JP2021131952A - Inspection method of battery - Google Patents

Abstract

To provide an inspection method of a battery which evaluates the resistance of a battery from a change in a current value Ib (t) of a current flowing from an external DC power supply to the battery.SOLUTION: An inspection method of a battery 1 includes a capacity acquisition step S10, a voltage application step S20 of continuing to apply an output voltage Vb from an external DC power supply EP to a battery 1, a current detection step S30 of detecting a current value Ib (t1) of a current I flowing through the battery 1, a resistance estimation step S40 of estimating a self-discharge resistance Rp (tn) and a series circuit resistance Re (tn) using an equation of a theoretical current value Ii (t), a correlation coefficient acquisition step S50 of obtaining a correlation coefficient Kr (tn) between the equation of the theoretical current value Ii (t) and the current value Ib (t1), and a battery evaluation step S60, S65 of evaluating the battery 1 on the basis of the self-discharge resistance Rp (tn) when the correlation coefficient Kr (tn) is equal to or greater than a reference correlation coefficient Krk.SELECTED DRAWING: Figure 3

Description

The present invention relates to a battery inspection method for evaluating battery resistance.

In the manufacture of batteries such as lithium ion secondary batteries, metallic foreign substances such as iron and copper may be mixed inside the electrode body, and the mixed metallic foreign substances may cause an internal short circuit in the battery. Therefore, it may be determined whether or not the battery has an internal short circuit.
The following methods are known as methods for inspecting this internal short circuit. That is, the battery is charged in advance, and an external DC power supply is connected to the battery. Next, the output voltage Vb (Vb = Va) equal to the pre-inspection battery voltage Va immediately before the inspection of the battery is continuously applied from the external DC power source to the battery. Then, after the current value Ib (t) of the current flowing from the external DC power supply to the battery becomes substantially constant and stable, the current value Ibs at the time of stabilization is detected. Next, when the detected stable current value Ibs is larger than the predetermined reference current value Ibk (Ibs> Ibk), the battery is determined to be a defective product with an internal short circuit. As a conventional technique related to such a battery inspection method, for example, Patent Document 1 can be mentioned.

JP-A-2019-016558

However, the above-mentioned battery inspection method has a problem that it takes time for the current value Ib (t) of the current flowing through the battery to reach a substantially constant stable current value Ibs.

The present invention has been made in view of the current situation, and provides a new battery inspection method for evaluating the resistance of the battery from a change in the current value Ib (t) of the current flowing from the external DC power source to the battery. It is something to do.

One aspect of the present invention for solving the above problems is a battery inspection method for evaluating the resistance of a battery, which includes a capacity acquisition step of acquiring the battery capacity Cp of the battery and an inspection of the battery from an external DC power source. A voltage application step in which an output voltage Vb equal to the pre-battery voltage Va is continuously applied and a current continues to flow from the external DC power source to the battery, and a current of the current at the application duration t1, t2, ... Of the output voltage Vb. As an equivalent circuit of the current detection process for detecting the values Ib (t1), Ib (t2), ... And the inspection circuit in which the external DC power supply is connected to the battery, the parallel circuit of the battery capacity Cp and the self-discharge resistance Rp is used. Assuming an equivalent circuit in which the series circuit resistors Re are connected in series and the output voltage Vb of the external DC power supply is applied to them, the equation of the theoretical current value Ii (t) flowing in this equivalent circuit and the equation of the theoretical current value Ii (t) already obtained have already been obtained. The self-discharge resistance Rp (tn) and the series circuit resistance Re ( The resistance estimation step for estimating tn), the equation of the theoretical current value Ii (t) including the estimated self-discharge resistance Rp (tn) and the series circuit resistance Re (tn), and the acquired current value Ib ( The correlation coefficient acquisition process for obtaining the correlation coefficient Kr (tn) with t1), Ib (t2), ..., Ib (tn) and the reference correlation coefficient Krk or more in which the above correlation coefficient Kr (tn) is predetermined. This is a battery inspection method including a battery evaluation step of evaluating the battery based on the estimated self-discharge resistance Rp (tn).

In the above-mentioned battery inspection method, the resistance of the battery is evaluated by performing the above-mentioned capacity acquisition step, voltage application step, current detection step, resistance estimation step, correlation coefficient acquisition step, and battery evaluation step. In the resistance estimation step, the self-discharge resistance Rp (tn) of the battery is estimated from the change in the current value Ib (t) of the current flowing from the external DC power supply to the battery, and in the battery evaluation step, the estimated self-discharge resistance Rp (tn) is estimated. ) To evaluate the battery. As described above, in the above-mentioned battery inspection method, the resistance of the battery can be evaluated from the change in the current value Ib (t) of the current flowing from the external DC power source to the battery.

In the battery evaluation step, as a method of evaluating the battery based on the self-discharge resistance Rp (tn), for example, when the self-discharge resistance Rp (tn) is smaller than the predetermined reference resistance Rpk (Rp (tn)). <Rpk) includes a method of determining the battery as a defective product having a small resistance (an internal short circuit has occurred). Another method is to rank the batteries into a plurality of groups according to the degree of resistance (internal short circuit) based on the magnitude of the self-discharge resistance Rp (tn).
In addition, the above-mentioned battery inspection method can be performed in the process of manufacturing a battery, or can be performed on a used battery mounted on an automobile or the like or placed on the market independently.

Further, in the above-mentioned battery inspection method, in the capacity acquisition step, the battery capacity Cp is such that the battery is subjected to the first battery voltage V1 to the second battery within the range of the battery voltage V of SOC 100% to SOC 0%. The amount of partial electricity discharged or charged in this partial voltage section ΔV = V1-V2 after forcibly discharging or charging up to the voltage V2 (except when the above battery is forcibly discharged or charged in the range of SOC 100% to SOC 0%). It is preferable to use a battery inspection method in which ΔQ is measured and obtained by Cp = ΔQ / ΔV.

As a method of obtaining the battery capacity Cp of the battery in the capacity acquisition step, for example, the battery is forcibly discharged or charged over the entire voltage section (SOC 100% to SOC 0%), and the discharge current value (or charging) at that time is charged. A method of calculating by the product of the current value) and the discharge time (or charge time) can be mentioned. On the other hand, in the above-mentioned inspection method, the partial electric energy ΔQ forcibly discharged or charged in the partial voltage section ΔV = V1-V2 is measured, and the battery capacity Cp is obtained by Cp = ΔQ / ΔV. There is no need to forcibly discharge or charge the battery.

It is a perspective view of the battery which concerns on embodiment. It is a flowchart of the manufacturing method of the battery which concerns on embodiment. It is a flowchart of the battery inspection method (inspection process) which concerns on embodiment. It is a circuit diagram of the inspection circuit which concerns on the inspection method of the battery which concerns on embodiment, and connected the external DC power source to the battery. For non-defective and defective batteries, the relationship between the application duration t of the output voltage Vb, the output voltage Vb, the battery voltage V (t), and the current value Ib (t) of the current flowing through the battery is schematically shown. It is a graph. For an example of a non-defective battery and an example of a defective battery, the relationship between the application duration t (range of t = 0 to ts) of the output voltage Vb and the measured current value Ib (t) of the current flowing through the battery. It is a graph which shows. For the non-defective battery shown in FIG. 6, the application duration t (range of t = 0 to te) of the output voltage Vb, the measured current value Ib (t) of the current flowing through the battery, and the theoretical current value Ii (t). ) Is a graph showing the relationship with. For the defective battery shown in FIG. 6, the application duration t (range of t = 0 to te) of the output voltage Vb, the measured current value Ib (t) of the current flowing through the battery, and the theoretical current value Ii ( It is a graph which shows the relationship with t). A semi-log graph showing the relationship between the application duration t (range of t = 0 to te) of the output voltage Vb and the estimated self-discharge resistance Rp (t) for the non-defective and defective batteries shown in FIG. be. For the non-defective and defective batteries shown in FIG. 6, a semi-log graph showing the relationship between the application duration t (range of t = 0 to te) of the output voltage Vb and the estimated series circuit resistance Re (t). be. 6 is a graph showing the relationship between the application duration t (range of t = 0 to te) of the output voltage Vb and the correlation coefficient Kr (t) of the non-defective battery shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a perspective view of the battery 1 according to the present embodiment. The battery 1 is a square and sealed lithium ion secondary battery mounted on a vehicle such as a hybrid car, a plug-in hybrid car, or an electric vehicle. The battery 1 includes a rectangular parallelepiped box-shaped battery case 10, a flat wound electrode body 20 and an electrolytic solution 17 housed therein, and a positive electrode terminal member 30 and a negative electrode terminal member 40 supported by the battery case 10. Etc. The nominal capacity of battery 1 is 5.0 Ah.

Next, a method of manufacturing the battery 1 including an inspection method for evaluating the resistance of the battery 1 will be described (see FIGS. 2 to 4). First, in the "assembly process S1" (see FIG. 2), the battery 1 is assembled. That is, the case lid member 13 of the battery case 10 is prepared, and the positive electrode terminal member 30 and the negative electrode terminal member 40 are fixedly attached to the case lid member 13 (see FIG. 1). After that, the positive electrode terminal member 30 and the negative electrode terminal member 40 are welded to the positive electrode plate and the negative electrode plate of the separately formed electrode body 20, respectively. After that, 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. After that, the electrolytic solution 17 is injected into the battery case 10 from the injection hole 13h, and the injection hole 13h is sealed by the sealing member 15. As a result, the battery 1 is formed.

Next, in the "first charging step S2" (see FIG. 2), the assembled battery 1 is first charged. Specifically, a restraint jig (not shown) is used to restrain the battery 1 in a compressed state in the battery thickness direction. In the present embodiment, with the battery 1 restrained, the initial charging step S2 to the inspection step S5 described later are performed. After that, a charging / discharging device (not shown) is connected to the battery 1 to charge the battery 1 for the first time to a battery voltage V corresponding to 90% SOC by constant current constant voltage (CCCV) charging at an ambient temperature of 20 ° C.

Next, in the "high temperature aging step S3", the charged battery 1 is left at an ambient temperature of 40 to 85 ° C. with the terminals open to perform high temperature aging. The battery voltage V of the battery 1 immediately after the initial charge is unstable and takes time to stabilize. However, by performing this high temperature aging step S3, the stabilization of the battery voltage V can be promoted. In the present embodiment, the battery voltage V of the battery 1 that has completed the high temperature aging step S3 is a battery voltage corresponding to about 86% of SOC.
Next, in the "cooling step S4", the battery 1 is left at an ambient temperature of 20 ° C. and then left to cool to bring the battery temperature of the battery 1 to 20 ° C.

Next, "inspection step S5" (see also FIG. 3) is performed. This inspection step S5 is performed at an environmental temperature of 20 ° C. The inspection step S5 includes a capacity acquisition step S10, a voltage application step S20, a current detection step S30, a resistance estimation step S40, a correlation coefficient acquisition step S50, and a battery evaluation steps S60 and S65.

First, in the "capacity acquisition step S10", the battery capacity Cp of the battery 1 is acquired. In the present embodiment, a charging / discharging device (not shown) is connected to the battery 1 (battery voltage V corresponding to about 86% SOC) after the cooling step S4 described above, and a battery corresponding to 85% SOC at a constant current of 1C. Forcibly discharges about 1% of SOC up to the voltage V. The battery voltage V corresponding to about 86% of SOC at the start of discharging corresponds to the above-mentioned "first battery voltage V1", and the battery voltage V corresponding to 85% of SOC at the end of discharging corresponds to the above-mentioned "No. 1". 2 Battery voltage V2 ”corresponds.

Then, the partial electric amount ΔQ (C) discharged in the partial voltage section ΔV = V1-V2 (V) from the first battery voltage V1 to the second battery voltage V2 is measured, and the battery capacity Cp = ΔQ / ΔV is used. , The local battery capacity Cp (F) of the battery 1 is calculated.
By obtaining the local battery capacity Cp in this way, it is not necessary to forcibly discharge or charge the battery 1 over the entire voltage section (range of SOC 100% to SOC 0%).
Further, the size of the battery capacity Cp varies from battery to battery 1. Therefore, the self-discharge resistance Rp and the series circuit resistance Re of the battery 1 can be more accurately estimated by performing the resistance estimation step S40 described later using the battery capacity Cp actually measured for each battery 1. Then, in the battery evaluation steps S60 and S65, the battery 1 can be evaluated more appropriately.

Next, in the "voltage application step S20", the output voltage Vb (Vb = Va) equal to the pre-inspection battery voltage Va is continuously applied from the external DC power supply EP to the battery 1, and the current is applied from the external DC power supply EP to the battery 1. Continue to flow I (see Figure 4). First, the external DC power supply EP is connected to the battery 1 after the capacity acquisition step S10 described above to form the inspection circuit 100. Specifically, the pair of probes P1 and P2 of the external DC power supply EP are brought into contact with the positive electrode terminal member 30 and the negative electrode terminal member 40 of the battery 1, respectively.

In the present embodiment, as the equivalent circuit 110 of the inspection circuit 100, as shown in FIG. 4, the series circuit resistance Re is connected in series to the parallel circuit 115 including the battery capacity Cp of the battery 1 and the self-discharge resistance Rp of the battery 1. It is assumed that the equivalent circuit is connected and the output voltage Vb of the external DC power supply EP is applied to them.
Specifically, the battery capacity Cp is the battery capacity of the battery 1 (battery component 1C), the self-discharge resistance Rp is a resistance mainly caused by an internal short circuit of the battery 1, and the battery resistance Rs is the battery 1 of the battery 1. It is a DC resistance. On the equivalent circuit, the battery resistance Rs is connected in series to the parallel circuit 115 of the battery capacity Cp and the self-discharge resistance Rp.

Further, in the inspection circuit 100, the wiring resistor Rw is a wiring resistor distributed in the external DC power supply EP and from the external DC power supply EP to the probes P1 and P2. Further, the contact resistance R1 is the contact resistance between one probe P1 of the external DC power supply EP and the positive electrode terminal member 30 of the battery 1, and the contact resistance R2 is the contact resistance between the other probe P2 of the external DC power supply EP and the negative electrode of the battery 1. This is the contact resistance with the terminal member 40. The sum of the wiring resistance Rw, the contact resistances R1 and R2, and the battery resistance Rs (Re = Rw + R1 + R2 + Rs) is the above-mentioned series circuit resistance Re of the inspection circuit 100.
The current I is the current flowing from the external DC power supply EP to the battery 1, and the self-discharge current ID is the current flowing in the battery 1 (battery component 1C) with self-discharge.

Further, the external DC power supply EP can control the output voltage Vb generated by its own DC power supply EPE in a variable and highly accurate manner, and also has a voltmeter EPV, so that the battery voltage V (V) can be measured. Further, the external DC power supply EP has an ammeter EPI, and can measure the current value Ib (μA) of the current I flowing from the external DC power supply EP (DC power supply EPE) to the battery 1 with high accuracy.

In the voltage application step S20, first, in step S21 (see FIG. 3), the battery voltage V (inspection) of the battery 1 is performed by the voltmeter EPV included in the external DC power supply EP under the condition of the current value Ib = 0 (μA). Pre-battery voltage Va) is detected. In the present embodiment, a value near 3.9 V is measured as the pre-inspection battery voltage Va.
After that, the process proceeds to step S22, and application of an output voltage Vb (Vb = Va) equal to the measured pre-inspection battery voltage Va is started on the battery 1.

After that, the process proceeds to step S23, and the correlation coefficient Kr (tn) acquired in the correlation coefficient acquisition step S50, which will be described later, is equal to or greater than the predetermined reference correlation coefficient Krk (Krk = 0.9 in this embodiment) (Kr ( It is determined whether or not tn) ≥ 0.9). Here, when NO, that is, when Kr (tn) ≥ 0.9 is not satisfied, the voltage application from the external DC power supply EP to the battery 1 is continued. That is, the output voltage Vb is continuously applied to the battery 1 from the external DC power supply EP, and the current I is continuously passed from the external DC power supply EP to the battery 1. On the other hand, when YES, that is, when Kr (tn) ≥ 0.9, the process proceeds to step S24, the application of the output voltage Vb is terminated, and the voltage application step S20 is terminated.

Further, after the application of the output voltage Vb is started (application duration t = 0 or later), the “current detection step S30” (see FIG. 3) is performed in parallel with the voltage application step S20, and the application duration t1, t2, ... In, the current values Ib (t1), Ib (t2), ... Of the current I flowing from the external DC power supply EP to the battery 1 are detected. In the present embodiment, the current value Ib (t) (μA) flowing through the battery 1 is detected by the ammeter EPI included in the external DC power supply EP every time the application duration t elapses for 1 sec. That is, the current values Ib (1), Ib (2), Ib (3), Ib (4), Ib (5), ... (ΜA) is detected respectively.

Then, in the present embodiment, when the detection results of the application duration t and the current value Ib (t) of 10 sets (10 sec minutes) are obtained, the process proceeds to the resistance estimation step S40. That is, in the first current detection step S30, the current values Ib (1), Ib (2), ..., Ib (10) (μA) at the application duration t = 1, 2, ..., 10 (sec) are obtained. If so, the process proceeds to the resistance estimation step S40. Further, in the second current detection step S30, the current values Ib (11), Ib (12), ..., Ib (20) (μA) at the application duration t = 11, 12, ..., 20 (sec) are obtained. Then, the process proceeds to the resistance estimation step S40.

Here, the theoretical current value Ii (t) of the current I flowing from the external DC power supply EP to the battery 1 will be described. The equation of the theoretical current value Ii (t) shown in the following <Equation 1> is the differential equation of the equivalent circuit 110 of the inspection circuit 100 described above under the initial conditions (theoretical current value Ii (t) under the initial condition (application duration t = 0). This is the equation solved by = 0).

Ｉｉ(t) ：理論電流値（μＡ）
ｔ ：印加継続時間（ｓｅｃ）
Ｖｂ ：出力電圧（Ｖ）
Ｒｐ ：自己放電抵抗（Ω）
Ｒｅ ：直列回路抵抗（Ω）
Ｃｐ ：電池容量（Ｆ）

Ii (t): Theoretical current value (μA)
t: Application duration (sec)
Vb: Output voltage (V)
Rp: Self-discharge resistance (Ω)
Re: Series circuit resistance (Ω)
Cp: Battery capacity (F)

Further, in FIG. 5, for each of the non-defective and defective batteries 1, the application duration t of the output voltage Vb by the external DC power supply EP, the output voltage Vb, the battery voltage V (t), and the batteries from the external DC power supply EP The outline of the relationship between the current I flowing in 1 and the current value Ib (t) is shown. As shown in FIG. 5, the battery voltage V (t) gradually decreases from the pre-inspection battery voltage Va with the passage of the application duration t, and then is a substantially constant value after the application duration t = stabilization time ts ( Battery voltage Vs) when stable. However, since the battery voltage V (t) of the defective battery 1 is significantly lower than that of the non-defective battery 1, the stable battery voltage Vs is also lower.
On the other hand, the current value Ib (t) gradually increases from 0 (zero) with the passage of the application duration t, and then is almost constant after the application duration t = stabilization time ts (current value Ibs at stabilization). It becomes. However, since the current value Ib (t) of the defective battery 1 is greatly increased as compared with that of the non-defective battery 1, the stable current value Ibs is also large.

The reason why the battery voltage V (t) and the current value Ib (t) change in this way is as follows. That is, in the battery 1, the self-discharge current ID flows out from the battery component 1C due to self-discharge, so that the voltage of the battery component 1C and the battery voltage V (t) gradually decrease. At that time, since the defective battery 1 has a larger self-discharge current ID due to a short circuit than the non-defective battery 1, the battery voltage V (t) drops significantly.
On the other hand, when the battery voltage V (t) becomes lower than the output voltage Vb, the current corresponding to the magnitude of the voltage difference ΔVb = Vb−V (t) from the external DC power supply EP toward the battery 1 (battery component 1C). I flows in and the battery 1 (battery component 1C) is charged.

While the voltage difference ΔVb = Vb−V (t) is small, the current I flowing from the external DC power supply EP into the battery 1 is small, so that the self-discharge current ID flowing out from the battery component 1C is larger than this current I. Therefore, the voltage of the battery component 1C and the battery voltage V (t) gradually decrease.
However, when the battery voltage V (t) further decreases and the current I increases to be substantially equal to the magnitude of the self-discharge current ID (in FIG. 5, at the stable time ts), the voltage of the battery component 1C and the battery voltage V The decrease in (t) almost stops, and the increase in the current value Ib (t) almost stops. Therefore, after the application duration t = the stabilization time ts, the battery voltage V (t) becomes the stable battery voltage Vs which is substantially constant, and the current value Ib (t) becomes the stable current value Ibs which is substantially constant.

Here, FIG. 6 shows an example of the non-defective battery 1 and an example of the defective battery 1 obtained by actually measuring the application duration t (range of t = 0 to stable time ts) of the output voltage Vb. The relationship with the obtained current value Ib (t) is shown. The stabilization time ts is, for example, about 15 to 30 hr (about 54,000 to 108,000 sec).
Further, in FIG. 7, for a non-defective battery, the application duration t (range of t = 0 to te) of the output voltage Vb, the actually measured current value Ib (t), and the theoretical current value Ii (t) are shown. The relationship is shown. Further, FIG. 8 shows the application duration t (range of t = 0 to te) of the output voltage Vb, the actually measured current value Ib (t), and the theoretical current value Ii (t) of the defective battery. Show the relationship with. The application duration t = te is one-fifth of the above-mentioned stabilization time ts.

In the graph of the theoretical current value Ii (t) of FIGS. 7 and 8, the battery capacity Cp of the equation <Equation 1> of the theoretical current value Ii (t) described above is acquired in the capacity acquisition step S10 described above. The values of the battery capacity Cp were substituted, and the values of the pre-inspection battery voltage Va measured in step S21 of the voltage application step S20 were substituted into the output voltage Vb (= pre-inspection battery voltage Va). Further, the self-discharge resistance Rp and the series circuit resistance Re of the equation <Equation 1> include the self-discharge resistance Rp (te) and the series circuit resistance Re (te) at the application duration t = te estimated in the resistance estimation step S40 described later. The values of te) were substituted respectively.

As can be seen from the graphs of FIGS. 6 to 8, in both the non-defective battery 1 and the defective battery 1, the current value Ib (t) of the current I flowing from the external DC power supply EP to the battery 1 is the application duration. It gradually increases with the passage of t and converges to a substantially constant value (current value Ibs at stable time). However, the current value Ib (t) of the defective battery 1 is significantly increased as compared with that of the non-defective battery 1. Therefore, it is appropriate to detect the current value Ib (t) = stable current value Ibs after the applied duration t = stable time ts and evaluate the battery 1 based on the magnitude of the stable current value Ibs. Battery 1 can be evaluated.

However, in this method, it is necessary to wait until the application duration t = the stabilization time ts elapses (the stable current value Ibs can be detected), and the inspection step S5 takes a long time. On the other hand, in both the non-defective battery 1 of FIG. 7 and the defective battery 1 of FIG. 8, the graph of the theoretical current value Ii (t) derived at the application duration t = te and the actually measured current The graphs with values Ib (t) are in good agreement with each other. From this, if the self-discharge resistance Rp and the series circuit resistance Re can be estimated appropriately, the inspection step S5 can be completed in a time shorter than the time te, which is one-fifth of the stable time ts, as will be described later. I can understand that there is.

Next, the “resistance estimation step S40” will be described. In this resistance estimation step S40, the above-mentioned equation <Equation 1> of the theoretical current value Ii (t) and the current values Ib (t1), Ib (t2) at the already obtained application durations t1, t2, ..., Tn ), ..., Ib (tn) are used to estimate the self-discharge resistance Rp (tn) and the series circuit resistance Re (tn).
Specifically, first, in the equation <Equation 1> of the theoretical current value Ii (t), the value of the battery capacity Cp of the battery 1 acquired in the above-mentioned capacity acquisition step S10 is substituted into the battery capacity Cp, and the value of the battery capacity Cp is substituted. The value of the pre-inspection battery voltage Va of the battery 1 measured in step S21 of the voltage application step S20 is substituted into the output voltage Vb (= pre-inspection battery voltage Va).

Next, in the first resistance estimation step S40, the current values Ib (1), Ib (2), Ib (3), ..., Ib at the application duration t = 1, 2, 3, ..., 10 (sec). (10) Since (μA) is obtained, these 10 sets of detection results are substituted into the equation <Equation 1> of the theoretical current value Ii (t), and the self-discharge resistance Rp (10) is obtained by the minimum square method. Estimate (Ω) and series circuit resistance Re (10) (Ω). Further, for example, in the second resistance estimation step S40, the current values Ib (1), Ib (2), ..., Ib (20) (μA) at the application duration t = 1, 2, ..., 20 (sec) are set. Since it has already been obtained, these 20 sets of detection results are substituted into the equation <Equation 1> of the theoretical current value Ii (t), and the self-discharge resistance Rp (20) (Ω) and the series circuit resistance are obtained by the minimum square method. Estimate Re (20) (Ω).

Here, with respect to the non-defective and defective batteries 1 shown in FIG. 6, the application duration t (range of t = 0 to te) of the output voltage Vb and the estimated self-discharge resistance Rp (t) are shown in FIG. FIG. 10 shows the relationship between the application duration t (range of t = 0 to te) of the output voltage Vb and the estimated series circuit resistance Re (t). The self-discharge resistance Rp (t) and the series circuit resistance Re (t) are the self-discharge resistance Rp (10), Rp (20), Rp (30), ... And the series circuit resistance every 10 seconds in this embodiment. Re (10), Re (20), Re (30), ... Can be obtained, but the graphs of FIGS. 9 and 10 show the self-discharge resistance Rp (t) and the series circuit resistance obtained at intervals larger than 10 sec. It is created using each value of Re (t).

As can be seen from FIG. 9, in both the non-defective battery 1 and the defective battery 1, the value of the self-discharge resistance Rp (t) becomes stable with the lapse of the application duration t, and each value is almost constant (true). (Value of) converges. Further, as can be seen from FIG. 10, in both the non-defective battery 1 and the defective battery 1, the value of the series circuit resistance Re (t) becomes stable with the lapse of the application duration t, and each value is substantially constant. It converges to (true value). From this, the equation of the theoretical current value Ii (t) and the correlation coefficient Kr (t) of the actually measured current values Ib (t1), Ib (t2), ... At the same time, it is considered that the value of Kr (t) increases and approaches Kr (t) = 1.

Next, in the "correlation coefficient acquisition step S50", the equation of the theoretical current value Ii (t) including the estimated self-discharge resistance Rp (tn) and the series circuit resistance Re (tn) and the current values acquired so far. The correlation coefficient Kr (tn) with Ib (t1), Ib (t2), ..., Ib (tn) is obtained.
Specifically, in the first correlation coefficient acquisition step S50, in the equation <Equation 1> of the theoretical current value Ii (t), the self-discharge resistance Rp and the series circuit resistance Re are combined with the first resistance estimation step S40. Substitute the self-discharge resistance Rp (10) and the series circuit resistance Re (10) estimated in. Then, the correlation coefficient Kr (10) between the equation of the theoretical current value Ii (t) and the current values Ib (1), Ib (2), Ib (3), ..., Ib (10) acquired so far. ).

Further, for example, in the second correlation coefficient acquisition step S50, the nearest (second) resistance estimation step to the self-discharge resistance Rp and the series circuit resistance Re in the equation <Equation 1> of the theoretical current value Ii (t). Substitute the self-discharge resistance Rp (20) and the series circuit resistance Re (20) estimated in S40. Then, the correlation coefficient Kr (20) between the equation of the theoretical current value Ii (t) and the current values Ib (1), Ib (2), Ib (3), ..., Ib (20) acquired so far. ).

Here, with respect to the non-defective battery 1 shown in FIG. 6, the relationship between the application duration t (range of t = 0 to te) of the output voltage Vb and the correlation coefficient Kr (t) is shown in FIG. As the correlation coefficient Kr (t), in the present embodiment, the correlation coefficients Kr (10), Kr (20), Kr (30), ... Are obtained every 10 seconds, but the graph in FIG. 11 shows the correlation coefficient from 10 seconds. Is also created using each value of the correlation coefficient Kr (t) obtained at large intervals.
As can be seen from FIG. 11, the correlation coefficient Kr (t) basically gradually increases with the passage of the application duration t and approaches Kr (t) = 1.

In this embodiment, as will be described later, the reference correlation coefficient Krk is set to Krk = 0.9. In the example shown in FIG. 11, the arrival time tg at which the correlation coefficient Kr (t) reaches the reference correlation coefficient Krk = 0.9 is further shorter than the time te (one-fifth of the stable time ts). There is. Further, although the description of specific data is omitted, the arrival time tg is even shorter than the time te (one-fifth of the stable time ts) even when looking at the results of the main inspection for a plurality of other batteries. It was.

Next, in the "battery evaluation steps S60 and S65", whether or not the correlation coefficient Kr (tn) is equal to or higher than the predetermined reference correlation coefficient Krk (Kr (tn) ≥ Krk) in step S60. judge. In the present embodiment, when the correlation coefficient Kr (tn) = 0.9 or more, the equation of the theoretical current value Ii (t) and the measured current values Ib (1), Ib (2), ..., Ib ( Considering that the correlation with tn) becomes sufficiently high and the self-discharge resistance Rp (tn) and the series circuit resistance Re (tn) included in this theoretical current value Ii (t) are close to the true values, respectively. The reference correlation coefficient Krk = 0.9 was set.
Specifically, in the first step S60, it is determined whether or not Kr (10) ≥ 0.9. Further, in the second step S60, it is determined whether or not Kr (20) ≥ 0.9.

Here, when NO, that is, when the correlation coefficient Kr (tn) ≥ 0.9 is not satisfied, the process returns to the above-mentioned current detection step S30. Then, in the current detection step S30, further 10 sets (10 sec minutes) of application duration t and current value Ib (t) are obtained. In the example shown in FIG. 11, the correlation coefficient Kr (tn) is smaller than the reference correlation coefficient Krk = 0.9 until the application duration t = arrival time tg. Therefore, NO in this step S60. Is judged.
On the other hand, if YES, that is, when the correlation coefficient Kr (tn) ≥ 0.9, the process proceeds to step S65, and the finally obtained (most recent) self-discharge resistance Rp (tn) magnitude. The battery 1 is evaluated based on the above. In the example shown in FIG. 11, since the correlation coefficient Kr (tn) is the reference correlation coefficient Krk = 0.9 when the application duration t = arrival time tg, it is determined to be YES in this step S60.

Specifically, in the present embodiment, when the self-discharge resistance Rp (tn) is smaller than the predetermined reference resistance Rpk (Rp (tn) <Rpk), the resistance of the battery 1 is low and an internal short circuit occurs. It is determined that the product is defective, and the battery 1 is removed.
Although the description of specific data is omitted, as described above, the time te (one-fifth of the stable time ts) is longer than that of the battery 1 inspected regardless of whether it is a non-defective product or a defective product. It is known that the correlation coefficient Kr (tn) ≥ 0.9 is satisfied with a shorter application duration t (arrival time tg). In the conventional inspection method, it is necessary to wait until the application duration t = stabilization time ts elapses, whereas in the present embodiment, the battery is applied in a shorter time than the application duration t = te (ts / 5). 1 can be evaluated.

Further, also in the voltage application step S20 performed in parallel, as described above, it is determined whether or not the correlation coefficient Kr (tn) becomes the reference correlation coefficient Krk = 0.9 or more (step S23). .. Then, when NO, that is, when Kr (tn) ≥ 0.9 is not satisfied, the application of the output voltage Vb is continued. On the other hand, when YES, that is, when Kr (tn) ≥ 0.9, the application of the output voltage Vb is terminated, and the voltage application step S20 is terminated.
As a result, the inspection step S5 is completed. When the inspection step S5 is completed, the external DC power supply EP is separated from the battery 1, and the restraint of the battery 1 by the restraint jig (not shown) is further released. Thus, the battery 1 is completed.

As described above, in the inspection method of the battery 1, the capacity acquisition step S10, the voltage application step S20, the current detection step S30, the resistance estimation step S40, the correlation coefficient acquisition step S50, and the battery evaluation steps S60 and S65 are performed. The resistance of the battery 1 is evaluated. In the resistance estimation step S40, the self-discharge resistance Rp (tn) of the battery 1 is estimated from the change in the current value Ib (t) of the current I flowing from the external DC power supply EP to the battery 1, and in the battery evaluation steps S60 and S65, the self-discharge resistance Rp (tn) is estimated. The battery 1 is evaluated based on the estimated self-discharge resistance Rp (tn). As described above, in the above-described battery 1 inspection method, the resistance of the battery 1 can be evaluated from the change in the current value Ib (t) of the current flowing from the external DC power supply EP to the battery 1.

Further, in the present embodiment, the local battery capacity Cp is obtained in the capacity acquisition step S10. That is, the partial electric energy ΔQ forcibly discharged in the partial voltage section ΔV = V1-V2 is measured, and the battery capacity Cp is obtained by Cp = ΔQ / ΔV. Therefore, it is not necessary to forcibly discharge or charge the battery 1 over the entire voltage section (range of SOC 100% to SOC 0%).

In the above, the present invention has been described according to the embodiment, but it goes without saying that the present invention is not limited to the embodiment and can be appropriately modified and applied without departing from the gist thereof.

1 Battery 100 Inspection circuit 110 Equivalent circuit 115 Parallel circuit Cp Battery capacity ΔV Partial voltage section ΔQ Partial electricity amount V Battery voltage V1 1st battery voltage V2 2nd battery voltage Va Pre-inspection battery voltage Vb Output voltage I Current Ib Current value Ii theory Current value t Application duration Rp Self-discharge resistance Rpk Reference resistance Re Series circuit resistance Kr Correlation coefficient Krk Reference correlation coefficient EP External DC power supply S1 Assembly process S2 Initial charging process S3 High temperature aging process S4 Cooling process S5 Inspection process S10 Capacity acquisition Step S20 Voltage application step S30 Current detection step S40 Resistance estimation step S50 Correlation coefficient acquisition step S60, S65 Battery evaluation step

Claims (1)

A battery inspection method that evaluates battery resistance.
The capacity acquisition process for acquiring the battery capacity Cp of the battery and
A voltage application step in which an output voltage Vb equal to the pre-inspection battery voltage Va is continuously applied from the external DC power source to the battery, and a current is continuously applied from the external DC power source to the battery.
A current detection step for detecting the current values Ib (t1), Ib (t2), ... Of the currents at the application durations t1, t2, ... Of the output voltage Vb, and
As an equivalent circuit of the inspection circuit in which the external DC power supply is connected to the battery, a series circuit resistor Re is connected in series to the parallel circuit of the battery capacity Cp and the self-discharge resistance Rp, and the output voltage of the external DC power supply is connected to these. Assuming an equivalent circuit to which Vb is applied,
The equation of the theoretical current value Ii (t) flowing in this equivalent circuit and the above-mentioned current values Ib (t1), Ib (t2), ..., Ib ( A resistance estimation process for estimating the self-discharge resistance Rp (tn) and the series circuit resistance Re (tn) using tn), and
The equation of the theoretical current value Ii (t) including the estimated self-discharge resistance Rp (tn) and the series circuit resistance Re (tn) and the acquired current values Ib (t1), Ib (t2), ..., Correlation coefficient acquisition process for obtaining the correlation coefficient Kr (tn) with Ib (tn), and
A battery evaluation step for evaluating the battery based on the estimated self-discharge resistance Rp (tn) when the correlation coefficient Kr (tn) becomes equal to or higher than a predetermined reference correlation coefficient Krk is provided. Battery inspection method.

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