JP7192323B2 - Method for reusing secondary battery, management device, and computer program - Google Patents

Description

The present invention relates to a reuse method, a management device, and a computer program for a secondary battery having multiple cells. In this specification, storage batteries that can be charged and discharged multiple times are collectively referred to as “secondary batteries.” shall be included in the following batteries.

A battery pack mounted on an electric vehicle (EV) or a plug-in hybrid electric vehicle (PHEV) includes, for example, a battery module (assembled battery) containing 8 to 20 battery cells (hereinafter referred to as cells) in a pack case. are housed in several

2. Description of the Related Art In recent years, there has been active research into reusing (recycling) vehicle-driving battery packs, battery modules, or cells that have been used in EVs and PHEVs for several years (see Patent Document 1, for example). Except for those used in extreme environments (excessive high temperature environment, repeated excessive high rate discharge), even if the battery pack is used for 10 years for driving a vehicle, the full charge capacity is about 70% of that of a new one. expected to be maintained. It is conceivable to remove such battery packs or battery modules from vehicles for reuse and transport them to factories. At a factory, for example, reusable cells in a battery module are selected, and the battery module is rebuilt (reconfigured) using the reusable cells. Reusable battery modules may be selected from the battery pack, and the reusable battery modules may be used to rebuild the battery pack.

JP 2016-152110 A

In Patent Document 1, the remaining capacity of a plurality of cells obtained by dismantling a battery pack with a history of use is measured, and the lower limit of the control range in a vehicle in which a battery pack with a remaining capacity greater than 0 is mounted. The battery modules whose remaining capacity is equal to or higher than the lower limit value set within the range of less than the value are sorted out. A battery pack is assembled using the selected battery modules.

Battery packs and battery modules for driving vehicles are large in volume and weight and need to be handled carefully, and it takes labor and cost to remove them from the vehicle brought in by the end user to a customer service window (for example, a car dealer) and transport them. It takes In order to reduce costs, it is desirable to avoid situations in which battery packs and battery modules that have been removed from vehicles and transported to factories are extremely deteriorated and cannot be reused after all.

An object of the present invention is to provide a secondary battery reuse method, a management device, and a computer program that enable detection (sorting) of batteries unsuitable for reuse before removal or transportation. be.

A method for reusing a secondary battery according to the present invention discharges a power storage device including a plurality of secondary battery cells electrically connected to each other, acquires changes in the voltage of each cell, and obtains information on the discharge. and the transition of the voltage, the reusability of the plurality of cells and/or the power storage device is evaluated.

According to the invention, cells not suitable for reuse can be detected (sorted) prior to removal or transport.

1 is a block diagram showing configurations of a vehicle and a management device according to Embodiment 1; FIG. 3 is a block diagram showing the configuration of a BMU; FIG. It is a perspective view of a battery module. 4 is a flow chart showing a process of recycling battery modules or cells. 4 is a flowchart showing a procedure of evaluation processing of reusability of cells of a battery module by a control unit of a management device; FIG. 4 is an explanatory diagram for explaining how to obtain the full charge capacity of a minimum capacity cell and other cells; 4 is a flowchart showing a procedure of a battery module or cell reusability evaluation process performed by a control unit of a management device; 4 is a graph showing the full charge capacity of each cell of battery modules (a), (b), and (c) among the battery modules of the battery pack. 4 is a graph showing the internal resistance of each cell of battery modules (a), (b), and (c) among the battery modules of the battery pack.

(Overview of embodiment)
A method for reusing a secondary battery according to an embodiment discharges a power storage device including a plurality of secondary battery cells electrically connected to each other, acquires changes in the voltage of each cell, and collects information on the discharge. and the transition of the voltage, the reusability of the plurality of cells and/or the power storage device is evaluated.

The "storage device" may be a battery pack or a battery module. The power storage device preferably does not have the voltage sensor (for example, voltage measurement circuit, cell monitoring IC) that measures the voltage of each cell, which is provided in a normal battery pack or battery module, removed.
The "discharge information" may include the discharge rate (for example, C rate), the environmental temperature during discharge, and the like. At least part of the “discharge information” may be set to a constant value.
The discharge may be performed on the load for evaluation, or may be performed on the load mounted on the vehicle. Since the discharge can be performed under substantially constant conditions, it is preferable to connect the power storage device to the load for evaluation and discharge the load.

“Evaluation of reusability of multiple cells and/or storage devices” means evaluation of reusability of individual cells of a battery module, evaluation of reusability of a battery module having multiple cells, or This refers to evaluation of the reusability of a battery pack with multiple battery modules.

A power storage device mounted on a vehicle often records a usage history (current history, voltage history, temperature history, etc.). The state of health (SOH) of the cell can be roughly estimated based on the recorded usage history. However, the accuracy of estimation based on such usage history may not be sufficiently high. Therefore, pre-evaluation (primary screening) of reusability may be performed by estimating SOH based on usage history, and the above-described method may be used for further evaluation (secondary screening).

According to the above-described method, the SOH can be estimated with higher accuracy by measuring the voltage behavior of each cell assembled in the power storage device.
Conventionally, when evaluating the SOH of a cell, it is common to remove the cell from the battery pack or battery module (dismantle the power storage device) and evaluate each individual cell. This conventional evaluation method is labor intensive and costly.
In light of the purpose of evaluating reusability at low cost, the present inventors have developed the above-described method that can detect the SOH of each cell using discharge information and voltage transitions before dismantling the power storage device. devised. The methods described above allow convenient detection of cells and/or storage devices that are not suitable for reuse prior to costly disassembly and transport to the factory.

In the above-described secondary battery reuse method, the full charge capacity of other cells is estimated based on the discharge information and the transition of the voltage of the cell with the smallest full charge capacity, and the full charge capacity of those cells reusability may be evaluated based on

The full charge capacity of the secondary battery cell decreases as it deteriorates. When discharging a power storage device containing multiple cells that are electrically connected to each other, the cell with the smallest full charge capacity (hereinafter also referred to as the smallest capacity cell) first reaches the discharge lower limit voltage reaches the lower limit voltage). For this minimum capacity cell, the full charge capacity can be measured directly through this discharge process. Since the other secondary battery cells have not yet reached the discharge lower limit voltage, the full charge capacity cannot be directly measured, but based on the voltage behavior of the minimum capacity cell in the discharge process described above, the other secondary battery cells Full charge capacity can be estimated. By evaluating the reusability based on the full charge capacity of multiple cells (minimum capacity cell and other cells), it is possible to improve the accuracy of the reusability evaluation of the cell and/or the storage device. can.

In the above-described secondary battery reuse method, the direct current internal resistance of each cell may be obtained based on the transition of the voltage, and the reusability may be evaluated based on the obtained direct current internal resistance.

The DC internal resistance of each cell can be obtained from the current value flowing through the power storage device in the discharge process and the voltage of each cell. By evaluating reusability in consideration of DC internal resistance, it is possible to improve the accuracy of evaluation.

In the above-described secondary battery reuse method, the power storage device may be charged while a balancer included in the power storage device is operated, and then the power storage device may be discharged to obtain changes in voltage of individual cells.

It is preferable that the balancers connected in parallel to individual cells, which are provided in a normal battery pack or battery module, are not removed from the power storage device to be evaluated for reusability. By charging the power storage device while operating the balancer, the voltages of the individual cells can be substantially uniformed at the end of charging. By discharging the power storage device from that state and acquiring the transition of the voltage of each cell, the accuracy of reusability evaluation can be improved.

A management device according to an embodiment discharges a power storage device including a plurality of secondary battery cells that are electrically connected to each other, and includes an acquisition unit that acquires a change in voltage of each cell, the information on the discharge, and the and an evaluation unit that evaluates the reusability of the plurality of cells and/or the power storage device based on changes in voltage.

According to the above configuration, the SOH of each cell can be detected by using the discharge information and voltage transition before the power storage device is dismantled. It can be conveniently screened prior to such dismantling and transport to the factory.

A computer program according to an embodiment causes a computer that evaluates the reusability of a plurality of secondary battery cells that are electrically connected to each other to discharge a power storage device that includes the cells, and changes the voltage of each cell. is obtained, and processing for evaluating the reusability of the plurality of cells and/or the power storage device is executed based on the discharge information and the voltage transition.

(Embodiment 1)
A recycling method will be described by taking an electric storage device (lithium ion secondary battery) mounted on a vehicle as an example.
FIG. 1 is a block diagram showing configurations of a vehicle 1 (in this embodiment, a four-wheeled vehicle such as an automobile) and a management device 13. As shown in FIG.
The vehicle 1 includes a lithium-ion secondary battery cell 2, a CMU (Cell Monitoring Unit) 5, a BMU (Battery Management Unit) 6, an integrated ECU (Electronic Control Unit) 7, a communication unit 8, a load 9, A current sensor 10 and a temperature sensor 11 are provided. The battery pack 4 includes a plurality of battery modules 3 in which a plurality of lithium ion secondary battery cells 2 are connected in series and/or in parallel. In this embodiment, a plurality of battery modules 3 in which a plurality of lithium ion secondary battery cells 2 are connected in series are connected in series.

The general ECU 7 controls the entire power supply of the vehicle 1 . The supervising ECU 7 also controls the engine when the vehicle 1 is an HEV vehicle or a gasoline vehicle. The supervising ECU 7 and the BMU 6 transmit and receive data by CAN communication, for example.

The management device 13 includes a control section 14 , a storage section 15 , an input section 16 and an interface section 17 . These components are communicatively connected to each other via a bus.
The input unit 16 accepts inputs of detection results of the current sensor 10 and the temperature sensor 11, SOC-OCV data 63 and usage history 64, which will be described later. The interface unit 17 is configured by, for example, a LAN interface or the like, and communicates with the integrated ECU 7 via a network 12 such as a LAN and the communication unit 8 by wire or wirelessly. Network 12 may be the Internet. The interface unit 17 is not limited to a LAN interface.
Alternatively, the management device 13 may communicate with the BMU 6 without going through the communication section 8 and the integrated ECU 7 .

The storage unit 15 is configured by, for example, a hard disk drive (HDD) or the like, and stores various programs and data. The storage unit 15 stores an evaluation program 151 for evaluating reusability of secondary batteries. The evaluation program 151 is provided in a state stored in a computer-readable recording medium 18 such as a CD-ROM, DVD-ROM, USB memory, etc., and is stored in the storage unit 15 by being installed in the management device 13. . Alternatively, the evaluation program 151 may be obtained from an external computer (not shown) connected to the network 12 and stored in the storage unit 15 .

The control unit 14 is composed of, for example, a CPU, a ROM, a RAM, and the like, and functions as a processing unit that executes a process of evaluating the reusability of the secondary battery by reading out and executing the evaluation program 151 from the storage unit 15. .

A case where the management device 13 evaluates the reusability of the secondary battery will be described below. (Alternatively, the BMU 6 or the supervising ECU 7 may function as the management device. When the BMU 6 or the supervising ECU 7 functions as the management device, there is no need to connect the management device 13 to the vehicle 1.) In this embodiment, , the battery module 3 including the CMU 5 functions as a "storage device".
The BMU 6 may be a battery ECU.

The CMU 5 is provided with a balancer (circuit) for eliminating voltage variations and a voltage sensor for detecting the voltage of each cell 2 (not shown). A balancer is a discharge circuit connected in parallel to each cell 2 and may have a switch and a resistor. The switch is turned on/off by a control signal from a control circuit included in CMU5. The voltage sensor transmits the detected cell 2 voltage to the BMU 6 .

The CMU 5 is an electronic control unit (monitoring board) that monitors the state of each cell 2 .
The CMU 5 performs balancing by discharging the high-voltage cell 2 so that the high-voltage cell 2 and the other cells 2 have the same voltage when there is a voltage variation between the cells 2 . That is, the switch of the balancer of cell 2 to be discharged is turned on to lower the voltage of the cell to match the voltage of the other cells.

FIG. 2 is a block diagram showing the configuration of BMU 6. As shown in FIG. The BMU 6 includes a control section 61 , a storage section 62 , an input section 66 and an interface section 67 . These components are communicatively connected to each other via a bus.

The input unit 66 receives input of detection results of the current sensor 10 , the temperature sensor 11 , and the voltage sensor of the CMU 5 . The interface unit 67 is configured by, for example, a CAN interface or the like, and performs wired or wireless communication with other devices such as the integrated ECU 7 . The interface unit 67 may be a LAN interface and/or a USB interface.

The storage unit 62 is configured by a hard disk drive (HDD) or the like, and stores various programs and data.

The storage unit 62 stores SOC-OCV data 63 indicating the relationship between SOC (State Of Charge) and OCV (Open Circuit Voltage) obtained in advance for a plurality of conditions through experiments. The storage unit 62 also stores a usage history (current history, voltage history, temperature history, etc.) 64 .

The control unit 61 is composed of, for example, a CPU, ROM, RAM, etc., and controls the operation of the BMU 6 by executing a computer program read from the storage unit 62 .

FIG. 3 is a perspective view of the battery module 3. FIG.
The battery module 3 includes a holding member 31 that holds a plurality of cells 2 (for example, a rectangular parallelepiped module case, a binding member that holds the cells 2 in a pressed state), a plurality of cells 2, and a CMU 5.

The cell 2 includes a rectangular parallelepiped case body 21 , a cover plate 22 , a pair of terminals 23 , 23 with different polarities provided on the cover plate 22 , and an electrode body 24 housed in the case body 21 . The electrode assembly 24 is formed by laminating a positive electrode plate, a separator, and a negative electrode plate.
The electrode body 24 may be of a winding type obtained by laminating a long belt-shaped positive electrode plate and a negative electrode plate with a separator interposed therebetween and winding them into a flat shape, or may be a rectangular plate-shaped positive electrode plate and a negative electrode plate. may be of a stack type in which the are stacked with separators interposed therebetween.
The cells 2 are not limited to prismatic cells, but may be cylindrical cells or pouch cells. From the viewpoint of reuse, a prismatic cell or a cylindrical cell is preferable because it has a robust metal case and can be expected to have a long service life. In particular, prismatic cells are preferable because they can increase the capacity of individual cells without lowering the energy density (without creating dead spaces between cells). Aluminum, an aluminum alloy, stainless steel, or the like can be used as the material of the case body of the prismatic cell. From the point of view of reuse, a prismatic cell having a case body 21 and a cover plate 22 made of stainless steel, which is less likely to swell, is preferable.

The positive electrode plate is formed by forming an active material layer on a positive electrode substrate, which is a plate-like (sheet-like) or long band-like metal foil made of aluminum, an aluminum alloy, or the like. The negative electrode plate is formed by forming an active material layer on a negative electrode base material, which is a plate-like (sheet-like) or long belt-like metal foil made of copper, a copper alloy, or the like. The separator is a microporous sheet made of synthetic resin. The separator may be a separate member from the positive electrode plate and the negative electrode plate, or may be integrated with the positive electrode plate or the negative electrode plate.

As the positive electrode active material contained in the positive electrode plate or the negative electrode active material used in the negative electrode plate, an appropriate known material can be used as long as it is a positive electrode active material or negative electrode active material capable of intercalating and deintercalating lithium ions.
Examples of the positive electrode active material include polyanion compounds such as LiMPO ₄ , LiMSiO ₄ , LiMBO ₃ (where M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), lithium titanate, and manganic acid. Spinel compounds such as lithium, lithium transition metal oxides such as LiMO ₂ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) and the like can be used.

Examples of negative electrode active materials include hard carbon, metals or alloys such as Si, Sn, Cd, Zn, Al, Bi, Pb, Ge, and Ag, chalcogenides containing these, and the like. An example of a chalcogenide is SiO.

Adjacent terminals 23 of adjacent cells 2 of the battery module 3 have different polarities, and these terminals 23 are electrically connected to each other by bus bars 32, thereby connecting a plurality of cells 2 in series.
Leads (external connection members) 33 , 33 for electrically connecting to the adjacent battery module 3 are provided on the terminals 23 , 23 of the cells 2 at both ends of the battery module 3 , which have different polarities.

Reuse of the battery pack 4, battery module 3 or cell 2 will be described in detail below.
FIG. 4 is a flow chart showing the process of recycling the battery module 3 or the cell 2. As shown in FIG.
Primary sorting is performed by the management device 13 based on the mileage of the vehicle acquired from the integrated ECU 7, the usage history 64 of each battery module 3 acquired from the BMU 6, and the like (S1). The management device 13 estimates the SOH of the cell 2 based on, for example, the usage history 64 of the battery module 3, and selects the battery module 3 whose SOH is equal to or greater than the threshold as the battery module 3 to be evaluated for reusability.

The management device 13 evaluates reusability (S2). The management device 13 evaluates whether the battery module 3 is reusable or whether the cells 2 included in the battery module 3 are reusable.

When the management device 13 evaluates that the reusability is satisfied, the battery pack 4 or the battery module 3 is transported to the factory (S3). If the battery module 3 is evaluated to include reusable cells 2, the battery module 3 may be transported, or only the reusable cells 2 may be transported. If the battery pack 4 is evaluated to include reusable battery modules 3, the battery pack 4 may be transported, or only the reusable battery modules 3 may be transported.

At the factory, the rebuildability is evaluated (S4). It is determined whether or not the cells 2 evaluated as reusable can be used in the rebuilt battery module. A recovery operation is performed on the cell 2 and predetermined tests such as capacity check and short circuit test are performed.
Alternatively, it is determined whether or not the battery module 3 evaluated as reusable can be used in a rebuilt battery pack. A recovery operation is performed on the battery module 3, and a predetermined test is performed.

In this way, using the cells 2 evaluated as reusable, for example, a battery module for an application different from the initial application is rebuilt. Alternatively, battery modules 3 evaluated as reusable are used to rebuild a battery pack for a different application from the initial application (S5).

The battery pack 4 has a plurality (eg, 10) of battery modules 3 each including a large number (eg, 8 to 20) of cells 2, and the price of a new battery pack 4 is relatively high. In the battery pack 4 mounted on the vehicle, the degree of deterioration of each battery module differs due to the influence of air cooling and the like. For example, the battery module 3 on the front side of the vehicle 1 may be more easily heated and deteriorated than the battery module 3 on the rear side. When the battery pack 4 as a whole has a full charge capacity maintenance rate of 70% when new, the capacity maintenance rate of the battery module on the front side of the vehicle is 60%, and the capacity maintenance rate of the battery module on the rear side is 75 to 80%. %.
It is not economically rational to collect or dispose of the entire used battery pack 4 for material recycling, and there is room for improvement from the viewpoint of resource conservation. By evaluating whether or not the battery module 3 is reusable, the entire battery pack 4 can be reused or the battery pack 4 can be rebuilt using reusable battery modules 3 . When the battery module 3 cannot be reused, the battery module 3 can be rebuilt using cells 2 evaluated as reusable. Remanufactured products can be cheaper than new products.

FIG. 5 is a flow chart showing the procedure of evaluation processing of the reusability of the cells 2 of the battery module 3 by the control unit 14 of the management device 13 .
The control unit 14 charges each cell 2 of each battery module 3 while performing balancing control by each CMU 5 (S11). By performing charging for evaluation while using the CMU 5 (balancer), the voltage of each cell 2 at the end of charging is substantially uniformed.
The control unit 14 discharges each battery module 3, acquires changes in the discharge voltage of each cell 2 using the CMU 5 (voltage sensor), and acquires conditions for discharge (S12). The discharge condition may be input through the input unit 16 . The discharge conditions include the discharge rate (C rate), the temperature obtained from the temperature sensor 11, and the like. The load 9 during discharge is preferably an evaluation load, as described above.

The control unit 14 calculates the internal resistance of each cell 2 (S13).
The control unit 14 calculates the SOC of the cell 2 by the current integration method. The control unit 14 reads the SOC-OCV data 63 from the storage unit 62 of the BMU 6 and acquires the OCV corresponding to the SOC. Based on the current I detected by the current sensor 10 and the cell voltage V detected by the voltage sensor, the control unit 14 calculates the internal resistance R by the following formula (1).
R=(V−OCV)/I (1)
The method of calculating the internal resistance is not limited to this, and other known methods may be adopted.

The control unit 14 acquires the full charge capacity of the minimum capacity cell (S14).
The control unit 14 calculates the full charge capacity of other cells (S15).

FIG. 6 is an explanatory diagram for explaining how to obtain the full charge capacities of the minimum capacity cell 2 and other cells 2 .
Here, the case where the battery module 3 includes three cells 2 (a), (b), and (c) will be described.

In the battery module 3 in which the cells 2 are connected in series, when the cell (a) with the minimum capacity reaches the discharge lower limit voltage (here, 2.8 V), the other cells (b) and (c) reach the lower limit voltage. No further discharge can be performed even if it has not reached This is because the cell (a) is overdischarged.
What the battery module 3 can actually measure is the transition of the discharge voltage of each cell 2 and the discharge electricity amount (Ah) of the entire battery module 3 . For the battery module 3 having three cells 2, if the battery module 3 discharges 87 Ah of electricity before the cell (a) reaches the discharge lower limit voltage, one cell 2 discharges 29 Ah.

The present inventors have found that the discharge curves of cells (b) and (c) are similar in shape to the discharge curve of the minimum capacity cell (this does not mean a mathematically strict similarity, but the slope of the curve at the end of discharge). is almost equal in each cell, and has a shape obtained by extending the discharge curve of the minimum capacity cell in the X-axis direction), and the idea of using the following calculation method was conceived.
The cut voltage of the cell (c) (the voltage when the minimum capacity cell (a) reaches the discharge lower limit voltage) is 3.52V. Assume that the SOC of the minimum capacity cell (a) is 91% when the voltage is 3.52V. Assuming that the discharge curve of cell (c) has a similar shape to the discharge curve of cell (a), in cell (C), 29 Ah corresponds to SOC 91%, so the full charge capacity at SOC 100% is , 29(Ah)/91(%)=31.9(Ah). Obtaining the full charge capacity of the cell (c) means virtually extending the discharge curve of the cell (c) to the discharge lower limit voltage (2.8 V) in the graph of FIG. The full charge capacity of the cell (b) is similarly obtained.
The method of calculating the full charge capacity of multiple cells is not limited to this. It may be calculated more simply based on the cut voltage.

The control unit 14 determines whether or not there is a cell (hereinafter referred to as a high-capacity cell) 2 whose full charge capacity obtained as described above is equal to or greater than a1 (Ah) in the battery module 3 (S16 ).
When the control unit 14 determines that there is no high-capacity cell (S16: NO), it determines to recycle the material of the cell 2 (S17), and ends the process. In S<b>17 , the control unit 14 may determine to discard the cell 2 .

When the controller 14 determines that there is a high-capacity cell (S16: YES), it determines whether the internal resistance of the high-capacity cell is c1 (Ω) or less (S18). When the control unit 14 determines that the internal resistance of the high-capacity cell is not less than c1 (S18: NO), the process proceeds to S17.
When the control unit 14 determines that the internal resistance of the high-capacity cell is equal to or less than c1 (S18: YES), it evaluates that the high-capacity cell is reusable (S19), and terminates the process.

According to this embodiment, the SOH can be estimated with high accuracy by discharging individual cells 2 and measuring the transition of the voltage without disassembling the battery module 3 . When the cells 2 are removed from the battery pack 4 or the battery module 3 and evaluated individually, labor and costs are great. According to this embodiment, the battery modules 3 including the cells 2 not suitable for reuse can be easily sorted out before dismantling and transportation to the factory, which are costly.

In this embodiment, balancing is performed in S11, but charging may be performed without balancing. However, the accuracy of reusability evaluation can be improved by balancing the voltages of the cells 2 at the end of charging. Although the discharge conditions are acquired in S12, it is not necessary to acquire the discharge conditions when the discharge rate is constant and the temperature is substantially constant.
If it is determined that the full charge capacity is high (S16: YES), it may be determined that the cell can be reused without checking the internal resistance. However, by judging whether the internal resistance of the high-capacity cell is c1 or less, the accuracy of the evaluation of the cell 2 is improved.

(Modification)
In the modified example, the reusability of the battery modules 3 and the cells 2 is evaluated.
FIG. 7 is a flow chart showing the procedure of evaluation processing of the reusability of the battery modules 3 and the cells 2 by the control unit 14 of the management device 13 .
The control unit 14 charges the cells 2 of each battery module 3 while performing balancing control by each CMU 5 (S21).
The control unit 14 discharges the battery module 3 and acquires the transition of the discharge voltage of the cell 2 and the discharge conditions (S22).
The controller 14 calculates the internal resistance (S23).
The control unit 14 acquires the full charge capacity of the minimum capacity cell (S24).
The control unit 14 calculates the full charge capacity of other cells (S25).

The control unit 14 calculates the variation (σ) of the capacity of the cells 2 of the battery module 3 based on the capacities of the minimum capacity cell 2 and the other cells 2 (S26).

The control unit 14 determines whether or not the full charge capacity of the minimum capacity cell is equal to or greater than a1 (Ah) (S27).
When the control unit 14 determines that the full charge capacity of the minimum capacity cell is equal to or greater than a1 (S27: YES), it determines whether the variation in capacity of the cells 2 of the battery module 3 is equal to or less than b1 (S28). ). If the controller 14 determines that the variation in cell capacity of the battery module 3 is not equal to or less than b1 (S28: NO), the process proceeds to S33.

When the control unit 14 determines that the variation in cell capacity of the battery module 3 is equal to or less than b1 (S28: YES), it determines whether or not there is a cell with internal resistance>c1 (S29). If the control unit 14 determines that there is a cell with internal resistance>c1 (S29: YES), the process proceeds to S33.
When the control unit 14 determines that there is no cell with internal resistance>c1 (S29: NO), the control unit 14 evaluates that the battery module 3 can be reused (S30), and terminates the process.

If it is determined that the full charge capacity of the minimum capacity cell is not equal to or greater than a1 (S27: NO), it is determined whether or not there is a cell (high capacity cell) having a capacity equal to or greater than a1 in the battery module 3 (S31). ). When the control unit 14 determines that there is no high-capacity cell (S31: NO), it determines to recycle the material of the cell 2 (S32), and terminates the process. The control unit 14 may determine to discard cell 2 .

When the control unit 14 determines that there is a high-capacity cell (S31: YES), it determines whether the internal resistance of the high-capacity cell is c1 or less (S33).
If the control unit 14 determines that the internal resistance of the high-capacity cell is not less than c1 (S33: NO), the process proceeds to S32.
When the control unit 14 determines that the internal resistance of the high-capacity cell is c1 or less (S33: YES), it evaluates that the high-capacity cell is reusable (S34), and terminates the process.

FIG. 8 is a graph showing the full charge capacity of each cell 2 of each battery module 3 in the battery pack 4. As shown in FIG. A case where each battery module 3 has eight cells 2 is shown. FIG. 8 shows only the full charge capacity of each cell 2 of battery modules (a), (b), and (c).
As shown in FIG. 8 , it can be seen that there are variations in the capacity of the eight cells 2 within the battery module 3 , and variations in capacity among the battery modules 3 within the battery pack 4 as well.

FIG. 9 is a graph showing the internal resistance (DC internal resistance) of each cell 2 of each battery module 3 in the battery pack 4 . In FIG. 9, only the internal resistances of battery modules (a), (b), and (c) are shown.
As shown in FIG. 9 , there are variations in the internal resistance of the eight cells 2 within the battery module 3 , and variations in internal resistance among the battery modules 3 within the battery pack 4 as well.

In this embodiment, when it is determined in S27 that the capacity of the cell 2 with the minimum capacity is equal to or greater than a1, the battery module 3 is not reused when the variation in the capacity of the cell 2 is greater than b1. Only cell 2 is reused. If the battery module 3 includes cells 2 whose capacities are significantly different from the average value, the battery module 3 cannot be reused by aligning the capacities of the cells 2 after transportation to the factory, and the battery pack 4 cannot be rebuilt. is.

If it is determined in S28 that the variation in capacity is equal to or less than b1, the battery module 3 is not reused and only the high-capacity cells 2 are reused when the cells 2 whose internal resistance is greater than c1 are included. This is because if the battery module 3 includes cells 2 with high internal resistance, the deterioration of the cells 2 is high and the service life of the rebuilt battery pack 4 is shortened.

As described above, the battery module 3 on the rear side of the vehicle 1 is less susceptible to deterioration than the battery module 3 on the front side, and thus has a higher capacity. Such battery modules 3 may be selected and the battery pack 4 may be rebuilt using the reusable battery modules 3 .

The present invention is not limited to the contents of the above-described embodiments, and various modifications are possible within the scope of the claims. That is, the technical scope of the present invention also includes embodiments obtained by combining technical means appropriately modified within the scope of the claims.

The method of reusing a secondary battery according to the present invention is not limited to use in vehicles, and can also be applied to secondary batteries used in distributed power supply devices such as regenerative power storage devices for railways and photovoltaic power generation systems.
The management device is also not limited to in-vehicle use. It is preferable that the management device is installed or brought to a user service window (a site where end users bring in power storage devices), and evaluates the reusability of the secondary battery there. The management device may be an information terminal installed at a user service window.
The management device may be a portable information terminal. The management device may have probes or cables for connecting to the vehicle. Preferably, the management device is a portable information terminal that performs wireless communication (for example, short-range wireless communication) with the vehicle and evaluates the reusability of the secondary battery.
The secondary battery is not limited to a lithium ion secondary battery, and may be other secondary batteries such as a capacitor (capacitor) type storage element such as a nickel hydrogen battery or an electric double layer capacitor.

INDUSTRIAL APPLICABILITY The present invention can be applied to evaluation of reusability of secondary battery cells such as lithium ion secondary batteries and/or power storage devices in which a plurality of such cells are assembled.

1 Vehicle 2 Cell 3 Battery Module (Power Storage Device)
4 Battery pack (storage device)
5 CMUs
6 BMUs
14 control unit (acquisition unit, evaluation unit)
61 control unit 15, 62 storage unit 151 evaluation program 63 SOC-OCV data 64 usage history 16, 66 input unit 17, 67 interface unit 7 integrated ECU
8 communication unit 10 current sensor 11 temperature sensor 13 management device

Claims (6)

Discharging a power storage device including a plurality of secondary battery cells electrically connected to each other to obtain the voltage of each cell,
estimating the full charge capacity of the other cell based on the discharge conditions , the transition of the voltage of the cell with the smallest full charge capacity, and the voltage of the other cells;
A method of reusing a secondary battery, which evaluates the reusability of the plurality of cells and/or the power storage device based on the full charge capacity of the cells. Discharging a power storage device including a plurality of secondary battery cells electrically connected to each other to obtain the voltage of each cell,
estimating the full charge capacity of the other cell based on the amount of discharge electricity of the discharge, the transition of the voltage of the cell with the smallest full charge capacity, and the voltage of the other cell;
A method of reusing a secondary battery, which evaluates the reusability of the plurality of cells and/or the power storage device based on the full charge capacity of the cells. obtaining the DC internal resistance of the individual cell based on said voltage ;
3. The method for reusing a secondary battery according to claim 1, wherein reusability is evaluated based on the obtained DC internal resistance. 4. The second method according to claim 1, wherein after charging the power storage device while operating a balancer included in the power storage device, the power storage device is discharged to obtain the voltage of each cell. How to reuse the next battery. an obtaining unit that discharges a power storage device that includes a plurality of secondary battery cells electrically connected to each other and obtains the voltage of each cell;
an estimating unit for estimating the full charge capacity of other cells based on the discharge conditions , the transition of the voltage of the cell with the smallest full charge capacity, and the voltages of the other cells;
and an evaluation unit that evaluates the reusability of the plurality of cells and/or the power storage device based on the full charge capacities of the cells. a computer that evaluates the reusability of a plurality of secondary battery cells that are electrically connected to each other;
Discharging a power storage device containing the cells to obtain the voltage of each cell,
estimating the full charge capacity of the other cell based on the discharge conditions , the transition of the voltage of the cell with the smallest full charge capacity, and the voltage of the other cells;
A computer program for executing a process of evaluating the reusability of the plurality of cells and/or the power storage device based on the full charge capacities of the cells.

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