JP2001339865A - Cell voltage equalization apparatus, method therefor, hybrid car and manufacturing method of battery assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize cell voltages or module voltages while energy for charging cells of a battery assembly is not wasted. SOLUTION: Circuits in which coils and switch parts are conected in series to each other and the respective coils are coupled electromagnetically with the other coils and connected in parallel to respective cells of a battery assembly, and a drive unit which drives the switches in the respective circuits, are provided. The cells are charged or discharged by electromotive forces induced in the respective coils by electromagnetic induction between the respective coils when the respective switch parts are driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a battery pack, and more particularly to a technique for equalizing voltages of a plurality of cells.

[0002]

2. Description of the Related Art For example, in a so-called hybrid car, an electric motor is used as a main power source or an auxiliary power source, and a secondary battery having a number of cells connected in series is used as the power source. As an example, a nickel-hydrogen secondary battery with a standard voltage of 1.2 V per cell
One in which cells are connected in series is known. When a secondary battery in which a large number of cells are connected in series as described above is used repeatedly by repeating charging and discharging, variations in cell voltages occur. Therefore, a management method is required that monitors not only the total voltage of all cells but also the voltage of each cell so that any cell is not continuously used in an overcharged state or an overdischarged state. As an example of the prior art relating to such a secondary battery management method, see Japanese Patent Application Laid-Open No. 11-196.
No. 537 is disclosed. The technology described in this publication is to measure a voltage of each module in a battery system in which a predetermined number of cells (unit cells) are connected in series as a module, and a plurality of modules are further connected in series. By controlling the conduction of the bypass circuit for a module higher than the average voltage, the module is discharged by an appropriate amount and the voltages of all the modules are equalized.

However, in the prior art, it is considered that the module voltage can be adjusted for a module having a module voltage higher than the average voltage, but the module voltage cannot be adjusted for a module having a module voltage lower than the average voltage. If the voltage is made equal to the module having the lowest voltage, the voltage of all modules can be equalized. However, this method wastes the charging energy of the battery, which is not preferable in terms of power efficiency and heat generation. For this reason, a technique capable of equalizing the voltage of a cell (unit cell) or the voltage of a module without wasting charging energy is desired. An object of the present invention is to solve the above-described problems and to provide a technology that can further improve the conventional technology. In the following description, both the above-mentioned cell (unit cell) and the above-mentioned module are collectively referred to as “cell”.

[0004]

In order to achieve the above object, the present invention provides: 1) a cell voltage equalizing device for equalizing the voltage between cells of a battery pack; A circuit that is connected and the coil is electromagnetically coupled to another coil and is connected in parallel to each of the cells; and a driving unit that drives a switch unit in each of the circuits. The cell is charged or discharged by an electromotive force generated in each coil by electromagnetic induction between the coils during driving, and the voltage between the cells is equalized. 2) an assembled battery having a plurality of cells, a circuit in which a coil and a switch unit are connected in series and the coil is electromagnetically coupled to another coil, and a circuit is connected in parallel to each of the plurality of cells. A driving unit for driving the plurality of switch units, wherein the cells are charged or discharged by an electromotive force generated in each of the coils due to electromagnetic induction between the coils when each of the switch units is driven. Are equalized. 3) In 1) or 2), a resonance capacitor is provided between a connection point between the switch section and the coil and an AC reference potential point. 4) In the above 1), 2) or 3), the drive section is configured to open and close the switch section when the voltage of the cell has a difference equal to or more than a predetermined value.

[0005] 5) As a cell voltage equalization method, a step of connecting a plurality of circuit sections in which a coil and a switch section are connected in series and the coil is electromagnetically coupled to another coil to each of a plurality of cells of an assembled battery in parallel. And repeatedly driving the plurality of switch units to open and close to generate an electromotive force in the coil by electromagnetic induction between the coils,
Charging or discharging the cells by the electromotive force to equalize the voltage between the cells; determining whether a voltage difference between the plurality of cells is within an allowable range; and It is configured to include a step of displaying or notifying that the equalization has been completed and a step of disconnecting the plurality of circuit units from the plurality of cells.

6) A hybrid car powered by an assembled battery is a circuit in which a coil and a switch section are connected in series and the coil is electromagnetically coupled to another coil, and is connected in parallel to each of a plurality of cells of the assembled battery. Circuit, a drive circuit unit for driving the switch unit, a motor unit driven as a power source by the battery pack, a power generation unit for generating at least charging power for the battery pack, the motor, A power adjustment inverter connected between the unit and the battery pack, and a system operation control unit for controlling the inverter, wherein a first instruction is given to the inverter from the system operation control unit. Drives the power generation unit by external force,
The generated power is supplied to the battery pack through the inverter to charge the battery pack, and the system operation control unit supplies a second power to the battery pack.
When the instruction is given, the power from the battery pack is supplied to the motor via the inverter to drive the motor,
At the time of or after charging the battery pack, or when neither the first instruction nor the second instruction is performed, the switch unit is opened / closed, and an electromotive force generated in the coil by electromagnetic induction between the coils. The battery of the battery pack is charged or discharged to equalize the voltage of the cell.

[0007] 7) A method of producing an assembled battery including cells, wherein the steps of manufacturing the cells, connecting the manufactured cells in series, and connecting the coil and the switch unit in series with each other so that the coil is electrically connected to another coil Through a step of connecting the coupled circuit to each of the plurality of cells in parallel, and a step of driving a switch unit in each of the circuits, the electromagnetic induction between the coils when driving each of the switch units. The cells are charged or discharged by the electromotive force generated in each coil to equalize the voltage between the cells.

Since the coils are electromagnetically coupled, when the switch is repeatedly opened and closed, electromagnetic induction occurs between the coils, and an electromotive force is induced in each coil by the other coil. If the electromotive force is higher than the cell voltage, the cell is charged by the electromotive force.
Conversely, if the electromotive force is lower than the cell voltage, the cell will pass a discharge current through the coil to compensate for the coil's back electromotive force. Then, an electromotive force is generated in another coil by the electromagnetic induction thereby, and another cell lower than this is charged by the electromotive force. Since the above occurs between the cells, the electromotive force of the coil and the cell voltage are equalized by the repeated opening and closing operations of the switch section for an appropriate time, and the voltage is equalized between the cells. Further, in the present invention, a cell having a high cell voltage charges a cell having a low cell voltage based on electromagnetic induction between coils that are electromagnetically coupled, so that basically no charge energy is wasted. Therefore, energy efficiency can be improved. Also, excess heat generation can be suppressed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of the present invention. The present embodiment is an example of an assembled battery in which two cells are connected in series. In the figure, 1 is an assembled battery, 101 is a positive terminal of the assembled battery, 102 is a negative terminal of the assembled battery, 11 is a cell A, 12 is a cell B, 11P is a positive terminal of the cell A, 1
1M is the negative terminal of cell A, 12P is the positive terminal of cell B,
12M is a negative terminal of the cell B. Reference numerals 21 and 22 denote switches, reference numerals 31 and 32 denote coils, and reference numeral 30 denotes a magnetic core.
The switch 21 and the coil 31 are connected in series, and are connected to the positive terminal 11P and the negative terminal 11M of the cell A. Similarly, the switch 22 and the coil 32 are connected to the cell B. The coil 31 and the coil 32 are wound around the magnetic core 30 with the same number of turns, and are electromagnetically coupled to each other. The switches 21 and 22 are opened and closed substantially simultaneously at the time of driving.

First, it is assumed that the voltage of the cell A is lower than the voltage of the cell B in the initial state. In this case, when the switching operation of the switch 21 and the switch 22 is started repeatedly, the cell voltage of the cell A is induced on the coil 32 side by the electromagnetic coupling of the coil, and at the same time, the cell voltage of the cell B is induced on the coil 31 side. You. Since a voltage higher than the cell voltage of the cell A is induced on the coil 31 side, the cell A is charged with the electromotive force of the coil 31. Conversely, since a voltage lower than the cell voltage of the cell B is induced on the coil 32 side, the cell B supplies a discharge current so as to compensate for the voltage (electromotive force) induced in the coil 32. When the switching operation of the switch 21 and the switch 22 continues, the charging of the cell A and the discharging of the cell B progress, and the voltages of the cells A and B eventually balance, and the current values of the charging and discharging become almost zero. . If the switches 21 and 22 are stopped in an open (off) state in this state, the cell voltages are equalized. The above cell voltage equalization operation can be interpreted as being performed by charging and discharging according to the voltage difference between the two cells. In addition, since a cell having a high cell voltage acts to charge a cell having a low cell voltage, charging energy is not wasted.

FIG. 2 shows a specific example of a coil used in the above embodiment. For example, a coil 31 and a coil 32 are wound with the same number of turns around a toroidal core such as ferrite. The toroidal core has a small amount of leakage magnetic flux and can obtain a dense electromagnetic coupling. FIG. 3 is a simulation result of a transition state of the cell voltage equalization in the embodiment. The cells of the assembled battery are simulated and replaced with 0.01 F (farad) capacitors, and the initial voltage of the capacitor corresponding to the cell A is set to 10 V, and the initial voltage of the capacitor corresponding to the cell B is set to 14 V. The switch was set to repeat opening and closing every 50 μs. Judging from the results shown in FIG. 3, the cell voltages approach each other's values with the passage of time, and the initial voltage becomes 10 V
, And settles to approximately 12V, which is an average of 14V, and the cell voltage is equalized. In an actual battery, the time required to settle down is longer because the capacity corresponds to a capacitor having a capacity of more than 0.01 F.

FIG. 4 is a diagram showing a second embodiment of the present invention. The present embodiment is an example of an assembled battery in which three cells are connected in series. In the figure, 13 is a cell C, 13P is a positive terminal of the cell C, 13M is a negative terminal of the cell C, 23 is a switch, and 33 is a coil. Others are the same as those in the first embodiment. The coil 31, the coil 32, and the coil 33 are electromagnetically coupled to each other, and the switch 21, the switch 22, and the switch 23 are repeatedly opened and closed substantially simultaneously. In the same manner as in the first embodiment, two cells perform charging and discharging according to the voltage difference therebetween, and in the second embodiment, three cells perform charging and discharging each other. As a result of the charging and discharging, the cell voltage is settled to a voltage value approximately equal to the initial voltage of the three cells. FIG. 5 is a simulation result of a transition state of equalization of cell voltages in the embodiment shown in FIG. Also in this simulation, the battery cell was simulated and replaced with a 0.01 F (farad) capacitor, and the initial voltage of the capacitor corresponding to the cell A was 10 V, and the initial voltage of the capacitor corresponding to the cell B was 1
2V, and the initial voltage of the capacitor corresponding to the cell C is 1
6V. Switches open and close 50μ
Repeated every s. From this result, each cell voltage approaches the average of the initial voltages of the three cells, and is approximately 0.0
After 25 seconds, the average value is almost settled. With an actual battery, this longer time to settle down is
This is the same as in the first embodiment.

FIG. 6 is a diagram showing a specific example of a coil used in the second embodiment. For example, a coil 31, a coil 32, and a coil 33 are wound around a toroidal core such as ferrite with the same number of turns. By expanding the first and second embodiments described above and increasing the number of coils and switches in accordance with the number of cells, it is possible to cope with an assembled battery having a larger number of cells.

FIG. 7 is a diagram showing a third embodiment of the present invention. This embodiment is an example of a configuration in which a MOSFET is used as a switch to absorb a high-voltage pulse generated in a coil while the switch is turned off (this is called turn-off). In the figure, 21, 22, 2
Reference numeral 3 denotes a MOSFET, 211, 221, and 231 drive pulse coupling circuits for applying a drive pulse to the gates of the MOSFETs 21, 22, and 23, respectively, and 41, 42, and 43 denote resonance capacitors. MO
The SFET is a P-channel type, and is turned on when a voltage several volts lower than the source terminal is applied to the gate terminal.
In this configuration, the illustrated drive pulse of 5 Vpp is applied to the gate of each MOSFET via the drive pulse coupling circuit, and is turned on during the low period (for example, about 50 μs) of the drive pulse and for the high period (for example, about 50 μs). Is turned off. When all MOSFETs transition from on to off (turn off), each coil tries to maintain the respective current flowing during the immediately preceding on period due to inductance, but is bound by the tight electromagnetic coupling between the coils, Resonance capacitors 41, 4 connected to the coils of
Between 2 and 43, all coils pass substantially the same resonance current. At this time, the voltage at the drain terminal of each MOSFET transitions in a negative sine wave form from the moment of turn-off, but when the voltage returns to the original voltage after half a cycle, the capacitance of the resonance capacitor is set so that the next turn-on timing is reached. Determine the value. In the present embodiment, the above condition is satisfied when the inductance value of each coil is 1 mH and the capacitance value of the resonance capacitor is 50 nF, and a voltage waveform as shown in FIG. 8 is obtained. By providing the resonance capacitor in this manner, a high voltage generated at the moment of turn-off can be suppressed, and a voltage difference applied to the switch at the moment of turn-on can be reduced.
The withstand voltage of ET and the burden of power can be reduced. Note that the connection configuration of the resonance capacitor is not limited to this configuration example, and one terminal of the capacitor is located at the connection point between the switch and the coil, and the other terminal is alternately regarded as a reference potential (AC
Other configurations may be used as long as they are at (reference potential).

FIG. 9 is a diagram showing a fourth embodiment of the present invention. In this embodiment, the switch is an N-channel type MOS.
FET is used. In contrast to the third embodiment, the MOSF
The connection position of the ET is set to the low side of each cell, and the polarity of the drive pulse is inverted. Other configurations are almost the same as those of the third embodiment. In the configuration of the fourth embodiment, the resonance waveform generated at the drain terminal of the MOSFET during the switch-off period is a half-period sine curve extending to the positive side. FIG. 10 is a diagram showing a fifth embodiment of the present invention. In the figure, reference numeral 50 denotes a cell voltage equalization device unit, which is a device unit by separating parts other than the assembled battery from the configuration of the fourth embodiment. A terminal pair of 51P and 51M is used as a terminal for connecting each cell.
A terminal pair of 2P and 52M and a terminal pair of 53P and 53M are provided. For example, in a battery pack used for a hybrid car, it is expected that the frequency at which the cell voltage becomes unbalanced is extremely low. For this reason, a device for cell voltage equalization is not provided for each hybrid car or the like, but a service station is provided with the device unit as in the present embodiment, and when necessary, this is used for a hybrid car or the like. There is also a method of performing cell voltage equalization processing by connecting to an assembled battery.

FIG. 11 is a view showing a sixth embodiment of the present invention. This embodiment is an example in which the cell voltage equalization device is applied to a hybrid car or the like. In FIG.
Is a switch control unit, 300 is a cell voltage monitoring unit, 400 is an inverter, 500 is a motor / generator, and 600 is a system operation control unit. The other points are the same as those in the first embodiment. The positive terminal 101 and the negative terminal 102 of the battery pack 1 are connected to a motor / generator 500 via an inverter 400. Motor / generator 500
When working as a motor, the power of the battery pack 1 is adjusted by the inverter 400 and supplied to the motor / generator 500 to serve as a power source for the vehicle. On the other hand, for example, when the vehicle is braked by regenerative braking, the motor / generator 500 functions as a generator, and the generated power is adjusted by an inverter and used for charging the assembled battery. In addition, even when the charging energy of the battery pack decreases, the generator 500 receives the power of the internal combustion engine or the like to generate power, adjusts the generated power with an inverter, supplies the power to the battery pack, and charges the battery pack. In this configuration, the motor and the generator are used in combination, but the motor and the generator may be provided separately. The system operation control unit 600 controls the inverter 400 according to the operation status. Switch control unit 2
00 controls repetitive opening and closing of the switches 21, 22 and 23 of the cell voltage equalization device. There are a plurality of control algorithms. For example, as a first method, the system operation control unit 600 Control the switch control unit 200 when charging the assembled battery by issuing a charge command to the assembled battery or after the charging is completed,
There is a method in which a switch is repeatedly opened and closed continuously. This method has the advantage that the cell voltage equalizing device is operated every time charging, so that the cell voltage can always be maintained in an equalized state. Further, for example, as a second method, there is a method in which, when the cell voltage monitoring unit 300 detects the nonuniformity of the cell voltage equal to or more than a predetermined value, the switch control unit is controlled to cause the switch to repeatedly open and close. This method is expected to reduce the frequency of operation of the cell voltage equalization device, and has the advantage of suppressing the energy loss caused by the resistance of the switch of the cell voltage equalization device, the resistance of the coil, and other factors. Still further, as a third method, when the system operation control unit 600 does not issue a command to charge the assembled battery or a command to drive the motor to the inverter 400, the system control unit 600 controls the switch control unit to control the cell voltage. May be performed.

According to the configurations of the first to sixth embodiments, the cell voltage can be equalized using the opening and closing of the switch and the electromagnetic induction between the coils. In addition, the equalization processing includes:
Since charging is performed in such a manner that a cell having a high cell voltage charges a cell having a low cell voltage, basically no charge energy is wasted. Also, unnecessary heat generation can be reduced. Further, in the present invention, in the production process of an assembled battery, for example, when charging or after charging the battery after cell production, a circuit in which a coil and a switch unit are connected in series, are connected in parallel to each of the plurality of cells, and the respective cells are connected. A group in which a switch unit in a circuit is driven to generate an electromotive force in each of the coils by electromagnetic induction between the coils, and the cells are charged or discharged by the electromotive force to equalize the voltage between the cells. The battery production method is also included in the scope. In each of the above descriptions, the circuit in which the coil and the switch unit are connected in series may be connected to all cells, or may be connected to some cells.

[0018]

As described above, according to the present invention,
Cell voltage can be equalized without wasting charging energy. Also, excess heat generation can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a specific example of a coil according to the first embodiment.

FIG. 3 is a diagram showing a simulation result of a transition state of cell voltage equalization in the first embodiment.

FIG. 4 is a diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a simulation result of a transition state of cell voltage equalization in the second embodiment.

FIG. 6 is a diagram showing a specific example of a coil used in the second embodiment.

FIG. 7 is a diagram showing a third embodiment of the present invention.

FIG. 8 is a diagram showing a voltage waveform at the drain terminal of the MOSFET.

FIG. 9 is a diagram showing a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a fifth embodiment of the present invention.

FIG. 11 is a diagram showing a sixth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Battery pack, 101 ... Positive electrode terminal of battery pack, 102 ...
Negative electrode terminal of the assembled battery, 11: cell A, 12: cell B,
13: cells C, 11P, 12P, 13P: positive terminals of cells, 11M, 12M, 13M: negative terminals of cells, 2
1, 22, 23 ... switch, 211, 221, 231 ...
Drive pulse coupling circuit, 30 ... magnetic core, 31, 32, 33
... Coil, 2, 3 ... Cell selection switch group, 41, 4
2, 43: resonance capacitor, 50: cell voltage equalizing device unit, 200: switch control unit, 300: cell voltage monitoring unit, 400: inverter, 500: motor and generator, 600: system operation control unit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/44 ZHV H01M 10/48 P 10/48 H02J 7/02 H H02J 7/02 7/10 R 7 / 10 B60K 9/00 CF term (reference) 5G003 BA03 CA11 CC04 FA06 5H030 AA01 AS08 BB01 BB21 DD05 FF41 5H115 PG04 PI16 PI29 PO09 PO16 PU01 PU25 PU26 QI04 TR19 TU12 TU16 TU17

Claims (8)

[Claims] 1. A cell voltage equalizing device for equalizing a voltage between cells of a battery pack, comprising: a coil and a switch unit connected in series; the coil being electromagnetically coupled to another coil; A circuit connected in parallel with each other, and a drive unit for driving a switch unit in each of the circuits, wherein when each of the switch units is driven, an electromagnetic force generated in each of the coils by electromagnetic induction between the coils. A cell voltage equalizing device wherein the cells are charged or discharged to equalize the voltage between the cells. 2. A battery pack having cells, a circuit in which a coil and a switch section are connected in series, the coil is electromagnetically coupled to another coil, and a circuit is connected in parallel to each of the plurality of cells; And a driving unit for driving the switch unit. When the switch units are driven, the cells are charged or discharged by an electromotive force generated in each coil by electromagnetic induction between the coils, and a voltage between the cells is changed. A cell voltage equalization device characterized in that equalization is performed. 3. The cell voltage equalizing device according to claim 1, wherein a resonance capacitor is provided between a connection point between the switch section and the coil and an AC reference potential point. 4. The cell voltage equalizing apparatus according to claim 1, wherein said drive section drives said switch section when the voltage of said cell has a difference of not less than a predetermined value. 5. A step of connecting a plurality of circuit sections in which a coil and a switch section are connected in series and the coil is electromagnetically coupled to another coil to each of a plurality of cells of the battery pack, and the plurality of switch sections. Repeatedly opening and closing to generate an electromotive force in the coil by electromagnetic induction between the coils; charging or discharging the cells by the electromotive force to equalize the voltage between the cells; A step of determining whether a voltage difference between cells is within an allowable range; a step of displaying or notifying that the equalization of voltage between the cells has been completed; and a step of displaying the plurality of cells of the plurality of circuit units. Disconnecting the connection to the cell voltage equalization method. 6. The method according to claim 5, wherein each of the steps is performed when the battery pack is charged. 7. A hybrid car using a battery pack as a power source, wherein a coil and a switch unit are connected in series, the coil is electromagnetically coupled to another coil, and connected in parallel to each of the plurality of cells of the battery pack. A circuit, a drive circuit for driving the switch, a motor driven as a power source by the battery pack, a power generator for generating at least charging power for the battery pack, the motor and the power generator. An inverter for power adjustment connected between the battery pack and a system operation control unit for controlling the inverter;
When the instruction is issued, the power generation unit is driven by an external force, the generated power is supplied to the battery pack via the inverter to charge the battery pack, and a second instruction is issued from the system operation control unit. When there is, the electric power from the battery pack is supplied to the motor via the inverter to drive the motor, and the battery is charged at the time of charging or after the charging, or the first battery.
When neither the instruction nor the second instruction is performed, the switch unit is opened and closed, and the cells of the battery pack are charged or discharged by an electromotive force generated in the coil due to electromagnetic induction between the coils. A hybrid car characterized by equalizing cell voltages. 8. A method for producing a battery pack having cells, comprising the steps of: manufacturing a cell; connecting the manufactured cells in series; and connecting a coil and a switch unit in series, wherein the coil is electrically connected to another coil. Connecting the coupled circuit to each of the plurality of cells in parallel, and driving a switch unit in each of the circuits, by electromagnetic induction between the coils when driving each of the switch units. A method for producing an assembled battery, characterized in that the cells are charged or discharged by an electromotive force generated in each coil to equalize the voltage between the cells.