Impedance measurement method, capacitor unit, capacitor unit holding device, and capacitor unit system

Abstract

To provide an impedance measurement method which enables proper measurement of battery impedance, and to provide a capacitor unit, capacitor unit holding device and capacitor unit system that are used for the impedance measurement method.SOLUTION: Four terminals T11-T14 of a measurement device 2 are connected to a battery 20 with capacitor units 7A-7D interposed between the terminals T11-T14 and the battery 20. The impedance of the battery 20 is then measured using the measurement device 2. The four capacitor units 7A-7D have the same capacitance as each other.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an impedance measuring method, a capacitor unit, a capacitor unit holding device, and a capacitor unit system. [Background technology]

[0002] Patent Document 1 discloses an impedance measurement system for measuring the impedance of a measurement target.

[0003] In addition, Non-Patent Document 1 states that when measuring the impedance of a battery using an impedance measuring instrument of the automatic balancing bridge type, the signal output terminal H out of the four terminals is used to prevent a direct current from flowing into the measuring instrument. C and voltage measurement terminal H P Furthermore, Non-Patent Document 1 discloses that a capacitor is connected to the signal output terminal H C The capacitance of the capacitor connected to the voltage measurement terminal H must be 32 μF or more. P It is disclosed that the capacitance of the capacitor connected to is 1 μF. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-49148 A [Non-patent literature]

[0005] [Non-Patent Document 1] "Impedance Measurement Handbook, November 2003 Edition" Agilent Technologies (Chapter 5, page 24) Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors are considering measuring the impedance of a battery using the measurement system described in Patent Document 1. In this case, by connecting a battery having electromotive force to a measuring instrument as a measurement target, direct current from the battery may flow into the measuring instrument and adversely affect electronic components (e.g., resistors) built into the measuring instrument. In order to avoid adverse effects on the measuring instrument, the present inventors are considering combining the technique of Non-Patent Document 1 with the measurement method described in Patent Document 1, interposing a capacitor between the measuring instrument and the battery, and using this capacitor to block the direct current.

[0007] However, the method described in Non-Patent Document 1 is premised on measurement in a specific frequency range (1 kHz or more), whereas Patent Document 1 measures the frequency response in a wide frequency range (1 Hz to 100 MHz). If the method described in Non-Patent Document 1 is adopted as is, there is a risk that accurate impedance measurement cannot be performed when measuring in a frequency range other than the specific frequency range (1 kHz or more). In addition, the method described in Non-Patent Document 1 is effective only for measurements using the automatic balancing bridge method, and cannot be used for measurements using impedance measuring instruments of other types (for example, instruments for measuring by frequency response analysis). In any case, the method described in Non-Patent Document 1 cannot be said to be the optimal method for measuring the impedance of a battery using a measuring instrument that measures impedance by the four-terminal pair method.

[0008] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, one object of the present invention is to provide an impedance measuring method capable of satisfactorily measuring the impedance of a battery using a measuring instrument that measures impedance by the four-terminal pair method.

[0009] Another object of the present invention is to provide a capacitor unit, a capacitor unit holding device, and a capacitor unit system that are suitable for measuring the impedance of a battery. [Means for solving the problem]

[0010] One embodiment of the present invention provides an impedance measuring method having the following features.

[0011] 1. An impedance measurement method for measuring the impedance of a battery as a measurement object using a measuring device having two voltage terminals and two current terminals to be connected to the measurement object and measuring the impedance of the measurement object by a four-terminal pair method, comprising the steps of: a connecting step of connecting the battery to the two voltage terminals and the two current terminals with a capacitor unit including a capacitor interposed between each of the two voltage terminals and the battery and between at least one of the two current terminals and the battery; a measuring step of measuring an impedance of the battery connected to the two voltage terminals and the two current terminals using the measuring device; the capacitor units connected to the two voltage terminals have the same capacitance; The impedance measuring method, wherein the capacitor unit connected to at least one of the two current terminals has a predetermined capacitance.

[0012] According to this method, a capacitor unit is interposed between each voltage terminal and the battery. The two capacitor units have the same capacitance. A capacitor unit having a predetermined capacitance is interposed in at least one of the two current terminals. These capacitor units cut off DC current when charge is stored in the capacitor. This makes it possible to prevent DC current from flowing into the measuring device. Since the capacitances of the two capacitor units connected to the two voltage terminals are the same, the voltages input to the two voltage terminals are not affected by the imbalance that occurs when the capacitors are connected to the voltage terminals. This allows the measuring device to accurately measure the impedance of the battery while preventing DC current from flowing from the battery to the measuring device.

[0013] 2. The impedance measuring method described in item 1, wherein the measuring instrument measures the impedance of the battery based on the difference between the voltages input to the two voltage terminals and the current input to one of the two current terminals.

[0014] According to this method, the measuring instrument measures the impedance of the battery based on the difference between the voltages input to the two voltage terminals. Since the capacitances of the two capacitor units connected to the two voltage terminals are the same, the value of the difference between the voltages input to the two voltage terminals is not affected by the connection of the capacitors to the voltage terminals. This allows the measuring instrument to accurately measure the impedance of the battery while preventing the flow of DC current from the battery to the measuring instrument.

[0015] 3. The connecting step includes a step of interposing the capacitor unit between each of the two voltage terminals and the battery, and between each of the two current terminals and the battery; 3. The impedance measuring method according to item 1 or 2, wherein the capacitor unit connected to the two voltage terminals and the capacitor unit connected to the two current terminals both have the same capacitance.

[0016] According to this method, the capacitances of the capacitors of the four capacitor units connected to the two voltage terminals and the two current terminals are the same, so that no phase shift occurs between the voltage and the current in the measuring device, and therefore the impedance can be accurately measured regardless of the measurement frequency used in the impedance measurement.

[0017] In addition, four capacitor units with the same capacitance are connected to four terminals. Since the capacitor units to be connected are the same for each terminal, there is no risk of connecting the capacitor units to the wrong destination. The person making the measurement only needs to connect each of the four capacitor units to the four terminals one by one without having to distinguish between them, which improves workability when connecting the capacitor units to the voltage terminals and current terminals.

[0018] 4. The method further includes a mounting step of mounting a plurality of the capacitor units on a measuring tool having a measuring head connected to the battery; The impedance measurement method according to any one of items 1 to 3, wherein the connection step includes a step of connecting the battery connected to the measurement head to the voltage terminal and the current terminal via the plurality of capacitor units attached to the measurement jig.

[0019] According to this method, with multiple capacitor units attached to a measurement jig and a battery connected to a measurement head, the capacitor units can be connected to the voltage and current terminals to connect the batteries to the voltage and current terminals, thereby achieving good connection between the voltage and current terminals and the batteries via the capacitor units.

[0020] 5. An impedance measuring method according to item 4, further comprising a charging step, prior to the measuring step, of charging the plurality of capacitor units attached to the measuring jig by the battery connected to the measuring head.

[0021] According to this method, a plurality of capacitor units attached to the measurement jig are charged before the measurement process by a battery connected to the measurement head of the measurement jig. By bringing the capacitor units into a balanced state before the measurement process, the measurement process can be started with charge already stored in the capacitors, and the capacitor units can effectively prevent DC current from flowing into the measuring instrument during the measurement process.

[0022] In addition, the capacitor unit attached to the measurement jig is kept in a balanced charge state by the battery connected to the measurement head of the measurement jig, so the capacitor unit can be kept in a balanced charge state without the need for a separate charger, power supply, etc.

[0023] In addition, by attaching the battery to be measured to the measurement jig while the capacitor unit is connected, charging of the capacitor unit begins immediately, so the charge of the capacitor unit can be balanced without the need for a separate charging procedure.

[0024] 6. The capacitor unit includes a central conductor having one end and the other end, an outer conductor not in contact with the central conductor, and the capacitor interposed in the central conductor; 6. The impedance measuring method according to claim 5, wherein the charging step includes a step of attaching a termination resistor unit to an end of the capacitor unit opposite to the connection side of the battery, and charging the capacitor with the battery while the central conductor and the outer conductor are connected via the termination resistor unit.

[0025] According to this method, in the charging step, a termination resistor unit is attached to the end of the capacitor unit opposite the end where the battery is connected. By attaching the termination resistor unit to the opposite end of the capacitor unit, the central conductor of the capacitor unit and the external conductor are connected via the termination resistor of the termination resistor unit. This allows current to flow through the central conductor of the capacitor unit, and the capacitors of the capacitor unit are in a charge-balanced state.

[0026] The resistance value of the termination resistor may be set to the same value (eg, 50Ω) as the input impedance (eg, 50Ω) and the output impedance (eg, 50Ω) of the two current terminals of the measuring device.

[0027] By matching the resistance value of the termination resistor with the input / output impedance of the current terminal of the measuring instrument, the charging process can be carried out in a state close to the state when connected to the measuring instrument (actual measurement situation). By charging in this state, the capacitor unit is in a balanced state of charge, and potential disturbances are unlikely to occur in the measurement system when connected to the measuring instrument. This makes it possible to stabilize the potential of the measurement system immediately after connecting the capacitor unit to the measuring instrument.

[0028] 7. The impedance measuring method according to item 5 or 6, wherein the measuring step is started after a predetermined time has elapsed from the start of the charging step.

[0029] According to this method, the charging process continues until a time has passed during which no charge appears to move in the capacitors of the capacitor unit. When no charge moves (hereinafter, this state may be referred to as a "charge-balanced state"), no direct current flows in or out of the capacitors. By starting the measurement process in this state, the flow of direct current into the measuring device can be prevented from the very start of the measurement process.

[0030] 8. The impedance measuring method according to any one of items 5 to 7, further comprising a forced discharging step of forcibly discharging the capacitors of the plurality of capacitor units prior to the charging step.

[0031] According to this method, the capacitor of the capacitor unit is forcibly discharged prior to the charging step. By forcibly discharging the capacitor unit before the charging step, the charging step can be started in a state where no charge exists in the capacitor of the capacitor unit.

[0032] It is possible to allow the capacitors of the capacitor units to discharge naturally rather than forcibly discharging them, but with natural discharge, the amount of charge remaining in the capacitor units after discharge may vary from one capacitor unit to another. Therefore, if natural discharge is performed before the charging process, the charging process may start in a state in which the amounts of charge stored in the multiple capacitor units vary from one another.

[0033] In contrast, according to this method, charging of the multiple capacitor units can be started in a state where the amount of charge stored in each capacitor of the multiple capacitor units is set to zero, thereby making it possible to bring the charges of the multiple capacitor units into a balanced state after the charging process.

[0034] 9. The capacitor unit comprises: a central conductor having one end and an opposite end; an outer conductor not in contact with the central conductor; the capacitor disposed in the central conductor; Item 9. The impedance measuring method according to item 8, wherein the forced discharge step includes a step of short-circuiting two poles of the capacitor by connecting both ends of the central conductor to the outer conductor.

[0035] According to this method, in the forced discharge step, both ends of the central conductor are connected to the outer conductor, thereby shorting the two poles of the capacitor. This allows the charge stored in the capacitor to be forcibly discharged. Therefore, the forced discharge can be achieved relatively easily.

[0036] Moreover, one embodiment of the present invention provides a capacitor unit having the following characteristics.

[0037] 10. A capacitor unit that can be inserted between a coaxial terminal of a measuring instrument that measures the impedance of an object to be measured by a four-terminal pair method and a battery to be measured that is connected to the terminal, a central conductor having one end and an other end; an outer conductor not in contact with the central conductor; a capacitor interposed in the central conductor.

[0038] According to this configuration, with the capacitor unit connected to a coaxial terminal of the measuring device, a capacitor is interposed between the terminal and the battery to be measured. When a charge is stored in the capacitor, the capacitor unit blocks direct current from the battery while allowing signals to be exchanged between the terminal and the coaxial terminal. This makes it possible to measure the impedance of the battery while preventing direct current from the battery from flowing into the measuring device. Therefore, a capacitor unit suitable for measuring the impedance of a battery can be provided.

[0039] 11. The capacitor unit according to item 10, wherein the capacitor includes a plurality of capacitor elements connected in parallel with each other.

[0040] According to this configuration, the capacitance of the capacitor can be changed by changing the number of capacitor elements connected in parallel. Increasing the number of capacitor elements increases the capacitance of the capacitor, making it possible to realize a large-capacity capacitor. The frequency characteristics of a capacitor depend on the capacitance of the capacitor. By increasing the capacitance of the capacitor, the signal frequencies that can pass through the capacitor unit can be expanded to the low-frequency side. This makes it possible to measure the impedance of the battery while preventing the inflow of direct current from the battery, even if the measurement frequency is low.

[0041] 12. The capacitor unit according to item 11, wherein the plurality of capacitor elements include a first capacitor element and a second capacitor element having a smaller capacitance than the first capacitor element.

[0042] According to this configuration, the capacitor includes not only the first capacitor element but also a second capacitor element having a smaller capacitance than the first capacitor element. The second capacitor element having a smaller capacitance easily passes high-frequency signals. By combining the second capacitor element with the first capacitor element to form a capacitor, high-frequency signals can be passed through the capacitor. By including multiple types of capacitor elements having different capacitances in the capacitor, the range of signal frequencies that can pass through the capacitor unit can be expanded to the low frequency side while maintaining high frequencies. This makes it possible to measure the impedance of the battery over a wide frequency range while preventing the inflow of direct current from the battery.

[0043] Moreover, one embodiment of the present invention provides a capacitor unit holding device having the following features.

[0044] 13. A capacitor unit holder for holding the capacitor unit according to any one of items 10 to 12, the capacitor unit having one end and another end, a first cap attached to the one end of the capacitor unit, the first cap electrically connecting the central conductor and the outer conductor when attached to the one end; The capacitor unit holding device further includes a second cap that is attached to the other end of the capacitor unit, and that electrically connects the central conductor and the outer conductor when attached to the other end.

[0045] According to this configuration, with the first cap attached to one end of the capacitor unit and the second cap attached to the other end of the capacitor unit, a short circuit is formed by the central conductor of the capacitor unit, the outer conductor of the capacitor unit, the first cap, and the second cap. This makes it possible to short-circuit the two poles of the capacitor attached to the central conductor of the capacitor unit, and to forcibly discharge the charge stored in the capacitor with a relatively simple configuration. Therefore, it is possible to provide a capacitor holding unit suitable for measuring the impedance of a battery.

[0046] 14. The capacitor unit holder includes a stand base that holds the capacitor unit in a vertical position with the one end and the other end aligned vertically, The second cap is fixed to the stand base, 14. The capacitor unit holding device according to claim 13, wherein the capacitor unit is held on the stand base with the second cap attached to the other end portion.

[0047] According to this configuration, when the capacitor unit is held by the stand, the second cap is attached to the other end of the capacitor unit. Then, the measurer can short-circuit two poles of the capacitor of the held capacitor unit by attaching the first cap to one end of the capacitor unit held by the stand. This makes it possible to forcibly continue discharging the capacitor unit while the capacitor unit is held by the capacitor unit holder.

[0048] Moreover, one embodiment of the present invention provides a capacitor unit system having the following features.

[0049] 15. A capacitor unit according to any one of items 10 to 12, A capacitor unit system comprising: a capacitor unit holding device according to item 13 or 14.

[0050] According to this configuration, with the capacitor unit connected to the coaxial terminal of the measuring device, a capacitor is interposed between the terminal and the battery to be measured. When a charge is stored in the capacitor, the capacitor unit blocks direct current from the battery while allowing signals to be exchanged between the terminal and the coaxial terminal. This makes it possible to measure the impedance of the battery while preventing direct current from flowing into the measuring device.

[0051] Furthermore, with the first cap attached to one end of the capacitor unit and the second cap attached to the other end of the capacitor unit, a short circuit is formed by the central conductor of the capacitor unit, the outer conductor of the capacitor unit, the first cap, and the second cap. This makes it possible to short-circuit the two poles of the capacitor attached to the central conductor of the capacitor unit, and to forcibly discharge the charge stored in the capacitor with a relatively simple configuration.

[0052] Therefore, a capacitor unit system suitable for measuring the impedance of a battery can be provided.

[0053] 16. The capacitor unit has one end and another end, Item 16. The capacitor unit system according to item 15, further comprising a termination resistor unit attached to the one end of the capacitor unit, the termination resistor unit having a termination resistor connected between the central conductor and the outer conductor when attached to the one end.

[0054] According to this configuration, a termination resistor unit is attached to one end of the capacitor unit. By attaching the termination resistor unit to one end of the capacitor unit, the central conductor of the capacitor unit and the outer conductor are connected via the termination resistor of the termination resistor unit. This causes a current to flow through the central conductor of the capacitor unit, and charge is accumulated in the capacitor of the capacitor unit. Therefore, good charging of the capacitor unit can be achieved.

[0055] The resistance value of the termination resistor may be set to the same value as the internal impedance of the measuring device (for example, 50Ω).

[0056] By matching the resistance value of the termination resistor with the internal impedance of the measuring instrument, charging can be started in a state close to the state when connected to the measuring instrument (actual measurement situation). By charging in this state, the capacitor unit is in a balanced state of charge, and potential disturbances are unlikely to occur in the measurement system when connected to the measuring instrument. This makes it possible to stabilize the potential of the measurement system immediately after connecting the capacitor unit to the measuring instrument. [Brief description of the drawings]

[0057] [Figure 1] FIG. 1 is a block diagram for explaining the configuration of a measurement system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic vertical sectional view for explaining a configuration example of a measurement jig included in the measurement system. [Diagram 3]FIG. 3 is a perspective view of the measuring jig, the capacitor unit, and the capacitor unit holding device. [Figure 4] FIG. 4 is a diagram for explaining the configuration of wiring from the measuring device to the battery to be measured. [Diagram 5] FIG. 5 is a schematic diagram for explaining the configuration of the capacitor unit. [Figure 6] FIG. 6 is a schematic circuit diagram for explaining a capacitor included in the capacitor unit. [Figure 7] FIG. 7 is a perspective view of the capacitor unit holding device. [Figure 8] FIG. 8 is a vertical cross-sectional view of the capacitor unit holding device. [Figure 9] FIG. 9 is a flow chart showing the procedure of a battery impedance measuring method using the measurement system. [Figure 10] FIG. 10 is a perspective view showing a state in which four capacitor units are held by the capacitor unit holder. [Figure 11] FIG. 11 is a diagram for explaining the configuration of the wiring from the capacitor unit holder to the upper cap. [Figure 12] FIG. 12 is a perspective view of the measuring jig, the capacitor unit, and the capacitor unit holding device in the charging step (S5 in FIG. 9). [Figure 13] FIG. 13 is a diagram for explaining the configuration of wiring from the battery under measurement to the termination resistor unit in the charging step (S5 in FIG. 9). [Figure 14] FIG. 14 is a schematic circuit diagram of the wiring shown in FIG. [Figure 15] FIG. 15 is a Nyquist diagram showing the results of measuring the impedance of a battery using the measurement system. [Figure 16] FIG. 16 is a Nyquist diagram showing the results of measuring the impedance of a battery using the measurement system. [Figure 17]FIG. 17 is a diagram for explaining the configuration of wiring from a measuring device to a battery to be measured in a measurement system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0059] FIG. 1 is a block diagram for explaining the configuration of a measurement system 1 according to a first embodiment of the present invention. The measurement system 1 includes a measurement device 2, a measurement tool 3, a control device 5, four capacitor units 7, and a capacitor unit holding device 8 (not shown in FIG. 1; see FIG. 3). The measurement system 1 measures the impedance of a battery 20 held by the measurement tool 3. When measuring the impedance using the measurement system 1, the four capacitor units 7 are attached to the measurement tool 3, and the coaxial cables 4 are connected to the corresponding capacitor units 7. That is, the measurement system 1 is configured by connecting the measurement tool 3 to the measurement device 2 via the capacitor units 7 and the coaxial cables 4. Data output by the measurement device 2 is input to the control device 5.

[0060] The measuring device 2 is a frequency response analyzer (FRA) for measuring the impedance of the battery 20 to be measured by frequency response analysis. Specifically, the measuring device 2 may be, for example, a Solartron 1260 measuring device, the specified measurement frequency range of which is 10 μHz to 32 MHz. The Solartron 1260 measuring device is capable of measurement by the four-terminal pair method, and is capable of sweeping from high to low frequencies.

[0061] The measuring device 2 includes a terminal group T1. The terminal group T1 includes four terminals T11 to T14. The four terminals T11 to T14 include a signal output terminal T11 (GEN) and a high-side voltage measurement terminal T12 (V H ) and low-side voltage measurement terminal T13 (V L) and current measurement terminal T14 (I- in ). The signal output terminal T11 and the current measurement terminal T14 are current terminals, and the high-side voltage measurement terminal T12 and the low-side voltage measurement terminal T13 are voltage terminals. All of these four terminals T11 to T14 are coaxial terminals having a pin-shaped signal transmission part in the center and a cylindrical shield part surrounding it.

[0062] The measurement jig 3 includes a holding container 21 and a lid 22 that closes the upper opening of the holding container 21. The battery 20 to be measured is accommodated inside the holding container 21. A heater 23 for heating the battery 20 is disposed inside the holding container 21. Electricity is supplied to the heater 23 through a lead wire 24. The lead wire 24 is drawn out of the measurement jig 3 through the lid 22 and connected to a temperature regulator 28 for controlling the heater 23. In order to control the heater 23 by the temperature regulator 28, a thermocouple 25 for detecting the temperature of the battery 20 to be measured is introduced inside the holding container 21. Since the temperature of the battery 20 to be measured can be considered to be equivalent to the surface temperature of the heater 23, the thermocouple 25 may be disposed so as to be in contact with the surface of the heater 23.

[0063] The measuring jig 3 is cooled by a cooling device 19 as necessary. This allows measurements to be performed at temperatures below room temperature. The cooling device 19 may be a stainless steel dewar containing a refrigerant such as liquid nitrogen. By controlling the power supply to the heater 23 while cooling the measuring jig 3 with the cooling device 19, the temperature of the battery 20 to be measured can be accurately controlled.

[0064] The control device 5 is, for example, a personal computer. The measuring device 2 and the temperature regulator 28 are connected to the control device 5. The control device 5 controls these devices to execute measurement control for acquiring measurement result data output by the measuring device 2 while causing the measuring device 2 to measure the battery 20 that is the measurement target.

[0065] Fig. 2 is a schematic vertical sectional view for explaining a configuration example of the measurement jig 3. In Fig. 2, in order to show as many components as possible, the arrangement of some of the components is changed, and therefore, it does not necessarily show the strict structure.

[0066] The measurement jig 3 includes a holding container 21 that houses the battery 20 to be measured, a lid 22 that closes the opening 21a of the holding container 21, a support assembly 32 that supports the battery 20, and a first electrode lead (measurement head) E1 and a second electrode lead (measurement head) E2 that contact the battery 20 at different positions.

[0067] In this embodiment, the holding container 21 is cylindrical with a bottom, has an opening 21a at the top, and has an outward flange 21b formed around the opening 21a. The lid 22 is attached to the holding container 21 with the lower surface of its peripheral portion aligned with the flange. An O-ring 33 serving as a seal member is sandwiched between the lid 22 and the flange. The lid 22 and the flange 21b are fixed by a clamp 34, thereby fixing the lid 22 to the holding container 21. The holding container 21, the lid 22, and the clamp 34 are made of, for example, stainless steel. The O-ring 33 is made of fluororesin or fluororubber.

[0068] The support assembly 32 is fixed to the underside of the lid 22, and is configured to be housed in the holding container 21 by attaching the lid 22 to the holding container 21. The support assembly 32 includes a plurality of (for example, four) support columns 35 fixed to the lid 22 and extending linearly toward the underside of the lid 22 along the axial direction of the holding container 21, a lower support plate 37 fixed to the middle of the support columns 35, an upper support plate 36 arranged above the lower support plate 37 so as to be movable up and down along the support columns 35, a coil spring 38 wound around each support column 35 between the upper support plate 36 and the underside of the lid 22, and a round nut 39 screwed to each support column 35 between the lower support plate 37 and the upper support plate 36. The four support columns 35 are arranged at equal angular intervals around the central axis of the container. A screw 35a is threaded on the outer periphery of the support column 35, and a round nut 39 is screwed to the screw 35a. The coil spring 38 biases the upper support plate 36 toward the round nut 39, i.e., downward. The support posts 35, the coil spring 38, and the round nut 39 are made of, for example, stainless steel. The upper support plate 36 and the lower support plate 37 are made of, for example, PTFE (polytetrafluoroethylene) or ceramics.

[0069] A first electrode lead E1 is fixed to the lower surface of the upper support plate 36, on the central axis of the holding container 21. The first electrode lead E1 has a contact E1a at its lower end that comes into contact with the battery 20 from above.

[0070] A second electrode lead E2 is fixed to the lower surface of the lower support plate 37 on the central axis of the holding container 21. The second electrode lead E2 has a contact E2a at its upper end, which contacts the battery 20 from below. A recess (a circular recess in plan view in this embodiment) is formed in the center of the upper surface of the lower support plate 37. A plate-shaped heater 23 is disposed in this recess. The contact E2a of the second electrode lead E2 penetrates the lower support plate 37 at the center position of the recess, and further penetrates the center position of the heater 23 and protrudes upward from the upper surface. The battery 20 is disposed on this contact E2a. The heater 23 is, for example, a silicon rubber heater or a ceramic heater. The lower support plate 37 is an example of a measurement target support member that supports the battery 20. A measurement target placement position for placing the battery 20 is set in the recess. The recess is a target support portion that supports the battery 20 , and its bottom surface (more precisely, the surface of the heater 23 ) is a support surface that supports the battery 20 .

[0071] With the bottom surface of the battery 20 to be measured in contact with the contact E2a of the second electrode lead E2, the upper support plate 36 can be lowered to bring the contact E1a of the first electrode lead E1 into contact with the top surface of the battery 20. Specifically, by turning the round nut 39 to move it downward, the upper support plate 36 is pressed down by the spring force of the coil spring 38, and the contact E1a of the first electrode lead E1 reaches the top surface of the battery 20 to be measured. Furthermore, by turning the round nut 39 to move it downward, the spring force of the coil spring 38 presses the contact E1a of the first electrode lead E1 against the top surface of the battery 20 to be measured, and thereby the bottom surface of the battery 20 to be measured is pressed against the contact E2a of the second electrode lead E2.

[0072] The battery 20 to be measured is, for example, a disk-shaped coin battery, with electrodes 20a, 20b formed in advance on its upper and lower surfaces, respectively. The electrode 20a is a positive electrode, and the electrode 20b is a negative electrode. These electrodes 20a and 20b contact the contacts E2a of the first electrode lead E1 and the second electrode lead E2, respectively. The coin battery may be a lithium battery. An example of a lithium coin battery is the CR2032.

[0073] The measuring jig 3 further includes a first coaxial cable 41, a second coaxial cable 42, a third coaxial cable 43, and a fourth coaxial cable 44. These coaxial cables 41 to 44 include core wires 41a to 44a, shield wires 41b to 44b surrounding the core wires 41a to 44a, and insulators 41c to 44c for insulating between the core wires 41a to 44a and the shield wires 41b to 44b. The core wires 41a to 44a are made of, for example, a twisted copper wire or a stainless steel wire. The shield wires 41b to 44b are made of, for example, a twisted copper wire or a stainless steel wire. The insulators 41c to 44c are made of, for example, PTFE, polyimide, or ceramics. For example, when the measuring jig 3 is to be heat-resistant to 250°C or more, the core wires and the shield wires may be made of stainless steel, and the insulator between them may be made of polyimide.

[0074] One end of the core wire 41a of the first coaxial cable 41 and one end of the core wire 42a of the second coaxial cable 42 are each connected to the first electrode lead E1. One end of the core wire 43a of the third coaxial cable 43 and one end of the core wire 44a of the fourth coaxial cable 44 are each connected to the second electrode lead E2.

[0075] The first coaxial cable 41 and the second coaxial cable 42 pass through a through hole (not shown) formed in the upper support plate 36, and their upper ends are respectively coupled to and supported by coaxial feedthroughs 46, 47 that pass through the lid 22. The third coaxial cable 43 and the fourth coaxial cable 44 pass through a through hole (not shown) formed in the lower support plate 37 and further pass through a through hole (not shown) formed in the upper support plate 36, and their upper ends are respectively coupled to and supported by coaxial feedthroughs 48, 49 that pass through the lid 22. The coaxial feedthroughs 46 to 49 are of an insulated type, and pass through the lid 22 and are fixed to the lid 22 with not only the core wire portion but also the shield portion being insulated from the lid 22.

[0076] In order to control the atmosphere inside holding container 21 of measuring jig 3, gas inlet pipe 26 and exhaust pipe 27 are attached to lid 22. For example, the atmosphere inside holding container 21 can be controlled by connecting exhaust pipe 27 to an exhaust facility (not shown) such as a vacuum pump and connecting gas inlet pipe 26 to a gas supply source (not shown) such as an inert gas tank. In this embodiment, gas valves 30, 31 are provided in gas inlet pipe 26 and exhaust pipe 27, respectively.

[0077] FIG. 3 is a perspective view of the measurement jig 3, the capacitor unit 7, and the capacitor unit holding device 8. As shown in FIG. 2 and FIG. 3, the four capacitor units 7 are detachably attached to the lid 22 of the measurement jig 3. The four capacitor units 7 are connected to one end (upper end) of the feedthroughs 46 to 49 fixed to the lid 22 on the outside of the lid 22. The capacitor unit 7 includes a central conductor 11 having one end and the other end, a cylindrical outer conductor 12 surrounding the central conductor 11 in an insulating state, and a capacitor 13 interposed in the middle of the central conductor 11. The four capacitor units 7 have the same capacitance (that is, the capacitances of the capacitors 13 are the same). Hereinafter, for convenience, the capacitor units 7 connected to the first to fourth coaxial cables 41 to 44 may be referred to as capacitor units 7A, 7B, 7C, and 7D, respectively. With the capacitor units 7A, 7B, 7C, and 7D connected to the feedthroughs 46-49, the first to fourth coaxial cables 41-44 are connected to the capacitor units 7A-7D.

[0078] 3, in this state, one end of each of the coaxial cables 4 is connected to one end 7e of the capacitor units 7A-7D (the end opposite to the battery connection side). Then, as shown in FIG. 1, the other end of each of the coaxial cables 4 is connected to the terminals T11-T14 of the measuring device 2. Thereby, the central conductor 11 and the outer conductor 12 of the capacitor units 7A-7D are connected to the signal transmission section and the shield section of the terminals T11-T14, respectively. In this state, the first to fourth coaxial cables 41-44 are connected to the terminals T11-T14 via the capacitor units 7A-7D. The four capacitor units 7A-7D may be connected to each other with a string or chain to prevent loss. Since the four capacitor units 7A-7D are used as a unit, there is no particular problem even if they are connected to each other.

[0079] 3, the capacitor unit holding device 8 includes a capacitor unit holder 81 that holds the four capacitor units 7 in a vertical position. The capacitor unit holder 81 is placed on the same table (not shown) as the measurement jig 3. The capacitor unit holding device 8 and the capacitor units 7 (the four capacitor units 7) form a dedicated capacitor unit system 6 suitable for measuring the impedance of the battery 20.

[0080] 4 is a diagram for explaining the configuration of the wiring from the measuring device 2 to the battery 20 to be measured. The core wire 41a of the first coaxial cable 41 connected to the first electrode lead E1 at a position relatively far from the battery 20 is a current terminal. The core wire 42a of the second coaxial cable 42 connected to the first electrode lead E1 at a position relatively close to the battery 20 is a voltage terminal. The core wire 43a of the third coaxial cable 43 connected to the second electrode lead E2 at a position relatively close to the battery 20 is a voltage terminal. The core wire 44a of the fourth coaxial cable 44 connected to the second electrode lead E2 at a position relatively far from the battery 20 is a current terminal.

[0081] The first electrode lead E1 side end of the shield wire 41b of the first coaxial cable 41 is directly connected to the first electrode lead E1 side end of the shield wire 42b of the second coaxial cable 42 by the first wire 61, and is directly connected to the second electrode lead E2 side end of the shield wire 43b of the third coaxial cable 43 by the second wire 62. The first electrode lead E1 side end of the shield wire 42b of the second coaxial cable 42 is directly connected to the second electrode lead E2 side end of the shield wire 44b of the fourth coaxial cable 44 by the third wire 63. The second electrode lead E2 side end of the shield wire 43b of the third coaxial cable 43 is directly connected to the second electrode lead E2 side end of the shield wire 44b of the fourth coaxial cable 44 by the fourth wire 64. "Direct connection" means that the connection is made without going through the shield wire of another coaxial cable. There is no line that directly connects between the first electrode lead E1 side end and the second electrode lead E2 side end of the shielded wires 41b, 44b of the first coaxial cable 41 and the fourth coaxial cable 44. Furthermore, there is no line that directly connects between the first electrode lead E1 side end and the second electrode lead E2 side end of the shielded wires 42b, 44b of the second coaxial cable 42 and the third coaxial cable 43.

[0082] The first coaxial cable 41 is connected to the signal output terminal T11 of the measuring device 2 via the capacitor unit 7A. The second coaxial cable 42 is connected to the high-side voltage measurement terminal T12 of the measuring device 2 via the capacitor unit 7B. The third coaxial cable 43 is connected to the low-side voltage measurement terminal T13 of the measuring device 2 via the capacitor unit 7C. The fourth coaxial cable 44 is connected to the current measurement terminal T14 of the measuring device 2 via the capacitor unit 7D. Measurement is thereby performed using the four-terminal pair method.

[0083] The measuring device 2 has an internal AC signal source 71, which outputs an AC signal to the signal output terminal T11. This AC signal is applied to the core wire 41a of the first coaxial cable 41 via the central conductor 11 of the capacitor unit 7A. As a result, a current (AC current) is supplied from the core wire 41a of the first coaxial cable 41. This current passes through the first electrode lead E1, the battery 20, and the second electrode lead E2, flows into the core wire 44a of the fourth coaxial cable 44, and is supplied to the ammeter 73 in the measuring device 2 via the central conductor 11 of the capacitor unit 7D. The current that passes through this ammeter 73 passes through the outer conductor 12 of the capacitor unit 7D, through the shield wire 44b of the fourth coaxial cable 44, and then through the first line 61 to the fourth line 64 to be guided to the shield wire 41b of the first coaxial cable 41, and from this shield wire 41b passes through the outer conductor 12 of the capacitor unit 7A and returns to the AC signal source 71.

[0084] The core wire 42a of the second coaxial cable 42 is connected to the high-side voltage measurement terminal T12 of the measuring device 2 via the central conductor 11 of the capacitor unit 7B. The core wire 43a of the third coaxial cable 43 is connected to the low-side voltage measurement terminal T13 of the measuring device 2 via the central conductor 11 of the capacitor unit 7C. The voltmeter 72 inside the measuring device 2 has a differential amplifier 74. The differential amplifier 74 outputs a signal corresponding to the potential difference between the high-side voltage measurement terminal T12 and the low-side voltage measurement terminal T13. Based on this signal, the voltmeter 72 measures the voltage between the core wire 42a of the second coaxial cable 42 and the core wire 43a of the third coaxial cable 43, thereby measuring the voltage across the battery 20 to be measured.

[0085] Then, based on the current measured by the ammeter 73 and the voltage measured by the voltmeter 72, the measuring device 2 calculates the impedance of the battery 20 being measured.

[0086] The target of the measuring device 2 is a battery 20 having an electromotive force. In a state where the positive and negative electrodes of the battery 20 are connected to the first electrode lead E1 and the second electrode lead E2, respectively, two current paths, a first current path and a second current path, are formed as follows. The first current path is a path from the first electrode lead E1 through the core wire 41a of the first coaxial cable 41, the central conductor 11 of the capacitor unit 7A, the AC signal source 71, the shield wire 41b of the first coaxial cable 41, the first wire 61 to the fourth wire 64, the shield wire 44b of the fourth coaxial cable 44, the ammeter 73, the central conductor 11 of the capacitor unit 7D, and the core wire 44a of the fourth coaxial cable 44 to the second electrode lead E2. The second current path runs from the first electrode lead E1, through the core wire 42a of the second coaxial cable 42, the central conductor 11 of the capacitor unit 7B, the shield wire 42b of the second coaxial cable 42, the first wire 61 to the fourth wire 64, the shield wire 43b of the third coaxial cable 43, the central conductor 11 of the capacitor unit 7C and the core wire 43a of the third coaxial cable 43, to the second electrode lead E2.

[0087] In the first current path, capacitor 13 is interposed in central conductor 11 of capacitor unit 7A. If the charge of capacitor 13 in capacitor unit 7A is balanced, no DC current flows in or out of capacitor 13, so no DC current flows in from battery 20 to capacitor unit 7A, and the DC current path (first current path) between battery 20 and measuring device 2 is blocked by capacitor 13.

[0088] On the other hand, in the second current path, capacitor 13 is interposed in central conductor 11 of capacitor unit 7B. If the charge of capacitor 13 in capacitor unit 7B is balanced, no DC current flows in or out of capacitor 13, so no DC current flows in from battery 20 to capacitor unit 7A, and the DC current path (first current path) between battery 20 and measuring device 2 is blocked by capacitor 13.

[0089] In this embodiment, the capacitance of the capacitors in the four capacitor units 7A to 7D is the same. The four capacitor units 7A to 7D also have the same shape and size. Therefore, four capacitor units 7 of the same type are provided and used as the four capacitor units 7A to 7D.

[0090] FIG. 5 is a schematic diagram for explaining a specific configuration of capacitor unit 7. As shown in FIG.

[0091] The capacitor unit 7 includes a central conductor 11, an outer conductor 12 not in contact with the central conductor 11, a capacitor 13, a cylindrical housing 14 surrounding the central conductor 11, the outer conductor 12, and the capacitor 13, and a one-end connector 15 and an other-end connector 16 connected to one end and the other end of the central conductor 11, respectively. In the example of FIG. 5, the outer conductor 12 coaxially surrounds the central conductor 11 in a non-contact state. The one-end connector 15 may include a central conductor 15a and an outer conductor 15b not in contact with the central conductor 15a. The outer conductor 15b may coaxially surround the central conductor 15a in a non-contact state. The other-end connector 16 may include a central conductor 16a and an outer conductor 16b not in contact with the central conductor 16a. The outer conductor 16b may coaxially surround the central conductor 16a in a non-contact state. The capacitor unit 7 is a passive coaxial component. The central conductor 11 includes a signal pattern 11a and a signal pattern 11b formed on the surface of a circuit board 17. The signal pattern 11a is connected to the central conductor 15a of the one-end connector 15. The signal pattern 11b is connected to the central conductor 16a of the other-end connector 16. A plurality of (for example, 12) capacitor elements 18 are mounted between the signal pattern 11a and the signal pattern 11b on the surface of the circuit board 17. The plurality of capacitor elements 18 constitute a capacitor 13. A ground pattern (not shown, for example, a solid pattern) is formed on the back surface of the circuit board 17. This ground pattern is connected to the outer conductor 15b of the one-end connector 15 and the outer conductor 16b of the other-end connector 16.

[0092] The housing 14 is formed, for example, from a metal material. By forming the housing 14 from a metal material, noise resistance is improved. The one-end connector 15 and the other-end connector 16 are configured by coaxial connectors (for example, BNC connectors).

[0093] 6 is a schematic circuit diagram for explaining the capacitor 13 included in the capacitor unit 7. The capacitor 13 includes a plurality of capacitor elements 18 connected in parallel with each other. The plurality of capacitor elements 18 include a plurality of (e.g., eleven) first capacitor elements 18A and one second capacitor element 18B. The capacitance of the second capacitor element 18B is sufficiently smaller than the capacitance of the first capacitor element 18A. The capacitance of the first capacitor element 18A is, for example, 47 μF. The capacitance of the second capacitor element 18B is, for example, 68 pF.

[0094] The capacitance of the capacitor 13 can be changed by changing the number of the first capacitor elements 18A connected in parallel. The capacitance of the capacitor 13 increases by increasing the number of the first capacitor elements 18A, and thus a large-capacity capacitor 13 can be realized. In general, the frequency characteristics of the capacitor 13 depend on the capacitance of the capacitor 13. By increasing the capacitance of the capacitor 13, the signal frequencies that can pass through the capacitor 13 can be expanded to the low-frequency side. When the number of the capacitor elements 18 of the capacitor 13 is 11, the capacitance of the capacitor 13 is about 500 μF, which is a large capacity. When the capacitance of the capacitor 13 is about 500 μF, low-frequency signals of about 100 mHz to 1 Hz can be passed well. This allows the signal frequencies that can pass through the capacitor unit 7 to be expanded to the low-frequency side. Then, by connecting the capacitor unit 7 to the terminals T11 to T14 of the measuring device 2, the impedance of the battery 20 can be accurately measured even when the measurement frequency is low.

[0095] The number of first capacitor elements 18A, 11, is an example and is not limited to this number. To increase the capacitance of capacitor 13, it is preferable that the number of first capacitor elements 18A is more than one, but it may be one. The number of first capacitor elements 18A included in capacitor unit 7 is determined according to the capacitance required for capacitor unit 7 and the storage volume of capacitor unit 7 in housing 14. In addition, the capacitance of first capacitor element 18A is not limited to 47 μF and may be another value.

[0096] Furthermore, a capacitor having a small capacitance generally allows high-frequency signals to pass relatively easily. By combining the second capacitor element 18B having a small capacitance (for example, 68 pF) with the first capacitor element 18A to configure the capacitor 13, not only low-frequency signals but also high-frequency signals can pass through the capacitor 13. The number of the second capacitor elements 18B is one example, and is not limited to this number. Furthermore, the capacitance of the second capacitor element 18B is not limited to 68 pF, and may be another value.

[0097] By using capacitor unit 7 including capacitor 13 composed of multiple types of capacitor elements 18A, 18B with different capacitances, it is possible to widen the frequency range of signals that can pass through capacitor unit 7. Then, by connecting capacitor unit 7 to measuring instrument 2, it is possible to effectively measure impedance over a wide frequency range while preventing the inflow of DC current from battery 20.

[0098] Fig. 7 is a perspective view of the capacitor unit holding device 8. Fig. 8 is a vertical cross-sectional view of the capacitor unit holding device 8.

[0099] The capacitor unit holding device 8 includes a capacitor unit holder 81 that holds the four capacitor units 7 in a vertical position, a lower cap (second cap, see FIG. 8) 83, and a connection terminal (second cap, see FIG. 8) .

[0100] The capacitor unit holder 81 is a stand base that holds four capacitor units 7 in a vertical position, and includes an upper plate 81b having an upper surface 81a. Eight sets of lower caps 83 and connection terminals 84 are arranged in two rows of four on the upper surface 81a of the capacitor unit holder 81. The connection terminals 84 are disposed on the upper surface 81a. Each lower cap 83 is disposed below a corresponding connection terminal 84.

[0101] The lower cap 83 is a coaxial short-circuit plug (for example, a BNC short-circuit plug) and is fixed to the capacitor unit holder 81 in a state insulated from the capacitor unit holder 81.

[0102] The connection terminal 84 is a coaxial feedthrough (e.g., a BNC female-BNC female adapter). The connection terminal 84 is coupled to the lower cap 83 from above and is mechanically and electrically connected to the connection terminal 84. The connection terminal 84 is insulated from the capacitor unit holder 81. A lower portion of the connection terminal 84 is attached to the lower cap 83, for example, by screw coupling. An upper portion of the connection terminal 84 is exposed on the upper surface 81a of the capacitor unit holder 81 and can be attached to the other end 7f of the capacitor unit 7, for example, by screw coupling. Eight connection terminals 84 are exposed on the upper surface 81a of the capacitor unit holder 81.

[0103] Eight through holes 82 are formed in the upper plate 81b of the capacitor unit holder 81. The through holes 82 are, for example, circular. With the connection terminals 84 fitted into the through holes 82 from above, nuts 86 are screwed onto the connection terminals 84 from below the upper plate 81b, thereby fixing the connection terminals 84 to the upper plate 81b. Then, the lower cap 83 is screwed onto the connection terminals 84 fixed to the upper plate 81b from below the upper plate 81b, thereby fixing the lower cap 83 to the upper plate 81b. With the lower cap 83 fastened to the connection terminals 84, an electrical connection between the lower cap 83 and the connection terminals 84 is established.

[0104] A support portion 85 for supporting one capacitor unit 7 from below is formed by one connection terminal 84 and one lower cap 83 coupled to the connection terminal 84. That is, eight support portions 85 for supporting the capacitor units 7 are arranged on the upper surface 81a of the capacitor unit holder 81.

[0105] The eight support parts 85 have the same size and shape. Therefore, it is possible to support the four capacitor units 7 by any of the support parts 85. Note that FIG. 8 shows a state in which the lower cap 83 has been removed from the rightmost support part 85.

[0106] FIG. 9 is a flow chart showing the procedure of the impedance measuring method of the battery 20 using the measurement system 1. FIG. 10 is a perspective view showing a state in which four capacitor units 7A to 7D are held by the capacitor unit holding device 8. FIG. 11 is a diagram for explaining the configuration of the wiring from the capacitor unit holder 81 to the upper cap 80 in the state shown in FIG. 10. FIG. 12 is a perspective view of the measurement tool 3, the capacitor unit 7, and the capacitor unit holding device 8 in the charging step (S5 in FIG. 9). FIG. 13 is a diagram for explaining the configuration of the wiring from the battery 20 to the termination resistor units 9A to 9D in the charging step (S5 in FIG. 9). FIG. 14 is a schematic circuit diagram of the wiring shown in FIG. 13. The procedure of the impedance measuring method of the battery 20 using the measurement system 1 will be explained with reference to FIGS. 1 to 9. FIGS. 10 to 15 will be referred to as appropriate.

[0107] In order to realize the interruption of DC current by capacitor units 7A-7D in measuring the impedance of battery 20, it is necessary that charge has been accumulated in capacitors 13 of capacitor units 7A-7D connected to terminals T11-T14 beforehand at the start of the measurement. For this reason, in the impedance measurement method shown in FIG. 9, a charging process (S5 in FIG. 9) is performed before the measurement process (S7 in FIG. 9), which starts with charging capacitor units 7A-7D and achieves a balanced state of charge. Also, in order to accurately measure the impedance of battery 20, it is necessary that the charges accumulated in capacitors 13 of capacitor units 7A-7D are in a balanced state at the start of the measurement process (S7 in FIG. 9) beforehand. Therefore, in the impedance measuring method shown in Fig. 9, a forced discharge step (S1 in Fig. 9) of forcibly discharging capacitor units 7A to 7D is performed before a charging step (S5 in Fig. 9).

[0108] When no measurement is being performed by the measuring device 2, the four capacitor units 7 are stored in a capacitor unit holding device 8, as shown in Figures 10 and 11. Specifically, the other ends 7f of the four capacitor units 7 are supported by four support portions 85 on an upper surface 81a of the capacitor unit holder 81. The capacitor unit holding device 8 further includes upper caps (first caps) 80 in the same number as the capacitor units 7, and in a state of being stored in the capacitor unit holder 81, the upper caps 80 are attached to one ends 7e (i.e., upper ends) of the capacitor units 7. Next, the lower caps 83 and the upper caps 80 will be described in order.

[0109] As shown in Fig. 11, the lower cap 83 includes a central conductor 83a and a cylindrical external conductor 83b that coaxially surrounds the central conductor 83a in a non-contact state. One end (the lower end shown in Fig. 11) of the central conductor 83a and one end (the lower end shown in Fig. 11) of the external conductor 83b are electrically connected to each other. In a state in which the other end 7f of the capacitor unit 7 is attached to the support part 85, i.e., in a state in which the capacitor unit 7 is supported by the support part 85, the lower cap 83 is connected to the other end 7f of the four capacitor units 7 via the connection terminals 84. In this state, the central conductor 11 and the external conductor 12 of the capacitor unit 7 are electrically connected to each other via the lower cap 83 and the connection terminals 84.

[0110] The upper cap 80 is a coaxial short-circuit plug (for example, a BNC short-circuit plug). As shown in Fig. 11, the upper cap 80 includes a central conductor 80a and a cylindrical outer conductor 80b that coaxially surrounds the central conductor 80a in a non-contact state. One end (the upper end shown in Fig. 11) of the central conductor 80a and one end (the upper end shown in Fig. 11) of the outer conductor 80b are electrically connected to each other. The upper cap 80 can be attached to one end 7e of the capacitor unit 7 by, for example, screw connection. By attaching the upper cap 80 to the one end 7e of the capacitor unit 7, the central conductor 11 and the outer conductor 12 of the capacitor unit 7 are electrically connected via the upper cap 80.

[0111] Therefore, by attaching the upper cap 80 to one end 7e of the capacitor unit 7 with the other end 7f of the capacitor unit 7 supported by the support portion 85, a short circuit is formed by the central conductor 11 of the capacitor unit 7, the outer conductor 12 of the capacitor unit 7, the upper cap 80, the connection terminal 84, and the lower cap 83. This shorts the two poles of the capacitor 13 interposed in the central conductor 11 of the capacitor unit 7. This forcibly discharges the charge accumulated in the capacitor 13 from the capacitor 13, and the capacitor 13 is forcibly discharged (S1 in FIG. 9: forced discharge step). By storing the four capacitor units 7 in the capacitor unit holder 81 with the upper cap 80 attached to the one end 7e, the four capacitor units 7 are maintained in a forcibly discharged state.

[0112] 10, the four termination resistor units 9 are fitted into the remaining four support parts 85 to which no capacitor units 7 are attached, out of the eight support parts 85 on the upper surface 81a of the capacitor unit holder 81. In other words, the remaining four support parts 85 are used for mounting the four termination resistor units 9.

[0113] To measure the impedance of the battery 20, the measurer removes the upper caps 80 from one ends 7e of the four capacitor units 7, takes out the four capacitor units 7 from the capacitor unit holder 81, and attaches them to the measurement jig 3 (S2 in FIG. 9: capacitor unit attachment step). Specifically, the four capacitor units 7 are connected to four feedthroughs 46-49 fixed to the lid 22 of the measurement jig 3, respectively. The four capacitor units 7 have the same shape and size, and the capacitances of the capacitors 13 are the same. Therefore, the four capacitor units 7 may be connected to any of the feedthroughs 46-49.

[0114] Next, as shown in FIG. 12, the measurer attaches a termination resistor unit 9 to each of the four capacitor units 7 attached to the measurement jig 3 (S3 in FIG. 9: termination resistor unit attachment step).

[0115] As shown in FIG. 13, the termination resistor unit 9 is, for example, a coaxial termination connector (for example, a BNC termination plug). The termination resistor unit 9 includes a central conductor 91, a cylindrical outer conductor 92 that coaxially surrounds the central conductor 91 in a non-contact state, and a termination resistor 93 that connects the central conductor 91 and the outer conductor 92. In a usage state of the termination resistor unit 9, one end (upper end shown in FIG. 13) of the central conductor 91 and one end (upper end shown in FIG. 13) of the outer conductor 92 are electrically connected to each other. The termination resistor unit 9 can be attached to one end 7e of the capacitor unit 7 by, for example, screw coupling. In a state where the termination resistor unit 9 is attached to the one end 7e of the capacitor unit 7, the central conductor 91 and the outer conductor 92 of the capacitor unit 7 are connected via the termination resistor 93. Hereinafter, the termination resistor units 9 attached to the capacitor units 7A, 7B, 7C, and 7D may be referred to as termination resistor units 9A, 9B, 9C, and 9D, respectively.

[0116] By attaching the termination resistor units 9A to 9D to the one ends 7e of the capacitor units 7A to 7D, the central conductor 11 and the outer conductor 12 of the capacitor unit 7 are connected via the termination resistors 93 of the termination resistor units 9A to 9D. The resistance values ​​of the termination resistors 93 of the termination resistor units 9A to 9D are the same value (e.g., 50 Ω) as the input impedance (e.g., 50 Ω) of the signal output terminal T11 of the measuring device 2 and the output impedance (e.g., 50 Ω) of the current measurement terminal T14.

[0117] After the termination resistor unit 9 is attached, the battery 20 to be measured is attached to the measurement jig 3 (S4 in FIG. 9: battery attachment step). Specifically, the measurer opens the lid 22, raises the upper support plate 36, and places the battery 20 in the recess of the lower support plate 37. The upper support plate 36 is then lowered to connect the first electrode lead E1 and the second electrode lead E2 to the top and bottom surfaces of the battery 20, respectively, and then the lid 22 is closed. This sets the battery 20 in the measurement jig 3. Because the battery 20 is connected to the first electrode lead E1 and the second electrode lead E2, as shown in FIG. 14, the series circuit of the capacitor unit 7A and the termination resistor unit 9A is connected in parallel to the series circuit of the capacitor unit 7D and the termination resistor unit 9D. In addition, the series circuit of the capacitor unit 7B and the termination resistor unit 9B is connected in parallel to the series circuit of the capacitor unit 7C and the termination resistor unit 9C. The parallel circuit of capacitor unit 7B and capacitor unit 7C and the parallel circuit of capacitor unit 7A and capacitor unit 7D are connected in series to battery 20. In this state, current flows from battery 20 to capacitor units 7A to 7D, and charge is accumulated in capacitors 13 of capacitor units 7A to 7D, eventually resulting in a balanced charge state.

[0118] Charging of capacitors 13 of capacitor units 7A-7D begins immediately after battery 20 is attached to measurement jig 3. Simultaneously with attaching battery 20 to measurement jig 3, the measurer starts activation of temperature regulator 28, causing heater 23 to begin increasing in temperature.

[0119] In this state, the device waits for a predetermined time (about 2 hours) (S5 in FIG. 9: charging step). As a result, the charges of the capacitors 13 of the capacitor units 7A to 7D are balanced. The above-mentioned predetermined time is set so that no charge transfer occurs among the capacitors 13 of the four capacitor units 7A to 7D.

[0120] In addition, the four upper caps 80 that are not used in the charging step (S5 in FIG. 9) are fitted into any four of the eight support parts 85 on the upper surface 81a of the capacitor unit holder 81, as shown in FIG. 12. In other words, the four support parts 85 are used for temporarily placing the four upper caps 80 that are not being used.

[0121] When the above-mentioned predetermined time has elapsed, the measurer removes the termination resistor unit 9 from one end 7e of the capacitor units 7A-7D, and connects one end of the coaxial cable 4 to one end 7e of the capacitor unit 7 as shown in Fig. 3, and connects the other end to terminals T11-T14 of the measuring device 2 (S6 in Fig. 9: connection step). As a result, the battery 20 is connected to the four terminals T11-T14 of the measuring device 2 via the four capacitor units 7A-7D.

[0122] In this state, the measurer measures the impedance of battery 20 using measuring device 2 (S7 in FIG. 9: measurement step). Because the measurement step (S7 in FIG. 9) is performed with the charges of capacitors 13 of capacitor units 7A-7D in a balanced state, the impedance of battery 20 can be measured using measuring device 2 while preventing the flow of DC current into measuring device 2. And because the measurement step (S7 in FIG. 9) starts with no charge movement in capacitor units 7A-7D, the flow of DC current into measuring device 2 can be prevented from the very start of the measurement step (S7 in FIG. 9).

[0123] 3, the four termination resistor units 9 not used for measurement are fitted into the remaining four support parts 85 on which the upper cap 80 is not placed, out of the eight support parts 85 on the upper surface 81a of the capacitor unit holder 81. In other words, the remaining four support parts 85 are used for temporarily placing the four unused termination resistor units 9.

[0124] After the measurement is completed, the measurer stops the temperature regulator 28. Then, the measurer removes the coaxial cables 4 from the four capacitor units 7, and removes the four capacitor units 7 from the lid 22 of the measurement jig 3 and returns them to the capacitor unit holder 81 (S8 in FIG. 9: storage step). Then, the measurer attaches the upper cap 80 to one end 7e of the capacitor unit 7 (S9 in FIG. 9: forced discharge step, see FIG. 10). This forcibly discharges the capacitors 13 of the capacitor unit 7. The measurer also opens the lid 22 of the measurement jig 3 and removes the battery 20 from the measurement jig 3.

[0125] 15 and 16 are Nyquist diagrams showing the results (example) of measuring the impedance of the battery 20 using the measurement system 1. The battery 20 is a coin-type lithium battery (for example, CR2032).

[0126] A Solartron 1260 model was used as the measuring device 2. The lower limit and upper limit measurement frequencies of the measuring device 2 were set to 10 mHz and 10 MHz, respectively. The AC voltage was set to 10 mV, and the number of measurement points per digit was set to 10. The temperature of the battery 20 was room temperature (25°C). The capacitor unit 7 was connected to terminals T11 to T14 of the measuring device 2. The capacitor 13 of the capacitor unit 7 includes eleven first capacitor elements 18A (see FIG. 6) having a capacitance of 47 μF and one second capacitor element 18B (see FIG. 6) having a capacitance of 68 pF. That is, the capacitance of the capacitor unit 7 is about 500 μF.

[0127] Fig. 15 shows the results of impedance measurement performed by omitting the forced discharge step (S1 in Fig. 9) and the charging step (S5 in Fig. 9) from the measurement method shown in Fig. 9, and Fig. 16 shows the results of impedance measurement performed by the measurement method shown in Fig. 9. In the impedance measurement in Fig. 15, the charging step (S5 in Fig. 9) for the capacitor unit 7 was not performed, but a predetermined amount of charge was accumulated in the capacitor unit 7. In Fig. 16, the measured value was disturbed at a measurement frequency of about 100 mHz, so the measurement was stopped at that point. Therefore, no measurement was performed at a measurement frequency below 100 mHz.

[0128] In Fig. 15, a disturbance in the measured impedance value was observed at a measurement frequency of about 66 kHz (see the arrow in the figure). In contrast, in Fig. 16, no particular disturbance in the measured impedance value was observed at the same measurement frequency (see the arrow in the figure). From this measurement result, it can be seen that the impedance value can be measured in a stable state by performing a forced discharge process (S1 in Fig. 9) and a charging process (S5 in Fig. 9) before the measurement process (S7 in Fig. 9).

[0129] As described above, according to this embodiment, the impedance of the battery 20 is measured by the measuring device 2 with the capacitor units 7A to 7D interposed between the terminals T11 to T14 and the battery 20. The capacitances of the capacitors 13 of the four capacitor units 7A to 7D are the same. The capacitor units 7A to 7D cut off the DC current when the charges of the capacitors 13 are balanced. Therefore, the capacitor units 7A to 7D can prevent the DC current from the battery 20 from flowing into the measuring device 2. Since the capacitances of the two capacitor units 7B, 7C connected to the high-side voltage measurement terminal T12 and the low-side voltage measurement terminal T13 are the same, the value of the difference between the voltages input to the high-side voltage measurement terminal T12 and the low-side voltage measurement terminal T13 is not affected by the connection of the capacitor units 7B, 7C to the measurement terminals T12, T13. Furthermore, since the capacitance of capacitor 13 of capacitor units 7A, 7D connected to signal output terminal T11 and current measurement terminal T14, respectively, is the same as that of capacitor units 7B, 7C connected to high-side voltage measurement terminal T12 and low-side voltage measurement terminal T13, respectively (since the amount of charge stored in capacitor units 7A, 7D is the same as the amount of charge stored in capacitor units 7B, 7C), no phase shift occurs between the voltage and current in measuring device 2. As a result, the flow of DC current from battery 20 to measuring device 2 is prevented, while measuring device 2 can accurately measure the impedance of battery 20.

[0130] In addition, the four capacitor units 7A-7D connected to the four terminals T11-T14 have the same shape and size and the capacitance of the capacitors 13 is the same, so there is no need to use different types of capacitor units 7 for each of the connection destination terminals T11-T14. In other words, the measurer need only connect each of the four capacitor units 7 to the four terminals T11-T14 one by one without distinguishing between them. Since there is no mistake in the connection destination of the capacitor units 7A-7D, the workability of connecting the capacitor units 7A-7D to the terminals T11-T14 is good.

[0131] Furthermore, the four capacitor units 7A-7D mounted on the measurement jig 3 are brought into a charge-balanced state (charging step (S5 in FIG. 9)) before the measurement step (S7 in FIG. 9) due to charge transfer originating from the battery 20 connected to the first and second electrode leads E1, E2 of the measurement jig 3. Therefore, the measurement step (S7 in FIG. 9) can be performed with the charge of the capacitor 13 in a balanced state. In particular, in this embodiment, the measurement step (S7 in FIG. 9) starts to be performed after the time (about 2 hours) for the capacitor 13 to reach a charge-balanced state has elapsed (charging step (S5 in FIG. 9)), so that the flow of DC current into the measurement device 2 can be prevented from occurring from the beginning of the measurement step (S7 in FIG. 9).

[0132] The resistance value of the termination resistors 93 of the termination resistor units 9A-9D is the same value (e.g., 50 Ω) as the input impedance (e.g., 50 Ω) of the signal output terminal T11 of the measuring device 2 and the output impedance (e.g., 50 Ω) of the current measurement terminal T14. This allows the charging step (S5 in FIG. 9) to be performed in a state close to the state when connected to the measuring device 2 (actual measurement situation), so that when the charged capacitor units 7A-7D are connected to the measuring device 2, potential disturbance is unlikely to occur in the measurement system. This allows the potential of the measurement system to be stabilized immediately after the capacitor units 7A-7D are connected to the measuring device 2.

[0133] Prior to the charging step (S5 in FIG. 9), the capacitors 13 of the capacitor units 7A to 7D are forcibly discharged (S1 in FIG. 9: forced discharge step). It is also possible to allow the capacitor units 7A to 7D to naturally discharge without forcibly discharging them. However, in the natural discharge, some amount of charge remains in the capacitors 13, and this amount of charge varies for each capacitor 13. If the charging step (S5 in FIG. 9) is started after the natural discharge, there is a risk that the charging step (S5 in FIG. 9) will be started in a state in which the amounts of charge stored in the four capacitor units 7A to 7D vary from one another. By forcibly discharging the capacitors 13 of the capacitor units 7A to 7D before the charging step (S5 in FIG. 9), the charging step (S5 in FIG. 9) can be started in a state in which no charge exists in the capacitors 13 of the capacitor units 7A to 7D. Since charging of the four capacitor units 7A to 7D can be started with the amount of charge stored in the four capacitor units 7A to 7D all set to zero, a state in which the charges of the four capacitor units 7A to 7D are balanced can be achieved after the charging step (S5 in FIG. 9). This allows the measurement step (S7 in FIG. 9) to be started with the charges of the four capacitor units 7A to 7D being balanced.

[0134] FIG. 17 is a diagram for explaining the configuration of wiring from measuring device 202 to battery 20 to be measured according to the second embodiment.

[0135] In FIG. 17, parts common to the first embodiment (the embodiment shown in FIGS. 1 to 16) are given the same reference numerals as in FIGS. 1 to 16, and description thereof will be omitted.

[0136] The measurement system according to the second embodiment differs from the measurement system 1 according to the first embodiment in that it includes a measurement device 202 instead of the measurement device 2. The measurement device 202 is a device for measuring the impedance of the battery 20 to be measured by the automatic balancing bridge method. Specifically, the measurement device 202 may be, for example, an E4990A model or a 4294A model from Keysight Corporation. These measurement devices from Keysight Corporation are capable of measurement by the four-terminal pair method and are capable of sweeping from high frequencies to low frequencies.

[0137] The measuring device 202 has four terminals T21 to T24. The four terminals T21 to T24 include a signal output terminal T21 (H C ) and voltage measurement terminal T22 (H P ) and Null point detection terminal T23 (L P ) and current measurement terminal T24 (L C ). The signal output terminal T21 and the current measurement terminal T24 are current terminals, and the voltage measurement terminal T22 and the null point detection terminal T23 are voltage terminals. All of these four terminals T21 to T24 are coaxial terminals having a pin-shaped signal transmission part in the center and a cylindrical shield part surrounding it.

[0138] In the second embodiment, the impedance of the battery 20 is measured using the measuring device 202 in the same manner as the impedance of the battery 20 is measured using the measuring device 2 in the first embodiment. Specifically, as shown in Figs. 1 and 3, with the four capacitor units 7 mounted on the measuring jig 3, one end of each of the coaxial cables 4 is connected to one end 7e of each of the capacitor units 7A to 7D, and the other end of each of the coaxial cables 4 is connected to the terminals T21 to T24 of the measuring device 202. As a result, the central conductor 11 and the outer conductor 12 of the capacitor units 7A to 7D are connected to the signal transmission section and the shield section of the terminals T21 to T24, respectively. As a result, the first to fourth coaxial cables 41 to 44 are connected to the terminals T21 to T24 of the measuring device 202, respectively.

[0139] Specifically, the first coaxial cable 41 is connected to a signal output terminal T21 of the measuring device 202 via a capacitor unit 7A. The second coaxial cable 42 is connected to a voltage measurement terminal T22 of the measuring device 202 via a capacitor unit 7B. The third coaxial cable 43 is connected to a null point detection terminal T23 of the measuring device 202 via a capacitor unit 7C. The fourth coaxial cable 44 is connected to a current measurement terminal T24 of the measuring device 202 via a capacitor unit 7D. Measurement is thereby performed using the four-terminal pair method.

[0140] The measuring device 202 has an internal AC signal source 271, which outputs an AC signal to the signal output terminal T21. This AC signal is applied to the core wire 41a of the first coaxial cable 41 via the central conductor 11 of the capacitor unit 7A. As a result, a current (AC current) is supplied from the core wire 41a of the first coaxial cable 41. This current passes through the first electrode lead E1, the battery 20, and the second electrode lead E2, flows into the core wire 44a of the fourth coaxial cable 44, and is supplied to the ammeter 274 in the measuring device 202 via the central conductor 11 of the capacitor unit 7D. The current that has passed through ammeter 274 passes through outer conductor 12 of capacitor unit 7D, shield wire 44b of fourth coaxial cable 44, and further passes through first wire 61 to fourth wire 64, and is guided to shield wire 41b of first coaxial cable 41, and from shield wire 41b passes through outer conductor 12 of capacitor unit 7A and returns to AC signal source 271. In this way, a current path is formed that passes from AC signal source 271 through battery 20, and further passes through ammeter 274 and returns to AC signal source 271.

[0141] Core wire 42a of second coaxial cable 42 is connected to voltmeter 272 inside measuring device 202 via central conductor 11 of capacitor unit 7B. Voltmeter 272 measures the voltage between core wire 42a and shield wire 42b of second coaxial cable 42.

[0142] The core wire 43a of the third coaxial cable 43 is connected to a null point detector 273 inside the measuring instrument 202 via the central conductor 11 of the capacitor unit 7C. The null point detector 273 outputs a control signal to a vector signal source 275 inside the measuring instrument 202 so that the potential difference between the core wire 43a and the shield wire 43b of the third coaxial cable 43 becomes zero (this is called virtual ground). This control signal makes the potential difference between the core wire 43a and the shield wire 43b of the third coaxial cable 43 the same potential, that is, makes the potential of the second electrode lead E2 and the potential of the shield wire 42b of the second coaxial cable 42 the same potential as the shield wire, thereby enabling the voltmeter 272 to measure the voltage across the battery 20 and the ammeter 274 to measure the current flowing through the battery 20.

[0143] The measuring device 202 calculates the impedance of the battery 20 based on the current measured by the ammeter 274 and the voltage measured by the voltmeter 272 .

[0144] According to the second embodiment, the impedance of the battery 20 is measured by the measuring device 202 with the capacitor units 7A-7D interposed between the terminals T21-T24 and the battery 20. The capacitances of the capacitors 13 of the four capacitor units 7A-7D are the same. When charge is accumulated in the capacitors 13, the capacitor units 7A-7D cut off the DC current. Therefore, the capacitor units 7A-7D can prevent the DC current from the battery 20 from flowing into the measuring device 202.

[0145] Since the capacitances of the two capacitor units 7B, 7C connected to the voltage measurement terminal T22 and the null point detection terminal T23 are the same, the voltage input to the voltage measurement terminal T22 and the null point detection terminal T23 is not affected by the imbalance caused by the connection of the capacitor units 7B, 7C to the terminal T22. In addition, since the capacitances of the capacitors 13 of the capacitor units 7A, 7D connected to the signal output terminal T21 and the current measurement terminal T24 are the same as those of the capacitor units 7B, 7C connected to the voltage measurement terminal T22 and the null point detection terminal T23, respectively, no phase shift occurs between the voltage and the current in the measuring device 202. As a result, the impedance of the battery 20 can be accurately measured by the measuring device 202 while preventing the flow of DC current from the battery 20 to the measuring device 202.

[0146] In one impedance measurement shown in FIG. 9, the same battery 20 may be measured in sequence by the measuring device 2 (measured by frequency response analysis) and the measuring device 202 (measured by the automatic balancing bridge method). In this case, the battery 20 is measured first by the measuring device 2, and then the battery 20 is measured by the measuring device 202. Specifically, after the measurement step (S7 in FIG. 9) using the measuring device 2 is completed, the other ends of the coaxial cables 4 are removed from the terminals T11 to T14 of the measuring device 2 and connected to the terminals T21 to T24 of the measuring device 202. Then, the measurer measures the impedance of the battery 20 using the measuring device 202 (S7 in FIG. 9: measurement step). After the measurement is completed, the measurer stops the temperature regulator 28. Then, the measurer removes the coaxial cables 4 from the four capacitor units 7, and removes the four capacitor units 7 from the lid 22 of the measurement jig 3 and returns them to the capacitor unit holder 81 (S8 in FIG. 9: storage step). Then, upper caps 80 are attached to one ends 7e of the four capacitor units 7 (S9 in FIG. 9: forced discharge step, see FIG. 10).

[0147] Although two embodiments of the present invention have been described above, the present invention can be embodied in further other forms.

[0148] For example, in the first embodiment, the capacitor units 7A to 7D are connected to all four terminals T11 to T14, and the capacitances of the capacitor units 7A to 7D are the same, but the capacitor unit 7A connected to the signal output terminal T11 may be eliminated. That is, the coaxial cable 4 connected to the first coaxial cable 41 may be directly connected to the signal output terminal T11. Even with the measurement system 1 employing such a connection mode, the capacitances of the two capacitor units 7B and 7C connected to the high-side voltage measurement terminal T12 and the low-side voltage measurement terminal T13 are the same, so that the value of the difference between the voltages input to the high-side voltage measurement terminal T12 and the low-side voltage measurement terminal T13 is not affected by the connection of the capacitor units 7B and 7C to the measurement terminals T12 and T13. Furthermore, since the capacitance of capacitor 13 of capacitor unit 7D connected to current measurement terminal T14 is the same as that of capacitor units 7B and 7C connected to the high-side voltage measurement terminal T12 and the low-side voltage measurement terminal T13, respectively, no phase shift occurs between the voltage and current in measuring device 2. This allows measuring device 2 to accurately measure the impedance of battery 20 while preventing the flow of DC current from battery 20 to measuring device 2.

[0149] It is also possible to leave the capacitor unit 7A connected to the signal output terminal T11 and eliminate the capacitor unit 7D connected to the current measurement terminal T14, thereby allowing the measuring device 2 to accurately measure the impedance of the battery 20 while preventing the flow of DC current from the battery 20 to the measuring device 2.

[0150] Furthermore, the capacitance of capacitor unit 7A and capacitor unit 7D may be different from the capacitance of capacitor units 7B and 7C. When the signal frequency used for impedance measurement is a signal frequency that passes through the capacitance of capacitor units 7A and 7D, the impedance of battery 20 can be accurately measured by measuring device 2.

[0151] Similarly, in the second embodiment, the capacitor unit 7A connected to the signal output terminal T21 may be eliminated. The capacitor unit 7A connected to the signal output terminal T21 may be left, and the capacitor unit 7D connected to the current measurement terminal T24 may be eliminated. The capacitances of the capacitor unit 7A and the capacitor unit 7D may be different from the capacitances of the capacitor units 7B and 7C.

[0152] In the first and second embodiments, the outer conductor 12 of the capacitor unit 7 is described as being cylindrical and coaxially surrounding the outer conductor 12, but the outer conductor 12 is not limited to being cylindrical and may be a square tube. The outer conductor 12 is not necessarily limited to being cylindrical and may be rod-shaped, rectangular parallelepiped-shaped, or the like.

[0153] Furthermore, in the first and second embodiments, the multiple capacitor elements 18 constituting the capacitor 13 have been described as including two types of capacitor elements 18A and 18B, but may include three or more types of capacitor elements.

[0154] In addition, instead of the configuration in which the lower cap 83 is disposed below the upper plate 81b in the first and second embodiments, a configuration in which the lower cap 83 is disposed on the upper surface 81a of the upper plate 81b may be adopted.

[0155] In addition, although the configuration in which lower cap 83 is connected to the other end 7f of capacitor unit 7 via connection terminal 84 has been exemplified, if the other end 7f of capacitor unit 7 and lower cap 83 are configured to be connectable to each other without via connection terminal 84, connection terminal 84 may be omitted and lower cap 83 may be attached directly to the other end 7f. In this case, the other end 7f of capacitor unit 7 is supported by lower cap 83 only.

[0156] Furthermore, the eight support portions 85 on the upper surface 81a of the capacitor unit holder 81 may be arranged in a manner other than two rows of four.

[0157] Furthermore, the number of support parts 85 provided on the capacitor unit holder 81 is set to be greater than the number (four) of capacitor units 7 included in the measurement system 1, but it may be the same number as the capacitor units 7, or may be less than the capacitor units 7. If the number is less than the capacitor units 7, then a plurality of capacitor unit holders 81 must be prepared when measuring the impedance of the battery 20 in the measurement system 1.

[0158] Furthermore, the capacitor unit holder 81 has been described as a stand that holds the four capacitor units 7 in a vertical position, but the capacitor unit holder 81 may be configured to hold the capacitor units 7 in a horizontal position.

[0159] In addition, various design modifications can be made within the scope of the claims. [Explanation of symbols]

[0160] 2:Measuring instrument 3: Measuring fixture 6: Capacitor unit system 7: Capacitor unit 7e: One end (the end opposite the battery connection side) 7f:Other end 8: Capacitor unit holding device 9: Termination resistor unit 11: Center conductor 12: Outer conductor 13: Capacitor 18: Capacitor element 18A: First capacitor element 18B: Second capacitor element 20:Battery 80: Top cap (first cap) 80a: Center conductor 80b: Outer conductor 81: Capacitor unit holder 83: Lower cap (second cap) 83a: Center conductor 83b: Outer conductor 84: Connection terminal (second cap) 91: Center conductor 92: Outer conductor 93: Termination resistor 202: Measuring instrument E1: First electrode lead (measurement head) E2: Second electrode lead (measurement head) T11: Signal output terminal (current terminal) T12: High side voltage measurement terminal (voltage terminal) T13: Low side voltage measurement terminal (voltage terminal) T14: Current measurement terminal (current terminal) T21: Signal output terminal (current terminal) T22: Voltage measurement terminal (voltage terminal) T23: Null point detection terminal (voltage terminal) T24: Current measurement terminal (current terminal)

Claims

1. 1. An impedance measurement method for measuring an impedance of a battery as a measurement object using a measuring device having two voltage terminals and two current terminals to be connected to the measurement object and measuring the impedance of the measurement object by a four-terminal pair method, comprising: a connecting step of connecting the battery to the two voltage terminals and the two current terminals with a capacitor unit including a capacitor interposed between each of the two voltage terminals and the battery and between at least one of the two current terminals and the battery; a measuring step of measuring an impedance of the battery connected to the two voltage terminals and the two current terminals using the measuring device; the capacitor units connected to the two voltage terminals have the same capacitance; The impedance measuring method, wherein the capacitor unit connected to at least one of the two current terminals has a predetermined capacitance.

2. 2. The impedance measuring method according to claim 1, wherein the measuring instrument measures the impedance of the battery based on a difference between voltages input to the two voltage terminals and a current input to one of the two current terminals.

3. the connecting step includes a step of interposing the capacitor unit between each of the two voltage terminals and the battery and between each of the two current terminals and the battery; 3. The impedance measuring method according to claim 1, wherein the capacitor unit connected to the two voltage terminals and the capacitor unit connected to the two current terminals have the same capacitance.

4. The method further includes a mounting step of mounting a plurality of the capacitor units on a measuring tool having a measuring head connected to the battery, 3. The impedance measurement method according to claim 1, wherein the connecting step includes a step of connecting the battery connected to the measurement head to the voltage terminal and the current terminal via the plurality of capacitor units attached to the measurement jig.

5. 5. The impedance measuring method according to claim 4, further comprising a charging step, prior to the measuring step, of charging the plurality of capacitor units attached to the measurement jig by the battery connected to the measurement head.

6. the capacitor unit includes a central conductor having one end and the other end, an outer conductor not in contact with the central conductor, and the capacitor interposed in the central conductor, 6. The impedance measurement method according to claim 5, wherein the charging step includes a step of attaching a termination resistor unit to an end of the capacitor unit opposite to the end connected to the battery, and charging the capacitor with the battery while the central conductor and the outer conductor are connected via the termination resistor unit.

7. 6. The impedance measuring method according to claim 5, wherein the measuring step is started after a predetermined time has elapsed from the start of the charging step.

8. 6. The impedance measuring method according to claim 5, further comprising a forced discharging step of forcibly discharging the capacitor of the capacitor unit prior to the charging step.

9. the capacitor unit includes a central conductor having one end and the other end, an outer conductor not in contact with the central conductor, and the capacitor interposed in the central conductor, 9. The impedance measuring method according to claim 8, wherein the forced discharge step includes a step of short-circuiting two poles of the capacitor by connecting both ends of the central conductor to the outer conductor.

10. A capacitor unit that can be interposed between a coaxial terminal of a measuring instrument that measures the impedance of an object to be measured by a four-terminal pair method and a battery to be measured that is connected to the coaxial terminal, a central conductor having one end and an other end; an outer conductor not in contact with the central conductor; a capacitor interposed in the central conductor.

11. The capacitor unit according to claim 10 , wherein the capacitor includes a plurality of capacitor elements connected in parallel with each other.

12. The capacitor unit according to claim 11 , wherein the plurality of capacitor elements include a first capacitor element and a second capacitor element having a smaller capacitance than the first capacitor element.

13. A capacitor unit holder for holding the capacitor unit according to any one of claims 10 to 12, the capacitor unit having one end and another end, a first cap attached to the one end of the capacitor unit, the first cap electrically connecting the central conductor and the outer conductor when attached to the one end; The capacitor unit holding device further includes a second cap that is attached to the other end of the capacitor unit, the second cap electrically connecting the central conductor and the outer conductor when attached to the other end.

14. the capacitor unit holder includes a stand base that holds the capacitor unit in a vertical position in which the one end and the other end are aligned vertically, The second cap is fixed to the stand base, The capacitor unit holding device according to claim 13 , wherein the capacitor unit is held on the stand base with the second cap attached to the other end portion.

15. A capacitor unit according to any one of claims 10 to 12, A capacitor unit system comprising: a capacitor unit holding device according to claim 13.

16. the capacitor unit having one end and another end, The capacitor unit system according to claim 15, further comprising a termination resistor unit attached to the one end of the capacitor unit, the termination resistor unit having a termination resistor connected between the central conductor and the outer conductor when attached to the one end.

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