JP4385703B2 - Inspection method for electric double layer capacitors - Google Patents

Description

  The present invention relates to an inspection method for determining the quality of an electric double layer capacitor.

  An electric double layer capacitor uses a large specific surface area as an electrode material and uses activated carbon that is electrochemically inert and combines with an electrolyte to use a large electric double layer capacity. It can be rapidly charged / discharged with a large current without being accompanied by a large current density, and its output density is higher than that of a chemical battery. It can be applied to large current generation circuits, instantaneous compensation power supplies, load leveling circuits, etc. Is expected.

  This electric double layer capacitor has a coin type for memory backup and a cylindrical type for power. In the coin type, a disk-shaped lower electrode, separator, and upper electrode are sequentially laminated on a low-profile cylindrical metal case with an open upper end, and an electrolyte is injected into the inside. A gasket for insulation and sealing is housed in the peripheral portion, a metal lid is covered on the upper surface, and the metal case and the metal lid are not crimped directly so as to have a caulking process.

  Further, as shown in FIG. 3, the configuration of the cylindrical electric double layer capacitor is such that the capacitor element 10 has a strip-shaped metal foil, punching metal, expanded metal, or the like as a current collector, and both or one side of the current collector. In addition, a polarizing electrode made of activated carbon, carbon and a binder is applied, and two of them are prepared. Between these current collectors, a strip for insulating and holding an electrolyte solution is interposed in the same manner. Each current collector is connected to one electrode terminal 11 one by one, wound in a spiral shape, and finally fixed with an adhesive tape 12. The electrode terminal 11 of the capacitor element 10 is connected to the fitting 17 of the sealing body 14, has a cylindrical shape with a bottom, and protrudes the lead terminal 16 to the outside in a metal case 13 having a concave groove 15 near the upper end. The electric double layer capacitor is configured by storing the electrolyte and injecting an electrolytic solution, bending the upper end of the metal case 13 inward, and sealing it.

  Such an electric double layer capacitor is generally inspected for leakage current as a performance inspection upon completion. This leakage current can be inspected by charging to a constant voltage with a constant current and examining the subsequent self-discharge characteristics.

  In other words, after charging the electric double layer capacitor, the voltage after leaving it for a certain period of time as it is is compared with the voltage immediately after the completion of charging to indirectly grasp the degree of leakage current. The change is shown in FIG. In this figure, for example, if the battery is left for 100 hours, and the voltage after a certain time has decreased from the voltage V0 during charging by Vt, if the voltage value Vt or the voltage decrease ratio is equal to or less than a specified value, the product is considered good. Judgment criteria are provided.

  Further, in Patent Document 1, voltage detection means for detecting that the voltage between the terminals of the electric double layer capacitor has reached a predetermined value, and the voltage between the terminals of the electric double layer capacitor supplied via the switch means, A voltage comparison unit that compares a degradation reference voltage and outputs a degradation signal when the voltage between the terminals reaches the degradation reference voltage, and energizes the electric double layer capacitor based on the detection output of the voltage detection unit. And when the voltage detecting means detects that the voltage between the terminals of the electric double layer capacitor has reached a predetermined value, the switch means is turned on only for a predetermined time, and within the predetermined time And a control means for determining that the electric double layer capacitor is in a deteriorated state when a deterioration signal is output from the voltage comparison means.

Further, in Patent Document 2, in the method for inspecting the leakage current of an electric double layer capacitor, after charging the electric double layer capacitor to a set voltage, the electric double layer capacitor is charged to maintain the set voltage, and the electric double layer capacitor is charged. The steady-state current Id that flows while maintaining the set voltage in the multilayer capacitor is measured, and the leakage current is evaluated based on the steady-state current. It is disclosed that the leakage current can be easily evaluated in a short time by measuring the steady current flowing during relaxation charging in this way.
JP 2001-297554 A JP 2003-133189 A

  However, the test method as shown in FIG. 4 has a problem that an accurate evaluation of the leakage current cannot be made unless several days are required as the time for leaving. Of course, in order to guarantee the quality, it is necessary to inspect the leakage currents of all completed electric double layer capacitors, but it takes a long time to measure the voltage after completion of charging after charging. In addition, electric double layer capacitors waiting for a standing test may accumulate, and the time from completion to inspection may be substantially several days or tens of days.

  In addition, due to the characteristics of the electric double layer capacitor, the discharge characteristics change when the charging time is different.Therefore, even if it is a non-defective product, if there is a terminal contact failure during charging, the problem is that it is judged as defective. Have.

  In addition, the techniques disclosed in Patent Documents 1 and 2 have problems such as a complicated apparatus, high cost, and a complicated measurement method.

  An object of the present invention is to solve such problems and to provide an inspection method for an electric double layer capacitor capable of determining the quality of the electric double layer capacitor in a short time by a relatively easy method. .

According to a first aspect of the present invention to solve the above problems, after charging the electric double layer capacitor to the measured voltage at a constant current, to self-discharge by the capacitor in the open state, when the self-discharge It is an inspection method for an electric double layer capacitor in which a voltage in the middle is measured at regular intervals, and a slope is calculated from the voltage at two points of the measured time to determine whether it is acceptable or not. After the start, it changes abruptly due to the effect of internal resistance, but after that it decreases almost linearly, so the slope becomes almost constant regardless of the time zone, so the voltage of the linearly decreasing voltage By calculating the inclination from two points, it has the effect that the quality of the electric double layer capacitor can be determined in a relatively short time.

  The invention according to claim 2 of the present invention is an inspection method in which the voltage at two points is V1 and V2, and the inclination is Va, and the inspection method is obtained by Va = 1n (V1 / V2). It has the effect that it is possible to accurately determine the quality by a simple calculation method.

  In the present invention, after charging the electric double layer capacitor with a constant current up to the measurement voltage, the capacitor is opened and self-discharged, and the slope is calculated from the two voltages of the self-discharge voltage to determine the quality. By using the inspection method, it is possible to accurately determine the quality of the electric double layer capacitor in a relatively short time, and even if there is a contact failure of the terminal during charging, By using this inspection method, a result equivalent to that during normal charging can be obtained, so that it is possible to determine whether the quality is reliable or not.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the inspection method of the present invention, first, the coin-type and cylindrical-type electric double layer capacitors are charged with a constant current so as to have a constant set voltage in the vicinity of the rated voltage, and held for a certain time. Thereafter, when left undisturbed, the voltage of the electric double layer capacitor draws a self-discharge voltage curve as shown in FIG.

  This self-discharge voltage is measured at two predetermined different measurement times, and the quality of the electric double layer capacitor is determined from the slopes of the two voltages (V1, V2).

  The slope of the voltage is obtained from Va = 1n (V1 / V2), and the slope of the voltage Va thus obtained is not different depending on the measurement time, and is almost the same regardless of the measurement time. Can have.

  In addition, when there is a contact failure of the terminal at the time of charging, it becomes the self-discharge voltage curve of FIG. 1 (B), and in the conventional voltage ratio evaluation, if it is other than the standard value, it is determined as a failure, By obtaining the voltage slope Va, the same effect as in FIG. 1A can be obtained, and a product that can be judged as a non-defective product appears.

  Furthermore, by making the time interval for measuring the two voltages (V1, V2) constant, it is not necessary to measure at a predetermined time, and the degree of freedom of measurement time is increased.

  Since the curve of the self-discharge voltage of the electric double layer capacitor varies depending on the charging time, the ambient temperature at which it self-discharges, the rated capacity of the capacitor, etc., it is necessary to determine the slope Va to be a non-defective product with each condition constant. Don't be.

  Further, when the electric double layer capacitor is actually defective, a curve as shown in FIG. 1C is shown. Therefore, even if the slope Va is obtained, it becomes a value different from a non-defective product.

  Hereinafter, it demonstrates further in detail based on an Example.

Example 1
Using a 2.5V 1.0F coin-type electric double layer capacitor as an electric double layer capacitor, the capacitor was charged with a voltage of 2.5V and a current of 1A for 10 minutes and then allowed to stand naturally. The self-discharge voltage characteristics of the electric double layer capacitor at this time are shown in FIG.

  2A, the voltage 12 hours after the start of natural standing after charging is 2.285V, and the voltage 24 hours later is 2.28V. The slope Va is obtained from these two voltages. When calculated from ln (V1 / V2), it is 0.00223. Further, the voltage after 36 hours from the start of natural standing after charging is 2.275 V, and the voltage after 48 hours is 2.27 V, so the slope Va at this time is 0.00221. Furthermore, even when measuring the voltage 120 hours after the start of natural standing after charging, it is 2.240V, the voltage after 12 hours is 2.235V, and the slope Va at this time is 0.00223. Become.

  Thus, if the self-discharge voltage is measured at 12-hour intervals, the slope Va will be in the range of 0.0022 to 0.0023 no matter what time it is measured. The quality can be determined, and the measurement time can be shortened.

  Further, even when the measurement time interval between the two voltages is 24 hours, for example, the slope Va after 12 hours and 36 hours from the start of natural standing after charging is 0.00443, and the natural voltage after charging is 0.00443. Even if the slope Va after 120 hours and 144 hours from the start of the standing is obtained, it becomes 0.00447. In this case, the quality of the product is judged by setting the slope Va to 0.0044 to 0.0045. can do.

  The range of the voltage gradient at the two points is preferably determined in consideration of the variation of the electric double layer capacitor.

(Example 2)
Example 1 was the same as Example 1 except that charging was performed with insufficient terminal connection of the electric double layer capacitor when charging. The self-discharge characteristics of the electric double layer capacitor at this time are shown in FIG.

  2B, the voltage 12 hours after the start of natural standing after charging is 2.095 V, and the voltage after 24 hours is 2.090 V. The slope Va is obtained from these two voltages. Is obtained from In (V1 / V2), it is 0.00229. The voltage after 36 hours from the start of natural standing after charging is 2.085 V, and the voltage after 48 hours is 2.081 V. Therefore, the slope Va at this time is 0.00221. Further, even if the voltage 120 hours after the start of natural standing after charging is measured, it is 2.053 V, and the voltage after 12 hours becomes 2.049 V, and the slope Va at this time is 0.00225. Become.

  Thus, even in the measurement of Example 2, if the self-discharge voltage is measured at 12-hour intervals, the slope Va is in the range of 0.0022 to 0.0023 no matter what time is measured. Even if the electric double layer capacitor is not sufficiently charged, it can be determined as a non-defective product if the slope of the voltage of the self-discharge voltage curve is within the standard.

  Further, even when the measurement time interval between the two voltages is set to 24 hours, for example, the slope Va after 12 hours and 36 hours from the start of natural leaving after charging is 0.00450. Even if the slope Va after 120 hours and 144 hours from the start of the standing is obtained, it becomes 0.00449. Even in this case, the range of the slope Va falls within the range of 0.0044 to 0.0045 as in the first embodiment. Product discrimination can be performed.

  The present invention relates to an inspection method for determining the quality of an electric double layer capacitor, and can determine the quality of an electric double layer capacitor in a relatively short time. Even if it is insufficient, by using this inspection method, it is possible to obtain a result equivalent to that at the time of normal charging.

The characteristic view which shows the self-discharge voltage curve in embodiment of this invention Characteristic diagram showing self-discharge voltage curve in Examples 1 and 2 Sectional view showing the configuration of a cylindrical electric double layer capacitor Characteristic diagram showing the same self-discharge voltage curve

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Capacitor element 11 Electrode terminal 12 Adhesive tape 13 Metal case 14 Sealing body 15 Groove of metal case 16 Lead terminal 17 Fitting metal fitting

Claims (2)

After charging the electric double layer capacitor with a constant current to the measurement voltage, the capacitor is opened and self-discharged, and the voltage during the self-discharge is measured at regular intervals. A method for inspecting an electric double layer capacitor in which a slope is calculated from a voltage at a point to determine whether it is acceptable or not. 2. The method for inspecting an electric double layer capacitor according to claim 1, wherein when the two voltages are V1 and V2 and the inclination is Va, the inclination is obtained by Va = 1n (V1 / V2).

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