JP2012138979A - Output equalization system of battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an output equalization system of a battery pack in which overdischarge prevention of each unit cell in a battery pack for an electric car such as a hybrid car, and extension of the distance traveled can be combined.SOLUTION: A supervisory control unit 80 controls a voltage monitoring circuit 60 to detect the cell voltage of all cells 11 (step 110) when the output of a battery pack 10 exceeds a predetermined value during acceleration of a vehicle (step 100). When the voltage variation of the cell voltage exceeds a threshold (ΔV) (step 120), the cell voltages thus detected are stored in a storage unit 90, and a predetermined time for performing equalization continuously is set (step 130). Thereafter, an equalization circuit 70 equalizes the cell voltages of the cells 11 stored in the storage unit 90 (step 140). Equalization is performed until a predetermined set time elapses.

Description

  The present invention relates to an assembled battery output equalizing system for equalizing outputs of a plurality of cells constituting an assembled battery, and is particularly effective in extending the travel distance of an electric vehicle such as a hybrid vehicle.

  Conventionally, for example, Patent Literature 1 proposes an assembled battery state-of-charge adjusting device configured by connecting a plurality of unit cells in series. Specifically, in Patent Document 1, a voltage detection unit that outputs a voltage signal corresponding to a voltage across each unit cell, a capacitor, and a voltage that boosts the voltage across the unit cell connected to both ends and supplies the voltage to the capacitor A charge state adjusting device including a converter has been proposed.

  In such a configuration, among the plurality of unit cells, the unit cell with the maximum voltage detected by the voltage detector is the maximum unit cell, and the unit cell with the minimum voltage is the minimum unit cell. When the voltage between both ends based on the state of charge (SOC) of each unit cell varies, the maximum unit cell is passed through the voltage converter so that the voltage of the capacitor becomes higher than the voltage across the maximum unit cell. The charge is transferred from the capacitor to the capacitor. Further, the charge is transferred from the capacitor to the minimum unit cell, and the voltage across each unit cell is equalized. Thereby, the state of charge (SOC) of each unit cell is equalized. The state of charge corresponds to the open circuit voltage when no current is flowing through the assembled battery.

Japanese Patent Laid-Open No. 2004-120871

  It is known that the internal resistance of each unit cell constituting the assembled battery changes with time. However, in the above conventional technique, control is performed so that the state of charge (SOC) of each unit cell is equalized. For this reason, when charging / discharging each unit cell by passing a large current through the assembled battery, a voltage rise / voltage drop occurs due to the internal resistance of the unit cell, and a battery with a larger internal resistance has a higher state of charge (SOC). There is a possibility that the voltage is lower than the lower limit voltage. Therefore, there is a problem that the unit cell having a large internal resistance is further deteriorated. Further, when the unit cell is further deteriorated, there is a problem that electric power necessary for accelerating the vehicle cannot be obtained, and normal traveling cannot be performed.

  In view of the above points, the present invention provides an assembled battery output equalization system capable of achieving both the prevention of overdischarge for each unit cell of an assembled battery for an electric vehicle such as a hybrid vehicle and the extension of a travel distance. The purpose is to provide.

  To achieve the above object, according to the first aspect of the present invention, a plurality of cells (11) are connected in series and are mounted on a vehicle and used as a drive source. 11) An assembled battery output equalization system comprising equalization means (70) for equalizing cell voltages of a plurality of cells (11) by moving electric power between them, characterized by the following points Yes.

  That is, a voltage monitoring means (60) for detecting the cell voltage of the cell (11) is provided for each of the plurality of cells (11). Moreover, the memory | storage means (90) which memorize | stores the cell voltage of the cell (11) detected by the voltage monitoring means (60) is provided.

  Further, the voltage monitoring means (60) detects the cell voltages of the plurality of cells (11) when the output of the assembled battery (10) exceeds a predetermined value during acceleration of the vehicle, and the detected cell voltages are stored in the storage means. Monitoring control means (80) that stores the data in (90) and causes the equalization means (70) to equalize so that the cell voltages of the plurality of cells (11) stored in the storage means (90) are equal to each other. It is characterized by having.

  According to this, instead of equalizing the state of charge when no current flows through the assembled battery (10), when the output of the assembled battery (10) exceeds a predetermined value during vehicle acceleration, that is, the assembled battery ( The equalization is performed based on the cell voltage of each cell (11) when a predetermined current flows through 10). For this reason, since the cell voltage of the deteriorated cell (11) is equalized so as to increase when a predetermined current flows through the assembled battery (10), the deteriorated cell (11) is maintained in a high charge state. be able to. Therefore, since the cell voltage of the deteriorated cell (11) does not need to fall below the lower limit voltage when the vehicle is accelerated, overdischarge of the deteriorated cell (11) can be prevented.

  And, since it is possible to prevent overdischarge of the deteriorated cell (11) and further prevent further deterioration of the cell (11) due to overdischarge, it is possible to obtain electric power necessary for acceleration of the vehicle from the assembled battery (10), The travelable time of the vehicle using the assembled battery (10), that is, the travel distance can be increased.

  From the above, it is possible to achieve both the prevention of overdischarge for each cell (11) of the assembled battery (10) for an electric vehicle such as a hybrid vehicle and the extension of the travel distance of the vehicle.

  In the invention according to claim 2, the monitoring control means (80) is configured to detect when the difference between the maximum value and the minimum value of the cell voltage of the cell (11) detected by the voltage monitoring means (60) exceeds a threshold value. The cell voltages of the plurality of cells (11) detected by the voltage monitoring unit (60) are stored in the storage unit (90), and the cell voltages of the plurality of cells (11) stored in the storage unit (90) are equal to each other. In this way, the equalization means (70) performs equalization.

  In this way, when the cell voltage variation is so large that it exceeds the threshold, the cell voltage is equalized, so that the state of charge of the deteriorated cell (11) can be maintained high, and overdischarge can be prevented. .

  In the invention according to claim 3, the monitoring control means (80) sets a predetermined time when the storage means (90) stores the cell voltage, and continues to equalize until the predetermined time elapses. The means (70) is characterized by performing equalization.

  Thereby, the cell voltage of the deteriorated cell (11) can be surely raised. Therefore, it is possible to prevent overdischarge of the deteriorated cell (11), and to obtain electric power necessary for accelerating the vehicle from the assembled battery (10).

  According to a fourth aspect of the present invention, the monitoring control means (80) is configured such that the difference between the maximum value and the minimum value of the cell voltage of the cell (11) detected by the voltage monitoring means (60) is a threshold value. If it does not exceed, it is possible to prevent the equalization means (70) from performing equalization.

  In the invention according to claim 5, when the output of the assembled battery (10) falls below a predetermined value, the monitoring control means (80) is based on the cell voltage stored in the storage means (90). 70), equalization is performed.

  Thereby, each cell (11) is equalized to the cell voltage when power is consumed by the assembled battery (10) during acceleration of the vehicle, so that the deteriorated cell (11) can be maintained in a high charge state. As a result, it is possible to achieve both the prevention of overdischarge of the cell (11) and the extension of the travel distance of the vehicle.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is an overall configuration diagram of an assembled battery control system including an output equalization system according to an embodiment of the present invention. It is the figure which showed an example of the equalization circuit. It is the flowchart which showed the content of the equalization process of a monitoring control part. (A) is the figure which showed equalization of the cell voltage at the time of discharge of the assembled battery by this invention, (b) is equalization of the cell voltage based on the charge condition (open circuit voltage) at the time of discharge of the conventional assembled battery FIG. It is the figure which showed equalization of the cell voltage at the time of charge of an assembled battery.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an assembled battery control system including an output equalization system according to the present embodiment. As shown in this figure, the assembled battery control system includes an assembled battery 10, an inverter 20 (INV in FIG. 1), a motor generator 30 (MG in FIG. 1), and an output equalization system 40. It is configured.

  The assembled battery 10 is a battery group configured by connecting a plurality of cells 11 as a minimum unit in series. A rechargeable lithium ion secondary battery is used as the cell 11. The assembled battery 10 is mounted on an electric vehicle such as a hybrid vehicle to serve as a drive source, and is used as a power source for driving a load such as the motor generator 30 or a power source for an electronic device. The “hybrid vehicle” includes both a hybrid vehicle equipped with the assembled battery 10 and a plug-in hybrid vehicle that can be charged from the outside. The positive output terminal 12 and the negative output terminal 13 of the assembled battery 10 are connected to the motor generator 30 via the inverter 20.

  The inverter 20 converts DC power output from the assembled battery 10 into AC power and supplies it to the motor generator 30, and converts AC power output from the motor generator 30 into DC power and supplies it to the assembled battery 10. A power conversion device having the function of:

  The motor generator 30 is a motor connected to the wheel shaft of the vehicle, and has a function as a power source for running the vehicle and a function as a generator. That is, the regenerative power of the wheel shaft is converted to AC power by the motor generator 30, converted to DC power by the inverter 20, and stored as energy in each cell 11 of the assembled battery 10. Further, during traveling of the vehicle by the assembled battery 10, the energy of each cell 11 of the assembled battery 10 is converted into AC power by the inverter 20 and supplied to the motor generator 30 to drive the wheel shaft.

  The output equalization system 40 is a system that monitors each cell 11 of the assembled battery 10 and equalizes the output (power) of each cell 11. Such an output equalization system 40 includes a current sensor 50, a voltage monitoring circuit 60, an equalization circuit 70, and a monitoring control unit 80.

  The current sensor 50 is a sensor that detects the magnitude of the current flowing between the assembled battery 10 and the inverter 20. The current flowing between the assembled battery 10 and the inverter 20 is a current that charges and discharges the assembled battery 10, and is an outflow current from the assembled battery 10 to the inverter 20 or an inflow current from the inverter 20 to the assembled battery 10.

  The voltage monitoring circuit 60 is a circuit that detects the cell voltage of the cell 11. The voltage monitoring circuit 60 is connected in parallel to the cell 11 and is provided for each of the plurality of cells 11. Such a voltage monitoring circuit 60 includes, for example, a voltage dividing circuit, a selection circuit, and a comparison circuit (not shown).

  The voltage dividing circuit is configured by connecting a plurality of resistors in series between the positive electrode side and the negative electrode side of each cell 11. A voltage dividing the cell voltage multiplied by the resistance voltage dividing ratio is generated at the connection point of each resistor.

  The selection circuit is composed of a plurality of switches having one end connected to a connection point of each resistor and the other end integrated into one contact. The divided voltage of each resistor is output to the comparison circuit by switching each switch. Switching of each switch is controlled by the monitoring control unit 80. Each switch may be switched automatically on the selection circuit side, and the number of the switch being conducted may be output to the monitoring control unit 80.

  The comparison circuit includes a comparator and a reference power source. A selection circuit is connected to the non-inverting input terminal of the comparator to apply a voltage divided by the voltage dividing circuit, and a reference voltage generated by a reference power supply is applied to the inverting input terminal. As a result, when the divided voltage applied to the non-inverting input terminal of the comparator exceeds the reference voltage applied to the inverting input terminal, a high-level comparison result is output to the output terminal of the comparator, and the divided voltage is reduced to the reference voltage. If not, a low level comparison result is output. The comparison result is output to the monitoring control unit 80.

  In such a configuration of the voltage monitoring circuit 60, the minimum value of the divided voltage of the voltage dividing circuit corresponds to the overcharge determination value, and the maximum value of the divided voltage corresponds to the overdischarge determination value. When the switch is switched, the comparison result of the comparator is normally inverted when any one of the switches is turned on. In other words, the cell voltage can be acquired by examining which switch has inverted the comparison result of the comparator. Thus, the cell voltage is determined in multiple stages between the overcharge determination value and the overdischarge determination value.

  The equalization circuit 70 is a circuit that equalizes the cell voltages of the plurality of cells 11 by moving power between the cells 11. Several active equalization schemes for transferring power between cells 11 are known.

  For example, by providing a coil (not shown) between the cells 11 and 11 and switching the cell 11 connected to the coil by operating a switch (not shown), the power of one cell 11 is temporarily stored in the coil. A converter system for moving to the other cell 11 later is known. There is also a method of storing the power of the cell 11 in a capacitor (not shown) instead of a coil.

  In this embodiment, a transformer method is employed. FIG. 2 is a schematic diagram when a transformer system is adopted as an example of the equalization circuit 70. As shown in this figure, a primary winding 71 is connected between the positive output terminal 12 and the negative output terminal 13 of the battery pack 10, and a secondary winding 72 is connected to both poles of each cell 11. Has been. The primary winding 71 and each secondary winding 72 are wound around a common iron core 73. The primary winding 71 and each secondary winding 72 are each provided with a switch 74, and the switch 74 is controlled by the monitoring controller 80. The equalizing circuit 70 shown in FIG. 1 includes a secondary winding 72, and the primary winding 71 is not shown in FIG.

  In such a transformer-type configuration, when the switch 74 connected to the primary winding 71 is turned on, a loop circuit is formed by the assembled battery 10 and the primary winding 71, and the primary current is generated in the primary winding 71. Flows and energy is accumulated in the iron core 73. Then, by turning on the switch 74 corresponding to the cell 11 having a low cell voltage, a secondary current flows through the cell 11 having a low cell voltage based on the energy accumulated in the iron core 73. In this way, the cell voltage is equalized by moving the power from the cell 11 with high power to the cell 11 with low power.

  Of course, the configuration of the transformer-type equalization circuit 70 shown in FIG. 2 is merely an example, and other configurations may be adopted even if the transformer method is used. Further, not only the transformer method but also a combination of each method may be used.

  The monitoring control unit 80 is a voltage monitoring function for monitoring the cell voltage, an overcharge / discharge detection function for detecting overcharge or overdischarge of the cell 11, a current detection function for detecting a current flowing through the assembled battery 10, and a charging of the assembled battery 10 It is a device having various functions such as a state detection function and an equalization function for equalizing cell voltages of the respective cells 11.

  As described above, the voltage detection function is a function in which the monitoring control unit 80 acquires the comparison result of the comparator of the comparison circuit from the voltage monitoring circuit 60 while switching each switch of the selection circuit of the voltage monitoring circuit 60. Thereby, the cell voltage of each cell 11 can be acquired based on the inversion result of each cell 11. The overcharge / discharge detection function is a function for determining overcharge or overdischarge of the cell 11 based on the comparison result of the comparator.

  The current detection function is a function of detecting a current flowing through the assembled battery 10 by the current sensor 50. The charge state detection function also determines the state of charge (SOC) of the assembled battery 10 based on the cell voltage of each cell 11 acquired by the voltage monitoring circuit 60 and the current flowing through the assembled battery 10 acquired by the current sensor 50. It is a function to acquire.

  The equalization function moves power from the cell 11 having a higher cell voltage to the cell 11 having a lower cell voltage by switching the switch of the equalization circuit 70 based on the cell voltage of each cell 11 acquired by the voltage monitoring circuit 60. This is a function of equalizing the cell voltage of each cell 11. For example, the monitoring control unit 80 controls so that the cell voltages of all the cells 11 simultaneously reach the lower limit voltage when the assembled battery 10 is discharged at a predetermined power. The lower limit voltage is a voltage indicating overdischarge of the cell 11.

  As the monitoring control unit 80 having the above functions, for example, a microcomputer constituted by a CPU or the like is employed. Such a monitoring control unit 80 includes a storage unit 90 that stores the cell voltage of each cell 11 detected by the voltage monitoring circuit 60. As the storage unit 90, for example, a memory such as a RAM is employed.

  As will be described in detail later, the monitoring control unit 80 causes the voltage monitoring circuit 60 to detect the cell voltage of each cell 11 when predetermined power is output from the assembled battery 10 during acceleration of the vehicle. The detected cell voltage is stored in the storage unit 90. When the monitor control unit 80 equalizes the cell voltages after storing the cell voltages in the storage unit 90, the monitor control unit 80 equalizes the cell voltages of the cells 11 stored in the storage unit 90 to be equal to each other. The equalizing circuit 70 is made to perform equalizing discharge.

  The above is the overall configuration of the output equalization system 40 and the assembled battery control system according to the present embodiment.

  Next, the equalization function of the monitoring control unit 80 in the output equalization system 40 will be described with reference to FIG. FIG. 3 is a flowchart showing the content of the equalization process of the monitoring control unit 80. The flowchart shown in FIG. 3 starts when the vehicle is turned on. Along with this, the equalization continuation determination constant for determining whether or not to continue the equalization process is reset. Here, the “equalization continuation determination constant” is a predetermined time during which equalization is continued, and when the equalization continuation determination constant is Keep, Keep = 0.

  In step 100, it is determined whether or not the output of the assembled battery 10 exceeds a predetermined value during acceleration of the vehicle. The “output of the assembled battery 10” is an output necessary for the vehicle to accelerate beyond a certain level. The predetermined value is, for example, 10 kW, and a different value is set depending on the vehicle type. Therefore, the current flowing through the current assembled battery 10 is detected by the current sensor 50, the output of the assembled battery 10 is calculated, and the calculation result is compared with a predetermined value.

  The “output of the assembled battery 10” is electric power that is normally obtained as a product of the voltage of the assembled battery 10 and the current flowing through the assembled battery 10 as described above. However, “the output of the assembled battery 10” may simply refer to the current flowing through the assembled battery 10. In this case, it is determined whether or not the current flowing through the assembled battery 10 exceeds 20A, for example.

  If it is determined in step 100 that the output of the assembled battery 10 exceeds a predetermined value, the process proceeds to step 110. In step 110, the cell voltages of all the cells 11 are measured. In the present embodiment, each cell voltage measured in step 110 is referred to as VC.

  Subsequently, in step 120, whether the difference (VCmax−VCmin) between the maximum value (VCmax) and the minimum value (VCmin) among the cell voltages of all the cells 11 acquired in step 110 exceeds the threshold value (ΔV). It is determined whether or not. The “difference between the maximum value (VCmax) and the minimum value (VCmin) of the cell voltages” is the voltage variation of each cell 11, and it is determined in this step whether or not the cell voltage of each cell 11 needs to be equalized. Is done.

  For example, when a lithium ion battery is adopted as the cell 11, the cell voltage is about 3.0V to 4.1V, and the voltage variation is about 0.1V to 0.5V, for example. The threshold value (ΔV) is set depending on how much voltage difference is considered as voltage variation. When the threshold value (ΔV) is a large value, the frequency of equalization is low, but when the threshold value (ΔV) is a small value, the equalization is frequently performed.

  In step 130, the equalization continuation determination constant Keep is set to Keep = 60. If the control flow period shown in FIG. 3 is 1 second, “60” of Keep = 60 means an equalization duration of 60 seconds. In the present embodiment, the equalization continuation determination constant Keep is a fixed value, but may be a variable value. For example, the equalization continuation determination constant Keep can be mapped according to the voltage variation of the cell voltage, that is, the threshold value (ΔV), and stored in the monitoring control unit 80. Specifically, when the voltage variation is 0.1 V, the equalization duration is set to 60 seconds, and when the voltage variation is 0.5 V, the equalization duration is set to 120 seconds. Thus, equalization continuation time becomes long, so that voltage variation is large.

  In step 130, the cell voltages of all the cells 11 acquired in step 110 are stored in the storage unit 90. That is, the cell voltages VC of all the cells 11 when the output of the assembled battery 10 exceeds 10 kW are stored as VCm (VCm = VC).

  As described above, in step 130, the cell voltage VCm is stored in the storage unit 90, and at this time, an equalization duration (a constant time) for continuously performing equalization is set.

  Next, in step 140, equalization processing based on the cell voltage VCm is performed. That is, the equalization circuit 70 equalizes the cell voltages so that the cell voltages VCm of the cells 11 stored in the storage unit 90 in step 130 are equal. The equalization of the cell voltage is performed by a transformer method that moves power from the cell 11 having a high cell voltage to the cell 11 having a low cell voltage, as described above, based on the cell voltage VCm stored in the storage unit 90.

  In step 150, the equalization continuation determination constant Keep is set to Keep = Keep-1.

  Thereafter, in step 160, it is determined whether or not the vehicle has finished traveling. That is, it is determined whether or not the vehicle is powered off. When the power of the vehicle is turned off, the equalization process of the monitoring control unit 80 shown in FIG. 3 ends. On the other hand, if the power is not turned off, the process returns to step 100. In this way, the control flow shown in FIG. As described above, the control flow cycle from step 100 to step 160 is 1 second.

  As described above, after it is determined in step 100 that the output of the assembled battery 10 has exceeded a predetermined value and the cell voltages of all the cells 11 are measured in step 110, the cell voltage of each cell 11 is measured in step 120. When the difference (VCmax−VCmin) between the maximum value (VCmax) and the minimum value (VCmin) does not exceed the threshold value (ΔV), the process proceeds to step 150. That is, when the voltage variation of the cell voltage is small, equalization by the equalization circuit 70 is not performed, and the value of the equalization continuation determination constant Keep is decreased by one in step 150 thereafter.

  If the output of the assembled battery 10 falls below a predetermined value in step 100 among the above steps, the process proceeds to step 170. In step 170, it is determined whether or not Keep is greater than zero. That is, it is determined whether or not the equalization process is continuing. If it is determined that Keep is greater than 0, the process proceeds to step 140 where equalization processing is performed. Thereafter, the value of Keep is decremented by 1 in step 150, and if it is determined in step 160 that the vehicle is not turned off, the process returns to step 100 again. If the output of the assembled battery 10 is not lower than the predetermined value and the value of Keep is greater than 0, the values of Step 100, Step 170, Step 140, Step 150, and Step 160 are kept until the value of Keep is 0. Repeat the loop. Thus, equalization by the equalization circuit 70 is continued until the equalization continuation determination constant set in step 130 is counted, that is, until a predetermined time elapses.

  Then, when the value of Keep becomes 0 and it is determined in Step 170 that the Keep does not exceed 0, the process proceeds to Step 160, and the cell voltage equalization process ends. And it returns to step 100 again, and the loop of step 100, step 170, and step 160 is repeated unless the output of the assembled battery 10 exceeds a predetermined value.

  On the other hand, if the voltage variation exceeds the threshold value (ΔV) in step 120, the equalization continuation determination constant Keep is set to “60” in step 130. Therefore, every time the process proceeds to step 130, “60” Is set. Therefore, the value of Keep is subtracted in step 150 after the acceleration of the vehicle ends and the output of the assembled battery 10 falls below a predetermined value.

  3 is started and the flowchart shown in FIG. 3 is started, and even if the output of the assembled battery 10 exceeds a predetermined value in step 100, the voltage variation in the subsequent step 120 becomes the threshold value (ΔV ), It is determined in step 150 that the value of Keep is “−1”. In this case, returning to step 100 again, if it is determined that the output of the assembled battery 10 has fallen below a predetermined value, it is determined in step 170 that Keep is not greater than zero. For this reason, the loop of step 100, step 170, and step 160 is repeated until the output of the assembled battery 10 exceeds a predetermined value, and equalization by the equalization circuit 70 is not performed.

  If it is determined in step 100 that the output of the assembled battery 10 does not exceed the predetermined value after the vehicle power is turned on, the Keep is not set in step 130, so that the steps 100, 170, and 160 are performed. Just repeat the loop.

  The effect of the equalization process will be described with reference to FIG. 4A is a diagram showing cell voltage equalization according to the present invention, and FIG. 4B is a diagram showing cell voltage equalization based on a conventional charge state (open circuit voltage). 4A and 4B, the horizontal axis indicates the charging current flowing through the assembled battery 10 in the positive direction, the discharging current flowing through the assembled battery 10 in the negative direction, and the vertical axis indicates the cell voltage. Is shown.

  Further, FIG. 4 shows cell voltages of three cells 11 of cell A, cell B, and cell C. Each of these cells 11 varies in deterioration, and the gradient of the cell voltage with respect to the current is different. Since the deteriorated cell 11 has a high internal resistance, the gradient of the cell voltage with respect to the current increases. Among the three cells 11 shown in FIG. 4, the deterioration of the cell A is the most advanced.

  And when electric power is taken out from the assembled battery 10, that is, when a discharge current flows through the assembled battery 10, an equal power line 13 appears as shown in FIG. The position of the equal power line 13 varies depending on the amount that the driver steps on the accelerator. When the amount of depression of the accelerator is large, the equal power line 13 appears on the left side of the position of the equal power line 13 shown in FIG.

  In addition, when there are voltage variations in the three cell voltages before the equalization process is performed, the cell voltages of the three cells 11 are scattered on the equal power line 13. Therefore, in the equalization process shown in FIG. 3, each cell voltage on the equal power line 13 is measured (step 110), stored in the storage unit 90 (step 130), and the stored cell voltages are made equal. Is equalized (step 140). As a result, the cell A having a large internal resistance, that is, a large inclination is equalized so that the cell voltage when “the discharge current flows through the assembled battery 10” becomes high. For example, the cell A receives power from the cell C that has not deteriorated.

  In this way, since the equalization process is performed so that the cell voltages when using the power of the assembled battery 10 assuming the acceleration of the vehicle are equalized, the cell voltage of each equalized cell 11 is “the assembled battery. When the discharge current flows through 10, the voltage becomes higher than the lower limit voltage indicating overdischarge. In other words, for the cell 11 that has deteriorated, the cell voltage when the discharge current flows through the assembled battery 10 is raised by the equalization process, so that it becomes difficult to fall below the lower limit voltage when the vehicle is accelerated. For this reason, when the discharge current flows through the assembled battery 10, it is possible to prevent over-discharge of the cell A that has deteriorated. Further deterioration of the cell 11 due to overdischarge can also be prevented. Further, as shown in FIG. 4A, the cell voltage of “when the discharge current flows through the assembled battery 10” is equalized, so that the cell voltage of each cell 11 is at the same position on the equal power line 13. As a result, the output (power) of each cell 11 can be equalized even if the deterioration of each cell 11 varies.

  On the other hand, conventionally, as shown in FIG. 4B, equalization processing is performed so that the open circuit voltage (SOC) when current does not flow through the assembled battery 10 is equalized. For this reason, when “a discharge current flows through the assembled battery 10”, the cell voltage of the cell A having a large slope of deterioration is less than the lower limit voltage, resulting in overdischarge. When even one overdischarged cell 11 occurs in this way, it is determined by the monitoring circuit or the like that the output required for acceleration cannot be output from the assembled battery 10, and no discharge current can flow through the assembled battery 10. That is, when one cell 11 cannot be used, an output necessary for acceleration cannot be output from the assembled battery 10, and the acceleration of the vehicle may be significantly reduced. For this reason, the travel distance of the vehicle does not increase.

  In this embodiment, since equalization is performed using each cell voltage when there is an output of the assembled battery 10 necessary for vehicle acceleration, the charged state (open circuit voltage) of the cell 11 is equal as in the prior art. It is not converted. However, as shown in FIG. 4A, for the cell voltage when the current flowing through the assembled battery 10 is 0, that is, the open circuit voltage, the open circuit voltage of the cell A that has deteriorated more than the other cells B and C. Therefore, the deteriorated cell A can be maintained for a long time. Therefore, it is possible to obtain electric power necessary for accelerating the vehicle from the assembled battery 10, and it is possible to extend the travelable time of the vehicle using the assembled battery 10, that is, the travel distance.

  As described above, both overdischarge prevention for each cell 11 of the assembled battery 10 for an electric vehicle such as a hybrid vehicle and the extension of the distance traveled by the electric vehicle such as the hybrid vehicle using only the assembled battery 10 are achieved. Can be planned.

  In the present embodiment, since the cell voltage is equalized when the voltage variation of the cell voltage exceeds the threshold (ΔV), the charged state of the deteriorated cell 11 can be maintained high, and the deterioration It is possible to prevent the cell 11 having progressed from being overdischarged. Further, the output of the cell 11 that has deteriorated can be made the same as that of the other cells 11. Further, the equalization process is continuously performed for a predetermined time, and even after the output of the assembled battery 10 falls below a predetermined value, the equalization is continuously performed until the predetermined time elapses. The voltage can be reliably raised. Therefore, the overdischarge of the deteriorated cell 11 is prevented, and the travel distance of the vehicle can be extended.

  As for the correspondence between the description of the present embodiment and the description of the claims, the equalization circuit 70 corresponds to the “equalization means” in the claims, and the voltage monitoring circuit 60 corresponds to the claims. Corresponds to “voltage monitoring means”. The storage unit 90 corresponds to “storage means” in the claims, and the monitoring control unit 80 corresponds to “monitoring control means” in the claims.

(Other embodiments)
The configuration of the output equalization system 40 shown in the above embodiment is an example, and the configuration is not limited to the configuration shown above, and other configurations including the features of the present invention may be adopted. For example, the storage unit 90 is a part of the monitoring control unit 80, but may be provided separately from the monitoring control unit 80. In addition, the configuration of the voltage monitoring circuit 60 and the configuration of the equalization circuit 70 are not limited to the configurations shown in the above embodiment, and other configurations may be used.

  Further, in the above embodiment, the case where the monitoring control unit 80 equalizes the cell voltage of each cell 11 when the assembled battery 10 is discharged has been described, but the same applies to the case where the assembled battery 10 is charged. FIG. 5 is a diagram showing equalization of the cell voltage during charging of the battery pack 10. In the case of charging the assembled battery 10, the monitoring control unit 80 causes the voltage monitoring circuit 60 to measure the cell voltage of each cell 11 when a charging current of, for example, 10 A flows from the inverter 20 to the assembled battery 10, and the storage unit 90. Remember me. And equalization of a cell voltage moves electric power from the cell A with a high cell voltage to the cell C with a low cell voltage as mentioned above based on the cell voltage VCm memorize | stored in the memory | storage part 90. FIG. In this case, for example, the monitoring control unit 80 performs equalization control so that the cell voltages of all the cells 11 simultaneously reach the upper limit voltage when the assembled battery 10 is charged. The upper limit voltage is a voltage indicating overcharge of the cell 11. Thereby, as shown in FIG. 5, the cell voltage of the cell C having a low cell voltage can be raised.

10 assembled battery 11 cell 60 voltage monitoring circuit (voltage monitoring means)
70 Equalization circuit (equalization means)
80 Monitoring control unit (monitoring control means)
90 storage unit (storage means)

Claims (5)

In the assembled battery (10) which is configured by connecting a plurality of cells (11) in series and is mounted on a vehicle and serving as a drive source, the plurality of cells are moved by moving power between the cells (11). An output equalization system for an assembled battery comprising equalization means (70) for equalizing the cell voltage of (11),
Voltage monitoring means (60) provided for each of the plurality of cells (11) and detecting a cell voltage of the cells (11);
Storage means (90) for storing the cell voltage of the cell (11) detected by the voltage monitoring means (60);
The voltage monitoring means (60) detects the cell voltages of the plurality of cells (11) when the output of the assembled battery (10) exceeds a predetermined value during acceleration of the vehicle, and the detected cell voltages are Monitoring that causes the storage means (90) to perform equalization so that the cell voltages of the plurality of cells (11) stored in the storage means (90) are equal to each other. And an output equalizing system for the assembled battery, comprising: a control means (80).   When the difference between the maximum value and the minimum value of the cell voltage of the cell (11) detected by the voltage monitoring means (60) exceeds a threshold value, the monitoring control means (80) The cell voltages of the plurality of cells (11) detected in (4) are stored in the storage means (90), and the cell voltages of the plurality of cells (11) stored in the storage means (90) are equal to each other. The output equalization system for an assembled battery according to claim 1, wherein the equalization means (70) performs equalization as described above.   The monitoring control means (80) sets a predetermined time when the storage means (90) stores the cell voltage, and continues to the equalization means (70) until the predetermined time elapses. 3. The battery pack output equalization system according to claim 1 or 2, wherein equalization is performed.   When the difference between the maximum value and the minimum value of the cell voltage of the cell (11) detected by the voltage monitoring means (60) does not exceed a threshold value, the monitoring control means (80) 70) The equalization system for an assembled battery according to any one of claims 1 to 3, wherein equalization is not performed in 70).   When the output of the assembled battery (10) falls below the predetermined value, the monitoring control means (80) causes the equalization means (70) to be based on the cell voltage stored in the storage means (90). 5. The assembled battery output equalization system according to claim 1, wherein equalization is performed.

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