JP2023089452A - Battery module inspection method - Google Patents

Abstract

To improve accuracy of inspecting a battery module.SOLUTION: An inspection method comprises the steps of performing charging processing; performing determination processing; and performing the charging processing and the determination processing again. The step of performing the charging processing includes charging all cells until the voltage of any cell reaches the upper limit voltage. The step of performing the determination processing includes determining whether or not the capacity of the cell is within an allowable capacity range and the voltage of the cell is within an allowable voltage range for each of all cells charged by the charging processing. The step of performing again includes, when a plurality of battery modules include a pending battery module including a cell of which capacity is within the allowable capacity range and voltage is not within the allowable voltage range, completely charging each cell included in the pending battery module and performing the charging processing and the determination processing again on the pending battery module of which each cell is completely charged.SELECTED DRAWING: Figure 8

Description

The present disclosure relates to a battery module inspection method.

The lithium-ion battery module disclosed in Japanese Patent Application Laid-Open No. 2021-044151 (Patent Document 1) does not require a circuit or the like for monitoring the state of charge of each cell, and there are single cells that are in an overcharged state. You can charge it like never before.

JP 2021-044151 A JP 2018-026210 A JP 2015-125091 A

In general, after manufacturing a battery module, an inspection for non-defective/defective products is performed. A battery module that satisfies a predetermined criterion is determined as a non-defective product, while a battery module that does not satisfy the criterion is determined as a defective product. There is always a demand for improving inspection accuracy in inspection of such battery modules.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to improve the inspection accuracy of battery modules.

(1) A battery module inspection method according to an aspect of the present disclosure is a method for inspecting a plurality of battery modules connected in series. Each of the multiple battery modules includes multiple cells connected in series. The inspection method includes a step of executing a charging process, a step of executing a determination process, and a step of executing the charging process and the determination process again. The step of executing the charging process includes charging all the cells included in the plurality of battery modules until the voltage of any one of the cells reaches a predetermined voltage, Calculating the capacity and detecting the voltage of each of all charged cells. The step of executing the determination process includes, for each of all the cells charged by the charging process, determining whether the capacity of the cell is within the permissible capacity range and whether the voltage of the cell is within the permissible voltage range. including the step of determining. The re-executing step includes, if there is a reserved battery module including a cell whose capacity is within the capacity allowable range and whose voltage is not within the voltage allowable range among the plurality of battery modules, each cell included in the reserved battery module and re-executing the charging process and the determination process for the reserved battery module in which each cell has been completely discharged.

(2) In the determining step, for each of all the cells charged by the charging process, the combination of the capacity and voltage of the cell is defined on the capacity-voltage plane using the maximum capacity curve and the minimum capacity curve. determining whether it is located in any one of the first to third regions of the The maximum capacity curve is a capacity-voltage curve that passes through the intersection of the upper limit voltage of the voltage tolerance range and the maximum capacity of the capacity tolerance range. A minimum capacity curve is a capacity-voltage curve that passes through the intersection of the upper voltage limit and the minimum capacity of the capacity tolerance range. The first region is a region sandwiched between the minimum capacity curve and the maximum capacity curve, in which the capacity is equal to or higher than the minimum capacity and the voltage is equal to or lower than the upper limit voltage. The second region is a region other than the first region among the sandwiched regions. The third area is an area other than the first area and the second area. A reserved battery module is a battery module that includes cells located in the second region but does not include cells located in the third region.

(3) Each of the plurality of battery modules is a lithium ion battery having a bipolar structure.

Although the details will be described later, the suspended battery module (suspended product) is erroneously determined to be defective even though it is actually a non-defective product because the voltage of the cells included in the defective product reaches a predetermined voltage. There is a possibility that In the configurations (1) to (3) above, complete discharge processing is performed on the reserved battery module, and charging processing and determination processing are performed again. As a result, it is possible to improve the inspection accuracy for the reserved battery module.

According to the present disclosure, it is possible to improve the inspection accuracy of the battery module.

1 is an overall configuration diagram of a battery inspection system according to an embodiment of the present disclosure; FIG. It is a schematic sectional drawing of a battery unit. 1 is a schematic cross-sectional view of a battery module; FIG. 7 is a flow chart showing a processing procedure of an inspection process in a comparative example; It is a figure for demonstrating the subject of the inspection process in a comparative example. It is a figure which shows an example of two types of curves in this Embodiment. FIG. 4 is a diagram for explaining a region defined by a maximum capacity curve and a minimum capacity curve; 4 is a flow chart showing a processing procedure of an inspection process in this embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

[Embodiment]
<Overall configuration of battery inspection system>
FIG. 1 is an overall configuration diagram of a battery inspection system according to an embodiment of the present disclosure. The battery inspection system 100 includes connection terminals 101 and 102 . Connection terminals 101 and 102 are configured to be electrically connectable to battery unit 1 . Battery unit 1 includes a plurality of battery modules 2 connected in series. Each of the plurality of battery modules 2 includes a plurality of cells. The battery inspection system 100 performs an inspection for determining whether each battery module 2 is a non-defective product or a defective product.

The configuration of the battery unit 1 will be described in more detail with reference to FIGS. 2 and 3. FIG. The battery unit 1 may be a newly manufactured new battery, or may be a used battery collected from a place of use.

Battery testing system 100 further includes DC power supply 5 , multiple voltage sensors 6 , current sensor 7 , temperature sensor 8 , and controller 9 .

The DC power supply 5 is configured to charge and discharge the battery unit 1 according to control commands from the controller 9 . DC power supply 5 is, for example, an AC/DC converter. DC power supply 5 converts AC power supplied from an external AC power supply (for example, commercial power supply) 900 into DC power. The DC power supply 5 can also step up or step down the voltage of the DC power according to a control command from the controller 9 .

Each of the multiple voltage sensors 6 is connected in parallel to a corresponding one of the multiple battery modules 2 . Each voltage sensor 6 detects the voltage V of each cell in the corresponding battery module 2 and outputs the detected value to the controller 9 .

Current sensor 7 is connected in series, for example, between DC power supply 5 and connection terminal 101 . The current sensor 7 detects the current I supplied from the DC power supply 5 to the battery unit 1 and outputs the detected value to the controller 9 .

The temperature sensor 8 detects the temperature T of the battery unit 1 (a representative battery module among the plurality of battery modules 2 ) and outputs the detected value to the controller 9 .

The controller 9 includes a processor 91 such as a CPU (Central Processing Unit), memory 92 such as ROM and RAM, and an input/output interface (not shown). The controller 9 completely discharges the battery module 2 and charges the battery module 2 by controlling the DC power supply 5 (charging process). In addition, the controller 9 performs determination processing for determining whether the battery module 2 is good/defective. The complete discharge process, charge process, and determination process described above will be described later in detail. Note that the controller 9 may be divided into two or more units for each function.

<Battery configuration>
FIG. 2 is a schematic cross-sectional view of the battery unit 1. FIG. The battery unit 1 includes a module laminate 31 , a pair of binding members 32 , a pair of insulating members 33 , a positive terminal 341 and a negative terminal 342 .

The module stack 31 includes multiple battery modules 2 and multiple conductive plates 310 . The battery modules 2 and the conductive plates 310 are alternately arranged in the stacking direction of the module stack 31 (vertical direction in FIG. 2). The conductive plate 310 electrically connects the battery modules 2 adjacent to each other. Each of the plurality of battery modules 2 has a voltage detection line for detecting the voltage of each of the plurality of cells included in the battery module (the voltage between two adjacent electrode layers 412 as described later). 20 are provided. Although the number of battery modules 2 is three in FIG. 2, the number of battery modules 2 is not particularly limited as long as it is two or more.

A pair of restraining members 32 restrain the module stack 31 from both sides in the stacking direction of the module stack 31 .

One of the pair of insulating members 33 is arranged between one of the pair of restraining members 32 and one end of the module laminate 31 in the stacking direction. The other of the pair of insulating members 33 is arranged between the other of the pair of restraining members 32 and the other end of the module stack 31 in the stacking direction.

The positive electrode terminal 341 is electrically connected to the conductive plate 310 (lower end) located at one end in the stacking direction of the module laminate 31 . The positive terminal 341 is electrically connected to the connection terminal 101 (see FIG. 1). The negative terminal 342 is electrically connected to the conductive plate 310 located at the other end (upper end) of the module laminate 31 in the stacking direction. The negative terminal 342 is electrically connected to the connection terminal 102 (see FIG. 1).

The battery module 2 is a battery having a bipolar structure (so-called bipolar battery). In this embodiment, the battery module 2 is a lithium ion secondary battery.

<Configuration of battery module>
FIG. 3 is a schematic cross-sectional view of the battery module 2. FIG. The battery module 2 includes a laminate 21 and a sealing portion 22 . Laminate 21 includes a plurality of bipolar electrodes 41, a plurality of separators 40, and an electrolytic solution.

The plurality of bipolar electrodes 41 are stacked in the stacking direction (vertical direction in FIG. 3). Bipolar electrode 41 includes electrode plate 411 and electrode layer 412 .

Electrode plate 411 is, for example, a rectangular metal foil. The electrode plate 411 has a first main surface 411a and a second main surface 411b arranged in the stacking direction.

The electrode layer 412 is arranged inside the periphery of the electrode plate 411 . The electrode layers 412 are arranged on both sides of the electrode plate 411 . Electrode layer 412 includes positive electrode 43 and negative electrode 44 . The positive electrode 43 is arranged on the first main surface 411 a of the electrode plate 411 . The positive electrode 43 contains a positive electrode active material. The positive electrode 43 may contain a conductive material and a binder in addition to the positive electrode active material. The negative electrode 44 is arranged on the second main surface 411 b of the electrode plate 411 . The negative electrode 44 contains a negative electrode active material.

A negative terminal electrode is provided at one end (upper end in FIG. 3) of the laminate 21 in the stacking direction. No positive electrode 43 is provided on the first major surface 411a of the negative terminal electrode. A positive terminal electrode is provided at the other end (lower end) of the laminate 21 in the stacking direction. No negative electrode 44 is provided on the second main surface 411b of the positive terminal electrode.

The separator 40 is made of insulating resin. The separator 40 is arranged between two adjacent electrode layers 412 (between the positive electrode 43 and the negative electrode 44). Specifically, it is arranged between the negative electrode 44 of the bipolar electrode 41 located on one side in the stacking direction and the positive electrode 43 of the bipolar electrode 41 located on the other side in the stacking direction. By arranging the electrode layer 412 (the positive electrode 43 and the negative electrode 44) and the separator 40 as described above, cells are formed between adjacent electrodes (including bipolar electrodes and terminal electrodes).

The sealing portion 22 is made of insulating resin (polypropylene, polyphenylene sulfide, etc.). The sealing part 22 seals the periphery of the plurality of bipolar electrodes 41 so that a space is formed between two bipolar electrodes 41 adjacent to each other. The sealing portion 22 hermetically seals the above space on its inside. The space contains an electrolytic solution. The electrolytic solution impregnates the positive electrode 43 , the negative electrode 44 and the separator 40 .

For the positive electrode active material, the negative electrode active material, the separator 40 and the electrolyte, conventionally known materials for the positive electrode active material, the negative electrode active material, the separator and the electrolyte of the lithium ion secondary battery can be used, respectively. As an example, olivine-type lithium iron phosphate (LiFePO ₄ ) can be used as the positive electrode active material. However, the positive electrode active material may be a ternary material in which a portion of lithium cobaltate is replaced with nickel and/or manganese. Graphite (carbon material) can be used as the negative electrode active material. Polyolefin can be used for the separator. The electrolytic solution contains an organic solvent (for example, a mixed solvent of DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), and EC (ethylene carbonate)), a lithium salt (for example, LiPF ₆ ), and an additive (for example, LiBOB (lithium bis (oxalate)borate) or Li[PF ₂ (C ₂ O ₄ ) ₂ ]) and the like.

<Comparative example>
In order to facilitate understanding of the characteristics of the inspection process in the present embodiment, first, the processing procedure of the inspection process in the comparative example will be described. The configuration of the battery inspection system according to the comparative example is the same as the configuration of the battery inspection system 100 according to the present embodiment (see FIGS. 1 to 3).

FIG. 4 is a flow chart showing the processing procedure of the inspection process in the comparative example. In S91, the controller 9 controls the DC power supply to discharge all the cells included in the battery unit to a fully discharged state.

At S<b>92 , the controller 9 controls the DC power supply to start charging the battery unit 1 . Since all the cells included in the battery unit 1 are connected in series, all the cells are charged with the same current value.

In S93, the controller 9 determines whether the voltage of any one of all the cells included in the battery unit has reached a predetermined upper limit voltage UL. The controller 9 returns the process to S92 and continues charging the battery unit until the voltage of any cell reaches the upper limit voltage UL (in other words, while the voltages of all cells are less than the upper limit voltage UL). .

When the voltage of any cell reaches upper limit voltage UL (YES in S93), controller 9 terminates charging of the battery unit (S94). Then, the controller 9 acquires the voltage of each of the cells included in the battery unit (S95).

In S96, the controller 9 determines the quality of each battery module based on the voltage acquired in S95. Specifically, the controller 9 determines for each battery module whether the voltages of all the cells included in the battery module are within a predetermined allowable range. The allowable range is a voltage range (LL≤V≤UL) between the lower limit voltage LL and the upper limit voltage UL, and can be experimentally determined in advance according to the required specifications of the cell.

If the voltages of all cells included in the battery module are within the allowable range (YES in S96), controller 9 determines that the battery module is non-defective (S97). On the other hand, if the voltage of at least one cell included in the battery module is outside the allowable range (NO in S96), controller 9 determines that the battery module is defective (S98). This completes a series of processes.

FIG. 5 is a diagram for explaining problems in the inspection process in the comparative example. The horizontal axis represents cell capacity (the amount of power stored in each cell). The vertical axis represents cell voltage (closed-circuit voltage of each cell detected by a voltage sensor). The same applies to FIGS. 6 and 7, which will be described later.

Here, two cells among the plurality of cells included in the battery unit will be described as an example. These cells are described as "first cell" and "second cell". The first cell and the second cell are included in different battery modules. Assume that the voltage of the first cell rises more easily than the voltage of the second cell when the same amount of power is charged.

More specifically, when the electrode layer 412 is formed on the electrode plate 411 during the manufacture of the bipolar electrode 41, the basis weight, which is the mass per unit area of the electrode layer 412, does not reach a specified amount. Sometimes. The first cell is a cell composed of a defective bipolar electrode with a basis weight. A second cell is a cell composed of normal bipolar electrodes. In this case, since the amount of the electrode layer included in the first cell is smaller than the amount of the electrode layer included in the second cell, the full charge capacity of the first cell becomes smaller than the full charge capacity of the second cell. obtain. Then, when the same amount of power is charged, the voltage of the first cell tends to rise excessively compared to the voltage of the second cell.

Charging starts from the fully discharged state (cell capacity=0) of both the first cell and the second cell. When each of the first cell and the second cell is charged with the electric energy of ΔAh, the voltage of the first cell reaches upper limit voltage UL (YES in S93 of FIG. 4). Then, charging of both the first cell and the second cell is completed (S94). The dashed line indicates that the second cell is not charged beyond the power amount ΔAh.

In this example, it is assumed that the first cell is actually a defective product (for example, a defective product with a basis weight), and the voltage of the first cell tends to rise excessively. However, when charging is completed, the voltage of the first cell is equal to the upper limit voltage UL and is within the allowable range. Therefore, the battery module including the first cell can be determined as non-defective (S97).

On the other hand, the second cell is actually good. If charging continues, the voltage of the second cell rises to the allowable range as indicated by the dashed line. In spite of this, the voltage of the second cell is below the lower limit voltage LL and out of the allowable range when charging is completed. Therefore, the battery module including the second cell is determined to be defective (S98).

As described above, in the comparative example, a battery module containing a defective cell (first cell) is determined to be a non-defective product, while a battery module containing a non-defective cell (second cell) is erroneously determined to be defective. may occur.

Therefore, in the present embodiment, a configuration is adopted in which the quality determination is performed for each battery module in consideration of the cell capacity as well as the cell voltage. More specifically, on the cell capacity-cell voltage plane, two types of curves are prepared in consideration of the permissible error (tolerance) of the basis weight of the electrode layer 412 (positive electrode 43 and negative electrode 44). Then, quality determination of each battery module (cell) is performed according to the area defined by the two types of curves.

<Area Defined by Two Types of Curves>
FIG. 6 is a diagram showing an example of two types of curves in this embodiment. In the present embodiment, in addition to the “allowable voltage range” defined by the upper limit voltage UL and the lower limit voltage LL for the cell voltage, the allowable range for the cell capacity is also defined. This allowable range is also referred to as "capacity allowable range". The allowable capacity range is a capacity range (MIN≤Ah≤MAX) between the minimum capacity MIN and the maximum capacity MAX, and can be determined experimentally in advance according to the required specifications of the cell.

More specifically, each of the plurality of bipolar electrodes 41 (each cell) is configured such that the capacity of the positive electrode 43 is smaller than the capacity of the negative electrode 44 . The maximum capacity MAX is the cell capacity when the basis weight of the positive electrode 43 is the maximum within the allowable error range. On the other hand, the minimum capacity MIN is the cell capacity when the basis weight of the positive electrode 43 is the minimum within the allowable error range.

The two types of curves are described as "maximum capacity curve Lmax" and "minimum capacity curve Lmin". A minimum capacity curve Lmin (see one-dot chain line) passes through an intersection point a between the upper limit voltage UL of the allowable voltage range and the minimum capacity MIN of the allowable capacity range. The maximum capacity curve Lmax (see the solid line) passes through the intersection point b between the upper limit voltage UL of the allowable voltage range and the maximum capacity MAX of the allowable capacity range. The intersection point between the maximum capacity curve Lmax and the lower limit voltage LL of the allowable voltage range is denoted as c. Both curves pass through point d when cell capacity=0.

FIG. 7 is a diagram for explaining a region defined by a maximum capacity curve Lmax and a minimum capacity curve Lmin. In this embodiment, as shown in FIG. 7, a "non-defective product area" and a "reserve area" are defined.

The non-defective product area is an area surrounded by a straight line ab, a curved line bc, and a straight line ca. Curve bc is a curve between point b and point c in the maximum capacity curve Lmax. The good area also includes the points on the three lines. The non-defective product region can also be said to be a region sandwiched between the minimum capacity curve Lmin and the maximum capacity curve Lmax in which the capacity is equal to or greater than the minimum capacity MIN and the voltage is equal to or less than the upper limit voltage UL.

A reserved area is an area surrounded by a straight line ac, a curved line cd, and a curved line ad. A curve cd is a curve between points c and d in the maximum capacity curve Lmax. A curve ad is a curve between points a and d in the minimum capacity curve Lmin. The reserved area includes points on curve cd and points on curve ad, but does not include points on line ac. The reserved area can also be said to be an area other than the non-defective product area in the area sandwiched between the minimum capacity curve Lmin and the maximum capacity curve Lmax.

Also, an area that is neither a non-defective product area nor a reserved area is called a "defective product area". In the present embodiment, as will be described below, the combination of the capacity and voltage of each cell (cell capacity, cell voltage) at the end of charging is located within the non-defective product region, the reserve region, or the defective product region. is determined.

Note that the non-defective product area corresponds to the "first area" according to the present disclosure. The reserved area corresponds to the "second area" according to the present disclosure. The defective product area corresponds to the "third area" according to the present disclosure. The upper limit voltage UL corresponds to the "predetermined voltage" according to the present disclosure.

<Processing flow>
FIG. 8 is a flow chart showing the processing procedure of the inspection process in this embodiment. This flowchart is executed when a predetermined condition is established (for example, when an operator operates a start switch (not shown)). Each step is realized by software processing by the controller 9 (processor 91 ), but may be realized by hardware (electric circuit) arranged in the controller 9 . A step is abbreviated as S below.

In S1, the controller 9 controls the DC power supply 5 to discharge all the cells included in the battery unit 1 to a completely discharged state (complete discharge process). In addition, when the battery unit 1 has never been charged (when it is charged for the first time after the electrolyte solution is injected), the complete discharge process of S1 can be omitted (skipped). The controller 9 can determine whether or not the complete discharge process is necessary according to whether or not the voltages are uniform between the cells. If the voltages do not match between cells (for example, if the voltage difference between the highest voltage and the lowest voltage exceeds a predetermined value), controller 9 determines that complete discharge processing is necessary. On the other hand, when the voltages between the cells are the same (for example, when the voltage difference is less than the predetermined value), the controller 9 can omit the complete discharge process.

In S2, the controller 9 controls the DC power supply 5 so as to start charging the battery unit 1 at a constant current, for example. As described above, all the cells in the battery unit 1 are connected in series, so all the cells are charged with the same current value. The controller 9 acquires the voltage of each cell, for example, every predetermined cycle while the battery unit 1 is being charged.

In S<b>3 , controller 9 determines whether the voltage of any one of all the cells included in battery unit 1 has reached upper limit voltage UL. The controller 9 returns the process to S2 and continues charging the battery unit 1 until the voltage of any cell reaches the upper limit voltage UL. When the voltage of any cell reaches upper limit voltage UL (YES in S3), the controller terminates charging of the battery unit (S4).

At S5, the controller 9 calculates the capacity of each cell. More specifically, the controller 9 can calculate the capacity of each cell by multiplying the charging current I to the battery unit 1 by the charging time t (I×t). It is an example that the charging current I to the battery unit 1 is a constant current. The controller 9 may calculate the capacity of each cell by integrating (Σ(I(t)×Δt)) the charging current I(t) that changes with time every unit time Δt.

In S<b>6 , the controller 9 acquires the voltage of each cell (all cells included in the battery unit 1 ) detected by the voltage sensor 6 . Note that the processes of S2 to S6 are also referred to as "charging process".

In S7 to S9, the controller 9 determines, for each battery module 2, in which region on the cell capacity-cell voltage plane each cell included in the battery module 2 is located. Specifically, in S7, the controller 9 determines whether or not all the cells included in a certain battery module 2 are located within the non-defective product area. If all cells are located within the non-defective product area (YES in S7), controller 9 determines that battery module 2 is non-defective (S10).

If at least one cell is not in the non-defective product area (NO in S7), controller 9 determines whether even one cell is in the reservation area (S8). If at least one cell is included in the reserved area (YES in S8), the controller 9 determines whether at least one cell is included in the defective area (S9). If there is no cell in the defective product area (NO in S9), that is, if all the cells outside the non-defective product area are cells located in the reserved area, the controller 9 reserves the battery module 2. (S11).

If there is no cell in the reserve area in S8 (NO in S8), that is, if all the cells outside the non-defective product area are located in the defective product area, the controller 9 determines that the battery module 2 is defective. It is judged to be non-defective (S12). Also, when there are cells located in the reservation area but cells located in the defective area are also included, that is, when cells in the reservation area and cells in the defective area are mixed, The controller 9 determines that the battery module 2 is defective (S12). Note that the processing of S7 to S12 is also called "determination processing".

As a result of the determination process, the battery module 2 determined as a non-defective product is shipped as a non-defective product. Battery modules 2 determined to be defective are discarded or recycled without being shipped. On the other hand, the battery module 2 determined to be on hold is sent to the additional process, where the complete discharge process is executed, and the charging process and the determination process are executed again. Specifically, the process returns to S1 after excluding the battery modules 2 determined to be non-defective or defective from the battery unit 1 . As a result, the controller 9 recharges (S2 to S4) all the cells of the battery module 2 determined to be on hold after all the cells are completely discharged (S1). Further, the controller 9 calculates the capacity of each cell and obtains the voltage of each cell (S5, S6). Then, the controller 9 determines in which region on the cell capacity-cell voltage plane each cell included in the battery module 2 determined to be on hold is located (S7 to S12).

In the additional process, the battery modules 2 determined to be defective have already been excluded. Therefore, unlike the description with reference to FIG. 5, the battery module 2 determined to be on hold does not include cells such as the first cell, the voltage of which is likely to rise excessively. Like the second cell, the cell included in the battery module 2 was located in the reserve area when the initial charging was completed (in other words, it progressed only to just before the non-defective area and did not reach the non-defective area). However, it is a cell that may be located in the non-defective product area if charging is continued. Therefore, there is a possibility that the battery module 2 will be determined to be non-defective by performing the additional process. Then, the battery module 2 can also be shipped, and the yield can be improved.

As described above, in the present embodiment, a category of "reserved goods" is provided. A suspended product may be erroneously determined to be defective even though it is actually a non-defective product because the voltage of a cell included in the defective product has reached the upper limit voltage UL. Therefore, in addition to the complete discharging process (S1) being executed for the reserved item, the charging process (S2 to S6) and the determination process (S7 to S12) are again executed. As a result, it is possible to improve the inspection accuracy for the reserved item.

The embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present disclosure is indicated by the scope of claims rather than the description of the above-described embodiments, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

1 battery unit, 2 battery module, 20 voltage detection line, 21 laminate, 22 sealing portion, 31 module laminate, 310 conductive plate, 32 restraint member, 33 insulating member, 341 positive electrode terminal, 342 negative electrode terminal, 40 separator, 41 Bipolar electrode 411 Electrode plate 411a First main surface 411b Second main surface 412 Electrode layer 43 Positive electrode 44 Negative electrode 5 DC power supply 6 Voltage sensor 7 Current sensor 8 Temperature sensor 9 Controller 91 Processor, 92 memory, 100 battery inspection system, 101, 102 connection terminals.

Claims (3)

A method for inspecting a plurality of battery modules connected in series, comprising:
each of the plurality of battery modules includes a plurality of cells connected in series;
The inspection method is
performing a charging process;
a step of performing a determination process;
and re-executing the charging process and the determination process,
The step of executing the charging process includes:
charging all the cells included in the plurality of battery modules until the voltage of any one of the cells reaches a predetermined voltage;
calculating the capacity stored in each of said all cells charged;
detecting the voltage of each of said all charged cells;
In the step of executing the determination process, for each of all the cells charged by the charging process, the capacity of the cell is within the allowable capacity range and the voltage of the cell is within the allowable voltage range. determining whether to
In the re-executing step, when there is a reserved battery module including a cell whose capacity is within the allowable capacity range and whose voltage is not within the allowable voltage range, among the plurality of battery modules,
fully discharging each cell contained in the reserve battery module;
and re-executing the charging process and the determination process for the reserved battery module in which each cell has been completely discharged. In the determining step, for each of all the cells charged by the charging process, a combination of capacity and voltage of the cell is defined on a capacity-voltage plane using a maximum capacity curve and a minimum capacity curve. Including the step of determining whether it is located in any of the first to third regions,
The maximum capacity curve is a capacity-voltage curve passing through the intersection of the upper limit voltage of the allowable voltage range and the maximum capacity of the allowable capacity range,
The minimum capacity curve is a capacity-voltage curve that passes through the intersection of the upper limit voltage and the minimum capacity of the allowable capacity range,
the first region is a region sandwiched between the minimum capacity curve and the maximum capacity curve, wherein the capacity is equal to or greater than the minimum capacity and the voltage is equal to or less than the upper limit voltage;
The second region is a region other than the first region among the sandwiched regions,
The third region is a region other than the first region and the second region,
The battery module inspection method according to claim 1, wherein the reserved battery module is a battery module that includes cells located in the second area but does not include cells located in the third area. 3. The battery module inspection method according to claim 1, wherein each of said plurality of battery modules is a lithium ion battery having a bipolar structure.

Images