Battery system

Abstract

To provide a battery system capable of reusing electric power discharged from a battery cell as electric power when equalizing power storage amounts of a plurality of battery cells.SOLUTION: And a control unit 9 configured to equalize charge amounts of the plurality of battery cells 21, 22, and 23 by discharging power of the battery cell 21 to the storage battery 3 by setting a positive electrode switch 31 connected between a positive electrode of the battery cell 21 and a positive electrode of the storage battery 3 and a negative electrode switch 32 connected between a negative electrode of the battery cell 21 and a negative electrode of the storage battery 3 to a connected state and setting the other positive electrode switches 33 and 35 and negative electrode switches 34 and 36 to a disconnected state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery system. [Background technology]

[0002] Patent document 1 describes a battery in which multiple chargeable and dischargeable cells are connected in series, in which the amount of discharge that would occur if each cell were discharged to match the remaining charge of one of the cells is calculated, and the remaining charge of the cell with the smallest discharge amount is equalized. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-73911 Summary of the Invention [Problem to be solved by the invention]

[0004] When equalizing the cells in this way, one of the cells will discharge, but a resistor is used in the discharge circuit, and the discharged power is consumed as heat.

[0005] Therefore, an object of the present invention is to provide a battery system that can reuse the power discharged from the battery cells as power when equalizing the charge amounts of a plurality of battery cells. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a high-voltage battery configured by connecting a plurality of battery cells in series, a power storage device in which positive electrodes of the plurality of battery cells are connected in parallel to one terminal and negative electrodes of the plurality of battery cells are connected in parallel to the other terminal, a plurality of positive electrode switches connected to a connection line between the positive electrode of each of the plurality of battery cells and one terminal of the power storage device, the connection line not being connected to the positive electrodes of the other plurality of battery cells, and a plurality of negative electrode switches connected to a connection line between the negative electrode of each of the plurality of battery cells and the other terminal of the power storage device, the connection line not being connected to the negative electrodes of the other plurality of battery cells. and a control unit that, when there is a battery cell among the plurality of battery cells whose charge amount is equal to or greater than a predetermined charge amount, sets one of the plurality of positive switches, which is connected to a connection line between the positive electrode of the battery cell whose charge amount is equal to or greater than the predetermined charge amount and the storage device, and sets one of the plurality of negative switches, which is connected to a connection line between the negative electrode of the battery cell whose charge amount is equal to or greater than the predetermined charge amount and the storage device, in a connected state, and sets the other positive switches and negative switches in a disconnected state to discharge the power of the battery cell to the storage device, thereby equalizing the charge amounts of the plurality of battery cells. [Effects of the Invention]

[0007] Thus, according to the present invention, when the charge amounts of a plurality of battery cells are equalized, the power discharged from the battery cells can be reused as power. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with a battery system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a circuit configuration diagram of a battery system according to an embodiment of the present invention when a battery cell is being discharged. [Figure 3] FIG. 3 is a circuit configuration diagram of a battery system according to an embodiment of the present invention when driving an accessory. [Figure 4]FIG. 4 is a flowchart showing the procedure of the battery cell equalization process of the battery system according to one embodiment of the present invention. [Figure 5] FIG. 5 is a circuit configuration diagram of a battery system according to a first alternative aspect of an embodiment of the present invention. [Figure 6] FIG. 6 is a circuit configuration diagram of a storage battery of a battery system according to a second alternative aspect of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] a power storage device having positive electrodes of the battery cells connected in parallel to one terminal and negative electrodes of the battery cells connected in parallel to the other terminal; a plurality of positive switches connected to a connection line between the positive electrodes of each of the battery cells and one terminal of the power storage device, the connection line not connected to the positive electrodes of the other battery cells; a plurality of negative switches connected to a connection line between the negative electrodes of each of the battery cells and the other terminal of the power storage device, the connection line not connected to the negative electrodes of the other battery cells; and a control unit that, when there is a battery cell whose charge amount is equal to or greater than a predetermined charge amount among the battery cells, connects one of the positive switches to the connection line between the positive electrode of the battery cell whose charge amount is equal to or greater than the predetermined charge amount and the power storage device, and connects one of the negative switches to the connection line between the negative electrode of the battery cell whose charge amount is equal to or greater than the predetermined charge amount and the power storage device, and disconnects the other positive switches and negative switches, thereby discharging power from the battery cells to the power storage device and equalizing the charge amounts of the battery cells.

[0010] As a result, the battery system according to one embodiment of the present invention can reuse the power discharged from the battery cells as power when equalizing the charge amounts of a plurality of battery cells. [Example]

[0011] Hereinafter, a battery system according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0012] In FIG. 1, a vehicle 1 equipped with a battery system according to one embodiment of the present invention includes a high-voltage battery 2, a storage battery 3 as a power storage device, a low-voltage battery 4, an auxiliary device 5, a first DC / DC converter 6, a second DC / DC converter 7, a charging device 8, and a control unit 9.

[0013] The high-voltage battery 2 is, for example, a nickel storage battery or a lithium storage battery, and is configured by connecting multiple battery cells 21, 22, and 23 in series. The high-voltage battery 2 supplies power to a drive motor (not shown) via an inverter (not shown). Battery cells 21, 22, and 23 are each provided with a battery status sensor 21a, 22a, and 23a that detects the cell voltage, temperature, charge current, and discharge current of the battery cells 21, 22, and 23. In this embodiment, the high-voltage battery 2 is configured with three battery cells, but this is not limited thereto, and the high-voltage battery 2 can be configured with three or more battery cells in the same manner.

[0014] The storage battery 3 is configured by, for example, a lead storage battery. The storage battery 3 is provided with a battery state sensor 3a that detects the temperature, charging current, and discharging current of the storage battery 3.

[0015] The positive electrode of the storage battery 3 is connected in parallel to the positive electrodes of the battery cells 21, 22, and 23. The negative electrode of the storage battery 3 is connected in parallel to the negative electrodes of the battery cells 21, 22, and 23.

[0016] Positive pole switches 31, 33, 35 that electrically connect or disconnect the positive pole of the storage battery 3 to the positive pole of each of the battery cells 21, 22, 23 are connected between the positive pole of the storage battery 3 and the positive pole of each of the battery cells 21, 22, 23, respectively, to connection lines that are not connected to the positive poles of the other battery cells 21, 22, 23. Negative pole switches 32, 34, 36 that electrically connect or disconnect the negative pole of the storage battery 3 to the negative pole of each of the battery cells 21, 22, 23 are connected between the negative pole of the storage battery 3 and the negative pole of each of the battery cells 21, 22, 23, respectively, to connection lines that are not connected to the negative poles of the other battery cells 21, 22, 23.

[0017] By connecting the positive pole switch 31 connected to the positive pole of any one of the battery cells 21, 22, 23, for example, the battery cell 21, and connecting the negative pole switch 32 connected to the negative pole, and disconnecting the other positive pole switches 33, 35 and negative pole switches 34, 36, a closed circuit can be formed in which only the storage battery 3 and the battery cell 21 are connected.

[0018] The low-voltage battery 4 is configured, for example, as a lead-acid battery. The low-voltage battery 4 supplies power to drive an auxiliary device 5, which is made up of an electrical system of the vehicle 1. The low-voltage battery 4 is provided with a battery state sensor 4a that detects the temperature, charging current, and discharging current of the low-voltage battery 4.

[0019] An auxiliary positive switch 51 is connected between the positive electrode of the low-voltage battery 4 and the positive electrode of the auxiliary device 5, and electrically connects or disconnects the positive electrode of the low-voltage battery 4 and the positive electrode of the auxiliary device 5. An auxiliary negative switch 52 is connected between the negative electrode of the low-voltage battery 4 and the negative electrode of the auxiliary device 5, and electrically connects or disconnects the negative electrode of the low-voltage battery 4 and the negative electrode of the auxiliary device 5.

[0020] The first DC / DC converter 6 boosts the voltage of the power output from the storage battery 3 and supplies it to the low-voltage battery 4 and the auxiliary equipment 5. The positive electrode of the first DC / DC converter 6 is connected to the positive electrode of the storage battery 3. The negative electrode of the first DC / DC converter 6 is connected to the negative electrode of the high-voltage battery 2.

[0021] A storage battery positive electrode switch 61 is connected between the positive electrode of the storage battery 3 and the positive electrode of the first DC / DC converter 6, and electrically connects or disconnects the positive electrode of the storage battery 3 and the positive electrode of the first DC / DC converter 6. A storage battery negative electrode switch 62 is connected between the negative electrode of the high-voltage battery 2 and the negative electrode of the first DC / DC converter 6, and electrically connects or disconnects the negative electrode of the high-voltage battery 2 and the negative electrode of the first DC / DC converter 6.

[0022] The second DC / DC converter 7 steps down the voltage of the power supplied from the high-voltage battery 2 and the charging device 8 and supplies it to the low-voltage battery 4. A charging positive electrode switch 71 is connected between the positive electrode of the high-voltage battery 2 and the positive electrode of the second DC / DC converter 7, and electrically connects or disconnects the positive electrode of the high-voltage battery 2 and the positive electrode of the second DC / DC converter 7. A charging negative electrode switch 72 is connected between the negative electrode of the high-voltage battery 2 and the negative electrode of the second DC / DC converter 7, and electrically connects or disconnects the negative electrode of the high-voltage battery 2 and the negative electrode of the second DC / DC converter 7.

[0023] The charging device 8 supplies power from an external power source to the high-voltage battery 2 and, via the second DC / DC converter 7, to the low-voltage battery 4. A charging device switch 81 is connected to the positive terminal of the charging device 8, which electrically connects or disconnects the positive terminal of the charging device 8 to or from the positive terminal of the high-voltage battery 2 and the positive terminal of the second DC / DC converter 7.

[0024] The charging device 8 detects whether or not a charging connector of an external power supply is connected to a charging port (not shown), and notifies the control unit 9. When the control unit 9 detects that a charging connector of an external power supply is connected to the charging port of the charging device 8, it places the charging positive switch 71, the charging negative switch 72, and the charging device switch 81 in a connected state, and places the other positive switches 31, 33, 35, the negative switches 32, 34, 36, the auxiliary equipment positive switch 51, the auxiliary equipment negative switch 52, the storage battery positive switch 61, and the storage battery negative switch 62 in a disconnected state, and charges the high-voltage battery 2 and the low-voltage battery 4 from the charging device 8.

[0025] The control unit 9 is composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, etc., input ports, and output ports.

[0026] The ROM of this computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the control unit 9.

[0027] That is, the CPU executes the program stored in the ROM using the RAM as a work area, and this computer unit functions as the control unit 9 in this embodiment.

[0028] To the input port of the control unit 9, various sensors including the battery state sensors 21a, 22a, 23a, battery state sensor 3a, battery state sensor 4a, and charging device 8 are connected.

[0029] The output port of the control unit 9 is connected to various control targets including the above-mentioned first DC / DC converter 6, second DC / DC converter 7, positive switches 31, 33, 35, negative switches 32, 34, 36, auxiliary equipment positive switch 51, auxiliary equipment negative switch 52, storage battery positive switch 61, storage battery negative switch 62, charging positive switch 71, charging negative switch 72, and charging device switch 81.

[0030] In this embodiment, when charging of the high-voltage battery 2 from the charging device 8 is completed, the control unit 9 detects the charge amount of each of the battery cells 21, 22, 23, and connects the positive pole switches 31, 33, 35 connected to the positive poles of the battery cells 21, 22, 23 whose charge amount is equal to or greater than a predetermined charge amount and the negative pole switches 32, 34, 36 connected to the negative poles, and disconnects the other positive pole switches 31, 33, 35 and negative pole switches 32, 34, 36 to discharge the battery 3, thereby performing equalization control to set the charge amount to a predetermined charge amount.

[0031] For example, when charging of the high-voltage battery 2 from the charging device 8 is completed, the control unit 9 detects the voltage indicating the charge amount of each of the battery cells 21, 22, 23, and discharges the power of the battery cells 21, 22, 23 whose voltage value is equal to or greater than a predetermined voltage value to the storage battery 3, thereby setting the voltage of the battery cells 21, 22, 23 to the predetermined voltage.

[0032] For example, the control unit 9 discharges the other battery cells 21, 22, 23 so that the voltage value of the battery cell 21, 22, 23 becomes the lowest voltage value.

[0033] The control unit 9 may set the voltage values ​​of the battery cells 21, 22, 23 that are higher than a preset voltage value to be equal to or lower than the preset voltage value.

[0034] The control unit 9 may determine the voltage value to be equalized depending on the amount of charge that the storage battery 3 can accept.

[0035] When discharging the battery cell 21, the control unit 9 connects the positive switch 31 and the negative switch 32 and disconnects the other switches, as shown in Figure 2, thereby forming a closed circuit between the battery cell 21 and the storage battery 3 and charging the storage battery 3 with the power discharged from the battery cell 21.

[0036] Similarly, when discharging the battery cell 22, the control unit 9 connects the positive switch 33 and the negative switch 34 and disconnects the other switches, thereby forming a closed circuit between the battery cell 22 and the storage battery 3, and charging the storage battery 3 with the power discharged from the battery cell 22.

[0037] When the control unit 9 drives the auxiliary equipment 5, if the amount of electricity stored in the storage battery 3 is equal to or greater than a predetermined amount, the control unit 9 drives the auxiliary equipment 5 using the storage battery 3 until the amount of electricity stored in the storage battery 3 falls below the predetermined amount.

[0038] As shown in Figure 3, the control unit 9 supplies power from the storage battery 3 to the auxiliary equipment 5 by connecting the negative pole switch 36, the storage positive pole switch 61, and the storage negative pole switch 62, and disconnecting the other positive pole switches 31, 33, and 35, the negative pole switches 32 and 34, the auxiliary equipment positive pole switch 51, the auxiliary equipment negative pole switch 52, the charging positive pole switch 71, the charging negative pole switch 72, and the charging device switch 81.

[0039] When the auxiliary equipment 5 is driven by the power of the storage battery 3, it is preferable to prevent the power of the low-voltage battery 4 from being consumed. Alternatively, the output of the low-voltage battery 4 may be suppressed so that the storage battery 3 is used preferentially to drive the auxiliary equipment 5. The control unit 9 may charge the low-voltage battery 4 with the power of the storage battery 3.

[0040] The battery cell equalization process performed by the battery system according to this embodiment configured as described above will be described with reference to Fig. 4. The battery cell equalization process described below is executed when charging of the high-voltage battery 2 is completed.

[0041] In step S1, the control unit 9 opens and disconnects all of the positive switches 31, 33, and 35 and the negative switches 32, 34, and 36. After executing the process of step S1, the control unit 9 executes the process of step S2.

[0042] In step S2, the control unit 9 detects the charge amounts of the battery cells 21, 22, and 23. After executing the process of step S2, the control unit 9 executes the process of step S3.

[0043] In step S3, the control unit 9 determines whether or not it is necessary to discharge the battery cells 21, 22, 23. Among the battery cells 21, 22, 23, the control unit 9 determines that the battery cells whose charge amount is equal to or greater than a predetermined charge amount need to be discharged.

[0044] If any of the battery cells 21, 22, and 23 is determined to require discharging, the control unit 9 executes the process of step S4. If any of the battery cells 21, 22, and 23 is determined to require discharging, the control unit 9 ends the battery cell equalization process.

[0045] In step S4, if the battery cell to be discharged is battery cell 21, the control unit 9 closes the positive switch 31 and negative switch 32 connected to battery cell 21 to establish a connected state, thereby discharging the power of battery cell 21 to the storage battery 3. If there are multiple battery cells whose charge amounts are equal to or greater than a predetermined charge amount, the control unit 9 sequentially discharges the power from the battery cells to the storage battery 3 in the same manner. For example, if battery cell 22 also falls into this category, after discharging of battery cell 21 is completed, the control unit 9 opens the positive switch 31 and negative switch 32 to establish a disconnected state, and closes the positive switch 33 and negative switch 34 to establish a connected state, thereby discharging the power of battery cell 22 to the storage battery 3. After executing the processing of step S4, the control unit 9 ends the battery cell equalization processing.

[0046] In this way, in this embodiment, when charging from the charging device 8 to the high-voltage battery 2 is completed, the control unit 9 detects the charge amount of each of the battery cells 21, 22, and 23, and if there is a battery cell whose charge amount is equal to or greater than a predetermined charge amount, for example, if the charge amount of the battery cell 21 is equal to or greater than the predetermined charge amount, the control unit 9 connects the positive electrode switch 31 connected to the positive electrode of the battery cell 21 and the negative electrode switch 32 connected to the negative electrode, and disconnects the other positive electrode switches 33, 35 and negative electrode switches 34, 36, thereby discharging the power of the battery cell 21 to the storage battery 3 and performing equalization control to set the charge amount to the predetermined charge amount.

[0047] As a result, the discharged power of the battery cells 21, 22, 23 when the charge amounts of the battery cells 21, 22, 23 of the high-voltage battery 2 are equalized can be stored in the storage battery 3 and reused as power.

[0048] In addition, when the control unit 9 drives the auxiliary equipment 5, if the amount of electricity stored in the storage battery 3 is equal to or greater than a predetermined amount, the control unit 9 drives the auxiliary equipment 5 using the storage battery 3 until the amount of electricity stored in the storage battery 3 falls below the predetermined amount.

[0049] This allows the discharged power of the battery cells 21, 22, and 23 to be accepted by the storage battery 3, and the discharged power of the battery cells 21, 22, and 23 when equalizing the charge amounts of the battery cells 21, 22, and 23 of the high-voltage battery 2 can be stored in the storage battery 3 and reused as power.

[0050] Furthermore, the electric power stored in the storage battery 3 can be used to drive the auxiliary machine 5, thereby improving the electric power efficiency of the vehicle 1.

[0051] Furthermore, by using the power of the storage battery 3 as a power source for dark current (current for standby with the system off) while the vehicle 1 is parked, it is possible to suppress discharge of the low voltage battery 4 due to dark current.

[0052] In addition, the discharged power that can be recovered is only up to the capacity of the storage battery 3. Therefore, in order to discharge the battery cells 21, 22, and 23 by equalization and to maximize the effect of recovering the discharged power, it is desirable to keep the charge amount of the storage battery 3 as small as possible.

[0053] Furthermore, in order to recover discharged power, in addition to the available capacity of the storage battery 3, the voltage of the storage battery 3 must be lower than the voltage of the battery cells 21, 22, and 23. Generally, the more charged the storage battery 3 is, the higher the voltage becomes, and even if the storage battery 3 has available capacity, it will not be able to discharge depending on the voltage of the battery cells 21, 22, and 23. In this sense, too, it is desirable to keep the amount of charge in the storage battery 3 as small as possible.

[0054] 5, in a first alternative aspect of the present embodiment, a capacitor 10 is provided instead of the storage battery 3 as a power storage device that stores the discharged power of the battery cells 21, 22, and 23. A resistor 11 is connected in series to the capacitor 10.

[0055] By doing so, it is possible to speed up the discharge of the battery cells 21, 22, 23, and the charging of the low-voltage battery 4, and to achieve a reduction in weight and size.

[0056] In a second alternative embodiment of the present invention, as shown in Fig. 6, a storage battery 3 as a power storage device is configured by connecting a plurality of storage batteries 101, 102, and 103 as power storage components in parallel. Battery switches 104, 105, and 106 are connected in series to the respective storage batteries 101, 102, and 103.

[0057] The battery switches 104, 105, and 106 electrically connect or disconnect the batteries 101, 102, and 103 from the battery cells 21, 22, and 23, respectively.

[0058] For example, the control unit 9 connects one of the storage battery switches 104, 105, 106 and disconnects the other storage battery switches 104, 105, 106 to store the discharged power of the battery cells 21, 22, 23 in one of the storage batteries 101, 102, 103, and when the charge amount of the stored storage battery 101, 102, 103 reaches or exceeds a certain charge amount, the control unit 9 connects the storage battery switches 104, 105, 106 of the other storage batteries 101, 102, 103 and disconnects the other storage battery switches 104, 105, 106 to store the discharged power of the battery cells 21, 22, 23 in one of the storage batteries 101, 102, 103.

[0059] In this way, the amount of power that can be discharged from and stored in the battery cells 21, 22, and 23 can be increased.

[0060] As the power storage components, in addition to the storage batteries 101, 102, and 103, capacitors or the like may also be used.

[0061] In this embodiment, an example has been described in which the control unit 9 performs various judgments and calculations based on various sensor information, but this is not limited to this. The vehicle 1 may be provided with a communication unit capable of communicating with an external device such as an external server, and various judgments and calculations may be performed by the external device based on the detection information of the various sensors transmitted from the communication unit. The judgment results and calculation results may be received by the communication unit, and various controls may be performed using the received judgment results and calculation results.

[0062] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0063] 1 vehicle 2 High Voltage Battery 3. Storage battery (energy storage device) 3a Battery Status Sensor 4 Low voltage battery 4a Battery Status Sensor 5 Auxiliary equipment 9 Control Unit 10 Capacitor (electrical storage device) 11 Resistance 21, 22, 23 Battery cells 21a, 22a, 23a Battery status sensors 31, 33, 35 Positive switch 32, 34, 36 Negative switch 61 Storage positive switch 62 Storage negative switch 101, 102, 103 Storage battery (electricity storage component) 104, 105, 106 Battery switch

Claims

1. a high-voltage battery configured by connecting a plurality of battery cells in series; a power storage device in which positive electrodes of the plurality of battery cells are connected in parallel to one terminal and negative electrodes of the plurality of battery cells are connected in parallel to the other terminal; a plurality of positive pole switches connected to a connection line between the positive pole of each of the plurality of battery cells and one terminal of the power storage device, the connection line not being connected to the positive poles of the other of the plurality of battery cells; a plurality of negative electrode switches connected to connection lines between the negative electrodes of the plurality of battery cells and the other terminal of the power storage device, the connection lines not being connected to the negative electrodes of the other plurality of battery cells; a control unit that, when there is a battery cell among the plurality of battery cells whose charge amount is equal to or greater than a predetermined charge amount, sets one of the plurality of positive pole switches, which is connected to a connection line between the positive pole of the battery cell whose charge amount is equal to or greater than the predetermined charge amount and the power storage device, and sets one of the plurality of negative pole switches, which is connected to a connection line between the negative pole of the battery cell whose charge amount is equal to or greater than the predetermined charge amount and the power storage device, in a connected state, and sets the other positive pole switches and negative pole switches in a disconnected state to discharge the power of the battery cell to the power storage device, thereby equalizing the charge amounts of the plurality of battery cells.

2. an auxiliary machine driven by a low voltage is connected to one terminal and the other terminal of the power storage device; 2. The battery system according to claim 1, wherein when the auxiliary equipment is driven, if the amount of electricity stored in the power storage device is equal to or greater than a predetermined amount, the control unit drives the auxiliary equipment using the power of the power storage device until the amount of electricity stored in the power storage device falls below the predetermined amount.

3. 3. The battery system according to claim 1, wherein the power storage device is a storage battery.

4. 3. The battery system according to claim 1, wherein the power storage device is a capacitor.

5. The power storage device is configured by connecting a plurality of power storage components in parallel, 3. The battery system according to claim 1, wherein a maximum voltage of the plurality of power storage components is equal to or lower than a maximum voltage of the plurality of battery cells.

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