JP5831217B2 - Voltage balance control device - Google Patents

Description

  The present invention relates to a voltage balance control device for a battery cell that enables a plurality of battery cells to exhibit the performance of an assembled battery that is connected in series to the maximum.

  In recent years, signs of widespread use of electric vehicles that run by motor drive using electric energy stored in batteries have become visibly noticeable. In this electric vehicle, electric energy is stored in a rechargeable battery, and the electric motor is driven using an electric motor as a drive source. In such an electric vehicle, an assembled battery in which a plurality of battery cells are connected in series is used as a power source of the electric motor. In this assembled battery, the progress of deterioration is different by repeating charging and discharging. The discharge characteristics of the battery cells are slightly different. However, since it is necessary to efficiently charge such an assembled battery and to maximize the performance of the battery, the difference in the amount of charge / discharge between the battery cells should be corrected by the cell voltage balance technology. Therefore, the battery pack is efficiently charged so that the battery performance can be maximized. As such a cell voltage balance technique, a voltage conversion circuit that converts the voltages of a plurality of rechargeable batteries into a GND reference, and an output circuit that outputs the lowest voltage value of the plurality of converted conversion voltages, Each battery has a circuit constituting a discharge loop of the corresponding battery, and the converted voltage is compared with the lowest voltage value by comparing the lowest voltage value with the converted voltage of the corresponding battery. There is a cell balance circuit provided with a circuit that turns on the discharge loop when a set value is exceeded (see Patent Document 1).

Japanese Patent Laid-Open No. 10-50352

  Therefore, in the conventional battery cell voltage balance control device, the battery cell having the lowest voltage value among the battery cells is turned on so that the voltage value of the other battery cell is matched with the discharge including the resistance. As a result of discharging the other battery cells in the circuit, unnecessary power consumption occurs, and the battery temperature rise and battery deterioration due to unnecessary power consumption are accelerated, and the increase in output decline is accelerated. Furthermore, there were problems such as a longer balance time.

  The present invention has been made in view of such circumstances, and suppresses the occurrence of unnecessary power consumption, thereby suppressing battery temperature increase, battery deterioration, and output decrease, and efficient charging. It is an object of the present invention to provide a battery cell voltage balance control device that enables maximum battery performance.

The present invention is a voltage balance control device that adjusts and controls the variation in battery voltage of a plurality of battery cells connected in series constituting an assembled battery, and is a charge / discharge device that shows the battery voltage / discharge capacity characteristics of each of the battery cells. Using the characteristic information acquisition means for acquiring characteristic information and the charge / discharge characteristic information acquired by the characteristic information acquisition means, the voltage between the plurality of battery cells having different degrees of deterioration is the amount of electricity stored in the battery cell. Is determined in a high charge state equal to or greater than a first predetermined amount, and a charge / discharge amount for each of the battery cells is determined, and the charge / discharge amount for each of the battery cells is controlled to control the battery in the high charge state. and a voltage balance control means for establishing a voltage balance between the cells, the charge and discharge characteristics information, coordinate the battery voltage and the battery discharge capacity of the battery cell The voltage balance control means is configured to move the charge / discharge map of each battery cell along the battery discharge capacity direction so that the voltage between the battery cells is increased in the high charge state. to determine the point where the match, and wherein a call.

According to the present invention, since the voltage balance between the battery cells in the high charge state is established by controlling the charge / discharge amount using the charge / discharge characteristic information, compared with the case of performing the voltage balance control according to the prior art, Generation of unnecessary power consumption can be suppressed, thereby suppressing battery temperature increase, battery deterioration, and output decrease, enabling efficient charging and maximizing battery performance. In addition, according to the first aspect of the present invention, since the charge / discharge amount for each battery cell is controlled using the charge / discharge characteristic information of each battery cell, the state of charge of the battery cell is Can also start voltage balance control. According to the first aspect of the present invention, the charge / discharge amount for each battery cell is determined so that the voltages between the plurality of battery cells having different degrees of deterioration match in a high charge state, and the charge / discharge for each battery cell is determined. Since the discharge amount is controlled, the voltage balance between the battery cells can be established with higher accuracy.

According to the present invention, since the charge / discharge amount is determined and the control is started in the low charge state where the storage amount of the battery cell is small, the voltage balance is established while charging from the low charge state to the high charge state. Therefore, the voltage balance can be established in a short time compared to starting the control in the high charge state. Moreover, in a low charge state, since the voltage difference between the some battery cells from which a deterioration degree differs is large, a voltage balance can be established more accurately.

According to the present invention, since the discharge of the battery cell and the charging of the other battery cell are performed simultaneously, the voltage balance can be controlled in a short time.

According to the present invention, since the battery cell stable state determining means for determining based on the passage of a predetermined period after the ignition switch is turned off is provided, the battery cell state in a stable state And the voltage balance between the battery cells can be established with higher accuracy.

It is a block diagram which shows the structure of the voltage balance control apparatus 100 of the battery cell which is the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the cell control units 6, 7, 8, and 9 shown in FIG. It is explanatory drawing which shows an example of charging / discharging characteristic map MP. It is explanatory drawing which shows the outline | summary of the voltage balance control by the control part. 3 is a flowchart showing the operation of the voltage balance control device 100.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a battery cell voltage balance control apparatus 100 according to the first embodiment of the present invention.
In the battery cell voltage balance control apparatus 100 of this embodiment, a plurality of battery cells 1, 2, 3, 4 are connected in series to form one assembled battery.
Also, the voltage is monitored for each of the plurality of battery cells 1, 2, 3, 4 constituting the assembled battery, and the cell charging current and the cell discharging current of the battery cells 1, 2, 3, 4 are controlled. A charging power source 10 having a DC / DC converter function for charging an assembled battery composed of the control units 6, 7, 8, 9 and the battery cells 1, 2, 3, 4, and the cell control units 6, 7, And an ECU 11 that controls charging of the battery cells 1, 2, 3, and 4 based on the monitored voltage value, the cell charging current, and the cell discharging current monitored at 8 and 9.

  The ECU 11 includes a CPU, a ROM that stores and stores a control program, a RAM as an operation area of the control program, an EEPROM that holds various data in a rewritable manner, an interface unit that interfaces with peripheral circuits, and the like. The The ECU 11 is a control ECU that controls electric power supplied from a plurality of battery cells 1, 2, 3, 4 to, for example, an electric motor of an electric vehicle. The ECU 11 receives various data, analyzes the received data, and issues various commands. Send.

  Further, the ECU 11 stores a charge / discharge characteristic map MP, which is an example of charge / discharge characteristic information, and the CPU executes the control program, whereby a selection unit (characteristic information acquisition unit) 131, a control unit (voltage balance). Control means) 132 and determination unit (battery cell stable state determination means) 133 are realized.

  The charge / discharge characteristic map MP stores, as map data, charge / discharge characteristics of the battery cells and changes in the charge / discharge characteristics (battery voltage / discharge capacity characteristics) accompanying the deterioration of the battery cells. FIG. 3 is an explanatory diagram showing an example of the charge / discharge characteristic map MP. The vertical axis in FIG. 3 indicates the battery voltage (V), and the horizontal axis indicates the battery discharge capacity (Ah). Moreover, in FIG. 3, the code | symbol 111 shows the charging / discharging characteristic map of the normal battery cell (capacity 50Ah) which has not deteriorated. Reference numeral 112 denotes a charge / discharge characteristic map of a battery cell (capacity: about 32 Ah) that has deteriorated, and shows a charge / discharge characteristic that rapidly decreases when the battery voltage falls below 3.4 volts.

  In FIG. 3, reference numeral 113 denotes a charge when a battery voltage is lowered by connecting a positive electrode terminal and a negative electrode terminal of a battery cell having charge / discharge characteristics indicated by reference numeral 111 with a discharge circuit to cause discharge. The discharge characteristics are shown. As shown in FIG. 3, when the battery cell in a predetermined state is discharged, the charge / discharge characteristic map is translated in the left direction. Conversely, when the battery cell is charged, the charge / discharge characteristic map is translated in the right direction.

  The charge / discharge characteristic map MP records a plurality of charge / discharge characteristics according to the degree of deterioration of the battery cells in addition to the one shown in FIG. Specifically, for example, a charge / discharge characteristic map of a battery cell in which the battery discharge capacity is decreased in units of 0.2 Ah is recorded. Thus, by recording the charge / discharge characteristic maps in various states, it is possible to grasp the charge / discharge characteristics of the battery cells in an arbitrary deterioration state.

  Returning to the description of FIG. 1, the selection unit 131 selects a charge / discharge characteristic map corresponding to each of the plurality of battery cells 1, 2, 3, and 4 from the plurality of charge / discharge characteristic maps in the charge / discharge characteristic map MP. select. That is, the characteristic information acquisition means selects (reads out) the charge / discharge characteristic map indicating the battery voltage / discharge capacity characteristic of each battery cell from the charge / discharge characteristic map MP by the selection unit 131, thereby obtaining the charge / discharge characteristic map. get. The selection unit 131 measures the capacity of the battery cell using an SOC (state of charge) measurement method, which is a well-known technique, and then calculates a charge / discharge characteristic map corresponding to the battery cell from the battery voltage of the battery cell. select.

  The control unit 132 controls the charge / discharge amount with respect to each battery cell using the charge / discharge characteristic map selected (acquired) by the selection unit 131, and the battery is charged in a high charge state in which the charged amount of the battery cell is close to full charge. Establish voltage balance between cells. More specifically, the control unit 132 determines the charge / discharge amount for each battery cell so that the voltages between the plurality of battery cells having different degrees of deterioration match in a high charge state, and the charge / discharge amount for each battery cell. To control.

  The control unit 132 determines the amount of movement of the charge / discharge characteristic map, that is, the amount of charge / discharge of each battery cell, so that the battery voltages between the plurality of battery cells having different degrees of deterioration coincide with each other when charging is completed. FIG. 4 is an explanatory diagram showing an outline of voltage balance control by the control unit 132. The vertical and horizontal axes in FIG. 4 indicate the battery voltage (V) and the battery discharge capacity (Ah), respectively, as in FIG. In FIG. 4, reference numeral 111 denotes a normal battery cell that has not deteriorated (capacity 50 Ah), and reference numeral 112 denotes a charge / discharge characteristic map of a battery cell (capacity approximately 32 Ah) that has deteriorated.

  In order to make the voltage between a plurality of battery cells with different degrees of deterioration such as these match in a high charge state including when charging is complete (for example, a range of SOC 80% or more indicated by reference H), The battery cell is charged, and the charge / discharge characteristic map is shifted to the right to the position of reference numeral 114, and discharged from the battery cell having deteriorated as indicated by reference numeral 112, and the charge / discharge characteristic map is shifted to the left. What is necessary is just to set it as the position of the code | symbol 115. FIG. Thereby, the battery voltage of the deteriorated battery cell in the high capacity state matches the battery voltage of the battery cell not deteriorated. When the assembled battery including the deteriorated battery cell is charged in this state, both the deteriorated battery cell of the assembled battery and the battery cell not deteriorated can be charged to SOC 100%.

  The control unit 132 converts the movement amount of the charge / discharge characteristics as shown in FIG. 4 into the charge / discharge amount of each battery cell so that the battery voltages between the plurality of battery cells having different degrees of deterioration coincide with each other when charging is completed. Determine the charge / discharge amount of each battery cell.

  Returning to the description of FIG. 1, the determination unit 133 determines the stable state of the battery cell based on the passage of a predetermined period after the ignition switch is turned off. The control unit 132 establishes the voltage balance after the determination unit 133 determines that the battery cell is stable. Thus, by determining the charge state and voltage of the battery cell while the battery cell is stable, the state of the battery cell can be grasped with higher accuracy, and the accuracy of voltage balance can be improved.

  FIG. 2 is a circuit diagram showing the configuration of the cell control units 6, 7, 8, and 9 shown in FIG. In FIG. 2, the cell control unit 6 includes switch circuits 61 and 64, a load resistance circuit 62, a cell voltage monitor 63, and a sub battery 121. In FIG. 2, for convenience, the switch circuits 61, 71, 81, 91, 64, 74, 84, 94, 101), the load resistance circuit (62, 72, 82, 92), the ammeter (65, 75, 85, 95) and the connection of the ECU 11 are not shown.

  The switch circuits 61 and 64 are configured by normally-open contacts that are closed based on a control signal output from the ECU 11. The load resistance circuit 62 is configured by a variable resistance circuit whose resistance value is variable based on a control signal output from the ECU 11. The cell voltage monitor 63 is connected in parallel to the positive output terminal and the negative output terminal of the battery cell 1 and detects the battery voltage of the battery cell 1. The battery voltage of the battery cell 1 detected by the cell voltage monitor 63 is output to the ECU 11.

  The switch circuit 61 and the load resistance circuit 62 are connected in series to constitute a cell discharge circuit of the battery cell 1, and the other terminal not connected to the load resistance circuit 62 of the switch circuit 61 is the positive output terminal of the battery cell 1. The other terminal of the load resistance circuit 62 that is not connected to the switch circuit 61 is connected to the negative output terminal of the battery cell 1.

  The sub battery 121 can charge the battery cell 1. The positive output terminal of the sub battery 121 is connected to the positive output terminal of the battery cell 1 via the switch circuit 64, and the negative output terminal of the sub battery 121 is connected to the negative output terminal of the battery cell 1. The battery cell 1 is charged by the sub battery 121 by closing the switch circuit 64. Note that the voltage when the battery cell 1 is charged by the sub-battery 121 is higher than the battery voltage of the battery cell 1.

  Hereinafter, the cell control units 7, 8, 9 have the same configuration as the cell control unit 6 except that the battery cells connected to them are the battery cells 2, 3, 4. To do. In addition, the switch circuit, the load resistance circuit, and the cell voltage monitor in the cell control units 7, 8, and 9 are distinguished by changing the reference numerals. Specifically, switch circuits 71, 81, 91, 74, 84, 94, load resistance circuits 72, 82, 92, cell voltage monitors 73, 83, 93, and sub batteries 122, 123, 124 were used.

  The switch circuit 101 and the current limiting circuit 102 are connected in series, and the series circuit of the switch circuit 101 and the current limiting circuit 102 is connected in series to the charging power supply 10. Then, the positive output terminal of the battery pack including a plurality of battery cells 1, 2, 3, 4 is connected to the positive output terminal of the power supply 10 for charging via a series circuit of the switch circuit 101 and the current limiting circuit 102. And the negative output terminal of the charging power source 10 is connected to the negative output terminal of the battery pack. The series circuit of the switch circuit 101 and the current limiting circuit 102 constitutes a charging circuit that charges an assembled battery including a plurality of battery cells 1, 2, 3, and 4 with a charging power source 10.

  The switch circuit 101 includes a normally open contact that is closed based on a control signal output from the ECU 11. The current limiting circuit 102 is configured by a variable resistance circuit whose resistance value is variable based on a control signal output from the ECU 11.

  In addition, ammeters 65, 75, 85, and 95 are connected to the battery cells 1, 2, 3, and 4, respectively, and charge / discharge amounts (current amounts) for the battery cells 1, 2, 3, and 4 are measured. To do. The amount of current measured by the ammeters 65, 75, 85, and 95 is output to the ECU 11.

Next, the operation of the voltage balance control device 100 will be described.
FIG. 5 is a flowchart showing the operation of the voltage balance control device 100. This operation is realized by the ECU 11 executing the flowchart shown in FIG. First, the determination unit 133 determines that a predetermined time has elapsed with the ignition switch turned off (step S1). In a state where the ignition switch is turned off, each battery cell is disconnected from the load. Further, the passage of a certain time corresponds to the elapsed time from when the ignition switch is turned off to when the state of the battery cell settles down.

  When the predetermined time has elapsed, the selection unit 131 detects the battery voltage and SOC of each battery cell (step S2). The selection unit 131 sets the battery voltage of the battery cell 1 by the cell voltage monitor 63, the battery voltage of the battery cell 2 by the cell voltage monitor 73, the battery voltage of the battery cell 3 by the cell voltage monitor 83, and the battery voltage of the battery cell 4. Is detected by the cell voltage monitor 93, and the capacity of each battery cell is measured by a known SOC measurement method.

  Next, the selection unit 131 uses the battery voltage and SOC detected in step S2 from the charge / discharge characteristic map MP. A charge / discharge characteristic map corresponding to each battery cell 1, 2, 3, 4 is selected (step S3). Subsequently, the control unit 132 determines the amount of movement of the charge / discharge characteristic map, that is, the charge / discharge amount of each battery cell, so that the battery voltages between the plurality of battery cells having different degrees of deterioration coincide with each other when charging is completed ( Step S4). And the control part 132 performs charge / discharge control based on the charge / discharge amount determined by step S4 (step S5), and complete | finishes the process of this flowchart.

  In the present embodiment, the timing for performing the voltage balance control by the voltage balance control device 100 is not limited, but for example, a low charge state (for example, as shown in FIG. The control may be started at SOC 30% or less. In the low charge state, the voltage difference between the battery cells having different degrees of deterioration is larger than in the high charge state, so that the control can be performed with higher accuracy. If the SOC difference is the same amount, the time is shorter. Thus, the SOC difference can be eliminated. For example, it is difficult to determine the variation of the accuracy of the cell voltage monitor of about 10 mV, but the error is large and difficult. However, if the variation is about 100 mV, it can be sufficiently determined. This improvement in accuracy is particularly effective when the number of battery cells of the assembled battery is large.

  Moreover, if voltage balance control is started from the low charge state, voltage balance can be established while charging from the low charge state to the high charge state, and voltage balance control is started from the high charge state. In comparison, voltage balance can be established in a short time.

  Further, the voltage balance control device 100 simultaneously charges or discharges each battery cell, so that the other battery cells are charged by supplying the current discharged from one battery cell to the other battery cells. It is also possible to do. Thereby, the electric power required for control of voltage balance can be reduced, and the voltage balance between battery cells can be established more efficiently.

  As described above, according to the voltage balance control device 100 according to the embodiment, it is possible to determine the charge / discharge amount necessary for achieving voltage balance and perform voltage balance control in any voltage state. . In the normal voltage balancer, the voltage variation is not eliminated at one time except when the battery is fully charged. On the other hand, the voltage balance control device 100 determines the charge / discharge amount and performs control. The voltage balance can be controlled efficiently by completing the process once.

  More specifically, according to the voltage balance control device 100, the charge / discharge amount is controlled using the charge / discharge characteristic map to establish the voltage balance between the battery cells in the high charge state. Compared to the case where the battery is used, it suppresses the generation of unnecessary power consumption, thereby suppressing the battery temperature rise, battery deterioration, and output reduction, enabling efficient charging and maximizing battery performance. It can be demonstrated. Moreover, according to the voltage balance control apparatus 100, since the charge / discharge amount with respect to each battery cell is controlled using the charge / discharge characteristic map of each battery cell, it is whatever the charge state of a battery cell is. Voltage balance control can be started.

  Moreover, according to the voltage balance control apparatus 100, the charge / discharge amount with respect to each battery cell is determined so that the voltage between several battery cells from which a deterioration degree differs in a high charge state, and charge / discharge with respect to each battery cell is determined. Since the amount is controlled, the voltage balance between the battery cells can be established with higher accuracy. In addition, according to the voltage balance control device 100, since the charge / discharge amount is determined and the control is started in the low charge state in which the storage amount of the battery cell is small, the charging is started from the low charge state to the high charge state. The voltage balance can be established, and the voltage balance can be established in a short time compared to starting the control in the high charge state. Moreover, in a low charge state, since the voltage difference between the some battery cells from which a deterioration degree differs is large, a voltage balance can be established more accurately.

  1, 2, 3, 4 ... battery cells, 5 ... load, 6, 7, 8, 9 ... cell control unit, 10 ... charging power source, 11 ... ECU (characteristic information acquisition means, voltage balance control) Means, battery cell stable state determination means), 100... Voltage balance control device, MP... Charge / discharge characteristics map, 131... Selection section (characteristic information acquisition means), 132. 133: Determination unit (battery cell stable state determination means).

Claims (4)

A voltage balance control device for adjusting and controlling variations in battery voltage of a plurality of battery cells connected in series constituting an assembled battery,
Characteristic information acquisition means for acquiring charge / discharge characteristic information indicating battery voltage / discharge capacity characteristics of each of the battery cells;
Using the charge / discharge characteristic information acquired by the characteristic information acquisition means, the voltage between the plurality of battery cells having different degrees of deterioration is a high charge state in which the storage amount of the battery cells is equal to or greater than a first predetermined amount. Voltage balance control for determining a charge / discharge amount for each of the battery cells so as to coincide with each other, and controlling the charge / discharge amount for each of the battery cells to establish a voltage balance between the battery cells in the high charge state and means, the,
The charge / discharge characteristic information is a charge / discharge characteristic map with the battery voltage and battery discharge capacity of the battery cell as coordinate axes,
The voltage balance control means determines the point at which the voltages between the battery cells match in the high charge state by moving the charge / discharge map of each battery cell along the battery discharge capacity direction.
Voltage balance control device according to claim and this. The voltage balance control means, said determining the charge and discharge amount in the second predetermined amount below the low charge state storage amount is less than the first predetermined amount of battery cells, each of the time of charging the pre-SL battery pack The voltage balance control device according to claim 1, wherein the charge / discharge amount for the battery cell is controlled . The voltage balance control device according to claim 1 or 2, wherein the voltage balance control means simultaneously discharges the battery cell and charges the other battery cell. Battery cell stable state determination means for determining a stable state of the battery cell based on the passage of a predetermined period after the ignition switch is turned off;
The voltage balance control means, according to the any one of claims 1 to 3 in which the battery cell is characterized in that to establish the voltage balance after being determined to be stable by the cells stable state determining means Voltage balance control device

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