CELL CONTROL UNIT, BATTERY CONTROL UNIT, BATTERY MANAGEMENT SYSTEM AND BATTERY SYSTEM

Abstract

Cell control device (1) comprising the following: a balancing unit (12) which balances the charge states of several secondary batteries (3) by discharging or charging them, a first time cue (8) that measures the time elapsed since the beginning of the equalization process, a receiving unit (14) that receives a balancing command signal containing information relating to the balancing times of the secondary batteries (3), and a first control unit (7) which controls the balancing unit (12) on the basis of the time elapsed since the start of balancing and the balancing command signal, wherein the elapsed time is measured by the first timer (8) and the balancing command signal is received by the receiving unit (14), wherein the receiving unit (14) receives the information about the multiple secondary batteries (3) through the single balancing command signal, characterized in that the first control unit (7) defines as balancing target cells respective cells whose balancing time among the several secondary batteries (3) is not 0, and controls the balancing unit (12) such that the balancing of odd-numbered cells among the balancing target cells and the balancing of even-numbered cells among the balancing target cells are carried out alternately and repeatedly.

Description

Technical field

[0001] The present invention relates to a cell control device and a battery control device as well as a battery management system and a battery system using them. Technical background

[0002] In hybrid electric vehicles (HEVs) and electric vehicles (EVs) powered by electricity supplied from secondary batteries, a composite battery (battery system) is generally used, in which a number of secondary battery cells are connected in series to provide the required high voltage. A battery management device is conventionally connected to such a composite battery via a wiring harness to calculate the capacity of individual battery cells or to ensure their protection. The battery management device controls the charge / discharge state of each battery cell.

[0003] It is known that the battery management device described above performs balancing to equalize the voltages of the individual battery cells by discharging them individually, thereby reducing voltage variations between the respective battery cells. The battery management device typically uses current from a low-voltage battery, such as a lead-acid storage battery, which is mounted separately from the vehicle's battery pack, to perform the balancing while the vehicle is stationary. Therefore, the current draw of the battery management device during balancing must be minimized to prevent the battery from being discharged while the vehicle is stationary.

[0004] In PTL 1, a technology for reducing the power consumption of the battery management device during balancing was proposed. A battery management device disclosed in PTL 1 is a battery control system that individually adjusts the capacities of several lithium secondary batteries contained in a composite battery, wherein the battery control system comprises: a voltage measuring device that measures the open-circuit voltage of all lithium secondary batteries, a computing device that calculates the capacity adjustment time of a corresponding lithium secondary battery based on the open-circuit voltage measured by the voltage measuring device, a capacity adjustment device that adjusts the capacity of the corresponding lithium secondary battery during the capacity adjustment time calculated by the computing device, and an operating control device that causes,that the voltage measuring device and the computing device operate for a predetermined time if the composite battery is not used for a predetermined period, wherein the capacity adjustment device initiates and continues the capacity adjustment of the lithium secondary battery within the predetermined time, even after the predetermined time has elapsed, and wherein the voltage measuring device and the computing device enter a low-power mode after the predetermined time has elapsed. List of citations from patent literature PTL 1: JP 2003-282159 A US 2018 / 0241100 A1 discloses a cell control device with the features in the preamble of claim 1. Another conventional cell control device is known from WO 2013 / 051688 A1. Summary of the invention: Technical problem

[0005] Because the technology described in PTL 1 involves the arrangement of multiple timers corresponding to multiple battery cells, the device is complicated, which is problematic. Solution to the problem

[0006] A cell control device according to the present invention has the features defined in claim 1.

[0007] A battery control unit according to the present invention is designed for communication with the cell control unit and comprises: a second control unit that calculates balancing times for the multiple secondary batteries, and a transmitter unit that sends a balancing command signal to the cell control unit containing information about the balancing times calculated by the second control unit, wherein the transmitter unit sends the information about the multiple secondary batteries by means of the single balancing command signal.

[0008] A battery management system according to the present invention comprises the cell control unit and the battery control unit.

[0009] A battery system according to the present invention comprises the following: the battery management system and several secondary batteries which are to be balanced by the battery management system. Advantageous effects of the invention

[0010] According to the present invention, the power consumption of the battery control device during balancing can be reduced with a simple configuration. Brief description of the drawings

[0011] They show: Fig. 1 a diagram of a battery management system and a battery system according to an embodiment of the present invention, Fig. 2 a diagram of an example of a compensation control according to a first embodiment of the present invention, Fig. 3 a flowchart of the compensation control according to the first embodiment of the present invention, Fig. 4. A flowchart of the balancing process for odd-numbered cells, Fig. 5. A flowchart of the leveling process for even-numbered cells, Fig. 6 a flowchart of a compensation control according to a second embodiment of the present invention, Fig. 7. A flowchart of the reconciliation processing for all cells, Fig. 8 a flowchart of a compensation control according to a third embodiment of the present invention and Fig. 9. A flowchart of the balancing process for individual cells. Description of embodiments (First embodiment)

[0012] Fig. Figure 1 is a diagram of a battery management system and a battery system according to an embodiment of the present invention. The diagram shown in Fig. The battery management system shown in Figure 1 comprises several cell control units (hereinafter referred to as "CCU") 1 and one battery control unit (hereinafter referred to as "BCU") 2 and controls m battery cells 3 connected in series (m being any natural number). The battery management system and m battery cells 3 form a battery system according to the present embodiment. It should be noted that the battery cell 3 may simply be referred to as a "cell" in the following description.

[0013] The battery system according to the present embodiment is installed on and used in a vehicle such as a hybrid electric vehicle (HEV) or an electric vehicle (EV), and supplies power to drive the vehicle's motor. The battery system according to the present embodiment is described below by way of example using a battery system for driving a vehicle's motor.

[0014] Each CCU 1 is connected to several battery cells 3 and controls the respective corresponding battery cells 3 based on a command from the BCU 2. The control of the battery cells 3 performed by the CCU 1 includes balancing, keeping variations in the state of charge (SOC) of the battery cells 3 within a specific range. Each CCU 1 balances corresponding battery cells 3 to extend the range of usable SOC in the battery cells 3. It should be noted that the balancing performed by the CCU 1 will be described in detail later.

[0015] The BCU 2 sends a balancing command signal to each CCU 1 so that each CCU 1 performs balancing. The balancing command signal contains information regarding balancing times for the multiple battery cells 3 to which each CCU 1 is connected. Additionally, the BCU 2 receives information from each CCU 1 regarding cell voltage, cell temperature, and current value and generates the balancing command signal based on this information.

[0016] Each battery cell 3 is implemented using a secondary battery of the lithium-ion type, feeds direct current to an inverter (not shown) so that it generates alternating current to drive a motor as a load, and is charged by direct current generated from the alternating current regenerated by the motor or by a commercial power supply. It should be noted that in Fig. Battery cells 3 are represented by BC1 to BCm, and lines connecting the CCU 1 and the positive and negative electrodes of the respective battery cells 3 are represented by L0 to Lm. Additionally, the BCU 2 is connected to a lead-acid storage battery 4.

[0017] Next, the CCU 1 and the BCU 2, which form the battery management system according to the present embodiment, will be described in detail.

[0018] First, the CCU 1 is described. The CCU 1 is powered using the battery cell 3 as a power source and includes an integrated cell control circuit (hereinafter referred to as the "cell control IC") 5, a first control unit 7, a first timer 8, a time control unit 9, a CCU-side wireless device 10, and a CCU-side antenna 11. The cell control IC 5 includes a balancing control unit 12 and an analog-to-digital converter (not shown). The CCU-side wireless device 10 includes a CCU-side transmitter 13 and a CCU-side receiver 14.

[0019] It should be noted that in Fig. In Figure 1, of the multiple CCUs 1 in the battery management system according to the present embodiment, a CCU 1A is shown, which is connected to the respective battery cells 3, i.e., BCm-2, BCm-1, and BCm, which are arranged on the side of the highest potential of the composite battery, and a CCU 1B is shown, which is connected to the respective battery cells 3, i.e., BC1, BC2, and BC3, which are arranged on the side of the lowest potential of the composite battery, and the CCUs 1 connected to other battery cells 3 are omitted. However, in the actual implementation, the number of CCUs 1 included in the battery management system and the number of battery cells 3 connected to each CCU 1 are not the same as those shown in Figure 1. Fig. The options shown in the example are limited and can be set as desired. The following describes the configuration and operation of multiple CCUs using CCU 1A as an example.

[0020] The CCU-side receiver 14, contained in the CCU-side wireless device 10, receives a wireless signal transmitted by the BCU 2 via the CCU-side antenna 11. For example, the CCU-side receiver 14 receives the balancing command signal described above, which contains information regarding the balancing time for each battery cell 3, an activation signal containing an activation command for the CCU 1, or the like, via the wireless signal from the BCU 2. When the wireless signal is received from the BCU 2, the CCU-side receiver 14 demodulates it and outputs the demodulated signal to the first control unit 7.

[0021] The CCU-side transmitter unit 13, contained in the CCU-side wireless device 10, modulates a signal input from the first control unit 7 to generate a wireless signal and transmits the wireless signal to the BCU 2 via the CCU-side antenna 11. For example, the CCU-side transmitter unit 13 transmits information such as cell voltage, cell temperature, and current value obtained for each battery cell 3 to the BCU 2 via the wireless signal.

[0022] It should be noted that phase-shift keying (PSK) is used in examples of a wireless signal modulation scheme employed in the CCU-side wireless device 10. Another example of a communication scheme using PSK modulation is IEEE 802.15.4.

[0023] The first control unit 7 performs balancing control for the battery cell 3 by controlling the balancing unit 12 contained in the cell control IC 5 based on the balancing command signal wirelessly received by the CCU-side receiver unit 14. The first control unit 7 performs the balancing control using the time measured by the first timer 8. The first timer 8 measures the time that has elapsed since the balancing unit 12 initiated balancing. It should be noted that the balancing control performed by the first control unit 7 will be described in detail later. Each first control unit 7 is implemented, for example, using a computing circuit such as a central processing unit (CPU), a field-programmable gate array (FPGA), or an application-specific integrated circuit (ASIC), and various programs used in combination with it.

[0024] The balancing unit 12 balances the individual battery cells 3 by discharging or charging each of the multiple battery cells 3 to which the CCU 1 is connected, controlled by the first control unit 7. The balancing unit 12 has multiple balancing switches (not shown), each connected between the positive and negative electrodes of each battery cell 3, and it can switch each of the multiple balancing switches on or off, controlled by the first control unit 7, to perform the balancing by discharging or charging the respective battery cells 3. The balancing unit 12 is implemented, for example, using some circuitry in the cell control IC 5, which is an integrated circuit, or various electrical components provided with the cell control IC 5.

[0025] The first control unit 7 executes a control action to put the CCU 1 into a predefined low-power mode after the balancing control of the balancing unit 12 has been completed. In low-power mode, the CCU 1 suspends the operation of all components within the CCU 1 except for the component required to receive the activation signal when it is sent by the BCU 2. This reduces power consumption after the balancing process is complete.

[0026] However, if an abnormality occurs in a case where the CCU 1 cannot be put into low-power mode, battery cell 3 will continue to discharge due to the operation of the CCU 1, which in the worst case can render the vehicle inoperable. Examples of such abnormalities include the inability to interrupt balancing after a predetermined balancing time has elapsed due to a failure of the first timer 8, a failure of the first control unit 7, or the like; a standby mode continuing after balancing has been interrupted, which consumes more power than the low-power mode; and the like. To solve this problem, the CCU 1 has the time control unit 9.

[0027] The timer unit 9 has a function to stop the CCU 1 if an abnormality occurs in the CCU 1, namely that it cannot be switched to low-power mode. A stop time is set in the timer unit 9 that is longer than the time required for balancing control, and the timer unit 9 can stop the CCU 1 as soon as the time elapsed since the start of balancing exceeds the stop time. A predefined fixed value, a setting from the BCU 2, or the like can be used as the stop time set in the timer unit 9. Furthermore, the timer unit 9 can monitor for abnormalities in the first timer 8 and stop the CCU 1 if an abnormality is detected. The timer unit 9 can be implemented, for example, as a function of the CCU used as the first control unit 7, or of the FPGA used for this purpose, or by hardware different from the first control unit 7.

[0028] When the activation signal wirelessly transmitted by the BCU 2 is received in low-power mode, the CCU 1 is activated and enables low-power mode. After activation, when the CCU-side receiving unit 14 receives the balancing command signal sent by the BCU 2, the first control unit 7 controls the balancing of the multiple battery cells 3 using the first timer 8.

[0029] Next, the BCU 2 is described. The BCU 2 is operated using the lead-acid battery 4 as a power source and comprises a power supply unit 15, a second control unit 16, a second timer 17, a BCU-side wireless device 18, and a BCU-side antenna 19. The BCU-side wireless device 18 includes a BCU-side transmitter unit 20 and a BCU-side receiver unit 21.

[0030] The power supply unit 15 supplies power to each part of the BCU 2 based on the power supplied by the lead storage battery 4.

[0031] The BCU-side receiver unit 21 receives the wireless signal transmitted by the CCU 1 via the BCU-side antenna 19. The wireless signal contains information such as the cell voltage, cell temperature, and current value of each battery cell 3, as detected by the CCU 1. When the wireless signal is received by the CCU 1, the BCU-side receiver unit 21 demodulates it and outputs the demodulated signal to the second control unit 16.

[0032] When the compensation command signal or the activation signal described above is entered by the second control unit 16, the BCU-side transmitter unit 20 modulates these signals to generate a wireless signal and sends this via the BCU-side antenna 19 to the CCU 1.

[0033] The second control unit 16 calculates the state of charge (SOC), state of health (SOH), permissible current, and similar parameters for each battery cell 3 based on the information contained in the signal received and demodulated by the BCU-side receiver unit 21. Furthermore, the second control unit 16 calculates the balancing time for each battery cell 3 based on the calculated SOC, generates the balancing command signal according to the calculation result, and outputs it to the BCU-side transmitter unit 20. When the balancing command signal is received by the second control unit 16, the BCU-side transmitter unit 20 modulates it to generate a wireless signal and transmits the wireless signal to the CCU 1 via the BCU-side antenna 19. This transmits the balancing times for the multiple battery cells 3 connected to the CCU 1 from the BCU 2 to the CCU 1.After the compensation command signal has been sent from the BCU-side transmitter unit 20, the second control unit 16 is put into a predefined low-power mode.

[0034] It should be noted that BCU 2 transmits information about the balancing times of the multiple battery cells 3 connected to CCU 1 to CCU 1 via a single balancing command signal. Therefore, the CCU-side receiver 14 in CCU 1 receives the information about the balancing times for the multiple battery cells 3 as balancing targets via the single balancing command signal sent by BCU 2. Accordingly, it is sufficient for the activation of BCU 2, which is required for executing the balancing process, and the transmission of the balancing command signal from BCU 2 to CCU 1 to each occur only once. This reduces the power consumption of BCU 2 during balancing.

[0035] The second timer 17 measures the elapsed time after the BCU 2 has been switched to low-power mode, and as soon as the elapsed time reaches a predetermined activation time, the second timer instructs the power supply unit 15 to reactivate the BCU 2. Thereafter, the power supply unit 15, responding to the command from the second timer 17, resumes the supply of operating current to each part of the BCU 2.

[0036] The second control unit 16 sets an activation time in the second timer 17 and then puts the BCU 2 into low-power mode. The second timer 17 instructs the power supply unit 15 to activate the BCU 2 after the set activation time has elapsed.

[0037] Once BCU 2 has been activated and has exited low-power mode, the activation signal is sent to CCU 1 to activate it. BCU 2 then sends an information acquisition command for each battery cell 3 to CCU 1. CCU 1 acquires the information for each battery cell 3 from BCU 2 according to the information acquisition command and transmits the information to BCU 2.

[0038] The BCU 2 calculates the state of charge (SOC) and the balancing time of each cell using the information about each battery cell 3 sent by the CCU 1 and sends the balancing command signal to the CCU 1. Here, some of the information about battery cell 3 acquired by the CCU 1 can be replaced by information acquired by the BCU 2. For example, a current value can be acquired by arranging shunt resistors in parallel with several battery cells 3 and sensing the voltage drop across the shunt resistors using an analog-to-digital converter (ADC) included in the BCU 2 (not shown). Furthermore, instead of the balancing time for each cell, information about the voltage and SOC of each cell can be sent from the BCU 2 to the CCU 1 via the balancing command signal. In this case, the CCU 1 can calculate the balancing time based on the voltage and SOC of each cell.This means that any information about the balancing time for each cell can be included in the balancing command signal, provided the CCU 1 can determine the balancing time for each cell.

[0039] After sending the balancing command signal, BCU 2 returns to low-power mode. When CCU 1 receives the balancing command signal from BCU 2, CCU 1 returns to low-power mode after the balancing process is completed.

[0040] Next, the balancing control performed by the first control unit 7 in the CCU 1 is described. Fig. Figure 2 is a diagram of an example of a compensation control system according to a first embodiment of the present invention. Fig. Figures (a) to (f) show an example of a balancing controller, where six battery cells 3 are connected to a CCU 1 and the state of charge (SOC) is balanced between the six battery cells 3. Fig. 2(a) to (f) correspond to “Cell 1” to “Cell 6” as six battery cells 3 connected to the same CCU 1, and the SOCs of these six battery cells 3 are represented by bar graphs. It should be noted that the SOC value of each battery cell 3 corresponds to the balancing time for each battery cell 3.

[0041] As described above, balancing in the battery system according to the present embodiment is carried out to equalize the state of charge (SOC) between several cells connected in series, thereby broadening the range of SOC usable in the battery cells 3. The balancing control according to the present embodiment is described below using passive balancing as an example, where the SOCs are balanced by discharging the respective battery cells 3. However, active balancing can also be applied, where the SOCs are balanced by discharging or charging the respective cells to transfer charge between them. When active balancing is used, the current consumption of all battery cells 3 can be reduced.

[0042] Furthermore, the voltage applied to the balancing unit 12 becomes high when several series-connected battery cells 3 adjacent cells are discharged simultaneously, necessitating a larger cell control IC 5. Therefore, the present embodiment stipulates that adjacent cells cannot be discharged simultaneously and that either all even-numbered connected battery cells 3 can be discharged from the low-potential side (hereinafter referred to as "even-numbered cell") or all odd-numbered connected battery cells 3 can be discharged from the low-potential side (hereinafter referred to as "odd-numbered cell") simultaneously.

[0043] The following describes the voltage applied to the balancing unit 12 when adjacent cells are discharged simultaneously. If one of the several battery cells 3 in Fig. When cell BCm-1, for example, is discharged, the balancing unit 12 activates the balancing switch, which is located between the connecting line Lm-1 connected to the positive electrode of cell BCm-1 and the connecting line Lm-2 connected to the negative electrode of cell BCm-1, in order to reduce the impedance between the connecting lines Lm-1 and Lm-2. During this time, the voltage between the connecting lines Lm-1 and Lm-2 is approximately twice the voltage before discharge because the potential of the connecting line Lm-1 approaches the potential of the connecting line Lm-2.On the other hand, when two adjacent cells, for example, cell BCm-1 and cell BCm-2, are discharged simultaneously, the balancing unit 12 activates the balancing switch between the connecting line Lm-2 (connected to the positive electrode of cell BCm-2) and the connecting line Lm-3 (connected to the negative electrode of cell BCm-2), in addition to the balancing switch between the connecting line Lm-1 and the connecting line Lm-2. This reduces the impedance between the connecting line Lm-1 and the connecting line Lm-2, as well as the impedance between the connecting line Lm-2 and the connecting line Lm-3. Meanwhile, the voltage between the connecting line Lm-1 and the connecting line Lm-3 is approximately three times the voltage before discharge, because the potential of the connecting line Lm-1 approaches the potential of the connecting line Lm-3.

[0044] As described above, when adjacent cells are discharged simultaneously, the voltage applied to the balancing unit 12 is higher than when only one cell is discharged. It should be noted that as the number of adjacent cells discharged simultaneously increases, the voltage applied to the balancing unit 12 increases proportionally to the number of adjacent cells. Therefore, it is understandable that the voltage withstand capability of the cell control IC 5, which incorporates the balancing unit 12, must be improved when adjacent cells are discharged simultaneously. In general, it is necessary to increase the size of an element to improve the voltage withstand capability, so simultaneous discharge of adjacent cells can lead to a larger cell control IC 5.

[0045] Fig. Figure 2(a) shows the SOCs of cells 1 to 6 before the start of equalization. Fig. 2(a) Cell 6 has the lowest SOC. Therefore, when balancing, the SOC of cell 6 is set as the target SOC, and cells 1 to 5 are discharged so that the SOCs of cells 1 to 5 become equal to the target SOC.

[0046] If balancing in Fig. When the state shown in Figure 2(a) is initiated, the first control unit 7 first discharges the odd-numbered cells, namely cell 1, cell 3, and cell 5. Of these odd-numbered cells, cell 5 has the SOC closest to the target SOC, i.e., the lowest SOC. Therefore, the first control unit 7 sets the discharge time of the odd-numbered cells so that the SOC of cell 5 is reduced to reach the target SOC, and discharges cells 1, 3, and 5 during the discharge time. This results in a Fig. 2(b) state is achieved.

[0047] When the discharge of the odd-numbered cells is complete and the Fig. Once the state shown in 2(b) is reached, the first control unit 7 discharges even-numbered cells, namely cell 2 and cell 4. Although cell 6 is also an even-numbered cell, it is excluded as a balancing target, with the state of charge (SOC) of cell 6 being set as the target SOC. Of these even-numbered cells that form the balancing targets, cell 2 has the SOC closest to the target SOC, i.e., the lowest SOC. Therefore, the first control unit 7 sets the discharge time of the even-numbered cells such that the SOC of cell 2 is reduced to reach the target SOC, and discharges cell 2 and cell 4 during the discharge time. This results in a Fig. State 2(c) shown is reached.

[0048] Subsequently, the discharge of the odd-numbered cells and the discharge of the even-numbered cells are performed alternately and repeatedly. This means that in the Fig. 2(c) state Cell 1 and Cell 3, whose SOC is not the target SOC, are discharged by the odd-numbered cells and a Fig. The state shown in 2(d) is reached. In the Fig. In the state shown in 2(d), cell 4, whose SOC is not the target SOC, is discharged by the even-numbered cells, and a state is created in Fig. The state shown in 2(e) is reached. In the Fig. In the state shown in 2(e), cell 1, whose SOC is not the target SOC, is discharged by the odd-numbered cells, and a state is created in Fig. The state shown in 2(f) is reached. This balances the SOCs of cells 1 to 6, as shown in Fig. 2(f) is shown.

[0049] It is evident that the balancing control described above, performed by the first control unit 7, enables the balancing of the SOCs between all six battery cells 3, whose SOCs were not uniform before the start of the balancing.

[0050] Fig. Figure 3 is a flowchart of the balancing control according to the first embodiment of the present invention. In the CCU 1 of the battery management system according to the present embodiment, the first control unit 7, for example, when the balancing command signal is sent from the BCU 2 and received by the CCU-side receiving unit 14, as shown in the flowchart, executes Fig. 3 shown compensation control.

[0051] In step S10, the first control unit 7 receives the balancing time for each cell from the CCU-side receiving unit 14. Here, the CCU-side receiving unit 14 receives and records information about the balancing time for each cell, which is contained in the balancing command signal received by the CCU-side receiving unit 14 from the BCU 2.

[0052] In step S20, the first control unit defines 7 balancing target cells based on the balancing time received in step S10 for each cell. Here, all cells except one, whose balancing time is 0 (i.e., the cell with the lowest SOC, which is the target SOC), are designated as balancing target cells.

[0053] In step S30, the first control unit 7 performs odd-numbered cell balancing to execute the odd-numbered cell balancing control. During odd-numbered cell balancing, the balancing for odd-numbered cells is performed among the balancing target cells defined in step S20. However, an odd-numbered cell excluded from the balancing targets in step S50, described below, is not a processing target in step S30. It should be noted that the odd-numbered cell balancing in step S30 is described in detail later with reference to the flowchart from Fig. 4 is described.

[0054] In step S40, the first control unit 7 updates the balancing time for each odd-numbered cell that is the balancing target cell. Here, the balancing time for each odd-numbered cell is updated by subtracting the unload time for odd-numbered cells, To, which is defined in step S30 during the odd-numbered cell balancing process, from the balancing time for each odd-numbered cell that is the balancing target cell. Note that a procedure for defining the unload time for odd-numbered cells, To, will be described later with reference to the odd-numbered cell balancing process.

[0055] In step S50, the first control unit 7 excludes from the balancing targets the cell whose balancing time has become 0 as a result of the update in step S40. This excludes the cell whose SOC became equal to the target SOC during the balancing process for odd-numbered cells in step S30 from the targets of the subsequent balancing.

[0056] In step S60, the first control unit 7 determines whether there is an even-numbered cell that is a balancing target. If the determination indicates that the balancing target cells still contain at least one even-numbered cell, the process continues in step S80, following the balancing processing for odd-numbered cells in step S30, and then the balancing processing for even-numbered cells. Conversely, the process continues in step S70 if the balancing target cells contain no even-numbered cells, i.e., if the SOCs of the even-numbered cells are all the same as the target SOC and the balancing is complete.

[0057] In step S70, the first control unit 7 determines whether there is an odd-numbered cell that is a balancing target. If the determination indicates that the balancing target cells still contain at least one odd-numbered cell, the process returns to step S30 and the balancing processing for odd-numbered cells continues. Conversely, if the balancing target cells do not contain any odd-numbered cells, i.e., if the SOCs of the odd-numbered cells are all the same as the target SOC and the balancing is complete, the flowchart ends. Fig. 3.

[0058] In step S80, the first control unit 7 performs the even-numbered cell balancing process to execute the even-numbered cell balancing control. During the even-numbered cell balancing process, the balancing for even-numbered cells is performed among the balancing target cells defined in step S20. However, an even-numbered cell excluded from the balancing targets in step S100, described below, is not a processing target in step S80. It should be noted that the even-numbered cell balancing process in step S80 is described in detail later with reference to the flowchart from [reference to flowchart]. Fig. 5 is described.

[0059] In step S90, the first control unit 7 updates the balancing time for each even-numbered cell that is the balancing target cell. Here, the balancing time for each even-numbered cell is updated by subtracting the even-numbered cell discharge time Te, which was set in step S80 during the even-numbered cell balancing process, from the balancing time for each even-numbered cell that is the balancing target cell. Note that a procedure for setting the even-numbered cell discharge time Te will be described later using the even-numbered cell balancing process as an example.

[0060] In step S100, the first control unit 7 excludes from the balancing targets the cell whose balancing time has become 0 as a result of the update in step S90. This excludes the cell whose SOC became equal to the target SOC during the balancing processing for even-numbered cells in step S80 from the targets of the subsequent balancing.

[0061] In step S110, the first control unit 7 determines whether there is an odd-numbered cell that is a balancing target. If the determination indicates that the balancing target cells still contain at least one odd-numbered cell, the process returns to step S30 and follows the balancing processing for even-numbered cells in step S80, followed by the balancing processing for odd-numbered cells. Conversely, the process continues in step S120 if the balancing target cells do not contain any odd-numbered cells, i.e., if the SOCs of the odd-numbered cells are all the same as the target SOC and the balancing is complete.

[0062] In step S120, the first control unit 7 determines whether there is an even-numbered cell that is a balancing target. If the determination indicates that the balancing target cells still contain at least one even-numbered cell, the process returns to step S80 and the balancing processing for even-numbered cells continues. Conversely, if the balancing target cells do not contain any even-numbered cells, i.e., if the SOCs of the even-numbered cells are all the same as the target SOC and the balancing is complete, the flowchart ends. Fig. 3.

[0063] In the CCU 1 of the battery management system according to the present embodiment, the balancing control described above is performed by the first control unit 7. During the balancing control, the balancing processing for odd-numbered cells in step S30 and the balancing processing for even-numbered cells in step S80 are executed alternately and repeatedly until the balancing of all target cells is complete. Therefore, as described in Fig. 2 described that balancing odd-numbered cells and balancing even-numbered cells are repeated alternately, so that the SOCs of the respective cells become equal to the target SOC.

[0064] Next, the balancing process for odd-numbered cells is described in step S30. Fig. Figure 4 is a flowchart of the balancing process for odd-numbered cells.

[0065] In step S31, the first control unit 7 identifies an odd-numbered cell whose current balancing time is shortest, i.e., an odd-numbered cell whose SOC is closest to the target SOC of the odd-numbered cells that are the current balancing target cells. The balancing time for each odd-numbered cell at this time is the balancing time received in step S10, i.e., the balancing time based on the balancing command signal received by the CCU-side receiver unit 14 from the BCU 2, when the balancing processing for odd-numbered cells is executed for the first time in step S30. On the other hand, for the second or subsequent execution of the balancing processing for odd-numbered cells, the balancing time updated in the immediately preceding step S40 is used. Then, the current balancing time for the identified odd-numbered cell, i.e.,The shortest balancing time among the balancing times for the odd-numbered cells, which are the current balancing target cells, is set as the discharge time for odd-numbered cells To.

[0066] In step S32, the first control unit 7 sets the discharge time To for odd-numbered cells in the first timer 8, as determined in step S31.

[0067] In step S33, the first control unit 7 initiates the balancing of the odd-numbered cells, which are the current target cells. The first control unit 7 activates one balancing switch, corresponding to each odd-numbered target cell, among the several balancing switches contained in the balancing unit 12, and deactivates the other balancing switches. This controls the balancing unit 12 so that the discharge is initiated in a state where the impedance between the positive and negative electrodes of each odd-numbered target cell is low.

[0068] In step S34, the first control unit 7 uses the first timer 8 to determine whether the odd-numbered cell discharge time To has elapsed after the odd-numbered cell balancing was initiated in step S33. The first timer 8 measures the time elapsed since the odd-numbered cell balancing began in step S33 and sends a notification to the first control unit 7 as soon as the elapsed time reaches the odd-numbered cell discharge time To specified in step S32. The first control unit 7 determines that the odd-numbered cell discharge time To has not elapsed, and the process remains in step S34 until the notification from the first timer 8 is received. Once the notification from the first timer 8 is received, the first control unit 7 determines that the odd-numbered cell discharge time To has elapsed, and the process continues in step S35.

[0069] In step S35, the first control unit 7 interrupts the balancing of the odd-numbered cells initiated in step S33. The first control unit 7 controls the balancing unit 12 in such a way that the discharge of each odd-numbered cell, which is the target cell for balancing, is interrupted by switching off all balancing switches contained in the balancing unit 12.

[0070] Once the balancing of the odd-numbered cells in step S35 is interrupted, the first control unit 7 terminates the flowchart. Fig. 4 and completes the balancing process for odd-numbered cells. The process then returns to the flowchart. Fig. 3 back and will continue in the next step S40.

[0071] Next, the balancing process for even-numbered cells is described in step S80. Fig. Figure 5 is a flowchart of the leveling process for even-numbered cells.

[0072] In step S81, the first control unit 7 identifies an even-numbered cell whose current balancing time is shortest, i.e., an even-numbered cell whose SOC is closest to the target SOC of the even-numbered cells that are the current balancing target cells. The balancing time for each even-numbered cell at this time is the balancing time received in step S10, i.e., the balancing time based on the balancing command signal received by the CCU-side receiver unit 14 from the BCU 2, when the balancing processing for even-numbered cells is executed for the first time in step S80. On the other hand, for the second or subsequent balancing processing for even-numbered cells, the balancing time updated in the immediately preceding step S90 is used. Then, the current balancing time for the identified even-numbered cell, i.e.,The shortest balancing time among the balancing times for the even-numbered cells, which are the current balancing target cells, is set as the discharge time for even-numbered cells Te.

[0073] In step S82, the first control unit 7 sets the discharge time for even-numbered cells Te in the first timer 8, as determined in step S81.

[0074] In step S83, the first control unit 7 initiates the balancing of the even-numbered cells, which are the current target cells. The first control unit 7 activates one balancing switch, corresponding to each even-numbered target cell, among the several balancing switches contained in the balancing unit 12, and deactivates the other balancing switches. This controls the balancing unit 12 so that the discharge is initiated in a state where the impedance between the positive and negative electrodes of each even-numbered target cell is low.

[0075] In step S84, the first control unit 7 uses the first timer 8 to determine whether the discharge time for even-numbered cells Te has elapsed after the balancing of the even-numbered cells was initiated in step S83. The first timer 8 measures the time elapsed since the start of the balancing of the even-numbered cells in step S83 and sends a notification to the first control unit 7 as soon as the elapsed time reaches the discharge time for even-numbered cells Te specified in step S82. The first control unit 7 determines that the discharge time for even-numbered cells Te has not elapsed, and the process remains in step S84 until the notification is received from the first timer 8. Once the notification is received from the first timer 8, the first control unit 7 determines that the discharge time for even-numbered cells Te has elapsed, and the process continues in step S85.

[0076] In step S85, the first control unit 7 interrupts the balancing of the even-numbered cells initiated in step S83. The first control unit 7 controls the balancing unit 12 in such a way that the discharge of each even-numbered cell, which is the target cell for balancing, is interrupted by switching off all balancing switches contained in the balancing unit 12.

[0077] Once the balancing of the even-numbered cells in step S85 is interrupted, the first control unit 7 terminates the flowchart from Fig. 5 and completes the balancing process for even-numbered cells. The process then returns to the flowchart. Fig. 3 back and will continue in the next step S90.

[0078] According to the first embodiment of the present invention described above, the following effects are achieved: (1) The CCU 1 comprises the balancing unit 12, which performs the balancing of the states of charge (SOCs) of the battery cells 3 by discharging or charging each of the multiple battery cells 3, which are secondary batteries; the first timer 8, which measures the time elapsed since the start of balancing; the CCU-side receiver 14, which receives the balancing command signal containing information about balancing times for the battery cells 3; and the first control unit 7, which controls the balancing unit 12 based on the time elapsed since the start of balancing and the balancing command signal, wherein the elapsed time is measured by the first timer 8 and the balancing command signal received by the CCU-side receiver 14. The CCU-side receiver 14 receives the information about the balancing times for the multiple battery cells 3 by means of a single balancing command signal.Therefore, BCU 2, which sends the balancing command signal to CCU 1, can transmit information about the balancing times for the multiple battery cells 3 connected to CCU 1 to CCU 1 via a single balancing command signal. This allows the power consumption of BCU 2 during balancing to be reduced with a simple configuration. (2) The first control unit 7 defines as the balancing target cells those cells whose balancing time among the multiple battery cells 3 is not 0 (step S20), and controls the balancing unit 12 such that the balancing of odd-numbered cells among the balancing target cells (steps S30 to S50) and the balancing of even-numbered cells among the balancing target cells (steps S80 to S100) are performed alternately and repeatedly. This allows the balancing of the multiple battery cells 3 to be performed in a short time without increasing the size of the cell control IC 5. (3) The balancing of odd-numbered cells performed by the first control unit 7 comprises the following steps: (a1) Determining the shortest balancing time among the balancing times for the odd-numbered cells which are the balancing target cells, as the discharge time for odd-numbered cells To in the first timer 8 based on the balancing command signal or the updated balancing time (steps S31 and S32) (a2) Causing the balancing unit 12 to initiate the discharge of the odd-numbered cells (step S33) (a3) Causing the balancing unit 12 to interrupt the discharge of the odd-numbered cells as soon as the time elapsed since the start of the discharge of the odd-numbered cells reaches the discharge time for odd-numbered cells To (steps S34 and S35), wherein the elapsed time is measured by the first timer 8 (a4) Update the balancing times for each of the odd-numbered cells that are the balancing target cells, based on the discharge time for odd-numbered cells To (step S40) (a5) Excluding an odd-numbered cell whose updated rebalancing time is 0 from the rebalancing target cells (step S50) Furthermore, the balancing of the even-numbered cells performed by the first control unit 7 comprises the following steps: (b1) Determining the shortest balancing time among the balancing times for the even-numbered cells which are the balancing target cells, as the discharge time for even-numbered cells Te in the first timer 8 based on the balancing command signal or the updated balancing time (steps S81 and S82) (b2) Causing the balancing unit 12 to initiate the discharge of the even-numbered cells (step S83) (b3) Causing the balancing unit 12 to interrupt the discharge of the even-numbered cells as soon as the time elapsed since the start of the discharge of the even-numbered cells reaches the discharge time for even-numbered cells Te (steps S84 and S85), wherein the elapsed time is measured by the first timer 8 (b4) Update the balancing time for each of the even-numbered cells that are the balancing target cells, based on the discharge time for even-numbered cells Te (step S90) (b5) Excluding an even-numbered cell whose updated rebalancing time is 0 from the rebalancing target cells (step S100) This allows the first control unit 7 to perform both the balancing of the odd-numbered cells and the balancing of the even-numbered cells appropriately. (4) The CCU-side receiver unit 14 receives the balancing command signal wirelessly. This eliminates the need for wiring between the CCU 1 and the BCU 2, further simplifying the configuration of the battery management system. (5) The CCU 1 includes the time control unit 9, which stops the CCU 1 if it experiences an abnormality. This prevents power from battery cell 3 from being wasted when an abnormality occurs in the CCU 1. (6) The BCU 2, which can communicate with the CCU 1, includes the second control unit 16, which calculates the balancing times for the multiple battery cells 3, which are secondary batteries, and the BCU-side transmitter unit 20, which sends the balancing command signal, containing information about the balancing time calculated by the second control unit 16, to the CCU 1. The BCU-side transmitter unit 20 sends the information about the balancing times for the multiple battery cells 3 by means of a single balancing command signal. This reduces the power consumption of the BCU 2 during balancing. (7) The BCU-side transmitter unit 20 transmits the balancing command signal wirelessly. This eliminates the need for wiring between the CCU 1 and the BCU 2, thus simplifying the configuration of the battery management system. (8) The BCU 2 has a second timer 17 that measures the elapsed time since the BCU 2 was put into the predefined low-power mode. The second control unit 16 sets a predefined activation time in the second timer 17 and then puts the BCU 2 into low-power mode. The second timer 17 reactivates the BCU 2 as soon as the time elapsed since the BCU 2 was put into low-power mode reaches the activation time. This allows the power consumption of the BCU 2 to be reduced while balancing is performed regularly. (Second embodiment)

[0079] Next, a second embodiment of the present invention will be described. According to the first embodiment described above, a balancing control method was described in which odd-numbered cells and even-numbered cells are grouped and discharged alternately. On the other hand, according to the present embodiment, a balancing control method is described in which all cells are discharged simultaneously. It should be noted that the configurations of a battery management system and a battery system according to the present embodiment and the configurations of a CCU 1 and a BCU 2 are the same as those described in the first embodiment with reference to Fig. 1. Furthermore, the BCU 2, similar to the first embodiment, sends information about balancing times for several battery cells 3 connected to the CCU 1 to the CCU 1 via a single balancing command signal. Therefore, a description of this is omitted below.

[0080] Fig. Figure 6 is a flowchart of the balancing control according to the second embodiment of the present invention. In the CCU 1 of the battery management system according to the present embodiment, the first control unit 7, for example, when the balancing command signal is sent from the BCU 2 and received by the CCU-side receiving unit 14, as shown in the flowchart, executes Fig. The compensation control shown in section 6 is shown.

[0081] In step S10A, the first control unit 7 receives the balancing time for each cell from the CCU-side receiving unit 14. Here, the CCU-side receiving unit 14 receives and records information about the balancing time for each cell, which is contained in the balancing command signal received by the CCU-side receiving unit 14 from the BCU 2, similar to the first embodiment.

[0082] In step S20A, the first control unit defines 7 balancing target cells based on the balancing time received in step S10A for each cell. Similar to the first embodiment, all cells except one, whose balancing time is 0 (i.e., the cell with the lowest SOC, which is the target SOC), are defined as balancing target cells.

[0083] In step S30A, the first control unit 7 performs a balancing process for all cells to execute the balancing control for all cells. During the balancing process for all cells, balancing is performed for all balancing target cells defined in step S20A. However, a cell excluded from the balancing targets in step S50A, described below, is not a processing target in step S30A. It should be noted that the balancing process for all cells in step S30A will be described in detail later with reference to the flowchart from Fig. 7 is described.

[0084] In step S40A, the first control unit 7 updates the balancing time for each cell that is the balancing target cell. Here, the balancing time for each cell is updated by subtracting the balancing time for each balancing target cell from the discharge time Ta, which was set for all cells in step S30A during the balancing process. Note that a procedure for setting the discharge time Ta for all cells will be described later in the description of the balancing process for all cells.

[0085] In step S50A, the first control unit 7 excludes from the balancing targets the cell whose balancing time has become 0 as a result of the update in step S40A. This excludes the cell whose SOC became equal to the target SOC during the balancing process for all cells in step S30A from the targets of the subsequent balancing.

[0086] In step S60A, the first control unit 7 determines whether there is a target cell for adjustment. If the determination indicates that there is at least one target cell for adjustment, the process returns to step S30A and the adjustment processing continues for all cells. Otherwise, the flowchart ends Fig. 6, if there is no target balancing cell, i.e., if the SOCs of all cells are equal to the target SOC and balancing is complete.

[0087] In the CCU 1 of the battery management system according to the present embodiment, the balancing control described above is executed by the first control unit 7. During the balancing control, the balancing process for all cells in step S30A is repeatedly executed until the balancing of all target cells is complete. Therefore, the state of charge (SOC) of each cell can be made equal to the target SOC.

[0088] Next, the balancing process for all cells is described in step S30A. Fig. 7 is a flowchart of the reconciliation processing for all cells.

[0089] In step S31A, the first control unit 7 identifies a cell whose current balancing time is shortest, i.e., whose SOC is closest to the target SOC among the current target cells. The balancing time for each cell at this time is the balancing time received in step S10A, i.e., the balancing time based on the balancing command signal received by the CCU-side receiving unit 14 from the BCU 2, when the balancing process is executed for all cells for the first time in step S30A. On the other hand, for the second or subsequent balancing processes for all cells, the balancing time updated in the immediately preceding step S40A is used. Then, the current balancing time for the identified cell, i.e., the shortest balancing time among the balancing times for the current target cells, is set as the discharge time Ta for all cells.

[0090] In step S32A, the first control unit 7 sets the discharge time Ta for all cells in the first timer 8, as determined in step S31A.

[0091] In step S33A, the first control unit 7 initiates the balancing of all current target cells. The first control unit 7 switches on one balancing switch, corresponding to each target cell, from among the several balancing switches contained in the balancing unit 12, and switches off the other balancing switches. This controls the balancing unit 12 so that the discharge is initiated in a state where the impedance between the positive and negative electrodes of each target cell is low.

[0092] In step S34A, the first control unit 7 uses the first timer 8 to determine whether the discharge time Ta for all cells has elapsed after the balancing of all target cells was initiated in step S33A. The first timer 8 measures the time elapsed after initiating the balancing of all target cells in step S33A and sends a notification to the first control unit 7 as soon as the elapsed time reaches the discharge time Ta for all cells specified in step S32A. The first control unit 7 determines that the discharge time Ta for all cells has not yet elapsed, and the process remains in step S34A until the notification from the first timer 8 is received. Once the notification from the first timer 8 is received, the first control unit 7 determines that the discharge time Ta for all cells has elapsed, and the process continues in step S35A.

[0093] In step S35A, the first control unit 7 interrupts the balancing of all target cells initiated in step S33A. The first control unit 7 controls the balancing unit 12 in such a way that the discharge of each target cell is interrupted by switching off all balancing switches contained in the balancing unit 12.

[0094] Once the balancing of all target cells in step S35A has been interrupted, the first control unit 7 terminates the flowchart. Fig. 7 and completes the reconciliation processing for all cells. The process then returns to the flowchart. Fig. 6 back and will continue in the next step S40A.

[0095] According to the second embodiment of the present invention described above, in addition to (1) and (4) to (8) described in the first embodiment, the following effects are observed:

[0096] (9) The first control unit 7 designates as the balancing target cells those cells whose balancing time among the multiple battery cells 3 is not 0 (step S20A), and controls the balancing unit 12 such that the balancing of all balancing target cells is performed repeatedly (steps S30A to S50A). This allows the balancing times for the multiple battery cells 3 to be further reduced, so that the current consumed by the CCU 1 from the battery cells 3 during the balancing process can be further reduced. However, it may be necessary to increase the size of the cell control IC 5 compared to the first embodiment.

[0097] (10) The balancing of all target cells performed by the first control unit 7 comprises the following steps: (c1) Determine the shortest balancing time among the balancing times for the balancing target cells as the discharge time Ta for all cells in the first timer 8 based on the balancing command signal or the updated balancing time (steps S31A and S32A) (c2) Causing balancing unit 12 to initiate the discharge of the balancing target cells (step S33A) (c3) Causing the balancing unit 12 to interrupt the discharge of the balancing target cells as soon as the time elapsed since the start of the discharge of the balancing target cells reaches the discharge time Ta for all cells (steps S34A and S35A), the elapsed time being measured by the first timer 8 (c4) Update the balancing time for each of the balancing target cells based on the discharge time Ta for all cells (step S40A) (c5) Exclude a cell whose updated rebalancing time is 0 from the rebalancing target cells (step S50A) This allows the first control unit 7 to appropriately perform the balancing of all balancing target cells. (Third embodiment)

[0098] Next, a third embodiment of the present invention is described. According to the present embodiment, a balancing control method is described in which cells are discharged individually one after the other. It should be noted that, similar to the second embodiment described above, the configurations of a battery management system and a battery system according to the present embodiment, and the configurations of a CCU 1 and a BCU 2, are the same as those described in the first embodiment with reference to Fig. 1. Furthermore, the BCU 2, similar to the first embodiment, sends information about balancing times for several battery cells 3 connected to the CCU 1 to the CCU 1 via a single balancing command signal. Therefore, a description of this is omitted below.

[0099] Fig. Figure 8 is a flowchart of the balancing control according to the third embodiment of the present invention. In the CCU 1 of the battery management system according to the present embodiment, the first control unit 7, for example, when the balancing command signal is sent from the BCU 2 and received by the CCU-side receiving unit 14, as shown in the flowchart, executes Fig. 8 shown compensation control.

[0100] In step S10B, the first control unit 7 receives the balancing time for each cell from the CCU-side receiving unit 14. Here, the CCU-side receiving unit 14 receives and records information about the balancing time for each cell, which is contained in the balancing command signal received by the CCU-side receiving unit 14 from the BCU 2, similar to the first and second embodiments.

[0101] In step S20B, the first control unit specifies 7 balancing target cells based on the balancing time received for each cell in step S10B. Similar to the first and second embodiments, all cells except one, whose balancing time is 0 (i.e., the cell with the lowest SOC, which is the target SOC), are specified as balancing target cells.

[0102] In step S30B, the first control unit 7 performs the individual cell balancing processing, executing the balancing control for each individual target cell. During individual cell balancing, balancing is performed sequentially, one at a time, for the target cells defined in step S20B. However, a cell excluded from the target cells in step S50B, as described below, is not a processing target in step S30B. Note that the individual cell balancing processing in step S30B will be described in detail later with reference to the flowchart from Fig. 9 is described.

[0103] In step S50B, the first control unit 7 excludes from the balancing targets the cell whose balancing was completed by the individual cell balancing process in step S30B. This excludes the cell whose SOC became equal to the target SOC during the individual cell balancing process in step S30B from the targets of the subsequent balancing process.

[0104] In step S60B, the first control unit 7 determines whether there is a target cell for adjustment. If the determination indicates that there is at least one target cell for adjustment, the process returns to step S30B and the adjustment processing for individual cells continues. Otherwise, the flowchart ends Fig. 8, if there is no target balancing cell, i.e., if the SOCs of all cells are equal to the target SOC and balancing is complete.

[0105] In the CCU 1 of the battery management system according to the present embodiment, the balancing control described above is executed by the first control unit 7. During the balancing control, the balancing process for individual cells in step S30B is repeatedly executed until the balancing of all target cells is complete. Therefore, the state of charge (SOC) of each cell can be made equal to the target SOC.

[0106] Next, the balancing process for individual cells is described in step S30B. Fig. 9 is a flowchart of the leveling process for individual cells.

[0107] In step S31B, the first control unit 7 selects as the current discharge target cell the cell with the lowest number among the current balancing target cells, i.e., a cell located on the side with the lowest potential. However, instead of the cell with the lowest number, the cell with the highest number can also be selected. Alternatively, any other cell can be selected. Any cell can be selected as the current discharge target cell, as long as any cell can be selected from the current balancing target cells.

[0108] In step S32B, the first control unit 7 sets a balancing time for the current discharge target cell selected in step S31B as the discharge time Tn for individual cells. The balancing time for the discharge target cell used is the balancing time received in step S10B, i.e., the balancing time based on the balancing command signal received by the CCU-side receiving unit 14 from the BCU 2.

[0109] In step S33B, the first control unit 7 sets the discharge time Tn for individual cells in the first timer 8, as determined in step S32B.

[0110] In step S34B, the first control unit 7 initiates the balancing of the current discharge target cell selected in step S31B. The first control unit 7 switches on one of the balancing switches corresponding to the current discharge target cell, among the several balancing switches contained in the balancing unit 12, and switches off the other balancing switches. This controls the balancing unit 12 so that the discharge is initiated in a state where the impedance between the positive and negative electrodes of the current discharge target cell is low.

[0111] In step S35B, the first control unit 7 uses the first timer 8 to determine whether the individual cell discharge time Tn has elapsed after the balancing of the current target cell was initiated in step S34B. The first timer 8 measures the time elapsed since the balancing of the current target cell began in step S34B and sends a notification to the first control unit 7 as soon as the elapsed time reaches the individual cell discharge time Tn specified in step S33B. The first control unit 7 determines that the individual cell discharge time Tn has not yet elapsed, and the process remains in step S35B until the notification is received from the first timer 8. Once the notification is received, the first control unit 7 determines that the individual cell discharge time Tn has elapsed, and the process continues in step S36B.

[0112] In step S36B, the first control unit 7 interrupts the balancing of the current discharge target cell initiated in step S34B. The first control unit 7 controls the balancing unit 12 in such a way that the discharge of the current discharge target cell is interrupted by switching off all balancing switches contained in the balancing unit 12.

[0113] Once the balancing of the current discharge target cell in step S36B has been interrupted, the first control unit 7 terminates the flowchart from Fig. 9 and completes the balancing process for individual cells. The process then returns to the flowchart. Fig. 8 back and will continue in the next step S50B.

[0114] According to the third embodiment of the present invention described above, in addition to (1) and (4) to (8) described in the first embodiment, the following effects are observed:

[0115] (11) The first control unit 7 designates as the balancing target cells those cells whose balancing time among the multiple battery cells 3 is not 0 (step S20B), and controls the balancing unit 12 such that the balancing of each individual balancing target cell is performed repeatedly (steps S30B and S50B). This makes balancing control for the multiple battery cells 3 easier to perform. However, compared to the first embodiment, the time required to balance all battery cells 3 is longer, and the current consumed by the CCU 1 from the battery cells 3 during the balancing process may be higher.

[0116] (12) The balancing of each individual balancing target cell, performed by the first control unit 7, comprises the following steps: (d1) Selecting a discharge target cell from the balancing target cells (step S31B) (d2) Setting a balancing time for the selected discharge target cell as discharge time Tn for individual cells in the first timer 8 based on the balancing command signal (steps S32B and S33B) (d3) Causing the balancing unit 12 to initiate the discharge of the discharge target cell (step S34B) (d4) Causing the balancing unit 12 to interrupt the discharge of the discharge target cell as soon as the time elapsed since the start of the discharge of the discharge target cell reaches the discharge time Tn for individual cells (steps S35B and S36B), wherein the elapsed time is measured by the first timer 8 (d5) Exclude the discharge target cell whose discharge is complete from the balancing target cells (step S50B) This allows the first control unit 7 to appropriately perform the balancing of each individual balancing target cell.

[0117] Because the CCU 1 is designed according to the present invention as described above, the balancing of the multiple battery cells 3 can be controlled by receiving a single balancing command signal, even if only one first timer 8 is provided for the multiple battery cells 3. Therefore, the power consumption of the BCU 2 during balancing can be reduced, and the power consumption of the battery system can be reduced.

[0118] Furthermore, according to the present invention, because the BCU 2 is designed as described above, balancing can be performed at a predetermined time. For example, the voltage of battery cell 3 becomes unstable immediately after the vehicle stops, thus reducing the accuracy of the SOC calculation. Therefore, more accurate balancing can be achieved by performing the SOC calculation and balancing at a time when the voltage of battery cell 3 is stable after the vehicle has stopped. Moreover, even if the change in the SOC of the multiple battery cells 3 is eliminated by performing balancing, a SOC variation will reappear over time due to a difference in the self-discharge rate between the battery cells 3. In this case as well, the SOC change can always be reduced because balancing can be performed regularly.Therefore, regardless of the time the vehicle starts driving, a wide SOC range can be used and the range can be increased by the battery cells 3.

[0119] It should be noted that, although the second control unit 16 in the BCU 2 sets the next activation time in the second timer 17 in each of the embodiments described above, a fixed value can be set in the second timer 17 to activate the BCU 2 regularly. The same effect can be achieved in this case as well. Furthermore, the same effect can also be achieved in a case where a higher-level system (not shown) activates the BCU 2 instead of the second timer 17.

[0120] Furthermore, according to each of the embodiments described above, the CCU 1 receives information about the balancing time for each battery cell 3 via the balancing command signal. However, information other than the balancing time can also be received, as long as it is information that can be used by the first control unit 7 to calculate the balancing time. For example, the CCU 1 can receive the cell voltage and the state of charge (SOC) of each battery cell 3, and the first control unit 7 can calculate the balancing time for each battery cell 3 based on the cell voltage and the SOC of each battery cell 3. In particular, in the case of a battery cell 3 where there is a high correlation between the cell voltage and the SOC, the cell voltage can be received instead of the balancing time, and the first control unit 7 can perform a control operation to equalize the cell voltages.Alternatively, the cell voltage of each battery cell 3 detected by the cell control IC 5 can be used to balance the respective battery cells 3.

[0121] Furthermore, after balancing is complete, CCU 1 can be switched to low-power mode once the next activation time has been set in the first timer 8. This allows CCU 1 to be activated even when BCU 2 is not activated, further reducing power consumption. For example, the state of health (SOH) can be accurately calculated by regularly activating CCU 1, recording changes in the information of each battery cell 3 over time, and measuring the self-discharge rate of each battery cell. Furthermore, if the self-discharge rate is known, the change in the state of charge (SOC) of each battery cell 3 can be recorded in CCU 1 even when BCU 2 is not activated. Therefore, balancing can be performed regularly. This reduces the variation in the SOC when BCU 2 is next activated.

[0122] Furthermore, the CCU 1 and the battery cells 3, as described in the respective embodiments, can be provided as a single battery pack. In such a configuration, replacing the CCU 1 and the battery cells 3 due to a fault or a version upgrade can be performed by replacing each battery pack together, thus facilitating easy replacement of the CCU 1 and the battery cells 3. Additionally, replacing the BCU 2 can also be simplified.

[0123] Furthermore, in each of the embodiments described above, an example was described in which communication between the CCU 1 and the BCU 2 is carried out wirelessly; however, the same effect can also be achieved if the communication is hardwired. Generally, wireless communication consumes more power than wired communication, so wireless communication benefits more from the effects of the present invention. It should be noted that even in the case of wired communication, it is preferred that the communication between the CCU 1 and the BCU 2 be isolated by an insulating means. Well-known isolation techniques such as a photocoupler, a photoMOS relay, a pulse transformer, a digital isolator, a capacitor, and the like can be used.Additionally, any connection method can be applied to the connection between the BCU 2 and several CCUs 1. For example, a so-called star connection method, in which the BCU 2 and several CCUs 1 are connected by the number of CCUs 1, a so-called back-read chain connection method, in which CCUs 1 are connected in series and only one CCU 1 at the highest level is connected to the BCU 2, a so-called unidirectional chain connection method, in which only one CCU 1 at the highest level and one CCU 1 at the lowest level are connected to the BCU 2, or the like can be used.

[0124] According to each embodiment described above, it is preferred that the balancing of the respective battery cells 3 is performed when the vehicle is stationary and not being charged by an external charger. The balancing process can be performed while the vehicle is driving or being charged by an external charger; however, in these cases, the BCU 2 must regularly calculate the permissible current charge / discharge amount and transmit the result of the calculation to a higher-level system. Therefore, it is difficult to put the BCU 2 into low-power mode. Furthermore, performing the balancing process while the vehicle is stationary and not being charged by an external charger ensures that ample time is available for the balancing process. Therefore, the discharge current can be reduced, thus simplifying the design of the CCU 1.For example, if the balancing process is performed quickly while the vehicle is driving or being charged by an external charger, heat is generated due to a high discharge current, which can lead to component damage or impaired functionality. To prevent component damage or impaired functionality, a heat dissipation structure must be applied to the CCU 1 in some cases. Conversely, if the balancing process is performed while the vehicle is stationary and not being charged by an external charger, the heat dissipation structure must be applied to the CCU 1, thus simplifying its design.

[0125] The embodiments and various modifications described above are merely examples, and the present invention is not limited to the content of these embodiments and modifications, provided that the features of the invention are not impaired. Moreover, although various embodiments and modifications have been described above, the present invention is not limited to their content. Other aspects conceivable within the scope of the technical concept of the present invention also fall within the scope of protection of the present invention.

[0126] The disclosure of the following priority application is included here by reference: Japanese patent application no. 2018-219305 (filed on November 22, 2018). Reference symbol list 1, 1A, 1B Cell Control Unit (CCU) 2 Battery Control Unit (BCU) 3 battery cells 4 lead-acid storage batteries 5 integrated cell control circuits (cell control ICs) 7 first control unit 8 first time cue 9 Time control unit 10-sided CCU wireless device 11 CCU-side antenna 12 compensation units 13 CCU-side transmitter unit 14-sided CCU receiver unit 15 Power supply unit 16 second control unit 17 second time cue 18-sided BCU wireless device 19-sided BCU antenna 20-sided BCU transmitter unit 21 BCU-side receiving unit

Claims

Cell control device (1) comprising: a balancing unit (12) which balances the charge states of several secondary batteries (3) by discharging or charging them, a first timer (8) which measures the time elapsed since the start of balancing, a receiving unit (14) which receives a balancing command signal containing information relating to the balancing times of the secondary batteries (3), and a first control unit (7) which controls the balancing unit (12) on the basis of the time elapsed since the start of balancing and the balancing command signal, wherein the elapsed time is measured by the first timer (8) and the balancing command signal is received by the receiving unit (14), wherein the receiving unit (14) receives the information about the several secondary batteries (3) by means of the individual balancing command signal, characterized in that the first control unit (7) defines respective cells as balancing target cells.whose balancing time among the multiple secondary batteries (3) is not 0, and controls the balancing unit (12) such that the balancing of odd-numbered cells among the target balancing cells and the balancing of even-numbered cells among the target balancing cells are performed alternately and repeatedly. Cell control device (1) according to claim 1, wherein the balancing of the odd-numbered cells comprises: determining the shortest balancing time among the balancing times for the odd-numbered cells, which are the target balancing cells, as the discharge time for the odd-numbered cells in the first timer (8) based on the balancing command signal or an updated balancing time; causing the balancing unit (12) to initiate the discharge of the odd-numbered cells; causing the balancing unit (12) to interrupt the discharge of the odd-numbered cells as soon as the time elapsed since the start of the discharge of the odd-numbered cells reaches the discharge time for the odd-numbered cells, the elapsed time being measured by the first timer (8); updating the balancing time for each of the odd-numbered cells, which are the target balancing cells.based on the discharge time for the odd-numbered cells and excluding an odd-numbered cell whose updated balancing time is 0 from the target balancing cells, and wherein the balancing of the even-numbered cells comprises: setting the shortest balancing time among the balancing times for the even-numbered cells, which are the target balancing cells, as the discharge time for the even-numbered cells in the first timer (8) based on the balancing command signal or an updated balancing time, causing the balancing unit (12) to initiate the discharge of the even-numbered cells, causing the balancing unit (12) to stop the discharge of the even-numbered cells as soon as the time elapsed since the start of the discharge of the even-numbered cells reaches the discharge time for the even-numbered cells, the elapsed time being measured by the first timer (8),Updating the balancing time for each of the even-numbered cells that are the balancing target cells, based on the discharge time for the even-numbered cells, and excluding an even-numbered cell whose updated balancing time is 0 from the balancing target cells. Cell control device (1) according to claim 1, wherein the first control unit (7) defines as balancing target cells respective cells whose balancing time among the multiple secondary batteries (3) is not 0, and controls the balancing unit (12) such that the balancing of all balancing target cells is performed repeatedly. Cell control device (1) according to claim 3, wherein the balancing of all target cells comprises: determining the shortest balancing time among the balancing times for the target cells as the discharge time for all cells in the first timer (8) based on the balancing command signal or an updated balancing time; causing the balancing unit (12) to initiate the discharge of the target cells; causing the balancing unit (12) to interrupt the discharge of the target cells as soon as the time elapsed since the start of the discharge of the target cells reaches the discharge time for all cells, the elapsed time being measured by the first timer (8); updating the balancing time for each of the target cells based on the discharge time for all cells; and excluding a cell whose updated balancing time is 0 from the target cells. Cell control device (1) according to claim 1, wherein the first control unit (7) defines as balancing target cells respective cells whose balancing time among the multiple secondary batteries (3) is not 0, and controls the balancing unit (12) such that the balancing of each individual balancing target cell is performed repeatedly. Cell control device (1) according to claim 5, wherein the balancing of each individual balancing target cell comprises: selecting a discharge target cell from the balancing target cells, setting a balancing time for the discharge target cell as the discharge time for individual cells in the first timer (8) based on the balancing command signal, causing the balancing unit (12) to initiate the discharge of the discharge target cell, causing the balancing unit (12) to interrupt the discharge of the discharge target cell as soon as the time elapsed since the start of the discharge of the discharge target cell reaches the discharge time for individual cells, the elapsed time being measured by the first timer (8), and excluding the discharge target cell whose discharge is complete from the balancing target cells. Cell control device (1) according to one of claims 1 to 6, wherein the receiving unit (14) receives the compensation command signal wirelessly. Cell control device (1) according to one of claims 1 to 6, which further comprises a time control unit (9) which stops the cell control device (1) when an abnormality occurs in it. Battery management system comprising: the cell control unit (1) according to any one of claims 1 to 8 and a battery control unit (2) designed to perform communication with the cell control unit (1) according to any one of claims 1 to 6, wherein the battery control unit (2) comprises: a second control unit (16) that calculates balancing times for the multiple secondary batteries (3), and a transmitter unit (20) that sends a balancing command signal to the cell control unit (1) containing information about the balancing times calculated by the second control unit (16), wherein the transmitter unit (20) sends the information about the multiple secondary batteries (3) by means of the single balancing command signal. Battery management system according to claim 9, wherein the transmitting unit (20) wirelessly transmits the balancing command signal. Battery management system according to claim 9, which further comprises a second timer (17) that measures the elapsed time since the battery control unit (2) has entered a predetermined low-power mode, wherein the second control unit (16) sets a predetermined activation time in the second timer (17) and then puts the battery control unit (2) into the low-power mode, and the second timer reactivates the battery control unit (2) as soon as the elapsed time since the battery control unit (2) was put into the low-power mode reaches the activation time. Battery system comprising: the battery management system according to one of claims 9 to 11 and several secondary batteries (3) which are to be balanced by the battery management system.

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