JP2002325370A - Method and device for charged state control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for charged state control, capable of effectively conducting uniformization of the charged state of each unit cell which constitutes a battery pack using a simple structure. SOLUTION: A cell dispersion adjustment device CEUi is provided with discharging circuits P1-P4, consisting of resistors and switches for each unit cell Ci1-Ci4, and generates operation signals SD1-SD4 for driving the switches of discharging circuits P1-P4 to be opened and closed, based on the potential Eij at the connecting points of unit cells Cij, Cij+1 (j=1 to 3) and the potential Erj at the connecting points of each resistor Ri, Ri+1 constituting a voltage- dividing circuit 20. The device is further provided with a discharge prohibition circuit 26 for inhibiting the operation of the discharging circuits P1-P4 by forcibly lowering the operation signals SD1-SD4 to a lower level. A BCU 12 enablers adjustment operation of voltage dispersion, using the discharge circuits P1-P4 by means of the cell dispersion adjustment device CEUi, by turning off the discharge inhibition circuit 26, only when the ignition switch is on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling the state of charge of a plurality of unit cells connected in series to form a battery pack.

[0002]

2. Description of the Related Art Conventionally, for the purpose of protecting the global environment, an electric vehicle (EV) that does not emit exhaust gas or a hybrid electric vehicle (HE) that can significantly reduce the emission of exhaust gas have been developed.
V) is being researched and developed, of which HEV is already in the stage of commercialization.

As secondary batteries (batteries) used as power sources for these HEVs and EVs, lead batteries, nickel-cadmium batteries, nickel-metal hydride batteries and the like are known.
Lithium batteries that have a high weight energy density (about four times that of lead batteries of the same capacity and about twice that of nickel-metal hydride batteries) and that can be expected to be smaller and lighter have attracted attention.

[0004] Further, since a voltage of about 300 V is required for driving a motor in an HEV or an EV to drive an automobile, the above-mentioned battery is formed by connecting a large number of unit cells (unit cells) in series. Used as a battery. For example,
It is necessary to connect 150 unit cells in a lead battery (about 2 V / cell), 250 unit cells in a nickel hydride battery (about 1.2 V / cell), and 80 unit cells in a lithium secondary battery (about 3.6 V / cell).

[0005] These unit cells are vulnerable to overcharge and overdischarge, and unless used at a voltage within a specified range of use, the decomposition of the material causes a significant decrease in capacity and abnormal heat generation, making it unusable. Could be. In each of the unit cells constituting the assembled battery, the chargeable capacity varies due to individual differences in performance, differences in ambient temperature, leakage current, and the like, and the current flowing through each unit cell during charging and discharging of the assembled battery is the same for all unit cells. Nevertheless, it is known that the remaining capacity (SOC) of each unit cell, and thus the voltage across each unit cell, varies.

That is, when used as a battery pack,
Cell voltage variations due to variations in the remaining capacity among the unit cells must be sufficiently suppressed so that each unit cell constituting the assembled battery is not overcharged or overdischarged. In a conventional battery pack using a lead battery, a NiCd battery, a nickel-metal hydride battery, or the like as a unit cell, the voltage across the battery pack is monitored, and the voltage across the battery (and thus the average cell voltage of each unit cell constituting the battery pack) is calculated. The overdischarge and overcharge of the unit cell could be prevented by controlling the charge and discharge to be within the predetermined voltage range. Or overdischarge progresses, causing a problem that performance is deteriorated to such an extent that the battery cannot be used.

[0007] That is, in a lead battery, a nickel cadmium battery, a nickel hydride battery secondary battery or the like constituted by using a water-soluble electrolytic solution, the unit is formed by electrolysis of water and substitution reaction (sealing reaction) generated at the time of overcharge. Since the variation between cells is eliminated to some extent (equal charging), overdischarge and overcharge can be prevented by controlling the voltage across the assembled battery (average cell voltage of each unit cell constituting the assembled battery). However, in a lithium battery configured using an organic electrolytic solution, the above-mentioned uniform charging is not performed because a sealing reaction does not occur, and the method of controlling the both-end voltage (average cell voltage) of the assembled battery causes variation. Is increasing, and overcharging and overdischarging progress.

On the other hand, as a method of eliminating variations in cell voltage between unit cells constituting a battery pack without depending on a sealing reaction, for example, a bypass circuit (discharge circuit) which operates according to an external command is used. Is connected in parallel with each unit cell, and when the cell voltage fluctuates, a bypass circuit connected to the unit cell having a higher cell voltage is operated to discharge the unit cell (Japanese Patent Laid-Open No. 6-253463). Japanese Patent Application Laid-Open No. H8-19188 discloses an apparatus that adjusts the voltage so as to reduce the variation in voltage between the unit cells by diversion (bypass) of a charging current so that the unit cells are not charged. I have.

However, in order to implement these, it is necessary to provide a cell voltage detection circuit (VSC) and a bypass circuit BP comprising a resistor and a switch for each of the unit cells C11 to Cmn as shown in the reference diagram of FIG. In addition, a control that is configured around the CPU and executes processing such as determining a variation state between unit cells based on a cell voltage detected in each VSC and controlling a bypass circuit according to the determination result. Equipment must be provided.

[0010] Due to the problems of withstand voltage, insulation and controllability, the number of cells that can be handled by one CPU is one.
The limit is about 0 to 20 cells. For this reason, HEV and E
In order to apply to a battery pack in which several tens to several hundreds of unit cells are connected in series, such as a battery pack used as a power source for V, the whole battery pack is made up of a plurality of cells consisting of n (eg, n = 10) unit cells Each of the cell groups CG1 to CGm is divided into groups CG1 to CGm, and the lower control apparatuses BCU_L1 to BCU_Lm which share voltage detection and variation adjustment are provided for each of the cell groups CG1 to CGm.
It is necessary to provide a higher-level control device BCU_H that controls Lm and adjust the entire assembled battery.

For example, even a lithium battery having a relatively small number of cells needs to provide 4 to 8 cell groups, that is, control devices.
Since many expensive electronic components such as a communication I / F for performing communication between the U and the CPU are required, there is a problem that the device becomes complicated and expensive, and the device becomes large.

On the other hand, without using expensive electronic components such as a CPU, a unit cell is discharged by detecting a variation between cell voltages autonomously, and the unit cells constituting the assembled battery are discharged. A simple equalizing circuit for eliminating voltage variations has also been proposed. As a simple equalizing circuit of this type, for example, a voltage dividing circuit composed of the same number of resistors as the unit cell equally divides the voltage between both ends of the assembled battery, and a feedback circuit using an operational amplifier provides a potential difference between the connection points of the unit cells. And discharging each unit cell so that the potential at the connection point of the corresponding voltage-dividing resistor coincides with the voltage (see JP-A-11-262188).
Publication), and the magnitude relationship between the potentials of the connection points of the unit cell and the voltage dividing circuit is determined using an operational amplifier, and from the result of the determination, a unit cell higher than the average voltage is specified using a logical operation.
The discharge of the specified unit cell is performed using a discharge circuit provided for each unit cell (Japanese Patent Laid-Open No. 2000-833).
No. 27 gazette) and the like.

[0013]

However, since these simple equalizing circuits always operate, when the voltage across the unit cell (cell voltage) does not correctly reflect the state of charge, the voltage variation is rather widened. As a result, there is a problem that the state of charge of each unit cell cannot be efficiently equalized.

That is, since the unit cell has an internal impedance, its cell voltage changes depending on the magnitude of the main current flowing through the battery pack. Moreover, since the internal impedance varies from unit cell to unit cell, the magnitude relationship of the cell voltage is switched depending on the magnitude of the main current, and the cell voltage does not correctly reflect the state of charge (remaining capacity) of the cell. It is.

In particular, when the battery pack is used as a power source for an HEV, a large main current flows during acceleration / deceleration,
In addition, since the main current greatly fluctuates according to the state of acceleration / deceleration, such a problem becomes significant. In addition, it is conceivable to set the discharge current flowing at the time of voltage adjustment small so as to reduce the influence of the fluctuation of the main current.
In the case of a vehicle in which the stop time during which the main current does not flow is short, there is a possibility that the time for correctly adjusting the voltage cannot be sufficiently secured, and the charging states of the unit cells may not be sufficiently equalized.

The present invention has been made in order to solve the above problems.
An object of the present invention is to provide a charge state control method and apparatus capable of efficiently equalizing the charge state of each unit cell constituting a battery pack with a simple configuration.

[0017]

According to a first aspect of the present invention, there is provided a method for controlling a state of charge of a battery pack, the method comprising the steps of: charging a unit cell to a cell voltage which is a voltage across the unit cell; It is determined whether or not the state is correctly adjusted, and the state is correctly reflected. Only when the state is the adjustable state, the variation of the cell voltage between the unit cells constituting the cell group is eliminated for each cell group. The state of charge of the unit cells is individually adjusted so as to be adjusted.

Therefore, according to the present invention, erroneous voltage adjustment is not performed based on a cell voltage that does not correctly reflect the state of charge of a unit cell, and the state of charge of a unit cell is efficiently and uniformly. Can be When the battery pack is composed of one cell group, the cell group indicates the battery pack itself.

In the charging state control device according to the second aspect, the adjusting operation control means operates the cell voltage adjusting means provided for each cell group only when the state of the battery pack is in the adjustable state. The cell voltage adjusting means individually adjusts the state of charge of the unit cells so as to eliminate the variation of the cell voltage, which is the voltage across the unit cells, between the unit cells constituting the cell group to be adjusted. I do.

That is, the state-of-charge control device of the present invention realizes the method described in claim 1, and therefore can provide the same effects as when the method described in claim 1 is implemented. The cell voltage adjusting means extracts, for example, a unit cell having the lowest cell voltage from the unit cells constituting the cell group, and replaces the cell voltage of the extracted unit cell with the cell voltage of another unit cell. Or a unit cell having a cell voltage higher than the average voltage of the unit cells constituting the cell group may be discharged until it becomes equal to the average voltage. May be configured.

In any case, in order to simplify the device configuration, the cell voltage adjusting means is provided by supplying power from a cell group to be adjusted by the cell voltage adjusting means. It is desirable to be configured to operate. By the way, the adjustable state in which the state of charge of the unit cell is correctly reflected in the cell voltage is, more specifically, a state in which the main current flowing through the assembled battery is not flowing or a change in the cell voltage due to the internal impedance. Is when the main current is so small that it can be ignored.

For example, if the connected device for charging / discharging the battery pack is stopped, the main current does not flow, so that the operating state of the connected device is detected. Means is provided, and when the operation state detected by the device operation state detection means indicates the stop of the connected device, the adjustment operation control means performs control assuming that the battery pack is in an adjustable state. You may.

According to a sixth aspect of the present invention, there is provided current detecting means for detecting the magnitude of the main current flowing through the battery pack.
When the main current detected by the current detecting means is equal to or less than a preset upper limit value, the adjusting operation control means may perform control assuming that the assembled battery is in an adjustable state.

Further, as set forth in claim 7, a group voltage detecting means for detecting a group voltage which is a voltage between both ends of each cell group constituting the assembled battery is provided, and the group voltage detected by the group voltage detecting means is detected. When the time rate of change is equal to or less than a preset upper limit, the adjustment operation control means may perform control assuming that the battery pack is in an adjustable state. That is, since the time rate of change of the group voltage also changes according to the magnitude of the main current, if the time rate of change of the group voltage is small, it can be estimated that the main current is small.

Here, when the assembled battery is composed of a plurality of cell groups, each voltage adjusting means provided for each cell group equalizes the state of charge of each unit cell in the cell group to be adjusted. However, there is a possibility that the state of charge will be different between different cell groups.

Therefore, when the assembled battery is composed of a plurality of cell groups, the variation of the group voltage, which is the voltage between both ends of each of the cell groups constituting the assembled battery, is eliminated. It is desirable to have a group voltage adjusting means for individually adjusting the state of charge of the cell group.

Next, in the charging state control device according to the ninth aspect,
By cell voltage monitoring means provided for each cell group,
It monitors whether the cell voltage of each unit cell constituting the cell group to be monitored is within a preset voltage range, and according to the monitoring result by the cell voltage monitoring means, the signal generation means Of the unit cells that make up the group,
A first signal level indicating a normal state if all cell voltages are within the voltage range; a second signal level indicating an overcharged state if any one of the cell voltages exceeds the voltage range; If at least the cell voltage falls below the voltage range, a cell state signal having a third signal level indicating an overdischarge state is generated.

In the charge state control device of the present invention thus configured, not only the state of charge of the unit cells is automatically equalized, but also the state of the unit cells forming the cell group is externally controlled by the cell state signal. The device can be notified, and the external device can monitor the cell state signal to detect the occurrence of an abnormal situation that cannot be recovered by the adjusting operation by the cell voltage adjusting means.

In order to simplify the device configuration,
It is desirable that the cell voltage monitoring means and the signal generation means be configured to operate by power supply from a cell group to be monitored by the cell voltage monitoring means. Then, the signal generating means is, for example,
As described in 1, a first current path that is always conductive and flows a constant current, a second current path that is conductive and flows a constant current in an overcharged state, and is conductive and constant in a state other than the overdischarge state Using the third current path through which the current flows, a current signal obtained by combining the currents flowing through the respective current paths can be generated as a cell state signal.

In this case, in the overdischarge state, the signal level is lower than in the normal state, that is, the current consumption used for generating the cell state signal is small. , The signal level is higher, that is, the current consumption used for generating the cell state signal is larger.

Therefore, according to the present invention, in the overdischarge state, the power supply from the monitored cell group to the signal generation means is reduced, so that the progress of the overdischarge state in the monitored cell group can be suppressed. Further, in the overcharged state, the power supply from the monitored cell group to the signal generating means increases, so that the overcharged state in the monitored cell group can be eliminated.

Further, in the present invention, since a multi-level cell state signal is used, the cell state signal can be transmitted on one of the transmission lines, and the connection between the apparatus and the apparatus utilizing the cell state signal can be established. Can be done easily. Next, claim 1
2. The charge state control device according to item 2, wherein the cell state signal transmission line for transmitting the cell state signal is provided with a switch for interrupting the cell state signal transmission line. A prohibition signal for prohibiting the operation of the adjustment means is generated, and the prohibition signal from the signal generation means stops the operation of the cell voltage adjustment means.

That is, according to the present invention, not only the output of the cell status signal but also the activation and deactivation of the cell voltage adjusting means can be performed by using the cell status signal transmission line. Wiring between the control device and the control device for controlling the adjusting means can be simplified.

In particular, when the battery pack is mounted on a vehicle, the switch on the cell status signal transmission line is turned on when the ignition switch of the vehicle is turned off. May be. That is, when the ignition switch is off, the connected devices for charging and discharging the battery pack are also stopped, and the battery pack is in an adjustable state without main current flowing. The voltage adjusting means can be made operable.

By the way, as the unit cell constituting the assembled battery, various kinds of cells such as a lead battery and a nickel-based battery can be used, but it is possible to occlude and release lithium ions. It is desirable to use a lithium-based secondary battery configured using electrodes made of a substance.

That is, since the lithium secondary battery has a high energy density and a high output voltage, even if the same high voltage is obtained, a battery pack having a small capacity and a large capacity can be constructed. The assembled battery itself and the charge state control device can be reduced in size and weight.

The charge state control device may be applied to an assembled battery used for any purpose. For example, as described in claim 15, an electric vehicle (EV) or a hybrid electric vehicle (HEV) If it is applied to a vehicle mounted as a power source, the reliability of EV and HEV,
Durability can be improved.

[0038]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram showing the entire configuration of a battery pack system according to a first embodiment, and here shows a state in which the battery pack is incorporated in a drive system of a hybrid vehicle (HEV).

As shown in FIG. 1, the assembled battery system 2 of this embodiment includes a main power line L, an inverter (INV) 6
The motor 8 is connected to a motor (MG) 8 which also functions as a motor and a generator via a power supply, and further starts and stops the motor 8 and operates the inverter 6 according to the running state of the vehicle and the state of the battery pack system 2. An HEV controller (VCU) 4 for controlling the direction and the like is provided.

The VCU 4 is set to run using the driving force of the engine when the engine is running at a constant speed with good operating efficiency. At this time, if the charge amount of the battery pack system 2 is insufficient, The driving force from the engine is transmitted to the electric motor 8, and the electric motor 8 operates as a generator.
Is set to be supplied to the battery pack system 2 via the inverter 6, and
To charge.

On the other hand, at the time of starting or at the time of full acceleration when the operation efficiency of the engine is low, electric power from the battery pack system 2 is supplied to the electric motor 8 via the inverter 6, and the motor 8 is supplied from the battery pack system 2. It is set so as to operate as a motor by the supplied electric power, and travels using the driving force from the electric motor 8.

The assembled battery system 2 of this embodiment includes an assembled battery 10 in which a plurality of unit cells are connected in series using a lithium battery, which is a rechargeable secondary battery, as a unit cell. The assembled battery 10 includes four unit cells Ci1 to Ci.
Each of the cell groups CGi (i = 1 to m) is divided into a plurality of cell groups CG1 to CGm composed of Ci4.
A cell variation adjusting device CEUi is provided as cell voltage adjusting means for eliminating the variation in cell voltage between i4.

The battery pack system 2 includes a current sensor (CS) 14 for detecting a main current flowing through the main power supply line L during charging and discharging of the battery pack 10, a current detection signal IB from the current sensor 14, and an ignition switch ( (Not shown), an ignition signal IG representing an operation state, and voltages obtained via cell group voltage detection lines LS1 to LSm + 1 branched from the main power supply line L at both ends of the battery pack 10 and at the boundary of the cell group CGi. Photocoupler PC connected in series between terminals CCP and CCN based on signals VS1-VSm + 1, etc.
(To be described later), the cell variation adjusting units CEUi are collectively started and stopped,
A battery pack controller (BCU) 12 is provided for executing processing such as outputting various commands CMD to the CU 4.

As shown in FIG. 2, the cell variation adjusting device CEUi includes resistors and switches connected in series, and is individually connected in parallel to each of the unit cells Ci1 to Ci4 constituting the cell group CGi. Discharge circuits P1 to P
4 and a voltage dividing circuit 20 in which the same number of resistors R1 to R4 as the number of unit cells in the cell group CGi are connected in series and connected in parallel to the cell group CGi.

In the following, the potential of the positive terminal of the cell group CGi is referred to as a cell potential Ec0, and the potential of the negative terminal is referred to as a cell potential Ec4. The unit cells Cij and Cij + 1 (j = 1 to
The potential at the connection point with 3) is defined as a cell side potential Ecj. Also,
The potential on the positive side end of the voltage dividing circuit 20 is changed to the resistance side potential Er0 (= E
c0), the potential at the negative end is defined as the resistance potential Er4 (= Ec4), and the potential at the connection point between the resistors Rij and Rij + 1 therebetween is defined as the resistance potential Erj.

The cell variation adjusting device CEUi
Is a comparison circuit 21 that generates determination signals S1L and S1H based on the cell-side potential Ec1 and the resistance-side potential Er1, and a determination signal S2L, S2L, based on the cell-side potential Ec2 and the resistance-side potential Er2.
Similarly to the comparison circuit 22 that generates S2H, the cell-side potential E
Based on c3 and the resistance-side potential Er3, the determination signals S3L, S3H
, And judgment signals S1L and S1H from the comparison circuit 21 and judgment signals S2L and S2 from the comparison circuit 22.
Based on 2H, the logic circuit 24 generates an operation signal SD2 for operating the switch of the discharge circuit P2, and discharge is performed based on the determination signals S2L and S2H from the comparison circuit 22 and the determination signals S3L and S3H from the comparison circuit 23. A logic circuit 25 for generating an operation signal SD3 for operating a switch of the circuit P3, and judgment signals S1L and S1 used as operation signals SD1 and SD4.
3H and a discharge prohibition circuit 26 for setting the operation signals SD2 and SD3 to a low level and setting the discharge circuits P1 to P4 so as not to operate.

The discharge prohibition circuit 26 is provided with a grounding circuit in which a diode and a resistor are connected in series for each signal line transmitting the operation signals SD1 to SD4. Terminal CCP, CCN
Common photocoupler P that becomes conductive by power supply between
It is connected to the negative electrode side end of the cell group CGi via C.

That is, when the photocoupler PC is on, the operation signals SD1 to SD4 are forced to the low level, and the switches constituting the discharge circuits P1 to P4 are kept in the off state. Discharge is prohibited, and when the photocoupler PC is off, discharge by the discharge circuits P1 to P4, that is, cell voltage variation adjustment by the cell variation adjustment device CEUi becomes possible. In addition, each cell variation adjusting device CEU1 to CEUm
The input side of the photocoupler PC is connected in series between the terminals CCP and CCN.
They are turned on and off all at once.

Next, each of the comparators 21 to 23 has the same configuration. As shown in FIG. 3A, the non-inverting input has a resistance side potential Erj, and the inverting input has a cell side potential Ecj. Well-known differential amplifier circuit AM comprising an operational amplifier to which
P and a first threshold value TH1 (= Ecj + VF) larger than the cell side potential Ecj by a specified value VF and a second threshold value TH2 (= Ecj−V) smaller than the cell side potential Ecj by a specified value VF.
F), a reference voltage source DEN, an output of the differential amplifier circuit AMP at a non-inverting input, and a first threshold TH at an inverting input.
Comparator CP1 composed of an operational amplifier to which 1 is applied
And a comparator CP2 comprising an operational amplifier having an output of the differential amplifier circuit AMP at the inverting input and a second threshold TH2 applied to the non-inverting input.
The output of P1 is a determination signal SjL, and the output of the comparator CP2 is a determination signal SjH. The specified value VF can be generated using, for example, a forward voltage of a diode, a breakdown voltage of a Zener diode, and the like.

That is, as shown in FIG. 3B, the determination signal SjL generated by each of the comparison circuits 21 to 23 has a range of ± VF centered on the potential of the resistance side potential Erj as the voltage allowable range Wj. When the cell-side potential Ecj is smaller than the lower limit (Erj−VF) of the voltage allowable range Wj, the cell-side potential Ecj becomes a high level.
It becomes a high level when it is larger than the upper limit of j (Erj-VF).

The logic circuits 24 and 25 correspond to those shown in FIG.
As shown in the figure, an inverting circuit NO for inverting the determination signal SjL
T1 and an inverting circuit NOT2 for inverting the determination signal Sj + 1H
AND circuit AND1 whose output becomes high when both the output of the inverting circuit NOT1 and the judgment signal Sj + 1L are at high level, and the output when both the judgment signal SjH and the output of the inverting circuit NOT2 are at high level. AND circuit AND2, which is at a high level, and AND circuits AND1, AND2
And an OR circuit OR whose output becomes a high level when at least one of them is at a high level.
The output of R becomes the operation signal SDj + 1.

That is, in the operation signal SDj + 1 generated by the logic circuits 24 and 25, the cell-side potential Ecj is equal to or higher than the lower limit (Erj-VF) of the voltage allowable range Wj and the cell-side potential Ecj + 1 is the lower limit of the voltage allowable range Wj + 1 (Erj + 1−V
F), or the cell side potential Ecj is larger than the upper limit (Erj + VF) of the voltage allowable range Wj, and the cell side potential Ecj + 1 is higher than the upper limit of the voltage allowable range Wj + 1 (Erj + 1 + V).
F) It becomes high level when it is less than or equal to.

In the cell variation adjusting device CEUi configured as described above, when the cell voltage of the unit cell Cij is higher than the average cell voltage of the cell group CGi obtained by the voltage dividing circuit 20, the operation signal SDj goes high. .
The discharge circuits P1 to P4 operate in accordance with the operation signals SD1 to SD4, and are higher than the average cell voltage of the cell group CGi until each of the cell-side potentials Ec1 to Ec3 is within the voltage allowable range W1 to W3. The unit cell having the cell voltage is discharged. As a result, each unit cell Ci1 to Ci4
Are substantially equal to the average cell voltage of the cell group CGi.

The BCU 12 is connected to the terminals CCP, CCN
When the photocoupler PC is turned on by supplying power during this time, the discharge prohibition circuit 26 causes the discharge circuits P1 to P1 to turn on.
The discharge by P4 is forcibly prohibited. The operations of the comparison circuits 21 to 23 and the logic circuits 24 and 25 are described in detail in JP-A-2000-83327.

Next, the BCU 12, as shown in FIG.
The voltage between the cell group voltage detection lines LSi and LSi + 1, that is, the group voltage VGi of the cell group CGi (= VSi
−VSi + 1) for detecting the group voltage VSCi.
And a group bypass circuit GBi that includes a resistor Rgp and a transistor Tgp and conducts between the cell group voltage detection lines LSi and LSi + 1.
m.

Further, the BCU 12 stores each cell group CG
Group voltage detection circuit VSC provided for each of 1 to CGm
A multiplexer (MPX) 3 for selecting any one of 1 to VSCm and taking in the group voltage VGi detected by the selected group voltage detection circuit VSCi.
0, and a decoder (DEC) 32 that selects one of the cell groups CG1 to CGm and outputs a control signal for turning on / off the transistor Tgp of the group bypass circuit GBi corresponding to the selected cell group CGi.
And a transistor Td that turns on and off a power supply line to the photocoupler PC of each of the cell variation adjusting devices CEU1 to CEUm connected in series between the terminals CCP and CCN.
A prohibition signal for prohibiting the operation of the cell variation adjusting device CEUi based on the group voltages VG1 to VGm obtained through the multiplexer 30, the signal IG indicating the operation state of the ignition switch, and the detection signal IB from the current sensor 14. And an arithmetic processing unit (CPU) 38 for executing processing such as generation of various commands CMD to the VCU 4, and a memory 40 for storing data and the like necessary for the processing. The control signal from the decoder 32 is configured to be supplied to the transistor Tgp via the photocoupler 36.

When the CPU 38 detects that the ignition switch has been turned on by the ignition signal IG, the CPU 38 turns on the transistor Td to inhibit the variation adjustment operation by the cell variation adjusters CEU1 to CEUm. When it is detected that the transistor Td is turned off, the transistor Td is turned off, and control is performed to enable a variation adjustment operation by the cell variation adjusters CEU1 to CEUm. This control corresponds to the device operating state detecting means and the adjusting operation control means in the present invention.

The CPU 38 monitors the group voltages VG1 to VGm while the ignition switch is turned on, and determines whether the group voltage Vg exceeds a preset upper limit value.
When a cell group CGi having Gi is detected, the group bypass circuit G corresponding to the cell group CGi is detected.
By conducting Bi, the cell group CGi
Control such as limiting charging of the battery. This control and the group bypass circuit GBi correspond to a group voltage adjusting unit in the present invention.

In the battery pack system 2 configured as described above, when the ignition switch is turned on, the VCU 4 appropriately switches the use state (motor or generator) of the electric motor 8 in accordance with the running state of the vehicle. 10
Are charged and discharged. When the ignition switch is turned off, the cell variation adjusting devices CEU1 to CEUm operate to equalize the cell voltages of the unit cells Ci1 to Ci4 for each cell group CGi, thereby repeatedly charging and discharging the battery pack 10. The variation of the cell voltage between the unit cells Cij caused by the above is eliminated.

As described above, in the battery pack system 2 of the present embodiment, the cell variation adjusting device CEUi for automatically equalizing the cell voltages of the unit cells Ci1 to Ci4 constituting the cell group CGi is provided by the cell group CGi. The cell variation adjusting device CEU1
To CEUm are configured to operate only when the ignition switch through which the main current flowing through the battery pack 10 does not flow is off.

Therefore, according to the battery pack system 2 of the present embodiment, the cell variation adjusting devices CEU1 to CEUm are:
A state in which the charge state (remaining capacity) of the unit cell is correctly reflected in the cell voltage of the unit cell Cij without being affected by the internal impedance of the unit cell Cij (this state is referred to as an adjustable state). ), The unit cell C can be adjusted by adjusting the cell voltage.
The state of charge of ij can be correctly equalized.

Further, according to the battery pack system 2 of the present embodiment, when the ignition switch through which the main current flows is turned on, the operation of the cell variation adjusting devices CEU1 to CEUm is prohibited, so that the state of charge is correctly reflected. Since the execution of the erroneous variation adjustment based on the cell voltage that is not performed is reliably prevented, the variation adjustment can be performed efficiently, and the operating state (the adjustable state and the adjustable state) of the vehicle equipped with the battery pack system 2 is not limited. The length of the current flowing in the discharge circuits P1 to P4 can be set arbitrarily according to the length of the period.

In this embodiment, the cell variation adjusting devices CEU1 to CEUm are operated only when the ignition switch is turned off. However, even when the ignition switch is turned on, the main current is not changed. If is small enough, the cell voltage can be considered to accurately reflect the state of charge, for example,
When the magnitude of the main current detected by the current sensor 14 (corresponding to current detection means) is equal to or smaller than a predetermined value, or when each of the group voltage detection circuits VSC1 to VSCm
The cell variation adjusting devices CEU1 to CEUm are operated even when the time change rates of the group voltages VG1 to VGm detected by (corresponding to the group voltage detecting means) are all equal to or less than a predetermined value. You may comprise. The control executed by the CPU 38 to realize these functions corresponds to an adjustment operation control unit. [Second Embodiment] Next, a second embodiment will be described.

FIG. 4 is a block diagram showing the overall configuration of the battery pack system according to the second embodiment, and shows a state in which the battery pack is incorporated in an HEV drive system, as in the first embodiment. The assembled battery system of the present embodiment is different from that of the first embodiment only in a part of the configuration. Therefore, the same components are denoted by the same reference numerals, and description thereof is omitted. The different parts will be mainly described.

As shown in FIG. 4, in the assembled battery system 2a of this embodiment, the cell variation adjusting devices CEU1 to CEUm in the assembled battery system 2 of the first embodiment are replaced by cell monitoring and adjusting devices CMU1 to CMUm. BC
In U12a, instead of terminals CCP and CCN, cell state signal transmission lines LC1 to LCm are wired between each cell monitoring and adjusting device CMU1 to CMUm and BCU12a.

In the BCU 12a, as shown in FIG. 5, the transistor Td is omitted, and instead, the signal level identification circuit VSLi for identifying the signal level of the cell status signal transmitted via the cell status signal transmission line LCi is used. A switch SW is provided for each of the cell groups CG1 to CGm, and a switch SW for making the cell state signal transmission line LCi conductive when the ignition switch is on is provided in conjunction with the operation state of the ignition switch.
A multiplexer 34 for selecting any one of Lm and taking in the signal level identification result from the selected signal level identification circuit.

Further, the cell monitoring and adjusting device CMUi monitors the state of charge of the unit cells Ci1 to Ci4 constituting the cell group CGi and generates a cell state signal.
MC, and unit cells Ci1 to Ci1 of a cell group CGi.
Cell variation adjustment unit CEC that equalizes the cell voltage of Ci4
Consists of

Of these, the cell variation adjusting unit CEC
The configuration is exactly the same as the cell variation adjusting device CEUi in the first embodiment, except that the switch circuit forming the discharge prohibition circuit 26 is configured using a transistor Tp instead of the photocoupler PC. Specifically, the collector and the emitter of the transistor Tp are connected in the same manner as the output side of the photocoupler PC, and the transistor Tp
The base of p is applied with a discharge prohibition signal (described later) from the cell monitoring control unit CMC, and when this discharge prohibition signal is input, the discharge by the discharge circuits P1 to P4, that is, the variation adjustment by the cell variation adjustment unit CEC. The operation is prohibited.

On the other hand, the cell monitoring control section CMC includes charge state determination circuits 41 to 44 for determining the charge state of each of the unit cells Ci1 to Ci4 for each of the unit cells Ci1 to Ci4 constituting the cell group CGi. . Each of the charge state determination circuits 41 to 44 has a similar configuration.
As shown in (2), a voltage corresponding to the voltage across the unit cell Cij (Ecj−Ecj + 1) is applied to the non-inverting input via a voltage dividing circuit composed of a resistor. A comparator CPH comprising an operational amplifier to which an upper limit reference voltage corresponding to the upper limit voltage of the unit cell Cij is applied via a constant voltage circuit, and a voltage across the unit cell Cij via a non-inverting input to a voltage dividing circuit comprising a resistor. And a comparator CPL composed of an operational amplifier to which a lower reference voltage corresponding to the lower limit voltage of the unit cell Cij is applied to an inverting input via a constant voltage circuit including a resistor and a voltage generating source. ing. The upper reference voltage and the lower reference voltage can be generated using, for example, a forward voltage of a diode, a breakdown voltage of a Zener diode, and the like.

That is, the overcharge determination signal JjH, which is the output of the comparator CPH, goes high only when the cell voltage of the unit cell Cij exceeds the upper limit voltage, and the overdischarge determination signal JjL, which is the output of the comparator CPL, It is set to low level only when the cell voltage of the unit cell Cij falls below the lower limit voltage.

The cell monitoring control unit CMC has three current paths D1 to D3 connected in parallel between the positive terminal of the cell group CGi and the cell state signal transmission line LCi. Among these, the first current path D1 includes a pair of resistors connected in series, and is connected to the cell state signal transmission line LCi.
When the upper switch SWi is closed, a constant current I1 is supplied to the cell state signal transmission line LCi, and a transistor bias circuit for connecting and disconnecting the transmission line D4 for transmitting a discharge prohibition signal to the cell variation adjusting unit CEC may be used. Operate. That is, when the switch SWi is closed, the transmission line D
4 is turned on, and the cell variation adjusting section C
It is configured to supply a discharge prohibition signal to the EC.

Next, the second current path D2 includes a transistor and a resistor. When the switch SWi on the cell state signal transmission line LCi is closed and the transistor on the second current path D2 is on, , Cell state signal transmission line LCi
Is supplied with a constant current I2. However, the bias circuit that drives the transistor on the second current path D2 is biased when any one of the overcharge determination signals J1H to J4H from the charge state determination circuits 41 to 44 has a high level. It is configured to pass a current.

That is, the second current path D2 is connected to the unit cell C
When any one of i1 to Ci4 is not in the overcharged state, it becomes a cutoff state, and when any one of the unit cells Ci1 to Ci4 becomes an overcharged state, it becomes conductive and applies a constant current I2 to the cell state signal transmission line LCi. Is to be supplied.

Similarly to the second current path D2, the third current path D3 includes a transistor and a resistor, the switch SWi on the cell state signal transmission line LCi is closed, and the third current path D3 is closed. When the transistor on D3 is turned on, a constant current I3 is supplied to the cell state signal transmission line LCi. However, the bias circuit that drives the transistor on the third current path D3 is provided with a bias current when any one of the overdischarge determination signals J1L to J4L from the charge state determination circuits 41 to 44 has a low level. It is configured to shut off.

That is, the third current path D3 is connected to the unit cell C
When any of i1 to Ci4 is not in the overdischarge state, it becomes conductive and supplies a constant current I3 to the cell state signal transmission line LCi, and any one of the unit cells Ci1 to Ci4 is in the overdischarge state. If there is, the state is cut off, and the supply of the constant current I3 to the cell state signal transmission line LCi is stopped.

Therefore, the first to third current paths D1 to D1
A cell state signal OCD obtained by combining supply currents from D3
The signal level of i (the magnitude of the current) depends on the cell group CG
When there is no overcharge state or overdischarge state among the unit cells Ci1 to Ci4 constituting i, the magnitude I based on the supply current from the first and third current paths D1 and D3 is used.
1 + I3 (first signal level), and when there is at least one overcharged state, the magnitude becomes I1 + I2 + I3 (second signal level) based on the supply current from all the current paths D1 to D3, and the overdischarge state When there is even one, the magnitude becomes I1 (third signal level) based on the supply current from the first current path D1.

Therefore, in the signal level discrimination circuit VSLi, the switches SWi are set to these first to third signal levels.
Are added to the fourth signal level (current 0) when the signal is open, and four signal levels are identified. In the cell monitoring controller, the charge state determination circuits 41 to 44 correspond to cell voltage monitoring means, and the other parts correspond to signal generation means.

In the battery pack system 2a of this embodiment thus configured, when the switch SWi on the cell state signal transmission line LCi is closed by turning on the ignition switch, the unit cells Ci1 to Ci4 The cell state signal OCDi representing the state of charge is transmitted to the cell state signal transmission line LC.
i, and is supplied to the BCU 12a, and the variation adjustment operation by the cell variation adjustment unit CEC is prohibited.

On the other hand, when the switch SWi is opened by turning off the ignition switch, the signal level of the cell state signal OCDi identified by the signal level identification circuit VSLi becomes the fourth signal level, and the cell variation adjustment is performed. The variation adjustment operation by the unit CEC becomes possible.

As described above, according to the battery pack system 2a of this embodiment, the cell variation adjusting unit CEC having the same function as the cell variation adjusting unit CEU is operated only when the ignition switch is turned off. As a result, the same effects as those of the battery pack system 2 of the first embodiment can be obtained.

In the battery pack system 2a according to the present embodiment, the cell monitoring control unit CMC includes the cell groups CG1 to CG.
For each Gm, the result of determining whether or not any of the unit cells Ci1 to Ci4 constituting the cell group CGi has an overcharged state or an overdischarged state is determined by a cell state signal OCD.
Output as i. That is, based on the cell state signal OCDi, the cell variation adjusting section CE
Since the abnormality of the unit cell Cij that cannot be eliminated by the operation of C can be detected, the reliability of the device can be improved.

In addition, the start and stop of the cell variation adjustment unit CEC are controlled by utilizing the change in the cell monitoring and control unit CMC caused by the switch SWi turning on and off the cell state signal transmission line LCi. So
There is no need to separately provide a dedicated control line for controlling the cell variation adjusting unit CEC, and the cell monitoring and adjusting units CMU1 to CMU1
The wiring between the CMUm and the BCU 12a can be simplified.

In the battery pack system 2a of the present embodiment, the fourth signal level corresponding to the current 0 is detected from the cell state signal OCDi when the switch SWi is opened. If the fourth signal level is detected while the switch SWi is closed, it can be determined that the cell state signal transmission line LCi has been disconnected or the cell monitoring and adjusting device CMUi has failed. Furthermore,
When the switch SWi is off, no current flows from the cell group CGi to the BCU 12a, so that a leak current (dark current) in a non-operating state of the vehicle in which the ignition switch is turned off can be reduced.

In the present embodiment, the switch SWi is opened and closed in conjunction with the ignition switch. However, the magnitude of the main current flowing through the battery pack 10, the state of the vehicle on which the device is mounted, and the like. CPU3 based on
8 may control the opening and closing of the switch SWi.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
It can be implemented in various aspects. For example, in the above embodiment, the cell group CGi is composed of four unit cells Ci1 to Ci4, but is not limited to this, and may be three or less or five or more. Note that, as the number of unit cells constituting the cell group CGi increases, the number of the cell groups CGi decreases, so that the configuration of the BCU 12a can be simplified.
In addition, the cell configuration of the cell monitoring and adjusting device CMUi is complicated due to problems such as withstand voltage of the elements used. Therefore, in the case of a lithium battery having an average cell voltage of 3.6 V, it is desirable to form a cell group with 4 to 6 unit cells. In particular, when these devices CEUi and CMUi are integrated into an IC, It is desirable that the number be within 6 due to the withstand voltage.

In the above embodiment, the unit cells Ci1 to Ci1 to
In order to eliminate the voltage variation between Ci4, discharge circuit P1
Although P4 to P4 are used, it is also possible to provide a power storage means including a secondary battery, a capacitor, or the like, and to transfer energy from a cell having a large remaining capacity to a cell having a small remaining capacity via the power storage means.

In the above embodiment, a lithium battery is used as a unit cell. However, for example, a lead battery or a nickel-based battery may be used, and any secondary battery can be used as a unit cell. In addition, in a secondary battery in which uniform charging is performed by a sealing reaction, it is not always necessary to perform overcharge / discharge detection, but when the present invention is applied to an assembled battery system including such a secondary battery, In addition, the performance of the assembled battery can be maximized, and the deterioration of the unit cell can be suppressed.

In the above embodiment, the battery pack 10 composed of the cell group CGi in which the unit cells are simply connected in series is provided.
However, the present invention is not limited to this, but is applicable to any cell group in which a plurality of unit cells are connected in series and parallel.

Further, in the above embodiment, the cell variation adjusting device CEUi and the cell variation adjusting unit CEC are configured to discharge a unit cell having a cell voltage higher than the average cell voltage in the cell group CGi. For example, detecting the lowest cell voltage in the cell group CGi,
Each unit cell may be configured to be discharged until the cell voltages of all the unit cells constituting the cell group CGi become equal to the minimum cell voltage.

The logic of each determination signal in the comparison circuits 21 to 23 and the charge state determination circuits 41 to 44 does not necessarily have to follow the one described in the above embodiment. However, it is desirable that the signal level at the time of detecting the overdischarge is set so as to minimize power takeout from the cell group CGi.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a battery pack system according to a first embodiment.

FIG. 2 is a block diagram illustrating a detailed configuration of a cell variation adjusting device and a BCU.

FIG. 3A is a circuit diagram illustrating a configuration of a comparison circuit;
FIG. 3B is an explanatory diagram illustrating an operation of the comparison circuit, and FIG. 3C is a circuit diagram illustrating a configuration of a logic circuit.

FIG. 4 is a block diagram illustrating an overall configuration of a battery pack system according to a second embodiment.

FIG. 5 is a block diagram illustrating a detailed configuration of a cell monitoring and adjusting device and a BCU.

FIG. 6 is a circuit diagram illustrating a configuration of a charge state determination circuit.

FIG. 7 is a reference diagram illustrating a configuration of a conventional device.

[Explanation of symbols]

2, 2a: assembled battery system, 4: HEV controller (VCU), 6: inverter, 8: electric motor, 10: assembled battery, 12, 12a: assembled battery controller (BCU), 1
4 current sensor, 20 voltage divider circuit, 21 to 23 comparison circuit, 24, 25 logic circuit, 26 discharge inhibition circuit, 3
0, 34: multiplexer, 40: memory, 41-44
... Charge state determination circuit, Cij ... unit cell, CGi ... cell group, CEUi ... cell variation adjusting device, CMUi ...
Cell monitoring and adjusting device, CEC: Cell variation adjusting unit, CM
C: cell monitoring control unit, AMP: differential amplifier circuit, CP1,
CP2, CPH, CPL Comparator, DEN Reference voltage source, D1 to D3 First to third current paths, D4 Transmission line, GBi Group bypass circuit, L Main power supply line, LSi Cell group voltage detection line , LCi: cell state signal transmission line, P1 to P4: discharge circuit, PC: photocoupler, SWi: switch, VSCi: group voltage detection circuit, VSLi: signal level identification circuit

Claims (15)

[Claims] 1. A rechargeable battery that can be charged and discharged is a unit cell, a plurality of unit cells connected in series is referred to as a cell group, and a battery pack composed of one or a plurality of cell groups connected in series is charged. A charge state control method for controlling a state, wherein the state of the battery pack is in an adjustable state in which the state of charge of the unit cell is correctly reflected in a cell voltage that is a voltage across the unit cell. Judge and individually adjust the state of charge of the unit cells for each of the cell groups so that the variation in cell voltage between the unit cells constituting the cell group is eliminated only when the cell group is in the adjustable state. A charge state control method. 2. A rechargeable battery that can be charged and discharged is a unit cell, and a plurality of unit cells connected in series is referred to as a cell group, and a battery pack composed of one or a plurality of cell groups connected in series is charged. A charge state control device for controlling a state, wherein the charge state control device is provided for each of the cell groups, and between the unit cells forming the cell group, a variation in a cell voltage that is a voltage across the unit cell is eliminated. A cell voltage adjusting means for individually adjusting the state of charge of the unit cell; and the cell voltage adjustment only when the state of the battery pack is in an adjustable state in which the state of charge of the unit cell is correctly reflected in the cell voltage. And a regulating operation control means for operating the means. 3. The cell voltage adjusting unit discharges a unit cell having a cell voltage higher than an average voltage of each unit cell constituting the cell group until the unit cell becomes equal to the average voltage. 3. The charging state control device according to 2. 4. The charging state control device according to claim 2, wherein the cell voltage adjusting means operates by supplying power from a cell group to be adjusted by the cell voltage adjusting means. 5. An apparatus according to claim 1, further comprising a device operating state detecting unit configured to detect an operating state of the connected device that charges and discharges the battery pack, wherein the adjusting operation control unit detects the operating state detected by the device operating state detecting unit. The charging state control device according to any one of claims 2 to 4, wherein when the connected device is stopped, the assembled battery is in an adjustable state. 6. A current detecting means for detecting a magnitude of a main current flowing through the battery pack, wherein the adjusting operation control means controls a main current detected by the current detecting means to a predetermined upper limit value. The charging state control device according to any one of claims 2 to 4, wherein the battery pack is in an adjustable state in the following cases. 7. A group voltage detecting means for detecting a group voltage which is a voltage between both ends of each cell group constituting the battery pack, wherein the adjusting operation control means includes a group voltage detected by the group voltage detecting means. 5. The charge state control device according to claim 2, wherein the battery pack is in an adjustable state when the time rate of change is equal to or less than a preset upper limit value. 6. 8. A system according to claim 1, further comprising a group voltage adjusting means for individually adjusting a state of charge of each of the cell groups so as to eliminate a variation in a group voltage that is a voltage between both ends of each of the cell groups constituting the assembled battery. The charging state control device according to claim 2, wherein 9. A cell voltage monitoring means provided for each cell group, for monitoring whether a cell voltage of each unit cell constituting the cell group is within a predetermined voltage range, A first signal level representing a normal state if all cell voltages of the unit cells constituting the cell group are within the voltage range, according to a monitoring result by the voltage monitoring means;
If any one of the cell voltages exceeds the voltage range, the second signal level indicates an overcharged state, and if any one of the cell voltages is below the voltage range, the second signal level indicates an overdischarged state.
9. The charge state control device according to claim 2, further comprising: a signal generation unit configured to generate a cell state signal having a signal level of the following. 10. The charging state control device according to claim 9, wherein said cell voltage monitoring means and said signal generation means are operated by power supply from a cell group to be monitored by said cell voltage monitoring means. . 11. A first current path which is always conductive and flows a constant current, a second current path which is conductive and flows a constant current during the overcharge state, and wherein the overdischarge state is Conduction at a time other than 3
11. The charging state control device according to claim 9, further comprising: generating a current signal obtained by combining currents flowing through the respective current paths as the cell state signal. 12. 12. A cell state signal transmission line for transmitting the cell state signal, wherein a switch for intermittently connecting the cell state signal transmission line is provided, wherein the signal generation unit is configured to control the cell voltage adjustment unit when the switch is turned on. 10. A prohibition signal for prohibiting the above operation is generated, and the cell voltage adjusting means stops the operation in response to the prohibition signal from the signal generation means.
A charge state control device according to claim 11. 13. The charging state control device according to claim 12, wherein the battery pack is mounted on a vehicle, and the switch is turned on when an ignition switch of the vehicle is turned off. 14. The lithium secondary battery according to claim 2, wherein the unit cell is a lithium secondary battery including electrodes made of a substance capable of inserting and extracting lithium ions. Or the state-of-charge control device according to the above. 15. The charging state control device according to claim 2, wherein the battery pack is mounted as a power source of an electric vehicle or a hybrid electric vehicle.