JP2013183555A - Cell balance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell balance device of an active system, suppressing an increase of the number of taps caused by an increased number of series connections of a plurality of battery cells provided in a battery pack, and suppressing dispersion between the taps.SOLUTION: The cell balance device includes: a battery pack having battery stacks, including a plurality of serially connected battery cells, that are connected in series; a plurality of primary coils connected in parallel with the battery pack; a plurality of secondary coils connected in parallel with each battery cell; and each switching circuit connected in series with each of the plurality of primary coils. The plurality of secondary coils connected to the plurality of battery cells constituting the battery stack are transformer coupled with one primary coil. Also, each of the plurality of primary coils is transformer coupled with a different secondary coil. With this, by switching the switching circuit connected to the primary coil, there is configured a transformer coupling circuit capable of equalizing cell battery voltages of the plurality of battery cells in each battery stack.

Description

  The present invention relates to a cell balance device that equalizes the voltages of a plurality of battery cells constituting an assembled battery, and more particularly to an active type cell balance device that transfers power between battery cells via a transformer.

A battery cell such as a lithium ion battery mounted on a hybrid vehicle or an electric vehicle is used as an assembled battery in which a plurality of battery cells are connected in series in order to obtain a high voltage.
When the voltage of each battery cell constituting such an assembled battery (hereinafter referred to as cell voltage) varies, the deterioration of the battery cell proceeds at an accelerated rate or the amount of available energy decreases. Therefore, it is desirable that each cell voltage is equal. However, the cell voltage may vary due to non-uniform capacity, internal resistance, self-discharge rate, and the like of each battery cell. Thus, conventionally, it has been proposed to eliminate variations in cell voltages using a cell balance device for equalizing the cell voltages.

  As a configuration of the cell balance device, conventionally, a switch and a resistor are connected to each battery cell, and when there is a battery cell having a high voltage in each battery cell, the battery cell is discharged. Thus, a passive method for equalizing the voltage of each battery cell is used. However, since the passive method in principle discharges excess power from the battery cell, power is wasted. In view of this, attention has been focused on an active cell balance device that equalizes the voltage of each battery cell by transferring power between the battery cells via a transformer.

  However, in the conventional active type cell balance device, one battery cell is connected to each tap of the transformer, so that the number of taps of the transformer increases as the number of series cells increases. As the number of taps in the transformer increases, the conventional active cell balance device has a problem in that variation between taps increases and the size of the transformer coupling circuit increases.

  Moreover, the technique regarding a cell balance apparatus is disclosed by the following patent documents 1-3.

JP 2001-136660 A JP 2002-223528 A Japanese Patent Laid-Open No. 2004-080992

  An object of the present invention is to suppress an increase in the number of taps of a transformer and variations between taps due to an increase in the number of battery cells included in an assembled battery in an active cell balance device.

  In order to solve the above-described problem, the cell balance device of the present invention is a cell balance device that equalizes the cell voltage of each battery cell included in a battery pack in which a plurality of battery stacks in which a plurality of battery cells are connected in series is included. A plurality of primary coils connected in parallel to each other and in parallel to the assembled battery, a plurality of secondary coils connected in parallel to each battery cell, and each of the plurality of primary coils connected in series. And a plurality of secondary coils connected to the plurality of battery cells constituting the battery stack are respectively transformer-coupled to one primary coil of the plurality of primary coils. The plurality of primary coils are transformer-coupled to a plurality of secondary coils connected to the plurality of battery cells that constitute the separate battery stacks.

  ADVANTAGE OF THE INVENTION According to this invention, the increase in the tap number of a transformer by the increase in the series number of the some battery cell with which an assembled battery is equipped and the variation between taps can be suppressed in an active type cell balance apparatus.

It is a block diagram which shows the cell balance apparatus of Embodiment 1. 3 is a flowchart of cell balance control according to the first embodiment. It is a block diagram which shows the cell balance apparatus of Embodiment 2. 6 is a flowchart of cell balance control according to the second embodiment.

[Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings.
The wording used in the following description is defined.

  The battery stack is a structural unit in which a plurality of battery cells are connected in series. For example, a battery stack is shown in which four battery cells are connected in series. In addition, the assembled battery is a structural unit in which a plurality of battery stacks are connected in series. For example, the battery pack includes four battery stacks connected in series.

FIG. 1 is a configuration diagram illustrating a cell balance device according to the first embodiment.
With reference to FIG. 1, the active type cell balance apparatus of Embodiment 1 is demonstrated.
In the following description, a cell balance device that equalizes cell voltages of a plurality of battery cells constituting an assembled battery mounted on a hybrid vehicle, an electric vehicle, or the like will be described. However, the cell balance device of the first embodiment is also applicable to the case of equalizing the cell voltages of a plurality of battery cells constituting an assembled battery used for other applications such as an assembled battery mounted on a notebook computer or the like. Can be applied.

In the following description, the cell balance device is assumed to be an active method unless otherwise specified.
The cell balance device of Embodiment 1 used to equalize each cell voltage of a battery pack in which 16 battery cells 1a to 1p are connected in series includes, for example, 16 secondary coils 2a to 2p, 16 Diodes 3a to 3p, 16 voltmeters 4a to 4p, 4 primary coils 5a to 5d, 4 switching circuits 6a to 6d, 4 cores 7a to 7d, and control unit 8, a storage unit 9, four voltmeters 10 a to 10 d, four battery stacks 11 a to 11 d, and four transformer coupling circuits 12 a to 12 d. As described above, FIG. 1 illustrates the cell balance device in the case where the number of battery stacks constituting the assembled battery and the number of battery cells constituting each battery stack are both four. In the following description, the cell balance device of the first embodiment will be described based on the configuration of FIG. In addition, the cell ballast apparatus of Embodiment 1 is applied by changing a structure suitably also when the number of the battery stacks which comprise an assembled battery, and the number of the battery cells which comprise each battery stack differ from FIG. be able to.

  Battery cell 1a-1p is comprised by storage batteries, such as a lithium ion battery, a lead battery, a nickel cadmium battery, and a nickel metal hydride battery, for example. And battery cell 1a-1p comprises an assembled battery by mutually connecting in series. The terminals A and A ′ of the assembled battery are connected to a load such as a charger or a motor (not shown). Furthermore, the assembled battery is configured to be charged when connected to a charger, and to be charged and discharged when connected to a load. In addition, you may replace the battery cells 1a-1p with the battery block which connected the some battery cell in series, respectively.

Secondary coil 2a-2p is comprised by winding electric wires, such as a copper wire, for example. The secondary coils 2a to 2p are connected in parallel to both ends of the battery cells 2a to 2p, respectively. When an alternating current is supplied to the primary coils 5a to 5c, the secondary coils 2a to 2p generate an induced current by electromagnetic induction, and the induced current is rectified by rectifier circuits 3a to 3p, respectively. It supplies to battery cell 1a-1p. Further, the number of turns of the secondary coils 2a to 2p is appropriately set so that an induced voltage suitable for charging the battery cells 2a to 2p can be obtained with respect to the number of turns of the primary coils 5a to 5c. As an example, in the case of the configuration of FIG. 1, since the number of battery cells 1a to 1p is 16, the winding ratio of each primary coil to each secondary coil is primary coil: secondary coil = 16: 1. It is good to set to. By using this winding ratio, a cell voltage that is an average value of the cell voltage values (hereinafter referred to as cell voltage values) of the battery cells 1a to 1p constituting the assembled battery calculated by the following equation (1). The average value Va can be supplied to each battery cell.
Average cell voltage Va = total cell voltage value of battery cells constituting the assembled battery / number of battery cells in series constituting the assembled battery (1)
In the case of the configuration of FIG. 1, since the number of battery cells constituting the assembled battery is 16 in series, 16 may be substituted for the denominator.

  The rectifier circuits 3a to 3p are composed of, for example, a semiconductor element such as a diode, and rectify the induced current generated in the secondary coils 2a to 2p. In FIG. 1, each rectifier circuit 3a to 3p is shown as a single diode in a simplified manner, but a known rectifier circuit may be used as appropriate.

  As the voltmeters 4a to 4p, known voltmeters can be adopted. And the voltmeters 4a-4p are connected in parallel with the battery cells 1a-1p, respectively, and measure each cell voltage. The voltmeters 4a to 4p output the measured cell voltage values to the control unit 8.

  Primary coils 5a-5d are constituted by winding electric wires, such as a copper wire, for example. The primary coils 5a to 5d are each connected in parallel to the assembled battery and are connected in parallel to each other. In addition, switching circuits 6a to 6d are connected in series to the primary coils 5a to 5d, respectively. When the switching circuits 6a to 6d perform switching operations, the primary coils 5a to 5d generate induced currents in the secondary coils 2a to 2p by electromagnetic induction when an alternating current is supplied from the assembled battery. The alternating current supplied from the assembled battery to the primary coils 5a to 5d is a pulsed current that periodically applies a voltage between the terminals A and A 'of the assembled battery by the switching circuit.

  For example, an electromagnetic relay, a field effect transistor, or the like can be employed for the switching circuits 6a to 6d. The switching circuits 6a to 6d are connected in series between the primary coils 5a to 5d and the assembled battery, respectively. The switching circuits 6a to 6d are controlled by the control unit 8 and perform a switching operation as necessary.

  For the cores 7a to 7d, for example, a ferromagnetic or ferrimagnetic material such as iron or ferrite can be used. A primary coil 5a and secondary coils 2a to 2d are wound around the core 7a. A primary coil 5b and secondary coils 2e to 2h are wound around the core 7b. Further, a primary coil 5c and secondary coils 2i to 2l are wound around the core 7c. A primary coil 5d and secondary coils 2m to 2p are wound around the core 7d. Thereby, transformer coupling circuits 12a to 12d in which the primary coil and the secondary coil are transformer-coupled so that power is transferred by electromagnetic induction between the coils wound around the cores 7a to 7d. It is configured. In the following description, the transformer coupling circuits 12a to 12d include a switching circuit connected in series to the primary coil in addition to the primary coil and the secondary coil. Depending on the application, the cores 7a to 7d may be omitted if an air-core coil is sufficient. Even in the case of using an air-core coil, power can be transferred by electromagnetic induction in each transformer coupling circuit as in the case where the cores 7a to 7d are provided.

  For the control unit 8, for example, a computer equipped with a memory as a work space such as an ECU (Electronic Control Unit) can be employed. The control unit 8 stores each cell voltage measured by the voltmeters 4a to 4p, each stack voltage which is a voltage between terminals of the battery stack measured by the voltmeters 10a to 10d, and the storage unit 9. The operation of the switching circuits 6a to 6d is controlled based on a specified variation value indicating a permissible range of variation in each cell voltage. Note that specific operation control of the switching circuits 6a to 6d of the control unit 8 will be described in detail in the operation description of the first embodiment with reference to the flowchart of FIG.

  For the storage unit 9, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like can be employed. The storage unit 9 stores OS programs and application programs. The storage unit 9 stores various data necessary for the processing of the control unit 8. These various data include at least a specified variation value.

The specified variation value is a value indicating a range in which variation of each cell voltage is allowed, and a setting method of the value may be appropriately selected by the user.
Here, an example of the variation prescribed value will be specifically described by describing the control of the switching circuit using the variation prescribed value performed by the control unit 8. First, the control unit 8 calculates a cell voltage average value Vs, which is an average value of the cell voltages in each stack, using the following formula (2).
Cell voltage average value Vs = total cell voltage value of battery cells constituting battery stack / series number of battery cells constituting battery stack (2)
In the case of the configuration of FIG. 1, the number of battery cells constituting the battery stack is four in series, so 4 may be substituted for the denominator.

Next, using the following formula (3), it is determined whether or not there is a battery cell having a cell voltage value that deviates (separates) from the cell voltage average value Vs in the battery stack at or above the specified variation value.
Cell voltage average value Vs−α <each cell voltage value <cell voltage average value Vs + α (3)
In the equation (3), α is a specified variation value, and is defined as a predetermined voltage value appropriately set by the user.

  Then, when there is a battery stack having a battery cell that shows a cell voltage value that deviates from the cell voltage average value Vs to a variation specified value or more, the control unit 8 belongs to a transformer coupling circuit for supplying current to the battery stack. Control to switch the switching circuit.

  As described above, the variation specified value is determined by the control unit 8 that each cell voltage in the battery stack varies when the cell voltage in the battery stack deviates from the cell voltage average value Vs. It may be set as a voltage value indicating the above.

  In addition, although an example of the specified variation value is shown above, in addition to this, the tolerance of the voltage value difference obtained by subtracting the lowest cell voltage value from the highest cell voltage value in the battery stack is also acceptable. As the range, a specified variation value may be set with a predetermined voltage value. When this variation regulation value is used, the control unit 8 subtracts the lowest cell voltage value from the highest cell voltage value in each battery stack. And the control part 8 determines whether the difference of the calculated voltage value is larger than a variation regulation value. As a result, when there is a battery stack in which the difference between the calculated voltage values is larger than the variation specified value, the control unit 8 determines that the cell voltages of the battery stack vary.

In addition, the specified variation value may be set as appropriate so that it can be determined that the cell voltages in the battery stack vary.
A known voltmeter can be adopted as the voltmeters 10a to 10d. And the voltmeters 10a-10d are connected in parallel with each battery stack 11a-11d, and measure each stack voltage. Then, the voltmeters 10 a to 10 d output the measured values of the stack voltages (hereinafter referred to as stack voltage values) to the control unit 8. The stack voltage value may be calculated for each of the battery stacks 11a to 11d using the cell voltage values acquired from the voltmeters 4a to 4p. Specifically, taking the case of the battery stack 11a as an example, the controller 8 may calculate the stack voltage value by adding the cell voltages of the battery cells 1a to 1d.

  The battery stacks 11a to 11d are obtained by connecting a plurality of battery cells in series. The secondary coils connected to the plurality of battery cells constituting each battery stack are transformer-coupled to the common primary coil as described in the description of the cores 7a to 7d. More specifically, the battery stack 11a is obtained by connecting battery cells 1a to 1d in series, and the battery stack 11b is obtained by connecting battery cells 1e to 1h in series. The battery stack 11c is obtained by connecting battery cells 1i to 1l in series, and the battery stack 11d is obtained by connecting battery cells 1m to 1p in series.

  Each of the transformer coupling circuits 12a to 12d includes one primary coil and a plurality of secondary coils that are commonly wound around the same core, and one switching circuit connected in series to the primary coil. . The transformer coupling circuits 12a to 12d transfer power by electromagnetic induction between the primary coil and the secondary coil included in each of the transformer coupling circuits 12a to 12d. In other words, power is not transferred by electromagnetic induction between different transformer coupling circuits. Specifically, the transformer coupling circuit 12a includes a core 7a, a primary coil 5a, secondary coils 2a to 2d, and a switching circuit 6a. The transformer coupling circuit 12b includes a core 7b, a primary coil 5b, secondary coils 2e to 2h, and a switching circuit 6b. Further, the transformer convenience circuit 12c includes a core 7c, a primary coil 5c, secondary coils 2i to 2l, and a switching circuit 6c. The transformer coupling circuit 12d includes a primary coil 5d, secondary coils 2m to 2p, and a switching circuit 6d in the core 7d.

FIG. 2 is a flowchart of cell balance control according to the first embodiment.
The cell balance control for equalizing each cell voltage according to the first embodiment will be described with reference to FIG.
In the following description, cell balance control of the battery stack 11a will be described. By performing the same control for the other battery stacks 11b to 11d, the cell voltages of the battery cells 1a to 1p included in the assembled battery can be equalized.

  The control unit 8 acquires the cell voltage values of the battery cells 1a to 1d from the voltmeters 4a to 4d (S201). Specifically, when a control start signal instructing to perform cell balance control is input, the control unit 8 causes the voltmeters 4a to 4d to request measurement value request signals for transmitting the measured cell voltage values. Is output. When the voltmeters 4 a to 4 d receive this measurement value request signal, the voltmeters 4 a to 4 d each transmit a cell voltage value to the control unit 8. Thereby, the control part 8 acquires each cell voltage value which the voltmeters 4a-4d measured. The control start signal may be set so as to be input to the control unit 8 at an arbitrary timing such as when input by a user using an input unit (not shown) or when the ignition key is turned on.

  Then, the control part 8 determines whether the shift | offset | difference of each cell voltage of battery cell 1a-1d which comprises the battery stack 11a is more than a variation regulation value (S202). This determination may be performed using the above-described variation regulation value.

  Here, the determination of the variation of each cell voltage using the above-described equations (2) and (3) will be described as an example. In the following description, specific values are substituted into Expression (2) and Expression (3).

First, the control part 8 calculates the cell voltage average value Vs of each cell voltage value of battery cell 1a-1d contained in the acquired battery stack 11a using following formula (2).
Cell voltage average value Vs = (cell voltage value 2a + cell voltage value 2b + cell voltage value 2c + cell voltage value 2d) / 4 (2)
In addition, cell voltage value 2a-2d of Formula (2) is a cell voltage value of each battery cell 2a-2d.

And the control part 8 determines whether there exists a battery cell which shows the cell voltage value which shifted | deviated from the cell voltage average value Vs in the battery stack 11a more than a variation regulation value using following formula (3). .
Cell voltage average value Vs−α <each cell voltage value <cell voltage average value Vs + α (3)
Each cell voltage value is the cell voltage value of each of the battery cells 1a to 1d, and when the cell voltage value is within the range indicated by the expression (3) (the deviation of the cell voltage is less than the specified variation value). Determines that the cell voltages of the battery cells 1a to 1d constituting the battery stack 11a do not vary. On the other hand, when the cell voltage value is not within the range indicated by the expression (3) (the deviation of the cell voltage is equal to or greater than the variation specified value), the cell voltages of the battery cells 1a to 1d constituting the battery stack 11a are: Judge that it is scattered.

  As described above, the control unit 8 determines whether or not the deviation of the cell voltages of the battery cells 1a to 1d constituting the battery stack 11a is equal to or greater than a specified value. This determination method is an example, and other determination methods may be applied as appropriate.

  In the flowchart of FIG. 2, when the control unit 8 determines that the deviation of the cell voltage is equal to or greater than the specified variation value (Yes in S202), the control unit 8 switches the switching circuit 6a (S203). Thereby, an induction current is generated in the secondary coils 2a to 2d by electromagnetic induction from the primary coil 5a, and the battery cell having a low cell voltage is preferentially charged in the battery stack 11a. Therefore, the cell voltages of the battery cells 1a to 1d constituting the battery stack 11a can be equalized.

  Then, the control unit 8 determines whether or not the deviation of the cell voltage is less than the specified variation value (S204). As a result, when the deviation of the cell voltage is greater than or equal to the specified variation value (No in S204), the process returns to S203 and continues switching of the switching circuit. If the cell voltage deviation is less than the specified variation value (Yes in S204), the switching circuit is stopped (S205).

Next, the control unit 8 acquires the stack voltage values of the battery stacks 11a to 11d from the voltmeters 10a to 10d, and uses the following formula (4) to calculate the average value of the stack voltage values (hereinafter referred to as the stack voltage average value). Is calculated) (S206).
Stack voltage average value = (stack voltage value 11a + stack voltage value 11b + stack voltage value 11c + stack voltage value 11d) / 4 (4)
In addition, the stack voltage values 11a to 11d in Expression (4) are stack voltage values of the battery stacks 11a to 11d.

  Then, the control unit 8 determines whether or not the stack voltage value of the battery stack 11a is less than the calculated stack voltage average value (S207). As a result, when the stack voltage value of the battery stack 11a is less than the stack voltage average value, the control unit 8 switches the switching circuit 6a (S208). Thus, by charging the battery cells 1a to 1d constituting the battery stack 11a, the stack voltage value of the battery stack 11a can be brought close to the stack voltage average value.

  Further, the control unit 8 determines whether or not the stack voltage value of the battery stack 11a is equal to the stack voltage average value (S209). It should be noted that “equivalent” may be when it falls within a range determined by the user. The determined range is stored in the storage unit 9 and read out by the control unit 8 to be used when the stack voltage value and the stack voltage average value are compared. As a result, when the stack voltage value of battery stack 11a is not equal to the average value (No in S209), the process returns to S208 and switching of the switching circuit is continued. If the stack voltage value of the battery stack 11a is equal to the average value (Yes in S209), the operation of the switching circuit 6a is stopped (S210), and the stack voltage values of the battery stacks 11b to 11d are the stack voltage average. It is determined whether or not the value is reached (S211). When the stack voltage value of each of the battery stacks 11a to 11d is equal to the stack voltage average value (Yes in S211), the cell balance control is terminated. If the stack voltage values of all the battery stacks 11a to 11d are not equal to the stack voltage average value (No in S211), the process returns to S207, and S207 to S211 are repeated.

In S202, when the cell voltage deviation is less than the specified variation value (No in S202), the control unit 8 immediately executes S206. In S207, when the stack voltage value of battery stack 11a is equal to or higher than the average value (No in S207), the process proceeds to S210.
By performing the above control in each of the battery stacks 11a to 11d, the cell voltages of the battery cells 1a to 1p constituting the assembled battery can be equalized. Specifically, the cell voltage variations of the battery cells 1a to 1d are eliminated in the battery stack 11a by the control of S201 to S205. Further, the control of S201 to S205 eliminates the variation in the cell voltage of the battery cells 1e to 1h in the battery stack 11b. Furthermore, the cell voltage variations of the battery cells 1i to 1l are eliminated in the battery stack 11c by the control of S201 to S205. And the dispersion | variation in the cell voltage of the battery cells 1m-1p is eliminated in the battery stack 11d by control of S201-S205. Next, under the control of S206 to S210, among the battery stacks 11a to 11d, the battery stack whose stack voltage is lower than the stack voltage average value is charged, and the battery stack whose stack voltage is equal to or higher than the stack voltage average value is discharged. As a result, the stack voltages of the battery stacks 11a to 11d are equalized. As described above, each cell voltage in each battery stack is equalized, and then the stack voltage of each battery stack is equalized, so that the cell voltages of the battery cells 1a to 1p are equalized.

  Further, the cell balance device of Embodiment 1 is configured such that the battery cells constituting the assembled battery are divided into a plurality of battery stacks, and each is connected to a separate transformer coupling circuit. Thereby, according to Embodiment 1, in the active type cell balance device, the increase in the number of taps of the transformer coupling circuit due to the increase in the series number of the plurality of battery cells included in the assembled battery and the variation between the taps are suppressed. can do.

In the first embodiment, the battery stacks 11a to 11d are connected to separate transformer coupling circuits 12a to 12d, respectively. Alternatively, some of the battery stacks 11a to 11d may be connected to the same transformer coupling circuit in the transformer coupling circuits 12a to 12d. However, in order to reduce the number of taps, at least two or more transformer coupling circuits are connected to the battery stacks 11a to 11d. That is, if a plurality of secondary coils connected to the same battery stack are connected to the same primary coil, and two or more primary coils are connected to secondary coils of some battery stacks good. An example will be specifically described with reference to FIG. 1. The primary coil 5a and the secondary coils 2a to 2h are transformer-coupled, and the primary coil 5c and the secondary coils 2i to 2l are transformer-coupled, and the primary coil 5d. And the secondary coils 2m to 2p are transcoupled to each other.
[Embodiment 2]
Embodiment 2 of the present invention will be described below with reference to the drawings.

FIG. 3 is a configuration diagram illustrating the cell balance device of the second embodiment.
3 is disclosed in order to simplify the description of the second embodiment, and the configuration thereof is four in the cell balance device of the first embodiment disclosed in FIG. In this configuration, the number of battery stacks is two. Therefore, the basic configuration of FIG. 3 is the same as that of FIG. In addition, the number of battery cells and the number of battery stacks constituting each battery stack can be arbitrarily set.

Hereinafter, the cell balance control of the second embodiment will be described with reference to FIG.
The cell balance control according to the second embodiment relates to cell balance control when the voltage difference between the stacks is large. In the following description, it is assumed that the stack voltage of the battery stack 11a is higher than the stack voltage of the battery stack 11b.

  The number of turns of the primary coil 5a and the primary coil 5b is the same. The number of turns of the secondary coils 2a to 2h is the same. Further, the winding ratio between each primary coil and each secondary coil is set to primary coil: secondary coil = 8: 1. Therefore, when the switching circuit 6a is switched, the induced voltage generated in each of the secondary coils 2a to 2d becomes a voltage of 1/8 (cell voltage average value Va) of the voltage of the entire assembled battery. That is, by switching the switching circuit 6a, the cell voltage average value Va is generated in the secondary coils 2a to 2d. Therefore, only the battery cell whose cell voltage is lower than the cell voltage average value Va is charged. Therefore, if the lowest cell voltage in the battery stack 11a is higher than the cell voltage average value Va, none of the battery cells in the battery stack are charged.

  Such a situation is assumed to occur when the voltage difference between the stacks is large. Therefore, in the second embodiment, first, the cell voltage is equalized only for the battery stack 11b having a low stack voltage, and thereafter, the control is performed to equalize the cell voltage of the battery stack 11a having a high stack voltage.

  As a result, when the cell voltage of the battery stack 11b having a low stack voltage is equalized, the battery stack 11a having a high stack voltage only discharges power through the terminals A and A '. The stack voltage decreases. In the battery stack 11a having a high stack voltage, the cell voltages can be equalized when any one of the cell voltages becomes lower than the cell voltage average value Va.

FIG. 4 is a flowchart of cell balance control according to the second embodiment.
The cell balance control for equalizing each cell voltage in the second embodiment will be described with reference to FIG. In the following description, cell balance control of the battery stack 11a will be described. Further, by performing the same control for the battery stack 11b, the cell voltages of the battery cells 1a to 1h included in the assembled battery can be equalized. In the cell balance control flow of the second embodiment in FIG. 4, the same reference numerals are given to the same flow as the cell balance control flow in the first embodiment in FIG. 2, and description thereof is omitted.

  First, the control unit 8 executes S201 and S202, and when the cell voltage deviation of the battery tack 11a is equal to or greater than a specified value (Yes in S202), calculates the cell voltage average value Va (S401).

  Next, the control unit 8 determines whether or not there is a battery cell having a cell voltage less than the calculated cell voltage average value Va among the battery cells 1a to 1d belonging to the battery stack 11a (S402).

  When there is no battery cell having a cell voltage lower than the calculated cell voltage average value Va among the battery cells 1a to 1d belonging to the battery stack 11a (No in S402), the control unit 8 switches the switching circuit 6a. Stop (S403). And the control part 8 acquires each cell voltage from the voltmeters 4a-4h (S404), returns to S402, and repeats S402-S406. In S403, if the switching circuit 6a has already been stopped, the switching circuit 6a may be stopped as it is. Thereby, in the battery stack 11b having a low stack voltage, the battery stack 11a discharges power via the terminals A and A ′ while charging a battery cell having a cell voltage lower than the cell voltage average value Va. . Therefore, the stack voltage of the battery stack 11a decreases. When the stack voltage of the battery stack 11a is higher than the stack voltage of the battery stack 11b, the stack voltage of the battery stack 11b is lower than the stack voltage average value. Therefore, among the battery cells 1e to 1h belonging to the battery stack 11b, there is a battery cell whose cell voltage is lower than the cell voltage average value Va. Therefore, the battery stack 11b performs control for charging the battery cell.

  Further, when there is a battery cell having a cell voltage lower than the cell voltage average value Va among the battery cells 1a to 1d belonging to the battery stack 11a (Yes in S402), the control unit 8 switches the switching circuit 6a ( S405). Thereby, the cell voltage of the battery stack 11a can be equalized.

  Then, the control unit 8 determines whether or not the deviation of the cell voltage is less than a specified value (S406). As this determination method, the determination method described in S202 of FIG. 2 may be used. As a result, when the cell voltage deviation is equal to or greater than the specified value (No in S406), the cell voltages of battery cells 1a to 1h are acquired (S404). And it returns to S402 and repeats S402-S406. If the deviation of the cell voltage value is less than the specified variation value (Yes in S406), the switching circuit 6a is stopped (S205). Then, the process proceeds to S206. The subsequent cell balance control is the same as S206 to S211 described in the first embodiment.

  As described above, in the second embodiment, the equalization of the voltage of the battery stack having the battery cells having the cell voltage lower than the cell voltage average value Va is performed with priority. Thereby, each switching circuit can be switched at the timing required for switching, such as when there is a difference in voltage between the battery stacks.

  In the above description, the assembled battery in which the two battery stacks of the battery stack 11a and the battery stack 11b are connected in series has been described. Can be applied. In that case, in S402, by monitoring the cell voltage belonging to each battery stack, a battery stack having battery cells less than the cell voltage average value Va is extracted, and switching of the transformer coupling circuit connected to the battery stack is performed. What is necessary is just to switch a circuit.

1a to 1n Battery cell 2a to 2n Secondary coil 3a to 3n Rectifier circuit 4a to 4n Voltmeter 5, 5a to 5d Primary coil 6, 6a to 6d Switching circuit 7, 7a to 7d Core 8 Control unit 9 Storage unit 10a to 10d Voltmeters 11a to 11d Battery stacks 12a to 12d Transformer coupling circuit

Claims (5)

In the cell balance device for equalizing the cell voltage of each battery cell that the assembled battery in which a plurality of battery stacks connected in series with a plurality of battery cells connected in series,
A plurality of primary coils connected in parallel to each other and in parallel to the assembled battery;
A plurality of secondary coils connected in parallel to each of the battery cells;
A switching circuit connected in series to each of the plurality of primary coils;
With
The plurality of secondary coils connected to the plurality of battery cells constituting the battery stack are respectively transformer-coupled to one primary coil of the plurality of primary coils,
The cell balance device, wherein the plurality of primary coils are transformer-coupled to a plurality of secondary coils connected to the plurality of battery cells that constitute separate battery stacks. A plurality of first voltmeters for measuring a cell voltage of each battery cell;
When there is the battery stack in which the deviation of the cell voltage value measured by each first voltmeter is equal to or greater than a specified value, a secondary coil connected to the plurality of battery cells constituting the battery stack; A primary coil that is transformer-coupled, and a controller that switches the switching circuits connected in series;
The cell balance device according to claim 1, further comprising: The number of the plurality of battery cells constituting the battery stack is the same number in each battery stack,
3. The cell balance device according to claim 1, wherein the number of the plurality of primary coils and the number of the plurality of switching circuits are the same as the number of the plurality of battery stacks. The control unit adds a stack voltage value that is a voltage value of each battery stack, calculates the stack voltage average value by dividing the added stack voltage value by the number of the battery stacks,
When there is a battery stack in which the stack voltage value is less than the stack voltage average value, a primary coil that is transformer-coupled with a secondary coil that is connected to the plurality of battery cells that form the battery stack, and a series connection 4. The cell balance device according to claim 3, wherein the switching circuit is switched. The control unit adds the cell voltage values of all battery cells included in the assembled battery, and divides the added cell voltage value by the number of all battery cells included in the assembled battery to calculate a cell voltage average value. And
When there is a battery stack including a battery cell in which the cell voltage value is lower than the cell voltage average value, a primary coil that is transformer-coupled to a secondary coil connected to the plurality of battery cells constituting the battery stack And the switching circuit connected in series is switched. 5. The cell balance device according to claim 1, wherein the switching circuit is connected in series.

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