Energy storage device

Abstract

To provide a battery pack (power storage device) achieving improvement in utilization efficiency of batteries mounted on a vehicle.SOLUTION: A battery pack 5 includes: a battery 19 in which two battery packs 19-1, 19-2 are connected in parallel, each battery pack including a plurality of lithium ion secondary batteries connected in series; a voltage detection circuit 13 detecting a voltage of each power storage element of the two battery packs; first determination means determining whether a difference between a maximum voltage and a minimum voltage of the detected cell voltages exceeds a predetermined threshold; connection cutoff means cutting off connection between a vehicle load 3 and the battery pack including the power storage element indicating the difference exceeding the predetermined threshold; equalization means equalizing capacity between the power storage elements constituting the battery pack in which the connection has been cut off; second determination means determining whether the voltage of the battery pack in which equalization has been performed is substantially the same with a voltage of the battery pack in which the connection has not been cut off; and establishment means establishing, when it is determined that the voltages are substantially same, the connection between the vehicle load 3 and the battery pack in which equalization has been performed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power storage device, and particularly to a power storage device capable of improving the utilization efficiency of a battery included in the power storage device.

Background Art

[0002] A lithium-ion secondary battery (LIB: Lithium Ion Battery, hereinafter referred to as LIB) used in a power storage device or the like is known for its high energy density, small size, and light weight as compared with other secondary batteries such as nickel-cadmium batteries and nickel-metal hydride batteries.

[0003] For example, Non-Patent Document 1 discloses a battery system for motor sports configured by combining an LIB employing lithium iron phosphate as a positive electrode active material and a battery management system (BMS: Battery Management System, hereinafter referred to as BMS) as a power storage device. This conventional battery system includes a main LIB and a sub LIB having a smaller battery capacity than the main LIB, and as a recovery measure from the over-discharged state (over-discharged state) of the main LIB, when an external button is pressed, switching from the main LIB to the sub LIB is performed.

[0004] On the other hand, an uninterruptible power supply (UPS: Uninterruptible Power Supply, hereinafter referred to as UPS) is widely used as a power supply device for stably supplying AC power to an important load such as a computer system. For example, Patent Document 1 discloses a UPS system capable of realizing a soft start at the time of restoration of an AC power supply. [[ID=​​​​​​​​​​​MEGA-Life Racing Battery [Searched November 30, 2022] Internet<URL:https: / / www.megalife.jp / feature> [Patent Documents]

[0006] [Patent Document 1] Patent No. 7027576 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the conventional battery system disclosed in Non-Patent Document 1, the sub-LIB is only used to recover from a dead main LIB and does not operate continuously. Therefore, in the conventional battery system, the sub-LIB has a long standby time and the battery utilization efficiency, or in other words, the amount of energy generated per unit volume occupied by the battery system in the vehicle, is low.

[0008] In view of this, the object of the present invention is to provide an energy storage device to be mounted on a vehicle that can improve the utilization efficiency of the battery and at the same time deal with battery abnormalities.

[0009] On the other hand, in recent years, there has been a growing demand for larger capacity energy storage devices. Similarly, there is increasing demand for larger capacity energy storage devices used in UPS systems, as disclosed in Patent Document 1, which supply power to equipment loads in the event of a power outage.

[0010] In recent years, support measures for UPS systems, such as relocating auxiliary power sources from external sources during power outages, have become known. However, such support measures are not always implemented in a timely manner. Therefore, in addition to the demand for larger capacity batteries, it is desirable to improve the battery utilization efficiency of the energy storage devices installed in UPS systems.

[0011] In view of this, an object of the present invention is to provide an energy storage device for a UPS system that can improve battery utilization efficiency in addition to meeting the demand for larger capacity, and can also deal with battery malfunctions. [Means for solving the problem]

[0012] To achieve this objective, the present invention, from a first perspective, A power storage device that supplies power to the vehicle load, The battery is configured by connecting two battery packs in parallel, each containing multiple lithium-ion secondary battery energy storage elements connected in series, and is constantly connected in parallel to the vehicle load. A voltage detection means for detecting the cell voltage across each energy storage element constituting each of the two battery packs, A first determination means that determines whether the difference between the maximum voltage and the minimum voltage among multiple cell voltages detected by the voltage detection means exceeds a predetermined threshold, When the first determination means determines that the difference exceeds a predetermined threshold, a connection disconnection means disconnects the connection between the battery pack, which includes an energy storage element showing the difference between the maximum voltage and the minimum voltage exceeding the predetermined threshold, and the vehicle load. An equalization means for equalizing the energy storage capacity among multiple energy storage elements constituting a battery pack whose connection to the vehicle load has been disconnected by a connection disconnection means, A second determination means for determining whether the module voltages at both ends of a battery pack whose storage capacity has been equalized by an equalization means are substantially the same as the module voltages at both ends of the other battery pack whose connection to the vehicle load has not been interrupted, When the second determination means determines that the module voltages are not substantially the same, the re-equalization means charges and / or discharges the other battery pack, which is not disconnected from the battery pack whose storage capacity has been equalized and / or from the vehicle load, so that the module voltages become substantially the same. When the second determination means determines that the voltages of each module are substantially the same, a connection establishment means establishes a connection between the battery pack whose storage capacity has been equalized and the vehicle load, A power storage device was constructed that includes the following features.

[0013] In this configuration, the battery used in the energy storage device is composed of two battery packs, each consisting of multiple lithium-ion secondary batteries connected in series, connected in parallel, and is constantly connected in parallel to the vehicle load. Therefore, unlike the battery system disclosed in Non-Patent Document 1, in which the sub-LIB is not constantly operating, power is constantly supplied to the vehicle load from the battery, which consists of two battery packs, corresponding to the main LIB and sub-LIB, connected in parallel. This increases the amount of energy generated per unit volume occupied by the energy storage device within the vehicle, thereby improving the battery's utilization efficiency.

[0014] Furthermore, according to this configuration, the first determination means determines whether the difference between the maximum voltage and the minimum voltage among the multiple cell voltages detected by the voltage detection means exceeds a predetermined threshold. A battery pack containing energy storage elements whose maximum and minimum voltages exceed the predetermined threshold is determined to have advanced degradation of each energy storage element constituting the battery pack, and the connection between the battery pack and the vehicle load is disconnected by the connection disconnection means. Subsequently, the equalization means equalizes the energy storage capacity among the multiple energy storage elements constituting the battery pack. This equalization process restores the battery composed of two battery packs connected in parallel, thereby improving the lifespan of the energy storage device.

[0015] Furthermore, in the first aspect, the present invention is The battery pack includes a third determination means for determining whether there is a battery pack containing an energy storage element in an overcharged or over-discharged state based on the cell voltage detected by the voltage detection means. The connection disconnection means disconnects the connection between the battery pack and the vehicle load, which the third determination means has determined to include an energy storage element whose cell voltage is in an overcharged or over-discharged state. It is characterized by the following:

[0016] According to this configuration, the third determination means determines whether there is a battery pack including a power storage element in an overcharged state or an overdischarged state, and when there is such a battery pack, the connection interruption means interrupts the connection between the battery pack and the vehicle load. Therefore, by replacing the battery pack whose connection to the vehicle load has been interrupted, it becomes possible to gradually address the abnormality of the power storage device.

[0017] Further, from a second aspect, the present invention is a power storage device that supplies power to a facility load in place of an AC power source during a power outage of the AC power source, a battery configured by connecting a plurality of battery packs in parallel, each battery pack being formed by connecting a plurality of power storage elements made of lithium ion secondary batteries in series, voltage detection means for detecting the cell voltages at both ends of each power storage element constituting each of the plurality of battery packs, first determination means for determining whether the difference between the maximum voltage and the minimum voltage among the plurality of cell voltages detected by the voltage detection means exceeds a predetermined threshold value, when it is determined by the first determination means that the difference exceeds the predetermined threshold value, connection interruption means for interrupting the connection between the battery pack including the power storage element showing the difference between the maximum voltage and the minimum voltage exceeding the predetermined threshold value and the facility load, equalization means for equalizing the storage capacities among the plurality of power storage elements constituting the battery pack whose connection to the facility load has been interrupted by the connection interruption means, second determination means for determining whether the module voltages at both ends of the battery pack for which the storage capacity equalization has been performed by the equalization means are substantially the same as the module voltages at both ends of the battery pack whose connection to the facility load has not been interrupted, When the second determination means determines that the module voltages are not substantially the same, a re-equalization means charges and / or discharges a battery pack whose connection to the battery pack and / or equipment load has not been interrupted so that the module voltages become substantially the same. when it is determined by the second determination means that each module voltage is substantially the same, connection establishment means for establishing the connection between the battery pack for which the storage capacity equalization has been performed and the facility load, constitutes a power storage device provided with

[0018] According to this configuration, the battery used in the energy storage device is composed of multiple battery packs, each containing multiple lithium-ion secondary batteries connected in series, connected in parallel. Therefore, when an AC power outage occurs, the battery is connected in parallel to the equipment load, and multiple battery packs operate simultaneously. Thus, unlike the battery system disclosed in Non-Patent Document 1, in which the sub-LIB does not operate continuously, when the battery is operating, power is supplied to the equipment load simultaneously from each of the multiple battery packs. As a result, the amount of energy generated per unit volume occupied by the energy storage device in the UPS system increases, and the battery utilization efficiency can be improved.

[0019] Furthermore, with this configuration, since the battery is made up of multiple battery packs connected in parallel, it becomes possible to meet the demand for larger capacity in energy storage devices installed in UPS systems.

[0020] Furthermore, according to this configuration, the first determination means determines whether the difference between the maximum voltage and the minimum voltage among the multiple cell voltages detected by the voltage detection means exceeds a predetermined threshold. A battery pack containing energy storage elements whose maximum and minimum voltages exceed the predetermined threshold is determined to have advanced degradation of each energy storage element constituting the battery pack, and the connection between the battery pack and the equipment load is disconnected by the connection disconnection means. Subsequently, the equalization means equalizes the energy storage capacity among the multiple energy storage elements constituting the battery pack. This equalization process restores the battery composed of multiple battery packs connected in parallel, thereby improving the lifespan of the energy storage device.

[0021] Furthermore, in a second aspect, the present invention is The battery pack includes a third determination means for determining whether there is a battery pack containing an energy storage element in an overcharged or over-discharged state based on the cell voltage detected by the voltage detection means. The connection disconnection means disconnects the connection between the battery pack and the equipment load, which the third determination means has determined to include an energy storage element whose cell voltage is in an overcharged or over-discharged state. It is characterized by the following:

[0022] In this configuration, the third determination means determines whether there is a battery pack containing an energy storage element whose cell voltage is in an overcharged or over-discharged state. If such a battery pack exists, the connection disconnection means disconnects the connection between the battery pack and the equipment load. Therefore, by replacing the battery pack whose connection to the equipment load has been disconnected, it becomes possible to address abnormalities in the energy storage device in stages. [Effects of the Invention]

[0023] As a result, the present invention provides a vehicle-mounted energy storage device that can improve battery utilization efficiency while also addressing battery malfunctions. Furthermore, it also provides an energy storage device for a UPS system that can improve battery utilization efficiency in conjunction with the demand for larger capacity while also addressing battery malfunctions. [Brief explanation of the drawing]

[0024] [Figure 1] This is a block diagram illustrating the configuration of a battery pack mounted on a vehicle according to a first embodiment of the present invention. [Figure 2] Figure 1 is a flowchart illustrating the operation of the battery pack. [Figure 3] This is a block diagram illustrating a UPS system equipped with a battery pack according to a second embodiment of the present invention. [Figure 4] (a) is a diagram illustrating the operation of the UPS system shown in Figure 3 in commercial power supply mode, and (b) is a diagram illustrating the operation of the UPS system shown in Figure 3 in battery pack power supply mode. [Figure 5] This is a block diagram illustrating the configuration of a battery pack according to a second embodiment, which is provided in the UPS system shown in Figure 3. [Figure 6] Figure 5 is a flowchart illustrating the operation of the battery pack. [Modes for carrying out the invention]

[0025] The following describes in detail an embodiment of the present invention with reference to the attached drawings.

[0026] Figure 1 is a block diagram illustrating the configuration of a battery pack 5, which is an energy storage device mounted on a vehicle, according to a first embodiment of the present invention.

[0027] The battery pack 5 according to this embodiment can be used, for example, as a 12V or 24V power supply that supplies power to the engine starting device of a vehicle. The battery pack 5 is, for example, an energy storage device installed in a vehicle that runs on fossil fuels such as gasoline or a hybrid vehicle, and is charged by a vehicle generator (e.g., an alternator) 1 and discharged to a vehicle load 3 installed in the vehicle to supply power to the vehicle load 3.

[0028] The battery pack 5 comprises a battery 19, which is composed of two battery packs 19-1 and 19-2, each consisting of multiple energy storage elements connected in series, connected in parallel; a battery management unit (BMU) 7 for managing the battery 19; a current detection unit 23; a discharge unit 20 consisting of discharge circuits 20-1 and 20-2; a temperature measurement unit 21 consisting of temperature measurement units 21-1 and 21-2; an output control circuit 15; and a current interruption circuit 17.

[0029] In this embodiment, each of the battery packs 19-1 and 19-2 is configured with eight energy storage elements connected in series, and the total voltage across each battery pack is 24[V]. However, the configuration of battery packs 19-1 and 19-2 is not limited to this.

[0030] Furthermore, the energy storage elements constituting each of the battery packs 19-1 and 19-2 in this embodiment are lithium-ion secondary batteries. In this embodiment, the energy storage element is constructed by housing an electrode stack together with an electrolyte in an outer casing, for example, a laminate film. The electrode stack is constructed by stacking a positive electrode, which has a positive electrode layer made of an olivine-type positive electrode active material such as LiFePO4 on a positive electrode current collector, for example, aluminum foil, and a negative electrode, which has a negative electrode layer made of a carbon material such as graphite on a negative electrode current collector, for example, copper foil, with a separator in between.

[0031] The current detection unit 23 is, for example, a current detection resistor (e.g., a shunt resistor), and in response to instructions from the central processing unit (hereinafter referred to as CPU) 9 located inside the BMU 7, it detects the current flowing to the battery 19 by detecting the potential difference across the ends of the current detection resistor.

[0032] The discharge circuits 20-1 and 20-2 that constitute the discharge unit 20 are provided corresponding to the battery packs 19-1 and 19-2, respectively. In each discharge circuit 20-1 and 20-2, a unit discharge circuit (not shown) is provided for each energy storage element that makes up the battery packs 19-1 and 19-2. The unit discharge circuit is composed of a series connection of a semiconductor switch, such as an FET (field-effect transistor), and a resistive element, and in response to instructions from the BMU 7, it discharges the capacity stored in the corresponding energy storage element.

[0033] The temperature measuring units 21-1 and 21-2 constituting the temperature measuring unit 21 are contact-type or non-contact-type temperature measuring instruments that measure the temperature [°C] of the corresponding battery packs 19-1 and 19-2 in response to instructions from the CPU 9 located inside the BMU 7. In this case, the temperature measuring units 21-1 and 21-2 may measure the temperature of a specific single energy storage element or a group of energy storage elements within the corresponding battery packs 19-1 and 19-2.

[0034] The current value detected by the current detection unit 23 and the measured values ​​measured by the temperature measurement units 21-1 and 21-2 are stored in the memory (hereinafter referred to as MEM) 11 located inside the BMU7.

[0035] The output control circuit 15 controls the output current or output voltage of the battery 19 in response to instructions from the BMU 7.

[0036] The current interruption circuit 17 is, for example, a semiconductor switch such as an FET or a relay. The battery 19 is always connected in parallel to the vehicle load 3, but the current interruption circuit 17 interrupts or establishes the connection between one or both of the battery packs 19-1 and 19-2 and the vehicle generator 1 and the vehicle load 3 in response to instructions from the BMU 7.

[0037] The BMU7 includes a CPU 9, a MEM 11, and a voltage detection circuit 13, and operates by being powered by a battery 19 consisting of two battery packs 19-1 and 19-2.

[0038] The CPU 9 executes the operations described later in Figure 2, according to the instructions of the computer program that describes the series of operations according to this embodiment, which is stored in MEM 11.

[0039] MEM11 is, for example, a non-volatile memory such as flash memory or EEPROM (Electrically Erasable Programmable Read-Only Memory), and stores a computer program describing the series of operations according to this embodiment, as well as voltage values, current values, temperature values, etc., detected in response to instructions from CPU9.

[0040] The voltage detection circuit 13 is connected to both ends of each energy storage element via voltage detection lines (not shown) and constitutes a voltage detection means for detecting the cell voltage at both ends of each energy storage element constituting the two battery packs 19-1 and 19-2. In this embodiment, the voltage detection circuit 13 measures the cell voltage of each energy storage element constituting the two battery packs 19-1 and 19-2, and / or the module voltage, which is the total voltage of the two battery packs 19-1 and 19-2, in response to instructions from the CPU 9. The voltage values ​​detected by the voltage detection circuit 13 are stored in the MEM 11 under the control of the CPU 9.

[0041] The CPU 9 constitutes a first determination means that determines whether the difference between the maximum voltage and the minimum voltage among the multiple cell voltages detected by the voltage detection circuit 13 exceeds a predetermined threshold. The current interruption circuit 17 constitutes a connection interruption means that, when the first determination means determines that the difference exceeds a predetermined threshold, interrupts the connection between the battery packs 19-1 and 19-2, which include the energy storage elements showing the difference between the maximum and minimum voltages exceeding the predetermined threshold, and the vehicle load 3. The CPU 9 also constitutes an equalization means that equalizes the energy storage capacity among the multiple energy storage elements constituting the battery packs 19-1 and 19-2, from which the connection with the vehicle load 3 has been interrupted by the current interruption circuit 17.

[0042] Furthermore, the CPU 9 constitutes a second determination means for determining whether the module voltages at both ends of the battery packs 19-1 and 19-2, whose storage capacity has been equalized by the equalization means, are substantially the same as the module voltages at both ends of the other battery pack 19-2 and 19-1, which are not connected to the vehicle load 3. In addition, the current interruption circuit 17 constitutes a connection establishment means for establishing the connection between the battery packs 19-1 and 19-2, whose storage capacity has been equalized and the vehicle load 3, when the second determination means determines that the respective module voltages are substantially the same.

[0043] Furthermore, the CPU 9 also constitutes a third determination means for determining whether there are any battery packs 19-1, 19-2 that include energy storage elements whose cell voltages, as detected by the voltage detection circuit 13, are in an overcharged or over-discharged state. The current interruption circuit 17, which constitutes the connection interruption means, interrupts the connection between the battery packs 19-1, 19-2, which the third determination means has determined to include energy storage elements whose cell voltages are in an overcharged or over-discharged state, and the vehicle load 3.

[0044] Figure 2 is a flowchart illustrating the operation of a battery pack 5 mounted on a vehicle according to this embodiment.

[0045] When the battery pack 5 is in operation, first, in step S01, the cell voltages across the energy storage elements constituting each of the battery packs 19-1 and 19-2 are detected by the voltage detection circuit 13, according to the instructions of the CPU 9.

[0046] Next, in step S02, the CPU 9, which constitutes the first determination means, determines whether the difference between the maximum voltage and the minimum voltage among the multiple cell voltages detected by the voltage detection circuit 13 exceeds a predetermined threshold, for example, 0.3V. Specifically, for each battery pack 19-1, 19-2, the CPU 9 calculates the difference between the maximum voltage and the minimum voltage among the multiple cell voltages detected, and determines whether the calculated difference exceeds the predetermined threshold.

[0047] In step S02, if it is determined that the difference between the maximum and minimum voltages among the detected cell voltages exceeds the predetermined threshold, then in step S03, the current interruption circuit 17 constituting the connection interruption means is interrupted by the CPU 9, thereby interrupting the connection between the battery packs 19-1 and 19-2, which include energy storage elements, and the vehicle load 3, where the difference between the maximum and minimum voltages exceeds the predetermined threshold.

[0048] Next, in step S04, the CPU 9, which constitutes the equalization means, equalizes the storage capacity among the multiple storage elements constituting the battery packs 19-1 and 19-2 from which the connection to the vehicle load 3 has been disconnected. Specifically, the CPU 9 instructs a unit discharge circuit provided in correspondence with the storage element showing the maximum voltage among the disconnected battery packs 19-1 and 19-2 to discharge the storage element showing the maximum voltage so that the voltage difference between it and the minimum voltage is, for example, 0.2V. This cell balancing operation may be performed not only for any of the battery packs 19-1 and 19-2 that include the storage element showing the maximum voltage, but also for all the battery packs 19-1 and 19-2 from which the connection to the vehicle load 3 has been disconnected, so that the difference between the storage element showing the maximum voltage and the storage element showing the minimum voltage falls within the predetermined voltage difference.

[0049] Next, in step S05, the CPU 9, which constitutes the second determination means, compares the module voltage, which is the total voltage across both ends of battery packs 19-1 and 19-2 whose storage capacity has been equalized by the equalization means after the connection with the vehicle load 3 has been interrupted, with the module voltage, which is the total voltage across both ends of battery packs 19-2 and 19-1 whose connection with the vehicle load 3 has not been interrupted. Specifically, the CPU 9 instructs the voltage detection circuit 13 to detect the module voltage across both ends of battery packs 19-1 and 19-2 whose storage capacity has been equalized, and the module voltage across both ends of battery packs 19-2 and 19-1 whose connection with the vehicle load 3 has not been interrupted. The CPU 9 then compares the module voltages detected by the voltage detection circuit 13.

[0050] Next, in step S06, the CPU 9, which constitutes the second determination means, determines whether the module voltages at both ends of battery packs 19-1 and 19-2, whose storage capacity has been equalized as a result of the comparison in step S05, and the module voltages at both ends of battery packs 19-2 and 19-1, whose connection has not been interrupted, are substantially the same. Whether or not they are substantially the same is determined by whether or not the voltage difference between each module voltage falls within a predetermined value.

[0051] If it is determined in step S06 that the batteries are not substantially the same, the process returns to step S04, and the equalization of storage capacity is performed again among the multiple storage elements constituting the battery packs 19-1 and 19-2 whose storage capacity has been equalized. After that, the processes in steps S05 and S06 are repeated. In this case, in order to return the battery packs 19-1 and 19-2, whose storage capacity equalization has been completed, to the battery 19 as soon as possible, the CPU 9 may instruct the charging circuit (not shown) and / or the discharging circuit 20 in the second equalization process to charge and / or discharge the battery packs 19-2 and 19-1, whose connections have not been interrupted, so that the module voltage across the battery packs 19-1 and 19-2, whose storage capacity has been equalized and the module voltage across the battery packs 19-2 and 19-1, whose connections have not been interrupted, fall within a predetermined voltage difference, for example, 0.2V.

[0052] On the other hand, if it is determined in step S06 that they are substantially the same, then in step S07, the current interruption circuit 17 constituting the connection establishment means is connected and controlled by the CPU 9, thereby establishing a connection between the battery packs 19-1 and 19-2, whose connections have been interrupted and whose storage capacities have been equalized, and the vehicle load 3.

[0053] Furthermore, if in step S02 it is determined that the difference between the maximum and minimum voltages among the detected cell voltages does not exceed a predetermined threshold, then in step S08, the CPU 9 constituting the third determination means determines whether there are any cell voltages among the detected cell voltages that are in an overcharged state or an over-discharged state.

[0054] If it is determined in step S08 that there are no cell voltages in an overcharged or over-discharged state, the process returns to step S01 and each of the above processes is repeated.

[0055] On the other hand, if it is determined in step S02 that there is a cell voltage that is in an overcharged state or an over-discharged state, then in step S09, the current interruption circuit 17, which constitutes the connection interruption means, interrupts the connection between the battery packs 19-1 and 19-2, which are determined to contain energy storage elements whose cell voltages are in an overcharged or over-discharged state, and the vehicle load 3. After that, the control processing of the battery pack 5 is terminated.

[0056] According to this embodiment of the battery pack 5, the battery 19 used in the battery pack 5 is configured by connecting two battery packs 19-1 and 19-2, each consisting of multiple lithium-ion secondary batteries connected in series, in parallel, and is always connected in parallel to the vehicle load 3. Therefore, unlike the battery system disclosed in Non-Patent Document 1, in which the sub-LIB is not always in operation, power is constantly supplied to the vehicle load 3 from the battery 19, which consists of two battery packs 19-1 and 19-2, corresponding to the main LIB and sub-LIB, connected in parallel. As a result, the amount of energy generated per unit volume occupied by the battery pack 5 within the vehicle increases, and the utilization efficiency of the battery 19 can be improved.

[0057] Furthermore, according to the battery pack 5 of this embodiment, in step S02, the CPU 9 constituting the first determination means identifies battery packs 19-1 and 19-2 in which the difference between the maximum voltage and the minimum voltage among the multiple cell voltages in each battery pack 19-1 and 19-2 exceeds a predetermined threshold. Battery packs 19-1 and 19-2 in which the difference exceeds the predetermined threshold are determined to have advanced deterioration of each energy storage element constituting the battery pack 19-1 and 19-2, and in step S03, the connection between the battery pack 19-1 and 19-2 and the vehicle load 3 is interrupted by the current interruption circuit 17 constituting the connection interruption means. Subsequently, in step S04, the CPU 9 constituting the equalization means equalizes the energy storage capacity among the multiple energy storage elements constituting the battery pack 19-1 and 19-2. This equalization allows for the recovery process of the battery 19 composed of two battery packs 19-1 and 19-2 connected in parallel, thereby improving the lifespan of the energy storage device.

[0058] Furthermore, according to the battery pack 5 of this embodiment, in step S08, the CPU constituting the third determination means determines whether there are battery packs 19-1, 19-2 that include energy storage elements whose cell voltage is in an overcharged or over-discharged state. If such battery packs 19-1, 19-2 exist, in step S09, the current interruption circuit 17 constituting the connection interruption means interrupts the connection between the battery packs 19-1, 19-2 and the vehicle load 3. Therefore, by replacing the battery packs 19-1, 19-2 whose connection to the vehicle load 3 has been interrupted, it becomes possible to deal with abnormalities in the battery pack 5 in a stepwise manner.

[0059] In the above embodiment, the battery pack 5 is an energy storage device installed in a vehicle that uses fossil fuels such as gasoline or in a hybrid vehicle (HV). As a variation of this, the battery pack 5 can also be an auxiliary energy storage device installed in an electric vehicle (EV) that supplies power to electrical components, etc. In this case, in an electric vehicle, when the electric motor that drives the vehicle is operating, if the voltage of the battery 19 is below a predetermined value, a charging current is generated from the drive energy storage device that drives the electric motor to the battery 19.

[0060] Next, a second embodiment of the present invention will be described.

[0061] In the first embodiment, a battery pack 5 that supplies power to the vehicle's load is disclosed as an energy storage device. In the second embodiment, a battery pack 5 that supplies power to equipment loads such as emergency lights and computer systems via a UPS in the event of a power outage is disclosed as an energy storage device.

[0062] Figure 3 is a block diagram illustrating a UPS system in which the battery pack 5 according to the second embodiment is provided.

[0063] This UPS system consists of a UPS 31 and a battery pack 5. In commercial power supply mode, the UPS 31 supplies power from the commercial AC power supply 27 to the equipment load 29 while charging the battery pack 5, and in battery pack power supply mode, it supplies power from the battery pack 5 to the equipment load 29.

[0064] The UPS31 illustrated in Figure 3 includes an AC input terminal T1, a battery terminal T2, an AC output terminal T3, a converter 33, a DC line 37, a capacitor 39, a step-down chopper 41, an inverter 43, switches S1 and S2, and a control unit 45.

[0065] Figure 4(a) illustrates the operation of a UPS system according to the second embodiment in commercial power supply mode.

[0066] In commercial power supply mode, the control unit 45 turns on switch S1 and off switch S2 so that AC power is supplied to the converter 33 from the commercial AC power supply 27 via switch S1. Specifically, the control unit 45 controls the converter 33 to convert the AC power supplied from the commercial AC power supply 27 via switch S1 and AC node 35a into DC power, and controls the inverter 43 to convert the DC power from the converter 33 into AC power and supply it to the equipment load 29. Meanwhile, the control unit 45 controls the step-down chopper 41 to store the DC power from the converter 33 in the battery in the battery pack 5.

[0067] Figure 4(b) illustrates the operation of the battery pack power supply mode of the UPS system according to the second embodiment.

[0068] In battery pack power supply mode, the control unit 45 turns on switch S2 and off switch S1 so that DC power is supplied from the battery pack 5 to the converter 33 via switch S2 and DC node 35b. Specifically, the control unit 45 controls the converter 33 to boost the DC power supplied from the battery pack 5 via switch S2 and supply it to the inverter 43. The control unit 45 also controls the inverter 43 to convert the DC power from the converter 33 to AC power and supply the converted AC power to all equipment loads 29 or preset equipment loads 29.

[0069] Figure 5 is a block diagram illustrating the configuration of a battery pack 5 provided in a UPS system according to the second embodiment. The battery pack 5 according to the second embodiment is an energy storage device that supplies power to equipment loads 29 in place of the commercial AC power supply 27 when the commercial AC power supply 27 is interrupted.

[0070] Regarding the configuration of the battery pack 5 illustrated in Figure 5, components that perform the same functions and roles as those in the battery pack 5 illustrated in Figure 1 are given the same reference numerals, and their explanations are omitted.

[0071] In the first embodiment of the battery pack 5, the battery 19 is configured by connecting two battery packs 19-1, 19-2, each consisting of, for example, eight energy storage elements connected in series, in parallel. In contrast, in the second embodiment of the battery pack 5, the battery 19 is a 48[V] power supply configured by connecting 18 battery packs 19-1, 19-2, ..., 19-18, each consisting of, for example, fifteen LIB energy storage elements connected in series, in parallel.

[0072] Furthermore, in the battery pack 5 according to the second embodiment, the voltage detection circuit 13 is connected to both ends of each energy storage element via a voltage detection line (not shown), and constitutes a voltage detection means for detecting the cell voltage at both ends of each energy storage element constituting each of the 18 battery packs 19-1, 19-2, ..., 19-18. The CPU 9 constitutes a first determination means for determining whether the difference between the maximum voltage and the minimum voltage among the multiple cell voltages detected by the voltage detection circuit 13 exceeds a predetermined threshold. The current interruption circuit 17 constitutes a connection interruption means for interrupting the connection between the battery packs 19-1, 19-2, ..., 19-18, which include the energy storage element showing the difference between the maximum voltage and the minimum voltage that exceeds the predetermined threshold, and the equipment load 29 when the first determination means determines that the difference exceeds the predetermined threshold.

[0073] Furthermore, the CPU 9 constitutes an equalization means for equalizing the storage capacity among multiple energy storage elements constituting the battery packs 19-1, 19-2, ..., 19-18 whose connection to the equipment load 29 has been interrupted by the connection interruption means. The CPU 9 also constitutes a second determination means for determining whether the module voltages at both ends of the battery packs 19-1, 19-2, ..., 19-18 whose storage capacity has been equalized by the equalization means are substantially the same as the module voltages at both ends of the battery packs 19-1, 19-2, ..., 19-18 whose connection to the equipment load 29 has not been interrupted. Furthermore, when the current interruption circuit 17 determines that the module voltages are substantially the same, it constitutes a connection establishment means for establishing a connection between the battery packs 19-1, 19-2, ..., 19-18 whose storage capacity has been equalized and the equipment load 29.

[0074] Furthermore, the CPU 9 constitutes a third determination means for determining whether there are any battery packs 19-1, 19-2, ..., 19-18 that include energy storage elements whose cell voltages, as detected by the voltage detection means, are in an overcharged or over-discharged state. The current interruption circuit 17, which constitutes the connection interruption means, interrupts the connection between the battery packs 19-1, 19-2, ..., 19-18 that the third determination means has determined to include energy storage elements whose cell voltages are in an overcharged or over-discharged state and the equipment load 29.

[0075] Figure 6 is a flowchart illustrating the operation of a battery pack 5 provided in a UPS system according to the second embodiment.

[0076] When the battery pack 5 is in operation, first, in step S11, the CPU 9 determines whether a power outage has occurred in the commercial AC power supply 27. If no power outage has occurred, the battery pack 5 is charged by the power supplied from the commercial AC power supply 27 in the commercial power supply mode described above. Therefore, the CPU 9 can determine that a power outage has occurred if the current detection unit 23 does not detect a current that exceeds a predetermined value corresponding to the charging current from the step-down chopper 41.

[0077] If it is determined in step S11 that no power outage has occurred, the process in step S11 is repeated. On the other hand, if it is determined that a power outage has occurred, the control unit 45 of the UPS 31 controls the UPS 31 to enter the battery pack power supply mode, which supplies power from the battery pack 5 to the equipment load 29. Next, in step S12, in the battery pack power supply mode, the voltage detection circuit 13 detects the cell voltages across each of the energy storage elements constituting each of the 18 battery packs 19-1, 19-2, ..., 19-18.

[0078] Next, in step S13, the CPU 9, which constitutes the first determination means, determines whether the difference between the maximum voltage and the minimum voltage among the multiple cell voltages detected by the voltage detection circuit 13 exceeds a predetermined threshold, for example, 0.3V. Specifically, the CPU 9 calculates the difference between the maximum voltage and the minimum voltage among the multiple cell voltages detected for each battery pack 19-1, 19-2, ..., 19-18, and determines whether the calculated difference exceeds the predetermined threshold.

[0079] In step S13, if it is determined that the difference between the maximum and minimum voltages among the detected cell voltages exceeds the predetermined threshold, then in step S14, the current interruption circuit 17 constituting the connection interruption means is interrupted by the CPU 9, thereby interrupting the connection between the battery packs 19-1, 19-2, ..., 19-18, which include energy storage elements whose difference exceeds the predetermined threshold between the maximum and minimum voltages, and the equipment load 29.

[0080] Next, in step S15, the CPU 9, which constitutes the equalization means, equalizes the storage capacity among the multiple storage elements constituting the battery packs 19-1, 19-2, ..., 19-18 from which the connection to the equipment load 29 has been disconnected. Specifically, the CPU 9 instructs a unit discharge circuit provided in correspondence with the storage element showing the maximum voltage among the disconnected battery packs 19-1, 19-2, ..., 19-18 to discharge the storage element showing the maximum voltage so that the voltage difference between it and the minimum voltage is, for example, 0.2V. This cell balancing operation may be performed not only for any of the battery packs 19-1, 19-2, ..., 19-18 that include the storage element showing the maximum voltage, but also for all the battery packs 19-1, 19-2, ..., 19-18 from which the connection to the vehicle load 3 has been disconnected, so that the difference between the storage element showing the maximum voltage and the storage element showing the minimum voltage falls within the predetermined voltage difference.

[0081] Next, in step S16, the CPU 9, which constitutes the second determination means, compares the module voltage, which is the total voltage across the battery packs 19-1, 19-2, ..., 19-18 whose storage capacity has been equalized by the equalization means after the connection with the equipment load 29 has been interrupted, with the module voltage, which is the total voltage across the battery packs 19-2, 19-1, whose connection with the equipment load 29 has not been interrupted. Specifically, the CPU 9 instructs the voltage detection circuit 13 to detect the module voltage across the battery packs 19-1, 19-2, ..., 19-18 whose storage capacity has been equalized, and the module voltage across the battery packs 19-1, 19-2, ..., 19-18 whose connection with the vehicle load 3 has not been interrupted. Then, the CPU 9 compares the module voltages detected by the voltage detection circuit 13.

[0082] Next, in step S17, the CPU 9, which constitutes the second determination means, determines whether the module voltages at both ends of the battery packs 19-1, 19-2, ..., 19-18, whose storage capacity has been equalized as a result of the comparison in step S16, are substantially the same as the module voltages at both ends of the battery packs 19-1, 19-2, ..., 19-18, whose connections have not been interrupted. Whether or not they are substantially the same is determined by whether or not the voltage difference between each module voltage falls within a predetermined value.

[0083] If it is determined in step S17 that the elements are not substantially the same, the process returns to step S15, and the equalization of storage capacity is performed again among the multiple storage elements that make up the battery packs 19-1, 19-2, ..., 19-18 whose storage capacities have been equalized. After that, the processes in steps S16 and S17 are repeated. In this case, the CPU 9 may, in order to return the battery packs 19-1, 19-2, ..., 19-18, whose capacity equalization has been completed, to the battery 19 as soon as possible, perform another equalization process instructing the charging circuit (not shown) and / or the discharging circuit 20 to charge and / or discharge the battery packs 19-1, 19-2, ..., 19-18, whose connections have not been interrupted, so that the module voltage across the battery packs 19-1, 19-2, ..., 19-18, whose storage capacity has been equalized, and the module voltage across the battery packs 19-1, 19-2, ..., 19-18, whose connections have not been interrupted, fall within a predetermined voltage difference, for example, 0.2V.

[0084] On the other hand, if it is determined in step S17 that they are substantially the same, then in step S18, the current interruption circuit 17 constituting the connection establishment means is connected and controlled by the CPU 9, thereby establishing a connection between the battery packs 19-1, 19-2, ..., 19-18, whose connections have been interrupted and whose storage capacities have been equalized, and the equipment load 29.

[0085] Furthermore, if in step S13 it is determined that the difference between the maximum and minimum voltages among the detected cell voltages does not exceed a predetermined threshold, then in step S19 the CPU 9, which constitutes the third determination means, determines whether there are any cell voltages among the detected cell voltages that are in an overcharged state or an over-discharged state.

[0086] If step S13 determines that there are no cell voltages in an overcharged or over-discharged state, the process returns to step S12, and each of the above processes is repeated.

[0087] On the other hand, if it is determined in step S19 that there is a cell voltage that is in an overcharged state or an over-discharged state, then in step S20, the current interruption circuit 17 constituting the connection interruption means interrupts the connection between the battery packs 19-1, 19-2, ..., 19-18, which are determined to contain energy storage elements whose cell voltages are in an overcharged or over-discharged state, and the equipment load 29. After that, the control processing of the battery pack 5 is terminated.

[0088] According to this second embodiment of the battery pack 5, the battery 19 used in the battery pack 5 is configured by connecting 18 battery packs 19-1, 19-2, ..., 19-18, each consisting of multiple lithium-ion secondary batteries connected in series, in parallel. Therefore, when a power outage occurs in the commercial AC power supply 27, the control unit 45 in the UPS 31 controls the battery 19 in parallel with the equipment load 29, causing the 18 battery packs 19-1, 19-2, ..., 19-18 to operate simultaneously. Thus, unlike the battery system disclosed in Non-Patent Document 1, in which the sub-LIB is not always in operation, when the battery 19 is operating, power is supplied to the equipment load 29 simultaneously from each of the 18 battery packs 19-1, 19-2, ..., 19-18 of the battery 19. This increases the amount of energy generated per unit volume occupied by the battery pack 5 in the UPS system, thereby improving the utilization efficiency of the battery 19.

[0089] Furthermore, according to the battery pack 5 of the second embodiment, the battery 19 is configured by connecting 18 battery packs 19-1, 19-2, ..., 19-18 in parallel, so the battery pack 5 installed in the UPS system can also meet the demand for larger capacity.

[0090] Furthermore, according to the battery pack 5 of the second embodiment, in step S13, the CPU 9 constituting the first determination means identifies battery packs 19-1, 19-2, ..., 19-18 in which the difference between the maximum voltage and the minimum voltage among the multiple cell voltages in each battery pack 19-1, 19-2, ..., 19-18 exceeds a predetermined threshold. Battery packs 19-1, 19-2, ..., 19-18 in which the difference exceeds the predetermined threshold are determined to have advanced deterioration of each energy storage element constituting them, and in step S14, the connection between the battery pack 19-1, 19-2, ..., 19-18 and the equipment load 29 is interrupted by the current interruption circuit 17 constituting the connection interruption means. Subsequently, in step S15, the CPU 9 constituting the equalization means equalizes the energy storage capacity among the multiple energy storage elements constituting the battery pack 19-1, 19-2, ..., 19-18. This equalization process allows for the recovery of the battery 19, which is composed of multiple battery packs 19-1, 19-2, ..., 19-18 connected in parallel, thereby improving the lifespan of the energy storage device.

[0091] Furthermore, according to the battery pack 5 of this embodiment, in step S19, the CPU constituting the third determination means determines whether there are any battery packs 19-1, 19-2, ..., 19-18 that include energy storage elements whose cell voltage is in an overcharged or over-discharged state. If such battery packs 19-1, 19-2, ..., 19-18 exist, in step S20, the current interruption circuit 17 constituting the connection interruption means interrupts the connection between the battery packs 19-1, 19-2, ..., 19-18 and the equipment load 29. As a result, by replacing the battery packs 19-1, 19-2, ..., 19-18 whose connection to the equipment load 29 has been interrupted, it becomes possible to deal with abnormalities in the battery pack 5 in a stepwise manner.

[0092] In the second embodiment, step S11 determines whether a power outage has occurred based on the charging current from the step-down chopper 41, but the present invention is not limited to this. For example, the present invention may be configured to determine whether a power outage has occurred upon receiving notification of a power outage from the control unit 45 of the UPS 31, and then execute step S11. In any case, the present invention is sufficient as long as it detects the voltage across the LIBs constituting each battery pack 19-1, 19-2, ..., 19-18 when a power outage occurs. [Industrial applicability]

[0093] According to the present invention, it is possible to provide a vehicle-mounted energy storage device that can improve the utilization efficiency of batteries while simultaneously addressing battery malfunctions. Furthermore, it is also possible to provide an energy storage device installed in a UPS system that can improve the utilization efficiency of batteries while simultaneously addressing battery malfunctions, in line with the demand for larger capacity. Therefore, the energy storage device of the present invention has extremely high industrial applicability. [Explanation of symbols]

[0094] 1: Vehicle generator 3: Vehicle load 5: Battery pack (energy storage device) 7: Battery Management Unit (BMU) 9: Central Processing Unit (CPU) 11: Memory (MEM) 13: Voltage detection circuit 15: Output control circuit 17: Current Interruption Circuit 19: Battery 19-1, 19-2, 19-18: Battery pack 20: Discharge Unit 20-1,20-2:Discharge circuit 21: Temperature measurement unit 21-1,21-2: Temperature measurement section 23: Current detection unit 27: Commercial AC power supply 29: Equipment load 31: Uninterruptible power supply (UPS) 33: Converter (CNV) 35a: AC node 35b: DC node 37: DC line 39: Capacitor 41: Step-down chopper (CHP) 43: Inverter (INV) 45: Control Unit

Claims

1. A power storage device that supplies power to the vehicle load, The battery is configured by connecting two battery packs in parallel, each containing multiple lithium-ion secondary battery energy storage elements connected in series, and is constantly connected in parallel to the vehicle load. Voltage detection means for detecting the cell voltage across each of the energy storage elements constituting each of the two aforementioned battery packs, A first determination means for determining whether the difference between the maximum voltage and the minimum voltage among the plurality of cell voltages detected by the voltage detection means exceeds a predetermined threshold, When the first determination means determines that the difference exceeds the predetermined threshold, a connection disconnection means disconnects the connection between the battery pack, which includes the energy storage element indicating the difference between the maximum voltage and the minimum voltage exceeding the predetermined threshold, and the vehicle load. An equalization means for equalizing the storage capacity among the plurality of energy storage elements constituting the battery pack whose connection to the vehicle load has been disconnected by the connection disconnection means, A second determination means for determining whether the module voltages at both ends of the battery pack whose storage capacity has been equalized by the equalization means are substantially the same as the module voltages at both ends of the other battery pack whose connection to the vehicle load is not interrupted, When the second determination means determines that the module voltages are not substantially the same, the re-equalization means charges and / or discharges the other battery pack, which is not disconnected from the battery pack and / or the vehicle load, so that the module voltages become substantially the same. When the second determination means determines that each module voltage is substantially the same, a connection establishment means establishes a connection between the battery pack whose storage capacity has been equalized and the vehicle load, A power storage device characterized by being equipped with the following features.

2. The battery pack includes a third determination means for determining whether the cell voltage detected by the voltage detection means is in an overcharged or over-discharged state, which includes the energy storage element. The connection disconnection means disconnects the connection between the battery pack and the vehicle load when the third determination means determines that the battery pack includes an energy storage element whose cell voltage is in an overcharged or over-discharged state. The energy storage device according to feature 1.

3. A power storage device that supplies power to equipment loads in place of the AC power supply during an AC power outage, A battery configured by connecting multiple battery packs in parallel, each containing multiple lithium-ion secondary battery energy storage elements connected in series, Voltage detection means for detecting the cell voltage across each of the energy storage elements constituting each of the multiple battery packs, A first determination means for determining whether the difference between the maximum voltage and the minimum voltage among the plurality of cell voltages detected by the voltage detection means exceeds a predetermined threshold, When the first determination means determines that the difference exceeds the predetermined threshold, a connection disconnection means disconnects the connection between the battery pack, which includes the energy storage element indicating the difference between the maximum voltage and the minimum voltage exceeding the predetermined threshold, and the equipment load. An equalization means for equalizing the energy storage capacity among the plurality of energy storage elements constituting the battery pack, whose connection to the equipment load has been disconnected by the connection disconnection means, A second determination means for determining whether the module voltages at both ends of the battery pack, whose storage capacity has been equalized by the equalization means, are substantially the same as the module voltages at both ends of the battery pack, whose connection to the equipment load is not interrupted. When the second determination means determines that the module voltages are not substantially the same, the re-equalization means charges and / or discharges the battery packs, which have had their storage capacity equalized and / or the connection between them and the equipment load has not been interrupted, so that the module voltages become substantially the same. When the second determination means determines that each module voltage is substantially the same, a connection establishment means establishes a connection between the battery pack whose storage capacity has been equalized and the equipment load, A power storage device characterized by being equipped with the following features.

4. The battery pack includes a third determination means for determining whether the cell voltage detected by the voltage detection means is in an overcharged or over-discharged state, which includes the energy storage element. The connection disconnection means disconnects the connection between the battery pack and the equipment load when the third determination means determines that the battery pack includes an energy storage element whose cell voltage is in an overcharged or over-discharged state. The energy storage device according to claim 3.

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