΣDex (N) is calculated based on the following formula (9).

  In the above equation (9), t_total is the time (total time) from the start of calculating the integrated value ΣDex (N) to the current cycle time. t− is the time (total time) when the evaluation value D (N) is smaller than the target value Dtar (−), and t + is the evaluation value D (N) less than the target value Dtar (+). This is the time (total time) that is increasing. ΣDex− (N−1) is a value obtained by integrating the difference between the negative evaluation value D (N) and the target value Dtar (−) in the cycle time up to the previous time. ΣDex + (N−1) is a value obtained by integrating the difference between the positive evaluation value D (N) and the target value Dtar (+) in the cycle time up to the previous time.

  When the integrated value ΣDex (N) is calculated, the controller 30 stores the calculated integrated value ΣDex (N) in the memory 31. When the integrated value ΣDex (N) is stored in the memory 31, the next evaluation value D (N + 1) becomes larger than the target value Dtar (+) or becomes smaller than the target value Dtar (−). The integrated value ΣDex (N) can be updated.

  In the present embodiment, the integrated value ΣDex (N) is calculated using the above formula (9), but the present invention is not limited to this. For example, every time the evaluation value D (N) exceeds the target values Dtar (−) and Dtar (+), the difference between the evaluation value D (N) and the target values Dtar (−) and Dtar (+) is integrated. Just be fine. That is, the integrated values ΣDex− (N−1) and ΣDex + (N−1) may be obtained and the integrated values ΣDex− (N−1) and ΣDex + (N−1) may be simply added.

  Further, in this embodiment, the difference between the evaluation value D (N) and the target values Dtar (−) and Dtar (+) is integrated, but the present invention is not limited to this. Specifically, each time the evaluation value D (N) exceeds the target values Dtar (−) and Dtar (+), the evaluation value D (N) itself can be integrated.

  In step S212, the controller 30 determines whether or not the integrated value ΣDex (N) is larger than the discharge threshold value Dthd. The discharge threshold Dthd is used to determine whether or not the ion concentration distribution inside the cell 11 is biased toward the discharge side, and can be set as appropriate. For example, the discharge threshold Dthd can be set to a value larger than 0, and information regarding the discharge threshold Dthd can be stored in the memory 31.

  When the integrated value ΣDex (N) is larger than the discharge threshold Dthd, the controller 30 determines in step S213 that the ion concentration distribution inside the unit cell 11 is biased toward the discharge side. That is, the controller 30 determines that the assembled battery 10 is in an excessively discharged state. On the other hand, when the integrated value ΣDex (N) is smaller than the discharge threshold Dthd, the controller 30 determines that the ion concentration distribution is not biased toward the discharge side, and proceeds to the process of step S214.

  In step S214, the controller 30 determines whether or not the integrated value ΣDex (N) is smaller than the charging threshold value Dthc. The charging threshold value Dthc is used to determine whether or not the ion concentration distribution inside the unit cell 11 is biased toward the charging side, and can be set as appropriate. For example, the charging threshold value Dthc can be set to a value smaller than 0, and information regarding the charging threshold value Dthc can be stored in the memory 31. Here, the discharge threshold value Dthd and the charge threshold value Dthc can be set to the same value, but in this case, there is a possibility that the discrimination between the excessive discharge and the excessive charge may occur, and control hunting occurs. End up.

  When the integrated value ΣDex (N) is smaller than the charging threshold value Dthc, the controller 30 determines in step S215 that the ion concentration distribution inside the unit cell 11 is biased toward the charging side. That is, the controller 30 determines that the assembled battery 10 is in an overcharged state. On the other hand, when the integrated value ΣDex (N) is larger than the charging threshold value Dthc, the controller 30 determines that the ion concentration distribution is not biased toward the charging side, and ends the processes shown in FIGS. 7A and 7B.

10: assembled battery, 11: single cell, 21a, 21b: system main relay,
22: Booster circuit, 23: Inverter, 24: Motor generator, 25: Current sensor,
26: Temperature sensor, 27: Monitoring unit, 30: Controller, 31: Memory

Claims (9)

A secondary battery whose resistance increases in accordance with the bias of ion concentration accompanying charging and discharging;
A controller for controlling charging / discharging of the secondary battery,
The controller is
When the deterioration value defined by the resistance is larger than a threshold value, limiting one of charging and discharging of the secondary battery,
When the amount of change in the deterioration value after the restriction is larger than the amount of change in the deterioration value before the restriction, the one restriction is canceled and the other of the charging and discharging is restricted.
A battery system characterized by that.   The controller continues the restriction when the amount of change in the deterioration value after restricting one of charging and discharging is smaller than the amount of change in the deterioration value before restricting one of charging and discharging. The battery system according to claim 1. The controller is
Based on the history of the current flowing through the secondary battery, determine the bias of the ion concentration,
When the deterioration value is larger than the threshold value and the ion concentration distribution is biased toward the discharge side, the discharge of the secondary battery is limited,
When the deterioration value is larger than the threshold value and the ion concentration distribution is biased toward the charging side, charging of the secondary battery is limited.
The battery system according to claim 1 or 2, wherein The controller is
An evaluation value for evaluating a degradation component that decreases the input / output performance of the secondary battery with the deviation of the ion concentration is calculated from a history of current when the secondary battery is charged and discharged,
When the integrated value obtained by integrating the evaluation values exceeding the target value exceeds the discharge threshold, it is determined that the ion concentration distribution is biased toward the discharge side,
When the integrated value exceeds the charging threshold, it is determined that the ion concentration distribution is biased toward the charging side,
The battery system according to claim 3.   5. The battery system according to claim 1, wherein when the controller limits one of charging and discharging, the controller does not limit the other of charging and discharging.   The said deterioration value is represented by ratio of the resistance of the said secondary battery in an initial state, and the resistance of the said present secondary battery, The one of Claim 1 to 5 characterized by the above-mentioned. Battery system. A control method for controlling charging / discharging of a secondary battery in which resistance increases in accordance with bias of ion concentration accompanying charging / discharging,
When the deterioration value defined by the resistance is larger than a threshold value, limiting one of charging and discharging of the secondary battery,
When the amount of change in the deterioration value after the restriction is larger than the amount of change in the deterioration value before the restriction, the one restriction is canceled and the other of the charging and discharging is restricted.
A control method characterized by that.   When the amount of change in the deterioration value after restricting one of charging and discharging is smaller than the amount of change in the deterioration value before restricting one of charging and discharging, the one restriction is continued. The control method according to claim 7. Based on the history of the current flowing through the secondary battery, determine the bias of the ion concentration,
When the deterioration value is larger than the threshold value and the ion concentration distribution is biased toward the discharge side, the discharge of the secondary battery is limited,
When the deterioration value is larger than the threshold value and the ion concentration distribution is biased toward the charging side, charging of the secondary battery is limited.
The control method according to claim 7 or 8, wherein