WO2022049798A1

WO2022049798A1 - Management device of storage battery, managing method of storage battery, electricity storage system, and battery-mounted apparatus

Info

Publication number: WO2022049798A1
Application number: PCT/JP2021/003967
Authority: WO
Inventors: Ryosuke Yagi; Ena Ishii; Yasuhiro Harada; Norio Takami
Original assignee: Kabushiki Kaisha Toshiba
Priority date: 2020-09-02
Filing date: 2021-02-03
Publication date: 2022-03-10
Also published as: JP7467288B2; JP2022042195A

Abstract

According to an embodiment, a management device of a storage battery is provided, the storage battery including a first battery connected to a first circuit, and a second battery connected to a second circuit. The second battery is larger in storage capacity and lower in allowable C rate than the first battery. A controller of the management device controls an operation of a DC/DC converter converting a voltage of electric power input to or output from the second circuit based on an input value to the storage battery when charging the storage battery, first SOC, that is, SOC of the first battery, second SOC, that is, SOC of the second battery, and a maximum allowable input value when charging the second battery corresponding to the second SOC.

Description

MANAGEMENT DEVICE OF STORAGE BATTERY, MANAGING METHOD OF STORAGE BATTERY, ELECTRICITY STORAGE SYSTEM, AND BATTERY-MOUNTED APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS

　　 This application is based upon and claims the benefit of priority from Japanese Patent Application No.2020-147501, filed September 2, 2020; the entire contents of which are incorporated herein by reference.

Field

　　 An embodiment relates to a management device of a storage battery, a managing method of a storage battery, an electricity storage system, and a battery-mounted apparatus.

Background

　　 Storage batteries are widely used as power supplies for small portable devices, power supplies mounted on vehicles in the field of mobility, and stationary power supplies used in power transmission networks such as smart grids. An electricity storage system including such storage batteries is provided with a management device managing a storage battery such as controlling charge and discharge of a storage battery. In particular, when a storage battery is used as a power supply for a vehicle, it is desired to enable safe and rapid charge of the storage battery at a large current and to enable long-term continuous output (discharge) from the storage battery by controlling charge and discharge of the storage battery.

　　 A storage battery formed from a nonaqueous electrolyte cell containing a titanium composite oxide as a negative electrode active material has a high safety in rapid charge at a large current. In addition, a nonaqueous electrolyte cell containing a carbonaceous material as a negative electrode active material has a large storage capacity. Accordingly, a storage battery formed from a nonaqueous electrolyte cell containing a carbonaceous material as a negative electrode active material enables long-term continuous discharge (output) by dischargig from a state in which SOC is high. By causing a management device or the like to control charge and discharge of a storage battery that includes two or more types of cells having active materials different from each other, an electricity storage system is desired to enable safe and rapid charge of the storage battery at a large current and to enable long-term continuous output from the storage battery.

Jpn. Pat. Appln. KOKAI Publication No.2017-118627 Jpn. Pat. Appln. KOKAI Publication No.2008-98149 International Publication No.2019/187132

FIG.1 is a schematic diagram showing a configuration of an electricity storage system according to a first embodiment. FIG.2 is a schematic diagram showing a relation ship of DCR at the time of charging for each of a first cell and a second cell of the embodiment. FIG.3 is a schematic diagram showing an example of changes over time in first SOC of a first battery and second SOC of a second battery at the time of charging a storage battery according to the first embodiment. FIG.4 schematically shows examples of input power to the storage battery, input power to the first battery, and to the second battery when the first SOC and the second input power SOC change as shown in FIG.3. FIG.5 is a flowchart showing an example of processing performed by a controller of a management device when charging the storage battery according to the first embodiment. FIG.6 is a schematic diagram showing an example of a relationship of an open circuit voltage to SOC for each of a first battery and a second battery of an embodiment. FIG.7 is a schematic diagram different from FIG.6 showing another example of a relationship of an open circuit voltage to SOC for each of the first battery and the second battery of the embodiment. FIG.8 is a schematic diagram different from FIGS.6 and 7 showing another example of a relationship of an open circuit voltage to SOC for each of the first battery and the second battery of the embodiment. FIG.9 is a flowchart showing an example of processing performed by the controller of the management device when charging the storage battery according to the second embodiment.

DETAILED DESCRIPTION

　　 In an embodiment, there is provided a management device of a storage battery, the storage battery including a first battery connected to a first circuit, and a second battery connected to a second circuit. The second battery is larger in storage capacity than the first battery and lower in allowable C rate than the first battery. The first circuit and the second circuit are electrically connected in parallel with a DC/DC conveter being disposed between the first circuit and the second circuit. The management device includes a controller. The controller controls an operation of the DC/DC converter which converts a voltage of electric power input to or output from the second circuit based on an input value to the storage battery when charging the storage battery, first SOC, that is, SOC of the first battery, second SOC, that is, SOC of the second battery, and a maximum allowable input value when charging the second battery corresponding to the second SOC.

　　 Hereinafter, an embodiment will be described with reference to the drawings.
　　 (First Embodiment)

　　 FIG.1 is a schematic diagram showing a configuration of an electricity storage system according to a first embodiment. An electricity storage system 1 includes a storage battery 2. The storage battery 2 is mounted onto a battery-mounted apparatus 3. Examples of the battery-mounted apparatus 3 include smartphones, vehicles, stationary power supplies, robots, and drones. Examples of a vehicle to be employed as the battery-mounted apparatus 3 include electric vehicles, plug-in hybrid vehicles, and electric motorcycles. Furthermore, examples of a robot to be mounted with the storage battery 2 include transfer robots such as an automated guided vehicle (AGV) used in factories and the like.

　　 The storage battery 2 includes a first battery 10 and a second battery 20. The first battery 10 includes one or more first cells 11, and the second battery 20 includes one or more second cells 21. In this embodiment, the first battery 10 is a battery module including a plurality of first cells 11. In the first battery 10, the first cells 11 are electrically connected in series. In an example shown in FIG.1, M-numbers of first cells 11 are disposed in the first battery 10, and the number of the first cells 11 in series in the first battery 10 is M. In this embodiment, the second battery 20 is a battery module including a plurality of second cells 21. In the second battery 20, the second cells 21 are electrically connected in series. In the example shown in FIG.1, N-numbers of second cells 21 are disposed in the second battery 20, and the number of the second cells 21 in series in the second battery 20 is N.

　　 The second cells 21 are larger in storage capacity than the first cells 11. Furthermore, the second cells 21 are lower in allowable C rate (allowable charging rate and allowable discharging rate) than the first cells 11. In other words, the second cells 21 are lower than the first cells 11 in allowable input and allowable output per unit storage capacity. Here, the allowable input and allowable output per unit storage capacity are expressed, for example, in [W / L]. Each of the first cells 11 is, for example, a nonaqueous electrolyte cell in which a titanium composite oxide is used as a negative electrode active material. Each of the second cells 21 is, for example, a nonaqueous electrolyte cell in which a carbonaceous material is used as a negative electrode active material.

　　 Examples of the titanium composite oxide used as the negative electrode active material in each of the first cells 11 of the first battery 10 include monoclinic niobium titanium composite oxide, orthorhombic titanium-containing composite oxide, lithium titanate having a ramsdellite structure, lithium titanate having a spinel structure, monoclinic titanium dioxide, anatase-type titanium dioxide, rutile-type titanium dioxide, and hollandite-type titanium composite oxide.

　　 As a positive electrode active material, each of the first cells 11 may use a lithium transition metal composite oxide. An example of the lithium transition metal composite oxide used as the positive electrode active material in each of the first cells 11 includes Li_uMeO₂ (0 < u ≦ 1, Me is at least one selected from the group consisting of Ni, Co, and Mn) having a layered structure such as a lithium nickel cobalt manganese composite oxide. A lithium iron phosphorus oxide is also an example of the lithium transition metal composite oxide used as the positive electrode active material in each of the first cells 11. Active materials similar to those recited in PTL 3 (International Publication No.2019/187132) may be used as the negative electrode active material and the positive electrode active material used in the plurality of first cells 11.

　　 In this embodiment, the first battery 10 is formed from a cell group having the plurality of first cells 11 connected in series. In the first battery 10, the first cells 11 are identical or substantially identical in, for example, capacity, size, and weight. In the first battery 10, the first cells 11 are electrically connected to each other via a bus bar 12.

　　 Examples of the carbonaceous material used as the negative electrode active material in each of the second cells 21 of the second battery 20 include graphite and amorphous carbon. As a positive electrode active material, each of the second cells 21 may use an active material similar to the positive electrode active material of the first cells 11.

　　 In this embodiment, the second battery 20 is formed from a cell group having the plurality of second cells 21 connected in series. In the second battery 20, the second cells 21 are identical or substantially identical in, for example, capacity, size, and weight. In the second battery 20, the second cells 21 are electrically connected to each other via a bus bar 22.

　　 As described above, the second cells 21 is larger in storage capacity than the first cells 11 and lower in allowable C rate than the first cells 11. In this embodiment, the first cells 11 are electrically connected in series in the first battery 10, and the second cells 21 are electrically connected in series in the second battery 20. Accordingly, the second battery 20 is larger in storage capacity than the first battery 10 and lower in allowable C rate than the first battery 10. As an example, the first battery 10 may be formed from only one first cell 11, and the second battery 20 may be formed from only one second cell 21. Even in this case, the second battery 20 is larger in storage capacity than the first battery 10 and lower in allowable C rate than the first battery 10.

　　 The first battery 10 is connected to a first circuit 13. Furthermore, the second battery 20 is connected to a second circuit 23. In the storage battery 2, the first battery 10 and the second battery 20 are electrically connected in parallel. In the electricity storage system 1, a DC/DC converter 5 is disposed between the first circuit 13 and the second circuit 23. Accordingly, the DC/DC converter 5 is arranged between the first battery 10 and the second battery 20. For example, a buck-boost chopper is embedded in the DC/DC converter 5. The DC/DC converter 5 converts a voltage of electric power input to or output from the second circuit 23. In other words, the DC/DC converter 5 converts a voltage of electric power output from the second circuit 23 and a voltage of electric power input to the second circuit 23.

　　 The storage battery 2 also includes a pair of external terminals 7. In the storage battery 2, electric power is input from an external charger or the like through the external terminals 7. Furthermore, in the storage battery 2, electric power is output to an external load or the like through the external terminals 7. In the storage battery 2, the first battery 10 is connected to the external terminals 7 via the first circuit 13 exclusively without involving the DC/DC converter 5. The second battery 20 is connected to the external terminals 7 via the DC/DC converter 5.

　　 Electric power input to the storage battery 2 is input to the first battery 10 without voltage conversion. Electric power output from the first battery 10 is output from the external terminals 7 without voltage conversion. On the other hand, electric power input to the storage battery 2 is subjected to voltage conversion by the DC/DC converter 5, and the converted electric power is input to the second battery 20. Furthermore, electric power output from the second battery 20 is subjected to voltage conversion by the DC/DC converter 5, and the converted electric power is output from the external terminals 7. Accordingly, when charging the second battery 20, the DC/DC converter 5 converts a voltage to be input to the second circuit 23 with respect to a voltage of the first circuit 13. When discharging the second battery 20, the DC/DC converter 5 converts a voltage output from the second circuit 23 with respect to a voltage of the first circuit 13.

　　 A voltage of the second battery 20 can be adjusted by controlling an operation of the DC/DC converter 5. For example, the operation of the DC/DC converter 5 can be controlled to make a voltage of the second battery 20 higher than a voltage of the first battery 10. Making a voltage of the second battery 20 higher than a voltage of the first battery 10 suppresses a current flowing through the second battery 20 to low levels.

　　 The electricity storage system 1 also includes a first switch 15 and a second switch 25. The first switch 15 is disposed on a line that electrically connects the external terminals 7 and the first battery 10 and can switch the state between ON and OFF. When the first switch 15 is in the OFF state, electric power input to the first battery 10 and electric power output from the first battery 10 are cut off. In other words, the first switch 15 in the OFF state stops charge and discharge of the first battery 10.

　　 Furthermore, the second switch 25 is disposed on a line that electrically connects the external terminals 7 and the second battery 20 and can switch the state between ON and OFF. When the second switch 25 is in the OFF state, electric power input to the second battery 20 and electric power output from the second battery 20 are cut off. In other words, the second switch 25 in the OFF state stops charge and discharge of the second battery 20.

　　 In addition, the electricity storage system 1 is provided with a first battery management unit (first BMU) 17, a second battery management unit (second BMU) 27, a communication unit 30, a data management unit 31, and a data storage unit 32. In the electricity storage system 1, for example, the

BMUs

17 and 27, the communication unit 30, the data management unit 31, and the data storage unit 32 constitute a management device configured to manage the storage battery 2. The management device controls charge and discharge of each of the first battery 10 and the second battery 20.

　　 The management device of the storage battery 2 includes a controller, and the controller includes a processor and a storage medium. The processor includes any one of central processing unit (CPU), graphics processing unit (GPU), application specific integrated circuit (ASIC), microcomputer, field programmable gate array (FPGA), and digital signal processor (DSP). The storage medium may include an auxiliary storage device in addition to a main storage device such as a memory. Examples of the storage medium include magnetic disks, optical disks (such as CD-ROM, CD-R, and DVD), magneto-optical disks (MO), and semiconductor memories. The numbers of processors and storage media included in the controller may be one or more. In the controller, for example, the processor executes a program stored in the storage medium so as to perform processing.

　　 In the example shown in FIG.1, the first BMU 17, the second BMU 27, the communication unit 30, and the data management unit 31 carry out part of the processing performed by the processor of the management device, and the storage medium of the of the management device functions as the data storage unit 32. Furthermore, in the example shown in FIG.1, the

BMUs

17 and 27, the communication unit 30, the data management unit 31, and the data storage unit 32 are mounted onto the battery-mounted apparatus 3, and the management device includes a processing device and the like mounted onto the battery-mounted apparatus 3. Accordingly, the processing by the management device is performed by the processing device and the like mounted onto the battery-mounted apparatus 3. For example, processing of the first BMU 17 is executed by a control circuit for the first battery 10, and processing of the second BMU 27 is executed by a control circuit for the second battery 20.

　　 The program executed by the processor of the controller of the management device may be stored in a computer (server) connected to the processor over a network such as the Internet or a server in a cloud environment. In this case, for example, the processor of the management device downloads the program over the network.

　　 Furthermore, at least a part of the management device may be constituted from an external processing device of the battery-mounted apparatus 3. The external processing device of the battery-mounted apparatus 3 is, for example, an external server of the battery-mounted apparatus 3, including a processor and a storage medium. When the external processing device of the battery-mounted apparatus 3 constitutes at least a part of the management device, at least part of the processing of the management device is performed by the processor of the external processing device of the battery-mounted apparatus 3, and data required for the processing is stored in the storage medium or the like of the external processing device of the battery-mounted apparatus 3. When the external processing device of the battery-mounted apparatus 3 constitutes at least a part of the management device, the processing device (computer) mounted onto the battery-mounted apparatus 3 enables communication with the external processing device of the battery-mounted apparatus 3 over the network.

　　 Furthermore, at least a part of the management device may be constituted from a cloud server in a cloud environment. Here, the infrastructure of the cloud environment includes a virtual processor such as a virtual CPU and includes a cloud memory. Accordingly, when the cloud server constitutes a part of the management device, at least part of the processing of the management device is performed by the virtual processor, and data required for the processing is stored in the cloud memory. When the cloud server constitutes a part of the management device, the processing device (computer) mounted onto the battery-mounted apparatus 3 enables communication with the cloud server.

　　 The first BMU 17 detects and acquires first SOC, that is, state of charge of the first battery 10 (arrow L1). The second BMU 27 detects and acquires second SOC, that is, state of charge of the second battery 20 (arrow L2). Accordingly, the first BMU 17 functions as a first SOC detection unit that detects the first SOC, and the second BMU 27 functions as a second SOC detection unit that detects the second SOC. Each of the first SOC and the second SOC is periodically detected, for example, at a predetermined timing. The SOC of each of the first battery 10 and the second battery 20 can be calculated by, for example, any one of current integration, a calculation method using the relationship of a voltage between terminals to the SOC of the battery (10 or 20), and an estimation method using a Kalman filter.

　　 The communication unit 30 acquires an input to the storage battery 2 when the storage battery 2 is charged. Accordingly, the communication unit 30 functions as an input value acquisition unit that acquires an input value to the storage battery 2. The input value to the storage battery 2 is specified by, for example, input power (charging power) to the storage battery 2 and a charging rate (C rate) of the storage battery 2. For example, when charging with an external charger of the battery-mounted apparatus 3 such as a charger installed in a charging station, the communication unit 30 acquires an input value to the storage battery 2, for example, by communication with the charger. Alternatively, when charging with a generator mounted onto the battery-mounted apparatus 3, the communication unit 30 acquires an input value to the storage battery 2 by, for example, communication with a controller that controls the generator. The communication unit 30 transmits the acquired input value to the storage battery 2 to the first BMU 17 (arrow L3). Accordingly, the first BMU 17 acquires the input value to the storage battery 2 (input power or charging rate) when the storage battery 2 is charged. The input value to the storage battery 2 is periodically acquired, for example, at a predetermined timing.

　　 Furthermore, the first BMU 17 generates a control command associated with the input value to the storage battery 2. The control command associated with the input value to the storage battery 2 is transmitted from the first BMU 17 to the communication unit 30 (arrow L4) and from the communication unit 30 to the charger or the like. Based on the transmitted control command, an output (output power) from the charger or the like is controlled, and the input to the storage battery 2 is controlled.

　　 The data management unit 31 manages data stored in the data storage unit 32. The data management unit 31 enables writing of data to the data storage unit 32 (arrow L5) and reading of data from the data storage unit 32 (arrow L6). The data storage unit 32 stores data indicating the relation between the second SOC of the second battery 20 and a maximum allowable input value when the second battery 20 is charged. The maximum allowable input value of the second battery 20 is the upper limit value in an allowable range of input to the second battery 20 at the time of charge and is specified by, for example, input power (charging power) or a charging rate (C rate) of the second battery 20. In one example, table data indicating the relation between the second SOC of the second battery 20 and the maximum allowable input value of the second battery 20 is stored in the data storage unit 32 in advance.

　　 The data management unit 31 may update the data indicating the relation between the second SOC of the second battery 20 and the maximum allowable input value of the second battery 20, corresponding to at least one of the operating time of the storage battery 2 and the deteriorated state of the second battery 20. Furthermore, the data storage unit 32 may store data in which the relation between the second SOC of the second battery 20 and the maximum allowable input value of the second battery 20 is determined depending on temperature of the second battery 20. In this case, the data management unit 31 may update the data in which the relation between the second SOC of the second battery 20 and the maximum allowable input value of the second battery 20 is determined depending on temperature of the second battery 20, corresponding to at least one of the operating time of the storage battery 2 and the deteriorated state of the second battery 20.

　　 The data management unit 31 acquires detection results of the second SOC of the second battery 20 from the second BMU 27 (arrow L7). Based on the acquired second SOC and the data stored in the data storage unit 32 indicating the relation between the second SOC and the maximum allowable input value of the second battery 20, the data management unit 31 acquires the maximum allowable input value at the time of charging the second battery 20 corresponding to the acquired second SOC. Then, the data management unit 31 transmits to the first BMU 17 the acquired second SOC and the maximum allowable input value of the second battery 20 corresponding to the second SOC (arrow L8). Accordingly, the first BMU 17 acquires the second SOC and the maximum allowable input value of the second battery 20 corresponding to the second SOC. Here, the data management unit 31 periodically acquires the second SOC and the maximum allowable input value of the second battery 20 corresponding to the second SOC, for example, at a predetermined timing. Accordingly, the first BMU 17 periodically acquires the second SOC and the maximum allowable input value of the second battery 20 corresponding to the second SOC, for example, at a predetermined timing.

　　 The first BMU 17 controls an operation of the first switch 15 based on, for example, the first SOC of the first battery 10 (arrow L9), and the second BMU 27 controls an operation of the second switch 25 based on, for example, the second SOC of the second battery 20 (arrow L10). The first BMU 17 controls the operation of the DC/DC converter 5 (arrow L11). The operation of the DC/DC converter 5 is controlled based on the input value to the storage battery 2 at the time of charging the storage battery 2, the first SOC, the second SOC, and the maximum allowable input value of the second battery 20 corresponding to the second SOC.

　　 FIG.2 is a schematic diagram showing arelation ship of direct current resistance (DCR) at the time of charging to SOC for each of a first cell and a second cell of the embodiment. In FIG.2, SOC of a single cell is taken along the abscissa axis, and DCR of the single cell is taken along the ordinate axis. Pattern α1 indicates changes in DCR of a first cell 11 containing lithium titanate as the negative electrode active material, and pattern α2 indicates changes in DCR of a first cell 11 containing a niobium titanium composite oxide as the negative electrode active material. Pattern β1 indicates changes in DCR of a second cell 21 containing graphite as the negative electrode active material and containing a lithium nickel cobalt manganese composite oxide as the positive electrode active material, and pattern β2 indicates changes in DCR of a second cell 21 containing graphite as the negative electrode active material and containing a lithium iron phosphorus oxide as the positive electrode active material. In FIG.2, patterns α1, α2, β1, and β2 each show DCR as a relative value regarding the highest DCR as 1 among a plurality of measurement points. The DCR at the time of charge is determined by hybrid pulse power characterization (HPPC) test. The results shown in FIG.2 are measured at 25°C.

　　 As shown in FIG.2, the relation of DCR to SOC in a single cell varies depending on, for example, the types of the negative electrode active material and the positive electrode active material and the capacities of the negative electrode active material and the positive electrode active material. However, in many types of cells, the resistance tends to increase in the range with SOC of 70% to 100% (range ε1 in FIG.2), that is, in a region with high SOC. In other words, in many types of cells, the resistance tends to be higher in the range with SOC of 70% to 100% than in the range with SOC of 30% to 70%. In particular, the first cell 11 containing the titanium composite oxide as the negative electrode active material (see patterns α1 and α2 in FIG.2) greatly increases in resistance in a region where the SOC is high. For this reason, when the charger or the like is connected to the external terminals 7 to charge the storage battery 2 rapidly at a large current, it is preferable that the first battery 10 including the first cells 11 should be used in a state where SOC is lower than 70%, that is, a state outside the high-SOC region.

　　 In each of the

batteries

10 and 20, maximum allowable input power Pimax is specified as the aforementioned maximum allowable input value in the charge. In each of the

batteries

10 and 20, the maximum allowable input power Pimax is calculated by Formula (1). In Formula (1), Vmax indicates an upper limit voltage value of a battery, Vocp indicates an open circuit voltage of the battery, and R indicates a resistance of the battery. The unit of the maximum allowable input power Pimax is, for example, [W], the units of the upper limit voltage value Vmax and the open circuit voltage Vocp are, for example, [V], and the unit of the resistance R is, for example, [Ω].
　　 Pimax = ((Vmax - Vocp)/R) × Vmax (1)

　　 Here, in each of the

batteries

10 and 20, the lower the SOC, the lower the open circuit voltage Vocp, and when the SOC dips to 30 to 70%, the resistance R also decreases. Accordingly, in each of the

batteries

10 and 20, with a decrease in SOC (one of the first SOC and the second SOC corresponding to each battery), the maximum allowable input power Pimax becomes large, and the maximum allowable input value increases.

　　 In addition, a maximum allowable output value at the time of discharge is specified for each of the

batteries

10 and 20. The maximum allowable output value is the upper limit value in an allowable range of output from a battery at the time of discharge and is specified by, for example, output power (discharging power) or a discharging rate (C rate) of the battery. For each of the

batteries

10 and 20, maximum allowable output power Pomax is specified as the maximum allowable output value at the time of discharge. For each of the

batteries

10 and 20, the maximum allowable output power Pomax is calculated by Formula (2). In Formula (2), Vmin indicates a lower limit voltage value of the battery, Vocp indicates the open circuit voltage of the battery, and R indicates the resistance of the battery. The unit of the maximum allowable output power Pomax is, for example, [W], and the unit of the lower limit voltage value Vmin is, for example, [V].
　　 Pomax = ((Vocp - Vmin)/R) × Vmin (2)

　　 Here, in each of the

batteries

10 and 20, the higher the SOC, the higher the open circuit voltage Vocp. Accordingly, in each of the

batteries

10 and 20, with an increase in SOC (one of the first SOC and the second SOC corresponding to each battery), the maximum allowable output power Pomax becomes large, and the maximum allowable output value increases.

　　 As described above using Formulae (1) and (2), each of the

batteries

10 and 20 increases input characteristics (charging capacity) with a decrease in SOC, and increases output characteristics (discharge capacity) with an increase in SOC. Furthermore, when charging the second battery 20 including the second cells 21 containing a carbonaceous material as the negative electrode active material, it is required to prevent precipitation of lithium in the second cells 21 from a viewpoint of preventing deterioration of the second battery 20 and from a safety viewpoint. For this reason, when charging the second battery 20, it is required to suppress an input to the second battery 20 (input power or charging rate) at the time of charge in a region with high second SOC where lithium precipitation is likely to occur, whereby preventing precipitation of lithium in the second cells 21.

　　 Therefore, in this embodiment, data indicating the relationship of charging conditions (input power or charging rate) of the second battery 20 to the second SOC of the second battery 20 is stored in the data storage unit 32. The controller including the first BMU 17 and the like control the operation of the DC/DC converter 5 based on the relation between the second SOC and the charging conditions of the second battery 20 so as to control the input to the second battery 20 such as input power (charging power) to the second battery 20 or the charging rate of the second battery 20. Accordingly, when charging the second battery 20, the input (charging capacity) to the second battery 20 is suppressed within a range where precipitation of lithium in the second cells 21 is prevented.

　　 The controller constituted by the first BMU 17 and the like controls the operation of the DC/DC converter 5 to make the first SOC of the first battery 10 lower than the second SOC of the second battery 20 and to keep the first SOC lower than the second SOC. Keeping the first SOC lower than the second SOC makes it possible to input (charge) the remaining input (such as a charging current) to the first battery 10 with the remaining input obtained by subtracting the maximum allowable input value of the second battery 20 from the input value to the storage battery 2 even when the storage battery 2 is charged with an input value larger than the maximum allowable input value of the second battery 20 in a case where the storage battery 2 is charged at a large current. Here, the controller controls the operation of the DC/DC converter 5 to charge the second battery 20 with the maximum allowable input value of the second battery 20 from the input to the storage battery 2 and charge the first battery 10 with the remaining input. Since the input to the second battery 20 is suppressed to level of the maximum allowable input value or less, even when the storage battery 2 is rapidly charged at a large current, the precipitation of lithium in the second cells 21 is effectively prevented. This enables safe and rapid charge of the storage battery 2 at a large current.

　　 When discharging the second battery 20, unlike the charge of the second battery 20, lithium is less likely to precipitate in the second cells 21. Furthermore, the second battery 20 has a larger storage capacity as described above. Therefore, discharging the storage battery 2 in a region where the second SOC of the second battery 20 is high enables long-term continuous output (discharge) from the storage battery 2. This makes it possible to continuously drive the battery-mounted apparatus 3 mounted with the storage battery 2 for a long period of time.

　　 Hereinafter described are details on an operating method of the storage battery 2 of this embodiment and on the management of the storage battery 2 by the controller such as controlling the charge of the storage battery 2 by the controller of the management device.

　　 FIG.3 is a schematic diagram showing an example of changes over time in first SOC of the first battery and in second SOC of the second battery when charging the storage battery according to the first embodiment. FIG.4 schematically shows examples of input power to the storage battery, input power to the first battery, and input power to the second battery when the first SOC and the second SOC change as shown in FIG.3. In the example shown in FIG.3, the first SOC and the second SOC change over time in the order of state γ1, state γ2, and state γ3. In FIG.4, the time is taken along the abscissa axis considering the start of charging the storage battery as a reference t0, and the electric power is taken along the ordinate axis. In FIG.4, input power P0i represents an input to the storage battery 2, input power P1i represents an input to the first battery 10, and input power P2i represents an input to the second battery 20.

　　 In this embodiment, the controller constituted by the first BMU 17 and the like controls an output from the charger or the like and controls the input power P0i to the storage battery 2 based on at least the first SOC and the second SOC. Furthermore, the controller controls drive of the DC/DC converter 5 and controls the input power P2i to the second battery 20 based on at least the first SOC and the second SOC.

　　 In the examples shown in FIGS.3 and 4, first SOC η1 and second SOC η2 reach the state γ1 at the start of charge t0 when the charger or the like is connected to the storage battery 2. Therefore, at the start of charge t0, the first SOC η1 is lower than the second SOC η2, and a difference (SOC subtracted value) Δη between the first SOC η1 and the second SOC η2 is large. At this time, the controller of the management device increases the input power P0i to the storage battery 2 by communication with the charger or the like and charges the storage battery 2 at a large current. In addition, the controller controls the drive of the DC/DC converter 5 to suppress the input power P2i to the second battery 20 to level of maximum allowable input power P2imax of the second battery 20 corresponding to the second SOC η2. Accordingly, the second battery 20 is charged with the maximum allowable input power P2imax. The controller inputs to the first battery 10 the remaining power (P0i - P2imax) obtained by subtracting the maximum allowable input power P2imax of the second battery 20 from the input power P0i to the storage battery 2 and charges the first battery 10 with the remaining power (P0i - P2imax). This increases the first SOC η1 of the first battery 10 rapidly.

　　 At the time t1 after a certain amount of time from the start time of charge t0 or immediately before or after the time t1, the first SOC η1 and the second SOC η2 reach the state γ2. In the state γ2, the first SOC η1 is lower than the second SOC η2, but the difference Δη between the first SOC η1 and the second SOC η2 is small. Accordingly, the controller of the management device reduces the output from the charger or the like by a control command or the like at the time t1 or immediately before or after the time t1 and reduces the input power P0i to the storage battery 2. This makes it possible to suppress the input to the storage battery 2. Furthermore, even after the input power P0i is reduced, the controller controls the drive of the DC/DC converter 5 to suppress the input power P2i to the second battery 20 to level of the maximum allowable input power P2imax of the second battery 20 and charges the second battery 20 with the maximum allowable input power P2imax. The controller then charges the first battery 10 with the remaining power (P0i - P2imax) obtained by subtracting the maximum allowable input power P2imax of the second battery 20 from the input power P0i to the storage battery 2. In this manner, the controller controls the input power P0i and the input power P2i so as to keep the first SOCη1 lower than the second SOCη2 after reducing the input powers P0i.

　　 Then, at the time t2 after a certain amount of time from the time t1 or immediately before or after the time t2, the first SOC η1 and the second SOC η2 reach the state γ3. In the state γ3, the second SOC η2 becomes SOC upper limit value η2max. Even in the state γ3, the first SOC η1 is lower than the second SOC η2. Based on the rise of the second SOC η2 to the SOC upprr limit value η2max, the controller of the management device turns off the

switches

15 and 25 and cuts off the input to the first battery 10 and to the second battery 20. The controller then stops the output from the charger or the like and stops the input of electric power to the storage battery 2 based on the rise of the second SOC η2 to the SOC upper limit value η2max. This stops the charge of the storage battery 2. The SOC upper limit value η2max may be 100% or may be lower than 100% as in the examples shown in FIGS.3 and 4. Furthermore, in the example shown in FIGS.3 and 4, the charge of the storage battery 2 is stopped at the time t2 or immediately before or after the time t2.

　　 FIG.5 is a flowchart showing an example of processing performed by the controller of the management device when charging the storage battery according to the first embodiment. The processing shown in FIG.5 is performed by the controller from the start to the end of charge of the storage battery 2 (or until the charge of the storage battery 2 is stopped).

　　 As shown in FIG.5, when the storage battery 2 is charged, the first BMU 17 transmits a command to the charger or the like to start power output so as to start input (charge) of the input power P0i to the storage battery 2 (S101). Through the communication unit 30 or the like, the first BTU 17 acquires the input power P0i to the storage battery 2 as the input value to the storage battery 2 (S102). The first BMU 17 also acquires the first SOC η1 of the first battery 10 (S103). Then, the second BMU 27 acquires the second SOC η2 of the second battery 20 (S104). Based on the acquired second SOCη2 and data stored in the data storage unit 32 showing the relation between the second SOC η2 and the maximum allowable input power P2imax of the second battery 20, the data management unit 31 acquires the maximum allowable input power P2imax of the second battery 20 corresponding to the second SOC η2 (S105). In one example shown in FIG.5, the maximum allowable input power P2imax is acquired as a maximum allowable input value at the time of charging the second battery 20.

　　 Next, the first BMU 17 and the like compare the input power P0i to the storage battery 2 with the maximum allowable input power P2imax of the second battery 20 and determine whether the input power P0i is larger than the maximum allowable input power P2imax (S106). When the input power P0i is larger than the maximum allowable input power P2imax (S106-Yes), the first BMU 17 controls the operation of the DC/DC converter 5 to charge the second battery 20 with the maximum allowable input power P2imax of the second battery 20 from the input power P0i to the storage battery 2 and charge the first battery 10 with the remaining power (P0i - P2imax) (S107). In other words, the operation of the DC/DC converter 5 is controlled in such a manner that the input power P1i to the first battery 10 becomes the power (P0i - P2imax) and the input power P2i to the second battery 20 becomes the maximum allowable input power P2imax.

　　 On the other hand, when the input power P0i is the maximum allowable input power P2imax or less (S106-No), for example, the first BMU 17 turns off the first switch 15 and stops input (charge) to the first battery 10, and charges the second battery 20 with all the input power P0i (S108). In other words, the input power P1i to the first battery 10 becomes zero, and the input power P2i to the second battery 20 becomes equal to the input power P0i to the storage battery 2. Accordingly, the second battery 20 is preferentially charged in the storage battery 2, and the second SOC of the second battery 20 rises.

　　 Next, the first BMU 17 and the like compare the first SOCη1 of the first battery 10 with the second SOCη2 of the second battery 20 and determine whether the first SOCη1 is lower than the second SOCη2 (S109). When the first SOCη1 is lower than the second SOCη2 (S109-Yes), the processing proceeds to S111. On the other hand, when the first SOCη1 is the second SOCη2 or higher (S109-No), the first BMU 17 and the like control output from the charger or the like and reduce the input power P0i, which is the input value to the storage battery 2, to level of or less than the maximum allowable input power P2imax, which is the maximum allowable input value to the second battery 20 (S110). The processing then proceeds to S111.

　　 The

BMUs

17 and 27, for example, determine whether the second SOC η2 of the second battery 20 is the SOC upper limit value η2max or higher, that is, whether the second SOC η2 rises to the level as high as the SOC upper limit value η2max (S111). When the second SOC η2 is the SOC upper limit value η2max or higher (S111-Yes), the first BMU 17 transmits a command to the charger or the like to stop power output to the storage battery 2 and stops input (charge) of input power P0i to the storage battery 2 (S112). Here, the

BMUs

17 and 27 turn off both of the

switches

15 and 25. On the other hand, when the second SOC η2 is lower than the SOC upper limit value η2max (S111-No), the processing returns to S102. The controller of the management device including, for example, the

BMUs

17 and 27 sequentially executes the processing from S102.

　　 Since the processing is performed in this manner, in this embodiment, even when the input value to the storage battery 2 is larger than the maximum allowable input value of the second battery 20, the operation of the DC/DC converter 5 is controlled to charge the second battery 20 with the maximum allowable input value of the second battery 20 and charge the first battery 10 with the remaining input. Accordingly, the input to the second battery 20 is suppressed to level of the maximum allowable input value or less. This effectively prevents the precipitation of lithium in the second cells 21, which enables safe and rapid charge of the storage battery 2 at a large current. Furthermore, since the precipitation of lithium in the second cells 21 is effectively prevented, the storage battery 2 is effectively prevented from deteriorating.

　　 In addition, since the aforementioned processing is performed, in this embodiment, appropriate control is performed to make the first SOC η1 of the first battery 10 lower than the second SOC η2 of the second battery 20 and to keep the first SOC η1 lower than the second SOC η2. When the first SOC η1 is the second SOC η2 or higher, the input value to the storage battery 2 is reduced to level of or less than the maximum allowable input value to the second battery 20. Accordingly, the input to the storage battery 2 is input to the second battery 20 exclusively, and the second battery 20 is preferentially charged. Therefore, even when the first SOC η1 becomes the second SOC η2 or higher, the second battery 20 is charged so that the second SOC rises exclusively, which rapidly brings the first SOC η1 lower than the second SOC η2.

　　 The first SOC η1 is appropriately kept in a state lower than the second SOC η2, which makes it possible to discharge the storage battery 2 while the second SOC η2 of the second battery 20 is in a high state. Discharging the storage battery 2 with the second SOC η2 of the second battery 20 in a high state enables long-term continuous output (discharge) from the storage battery 2. This makes it possible to continuously drive the battery-mounted apparatus 3 mounted with the storage battery 2 for a long period of time.

　　 In this manner, this embodiment enables safe and rapid charge of the storage battery 2 at a large current and enables long-term continuous output from the storage battery 2. In other words, it is possible to achieve both safety during charge or the like and prolonged driving time of the battery-mounted apparatus 3.
　　 (Second embodiment)

　　 Hereinafter described is a second embodiment. In the following description, those similar to the first embodiment and the like will not be described.

　　 In the aforementioned embodiment and the like, the controller of the management device controls the operation of the DC/DC converter 5 and the input to the storage battery 2 to make the first SOC of the first battery 10 lower than the second SOC of the second battery 20 and to keep the first SOC lower than the second SOC. On the other hand, in this embodiment, a reference range from a lower limit value Δηmin to an upper limit value Δηmax is specified in regard to an SOC subtracted value Δη obtained by subtracting first SOC η1 from second SOC η2. A controller of a management device in this embodiment controls an operation of a DC/DC converter 5 and an input to a storage battery 2 to set the SOC subtracted value Δη within the reference range and to keep the SOC subtracted value Δη within the reference range. The reference range of the SOC subtracted value Δη is set according to, for example, the type of active materials in first cells 11 and second cells 21. Information associated with the reference range of the SOC subtracted value Δη is stored in, for example, a data storage unit 32.

　　 FIG.6 is a schematic diagram showing an example of a relationship of an open circuit voltage to SOC for each of a first battery and a second battery of the embodiment. FIG.7 is a schematic diagram different from FIG.6 showing another example of a relationship of an open circuit voltage to SOC for each of the first battery and the second battery of the embodiment. FIG.8 is a schematic diagram different from FIGS.6 and 7 showing another example of a relationship of an open circuit voltage to SOC for each of the first battery and the second battery of the embodiment. In FIGS.6 to 8, the SOC is taken along the abscissa axis, and the voltage is taken along the ordinate axis. In any of the examples shown in FIGS.6 to 8, the first cells 11 included in a first battery 10 use a monoclinic niobium titanium composite oxide, a kind of titanium composite oxide, as a negative electrode active material, and the second cells 21 included in a second battery 20 use graphite, a kind of carbonaceous material, as a negative electrode active material.

　　 In any of the examples shown in FIGS.6 to 8, the number N of the second cells 21 in series in the second battery 20 is 99. However, the numbers M of the first cells 11 in series in the first battery 10 are different from each other between the examples shown in FIGS.6 to 8. The numbers M of the first cells 11 in series in the first battery 10 are, for example, 160 in FIG.6, 150 in FIG.7, and 182 in FIG.8.

　　 In the examples shown in FIGS.6 to 8, as compared with the second battery 20, a voltage of the first battery 10 changes significantly in response to changes in SOC. Furthermore, in the example shown in FIG.6, when the storage battery 2 is charged while both the first SOC of the first battery 10 and the second SOC of the second battery 20 are 70% or more, a voltage of the first battery 10 is higher than a voltage of the second battery 20. When a voltage of the first battery 10 is higher than a voltage of the second battery 20, malfunction of the DC/DC converter 5 causes charge and discharge between the first battery 10 and the second battery 20 so as to equalize the voltage of the first battery 10 and the voltage of the second battery 20. At this time, electric power or the like discharged from the high-voltage first battery 10 is charged to the low-voltage second battery 20. In the storage battery 2, even when malfunction of the DC/DC converter 5 causes charge and discharge between the first battery 10 and the second battery 20, it is desired to prevent overcharge of the second battery 20 while the second SOC of the second battery 20 is charged over 100%.

　　 Accordingly, in this embodiment, the reference range from the lower limit value Δηmin to the upper limit value Δηmax is specified in regard to the SOC subtracted value Δη obtained by subtracting the first SOC η1 from the second SOC η2. The operation of the DC/DC converter 5 and the input to the storage battery 2 are controlled to set the SOC subtracted value Δη within the reference range and to keep the SOC subtracted value Δη within the reference range. This reduces a voltage difference ΔV between a voltage of the first battery 10 and a voltage of the second battery 20 when the storage battery 2 is charged. Reducing the voltage difference ΔV effectively prevents overcharge or the like of the second battery 20 even when malfunction of the DC/DC converter 5 causes charge and discharge between the first battery 10 and the second battery 20.

　　 Furthermore, when employing the negative electrode active materials of the first cells 11 and the second cells 21 similar to the examples shown in FIGS.6 to 8, it is desirable that the number M of the first cells 11 in series in the first battery 10 and the number N of the second cells 21 in series in the second battery 20 should be set such that voltage fluctuation ranges of the first battery 10 and the second battery 20 satisfy the following relation. In other words, when specifying a voltage fluctuation range ΔX1 of the first battery 10 with the first SOC of 10% to 90% and a voltage fluctuation range ΔX2 of the second battery 20 with the second SOC of 10% to 90%, it is desirable to determine the number M of the first cells 11 in series and the number N of the second cells 21 in series such that the voltage fluctuation range ΔX2 falls within the voltage fluctuation range ΔX1. In this case, a voltage of the second battery 20 with the second SOC of 90% is equal to or lower than a voltage of the first battery 10 with the first SOC of 90%, and a voltage of the second battery 20 with the second SOC of 10% is equal to or higher than a voltage of the first battery 10 with the first SOC of 10%. The voltage fluctuation ranges ΔX1 and ΔX2 are shown in FIGS.6 to 8.

　　 The voltage of the second battery 20 with the second SOC of 90% being equal to or lower than the voltage of the first battery 10 with the first SOC of 90% effectively prevents the voltage of the first battery 10 from decreasing significantly relative to the voltage of the second battery 20 when charging and discharging the storage battery 2. This makes it possible to effectively prevent a decrease in output voltage from the storage battery 2 and to supply sufficient electric power to a load when the storage battery 2 is discharged.

　　 Furthermore, the voltage of the second battery 20 with the second SOC of 10% being equal to or higher than the voltage of the first battery 10 with the first SOC of 10% effectively prevents the voltage of the first battery 10 from increasing significantly relative to the voltage of the second battery 20 when charging and discharging the storage battery 2. This makes it possible to effectively prevent an excessive increase in input voltage from the first circuit 13 to the DC/DC converter 5, and it is not necessary to significantly increase a breakdown voltage of the DC/DC converter 5. Furthermore, when the voltage of the second battery 20 with the second SOC of 10% is equal to or higher than the voltage of the first battery 10 with the first SOC of 10%, the number M of the first cells 11 in series in the first battery 10 does not increase excessively. This makes it possible to suppress the cost and the like in manufacturing the first battery 10 and the storage battery 2.

　　 Provided that the negative electrode active materials of the first cells 11 and the second cells 21 are similar to the examples of FIGS.6 to 8 and that the number N of the second cells 21 in series is 99 as in the example shown in FIGS.6 to 8. In this case, the number M of the first cells 11 in series is required to fall within a range of 150 to 182 in order to keep the voltage fluctuation range ΔX2 of the second battery 20 within the voltage fluctuation range ΔX1 of the first battery 10. In other words, when the number N in series is 99, the number M in series to keep the voltage fluctuation range ΔX2 within the voltage fluctuation range ΔX1 is required to be in a range of 150 to 182.

　　 Furthermore, the first SOC η1 of the first battery 10 when a voltage of the second battery 20 with the second SOC of 100% and a voltage of the first battery 10 are equal is specified as a parameter η1a. In addition, a parameter Δηa is specified by subtracting the parameter η1a from 100% (or 1.00). When the negative electrode active materials of

cells

11 and 21 are similar to the examples of FIGS.6 to 8, the lower limit value Δηmin and the upper limit value Δηmax of the reference range of the SOC subtracted value Δη are set based on the parameters η1a and Δηa. The parameters η1a and Δηa are shown in FIGS.6 to 8.

　　 In one example, the lower limit value Δηmin and the upper limit value Δηmax of the reference range are set on condition that the number N of the second cells 21 in series is 99 as in the examples of FIGS.6 to 8. In this case, when setting the lower limit value Δηmin of the reference range of the SOC subtracted value Δη, the parameters η1a and Δηa are calculated on condition that the number M of the first cells 11 in series is 150, that is, the lower limit value of the aforementioned range. In other words, the number M and the number N in series are set as in the example shown in FIG.7, and then, the parameters η1a and Δηa are calculated. When the number M in series is 150 and the number N in series is 99, the voltage of the first battery 10 with the first SOC of about 90% becomes equal to the voltage of the second battery 20 with the second SOC of 100%. Accordingly, the parameter η1a is about 90%, and the parameter Δηa is about 10% (about 0.10). In this example, the lower limit value Δηmin of the reference range of the SOC subtracted value Δη is set equal or substantially equal to the calculated parameter Δηa. Accordingly, the lower limit value Δηmin of the reference range is set to, for example, 0.10 (10%).

　　 Furthermore, in this example, when setting the upper limit value Δηmax of the reference range of Δη, the parameters η1a and Δηa are calculated on condition that the number M of the first cells 11 in series is 182, that is, the upper limit value of the aforementioned range. In other words, the number M and the number N in series are set as in the example shown in FIG.8, and then, the parameters η1a and Δηa are calculated. When the number M in series is 182 and the number N in series is 99, a voltage of the first battery 10 with the first SOC of about 65% becomes equal to the voltage of the second battery 20 with the second SOC of 100%. Accordingly, the parameter η1a is about 65%, and the parameter Δηa is about 35% (about 0.35). In this example, the upper limit value Δηmax of the reference range of the SOC subtracted value Δη is set equal or substantially equal to the calculated parameter Δηa. Accordingly, the upper limit value Δηmax of the reference range is set to, for example, 0.35 (35%).

　　 In one example of this embodiment, the negative electrode active materials of the first cells 11 and the second cells 21 are similar to the examples shown in FIGS.6 to 8, and the reference range from 0.10 to 0.35 is specified in regard to the SOC subtracted value Δη obtained by subtracting the first SOC η1 from the second SOC η2. The controller of the management device (including the first BMU 17 and the like) controls the operation of the DC/DC converter 5 and the input to the storage battery 2 to set the SOC subtracted value Δη within the reference range and to keep the SOC subtracted value Δη within the reference range. This makes it possible to effectively prevent overcharge or the like of the second battery 20 when charging the storage battery 2 even when malfunction of the DC/DC converter 5 causes charge and discharge between the first battery 10 and the second battery 20.

　　 Furthermore, in this embodiment, the lower limit value Δηmin of the reference range of the SOC subtracted value Δη is set to a value higher than zero regardless of the type of the active materials in the first cells 11 and the second cells 21. Accordingly, controlling the drive of the DC/DC converter 5 to set the SOC subtracted value Δη within the reference range and to keep the SOC subtracted value Δη within the reference range makes it possible to keep the first SOC η1 of the first battery 10 lower than the second SOC η2 of the second battery 20.

　　 FIG.9 is a flowchart showing an example of processing performed by the controller of the management device when charging the storage battery according to the second embodiment. The processing shown in FIG.9 is executed by the controller from the start to the end of charge (stop of charge) of the storage battery 2.

　　 As shown in FIG.9, in this embodiment, the controller of the management device executes the processing S101 to S108, S111, and S112 as in the first embodiment and the like. However, in this embodiment, instead of the processing S109 and S110, the following processing S115 to S118 is executed.

　　 In this embodiment, when the processing S107 or S108 is executed, the first BMU 17 and the like subtract the first SOC η1 of the first battery 10 from the second SOC η2 of the second battery 20 to calculate the SOC subtracted value Δη. The first BMU 17 and the like determine whether the calculated SOC subtracted value Δη is within the reference range from the lower limit value Δηmin to the upper limit value Δηmax. At this time, the first BMU 17 and the like determine whether the SOC subtracted value Δη is the lower limit value Δηmin or more (S115). When the SOC subtracted value Δη is the lower limit value Δηmin or more (S115-Yes), the first BMU 17 and the like determine whether the SOC subtracted value Δη is the upper limit vvalue Δmax or less (S116). When the SOC subtracted value Δη is the upper limit value Δηmax or less (S116-Yes), the first BMU 17 and the like determine that the SOC subtracted value Δη is within the reference range, and the processing proceeds to S111.

　　 In S115, when the SOC subtracted value Δη is less than the lower limit value Δηmin of the reference range (S115-No), the first BMU 17 and the like control an output from the charger or the like and reduce input power P0i, which is an input value to the storage battery 2, to level of or less than a maximum allowable input power P2imax, which is a maximum allowable input value to the second battery 20 (S117). The processing then proceeds to S111. Furthermore, in S116, when the SOC subtracted value Δη is more than the upper limit value Δηmax of the reference range (S116-No), the first BMU 17 and the like control the output from the charger or the like and increase the input power P0i to the storage battery 2 such that input power P1i to the first battery 10 becomes larger than input power P2i to the second battery 20 (S118). At this time, the first BMU 17 and the like make the input power P0i to the storage battery 2 larger than twice the maximum allowable input power P2imax of the second battery 20 so as to make the input power P1i to the first battery 10 larger than the input power P2i to the second battery 20. The processing then proceeds to S111.

　　 Since the processing is performed in this manner, even in this embodiment as in the first embodiment and the like, when the input value to the storage battery 2 is larger than the maximum allowable input value of the second battery 20, the operation of the DC/DC converter 5 is controlled so as to charge the second battery 20 with the maximum allowable input value of the second battery 20 and to charge the first battery 10 with the remaining input. Accordingly, the input to the second battery 20 is suppressed to level of the maximum allowable input value or less. Therefore, this embodiment also enables safe and rapid charge of the storage battery 2 at a large current and effectively prevents deterioration of the storage battery 2.

　　 Furthermore, since the aforementioned processing is performed, in this embodiment, appropriate control is performed to set the SOC subtracted value Δη obtained by subtracting the first SOC η1 from the second SOC η2 within the reference range from the lower limit value Δηmin to the upper limit value Δηmax, and to keep the SOC subtracted value Δη within the reference range. When the SOC subtracted value Δη is less than the lower limit value Δηmin of the reference range, the input to the storage battery 2 is reduced to level of or less than the maximum allowable input value to the second battery 20. Accordingly, the input to the storage battery 2 is input to the second battery 20 exclusively, and the second battery 20 is preferentially charged. Therefore, even when the SOC subtracted value Δη becomes lower than the lower limit value Δηmin, the second battery 20 is charged such that the second SOC rises exclusively, which causes the SOC subtracted value Δη to rapidly fall within the reference range.

　　 When the SOC subtracted value Δη is larger than the upper limit value Δηmax of the reference range, the input value to the storage battery 2 is increased to make an input to the first battery 10 larger than the input to the second battery 20. Accordingly, the first battery 10 is preferentially charged. Therefore, even when the SOC subtracted value Δη becomes larger than the upper limit value Δηmax, the first battery 10 is charged such that the first SOC rises significantly higher than the second SOC of the second battery 20, which causes the SOC subtracted value Δη to rapidly fall within the reference range. Appropriately keeping the SOC subtracted value Δη within the reference range effectively prevents overcharge or the like of the second battery 20 even when malfunction of the DC/DC converter 5 causes charge and discharge between the first battery 10 and the second battery 20.

　　 Furthermore, in this embodiment, since the lower limit value Δηmin of the reference range of the SOC subtracted value Δη is larger than zero, appropriately keeping the SOC subtracted value Δη within the reference range makes it possible to appropriately keep the first SOC η1 of the first battery 10 lower than the second SOC η2 of the second battery 20. Even in this embodiment, keeping the first SOC η1 in a state lower than the second SOC η2 enables discharge from the storage battery 2 while the second SOC η2 of the second battery 20 is in a high state. Accordingly, this embodiment also enables long-term continuous output (discharge) from the storage battery 2.

　　 In this manner, this embodiment also enables safe and rapid charge of the storage battery 2 at a large current and enables long-term continuous output from the storage battery 2. In other words, it is possible to achieve both safety during charge or the like and prolonged driving time of the battery-mounted apparatus 3. In this embodiment, even when malfunction of the DC/DC converter 5 causes charge and discharge between the first battery 10 and the second battery 20, it is possible to effectively prevent overcharge or the like of the second battery 20.

　　 In an embodiment, note that a computer may be provided with a management program that causes the computer to execute the aforementioned processing. The management program causes the computer to control an operation of a DC/DC converter which converts a voltage of electric power input to or output from a second circuit based on an input value to a storage battery when charging the storage battery, first SOC, that is, SOC of a first battery, second SOC, that is, SOC of a second battery, and a maximum allowable input value when charging the second battery corresponding to the second SOC.

　　 A storage battery according to at least one of the embodiments or examples controls an operation of a DC/DC converter which converts a voltage of electric power input to or output from a second circuit based on an input value to the storage battery when charging the storage battery, first SOC, that is, SOC of a first battery, second SOC, that is, SOC of a second battery, and a maximum allowable input value when charging the second battery corresponding to the second SOC. Accordingly, there is provided a management device of the storage battery, a managing method of a storage battery, an electricity storage system, and a battery-mounted apparatus which enable safe and rapid charge of the storage battery at a large current and enable long-term continuous output from the storage battery.

　　 While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

1...electricity storage system; 2...storage battery; 3...battery-mounted device; 5...DC/DC converter; 10...first battery; 11...first cell; 13...first circuit; 17...first battery management unit; 20...second battery; 21...second cell; 23...second circuit; 27...second battery management unit; 30...communication unit; 31...data management unit; 32...data storage unit.

Claims

　　 A management device of a storage battery including a first battery connected to a first circuit, and a second battery connected to a second circuit, the second battery being larger in storage capacity than the first battery and lower in allowable C rate than the first battery, the first circuit and the second circuit being electrically connected in parallel with a DC/DC converter being disposed between the first circuit and the second circuit, the management device comprising
　　 a controller configured to control an operation of the DC/DC converter which converts a voltage of electric power input to or output from the second circuit based on an input value to the storage battery when charging the storage battery, first SOC, that is, SOC of the first battery, second SOC, that is, SOC of the second battery, and a maximum allowable input value when charging the second battery corresponding to the second SOC.
　　 The management device according to claim1, wherein the controller is configured to control the operation of the DC/DC converter to make the first SOC lower than the second SOC and to keep the first SOC lower than the second SOC.
　　 The management device according to claim2, wherein the controller is configured to reduce the input value to the storage battery to level of or less than the maximum allowable input value to the second battery based on the first SOC being the second SOC or higher.
　　 The management device according to claim1, wherein the controller is configured to control the operation of the DC/DC converter to set a SOC subtracted value obtained by subtracting the first SOC from the second SOC within a reference range from a lower limit value to an upper limit value and to keep the SOC subtracted value within the reference range.
　　 The management device according to claim4, wherein the controller is configured to reduce the input value to the storage battery to level of or less than the maximum allowable input value to the second battery based on the SOC subtracted value being less than the lower limit value of the reference range.
　　 The management device according to claim4 or 5, wherein
　　 the first battery includes a monoclinic niobium titanium composite oxide, a kind of titanium composite oxide, as a negative electrode active material,
　　 the second battery includes a carbonaceous material as a negative electrode active material, and
　　 the controller is configured to control the operation of the DC/DC converter by setting the lower limit value and the upper limit value of the reference range of the SOC subtracted value to 0.10 and 0.35, respectively.
　　 The management device according to any one of claims1 to 5, wherein
　　 the first battery includes a titanium composite oxide as a negative electrode active material,
　　 the second battery includes a carbonaceous material as a negative electrode active material, and
　　 the controller is configured to control the operation of the DC/DC converter to control charge of the first battery and the second battery.
　　 The management device according to any one of claims1 to 7, wherein
　　 the input value to the storage battery is input power to the storage battery or a charging rate when charging the storage battery, and
　　 the maximum allowable input value of the second battery is specified by input power to the second battery or a charging rate when charging the second battery.
　　 An electricity storage system comprising:
　　 the management device according to any one of claims1 to 8;
　　 the storage battery including the first battery and the second battery, and managed by the management device; and
　　 the DC/DC converter configured to convert a voltage of electric power input to or output from the second circuit to which the second battery is connected, and configured to perform the operation controlled by the controller of the management device.
　　 The electricity storage system according to claim9, further comprising a battery-mounted apparatus mounted with the storage battery.
　　 A battery-mounted apparatus comprising:
　　 the management device according to any one of claims1 to 8;
　　 the storage battery includes the first battery and the second battery, and managed by the management device; and
　　 the DC/DC converter configured to convert a voltage of electric power input to or output from the second circuit to which the second battery is connected, and configured to perform the operation controlled by the controller of the management device.
　　 A managing method of a storage battery including a first battery connected to a first circuit, and a second battery connected to a second circuit, the second battery being larger in storage capacity than the first battery and lower in allowable C rate than the first battery, the first circuit and the second circuit being electrically conected in parallel with a DC/DC converter being disposed between the first circuit and the second circuit, the managing method comprising
　　 controlling an operation of a DC/DC converter which converts a voltage of electric power input to or output from the second circuit based on an input value to the storage battery when charging the storage battery, first SOC, that is, SOC of the first battery, second SOC, that is, SOC of the second battery, and a maximum allowable input value when charging the second battery corresponding to the second SOC.