JP2014157662A - Battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress excessive limitation of output of a secondary battery while suppressing deterioration of the secondary battery.SOLUTION: A battery system comprises: a current sensor (202) for detecting a current value of a secondary battery (1) during charge/discharge; and a controller (300) for controlling discharge of the secondary battery so that discharge power of the secondary battery does not exceed an upper limit value. The controller calculates an evaluation value from a charge/discharge state detected using the current sensor. The evaluation value is a value for evaluating a deterioration component which raises internal resistance of the secondary battery accompanying lack of uniformity of salt concentration caused by the discharge of the secondary battery. The controller decreases the upper limit value as a value related to the evaluation value has reached a first threshold. The controller increases the first threshold when a value related to the internal resistance of the secondary battery is smaller than a second threshold.

Description

  The present invention relates to a battery system that can improve the output performance of a secondary battery according to the secondary battery.

  In the technique described in Patent Document 1, in order to suppress the deterioration of the secondary battery due to the high-rate discharge, an evaluation value for evaluating the deterioration of the secondary battery is defined, and when the evaluation value exceeds the target value, The discharge (output) of the secondary battery is limited.

JP 2009-123435 A

  In the technique described in Patent Literature 1, if the target value is fixed, the discharge of the secondary battery may be excessively limited. There are cases where manufacturing variations occur in the secondary battery, and variations in the output performance of the secondary battery may occur along with the manufacturing variations.

  Here, in all the secondary batteries, if the target value is fixed based on the viewpoint of suppressing deterioration due to high-rate discharge, depending on the secondary battery, although the evaluation value has reached the target value. In some cases, deterioration due to high-rate discharge is acceptable. In this case, since the evaluation value exceeds the target value, discharge of the secondary battery is limited. That is, the output performance of the secondary battery cannot be fully exhibited.

  The battery system according to the present invention includes a current sensor that detects a current value at the time of charge and discharge of the secondary battery, a controller that controls the discharge of the secondary battery so that the discharge power of the secondary battery does not exceed the upper limit value, Have The controller calculates an evaluation value from the charge / discharge state detected using the current sensor. The evaluation value is a value for evaluating a deteriorating component that increases the internal resistance of the secondary battery as the salt concentration is biased by the discharge of the secondary battery.

  Here, the controller decreases the upper limit value in response to the value relating to the evaluation value reaching the first threshold value. Further, the controller increases the first threshold when the value related to the internal resistance of the secondary battery is smaller than the second threshold.

  In the present invention, the upper limit value is decreased in response to the value related to the evaluation value reaching the first threshold value. In other words, the upper limit value is not decreased unless the value related to the evaluation value reaches the first threshold value. It will be. Here, the discharge (output) of the secondary battery is limited by lowering the upper limit value.

  When the value related to the internal resistance of the secondary battery is smaller than the second threshold, an increase in the internal resistance can be allowed. In other words, it is possible to allow an increase in internal resistance due to the above-described deterioration component without limiting the discharge (output) of the secondary battery. Therefore, in the present invention, by increasing the first threshold value, it is difficult for the value related to the evaluation value to reach the first threshold value, and the discharge (output) of the secondary battery is hardly restricted. Thereby, the output performance of a secondary battery can be improved.

  Further, when the first threshold value is increased, the value related to the internal resistance does not reach the second threshold value. That is, the first threshold value is increased while confirming that the value related to the internal resistance has not reached the second threshold value. Thereby, it can confirm that the internal resistance of a secondary battery is not increasing too much, and it can improve the output performance of a secondary battery, protecting a secondary battery.

  As described above, in the present invention, since the first threshold value is changed while grasping the actual internal resistance of the secondary battery, even when the output performance of the secondary battery varies. The output performance corresponding to this variation can be ensured. That is, the output performance can be sufficiently exhibited for each secondary battery.

  When the value related to the internal resistance reaches the second threshold value, the first threshold value can be lowered. If the first threshold value is decreased, the value related to the evaluation value can easily reach the first threshold value, and the discharge (output) of the secondary battery can be limited by the decrease in the upper limit value. If the discharge of the secondary battery is restricted, the salt concentration unevenness can be suppressed, and the increase in internal resistance due to the salt concentration unevenness can be suppressed.

  As the value related to the evaluation value, the evaluation value itself can be used. Further, when the evaluation value exceeds the target value, a value obtained by integrating the evaluation values exceeding the target value (integrated value) can be used as a value related to the evaluation value. The integrated value may be a value obtained by integrating the difference between the target value and the evaluation value, or may be a value obtained by integrating the evaluation value itself when the target value is exceeded. Here, the first threshold value may be set according to the value related to the evaluation value.

  As the value related to the internal resistance, a value resulting from the above-described degradation component can be used. In addition, as a value related to the internal resistance, the above-described deterioration component (referred to as a first deterioration component) and a deterioration component (referred to as a second deterioration component) that increase the internal resistance of the secondary battery due to wear of the material constituting the secondary battery Values resulting from and can also be used.

  The internal resistance of the secondary battery may include an internal resistance due to the first deterioration component and an internal resistance due to the second deterioration component. As described above, in the present invention, since an increase in internal resistance due to a deviation in salt concentration is allowed, the value related to the internal resistance includes at least the internal resistance due to the first deterioration component. Just do it.

  Here, when using a value due to only the first deterioration component as a value related to the internal resistance, the internal resistance due to the second deterioration component may be subtracted from the internal resistance of the secondary battery. The second deterioration component can be estimated from the period in which the secondary battery is used.

  In addition, since the first deterioration component is generated due to the salt concentration unevenness, the first deterioration component is not generated if the salt concentration unevenness is eliminated. Therefore, if the internal resistance of the secondary battery is calculated in a state where the first deterioration component is not generated, this internal resistance becomes the internal resistance due to the second deterioration component. Thus, it is possible to learn the internal resistance due to the second deterioration component.

  As the value related to the internal resistance, the value of the internal resistance itself can be used, or the resistance change rate can also be used. The rate of change in resistance can be represented by a ratio (Rc / Rini) of the internal resistance (Rini) of the secondary battery before deterioration and the internal resistance (Rc) of the secondary battery after deterioration. Here, the resistance change rate increases from 1 as the deterioration of the secondary battery progresses.

  The secondary battery can be mounted on a vehicle. If electric energy when the secondary battery is discharged is converted into kinetic energy, the vehicle can be driven using this kinetic energy. Moreover, a lithium ion secondary battery can be used as a secondary battery.

It is a figure which shows the structure of a battery system. It is a flowchart which shows the process which controls discharge (output) of an assembled battery. It is a flowchart which shows the process which controls discharge (output) of an assembled battery. It is a figure which shows the relationship between battery temperature and a forgetting factor. It is a figure which shows the relationship between battery temperature and a limit value. It is a figure explaining the method of calculating an integrated value with respect to the change of an evaluation value. It is a flowchart which shows the process which changes the threshold value E based on resistance change rate. It is a figure which shows the resistance change rate and the change (an example) of the threshold value E. It is the schematic which shows the structure of a secondary battery. It is a figure explaining the salt concentration distribution of the electrolyte solution in a secondary battery. It is a figure which shows the relationship between the salt concentration of electrolyte solution, and reaction resistance. It is a figure explaining the fall of the salt concentration of the electrolyte solution in an electrode. It is a figure explaining the fall of the salt concentration of the electrolyte solution in an electrode. It is a figure which shows the list of variables etc. which are used with a battery model type | formula. It is a conceptual diagram explaining a battery model. It is a conceptual diagram which shows the active material model shown by the polar coordinate. It is a figure which shows the relationship between the terminal voltage of a secondary battery, and various average electric potential. It is a figure explaining the temperature dependence of a diffusion coefficient. It is a figure which shows the relationship between an open circuit voltage (positive electrode) and local SOC. It is a figure which shows the relationship between an open circuit voltage (negative electrode) and local SOC. It is the schematic which shows the internal structure of a controller. It is a correlation diagram between the salt concentration of the electrolyte solution between electrodes, and an electric current estimation error.

  Examples of the present invention will be described below.

  FIG. 1 is a diagram illustrating a configuration of a battery system according to the present embodiment. The battery system shown in FIG. 1 can be mounted on a vehicle. Vehicles include HV (Hybrid Vehicle), PHV (Plug-in Hybrid Vehicle), and EV (Electric Vehicle). Note that the present invention can be applied to any system that charges and discharges secondary batteries.

  The HV includes other power sources such as an internal combustion engine or a fuel cell in addition to an assembled battery described later as a power source for running the vehicle. In PHV, an assembled battery can be charged using power from an external power source in HV. The EV includes only the assembled battery as a power source of the vehicle, and can receive the power supply from the external power source to charge the assembled battery. The external power source is a power source (for example, commercial power source) provided separately from the vehicle outside the vehicle.

  The assembled battery 100 includes a plurality of secondary batteries 1 that are electrically connected in series. Examples of the secondary battery 1 as a single battery include a nickel metal hydride battery and a lithium ion battery. The number of secondary batteries 1 can be appropriately set based on the required output of the assembled battery 100 and the like.

  The positive electrode of the secondary battery 1 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 secondary battery 1 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 the secondary battery 1 is charged, the positive electrode releases ions into the electrolytic solution, and the negative electrode occludes ions in the electrolytic solution. Further, when the secondary battery 1 is discharged, the positive electrode occludes ions in the electrolytic solution, and the negative electrode releases ions into the electrolytic solution.

  In the assembled battery 100 of the present embodiment, all the secondary batteries 1 are electrically connected in series, but the present invention is not limited to this. That is, the assembled battery 100 can include a plurality of secondary batteries 1 electrically connected in parallel. The monitoring unit 201 detects the voltage value Vb of the assembled battery 100, detects the voltage value Vb of each secondary battery 1, and outputs the detection result to the controller 300.

  When the plurality of secondary batteries 1 constituting the assembled battery 100 are divided into a plurality of battery blocks, the monitoring unit 201 can also detect the voltage value Vb of each battery block. Each battery block is composed of a plurality of secondary batteries 1 electrically connected in series, and the assembled battery 100 is configured by electrically connecting the plurality of battery blocks in series.

  The current sensor 202 detects the current value Ib flowing through the assembled battery 100 and outputs the detection result to the controller 300. In this embodiment, the current value Ib at the time of discharging is a positive value (Ib> 0), and the current value Ib at the time of charging is a negative value (Ib <0). In the present embodiment, the current sensor 202 is provided in the positive electrode line PL connected to the positive electrode terminal of the assembled battery 100, but the present invention is not limited to this. That is, the current sensor 202 only needs to detect the current value Ib. For example, the current sensor 202 can be provided on the negative electrode line NL connected to the negative electrode terminal of the assembled battery 100. A plurality of current sensors 202 can also be provided.

  The temperature sensor 203 detects the temperature Tb of the assembled battery 100 (secondary battery 1) and outputs the detection result to the controller 300. The number of temperature sensors 203 can be set as appropriate. Here, if a plurality of temperature sensors 203 are used, the temperatures Tb of the plurality of secondary batteries 1 arranged at different positions can be detected.

  The controller 300 includes a memory 300a, and the memory 300a stores various types of information for the controller 300 to perform predetermined processing (for example, processing described in the present embodiment). In this embodiment, the memory 300a is built in the controller 300, but the memory 300a can be provided outside the controller 300.

  A system main relay SMR-B is provided in the positive electrode line PL. System main relay SMR-B is switched between ON and OFF by receiving a control signal from controller 300. A system main relay SMR-G is provided in the negative electrode line NL. System main relay SMR-G is switched between on and off by receiving a control signal from controller 300.

  A system main relay SMR-P and a current limiting resistor 204 are electrically connected in parallel to the system main relay SMR-G. System main relay SMR-P and current limiting resistor 204 are electrically connected in series. System main relay SMR-P is switched between ON and OFF by receiving a control signal from controller 300. The current limiting resistor 204 is used to suppress inrush current from flowing when the assembled battery 100 is connected to a load (specifically, the inverter 205).

  When connecting the assembled battery 100 to the inverter 205, the controller 300 first switches the system main relay SMR-B from off to on and switches the system main relay SMR-P from off to on. As a result, a current flows through the current limiting resistor 204.

  Next, the controller 300 switches the system main relay SMR-G from off to on and switches the system main relay SMR-P from on to off. Thereby, the connection between the assembled battery 100 and the inverter 205 is completed, and the battery system shown in FIG. 1 is in a start-up state (Ready-On). Information related to the ignition switch of the vehicle is input to the controller 300, and the controller 300 activates the battery system shown in FIG. 1 in response to the ignition switch switching from OFF to ON.

  On the other hand, when the ignition switch is switched from on to off, the controller 300 switches the system main relays SMR-B and SMR-G from on to off. Thereby, the connection between the assembled battery 100 and the inverter 205 is cut off, and the battery system shown in FIG. 1 enters a stopped state (Ready-Off).

  The inverter 205 converts the DC power from the assembled battery 100 into AC power and outputs the AC power to the motor / generator 206. For example, a three-phase AC motor can be used as the motor / generator 206. Motor generator 206 receives AC power from inverter 205 and generates kinetic energy for running the vehicle. The kinetic energy generated by the motor / generator 206 is transmitted to the wheels so that the vehicle can run.

  When the vehicle is decelerated or stopped, the motor generator 206 converts kinetic energy generated during braking of the vehicle into electrical energy (AC power). The inverter 205 converts the AC power generated by the motor / generator 206 into DC power, and outputs the DC power to the assembled battery 100. Thereby, the assembled battery 100 can store regenerative electric power.

  In this embodiment, the assembled battery 100 is connected to the inverter 205, but the present invention is not limited to this. Specifically, a booster circuit can be provided in a current path connecting the assembled battery 100 and the inverter 205. The booster circuit can boost the output voltage of the assembled battery 100 and output the boosted power to the inverter 205. Further, the booster circuit can step down the output voltage of the inverter 205 and output the reduced power to the assembled battery 100.

  When the secondary battery 1 is continuously charged or discharged, the internal resistance of the secondary battery 1 increases depending on the current rate (particularly, the high rate) at the time of charging and discharging, and the input / output performance of the secondary battery 1 is reduced. There may be a phenomenon that begins to drop rapidly. If this phenomenon occurs continuously, the secondary battery 1 may be deteriorated, and such deterioration is called high-rate deterioration. As one of the causes of the high rate deterioration, it is considered that the salt concentration in the electrolyte solution of the secondary battery 1 is biased by continuously performing charging or discharging at a high rate. In high-rate charging and high-rate discharging, the salt concentration is in an opposite state.

  In this embodiment, charging / discharging of the secondary battery 1 (the assembled battery 100) is controlled so that high-rate deterioration can be suppressed. In particular, in this embodiment, the discharge of the secondary battery 1 is controlled in order to suppress deterioration due to high-rate discharge.

  Here, in this embodiment, an evaluation value D (N) is defined as a value for evaluating high-rate deterioration. Based on the evaluation value D (N), charge / discharge control for suppressing high rate deterioration is performed.

  Charge / discharge control based on the evaluation value D (N) will be described using the flowcharts shown in FIGS. The processing shown in FIGS. 2 and 3 is repeatedly performed at a preset time interval (cycle time). The processes shown in FIGS. 2 and 3 are executed by the controller 300.

  In step S101, the controller 300 detects the current value Ib based on the output signal of the current sensor 202. When the battery pack 100 is being discharged, the current value Ib is a positive value, and when the battery pack 100 is being charged, the current value Ib is a negative value.

  In step S102, the controller 300 calculates (estimates) the SOC (State Of Charge) of the assembled battery 100 based on the current value Ib detected in the process of step S101. The SOC is the ratio of the current charge capacity to the full charge capacity. The controller 300 can calculate the SOC of the assembled battery 100 by accumulating the current value Ib when the assembled battery 100 is charged and discharged.

  On the other hand, the SOC of the assembled battery 100 can be estimated based on the voltage value Vb of the assembled battery 100 detected by the monitoring unit 201. Since the SOC of the assembled battery 100 has a corresponding relationship with the OCV (Open Circuit Voltage) of the assembled battery 100, the SOC can be specified from the OCV if the corresponding relationship between the SOC and the OCV is obtained in advance. The OCV can be obtained from the voltage value Vb (CCV: Closed Circuit Voltage) of the assembled battery 100 and the voltage change amount due to the internal resistance of the assembled battery 100.

  Here, when the assembled battery 100 is not charged / discharged, the OCV of the assembled battery 100 can be detected using the monitoring unit 201. Note that the method of estimating the SOC of the battery pack 100 is not limited to the above-described method, and a known method can be appropriately employed.

  In step S103, the controller 300 detects the temperature Tb of the assembled battery 100 based on the output signal of the temperature sensor 203. In step S104, the controller 300 calculates a forgetting factor based on the SOC calculated in the process of step S102 and the battery temperature Tb detected in the process of step S103. The forgetting factor is a factor corresponding to the diffusion rate of ions in the electrolyte solution of the secondary battery 1. The forgetting factor is set in 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. 2 and 3 are repeated.

  For example, the controller 300 can specify the forgetting factor A using the map shown in FIG. In FIG. 4, the vertical axis represents the forgetting factor A, and the horizontal axis represents the temperature Tb of the assembled battery 100. The map shown in FIG. 4 can be acquired in advance by an experiment or the like, and can be stored in the memory 300a.

  In the map shown in FIG. 4, the forgetting factor A can be specified by specifying the SOC calculated in the process of step S102 and the battery temperature Tb detected in the process of step S103. The forgetting factor A increases as the ion diffusion rate increases. Therefore, as shown in FIG. 4, if the temperature Tb of the assembled battery 100 is the same, the forgetting factor A increases as the SOC of the assembled battery 100 increases. If the SOC of the assembled battery 100 is the same, the forgetting factor A increases as the temperature Tb of the assembled battery 100 increases.

  In step S105, the controller 300 calculates a decrease amount D (−) of the evaluation value D. The decrease amount D (−) of the evaluation value D is associated with the diffusion of ions from the time when the previous (most recent) evaluation value D (N−1) is calculated until one cycle time Δt elapses. Calculated according to the decrease in salt concentration bias. For example, the controller 300 can calculate the decrease amount D (−) of the evaluation value D 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) indicates an evaluation value calculated last time (most recent time). The evaluation value D (0) as the 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 decrease amount D (−) of the evaluation value D increases. In other words, the greater the forgetting factor A or the longer the cycle time Δt, the greater the reduction amount D (−) of the evaluation value 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 that can specify a decrease in the salt concentration bias may be used.

  In step S106, the controller 300 reads the current coefficient stored in advance in the memory 300a. In step S107, the controller 300 calculates a limit value based on the SOC of the assembled battery 100 calculated in the process of step S102 and the battery temperature Tb detected in the process of step S103.

  For example, the controller 300 can calculate the limit value using the map shown in FIG. The map shown in FIG. 5 can be acquired in advance by experiments or the like, and can be stored in the memory 300a. In FIG. 5, the vertical axis represents the limit value, and the horizontal axis represents the temperature Tb of the assembled battery 10. In the map shown in FIG. 5, the limit value can be specified by specifying the SOC calculated in the process of step S102 and the battery temperature Tb detected in the process of step S103.

  In the map shown in FIG. 5, if the temperature Tb of the assembled battery 100 is the same, the limit value increases as the SOC of the assembled battery 100 increases. If the SOC of the assembled battery 100 is the same, the limit value increases as the temperature Tb of the assembled battery 100 increases.

  In step S108, the controller 300 calculates the increase amount D (+) of the evaluation value D. The increase amount D (+) of the evaluation value D is the salt concentration accompanying discharge from the time when the previous (most recent) evaluation value D (N-1) is calculated until one cycle time Δt elapses. It is calculated according to an increase in the bias. For example, the controller 300 can calculate the increase amount D (+) of the evaluation value D 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. Ib indicates a current value, and the value detected in the process of step S101 is used. Δt is the cycle time.

  As can be seen from the above formula (3), the larger the current value Ib or the longer the cycle time Δt, the larger the increase D (+) of the evaluation value D. Note that the calculation method of the increase amount D (+) is not limited to the calculation method described in the present embodiment, and any method that can specify an increase in the salt concentration bias may be used.

  In step S109, the controller 300 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 (most recent) cycle time Δt. The evaluation value D (0) as the initial value can be set to 0, for example. D (−) represents the amount of decrease in the evaluation value D, and the value calculated in the process of step S105 is used. D (+) indicates the increase amount of the evaluation value D, and the value calculated in the process of step S108 is used.

  In this example, as shown in the above formula (4), the evaluation value D (N) is considered in consideration of the increase D (+) in the salt concentration bias and the decrease D (−) in the salt concentration bias. ) Can be calculated. Thereby, the change (increase / decrease) in the salt concentration bias considered to be a cause of 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 the state of the assembled battery 100 is to the state where the high rate deterioration occurs.

  In the present embodiment, the evaluation value D (N) is calculated for the assembled battery 100, but is not limited thereto. Specifically, the evaluation value D (N) can be calculated for each secondary battery 1 or each battery block. In this case, the evaluation value D (N) may differ depending on the secondary battery 1 or the battery block. When the evaluation value D (N) varies, for example, the largest evaluation value D (N) can be specified, and control described later can be performed based on the evaluation value D (N).

  In step S110, the controller 300 determines whether or not the evaluation value D (N) calculated in the process of step S109 is larger than a predetermined target value Dtar (+). 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 evaluation value D (N) is larger than the target value Dtar (+), the process proceeds to step S111. On the other hand, if the evaluation value D (N) is smaller than the target value Dtar (+), the process proceeds to step S117.

  In this embodiment, as shown in FIG. 6, the target value Dtar (+) is set on the plus side of the evaluation value D (N). The target value Dtar (+) is a positive value. FIG. 6 is a diagram illustrating a change (an example) in the evaluation value D (N). In FIG. 6, the vertical axis represents the evaluation value D (N), and the horizontal axis represents time.

  In step S111, the controller 300 integrates the evaluation values D (N). Specifically, as shown in FIG. 6, when the evaluation value D (N) is larger than the target value Dtar (+), a portion of the evaluation value D (N) that is larger than the target value Dtar (+) ( Integration is performed for the hatched area in FIG. 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 to obtain an integrated value ΣDex (N). Since the integrated evaluation value D (N) is a positive value, the integrated value ΣDex (N) is also a positive value.

  In this embodiment, when the integrated value ΣDex (N) is calculated, the difference between the evaluation value D (N) and the target value Dtar (+) is integrated, but the present invention is not limited to this. Specifically, when the evaluation value D (N) is larger than the target value Dtar (+), the evaluation value D (N) itself is integrated instead of the difference between the evaluation value D (N) and the target value Dtar (+). can do. In this case, a threshold E described later may be set in consideration of integrating the evaluation values D (N) itself.

  In step S112, the controller 30 determines whether or not the integrated value ΣDex (N) is smaller than the threshold value E. The threshold value E (corresponding to the first threshold value of the present invention) E is an upper limit value for allowing high-rate deterioration due to discharge, and is a positive value. That is, until the integrated value ΣDex (N) exceeds the threshold value E, high rate deterioration can be allowed. In other words, when the integrated value ΣDex exceeds the threshold value E, high-rate deterioration cannot be allowed, so that the discharge of the assembled battery 100 is limited as will be described later.

  The high rate deterioration occurs due to the salt concentration unevenness, and the salt concentration unevenness depends on the temperature Tb, SOC, and current value Ib of the secondary battery 1. For this reason, the evaluation value D (N) and the integrated value ΣDex (N) also depend on the temperature Tb, SOC, and current value Ib of the secondary battery 1. Therefore, the threshold value E can be set according to the temperature Tb, SOC, and current value Ib of the secondary battery 1.

  Specifically, first, a correspondence relationship between at least one of the battery temperature Tb, the SOC, and the current value Ib and the threshold value E can be obtained in advance by an experiment or the like. If this correspondence is used, the threshold value E can be specified by specifying at least one of the battery temperature Tb, the SOC, and the current value Ib. In the process shown in FIG. 2, since the current value Ib, the SOC, and the battery temperature Tb are acquired in the processes of steps S101 to S103, the threshold value E is specified using the acquired information.

  In the present embodiment, as described later, the threshold value E is not fixed, but the threshold value E is changed according to the change in the resistance change rate gr. As described above, when at least one of battery temperature Tb, SOC, and current value Ib is associated with threshold E, threshold E specified from at least one of battery temperature Tb, SOC, and current value Ib. Is changed according to the change in the resistance change rate gr.

  If the integrated value ΣDex (N) is smaller than the threshold value E in step S112, the process proceeds to step S113. On the other hand, when the integrated value ΣDex (N) is larger than the threshold value E, the process proceeds to step S114.

  In step S113, the controller 300 sets the output limit value Wout_lim used for the discharge control of the assembled battery 100 to the maximum value Wout_max. The output limit value Wout_lim is an upper limit power value [kW] that allows the assembled battery 100 to be discharged. The controller 300 controls the output (discharge) of the assembled battery 100 so that the output power of the assembled battery 100 does not become higher than the output limit value Wout_lim.

  The maximum value Wout_max can be determined in advance. When limiting the output of the battery pack 100, the output limit value Wout_lim is set to a value smaller than the maximum value Wout_max. The output limit value Wout_lim can be changed between the maximum value Wout_max and the minimum value. The minimum value of the output limit value can be set to 0 [kW], for example. In this case, the assembled battery 100 is not discharged.

  In step S114, the controller 300 sets the output limit value Wout_lim to a value smaller than the maximum value Wout_max. When the process proceeds from step S112 to step S114, since the high-rate deterioration cannot be allowed, the output of the assembled battery 100 is limited by reducing the output limit value Wout_lim. Here, the output of the assembled battery 100 is limited as the output limit value Wout_lim is decreased.

  For example, the controller 300 can set the amount by which the output limit value Wout_lim is decreased with respect to the maximum value Wout_max in accordance with the difference between the integrated value ΣDex (N) and the threshold value E. Specifically, the controller 300 can calculate the output limit value Wout_lim based on the following formula (5).

  In the above formula (5), L represents a coefficient. E represents the threshold value described in the process of step S112. The value of “L × (E−ΣDex (N))” shown in the above equation (5) indicates the amount by which the output limit value Wout_lim is decreased. By changing the coefficient L, the output limit value Wout_lim is decreased. The amount can be adjusted. Specifically, the amount of decrease can be adjusted in consideration of vehicle drivability.

  In step S <b> 115, the controller 300 transmits a command related to output control of the assembled battery 100 to the inverter 205. This command includes information related to the output limit value Wout_lim set in the process of step S113 or step S114. Thereby, the output of the assembled battery 100 is controlled so that the output power of the assembled battery 100 does not exceed the output limit value Wout_lim.

  In step S116, the controller 300 stores the current evaluation value D (N) and the integrated value ΣDex (N) in the memory 300a. By storing the evaluation value D (N) in the memory 300a, a change in the evaluation value D (N) can be monitored. Further, by storing the integrated value ΣDex (N) in the memory 300a, the integrated value ΣDex (N) is updated when the next evaluation value D (N + 1) becomes larger than the target value Dtar (+). Can do.

  When the process proceeds from step S110 to step S117, the controller 300 stores the evaluation value D (N) in the memory 300a. When the process proceeds from step S110 to step S117, since the integrated value ΣDex (N) is not calculated, only the current evaluation value D (N) is stored in the memory 300a. Thereby, the change of the evaluation value D (N) can be monitored.

  As described above, according to the processing shown in FIGS. 2 and 3, the output control (feedforward control) of the secondary battery 1 is performed so that the integrated value ΣDex (N) does not reach the threshold value E.

  According to the present embodiment, when the integrated value ΣDex (N) is larger than the threshold value E, high rate deterioration due to discharge can be suppressed by limiting the output of the assembled battery 100. If the output of the assembled battery 100 is limited, it is possible to suppress an uneven salt concentration. Here, since the high rate deterioration occurs due to the salt concentration unevenness, the high rate deterioration can be suppressed by suppressing the salt concentration unevenness.

  By limiting the output of the assembled battery 100 in this way, the integrated value ΣDex (N) can be changed in a direction smaller than the threshold value E. On the other hand, the output limit value Wout_lim remains set at the maximum value Wout_max until the integrated value ΣDex (N) reaches the threshold value E, so that the output power of the assembled battery 100 can be ensured to the maximum.

  In the present embodiment, the evaluation value D (N) is stored in the memory 300a for each cycle time Δt, and the current evaluation value D (N−1) is stored using the previous (most recent) evaluation value D (N−1) stored in the memory 300a. Although D (N) is calculated, the present invention is not limited to this. For example, the evaluation value D (N) can be calculated based on the history of the current value Ib.

  Since the evaluation value D (N) changes according to the change in the current value Ib, the evaluation value D (N) can be calculated if the history of the current value Ib is acquired. For example, only the history of the current value Ib can be stored in the memory 300a, and the evaluation value D (N) at a specific cycle time Δt can be calculated using the history of the current value Ib.

  Further, in this embodiment, when the integrated value ΣDex (N) exceeds the threshold value E, the output of the assembled battery 100 is limited. However, the present invention is not limited to this. Specifically, when the evaluation value D (N) exceeds the target value Dtar (+), the output of the assembled battery 100 can be limited. When limiting the output of the assembled battery 100, the output limit value Wout_lim can be calculated in the same manner as in the above equation (5).

  Specifically, in the above formula (5), the target value Dtar (+) can be used instead of the threshold value E, and the evaluation value D (N) can be used instead of the integrated value ΣDex (N). When the output of the battery pack 100 is limited in response to the evaluation value D (N) exceeding the target value Dtar (+), as in the case of changing the threshold value E, according to the change in the resistance change rate gr, The target value Dtar (+) can be changed.

  Next, processing for changing the threshold value E will be described. In the present embodiment, as will be described below, the resistance change rate gr of the secondary battery 1 is calculated, and the threshold value E is changed according to the relationship between the resistance change rate gr and the threshold value R. Here, the threshold value (corresponding to the second threshold value of the present invention) R is a value related to the resistance change rate gr.

  First, the resistance change rate gr can be expressed by the following formula (6).

  In the above formula (6), Rini is the internal resistance when the secondary battery 1 is in the initial state, and Rc is the current internal resistance of the secondary battery 1. The initial state is a state in which the secondary battery 1 is not deteriorated, for example, a state immediately after the secondary battery 1 is manufactured. When the secondary battery 1 is not deteriorated, the internal resistance of the secondary battery 1 is Rini, and the resistance change rate gr remains “1”. Generally, as the secondary battery 1 continues to be used, the internal resistance of the secondary battery 1 increases. Therefore, if the secondary battery 1 is used continuously, the resistance change rate gr becomes larger than “1”.

  The internal resistance Rini can be obtained in advance, and information regarding the internal resistance Rini can be stored in the memory 300a. The internal resistance Rc can be calculated based on the current value Ib and the voltage value Vb of the secondary battery 1 as will be described later. If the internal resistance Rc is calculated, the resistance change rate gr can be calculated.

  In the present embodiment, after confirming that the resistance change rate gr calculated from the above equation (6) is larger than the threshold value R, the control for suppressing the high rate deterioration is started. Here, the threshold value R is a value set on the basis of the maximum value of the resistance change rate gr that can permit the use (charge / discharge) of the secondary battery 1. When the resistance change rate gr of the secondary battery 1 reaches the maximum value, the secondary battery 1 becomes unusable.

  Specifically, the maximum value of the resistance change rate gr may be set as the threshold value R, and a value lower than the maximum value of the resistance change rate gr by a predetermined value may be set as the threshold value R. Here, if the threshold value R is set to a value lower than the maximum value of the resistance change rate gr, a margin can be provided between the threshold value R and the maximum value, and the actual resistance change rate gr has the maximum value. It can suppress exceeding. The threshold value R can be set in advance in consideration of the input / output characteristics of the secondary battery 1 and the information on the threshold value R can be stored in the memory 300a.

  The internal resistance of the secondary battery 1 changes according to the temperature and SOC of the secondary battery 1. For this reason, the threshold value R regarding the resistance change rate gr can also be set according to the temperature Tb and SOC of the secondary battery 1. Specifically, a map indicating a correspondence relationship between the threshold value R and at least one of the battery temperature Tb and the SOC can be determined in advance by an experiment or the like.

  Using this map, by specifying at least one of battery temperature Tb and SOC, threshold R corresponding to at least one of battery temperature Tb and SOC can be specified. Note that a map indicating the correspondence relationship between the threshold value R and at least one of the battery temperature Tb and the SOC can be stored in the memory 300a.

  The internal resistance of the secondary battery 1 includes internal resistance accompanying wear deterioration in addition to the internal resistance accompanying high rate deterioration described above. The wear deterioration is a deterioration of the material constituting the secondary battery 1 by continuing to use the secondary battery 1. If the internal resistance of the secondary battery 1 increases due to wear deterioration, the resistance change rate gr also increases. On the other hand, since the high rate deterioration occurs due to the salt concentration unevenness, if the salt concentration unevenness is alleviated, the internal resistance accompanying the high rate deterioration is reduced, and the resistance change rate gr is also reduced.

  For this reason, when the high-rate deterioration and the wear deterioration are mixed in the deterioration state of the secondary battery 1, the resistance change rate gr increases or decreases. Since wear deterioration is a deteriorating component that cannot be eliminated, the internal resistance accompanying wear deterioration continues to rise. On the other hand, the internal resistance accompanying high-rate deterioration increases or decreases depending on the salt concentration bias. Therefore, in the secondary battery 1 in which high rate deterioration and wear deterioration coexist, the resistance change rate gr increases or decreases.

  In the present embodiment, the controller 300 increases the threshold E until the resistance change rate gr exceeds the threshold R. When the resistance change rate gr exceeds the threshold value R, the controller 300 reduces the threshold value E.

  If the resistance change rate gr does not reach the threshold value R, an increase in internal resistance due to high rate deterioration can be allowed. That is, if the resistance change rate gr does not exceed the threshold value R, the output restriction of the secondary battery 1 can be relaxed. As described above, the output limit value Wout_lim of the secondary battery 1 is set according to the magnitude relationship between the integrated value ΣDex (N) and the threshold value E.

  Here, if the threshold value E is raised, the integrated value ΣDex (N) does not easily reach the threshold value E, and the output of the secondary battery 1 is not limited. That is, the output limit value Wout_lim of the secondary battery 1 can be set to the maximum value Wout_max. Therefore, when the resistance change rate gr does not reach the threshold value R, the threshold value E can be increased. Thus, the output performance of the secondary battery 1 can be improved by increasing the threshold value E and relaxing the output restriction of the secondary battery 1.

  When the target value Dtar (+) is changed based on the resistance change rate gr, the target value Dtar (+) can be increased while the resistance change rate gr has not reached the threshold value R. . If the target value Dtar (+) is increased, the evaluation value D (N) is less likely to exceed the target value Dtar (+), and the output of the secondary battery 1 can be suppressed from being limited. That is, if the evaluation value D (N) does not exceed the target value Dtar (+), the output limit value Wout_lim can be set to the maximum value Wout_max, and the output performance of the secondary battery 1 can be improved.

  When the control shown in FIGS. 2 and 3 is performed, if the threshold value E is set to a fixed value, the output of the secondary battery 1 may be excessively limited. Manufacturing variations may occur in the secondary battery 1, and variations may also occur in the deterioration state of the secondary battery 1 due to the manufacturing variations. When all the manufactured secondary batteries 1 are to be protected, a threshold value (fixed value) E can be set with reference to the secondary battery 1 that is most likely to deteriorate. Further, among the plurality of secondary batteries 1 whose deterioration states vary, for example, the threshold value (fixed value) E can be set with reference to the secondary battery 1 whose deterioration state shows a median value.

  As described above, when the deterioration state of the secondary battery 1 varies, even if the integrated value ΣDex (N) reaches the threshold value (fixed value) E, depending on the secondary battery 1, high-rate deterioration occurs. May be further tolerated. If the output of the secondary battery 1 is limited in response to the integrated value ΣDex (N) reaching the threshold value (fixed value) E, although the high-rate deterioration can be allowed, the secondary battery The output performance of 1 cannot be fully exhibited. In this case, the output of the secondary battery 1 is excessively limited, and the output performance of the secondary battery 1 cannot be improved.

  Therefore, in this embodiment, the resistance change rate gr indicating the actual deterioration state of the secondary battery 1 is monitored, and if the resistance change rate gr does not reach the threshold value R, the threshold value E is increased. If the threshold value E is changed in this way, output control can be performed in consideration of the actual deterioration state of the secondary battery 1. Accordingly, it is possible to maximize the output performance of the secondary battery 1 while confirming that the resistance change rate gr of the secondary battery 1 is lower than the threshold value R and protecting the secondary battery 1.

  The process for changing the threshold value E will be described with reference to the flowchart shown in FIG. Here, the process shown in FIG. 7 is executed by the controller 300. Further, the process shown in FIG. 7 can be performed at a cycle (cycle time Δt) in which the processes shown in FIGS. 2 and 3 are performed.

  In step S201, the controller 300 calculates the resistance change rate gr of the secondary battery 1. Here, a method of calculating the resistance change rate gr will be described later. In step S202, the controller 300 determines whether or not the resistance change rate gr calculated in the process of step S201 is higher than the threshold value R. When the resistance change rate gr is higher than the threshold value R, the controller 300 performs the process of step S203. On the other hand, when the resistance change rate gr is lower than the threshold value R, the controller 300 performs the process of step S204.

  In step S203, the controller 300 lowers the threshold value E set this time lower than the threshold value E set last time. Here, the amount by which the threshold value E is lowered can be set as appropriate. If the threshold value E is lowered too much, the integrated value ΣDex (N) easily reaches the threshold value E, and the output limit value Wout_lim tends to fall excessively. Thereby, for example, the drivability when the vehicle is driven using the output of the secondary battery 1 may be adversely affected.

  For this reason, it is preferable to gradually lower the threshold E while confirming that the resistance change rate gr is lower than the threshold R. For example, the threshold value E can be lowered at a constant rate of change. Moreover, the change rate (decrease rate) of the threshold value E can be varied. Here, as the difference between the resistance change rate gr and the threshold value R decreases, the change rate (decrease rate) of the threshold value E can be increased. In other words, as the difference between the resistance change rate gr and the threshold value R increases, the change rate (decrease rate) of the threshold value E can be lowered.

  In step S204, the controller 300 raises the threshold value E set this time higher than the threshold value E set last time. Here, the amount by which the threshold value E is raised can be set as appropriate. For example, the threshold E can be increased at a constant rate of change. Further, the change rate (increase rate) of the threshold value E can be varied. For example, as the difference between the resistance change rate gr and the threshold value R increases, the change rate (rise rate) of the threshold value E can be increased. In other words, the smaller the difference between the resistance change rate gr and the threshold value R, the lower the change rate (rising rate) of the threshold value E.

  In step S205, the controller 300 sets a threshold value E. The setting content of the threshold value E differs depending on the processing in step S203 or step S204. Information on the set threshold value E is stored in the memory 300a and is used when the processing shown in FIGS. 2 and 3 is performed next time. In the processing shown in FIG. 7, control (feedback control) for decreasing the threshold E is performed in response to the resistance change rate gr exceeding the threshold R.

  FIG. 8 shows changes (one example) in the resistance change rate gr and the threshold value E when the processes shown in FIGS. 2, 3, and 7 are performed. As shown in FIG. 8, when the secondary battery 1 is in the initial state (time 0), the resistance change rate gr is “1”. When the secondary battery 1 is in the initial state (time 0), the threshold value E is set to the initial value E_ini. The initial value E_ini can be set as appropriate.

  For example, as described above, the initial value E_ini can be set based on the secondary battery 1 that is most likely to deteriorate. Further, the initial value E_ini can be set with reference to the secondary battery 1 whose deterioration state shows the median value. Information regarding the initial value E_ini can be stored in the memory 300a.

  From time 0 to time t1, the resistance change rate gr does not increase and remains “1”. Further, the threshold value E remains at the initial value E_ini from time 0 to time t1. Then, after the time t1, when the resistance change rate gr rises above “1”, the threshold E rises above the initial value E_ini.

  In this embodiment, the threshold value E is increased when the resistance change rate gr is higher than “1”, but the present invention is not limited to this. Specifically, even if the resistance change rate gr remains “1”, the threshold value E can be started to increase. In the example shown in FIG. 8, the threshold E is raised after confirming that the resistance change rate gr has risen above “1”.

  After time t1, the resistance change rate gr continues to increase, but the resistance change rate gr does not reach the threshold value R. For this reason, the threshold value E continues to rise with respect to the initial value E_ini. When the resistance change rate gr reaches the threshold value R at time t2, the threshold value E starts to decrease. As described above, by reducing the threshold value E, the output of the secondary battery 1 is easily limited.

  If the output of the secondary battery 1 is limited, the internal resistance due to the high rate deterioration is easily lowered, and the resistance change rate gr is easily lowered. In the example illustrated in FIG. 8, the resistance change rate gr is decreased and departed from the threshold R by decreasing the threshold E after the time t2.

  If it is confirmed that the resistance change rate gr is reduced and the resistance change rate gr is separated from the threshold value R by a predetermined amount at time t3, the process of reducing the threshold value E can be stopped. That is, after time t3, the threshold value E can be maintained at the value when the threshold value E lowering process is stopped. Then, if it is confirmed that the resistance change rate gr is lower than the threshold value R, the threshold value E can be increased. In the example shown in FIG. 8, the threshold value E is raised before time t4.

  When the resistance change rate gr reaches the threshold value R at time t4, as described above, the increase in the threshold value E stops and the threshold value E starts to decrease. Here, when the resistance change rate gr reaches the threshold value R, the process of increasing the threshold value E is stopped, and the threshold value E can be maintained at this value. However, in this case, the resistance change rate gr tends to exceed the threshold value R. For this reason, as shown in FIG. 8, after the resistance change rate gr reaches the threshold value R, it is preferable to lower the threshold value E until the resistance change rate gr decreases by a predetermined amount with respect to the threshold value R.

  Even if the resistance change rate gr exceeds the threshold value R, the output control shown in FIGS. 2 and 3 is performed based on the threshold value E set when the resistance change rate gr reaches the threshold value R. Therefore, it is possible to suppress the resistance change rate gr from rapidly increasing.

  If the resistance change rate gr suddenly increases, the output limit corresponding to this must be performed, and the output limit value Wout_lim may decrease rapidly. In this case, the drivability when the vehicle is driven using the output of the secondary battery 1 may be adversely affected. If a rapid increase in the resistance change rate gr is suppressed as in the present embodiment, a rapid decrease in the output limit value Wout_lim can be suppressed. Thereby, the bad influence with respect to drivability can be reduced.

  In this embodiment, the resistance change rate gr is calculated, and the threshold value E is changed based on the resistance change rate gr. However, the present invention is not limited to this. As described using the above formula (6), the resistance change rate gr is calculated from the internal resistance Rini when the secondary battery 1 is in the initial state and the current internal resistance Rc of the secondary battery 1. . Here, the resistance change rate gr changes in accordance with the internal resistance Rc. For this reason, the threshold value E can be changed based on the internal resistance Rc instead of the resistance change rate gr.

  When the threshold value E is changed based on the internal resistance Rc, the internal resistance of the secondary battery 1 corresponding to the threshold value R can be used instead of the threshold value R. If the internal resistance Rini when the secondary battery 1 is in the initial state is known, the internal resistance corresponding to the threshold value R can be specified.

  Next, a method for calculating the resistance change rate gr will be described. As described above, the deterioration of the secondary battery 1 is a mixture of high-rate deterioration and wear deterioration. For this reason, if the internal low resistance Rc of the secondary battery 1 is calculated, it is possible to calculate the resistance change rate gr due to the high rate deterioration and wear deterioration. On the other hand, if the resistance change rate gr caused by wear deterioration is specified (estimated), the resistance change rate gr caused by high rate deterioration can be calculated.

  In the process shown in FIG. 7, the resistance change rate gr caused by high rate deterioration and wear deterioration can be used as the resistance change rate gr, or the resistance change rate gr caused by high rate deterioration can be used. Here, since the decrease in the resistance change rate gr is due to the elimination of the high rate deterioration, the resistance change rate gr including the high rate deterioration may be used as the resistance change rate gr used for changing the threshold value E.

  Here, the threshold value R may be appropriately set according to the content of the resistance change rate gr. The threshold value R when the resistance change rate gr caused by high rate deterioration and wear deterioration is higher than the threshold value R when the resistance change rate gr caused by high rate deterioration is used.

  The internal resistance Rc of the secondary battery 1 can be calculated from the current value Ib and the voltage value Vb of the secondary battery 1. Specifically, when the secondary battery 1 is being charged / discharged, the current value Ib is detected based on the output of the current sensor 202 and the voltage value Vb is detected based on the output of the monitoring unit 201. Then, the relationship between the detected current value Ib and the voltage value Vb is plotted in a coordinate system having the current value Ib and the voltage value Vb as coordinate axes.

  When the secondary battery 1 is being charged / discharged, the current value Ib is dispersed. Therefore, if a straight line approximating a plurality of points (Ib-Vb relationship) plotted in the coordinate system is calculated, the slope of the approximate straight line can be calculated. It becomes the internal resistance Rc of the secondary battery 1. If the internal resistance Rini when the secondary battery 1 is in the initial state is measured in advance, the resistance change rate gr can be calculated every time the internal resistance Rc is calculated.

  On the other hand, the internal resistance Rc of the secondary battery 1 can also be calculated based on the following formula (7).

  In the above formula (7), CCV (Closed Circuit Voltage) is the voltage value of the secondary battery 1 that is energized, and OCV (Open Circuit Voltage) is the voltage value of the secondary battery 1 that is not energized. Ib is a current value flowing through the secondary battery 1, and Rc is an internal resistance of the secondary battery 1.

  According to the above formula (7), when the secondary battery 1 is charged or discharged, the voltage value CCV changes by “Ib × Rc” with respect to the voltage value OCV. Specifically, since the current value Ib at the time of charging is a negative value, the voltage value CCV when charging the secondary battery 1 is equivalent to “Ib × Rc” with respect to the voltage value OCV. To rise. Further, since the current value Ib at the time of discharging is a positive value, the voltage value CCV when the secondary battery 1 is discharged is reduced by “Ib × Rc” with respect to the voltage value OCV.

  According to the above equation (7), the internal resistance Rc can be calculated by detecting the voltage values CCV, OCV and the current value Ib. If the secondary battery 1 is left without being charged / discharged, the voltage value OCV of the secondary battery 1 can be measured.

  Here, since the secondary battery 1 is polarized due to energization, it is preferable to measure the voltage value OCV of the secondary battery 1 in a state where the polarization is eliminated. For example, if the time during which polarization is eliminated (polarization elimination time) is obtained in advance by experiment or the like, the voltage value OCV of the secondary battery 1 after the polarization elimination time has elapsed after the energization of the secondary battery 1 is stopped. Can be measured.

  After the voltage value OCV of the secondary battery 1 is measured, if the secondary battery 1 is charged or discharged with a constant current value Ib, the voltage value CCV of the secondary battery 1 can be detected. The voltage value OCV measured before energization of the secondary battery 1 and the current value (constant value) Ib and the voltage value CCV detected when the secondary battery 1 is charged or discharged are expressed by the above equation (7). If substituted, the internal resistance Rc can be calculated.

  When the secondary battery 1 is charged using electric power from the external power source, the secondary battery 1 is charged under a constant current. For this reason, if the voltage value OCV of the secondary battery 1 is measured before or after the secondary battery 1 is charged and the voltage value CCV when the secondary battery 1 is charged is detected, the above formula (7) is satisfied. Thus, the internal resistance Rc of the secondary battery 1 can be calculated.

  If the internal resistance Rini when the secondary battery 1 is in the initial state is obtained in advance, the resistance change rate gr is calculated every time the internal resistance Rc of the secondary battery 1 is calculated using the above formula (7). can do.

  The internal resistance Rc calculated as described above is the internal resistance of the secondary battery 1 including high rate deterioration and wear deterioration. When grasping the internal resistance associated with high-rate degradation, as described below, the internal resistance associated with wear degradation may be subtracted from the internal resistance including high-rate degradation and wear degradation.

  The internal resistance associated with wear deterioration increases with time. For this reason, the relationship between the internal resistance accompanying wear deterioration and the elapsed time can be obtained in advance by experiments or the like. The elapsed time can be the time after the secondary battery 1 is used for the first time. Here, information indicating the correspondence between the internal resistance and the elapsed time due to wear deterioration can be stored in the memory 300a.

  If the elapsed time up to the present is measured, the internal resistance associated with wear deterioration corresponding to the elapsed time can be specified. Then, by subtracting the internal resistance associated with wear degradation from the internal resistance Rc including high rate degradation and wear degradation, the internal resistance associated with high rate degradation can be calculated. Here, the internal resistance associated with wear degradation is estimated from the elapsed time, but as will be described below, the internal resistance associated with wear degradation can also be learned.

  The high rate deterioration occurs due to a salt concentration unevenness inside the secondary battery 1. For this reason, if the unevenness of the salt concentration is eliminated, the high rate deterioration can be eliminated. The uneven salt concentration can be resolved by leaving the secondary battery 1 without charging / discharging. Therefore, if the time (for example, the maximum time) that can eliminate the uneven concentration of salt is obtained in advance by experiments or the like, the high-rate deterioration is resolved by confirming that this time has passed. Can be determined.

  After confirming that the high-rate deterioration has been eliminated, if the internal resistance Rc of the secondary battery 1 is calculated as described above, the internal resistance Rc becomes an internal resistance accompanying wear deterioration. As described above, if the internal resistance associated with wear deterioration is learned, the internal resistance associated with high-rate deterioration can be specified based on the internal resistance Rc calculated after learning.

  Specifically, the internal resistance Rc calculated when high-rate deterioration occurs is higher than the internal resistance (learned value) associated with wear deterioration. For this reason, if the internal resistance (learned value) accompanying wear deterioration is subtracted from the calculated internal resistance Rc, the internal resistance accompanying high-rate deterioration can be specified.

  The time for the internal resistance to change with wear deterioration is longer than the time for the internal resistance to change with high-rate deterioration. For this reason, after learning the internal resistance associated with wear degradation, the internal resistance associated with wear degradation is less likely to change than the internal resistance associated with high rate degradation. Therefore, if the internal resistance associated with wear deterioration is learned, the internal resistance associated with high-rate deterioration can be specified as described above. Here, by learning the internal resistance associated with wear deterioration, the estimation accuracy of the internal resistance associated with high rate deterioration can be improved.

  On the other hand, the resistance change rate gr of the secondary battery 1 can be calculated (estimated) using a battery model described below. First, the battery model will be described.

  FIG. 9 is a schematic diagram showing the configuration of the secondary battery 1. The secondary battery 1 includes a negative electrode (also referred to as an electrode) 12, a separator 14, and a positive electrode (also referred to as an electrode) 15. The separator 14 is located between the negative electrode 12 and the positive electrode 15 and contains an electrolytic solution. A coordinate axis x shown in FIG. 9 indicates a position in the thickness direction of the electrode.

Each of the negative electrode 12 and the positive electrode 15 is composed of an aggregate of spherical active materials 18. When the secondary battery 1 is discharged, a chemical reaction that releases lithium ions Li ⁺ and electrons e ⁻ is performed on the interface of the active material 18 of the negative electrode 12. Further, a chemical reaction that absorbs lithium ions Li ⁺ and electrons e ⁻ is performed on the interface of the active material 18 of the positive electrode 15. On the other hand, when the secondary battery 1 is charged, a chemical reaction opposite to the above-described chemical reaction is performed on the interface of the active material 18 in the positive electrode 12 and the negative electrode 15.

The negative electrode 12 has a current collector plate 13 made of copper or the like, and the current collector plate 13 is electrically connected to the negative electrode terminal 11 n of the secondary battery 1. The positive electrode 15 has a current collector plate 16 made of aluminum or the like, and the current collector plate 16 is electrically connected to the positive electrode terminal 11 p of the secondary battery 1. The secondary battery 1 is charged / discharged by the exchange of lithium ions Li ⁺ between the negative electrode 12 and the positive electrode 15, and a charging current Ib (Ib <0) or a discharging current Ib (Ib> 0) is generated.

When the secondary battery 1 is discharged, lithium ions Li ⁺ released from the negative electrode 12 move to the positive electrode 15 by diffusion and migration and are absorbed by the positive electrode 15. At this time, if a delay occurs in the diffusion of lithium ions Li ⁺ in the electrolytic solution, the lithium ion Li ⁺ concentration (that is, the salt concentration of the electrolytic solution) increases in the electrolytic solution in the negative electrode 12. On the other hand, in the electrolytic solution in the positive electrode 15, the lithium ion Li ⁺ concentration decreases. This is shown in FIG. The average salt concentration shown in FIG. 10 is a value when the salt concentration of the electrolytic solution becomes uniform in the entire secondary battery 1. For example, the salt concentration of the electrolytic solution can be made uniform by leaving the secondary battery 1 for a long time.

FIG. 11 shows the relationship between the electrolyte salt concentration and the reaction resistance. The reaction resistance is a resistance that acts as an electrical resistance equivalently when a reaction current is generated at the interface of the active material 18, in other words, a resistance component related to the entry and exit of lithium ions Li ^{+ on} the electrode surface. Reaction resistance is also called charge transfer resistance.

According to the characteristic diagram shown in FIG. 11, it can be seen that the reaction resistance is a function of the electrolyte salt concentration. In particular, in the region where the electrolyte salt concentration is higher than the threshold value c _th , the change in reaction resistance is moderate with respect to the change in electrolyte salt concentration. Further, in the region where the electrolyte salt concentration is lower than the threshold value c _th , the change in reaction resistance is abrupt with respect to the change in electrolyte salt concentration. That is, in the region lower than the threshold value c _th electrolyte salt concentration, in the electrolyte salt concentration is compared with a threshold value c _th higher than the region, a large rate of change in the reaction resistance to the electrolyte salt concentration.

Considering FIGS. 10 and 11, even when the electrolyte salt concentration in the positive electrode 15 decreases during discharge, the reaction resistance decreases when the electrolyte salt concentration in the positive electrode 15 is higher than the threshold value c _th. It turns out that almost does not occur. On the other hand, when the electrolyte salt concentration in the positive electrode 15 is lower than the threshold value c _th , it can be seen that a decrease in the electrolyte salt concentration in the positive electrode 15 causes an increase in reaction resistance.

As a cause of such an increase in reaction resistance, for example, as shown in FIG. 12A, it is considered that the electrolyte salt concentration in the positive electrode becomes lower than the threshold value c _{th as} the average salt concentration of the electrolyte decreases. It is done. Further, for example, as shown in FIG. 12B, it is conceivable that the electrolyte salt concentration in the positive electrode becomes lower than the threshold value c _th when the discharge is repeated and the electrolyte salt concentration in the positive electrode is cumulatively reduced. It is done.

The case where the reaction resistance is increased by decreasing the electrolyte salt concentration in the positive electrode 15 at the time of discharging is exemplified, but the reaction resistance is also increased by decreasing the electrolyte salt concentration in the negative electrode 12 at the time of charging. . The combination of the reaction resistance and the pure electrical resistance (pure resistance) against the movement of the electrons e ⁻ at the electrodes 12 and 15 is the battery resistance (internal resistance) when the secondary battery 1 is viewed macroscopically. Corresponds to DC resistance component.

  The basic battery model formula used in the present embodiment is represented by a basic equation consisting of the following formulas (8) to (18). FIG. 13 shows a list of variables and constants used in the battery model formula.

  Regarding the variables and constants in the model formula described below, the subscript e indicates a value in the electrolytic solution, and s indicates a value in the active material. The subscript j distinguishes between the positive electrode and the negative electrode. When j is 1, the value at the positive electrode is indicated. When j is 2, the value at the negative electrode is indicated. When the variables or constants in the positive electrode and the negative electrode are described comprehensively, the suffix j is omitted. In addition, the notation (t) indicating that it is a function of time, the notation (T) indicating the dependency of the battery temperature, the (θ) indicating the dependency of the local SOC θ, and the like are indicated in the specification. Sometimes omitted. The symbol # attached to a variable or constant represents an average value.

  The above formulas (8) and (9) are formulas indicating an electrochemical reaction in the electrode (active material), and are called Butler-Volmer formulas.

  The following formula (10) is established as a formula for the conservation law of lithium ion concentration in the electrolytic solution. As an equation relating to the law of conservation of lithium concentration in the active material, the diffusion equation of the following equation (11) and the boundary condition equations shown in the following equations (12) and (13) are applied. The following formula (12) shows the boundary condition at the center of the active material, and the following formula (13) shows the boundary condition at the interface of the active material in contact with the electrolytic solution (hereinafter also simply referred to as “interface”).

Local SOCθ _j that is a local lithium concentration distribution at the active material interface is defined by the following formula (14). C _sej in the following formula (14) indicates the lithium concentration at the active material interface between the positive electrode and the negative electrode, as shown in the following formula (15). c _{sj, max} indicates the limit lithium concentration in the active material.

The following equation (16) is established as an equation relating to the charge conservation law in the electrolytic solution, and the following equation (17) is established as an equation relating to the charge conservation law in the active material. As an electrochemical reaction formula at the active material interface, the following formula (18) indicating the relationship between the current density I (t) and the reaction current density j _j ^Li is established.

  The battery model formula represented by the basic equations of the above formulas (8) to (18) can be simplified as described below. The simplification of the battery model formula can reduce the calculation load and the calculation time.

  It is assumed that the electrochemical reaction in each of the negative electrode 12 and the positive electrode 15 is uniform. That is, it is assumed that the reaction in the x direction occurs uniformly in each of the electrodes 12 and 15. In addition, since it is assumed that the reactions in the plurality of active materials contained in the electrodes 12 and 15 are uniform, the active materials of the electrodes 12 and 15 are treated as one active material model. Thereby, the structure of the secondary battery 1 shown in FIG. 9 can be modeled into the structure shown in FIG.

  In the battery model shown in FIG. 14, it is possible to model electrode reactions on the surfaces of the active material model 18p (j = 1) and the active material model 18n (j = 2) at the time of charge / discharge. Further, in the battery model shown in FIG. 14, it is possible to model the diffusion (diameter direction) of lithium inside the active material models 18p and 18n and the diffusion (concentration distribution) of lithium ions in the electrolytic solution. Furthermore, potential distribution and temperature distribution can be modeled in each part of the battery model shown in FIG.

As shown in FIG. 15, the lithium concentration c _{s in each} of the active material models 18p and 18n is expressed by the coordinate r in the radial direction of the active material models 18p and 18n (r: distance from the center of each point, r _s : active It can be expressed as a function on the radius of the material. Here, it is assumed that there is no position dependency in the circumferential direction of the active material models 18p and 18n. The active material model shown in FIG. 15 is used to estimate the lithium diffusion phenomenon inside the active material due to the electrochemical reaction at the interface. The lithium concentration c _{s, k} (t) is estimated according to the diffusion equation described later for each region (k = 1 to N) divided into N (N: natural number of 2 or more) in the radial direction of the active material models 18p and 18n. Is done.

  According to the battery model shown in FIG. 14, the basic equations (8) to (13) and (15) can be expressed by the following equations (8 ') to (13') and (15 ').

In the above equation (10 ′), it is assumed that c _ej (t) is a constant value by assuming that the concentration of the electrolytic solution does not change with time. For the active material models 18n and 18p, the diffusion equations (11) to (13) are transformed into the diffusion equations (11 ′) to (13 ′) considering only the distribution in the polar coordinate direction. In the above formula (15 ′), the lithium concentration c _{sej at} the active material interface corresponds to the lithium concentration c _si (t) in the outermost region of the N-divided regions shown in FIG.

The above equation (16) relating to the law of conservation of electric charge in the electrolysis solution is simplified to the following equation (19) using the above equation (10 ′). That is, the potential φ _{ej of the} electrolytic solution is approximated as a quadratic function of x. The average potential φ _ej # in the electrolytic solution used for calculating the overvoltage η _j # is obtained by the following equation (20) obtained by integrating the following equation (19) with the electrode thickness L _j .

For the negative electrode 12, the following formula (21) is established based on the following formula (19). Therefore, the potential difference between the electrolyte average potential φ _e2 # and the electrolyte potential at the boundary between the negative electrode 12 and the separator 14 is expressed by the following formula (22). For the positive electrode 15, the potential difference between the electrolyte average potential φ _e1 # and the electrolyte potential at the boundary between the positive electrode 15 and the separator 14 is expressed by the following formula (23).

The above formula (17) relating to the law of conservation of charge in the active material can also be simplified to the following formula (24). That is, the potential φ _sj of the active material is also approximated as a quadratic function of x. The average potential φ _sj # in the active material used for calculation of the overvoltage η _j # is obtained by the following formula (25) obtained by integrating the following formula (24) with the electrode thickness L _j . Therefore, with respect to the positive electrode 15, the potential difference between the active material average potential φ _s1 # and the active material potential at the boundary between the active material 18p and the current collector plate 16 is expressed by the following formula (26). Similarly, the following formula (27) is established for the negative electrode 12.

FIG. 16 shows the relationship between the terminal voltage V (t) of the secondary battery and each average potential obtained as described above. In FIG. 16, since the reaction current density j _j ^Li is 0 in the separator 14, the voltage drop at the separator 14 is proportional to the current density I (t), and L _s / κ _s ^eff · I (t) Become.

In addition, by assuming that the electrochemical reaction in each electrode is uniform, the current density I (t) per unit area of the electrode plate and the reaction current density (lithium generation amount) j _j ^Li are as follows. Formula (28) is materialized.

  Based on the potential relationship shown in FIG. 16 and the above equation (28), the following equation (29) is established for the battery voltage V (t). The following formula (29) is based on the potential relational formula of the following formula (30) shown in FIG.

Next, an average overvoltage η # (t) is calculated. ^Assuming that j _j ^Li is constant and the charge / discharge efficiency is the same in the Butler-Bolmer relational expression and α _aj and α _cj are 0.5, the following equation (31) is established. The average overvoltage η # (t) is obtained by the following equation (32) by inversely transforming the following equation (31).

The average potentials φ _s1 and φ _s2 are obtained using FIG. 16, and the obtained values are substituted into the above equation (29). Further, the average overvoltages η ₁ # (t) and η ₂ # (t) obtained from the above equation (32) are substituted into the above equation (30). As a result, a voltage-current relationship model formula (M1a) according to the electrochemical reaction model formula is derived based on the formulas (8 ′), (28), and (9 ′).

  The active material diffusion model equation (M2a) for the active material models 18p and 18n is obtained by the above equation (11 ′) and the boundary condition equations (12 ′) and (13 ′) which are the lithium concentration conservation law (diffusion equation). .

The first term on the right side of the model equation (M1a) represents an open circuit voltage (OCV) determined by the concentration of the reactant (lithium) on the active material surface, and the second term on the right side represents an overvoltage (η ₁ # −η ₂ #), and the third term on the right side shows the voltage drop due to the battery current. That is, the DC pure resistance of the secondary battery 1 is represented by Rd (T) in the above formula (M1a).

In the above formula (M2a), the diffusion coefficients D _s1 and D _s2 used as parameters for defining the diffusion rate of lithium as a reactant have temperature dependence. Accordingly, the diffusion coefficients D _s1 and D _s2 can be set using, for example, the map shown in FIG. The map shown in FIG. 17 can be acquired in advance.

In FIG. 17, the battery temperature Tb on the horizontal axis is a temperature acquired using the temperature sensor 203. As shown in FIG. 17, the diffusion coefficients D _s1 and D _s2 decrease as the battery temperature Tb decreases. In other words, the diffusion coefficients D _s1 and D _s2 increase as the battery temperature Tb increases.

Regarding the diffusion coefficients D _s1 and D _s2 , not only the dependency of the battery temperature Tb but also the dependency of the local SOC θ may be considered. In this case, a map indicating the relationship between the battery temperature Tb, the local SOC θ, and the diffusion coefficients D _s1 and D _s2 may be prepared in advance.

As shown in FIG. 18A, the open circuit voltage U ₁ included in the formula (M1a) decreases as the local SOC θ increases. Also, open circuit voltage _{U 2,} as shown in FIG. 18B, increases according to the increase of local SOC [theta]. If the maps shown in FIGS. 18A and 18B are prepared in advance, the open-circuit voltages U ₁ and U ₂ corresponding to the local SOC θ can be specified.

Exchange current densities i ₀₁ and i ₀₂ included in the above formula (M1a) have a dependency on local SOC θ and battery temperature Tb. Therefore, if a map showing the relationship between the exchange current densities i ₀₁ and i ₀₂ , the local SOC θ and the battery temperature Tb is prepared in advance, the exchange current densities i ₀₁ and i ₀₂ are specified from the local SOC θ and the battery temperature Tb. Can do.

  The DC pure resistance Rd has temperature dependence. Therefore, if a map showing the relationship between DC pure resistance Rd and battery temperature Tb is prepared in advance, DC pure resistance Rd can be specified from battery temperature Tb. In addition, about the map mentioned above, it can create based on experimental results, such as the well-known alternating current impedance measurement regarding the secondary battery 1. FIG.

  The battery model shown in FIG. 14 can be further simplified. Specifically, a common active material model can be used as the active material of the electrodes 12 and 15. By treating the active material models 18n and 18p shown in FIG. 14 as one active material model, the following equation (33) can be replaced. In the following formula (33), the suffix j indicating the distinction between the positive electrode 15 and the negative electrode 12 is omitted.

The model formulas (M1a) and (M2a) can be expressed by the following formulas (M1b) and (M2b). In the battery model using one active material model, the following formula (28 ′) is applied instead of the above formula (28) as a relational expression of the current density I (t) and the reaction current density j _j ^Li. The

  The following equation (M1c) is obtained by first-order approximation (linear approximation) of the arcsinh term in the above equation (M1a). By performing linear approximation in this way, it is possible to reduce the calculation load and the calculation time.

In the above formula (M1c), as a result of the linear approximation, the second term on the right side is also represented by the product of the current density I (t) and the reaction resistance Rr. The reaction resistance Rr is calculated from the exchange current densities i ₀₁ and i ₀₂ depending on the local SOC θ and the battery temperature Tb, as shown in the above equation (34). Therefore, when the above formula (M1c) is used, a map showing the relationship between the local SOC θ, the battery temperature Tb, and the exchange current densities i ₀₁ and i ₀₂ may be prepared in advance. According to the above formula (M1c) and the above formula (34), the above formula (35) is obtained.

  If the arcsinh term of the second term on the right side in the above equation (M1b) is linearly approximated, the following equation (M1d) is obtained.

The above formula (M1b) can be expressed as the following formula (M1e).

The DC resistance change rate gr included in the above formula (M1e) is represented by the following formula (36).

  In the above formula (36), Ran is the DC resistance of the secondary battery 1 in the initial state, and Ra is the DC resistance of the secondary battery 1 after use (after charge / discharge). The DC resistance change rate gr corresponds to the resistance change rate gr represented by the above formula (6).

The above formula (M1e) is expressed by the following formula (M1f) by performing linear approximation.

  FIG. 19 is a schematic diagram illustrating an internal configuration of the controller 300. Battery state estimation unit 310 includes a diffusion estimation unit 311, an open-circuit voltage estimation unit 312, a current estimation unit 313, a parameter setting unit 314, and a boundary condition setting unit 315. In the configuration shown in FIG. 19, the battery state estimation unit 310 calculates the current density I (t) by using the above formula (M1f) and the above formula (M2b), and the calculation result is sent to the resistance change rate calculation unit 320. Output.

  In this embodiment, the current density I (t) is calculated using the above formula (M1f), but the present invention is not limited to this. Specifically, the current density I (t) can be calculated based on any combination of the above formulas (M1a) to (M1e) and the above formula (M2a) or (M2b). In this embodiment, since the resistance change rate gr is used, when using the above equations (M1a) to (M1d), the arcsinh term or the term obtained by linear approximation of the arcsinh term in these equations is used. The current density I (t) is multiplied by the resistance change rate gr.

  The diffusion estimation unit 311 calculates the lithium concentration distribution inside the active material based on the boundary condition set by the boundary condition setting unit 315 using the above formula (M2b). The boundary condition is set based on the above formula (12 ') or (13'). Diffusion estimation unit 311 calculates local SOC θ based on the calculated lithium concentration distribution using equation (14). Diffusion estimation unit 311 outputs information on local SOC θ to open-circuit voltage estimation unit 312.

The open circuit voltage estimation unit 312 specifies the open circuit voltages U ₁ and U ₂ of the electrodes 12 and 15 based on the local SOC θ calculated by the diffusion estimation unit 311. Specifically, the open-circuit voltage estimation unit 312 can specify the open-circuit voltages U ₁ and U ₂ by using the maps shown in FIGS. 18A and 18B. The open-circuit voltage estimation unit 312 can calculate the open-circuit voltage of the secondary battery 1 based on the open-circuit voltages U ₁ and U ₂ . Open-circuit voltage of the secondary battery 1 is obtained by subtracting the open circuit voltage U ₂ from the open-circuit voltage U _1.

Parameter setting unit 314 sets parameters used in the battery model equation according to battery temperature Tb and local SOC θ. The temperature Tb detected by the temperature sensor 203 is used as the battery temperature Tb. The local SOC θ is acquired from the diffusion estimation unit 311. Parameters set by the parameter setting unit 314 include the diffusion constant D _{s in} the above formula (M2b), the current density i ₀ in the above formula (M1f), and the DC resistance Rd.

The current estimation unit 313 calculates (estimates) the current density I (t) using the following formula (M3a). The following formula (M3a) is a formula obtained by modifying the above formula (M1f). In the following formula (M3a), the open circuit voltage value U (θ, t) is the open circuit voltage value U (θ) estimated by the open circuit voltage estimation unit 312. The voltage value V (t) is the battery voltage Vb acquired using the monitoring unit 201. Rd (t) and i ₀ (θ, T, t) are values set by the parameter setting unit 314. In the above formula (M3a), gr is the resistance change rate gr calculated by the resistance change rate calculation unit 320.

  In addition, even when any of the above formulas (M1a) to (M1e) is used, the current density I (t) can be calculated by the same method as the above formula (M3a).

The boundary condition setting unit 315 calculates the reaction current density (lithium generation amount) j _j ^Li from the current density I (t) calculated by the current estimation unit 313 using the above formula (28) or (28 ′). . Then, the boundary condition setting unit 315 updates the boundary condition in the equation (M2b) using the equation (13 ′).

  The resistance change rate calculation unit 320 calculates the resistance change rate gr represented by the above formula (36). Specifically, the resistance change rate calculation unit 320 calculates the resistance change rate gr using the following equation (37).

  DC resistance Ra changes in accordance with changes in local SOC θ and battery temperature Tb. Therefore, by performing an experiment using the secondary battery 1 in the initial state, a map showing the relationship between the DC resistance Ra, the local SOC θ, and the battery temperature Tb can be acquired in advance. This map can be stored in the memory 300a. The DC resistance Ra changes not only due to changes in the local SOC θ and battery temperature Tb, but also due to aging due to use (charging / discharging) of the secondary battery 1.

  In the above equation (37), the open circuit voltage U (θ) is a value estimated by the open circuit voltage estimation unit 312, and V (t) is the battery voltage Vb obtained from the monitoring unit 201. Ran is a value specified from a map indicating the relationship between the battery temperature Tb, the local SOC θ, and the DC resistance Ra by specifying the battery temperature Tb and the local SOC θ. The current density I (t) is a value obtained by dividing the current value Ib measured by the current sensor 202 by the unit plate area.

  As described above, the resistance change rate gr of the secondary battery 1 can be calculated by using the battery model. As described above, the threshold value E can be changed based on the change in the resistance change rate gr. Here, when grasping the resistance change rate gr caused by high rate deterioration, the resistance change rate gr caused by wear deterioration may be subtracted from the resistance change rate gr calculated as described above. The resistance change rate gr due to wear deterioration can be estimated from the elapsed time as described above.

  On the other hand, when an error occurs between the current density I (t) estimated by the battery model and the current density corresponding to the current value Ib detected by the current sensor 202, the high rate is calculated based on this error. The internal resistance accompanying the deterioration can be estimated. Here, the current density estimated by the battery model is referred to as an estimated current density, and the current density corresponding to the current value Ib detected by the current sensor 202 is referred to as a measured current density.

  For example, by simplifying the diffusion equation of the salt concentration (lithium ion concentration) of the electrolytic solution, the salt concentration change in the electrolytic solution in the electrode can be estimated by the following equations (38) and (39).

The formula (38), in (39), .DELTA.c _e is the difference between the salt concentration of the electrolytic solution in Fukyokunai, the salt concentration of the electrolytic solution in the positive electrode (see FIG. 10). D _eff is the effective diffusion coefficient of the electrolytic solution, ε _e is the volume fraction of the electrolytic solution, t ₊ ⁰ is the transport number of lithium ion Li ⁺ , and F is the Faraday constant. Δt is a time interval (time increment) for performing the current density estimation process, and Δx is a diffusion distance (see FIG. 10). Tb is the battery temperature and I (t) is the current density.

For example, when discharging the secondary battery 1, the salt concentration difference .DELTA.c _e, as shown in FIG. 10, the amount of increase in the salt concentration at the negative electrode, and the sum of the decrease in the salt concentration at the positive electrode. The amount of increase and decrease in salt concentration is the amount of change with respect to the average salt concentration.

The formula (38), shown in Figure 20 the electrolytic solution and the salt concentration difference .DELTA.c _e of between estimated electrode, the correlation between the current estimation error (Im-Ir) of the (39). Here, Im is an estimated current density, and Ir is a measured current density. According to Figure 20, when the salt concentration difference .DELTA.c _e increases, there is a tendency that the current estimation error increases.

Therefore, the value of the current estimation error (Im-Ir) when the salt concentration difference .DELTA.c _e is large, can be utilized as an internal resistance due to high-rate deterioration. Here, as a condition that the salt concentration difference Δc _e is large, for example, a condition that the value of the salt concentration difference Δc _e is equal to or greater than a predetermined value, or a value of the salt concentration difference Δc _e is set in advance. There is a condition of existing within a predetermined range.

  In this embodiment, the difference between the estimated current density Im and the measured current density Ir is used. However, the present invention is not limited to this, and the ratio of the estimated current density Im and the measured current density Ir can also be used.

The current estimation error (Im-Ir) is generated in the region salt concentration difference .DELTA.c _e is large, the increase in the battery resistance is the salt concentration of the electrolyte in the electrode generated by reducing the actual secondary This is probably because the battery 1 and the battery model are different. On the other hand, the voltage change amount ΔV due to the increase in battery resistance is equal between the actual secondary battery 1 and the battery model. For this reason, the following expression (40) is established, where Rr is an increase in battery resistance that actually appears and Rm is an increase in battery resistance in the battery model.

  In this embodiment, the following formula (41) is defined in relation to the above formula (40).

  ΔV (t1) indicates the voltage drop amount of the secondary battery 1. Ir (t1) is the current density obtained from the current value Ib detected by the current sensor 202, and Rr (t1) is the internal resistance of the secondary battery 1 when the current value Ib is obtained. Im (t1) is the current density I (t) estimated by the current estimation unit 313, and Rm (t1) is the secondary battery 1 corresponding to the current density I (t) estimated by the current estimation unit 313. Is the internal resistance.

  Im (t0) is a current density when high-rate deterioration is eliminated by leaving the secondary battery 1 left, and Rm (t0) is an internal resistance of the secondary battery 1 corresponding to the current density Im (t0). is there.

  In the above equation (41), the relationship of the following equation (42) is established.

  In the above formula (42), the internal resistance Rm (t1) may include an internal resistance due to high rate deterioration. For this reason, the internal resistance Rm (t1) is higher than the internal resistance Rm (t0) when no high-rate deterioration has occurred.

  According to the above formula (M1f), the above formula (41) can be expressed by the following formula (43).

  In the above equation (43), the value (I × Rd) relating to the component that does not affect the high rate deterioration is omitted. Further, it is assumed that the temperature T (t0) is the temperature T (t1). Assuming this, the above equation (43) is expressed by the following equation (44).

  The above equation (44) can be transformed into the following equation (45).

  According to the above equation (45), if the resistance change rates gr (t1) and gr (t0) are calculated and the current density I (t1) is estimated by the current estimation unit 313, no high-rate deterioration has occurred. Current density I (t0) can be estimated.

  The resistance increase amount ΔRh accompanying the high rate deterioration corresponds to the difference between the internal resistance Rr including the high rate deterioration and the battery resistance Rr0 not including the high rate deterioration, as shown in the following formula (46).

  If both sides of the above equation (46) are multiplied by the current value Ir, the voltage change amount ΔVhr accompanying the high rate deterioration can be calculated as shown in the following equation (47).

  Assuming that the estimated resistance Rm calculated from the estimated current density Im has little influence of high-rate deterioration and can be ignored, the resistance Rr0 can be regarded as the estimated resistance Rm. Therefore, the above equations (46) and (47) are expressed by the following equations (48) and (49).

  On the other hand, since the high rate deterioration can be observed as an error between the estimated current Im and the measurement current Ir, the voltage change amount ΔVhm accompanying the high rate deterioration is expressed by the following equation (50).

  In the above equation (50), ΔI is a current estimation error.

  Assuming that the voltage drop amount ΔVhr as the measured value is equal to the voltage drop amount ΔVhm as the estimated value, the following equation (51) is obtained from the above equations (48) to (50).

  The following formula (52) is obtained from the above formula (51).

  Moreover, if the said Formula (41) is used, high rate resistance raise amount (DELTA) Rh (t1) can be represented by a following formula (53).

  The correction coefficient ξ included in the equation (53) is represented by the following equation (54).

  According to the above equation (54), when the high rate deterioration has not occurred based on the resistance change rates gr (t1), gr (t0) and the current density Im (t1) estimated by the current estimation unit 313. Current density Im (t0) can be calculated. If the current density Im (t0) is calculated, the battery resistance Rm (t0) can be calculated (estimated) based on the above equation (41). That is, the internal resistance Rm (t0) can be calculated by dividing the voltage change amount ΔV (t1) by the current density Im (t0).

  If the current density Im (t0) and the internal resistance Rm (t0) can be calculated, the high-rate resistance increase ΔRh (t1) can be calculated using the above equation (53). If the high rate resistance increase amount ΔRh (t1) is calculated, the threshold value E can be changed according to the change in the high rate resistance increase amount ΔRh (t1) as described above.

100: assembled battery, 1: secondary battery, 201: monitoring unit, 202: current sensor,
203: Temperature sensor, 204: Current limiting resistor, 205: Inverter,
206: Motor generator, 300: Controller, 300a: Memory SMR-B, SMR-G, SMR-P: System main relay,
PL: positive line, NL: negative line

Claims (9)

A current sensor for detecting a current value at the time of charge and discharge of the secondary battery;
A controller for controlling the discharge of the secondary battery so that the discharge power of the secondary battery does not exceed an upper limit value,
The controller is
An evaluation value for evaluating a degradation component that increases the internal resistance of the secondary battery in association with a deviation in salt concentration due to the discharge of the secondary battery is calculated from the charge / discharge state detected using the current sensor. ,
In response to the value relating to the evaluation value reaching the first threshold value, the upper limit value is reduced,
When the value related to the internal resistance of the secondary battery is smaller than a second threshold, the first threshold is increased;
A battery system characterized by that.   The battery system according to claim 1, wherein the controller decreases the upper limit value in response to the evaluation value reaching the first threshold value.   The battery system according to claim 1, wherein the controller decreases the upper limit value in response to an integrated value obtained by integrating the evaluation values exceeding a target value reaching the first threshold value.   4. The battery system according to claim 1, wherein the controller increases the first threshold when the internal resistance due to the deterioration component is smaller than the second threshold. 5. .   The controller, when the internal resistance due to the deterioration component and the deterioration component that increases the internal resistance of the secondary battery due to wear of the material constituting the secondary battery is smaller than the second threshold, The battery system according to any one of claims 1 to 3, wherein the first threshold value is raised.   When the resistance change rate expressed by the ratio between the internal resistance of the secondary battery before deterioration and the internal resistance of the secondary battery after deterioration is smaller than the second threshold, the controller The battery system according to claim 1, wherein the battery system is raised.   The battery system according to claim 1, wherein the controller decreases the first threshold in response to a value related to the internal resistance reaching the second threshold.   The battery system according to any one of claims 1 to 7, wherein the secondary battery outputs electrical energy converted into kinetic energy for running the vehicle. The battery system according to claim 1, wherein the secondary battery is a lithium ion secondary battery.