JP2019113469A - Self-discharge inspection method for power storage device - Google Patents

Abstract

To provide a power storage device self-discharge inspection method for a power storage device with which it is possible to the acceptability of a power storage device in a short time by a new technique different from a technique that acquires a voltage drop amount ΔVa.SOLUTION: The self-discharge inspection method for a power storage device 1 comprises: an SOC adjustment step S4 for adjusting the SOC of a power storage device 1 to an inspection SOC (KS) within a super-average differential OCV range SA; a voltage application step S5 for continuously applying an output voltage VS from an external power supply EP to the power storage device 1 and continuously sending a current IB to the power storage device 1; current acquisition steps S6, S26 for acquiring a temporal change of the current IB or a converged current value IBs into which the current IB converges; and determination steps S7, S27 for determining the acceptability of the power storage device 1 on the basis of the temporal change of the current IB or the converged current value IBs.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a self-discharge inspection method of a storage device that determines the quality of the storage device by inspecting the magnitude of the self-discharge of the storage device.

  In the production of a storage device such as a lithium ion secondary battery, metallic foreign matter such as iron or copper may be mixed into the inside of the electrode body, and an internal short circuit may occur in the storage device due to the mixed metallic foreign matter . For this reason, in the process of manufacturing the storage device, it may be inspected whether or not an internal short circuit has occurred in the storage device.

  As the inspection method of this internal short circuit, the following is known, for example. That is, after the assembled power storage device is initially charged, the power storage device is left to self-discharge (discharge in the open state of the terminal), and the voltage drop amount ΔVa due to self-discharge from the device voltage measured before and after this self-discharge. Ask for Then, when the voltage decrease amount ΔVa is larger than the reference decrease amount ΔVb (ΔVa> ΔVb), the power storage device is determined as a defective product in which an internal short circuit occurs. In addition, as related prior art, patent document 1 (refer the claim etc. of patent document 1) is mentioned.

JP, 2010-153275, A

  However, in the method of determining the quality of the power storage device based on the amount of voltage drop amount ΔVa as described above, in consideration of the measurement resolution of the voltmeter (for example, 10 μV), to appropriately determine the quality of the power storage device. It is necessary to wait until, for example, 20 times or more (200 μV or more) until the difference between the non-defective voltage drop amount ΔVa and the non-defective product voltage drop amount ΔVa becomes sufficiently large with respect to the measurement resolution of voltage measurement. However, if the capacity of the storage device is large or the allowable short circuit current is small, the measurement time (time for self-discharge) of the voltage drop amount ΔVa may take a long time, for example, several days or more, and the inspection time is long. It was hanging.

Therefore, the present inventors continue to apply the output voltage VS equal to the OCV of the storage device from the external DC power supply to the storage device, and keep the current IB flowing from the external DC power supply to the storage device, thereby changing the current IB with time. Alternatively, a self-discharge test (short-circuit test) that detects the magnitude of the convergence current value IBs in which the current IB has converged and determines the quality of the storage device based on the time-dependent change of the detected current IB or the magnitude of the convergence current value IBs ) Has been proposed.
Furthermore, it has been found that the convergence of the current IB can be accelerated by setting the SOC of the storage device in an appropriate range when performing a self-discharge test by this method.

  The present invention has been made in view of the present situation, and is a new method different from the method of acquiring the voltage drop amount ΔVa, and a self-discharge test of the storage device capable of determining the quality of the storage device in a short time. Intended to provide a method.

  One aspect of the present invention for solving the above problems is an SOC adjustment step of adjusting the SOC of the storage device to a predetermined inspection SOC within a super average differential OCV range, and the storage device adjusted to the inspection SOC The voltage application step of continuing to apply the output voltage VS from the external DC power supply and continuing the flow of the current IB from the external DC power supply to the storage device, the time-dependent change of the current IB or the convergence current value IBs at which the current IB converges A self-discharge inspection method of a power storage device, comprising: a current obtaining step to obtain; and a determining step of determining the quality of the power storage device based on a change with time of the current IB or the convergence current value IBs obtained. .

The above-described self-discharge inspection method of the storage device includes the above-described SOC adjustment step, voltage application step, current acquisition step, and determination step, so a new method different from the conventional method of measuring the voltage drop amount ΔVa And in a short time, it is possible to determine the quality of the power storage device.
Furthermore, in the above-described self-discharge inspection method, prior to the voltage application step, the storage device is adjusted to the inspection SOC within the super average differential OCV range in the SOC adjustment step. By performing the voltage application step using the storage device in which the inspection SOC is in the super average differential OCV range, the power storage device in which the current convergence time ta until the current IB converges is out of the super average differential OCV range Can be made shorter than when performing a voltage application process using Therefore, in the above-described self-discharge inspection method, the current acquisition step and the determination step can be performed earlier than in the case of using the storage device whose SOC is outside the super average differential OCV range, and the self-discharge inspection can be performed in a short time. Can be done with

  In addition, "average differential OCV" is SOC-ΔOCV / ΔSOC obtained by differentiating by SOC the "SOC-OCV curve" showing the relationship between SOC (0 to 100%) and OCV (open circuit voltage) of the storage device. “Curve” refers to the average value of ΔOCV / ΔSOC in the range of SOC 0-100%. The “super-average differential OCV range” refers to a range of SOC in which ΔV / ΔSOC is higher than the average differential OCV.

  In general, in the lithium-nickel-cobalt-manganese-based lithium ion secondary battery, the SOC-ΔOCV / ΔSOC curve shows that ΔOCV / ΔSOC increases as the SOC decreases in the low SOC range (for example, SOC = 0-20%) In the middle SOC range (for example, SOC = 20-70%), ΔOCV / ΔSOC is generally small and almost constant, and in the high SOC range (for example, SOC = 70-100%), the SOC is The larger the curve, the larger the ΔOCV / ΔSOC. Therefore, in this case, the “super-average differential OCV range” is the SOC range in which ΔOCV / ΔSOC is higher than the average differential OCV in this SOC-ΔOCV / ΔSOC curve (for example, SOC = 0-13%, SOC90 This corresponds to two ranges of −100%, or only SOC = 0-13%.

The above-mentioned self-discharge inspection method of a storage device can be performed in the manufacturing process of the storage device, and also performed on a used storage device mounted on a car or the like or after being put on the market alone. It can also be done.
Examples of the "storage device" include a battery such as a lithium ion secondary battery, a capacitor such as an electric double layer capacitor, and a lithium ion capacitor.

In the “voltage application step”, a step of continuing to apply a voltage (VS = VB1) equal to the device voltage VB1 (open voltage) of the storage device immediately before the test as the output voltage VS applied from the external DC power supply Thereafter, there is also a step of gradually or stepwise increasing the output voltage VS from the device voltage VB1.
The “convergence current value IBs” is a current value that can be considered that the magnitude of the current IB is substantially constant. For example, the change in the current IB (t) obtained every predetermined time is within a predetermined range (for example, The current value when it becomes ± 0.1 μA or less / sec). Further, as a method of obtaining the convergence current value IBs, in addition to a method of measuring the magnitude of the convergence current value IBs, before the current IB converges, the magnitude of the convergence current value IBs is Also includes estimation.

As a method of determining the quality of the power storage device based on the “convergent current value IBs” in the “determination step”, for example, when the convergent current value IBs is larger than the reference current value IK (IBs> IK), There is a method of determining a storage device as a defective product. Further, there is also a determination method of ranking the degree of self-discharge of the storage device based on the magnitude of the convergence current value IBs.
Further, as a method of determining the quality of the power storage device based on "time-dependent change of current IB", for example, when current increase amount ΔIB of current IB increased in a predetermined detection period QT is larger than reference increase amount ΔIBK (ΔIB> ΔIBK), there is a method of determining the storage device as a defective product. Also, there is a determination method of ranking the degree of self-discharge of the power storage device based on the magnitude of the current increase amount ΔIB.

  Furthermore, in the self-discharge inspection method of the storage device, the SOC adjustment step adjusts the SOC of the storage device to a predetermined inspection SOC within a high differential OCV range within the super average differential OCV range. It is preferable to set it as the self discharge inspection method of the electrical storage device to be.

By adjusting the SOC of the storage device to the SOC within the high differential OCV range, the self-discharge test can be performed in a shorter time.
The “high differential OCV range” refers to the SOC range in which ΔV / ΔSOC is higher than twice the average differential OCV in the SOC-ΔOCV / ΔSOC curve of the “super-average differential OCV range” (for example, the above In the example of a lithium nickel cobalt manganese oxide-based lithium ion secondary battery, the SOC

  Moreover, the self-discharge which performs the self-discharge test of the said electrical storage device by the first charge process of carrying out the first charge of the assembled uncharged electrical storage device initially, and the self-discharge inspection method of the electrical storage device in any one of said And a test process.

  In the method of manufacturing the storage device described above, since the self-discharge inspection step of performing the self-discharge inspection of the storage device is provided after the initial charging step, it is possible to manufacture the storage device properly subjected to the self-discharge inspection at the initial stage of the storage device. .

It is a perspective view of the battery concerning an embodiment. It is a flowchart of the manufacturing method of a battery including the self-discharge test method of the battery which concerns on embodiment. It is a graph (SOC-OCV curve) which shows the relation between SOC of a battery, and battery voltage VB (OCV). It is the SOC- (DELTA) OCV / (DELTA) SOC curve which differentiated the SOC-OCV curve of FIG. 3 by SOC. It is an equivalent circuit schematic of the state which connected the external DC power supply to the battery regarding the self-discharge test method of the battery which concerns on embodiment. It is a graph which shows the relationship of voltage application time t and electric current IB (t) at the time of performing a self-discharge test about the battery with large local battery capacity Cx, and a small battery. It is a graph which shows typically the relationship of the voltage application time t, the output voltage VS, the battery voltage VB (t), and electric current IB (t) at the time of performing a self-discharge test about each battery of non-defective goods and inferior goods.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a perspective view of a battery (power storage device) 1 according to the present embodiment. The battery 1 is a rectangular and sealed lithium ion secondary battery mounted on a vehicle such as a hybrid car, a plug-in hybrid car, and an electric car. The battery 1 includes a battery case 10, an electrode body 20 housed inside the battery case 10, and a positive electrode terminal member 50 and a negative electrode terminal member 60 supported by the battery case 10. Among them, the battery case 10 has a rectangular box shape and is made of metal (in the present embodiment, aluminum).

  The electrode assembly 20 is a flat wound electrode assembly, and a strip-like positive electrode plate and a strip-like negative electrode plate are superimposed on each other via a pair of separators made of a porous resin film and an axial line It is wound around and compressed into a flat shape. In the present embodiment, the positive electrode active material contained in the positive electrode active material layer of the positive electrode plate is a lithium transition metal composite oxide, specifically lithium nickel cobalt manganese oxide, and is contained in the negative electrode active material layer of the negative electrode plate. The negative electrode active material to be used is a carbon material, specifically, graphite. In addition, an electrolytic solution (not shown) is accommodated in the battery case 10, and a part thereof is impregnated in the electrode body 20.

  Then, the manufacturing method of the battery 1 including the self-discharge test method of the said battery 1 is demonstrated (refer FIG. 2). First, in "assembly step S1", an uncharged battery (uncharged storage device) 1x is assembled. Specifically, the case lid member 13 of the battery case 10 is prepared, and the positive electrode terminal member 50 and the negative electrode terminal member 60 are fixed thereto. Thereafter, the positive electrode terminal member 50 and the negative electrode terminal member 60 are respectively welded to the positive electrode plate and the negative electrode plate of the electrode body 20 separately formed. Thereafter, the electrode body 20 is inserted into the case body member 11 of the battery case 10, and the opening of the case body member 11 is closed by the case lid member 13. Then, the case body member 11 and the case lid member 13 are welded to form the battery case 10. Thereafter, an electrolytic solution (not shown) is injected into the battery case 10 through the injection hole 13 h, and the injection hole 13 h is sealed by the sealing member 15. Thereby, an uncharged battery 1x is formed.

  Next, in the "first charging step S2", the assembled uncharged battery 1x is initially charged. Specifically, the battery 1x is restrained in a compressed state in the battery thickness direction using a restraint jig (not shown). In the present embodiment, from the initial charging step S2 to the self-discharge inspection step S3 described later, the battery 1x (battery 1) is compressed. Thereafter, a charge / discharge device (not shown) is connected to battery 1x, and battery voltage (device voltage) VB = 3.97 V corresponding to SOC 90% by constant current constant voltage (CCCV) charging under an environmental temperature of 25 ° C. Charge the battery 1x for the first time (CCCV charge). In this embodiment, after charging until the battery voltage VB = 3.97 V with a constant current of 1 C, the battery voltage VB = 3.97 V is maintained until the charging current value becomes 1/10 C.

Next, "self-discharge inspection step S3" is performed. The self-discharge inspection step S3 includes an SOC adjustment step S4, a voltage application step S5, a current acquisition step S6 and a determination step S7.
First, in the "SOC adjustment step S4", the SOC of the battery 1 is adjusted to a predetermined inspection SOC (KS) within the super average differential OCV range SA.

  Here, FIG. 3 shows an SOC-OCV curve of the SOC of the battery 1 and the battery voltage VB (OCV). Further, FIG. 4 shows an SOC-ΔOCV / ΔSOC curve obtained by differentiating the SOC-OCV curve of FIG. 3 by SOC. The SOC-OCV curve in FIG. 3 shows a curve shape in which the battery voltage VB increases as the SOC increases. On the other hand, in the SOC-ΔOCV / ΔSOC curve of FIG. 4, in the low SOC range of SOC = 0-20%, ΔOCV / ΔSOC increases as the SOC decreases, and in the middle SOC range of SOC = 20-70%, The ΔOCV / ΔSOC is generally small and substantially constant, and in the high SOC range of SOC = 70-100%, a curve shape in which ΔOCV / ΔSOC increases as the SOC increases is shown.

  If battery 1 is considered as a capacitor (see also FIG. 5), the relationship of VB = Q / C should be established among battery voltage VB (V), charge amount Q (C) and battery capacity C (F) It is. However, in practice, battery 1 differs from a capacitor, and as shown in FIG. 3, battery voltage VB is not proportional to the charge amount Q (SOC) stored in battery 1. That is, the local battery capacity Cx (= 1 / (ΔOCV / ΔSOC)), which is a local battery capacity, is a function of the SOC which changes with the charge amount Q (SOC) stored in the battery 1. As shown in FIG. 4, ΔOCV / ΔSOC increases as the SOC decreases in the low SOC range of SOC = 0-20%, and is generally smaller in the medium SOC range of SOC = 20-70%. It is substantially constant, and in the high SOC range of SOC = 70-100%, the larger the SOC, the larger. Therefore, the local battery capacity Cx (= 1 / (. DELTA.OCV / .DELTA.SOC)), which is the reciprocal of .DELTA.OCV / .DELTA.SOC, becomes smaller as the SOC becomes smaller in the range of the low SOC, and becomes large largely in the range of the middle SOC And, it is generally constant, and in the high SOC range, it tends to be smaller as the SOC is larger.

  Therefore, the current IB (t) flowing from the external DC power supply EP to the battery 1 converges as the voltage application step S5 to be described later is performed by the SOC (the SOC of ΔOCV / ΔSOC in FIG. The convergence time ta can be shortened, and the current detection step S6 for detecting the convergence current value IBs can be performed early. Therefore, prior to this, in the SOC adjustment step S4, the SOC of the battery 1 is adjusted to an SOC where the local battery capacity Cx becomes smaller (ΔOCV / ΔSOC becomes larger).

  In this embodiment, specifically, in the SOC-ΔOCV / ΔSOC curve of FIG. 4, “average differential OCV” which is an average value of ΔOCV / ΔSOC in the range of SOC 0 to 100% is LA = 0.011. . Therefore, the "super average differential OCV range SA", which is the range of SOC in which ΔOCV / ΔSOC becomes larger than this average differential OCV (LA = 0.011), is SOC 0-13% and SOC 90-100%. Furthermore, “high differential OCV range SB”, which is a range of SOC in which ΔOCV / ΔSOC becomes larger than twice the average differential OCV (2 × LA = 0.022), is SOC0−9.5%.

The value of ΔOCV / ΔSOC at each point in FIG. 4 was calculated as follows based on the data at each point in FIG. For example, the value of ΔOCV / ΔSOC at SOC 5% is obtained at three points including ΔOCV / ΔSOC at SOC 0% and ΔOCV / ΔSOC at 10% before and after that. Specifically, the slope of the interval from SOC 0% to SOC 5%, that is, the slope of the interval from SOC 5% to SOC 10%, (OCV at OCV at SOC 5%, OCV at SOC 0%) / (5% −0%) That is, an average of (OCV at 5% of SOC, OCV at 5% of SOC) / (10% to 5%) was taken as a derivative value (ΔOCV / ΔSOC) at 5% of SOC.
As the value of ΔOCV / ΔSOC at SOC 0%, the slope of the section from SOC 0% to SOC 5% was used as it is. Further, as the value of ΔOCV / ΔSOC at SOC 100%, the slope of the section from SOC 95% to SOC 100% was used as it is. Thus, the value of ΔOCV / ΔSOC at each point was obtained.

  Moreover, "average differential OCV" (LA = 0.011) which is an average value of (DELTA) OCV / (DELTA) SOC in the range of SOC0-100% was calculated as follows. In the graph described in FIG. 4, the area below the graph is determined, and the area of the trapezoid of each section of SOC (for example, section of SOC0-5%, section of SOC5-10%, etc.) is calculated and added. The total area was divided by 100 (SOC 100%) to obtain an average value of ΔOCV / ΔSOC (average differential OCV).

  In the SOC adjustment step S4 of the present embodiment, the SOC of the battery 1 is adjusted to the inspection SOC (KS = SOC 8%) which is within the super average differential OCV range SA and further within the high differential OCV range SB. Specifically, at an environmental temperature of 25 ° C., the battery voltage VB = 3.97 V corresponding to 90% of SOC at a constant current of 1 C by a charge / discharge device (not shown) connected to the battery 1 corresponds to 8% of SOC The SOC of the battery 1 was adjusted by forcibly discharging the battery voltage VB to 3.38V.

  Further, in the present embodiment, a local battery capacity Cx which is a local battery capacity in an inspection SOC (in the present embodiment, KS = SOC 8%) in which “voltage application step S5” described below is performed in the SOC adjustment step S4. Ask for Specifically, a voltage section until the battery voltage VB = 3.38 V corresponding to SOC 8% from the battery voltage VB = 3.41 V corresponding to the SOC 9% of the battery 1 (ΔOCV = 3.41-3.38 The amount of discharged electricity .DELTA.Q discharged to = 0.03 V) is measured, and this is used to obtain a local battery capacity Cx (= .DELTA.Q / .DELTA.OCV).

  Next, in the “voltage application step S5”, the output voltage VS is continuously applied from the external DC power supply EP to the battery 1 adjusted to the inspection SOC (KS = SOC 8%), and the current IB is supplied to the battery 1 from the external DC power supply EP. Keep flowing (see FIG. 5). Specifically, first, the external DC power supply EP is connected to the battery 1 by bringing the pair of probes P1, P2 of the external DC power supply EP into contact with the positive electrode terminal member 50 and the negative electrode terminal member 60 of the battery 1, respectively.

  In FIG. 5, the wiring resistance Rw indicates wiring resistance distributed in the external DC power supply EP and from the external DC power supply EP to the probes P1 and P2. The contact resistance R1 is a contact resistance between one probe P1 of the external DC power supply EP and the positive electrode terminal member 50 of the battery 1, and the contact resistance R2 is the other probe P2 of the external DC power supply EP and the negative electrode of the battery 1 It is a contact resistance with the terminal member 60. The battery component 1C is a battery component of the battery 1, the battery resistance Rs is a direct current resistance of the battery 1, and the self-discharge resistance Rp is a resistance mainly generated by an internal short circuit of the battery 1. In the equivalent circuit, the battery resistance Rs is connected in series to the battery component 1C, and the self-discharge resistance Rp is connected in parallel to the battery component 1C. The circuit resistance Re is the sum of the wiring resistance Rw, the contact resistances R1 and R2, and the battery resistance Rs (Re = Rw + R1 + R2 + Rs). Further, current IB is a current flowing from external DC power supply EP to battery 1, and current ID is a self-discharge current flowing in battery 1 (battery component 1C) along with self-discharge.

  Further, the external DC power supply EP can variably control the output voltage VS generated by its own DC power supply EPE with high accuracy, and is a precision DC configured to be able to measure the current IB flowing from the DC power supply EPE to the outside with high accuracy. It is a power source. The external DC power supply EP further includes a voltmeter EPV capable of measuring the battery voltage VB and an ammeter EPI capable of measuring the current IB flowing from the external DC power supply EP to the battery 1.

  After the external direct current power supply EP is connected to the battery 1, the battery voltage VB (open circuit voltage VB1) of the battery 1 is measured by a voltmeter EPV included in the external direct current power supply EP under the condition of current IB = 0. In the present embodiment, a value near 3.38 V is measured as the pre-test battery voltage (open circuit voltage) VB1. Thereafter, after time t = 0, the output voltage VS (VS = VB1) equal to the measured pre-test battery voltage VB1 is continuously applied to the battery 1, and the current IB is continuously supplied from the external DC power supply EP to the battery 1.

  Here, a theoretical formula of the current IB (t) flowing from the external DC power supply EP to the battery 1 will be described. The theoretical equation of <Equation 1> below is an equation in which the differential equation of the equivalent circuit in which the external DC power supply EP is connected to the battery 1 is solved under initial conditions (voltage application time t = 0).

t: Voltage application time (sec)
IB: Current (μA)
VS: Output voltage (V)
VB1: Battery voltage before inspection (V)
Rp: Self-discharge resistance (Ω)
Re: Circuit resistance (Ω)
Cx: Local battery capacity (F)

  Consider the exponent {− (Re + Rp) t / ReRpCx} of the number of Napiers (e) related to the convergence time (voltage application time t) in the above theoretical formula <1>. The numerator and denominator of this exponent are respectively divided by Rp to obtain {-(Re / Rp + 1) t / ReCx}. Here, when the self-discharge resistance Rp is sufficiently larger than the circuit resistance Re (for example, the self-discharge resistance Rp is several hundreds Ω for a circuit resistance Re of several Ω, etc.), Re / Rp is sufficient compared to 1 The value can be ignored and the above index can be approximated as {−t / ReCx}. Then, the following approximate expression of <expression 2> is obtained from the theoretical expression of <expression 1>.

FIG. 6 shows the relationship between the voltage application time t and the current IB (t) for the battery 1 with a small local battery capacity Cx and the battery 1 with a large local battery capacity Cx. These graphs are graphs drawn based on the equation of the current IB (t) shown in the above <Equation 2>, and the graph shown by a solid line as “local battery capacity Cx: small” is an equation of <Equation 2> Is a graph with a local battery capacity Cx = 5,500 F, and a graph shown by a broken line as “local battery capacity Cx: large” is a graph with a local battery capacity Cx = 55,000 F in the equation <Equation 2>. It is.
In the graph of FIG. 6, the output voltage VS = the battery voltage before inspection VB1 uses the voltage value (specifically, VS = VB1 = 4.0 V) measured in the above-described voltage application step S5. In addition, the circuit resistance Re and the self-discharge resistance Rp are average values of the results of measurement of the circuit resistance Re and the self-discharge resistance Rp in advance for a number of non-defective batteries 1 (specifically, Re = 0.1Ω, Rp = 200 kΩ) were used respectively.

  Here, FIG. 7 schematically shows the relationship among the voltage application time t, the output voltage VS, the battery voltage VB (t), and the current IB (t) for each of the non-defective and defective batteries 1. As shown in FIG. 7, in the present embodiment, the output voltage VS applied from the external DC power supply EP to the battery 1 is the pre-test battery voltage VB1 measured immediately before the voltage application regardless of the passage of the voltage application time t. Make the same size. On the other hand, the battery voltage VB (t) gradually decreases with the elapse of the voltage application time t from the pre-test battery voltage VB1, and after the convergence time ta, it converges and becomes a constant value (converged battery voltage VB2). However, the battery voltage VB (t) of the defective battery 1 is significantly lower than that of the non-defective battery 1, so that the convergence battery voltage VB2 also has a relatively low value.

  The reason why the battery voltage VB (t) and the current IB (t) change in this way is as follows. In the battery 1, when the self discharge current ID flows out from the battery component 1C due to the self discharge, the voltage of the battery component 1C and the battery voltage VB (t) gradually decrease. At this time, the battery voltage VB (t) drops quickly because the non-defective battery 1 has a large self-discharge current ID as compared with the non-defective battery 1. On the other hand, when battery voltage VB (t) is lower than output voltage VS (VS <VB (t)), the voltage difference ΔV = VS−VB (t) from external DC power supply EP toward battery 1 (battery component 1C) The current IB corresponding to the magnitude of the current flows, and the battery 1 (battery component 1C) is charged. Since the current IB is small while the voltage difference ΔV = VS−VB (t) is small, the self-discharge current ID flowing out of the battery component 1C is larger than the current IB flowing into the battery 1 from the external DC power supply EP (ID> IB (T), the voltage of the battery component 1C and the battery voltage VB (t) gradually decrease. However, when battery voltage VB (t) further decreases and current IB increases and becomes approximately equal to the magnitude of self-discharge current ID (IB = ID) (when convergence time ta in FIG. 7), battery component 1C And the battery voltage VB is maintained at the convergent battery voltage VB2 (the self-discharge current ID flowing through the self-discharge resistor Rp is the current IB from the external DC power supply EP). Will be covered by

On the other hand, current IB (t) flowing from external DC power supply EP to battery 1 gradually increases with the lapse of voltage application time t from IB (0) = 0 (zero) at time t = 0 when voltage application is started. However, after the convergence time ta, it converges and becomes a substantially constant value (convergence current value IBs) (see also FIG. 6 as well as FIG. 7).
In the graph of FIG. 6, after the start of voltage application (t = 0), the change in current IB (t) every 60 seconds becomes within a predetermined range (± 0.1 μA or less). The time t is taken as the convergence time ta. Further, the current value IB (ta) at this convergence time ta is taken as the convergence current value IBs. In the example of “local battery capacity Cx: small” shown by the solid line in FIG. 6, the convergence time ta = 1,500 sec (about 0.42 hr), and in the example of “local battery capacity Cx: large”, the convergence time ta = 1 It was 13,000 sec (about 3.61 hr). In all cases, the convergence current value IBs is IBs = 20 μA.

As is apparent from the graph of FIG. 6 and the equation <Equation 2>, the smaller the local battery capacity Cx, the shorter the convergence time ta. Therefore, the smaller the local battery capacity Cx is, the later mentioned current knowledge detecting the convergence current value IBs Acquisition process S6 can be performed at an early stage.
On the other hand, as described above, the local battery capacity Cx (= 1 / (ΔOCV / ΔSOC)) changes according to the size of the SOC (see FIGS. 3 and 4). In the aforementioned SOC adjustment step S4, the SOC of the battery 1 is adjusted to an SOC that reduces the local battery capacity Cx. Specifically, the SOC of the battery 1 is adjusted to the inspection SOC (KS = SOC 8%) within the super-average differential OCV range SA and further within the high differential OCV range SB. Therefore, since the convergence time ta of the current IB (t) in the voltage application step S5 is particularly shortened, the convergence current value IBs can be detected early in the current acquisition step S6.

  Further, after the start of voltage application (after t = 0), in parallel with voltage application process S5, convergence of the current IB (t) flowing from external DC power supply EP to battery 1 is converged in "current acquisition process S6". Get the current value IBs. In this embodiment, the relationship between the local battery capacity Cx and the convergence time ta is obtained in advance by experiments using a large number of batteries, and based on this relationship, the local battery capacity obtained in the aforementioned SOC adjustment step S4. The convergence time ta is predicted from Cx. Then, when the predicted convergence time ta comes, the current value IB (ta) is measured, and this is taken as a convergence current value IBs.

  When the current detection step S6 is completed, the voltage application from the external DC power supply EP to the battery 1 is stopped to end the voltage application step S5. Thereafter, the external DC power supply EP is separated from the battery 1, and the compression of the battery 1 by the restraint jig (not shown) is released.

  In addition, separately in the “determination step S7”, the quality of the battery 1 is determined based on the magnitude of the convergence current value IBs acquired in the current acquisition step S6. Specifically, when the convergence current value IBs is larger than the reference current value IK (see FIG. 7) (IBs <IK), the battery 1 is determined to be defective, and the battery 1 is removed. On the other hand, when the convergence current value IBs is equal to or greater than the reference current value IK (IBs ≧ IK), the battery 1 is determined to be a non-defective product. Thus, the battery 1 is completed.

As described above, since the self-discharge inspection method of the battery 1 includes the SOC adjustment step S4, the voltage application step S5, the current acquisition step S6 and the determination step S7, the conventional method of measuring the voltage drop amount .DELTA.Va Can determine the quality of the battery 1 in a new method and in a short time.
Moreover, in the self-discharge inspection method of the battery 1, before performing the voltage application step S5, the inspection SOC within the super average differential OCV range SA (KS, KS = 8% in the present embodiment) in the SOC adjustment step S4. Adjust to Thus, current convergence time ta until current IB converges is performed by performing voltage application step S5 using battery 1 with inspection SOC set within super-average differential OCV range SA where local battery capacity Cx is small. The test SOC can be made shorter than in the case where the voltage application step S5 is performed using the battery 1 outside the super average differential OCV range SA. Therefore, the current acquisition step S6 and the determination step S7 can be performed earlier than when the battery 1 whose SOC is outside the super average differential OCV range SA is used, and the self-discharge test can be performed in a short time. .

  Furthermore, in the self-discharge inspection method of the battery 1 of the present embodiment, the SOC of the battery 1 is adjusted to the inspection SOC (KS) within the high differential OCV range SB of the super average differential OCV range SA in the SOC adjustment step S4. Therefore, the self-discharge test can be performed in a shorter time.

(Modified form)
Then, the modification of the said embodiment is demonstrated. In the embodiment, the convergence current value IBs at which the current IB (t) flowing from the external DC power supply EP to the battery 1 converges is detected in the current acquisition step S6, and the subsequent determination step S7 is based on the convergence current value IBs. The quality of the battery 1 was judged. On the other hand, in this modification, in the current acquisition step S26, “the change with time of the current IB” flowing from the external DC power supply EP to the battery 1 before the current IB (t) converges is known. This embodiment differs from the embodiment in that the quality of the battery 1 is determined in the subsequent determination step S27 based on the time-dependent change of the acquired current IB.

  That is, in this modification, self-discharge inspection process S23 is performed about battery 1 which passed assembly process S1 and initial charge process S2 like embodiment. Among them, in the SOC adjustment step S4, as in the embodiment, the SOC of the battery 1 is adjusted to the inspection SOC (KS = 8%), and in the voltage application step S5, the output voltage VS is applied to the battery 1 from the external DC power supply EP. Then, the current IB continues to flow from the external DC power supply EP to the battery 1 (see FIG. 5).

  On the other hand, unlike in the embodiment, in the current acquisition step S26, the change over time of the current IB (t) is not detected but the convergence current value IBs of the current IB (t) flowing from the external DC power supply EP to the battery 1 is detected. Detect Specifically, in a predetermined detection period QT after the start of voltage application (t = 0) (in this modification, a predetermined period of voltage application time t1 = 700 sec to t2 = 1, a period of 700 seconds up to 400 sec), A current increase amount ΔIB (= IB (t2) −IB (t1)) of the increased current IB (t) is obtained (see FIG. 6).

  Then, in the determination step S27, unlike the embodiment, when the current increase amount ΔIB is larger than the reference increase amount ΔIBK (ΔIB> ΔIBK), the battery 1 is determined to be defective. On the other hand, when the current increase amount ΔIB is equal to or less than the reference increase amount ΔIBK (ΔIB ≦ ΔIBK), the battery 1 is determined to be non-defective.

  It is also possible to determine the quality of the battery 1 based on the temporal change of the current IB (t) flowing from the external DC power supply EP to the battery 1 as in the present modified embodiment. Thus, also in the self-discharge inspection method of the present modification, the quality of the battery 1 can be determined in a short time by a new method different from the conventional method of measuring the voltage drop amount ΔVa.

  Moreover, since the battery 1 is used in the SOC adjustment step S4 where the inspection SOC is the SOC (KS = 8%) within the super average differential OCV range SA where the local battery capacity Cx is small, the inspection SOC is the super average differential OCV The current detection step S26 and the determination step S27 can be performed earlier than when the battery 1 out of the range SA is used in the voltage application step S5, and the self-discharge inspection can be performed in a short time. Furthermore, in this modification, the current detection step S26 can be performed earlier than the current IB (t) converges, ie, earlier than the voltage application time t reaches the aforementioned convergence time ta. Self-discharge test can be performed in a shorter time.

Although the present invention has been described above in accordance with the embodiment and the modified embodiment, the present invention is not limited to the above embodiment and the like, and can be appropriately modified and applied without departing from the scope of the invention Needless to say.
For example, in the embodiment, in the voltage application step S5, the output voltage VS applied from the external DC power supply EP to the battery 1 is constant (VS = VB1) regardless of the elapse of the voltage application time t. Absent. For example, the output voltage VS at the start of voltage application (voltage application time t = 0) has a magnitude (VS = VB1) equal to the pre-test battery voltage VB1 of the battery 1, while the output voltage VS after voltage application is There is also a method of gradually or stepwise rising.

  Further, in the current acquisition step S6 according to the embodiment, the convergence time ta is predicted from the local battery capacity Cx obtained in the SOC adjustment step S4, and the current value IB (ta) at this convergence time ta is taken as the convergence current value IBs. However, the method of obtaining the convergence current value IBs is not limited to this. For example, in the current acquisition step S6, the timing (ie, convergence) at which the change in the current IB (t) detected every predetermined time (for example, 60 seconds) falls within a predetermined range (for example, ± 0.1 μA or less). The current value IB (ta) at time ta) can also be the convergence current value IBs.

1 Battery (power storage device)
1x Uncharged Battery (Uncharged Storage Device)
1C (Battery) Battery component S1 Assembly step S2 Initial charge step S3, S23 Self-discharge inspection step S4 SOC adjustment step S5 Voltage application step S6, S26 Current acquisition step S7, S27 Determination step EP External DC power source Re Circuit resistance Rp Self Discharge resistance Cx Local battery capacity t Voltage application time ta Convergence time VB, VB (t) Battery voltage (device voltage)
VB1 Battery voltage before inspection VS Output voltage IB, IB (t) Current IBs (flowing from the external DC power supply to the battery) Convergence current value IK Reference current value SA Super average differential OCV range SB High derivative OCV range KS Inspection SOC
LA mean derivative OCV

Claims (1)

An SOC adjustment step of adjusting the SOC of the storage device to a predetermined inspection SOC within a super average differential OCV range;
A voltage application step of continuously applying the output voltage VS from the external DC power supply to the storage device adjusted to the inspection SOC and continuing to flow the current IB from the external DC power supply to the storage device;
A current obtaining step of obtaining a time-dependent change of the current IB or a convergence current value IBs at which the current IB converges;
Determining whether the storage device is good or bad based on the temporal change of the current IB or the convergence current value IBs, the self-discharge inspection method of the storage device.

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