Energy Storage Device

Abstract

To provide an energy storage device that has a product form for connection to an external device, reduces damage to a contactor in a battery pack with a built-in contactor, and is also compatible with a battery pack without a built-in contactor. [Solution] The energy storage device 10 is divided into a battery container 20 and a backpack container 30. The battery container 20 has a plurality of battery units 40 connected in parallel or in series / parallel in a matrix. The backpack container 30 includes a power conversion device 32 and an energy management system 34. Each battery unit 40 includes a plurality of battery packs 42 connected in series and a high-voltage box 44. Each battery pack 42 has been used in an electric vehicle and is collected and remains undisassembled. The high-voltage box 44 includes a contactor 46 connected in series to the plurality of battery packs 42 and a battery management system 48.

Description

[Technical Field]

[0001] The present invention relates to an energy storage device comprising multiple battery packs for primary use in an electric vehicle. [Background technology]

[0002] Conventionally, battery packs installed in electric vehicles and hybrid vehicles are assumed to be replaced with new battery packs when certain conditions are met. However, even used battery packs have sufficient performance for applications other than automobiles, and with the spread of electric vehicles and hybrid vehicles, a large amount of used battery packs is expected to be generated, so there is a desire to reuse them. On the other hand, energy storage devices installed in buildings are expensive and often have limited capacity, so there is a desire to increase their capacity and reduce their price. In response to these needs, energy storage devices using used battery packs have been proposed.

[0003] US Patent No. 6,299,949 describes an integrated battery energy storage system that includes multiple second-life electric vehicle battery packs connected in a series / parallel configuration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Table 2025-508433 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the storage system described in Patent Document 1 has the problem that while it takes into consideration the product form of the storage system itself, it does not consider the product form between the storage system and external devices such as a solar power generation unit or a power grid. Furthermore, since the power supply to the multiple battery packs that make up each storage system is turned on and off by controlling the contactors built into each battery pack, rather than a single contactor, there is a problem that the contacts of the contactors are easily damaged. Furthermore, there is a problem that it cannot be used with low-voltage battery packs that do not have built-in contactors.

[0006] The present invention has been made in consideration of the above-mentioned problems of the conventional technology, and an object of the present invention is to provide an energy storage device that has a product form for connection to an external device, reduces damage to the contactor in a battery pack that has a built-in contactor, and is also compatible with battery packs that do not have a built-in contactor. In addition to the above object, another object of the present invention is to provide a large-capacity, low-cost energy storage device. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the inventors conducted extensive research and found that, first, by housing a power conversion device and an energy management system in the housing of a backpack container, a product configuration for connection to external devices can be provided, and by connecting contactors in series to multiple battery packs, damage to the contactors can be reduced in battery packs that have built-in contactors, and that the invention can also be used with battery packs that do not have built-in contactors.

[0008] The inventors have also discovered that energy storage devices can be made large-capacity and low-cost by manufacturing backpack containers in one location to reduce costs and by manufacturing battery containers at a collection site for used battery packs to minimize transportation costs for used battery packs, which led to the present invention.

[0009] That is, the first aspect of the present invention is a battery container having a plurality of battery units connected in parallel or in series / parallel in a matrix, and a backpack container equipped with a power conversion device and an energy management system, each battery unit having a plurality of battery packs connected in series and a high-voltage box, each battery pack having been used primarily in an electric vehicle and having not been disassembled as it was collected, the high-voltage box having contactors connected in series to the plurality of battery packs and a battery management system, the contactors electrically connecting or disconnecting the plurality of battery packs and the power conversion device, The battery management system has the function of collecting battery data output by each battery pack, calculating an SOH value based on the battery data, and transmitting battery information including at least a portion of the battery data and the SOH value to the energy management system, and the power conversion device converts DC discharge power from the multiple battery packs and outputs it to an external device, and converts power from the external device into DC charging power and outputs it to the multiple battery packs, and the energy management system turns contactors on and off to control the charging and discharging of the multiple battery packs and notifies the external device of battery information from the battery management system, thereby providing an energy storage device.

[0010] Here, in the first embodiment of the present invention, it is preferable that the difference between the maximum and minimum SOH values ​​of the battery packs constituting any one of the plurality of battery units is 0.5% or less, and the difference between the maximum and minimum OCV values ​​is 0.6 V or less. It is preferable that the ranges of the SOH values ​​of the plurality of battery packs constituting any two of the plurality of battery units do not overlap with each other. The battery management system preferably further has a function of transmitting only battery information required for maintenance work from among the battery data to the energy management system in order to reduce the amount of data transmitted to the energy management system.

[0011] Furthermore, in the first embodiment of the present invention, it is preferable that the weight of the entire contents contained in each housing of the backpack container is half or less of that of the battery container. The total weight of the contents contained in the battery container casing is preferably 500 to 6200 kg. The backpack container preferably has a volume of space containing all of the contents in each housing that is half or less of that of the battery container. The volume of the space that contains all the items stored inside the battery container is 12.0 to 76.0 m 3 It is preferable that: The weight of each battery pack is 50 to 250 kg, and the volume of the rectangular parallelepiped that contains each battery pack is 0.025 to 0.250 m 3 It is preferable that:

[0012] In addition, a second form of the present invention provides a manufacturing method for an energy storage device of the first form of the present invention, wherein the manufacturing process for each battery pack constituting any one of a plurality of battery units includes an acquisition process in which a computer acquires the OCV value and SOH value of each recovered battery pack; a classification process in which the computer classifies each battery pack into a plurality of groups based on the magnitude of the SOH value of each battery pack; a selection process in which the computer selects a plurality of battery packs from those belonging to any one group; and an adjustment process in which a charging / discharging device adjusts the OCV value of each battery pack so that the OCV value of each selected battery pack is within ±0.3 V of a preset reference voltage.

[0013] Here, in the second embodiment of the present invention, it is preferable to further include an equalization step in which the battery packs are connected in parallel to each other and left for at least 5 hours or more, thereby equalizing the OCV values ​​of the battery packs themselves. The selection process is preferably a process in which the computer selects a plurality of battery packs from those belonging to any one group to form any one battery unit, and selects a plurality of battery packs from those belonging to another one group to form another one battery unit. [Effects of the Invention]

[0014] According to the present invention, the battery pack has a product form for connecting to an external device, and in a battery pack having a built-in contactor, damage to the contactor can be reduced, and it can also be used for a battery pack that does not have a built-in contactor. Furthermore, in addition to the above effects, the present invention can achieve large capacity and low cost. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram illustrating an energy storage device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The energy storage device of the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings. Figure 1 is a block diagram showing the energy storage device of the present invention.

[0017] The energy storage device 10 of the present invention is divided into a battery container 20 and a backpack container 30. The battery container 20 has a plurality of battery units 40 connected in parallel or in series / parallel in a matrix. The backpack container 30 includes a power conversion device 32 and an energy management system 34. Each battery unit 40 includes a plurality of battery packs 42 connected in series and a high-voltage box 44. Each battery pack 42 has been used in an electric vehicle and is not disassembled as it was collected. The high-voltage box 44 includes a contactor 46 connected in series to the plurality of battery packs 42 and a battery management system 48. Note that if the battery packs 42 are low-voltage types without built-in contactors, the battery packs 42 may be called a battery module.

[0018] The contactors 46 electrically connect or disconnect the multiple battery packs 42 and the power conversion device 32. The battery management system 48 has functions of collecting battery data output by each battery pack 42, calculating an SOH value based on the battery data, and transmitting battery information including at least a portion of the battery data and the SOH value to the energy management system 34. The power conversion device 32 converts DC discharge power from the multiple battery packs 42 and outputs it to an external device (not shown), and converts power from the external device into DC charging power and outputs it to the multiple battery packs 42. The energy management system 34 turns the contactors 46 on and off to control charging and discharging of the multiple battery packs 42, and notifies the external device of battery information from the battery management system 48. Here, SOH refers to the battery capacity retention rate, which indicates the state of battery deterioration.

[0019] That is, a battery unit 40 is constructed by connecting a plurality of used battery packs 42 recovered from electric vehicles in series, connecting contactors 46 of a high-voltage box 44 to the power cables of the plurality of battery packs 42, and connecting a battery management system 48 of the high-voltage box 44 to the control cables of the plurality of battery packs 42. The plurality of battery units 40 are connected in parallel or in a series-parallel matrix configuration and housed in the housing of the battery container 20. A power conversion device 32 is connected to the power cables between the contactors 46 and an external device, and an energy management system 34 is connected to the control cables between the battery management system 48 and the external device, and these are housed in the housing of the backpack container 30.

[0020] The housing of the battery container 20 may be a ready-made 10-foot, 20-foot, or 40-foot container. The power conversion device 32 is a DC-DC converter when the input / output power of the external device is DC, and a power conditioner (hereinafter referred to as PCS) when the input / output power of the external device is AC, but if the input / output power of the external device is both AC and DC, both may be connected in parallel. The energy management system 34 and battery management system 48 are composed of electrical circuits and include a CPU as needed.

[0021] The SOH can be calculated by using the voltage or coulomb counting method to determine the charge rate before and after charging, and then dividing the full charge capacity calculated from the charge rate and the charge at that time by the initial full charge capacity obtained in advance. The SOH can also be calculated by applying two different current loads and comparing the internal resistance calculated from the corresponding voltage and current with a previously prepared internal resistance vs. SOH comparison table.

[0022] With this configuration, the energy storage device of the present invention has a product form for connection to an external device, reduces damage to the contactor in battery packs that have a built-in contactor, and can also be used with battery packs that do not have a built-in contactor. Furthermore, in addition to the above effects, the energy storage device of the present invention can be made large-capacity and low-cost.

[0023] Next, the SOH and OCV of each battery pack constituting any one battery unit will be described in detail. Note that in this description, three battery units 40a, 40b, and 40c are shown as the plurality of battery units 40, and nine battery packs 42a, 42b, and 42c are shown as the plurality of battery packs 42, but the numbers of battery units 40 and battery packs 42 are not limitative. Among the battery units 40, the battery packs 42a constituting any one battery unit 40a preferably have a difference between the maximum and minimum SOH of 0.5% or less (preferably 0.4% or less, more preferably 0.3% or less) and a difference between the maximum and minimum OCV of 0.6V or less (preferably 0.4V or less, more preferably 0.2V or less). This also applies to the battery packs 42b constituting battery unit 40b and the battery packs 42c constituting battery unit 40c. Here, OCV refers to the open-circuit voltage, i.e., the voltage when no current is flowing through the battery. Like internal resistance, OCV can be calculated from two corresponding voltages and currents when two current loads of different magnitudes are applied.

[0024] That is, among the battery packs 42 constituting the battery section 40, the smallest SOH value is the SOH value of the entire battery pack, and the smallest OCV value is the OCV value of the entire battery pack. Therefore, when comparing the SOH and OCV values ​​of the multiple battery packs 42 constituting the battery section 40, it is preferable that the difference between the maximum and minimum SOH values ​​and the difference between the maximum and minimum OCV values ​​are both sufficiently small. If the difference between the maximum and minimum SOH values ​​of a battery pack 42 exceeds 0.5%, the battery capacity that cannot be charged or discharged increases, thereby reducing the battery capacity of the entire battery pack. If the difference between the maximum and minimum OCV values ​​of a battery pack 42 exceeds 0.6 V, the battery capacity that cannot be charged or discharged increases, thereby reducing the battery capacity of the entire battery pack.

[0025] With this configuration, the energy storage device of the present invention can minimize the decrease in overall battery capacity due to variations in SOH and OCV, thereby contributing to an increase in capacity.

[0026] It is preferable that the SOH value ranges of the plurality of battery packs 42a, 42b constituting any two battery units 40a, 40b among the plurality of battery units 40 do not overlap with each other. The same applies to the case where the plurality of battery packs 42a, 42c constituting two battery units 40a, 40c are combined, and the case where the plurality of battery packs 42b, 42c constituting two battery units 40b, 40c are combined.

[0027] In other words, when comparing the ranges of the OCV values ​​of the multiple battery packs 42a constituting the battery unit 40a and the multiple battery packs 42b constituting the battery unit 40b, it is preferable that the range of the OCV values ​​of one is completely outside the range of the OCV values ​​of the other, with no overlap.

[0028] With this configuration, the energy storage device of the present invention will not be equipped with only battery packs with high SOH values ​​or only battery packs with low SOH values, thereby reducing variation in product lifespan.

[0029] Next, the data of each battery pack required for maintenance work will be described in detail. Preferably, the battery management system 48 further has a function of transmitting only battery information required for maintenance work from among the battery data to the energy management system 34 in order to reduce the amount of data transmitted to the energy management system 34.

[0030] For example, the battery data is composed of unique data and measurement data. The unique data includes the manufacturer name, model name, and serial number of each battery pack 42, which are output at startup. The measurement data includes the cell voltage (the voltage of each battery cell in the battery pack 42), pack temperature (the temperature of each battery pack 42), pack voltage (the voltage of each battery pack 42), and pack current (the current of each battery pack 42), which are output at set intervals. The battery information required for maintenance work is composed of the unique data, a portion of the measurement data extracted from the measurement data, and alarms. The portion of the measurement data and alarms are preferably classified into the following three types: the first is measurement data and an alarm indicating that each value exceeds the allowable range, such as in the event of a malfunction; the second is measurement data and an alarm indicating that the difference between each cell voltage and each pack voltage exceeds the allowable range, such as in the event of an imbalance; and the third is the SOH value and an alarm indicating that the SOH value exceeds a preset allowable range.

[0031] With this configuration, the energy storage device of the present invention does not require the connection of a new device, which can contribute to lower prices.

[0032] Next, the weight of all the contents stored in the housing of each container and the volume of the space that contains all the contents will be described in detail. The backpack container 30 preferably has a total weight of the contents stored in each housing that is half or less of that of the battery container 20. Also, the backpack container 30 preferably has a volume of the space that contains all of the contents stored in each housing that is half or less of that of the battery container 20.

[0033] Specifically, the items housed within the housing of the backpack container 30 include battery packs 42, high-voltage boxes 44, cooling fans, and cables connecting them, which are large in weight and volume and therefore require high transportation costs. Therefore, by manufacturing these items at a collection site for used battery packs 42, it is possible to minimize the transportation costs of the used battery packs 42. The items housed within the housing of the battery container 20 include power conversion devices 32, energy management systems 34, air conditioners, control power supplies, and cables connecting these, which are small in weight and volume and therefore require low transportation costs. Therefore, it is possible to reduce costs by manufacturing these items all at one location. Note that the air conditioners and control power supplies may be incorporated into the housing of the battery container 20 at the collection site for used battery packs 42.

[0034] With this configuration, the energy storage device of the present invention can minimize the transportation costs of used battery packs, thereby making it possible to reduce the price.

[0035] The weight of the entire contents contained within the housing of the battery container 20 is preferably 500 to 6200 kg (preferably 750 to 6100 kg, more preferably 1000 to 6000 kg). If the total weight of the contents inside the battery container 20 housing is less than 500 kg, the number of battery packs 42 mounted will be too small, resulting in insufficient battery capacity. If it exceeds 6,200 kg, the total weight will be heavy, resulting in increased work to consider laws and regulations regarding manufacturing, transportation, installation, and maintenance work.

[0036] The volume of the space that contains all the contents inside the battery container 20 is 12.0 to 76.0 m 3 (Preferably 13.0 to 67.0 m 3 , more preferably 14.0 to 33.0 m 3 ) is preferred. The volume of the space that contains all the contents inside the battery container 20 is 12.0 m 3 If the number of battery packs 42 mounted is too small, the battery capacity will be insufficient, and 3In the case of over 40 feet, the cost of manufacturing the enclosure will be high because it cannot be accommodated in a 40-foot (tall) container.

[0037] With this configuration, the energy storage device of the present invention can minimize the transportation costs of used battery packs, thereby making it possible to reduce the price.

[0038] Next, the weight of each battery pack and the volume of the rectangular parallelepiped that contains each battery pack will be described in detail. The weight of each battery pack 42 is 50 to 250 kg (preferably 100 to 240 kg, more preferably 110 to 230 kg), and the volume of a rectangular parallelepiped containing each battery pack 42 is 0.025 to 0.250 m 3 (Preferably 0.060 to 0.235 m 3 , more preferably 0.070 to 0.220 m 3 ) is preferred.

[0039] If the weight of each battery pack 42 is less than 50 kg, the battery capacity will be insufficient, and if it exceeds 250 kg, it will be too heavy to be mounted on an electric vehicle. 3 If it is less than 0.250m, the battery capacity will be insufficient. 3 If the battery pack 42 exceeds this limit, it will be too large to be installed in an electric vehicle. If the battery pack 42 is a lithium-ion battery, the lithium-ion battery itself is vulnerable to impact, so the housing of the battery pack 42 must be particularly sturdy when it is installed in an electric vehicle. As a result, the weight of the battery pack 42 becomes heavy, reaching 100 kg or more for electric buses and electric trucks.

[0040] With this configuration, the energy storage device of the present invention can minimize the transportation costs of used battery packs, thereby making it possible to reduce the price.

[0041] Next, the manufacturing process of each battery pack constituting any one battery unit will be described in detail. The manufacturing process for each battery pack 42a constituting any one battery unit 40a among the plurality of battery units 40 preferably includes an acquisition step, a classification step, a selection step, and an adjustment step. In the acquisition step, a computer (not shown) acquires the OCV and SOH values ​​of each recovered battery pack 42. In the classification step, the computer classifies each battery pack 42 into multiple groups, for example, a first group, a second group, and a third group, based on the SOH value of each battery pack 42. In the selection step, the computer selects multiple battery packs 42a from those belonging to the first group. In the adjustment step, a charging / discharging device (not shown) adjusts the OCV value of each selected battery pack 42a so that the OCV value of each selected battery pack 42a is within ±0.3 V (preferably within ±0.2 V, more preferably within ±0.1 V) of a preset reference voltage.

[0042] The same applies to the manufacturing process of each battery pack 42b constituting battery unit 40b among the plurality of battery units 40, and the manufacturing process of each battery pack 42c constituting battery unit 40c.

[0043] For example, battery data is collected from each recovered battery pack 42, and the SOH values ​​calculated based on the battery data are compared. The battery packs with high SOH values ​​and large battery capacities are classified into a first group, those with slightly lower SOH values ​​and slightly lower battery capacities into a second group, and those with lower SOH values ​​and small battery capacities into a third group. Then, a battery pack 42 belonging to one of the first to third groups is selected as the battery pack 42a constituting the battery unit 40a. The same applies to the battery pack 42b constituting the battery unit 40b and the battery pack 42c constituting the battery unit 40c. The computer is a general-purpose product used for managing the manufacturing process. The charging / discharging device is, for example, a Myway Plus regenerative DC power supply MWBFP3-1250-J02, which can be connected in series and parallel to support up to 1000V / 280A.

[0044] Next, the OCV value of each battery pack 42a is compared with a preset reference voltage, and each battery pack 42a is charged and discharged to adjust the OCV value to within ±0.3V of the reference voltage. Each battery pack 42b and each battery pack 42c are adjusted in the same way. If the difference between the OCV value of battery pack 42 and the reference voltage exceeds 0.3V, the battery capacity that cannot be charged or discharged increases, reducing the battery capacity of the entire battery pack. If the battery pack 42 is an LFP lithium-ion battery, the reference voltage is preferably 88 to 91% of the fully charged voltage.

[0045] By adopting such a configuration, the manufacturing method of the energy storage device of the present invention can minimize the decrease in overall battery capacity due to variations in SOH and OCV, thereby contributing to an increase in capacity.

[0046] The manufacturing process for each battery pack 42a constituting any one battery unit 40a preferably further includes an equalization process. In the equalization process, the battery packs 42a are connected in parallel and left for at least five hours (preferably six hours or more, and more preferably seven hours or more) to equalize the OCV values ​​of the battery packs 42a themselves. The same process is performed for each battery pack 42b and each battery pack 42c.

[0047] In other words, even if the battery packs 42a are charged and discharged so that the OCV value of each battery pack 42a is within ±0.3V of the reference voltage, the OCV values ​​of each battery pack 42a cannot be completely equalized, but if the battery packs 42a are left connected in parallel for at least five hours, the OCV values ​​of each battery pack 42a can be completely equalized. If the battery packs 42a are left for less than five hours, the battery capacity that cannot be charged or discharged increases, reducing the battery capacity of the entire battery pack.

[0048] By adopting such a configuration, the manufacturing method of the energy storage device of the present invention can minimize the decrease in the overall battery capacity due to variations in OCV, thereby contributing to an increase in capacity.

[0049] The selection step is preferably a step in which the computer selects multiple battery packs 42a from among those belonging to one arbitrary group to configure one arbitrary battery unit 40a, and selects multiple battery packs 42b from among those belonging to another arbitrary group to configure another arbitrary battery unit 40b. The same applies when the combination is one arbitrary battery unit 40a and one other arbitrary battery unit 40c, and when the combination is one arbitrary battery unit 40b and one other arbitrary battery unit 40c.

[0050] For example, it is preferable to select battery pack 42 belonging to the first group as battery pack 42a constituting battery unit 40a, select battery pack 42 belonging to the second group as battery pack 42b constituting battery unit 40b, and select battery pack 42 belonging to the third group as battery pack 42c constituting battery unit 40c.

[0051] By adopting such a configuration, the manufacturing method of the energy storage device of the present invention does not load only battery packs with high SOH values ​​or only battery packs with low SOH values, thereby reducing the variation in product lifespan. The energy storage device of the present invention is basically configured as described above.

[0052] The energy storage device of the present invention has been described in detail above, but the present invention is not limited to the above description, and various improvements and modifications may be made without departing from the spirit and scope of the present invention. [Industrial Applicability]

[0053] The energy storage device of the present invention has a product form for connection to external devices, and has the effect of reducing damage to the contactor in battery packs with built-in contactors and being compatible with battery packs without built-in contactors. In addition, it has the effect of being able to achieve large capacity and low price, making it industrially useful. [Explanation of symbols]

[0054] 10 Energy storage device 20 Battery Container 30 Backpack Container 32 Power conversion device 34 Energy Management System 40, 40a, 40b, 40c battery section 42, 42a, 42b, 42c battery packs 44 High Voltage Box 46 Contactor 48 Battery Management System

Claims

1. a battery container having a plurality of battery units connected in parallel or in series and parallel in a matrix; a backpack container equipped with a power conversion device and an energy management system; Each battery unit includes a plurality of battery packs connected in series with each other and a high-voltage box; Each battery pack has been used for the first time in an electric vehicle and has not been disassembled in the state in which it was collected. the high-voltage box includes a contactor connected in series to the plurality of battery packs and a battery management system; the contactor electrically connects or disconnects the plurality of battery packs and the power conversion device; the battery management system has a function of collecting battery data output from each battery pack, calculating a value of SOH based on the battery data, and transmitting battery information including at least a portion of the battery data and the value of SOH to the energy management system; the power conversion device converts DC discharge power from the plurality of battery packs and outputs the converted power to an external device, and converts power from the external device into DC charging power and outputs the DC charging power to the plurality of battery packs; The energy management system controls charging and discharging of the plurality of battery packs by turning the contactors on and off, and notifies an external device of the battery information from the battery management system.

2. 2. The energy storage device according to claim 1, wherein a plurality of battery packs constituting any one of the plurality of battery units have a difference between the maximum and minimum SOH values ​​of 0.5% or less and a difference between the maximum and minimum OCV values ​​of 0.6 V or less.

3. The energy storage device according to claim 2 , wherein the ranges of SOH values ​​of the plurality of battery packs constituting any two battery units among the plurality of battery units do not overlap with each other.

4. The energy storage device according to claim 1, wherein the battery management system further has a function of transmitting only battery information necessary for maintenance work from among the battery data to the energy management system in order to reduce the amount of data transmitted to the energy management system.

5. The energy storage device according to any one of claims 1 to 4, wherein the backpack container has a total weight of contents contained in each housing that is half or less of that of the battery container.

6. 6. The energy storage device according to claim 5, wherein the weight of the entire contents contained in the housing of the battery container is 500 to 6,200 kg.

7. The energy storage device according to any one of claims 1 to 4, wherein the backpack container has a spatial volume that encompasses all of the contents contained in each of the battery containers, the volume being half or less of the volume of the space that encompasses all of the contents contained in each of the battery containers.

8. The volume of the space that contains all the contents in the housing of the battery container is 12.0 to 76.0 m ３ 8. The energy storage device according to claim 7, wherein:

9. The weight of each battery pack is 50 to 250 kg, and the volume of the rectangular parallelepiped containing each battery pack is 0.025 to 0.250 m ３ The energy storage device according to any one of claims 1 to 4, wherein

10. 2. A method for manufacturing the energy storage device of claim 1, comprising: The manufacturing process of each battery pack constituting any one of the plurality of battery units includes: an acquisition step in which a computer acquires an OCV value and an SOH value of each recovered battery pack; a classification step in which the computer classifies each battery pack into a plurality of groups based on the magnitude of the SOH value of each battery pack; a selection step in which the computer selects a plurality of battery packs from among those belonging to any one group; and an adjustment step in which the charging / discharging device adjusts the OCV value of each selected battery pack so that the OCV value of each selected battery pack is within ±0.3 V of a preset reference voltage.

11. The method for manufacturing an energy storage device according to claim 10, further comprising an equalization step of equalizing the OCV values ​​of the battery packs themselves by leaving the battery packs connected in parallel with each other for at least five hours or more.

12. 12. The method for manufacturing an energy storage device according to claim 10 or 11, wherein the selection step is a step in which the computer selects a plurality of battery packs from those belonging to any one group to configure any one battery unit, and selects a plurality of battery packs from those belonging to another group to configure another battery unit.

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