Estimation method, estimation device, and computer program

Abstract

This invention provides an estimation method that enables the estimation of the capacity of an energy storage element without interrupting its operation. [Solution] The estimation method obtains the voltage drop amount over a predetermined period in a storage element in a standby state where no charging or discharging operations are being performed, and estimates the capacity of the storage element based on the obtained voltage drop amount and the correlation between the voltage drop amount and the capacity of the storage element.

Description

Technical Field

[0001] The present invention relates to an estimation method, an estimation apparatus, and a computer program.

Background Art

[0002] Electric storage elements are widely used in batteries for power supply devices, batteries for mobile body power or auxiliary equipment in vehicles, railways, aircraft and the like, and batteries for renewable energy power plants that compensate for stable power supply, among other applications. Electric storage elements deteriorate as charging and discharging are repeated. In order to properly operate an electric storage element, it is important to accurately grasp the capacity of the electric storage element.

[0003] Patent Document 1 discloses a full charge-discharge method technology that measures the capacity of an electric storage element by: removing a part of electric storage elements from an electric storage system equipped with electric storage elements, charging the removed electric storage element to a fully charged state, and then completely discharging the electric storage element at a constant discharge current.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] When the full charge-discharge method is employed, it is necessary to stop the operation of the electric storage system in order to diagnose the capacity of the electric storage element.

[0006] An object of the present disclosure is to provide an estimation method and the like that enable capacity estimation of an electric storage element without stopping operation.

Means for Solving the Problem

[0007] One aspect of the estimation method relating to this disclosure involves obtaining the voltage drop amount over a predetermined period in a storage element in a standby state where no charging or discharging operations are being performed, and estimating the capacity of the storage element based on the obtained voltage drop amount and the correlation between the voltage drop amount and the capacity of the storage element.

[0008] An estimation device relating to one aspect of this disclosure includes a processing unit that acquires the amount of voltage drop over a predetermined period in a storage element in a standby state where no charging or discharging operations are being performed, and that performs a process to estimate the capacity of the storage element based on the acquired amount of voltage drop and the correlation between the amount of voltage drop and the capacity of the storage element.

[0009] A computer program relating to one aspect of this disclosure obtains the amount of voltage drop over a predetermined period in a storage element in a standby state where no charging or discharging operations are being performed, and causes the computer to perform a process to estimate the capacity of the storage element based on the obtained amount of voltage drop and the correlation between the amount of voltage drop and the capacity of the storage element. [Effects of the Invention]

[0010] According to this disclosure, the capacity of the energy storage element can be estimated without stopping its operation. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram illustrating the overview of the estimation system. [Figure 2] This is a block diagram showing an example configuration of an uninterruptible power supply (UPS). [Figure 3] This is a block diagram showing an example configuration of an estimation device. [Figure 4] This diagram illustrates the capacity estimation method performed by the estimation device. [Figure 5] This flowchart shows an example of the processing steps performed by the estimation device. [Modes for carrying out the invention]

[0012] This disclosure will be described in detail with reference to drawings illustrating embodiments thereof.

[0013] (1) An estimation method according to one aspect of the present disclosure obtains the amount of voltage drop over a predetermined period in a storage element in a standby state where no charging or discharging operations are being performed, and estimates the capacity of the storage element based on the obtained amount of voltage drop and the correlation between the amount of voltage drop and the capacity of the storage element.

[0014] According to the estimation method described in (1) above, the capacity can be estimated using the voltage drop of the energy storage element during operation, making it possible to estimate the capacity of the energy storage element without stopping the operation of the system equipped with the energy storage element. Special energizing work or data measurement for capacity estimation is unnecessary, and capacity estimation can be easily performed using relatively short-term measurement values ​​collected as operational data.

[0015] One possible method for estimating capacity is to create partial charge-discharge curves for energy storage elements from system operation data and estimate the capacity from these partial charge-discharge curves. However, this method only yields partial charge-discharge curves, making it difficult to improve the accuracy of capacity diagnosis. In particular, for energy storage elements used in uninterruptible power supplies (UPS), considering their intended use, it is undesirable to shut down the power supply's input / output for extended periods for capacity diagnosis. In methods using partial charge-discharge characteristics, since UPS units are not used when there is no power outage, only charge-discharge curves over a narrower range can be obtained, resulting in an even greater decrease in the accuracy of capacity diagnosis.

[0016] The estimation method described herein utilizes standby operation data detected by various systems, including uninterruptible power supplies, thereby improving the accuracy of capacity diagnosis for various energy storage elements. Even in a standby state where no charging or discharging is occurring, i.e., when no power is supplied, a dark current flows through the energy storage element. Dark current is a small current output from the energy storage element in its standby state. In a standby state where a constant dark current flows, the voltage fluctuates in response to the dark current, so by focusing on the standby state, the voltage drop can be detected with high accuracy. By utilizing the known correlation between the voltage drop and capacity of energy storage elements, the capacity corresponding to the voltage drop of the energy storage element can be estimated efficiently and accurately.

[0017] (2) In the estimation method of (1) above, a voltage drop amount per unit current may be obtained by dividing the voltage drop amount over the predetermined period by a dark current flowing through the power storage element, and the capacity of the power storage element may be estimated based on the obtained voltage drop amount per unit current and the correlation between the voltage drop amount per unit current and the capacity.

[0018] According to the configuration of (2) above, the total voltage drop amount over a predetermined period can be converted into a voltage drop amount per unit current by using the dark current flowing through the power storage element in a standby state. The voltage drop amount per unit current corresponds to a direct current resistance component that causes the voltage drop of the total voltage drop amount over the predetermined period. By using the direct current resistance component obtained from the total voltage drop amount, the capacity corresponding to the direct current resistance component can be accurately estimated by using the correlation between the known direct current resistance component and the capacity. The dark current value and direct current resistance of the power storage element in the standby state can be visualized, so that the operating state of the system can be accurately grasped.

[0019] In the estimation method of (1) above, the direct current resistance component that causes the voltage drop of the voltage drop amount may be obtained by dividing the voltage drop amount by the dark current flowing through the power storage element, and the capacity may be estimated based on the obtained direct current resistance component and the correlation between the direct current resistance component that causes the voltage drop and the capacity.

[0020] (3) In the estimation method of (1) or (2) above, the length of the predetermined period may be equal to or less than the length of a period in which the amount of change in the capacity of the power storage element when a dark current flows reaches a predetermined value.

[0021] According to the configuration of (3) above, a period that generates a voltage drop necessary and sufficient for accurately estimating the capacity can be set.

[0022] (4) In the estimation method according to any one of (1) to (3) above, the power storage element may be one used in an uninterruptible power supply.

[0023] According to the configuration described in (4) above, the capacity of the energy storage element for the uninterruptible power supply, in which system shutdown is particularly undesirable, can be estimated, thus allowing the effects of the present invention to be demonstrated more significantly.

[0024] (5) In the estimation method described in (4) above, the uninterruptible power supply may include a first operating mode in which the energy storage element is not charged or discharged, and a second operating mode in which the energy storage element is charged.

[0025] According to the configuration described in (5) above, the voltage drop in the unpowered state can be accurately detected using a storage element in the first operating mode, which does not perform charging or discharging operations.

[0026] (6) An estimation device according to one aspect of the present disclosure includes a processing unit that acquires the amount of voltage drop over a predetermined period in a storage element in a standby state where no charging or discharging operations are being performed, and that performs a process to estimate the capacity of the storage element based on the acquired amount of voltage drop and the correlation between the amount of voltage drop and the capacity of the storage element.

[0027] (7) A computer program according to one aspect of the present disclosure obtains the amount of voltage drop over a predetermined period in a storage element in a standby state where no charging or discharging operations are being performed, and causes the computer to perform a process to estimate the capacity of the storage element based on the obtained amount of voltage drop and the correlation between the amount of voltage drop and the capacity of the storage element.

[0028] This disclosure will be described in detail with reference to drawings illustrating embodiments thereof.

[0029] Figure 1 shows an overview of the estimation system 100. The estimation system 100 of this embodiment comprises an energy storage device 1 having an energy storage element 10 and an estimation device 2. The energy storage device 1 and the estimation device 2 are communicated together via a network N. The number of energy storage devices 1 is not limited.

[0030] The energy storage element 10 is preferably a rechargeable battery such as a lithium-ion battery or a lead-acid battery, or a capacitor. The energy storage element 10 may also be an all-solid-state battery, a lead-acid battery, a redox flow battery, a zinc-air battery, an alkaline manganese battery, a lithium-sulfur battery, a sodium-sulfur battery, a silver-zinc oxide battery, a nickel-metal hydride battery, a molten salt thermal battery, etc. The energy storage element 10 may also be an energy storage cell such as a lithium-ion battery, a module with multiple energy storage cells connected together, a bank with multiple modules connected together, a domain with multiple banks, or an energy storage unit with multiple domains.

[0031] The energy storage device 1 can be used, for example, in uninterruptible power supplies (UPS), DC power supplies, thermal power generation systems, mega solar power generation systems, wind power generation systems, and stabilized power supply systems for railways. The energy storage device 1 is not limited to industrial use; it may also be for household use.

[0032] The energy storage device 1 includes measuring devices, a management device, and a communication device (not shown). The communication device may be integrated with the management device. The measuring devices repeatedly measure the current, voltage, and temperature of the energy storage element 10 at appropriate intervals. The management device acquires the measured values ​​such as current, voltage, and temperature in a time series via the communication device and manages the energy storage device 1 based on the acquired measured values ​​and values ​​calculated from those measured values ​​(e.g., SOC (State of Charge)). The management device provides operational data, including the current, voltage, temperature, and SOC of the energy storage element 10, to the estimation device 2 via the communication device.

[0033] Estimation device 2 is an information processing device capable of various information processing and information transmission / reception related to the estimation of the capacity of the energy storage element 10. Estimation device 2 is, for example, a server computer, a personal computer, a quantum computer, etc. Estimation device 2 can transmit and receive information with the energy storage device 1 via the network N.

[0034] Network N is a wired or wireless network, including, for example, the internet, a carrier network that implements wireless communication according to a predetermined mobile communication standard, or a general optical fiber line. Network N may also include a local network, such as one used by the manufacturer or maintenance company of the energy storage device 1.

[0035] The estimation method, estimation apparatus, and computer program of this disclosure will be explained below, using the case of estimating the capacity of the energy storage device 1 used in an uninterruptible power supply as an example.

[0036] Figure 2 is a block diagram showing an example configuration of an uninterruptible power supply (UPS) 3. The UPS 3 comprises a power storage device 1, a control device 31, a power converter 32, a switching unit 33, an input terminal 34a, and an output terminal 34b.

[0037] Input terminal 34a receives AC power supplied from grid power 41. Output terminal 34b is connected to load 42. AC power is output to load 42 via output terminal 34b.

[0038] The input terminal 34a and the output terminal 34b are connected by a main circuit 35. The main circuit 35 includes branch circuits 36 that branch off at a branching point. The other end of the branch circuit 36 ​​is connected to the energy storage device 1. A power converter 32 is provided between the branching point of the branch circuit 36 ​​and the energy storage device 1. The uninterruptible power supply 3 also includes a bypass circuit 37 that bypasses the AC power input to the input terminal to the output terminal 34b without performing power input or output to the energy storage device 1 and the power converter 32. One end of the bypass circuit 37 is connected to the section of the main circuit 35 from the connection point with input terminal 34a to the branching point, and the other end is connected to the section of the main circuit 35 from the branching point to the connection point with output terminal 34b.

[0039] The control device 31 is connected to the power converter 32 and the switching unit 33 via a communication line. The control device 31 includes an arithmetic circuit such as a CPU (Central Processing Unit) (not shown), a storage device such as ROM (Read Only Memory) and RAM (Random Access Memory), I / O terminals, etc., and controls the operation of the uninterruptible power supply 3.

[0040] The power converter 32 includes a bidirectional DC / AC converter, a switching element, a capacitor, and the like. The power converter 32 converts AC power and DC power bidirectionally. Alternatively, the power converter 32 may include a DC / AC inverter, an AC / DC converter, a DC / DC converter, and the like.

[0041] When the grid power supply 41 is functioning normally, the power converter 32 converts the AC power supplied from the grid power supply 41 into the desired DC power and supplies it to the energy storage device 1. When the grid power supply 41 is malfunctioning, the power converter 32 converts the DC power supplied from the energy storage device 1 into the desired AC power and supplies it to the load 42. In response to a command from the control device 31, the power converter 32 selectively performs either charging the energy storage device 1 from the grid power supply 41 or discharging the energy storage device 1 to the load 42.

[0042] The switching unit 33 includes a first switching unit 33a, a second switching unit 33b, and a third switching unit 33c. Each of the first to third switching units 33a to 33c is a switch that includes, for example, two transistors or thyristors connected in antiparallel to each other. Each of the first to third switching units 33a to 33c switches on / off without interruption in response to a command from the control device 31.

[0043] The first switching section 33a is provided in the section from the connection point of the main circuit 35 to one end of the bypass circuit 37 to the branching point. The second switching section 33b is provided in the section from the connection point of the branch circuit 36 ​​to the main circuit 35 to the power converter 32. The third switching section 33c is provided in the bypass circuit 37.

[0044] The uninterruptible power supply (UPS) 3 has operating modes including standby mode, charging operation mode, and abnormal operation mode. The UPS 3 can selectively execute one of the standby mode, charging operation mode, or abnormal operation mode. When the grid power supply 41 is functioning normally, the UPS 3 operates in standby mode or charging operation mode. In the event of an abnormality, such as a power outage, when power from the grid power supply 41 is cut off, the UPS 3 operates in abnormal operation mode.

[0045] In standby mode, the third switching unit 33c is turned on, and the first switching unit 33a and the second switching unit 33b are turned off. In standby mode, power from the grid power supply 41 is supplied to the load 42 via the bypass circuit 37 and the third switching unit 33c, and no power input or output is performed to the energy storage device 1. In standby mode, the energy storage device 1 is in a standby state and is not performing any charging or discharging operations.

[0046] In the abnormal operation mode, the second switching unit 33b is turned on, and the first switching unit 33a and the third switching unit 33c are turned off. In the abnormal operation mode, the discharge operation of the energy storage device 1 supplies power from the energy storage device 1 to the load 42 via the branch circuit 36, the second switching unit 33b, and the main circuit 35.

[0047] In charging operation mode, the first switching unit 33a and the second switching unit 33b are turned on, and the third switching unit 33c is turned off. In charging operation mode, power from the grid power supply 41 is supplied to the load 42 via the main circuit 35 and the first switching unit 33a, and is also supplied to the energy storage device 1 via the main circuit 35, the first switching unit 33a, the branch circuit 36, and the second switching unit 33b, thereby charging the energy storage device 1.

[0048] Figure 3 is a block diagram showing an example configuration of the estimation device 2. The estimation device 2 comprises a processing unit 21, a storage unit 22, a communication unit 23, a display unit 24, and an operation unit 25.

[0049] The processing unit 21 comprises one or more processors such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). The processing unit 21 includes memory, which is a temporary storage medium such as SRAM (Static Random Access Memory) and DRAM (Dynamic Random Access Memory). The processing unit 21 may also include functions such as a timer for measuring the elapsed time from the time a measurement start instruction is given to the time a measurement end instruction is given, a counter for counting numbers, and a clock for outputting date and time information. The processing unit 21 may be implemented in software, or part or all of it may be implemented in hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array).

[0050] The storage unit 22 includes, for example, a non-volatile storage device such as a hard disk or flash memory. The storage unit 22 is separate from the estimation device 2 and may be one or more externally connected external storage devices. The storage unit 22 stores various computer programs and data referenced by the processing unit 21. In this embodiment, the storage unit 22 stores a program 221 for causing the computer to execute processing related to the estimation of the capacity of the energy storage element 10, an operation DB (Data Base) 222, correlation information 223, and dark current information 224.

[0051] The operation DB222 is a database that stores operation data for each energy storage element 10. The operation DB222 stores, for example, an energy storage element ID for identifying the energy storage element 10, the date and time of measurement of the operation data, and the operation data itself, in association with each other. The operation data includes, for example, the current, voltage, temperature, and state of charge (SOC) of the energy storage element 10. The estimation device 2 stores the operation data in the operation DB222 each time it acquires operation data from each energy storage device 1.

[0052] Correlation information 223 includes information showing the correlation between the DC resistance component of the energy storage element 10 and its storage capacity. Dark current information 224 includes information regarding the dark current value of the energy storage element 10.

[0053] The computer program (program product) including program 221 may be provided on a non-temporary recording medium 2A on which the computer program is recorded in a readable format. The recording medium 2A is a portable memory such as a CD-ROM, USB memory, or SD (Secure Digital) card. The processing unit 21 reads the desired computer program from the recording medium 2A using a reading device (not shown) and stores the read computer program in the storage unit 22. Alternatively, the computer program may be provided by communication. Program 221 may be a single computer program or may consist of multiple computer programs. Program 221 may also be executed on a single computer or executed collaboratively by multiple computers.

[0054] The communication unit 23 is equipped with a communication device that enables communication via the network N. The processing unit 21 sends and receives data to and from the energy storage device 1 via the communication unit 23.

[0055] The display unit 24 includes a display device such as a liquid crystal display or an organic EL (Electro-Luminescence) display. The display unit 24 displays various information according to instructions from the processing unit 21.

[0056] The operation unit 25 is an interface that receives user input. The operation unit 25 includes, for example, a keyboard, mouse, touch panel device with a built-in display, speaker, and microphone. The operation unit 25 receives user input and sends control signals to the processing unit 21 according to the content of the operation.

[0057] The estimation device 2 may be configured to receive operations via an externally connected computer and output information to be notified to the external computer. In this case, the estimation device 2 does not need to have a display unit 24 and an operation unit 25.

[0058] In this embodiment, the estimation device 2 is installed at a location separate from the energy storage device 1. Alternatively, the estimation device 2 may be installed within the facilities of any of the energy storage devices 1. The management device of the energy storage device 1 or the control device 31 of the uninterruptible power supply 3 may function as the estimation device 2.

[0059] Figure 4 illustrates the capacity estimation method performed by the estimation device 2. The estimation method of this embodiment estimates the capacity of the energy storage element 10 based on the voltage drop in the standby state of the energy storage element 10. Here, "capacity" may refer to the energy storage capacity of the energy storage element 10 or its discharge capacity. The capacity may also be expressed as an amount of electricity or as a ratio such as the capacity retention rate (SOH: State of Health).

[0060] The standby state refers to a state in which the energy storage element 10 is not performing any charging or discharging operations. In the standby state, the energy storage element 10 is not being charged by the grid power supply 41, and there is no discharge from the energy storage element 10 to the load 42.

[0061] Whether or not the energy storage element 10 is in a standby state can be determined, for example, based on the operating mode of the uninterruptible power supply 3. If the operating mode of the uninterruptible power supply 3 is standby mode, the energy storage element 10 is determined to be in a standby state. If the operating mode of the uninterruptible power supply 3 is not standby mode, the energy storage element 10 is determined to be not in a standby state. Alternatively, the energy storage element 10 may be determined to be in a standby state if the value of the current flowing through the energy storage element 10 is less than a preset current threshold.

[0062] When the energy storage element 10 is in standby mode, a dark current flows through it. Dark current is a small current output from the energy storage element 10 when it is in standby mode. Dark current cannot usually be accurately detected by measuring devices such as current sensors. When a certain amount of dark current flows through the energy storage element 10 in standby mode, the voltage of the energy storage element 10 drops.

[0063] As shown in the upper part of Figure 4, the estimation device 2 acquires the voltage drop of the energy storage element 10 over a predetermined sampling period during the duration of the standby state. The voltage drop over the sampling period is denoted as ΔV [V]. The voltage drop ΔV is the difference between the voltage value at the start of the sampling period (t1 in Figure 4) and the voltage value at the end of the sampling period (t2 in Figure 4) in the energy storage element 10.

[0064] The start time of the sampling period may be, for example, the start time of the standby state. The length of the sampling period may be set to a length that is sufficient for the voltage drop to settle to a certain value, or a length that is sufficient to produce a certain voltage drop. The length of the sampling period may be, for example, a predetermined fixed sampling time, or it may be less than or equal to the length of the period during which the change in the SOC (State of Charge) of the energy storage element 10, which is expected when discharged at a predetermined dark current value, reaches a predetermined value.

[0065] Estimation device 2 converts the acquired voltage drop ΔV during the sampling period into a voltage drop per unit current. The voltage drop per unit current is calculated by dividing the voltage drop ΔV by the dark current flowing through the energy storage element 10. The voltage drop per unit current corresponds to the DC resistance component that produces a voltage drop corresponding to the dark current flowing through the energy storage element 10. The DC resistance component includes ohmic resistance, transport-diffusion resistance, and charge resistance, etc.

[0066] Let Id [A] be the dark current value flowing through the energy storage element 10, and DCR [Ω] be the DC resistance component value. The DC resistance component value DCR is expressed by the following formula using the voltage drop ΔV and the dark current value Id. DCR = ΔV / Id

[0067] The dark current value Id can be estimated in advance, for example, based on the design of the uninterruptible power supply 3. Specifically, the dark current value Id can be the value obtained by dividing the total amount of electricity stored in the energy storage element 10 during the charging operation mode performed immediately before a specific standby mode by the total time of the specific standby mode. Alternatively, the dark current value Id may be estimated based on the operational data of the energy storage element 10. Specifically, the dark current value Id can be the value obtained by dividing the amount of electricity corresponding to a specific voltage by the integration time, based on the voltage value of the energy storage element 10 for a predetermined period obtained from the initial operational data of the energy storage element 10 and the amount of electricity-voltage characteristics obtained by current integration. The estimated dark current value Id is stored in advance in the storage unit 22 of the estimation device 2 as dark current information 224. The dark current value Id may be prepared separately for each energy storage element to be estimated, or for each type of energy storage element that distinguishes the energy storage element 10 according to its configuration and application.

[0068] The estimation device 2 estimates the capacity value of the energy storage element 10 based on the derived DC resistance component value DCR and the correlation between the DC resistance component and capacity of the energy storage element 10.

[0069] The correlation between the DC resistance component and capacitance is predetermined, for example, based on measured data from durability tests. The correlation between the DC resistance component and capacitance may be set taking into account the length of the sampling period for the voltage drop ΔV. As shown in the lower part of Figure 4, the correlation between the DC resistance component and capacitance is, as an example, a DC resistance component-capacitance curve showing the relationship between the DC resistance component and capacitance, or an approximation function representing the said DC resistance component-capacitance curve. The DC resistance component-capacitance curve is obtained by plotting the capacitance and DC resistance component obtained from measured data on a two-dimensional coordinate system with capacitance on the horizontal axis and DC resistance component on the vertical axis, and creating an approximation line for these plots. The approximation method is not particularly limited and may be approximated by an appropriate function. The derived DC resistance component-capacitance curve or approximation formula is stored in advance in the storage unit 22 of the estimation device 2 as correlation information 223. The correlation between the DC resistance component and the capacitance may be provided separately for each energy storage element being estimated, or for each type of energy storage element, distinguishing the energy storage element 10 according to its configuration, application, etc.

[0070] Estimation device 2 identifies the capacitance value corresponding to the derived DC resistance component value DCR based on the DC resistance component-capacitance curve or approximation formula. The identified capacitance value is estimated to be the capacitance value of the energy storage element 10.

[0071] In the estimation process described above, the voltage drop ΔV during the sampling period does not necessarily have to be converted to the DC resistance component DCR; it may be converted to an index other than the DC resistance component DCR. The capacitance estimation method based on the DC resistance component DCR is not limited to the example described above.

[0072] Figure 5 is a flowchart showing an example of a processing procedure performed by the estimation device 2. The processing in the following flowchart is executed by the processing unit 21 according to the program 221 stored in the memory unit 22 of the estimation device 2.

[0073] The processing unit 21 of the estimation device 2 determines whether the energy storage element 10 is in a standby state by, for example, determining whether the operating mode of the uninterruptible power supply 3 is in standby mode (step S11).

[0074] If the uninterruptible power supply 3 is not operating in standby mode and the processing unit 21 determines that the energy storage element 10 is not in standby mode (S11: NO), the processing unit 21 returns to step S11 and waits until the element enters standby mode.

[0075] If the uninterruptible power supply 3 is in standby mode and the energy storage element 10 is determined to be in standby mode (S11: YES), the processing unit 21 determines whether a predetermined sampling period has elapsed since the standby state began (step S12).

[0076] If it is determined that the sampling period has not elapsed (S12: NO), the processing unit 21 returns to step S12 and waits until the sampling period has elapsed.

[0077] If it is determined that the sampling period has elapsed (S12: YES), the processing unit 21 calculates the voltage drop ΔV of the energy storage element 10 during the sampling period based on the operation data stored in the operation DB 222 (step S13). In step S13, the processing unit 21 calculates the voltage drop ΔV from the start to the end of the sampling period by calculating the difference between the voltage value of the energy storage element 10 at the start of the sampling period and the voltage value of the energy storage element 10 at the end of the sampling period.

[0078] The processing unit 21 obtains a dark current value Id corresponding to the energy storage element 10 by referring to the dark current information 224 stored in the memory unit 22 (step S14). The processing unit 21 calculates the DC resistance component value DCR that produces a voltage drop corresponding to the voltage drop amount ΔV by dividing the calculated voltage drop amount ΔV by the obtained dark current value Id (step S15). The DC resistance component value DCR corresponds to the voltage drop amount per unit current.

[0079] The processing unit 21 refers to the correlation information 223 stored in the memory unit 22 to obtain the correlation between the DC resistance component and capacitance corresponding to the energy storage element 10 (step S16). Based on the obtained correlation between the DC resistance component and capacitance, the processing unit 21 estimates the capacitance corresponding to the calculated DC resistance component value DCR (step S17).

[0080] The processing unit 21 displays the capacity estimation result on the display unit 24 (step S18), and then terminates the series of processes.

[0081] According to this embodiment, the capacity of the energy storage element can be estimated based on the voltage drop of the energy storage element in the standby state measured during operation.

[0082] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the claims and equivalents thereof. The sequences shown in each embodiment are not limiting, and within the bounds of consistency, the order of each processing step may be changed, and multiple processes may be executed in parallel. The processing entity for each process is not limiting, and within the bounds of consistency, the processing of each device may be executed by other devices.

[0083] The matters described in each embodiment can be combined with each other. Furthermore, the independent and dependent claims described in the claims can be combined with each other in any combination, regardless of the form of reference. In addition, the claims use a form in which claims referencing two or more other claims (multi-claim form), but are not limited to this. A form in which multi-claims referencing at least one multi-claim (multi-multi-claim) may also be used. [Explanation of symbols]

[0084] 100 Estimation Systems 1. Energy storage device 10 Energy storage elements 2 Estimation device 21 Processing Unit 22 Memory section 23 Communications Department 24 Display 25 Control section 221 Programs 2A recording medium 3 Uninterruptible power supply

Claims

1. The voltage drop over a predetermined period is obtained in a power storage element in a standby state where no charging or discharging operations are being performed. Based on the acquired voltage drop and the correlation between the voltage drop and capacity of the energy storage element, the capacity of the energy storage element is estimated. Estimation method.

2. The voltage drop per unit current is obtained by dividing the voltage drop amount during the predetermined period by the dark current flowing through the energy storage element. Based on the acquired voltage drop per unit current and the correlation between the voltage drop per unit current and the capacity, the capacity of the energy storage element is estimated. The estimation method according to claim 1.

3. The length of the predetermined period is less than or equal to the length of the period during which the change in the capacity of the energy storage element when a dark current flows is equal to a predetermined value. The estimation method according to claim 1 or claim 2.

4. The aforementioned energy storage element is used in an uninterruptible power supply. The estimation method according to claim 1 or claim 2.

5. The uninterruptible power supply (UPS) includes a first operating mode in which the energy storage element is not charged or discharged, and a second operating mode in which the energy storage element is charged. The estimation method according to claim 4.

6. The voltage drop over a predetermined period is obtained in a power storage element in a standby state where no charging or discharging operations are being performed. Based on the acquired voltage drop and the correlation between the voltage drop and capacity of the energy storage element, the capacity of the energy storage element is estimated. It includes a processing unit that performs processing. Estimation device.

7. The voltage drop over a predetermined period is obtained in a power storage element in a standby state where no charging or discharging operations are being performed. Based on the acquired voltage drop and the correlation between the voltage drop and capacity of the energy storage element, the capacity of the energy storage element is estimated. A computer program that causes a computer to perform a process.

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