JP6668983B2 - Battery system - Google Patents

Description

  The present invention relates to a battery system, and more particularly, to a battery system including a nickel hydride battery.

When Ni ₂ O ₃ H is generated in the positive electrode of the nickel-metal hydride battery, the capacity of the nickel-metal hydride battery decreases as the amount of Ni ₂ O ₃ H increases. Therefore, control for suppressing the generation of Ni ₂ O ₃ H has been proposed. For example, Japanese Unexamined Patent Application Publication No. 2011-233423 (Patent Document 1) discloses a technique for suppressing the generation of Ni ₂ O ₃ H by setting the configuration of the positive electrode (such as the ratio between the height and the length of the positive electrode) to a specific configuration. I do.

JP 2011-233423 A

If the reduction in the full charge capacity due to the generation of Ni ₂ O ₃ H is not taken into consideration, various charge / discharge controls of the nickel-metal hydride battery may be adversely affected. As an example, when the full charge capacity due to the generation of Ni 2 _O 3 _H was reduced to some extent, it is required to suppress the formation of more Ni 2 _O 3 _H. Otherwise, the amount of generated Ni ₂ O ₃ H becomes excessively large, and as a result, the full charge capacity may be lower than the required amount.

Alternatively, as another example, in a SOC (State Of Charge) estimation process of a nickel-metal hydride battery using a so-called current integration method, the full charge capacity of the nickel-metal hydride battery is used, but the full charge capacity is generated due to generation of Ni ₂ O ₃ H. However, if this is not taken into account even though the SOC has decreased, the estimation accuracy of the SOC may decrease. As a result, there is a possibility that various charge / discharge controls according to the SOC cannot be appropriately executed.

In view of such circumstances, in order to appropriately control the charge / discharge of the nickel-metal hydride battery, that is, to adequately protect the nickel-metal hydride battery and sufficiently exhibit the performance of the nickel-metal hydride battery, it is necessary to use Ni ₂ O ₃ H. It is desirable to calculate the generation amount with high accuracy.

The present invention has been made to solve the above-described problems, and an object of the present invention is to accurately calculate the amount of Ni ₂ O ₃ H generated in a positive electrode of a nickel-metal hydride battery in a battery system including the nickel-metal hydride battery. That is.

A battery system according to an aspect of the present invention includes a nickel-metal hydride battery and a control device that controls charging and discharging of the nickel-metal hydride battery. The control device includes a memory. The memory stores data indicating the correspondence between the SOC of the nickel-metal hydride battery and the amount of Ni ₂ O ₃ H generated in the positive electrode of the nickel-metal hydride battery. The control device estimates the SOC of the nickel-metal hydride battery using at least one of the voltage and the current of the nickel-metal hydride battery, and calculates the amount of generated Ni ₂ O ₃ H by referring to the data from the estimated SOC. I do.

The present inventor has found that there is a correlation between the amount of Ni ₂ O ₃ H generated in the positive electrode of the nickel-metal hydride battery and the SOC of the nickel-metal hydride battery. Therefore, according to the above configuration, the amount of generated Ni ₂ O ₃ H can be calculated with high accuracy from the SOC by storing the correlation in advance in the memory as data. Therefore, the charge / discharge of the nickel-metal hydride battery can be appropriately controlled by using the calculation result. For example, control for suppressing further generation of Ni ₂ O ₃ H can be performed.

According to the present invention, in a battery system including a nickel-metal hydride battery, the amount of Ni ₂ O ₃ H generated in the positive electrode of the nickel-metal hydride battery can be calculated with high accuracy.

1 is a block diagram schematically showing an overall configuration of an electric vehicle equipped with a battery system according to the present embodiment. FIG. 3 is a diagram illustrating a configuration of a cell. Is a diagram showing an example of experimental results on the relationship between the presence ratio and the full charge capacity of Ni 2 _O 3 _H in the positive electrode. FIG. 4 is a diagram for explaining a change in a nickel compound in a positive electrode according to an SOC of a nickel-metal hydride battery. FIG. 5 is a diagram showing an example of an analysis result of a nickel compound contained in a positive electrode of a battery by an X-ray diffraction method. 9 is a flowchart illustrating a processing procedure of a first experiment. FIG. 4 is a diagram illustrating an example of a relationship between the ratio of Ni ₂ O ₃ H in a sample and a peak area ratio in an X-ray diffraction method, which is obtained through a first experiment. It is a flowchart which shows the processing procedure of a 2nd experiment. FIG. 3 is a diagram conceptually illustrating an example of a map created in the present embodiment. 5 is a flowchart illustrating Ni ₂ O ₃ H generation suppression control of a battery.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions have the same reference characters allotted, and description thereof will not be repeated.

  Hereinafter, a configuration in which the battery system according to the embodiment of the present invention is mounted on an electric vehicle will be described as an example. The electric vehicle may be a hybrid vehicle (including a plug-in hybrid vehicle), an electric vehicle, or a fuel vehicle. Further, the use of the battery system is not limited to a vehicle, but may be a stationary use.

[Embodiment]
<Configuration of battery system>
FIG. 1 is a block diagram schematically showing an overall configuration of an electric vehicle equipped with a battery system according to the present embodiment. The vehicle 1 includes a motor generator (MG) 10, a power transmission gear 20, a driving wheel 30, a power control unit (PCU) 40, and a system main relay (SMR) 50. And a battery system 2. The battery system 2 includes an assembled battery 100, a voltage sensor 210, a current sensor 220, a temperature sensor 230, and an electronic control unit (ECU) 300.

  Motor generator 10 is, for example, a three-phase AC rotating electric machine. The output torque of motor generator 10 is transmitted to drive wheels 30 via a power transmission gear 20 including a speed reducer and a power split mechanism. The motor generator 10 can also generate electric power by the rotational force of the drive wheels 30 during the regenerative braking operation of the vehicle 1. In a hybrid vehicle equipped with an engine (not shown) in addition to motor generator 10, a necessary vehicle driving force is generated by operating engine and motor generator 10 in a coordinated manner. Although FIG. 1 shows a configuration in which only one motor generator is provided, the number of motor generators is not limited to this, and a configuration in which a plurality (for example, two) of motor generators may be provided.

  Although not shown, PCU 40 includes an inverter and a converter. When the battery pack 100 is discharged, the converter boosts the voltage supplied from the battery pack 100 and supplies the boosted voltage to the inverter. The inverter converts DC power supplied from the converter into AC power and drives motor generator 10. On the other hand, when charging battery pack 100, the inverter converts AC power generated by motor generator 10 into DC power and supplies the DC power to the converter. The converter steps down the voltage supplied from the inverter and supplies it to battery pack 100.

  SMR 50 is electrically connected to a power line connecting battery pack 100 and PCU 40. When SMR 50 is closed in response to a control signal from ECU 300, power can be exchanged between battery pack 100 and PCU 40.

  The battery pack 100 is a rechargeable DC power supply, and includes a plurality of nickel-metal hydride battery cells (single cells) 110 in the present embodiment. The detailed configuration of each cell 110 included in the battery pack 100 will be described with reference to FIG.

  The voltage sensor 210 detects a terminal voltage (hereinafter, also referred to as a “cell voltage”) Vb of each cell 110. The current sensor 220 detects a current Ib input to and output from the battery pack 100. The temperature sensor 230 detects the temperature (hereinafter, also referred to as “cell temperature”) Tb of each cell 110. Each sensor outputs the detection result to ECU 300.

  The ECU 300 includes a CPU (Central Processing Unit) 301, a memory (ROM (Read Only Memory) and RAM (Random Access Memory)) 302, an input / output buffer (not shown), and the like. ECU 300 controls each device based on a signal received from each sensor and a map and a program stored in memory 302 such that vehicle 1 and battery system 2 are brought into desired states. The main process executed by the ECU 300 includes a process of estimating the SOC (State Of Charge) of the cell 110 (or the assembled battery 100). The ECU 300 estimates the SOC of the cell 110 (or the assembled battery 100) according to a so-called current integration method using the integrated current value and the full charge capacity of the assembled battery 100. This processing will be described later.

  FIG. 2 is a diagram showing the configuration of the cell 110. Since the configuration of each cell 110 included in the assembled battery 100 is common, only one cell 110 is representatively shown in FIG. The cell 110 is, for example, a rectangular sealed cell, and includes a case 120, a safety valve 130 provided in the case 120, an electrode body 140 housed in the case 120, and an electrolyte (not shown). Note that FIG. 2 shows the electrode body 140 with a part of the case 120 seen through.

  The case 120 includes a case main body 121 and a lid 122, both of which are made of metal. The lid 122 is hermetically sealed by being welded all around the opening of the case main body 121. When the pressure inside the case 120 exceeds a predetermined value, the safety valve 130 discharges a part of the gas (such as hydrogen gas) inside the case 120 to the outside.

  Electrode body 140 includes a positive electrode, a negative electrode, and a separator. The positive electrode is inserted in, for example, a bag-shaped separator, and the positive electrode and the negative electrode inserted in the separator are alternately stacked. The positive electrode and the negative electrode are electrically connected to a positive terminal and a negative terminal (not shown), respectively.

As the material of the electrode body 140 and the electrolytic solution, various conventionally known materials can be used. In the present embodiment, as an example, the positive electrode includes a positive electrode active material layer containing nickel hydroxide (Ni (OH) ₂ or NiOOH) and an active material support such as foamed nickel. The negative electrode contains a hydrogen storage alloy. As the separator, a nonwoven fabric made of a synthetic fiber subjected to a hydrophilic treatment is used. As the electrolyte, an alkaline aqueous solution containing potassium hydroxide (KOH), sodium hydroxide (NaOH), or the like is used.

<Generation of Ni ₂ O ₃ H>
It is known that when Ni ₂ O ₃ H is generated in the positive electrode of a nickel-metal hydride battery, the full charge capacity of the nickel-metal hydride battery is reduced.

FIG. 3 is a diagram illustrating an example of an experimental result regarding the relationship between the abundance ratio of Ni ₂ O ₃ H in the positive electrode and the full charge capacity. In FIG. 3, the abscissa indicates the abundance ratio of Ni ₂ O ₃ H in the positive electrode, and the ordinate indicates the full charge capacity of the nickel-metal hydride battery. From this experimental result, it can be seen that the full charge capacity decreases as the proportion of Ni ₂ O ₃ H increases.

Unless the reduction in the full charge capacity due to the generation of Ni ₂ O ₃ H is taken into consideration, various charge / discharge controls of the battery pack 100 may be adversely affected. As an example, when the full charge capacity has decreased to some extent due to the generation of Ni ₂ O ₃ H, it is required to suppress a further decrease in the full charge capacity. Otherwise, the amount of Ni ₂ O ₃ H generated (or abundance ratio) becomes excessively large, and as a result, the full charge capacity may be lower than the required amount.

Alternatively, as another example, in the battery system 2, as described above, the SOC of the battery pack 100 (or the cell 110) is estimated using the full charge capacity of the battery pack 100 (or the cell 110). Therefore, if the full charge capacity is reduced due to the generation of Ni ₂ O ₃ H but not taken into account, the SOC estimation accuracy may be reduced. As a result, there is a possibility that various charge / discharge controls according to the SOC cannot be appropriately executed.

In view of such circumstances, the charge and discharge of the battery pack 100 is appropriately controlled, that is, the performance of the battery pack 100 is sufficiently exhibited while protecting the battery pack 100 by suppressing excessive generation of Ni ₂ O ₃ H. In order to do so, it is desirable to calculate the amount of generated Ni ₂ O ₃ H with high accuracy.

As described in detail with reference to FIGS. 4 and 5 below, the present inventor has found that the amount of Ni ₂ O ₃ H generated in the positive electrode changes according to the SOC of the battery pack 100 (or the cell 110). I found it. Therefore, the following configuration is employed in battery system 2 according to the present embodiment. That is, a map MP (see FIG. 9) showing the correspondence between the SOC of the cell 110 (or the assembled battery 100) and the amount of generated Ni ₂ O ₃ H in the positive electrode of the cell 110 (or the assembled battery 100) will be described later. It is created in advance based on the experimental results and stored in the memory 302. Then, the SOC of the cell 110 (or the assembled battery 100) is estimated, the amount of generated Ni ₂ O ₃ H is calculated by referring to the map MP from the estimated SOC, and the calculated generation of Ni ₂ O ₃ H is performed. The charge / discharge of the battery pack 100 is controlled using the amount.

<Change of nickel compound>
FIG. 4 is a diagram for explaining a change in the nickel compound in the positive electrode according to the SOC of the nickel-metal hydride battery. FIG. 4 shows a discharge curve of the nickel-metal hydride battery. The horizontal axis indicates the SOC of the nickel-metal hydride battery, and the vertical axis indicates the voltage of the nickel-metal hydride battery.

As shown in FIG. 4, when the SOC is generally 0%, the nickel compound in the positive electrode is nickel (II) hydroxide (Ni (OH) ₂ ), and the valence of nickel is divalent. On the other hand, when the SOC is 100%, the nickel compound in the positive electrode is nickel oxyhydroxide (NiOOH), and the valence of nickel is trivalent.

As described above, the nickel compound present in the positive electrode of the nickel-metal hydride battery changes according to the SOC of the nickel-metal hydride battery. In a low SOC region (low SOC region), the presence ratio of Ni (OH) ₂ is higher than the presence ratio of NiOOH, and in a middle SOC region (middle SOC region), Ni (OH) ₂ and NiOOH Are present in substantially equal amounts, and in a region where the SOC is high (high SOC region), the abundance ratio of NiOOH is higher than the abundance ratio of Ni (OH) ₂ .

<Durability test>
The inventor conducted a durability test of the cell 110 (single cell) as described below over several years. That is, the cell 110 is maintained in a temperature range of wisdom (for example, a temperature in a range of 0 ° C. to 45 ° C.) and the SOC of the cell 110 is within a predetermined region (for example, in a middle SOC region of 40% to 60%). The charge and the discharge were repeatedly performed so as to be maintained at. Then, the electrode body 140 was taken out of the cell 110 after the durability test, and the positive electrode was analyzed by X-ray diffraction (XRD).

  FIG. 5 is a diagram showing an example of the analysis result (diffraction pattern) of the nickel compound contained in the positive electrode of the cell 110 by XRD. In FIG. 5, the horizontal axis indicates the diffraction angle (2θ), and the vertical axis indicates the diffraction intensity.

FIG. 5 shows, in order from the top, a diffraction pattern when the cell 110 is new, and a diffraction pattern after the endurance test in which the SOC of the cell 110 is maintained in a medium SOC region (for example, a region of SOC = 40% to 60%). It is shown. The diffraction peaks at the diffraction angles D1 to D4 indicated by “▽” in the figure include the influence of the diffraction by Ni ₂ O ₃ H. FIG. 5 shows that when the battery pack 100 is new, Ni ₂ O ₃ H does not exist in the positive electrode.

Further, in order to verify whether Ni ₂ O ₃ H is generated in the low SOC region, the cell 110 was left for several months (for example, half a year) after being completely discharged (discharged until the SOC became almost 0%). This leaving was performed by an accelerated test in a high temperature (for example, 65 ° C.) environment in which Ni ₂ O ₃ H is easily generated in order to shorten the verification period. As a result of disassembling and analyzing the cell 110 after standing, it was confirmed that almost no Ni ₂ O ₃ H was generated, although not shown because it was almost the same as the XRD analysis result of a new product. That is, when the SOC is maintained in the low SOC region (for example, almost 0%), almost no Ni ₂ O ₃ H is generated. On the other hand, as shown in the lower part of FIG. 5, when the SOC of the cell 110 is maintained in the middle SOC region, it can be seen that the generation of Ni ₂ O ₃ H can proceed.

As described above, the amount of generated Ni ₂ O ₃ H depends on the SOC. As described with reference to FIG. 4, since the valence of nickel changes according to the SOC, it can be rephrased that the amount of generated Ni ₂ O ₃ H is dependent on the valence of nickel.

<Create map>
In the present embodiment, the map MP is created in advance by determining the correspondence between the SOC of the battery pack 100 (or the cell 110) and the amount of generated Ni ₂ O ₃ H through a plurality of experiments as described above. You. Hereinafter, a method of creating the map MP will be described first, and then, a specific example of charge / discharge control of the battery pack 100 will be described. Although the map MP corresponds to “data” according to the present invention, a function may be defined instead of the map.

An experiment for creating the map MP can be performed, for example, as follows. First, the mixing ratio of Ni ₂ O ₃ H in the positive electrode and the area surrounded by the diffraction peak corresponding to Ni ₂ O ₃ H obtained by analyzing the positive electrode using XRD (hereinafter, also referred to as “peak area”) An experiment is performed to examine the relationship with the ratio. This experiment is hereinafter referred to as “first experiment”. Thereafter, an experiment is performed to examine the relationship between the SOC of the cell 110 and the amount of Ni ₂ O ₃ H generated in the positive electrode, using the cell 110 that has undergone the durability test and the results of the first experiment. This experiment is hereinafter referred to as “second experiment”. Then, using the second experimental result, a map MP indicating the correspondence between the SOC of the cell 110 (or the assembled battery 100) and the amount of generated Ni ₂ O ₃ H is finally created. Hereinafter, each experiment will be described in order.

  FIG. 6 is a flowchart illustrating a processing procedure of the first experiment. Each step (hereinafter, step is also abbreviated as “S”) shown in FIG. 6 and a flowchart of FIG. 8 described later is performed by an experimenter.

The experimenter prepares a sample in which a predetermined amount (for example, a predetermined amount Q1) of Ni ₂ O ₃ H powder is uniformly mixed with a new electrode (positive electrode) powder (β-Ni (OH) ₂ ) (S110). Thereafter, the experimenter analyzes the sample by XRD (S120). Specifically, an experimenter calculates an X-ray peak area at a predetermined diffraction angle. The X-ray diffraction angle is determined as follows.

As described with reference to FIG. 5, for example, the diffraction peaks at the diffraction angles D1 to D4 are mainly affected by the diffraction by Ni ₂ O ₃ H, and are affected by the diffraction by other nickel compounds (eg, Ni (OH) ₂ ). Hardly receive. Therefore, by using X-rays having any of the diffraction angles D1 to D4, the area of the diffraction peak caused by Ni ₂ O ₃ H can be measured. In the present embodiment, a specific diffraction angle (for example, D1) is used for analysis by XRD. Note that two or more diffraction angles may be used.

When the sample is analyzed by XRD in S110, the experimenter records the peak area at the diffraction angle D1 from the XRD analysis result (S130). As described above, by performing the processing of S110 to S130, the peak area at the diffraction angle D1 when a predetermined amount (for example, the predetermined amount Q1) of Ni ₂ O ₃ H is mixed in the sample is obtained. Instead of the peak area at the diffraction angle D1, for example, the total value of the peak areas at the respective diffraction angles D1 to D4 may be used.

Then, similarly to the diffraction peak assigned to the _{Ni 2 O 3 H, Ni (} OH) a predetermined amount of _Ni 2 _{O 3} H in view of the diffraction peak attributable to ₂ (not shown D1 ') (e.g., Q1) mixed The peak area at the diffraction angle D1 'obtained when this is performed is obtained.

In the first experiment, the amount of Ni ₂ O ₃ H mixed into the sample is changed (for example, other predetermined amounts Q2, Q3, etc.), and a series of processes of S110 to S130 is performed a plurality of times. As a result, the ratio of Ni ₂ O ₃ H in the sample (the amount of Ni ₂ O ₃ H / (the amount of Ni (OH) ₂ + the amount of Ni ₂ O ₃ H)) and the peak area ratio (D1 / D1 + D1 ′) at the diffraction angle D1. ) Can be obtained.

FIG. 7 is a diagram showing an example of the relationship between the ratio of Ni ₂ O ₃ H in the sample and the peak area ratio in XRD, obtained through the first experiment. In FIG. 7, the horizontal axis represents the ratio of Ni ₂ O ₃ H in the sample (Ni ₂ O ₃ H amount / (Ni (OH) ₂ amount + Ni ₂ O ₃ H amount)), and the vertical axis represents the peak area ratio ( D1 / D1 + D1 ′).

When a predetermined amount of Ni ₂ O ₃ H was mixed into the sample, the peak area ratio at the diffraction angle D1 was A1, A2, A3, respectively. From the above experimental results, the relationship between the ratio of Ni ₂ O ₃ H in the sample and the peak area ratio at the diffraction angle D1 can be obtained. Note that the relationship as shown in FIG. 7 may be defined by using the peak intensity instead of the peak area (peak area ratio).

  FIG. 8 is a flowchart illustrating a processing procedure of the second experiment. After setting the durability conditions (voltage and cell temperature Tb), the experimenter performs a durability test of a new cell 110 (single cell) in various SOC regions (S210). Each endurance test is performed by repeating charging and discharging of the cell 110 so that the SOC of the cell 110 falls within a predetermined area. As a result, SOC dependency can be introduced into the map MP. Alternatively, the experimenter may calculate the SOC by measuring the remaining capacity of the cell 110 after the durability test.

Further, the experimenter takes out the positive electrode contained in the cell 110 and analyzes it by XRD (S220) . Its to the experimenter was obtained by the first experiment, the relationship between the peak area ratio in percentage and XRD of Ni 2 _O 3 _H in the sample with reference to (see FIG. 7), the S130 The amount of generated Ni ₂ O ₃ H is calculated from the peak area ratio obtained from the analysis result (S230).

Thereafter, the experimenter records the correspondence between the SOC, the voltage and the cell temperature Tb and the amount of Ni ₂ O ₃ H calculated in S230 (S240). The experimenter performs such a series of processes (the processes of S210 to S240) on a plurality of conditions (SOC region, voltage, and cell temperature Tb). For each of a plurality of conditions, calculated Ni 2 _O 3 _H Period of durability test of the amount of (preferably Ni 2 _O 3 _H are generated easily charging period) by dividing, per unit time Ni _The amount of ₂ O ₃ H generated can be calculated. Therefore, the map MP can be created.

FIG. 9 is a diagram conceptually showing an example of the map MP created in the present embodiment. In the map MP, for example, the voltage of the cell 110 (more specifically, a value obtained by removing the voltage change due to the metal resistance of the battery system 2 from the cell voltage Vb) (V0, V1, V2,...) For each combination of the SOC (X0, X1, X2...) Of 110 and the cell temperature Tb (T0, T1, T2...), The Ni ₂ O ₃ H per unit time in the positive electrode of the cell 110 The generation amounts (R00, R01, R10,...) Are associated with each other. Under the condition of the same SOC, the higher the voltage or the higher the cell temperature Tb, the larger the amount of Ni ₂ O ₃ H generated per unit time. As described above, in the present embodiment, the map MP is created in advance through the first and second experiments, and the created map MP is stored in the memory 302.

<Ni ₂ O ₃ H generation suppression control>
Various charge / discharge controls of the battery pack 100 are performed using the map MP created as described above. As an example, when the generation amount of Ni ₂ O ₃ H exceeds a predetermined amount, control for suppressing further generation of Ni ₂ O ₃ is executed. This control is referred to as “Ni ₂ O ₃ H generation suppression control” and will be described below.

FIG. 10 is a flowchart illustrating Ni ₂ O ₃ H generation suppression control of the battery pack 100. The process shown in this flowchart is called from a main routine (not shown) and executed at a predetermined control cycle (= unit time). Each step included in these flowcharts is basically realized by software processing by ECU 300, but a part or all of the steps may be realized by hardware (electric circuit) manufactured in ECU 300. It is assumed that the amount of generated Ni ₂ O ₃ H calculated in the previous control cycle is stored in the memory 302 of the ECU 300.

  In S310, ECU 300 acquires signals indicating cell voltage Vb, current Ib, and cell temperature Tb from voltage sensor 210, current sensor 220, and temperature sensor 230, respectively. Note that, for example, at the time of charging, ECU 300 calculates a voltage obtained by subtracting the amount of voltage change due to metal resistance from cell voltage Vb. The voltage change amount is calculated based on a product of the metal resistance and the current Ib which are obtained in advance.

  In S320, ECU 300 calculates the SOC of cell 110. A known method can be used for calculating the SOC. That is, the SOC may be calculated using data indicating a correlation between the SOC and the OCV, which is defined in advance, or the SOC may be calculated from the integrated value of the current Ib and the full charge capacity of the cell 110 by the current integration method. May be calculated.

In S330, ECU 300 refers to map MP (see FIG. 9) stored in memory 302, and calculates the SOC calculated in S320 and the unit time corresponding to the voltage and cell temperature Tb obtained in S310. Of Ni ₂ O ₃ H is calculated.

In S340, ECU 300 adds the product of the calculated _Ni 2 _{O 3} H in S330, the generation amount of _Ni 2 _{O 3} H calculated in the previous control cycle (the value stored in the memory 302) Thus, the current generation amount of Ni ₂ O ₃ H is calculated. The calculated value is stored in the memory 302.

In S350, ECU 300 determines whether or not the amount of Ni ₂ O ₃ H calculated in S340 is equal to or greater than a predetermined reference amount. For example, if there is at least one cell in which Ni ₂ O ₃ H is equal to or more than the reference amount (YES in S350), ECU 300 advances the process to S360, and sets the cell in which Ni ₂ O ₃ H is equal to or more than the reference amount. The PCU 200 is controlled such that the cell voltage Vb is limited to less than the predetermined voltage and the cell temperature Tb is limited to less than the predetermined temperature. Thereafter, the processing returns to the main routine. Thereby, further generation of Ni ₂ O ₃ H can be suppressed. As a result, it is possible to suppress a further decrease in the full charge capacity of the battery pack 100 and prevent the full charge capacity from falling below a required amount.

Although the effect of suppressing the generation of Ni ₂ O ₃ H is relatively small, only one of the cell voltage Vb and the cell temperature Tb may be limited. Alternatively, since the generation of Ni ₂ O ₃ H is accelerated by the reaction unevenness in the positive electrode, in order to reduce the reaction unevenness and suppress the generation of Ni ₂ O ₃ H, the cell voltage Vb and the cell temperature Tb are replaced. Alternatively or additionally, the current Ib of the battery pack 100 may be limited to less than a predetermined value.

On the other hand, if the amount of generated Ni ₂ O ₃ H is less than the predetermined amount in S350 (NO in S350), ECU 300 returns the process to the main routine without executing the process of S360.

As described above, according to the present embodiment, the amount of generated Ni ₂ O ₃ H can be calculated with high accuracy by considering the SOC of the cell 110 (or the assembled battery 100). Then, by suppressing further generation of Ni ₂ O ₃ H according to the calculation result, it is possible to prevent deterioration of the battery pack 100 which causes a decrease in the full charge capacity of the battery pack 100. Therefore, the performance of the battery pack 100 can be sufficiently exhibited. For example, when the vehicle 1 is equipped with an engine (not shown), it is possible to suppress a decrease in the fuel efficiency of the vehicle 1 due to a decrease in the full charge capacity of the battery pack 100.

Although described control for inhibiting the formation of FIG. 10, Ni 2 _O 3 _H, it is also possible to use information on the amount of Ni 2 _O 3 _H in the other control. For example, in the SOC estimation by the current integration method, the correlation between the generation amount of Ni ₂ O ₃ H and the reduction amount of the full charge capacity is obtained in advance, so that the generation amount of Ni ₂ O ₃ H is used. Full charge capacity can be corrected. By using the corrected full charge capacity, it is possible to improve the estimation accuracy of the SOC.

  The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description of the embodiments, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Vehicle, 2 battery system, 10 motor generator, 20 power transmission gear, 30 drive wheels, 40 PCU, 50 SMR, 100 assembled battery, 110 cell, 120 case, 121 case main body, 122 lid, 130 safety valve, 140 electrode body , 210 voltage sensor, 220 current sensor, 230 temperature sensor, 300 ECU, 301 CPU, 302 memory.

Claims (1)

Nickel-metal hydride batteries,
Including a memory, a control device for controlling the charge and discharge of the nickel-metal hydride battery,
The memory stores data indicating a correspondence relationship between an SOC (State Of Charge) of the nickel-metal hydride battery and a generation amount of Ni ₂ O ₃ H in a positive electrode of the nickel-metal hydride battery,
The control device estimates the SOC of the nickel-metal hydride battery using at least one of the voltage and the current of the nickel-metal hydride battery, and refers to the data from the estimated SOC to generate the amount of Ni ₂ O ₃ H. Calculate the battery system.

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