Internal resistance inspection method of secondary battery and manufacturing method of secondary battery

Abstract

The present invention relates to a method for inspecting the internal resistance of a secondary battery, which comprises the following steps: a pre-charging step of charging the secondary battery to a set SOC; a discharge measuring step of discharging the secondary battery at a set discharge rate for a set time (t) or longer in a manner to eliminate polarization, component resistance, and reaction resistance; a charge measuring step of charging the secondary battery at a charge rate having the same current value as the set discharge rate for a set time (t) or longer; and an internal resistance calculation step of calculating the internal resistance based on a first voltage value (V ) at a time when the set time (t) has passed in the discharge measuring step. 1 ) and the first current value (I 1 ) and the second voltage value (V 2 ) and the second current value (I 2 ) is used to calculate the internal resistance of the secondary battery.

Description

Technical Field

[0001] The present invention relates to a method for inspecting the internal resistance of a secondary battery and a method for manufacturing a secondary battery, and more particularly to a method for inspecting the internal resistance of a secondary battery and a method for manufacturing a secondary battery capable of obtaining the internal resistance of the secondary battery with high accuracy in a shorter time. Background Art

[0002] In order to properly charge a secondary battery, such as one mounted on a vehicle, it is necessary to control the voltage and current, and therefore it is necessary to measure the internal resistance of the secondary battery. In order to accurately measure the internal resistance, it is necessary to eliminate polarization (the apparent voltage change associated with the application of current). This polarization is eliminated over time, and the voltage converges to OCV (open circuit voltage).

[0003] Fig. 9 2 is a graph showing the relationship between the time t[s] and the voltage V[V] for eliminating the conventional polarization. In the prior art, in order to eliminate the polarization, Fig. 9 As shown, the battery is charged to the SOC (State Of Charge) at which the internal resistance is checked. At the end time t 0 After that, rest for a certain rest time t R of charging, then at time t P1 ,t P2 Apply 10A or 60A pulses 1 , P 2 , calculate the internal resistance.

[0004] In the existing method, the rest time t is required R , internal resistance inspection takes a long time.

[0005] Fig.10 FIG. 1 is a diagram showing the relationship between the time t[s], the voltage V[V], and the current I[A] in the internal resistance detection step described in Patent Document 1. Fig.10 The steps shown perform the internal resistance detection step and achieve a shortened internal resistance inspection time. In this step, the battery is charged with an internal resistance detection voltage (EV2) below the final charging voltage (EVT) to detect the internal resistance. In this step, the battery is pulse charged with a constant voltage and constant current, and the internal resistance is detected based on the difference between the battery voltage during charging and the battery voltage during charging suspension. The internal resistance value R of battery 1 is calculated by R = (E1-E0) / I. Among them, in this formula, E1 is the battery voltage when charging with a current I, E0 is the battery voltage when charging is suspended, and I is the charging current.

[0006] According to such an internal resistance detection step, the internal resistance can be obtained in a short time.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2002-142379 Summary of the invention

[0010] Problems to be solved by the invention

[0011] However, in the invention described in Patent Document 1, although the internal resistance can be determined in a short time, the influence of polarization is still significant during pulse charging in the middle of charging, and it cannot necessarily be said that accurate internal resistance measurement without being affected by polarization is possible.

[0012] The problem to be solved by the method for inspecting the internal resistance of a secondary battery and the method for manufacturing a secondary battery of the present invention is to obtain the internal resistance of a secondary battery with good accuracy in a shorter time.

[0013] Means for solving problems

[0014] In order to solve the above-mentioned problems, the internal resistance inspection method of the present invention is a method for inspecting the internal resistance of a secondary battery as a measurement object, characterized in that it comprises the following steps: a pre-charging step of charging the secondary battery to a set SOC; a discharge measurement step of discharging the secondary battery at a set discharge rate for a preset time t or longer after the pre-charging step; a charging measurement step of charging the secondary battery at a charging rate having the same current value as the set discharge rate for a preset time t or longer after the discharge measurement step; and an internal resistance calculation step of calculating the internal resistance based on a first voltage value V at a time when the preset time t has passed in the discharge measurement step. 1 and the first current value I 1 and the second voltage value V at the time when the preset time t has passed in the charging measurement step. 2 and the second current value I 2 The internal resistance of the secondary battery is calculated from the difference.

[0015] In the internal resistance inspection method, in the discharge measurement step, the predetermined time t may be set so that polarization elimination, component resistance, and reaction resistance can be responded to.

[0016] The above-mentioned internal resistance inspection method may include a reference resistance value obtaining step, in which a reference resistance value of the secondary battery serving as the above-mentioned measurement object is obtained before the above-mentioned internal resistance inspection method of the secondary battery; and further include a calibration step, in which the above-mentioned reference resistance value is used as a reference to determine the above-mentioned pre-set time t used in the above-mentioned discharge measurement step and the above-mentioned charge measurement step.

[0017] In the internal resistance inspection method, the reference resistance value obtaining step may include the following steps: a polarization elimination step of stopping the application of current until the influence of polarization does not affect the measurement; and an internal resistance obtaining step of applying a set current value I P The pulse current for charging is applied at the same time as the pulse current I P The pulse current for discharge is used to obtain the voltage value V of the above charging and the above discharging respectively. P and current value I P In the above internal resistance obtaining step, the above set current value I is changed P , repeatedly apply pulse current multiple times, and based on these obtained voltage values ​​V P and current value I P The above-mentioned reference resistance value is obtained.

[0018] In the internal resistance inspection method, in the pre-charging, the battery is charged to an SOC region where the voltage is stable with respect to the capacity, that is, a flat region.

[0019] The internal resistance inspection method can be preferably performed when the secondary battery is a nickel-metal hydride storage battery.

[0020] In addition, a method for manufacturing a secondary battery may include such a method for inspecting the internal resistance of a secondary battery.

[0021] Effects of the Invention

[0022] According to the method for testing the internal resistance of a secondary battery and the method for manufacturing a secondary battery of the present invention, the internal resistance of the secondary battery can be obtained with high accuracy in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a perspective view showing the structure of the nickel-metal hydride storage battery according to the present embodiment.

[0024] Figure 2 It is a cross-sectional view of a stack of battery cells provided in the nickel-metal hydride storage battery of the present embodiment.

[0025] Figure 3 This is a schematic diagram showing a partial configuration of an example of a nickel-metal hydride storage battery manufacturing apparatus as an internal resistance inspection apparatus.

[0026] Figure 4 This is a timing chart showing the internal resistance inspection method of this embodiment in a time series.

[0027] Figure 5 is a flowchart showing the steps of the internal resistance inspection method.

[0028] Figure 6 is a scatter plot for obtaining reference resistance values.

[0029] Figure 7 This is a diagram comparing the internal resistance of nickel-metal hydride storage batteries measured with respect to a reference resistance value Rs [Ω] and a change time t [s].

[0030] Figure 8 It is shown Figure 4 FIG. 1 is a timing chart of the internal resistance inspection portion in the present embodiment.

[0031] Fig. 9 1 is a diagram showing the relationship between the time t [s] and the voltage V indicating the conventional polarization elimination.

[0032] Fig.10 1 is a diagram showing the relationship among time t [s], voltage V [V], and current I in the internal resistance detection step described in Patent Document 1. DETAILED DESCRIPTION

[0033] The following reference Figures 1 to 8 The method for inspecting the internal resistance of a secondary battery and the method for manufacturing a secondary battery according to the present invention will be described with reference to one embodiment of a method for inspecting the internal resistance of a nickel-metal hydride storage battery 11 and a method for manufacturing the same.

[0034] (Configuration of this embodiment)

[0035] <Overview of this Embodiment>

[0036] Figure 4 The internal resistance test method of this embodiment is a time chart showing the internal resistance test method of this embodiment in a time series. The purpose of the internal resistance test method of this embodiment is to obtain the internal resistance value R of a secondary battery with good accuracy in a shorter time. Specifically, instead of Fig. 9 The conventional rest time t for eliminating polarization after charging is shown as R In this embodiment, by discharging and charging after pre-charging, the polarization caused by pre-charging is quickly eliminated. Figure 4As shown, the battery is discharged for a period of time t immediately after pre-charging, and polarization is eliminated in a short time by a reverse current. In addition, charging for the same time t is immediately performed thereafter, thereby eliminating polarization in a short time by a reverse current. By making the charging and discharging time the same time t, the influence of polarization when measuring the internal resistance can be offset and the influence can be eliminated, thereby shortening the time to obtain the internal resistance of the secondary battery.

[0037] However, in order not to reduce the acquisition accuracy, the internal resistance inspection method of the present embodiment has the following features.

[0038] First, the internal resistance value R is obtained by precharging in a state where the voltage is charged to a stable SOC region with respect to the capacity, that is, a flat region. This is because if the voltage change accompanying the capacity change is large, it is estimated that the internal resistance may increase.

[0039] Next, the internal resistance value R is obtained from the difference in current value and voltage value at two points of discharge and charge at a specific time point after pre-charging. In this case, in this embodiment, the internal resistance measurement method is calibrated for accurate measurement. Therefore, the internal resistance of the nickel-metal hydride storage battery 11 as the object is measured in advance to accurately obtain the reference resistance value R as the calibration reference. The reference resistance value Rs is obtained by actually measuring the characteristics of the nickel-metal hydride storage battery 11 as the measurement object.

[0040] Based on the reference resistance value Rs obtained in this way, the length of the common “time t” that determines the measurement time point of the discharge time and the charge time in the internal resistance test method of the present embodiment is set.

[0041] In order to obtain the reference resistance value Rs reliably, a rest time sufficient for measuring the reference resistance value Rs is used to measure the nickel-hydrogen storage battery 11 in which polarization is eliminated to a degree that does not affect the measurement. Thereafter, the current value I is changed while the voltage V of the nickel-hydrogen storage battery 11 is stable, and multiple pulses are applied to the nickel-hydrogen storage battery 11. These current / voltages are plotted and linear fitting is performed to obtain the reference resistance value Rs. In addition, a plurality of different nickel-hydrogen storage batteries 11 can be used as measurement objects to obtain a more reliable reference resistance value Rs.

[0042] Regarding the time to obtain the internal resistance value R according to the voltage difference between the two points of discharge and charge, the "time t" to obtain the internal resistance is set in consideration of the difference in the response speed of each resistance component of the internal resistance relative to the current application. Regarding the difference in the response speed of each resistance component, specifically, the elimination of polarization is responded to first. That is, the resistance component caused by polarization is responded to. Regarding the elimination of polarization, it can be eliminated almost instantly when a reverse current is applied. Then the component resistance is responded to. And finally the reaction resistance is responded to. Therefore, the time before the reaction resistance is fully responded cannot be accurately measured. Whether there is such a response of the reaction resistance varies depending on the secondary battery and the current value as the object. That is, the time until the reaction resistance fully responds depends on the secondary battery and the current value as the object. Therefore, the measurement time that can accurately obtain the internal resistance needs to be determined based on the secondary battery as the actual measurement object and the current value used in the measurement.

[0043] <Construction of Nickel-Metal Hydride Storage Battery 11>

[0044] Figure 1 It is a perspective view showing the structure of the nickel-metal hydride storage battery 11 according to the present embodiment. Figure 2 1 is a cross-sectional view of a laminate 25 of battery cells 12 provided in the nickel-metal hydride storage battery 11 of the present embodiment. First, a method for manufacturing the nickel-metal hydride storage battery 11 of the present embodiment will be described.

[0045] <Battery Module>

[0046] like Figure 1 As shown, the nickel-metal hydride storage battery 11 is constituted in the form of a battery module having a plurality of battery cells 12. The plurality of battery modules of the present embodiment are bound together to constitute a vehicle-mounted battery pack as a structure including electrical components, a cover, and the like. The nickel-metal hydride storage battery 11 is, for example, a square plate-shaped sealed battery. The nickel-metal hydride storage battery 11 includes an integrated battery container 13 capable of accommodating a plurality of (here 6) battery cells 12, and a cover 14 that seals the opening of the integrated battery container 13. The integrated battery container 13 and the cover 14 are formed of, for example, a resin material. A plurality of (here 6) battery cells 12 electrically connected in series are accommodated in the integrated battery container 13. The power of these battery cells 12 is taken out from the positive terminal 13a and the negative terminal 13b provided in the integrated battery container 13.

[0047] <Battery Cell 12>

[0048] like Figure 2As shown, the battery cell 12 includes: a laminate 25 composed of an electrode group 20 and collector plates 21 and 22, and an electrolyte (not shown) stored in the integrated battery tank 13 together with the laminate 25. The electrode group 20 is formed by laminating a plate-shaped positive electrode plate 15 and a negative electrode plate 16 with a separator 17 interposed therebetween. The end 15a of the positive electrode plate 15 is bonded to the bonding surface of the positive collector plate 21. The end 16a of the negative electrode plate 16 is bonded to the bonding surface of the negative collector plate 22.

[0049] <Negative Electrode Plate 16>

[0050] Next, the negative electrode plate 16 will be described. The negative electrode plate 16 includes a core material and a hydrogen storage alloy supported on the core material. The type of hydrogen storage alloy is not particularly limited, and may be, for example, an alloy of a mixed rare earth metal as a mixture of rare earth elements and nickel, or an alloy in which a part of the alloy is replaced by metals such as aluminum, cobalt, and manganese. The negative electrode plate 16 is manufactured as follows: a thickening material such as carbon black and a binding material such as a styrene-butadiene copolymer are added to the hydrogen storage alloy, and the hydrogen storage alloy processed into a paste is filled into a core material such as a punching metal, and then the filled core material is dried, rolled, and cut, thereby manufacturing the negative electrode plate.

[0051] <Electrolyte>

[0052] Next, the electrolyte solution will be described. The electrolyte solution is held in the separator 17 and performs ion conduction between the positive electrode plate 15 and the negative electrode plate 16 .

[0053] The electrolyte is an alkaline aqueous solution containing potassium hydroxide (KOH) as a main component of the solute.

[0054] <Positive electrode plate 15>

[0055] Next, the positive electrode plate 15 is described. The positive electrode plate 15 has a substrate composed of a three-dimensional porous body made of nickel, and a positive electrode composite material supported on the substrate. The substrate has the function of a carrier for supporting the filling material, and the function of a collector. The paste as the positive electrode composite material contains positive electrode active material particles with nickel hydroxide as the main component, cobalt (Co) as a metal that functions as a conductive material, a thickening material, and a bonding material. In this embodiment, metal cobalt (Co) is exemplified, but cobalt oxide represented by cobalt monoxide (CoO), cobalt compounds, etc. may also be contained.

[0056] <Nickel-metal hydride storage battery manufacturing device 30>

[0057] Figure 3 1 is a schematic diagram showing a partial configuration of a manufacturing device 30 for a nickel-metal hydride storage battery 11 as an example of an internal resistance inspection device for a secondary battery. The functions of the manufacturing device 30 for the nickel-metal hydride storage battery 11 include: Figure 3The functions of the internal resistance inspection device shown. The manufacturing device 30 constituting the internal resistance inspection device includes a charging and discharging device 32 that can charge and discharge the nickel-metal hydride storage battery 11, and a control device 31 that controls the charging and discharging device 32. The control device 31 includes a computer, and controls the charging and discharging device 32 by a control signal. The charging and discharging device 32 charges or discharges the nickel-metal hydride storage battery 11 based on the signal control from the control device 31. The control device 31 controls the charging and discharging of the nickel-metal hydride storage battery 11 at a specific voltage or current based on a stored program. The control is performed based on the measurement results obtained by the voltmeter 34 that measures the voltage of the battery module of the nickel-metal hydride storage battery 11, and the ammeter 33 that measures the current flowing through the nickel-metal hydride storage battery 11. The charging and discharging are performed using the functions of the manufacturing device 30 of these nickel-metal hydride storage batteries 11.

[0058] (Function of this embodiment)

[0059] <Method for Manufacturing Nickel-Medium Hydrogen Storage Battery 11>

[0060] Next, a method for manufacturing the nickel-metal hydride storage battery 11 will be described. The method for manufacturing the nickel-metal hydride storage battery 11 includes a positive electrode manufacturing step, a negative electrode manufacturing step, an assembling step, an activation step, and an inspection step.

[0061] <Positive electrode production steps>

[0062] In the positive electrode manufacturing step, a specific amount of cobalt and a thickening material are added to the positive electrode active material particles having a coating layer, and kneaded to form a paste. Then, the paste is filled into a substrate composed of a three-dimensional porous body made of nickel obtained by foaming the paste. After drying, the substrate is press-formed and cut into a specific size to manufacture the positive electrode plate 15.

[0063] <Negative electrode production steps>

[0064] In the negative electrode manufacturing step, the hydrogen storage alloy powder is immersed in an alkaline aqueous solution, stirred, washed with water, and dried. A binder and the like are further added to the dried hydrogen storage alloy powder, and kneaded to produce an active material paste. The active material paste is then applied to a core material such as a punching metal, and the core material is dried, rolled, and cut to produce a negative electrode plate 16.

[0065] <Assembly steps>

[0066] In the assembly step, the positive electrode plate 15 and the negative electrode plate 16 are stacked via a separator 17 made of a nonwoven fabric of an alkali-resistant resin. In addition, the end 15a of the positive electrode plate 15 is bonded to the collector plate 21 by welding or the like, and the end 16a of the negative electrode plate 16 is bonded to the collector plate 22 by welding or the like to produce a laminate 25. The laminate 25 is further housed in an integrated battery tank 13 together with an electrolyte solution having potassium hydroxide as a main component of the solute, and the integrated battery tank 13 is sealed.

[0067] <Activation Step>

[0068] The activation step includes: a Co charging step for activating the Co of the positive electrode; a conditioning step such as activation charge and discharge for activating the hydrogen storage alloy of the negative electrode; and an aging step. After these steps, the nickel-metal hydride storage battery as a product is completed.

[0069] <Inspection steps>

[0070] In the inspection step, an OCV inspection step, an internal resistance inspection step, etc. are performed using a performance test of a product before shipment. In the internal resistance inspection step, the internal resistance inspection method of the present embodiment is implemented.

[0071] <Internal resistance inspection method>

[0072] Figure 5 is a flowchart showing the steps of the internal resistance inspection method. Figure 5 , the steps of the internal resistance inspection method are explained.

[0073] <Obtaining Reference Resistance Value Rs (S1)>

[0074] Before the internal resistance inspection method is started, a reference resistance value Rs is obtained in advance (S1). That is, the reference resistance value obtaining step (S1) of obtaining the reference resistance value of the secondary battery is performed before the pre-charging step (S5) of charging the secondary battery to a set SOC.

[0075] Figure 6It is a scatter plot for obtaining the reference resistance value Rs. The horizontal axis of the figure is the current value I [A], and the vertical axis is the voltage value V [V]. In order to accurately obtain the reference resistance value Rs, a sufficient rest time of, for example, more than 30 minutes is used to measure the voltage of the nickel-hydrogen storage battery 11 after polarization is eliminated to a degree that will not affect the measurement. This step is equivalent to the polarization elimination step of the present invention. Thereafter, a pulse current is applied by changing the current value while the voltage is stable. The applied current value is, for example, 10 to 50 [A]. In the present embodiment, the voltage is measured 4.9 seconds after the current is applied, and a combination of current I and voltage V is obtained for a total of 8 points, namely, Pa, Pb, Pc, and Pd for charging at a changed current value, and Pa', Pb', Pc', and Pd' for discharging at the same current value as charging. As shown Figure 6 As shown, these Pa, Pb, Pc, Pd, Pa', Pb', Pc', and Pd' are plotted. The plotted points are fitted with a straight line by, for example, the least square method. Then, the reference resistance value Rs is obtained according to ΔV[V] / ΔI[A]=Rs[Ω]. In one example, under a voltage-stable state, a plurality of discharge pulse currents and a plurality of charge pulse currents are applied to the nickel-hydrogen storage battery 11, and a plurality of voltage values ​​of the voltage of the nickel-hydrogen storage battery 11 are measured. In one example, a plurality of discharge pulse currents and a plurality of charge pulse currents may have the same current value. In one example, the voltage of the nickel-hydrogen storage battery 11 may be measured after a specific time has passed after the discharge pulse current or the charge pulse current is applied. In one example, the reference resistance value Rs is obtained based on the measured plurality of voltage values ​​and the corresponding plurality of current values. It is further preferred to use a plurality of different nickel-hydrogen storage batteries 11 as measurement objects to obtain a more reliable reference resistance value Rs. This step is equivalent to the reference resistance value obtaining step of the present invention.

[0076] <Measurement of internal resistance value R by changing time t (S2)>

[0077] Figure 7 1 is a graph comparing the internal resistance value R of the nickel-metal hydride storage battery 11 measured by varying the time t [s] with the reference resistance value Rs. Figure 6 Similarly, the horizontal axis of the graph is the current value [A], and the vertical axis is the voltage value [V]. Figure 6 The graph of the reference resistance value Rs is shown.

[0078] Initially, since the appropriate time t is unknown, the internal resistance inspection method is attempted by setting the time t to 90 [s], for example. Figure 7 The slope of the straight line at t = 90 [s] is greater than the slope of the straight line of the reference resistance value Rs, that is, the internal resistance is large. Therefore, the time is set to t = 30 [s] and the internal resistance inspection method is tried. In this way, Figure 7 The slope of the straight line at time t = 30 [s] is smaller than the slope of the straight line of the reference resistance value Rs, that is, the internal resistance is small. So, next, set the middle time t = 60 [s] and try to implement the internal resistance inspection method. In this way, Figure 7 The straight line at time t=60[s] has the same slope as the straight line of the reference resistance value Rs, and the straight lines overlap. That is, the internal resistance is equal. Therefore, it can be seen that in this embodiment, when the time is set to t=60[s], the internal resistance of the nickel-metal hydride storage battery 11 can be accurately measured using the internal resistance inspection method of this embodiment. In this way, by adjusting the setting of time t, the accuracy of the internal resistance inspection method of this embodiment can be improved.

[0079] <Determination of time t (S3)>

[0080] Next, in order to accurately measure the internal resistance of the nickel-metal hydride storage battery 11 by the internal resistance inspection method of this embodiment, the time t(s) obtained by the above steps is set to t=60 seconds. As described above, the time until the reaction resistance fully responds depends on the secondary battery and the current value as the object, so by implementing S1 to S3, the time t(s) can be set for each secondary battery and current value as the object. In one example, the time t(s) represents the time until the reaction resistance responds, for example, the time until the reaction resistance fully responds. The time t(s) can be set according to the secondary battery and the current value as the object, and is not limited here.

[0081] <Internal resistance check starts (S4)>

[0082] The calibration process of the internal resistance inspection device of the present embodiment is completed through the above steps, and thus the internal resistance inspection method of an actual product can be implemented.

[0083] <Pre-charge (S5)>

[0084] First, pre-charge (S5) is performed. During pre-charge, the nickel-metal hydride battery 11 is charged to the SOC region where the voltage is stable relative to the capacity, that is, the flat region (for example, 20-80%). If the hydrogen storage alloy is in a coexistence state of a solid solution and a hydride, there will be a region (called a flat region) where the amount of hydrogen dissolved increases but the hydrogen pressure does not increase. When all of it becomes a hydride, as the hydrogen pressure rises, the amount of hydrogen dissolved begins to increase again, but usually the increase in the amount of hydrogen dissolved is small relative to the increase in pressure (even if the pressure increases to several MPa or tens of MPa). The area where hydrogen storage alloys are used for hydrogen storage and release is mainly a flat area where pressure control is easy and the storage amount changes significantly.

[0085] Therefore, in this embodiment, the internal resistance is obtained by charging to the state of the SOC region where the voltage is stable relative to the capacity, that is, the flat region, through pre-charging. This is because if the voltage change accompanying the capacity change is large, it is estimated that the internal resistance may increase. In this embodiment, the nickel-metal hydride storage battery 11 is charged to the target SOC, for example, SOC80%, at an arbitrary value of the charging rate of 3 to 6C.

[0086] After charging to the target SOC ( S6 : YES), charging is stopped ( S7 ).

[0087] <Discharge Measurement (S8)>

[0088] Figure 8 Yes means Figure 4 The timing chart of the internal resistance inspection part of this embodiment is shown in FIG. As a premise, the optimal time t varies depending on the type and lot number of the battery to be measured. The production steps in the factory have a takt time for the process operation, so from the perspective of production efficiency, it is not preferable to change t every time. 0 ~t 1 The discharge time is t1 to t2, and the charging time is t1 to t2. Therefore, the discharge time and the charging time are set by roughly predicting the time including the time t. The current and the voltage are accurately measured at the time point of the time t.

[0089] At time t 0 After the pre-charge is completed (S7), the discharge measurement is started (S8). In the discharge measurement, the nickel-metal hydride storage battery 11 is discharged at a discharge rate of any value between 3 and 6 C. From the time t 0 Start counting and continue discharging until at least time t has passed. The time t[s] is 60[s] in this embodiment. When discharging starts, polarization is eliminated first. Therefore, in region A, the voltage drops sharply and reaches OCV. After polarization is eliminated, the component resistance is responded to in region B. Therefore, the voltage decreases slowly. In addition, in region C, the reaction resistance is responded to, so the voltage decreases more slowly.

[0090] Here, the discharge is continued while the time t[s] is measured by the measuring device of the control device 31 until t[s]=60[s] (S9: No). After the time t[s]=60[s] (S9: Yes), the current I at the time when the time t has passed is measured and stored. 1 and voltage V 1 (S10). Then, the discharge is terminated and charging is started (S11). It should be noted that in this embodiment, the discharge is continued for a while after the time t has passed. 1 'Finish.

[0091] This step is equivalent to the discharge measurement step of the present invention. 1 Equivalent to the first current value, voltage V 1 Equivalent to the first voltage value.

[0092] <Charging Measurement (S11)>

[0093] The time t from the end of the charge measurement (S11) to the end of the discharge measurement 1 'Start. In the charge measurement, the charge is started by changing the current flow to the same current value as the discharge rate in the discharge measurement. That is, at time t 1 ', and start charging using a charging rate with the same current value as the discharge rate measured by discharge.

[0094] In the charge measurement, from the time t 1 'Start measuring, and continue charging until at least time t has passed. The time t[s] used for measurement is 60[s], which is the same as the discharge time. When charging starts, polarization is eliminated first. Therefore, in area A', the voltage rises sharply and reaches OCV. After the polarization is eliminated, in area B', the component resistance responds. Therefore, the voltage rises slowly. In addition, in area C', the reaction resistance responds, so the voltage rises more slowly.

[0095] Here, the discharge is continued while the time t[s] is measured by the measuring device of the control device 31 until the time t[s]=60[s] is reached (S12: No). Then, after the time t[s]=60[s] (S12: Yes), the current I at the time when the time t has passed is measured and stored. 2 and voltage V 2 (S13) It should be noted that in this embodiment, charging is continued for a short time after the time t has passed. 2 'Finish.

[0096] This step is equivalent to the charging measurement step of the present invention. 2 Equivalent to the second current value, voltage V 2 Equivalent to the second voltage value.

[0097] <Calculation of internal resistance R>

[0098] According to the current I 1 , voltage V 1 The current I measured in the measurement (S10) 1 , voltage V 1 With the current I 2 , voltage V 2 The current I measured in the measurement (S13) 2 , voltage V 2, calculate the internal resistance value R of the nickel-metal hydride storage battery 11 to be measured. Here, the mathematical formula "R = (V 2 -V 1 ) / (I 2 -I 1 )” calculates the internal resistance value R (S14).

[0099] <Internal resistance check>

[0100] The internal resistance value R calculated in this way is compared with the reference resistance value Rs (S15). Here, it is determined whether the calculated internal resistance value R falls within the allowable range based on the reference resistance value Rs. When the calculated internal resistance value R does not fall within the allowable range based on the reference resistance value Rs (S15: No), it is determined that the internal resistance of the nickel-metal hydride storage battery 11 does not meet the product's shipping standard, and the shipment of the nickel-metal hydride storage battery 11 is suspended (S16). On the other hand, when the calculated internal resistance value R falls within the allowable range based on the reference resistance value Rs (S15: Yes), it is determined that the nickel-metal hydride storage battery 11 has passed the inspection (S17), and the implementation of the internal resistance inspection method of this embodiment is terminated (end). Thereafter, for the nickel-metal hydride storage battery 11 that has passed the inspection (S17), it is determined that the internal resistance meets the product's shipping standard, such as being stored in a battery pack for vehicle use, stacking batteries, or installing auxiliary equipment, and preparations for shipment are made through subsequent steps.

[0101] (Effects of this embodiment)

[0102] The method for manufacturing a nickel-metal hydride storage battery including the internal resistance inspection method of the present embodiment exerts the following effects.

[0103] (1) In conventional internal resistance inspection, it is necessary to rest for about 30 minutes to eliminate polarization. However, in the present embodiment, polarization is eliminated quickly by using charge and discharge, so the internal resistance of the nickel-metal hydride storage battery can be measured quickly.

[0104] (2) In the discharge measurement and the charge measurement for measuring the internal resistance, the current and the voltage are measured for the same time t, so the influence of polarization is offset, and the measurement result is not affected by the polarization.

[0105] (3) In the internal resistance inspection method of the present embodiment, not only polarization but also component resistance and the response time of reaction resistance are taken into consideration, so that measurement errors caused by these influences can be suppressed.

[0106] (4) In addition, the internal resistance characteristics of the nickel-metal hydride storage battery 11 to be inspected are measured in detail in advance, and a reference resistance value Rs is obtained in advance. The internal resistance inspection method is calibrated based on the reference resistance value Rs. Therefore, even if the secondary battery to be measured is changed, the internal resistance can be accurately inspected using the internal resistance inspection method of this embodiment.

[0107] (5) The calibration of the internal resistance inspection method is obtained by changing the current value by multiple pulses, so errors are not easily generated and accurate calibration can be performed.

[0108] (6) In the calibration of the internal resistance inspection method, the internal resistance inspection method of the present embodiment is actually performed by adjusting the length of the time t used for measurement, so that precise adjustment can be performed.

[0109] (7) During the inspection, the battery is charged to an SOC region where the voltage is stable with respect to the capacity. Therefore, it is possible to suppress the occurrence of an error in the internal resistance due to a large voltage change accompanying a capacity change.

[0110] (8) In the internal resistance inspection method of the present embodiment, since determination can be easily made based on voltage and current, it can be implemented using a simple device.

[0111] (9) By using such an internal resistance inspection method, it is possible to effectively prevent the shipment of products having internal resistance problems in advance.

[0112] (10) By obtaining an accurate reference resistance value Rs for each product, it is possible to perform an inspection suitable for the battery.

[0113] (Other Examples of the Present Embodiment)

[0114] As mentioned above, although this invention was demonstrated using embodiment, this invention is not limited to embodiment, It can also be implemented as follows.

[0115] Regarding the acquisition of the reference resistance value Rs, the method is not limited to that of the embodiment, and the reference resistance value Rs may be obtained by other methods depending on the secondary battery to be inspected.

[0116] · Figure 5 The flowchart shown is an embodiment of the present invention, and those skilled in the art may add to, delete, change the order of, and make changes to the steps.

[0117] In this embodiment, the battery module of the nickel-metal hydride storage battery 11 for vehicle use is described as an example, but its use is not limited, and it can be used not only for ships and aircraft, but also for judging the battery status of ground-mounted batteries. In addition, it is not limited to battery modules, and individual single cells can also be used as inspection objects.

[0118] The battery module of the secondary battery has been described by taking the nickel-metal hydride storage battery 11 as an example, but a lithium-ion secondary battery or the like may also be used, and the type of battery is not limited.

[0119] The modes described in the respective embodiments and modifications can be implemented by replacing each other unless there is any contradiction.

[0120] The present embodiment is an example of the present invention, and it is possible for a person skilled in the art to implement the present invention by adding, deleting or changing the configuration thereof without departing from the scope of the claims.

Claims

1. A method for testing the internal resistance of a secondary battery, the method being for testing the internal resistance of a secondary battery as a measurement object, wherein the method comprises the following steps: A pre-charging step of charging the secondary battery to a set SOC; a discharge measurement step, after the pre-charging step is completed, discharging the secondary battery at a set discharge rate for a predetermined time (t) or longer; a charging measurement step, after the discharge measurement step is completed, charging the secondary battery at a charging rate having the same current value as the set discharge rate for a period of time (t) or longer than the preset time; and an internal resistance calculation step of calculating the internal resistance of the secondary battery based on a difference between a first voltage value (V1) and a first current value (I1) at a time when the preset time (t) has passed in the discharge measurement step and a second voltage value (V2) and a second current value (I2) at a time when the preset time (t) has passed in the charge measurement step, The SOC is set to be in the SOC region where the voltage is stable with respect to the capacity, that is, the flat region. The predetermined time (t) is set so as to eliminate polarization, and to respond to component resistance and reaction resistance.

2. The method for inspecting the internal resistance of a secondary battery according to claim 1, wherein: A reference resistance value obtaining step is provided for obtaining a reference resistance value of the secondary battery as the measurement object before the internal resistance inspection method of the secondary battery; The method further comprises a calibration step of determining the preset time (t) used in common in the discharge measurement step and the charge measurement step, based on the reference resistance value.

3. The method for inspecting the internal resistance of a secondary battery according to claim 2, wherein: The reference resistance value obtaining step comprises the following steps: Polarization elimination step, which stops the application of current until the influence of polarization has no effect on the measurement; as well as Internal resistance acquisition step, applying a set current value (I P ) is used to charge the pulse current, and at the same time, a current value (I P ) to discharge the pulse current, and obtain the voltage value (V P ) and current value (I P ), In the internal resistance obtaining step, the set current value (I P ), repeatedly applying pulse current multiple times, and based on the voltage values ​​obtained (V P ) and current value (I P ) to obtain the reference resistance value.

4. The internal resistance inspection method of a secondary battery according to claim 1 or 2, characterized in that: The secondary battery is a nickel-hydrogen storage battery.

5. A method for manufacturing a secondary battery, characterized in that: The method includes the internal resistance inspection method of a secondary battery according to any one of claims 1 to 4.

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