Power storage system, secondary battery capacity estimation device, and lead-acid battery capacity estimation method

Abstract

The present invention discloses a technology capable of improving the estimation accuracy of the battery capacity of a secondary battery. The power storage system includes a lead-acid battery, a motor operated by power from the lead-acid battery, a reporting unit, and a battery management unit. The battery management unit determines a first capacity change amount of the lead-acid battery related to the open circuit voltage from a reference state due to a first degradation cause based on the open circuit voltage of the lead-acid battery, determines a second capacity change amount of the lead-acid battery not related to the open circuit voltage due to a second degradation cause based on the first capacity change amount and the change amount of the overall internal resistance of the lead-acid battery from the reference state, and determines at least one of the battery capacity of the lead-acid battery and the change amount of the battery capacity from the reference state based on the first capacity change amount and the second capacity change amount. The reporting unit performs a reporting action corresponding to at least one of the battery capacity determined by the battery management unit and the change amount of the battery capacity from the reference state.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a power storage system. Background Art

[0002] Secondary batteries are widely used. For example, they are mounted on mobile objects such as automobiles and used as a power supply source for supplying power to electric motors, to starters when starting engines, and to various electrical devices such as lighting devices.

[0003] For example, if a secondary battery is used for a long time, it will deteriorate and the battery capacity (maximum dischargeable capacity or capacity when fully charged) will decrease. Therefore, in the past, there is a known battery control device that detects the internal resistance value of the secondary battery and determines the degree of deterioration of the secondary battery based on the detected internal resistance value (for example, see Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-185122

[0005] For example, a mobile body has a display unit, and a display pattern corresponding to the remaining battery power of a secondary battery is displayed on the display unit. Usually, the display pattern corresponding to the remaining battery power is displayed in different patterns according to the ratio of the current remaining battery power (remaining capacity) to the battery capacity. The user of the mobile body observes the display pattern displayed on the display unit to grasp the remaining battery power of the secondary battery and judge whether the secondary battery needs to be charged. However, if the secondary battery deteriorates and the battery capacity decreases, for example, even if the display pattern is the same, the actual remaining battery power becomes less, the period until charging is required becomes shorter, and the actual remaining battery power cannot be correctly grasped based on the display pattern. As a result, it becomes a cause of erroneous judgment as to whether the secondary battery needs to be charged. As described above, it is preferable to estimate the battery capacity of the secondary battery with high accuracy even when the degradation of the secondary battery progresses, and based on the estimated result, for example, respond to the user by urging the replacement of the secondary battery.

[0006] However, the battery control device that determines the degree of deterioration of the secondary battery based only on the detected internal resistance value cannot accurately estimate the degree of deterioration of the secondary battery or the battery capacity, and thus cannot appropriately handle the secondary battery. Summary of the invention

[0007] This specification discloses a technique that can improve the accuracy of estimating the battery capacity of a secondary battery.

[0008] The power storage system disclosed in the present specification is a power storage system comprising a lead-acid battery, an electric motor operated by electric power from the lead-acid battery, a reporting unit and a battery management unit, wherein the battery management unit determines, based on the open circuit voltage of the lead-acid battery, a first capacity change amount of the lead-acid battery caused by a first degradation cause from a reference state that is related to the open circuit voltage, determines, based on the first capacity change amount and a change amount of the overall internal resistance of the lead-acid battery from the reference state, a second capacity change amount of the lead-acid battery caused by a second degradation cause that is not related to the open circuit voltage, determines, based on the first capacity change amount and the second capacity change amount, at least one of the battery capacity of the lead-acid battery and the change amount of the battery capacity from the reference state, and the reporting unit performs a reporting action corresponding to at least one of the battery capacity determined by the battery management unit and the change amount of the battery capacity from the reference state. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is an explanatory diagram schematically showing the structure of a golf cart 60 according to the present embodiment.

[0010] Figure 2 It is an explanatory diagram schematically showing the electrical structure of the golf cart 60.

[0011] Figure 3 It is an explanatory diagram schematically showing the structure of the BMU 400 .

[0012] Figure 4 It is a perspective view showing the external appearance structure of the lead-acid battery 100 .

[0013] Figure 5 Yes means Figure 4 An explanatory diagram of the YZ cross-sectional structure of the lead acid battery 100 at the position of VV.

[0014] Figure 6 Yes means Figure 4 An explanatory diagram of the YZ cross-sectional structure of the lead-acid battery 100 at the position of VI-VI.

[0015] Figure 7 This is a flowchart showing the flow of battery management processing.

[0016] Figure 8 1 is an explanatory diagram showing the relationship between each deterioration factor of the lead-acid battery 100 and the open circuit voltage, internal resistance, and battery capacity.

[0017] Fig. 9 This is a flowchart showing the flow of the first estimation process.

[0018] Fig.10 This is an explanatory diagram showing various correlations.

[0019] Fig.11 1 is an explanatory diagram showing the relationship between the voltage variation trend and the discharge amount of the lead storage battery 100 .

[0020] Fig.12 It is an explanatory diagram showing the voltage change of the lead acid battery 100 when discharging to a load.

[0021] Fig.13 This is a flowchart showing the flow of the second estimation process. DETAILED DESCRIPTION

[0022] The technology disclosed in this specification can be implemented in the following forms.

[0023] (1) The power storage system disclosed in the present specification is a power storage system comprising a lead-acid battery, a motor operated by power from the lead-acid battery, a reporting unit, and a battery management unit, wherein the battery management unit determines, based on the open circuit voltage of the lead-acid battery, a first capacity change amount of the lead-acid battery caused by a first degradation cause from a reference state that is related to the open circuit voltage, determines, based on the first capacity change amount and a change amount of the overall internal resistance of the lead-acid battery from the reference state, a second capacity change amount of the lead-acid battery caused by a second degradation cause that is not related to the open circuit voltage, and determines, based on the first capacity change amount and the second capacity change amount, at least one of the battery capacity of the lead-acid battery and the change amount of the battery capacity from the reference state, and the reporting unit performs a reporting action corresponding to at least one of the battery capacity determined by the battery management unit and the change amount of the battery capacity from the reference state.

[0024] As a result of earnest studies by the inventors of the present application, the following viewpoints (a) and (b) have been newly discovered.

[0025] (a) There are many causes of deterioration (causes of changes in battery capacity) of secondary batteries (especially lead-acid batteries) (for example, in the case of lead-acid batteries, sulfation, grid corrosion). Among the above-mentioned multiple deterioration causes, there are deterioration causes in which the change characteristics of the correlation between the capacity and the internal resistance of the secondary battery accompanying the development of each deterioration cause are different from each other, and the degree of development of the above-mentioned deterioration causes varies depending on the use environment of the secondary battery, etc.

[0026] (b) Among the deterioration causes in which the correlation between the capacity and internal resistance of the secondary battery is different, there is a case where the capacity of the secondary battery (battery capacity) that changes with the development of each deterioration cause is correlated with the open circuit voltage of the secondary battery (hereinafter referred to as "correlated cause") and a case where the capacity of the secondary battery (battery capacity) that changes with the development of each deterioration cause is not correlated with the open circuit voltage (hereinafter referred to as "uncorrelated cause").

[0027] Therefore, in the present power storage system, in view of the above viewpoint (a), the first capacity change amount due to the first degradation cause (related cause) and the second capacity change amount due to the second degradation cause (unrelated cause) of the lead storage battery are determined separately. First, the battery management unit determines the first capacity change amount due to the first degradation cause from a reference state (for example, a state when the lead storage battery is new) related to the open circuit voltage of the lead storage battery based on the open circuit voltage of the lead storage battery. Next, the battery management unit determines the second capacity change amount due to the second degradation cause that is unrelated to the open circuit voltage based on the first capacity change amount and the change amount of the overall internal resistance of the lead storage battery from the reference state. Moreover, the battery management unit determines at least one of the battery capacity of the lead storage battery and the change amount of the battery capacity from the reference state based on the first capacity change amount and the second capacity change amount. The reporting unit performs a reporting action corresponding to at least one of the battery capacity determined by the battery management unit and the change amount of the battery capacity from the reference state. This makes it possible to estimate the battery capacity of the lead-acid battery with high accuracy and perform appropriate measures according to the battery capacity.

[0028] (2) In the power storage system, the first degradation cause is sulfation of the negative electrode of the lead storage battery, and the second degradation cause is corrosion of the grid of the lead storage battery. According to this power storage system, the battery capacity of the lead storage battery can be estimated with high accuracy by separately determining the capacity reduction amount due to sulfation and the capacity reduction amount due to corrosion of the grid.

[0029] (3) The capacity estimation device of a secondary battery disclosed in the present specification is a capacity estimation device of a secondary battery, comprising: an open circuit voltage determination unit, which determines the value of the open circuit voltage of the secondary battery; a first capacity determination unit, which determines the amount of change of the first capacity of the secondary battery from a reference state based on a first correlation between the first capacity of the secondary battery due to a first degradation cause and the open circuit voltage and the determined value of the open circuit voltage; a first internal resistance determination unit, which determines the amount of change of the first internal resistance due to the first degradation cause based on a second correlation between the first capacity and the first internal resistance of the secondary battery and the determined amount of change of the first capacity; and an overall resistance determination unit, which determines determining an amount of change in the overall internal resistance of the secondary battery; a second internal resistance determining unit, which determines an amount of change in the second internal resistance by subtracting the determined amount of change in the first internal resistance from the determined amount of change in the overall internal resistance; a second capacity determining unit, which determines an amount of change in the second capacity of the secondary battery from the reference state based on a third correlation between the second capacity and the second internal resistance formed due to a second degradation cause of the secondary battery that is unrelated to the open circuit voltage, and the determined amount of change in the second internal resistance; and a first battery capacity determining unit, which determines a battery capacity of the secondary battery based on the determined amount of change in the first capacity and the determined amount of change in the second capacity.

[0030] In the capacity estimation device of the present secondary battery, first, the change in the first capacity of the secondary battery from the reference state due to the first degradation cause (related cause) is determined. Specifically, based on the first correlation between the first capacity and the open circuit voltage related to the open circuit voltage, the change in the first capacity corresponding to the value of the determined open circuit voltage is determined. Next, the change in the second capacity of the secondary battery from the reference state due to the second degradation cause (unrelated cause) is determined. Here, the second capacity is related to the second internal resistance associated with the development of the second degradation cause, so if the change in the second internal resistance can be determined, the change in the second capacity can be determined. In addition, the change in the overall internal resistance of the secondary battery from the reference state includes the change in the first internal resistance associated with the development of the first degradation cause and the change in the second internal resistance associated with the development of the second degradation cause, but the change in the first internal resistance and the change in the second internal resistance cannot be distinguished based only on the change in the overall internal resistance.

[0031] Therefore, in the capacity estimation device of the present secondary battery, based on the above viewpoint (b), the second correlation between the first capacity caused by the first degradation cause and the first internal resistance caused by the first degradation cause is utilized. Specifically, the change in the first internal resistance is determined based on the second correlation and the determined change in the first capacity. In addition, the change in the overall internal resistance of the secondary battery is determined. Moreover, the change in the second internal resistance is determined by subtracting the determined change in the first internal resistance from the determined change in the overall internal resistance. Next, the change in the second capacity is determined based on the third correlation between the second capacity and the second internal resistance and the determined change in the second internal resistance. Thus, the change in the first capacity caused by the first degradation cause and the change in the second capacity caused by the second degradation cause can be determined separately. Moreover, the battery capacity of the secondary battery can be determined with high accuracy based on the determined change in the first capacity and the determined change in the second capacity.

[0032] (4) It may also be configured that the capacity estimating device of the secondary battery further comprises: a condition judgment unit, which judges whether a switching condition is satisfied, wherein the switching condition comprises at least one of the temperature of the secondary battery being above a prescribed temperature and the overcharge amount of the secondary battery being above a reference amount; and a second battery capacity determination unit, which, when it is determined that the switching condition is satisfied, determines the battery capacity of the secondary battery by other estimation methods that do not utilize the open circuit voltage.

[0033] In the capacity estimation device of the secondary battery, when it is determined that at least one of the switching conditions including the temperature of the secondary battery being above a specified temperature and the overcharge amount of the secondary battery being above a reference amount is satisfied, the battery capacity of the secondary battery is determined by other estimation methods that do not utilize the open circuit voltage. For example, sometimes the first correlation related to the open circuit voltage changes due to the increase in the temperature of the secondary battery, and the estimation accuracy of the battery capacity of the secondary battery obtained by the first battery capacity determination unit decreases. In such a case, according to the capacity estimation device of the secondary battery, other estimation methods that do not utilize the open circuit voltage are executed, so that the reduction in the estimation accuracy of the battery capacity of the secondary battery caused by the change in the correlation related to the open circuit voltage can be suppressed.

[0034] (5) It may also be configured that the capacity estimating device of the secondary battery further comprises: an acquisition unit that acquires the current and voltage of the secondary battery; and a voltage determination unit that determines the value of the voltage of the secondary battery when the value of the current of the secondary battery is a reference value multiple times based on the current and the voltage acquired by the acquisition unit, and the second battery capacity determination unit determines the value of the battery capacity of the secondary battery corresponding to the changing trend of the voltage values ​​determined multiple times based on the fourth correlation between the changing trend of the voltage of the secondary battery and the battery capacity of the secondary battery.

[0035] In the capacity estimation device of the secondary battery, when it is determined that the switching condition is satisfied, the value of the voltage of the secondary battery when the value of the current of the secondary battery is a reference value is determined multiple times based on the acquired current and voltage. Next, based on the fourth correlation between the change trend (inclination) of the voltage of the secondary battery and the battery capacity of the secondary battery, the value of the battery capacity of the secondary battery corresponding to the change trend of the determined multiple voltage values ​​is determined. Thus, even if the correlation related to the open circuit voltage changes, the value of the battery capacity of the secondary battery can be estimated with higher accuracy than the previous estimation method of estimating the battery capacity of the secondary battery based on the value of the overall internal resistance of the secondary battery.

[0036] (6) The method for estimating the capacity of a lead-acid battery disclosed in the present specification is a method for estimating the capacity of a lead-acid battery, comprising the following steps: determining a first capacity change amount of the lead-acid battery from a reference state due to a first degradation cause and related to the open circuit voltage based on an open circuit voltage of the lead-acid battery; determining a second capacity change amount of the lead-acid battery not related to the open circuit voltage due to a second degradation cause based on the first capacity change amount and a change amount in the overall internal resistance of the lead-acid battery from the reference state; and determining the battery capacity of the lead-acid battery based on the first capacity change amount and the second capacity change amount.

[0037] In addition, the technology disclosed in this specification can be implemented in various forms, for example, it can be implemented in the form of a computer program for realizing the capacity estimation device, the capacity estimation method, the functions of the above-mentioned device or method, a non-transitory recording medium recording the computer program, etc. In addition, the technology disclosed in this specification can also be applied to a management device that manages mobile objects from a remote location (for example, a centralized management device in a factory, an external server, etc.).

[0038] A. Implementation method: A-1. Structure:

[0039] Figure 1 1 is an explanatory diagram schematically showing the structure of a golf cart 60 according to this embodiment. Figure 1As shown, the golf cart 60 includes a lead-acid battery 100 as a battery, a drive motor 300 as an electric motor, a BMU (Battery Management Unit) 400 for managing the state of the lead-acid battery 100, and an operation unit 62. The golf cart 60 is a mobile body that travels using the power of the drive motor 300 operated by the power from the lead-acid battery 100, and can travel on a predetermined road on a golf course by automatic operation.

[0040] The operation unit 62 is disposed, for example, near the steering wheel of the golf cart 60. Figure 1 As shown in the enlarged form in FIG. 1 , the operation unit 62 is provided with a display unit 64, which is composed of a liquid crystal display and displays various images and information, and a display pattern 66 corresponding to the battery remaining capacity of the lead-acid battery 100 is displayed on the display unit 64. Specifically, "F" on the screen of the display unit 64 means that the lead-acid battery 100 is in a fully charged state (for example, the voltage of the lead-acid battery 100 is above a predetermined voltage upper limit value), and "E" on the screen of the display unit 64 means that the lead-acid battery 100 is undercharged (for example, the voltage of the lead-acid battery 100 is below a predetermined voltage lower limit value). The multiple bars of different lengths on the screen of the display unit 64 are displayed in different patterns according to the ratio (hereinafter referred to as "charging rate") of the current capacity (remaining capacity) to the battery capacity of the lead-acid battery 100 (the maximum dischargeable capacity of the lead-acid battery 100 or the capacity when fully charged). Specifically, as the charge rate of the lead-acid battery 100 decreases and approaches an undercharged state, only the bar near "E" lights up, and as the charge rate of the lead-acid battery 100 increases and approaches a fully charged state, the bar near "E" lights up to a bar near "F".

[0041] Thus, if the user of the golf cart 60 observes the display pattern 66 displayed on the display unit 64, he can understand the remaining battery capacity of the lead-acid battery 100 by sensory perception. The lead-acid battery 100 provided in the golf cart 60 can be charged by a charger (not shown). Therefore, if the user of the golf cart 60 observes the display pattern 66 displayed on the display unit 64 and determines that the lead-acid battery 100 is close to an undercharged state, the lead-acid battery 100 can be charged by the charger. In a mobile body that needs to be charged frequently, such as the golf cart 60, a higher accuracy is particularly sought for the estimation of the battery capacity. In addition, the lead-acid battery 100 is heavier than other secondary batteries, so it is often carried in a mobile body such as the golf cart 60 for stable driving. The golf cart 60 is equivalent to the power storage system of the claims, the lead-acid battery 100 is equivalent to the secondary battery of the claims, the BMU 400 is equivalent to the battery management unit and the capacity estimation device of the claims, and the display unit 64 is equivalent to the reporting unit of the claims.

[0042] Figure 2 60 is an explanatory diagram schematically showing the electrical structure of the golf cart 60. Figure 2 As shown, the golf cart 60 includes a voltage detector 450, a current detector 460, and a temperature detector 470 in addition to the lead acid battery 100, the drive motor 300, and the BMU 400. The lead acid battery 100 is a battery pack in which a plurality of cells C are connected in series.

[0043] (Structure of Each Detection Section)

[0044] The voltage detection unit 450 is connected in parallel to the lead-acid battery 100, and outputs a detection result corresponding to the overall voltage value of the lead-acid battery 100. The current detection unit 460 is connected in series to the lead-acid battery 100, and outputs a detection result corresponding to the value of the current (charging and discharging current) flowing to the lead-acid battery 100. The temperature detection unit 470 is arranged near the lead-acid battery 100, and outputs a detection result corresponding to the temperature of the lead-acid battery 100.

[0045] (Structure of BMU400)

[0046] Figure 3 4 is an explanatory diagram schematically showing the configuration of the BMU 400. The BMU 400 includes a control unit 410, a storage unit 420, an input unit 430, and an interface unit 440. The above-mentioned units are connected to each other via a bus so as to be communicable.

[0047] The input unit 430 receives input of detection results from the voltage detection unit 450, the current detection unit 460, and the temperature detection unit 470. The interface unit 440 is composed of, for example, a LAN interface or a USB interface, and communicates with other devices (for example, the operation unit 62) by wire or wirelessly.

[0048] The storage unit 420 is composed of, for example, a hard disk drive (HDD) and stores various programs and data. For example, a battery management program 421 for executing the battery management process described later is stored in the storage unit 420. The battery management program 421 is provided in a state stored in a computer-readable recording medium (not shown) such as a CD-ROM, a DVD-ROM, or a USB memory, and is stored in the storage unit 420 by being installed in the BMU 400. In addition, each mapping data 422 described later is stored in the storage unit 420. Each mapping data 422 is input to the BMU 400 via the interface unit 440 and stored in the storage unit 420.

[0049] The control unit 410 is composed of, for example, a CPU, a ROM, a RAM, etc., and controls the operation of the BMU 400 by executing a computer program read from the storage unit 420. For example, the control unit 410 functions as a processing unit that performs a battery management process described later by reading and executing a battery management program 421. Specifically, the control unit 410 includes a condition determination unit 510, a display control unit 520, a first estimation processing unit 530, and a second estimation processing unit 540. In addition, the first estimation processing unit 530 includes an open circuit voltage determination unit 531, a sulfation capacity determination unit 532, a sulfation resistance determination unit 533, an overall resistance determination unit 534, a grid corrosion resistance determination unit 535, a grid corrosion capacity determination unit 536, and a first battery capacity determination unit 537. In addition, the second estimation processing unit 540 includes a current and voltage acquisition unit 541, a voltage determination unit 542, and a second battery capacity determination unit 543. The functions of these units will be described in the description of the battery management process described later.

[0050] (Structure of Lead Acid Battery 100)

[0051] Figure 4 is a perspective view showing the appearance structure of the lead-acid battery 100. Figure 5 Yes means Figure 4 An explanatory diagram of the YZ cross-sectional structure of the lead acid battery 100 at the position of VV, Figure 6 Yes means Figure 4 FIG. 1 is an explanatory diagram of the YZ cross-sectional structure of the lead-acid battery 100 at the position of VI-VI. Figure 5 and Figure 6 In the figure, for convenience, in order to easily understand the structure of the electrode group 20 described later, the structure is expressed in a form different from the actual one. In each figure, the XYZ axes that are orthogonal to each other for determining the direction are shown. In this specification, for convenience, the positive direction of the Z axis is referred to as the "upward direction" and the negative direction of the Z axis is referred to as the "downward direction", but the lead-acid battery 100 can actually be set in a direction different from this direction.

[0052] like Figures 4 to 6 As shown, the lead acid battery 100 includes a case 10, a positive terminal 30, a negative terminal 40, and a plurality of electrode plate groups 20. Hereinafter, the positive terminal 30 and the negative terminal 40 are also collectively referred to as "terminals 30, 40".

[0053] (Structure of Housing 10)

[0054] The housing 10 has a battery slot 12 and a cover 14. The battery slot 12 is a substantially rectangular container having an opening on the upper surface, and is formed of, for example, a synthetic resin. The cover 14 is a component configured to block the opening of the battery slot 12, and is formed of, for example, a synthetic resin. The peripheral portion of the lower surface of the cover 14 and the peripheral portion of the opening of the battery slot 12 are joined, for example, by heat welding, thereby forming a space in the housing 10 that ensures airtightness between it and the outside. The space in the housing 10 is divided by a partition wall 58 into a plurality of (for example, 6) battery chambers 16 arranged in a prescribed direction (in the present embodiment, the X-axis direction). Hereinafter, the direction in which the plurality of battery chambers 16 are arranged (the X-axis direction) is referred to as the "battery arrangement direction".

[0055] Each battery chamber 16 in the housing 10 accommodates one electrode group 20. Therefore, for example, when the space in the housing 10 is divided into six battery chambers 16, the lead acid battery 100 includes six electrode groups 20. In addition, each battery chamber 16 in the housing 10 accommodates an electrolyte 18 containing dilute sulfuric acid, and the entire electrode group 20 is immersed in the electrolyte 18. The electrolyte 18 is injected into the battery chamber 16 from a liquid injection port (not shown) provided in the cover 14.

[0056] (Structure of Electrode Plate Group 20)

[0057] The electrode plate group 20 includes a plurality of positive electrode plates 210, a plurality of negative electrode plates 220, and a separator 230. The plurality of positive electrode plates 210 and the plurality of negative electrode plates 220 are arranged so that the positive electrode plates 210 and the negative electrode plates 220 are alternately arranged. Hereinafter, the positive electrode plates 210 and the negative electrode plates 220 are also collectively referred to as "electrode plates 210, 220".

[0058] The positive electrode plate 210 has a positive electrode collector 212 and a positive electrode active material 216 supported by the positive electrode collector 212. The positive electrode collector 212 is a conductive component having a skeleton arranged in a substantially grid-like or mesh-like shape, and is formed of, for example, lead or a lead alloy. In addition, the positive electrode collector 212 has a positive electrode ear 214 protruding upward near its upper end. The positive electrode active material 216 contains lead dioxide. The positive electrode active material 216 may also contain a known additive.

[0059] The negative electrode plate 220 includes a negative electrode collector 222 and a negative electrode active material 226 supported by the negative electrode collector 222. The negative electrode collector 222 is a conductive member having a skeleton arranged in a substantially grid-like or mesh-like shape, and is formed of, for example, lead or a lead alloy. In addition, the negative electrode collector 222 has a negative electrode ear 224 protruding upward near its upper end. The negative electrode active material 226 includes lead. The negative electrode active material 226 may also include a known additive.

[0060] The spacer 230 is formed of an insulating material (e.g., glass, synthetic resin). The spacer 230 is disposed between the adjacent positive electrode plate 210 and the negative electrode plate 220. The spacer 230 may be formed as an integral component or as a collection of multiple components provided for each combination of the positive electrode plate 210 and the negative electrode plate 220.

[0061] The positive electrode ears 214 of the plurality of positive electrode plates 210 constituting the electrode plate group 20 are connected to the positive electrode side bus bar 52 formed of, for example, lead or a lead alloy. That is, the plurality of positive electrode plates 210 are electrically connected in parallel via the positive electrode side bus bar 52. Similarly, the negative electrode ears 224 of the plurality of negative electrode plates 220 constituting the electrode plate group 20 are connected to the negative electrode side bus bar 54 formed of, for example, lead or a lead alloy. That is, the plurality of negative electrode plates 220 are electrically connected in parallel via the negative electrode side bus bar 54. Hereinafter, the positive electrode side bus bar 52 and the negative electrode side bus bar 54 are also collectively referred to as "bus bars 52, 54".

[0062] In the lead-acid battery 100, the negative-pole bus 54 housed in one battery chamber 16 is connected to the positive-pole bus 52 housed in another battery chamber 16 adjacent to one side (e.g., the positive side of the X-axis) of the battery chamber 16 via a connecting component 56 formed of, for example, lead or a lead alloy. In addition, the positive-pole bus 52 housed in the battery chamber 16 is connected to the negative-pole bus 54 housed in another battery chamber 16 adjacent to the other side (e.g., the negative side of the X-axis) of the battery chamber 16 via the connecting component 56. That is, the plurality of electrode assemblies 20 provided in the lead-acid battery 100 are electrically connected in series via the busbars 52, 54 and the connecting component 56. In addition, as Figure 5 As shown, the positive electrode side bus bar 52 accommodated in the battery chamber 16 at the end portion on one side (the negative direction side of the X axis) in the battery arrangement direction is not connected to the connecting member 56, but is connected to the positive electrode post 34 described later. Figure 6 As shown, the negative electrode bus bar 54 accommodated in the battery chamber 16 located at the end portion on the other side (X-axis positive direction side) in the battery arrangement direction is not connected to the connection member 56 but to the negative electrode post 44 described later.

[0063] (Structure of Terminal Portions 30 and 40)

[0064] The positive terminal portion 30 is arranged near the end of the case 10 on one side (negative side in the X-axis direction) in the battery arrangement direction, and the negative terminal portion 40 is arranged near the end of the case 10 on the other side (positive side in the X-axis direction) in the battery arrangement direction.

[0065] like Figure 5As shown, the positive-side terminal portion 30 includes a positive-side bushing 32 and a positive electrode post 34. The positive-side bushing 32 is a substantially cylindrical conductive component formed with a hole extending therethrough in the up-down direction, and is formed, for example, of a lead alloy. The lower portion of the positive-side bushing 32 is embedded in the cover 14 by insert molding, and the upper portion of the positive-side bushing 32 protrudes upward from the upper surface of the cover 14. The positive electrode post 34 is a substantially cylindrical conductive component, and is formed, for example, of a lead alloy. The positive electrode post 34 is inserted into the hole of the positive-side bushing 32. The upper end portion of the positive electrode post 34 is located at substantially the same position as the upper end portion of the positive-side bushing 32, and is joined to the positive-side bushing 32 by, for example, welding. The lower end of the positive electrode column 34 protrudes downward than the lower end of the positive electrode side bushing 32 and protrudes downward than the lower surface of the cover 14, and as described above, is connected to the positive electrode side bus 52 housed in the battery chamber 16 at the end on one side of the battery arrangement direction (the negative direction side of the X-axis).

[0066] like Figure 6 As shown, the negative-side terminal portion 40 includes a negative-side bushing 42 and a negative-electrode post 44. The negative-electrode side bushing 42 is a substantially cylindrical conductive component formed with a hole extending therethrough in the up-down direction, and is formed, for example, of a lead alloy. The lower portion of the negative-electrode side bushing 42 is embedded in the cover 14 by insert molding, and the upper portion of the negative-electrode side bushing 42 protrudes upward from the upper surface of the cover 14. The negative-electrode post 44 is a substantially cylindrical conductive component, and is formed, for example, of a lead alloy. The negative-electrode post 44 is inserted into the hole of the negative-electrode side bushing 42. The upper end portion of the negative-electrode post 44 is located at substantially the same position as the upper end portion of the negative-electrode side bushing 42, and is joined to the negative-electrode side bushing 42 by, for example, welding. The lower end of the negative electrode column 44 protrudes downward than the lower end of the negative electrode side bushing 42 and protrudes downward than the lower surface of the cover 14, and as described above, is connected to the negative electrode side bus 54 housed in the battery chamber 16 at the end located on the other side of the battery arrangement direction (the positive direction of the X-axis).

[0067] When the lead-acid battery 100 is discharged, a load (not shown) is connected to the positive-side bushing 32 of the positive-side terminal portion 30 and the negative-side bushing 42 of the negative-side terminal portion 40, and power generated by the reaction at the positive plate 210 of each electrode group 20 (a reaction of generating lead sulfate from lead dioxide) and the reaction at the negative plate 220 (a reaction of generating lead sulfate from lead (spongy lead)) is supplied to the load. In addition, when the lead-acid battery 100 is charged, a power source (not shown) is connected to the positive-side bushing 32 of the positive-side terminal portion 30 and the negative-side bushing 42 of the negative-side terminal portion 40, and the reaction at the positive plate 210 of each electrode group 20 (a reaction of generating lead dioxide from lead sulfate) and the reaction at the negative plate 220 (a reaction of generating lead (spongy lead) from lead sulfate) are generated by the power supplied from the power source, thereby charging the lead-acid battery 100.

[0068] A-2. Battery management processing:

[0069] Next, a description will be given of a battery management process executed by the BMU 400 . The battery management process is a process of estimating the battery capacity of the lead-acid battery 100 and causing the display unit 64 to display content corresponding to the estimated battery capacity.

[0070] Figure 7 : is a flowchart showing the flow of battery management processing. First, the condition judgment unit 510 judges whether the estimated timing of the battery capacity of the lead-acid battery 100 should be estimated has arrived (S110). The condition judgment unit 510 judges that the estimated timing has arrived, for example, based on the moment when the drive motor 300 of the golf cart 60 stops, or based on the condition that a specified time has passed since the charging of the lead-acid battery 100 based on the charger is completed. In addition, the condition judgment unit 510 can recognize that the drive motor 300 has stopped when it is judged that the current flowing to the lead-acid battery 100 is below the current lower limit value based on the detection result from the current detection unit 460. In addition, the condition judgment unit 510 can recognize that the charging of the lead-acid battery 100 is completed when it is judged that the voltage value of the lead-acid battery 100 becomes above the above-mentioned voltage upper limit value based on the detection result from the voltage detection unit 450, or when a charging completion notification from the above-mentioned charger is received.

[0071] When it is determined that the estimated timing has not arrived (S110: No), the condition determination unit 510 repeats the determination of S110. On the other hand, when it is determined that the estimated timing has arrived (S110: Yes), the condition determination unit 510 determines whether the switching condition is satisfied (S120). Here, the switching condition is a condition for performing the second estimation process instead of the first estimation process, specifically, including at least one of the temperature of the lead-acid battery 100 being above a prescribed temperature and the overcharge amount of the lead-acid battery 100 being above a reference amount. In addition, the condition determination unit 510 can identify that the temperature of the lead-acid battery 100 becomes above a prescribed temperature based on the detection result from the temperature detection unit 470. In addition, the condition determination unit 510 can identify that the overcharge amount of the lead-acid battery 100 becomes above a reference amount based on the detection results of the voltage detection unit 450 and the current detection unit 460.

[0072] When it is determined that the switching condition is not satisfied (S120: No), the first estimation processing unit 530 performs the first estimation processing (S130). When it is determined that the switching condition is not satisfied (S120: Yes), the second estimation processing unit 540 performs the second estimation processing (S140). The contents of the first estimation processing and the second estimation processing will be described later. If the first estimation processing or the second estimation processing is performed, the display control unit 520 determines whether the battery capacity of the lead-acid battery 100 estimated by the first estimation processing or the second estimation processing is less than the degradation threshold (S150). When it is determined that the battery capacity of the lead-acid battery 100 is less than the degradation threshold (S150: Yes), error processing is performed (S160). Specifically, the display control unit 520 causes a display for urging the replacement of the lead-acid battery 100 to be displayed on the display unit 64. For example, Figure 1 The battery symbol displayed on the screen of the display unit 64 is flashed. If the error processing (S160) is executed, the process returns to S110. On the other hand, if it is determined that the battery capacity of the lead storage battery 100 is not less than the deterioration threshold (S150: No), the error processing (S150) is skipped and the process returns to S110.

[0073] A-3. First presumption:

[0074] Next, the first estimation process is described. The first estimation process is a process of determining the reduction amount of the battery capacity of the lead-acid battery 100 accompanying the development of the degradation cause for each degradation cause of the lead-acid battery 100, and estimating the battery capacity of the lead-acid battery 100 based on the determined capacity reduction amount for each degradation cause. The degradation causes of this embodiment are sulfation (crystallization of lead sulfate) generated by the negative electrode plate 220 in the lead-acid battery 100 and corrosion (e.g., oxidative corrosion) of the positive electrode collector 212 and the negative electrode collector 222 in the lead-acid battery 100 (hereinafter referred to as "grid corrosion").

[0075] (Relationship between each degradation factor and open circuit voltage, internal resistance, and battery capacity)

[0076] Figure 8 1 is an explanatory diagram showing the relationship between each deterioration factor (sulfation, grid corrosion) of the lead-acid battery 100 and the open circuit voltage, internal resistance and battery capacity. Figure 8 As shown on the left side of FIG. , the decrease in battery capacity associated with the degradation of the lead-acid battery 100 ( Figure 8 The difference between the new capacity and the deteriorated capacity of the lead-acid battery 100 includes the capacity reduction amount of the lead-acid battery 100 from the time of new product accompanying the development of sulfation (hereinafter referred to as "sulfation capacity reduction amount ΔCA") and the capacity reduction amount of the lead-acid battery 100 from the time of new product accompanying the development of grid corrosion (hereinafter referred to as "grid corrosion capacity reduction amount ΔCB"). Figure 8 As can be seen from the graph related to internal resistance and battery capacity shown on the right side of , if sulfation progresses, the internal resistance of the lead-acid battery 100 increases due to the insulating lead sulfate remaining in the active material, and the battery capacity of the lead-acid battery 100 decreases due to the increase of active materials that do not participate in the reaction. Similarly, if grid corrosion progresses, the internal resistance of the lead-acid battery 100 increases due to the increase in resistance between the positive electrode collector 212 (grid body) and the positive electrode active material 216, and the battery capacity of the lead-acid battery 100 decreases due to the increase of active materials that do not participate in the reaction. Among them, the change characteristics of the correlation between the internal resistance and the battery voltage of the lead-acid battery 100 accompanying the development of sulfation and the change characteristics of the correlation between the internal resistance and the battery voltage of the lead-acid battery 100 accompanying the development of grid corrosion are different from each other. In addition, the degree of development of sulfation and the degree of development of grid corrosion differ from each other depending on the use environment of the lead-acid battery 100, etc. Therefore, in order to estimate the battery capacity of the lead-acid battery 100 with high accuracy, it is preferable to determine the sulfation capacity reduction amount ΔCA and the grid corrosion capacity reduction amount ΔCB separately.

[0077] In addition, if Figure 8 As can be seen from the figure related to the open circuit voltage shown on the right side of , if sulfation develops, although the open circuit voltage of the lead-acid battery 100 decreases, even if the grid corrosion develops, the open circuit voltage of the lead-acid battery 100 does not change. This means that although the sulfation capacity reduction amount ΔCA is related to the open circuit voltage, the grid corrosion capacity reduction amount ΔCB is not related to the open circuit voltage. The reason can be considered as follows. If sulfation occurs, even if the lead-acid battery 100 is charged, lead sulfate is not reduced, so the concentration of the electrolyte 18 decreases, and the open circuit voltage decreases accordingly. On the other hand, since even if grid corrosion occurs, it does not affect the concentration of the electrolyte 18, the open circuit voltage does not change.

[0078] As described below, in the first estimation process, the sulfation capacity reduction amount ΔCA and the grid corrosion capacity reduction amount ΔCB are determined separately by utilizing the fact that the sulfation capacity reduction amount ΔCA is correlated with the open circuit voltage but the grid corrosion capacity reduction amount ΔCB is not correlated with the open circuit voltage. In addition, sulfation corresponds to the first degradation cause in the claims, and the sulfation capacity reduction amount ΔCA corresponds to the first capacity change amount in the claims. Grid corrosion corresponds to the second degradation cause in the claims, and the grid corrosion capacity reduction amount ΔCB corresponds to the second capacity change amount in the claims.

[0079] (Contents of the first presumption process)

[0080] Fig. 9 This is a flowchart showing the flow of the first estimation process. Fig.10This is an explanatory diagram showing various correlations. Fig.10 (A) shows the first correlation between the open circuit voltage and the discharge amount of the lead-acid battery 100 accompanying the development of sulfation. Specifically, the multiple points plotted in (A) of the figure show the measurement results of the open circuit voltage and the discharge amount of the lead-acid battery 100 from a fully charged state for multiple lead-acid batteries 100 with different degrees of sulfation development and almost the same degrees of grid corrosion development. And, in (A) of the figure, an approximate line G1 of multiple measurement results is shown. In addition, Fig.10 (B) shows the second correlation between the internal resistance and the discharge amount of the lead-acid battery 100 related to the development of sulfation. Specifically, the multiple points plotted in (B) of the figure represent the measurement results of the internal resistance of the lead-acid battery 100 and the discharge amount from the fully charged state for multiple lead-acid batteries 100 with different degrees of sulfation development and almost the same degree of grid corrosion development. And (B) of the figure shows the approximate line G2 of the multiple measurement results. In addition, Fig.10 (C) shows the third correlation between the internal resistance and the discharge amount of the lead-acid battery 100 accompanying the development of the grid corrosion. Specifically, the multiple points plotted in (C) of the figure show the measurement results of the internal resistance of the lead-acid battery 100 and the discharge amount from the fully charged state for multiple lead-acid batteries 100 with different degrees of grid corrosion development and almost the same degree of sulfation development. And (C) of the figure shows the approximate line G3 of the multiple measurement results.

[0081] In addition, in order to obtain Fig.10 The measurement results shown in (A) and (B) of FIG. 1 were obtained by charging and discharging the lead acid battery 100 under the first test condition for causing the lead acid battery 100 to be undercharged, thereby mainly causing sulfation to progress in the lead acid battery 100. The first test condition was as follows.

[0082] <First test condition>

[0083] Under the condition of an ambient temperature of 25° C., the following cycles 1 to 3 are repeated until the discharge end voltage of the lead storage battery 100 reaches a predetermined value.

[0084] (Cycle 1): Perform the first charge and discharge test. In the first charge and discharge test, after a constant current discharge of 4 hours (discharge amount 48Ah) with a discharge current of 12A, a constant current charge with a charging current of less than 60A and more than 30A is started. Thereafter, each time the voltage of the lead-acid battery 100 reaches a reference voltage (e.g., 14.4V), the charging current value is switched to 12A, 6A, 3A, and 1.5A in sequence, and then the charging current value is maintained at 1.5A. Thereafter, after 1 hour has passed from the start time of charging of the first charge and discharge test, the first charge and discharge test ends. If the first charge and discharge test of the amount of one time ends, this cycle 1 ends and moves to cycle 2.

[0085] (Cycle 2): Repeat the second charge and discharge test 8 times. In the second charge and discharge test, after a constant current discharge of 3 hours (discharge amount 36Ah) with a discharge current of 12A, a constant current charge of less than 60A and more than 30A is started. Thereafter, each time the voltage of the lead-acid battery 100 reaches the above-mentioned reference voltage, the charging current value is switched to 12A, 6A, 3A, and 1.5A in sequence, and then the charging current value is maintained at 1.5A. Thereafter, after 1 hour has passed from the start time of charging of the second charge and discharge test, this second charge and discharge test ends. If 8 complete second charge and discharge tests are completed, this cycle 2 ends and moves to cycle 3.

[0086] (Cycle 3): Perform a third charge and discharge test. In the third charge and discharge test, after a constant current discharge of 3 hours (discharge amount 36Ah) with a discharge current of 12A, a constant current charge of 12A is started. Thereafter, each time the voltage of the lead-acid battery 100 reaches the above-mentioned reference voltage, the charging current value is switched to 6A, 3A, and 1.5A in sequence, and thereafter, the charging current value is maintained at 1.5A. Thereafter, in the third charge and discharge test, 2.5 hours have passed since the charging current value was switched to 1.5A and the voltage of the lead-acid battery 100 reached the above-mentioned reference voltage, and the third charge and discharge test is terminated. If a complete third charge and discharge test is completed, this cycle 3 is terminated and cycle 1 is returned.

[0087] In addition, in order to obtain Fig.10 The measurement result shown in (C) is that the lead acid battery 100 is charged and discharged under the second test condition for making the lead acid battery 100 into an overcharged state, thereby mainly causing grid corrosion to progress in the lead acid battery 100. The second test condition is as follows.

[0088] <Second test condition>

[0089] Under the condition of an ambient temperature of 25° C., the following cycle 4 is repeated until the discharge end voltage of the lead storage battery 100 reaches a predetermined value.

[0090] (Cycle 4): Implement the 4th charge and discharge test. In the 4th charge and discharge test, after a constant current discharge of 4 hours (discharge amount 48Ah) with a discharge current of 12A, a constant current charge of 12A was started, and thereafter, each time the voltage of the lead-acid battery 100 reached the above-mentioned reference voltage, the charging current value was switched to 6A, 3A, and 1.5A in sequence, and thereafter, the charging current value was maintained at 1.5A. In addition, in the 4th charge and discharge test, after 2.5 hours from the moment when the charging current value was switched to 1.5A, a complete implementation of this cycle 4 was completed, and cycle 4 was repeated again.

[0091] (Regarding determination of sulfation capacity reduction ΔCA)

[0092] like Fig. 9 As shown, the first estimation processing unit 530 first determines the sulfation capacity reduction amount ΔCA (S210 to S220). Specifically, the open circuit voltage determination unit 531 determines the value of the open circuit voltage (OCV) of the lead-acid battery 100 (S210). In addition, the first estimation processing is executed on the condition that the above-mentioned estimation timing has arrived (S110: Yes). Therefore, at this time, a predetermined time has passed since the time when the drive motor 300 of the golf cart 60 has stopped or the charging of the lead-acid battery 100 has ended. In this embodiment, the predetermined time is a time sufficient to measure the open circuit voltage. When the first estimation processing is executed, the voltage value of the lead-acid battery 100 at the current time is made the value of the open circuit voltage based on the detection result from the voltage detection unit 450. In addition, when a dark current flows into the lead-acid battery 100 at the time when the drive motor 300 stops, it is preferable to make the value obtained by performing a correction process corresponding to the current amount of the dark current on the voltage value of the lead-acid battery 100 at the current time as the value of the open circuit voltage. In addition, various other known methods can be used as a method for determining the open circuit voltage.

[0093] Next, the sulfation capacity determination unit 532 determines the sulfation capacity reduction amount ΔCA (S220). Specifically, the sulfation capacity determination unit 532 uses the value of the open circuit voltage determined by the open circuit voltage determination unit 531 and the Fig.10The sulfation capacity reduction amount ΔCA is determined based on information related to the first correlation shown in (A) of the figure. In the present embodiment, as information related to the first correlation, the first mapping data (check table) representing the correspondence between the open circuit voltage value and the discharge amount in the multiple measurement results shown in (A) of the figure is used. That is, the sulfation capacity determination unit 532 refers to the first mapping data to extract the discharge amount corresponding to the open circuit voltage value determined by the open circuit voltage determination unit 531, so that the difference between the discharge amount corresponding to the initial value of the open circuit voltage when the product is new and the discharge amount extracted this time becomes the sulfation capacity reduction amount ΔCA. In addition, it is preferred that the initial value of the open circuit voltage is pre-stored in the storage unit 420. In addition, as information related to the first correlation, a function representing the approximate line G1 (e.g., a linear function, a quadratic function) may also be used. The sulfation capacity determination unit 532 is equivalent to the first capacity determination unit in the claims, and the sulfation capacity reduction amount ΔCA is equivalent to the change in the first capacity in the claims.

[0094] (Determination of grid corrosion capacity reduction ΔCB)

[0095] The first estimation processing unit 530 determines the grid corrosion capacity reduction amount ΔCB (S230-S260). Specifically, the sulfation resistance determination unit 533 determines the increase in the internal resistance of the lead-acid battery 100 from the time of the new product accompanying the progress of sulfation (hereinafter referred to as "sulfation resistance increase amount ΔRA") (S230). Specifically, the sulfation resistance determination unit 533 uses the sulfation capacity reduction amount ΔCA determined by the sulfation capacity determination unit 532 and the sulfation resistance reduction amount ΔCA determined by the sulfation capacity determination unit 532. Fig.10 The sulfation resistance increase ΔRA is determined by using information related to the second correlation shown in (B) of the figure. In the present embodiment, as information related to the second correlation, the second mapping data representing the correspondence between the value of the internal resistance and the discharge amount in the multiple measurement results shown in (B) of the figure is used. That is, the sulfation resistance determination unit 533 refers to the second mapping data, extracts the internal resistance corresponding to the discharge amount extracted by the sulfation capacity determination unit 532, and makes the difference between the initial value of the internal resistance corresponding to the initial value of the discharge amount when the new product is new and the value of the internal resistance extracted this time become the sulfation resistance increase ΔRA. In addition, it is preferred that the initial value of the discharge amount is pre-stored in the storage unit 420. In addition, as information related to the second correlation, a function representing the approximate line G2 (for example, a linear function, a quadratic function) can also be used. The sulfation resistance determination unit 533 is equivalent to the first internal resistance determination unit in the claims, and the sulfation resistance increase ΔRA is equivalent to the change in the first internal resistance in the claims.

[0096] Next, the overall resistance determination unit 534 determines the overall internal resistance increase ΔR of the lead-acid battery 100 (S240). Specifically, the overall resistance determination unit 534 calculates the value of the overall internal resistance of the lead-acid battery 100 by dividing the value of the voltage of the lead-acid battery 100 by the value of the current flowing to the lead-acid battery 100 based on the detection results from the voltage detection unit 450 and the detection results from the current detection unit 460. Moreover, the overall resistance determination unit 534 makes the difference between the initial value of the overall internal resistance when the product is new and the value of the overall internal resistance calculated this time become the overall internal resistance increase ΔR. In addition, in addition to this, the method for determining the overall internal resistance of the lead-acid battery 100 can also adopt various known methods. Preferably, the initial value of the overall internal resistance is pre-stored in the storage unit 420. The overall internal resistance increase ΔR is equivalent to the change in the overall internal resistance in the claims.

[0097] Next, the grid corrosion resistance determination unit 535 determines the increase in the internal resistance of the lead-acid battery 100 from the time of being new (hereinafter referred to as "grid corrosion resistance increase ΔRB") accompanying the development of grid corrosion (S250). Specifically, the grid corrosion resistance determination unit 535 calculates the grid corrosion resistance increase ΔRB (=ΔR-ΔRA) by subtracting the sulfation resistance increase ΔRA determined by the sulfation resistance determination unit 533 from the total internal resistance increase ΔR determined by the total resistance determination unit 534. The grid corrosion resistance determination unit 535 is equivalent to the second internal resistance determination unit in the claims, and the grid corrosion resistance increase ΔRB is equivalent to the change amount of the second internal resistance in the claims.

[0098] Next, the grid corrosion capacity determination unit 536 determines the grid corrosion capacity reduction amount ΔCB (S260). Specifically, the grid corrosion capacity determination unit 536 uses the grid corrosion resistance increase amount ΔRB determined by the grid corrosion resistance determination unit 535 and the Fig.10The grid corrosion capacity reduction amount ΔCB is determined by using information related to the third correlation shown in (C) of the figure. In the present embodiment, as information related to the third correlation, the third mapping data representing the correspondence between the value of the internal resistance and the discharge amount in the multiple measurement results shown in (C) of the figure is used. That is, the grid corrosion capacity determination unit 536 refers to the third mapping data, extracts the discharge amount corresponding to the value obtained by adding the grid corrosion resistance increase amount ΔRB to the initial value of the internal resistance when the product is new, and makes the difference between the discharge amount corresponding to the initial value of the internal resistance when the product is new and the discharge amount extracted this time become the grid corrosion capacity reduction amount ΔCB. In addition, it is preferred that the initial value of the internal resistance is pre-stored in the storage unit 420. In addition, as information related to the third correlation, a function representing the approximate line G3 (for example, a linear function, a quadratic function) may also be used. The grid corrosion capacity determination unit 536 is equivalent to the second capacity determination unit in the claims, and the grid corrosion capacity reduction amount ΔCB is equivalent to the change in the second capacity in the claims.

[0099] (For determination of battery capacity)

[0100] Next, the first battery capacity determination unit 537 determines the current battery capacity of the lead-acid battery 100 based on the sulfation capacity reduction amount ΔCA determined by the sulfation capacity determination unit 532 and the grid corrosion capacity reduction amount ΔCB determined by the grid corrosion capacity determination unit 536. Specifically, the first battery capacity determination unit 537 determines the current battery capacity of the lead-acid battery 100 by subtracting the sulfation capacity reduction amount ΔCA and the grid corrosion capacity reduction amount ΔCB from the initial value of the battery capacity (discharge amount) at the time of the new product. In addition, according to the first estimation process, for a plurality of (for example, 10) lead-acid batteries 100 having different degrees of development of each deterioration factor, the error between the estimated value of the battery capacity based on the first estimation process and the actual measured value of the battery capacity can be within 10%.

[0101] A-4. Second presumption:

[0102] Next, the second estimation process is described. The second estimation process estimates the battery capacity of the lead-acid battery 100 based on the change trend of the voltage of the lead-acid battery 100 when the value of the current flowing into the lead-acid battery 100 is a reference value. The reference value is, for example, the nominal current value of the lead-acid battery 100.

[0103] (Relationship between the voltage variation trend and battery capacity of the lead storage battery 100)

[0104] Fig.11 1 is an explanatory diagram showing the relationship between the voltage variation trend and the discharge amount of the lead storage battery 100 . Fig.11The discharge curves (GB1 to GB3) show the change in voltage when the lead-acid battery 100 is discharged under a constant current state with the current value of the reference value for each lead-acid battery 100 having different discharge amounts (battery capacities) from a fully charged state. The discharge curve GB1 is the discharge curve of the lead-acid battery 100 with the largest battery capacity, and the discharge curve GB3 is the discharge curve of the lead-acid battery 100 with the smallest battery capacity. Fig.11 As can be seen, there is a correlation between the voltage variation trend (the slope of the discharge curve) and the battery capacity of the lead acid battery 100. Therefore, the battery capacity of the lead acid battery 100 can be estimated by using the fourth correlation between the voltage variation trend and the battery capacity.

[0105] on the other hand, Fig.12 1 is an explanatory diagram showing the voltage change of the lead storage battery 100 when discharging to the load (drive motor 300). Fig.12 As shown, it can be known that when discharging to the load (when the lead-acid battery 100 is used), the current flowing in the lead-acid battery 100 changes due to the action state of the load, and with this, the waveform GR of the voltage of the lead-acid battery 100 changes drastically. Therefore, it is impossible to directly compare the actual voltage change when the lead-acid battery 100 is used with the inclination (hereinafter referred to as "reference inclination") of each discharge curve during the above-mentioned constant current. Therefore, as described below, according to the actual voltage change when the lead-acid battery 100 is used, the value of the current of the lead-acid battery 100 is determined to be the value of multiple voltages VT when the reference value is determined, and the change trend of the approximate straight line GA of the multiple voltage values ​​VT determined is used as the actual change trend of the voltage of the lead-acid battery 100 (hereinafter referred to as "measured inclination").

[0106] (Contents of the Second Presumption Process)

[0107] Fig.13 : is a flowchart showing the flow of the second estimation process. Fig.13 As shown, the current and voltage acquisition unit 541 acquires the current value and the voltage value of the lead storage battery 100 based on the detection results from the voltage detection unit 450 and the detection results from the current detection unit 460 during a predetermined period (S310). Fig.12 The current and voltage acquisition unit 541 is equivalent to the acquisition unit in the claims.

[0108] Next, the voltage determination unit 542 selects a plurality of voltage values ​​VT when the current value is the reference value from the plurality of voltage values ​​acquired by the current and voltage acquisition unit 541 (S320). Next, the second battery capacity determination unit 543 determines the measured inclination of the plurality of voltage values ​​VT selected by the voltage determination unit 542 (S330).

[0109] Next, the second battery capacity determination unit 543 determines whether the estimation condition (S340) is satisfied. The estimation condition is a condition for making the estimation accuracy of the battery capacity based on the second estimation process become a condition above the prescribed level. The estimation condition includes that the lead-acid battery 100 has reached a prescribed depth of discharge. In order to make the estimation accuracy of the battery capacity based on the second estimation process become above the prescribed level, it is necessary to make the determination accuracy of the measured inclination become above the prescribed level, and in order to make the determination accuracy of the measured inclination become above the prescribed level, it is necessary to select and obtain the value VT of the voltage by the voltage determination unit 542 during the period of discharging to the level of the deeper depth of discharge. That is, when the lead-acid battery 100 is repeatedly charged and discharged in a state with a shallower depth of discharge, the determination accuracy of the measured inclination is low, so the second estimation process cannot be used. In addition, in the case of recognizing that the charging of the lead-acid battery 100 based on the charger has begun without determining the depth of discharge of the lead-acid battery 100, it can also be regarded as that the lead-acid battery 100 has reached the prescribed depth of discharge. This is effective only when the lead storage battery 100 is in a state of deep discharge and when charging is performed by a charger.

[0110] If it is determined that the estimation condition is not satisfied (S340: No), the second estimation processing unit 540 returns to S310. If it is determined that the estimation condition is satisfied (S340: Yes), the mapping table indicating the correlation between the battery capacity and the reference inclination is referred to, the discharge amount corresponding to the reference inclination closest to the measured inclination is extracted, and the discharge amount extracted this time is determined as the current battery capacity of the lead-acid battery 100. In addition, the difference between the initial value of the discharge amount and the discharge amount extracted this time can be determined as the change in the battery capacity of the lead-acid battery 100 from the time when it was new.

[0111] A-5. Differentiation of the first and second inference processing:

[0112] As described above, according to the first estimation process, by determining the amount of reduction in battery capacity accompanying the development of the deterioration cause of the lead-acid battery 100 alone, the battery capacity of the lead-acid battery 100 can be estimated with high accuracy. However, as described above, in the first estimation process, the correlation between the open circuit voltage and the battery capacity accompanying the development of sulfation is used. Here, for example, if the temperature of the lead-acid battery 100 becomes higher than the prescribed temperature, or the overcharge amount of the lead-acid battery 100 becomes higher than the reference amount, the concentration of the electrolyte 18 changes, and therefore, there is a possibility that the correlation between the open circuit voltage and the battery capacity accompanying the development of sulfation changes, and the battery capacity of the lead-acid battery 100 cannot be estimated with high accuracy.

[0113] Therefore, as described above, in the battery management process, when it is determined that the switching condition is not satisfied (S120: No), the first estimation process (S130) is executed, and when it is determined that the switching condition is satisfied (S120: Yes), the second estimation process (S140) is executed. In the second estimation process, the correlation between the open circuit voltage and the battery capacity accompanying the development of sulfation is not used, so it is possible to suppress the reduction in the estimation accuracy of the battery capacity of the lead-acid battery 100 due to the change of the correlation. However, as described above, when the lead-acid battery 100 is repeatedly charged and discharged in a state with a relatively shallow depth of discharge, the second estimation process cannot be used. Therefore, in the present embodiment applied to the golf cart 60 in which there is a high possibility that the lead-acid battery 100 is repeatedly charged and discharged in a state with a relatively shallow depth of discharge, it is preferable to perform the first estimation process.

[0114] B. Modifications:

[0115] The technology disclosed in this specification is not limited to the above-mentioned embodiment, and can be modified in various forms within the scope not departing from the gist thereof. For example, the following modifications are also possible.

[0116] In the above embodiment, the golf cart 60 is exemplified as the power storage system, but the present invention is not limited thereto, and may be a mobile object such as a kart running in an amusement park or a transport vehicle running in a factory, or may be a device fixedly arranged at a predetermined position. In short, it only needs to have a secondary battery.

[0117] In addition, in the above-mentioned embodiment, the lead-acid battery 100 is exemplified as a secondary battery, but it is not limited to this, and it may also be a lithium-ion battery or the like. In addition, the deterioration cause is not limited to sulfation and grid corrosion, and it may also be other deterioration causes. In short, in a secondary battery, if the amount of change in battery capacity accompanying the development of the deterioration cause is related to the open circuit voltage, and the amount of change in battery capacity accompanying the development of the deterioration cause is not related to the open circuit voltage, the amount of change in capacity caused by these deterioration causes can be determined separately, thereby being able to estimate the battery capacity of the secondary battery with high accuracy.

[0118] In addition, in the above-mentioned embodiment, as a battery management unit and a capacity estimation device, a BMU400 arranged outside the lead-acid battery 100 is exemplified, but it is not limited to this. For example, it may also be a control unit possessed by the secondary battery, or it may be a server or the like outside the mobile body, and remotely manage the state (deterioration state, etc.) of the secondary battery (lead-acid battery) possessed by the mobile body.

[0119] In addition, in the above-mentioned embodiment, the overall battery capacity of the lead-acid battery 100 is estimated, but the present invention is not limited thereto, and the battery capacity may be estimated individually for the battery C included in the lead-acid battery 100. In addition, instead of determining the battery capacity of the lead-acid battery 100, the amount of change in the battery capacity from the time of new product (the sum of the sulfation capacity reduction amount ΔCA and the grid corrosion capacity reduction amount ΔCB) may be determined, or both the battery capacity of the lead-acid battery 100 and the amount of change in the battery capacity from the time of new product may be determined.

[0120] In the above embodiment, the total resistance determination unit 534 obtains the voltage and current of the lead-acid battery 100 from the outside to calculate the internal resistance value, but the internal resistance value of the lead-acid battery 100 may be obtained from the outside. In the above embodiment, the first battery capacity determination unit 537 simply subtracts the sulfation capacity reduction amount ΔCA and the grid corrosion capacity reduction amount ΔCB from the initial value of the battery capacity, but it may be possible to multiply at least one of the sulfation capacity reduction amount ΔCA and the grid corrosion capacity reduction amount ΔCB by a weighting coefficient in consideration of the various characteristics of the lead-acid battery 100 and the surrounding environment, and then subtract the result from the initial value of the battery capacity.

[0121] In the above embodiment, the reference state is the state of the lead acid battery 100 when it is new, but the present invention is not limited thereto and may be the state when a predetermined time has passed since the start of use of the lead acid battery 100 or the state when the lead acid battery 100 has been charged a predetermined number of times since the start of use.

[0122] In the above embodiment, the display unit 64 is exemplified as the notification unit, but the present invention is not limited thereto, and a sound generating unit such as a speaker, a communication unit that outputs a communication signal to an external device, or the like may be used.

[0123] In the above-mentioned embodiment, the first estimation process may be always executed, and the second estimation process may not be executed. In addition, the conventional estimation process of estimating the battery capacity based on the value of the internal resistance of the secondary battery may be performed instead of the second estimation process. Moreover, even if only the second estimation process is executed alone, the estimation accuracy of the battery capacity of the secondary battery can be improved more than the conventional estimation process.

[0124] Description of Reference Numerals

[0125] 10... housing; 12... battery tank; 14... cover; 16... battery chamber; 18... electrolyte; 20... plate group; 30... positive terminal; 32... positive bushing; 34... positive column; 40... negative terminal; 42... negative bushing; 44... negative column; 52... positive bus bar; 54... negative bus bar; 56... connection member; 58... partition wall; 60... golf cart; 62... operation unit; 64... display unit; 66... ​​display 100 ... lead-acid battery; 210 ... positive plate; 212 ... positive current collector; 214 ... positive ear; 216 ... positive active material; 220 ... negative plate; 222 ... negative current collector; 224 ... negative ear; 226 ... negative active material; 230 ... spacer; 300 ... drive motor; 400 ... BMU; 410 ... control unit; 420 ... storage unit; 421 ... battery management program; 422 ... mapping data; 430 ... input unit ; 440...interface unit; 450...voltage detection unit; 460...current detection unit; 470...temperature detection unit; 510...condition determination unit; 520...display control unit; 530...estimation processing unit; 531...open circuit voltage determination unit; 532...sulfation capacity determination unit; 533...sulfation resistance determination unit; 534...overall resistance determination unit; 535...grid corrosion resistance determination unit; 536...grid corrosion capacity determination unit; 537...battery capacity determination unit; 54 0... estimation processing unit; 541... current and voltage acquisition unit; 542... voltage determination unit; 543... battery capacity determination unit; C... battery; CA... sulfation capacity reduction Δ; CB... grid corrosion capacity reduction Δ; G1~G3... approximate line; GA... approximate straight line; GB1~GB3... discharge curve; GR... waveform; ΔR... overall internal resistance increase; ΔRA... sulfation resistance increase; ΔRB... grid corrosion resistance increase; VT... voltage value.

Claims

1. A device for estimating the capacity of a secondary battery, characterized in that: have: an open circuit voltage determination unit that determines a value of an open circuit voltage of the secondary battery; a first capacity determination unit that determines a change amount of the first capacity of the secondary battery from a reference state based on a first correlation between a first capacity and the open circuit voltage due to a first degradation cause of the secondary battery related to the open circuit voltage and the determined value of the open circuit voltage; a first internal resistance determination unit that determines an amount of change in the first internal resistance due to the first degradation cause based on a second correlation between the first capacity and the first internal resistance of the secondary battery and the determined amount of change in the first capacity; an overall resistance determination unit that determines an amount of change in overall internal resistance of the secondary battery; a second internal resistance determination unit that determines a second internal resistance variation by subtracting the determined first internal resistance variation from the determined total internal resistance variation; a second capacity determination unit that determines a change amount of the second capacity from the reference state of the secondary battery based on a third correlation between the second capacity and the second internal resistance formed due to a second degradation cause of the secondary battery that is not related to the open circuit voltage, and the determined change amount of the second internal resistance; as well as A first battery capacity determination unit determines a battery capacity of the secondary battery based on the determined amount of change in the first capacity and the determined amount of change in the second capacity.

2. The capacity estimation device for a secondary battery according to claim 1, characterized in that: Also available: a condition determination unit configured to determine whether a switching condition is satisfied, the switching condition comprising: at least one of a temperature of the secondary battery being above a predetermined temperature and an overcharge amount of the secondary battery being above a reference amount; and A second battery capacity determination unit determines the battery capacity of the secondary battery by another estimation method that does not use the open circuit voltage, when it is determined that the switching condition is satisfied.

3. The capacity estimation device for a secondary battery according to claim 2, characterized in that: Also available: an acquisition unit that acquires a current and a voltage of the secondary battery; and a voltage determination unit that determines, based on the current and the voltage acquired by the acquisition unit, a value of the voltage of the secondary battery when the value of the current of the secondary battery is a reference value a plurality of times, The second battery capacity determination unit determines a value of the battery capacity of the secondary battery corresponding to the determined variation trends of the voltage values ​​of the plurality of times based on a fourth correlation between the variation trend of the voltage of the secondary battery and the battery capacity of the secondary battery.

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