Battery control device and battery system

Abstract

A battery control device controls a battery system including a plurality of battery cells connected in series, and a bypass circuit that bypasses each of the battery cells. Discharging is performed from each of the battery cells until the remaining amount of the battery cells decreases to a predetermined value. In the case where the remaining amount of the battery cells decreases to the predetermined value, each of the battery cells is bypassed by the bypass circuit. In the case where the remaining amount of all of the plurality of battery cells decreases to the predetermined value, discharging is performed from all of the plurality of battery cells.

Description

Technical Field

[0001] The invention relates to a battery control device and a battery system. Background Art

[0002] As a discharge system for controlling the discharge of a battery device (hereinafter referred to as a "battery pack") consisting of a plurality of batteries (hereinafter referred to as "battery cells") connected in series, there is a known construction in which a battery cell to be excluded from discharge is selected based on the state of each battery cell, and discharge is performed from another battery cell by bypassing the battery cell to be excluded from discharge (for example, refer to Patent Document 1).

[0003] Patent Document 1: JP-A-2013-31247

[0004] In the discharge system described in Patent Document 1, when a battery cell whose discharge reaches the discharge termination voltage is selected as a battery cell to be excluded from discharge, and discharge is performed from other battery cells in sequence by bypassing the battery cell, discharge of all battery cells can be performed without leaving discharge capacity.

[0005] However, a discharge current limit value, which is an allowable value of the discharge current, and a system minimum current value, which is a current value required for the system of the power supply destination to operate in the power saving mode, are set in each battery cell. Here, the discharge current limit value decreases as the remaining amount of the battery decreases, so it is necessary to select a battery cell whose discharge current limit value decreases to the system minimum current value as a battery cell to be excluded from discharge. Therefore, it is difficult to discharge all battery cells without a remaining discharge capacity, and the time to obtain a desired output is shortened. Summary of the invention

[0006] The present invention has been made in consideration of these circumstances, and an object of the present invention is to provide a battery control device and a battery system which can discharge all or all but a part of a plurality of battery cells by using a discharge capacity having high efficiency and can extend the time during which a desired output is obtained.

[0007] According to one aspect of the present invention, there is provided a battery control device, which controls a battery system including a plurality of battery cells connected in series, and a bypass circuit that bypasses each of the battery cells, performs discharge from each of the battery cells until the remaining amount of the battery cell decreases to a predetermined value, bypasses the battery cell by the bypass circuit when the remaining amount of the battery cell decreases to the predetermined value, and performs discharge from all or all of the plurality of battery cells except for a part thereof when the remaining amount of all or all of the plurality of battery cells decreases to the predetermined value.

[0008] According to another aspect of the present invention, there is provided a battery control device that controls a battery system including a plurality of batteries connected in series, and a bypass circuit that bypasses each of the batteries. The battery control device performs: a first process that preferentially performs bypassing by the bypass circuit for a battery whose remaining discharge amount until discharge is completed is smaller than that of other batteries, thereby reducing the difference in the remaining discharge amount until discharge of the plurality of batteries is completed, and a second process that completes discharge of the plurality of batteries after the first process.

[0009] According to another aspect of the present invention, there is provided a battery system, comprising: a plurality of battery cells connected in series; a bypass circuit that bypasses each of the battery cells; and a battery control device that controls the bypass circuit. The battery control device performs discharge from each of the battery cells until the remaining amount of the battery cell decreases to a predetermined value, bypasses the battery cell through the bypass circuit when the remaining amount of the battery cell decreases to the predetermined value, and performs discharge from all or all of the battery cells except for a part thereof when the remaining amount of all or all of the battery cells except for a part thereof decreases to the predetermined value.

[0010] According to another aspect of the present invention, there is provided a battery system, comprising: a plurality of batteries connected in series; a bypass circuit that bypasses each of the batteries; and a battery control device that controls the bypass circuit. The battery control device performs: a first process that preferentially bypasses a battery whose remaining discharge amount until discharge is completed is smaller than that of other batteries through the bypass circuit, thereby reducing the difference in the remaining discharge amount until discharge of the plurality of batteries is completed, and a second process that completes discharge of the plurality of batteries after the first process. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 FIG. 1 is a diagram schematically showing a battery system including a battery control device according to an embodiment of the present invention.

[0012] Figure 2 is a diagram for describing a method of setting a predetermined value.

[0013] Figure 3 This is a timing diagram for describing the discharge control of a battery pack by a battery control device.

[0014] Figure 4 FIG. 4 is a view schematically showing a battery system including a battery control device according to another embodiment of the present invention.

[0015] Figure 5 is a timing chart for describing the discharge control of the comparative example.

[0016] Figure 6 Is used to describe Figure 5 The timing chart in the table shows the discharge control of the comparative example.

[0017] Figure 7 is a timing chart for describing discharge control according to still another embodiment of the present invention.

[0018] Figure 8 Is used to describe Figure 7 A table of discharge control according to another embodiment of the present invention is shown in the timing diagram.

[0019] Fig. 9 Is used to describe Figure 8 The table in FIG. 1 is a table showing variations of the discharge control.

[0020] Fig.10 Is used to describe Figure 7 A timing diagram of a variation of the discharge control shown in the timing diagram in FIG. DETAILED DESCRIPTION

[0021] Hereinafter, description will be made based on the preferred embodiments of the present invention. Note that the present invention is not limited to the following embodiments and can be appropriately modified within the scope not exceeding the gist of the present invention. In addition, in the following embodiments, illustrations or descriptions of some configurations are omitted, but it goes without saying that, within the scope that does not cause any conflict with the contents described below, known or well-known technologies can be appropriately applied to the omitted technical details.

[0022] Figure 1 Schematically shows a view of a battery system 1 including a battery control device 100 according to an embodiment of the present invention. As shown in the figure, the battery system 1 includes a battery pack 10, a bypass circuit 20, and a battery control device 100. The battery pack 10 is a built-in vehicle or fixed power source including n (n is an integer of 2 or more) battery cells C1 to Cn connected in series. Although not particularly limited, the battery pack 10 of the present embodiment is a recycled battery, and there are differences in the degree of deterioration of each battery cell C1 to Cn. For example, the battery cells C1 to Cn are secondary batteries such as lithium-ion batteries and lithium-ion capacitors, and are charged by supplying power from an external system ES, and supplying power to the external system ES by discharging the charged electric energy. Note that the battery system 1 may include n (n is an integer of 2 or more) battery modules or battery packs connected in series, and a bypass circuit 20.

[0023] The battery pack 10 includes a plurality of voltage measuring units 12, a current measuring unit 13, and a battery temperature measuring unit 14. Each voltage measuring unit 12 is connected between each positive terminal and each negative terminal of the battery cells C1 to Cn. The voltage measuring unit 12 measures the inter-terminal voltage of each battery cell C1 to Cn.

[0024] The current measuring unit 13 is provided in a current path of the battery pack 10. The current measuring unit 13 measures the charge and discharge current of the battery pack 10. In addition, the battery temperature measuring unit 14 is provided in the battery pack 10. The battery temperature measuring unit 14 measures the battery temperature of the battery pack 10.

[0025] The bypass circuit 20 includes n (n is an integer of 2 or more) bypass circuits B1 to Bn, wherein each bypass circuit B1 to Bn is arranged in each battery cell C1 to Cn. Each bypass circuit B1 to Bn includes a bypass line BL and switches S1 and S2. The bypass line BL is a power line that bypasses each battery cell C1 to Cn. The switch S1 is arranged in the bypass line BL. For example, the switch S1 is a mechanical switch. The switch S2 is arranged between each positive electrode of the battery cells C1 to Cn and one end of the bypass line BL. For example, the switch S2 is a semiconductor switch.

[0026] The battery cell C1 on the starting end side and the battery cell Cn on the terminal side are connected to the external system ES. In the case where the switch S1 is turned off and the switch S2 is turned on in all the bypass circuits B1 to Bn, discharge from all the battery cells C1 to Cn to the external system ES is performed. On the other hand, in the case where the switch S2 is turned off and the switch S1 is turned on in any bypass circuit B1 to Bn, any battery cell C1 to Cn corresponding to any bypass circuit B1 to Bn is bypassed.

[0027] The battery control device 100 is connected to the battery pack 10 and the bypass circuit 20 and performs monitoring and control of the battery cells C1 to Cn and switching control of the bypass circuits B1 to Bn. The battery control device 100 of this embodiment switches the bypass circuits B1 to Bn based on the remaining current capacity of the battery cells C1 to Cn.

[0028] The battery control device 100 includes a measurement value acquisition unit 101 , a remaining quantity calculation unit 102 , a storage unit 103 , and a bypass control unit 104 .

[0029] The measurement value acquisition unit 101 is connected to the voltage measurement unit 12, the current measurement unit 13, and the battery temperature measurement unit 14. The measurement value acquisition unit 101 acquires measurement values ​​from the voltage measurement unit 12, the current measurement unit 13, and the battery temperature measurement unit 14, and stores the measurement values ​​in the storage unit 103.

[0030] The remaining amount calculation unit 102 calculates the remaining amount of each battery cell C1 to Cn based on the measurement value acquired by the measurement value acquisition unit 101. The remaining amount calculation unit 102 of this embodiment calculates the remaining current capacity of each battery cell C1 to Cn based on the change in the voltage value of each battery cell C1 to Cn acquired by the measurement value acquisition unit 101, and stores the remaining current capacity in the storage unit 103. Note that in calculating the remaining current capacity of each battery cell C1 to Cn, other known methods may be used.

[0031] The storage unit 103 stores the measured values ​​acquired by the measured value acquisition unit 101 and the calculated values ​​calculated by the remaining amount calculation unit 102. In addition, the storage unit 103 stores a program executed by the battery control unit 100.

[0032] The bypass control unit 104 controls the disconnection / connection switching of the switches S1 and S2 of each bypass circuit B1 to Bn based on the remaining current capacity of each battery cell C1 to Cn calculated by the remaining amount calculation unit 102. Specifically, in the case where the remaining current capacity of each battery cell C1 to Cn exceeds the predetermined value Rp, the bypass control unit 104 disconnects the switch S1 and connects the switch S2 for the corresponding one bypass circuit B1 to Bn. That is, in this case, the battery cells C1 to Cn are not bypassed. On the other hand, in the case where the remaining current capacity of each battery cell C1 to Cn is reduced to a predetermined value Rp or less, the bypass control unit 104 disconnects the switch S2 and connects the switch S1 for the corresponding one bypass circuit B1 to Bn. That is, in this case, the battery cells C1 to Cn are bypassed.

[0033] Here, for the battery cells C1 to Cn immediately set to the bypass state, the bypass control unit 104 continues the bypass state until the remaining current capacity of all other battery cells C1 to Cn decreases to a predetermined value Rp. Then, for all bypass circuits B1 to Bn, the bypass control unit 104 turns off the switch S1 and turns on the switch S2, thereby performing discharge from all battery cells C1 to Cn at the same time.

[0034] Figure 2 is a graph for describing a method of setting the predetermined value Rp. The upper graph in the accompanying drawing shows the relationship between the remaining current capacity of the battery cell C1 and the discharge current limit value of the battery cell C1. In addition, the lower graph in the accompanying drawing shows the relationship between the remaining current capacity of the battery cells C1 and C2 and the discharge current limit values ​​of the battery cells C1 and C2. Here, the discharge current limit value is an allowable value of the discharge current set from the perspective of maintaining the performance of each component constituting the battery cells C1 to Cn or preventing damage to each component.

[0035] like Figure 2As shown in the graph in , during the period when the remaining current capacity of battery cells C1 and C2 decreases from the maximum state (full charge: Rmax), the discharge current limit value of battery cells C1 and C2 is constant at the beginning, but decreases from the middle. Here, the discharge current limit value of each battery cell C1 to Cn is different from each other and also different between the unit cells C1 to Cn. In addition, the relationship between the discharge current limit value and the remaining current capacity of each battery cell C1 to Cn is also different from each other and also different between the battery cells C1 to Cn. In particular, the battery pack 10 of the present embodiment is a recycled battery pack, and there are differences in the degree of deterioration of each battery cell C1 to Cn. Therefore, in the battery pack 10 of the present embodiment, the deviation of the discharge current limit value between the battery cells C1 to Cn, or the deviation of the relationship between the discharge limit current value and the remaining current capacity is large.

[0036] In addition, from the perspective of the operation of the external system ES corresponding to the power supply from the battery pack 10, the system standard current value and the system minimum current value are set in each battery cell C1 to Cn. The system standard current value is a current value higher than the system minimum current value, and is a threshold value as to whether to impose restrictions on the power consumption of the external system ES. For example, in the case where the external system ES is an electric vehicle, the system standard current value corresponds to the current value of the maximum power consumption when traveling without any restrictions within the speed determined in the vehicle specifications. In the case where the discharge current limit value of each battery cell C1 to Cn becomes equal to or less than the system standard current value, the driving speed of the electric vehicle is limited to 60km / h or less, and the external system ES operates in power saving mode. On the other hand, the system minimum current value is the maximum current value required for the external system ES to operate in power saving mode. For example, in the case where the external system ES is an electric vehicle, the system minimum current value corresponds to the maximum power consumption current value when the vehicle travels at a speed of 60km / h or less. When the discharge current limit value of each battery cell C1 to Cn becomes equal to or less than the system minimum current value, it is determined that traveling at a speed of 60 km / h cannot be ensured, and thus driving of the vehicle is stopped due to the power shortage state.

[0037] Here, the predetermined value Rp is set so that the difference ΔR (=Rp-R0) between the predetermined value Rp and the remaining current capacity R0 at the time point when the discharge current limit value and the system minimum current value match each other is constant in all battery cells C1 to Cn. In addition, the predetermined value Rp is set to be equal to or greater than the remaining current capacity R1 at the time point when the discharge current limit value and the system standard current value match each other. In addition, in the present embodiment, the predetermined value Rp is set to be equal to or greater than the remaining current capacity R2 at the time point when the discharge current limit value decreases from the maximum value Imax.

[0038] Figure 31 is a timing chart for describing discharge control of the battery pack 10 by the battery control device 100. As shown in the timing chart, an example in which all the battery cells C1 to Cn are discharged from a fully charged state will be described.

[0039] In a state where all the battery cells C1 to Cn are fully charged, the battery control device 100 performs discharge from all the battery cells C1 to Cn. That is, for all the bypass circuits B1 to Bn, the switch S1 is turned off and the switch S2 is turned on. The battery control device 100 monitors the remaining current capacity of each battery cell C1 to Cn calculated by the remaining amount calculation unit 102, and always judges whether the remaining current capacity of each battery cell C1 to Cn exceeds the predetermined value Rp.

[0040] When a battery cell (e.g., C1 shown in the drawing) whose remaining current capacity is a predetermined value Rp is detected, the battery control device 100 turns off the switch S2 and turns on the switch S1 for the bypass circuit B1 corresponding to the battery cell C1. That is, the battery control unit 100 bypasses the battery cell C1 whose remaining current capacity is reduced to the predetermined value Rp, and performs discharge from all other battery cells C2, C3, ..., Cn.

[0041] Whenever a battery cell C2 to Cn whose remaining current capacity is equal to or less than a predetermined value Rp is detected, the battery control device 100 sequentially performs the following control: bypassing the corresponding battery cells C2 to Cn, and performing discharge from all other battery cells C3 to Cn. For example, as shown in the figure, for the bypass circuit B2 corresponding to the battery cell C2 whose remaining current capacity is the predetermined value Rp, the battery control device 100 turns off the switch S2 and turns on the switch S1. That is, the battery control unit 100 bypasses the battery cell C2 whose remaining current capacity is reduced to the predetermined value Rp, and performs discharge from all other battery cells C3, ..., Cn.

[0042] The battery control device 100 performs the above process until the remaining current capacity of all the battery cells C1 to Cn is reduced to the predetermined value Rp, and after the remaining current capacity of all the battery cells C1 to Cn is reduced to the predetermined value Rp, for the bypass circuits B1 to Bn of all the battery cells C1 to Cn, the battery control device 100 turns off the switch S1 and turns on the switch S2. That is, after the remaining current capacity of all the battery cells C1 to Cn uniformly becomes the predetermined value Rp, the battery control device 100 releases the bypass of all the battery cells C1 to Cn and performs discharge from all the battery cells C1 to Cn. Accordingly, the discharge current limit values ​​of all the unit cells C1 to Cn are simultaneously reduced to the system minimum current value. Therefore, all the battery cells C1 to Cn can be discharged by using a larger discharge capacity.

[0043] Here, when the discharge power is kept constant except for the discharge current limiting period, the battery cells C1 to Cn whose residual current capacity has been reduced to the predetermined value Rp are bypassed in sequence, so the discharge voltage is sequentially reduced, but the discharge current is sequentially increased. Therefore, the desired output can be obtained for a long time in one discharge cycle of the battery pack 10.

[0044] In addition, the discharge current limit period can be put into a period (end period) in one discharge cycle of the battery pack 10. In particular, in an electric vehicle, when the discharge current limit value of the battery cells C1 to Cn fluctuates up and down with the system standard current value set as the boundary value, the power saving mode and the release of the mode are repeated, which makes the user feel uncomfortable. Here, in the present embodiment, the predetermined value Rp is set to be equal to or greater than the remaining current capacity R1 at the time point when the discharge current limit value and the system standard current value match each other. Accordingly, in an electric vehicle, the power saving mode and the release of the mode can be prevented from being repeated, and the user's discomfort can be eliminated.

[0045] Here, from the perspective of ensuring load operation, it is necessary to prevent the total voltage [V] of the battery system 1 during discharge from falling below the minimum allowable total voltage V L For example, the minimum allowable total voltage V L It is set based on the load specification and is determined by the input voltage of the DC / AC inverter in the case of a system-related fixed battery system, and is determined by the input voltage range of the motor inverter in the case of a built-in vehicle battery system. Here, in this embodiment, bypass control of the battery cells C1 to Cn by the bypass circuits B1 to Bn is performed so that the total voltage [V] of the battery system 1 is maintained at the minimum allowable voltage V from the start of discharge to the completion of discharge. L or larger.

[0046] In addition, in the present embodiment, during the bypass control of the battery cells C1 to Cn by the bypass circuits B1 to Bn, the discharge power limit value [W] is maintained at the minimum allowable discharge power P L Here, the discharge power limit value [W] is a value obtained by multiplying the minimum value among the discharge current limit values ​​of the battery cells C1 to Cn by the total voltage of the battery system 1. Note that the minimum allowable discharge power P L It can be a constant value or a value that fluctuates depending on various conditions.

[0047] Hereinabove, the present invention has been described with reference to the embodiments, but the present invention is not limited to the above embodiments and may be modified within a scope not exceeding the gist of the present invention, or known or well-known techniques may be appropriately incorporated therein.

[0048] For example, in the above embodiment, the remaining amount of each battery cell C1 to Cn is defined as the remaining current capacity, but the remaining amount of each battery cell C1 to Cn may also be defined according to the state of charge (SOC) or voltage of each battery cell C1 to Cn.

[0049] In addition, in the above embodiment, control is performed to discharge all the battery cells C1 to Cn until the discharge current limit value decreases to the system minimum current value. However, for example, the same control may be performed for a plurality of battery cells other than a battery cell that is cracking or a battery cell with a high temperature.

[0050] Figure 4 1 is a view schematically showing a battery system 1′ including a battery control device 200 according to another embodiment of the present invention. The battery system 1′ shown in the figure includes a battery pack 10, a bypass circuit 20, and a battery control device 200. Note that the same reference numerals will be used for the same configurations as in the above-mentioned embodiment, and the description related to the above-mentioned embodiment will be cited.

[0051] The battery control device 200 of the present embodiment includes a remaining discharge capacity calculation unit 202 instead of the remaining amount calculation unit 102 in the above-mentioned embodiment. The battery control device 200 is connected to the battery pack 10 and the bypass circuit 20, and performs monitoring and control of each battery cell C1 to Cn and switching control of each bypass circuit B1 to Bn. The battery control device 200 controls the discharge of the battery pack 10 by switching each bypass circuit B1 to Bn based on the remaining discharge capacity RD until the discharge of each battery cell C1 to Cn is completed. Note that in the following description, the remaining discharge capacity RD until the discharge of each battery cell C1 to Cn is simply referred to as "remaining discharge capacity RD". The remaining discharge capacity RD is a capacity that can be discharged to reach the discharge end voltage when discharging each battery cell C1 to Cn.

[0052] The remaining discharge capacity calculation unit 202 calculates the remaining discharge capacity RD of each battery cell C1 to Cn based on the measurement value measured by the measurement value acquisition unit 101, and stores the remaining discharge capacity RD in the storage unit 103. The remaining discharge capacity calculation unit 202 of the present embodiment calculates the remaining discharge capacity RD [Ah] of each battery cell C1 to Cn by the following expression (1):

[0053] RD[Ah]=CC×SOC / 100...(1)

[0054] Assume that CC represents the current battery capacity (current capacity [Ah] in this embodiment) of each battery cell C1 to Cn, and the remaining discharge capacity calculation unit 202 calculates by using the following expression (2). SOC is the state of charge (SOC) [%] of each battery cell C1 to Cn, and can be estimated by various known methods such as a current integration method, an open circuit voltage acquisition method (voltage method), and a method combining the current integration method and the voltage method.

[0055] CC[Ah]=C0×SOH / 100...(2)

[0056] Assume that C0 represents the current capacity (Ah) of each battery cell C1 to Cn when it is a new product and is stored in the storage unit 103. In addition, SOH represents the state of health (SOH) of each battery cell C1 to Cn and is estimated by the remaining discharge capacity calculation unit 202 based on the measurement value acquired by the measurement value acquisition unit 101.

[0057] As a method of calculating the SOH of each battery cell C1 to Cn, various known methods of estimating the change in SOC over time and / or the increase in internal resistance over time can be used. Examples of methods of estimating SOH include a method by charge and discharge testing, a method by current integration method, a method by open circuit voltage measurement, a method by terminal voltage measurement, a model-based method (the above method is a method using the change in SOC over time), a method by AC impedance measurement, a method by a model-based adaptive digital filter, a method by linear regression from IV characteristics (current-voltage characteristics) (the slope of the straight line in the IV characteristics), and a method by step response (the above method is a method of performing estimation by using the increase in internal resistance over time).

[0058] The storage unit 103 stores the measurement values ​​acquired by the measurement value acquisition unit 101 and the calculated value of the remaining discharge capacity RD of each battery cell C1 to Cn calculated by the remaining discharge capacity calculation unit 202. In addition, the storage unit 103 stores a program executed by the battery control device 200.

[0059] The bypass control unit 104 controls the disconnection / on switching of the switches S1 and S2 of each bypass circuit B1 to Bn based on the remaining discharge capacity RD of each battery cell C1 to Cn calculated by the remaining discharge capacity calculation unit 202. Specifically, the bypass control unit 104 performs bypassing through each bypass circuit B1 to Bn preferentially for the battery cell C1 to Cn having a smaller remaining discharge capacity RD than the other battery cells C1 to Cn, thereby reducing the difference in the remaining discharge capacity RD among the plurality of battery cells C1 to Cn (first process). In addition, the bypass control unit 104 bypasses each battery cell C1 to Cn through each bypass circuit B1 to Bn, thereby making the remaining discharge capacity RD of all battery cells C1 to Cn equal during the execution of the first process. In addition, after executing the first process, the bypass control unit 104 connects all battery cells C1 to Cn having equal remaining discharge capacity RD in series through the bypass circuits B1 to Bn, and performs discharge from all the battery cells C1 to Cn connected in series until the discharge is completed (second process).

[0060] The bypass control unit 104 opens the switch S2 and closes the switch S1 for each bypass circuit B1 to Bn corresponding to each battery cell C1 to Cn to be bypassed. On the other hand, the bypass control unit 104 opens the switch S1 and closes the switch S2 for the bypass circuits B1 to Bn corresponding to the battery cells C1 to Cn connected in series.

[0061] Figure 5 is a timing chart for describing the discharge control of the comparative example. Figure 6 Is used to describe Figure 5 1 is a table of the discharge control of the comparative example shown in the timing chart in FIG. As shown in the figure, in the discharge control of the comparative example, the discharge of the eight battery cells C1 to C8 is controlled.

[0062] like Figure 5 and Figure 6 As shown, the initial discharge residual capacities RD of the eight battery cells C1 to C8 are assumed to be 100 [Ah], 99 [Ah], 98 [Ah], 95 [Ah], 90 [Ah], 89 [Ah], 87 [Ah], and 86 [Ah], respectively. In the discharge control of the comparative example, first, at time t0, the bypass control unit (not shown) connects the eight battery cells C1 to C8 in series. For the period from time t0 to t1, the discharge from the eight battery cells C1 to C8 is performed until the residual discharge capacity RD of any one of the eight battery cells C1 to C8 connected in series reaches 0 [Ah]. Specifically, the discharge amount of the eight battery cells C1 to C8 is 86 [Ah], and the battery cell C8 whose initial residual discharge capacity RD is the minimum value of 86 [Ah] is completely discharged.

[0063] Next, at time t1, the bypass control unit bypasses the fully discharged battery cell C8 through the bypass circuit B8, and causes the seven battery cells C1 to C7 to enter a state of being connected in series. From time t1 to t2, the discharge from the seven battery cells C1 to C7 is performed until the remaining discharge capacity RD of any one of the seven battery cells C1 to C7 connected in series reaches 0 [Ah]. Specifically, the discharge amount of the seven battery cells C1 to C7 is 1 [Ah], and the battery cell C7 whose remaining discharge capacity RD is the minimum value 1 [Ah] is completely discharged.

[0064] Next, at time t2, the bypass control unit bypasses the fully discharged battery cell C7 through the bypass circuit B7, and causes the six battery cells C1 to C6 to enter a state of being connected in series. From time t2 to t3, the six battery cells C1 to C6 are discharged until the remaining discharge capacity RD of any one of the six battery cells C1 to C6 connected in series reaches 0 [Ah]. Specifically, the discharge amount of the six battery cells C1 to C6 is 2 [Ah], and the battery cell C6 whose remaining discharge capacity RD is the minimum value 2 [Ah] is completely discharged.

[0065] Next, at time t3, the bypass control unit bypasses the fully discharged battery cell C6 through the bypass circuit B6, and causes the five battery cells C1 to C5 to enter a state of being connected in series. From time t3 to t4, the five battery cells C1 to C5 are discharged until the remaining discharge capacity RD of any one of the five battery cells C1 to C5 connected in series reaches 0 [Ah]. Specifically, the discharge amount of the five battery cells C1 to C5 is 1 [Ah], and the battery cell C5 whose remaining discharge capacity RD is the minimum value 1 [Ah] is completely discharged.

[0066] Next, at time t4, the bypass control unit bypasses the fully discharged battery cell C5 through the bypass circuit B5, and causes the four battery cells C1 to C4 to enter a state of being connected in series. From time t4 to t5, the four battery cells C1 to C4 are discharged until the remaining discharge capacity RD of any one of the four battery cells C1 to C4 connected in series reaches 0 [Ah]. Specifically, the discharge amount of the four battery cells C1 to C4 is 5 [Ah], and the battery cell C4 whose remaining discharge capacity RD is the minimum value of 5 [Ah] is completely discharged.

[0067] Next, at time t5, the bypass control unit bypasses the fully discharged battery cell C4 through the bypass circuit B4, and causes the three battery cells C1 to C3 to enter a state of being connected in series. From time t5 to t6, the three battery cells C1 to C3 are discharged until the remaining discharge capacity RD of any one of the three battery cells C1 to C3 connected in series reaches 0 [Ah]. Specifically, the discharge amount of the three battery cells C1 to C3 is 3 [Ah], and the battery cell C3 whose remaining discharge capacity RD is the minimum value 3 [Ah] is completely discharged.

[0068] Next, at time t6, the bypass control unit bypasses the fully discharged battery cell C3 through the bypass circuit B3, and causes the two battery cells C1 to C2 to enter a state of being connected in series. From time t6 to t7, discharge from the two battery cells C1 to C2 is performed until the remaining discharge capacity RD of any one of the two battery cells C1 to C2 connected in series reaches 0 [Ah]. Specifically, the discharge amount of the two battery cells C1 to C2 is 1 [Ah], and the battery cell C2 whose remaining discharge capacity RD is the minimum value 1 [Ah] is completely discharged.

[0069] Next, at time t7, the bypass control unit bypasses the completely discharged battery cell C2 through the bypass circuit B2, and causes one battery cell C1 to enter the connected state. From time t7 to t8, discharge from one battery cell C1 is performed until the remaining discharge capacity RD of one connected battery cell C1 reaches 0 [Ah]. Specifically, the discharge amount of one battery cell C1 is 1 [Ah], and the battery cell C1 with a remaining discharge capacity RD of 1 [Ah] is completely discharged.

[0070] Here, from the perspective of ensuring load operation, it is necessary to prevent the total voltage of the battery system during discharge from falling below the minimum allowable total voltage V L For example, the minimum allowable total voltage V L It is set based on the load specification and is determined by the input voltage of the DC / AC inverter in the case of a system-linked stationary battery system, and is determined by the input voltage range of the motor inverter in the case of a built-in vehicle battery system.

[0071] However, in the discharge control of the comparative example, at the point in time when the number of battery cells C1 to C8 connected in series is reduced to 1 to 3, there is a concern that the total voltage of the battery system may fall below the minimum allowable total voltage V L Here, in the discharge control of the present embodiment, the above-mentioned first process and second process are executed so that the total voltage of the battery system 1 is maintained equal to or greater than the minimum allowable total voltage V from the start of discharge to the completion of discharge. LHereinafter, the discharge control of this embodiment will be described in detail.

[0072] Figure 7 is a timing chart for describing the discharge control of this embodiment. Figure 8 Is used to describe Figure 7 1 is a table of the discharge control of the present embodiment shown in the timing chart in FIG. As shown in the figure, in the discharge control of the present embodiment, the discharge of the eight battery cells C1 to C8 is controlled.

[0073] like Figure 7 and Figure 8 As shown in FIG. 1 , the initial remaining discharge capacities RD of the eight battery cells C1 to C8 are assumed to be 100 [Ah], 99 [Ah], 98 [Ah], 95 [Ah], 90 [Ah], 89 [Ah], 87 [Ah], and 86 [Ah], respectively. In the discharge control of this embodiment, the bypass control unit 104 (refer to Figure 1 ) bypasses the battery cell C1 to C8 with a relatively smaller residual discharge capacity RD than other relatively smaller battery cells C1 to C8, thereby reducing the difference in the residual discharge capacity RD among the plurality of battery cells C1 to C8 (first process). In the first process, the bypass control unit 104 continuously bypasses the battery cell (C8 in the example) whose initial residual discharge capacity RD is the minimum value from the beginning to the end of the process, and bypasses other battery cells (C1 to C7 in the example) or connects other battery cells in series. Accordingly, the residual discharge capacity RD of all battery cells C1 to C8 uniformly becomes the minimum value of the initial residual discharge capacity RD (86Ah in the example). In addition, in the first process, the bypass control unit 104 does not bypass the battery cell (C1 in the example) whose initial residual discharge capacity RD is the maximum value from the beginning to the end of the process and maintains the battery cell in a connected state. The bypass control unit 104 connects or bypasses other battery cells (C2 to C7 in the example), thereby further increasing the number of bypasses as the residual discharge capacity RD becomes smaller, thereby gradually reducing the difference in the residual discharge capacity RD. Note that the first process described here is merely exemplary and can be modified appropriately.

[0074] Here, in the first process, the bypass control unit 104 selects the battery cells C1 to C8 to be bypassed to satisfy that the total voltage of the battery system 1 ′ is equal to or greater than the minimum allowable total voltage V L In the example, the bypass control unit 104 connects three or more battery cells C1 to C7 in series from the beginning to the end of the first process to maintain the total voltage of the battery system 1' greater than the minimum allowable total voltage V L .

[0075] exist Figure 7In the example of the first process shown, first, at time t1, the bypass control unit 104 bypasses the battery cells C5, C6, and C7 whose initial remaining discharge capacity RD is relatively smaller than the other battery cells, in addition to bypassing the battery cell C8 whose remaining discharge capacity RD is the minimum value, and connects in series the battery cells C1, C2, C3, and C4 whose initial remaining discharge capacity RD is relatively larger than the other battery cells. For from time t1 to t2, discharge from the four battery cells C1 to C4 connected in series is performed. The discharge amount of the four battery cells C1 to C4 is 7 [Ah]. Note that, for example, the remaining discharge capacity RD of the battery cell C4 can also be reduced to 86 [Ah] as a target value by setting the discharge amount from the four battery cells C1 to C4 to 9 [Ah].

[0076] Next, at time t2, the bypass control unit 104 bypasses the battery cell C3 in addition to the battery cells C5 to C8, and connects the other battery cells C1, C2, and C4 in series. For from time t2 to t3, discharge from the three battery cells C1, C2, and C4 connected in series is performed. The discharge amount from the three battery cells C1, C2, and C4 is 2 [Ah]. Accordingly, the remaining discharge capacity RD of the battery cell C4 is reduced to 86 [Ah] as the target value.

[0077] Next, at time t3, the bypass control unit 104 bypasses the battery cell C4 whose remaining discharge capacity RD has been reduced to the target value in conjunction with the battery cells C5 to C8, and the bypassed battery cell C3 maintains the connection state. For from time t3 to t4, discharge is performed from the three battery cells C1, C2, and C3 connected in series. The discharge amount from the three battery cells C1, C2, and C3 is 1 [Ah].

[0078] Next, at time t4, the bypass control unit 104 bypasses the battery cells C2 and C6 whose remaining discharge capacity RD has been reduced to the target value in conjunction with the battery cells C4 to C8, and maintains the bypassed battery cells C5 and C7 in a connected state. For from time t4 to t5, discharge from the four battery cells C1, C3, C5, and C7 connected in series is performed. The discharge amount from the four battery cells C1, C3, C5, and C7 is 1 [Ah]. Accordingly, the remaining discharge capacity RD of the battery cell C7 is reduced to 86 [Ah] as the target value. In addition, the remaining discharge capacity RD of the battery cells C1, C2, C3, C5, and C6 uniformly becomes 89 [Ah].

[0079] Next, at time t5, the bypass control unit 104 bypasses the battery cells C4, C7, and C8 whose remaining discharge capacity RD has been reduced to the target value, and maintains the bypassed battery cells C2 and C6 in the connected state. For from time t5 to t6, discharge from the five battery cells C1, C2, C3, C5, and C6 connected in series is performed. The discharge amount from the five battery cells C1, C2, C3, C5, and C6 is 3 [Ah]. Accordingly, the remaining discharge capacity RD of the battery cells C1, C2, C3, C5, and C6 is reduced to 86 [Ah] as the target value, and the remaining discharge capacity RD of the battery cells C1 to C8 uniformly becomes 86 [Ah] as the target value.

[0080] Next, at time t6, the bypass control unit 104 connects all the battery cells C1 to C8 in series. From time t6 to completion of discharge, discharge from all the battery cells C1 to C8 connected in series is performed (second process). The discharge amount of all the battery cells C1 to C8 in the second process is 86 [Ah]. Accordingly, all the battery cells C1 to C8 complete discharge.

[0081] As described above, the battery control device 200 of the present embodiment performs the first process of reducing the difference in the remaining discharge capacity RD of the plurality of battery cells C1 to Cn by preferentially bypassing the battery cells C1 to Cn having a relatively smaller remaining discharge capacity RD than the other battery cells C1 to Cn through the bypass circuits B1 to Bn, rather than bypassing the battery cells C1 to Cn that have completed discharge in sequence as in the above-mentioned comparative example. In addition, after performing the first process, the battery control device 200 connects all the battery cells C1 to Cn in series and performs discharge therefrom until the discharge is completed. Accordingly, during the period in which the discharge of all the battery cells C1 to Cn is completed after the first process is performed, all the battery cells C1 to Cn can be maintained in a state of being connected in series. Therefore, during this period, the total voltage of the battery system 1′ can be maintained at a higher state compared with the above-mentioned comparative example. In addition, since the total voltage can be maintained at a higher state, the time for which the desired discharge power can be output from the battery pack 10 can be further extended compared with the above-mentioned comparative example.

[0082] In addition, in the first process, the battery control device 200 of the present embodiment reduces the remaining discharge capacity RD of the plurality of battery cells C1 to Cn to the minimum value at the start time of the first process. Accordingly, the discharge completion time of all battery cells C1 to Cn becomes consistent, and the bypass time of the battery cells C1 to Cn that complete the discharge also becomes consistent.

[0083] In addition, the battery control device 200 of the present embodiment selects the battery cells C1 to Cn to be bypassed so that the total voltage of the battery system 1′ during the execution of the first process is maintained equal to or greater than the minimum allowable total voltage VL Accordingly, in the first process, the total voltage of the battery system 1′ is prevented from being lower than the minimum allowable total voltage V of the power system (not shown). L At the same time, the remaining discharge capacities RD of the plurality of battery cells C1 to Cn can be made consistent.

[0084] Fig.10 Is used to describe Figure 7 1 is a timing chart of a variation of the discharge control shown in the timing chart in FIG. In the discharge control shown in the figure, the discharge power limit value [W] in the first process is maintained equal to or greater than the minimum allowable discharge power P L Here, the discharge power limit value [W] is a value obtained by multiplying the minimum value among the discharge current limit values ​​of the battery cells C1 to Cn by the total voltage of the battery system 1. Note that the minimum allowable discharge power P L It can be a constant value or a value that fluctuates depending on various conditions.

[0085] In the above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above embodiment, and modifications can be made within the scope not exceeding the gist of the present invention, or known or well-known technologies can be appropriately incorporated therein.

[0086] For example, in the above-mentioned embodiment, the remaining discharge amount until the discharge of each battery cell C1 to Cn is completed is defined by the remaining discharge capacity RD [Ah] which is the current capacity, but the remaining discharge amount until the discharge of each battery cell C1 to Cn is completed may also be defined by content related to an indicator, or may also be defined by SOC, open circuit voltage (OCV), etc.

[0087] In addition, in the above-mentioned embodiment, in the first process, the remaining discharge capacity RD of the plurality of battery cells C1 to Cn is reduced to the minimum value at the start time of the first process, but the remaining discharge capacity RD of the plurality of battery cells C1 to Cn may also be reduced until the remaining discharge capacity RD is less than the minimum value at the start time of the first process.

[0088] In addition, from the perspective of maintaining the discharge completion timing of all the battery cells C1 to Cn consistent when the remaining discharge capacities RD of all the battery cells C1 to Cn are finally exhausted, it is preferred that the remaining discharge capacities RD of the plurality of battery cells C1 to Cn become consistent in the first process. However, it is not necessary to make the remaining discharge capacities RD of the plurality of battery cells C1 to Cn consistent in the first process, and the difference in the remaining discharge capacities RD of the plurality of battery cells C1 to Cn may be reduced in the first process.

[0089] In addition, the combination of the connected battery cells C1 to C8 at each time or the discharge amount of each battery cell C1 to C8 at each time is only illustrative. Fig. 9 As shown in the table in , a combination of the battery cells C1 to C8 connected at each time may be selected, or the discharge amount of each battery cell C1 to C8 at each time may be adjusted.

[0090] In the battery control device of the present invention, the predetermined value may be any one of a remaining current capacity of the battery cell, a charging rate of the battery cell, and a voltage of the battery cell.

[0091] In the battery control device of the present invention, the predetermined value can be set based on the following numerical values: a discharge current limit value which is an allowable value of the discharge current of the battery cell, a system minimum current value which is a current value required for the system of the power supply destination to operate in a power saving mode, and a system standard current value, wherein the system standard current value is a threshold value for imposing restrictions on the power consumption of the system of the power supply destination, which is higher than the system minimum current value and lower than the maximum value of the discharge current limit value.

[0092] In the battery control device of the present invention, the predetermined value is set to be equal to or larger than the remaining amount at which the discharge current limit value and the system standard current value match each other.

[0093] In the battery control device of the present invention, the total voltage of the battery system during the process of bypassing the battery cell through the bypass circuit can be equal to or greater than the minimum allowable total voltage of the battery system, or the discharge power limit value during the process of bypassing the battery cell through the bypass circuit can be equal to or greater than the minimum allowable discharge power.

[0094] In the battery control device of the present invention, in the first process, the remaining discharge amount until the discharge of the plurality of batteries is completed can be reduced to be equal to or less than the minimum value at the start time of the first process.

[0095] In the battery control device of the present invention, the total voltage of the battery system during the execution of the first process can be equal to or greater than the minimum allowable total voltage of the battery system, or the anti-electric power limit value during the process of bypassing the battery cell through the bypass circuit can be equal to or greater than the minimum allowable discharge power.

[0096] According to the present invention, the following controls are sequentially performed: bypassing a battery cell whose remaining amount is reduced to a predetermined value or less, performing discharge from all or a part of other battery cells. In addition, the remaining amount of all or a part of a plurality of battery cells is made consistent with a predetermined value, bypassing for all or a part of a plurality of battery cells is released, and discharging is performed from all or a part of a plurality of battery cells. In addition, according to the present invention, the difference in the remaining discharge amount until the discharge of a plurality of batteries is completed is reduced by preferentially bypassing a battery whose remaining discharge amount until the discharge is completed is smaller than that of other batteries, and then the discharge of a plurality of batteries is completed. Accordingly, in all or a part of a plurality of battery cells except for a part thereof, the discharge can be efficiently performed by using the discharge capacity, and the time to obtain the desired output can be extended.

Claims

1. A battery control device that controls a battery system including a plurality of battery cells connected in series, and a bypass circuit that bypasses each of the battery cells, in, The battery control device performs, a first process of discharging each of the battery cells until the remaining amount of the battery cell decreases to a predetermined value, and after the remaining amount of the battery cell decreases to the predetermined value, bypassing the battery cell through the bypass circuit to set the remaining amount of all of the plurality of battery cells to the predetermined value, and a second process of discharging all of the plurality of battery cells having the remaining amounts set to the predetermined values ​​after the first process, wherein during execution of the first process and the second process except for a discharge current limiting period, the discharge power from the battery system is constantly maintained, The predetermined value is set based on a discharge current limit value, a system minimum current value, and a system standard current value, wherein the discharge current limit value is an allowable value of the discharge current of the battery unit, the system minimum current value is a current value required for the system of the power supply destination to operate in a power saving mode, and the system standard current value is a threshold value that imposes restrictions on the power consumption of the system of the power supply destination, which is higher than the system minimum current value and lower than the maximum value of the discharge current limit value. wherein the predetermined value is set to be equal to or greater than the remaining amount at a time point when the discharge current limit value is equal to the system standard current value; and Herein, the predetermined value is set so that a difference between the remaining current capacities at a time point when the discharge current limit value and the system minimum current value are equal to each other becomes constant across all the battery cells.

2. The battery control device according to claim 1, in, The predetermined value is a remaining current capacity of the battery cell.

3. The battery control device according to claim 1 or 2, in, The total voltage of the battery system during the process of bypassing the battery cell through the bypass circuit is equal to or greater than the lowest allowed total voltage of the battery system, or the discharge power limit value during the process of bypassing the battery cell through the bypass circuit is equal to or greater than the lowest allowed discharge power.

4. A battery control device that controls a battery system including a plurality of batteries connected in series, a plurality of bypass circuits that bypass each of the batteries, a first switch provided in the bypass circuit, and a second switch provided between each of the batteries and one end of the bypass circuit, wherein the degree of degradation of each of the batteries is different, in, The battery control device performs: a first process of reducing the difference in the remaining discharge amounts until the discharge of a plurality of the batteries is completed by preferentially performing bypassing through the bypass circuit for a battery whose remaining discharge amount until the discharge is completed is smaller than that of the other batteries, by turning off the second switch and turning on the first switch for each bypass circuit corresponding to each battery to be bypassed, and a second process, after the first process, by opening the first switch and closing the second switch for bypass circuits corresponding to batteries connected in series, thereby completing the discharge of the plurality of batteries; The first process starts from the start of discharge. wherein, in the first process, from the start time of the discharge to the end time of the first process, the battery having the largest remaining discharge amount at the start time of the discharge until the discharge is completed is connected uninterruptedly without being bypassed, and other batteries are connected or bypassed, so that the number of bypasses further increases as the remaining discharge amount is smaller, and therefore, the remaining discharge amount until the discharge of all of the multiple batteries is completed is set to the minimum value of the remaining discharge amount of the multiple batteries until the discharge is completed at the start time of the discharge, wherein, in the second process, the remaining discharge amounts until completion of discharge of all of the plurality of batteries having the minimum value of the remaining discharge amounts until completion of discharge of the plurality of batteries set at the start time of the first process are discharged until all of the plurality of batteries complete discharge at the same time.

5. The battery control device according to claim 4, in, The total voltage of the battery system during execution of the first process is equal to or greater than a minimum allowable total voltage of the battery system, or the discharge power limit value during execution of the first process is equal to or greater than a minimum allowable discharge power.

6. A battery system comprising: a plurality of battery cells connected in series; a bypass circuit that bypasses each of the battery cells; as well as a battery control device that controls the bypass circuit, Wherein, the battery control device executes, a first process of discharging each of the battery cells until the remaining amount of the battery cell decreases to a predetermined value, and after the remaining amount of the battery cell decreases to the predetermined value, bypassing the battery cell through the bypass circuit to set the remaining amount of all the plurality of battery cells to the predetermined value; and a second process of discharging all of the plurality of battery cells having the remaining amounts set to the predetermined values ​​after the first process, wherein during execution of the first process and the second process except for a discharge current limiting period, the discharge power from the battery system is constantly maintained, The predetermined value is set based on a discharge current limit value, a system minimum current value, and a system standard current value, wherein the discharge current limit value is an allowable value of the discharge current of the battery unit, the system minimum current value is a current value required for the system of the power supply destination to operate in a power saving mode, and the system standard current value is a threshold value that imposes restrictions on the power consumption of the system of the power supply destination, which is higher than the system minimum current value and lower than the maximum value of the discharge current limit value. wherein the predetermined value is set to be equal to or greater than the remaining amount at a time point when the discharge current limit value is equal to the system standard current value; and Herein, the predetermined value is set so that a difference between the remaining current capacities at a time point when the discharge current limit value and the system minimum current value are equal to each other becomes constant across all the battery cells.

7. A battery system comprising: A plurality of batteries connected in series, wherein the degree of degradation of each of the batteries differs; a plurality of bypass circuits which bypass each of the batteries, a first switch provided in the bypass circuit, and a second switch provided between each battery and one end of the bypass circuit; as well as a battery control device that controls the bypass circuit, Wherein, the battery control device performs: a first process of reducing the difference in the remaining discharge amounts until the discharge of a plurality of the batteries is completed by preferentially performing bypassing through the bypass circuit for a battery whose remaining discharge amount until the discharge is completed is smaller than that of the other batteries, by turning off the second switch and turning on the first switch for each bypass circuit corresponding to each battery to be bypassed, and a second process, after the first process, by opening the first switch and closing the second switch for bypass circuits corresponding to batteries connected in series, thereby completing the discharge of the plurality of batteries; The first process starts from the start of discharge. wherein, in the first process, from the start time of the discharge to the end time of the first process, the battery having the largest remaining discharge amount at the start time of the discharge until the discharge is completed is connected uninterruptedly without being bypassed, and other batteries are connected or bypassed, so that the number of bypasses further increases as the remaining discharge amount is smaller, and therefore, the remaining discharge amount until the discharge of all of the multiple batteries is completed is set to the minimum value of the remaining discharge amount of the multiple batteries until the discharge is completed at the start time of the discharge, wherein, in the second process, the remaining discharge amounts until completion of discharge of all of the plurality of batteries having the minimum value of the remaining discharge amounts until completion of discharge of the plurality of batteries set at the start time of the first process are discharged until all of the plurality of batteries complete discharge at the same time.

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