Battery control device, battery system, and battery control method

Abstract

A battery control device is configured to control a battery system including batteries connected in series and a bypass circuit configured to selectively bypass each of the batteries. The battery control device includes: a processor; and a memory having instructions, when executed by the processor, to cause the battery control device to perform operations, the operations including: performing a first process that causes the bypass circuit to preferentially bypass a battery with a smaller remaining charge until completion of charging than other batteries, and charging at least one of the batteries such that the difference in remaining charge until completion of charging among the batteries decreases; and performing a second process that, after the first process, charges the batteries until charging is complete.

Description

Technical Field

[0001] This disclosure relates to a battery control device, a battery system, and a battery control method. Background Technology

[0002] As a system configured to control the charging of a battery device comprising multiple batteries connected in series, Patent Document 1 describes a system configured to select a battery to be avoided from charging based on the state of each battery and bypass the battery to be avoided from charging in order to charge the other batteries.

[0003] Patent Document 1: JP-A-2013-031249 Summary of the Invention

[0004] In the system described in Patent Document 1, all batteries are charged by connecting multiple batteries in series to perform constant current constant voltage charging (CCCV charging). Then, the process of bypassing fully charged batteries as batteries to avoid charging is performed sequentially, and CCCV charging is performed on the other batteries to fully charge them. However, ultimately, while the other batteries are bypassed, CCCV charging is only performed on one battery, resulting in a low overall system voltage.

[0005] In view of the above, the purpose of this disclosure is to provide a battery control device, a battery system, and a battery control method that can prevent a drop in total voltage during charging in a battery system comprising multiple batteries connected in series.

[0006] This disclosure provides a battery control device configured to control a battery system including a plurality of batteries connected in series and a bypass circuit configured to selectively bypass each of the plurality of batteries. The battery control device includes: a processor; and a memory having instructions, when executed by the processor, to cause the battery control device to perform operations, the operations including: performing a first process to cause the bypass circuit to preferentially bypass a battery among the plurality of batteries with a smaller remaining charge until completion of charging than other batteries, and charging at least one of the plurality of batteries such that the difference in remaining charge until completion of charging among the plurality of batteries decreases; and performing a second process after the first process to charge the plurality of batteries until completion of charging.

[0007] This disclosure provides a battery system comprising: a plurality of batteries connected in series; a bypass circuit configured to selectively bypass each of the plurality of batteries; and a battery control device configured to control the bypass circuit, wherein the battery control device includes: a processor; and a memory having instructions, when executed by the processor, to cause the battery control device to perform operations, the operations including: performing a first process to cause the bypass circuit to preferentially bypass a battery among the plurality of batteries with a smaller remaining charge until completion of charging than other batteries, and charging at least one of the plurality of batteries such that the difference in remaining charge until completion of charging among the plurality of batteries decreases; and performing a second process after the first process to charge the plurality of batteries until completion of charging.

[0008] This disclosure provides a battery control method executed by using a battery control device configured to control a battery system including a plurality of batteries connected in series and a bypass circuit configured to selectively bypass each of the plurality of batteries. The battery control method includes: performing a first process in which the bypass circuit preferentially bypasses a battery among the plurality of batteries whose remaining charge until completion is smaller than that of other batteries, and charging at least one of the plurality of batteries such that the difference in remaining charge until completion of charging of the plurality of batteries decreases; and performing a second process after the first process in which the plurality of batteries are charged until completion of charging.

[0009] According to this disclosure, in a battery system comprising multiple batteries connected in series, a drop in total voltage during charging can be prevented. Attached Figure Description

[0010] Figure 1 This is a schematic diagram showing a battery system including a battery control device according to a first embodiment of the present disclosure;

[0011] Figure 2 This shows a timing diagram of the charging control in the comparative example;

[0012] Figure 3 It is shown in Figure 2 The timing diagram shows the charging control table in the comparative example;

[0013] Figure 4 This is a timing diagram illustrating the charging control in a first embodiment of this disclosure;

[0014] Figure 5 It is shown in Figure 4 The timing diagram shows the charging control table in the first embodiment of this disclosure; and

[0015] Figure 6 This is a timing diagram illustrating the charging control in a second embodiment of the present disclosure. Detailed Implementation

[0016] The present disclosure will now be described with reference to preferred embodiments. The present disclosure is not limited to the embodiments described below, and embodiments may be appropriately modified without departing from the essence of the present disclosure. In the embodiments described below, some constructions are not shown or described, but known or publicly known techniques may be appropriately applied to the omitted technical details without conflicting with the content described below.

[0017] Figure 1 This is a schematic diagram illustrating a battery system 1 including a battery control device 100 according to a first embodiment of the present disclosure. As shown, the battery system 1 includes a battery pack 10, a bypass circuit 20, a charging circuit 30, and a battery control device 100. The battery pack 10 is an on-board or stationary power source, comprising n (n is an integer greater than or equal to 2) battery cells C1 to Cn connected in series. Although not particularly limited, the battery pack 10 in the first embodiment is obtained by regenerating used batteries, and the battery cells C1 to Cn have different degrees of degradation. For example, the battery cells C1 to Cn are secondary batteries such as lithium-ion batteries and lithium-ion capacitors, and are charged by receiving power from an external system ES through the charging circuit 30, and supplying the charged power to the external system ES. The battery system 1 may include n battery modules or battery packs connected in series, instead of n battery cells C1 to Cn connected in series, and may include a bypass circuit that bypasses each battery module or battery pack.

[0018] The battery pack 10 includes multiple voltage measuring units 12, current measuring units 13, and battery temperature measuring units 14. The voltage measuring units 12 are connected between the positive and negative terminals of each of the battery cells C1 to Cn. The voltage measuring units 12 measure the voltage between the terminals of each of the battery cells C1 to Cn.

[0019] A current measuring unit 13 is installed in the current path of the battery pack 10. The current measuring unit 13 measures the charging and discharging current of the battery pack 10. In addition, the battery pack 10 is provided with a battery temperature measuring unit 14. The battery temperature measuring unit 14 measures the battery temperature of the battery pack 10.

[0020] The bypass circuit 20 includes n (n is an integer greater than or equal to 2) bypass circuits B1 to Bn for 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 of the battery cells C1 to Cn. Switch S1 is disposed on the bypass line BL. Switch S1 is, for example, a mechanical switch. Switch S2 is disposed between the positive terminal of each of the battery cells C1 to Cn and one end of the bypass line BL. Switch S2 is, for example, a semiconductor switch.

[0021] Battery unit C1 at the beginning is connected to the external system ES via charging circuit 30, and battery unit Cn at the end is also connected to the external system ES. When switch S1 in all bypass circuits B1 to Bn is open and switch S2 is closed, all battery units C1 to Cn are connected in series to the external system ES and charging circuit 30. On the other hand, when switch S2 in any bypass circuit B1 to Bn is open and switch S1 is closed, the battery units C1 to Cn corresponding to the bypass circuits B1 to Bn are bypassed.

[0022] The battery control device 100 is connected to the battery pack 10, the bypass circuit 20, and the charging circuit 30, and performs monitoring and control on each of the battery cells C1 to Cn, switching control on each of the bypass circuits B1 to Bn, and charging control via the charging circuit 30. In the first embodiment, the battery control device 100 switches each of the bypass circuits B1 to Bn based on the remaining charging capacity RC of each of the battery cells C1 to Cn until full charging is achieved, and controls the charging of the battery pack 10 via the charging circuit 30. In the following description, the remaining charging capacity RC of the battery cells C1 to Cn until full charging is achieved is simply referred to as the remaining charging capacity RC. The remaining charging capacity RC is the capacity that can charge each of the battery cells C1 to Cn until the charging termination voltage is reached, and is not the capacity that can discharge to reach the discharge termination voltage of each of the battery cells C1 to Cn.

[0023] The battery control device 100 includes a measurement value acquisition unit 101, a remaining charge capacity calculation unit 102, a storage unit 103, a bypass control unit 104, and a charging control unit 105. The battery control device 100 may include a processor and a memory having instructions, when executed by the processor, to cause the battery control device 100 to perform operations including a first process and a second process, described later, via the measurement value acquisition unit 101, the remaining charge capacity calculation unit 102, the bypass control unit 104, and the charging control unit 105. The storage unit 103 is an example of a memory.

[0024] 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 acquired measurement values ​​in the storage unit 103.

[0025] The remaining charging capacity calculation unit 102 calculates the remaining charging capacity RC of each of the battery units C1 to Cn based on the measurement values ​​obtained by the measurement value acquisition unit 101, and stores the calculated values ​​in the storage unit 103. The remaining charging capacity calculation unit 102 in the first embodiment calculates the remaining charging capacity RC[Ah] of each of the battery units C1 to Cn using the following formula (1).

[0026] RC[Ah]=CC×(100-SOC) / 100…(1)

[0027] Here, CC is the current battery capacity (current capacity [Ah] in the first embodiment) of each of the battery cells C1 to Cn, and is calculated by the remaining charge capacity calculation unit 102 using the following formula (2). SOC is the state of charge (SOC) [%] of each of the battery cells C1 to Cn, and can be estimated using various known methods such as the current integration method, the method for obtaining SOC from the open-circuit voltage (voltage method), and the method combining the current integration method and the voltage method.

[0028] CC[Ah]=C0×SOH / 100…(2)

[0029] Here, C0 is the current capacity (Ah) of each of the battery cells C1 to Cn when the battery cell is new, and it is stored in the storage unit 103. In addition, SOH is the state of health (SOH) of each of the battery cells C1 to Cn, and it is estimated by the remaining charge capacity calculation unit 102 based on the measurement value obtained by the measurement value acquisition unit 101.

[0030] As a method for calculating the State of Harmony (SOH) of each of the battery cells C1 to Cn, various known estimation methods can be used, including those based on the time-varying SOC and / or the time-increasing internal resistance. Examples of SOH estimation methods include: methods based on charge-discharge tests, methods based on current integration, methods based on open-circuit voltage measurements, methods based on terminal voltage measurements, and model-based methods (these all use methods that use the time-varying SOC); as well as methods based on AC impedance measurements, methods using model-based adaptive digital filters, methods based on linear regression of the IV characteristic (current-voltage characteristic) (the slope of the IV characteristic line), and methods based on step response (these all use estimation methods that use the time-increasing internal resistance).

[0031] Storage unit 103 stores the measured values ​​acquired by measurement value acquisition unit 101 and the calculated values ​​of the remaining charging capacity RC of each of battery units C1 to Cn acquired by remaining charging capacity calculation unit 102. Furthermore, storage unit 103 stores the program executed by battery control device 100.

[0032] The bypass control unit 104 controls the switching of switches S1 and S2 of each of the bypass circuits B1 to Bn, based on the remaining charging capacity RC of each of the battery units C1 to Cn calculated by the remaining charging capacity calculation unit 102. The charging control unit 105 controls the charging from the charging circuit 30 to the series-connected battery units C1 to Cn, based on the remaining charging capacity RC of each of the battery units C1 to Cn calculated by the remaining charging capacity calculation unit 102.

[0033] Specifically, the bypass control unit 104 preferentially bypasses battery cells C1 to Cn with smaller remaining charging capacity RC than other battery cells C1 to Cn via bypass circuits B1 to Bn, and the charging control unit 105 charges the multiple battery cells C1 to Cn connected in series, thereby reducing the difference in the remaining charging capacity RC of the multiple battery cells C1 to Cn (first process). The charging control unit 105 controls the charging amount of the multiple battery cells C1 to Cn connected in series, so that the remaining charging capacity RC of all battery cells C1 to Cn is equal during the execution of the first process. Then, after the first process is executed, the bypass control unit 104 connects all battery cells C1 to Cn with equal remaining charging capacity RC in series via bypass circuits B1 to Bn, and the charging control unit 105 charges all battery cells C1 to Cn connected in series until charging is completed (second process).

[0034] The bypass control unit 104 disconnects switch S2 and closes switch S1 for each of the bypass circuits B1 to Bn corresponding to the battery cells C1 to Cn to be bypassed. On the other hand, the bypass control unit 104 disconnects switch S1 and closes switch S2 for each of the bypass circuits B1 to Bn corresponding to the battery cells C1 to Cn to be connected in series.

[0035] Figure 2 This shows a timing diagram of the charging control in the comparative example. Furthermore, Figure 3 It shows Figure 2 The timing diagrams show the charging control table in the comparative example. As shown in these diagrams, in the charging control according to the comparative example, the charging of eight battery cells C1 to C8 is controlled.

[0036] like Figure 2 and Figure 3 As shown, the initial remaining charge capacity RC of the eight battery cells C1 to C8 is set to 100 [Ah], 99 [Ah], 98 [Ah], 95 [Ah], 90 [Ah], 89 [Ah], 87 [Ah], and 86 [Ah], respectively. In the charging control according to the comparative example, firstly, during the time from time t0 to time t1, the bypass control unit (not shown) connects the eight battery cells C1 to C8 in series, and the charging control unit (not shown) charges the eight battery cells C1 to C8 connected in series until any one of the remaining charge capacity RC is 0 [Ah]. Specifically, the charge amount of the eight battery cells C1 to C8 is set to 86 [Ah], and the battery cell C8 with the smallest initial remaining charge capacity RC of 86 [Ah] is fully charged.

[0037] Next, at time t1, the bypass control unit bypasses the fully charged battery unit C8 via bypass circuit B8, and connects the seven battery units C1 to C7 in series. From time t1 to time t2, the charging control unit charges the seven series-connected battery units C1 to C7 until any one of them has a remaining charge capacity RC of 0 [Ah]. Specifically, the charge amount of the seven battery units C1 to C7 is set to 1 [Ah], and battery unit C7, which has the smallest remaining charge capacity RC of 1 [Ah], is fully charged.

[0038] Next, at time t2, the bypass control unit bypasses the fully charged battery unit C7 via bypass circuit B7, and connects the six battery units C1 to C6 in series. From time t2 to time t3, the charging control unit charges the six series-connected battery units C1 to C6 until any one of them has a remaining charge capacity RC of 0 [Ah]. Specifically, the charge amount for the six battery units C1 to C6 is set to 2 [Ah], and battery unit C6, with the smallest remaining charge capacity RC of 2 [Ah], is fully charged.

[0039] Next, at time t3, the bypass control unit bypasses the fully charged battery cell C6 via bypass circuit B6, and connects the five battery cells C1 to C5 in series. From time t3 to time t4, the charging control unit charges the five series-connected battery cells C1 to C5 until any one of them has a remaining charge capacity RC of 0 [Ah]. Specifically, the charge amount of the five battery cells C1 to C5 is set to 1 [Ah], and battery cell C5, which has the smallest remaining charge capacity RC of 1 [Ah], is fully charged.

[0040] Next, at time t4, the bypass control unit bypasses the fully charged battery unit C5 via bypass circuit B5, and connects the four battery units C1 to C4 in series. From time t4 to time t5, the charging control unit charges the four series-connected battery units C1 to C4 until any one of them has a remaining charge capacity RC of 0 [Ah]. Specifically, the charge amount for the four battery units C1 to C4 is set to 5 [Ah], and battery unit C4, which has the smallest remaining charge capacity RC of 5 [Ah], is fully charged.

[0041] Next, at time t5, the bypass control unit bypasses the fully charged battery cell C4 via bypass circuit B4, and connects the three battery cells C1 to C3 in series. From time t5 to time t6, the charging control unit charges the three series-connected battery cells C1 to C3 until any one of them has a remaining charge capacity RC of 0 [Ah]. Specifically, the charge amount for the three battery cells C1 to C3 is set to 3 [Ah], and battery cell C3, which has the smallest remaining charge capacity RC of 3 [Ah], is fully charged.

[0042] Next, at time t6, the bypass control unit bypasses the fully charged battery cell C3 via bypass circuit B3, and connects the two battery cells C1 and C2 in series. From time t6 to time t7, the charging control unit charges the two series-connected battery cells C1 and C2 until either of their remaining charging capacities RC is 0 [Ah]. Specifically, the charge amount for both battery cells C1 and C2 is set to 1 [Ah], and battery cell C2, with the minimum remaining charging capacity RC of 1 [Ah], is fully charged.

[0043] Finally, at time t7, the bypass control unit bypasses the fully charged battery unit C2 via bypass circuit B2 and puts a battery unit C1 into a connected state. From time t7 to time t8, the charging control unit charges the connected battery unit C1 until the remaining charging capacity RC is 0 [Ah]. Specifically, the charging amount of a battery unit C1 is set to 1 [Ah], and the battery unit C1 with a remaining charging capacity RC of 1 [Ah] is fully charged.

[0044] From the perspective of ensuring the operation of the load and charging circuit, it is necessary to prevent the total voltage of the battery system from dropping to the minimum permissible total voltage V, even during charging. L The following is the minimum permissible total voltage V. L Based on specifications such as charging circuits, examples of which include the minimum AC / DC output voltage required for charging from the power system in the case of grid-connected stationary battery systems, and examples of which include the minimum output voltage of regenerative power conversion circuits, on-board chargers (OBCs), etc. in the case of on-board battery systems.

[0045] However, in the charging control according to the comparative example, when the number of series-connected battery cells C1 to C8 is reduced to one or two, the total voltage of the battery system can drop below the minimum permissible total voltage V. L Therefore, in the charging control according to the first embodiment, the first process and the second process are performed such that the total voltage of the battery system 1 remains at the minimum allowable total voltage V from the start of charging to the completion of charging. L Or higher. The charging control in the first embodiment will now be described in detail.

[0046] Figure 4 This shows a timing diagram of the charging control in the first embodiment. Furthermore, Figure 5 It shows Figure 4 The timing diagrams show the charging control table in the first embodiment. As these diagrams show, in the charging control according to the first embodiment, the charging of eight battery cells C1 to C8 is controlled.

[0047] like Figure 4 and Figure 5 As shown, the initial remaining charging capacities RC of the eight battery cells C1 to C8 are set to 100 [Ah], 99 [Ah], 98 [Ah], 95 [Ah], 90 [Ah], 89 [Ah], 87 [Ah], and 86 [Ah], respectively. In the charging control according to the first embodiment, the bypass control unit 104 (see...) Figure 1 ) preferentially bypasses battery cells C1 to C8, which have relatively smaller remaining charging capacity RC than other battery cells, and the charging control unit 105 (see Figure 1 The process involves charging multiple battery cells C1 to Cn connected in series, reducing the difference in their remaining charge capacity RC (first process). In this first process, the bypass control unit 104 continuously bypasses the battery cell with the smallest initial remaining charge capacity RC (C8 in the illustrated example) from the beginning to the end of the process, and bypasses or connects other battery cells (C1 to C7 in the illustrated example) in series, thereby ensuring that the remaining charge capacity RC of all battery cells C1 to C8 equals the minimum initial remaining charge capacity RC (86 Ah in the illustrated example). Furthermore, in the first process, the bypass control unit 104 connects to the battery cell with the largest initial remaining charge capacity RC (C1 in the illustrated example) without bypassing the battery cell, and connects or bypasses other battery cells (C2 to C7 in the illustrated example), increasing the number of bypasses as the remaining charge capacity RC decreases, thus gradually reducing the difference in remaining charge capacity RC. This first process is an example and can be modified accordingly.

[0048] Here, in the first process, the bypass control unit 104 selects the battery cells C1 to C8 to be bypassed, such that the total voltage of the battery system 1 is equal to the minimum permissible total voltage V. L Or the above conditions. In the illustrated 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 above the minimum allowable total voltage V. L .

[0049] exist Figure 4In the example of the first process shown, firstly, at time t1, the bypass control unit 104 bypasses battery units C5, C6, and C7, which have initial remaining charging capacities RC relatively smaller than other battery units, except for battery unit C8, which has the smallest remaining charging capacity RC, and connects battery units C1, C2, C3, and C4, which have initial remaining charging capacities RC relatively larger than other battery units connected in series. During the time interval from time t1 to time t2, the charging control unit 105 charges the four battery units C1 to C4 connected in series. The charging amount for the four battery units C1 to C4 is 7 [Ah]. For example, the remaining charging capacity RC of battery unit C4 can be reduced to a target value of 86 [Ah] by setting the charging amount for the four battery units C1 to C4 to 9 [Ah].

[0050] Next, at time t2, the bypass control unit 104 bypasses battery unit C3 in addition to battery units C5 to C8, and connects other battery units C1, C2, and C4 in series. From time t2 to time t3, the charging control unit 105 charges the three series-connected battery units C1, C2, and C4. The total charge of the three battery units C1, C2, and C4 is 2 [Ah]. Therefore, the remaining charge capacity RC of battery unit C4 decreases to the target value of 86 [Ah].

[0051] Next, at time t3, the bypass control unit 104, together with battery units C5 to C8, bypasses battery unit C4, whose remaining charging capacity RC has decreased to the target value, and connects to the bypassed battery unit C3. During the time interval from time t3 to time t4, the charging control unit 105 charges the three battery units C1, C2, and C3 connected in series. The charging amount of the three battery units C1, C2, and C3 is 1 [Ah].

[0052] Next, at time t4, the bypass control unit 104 bypasses battery units C2 and C6 along with battery units C4 and C8, which have a target remaining charge capacity RC, and connects the bypassed battery units C5 and C7. During the time interval from time t4 to time t5, the charging control unit 105 charges the four battery units C1, C3, C5, and C7 connected in series. The charge amount for the four battery units C1, C3, C5, and C7 is 1 [Ah]. Therefore, the remaining charge capacity RC of battery unit C7 decreases to the target value of 86 [Ah]. Furthermore, the remaining charge capacity RC of battery units C1, C2, C3, C5, and C6 is equal to 89 [Ah].

[0053] Next, at time t5, the bypass control unit 104 bypasses battery units C4, C7, and C8, which have a target remaining charging capacity RC, and connects the bypassed battery units C2 and C6. From time t5 to time t6, the charging control unit 105 charges the five battery units C1, C2, C3, C5, and C6 connected in series. The charging amount of the five battery units C1, C2, C3, C5, and C6 is 3 [Ah]. Therefore, the remaining charging capacity RC of battery units C1, C2, C3, C5, and C6 is reduced to the target value of 86 [Ah], and the remaining charging capacity RC of all battery units C1 to C8 is equal to the target value of 86 [Ah].

[0054] Next, during the time from time t6 until the charging is complete, the charging control unit 105 charges all battery cells C1 to C8 connected in series (second process). In the second process, the total charge of all battery cells C1 to C8 is 86 [Ah]. Therefore, all battery cells C1 to C8 are fully charged.

[0055] As described above, unlike the comparative example where battery cells C1 to Cn are bypassed sequentially after charging, the battery control device 100 in the first embodiment preferentially bypasses battery cells C1 to Cn with a relatively smaller remaining charging capacity RC than the other battery cells C1 to Cn via bypass circuits B1 to Bn, thereby reducing the difference in the remaining charging capacity RC of the multiple battery cells C1 to Cn. Then, after performing the first process, the battery control device 100 connects all battery cells C1 to Cn in series and charges all battery cells C1 to Cn until charging is complete. Therefore, after performing the first process, the state in which all battery cells C1 to Cn are connected in series can be maintained until charging of all battery cells C1 to C8 is complete. Therefore, during this period, the total voltage of the battery system 1 can be maintained at a higher level than in the comparative example. Furthermore, since the total voltage can be maintained at a higher level, the period during which the desired charging power can be input from the charging circuit 30 to the battery pack 10 can be set to be longer than in the comparative example.

[0056] Furthermore, in the first process, the battery control device 100 in the first embodiment reduces the remaining charging capacity RC of the plurality of battery cells C1 to Cn to the minimum value at the start of the first process. Therefore, the charging completion timing of all battery cells C1 to Cn can be the same, and the timing of bypassing the charging completion of battery cells C1 to Cn can also be the same.

[0057] Furthermore, in the first embodiment, the battery control device 100 selects battery cells C1 to Cn to be bypassed such that the total voltage of the battery system 1 during the execution of the first process is maintained at the minimum permissible total voltage V of the battery system 1.L Or higher. Therefore, in the first process, the total voltage of the battery system 1 is prevented from dropping below the minimum permissible total voltage V of the charging circuit 30 and the power supply system (not shown). L Meanwhile, the remaining charging capacity RC of multiple battery cells C1 to Cn can be the same.

[0058] Figure 6 This is a timing diagram illustrating the charging control of the second embodiment. In the charging control shown in this diagram, the charging power limit value [W] during the execution of the first process remains at the minimum allowable charging power P. L Or above. Here, the charging power limit [W] is a value obtained by multiplying the minimum of the charging current limits of battery cells C1 to Cn by the total voltage of battery system 1. Furthermore, the minimum permissible charging power P... L For example, it is the lower limit of the allowed charging power of the battery system 1, to ensure that the upper limit of the power generated by the photovoltaic power generation system can be continuously charged.

[0059] Minimum allowable charging power P L It can be a constant value or a value that varies depending on various conditions. For example, because the power generated by the photovoltaic power generation system is greater during sunny days, the minimum allowable charging power P... L The minimum allowable charging power P can be set higher, and because the power generated by the photovoltaic power generation system is lower in the early morning, evening, cloudy, and rainy weather, the minimum allowable charging power P is [not specified]. L It can also be set to a lower value.

[0060] Although this disclosure has been described based on embodiments, it is not limited to the embodiments described above. Suitable modifications may be made to this disclosure without departing from its essential content, or known and public techniques may be appropriately combined therein.

[0061] For example, in the above embodiment, the remaining charge amount of each of the battery cells C1 to Cn until completion of charging is specified by the remaining charge capacity RC[Ah], which is the current capacity. However, the remaining charge amount of each of the battery cells C1 to Cn until completion of charging can also be specified by a quantity related to an exponent, and can also be specified by SOC, OCV (open circuit voltage), etc.

[0062] Furthermore, in the above embodiments, during the first process, the remaining charging capacity RC of the plurality of battery cells C1 to Cn is reduced to its minimum value at the start of the first process. However, the remaining charging capacity RC of the plurality of battery cells C1 to Cn may also be reduced to below its minimum value at the start of the first process.

[0063] Furthermore, from the viewpoint of ultimately depleting the remaining charging capacity RC of all battery cells C1 to Cn and ensuring that the charging completion timing of all battery cells C1 to Cn is the same, it is preferable to make the remaining charging capacity RC of the multiple battery cells C1 to Cn the same in the first process. However, it is not necessary to make the remaining charging capacity RC of the multiple battery cells C1 to Cn the same in the first process, and the difference in the remaining charging capacity RC of the multiple battery cells C1 to Cn can be sufficiently reduced in the first process.

[0064] Furthermore, the first process can be executed to satisfy one of the conditions in the first embodiment, namely, the total voltage of the battery system 1 is maintained at the minimum permissible total voltage V during the execution of the first process. L Or above, and satisfying the condition in the second embodiment, namely, the charging power limit value [W] during the execution of the first process remains at the minimum allowable charging power P. L Or, or be executed to satisfy both conditions simultaneously. That is, the first process can be executed such that at least one of the total voltage value of the battery system 1 and the charging power limit value during the execution of the first process is maintained at or above the minimum permissible value allowed by the battery system 1.

Claims

1. A battery control device configured to control a battery system including a plurality of batteries connected in series and a bypass circuit configured to selectively bypass each of the plurality of batteries, the battery control device comprising: a processor; and a memory having instructions that, when executed by the processor, cause the battery control device to perform operations including: performing a first process to cause the bypass circuit to preferentially bypass, among the plurality of batteries, a battery having a smaller remaining charge amount to complete charging than other batteries, and to charge at least one of the plurality of batteries such that a difference in the remaining charge amount to complete charging of the plurality of batteries decreases; and performing a second process, after the first process, to charge the plurality of batteries to complete charging; wherein, during performance of the first process, the battery to be bypassed by the bypass circuit is selected such that at least one of a total voltage value of the battery system during performance of the first process and a charge power limit value during the performance of the first process remains at or above a minimum allowable value allowable for the battery system.

2. The battery control device according to claim 1, wherein the first process includes charging the at least one of the plurality of batteries such that the remaining charge amount of the plurality of batteries decreases to a minimum value of the remaining charge amount of the plurality of batteries at the start of the first process or below.

3. The battery control device according to claim 1 or 2, wherein, in the first process, the battery having the smallest remaining charge amount at the start of the first process is bypassed by the bypass circuit without being connected from the start to the end of the first process, and the other batteries are selectively bypassed or connected in series by the bypass circuit such that the remaining charge amount of all the batteries is equal to the minimum value at the start of the first process; or the battery having the largest remaining charge amount at the start of the first process is kept connected without being bypassed by the bypass circuit from the start to the end of the first process, and the other batteries are selectively bypassed or connected in series by the bypass circuit such that the number of bypasses increases as the remaining charge amount decreases, thereby gradually reducing the difference in the remaining charge amount among all the batteries.

4. A battery system comprising: a plurality of batteries connected in series; a bypass circuit configured to selectively bypass each of the plurality of batteries; and a battery control device configured to control the bypass circuit, wherein the battery control device includes: a processor; and a memory having instructions that, when executed by the processor, cause the battery control device to perform operations including: performing a first process to cause the bypass circuit to preferentially bypass, among the plurality of batteries, a battery having a smaller remaining charge amount to complete charging than other batteries, and to charge at least one of the plurality of batteries such that a difference in the remaining charge amount to complete charging of the plurality of batteries decreases; and performing a second process, after the first process, to charge the plurality of batteries to complete charging; performing a second process after the first process, charging the plurality of storage batteries until charging is completed; wherein, during the execution of the first process, the storage battery to be bypassed by the bypass circuit is selected so that at least one of a total voltage value of the storage battery system during the execution of the first process and a charge power limit value during the execution of the first process remains at or above a minimum allowable value allowed by the storage battery system.

5. A storage battery control method executed by using a storage battery control device configured to control a storage battery system including a plurality of storage batteries connected in series and a bypass circuit configured to selectively bypass each of the plurality of storage batteries, the storage battery control method comprising: performing a first process in which the bypass circuit preferentially bypasses a storage battery having a smaller remaining charge amount until charging is completed than other storage batteries, and charging at least one of the plurality of storage batteries so that a difference in the remaining charge amount of the plurality of storage batteries until charging is completed decreases; and performing a second process after the first process, charging the plurality of storage batteries until charging is completed; wherein, during the execution of the first process, the storage battery to be bypassed by the bypass circuit is selected so that at least one of a total voltage value of the storage battery system during the execution of the first process and a charge power limit value during the execution of the first process remains at or above a minimum allowable value allowed by the storage battery system.

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