JP5556745B2 - Battery voltage control system - Google Patents

Description

  The present invention relates to an assembled battery voltage control system.

  Conventionally, a battery management system provided with a plurality of monitoring devices that divide a plurality of battery cells connected in series into cell blocks composed of a plurality of battery cells and monitor each cell block for each cell block is disclosed in Patent Document 1, for example. Proposed in Each monitoring device can equalize the cell voltages of the battery cells in the corresponding cell block.

JP 2010-161918 A

  For example, in an electric vehicle such as a hybrid vehicle, a large number of battery cells are handled. Therefore, a plurality of monitoring devices are combined to form one monitoring unit, and a plurality of monitoring units are combined to form a system. Here, since each monitoring unit operates independently, the cell voltage of the battery cell corresponding to the said monitoring unit can be equalized by exchanging information of each cell block within the monitoring unit. However, since there is no communication means for exchanging information in units of cell blocks between a plurality of monitoring units, it has been impossible to equalize the cell voltages of all battery cells connected in series.

  Although an electric vehicle has been described as an example in which a large number of battery cells are handled, this is an example of a field in which battery cells are handled, and not only an electric vehicle but also a single system configured from a plurality of monitoring units. The above problem occurs.

  In view of the above points, the present invention provides an assembled battery voltage control system capable of equalizing the cell voltages of all battery cells even when a plurality of battery monitoring units are combined to form one system. Objective.

  In order to achieve the above object, according to the first aspect of the present invention, an upper ECU that rotates a cooling fan that cools a plurality of units in a predetermined rotation pattern, and a corresponding unit that is provided for each unit are configured. A plurality of battery monitoring units that perform a monitoring operation for monitoring the state of the battery cell to be performed, and equalize the cell voltage in the unit corresponding to the battery monitoring unit by flowing a current through the battery cell by performing this monitoring operation And.

  The plurality of battery monitoring units are configured exclusively for transmission that only transmits the monitoring result to the host ECU, have a rotation pattern on the unit side, and input the rotation speed signal from the cooling fan, The rotation speed is acquired, and the monitoring operation is performed when the rotation pattern based on the acquired rotation speed matches the rotation pattern on the unit side.

  The host ECU receives the cell voltage monitoring results from the plurality of battery monitoring units, and determines and determines a rotation pattern for causing any one of the plurality of battery monitoring units to perform a monitoring operation based on the monitoring results. By operating the cooling fan based on the rotation pattern, the cell voltages of all the battery cells constituting the plurality of units are equalized.

  As described above, since each battery monitoring unit inputs the rotation speed signal of the cooling fan, it is possible to cause one of the battery monitoring units to perform a monitoring operation using the rotation pattern of the cooling fan. it can. For this reason, even if each battery monitoring unit is not provided with a means for communicating between the battery monitoring units, each battery monitoring unit is provided with a receiving means for receiving a monitoring operation execution command from the host ECU. Even if not, the cell voltages of all the battery cells can be equalized.

  In the invention according to claim 2, a monitoring operation is performed to monitor the state of the battery cell that is provided corresponding to each unit and constitutes the corresponding unit, and a current is supplied to the battery cell by performing this monitoring operation. A plurality of battery monitoring units for equalizing cell voltages in a unit corresponding to the battery monitoring unit, and a power source and a battery monitoring unit provided corresponding to the plurality of battery monitoring units, respectively, And a plurality of relays that electrically connect or disconnect each other, and a host ECU that controls on / off of each of the plurality of relays.

  The plurality of battery monitoring units are configured exclusively for transmission that only transmits the monitoring result to the host ECU, and when the relay corresponding to the battery monitoring unit is turned on, the battery monitoring unit performs the monitoring operation to perform the monitoring operation. While the cell voltage is equalized in the unit corresponding to the monitoring unit, the monitoring operation is not performed when the relay corresponding to the battery monitoring unit is turned off.

  Further, the host ECU receives the cell voltage monitoring results from the plurality of battery monitoring units and determines which of the plurality of battery monitoring units to perform the monitoring operation based on the monitoring results, By turning on a relay corresponding to the determined battery monitoring unit and causing the battery monitoring unit to perform a monitoring operation, the cell voltages of all the battery cells constituting the plurality of units are equalized.

  Thus, by using the control of the relay that connects the battery monitoring unit and the power source, it is possible to perform a monitoring operation that causes any battery monitoring unit to consume current. For this reason, even if each battery monitoring unit is not provided with a means for communicating between the battery monitoring units, each battery monitoring unit is provided with a receiving means for receiving a monitoring operation execution command from the host ECU. Even if not, the cell voltages of all the battery cells can be equalized.

  In the invention according to claim 3, a monitoring operation is performed to monitor the state of the battery cell that is provided corresponding to each unit and constitutes the corresponding unit, and a current is passed through the battery cell by performing this monitoring operation. A plurality of battery monitoring units that equalize cell voltages in a unit corresponding to the battery monitoring unit, a host ECU that receives cell voltage monitoring results from the plurality of battery monitoring units, a plurality of battery monitoring units, and a host ECU And a plurality of signal lines respectively connecting the two.

The plurality of battery monitoring units are each configured exclusively for transmission that transmits only the monitoring result to the host ECU, and the host ECU monitors the plurality of batteries based on the monitoring results received from the plurality of battery monitoring units. It determines whether to perform a monitoring operation to any of the battery monitoring unit of the units, by causing the monitoring operation to the battery monitoring unit via a signal line corresponding to the determined battery monitoring unit, a plurality of units It is characterized by equalizing cell voltages of all the battery cells to be configured.

  As described above, by using the dedicated signal line that connects the battery monitoring unit and the host ECU, it is possible to cause one of the battery monitoring units to perform a monitoring operation to consume current. For this reason, even if the means for communicating between each battery monitoring unit is not provided in each battery monitoring unit, the cell voltage of all the battery cells can be equalized.

1 is an overall configuration diagram of a battery system including an assembled battery voltage control system according to a first embodiment of the present invention. It is a figure for demonstrating equalizing the cell voltage of all the battery cells between two battery monitoring units. It is a whole block diagram of the battery system containing the assembled battery voltage control system which concerns on 2nd Embodiment of this invention. It is a whole block diagram of the battery system containing the assembled battery voltage control system which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a battery system including an assembled battery voltage control system according to the present embodiment. As shown in the figure, the battery system includes an assembled battery 10, a cooling fan 20, a battery 30, a relay 40, a plurality of battery monitoring units 50, and a host ECU 60. Of these, the relay 40, the plurality of battery monitoring units 50, and the host ECU 60 constitute an assembled battery voltage control system.

  The assembled battery 10 is a battery group configured by connecting a plurality of battery cells 11 as a minimum unit in series. A rechargeable lithium ion secondary battery is used as the battery cell 11. The assembled battery 10 is mounted on an electric vehicle such as a hybrid vehicle, and is used as a power source for driving a load such as an inverter or a motor or a power source for an electronic device.

  And each battery cell 11 is grouped for every predetermined number, and the block 12 is comprised. Further, a plurality of units 13 are configured by grouping a plurality of blocks 12 every predetermined number.

  The cooling fan 20 is a blower fan for blowing air to the assembled battery 10 to cool each battery cell 11. The cooling fan 20 is configured to rotate according to a command value input from the host ECU 60. The command value is, for example, 300 revolutions per minute.

  The battery 30 supplies power to each battery monitoring unit 50 and the host ECU 60, and is a power source different from the plurality of units 13. Such a battery 30 is a vehicle-mounted battery of 14V, for example.

  The relay 40 is a switch unit that electrically connects or disconnects each battery monitoring unit 50 and the battery 30. The relay 40 is controlled by the host ECU 60. When the relay 40 is turned on, power is supplied from the battery 30 to each battery monitoring unit 50, and each battery monitoring unit 50 is fully driven. For example, an IGCT relay is employed as the relay 40.

  The plurality of battery monitoring units 50 are devices corresponding to each unit 13 and performing a monitoring operation for monitoring the battery state of the battery cells 11 constituting the corresponding unit 13. Each battery monitoring unit 50 includes a plurality of monitoring ICs 51 and a microcomputer 52 (hereinafter referred to as a microcomputer 52).

  The monitoring IC 51 is an IC that is provided for each block 12, detects the battery state of each battery cell 11 constituting the corresponding block 12, and outputs information on the detected battery state. Here, the “battery state” is a cell voltage, an internal resistance, or the like of the battery cell 11. That is, the monitoring IC 51 performs the above monitoring operation. Each monitoring IC 51 receives power from the corresponding block 12 and operates.

  This monitoring operation is an operation for detecting a cell voltage, an internal resistance, or the like by passing a current through the battery cell 11, and the monitoring IC 51 has a battery voltage detection function for each battery cell 11 or a battery voltage variation suppression function (that is, equalization). Processing). The battery voltage detection function is a function executed mainly when the vehicle is running, and the equalization is a function executed mainly when the vehicle is stopped. When this monitoring operation is performed, the battery cell 11 consumes current. Therefore, performing the monitoring operation also equalizes cell voltages in the unit 13 corresponding to the battery monitoring unit 50. Note that the current consumption during the battery voltage detection function of the monitoring IC 51 is greater than that during equalization.

  The microcomputer 52 is a control circuit that executes a predetermined function in accordance with a program stored in a ROM or the like by a microcomputer having a CPU, ROM, EEPROM, RAM, or the like (not shown). The microcomputer 52 operates based on the power supplied from the battery 30 via the relay 40. When the relay ECU 40 is turned off by the host ECU 60 and battery power is no longer supplied from the battery 30 to the microcomputer 52, the battery monitoring unit 50 shifts to the low consumption mode. Thereby, the battery monitoring unit 50 does not perform the monitoring operation that consumes the current of the battery cell 11.

  The microcomputer 52 receives the monitoring result from each monitoring IC 51 and performs equalization processing so that the battery cells 11 are equal between the blocks 12. Thereby, the cell voltage of each battery cell 11 is equalized in the unit 13.

  Then, the microcomputer 52 outputs battery state data such as cell voltage, current, and battery temperature necessary for battery control acquired by the monitoring operation to the host ECU 60 through serial communication as a monitoring result. Here, with regard to transmission / reception of monitoring result data, the battery monitoring unit 50 is configured as a transmission-only monitoring unit that only transmits data to the host ECU 60. That is, the battery monitoring unit 50 is a monitoring device dedicated to transmission, and includes a transmission means for that purpose. In other words, the battery monitoring unit 50 does not include a receiving unit that receives data from the host ECU 60 and cannot receive data from the host ECU 60.

  Further, the microcomputer 52 receives a rotation speed signal (pulse signal) from the cooling fan 20 and detects the actual rotation speed of the cooling fan 20 based on the rotation speed signal. The microcomputer 52 feeds back the acquired actual rotational speed data to the host ECU 60 by serial communication.

  Then, the microcomputer 52 performs the monitoring operation when the rotation pattern based on the acquired rotation number matches the rotation pattern for performing the monitoring operation. For this reason, the microcomputer 52 stores in advance a rotation pattern on the unit side for performing the monitoring operation. Here, the “rotation pattern” means that the number of rotations per second changes, for example, from high → low → medium →. A plurality of rotation patterns are set in advance in the host ECU 60, and which rotation pattern causes which battery monitoring unit 50 to perform a monitoring operation is determined in advance. This rotation pattern may be a pattern that cannot occur on the actual vehicle.

  As described above, each monitoring IC 51 is supplied with power from the corresponding block 12, the microcomputer 52 is supplied with power from the battery 30, the monitoring IC 51 side is a high voltage system, and the microcomputer 52 side is a low voltage system. Has been. As described above, since the monitoring IC 51 and the microcomputer 52 have different voltage levels to be handled, the monitoring IC 51 and the microcomputer 52 are configured to exchange signals via an insulating element (not shown) such as a photocoupler. Moreover, although two battery monitoring units 50 are shown in FIG. 1, there are actually a plurality of battery monitoring units 50.

  The host ECU 60 is a control device that manages a plurality of battery monitoring units 50. The host ECU 60 communicates the allowable charge / discharge amount to a vehicle control ECU (not shown) based on the monitoring result received from each battery monitoring unit 50.

  The host ECU 60 controls the ON / OFF of the relay 40 to cause each battery monitoring unit 50 to perform a monitoring operation, rotates the cooling fan 20 in a predetermined rotation pattern, and receives it from each battery monitoring unit 50. The cooling fan 20 is feedback-controlled based on the actual rotational speed.

  Further, the host ECU 60 receives the monitoring results such as the cell voltage from each battery monitoring unit 50, and determines which battery monitoring unit 50 is to perform the monitoring operation based on the monitoring results. That is, in order to determine whether there is variation between the battery monitoring units 50 and equalize the cell voltages of all the battery cells 11 constituting the assembled battery 10, the host ECU 60 consumes the current in the battery cell 11 of which unit 13. The rotation pattern for causing the unit 13 to perform the monitoring operation is determined. Then, upper ECU 60 operates cooling fan 20 based on the determined rotation pattern. Thereby, each battery monitoring unit 50 performs a monitoring operation when the rotation pattern indicated by the rotation speed signal input from the cooling fan 20 matches the rotation pattern on the unit side. In this way, the host ECU 60 equalizes the cell voltages of all the battery cells 11.

  As described above, the cell voltages of all the battery cells 11 are equalized among the plurality of battery monitoring units 50. For example, in the case where the cell voltages are equalized between two battery monitoring units 50, refer to FIG. I will explain. The horizontal axis of the graph shown in FIG. 2 indicates time, and the vertical axis indicates the voltage of the unit 13. The voltages of the two units 13 are V1 and V2, and V1> V2.

  In such a case, the host ECU 60 receives the monitoring result from each battery monitoring unit 50, and determines the battery monitoring unit 50 that performs the monitoring operation and the operation time of the monitoring operation from the monitoring result. In the example of FIG. 2, it is determined that the battery monitoring unit 50 having a high voltage of the unit 13 is to perform the monitoring operation. Then, the host ECU 60 rotates the cooling fan 20 in a rotation pattern for causing the battery monitoring unit 50 to perform a monitoring operation.

  The two battery monitoring units 50 (microcomputers 52) receive the rotation number signal from the cooling fan 20 and acquire the rotation pattern. The battery monitoring unit 50 having a high voltage of the unit 13 performs the monitoring operation because the rotation pattern becomes a command to perform the monitoring operation. The other battery monitoring unit 50 does not perform the monitoring operation because the rotation pattern is not a command for performing the monitoring operation.

  Note that “performing the monitoring operation” means performing an operation that consumes current. For example, the arrangement may be such that the monitoring IC 51 of the corresponding battery monitoring unit 50 is set to the equalization mode and the monitoring IC 51 of the non-corresponding battery monitoring unit 50 is left in the voltage detection mode. Therefore, “no monitoring operation” means that the battery monitoring unit 50 does not operate at all, but performs an operation that hardly consumes current as in the voltage detection mode.

  Thereby, as shown in FIG. 2, V1 decreases along with the monitoring operation. V2 gradually decreases because the monitoring IC 51 consumes current without performing the monitoring operation. Even if the cell voltages are equalized in each unit 13, the voltage between the units 13 varies, and the slopes of V1 and V2 vary.

  When the operation time elapses, the host ECU 60 finishes rotating the cooling fan 20 with the rotation pattern for performing the monitoring operation, and rotates the cooling fan 20 with a completely different rotation pattern. Thereby, the monitoring operation of the battery monitoring unit 50 corresponding to V1 ends. And V1 and V2 become the same voltage after progress of operation time.

  As described above, the cell voltage is equalized in the unit 13 of each battery monitoring unit 50, but the cell voltage is further equalized between the units 13.

  In FIG. 2, the case of two battery monitoring units 50 has been described. However, even if there are three or more battery monitoring units 50, the battery monitoring unit 50 having a high voltage of the unit 13 performs a monitoring operation to consume current. Thus, it is the same for adjusting each voltage to the voltage of the smallest unit 13.

  As described above, the present embodiment is characterized in that a monitoring operation for consuming current in any one of the battery monitoring units 50 is performed using the rotation pattern of the cooling fan 20. Thereby, even if the communication means for communicating between each battery monitoring unit 50 is not provided in each battery monitoring unit 50, the cell voltages of all the battery cells can be equalized. Further, even if each battery monitoring unit 50 is not provided with a receiving means for receiving a monitoring operation execution command from the host ECU 60, the cell voltages of all the battery cells can be equalized.

  Note that the battery 30 corresponds to the “power supply” in the claims as to the correspondence between the description in the present embodiment and the description in the claims.

(Second Embodiment)
In the present embodiment, parts different from the first embodiment will be described. In the first embodiment, the cell voltages of all the battery cells are equalized by causing the desired battery monitoring unit 50 to perform a monitoring operation according to the rotation pattern of the cooling fan. The present embodiment is characterized in that the cell voltages of all the battery cells are equalized by the control of the relay 40 that connects the battery monitoring unit 50 and the battery 30.

  FIG. 3 is an overall configuration diagram of a battery system including the assembled battery voltage control system according to the present embodiment. As shown in this figure, in this embodiment, relays 40 are provided corresponding to the battery monitoring units 50, respectively. The host ECU 60 controls on / off of each relay 40. The configuration other than the relay 40 is the same as that of the first embodiment.

  Then, as described above, each battery monitoring unit 50 performs the monitoring operation when the relay 40 corresponding to the battery monitoring unit 50 is turned on, thereby causing the cell voltage in the unit 13 corresponding to the battery monitoring unit 50. Perform equalization. Each battery monitoring unit 50 shifts to the low consumption mode when the relay 40 corresponding to the battery monitoring unit 50 is turned off by the host ECU 60 and does not perform the monitoring operation.

  In this embodiment, the cell voltage is equalized between the units 13 by utilizing the fact that the relay 40 is turned off and the battery monitoring unit 50 shifts to the low consumption mode.

  That is, the host ECU 60 receives the cell voltage monitoring result from each battery monitoring unit 50 and determines which battery monitoring unit 50 is to perform the monitoring operation and the operation time based on the monitoring result. This is the same as in the first embodiment. In this embodiment, the host ECU 60 turns on the relay 40 corresponding to the determined battery monitoring unit 50 to cause the battery monitoring unit 50 to perform the monitoring operation until the operation time has elapsed, so that the battery monitoring that does not require the monitoring operation is performed. The relay 40 corresponding to the unit 50 is turned off.

  As a result, the voltage of the unit 13 on which the monitoring operation is performed decreases over the operation time as shown in FIG. 2, so that the cell voltages are equalized among all the units 13. That is, the cell voltages of all the battery cells 11 constituting the plurality of units 13 are equalized.

  As described above, in the present embodiment, the relay 40 that connects the battery monitoring unit 50 and the battery 30 is controlled by the host ECU 60, so that only the battery monitoring unit 50 corresponding to the relay 40 that is turned on consumes current. The monitoring operation to be performed can be performed. Thereby, even if each battery monitoring unit 50 is not provided with a communication means for communicating between the battery monitoring units 50, a receiving means for receiving a monitoring operation execution command from the host ECU 60 is provided for each battery monitoring unit. Even if the unit 50 is not provided, the cell voltages of all the battery cells can be equalized.

(Third embodiment)
In the present embodiment, parts different from the first and second embodiments will be described. In the present embodiment, the host ECU 60 and each battery monitoring unit 50 are connected by a dedicated signal line, and the host ECU 60 monitors each battery monitoring unit 50 for the purpose of equalizing the cell voltage via this signal line. It is characterized by commanding operation.

  FIG. 4 is an overall configuration diagram of a battery system including the assembled battery voltage control system according to the present embodiment. As shown in this figure, the present embodiment is provided with a plurality of signal lines 70 for connecting each battery monitoring unit 50 and the host ECU 60 to the configuration shown in FIG. The configuration other than the signal line 70 is the same as that of the first embodiment.

  The host ECU 60 determines which battery monitoring unit 50 is to perform the monitoring operation and the operation time based on the monitoring results received from the plurality of battery monitoring units 50. This is the same as in the first embodiment. In this embodiment, the host ECU 60 issues a command for performing a monitoring operation via the signal line 70 corresponding to the determined battery monitoring unit 50. The “command for performing the monitoring operation” is a signal such as a high level or a low level. This causes the battery monitoring unit 50 to perform a monitoring operation, and does not allow the battery monitoring unit 50 that does not require a voltage drop of the unit 13 to perform the monitoring operation.

  Thereby, as shown in FIG. 2, the voltage of the unit 13 where the monitoring operation is performed decreases over the operation time. Therefore, the cell voltages of all the battery cells 11 constituting the plurality of units 13 are equalized.

  The host ECU 60 may receive the monitoring result from each battery monitoring unit 50 again after the monitoring operation, and verify whether or not the cell voltage is equalized normally based on the monitoring result.

  As described above, the present embodiment is characterized in that the dedicated signal line 70 for connecting each battery monitoring unit 50 and the host ECU 60 is used. Thereby, it is possible to cause one of the battery monitoring units 50 to perform a monitoring operation for consuming current. Moreover, even if the means for communicating between each battery monitoring unit 50 is not provided in each battery monitoring unit 50, the cell voltages of all the battery cells can be equalized.

(Other embodiments)
The configurations shown in the above embodiments are examples, and the present invention is not limited to the configurations described above, and other configurations that can realize the present invention may be employed. For example, the configurations shown in the above embodiments can be combined. Specifically, a combination of the configuration of the rotation pattern and the configuration of the plurality of relays 40, a combination of the rotation pattern and the dedicated signal line 70, and a combination of the plurality of relays 40 and the dedicated signal line 70 can be realized. Thus, the reliability of equalization of the cell voltage can be improved by combining the configurations of the respective embodiments. Moreover, even if one of them does not function, the other functions, so that redundancy can be ensured.

  Moreover, although 1st Embodiment demonstrated using the single cooling fan 20, the form using the some cooling fan 20 may be sufficient. Moreover, you may utilize the signal of the load which operate | moves according to the command value which not only the cooling fan 20 but high-order ECU60 issued.

10 battery pack 11 battery cell 12 block 13 unit 20 cooling fan 30 battery (power supply)
40 relay 50 battery monitoring unit 60 host ECU
70 signal line

Claims (3)

A plurality of battery cells connected in series are grouped into a predetermined number to form a block, and a plurality of blocks are grouped into a predetermined number to form a plurality of units, which constitute the plurality of units. A battery pack voltage control system for equalizing cell voltages of battery cells,
A host ECU that rotates a cooling fan that cools the plurality of units in a predetermined rotation pattern;
A monitoring operation for monitoring the state of the battery cell that is provided corresponding to each unit and that configures the corresponding unit is performed, and when the monitoring operation is performed, a current is supplied to the battery cell to correspond to the battery monitoring unit. A plurality of battery monitoring units for equalizing the cell voltage in the unit,
The plurality of battery monitoring units are configured exclusively for transmission that transmits only the monitoring result to the host ECU, have a rotation pattern on the unit side, and input the rotation number signal from the cooling fan, thereby cooling the cooling unit. The rotation speed of the fan is acquired, and when the rotation pattern based on the acquired rotation speed matches the rotation pattern on the unit side, the monitoring operation is performed.
The host ECU receives a cell voltage monitoring result from the plurality of battery monitoring units and determines a rotation pattern for causing any of the plurality of battery monitoring units to perform the monitoring operation based on the monitoring result, An assembled battery voltage control system that equalizes cell voltages of all battery cells constituting the plurality of units by operating the cooling fan based on the determined rotation pattern. A plurality of battery cells connected in series are grouped into a predetermined number to form a block, and a plurality of blocks are grouped into a predetermined number to form a plurality of units, which constitute the plurality of units. A battery pack voltage control system for equalizing cell voltages of battery cells,
A monitoring operation for monitoring the state of the battery cell that is provided corresponding to each unit and that constitutes the corresponding unit is performed, and the current is supplied to the battery cell by performing this monitoring operation, thereby corresponding to the battery monitoring unit. A plurality of battery monitoring units that equalize cell voltages in the unit;
A plurality of relays provided corresponding to each of the plurality of battery monitoring units, electrically connecting or disconnecting the battery monitoring unit with a power source different from the plurality of units;
A host ECU for controlling on / off of each of the plurality of relays,
The plurality of battery monitoring units are configured exclusively for transmission that only transmits monitoring results to the host ECU, and when the relay corresponding to the battery monitoring unit is turned on, the monitoring operation is performed by performing the monitoring operation. While performing equalization of the cell voltage in the unit corresponding to the battery monitoring unit, when the relay corresponding to the battery monitoring unit is turned off, the monitoring operation is not performed,
The host ECU receives cell voltage monitoring results from the plurality of battery monitoring units and determines which of the plurality of battery monitoring units performs the monitoring operation based on the monitoring results. Then, by turning on the relay corresponding to the determined battery monitoring unit and causing the battery monitoring unit to perform the monitoring operation, the cell voltages of all the battery cells constituting the plurality of units are equalized. A battery pack voltage control system. A plurality of battery cells connected in series are grouped into a predetermined number to form a block, and a plurality of blocks are grouped into a predetermined number to form a plurality of units, which constitute the plurality of units. A battery pack voltage control system for equalizing cell voltages of battery cells,
A monitoring operation for monitoring the state of the battery cell that is provided corresponding to each unit and that constitutes the corresponding unit is performed, and the current is supplied to the battery cell by performing this monitoring operation, thereby corresponding to the battery monitoring unit. A plurality of battery monitoring units that equalize cell voltages in the unit;
A host ECU that receives cell voltage monitoring results from the plurality of battery monitoring units;
A plurality of signal lines respectively connecting the plurality of battery monitoring units and the host ECU;
The plurality of battery monitoring units are each configured exclusively for transmission that only transmits a monitoring result to the host ECU,
The high-level ECU, the plurality of on the basis of each monitoring results received from the battery monitoring unit determines whether to perform the monitoring operation on any of the battery monitoring unit of the plurality of battery monitoring unit, the determined battery monitoring A battery pack voltage control characterized by equalizing cell voltages of all the battery cells constituting the plurality of units by causing the battery monitoring unit to perform the monitoring operation via a signal line corresponding to the unit. system.

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