JP2013243869A - Device for controlling secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid excessively limiting charging of a secondary battery.SOLUTION: A control device for controlling charging of a secondary battery such that charging power of the secondary battery does not exceed an upper limit value includes: a current sensor for detecting a current while the secondary battery is charged/discharged; and a controller for calculating, from a state of charge/discharge detected by the current sensor, an evaluation value for evaluating a degradation component that lowers input/output performance of the secondary battery with a variation in ion concentration within the secondary battery. The controller increases the upper limit value when determining that an ion concentration distribution in the secondary battery is a state of overdischarge on the basis of an integral value of evaluation values exceeding a discharge side desired value.

Description

  The present invention relates to a control device that evaluates an ion concentration bias in a secondary battery and controls charging of the secondary battery.

  When controlling the charging of the secondary battery, an upper limit voltage that allows the charging of the secondary battery is set in advance, and the charging of the secondary battery is controlled so that the voltage of the secondary battery does not become higher than the upper limit voltage. ing. Thereby, the overcharge of a secondary battery can be suppressed.

JP 2010-268642 A JP 2011-125210 A

  The ion concentration inside the secondary battery changes based on the charge / discharge history of the secondary battery. For example, when the secondary battery is continuously discharged, the secondary battery is overdischarged because the ion concentration is biased toward the discharge side. When the secondary battery is continuously charged, the secondary battery is overcharged because the ion concentration is biased toward the charging side.

  When the secondary battery is in an overdischarged state, if the secondary battery is charged, the bias of the ion concentration can be changed to the opposite side (the charging side) to eliminate the overdischarged state. Can do. For this reason, when controlling the charging of the secondary battery, it is possible to consider the deviation of the ion concentration.

  The present invention is a control device for controlling the charging of a secondary battery so that the charging power of the secondary battery does not exceed an upper limit value, a current sensor for detecting a current during charging and discharging of the secondary battery, and a secondary battery A controller that calculates an evaluation value for evaluating a deterioration component that degrades the input / output performance of the secondary battery in accordance with the deviation of the ion concentration in the battery from the charge / discharge state detected using the current sensor. . The controller increases the upper limit value when it is determined that the ion concentration distribution in the secondary battery is in an excessive discharge state by using a value obtained by integrating evaluation values exceeding the target value on the discharge side.

  According to the present invention, by using the evaluation value, it is possible to confirm the deviation of the ion concentration. Here, when the evaluation value exceeds the target value, it is possible to determine whether or not the secondary battery is in an excessively discharged state by integrating the evaluation values (part or all). When the secondary battery is in an excessive discharge state, the secondary battery can be changed in a direction to eliminate the excessive discharge state by charging the secondary battery. For this reason, the upper limit value used for the charge control of the secondary battery can be increased compared to when the secondary battery is not in an excessively discharged state. If the upper limit value is increased, the secondary battery can be easily charged, and more power can be stored in the secondary battery.

It is a figure which shows the structure of a battery system. It is a flowchart which shows the process which controls charge of an assembled battery. It is a flowchart which shows the process which controls charge of an assembled battery. It is a flowchart which shows the process which controls charge 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. It is a figure which shows the relationship between the coefficient F and an electric current. It is a figure which shows the relationship between the coefficient G and an upper limit voltage. It is a figure which shows the change of the upper limit voltage according to an integrated value.

  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 is mounted on a vehicle. 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 DC power 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. The kinetic energy generated by the motor generator 24 is transmitted to the wheels. 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 set to a positive value and the charging current is set to 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 voltage of each battery block can be detected by the monitoring unit 27. 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.

  Next, processing for controlling charging / discharging of the assembled battery 10 will be described with reference to the flowcharts shown in FIGS. 2A to 2C. The processing shown in FIGS. 2A to 2C is repeatedly performed at a preset time interval (cycle time). 2A to 2C is performed by a CPU included in the controller 30 executing a program stored in the memory 31.

  In step S <b> 101, 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 S102, 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 S101. 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> 103, 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 S104, the controller 30 calculates a forgetting factor based on the SOC calculated in step S102 and the temperature acquired in step S103. 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 (1).

  In the above formula (1), A represents a forgetting factor, and Δt represents a cycle time when the processes shown in FIGS. 2A to 2C 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. 3, the vertical axis is the forgetting factor A, and the horizontal axis is the temperature. The map shown in FIG. 3 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. 3, the forgetting factor A can be specified by specifying the SOC acquired in the process of step S102 and the temperature acquired in the process of step S103. The forgetting factor A increases as the ion diffusion rate increases. In the map shown in FIG. 3, 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 S105, 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.

  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 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 decrease amount D (−) of the evaluation value based on the following formula (2).

  In the above formula (2), A and Δt are the same as in the above formula (1). 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 (1), 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> 106, the controller 30 reads a current coefficient stored in advance in the memory 31. In step S107, the controller 30 calculates a limit value based on the SOC calculated in the process of step S102 and the temperature acquired in the process of step S103.

  For example, the controller 30 can calculate the limit value using the map shown in FIG. The map shown in FIG. 4 can be acquired in advance by experiments or the like, and can be stored in the memory 31. In FIG. 4, the vertical axis is the limit value, and the horizontal axis is the temperature. In the map shown in FIG. 4, the limit value can be specified by specifying the SOC acquired in the process of step S102 and the temperature acquired in the process of step S103.

  In the map shown in FIG. 4, 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 S108, the controller 30 calculates an increase D (+) in 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 (3).

  In the above equation (3), B represents a current coefficient, and the value acquired in the process of step S106 is used. C indicates a limit value, and the value acquired in the process of step S107 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 S101 is used. Δt is the cycle time.

  As can be seen from the above equation (3), 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 S109, 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 (4).

  In the above equation (4), 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 S105 and S108 are used.

  When the formula (4) is modified based on the formulas (2) and (3), the following formula (5) is obtained.

  In the present embodiment, as represented by the above formula (4), the evaluation value D (N) can be calculated in consideration of an increase in ion concentration bias and a decrease in ion concentration bias. 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 S110, the controller 30 determines whether or not the evaluation value D (N) calculated in the process of step S109 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 S111. Otherwise, the process proceeds to step S121.

  In the present embodiment, as shown in FIG. 5, the target value Dtar (−) is set on the negative 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. 5 is a diagram illustrating a change (an example) of the evaluation value D (N).

  In step S111, the controller 30 integrates the evaluation values D (N). Specifically, as shown in FIG. 5, 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. 5) 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 this embodiment, the integrated value ΣDex (N) is calculated based on the following equation (6).

  In the above equation (6), 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 until the previous time, and ΣDex + (N−1) is In the cycle time up to the previous time, the difference between the positive evaluation value D (N) and target value Dtar (+) is integrated.

  In this embodiment, the integrated value ΣDex (N) is calculated using the above equation (6), 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 S112, the controller 30 determines whether or not the detection voltage V of the monitoring unit 27 is lower than the upper limit voltage Vlim. The upper limit voltage Vlim is a voltage determined in advance to protect the assembled battery 10 (single battery 11) by suppressing overcharging of the assembled battery 10, the single battery 11 or the battery block. The upper limit voltage Vlim is set according to the characteristics of the assembled battery 10 (unit cell 11). Here, when the monitoring unit 27 detects the voltage of the assembled battery 10, the upper limit voltage Vlim is a voltage corresponding to the assembled battery 10. Moreover, when the monitoring unit 27 detects the voltage of the single battery 11 or the battery block, the upper limit voltage Vlim is a voltage corresponding to the single battery 11 or the battery block.

  When the detected voltage V is lower than the upper limit voltage Vlim, the process proceeds to step S120, and when the detected voltage V is higher than the upper limit voltage Vlim, the process proceeds to step S113. In step S113, 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 greater than zero. Here, the state where the ion concentration distribution is biased toward the discharge side is called excessive discharge.

  When the integrated value ΣDex (N) is larger than the discharge threshold value Dthd, the controller 30 determines that the ion concentration distribution inside the unit cell 11 is biased toward the discharge side, and proceeds to the process of step S114. On the other hand, when the integrated value ΣDex (N) is smaller than the discharge threshold value Dthd, the controller 30 determines that the ion concentration distribution is not biased toward the discharge side, and proceeds to the process of step S115.

  In this embodiment, the upper limit voltage Vlim is set based on the following equation (7).

In the above formula (7), Vlim _n is an upper limit voltage set this time, and Vlim _n−1 is an upper limit voltage set last time (nearest). α is a coefficient (positive value) depending on the temperature and SOC of the assembled battery 10, the single battery 11 or the battery block, and F is a coefficient depending on the current flowing through the assembled battery 10 (the single battery 11 or the battery block). (Positive value). If a map showing the correspondence relationship between the coefficient α, the temperature, and the SOC is obtained in advance by an experiment or the like, the coefficient α can be specified by specifying the temperature and the SOC.

  On the other hand, if a map showing the correspondence between the coefficient F and the current is obtained in advance by experiments or the like, the coefficient F can be specified by specifying the current. Here, FIG. 6 shows a correspondence relationship (an example) between the coefficient F and the current. According to the map shown in FIG. 6, the coefficient F increases as the current decreases. In other words, the coefficient F decreases as the discharge current increases, and the coefficient F increases as the charging current increases.

In the above formula (7), β is a coefficient (positive value) depending on the temperature and SOC of the assembled battery 10, the single battery 11 or the battery block, and G is a coefficient (dependent on the upper limit voltage Vlim _n−1 ) ( A positive value). If a map showing the correspondence relationship between the coefficient β, the temperature, and the SOC is obtained in advance by experiment or the like, the coefficient β can be specified by specifying the temperature and the SOC.

On the other hand, if a map indicating the correspondence relationship between the coefficient G and the upper limit voltage Vlim _n−1 is obtained in advance by experiments or the like, the coefficient G can be specified by specifying the upper limit voltage Vlim _n−1 . Here, FIG. 7 shows a correspondence relationship (an example) between the coefficient G and the upper limit voltage Vlim _n−1 . According to the map shown in FIG. 7, as the upper limit voltage Vlim _n-1 is high, the coefficient G becomes large, as the upper limit voltage Vlim _n-1 becomes low, the coefficient G becomes small.

The second term (value of αFΔt) on the right side of the above formula (7) is used to reduce the upper limit voltage Vlim _n . As shown in the above equation (7), the second term on the right side is subtracted from the previous upper limit voltage Vlim _n−1 . Therefore, the upper limit voltage Vlim _n is reduced by the second term on the right side. By reducing the upper limit voltage Vlim _n , the charging of the assembled battery 10 is further limited by this reduction.

As shown in FIG. 6, the coefficient F included in the second term on the right side increases as the discharge current decreases and as the charge current increases. For this reason, the upper limit voltage Vlim _n tends to decrease as the discharge current decreases and the charging current increases. In other words, as the discharge current increases, the coefficient F decreases, so that the upper limit voltage Vlim _n is less likely to decrease.

The third term (value of βGΔt) on the right side of the above equation (7) is used to mitigate the decrease in the upper limit voltage Vlim _n . As shown in the above equation (7), the third term on the right side is added to the previous upper limit voltage Vlim _n−1 . Therefore, the upper limit voltage Vlim _n can be increased by the third term on the right side. By increasing the upper limit voltage Vlim _n , the assembled battery 10 can be further charged by this increase. Therefore, the third term on the right side relaxes the charging limitation of the assembled battery 10.

  In the process of step S114, the coefficient α included in the second term on the right side of the equation (7) is set. Specifically, the coefficient αd is set as the coefficient α. The value of the coefficient αd can be set as appropriate.

  In step S115, 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. Here, a state where the ion concentration distribution is biased toward the charging side is referred to as excessive charging.

  When the integrated value ΣDex (N) is smaller than the charging threshold value Dthc, the controller 30 determines that the ion concentration distribution inside the unit cell 11 is biased toward the charging side, and proceeds to the process of step S116. 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 proceeds to the process of step S117.

In step S116, the controller 30 sets the coefficient αc as the coefficient α included in the second term on the right side of the equation (7). Here, the coefficient αc is a value larger than the coefficient αd used in the process of step S114. Therefore, the upper limit voltage Vlim _n calculated by setting the coefficient αd is higher than the upper limit voltage Vlim _n calculated by setting the coefficient αc.

In step S117, the controller 30 sets the coefficient αn as the coefficient α included in the second term on the right side of the equation (7). Here, the coefficient αn is larger than the coefficient αd used in the process of step S114 and smaller than the coefficient αc used in the process of step S116. Therefore, the upper limit voltage Vlim _n calculated by setting the coefficient αn is lower than the upper limit voltage Vlim _n calculated by setting the coefficient αd and higher than the upper limit voltage Vlim _n calculated by setting the coefficient αc.

  As described above, the coefficient α is set according to the temperature and the SOC, and is set to any one of the coefficients αd, αc, and αn according to the integrated value ΣDex (N).

  FIG. 8 shows the relationship of the upper limit voltage Vlim calculated by setting the coefficients αd, αc, αn. When charging / discharging of the assembled battery 10 (unit cell 11) is not performed, the upper limit voltage Vlim is set to a predetermined value (maximum value) Vlim_max. Here, if the detection voltage V by the monitoring unit 27 becomes higher than the upper limit voltage Vlim due to charging of the assembled battery 10 (unit cell 11), the upper limit voltage Vlim is reduced based on the above equation (7). That is, in FIG. 8, charging of the assembled battery 10 (unit cell 11) is started at time t1, and when the detection voltage V becomes higher than the upper limit voltage Vlim, the upper limit voltage Vlim starts to decrease.

When lowering the upper limit voltage Vlim, as described above, the upper limit voltage Vlim _n is set based on the integrated value ΣDex (N). That is, when the integrated value ΣDex (N) is larger than the discharge threshold Dthd, in other words, when the assembled battery 10, the single battery 11 or the battery block is in an excessive discharge state, the upper limit voltage Vlim _n is calculated by setting the coefficient αd. Is done. Here, in the upper limit voltage Vlim _n calculated by setting the coefficient αd, the amount of decrease in the upper limit voltage Vlim is the smallest as shown in FIG.

When the integrated value ΣDex (N) is smaller than the charging threshold value Dthc, in other words, when the assembled battery 10, the single battery 11 or the battery block is in an overcharged state, the upper limit voltage Vlim _n is calculated by setting the coefficient αc. . Here, in the upper limit voltage Vlim _n calculated by setting the coefficient αc, as shown in FIG. 8, the amount of decrease in the upper limit voltage Vlim is the largest.

When the integrated value ΣDex (N) is smaller than the discharge threshold value Dthd and larger than the charge threshold value Dthc, in other words, when the assembled battery 10, the cell 11 or the battery block is neither overdischarged nor overcharged, the coefficient αn The upper limit voltage Vlim _n is calculated by setting. Here, the amount of decrease of the upper limit voltage Vlim _n calculated by setting the coefficient αn is larger than the amount of decrease of the upper limit voltage Vlim _n accompanying the setting of the coefficient αd, and the amount of decrease of the upper limit voltage Vlim _n accompanying the setting of the coefficient αc. Smaller than.

  When the battery pack 10 (unit cell 11) is no longer charged at time t2 shown in FIG. 8, the value of the third term (βGΔt) on the right side of the equation (7) is the second value on the right side of the equation (7). It becomes larger than the value of the term (αFΔt). As a result, the upper limit voltage Vlim begins to rise, and the upper limit voltage Vlim approaches the predetermined value Vlim_max as time elapses. In this embodiment, the coefficients α, β, F, and G shown in the above equation (7) are set so that the upper limit voltage Vlim exhibits the behavior described above.

  When the coefficient α is set in the process of step S114, step S116, or step S117, the controller 30 sets the input limit value Win of the assembled battery 10 (unit cell 11) in step S118. The input limit value Win is an upper limit power that allows charging (input) of the battery pack 10 (unit cell 11). Here, charging of the assembled battery 10 (unit cell 11) is controlled so that the input power of the assembled battery 10 (unit cell 11) does not become higher than the input limit value Win.

  In step S118, the controller 30 calculates an input limit value Win that is an upper limit of the input power based on the following equation (8).

  In the above equation (8), Win_b is a preset input limit value (input power), and K is a coefficient (positive value). The input limit value Win_b can be changed according to the temperature and SOC of the assembled battery 10, the single battery 11, or the battery block. That is, a map indicating the correspondence between the input limit value Win_b and the temperature and a map indicating the correspondence between the input limit value Win_b and the SOC are prepared in advance, and the input limit value Win_b corresponding to the temperature and the SOC can be used. .

  V shown in the above equation (8) is a detection voltage by the monitoring unit 27, and Vlim is an upper limit voltage calculated based on the coefficients αd, αc, αn set in the process of step S114, step S116 or step S117. It is. In the process of step S118, since the detection voltage V is higher than the upper limit voltage Vlim, the input limit value Win is set according to the difference between the detection voltage V and the upper limit voltage Vlim as shown in the above equation (8). It becomes higher than the input limit value Win_b. For example, when a lithium ion secondary battery is used as the single battery 11, the input limit value Win calculated from the above formula (8) can be used as a limit value for suppressing lithium deposition accompanying overcharge. .

  In step S119, the controller 30 outputs a command related to charge control of the assembled battery 10 based on the input limit value Win calculated in the process of step S118. Specifically, the controller 30 controls the operation of the booster circuit 22 and the inverter 23 based on the input limit value Win calculated in the process of step S118, so that the input power of the battery pack 10 (unit cell 11) is controlled. The battery pack 10 (unit cell 11) is charged within a range that does not become higher than the input limit value Win.

  In step S <b> 120, the controller 30 stores the current evaluation value D (N) and integrated value ΣDex (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. Further, by storing the integrated value ΣDex (N) 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 (−). Sometimes, the integrated value ΣDex (N) can be updated.

  When the process proceeds from step S110 to step S121, the controller 30 stores only the current evaluation value D (N) in the memory 31. Thereby, the change of the evaluation value D (N) can be monitored. Note that, when the process proceeds from the process of step S110 to the process of step S121, the integrated value ΣDex (N) is not calculated, and therefore the integrated value ΣDex (N) is not stored in the memory 31.

  According to the present embodiment, when the unit cell 11 is in an excessive discharge state, the upper limit voltage Vlim is hardly lowered by setting the coefficient α to the coefficient αd. That is, as shown in FIG. 8, the upper limit voltage Vlim (α = αd) when the unit cell 11 is in an excessively discharged state is equal to the upper limit voltage Vlim when the unit cell 11 is not in an excessively discharged state or an excessively charged state. α = αn).

  As the upper limit voltage Vlim is increased, the charging limit of the unit cell 11 can be relaxed. Therefore, in this embodiment, when the unit cell 11 is in an excessive discharge state, the charging limitation is relaxed. When the unit cell 11 is in a state of excessive discharge, the unit cell 11 can be changed in a direction to cancel the state of excessive discharge by charging the unit cell 11. If the direction is changed to cancel the excessive discharge state, it is possible to suppress the high rate deterioration accompanying the discharge.

  For this reason, in this embodiment, when the unit cell 11 is in an excessive discharge state, the upper limit voltage Vlim is increased in order to eliminate the excessive discharge state. If the upper limit voltage Vlim is increased, the charging of the unit cell 11 becomes difficult to be restricted, and more power can be stored in the unit cell 11.

  On the other hand, when the unit cell 11 is in an overcharged state, the upper limit voltage Vlim is easily lowered by setting the coefficient α to the coefficient αc. That is, as shown in FIG. 8, the upper limit voltage Vlim (α = αc) when the unit cell 11 is in an overcharged state is equal to the upper limit voltage Vlim when the unit cell 11 is not in an overdischarged or overcharged state. α = αn).

  Since the charging of the cell 11 can be restricted as the upper limit voltage Vlim is lowered, in this embodiment, the charging is restricted when the cell 11 is in an overcharged state. If the unit cell 11 is in an overcharged state and the unit cell 11 continues to be charged, the overcharged state is advanced, and high-rate deterioration associated with charging proceeds.

  For this reason, in this embodiment, when the unit cell 11 is in an overcharged state, the upper limit voltage Vlim is lowered in order to suppress the overcharged state. If the upper limit voltage Vlim is lowered, the charging of the unit cell 11 is likely to be restricted, and high-rate deterioration associated with charging can be suppressed.

  The processing shown in FIGS. 2A to 2C can be performed not only when the vehicle is running due to charging / discharging of the assembled battery 10 but also when electric power from an external power source is supplied to the assembled battery 10. The external power source is a power source provided outside the vehicle and provided separately from the vehicle (battery system shown in FIG. 1). As the external power source, for example, a commercial power source can be used.

  When the external power supply supplies AC power, a charger for converting AC power to DC power and supplying DC power to the assembled battery 10 is required. The charger may be provided in the battery system shown in FIG. 1 or may be provided outside the vehicle (battery system shown in FIG. 1) separately from the vehicle. According to the present embodiment, when supplying electric power from the external power source to the assembled battery 10, when the unit cell 11 is in an excessively discharged state, the upper limit voltage Vlim increases and the unit cell 11 is in an excessively charged state. Sometimes, the upper limit voltage Vlim decreases.

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 (1)

A control device for controlling the charging of the secondary battery so that the charging power of the secondary battery does not exceed the upper limit value,
A current sensor for detecting current during charging and discharging of the secondary battery;
An evaluation value for evaluating a deterioration component that degrades the input / output performance of the secondary battery in accordance with the bias of the ion concentration in the secondary battery is calculated from the charge / discharge state detected using the current sensor. A controller, and
The controller increases the upper limit value when it is determined that the ion concentration distribution in the secondary battery is in an excessive discharge state using a value obtained by integrating the evaluation values exceeding the target value on the discharge side. A control device characterized by.