vehicle

Abstract

To strike a balance between resolution of voltage variation of a unit cell and deterioration in fuel economy.SOLUTION: When a maximum voltage difference MAX[ΔVB] of a voltage difference ΔVB of a unit cell comprising nickel-hydrogen battery cells becomes equal to or more than a specified value (S11 affirmative determination), a vehicle executes variation inhibitory control of increasing the SOC control central of a battery (S14, S14), at this time, when a mode M=2 is met, the vehicle does not execute the variation inhibitory control (S12). When the time where an internal pressure of a battery module is equal to or more than a specified value continues for a specified period of time or more, the mode M is set to the mode M=2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to vehicles. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2000-14029 (Patent Document 1) discloses a battery control device for a hybrid vehicle having a battery pack in which multiple battery blocks are connected in series. This battery control device issues a request to charge the battery when the voltage difference between the battery blocks reaches or exceeds a predetermined value. By issuing a charge request, subsequent discharge is prohibited, the charged state of the battery pack can be restored, and in particular, over-discharge of one battery cell in the battery pack can be prevented. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-14029 A Summary of the Invention [Problem to be solved by the invention]

[0004] The battery pack in Patent Document 1 uses nickel-metal hydride batteries. Nickel-metal hydride batteries have the characteristic that the self-discharge amount increases as the SOC (State Of Charge) increases (approaching a high SOC region). By utilizing this characteristic, when the voltage difference between the cells (battery cells) is large and the voltage variation among the cells becomes large, the battery pack can be used in a high SOC region to reduce the voltage variation among the cells. Therefore, by charging the battery pack when the voltage difference among the cells is large and using the battery pack in a high SOC region, it is possible to suppress over-discharge of the cells and reduce (eliminate) the voltage variation among the cells.

[0005] When a battery pack (single cell) is used in a high SOC range to eliminate the variation in cell performance, the amount of gas generated inside the cell increases, which can cause the internal pressure of the battery to rise. If the input and output power of the battery pack is restricted in order to suppress this internal pressure rise, this will result in a deterioration in the fuel efficiency of hybrid vehicles.

[0006] An object of the present disclosure is to simultaneously eliminate voltage variations among cells and suppress deterioration of fuel efficiency. [Means for solving the problem]

[0007] The vehicle according to the present disclosure includes a battery pack in which a plurality of unit cells, each of which is a nickel-metal hydride battery, are connected in series, a drive device that is driven by the power stored in the battery pack, and a control device that controls charging and discharging of the battery pack so that the SOC of the battery pack is within a first predetermined range centered on a first SOC control center. The control device is configured to execute variation suppression control when a voltage difference between the plurality of unit cells becomes equal to or greater than a predetermined value, thereby performing charging and discharging so that the SOC is within a second predetermined range centered on a second SOC control center that is larger than the first SOC control center, and not to execute variation suppression control when the internal pressure of the battery pack is equal to or greater than a set value.

[0008] According to this configuration, the vehicle includes a drive device driven by power stored in the battery pack, and the battery pack is controlled to charge and discharge so that the SOC is within a first predetermined range centered on a first SOC control center. For example, the vehicle may be a hybrid vehicle that charges the battery pack with output power from a generator driven by an internal combustion engine, and drives the drive device with power discharged from the battery pack.

[0009] When the voltage difference between the cells reaches or exceeds a predetermined value, the control device executes variation suppression control, which performs charging and discharging so that the SOC falls within a second predetermined range centered on a second SOC control center that is greater than the first SOC control center. Since nickel-metal hydride cells have a characteristic that the self-discharge amount increases as the SOC increases (approaching the high SOC region), the variation suppression control allows the battery pack to be used in a high SOC region (relative to the first predetermined range), thereby reducing the voltage difference between the cells and reducing (eliminating) the voltage variation between the cells.

[0010] When the internal pressure of the battery pack is equal to or higher than a set value, the variation suppression control is not executed. By executing the variation suppression control, the usage range of the battery pack becomes a high SOC range, and the amount of gas generated by the single cells increases. When the internal pressure of the battery rises to or above a set value, the variation suppression control is not executed. This makes it possible to suppress the rise in the internal pressure of the battery pack, so there is no need to limit the input / output power of the battery pack, and deterioration of the vehicle's fuel efficiency can be suppressed. Effect of the Invention

[0011] According to the present disclosure, it is possible to both eliminate voltage variations among cells and suppress deterioration of fuel efficiency. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a configuration of a vehicle according to an embodiment of the present invention; [Diagram 2] 4 is a flowchart showing an example of a variation suppression control process executed by an HV-ECU. [Diagram 3] 4 is a flowchart showing an example of a mode determination process executed by an HV-ECU. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and the description thereof will not be repeated.

[0014] FIG. 1 is a diagram showing a configuration of a vehicle V according to this embodiment. The vehicle V is a hybrid vehicle including an internal combustion engine 10, a first motor generator (hereinafter referred to as "first MG") 20, a second motor generator (hereinafter referred to as "second MG") 30, a power split device 40, a PCU (Power Control Unit) 50, and a battery 60. The power split device 40 is formed of a planetary gear mechanism. An output shaft 11 of the internal combustion engine 10 is connected to an input shaft 41 that rotates integrally with a carrier of the power split device 40. A rotor of the first MG 20 is connected to a sun gear of the power split device 40. A rotor of the second MG 30 is connected to an output shaft 42 that rotates integrally with a ring gear of the power split device 40. The power split device 40 splits the power output from the internal combustion engine 10 into power for driving the first MG 20 and power for driving drive wheels 80.

[0015] The first MG 20 and the second MG 30 are AC rotating electric machines, for example, interior permanent magnet synchronous motors (IPM motors), and have a function as an electric motor (motor) and a function as a generator (generator). The first MG 20 is mainly used as a generator driven by the internal combustion engine 10 via the power split device 40. Electric power generated by the first MG 20 is supplied to the second MG 30 or the battery 60 via the PCU 50. The second MG 30 mainly operates as an electric motor, and drives the drive wheels 80 via the differential gear 70. The second MG 30 is driven by receiving at least one of electric power from the battery 60 and electric power generated by the first MG 20. On the other hand, when the vehicle V is braking or going downhill, the second MG 30 operates as a generator to perform regenerative power generation. The electric power generated by the second MG 30 is collected by the battery 60 via the PCU 50.

[0016] The PCU 50 converts the DC power received from the battery 60 into AC power for driving the first MG 20 and the second MG 30. The PCU 50 converts the AC power generated by the first MG 20 and the second MG 30 into DC power for charging the battery 60.

[0017] The battery 60 is an assembled battery in which a plurality of electric cells (battery cells) 5 are connected in series. In this embodiment, the battery 60 (assembled battery) is a bipolar nickel-metal hydride battery. The battery 60 includes an electric cell 5 in which an electrode plate (metal foil, current collector) 1, a negative electrode (negative electrode active material) 2, a separator 4, a positive electrode (positive electrode active material) 3, and an electrode plate 1 are stacked in this order. A battery module is formed by stacking a plurality of electric cells 5 while sharing the electrode plate 1. For example, the battery module may be formed by stacking 24 electric cells 5. The battery 60 (assembled battery) is formed by connecting a plurality of battery modules in series. The positive electrode active material may be nickel hydride, and the negative electrode active material may be a hydrogen storage alloy.

[0018] The battery 60 is provided with a monitoring module 61. The monitoring module 61 includes a voltage sensor that detects the voltage VB of the single cell 5, and a current sensor and a temperature sensor that detect the input / output current IB and temperature TB of the battery 60, respectively. The monitoring module 61 outputs the detection values ​​of each sensor to an HV-ECU (Electronic Control Unit) 100. The monitoring module 61 also calculates the SOC of the battery 60 and outputs it to the HV-ECU 100.

[0019] The vehicle V includes an HV-ECU 100, an MG-ECU 200, an EG-ECU 300, and various sensors 400. The ECUs are configured to be able to communicate with each other via a CAN (Controller Area Network).

[0020] The HV-ECU 100 executes a predetermined calculation process based on information from the various sensors 400 and information from the monitoring module 61. The HV-ECU 100 outputs various commands to the MG-ECU 200 and the EG-ECU 300 based on the results of the calculation process. The MG-ECU 200 controls the PCU 50, and controls the first MG 20 and the second MG 30. The EG-ECU 300 controls the internal combustion engine 10.

[0021] When a start switch (power switch or ignition switch) (not shown) is turned ON to start the vehicle V, the HV-ECU 100 is started and goes into a Ready-ON state. In the Ready-ON state, the HV-ECU 100 closes (ON) a system main relay (SMR) 62 provided in a power line connecting the battery 60 and the PCU 50, enabling power to be exchanged between the battery 60 and the PCU 50. When the start switch is turned OFF, the HV-ECU 100 opens (OFF) the SMR 62, cutting off the electrical connection between the battery 60 and the PCU 50, and goes into a Ready-OFF state.

[0022] For driving control of the vehicle V, the HV-ECU 100 calculates a required drive torque Tr based on, for example, the accelerator opening AP, the vehicle speed SPD, etc., and multiplies the required drive torque Tr by the rotation speed of the drive wheels 80 to obtain a required power Pd. The HV-ECU 100 subtracts a charge / discharge power Pb (a positive value when discharging from the battery 60) based on the SOC of the battery 60 from the required power Pd to set a required power Pe required of the internal combustion engine 10. Then, the target engine rotation speed Ne*, the target engine torque Te*, the command torque Tm1 of the first MG 20, and the command torque Tm2 of the second MG 30 are set so that the required power Pe is output from the internal combustion engine 10 and the required drive torque Tr is output to the drive wheels 80. The HV-ECU 100 outputs a command to the EG-ECU 300 to operate the internal combustion engine 10 at the target engine speed Ne* and target engine torque Te*, and outputs a command to the MG-ECU 200 to drive the first MG 20 and the second MG 30 at command torques Tm1 and Tm2.

[0023] The HV-ECU 100 uses the control SOCi to control charging and discharging of the battery 60. The control SOCi is calculated based on the SOC calculated by the monitoring module 61. In the charging and discharging control, the control SOCi is controlled to be within a range between an upper limit value Xi and a lower limit value Yi. For example, during driving, the charging and discharging power Pb is calculated so that the battery 60 is charged when the control SOCi falls below the lower limit value Yi, and the battery 60 is discharged when the control SOCi exceeds the upper limit value Xi.

[0024] During the manufacture of the battery 60, minute foreign matter may be mixed in. In this case, a minute short circuit may occur in the cell 5, causing a drop in the voltage of the cell (battery cell) 5, resulting in variation in the voltage VB of the cell 5. The self-discharge amount of the cell 5 made of a nickel-metal hydride battery increases as the SOC increases. By using the battery 60 in a high SOC region, the self-discharge amount of the cell 5 with a high voltage (high SOC) increases, and the voltage difference ΔVB between the cells 5 can be eliminated (reduced). In this embodiment, the process of eliminating (reducing) the voltage difference ΔVB between the cells 5 is also referred to as "variation suppression control."

[0025] 2 is a flowchart showing an example of a variation suppression control process executed by HV-ECU 100. This flowchart is repeatedly processed at predetermined intervals when in the Ready-ON state. In step (hereinafter, step is abbreviated as "S") 10, it is determined whether flag F1 is 1. Flag F1 is set to 1 in S15, which will be described later. If flag F1 is 1, the process proceeds to S16, and if flag F1 is 0, the process proceeds to S11.

[0026] In S11, it is determined whether the maximum voltage difference MAX[ΔVB], which is the maximum value of the voltage differences ΔVB between adjacent cells 5, is greater than a predetermined value α. The voltage difference ΔVB is calculated based on the voltage VB of each cell 5. The predetermined value α may be, for example, 1 [V]. If the maximum voltage difference MAX[ΔVB] is greater than the predetermined value α (MAX[ΔVB]>α), the process proceeds to S12, and if the maximum voltage difference MAX[ΔVB] is equal to or less than the predetermined value α (MAX[ΔVB]≦α), the current routine is terminated.

[0027] In S12, it is determined whether the current mode M is "0," "1," or "2." In a single cell 5 made of a nickel-metal hydride battery, a memory effect may occur due to repeated charging and discharging. When mode M is "0" (mode M=0), the memory effect does not occur in the battery 60 (single cell 5). When mode M is "1" (mode M=1), the memory effect occurs in the battery 60. When mode M is "2," the memory effect occurs in the battery 60 in the low SOC region (a region where SOC is equal to or lower than B [%], where B may be, for example, 60 [%]).

[0028] When the memory effect occurs, the amount of gas generated in the cells 5 increases. Furthermore, when the variation suppression control is executed, the battery 60 is used in a high SOC region, so the amount of gas generated in the cells 5 increases. For this reason, if the variation suppression control is executed when the memory effect occurs, there is a concern that the internal pressure of the battery 60 (battery module) will further increase. For this reason, when the memory effect occurs, the execution of the variation suppression control is suppressed. Note that when the memory effect occurs, the internal pressure of the battery 60 increases, so the occurrence of the memory effect can be estimated from the internal pressure of the battery 60. A method for determining Mode M will be described later.

[0029] In S12, if mode M=0, the process proceeds to S13. If mode M=1, the process proceeds to S14. If mode M=2, the current routine is terminated.

[0030] In S13, the SOC control center of the battery 60 is raised. The SOC control center is raised by calculating the control SOCi from SOCi-0 shown by the dashed line in the SOCi calculation map (see the lower part of FIG. 2). As shown in FIG. 2, SOCi-0 is a value obtained by subtracting an amount of raising k from SOC when the SOC calculated by the monitoring module 61 is between A and C. k may be, for example, 5%. In addition, when the SOC is between A0 and A and between C and C0, the amount of raising k is gradually decreased. In addition, when the SOC is equal to or lower than A0 and equal to or higher than C0, k is 0. In addition, in the SOCi calculation map, the solid line indicates the value of control SOCi=SOC, and is used when the SOC control center is not raised.

[0031] The charge and discharge control of the battery 60 controls the control SOCi to be within the range between the upper limit Xi and the lower limit Yi. If the SOC control center is not raised, the control SOCi is the value of the SOC (control SOCi=SOC), so the SOC of the battery 60 is controlled to be within the range between the SOC upper limit X corresponding to the upper limit Xi and the SOC lower limit Y corresponding to the lower limit Yi. Therefore, the SOC control center becomes (X+Y) / 2 (for example, when X=40[%] and Y=60[%], the SOC control center becomes 50[%]). The SOC control center ((X+Y) / 2) corresponds to the "first SOC control center" in this disclosure.

[0032] The SOC control center is raised by using SOCi-0, which is the value obtained by subtracting the amount of raising k from the SOC, as the control SOCi. Therefore, the SOC of the battery 60 is controlled to be within the range between "SOC upper limit value X+k" and "SOC lower limit value+k", and the SOC control center becomes "((X+Y) / 2)+k", and the SOC control center becomes larger. The SOC control center (((X+Y) / 2)+k) corresponds to the "second SOC control center" of this disclosure.

[0033] In S14, the SOC control center is raised by calculating the control SOCi from SOCi-1 indicated by the dashed line in the SOCi calculation map (see the lower part of Fig. 2). As shown in Fig. 2, when the SOC is between A0 and B (B < C), SOCi-1 is a value obtained by subtracting the raising amount k from the SOC in the same form as SOCi-0. Also, in the region where the SOC is B or more, SOCi-1 has the same value as the SOC (SOCi-1 = SOC). Therefore, in the region where the SOC is B or less, the SOC control center increases as described above.

[0034] In S15 following S13 and S14, after setting the flag F1 to 1 and starting the timer T, the process proceeds to S16. In S16, it is determined whether the timer T has reached or exceeded the cancellation time H. The cancellation time H is the time required to cancel the voltage difference ΔVB (maximum voltage difference MAX[ΔVB]), taking advantage of the fact that the self-discharge amount of the single battery 5 increases as the SOC increases. The cancellation time H is calculated in a subroutine (not shown). The self-discharge current of the single battery 5 changes according to the SOC and the temperature TB, and shows different values in the Ready-ON state (during running) and the Ready-OFF state (during soaking). Also, the self-discharge current shows different values depending on the presence or absence of the memory effect. In the subroutine (not shown), using the process of S15 as a trigger, the self-discharge current that changes moment by moment is obtained from the Ready-ON / OFF state, the SOC, the temperature TB, and the presence or absence of the memory effect, etc., and the cancellation time H is calculated based on the self-discharge current. Note that the relationship between the self-discharge current and the cancellation time H is obtained in advance by experiments or the like.

[0035] In S16, if the timer T is less than the cancellation time H, the current routine ends. If the timer T is equal to or greater than the cancellation time H, the process proceeds to S17. In S17, the raising of the SOC control center is stopped (cancelled), and after setting the flag F1 to 0, the current routine ends. The stop of the raising of the SOC control center is performed by using the value of the SOC as the control SOCi (calculating the control SOCi using the solid line where the control SOCi = SOC in the SOCi calculation map).

[0036] 3 is a flowchart showing an example of a mode determination process executed by the HV-ECU 100. This flowchart is executed when the Ready-OFF state is changed to the Ready-ON state. In S20, it is determined whether the current mode M is "2". If the current mode M is "2", the current routine is ended, and if the mode M is not "2", the process proceeds to S21.

[0037] In S21, it is determined whether or not flag F2 is 1. Flag F2 is set to 1 in S23 described later. When flag F2 is 0, the process proceeds to S22, and when flag F2 is 1, the process proceeds to S24. In S22, it is determined whether or not the internal pressure PA of the battery module is equal to or lower than a predetermined value S1. The internal pressure PA is estimated based on voltage VB and temperature TB. When the internal pressure PA is equal to or lower than the predetermined value S1, the process proceeds to S23, where flag F2 is set to 1, and the process proceeds to S24. When the internal pressure PA is greater than the predetermined value S1, the process proceeds to S26.

[0038] In S24, it is determined whether the internal pressure PA is equal to or greater than a predetermined value S2. The predetermined value S2 is greater than the predetermined value S1, and corresponds to the "set value" in this disclosure. If the internal pressure PA is equal to or greater than the predetermined value S2, the process proceeds to S25, and if the internal pressure PA is less than the predetermined value S2, the process proceeds to S26. In S25, it is determined whether the time (continuation time) R during which the internal pressure PA is equal to or greater than the predetermined value S2 has elapsed for a predetermined time Rm or more. If the time R has not elapsed the predetermined time Rm, the process proceeds to S26, and if the time R has elapsed the predetermined time Rm, the process proceeds to S27.

[0039] In S26, it is determined whether or not the Ready-OFF state is established. If the Ready-ON state is established, the process returns to S21, and if the Ready-OFF state is established, the process proceeds to S30, where the flag F2 is set to 0, and the current routine is terminated.

[0040] The processes from S21 to S26 are executed for each battery module, and if a positive determination is made in S25 in any battery module, the process of S27 is executed. In S27, it is determined whether the current mode M is "0". If the mode M is "0", the process proceeds to S28, where the mode M is set to "1" and the flag F2 is set to 0, and the process proceeds to S26. If the mode M is not "0" (in this case, the current mode M is "1"), the process proceeds to S29, where the mode M is set to "2", and the process proceeds to S30.

[0041] When the memory effect occurs in the single cell 5, the internal pressure of the battery 60 (battery module) rises. As shown in the time chart in the lower part of FIG. 3, in a state of mode M=0 in which the memory effect does not occur, when the internal pressure PA becomes equal to or greater than the predetermined value S2 from a state of being equal to or less than the predetermined value S1, and the state of the internal pressure PA≧predetermined value S2 continues for a predetermined time Rm, the mode M transitions from mode M=0 to mode M=1. Mode M=1 is a state in which the memory effect occurs in the battery 60. In mode M=1, the charge / discharge control (variation suppression control) centered on the second SOC control center is executed in a region in which the SOC is equal to or less than B (FIG. 2, S14). In a state of mode M=1, when the internal pressure PA becomes equal to or greater than the predetermined value S2 from a state of being equal to or less than the predetermined value S1, and the state of the internal pressure PA≧predetermined value S2 continues for a predetermined time Rm, the mode M transitions from mode M=1 to mode M=2. Mode M=2 is a state in which the memory effect occurs even in a low SOC region in which the SOC is equal to or less than B. In order to eliminate the memory effect, when the battery 60 is refresh-charged, the mode M may be set to mode M=0.

[0042] According to this embodiment, charging and discharging of battery 60, which is made up of nickel-metal hydride cells 5 connected in series, is controlled so that the SOC of battery 60 falls within a first predetermined range centered on a first SOC control center ((X+Y) / 2). When maximum voltage difference MAX[ΔVB], which is the maximum value of the voltage difference between cells 5, exceeds a predetermined value α, if mode M is "0" or "1", charging and discharging are controlled so that the SOC of battery 60 falls within a second predetermined range centered on a second SOC control center (((X+Y) / 2)+k) for a period of resolution time H from when maximum voltage difference MAX[ΔVB] exceeds the predetermined value α.

[0043] When the battery 60 is charged and discharged so that the SOC falls within the second predetermined range, charging of the cells 5 is promoted, over-discharging of the cells 5 can be suppressed, and the battery 60 is used in a region where the SOC is higher than the first predetermined range (high SOC region). The self-discharge amount of the cells 5 increases as the SOC increases. By using the battery 60 in the high SOC region during the resolution time H, the self-discharge amount of the cells 5 with high voltages (high SOC) increases, and the voltage difference ΔVB between the cells 5 can be resolved (reduced).

[0044] In mode M=1, variation suppression control (charge / discharge control centered on the second SOC control center) is performed in the region where the SOC is equal to or lower than B, and variation suppression control is not substantially performed in the region where the SOC is higher than B. However, when the memory effect is present, the self-discharge current of the cells 5 becomes large. Therefore, even if variation suppression control is not performed in the region where the SOC is higher than B, the voltage difference ΔVB between the cells 5 can be satisfactorily eliminated.

[0045] According to this embodiment, in mode M=2, the variation suppression control (raising the SOC control center) is not executed. In mode M=2, the memory effect occurs even in a low SOC region where the SOC is equal to or lower than B. If the variation suppression control is executed in mode M=2, the usage region of the battery 60 will be a high SOC region, the amount of gas generated inside the battery 60 will increase, and the internal pressure PA of the battery module may further increase. In order to avoid this increase in the internal pressure PA, the variation suppression control is not executed in mode M=2. As a result, it is not necessary to limit the input / output power of the battery 60 in order to suppress the increase in the internal pressure of the battery 60 (battery module), and therefore the deterioration of the fuel efficiency of the vehicle V can be suppressed.

[0046] In the above embodiment, the voltage difference ΔVB between the cells 5 is the difference in voltage VB between adjacent cells 5, but it may be the difference between the average voltage of the cells 5 included in the battery 60 and the voltage VB of that cell 5. Also, the monitoring module 61 detects the voltage VB of the cell (battery cell) 5, but it may be possible to detect the voltages of a plurality of cells 5 (e.g., 3 to 6 cells) connected in series and use the detected voltage as the voltage VB to execute the SOC control center raising process. Also, the voltage of the battery module may be used as the voltage VB.

[0047] (Modification) In the above embodiment, the mode M is determined by the mode determination process (FIG. 3), and the mode of the variation suppression control and whether or not it can be executed are determined according to the determined mode M. However, instead of the mode determination process of FIG. 3, whether or not the variation suppression control can be executed may be determined based on the internal pressure PA during a trip (from Ready-ON to Ready-OFF) of the vehicle V. For example, an average value of the internal pressure PA during a trip (internal pressure PA from Ready-ON to Ready-OFF) is calculated and stored in the memory of the HV-ECU 100. Then, when the simple moving average of the average values ​​of the internal pressure PA over 10 trips (10 trips) exceeds a predetermined value d, the variation suppression control may not be executed. When the simple moving average exceeds the predetermined value d, it is estimated that the memory effect is occurring.

[0048] In this case, for example, if the average value of the internal pressure PA in a trip of one hour or more is greater than a predetermined value e greater than the simple moving average of 10 trips prior to the start of the trip, the trip is determined to have been mountain driving, and the average value of the internal pressure PA for the trip may be excluded from the simple moving average data.

[0049] In addition, when using a simple moving average of the average value of the internal pressure PA over 10 trips, if the simple moving average is below a predetermined value f, it may be determined that the user of the vehicle V is repeatedly driving with a low driving load, and variation suppression control may be executed.

[0050] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0051] 5 battery cell, 10 internal combustion engine, 20 first MG, 30 second MG, 40 power split device, 50 PCU, 60 battery, 61 monitoring module, 62 SMR, 100 HV-ECU, 200 MG-ECU, 300 EG-ECU, 400 various sensors, V vehicle.

Claims

[Claim 1] a battery pack in which a plurality of unit cells, each of which is a nickel-metal hydride battery, are connected in series; a drive device driven by the power stored in the battery pack; a control device that controls charging and discharging of the battery pack so that the SOC of the battery pack falls within a first predetermined range centered on a first SOC control center; The control device includes: When a voltage difference between the plurality of single cells becomes equal to or greater than a predetermined value, a variation suppression control is executed to charge and discharge the SOC so that the SOC falls within a second predetermined range centered on a second SOC control center that is greater than the first SOC control center; The vehicle is configured not to execute the variation suppression control when the internal pressure of the battery pack is equal to or higher than a set value.

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