Charging rate measurement device, charging rate measurement program, battery pack, and saddle-type vehicle

Abstract

To provide a charging rate measurement device that can obtain good measurement accuracy of a charging rate in a battery having a large energy capacity and a small installation space.SOLUTION: A charging rate measurement device is connected to a lithium-ion secondary battery and measures a charging rate of the lithium-ion secondary battery. The charging rate measurement device comprises: a voltage measurement unit; a characteristic storage unit; a charging rate acquisition unit which acquires the charging rate of the lithium-ion secondary battery from a battery voltage measured by the voltage measurement unit with reference to a voltage-charging rate characteristic; a history storage unit which stores a starting charging rate; and a deterioration progress acquisition unit. When the starting charging rates at the starts of a plurality of times of immediately preceding charges are higher than a prescribed charging rate, the charging rate acquisition unit acquires the charging rate of the lithium-ion secondary battery with reference to a lithium correction characteristic in which a charging rate index within a specified voltage range of the voltage-charging rate characteristic is increased, and when the deterioration progress of the lithium-ion secondary battery is greater than a reference progress, reduces the amount of increase of the charging-rate index in the lithium correction characteristic in comparison to a case where the deterioration progress is small.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charging rate measurement device, a charging rate measurement program, a battery pack, and a saddle-type vehicle. [Background technology]

[0002] For example, Patent Document 1 discloses a battery pack for a saddle-ride type vehicle. The battery pack in Patent Document 1 includes multiple batteries and a control unit using a battery management controller. The control unit detects the voltage of the batteries and measures the charging rate of the batteries from the detected voltage. The control unit controls charging and discharging based on the charging rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-232280 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, batteries used to drive load devices such as saddle-type vehicles are sometimes required to have a large energy capacity and to have a small installation space (for example, Patent Document 1,

[0005] The battery charging rate is an index closely related to the amount of power that can be continuously supplied to a load device, for example. Therefore, there are cases where high accuracy in measuring the charging rate is required.

[0005] The object of the present invention is to obtain good measurement accuracy of the charge rate in batteries with a large energy capacity and small installation space. [Means for solving the problem]

[0006] For example, battery packs containing lithium-ion secondary batteries are used to drive straddle-type vehicles. Lithium-ion secondary batteries have a larger energy capacity per unit volume and require less space than, for example, nickel-metal hydride secondary batteries. Furthermore, unlike, for example, nickel-metal hydride secondary batteries, lithium-ion secondary batteries are said to not exhibit the so-called memory effect. For example, a webpage explaining the characteristics of lithium-ion secondary batteries (https: / / www.eco-hatsu.com / battery / faq / 26 / ) states that "Lithium-ion batteries generally do not exhibit a memory effect." If the memory effect does not occur, the charge rate can be obtained from the measured voltage by, for example, referencing a unique voltage-charge rate characteristic that has been prepared in advance.

[0007] However, the present inventors have verified the accuracy of measuring the charging rate under various charging and discharging conditions for the characteristics of various lithium ion secondary batteries, and have found that the accuracy of measuring the charging rate may sometimes decrease. The inventors conducted further research and found that when the initial charging rate at the start of the previous multiple chargings of a lithium ion secondary battery is higher than a reference charging rate, the voltage relative to the charging rate decreases in a certain range compared to when the initial charging rate is not higher, thereby reducing the accuracy of charging rate measurement. Furthermore, the inventors conducted further research and found that as the deterioration of a lithium ion secondary battery progresses, the amount of voltage decrease relative to the charging rate decreases even when the initial charging rate is higher than the reference charging rate. The present invention was completed based on the above findings.

[0008] In order to achieve the above object, according to one aspect of the present invention, a vehicle has the following configuration. (1) A charging rate measuring device connected to a lithium ion secondary battery to measure the charging rate of the lithium ion secondary battery, The charging rate measuring device is a voltage measurement unit for measuring a battery voltage of the lithium ion secondary battery; a characteristics storage unit that stores voltage-charging rate characteristics that represent the characteristics of the lithium ion secondary battery; a charging rate acquisition unit that acquires the charging rate of the lithium ion secondary battery from the battery voltage measured by the voltage measurement unit, by referring to the voltage-charging rate characteristics; a history storage unit that stores an initial charging rate, which is a charging rate at the start of past charging of the lithium ion secondary battery; a deterioration progress obtaining unit for obtaining a deterioration progress of the lithium ion secondary battery; Equipped with When the initial charging rate at the start of the immediately preceding multiple chargings is higher than a predetermined charging rate, the charging rate acquisition unit acquires the charging rate of the lithium ion secondary battery by referring to a lithium corrected characteristic in which a charging rate index in a specific voltage range of the voltage-charging rate characteristic is increased for the lithium ion secondary battery, and when the degree of deterioration of the lithium ion secondary battery is greater than a reference degree of deterioration, the amount of increase in the charging rate index in the lithium corrected characteristic is reduced compared to when the degree of deterioration is small.

[0009] According to the charging rate measurement device of (1), if the initial charging rate at the start of the most recent multiple charging cycles is higher than a predetermined charging rate, the charging rate acquisition unit acquires the charging rate of the lithium ion secondary battery by referring to the lithium corrected characteristic in which the charging rate index in a specific voltage range of the voltage-charging rate characteristic is increased. If the degree of deterioration of the lithium ion secondary battery is higher than the reference degree of deterioration, the amount of increase in the lithium corrected characteristic is reduced compared to when the degree of deterioration is small. Therefore, even if a lithium ion secondary battery is used in which the charging rate in a specific voltage range of the voltage-charging rate characteristic decreases with repeated charging and discharging, and the amount of decrease is smaller as the degree of deterioration increases, high accuracy can be achieved in measuring the charging rate over the entire usable period of the lithium ion secondary battery. Therefore, high accuracy can be achieved in measuring the charging rate of a lithium ion secondary battery that has a large energy capacity and requires a small installation space.

[0010] The charging rate measuring device is, for example, a battery management system (BMS) or a battery management controller (BMC) that is mounted on a battery pack having a lithium-ion secondary battery and controls the charging and discharging of the lithium-ion secondary battery. However, the charging rate measuring device is not particularly limited and may be, for example, a charging rate display device that displays the measured charging rate. Furthermore, the charging rate measuring device may be located at a position away from the lithium-ion secondary battery.

[0011] A lithium-ion secondary battery is a battery that charges and discharges by the movement of lithium ions. A lithium-ion secondary battery is a rechargeable battery. A lithium-ion secondary battery, for example, has a positive electrode containing lithium oxide. A lithium-ion secondary battery, for example, has a negative electrode containing lithium. Furthermore, for example, a lithium-ion secondary battery has a negative electrode containing a silicon-based material. When a lithium-ion secondary battery has an electrode containing a silicon-based material, its capacity increases. However, in this case, if the initial charge rate at the start of the previous multiple charging cycles is higher than the reference charge rate, the charge rate in a specific voltage range tends to increase. Therefore, referring to the voltage-charge rate characteristic tends to reduce the measurement accuracy of the charge rate. However, by referring to the lithium correction characteristic and reducing the increase in the lithium correction characteristic when the deterioration progress is greater than the reference progress, good measurement accuracy can be achieved.

[0012] The battery voltage is, for example, the voltage of a battery pack having a plurality of lithium-ion secondary battery cells connected in series. However, the battery voltage is not particularly limited and may be, for example, the voltage of a single lithium-ion secondary battery cell. The battery voltage is, for example, a closed circuit voltage. More specifically, the battery voltage can be obtained by correcting the voltage during discharge according to the magnitude of the discharge current. In this case, a precise charge rate can be obtained even while the load device is operating. However, the battery voltage is not limited to this, and can also be the voltage when an open circuit to the load is opened, for example.

[0013] For example, after two consecutive charges starting at a starting charging rate higher than a predetermined charging rate, the charging rate acquisition unit acquires the charging rate of the lithium ion secondary battery by referring to the lithium correction characteristic, and if the deterioration progress degree is greater than the reference progress degree, reduces the increase amount in the lithium correction characteristic. However, the condition is that the number of previous charges starting at a starting charging rate higher than the predetermined charging rate may be multiple, for example, three or more. For example, after 10 or more consecutive charges starting at a starting charging rate higher than the predetermined charging rate, the charging rate acquisition unit acquires the charging rate of the lithium ion secondary battery by referring to the lithium correction characteristic, and if the deterioration progress degree is greater than the reference progress degree, reduces the increase amount in the lithium correction characteristic.

[0014] The voltage-charging rate characteristic is a characteristic that indicates the relationship between the voltage and charging rate of a battery. Specifically, the characteristic is characteristic map data. The voltage-charging rate characteristic is, for example, a relationship that indicates the reference characteristic between the voltage and charging rate of a battery after it has been charged from a state where the charging rate is lower than a predetermined charging rate. The voltage-charging rate characteristic is, for example, a characteristic that is referenced after the battery has been charged from a state where the charging rate is lower than a predetermined charging rate. The voltage-charging rate characteristic is stored in the characteristic storage unit as a characteristic obtained, for example, based on previous measurement results of a battery of the same type as the battery being measured. The voltage-charging rate characteristic may also be, for example, a characteristic obtained based on previous measurement results of the battery itself being measured. The lithium corrected characteristic is, for example, a voltage-charging rate characteristic that shows the relationship between the voltage and charging rate of a battery after charging from a charging rate state higher than a predetermined charging rate. In the lithium corrected characteristic, a portion of the voltage-charging rate characteristic is corrected. In the lithium corrected characteristic, the charging rate indicator in a specific voltage range is increased compared to the voltage-charging rate characteristic without correction. The increase in the charging rate indicator in the lithium corrected characteristic may be gradually decreased when the degree of deterioration is greater than the reference degree of deterioration. Alternatively, this increase may be gradually decreased as the degree of deterioration increases. The lithium corrected characteristic is stored in the characteristic storage unit as characteristic map data acquired based on previous measurement results of a battery of the same type as the measurement target. However, the lithium corrected characteristic may also be a correction formula or correction data map applied to a portion of the voltage-charging rate characteristic to correct the reference result. Furthermore, multiple sets of voltage-charging rate characteristics may be stored according to the degree of deterioration of the battery. In this case, the voltage-charging rate characteristics according to the degree of deterioration of the battery to be measured can be referenced. Furthermore, a lithium correction characteristic may be provided for each of the multiple sets of voltage-charging rate characteristics. Furthermore, for some of the multiple sets of voltage-charging rate characteristics, no lithium correction characteristic may be provided, as they may not be substantially corrected. The specific voltage range is set, for example, within a range smaller than the voltage corresponding to half of full charge. The specific voltage range is set, for example, within a range greater than the voltage corresponding to 5% and smaller than the voltage corresponding to a charging rate less than 25% in the voltage-charging rate characteristics. In this case, it is easy to respond to changes in the characteristics of lithium-ion secondary batteries having electrodes containing silicon-based materials.

[0015] The degradation degree represents the extent to which a lithium-ion secondary battery has been used from the start of use until the end of its life. A low degradation degree refers to a degradation degree that is lower than a reference degradation degree. When the degradation degree is higher than the reference degradation degree, reducing the increase in the lithium-ion secondary battery characteristic compared to when the degradation degree is low may, for example, mean that the increase in the lithium-ion secondary battery characteristic decreases as the degradation degree increases. As a result of reducing the increase in the lithium-ion secondary battery characteristic compared to when the degradation degree is low, the charge rate indicator in a specific voltage range of the lithium-ion secondary battery characteristic is equal to or exceeds the indicator in the voltage-charge rate characteristic before the increase, for example, a predetermined number of charge / discharge cycles since the start of use. The reference degradation degree is a standard for the degradation degree set from the start of use until the end of its life. The specific reference degradation degree is determined depending on the type of lithium-ion secondary battery.

[0016] According to one aspect of the present invention, the vehicle can adopt the following configuration. (2) A charging rate measuring device according to (1), The charging rate acquisition unit reduces an increase in the charging rate index in the lithium correction characteristic when the initial charging rate at the start of the immediately preceding charging is lower than the predetermined charging rate.

[0017] When the initial charging rate at the start of the previous charging is lower or higher than a predetermined charging rate, the voltage drop relative to the charging rate in a specific voltage range in the voltage-charging rate characteristic of the lithium ion secondary battery is reduced. According to the configuration (2), when the initial charging rate at the start of the previous charging is lower or higher than a predetermined charging rate, the increase in the lithium correction characteristic is reduced, so even in this case, good accuracy in measuring the charging rate of the lithium ion secondary battery can be obtained.

[0018] (3) In the charging rate measuring device of (1) or (2), the deterioration progress acquisition unit acquires, as the deterioration progress, the cumulative charge amount of the lithium ion secondary battery, the cumulative discharge amount of the lithium ion secondary battery, the capacity of the lithium ion secondary battery, the internal resistance of the lithium ion secondary battery, the capacity of the lithium ion secondary battery, or the deviation of each voltage of the lithium ion secondary battery.

[0019] According to the configuration (3), the precise degree of deterioration of the lithium ion secondary battery can be obtained indirectly and easily.

[0020] (4) A charging rate measuring device according to any one of (1) to (3), The predetermined charging rate is set between 20% and 50% of the fully charged charging rate.

[0021] According to the configuration (4), good accuracy in measuring the charging rate can be obtained for lithium ion secondary batteries in which the voltage drops relative to the charging rate in a certain voltage range when charging starts from a charging rate within a predetermined range.

[0022] (5) A charging rate measuring device according to any one of (1) to (4), The battery includes a discharge prohibition unit that prohibits discharging of the lithium ion secondary battery when the charging rate acquired by the charging rate acquisition unit is below a charging rate lower limit value.

[0023] According to the configuration of (5), when the charging rate falls below the charging rate lower limit, discharging of the lithium ion secondary battery is prohibited, thereby suppressing shortening of the usable period of the lithium ion secondary battery. Furthermore, since the charging rate is precisely obtained by referring to the lithium correction characteristic, it is possible to suppress shortening of the usable period while discharging the lithium ion secondary battery to the maximum limit.

[0024] (6) A charging rate measuring device according to any one of (1) to (5), the lithium ion secondary battery connected to the charging rate measuring device; A battery pack equipped with

[0025] According to the configuration (6), it is possible to obtain better measurement accuracy of the charging rate in a lithium ion secondary battery that has a large energy capacity and requires a small installation space, thereby increasing the actual capacity that the lithium ion secondary battery can charge and discharge compared to a case where this configuration is not provided.

[0026] (7) The battery pack (6), a motor that receives power from the battery pack; a wheel driven by the motor; A saddle-type vehicle equipped with a

[0027] According to the configuration (7), the effective charging and discharging capacity of the lithium ion secondary battery can be increased, so that a saddle-type vehicle equipped with a battery pack having a large energy capacity can be made smaller.

[0028] A straddled vehicle is a vehicle in which a rider sits astride a saddle. Examples of straddled vehicles include scooters, mopeds, off-road vehicles, and on-road motorcycles. Furthermore, straddled vehicles are not limited to motorcycles and may include, for example, three-wheeled motor vehicles and ATVs (All-Terrain Vehicles). A three-wheeled motor vehicle may have two front wheels and one rear wheel, or one front wheel and two rear wheels. A straddled vehicle is steered by shifting the rider's weight. For this reason, straddled vehicles are required to be small and lightweight. Furthermore, it is preferable that a vehicle be configured to be able to turn in a lean position. A vehicle configured to be able to turn in a lean position is configured to turn in a position tilted toward the center of a curve. As a result, a vehicle configured to be able to turn in a lean position can resist the centrifugal force acting on the vehicle when turning. An example of a vehicle that can turn in a lean position is a straddle-type vehicle (e.g., a motorcycle or a three-wheeled vehicle) that can turn in a lean position. Vehicles that can turn in a lean position require agility, so it is important that they are small and lightweight.

[0029] (8) A charging rate measurement program for causing a computer provided in a charging rate measurement device connected to a lithium ion secondary battery to perform an operation of measuring the charging rate of the lithium ion secondary battery, The charging rate measurement program a voltage measurement function for measuring a battery voltage of the lithium ion secondary battery; a characteristic storage function for storing voltage-charging rate characteristics representing the characteristics of the lithium ion secondary battery; a charging rate acquisition function that acquires the charging rate of the lithium ion secondary battery from the battery voltage measured by the voltage measurement function, by referring to the voltage-charging rate characteristics; a history storage function for storing a starting charging rate, which is a charging rate at the start of past charging of the lithium ion secondary battery; A deterioration degree acquisition function for acquiring a deterioration degree of the lithium ion secondary battery is realized, As the charging rate acquisition function, if the initial charging rate at the start of the immediately preceding multiple chargings is higher than a predetermined charging rate, the charging rate of the lithium ion secondary battery is acquired by referring to a lithium corrected characteristic in which the charging rate index in a specific voltage range of the voltage-charging rate characteristic is increased for the lithium ion secondary battery, and if the deterioration progress of the lithium ion secondary battery is greater than a reference progress, the increase in the charging rate index in the lithium corrected characteristic is reduced compared to when the deterioration progress is small.

[0030] According to the configuration (8), the substantial charge / discharge capacity of the lithium ion secondary battery can be increased.

[0031] The terminology used herein is for the purpose of defining particular embodiments only and is not intended to limit the invention. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed components. As used herein, the use of the terms "including," "comprising," or "having," and variations thereof, identifies the presence of stated features, steps, operations, elements, components, and / or equivalents thereof, but may include one or more of the steps, operations, elements, components, and / or groups thereof. As used herein, the terms "attached," "connected," "coupled," and / or equivalents thereof are used broadly and encompass both direct and indirect attachments, connections, and couplings. Furthermore, "connected" and "coupled" are not limited to physical or mechanical connections or couplings, but can include direct or indirect electrical connections or couplings. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms, such as those defined in commonly used dictionaries, should be interpreted to have a meaning consistent with the meaning in the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein. It is understood that numerous techniques and processes are disclosed in the description of the present invention. Each of these has distinct advantages, and each can also be used with one or more, or in some cases all, of the other disclosed techniques. Therefore, for the sake of clarity, this description will refrain from unnecessarily repeating every possible combination of individual steps. Nevertheless, the specification and claims should be read with the understanding that all such combinations are within the scope of the present invention and claims. This specification describes a new charging rate measurement device, a charging rate measurement program, a battery pack, and a saddle-type vehicle. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without these specific details. The present disclosure should be considered as an example of the present invention, and is not intended to limit the present invention to the specific embodiments shown in the following drawings or description. [Effects of the Invention]

[0032] According to the present invention, it is possible to provide a charging rate measuring device, a charging rate measuring program, a battery pack, and a saddle-type vehicle that can measure the charging rate with good accuracy in a battery that has a large energy capacity and requires a small installation space. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a diagram illustrating a battery system including a charging rate measuring device according to an embodiment; [Figure 2] 2 is a chart showing voltage-charging rate characteristics in the example of the charging rate measuring device shown in FIG. 1. [Figure 3] 1. FIG. 4 is a block diagram showing another example of the charging rate measuring device shown in FIG. [Figure 4] 1. FIG. 4 is a block diagram showing another example of the charging rate measuring device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0034] FIG. 1 is a diagram illustrating a battery system including a charging rate measurement device according to one embodiment. Part (a) of FIG. 1 is a block diagram illustrating a schematic configuration of a battery system including a charging rate measurement device. Part (b) of FIG. 1 is a block diagram illustrating a functional configuration of the charging rate measurement device. Part (c) of FIG. 1 is a flowchart illustrating the operation of the charging rate measurement device. Part (d) of FIG. 1 is a chart illustrating voltage-charging rate characteristics when the degree of deterioration is low. Part (e) of FIG. 1 is a chart illustrating voltage-charging rate characteristics when the degree of deterioration is high.

[0035] The battery system S shown in Fig. 1 functions as a power source that supplies power to external electrical devices. The battery system S can receive power from an external source and be charged. The battery system S includes a charging rate measuring device 1 and a lithium ion secondary battery 2. The lithium ion secondary battery 2 is made up of a plurality of cells connected in series. The lithium ion secondary battery 2 has electrodes containing, for example, a silicon-based material.

[0036] The charging rate measuring device 1 is connected to the lithium ion secondary battery 2 and measures the charging rate of the lithium ion secondary battery 2. The charging rate measuring device 1 outputs a signal representing the measured charging rate. The charging rate measuring device 1 is a computer including a processor 101 and a storage device 102. A charging rate measuring program 103 is stored in the storage device 102. The processor 101 executes the charging rate measuring program 103 to realize each function of the charging rate measuring device 1. The storage device 102 also stores various data such as voltage-charging rate characteristic data 104.

[0037] The charging rate measuring device 1 includes a voltage measuring unit 11, a characteristic storage unit 12, a charging rate acquiring unit 13, a history storage unit 14, and a deterioration progress acquiring unit 15. The voltage measurement unit 11, the charging rate acquisition unit 13, and the deterioration progress degree acquisition unit 15 are configured by the processor 101 executing the charging rate measurement program 103. The characteristics storage unit 12 and the history storage unit 14 are configured by the processor 101 executing the charging rate measurement program 103 and the storage device 102. By executing the charging rate measurement program 103, the processor 101 realizes the charging rate measurement function of the charging rate measurement device 1 described below, the voltage measurement function of the voltage measurement unit 11, the characteristic storage function of the characteristic storage unit 12, the charging rate acquisition function of the charging rate acquisition unit 13, the history storage function of the history storage unit 14, and the deterioration progress acquisition function of the deterioration progress acquisition unit 15.

[0038] The voltage measurement unit 11 measures the battery voltage of the lithium ion secondary battery 2. The voltage measurement unit 11 measures the battery voltage using an A / D converter (not shown) provided in the charging rate measurement device 1, for example.

[0039] The history storage unit 14 stores an initial charging rate, which is the charging rate at the start of past charging of the lithium ion secondary battery 2. The history storage unit 14 stores the initial charging rates for multiple past chargings. More specifically, the history storage unit 14 stores at least the number of times that the charging rate at the start of charging of the lithium ion secondary battery 2 has been higher than a predetermined charging rate C1 (part (d) of FIG. 1) in the most recent consecutive cases.

[0040] The deterioration progress degree acquiring unit 15 acquires the deterioration progress degree of the lithium ion secondary battery 2. The deterioration progress degree acquiring unit 15 acquires, for example, the accumulated charging current or the accumulated discharging current since the lithium ion secondary battery 2 was first used as the deterioration progress degree.

[0041] The characteristic storage unit 12 stores the voltage-charging rate characteristic Qa. More specifically, the voltage-charging rate characteristic Qa is data representing the relationship between the voltage and charging rate of the lithium ion secondary battery 2. More specifically, the voltage-charging rate characteristic Qa is map data that associates the voltage and charging rate of the lithium ion secondary battery 2. The solid lines in parts (d) and (e) of FIG. 1 represent the voltage-charging rate characteristic Qa of the lithium ion secondary battery 2. The solid line in part (e) of FIG. 1 represents the voltage-charging rate characteristic Qa in a state where the degree of degradation is greater than that of the characteristic shown in part (d), i.e., where the degradation has progressed. The vertical axis in parts (d) and (e) of Figure 1 represents the battery voltage. The horizontal axis represents the amount of discharged power from the fully charged state to the end of discharge state. The horizontal axis also represents the charge rate of the lithium-ion secondary battery 2. The charge rate in the fully charged state is 100%, and the charge rate in the end of discharge is 0%. The charge rate decreases as the amount of discharged power increases. Therefore, on the horizontal axis in parts (d) and (e) of Figure 1, the discharged power amount index, i.e., the value of the discharged power amount, increases toward the right. In contrast, the value of the charge rate index increases toward the left. The battery voltage of the lithium ion secondary battery 2 changes depending on the charging rate. More specifically, the lithium ion secondary battery 2 has a voltage-charging rate characteristic Qa in which the battery voltage decreases as the charging rate decreases. 1, the solid lines indicate the voltage-charge rate characteristic Qa of the lithium ion secondary battery 2 when the initial charge rate at the start of the most recent charging of the lithium ion secondary battery 2 is lower than the predetermined charge rate C1. The dashed lines indicate the lithium corrected characteristic Qb with an increased charge rate index in the specific voltage range Vr.

[0042] The voltage-charging rate characteristic Qa and the lithium corrected characteristic Qb are stored in the characteristic storage unit 12. The voltage-charging rate characteristic Qa stored in the characteristic storage unit 12 is, for example, a standard characteristic obtained from a previous measurement of a battery of the same type as the lithium ion secondary battery 2. However, the voltage-charging rate characteristic Qa and the lithium corrected characteristic Qb may also be characteristics obtained from a measurement of the lithium ion secondary battery 2 itself when the lithium ion secondary battery 2 is manufactured or used. The characteristic storage unit 12 also stores voltage-charging rate characteristics Qa in an initial state shown in part (d) of Fig. 1, and voltage-charging rate characteristics Qa in a state where the degree of degradation is high shown in part (e) of Fig. 1. The voltage-charging rate characteristics Qa stored in the characteristic storage unit 12 are not limited to the two shown in the figure, and may store three or more voltage-charging rate characteristics Qa corresponding to the respective stages of degradation.

[0043] The charging rate acquisition unit 13 acquires the charging rate of the lithium ion secondary battery 2 from the battery voltage measured by the voltage measurement unit 11, by referring to the voltage-charging rate characteristics (e.g., Qa in part (d) of Figure 1) stored in the characteristic storage unit 12. However, if the initial charging rate at the start of the most recent multiple charging is higher than a predetermined charging rate C1, the charging rate acquisition unit 13 acquires the charging rate of the lithium ion secondary battery 2 by referring to the lithium corrected characteristic Qb. The lithium corrected characteristic Qb is a characteristic in which the charging rate index in the specific voltage range Vr of the voltage-chart-rate characteristic Qa is increased. Furthermore, if the deterioration progress of the lithium ion secondary battery 2 is greater than the reference progress D1, the charging rate acquisition unit 13 acquires the charging rate of the lithium ion secondary battery 2 by referring to the lithium corrected characteristic Qb in which the increase in the charging rate index in the specific voltage range Vr is reduced, as shown in part (e) of FIG. 1.

[0044] An example of the operation of the charging rate measuring device 1 will be described with reference to the flowchart in part (c) of FIG. In the charging rate measurement device 1, the charging rate measurement program 103 is executed by the processor 101, thereby implementing the functions of the units shown in part (b) of Fig. 1. The operation of each step is repeated.

[0045] The voltage measurement unit 11 measures the battery voltage of the lithium ion secondary battery 2 (S11). The charging rate of the lithium ion secondary battery 2 is acquired based on the voltage measured at the time the voltage is measured.

[0046] The deterioration progress obtaining unit 15 obtains the deterioration progress of the lithium ion secondary battery 2 (S12).

[0047] The charging rate acquisition unit 13 determines whether the previous charging of the lithium ion secondary battery 2 started from a high charging rate state (S13). More specifically, the charging rate acquisition unit 13 determines whether the starting charging rate at the start of the previous multiple chargings is higher than a predetermined charging rate C1. The history storage unit 14 stores the starting charging rates at the start of past chargings. The charging rate acquisition unit 13 acquires the starting charging rates at the start of the previous multiple chargings from the history storage unit 14. If the initial charging rate at the start of the previous multiple charging is lower than the predetermined charging rate C1 (No in S13), the charging rate acquisition unit 13 refers to the voltage-charging rate characteristic Qa and acquires the charging rate of the lithium ion secondary battery 2 from the battery voltage (S15).

[0048] If the initial charging rate at the start of the previous multiple charging is higher than the predetermined charging rate C1 (Yes in S13), the charging rate acquisition unit 13 corrects the voltage-charging rate characteristic Qa to the lithium corrected characteristic Qb (S14).The charging rate acquisition unit 13 acquires the charging rate of the lithium ion secondary battery 2 from the battery voltage by referring to the lithium corrected characteristic Qb (S15). In the lithium corrected characteristic Qb, the charging rate indicator in the specific voltage range Vr of the voltage-charging rate characteristic Qa is increased. Parts (d) and (e) of Fig. 1 show schematic examples of histories H1 and H2 of the change in the charging rate accompanying the charging and discharging of the lithium-ion secondary battery 2. Histories H1 and H2 show the change in which charging starts multiple times in succession when the charging rate is higher than a predetermined charging rate C1 (i.e., to the left of C1 on the graph), followed immediately by discharging until the charging rate reaches 0. In the case of histories H1 and H2, the charging rate acquisition unit 13 corrects the voltage-charging rate characteristic Qa to the lithium corrected characteristic Qb (S14), and acquires the charging rate of the lithium ion secondary battery 2 from the battery voltage by referring to the lithium corrected characteristic Qb (S15).

[0049] The reference number of times that the initial charging rate is higher than the predetermined charging rate C1, as determined in step S13, differs depending on the type of lithium ion secondary battery 2. This number is set, for example, between 2 and 20 times.

[0050] When the degree of deterioration of the lithium ion secondary battery 2 is greater than the reference degree of deterioration D1, the charging rate acquisition unit 13 reduces the amount of increase in the charging rate index in the specific voltage range Vr in the lithium corrected characteristic Qb. More specifically, the charging rate acquisition unit 13 reduces the amount of increase in the charging rate index in the specific voltage range Vr in the lithium corrected characteristic Qb (part (e) of FIG. 1) compared to when the degree of deterioration is less than the reference degree of deterioration D1 (part (d) of FIG. 1). The charging rate acquisition unit 13 acquires the charging rate of the lithium ion secondary battery 2 by referring to the lithium corrected characteristic Qb in which the amount of increase in the charging rate index has been reduced (S15).

[0051] Research by the inventors has revealed that, for some lithium-ion secondary batteries 2, when the initial charging rate at the start of multiple charging is higher than a reference charging rate, the voltage relative to the charging rate decreases within a certain range of the voltage-charging rate characteristic Qa, compared to when the initial charging rate is not higher. In other words, for some lithium-ion secondary batteries 2, the charging rate increases relative to the voltage within a certain range of the voltage-charging rate characteristic Qa. For example, lithium-ion secondary batteries 2 having a negative electrode containing a silicon-based material exhibit this tendency more strongly. Furthermore, it has been found that as the deterioration of the lithium-ion secondary battery 2 progresses, the amount of decrease in voltage relative to the charging rate decreases, even when the initial charging rate is higher than the reference charging rate. In other words, it has been found that the increase in the charging rate relative to the voltage decreases within a certain range.

[0052] According to this embodiment, when the initial charging rate at the start of the most recent multiple charging is higher than a predetermined charging rate C1, the charging rate acquisition unit 13 acquires the charging rate of the lithium ion secondary battery 2 by referring to the lithium corrected characteristic Qb in which the charging rate index in a specific voltage range is increased, and when the degree of deterioration of the lithium ion secondary battery 2 is higher than the reference degree of deterioration D1, the charging rate acquisition unit 13 acquires the charging rate by referring to the lithium corrected characteristic Qb in which the increase in the charging rate index is reduced compared to when the degree of deterioration is small, as shown in part (e) of Figure 1. Therefore, good measurement accuracy can be obtained even when a lithium ion secondary battery 2 is used in which the charging rate in the specific voltage range Vr in the voltage-charging rate characteristic Qa decreases when charging from an initial charging rate higher than the reference charging rate is repeated, and the amount of this decrease decreases as the degree of deterioration increases. Therefore, good measurement accuracy can be obtained for the charging rate of a lithium ion secondary battery 2 that has a large energy capacity and requires a small installation space.

[0053] FIG. 2 is a chart showing voltage-charging rate characteristics in the example of the charging rate measuring device shown in FIG.

[0054] 2 shows an example of a history H3 of changes in the charging rate associated with charging and discharging of the lithium-ion secondary battery 2. According to the history H3, the initial charging rate Ca at the start of the most recent charging is smaller than the predetermined charging rate C1. In this case, the charging rate acquisition unit 13 may reduce the increase in the charging rate index in the lithium corrected characteristic Qb below the increase in the lithium corrected characteristic Qb shown in part (d) of FIG.

[0055] If the initial charging rate Ca at the start of the previous charging is lower than the predetermined charging rate C1, the voltage drop relative to the charging rate in a specific voltage range Vr in the characteristics of the lithium-ion secondary battery 2 is mitigated. In the example described with reference to Fig. 2, if the initial charging rate Ca at the start of the previous charging is lower than the predetermined charging rate C1, the increase in the lithium corrected characteristic Qb is reduced, thereby achieving good accuracy in measuring the charging rate.

[0056] It has also been described that the deterioration progress obtaining unit 15 of the charging rate measuring device shown in FIG. 1 obtains the accumulated charge amount or the accumulated discharge amount as the deterioration progress. However, the indicators obtained by the deterioration progress obtaining unit 15 are not limited to these. In one example, the deterioration progress obtaining unit 15 may obtain the accumulated charge amount, the accumulated discharge amount, the internal resistance, the battery capacity, or the deviation of the voltage. Furthermore, the deterioration progress obtaining unit 15 may obtain a combination of these. The internal resistance can be obtained, for example, by measuring the current and voltage when the lithium-ion secondary battery 2 is being charged or discharged, and then from the current and voltage. The battery capacity can be obtained, for example, from the voltage when fully charged, using a relationship characteristic measured in advance. The fully charged state is detected as a state in which substantially no charging current flows even when a charging voltage is applied. The voltage deviation can be obtained, for example, by detecting the voltage of each cell in the lithium-ion secondary battery 2, and then as the difference between the maximum and minimum values of the detected voltage.

[0057] According to the above example of the index, it is possible to obtain a precise degree of deterioration of the lithium ion secondary battery 2 using an index that is easy to obtain depending on the type of system.

[0058] FIG. 3 is a block diagram showing another example of the charging rate measuring device shown in FIG. 3, the charging rate measuring device 1 may be configured together with a lithium ion secondary battery 2 to form a battery pack P. In other words, the battery pack P includes the charging rate measuring device 1 and the lithium ion secondary battery 2.

[0059] The charging rate measurement device 1 may also include a discharge prohibition unit 105 that prohibits discharging of the lithium ion secondary battery 2. When the charging rate acquired by the charging rate acquisition unit 13 is below a charging rate lower limit, the discharge prohibition unit 105 prohibits discharging of the lithium ion secondary battery 2. As the charging rate lower limit, for example, a lower limit that makes it easy to maintain the usable period of the lithium ion secondary battery 2 is set. The charging rate lower limit is set, for example, within a range of 1% to 9% of a fully charged state.

[0060] If the charging rate of the lithium ion secondary battery 2 falls below the charging rate lower limit while the lithium ion secondary battery 2 is being discharged, discharging is prohibited. Therefore, the charging rate of the lithium ion secondary battery 2 is unlikely to fall below the charging rate lower limit. As a result, shortening of the usable period of the lithium ion secondary battery 2 is suppressed. Furthermore, since the charging rate is precisely obtained by also referring to the lithium corrected characteristic Qb, it is possible to suppress shortening of the usable period while discharging the lithium ion secondary battery 2 to the maximum limit.

[0061] In addition, in the example shown in FIG. 3, better measurement accuracy of the charging rate of the lithium ion secondary battery 2 can be obtained, thereby increasing the actual capacity that can be charged and discharged as the battery pack P compared to, for example, a battery pack that does not have this configuration.

[0062] FIG. 4 is a block diagram showing another example of the charging rate measuring device shown in FIG. The charging rate measuring device 1 may be provided in a saddle-riding type vehicle 3, as shown in FIG. 4. The saddle-riding type vehicle 3 includes a battery pack P, a motor 4, and wheels 5. The rotation of the wheels 5 causes the saddle-riding type vehicle 3 to move. The wheels 5 are driven by the motor 4. The motor 4 receives a supply of power from the battery pack P.

[0063] The straddle-type vehicle 3 of FIG. 4 can increase the effective charging and discharging capacity of the lithium-ion secondary battery 2, and therefore can reduce the size of the straddle-type vehicle 3 equipped with a battery pack P having a large energy capacity. [Explanation of symbols]

[0064] 1: Charging rate measuring device 2: Lithium-ion secondary battery 3: Saddle-type vehicle 4: Motor 5: Wheels 11: Voltage measurement section 12: Characteristics memory section 13: Charge rate acquisition section 14: History memory section 15: Deterioration progress acquisition section 103:Charging rate measurement program 105:Discharge inhibition part C1: Predetermined charging rate D1: Standard progress rate P: Battery pack Qa: Voltage-charging rate characteristics Qb: Lithium correction characteristic Vr: Specific voltage range

Claims

1. A charging rate measurement device connected to a lithium ion secondary battery to measure the charging rate of the lithium ion secondary battery, The charging rate measuring device is a voltage measurement unit for measuring a battery voltage of the lithium ion secondary battery; a characteristics storage unit that stores voltage-charging rate characteristics that represent the characteristics of the lithium ion secondary battery; a charging rate acquisition unit that acquires the charging rate of the lithium ion secondary battery from the battery voltage measured by the voltage measurement unit by referring to the voltage-charging rate characteristics; a history storage unit that stores an initial charging rate, which is a charging rate at the start of past charging of the lithium ion secondary battery; a deterioration progress obtaining unit for obtaining a deterioration progress of the lithium ion secondary battery; Equipped with When the initial charging rate at the start of the immediately preceding multiple chargings is higher than a predetermined charging rate, the charging rate acquisition unit acquires the charging rate of the lithium ion secondary battery by referring to a lithium corrected characteristic in which a charging rate index in a specific voltage range of the voltage-charging rate characteristic is increased for the lithium ion secondary battery, and when the degree of deterioration of the lithium ion secondary battery is greater than a reference degree of deterioration, the amount of increase in the charging rate index in the lithium corrected characteristic is reduced compared to when the degree of deterioration is small.

2. The charging rate measuring device of claim 1, The charging rate acquisition unit reduces an increase in the charging rate index in the lithium correction characteristic when the initial charging rate at the start of the immediately preceding charging is lower than the predetermined charging rate.

3. 3. A charging rate measuring device according to claim 1, wherein the deterioration progress acquisition unit acquires, as the deterioration progress, the cumulative charge amount of the lithium ion secondary battery, the cumulative discharge amount of the lithium ion secondary battery, the capacity of the lithium ion secondary battery, the internal resistance of the lithium ion secondary battery, the capacity of the lithium ion secondary battery, or the deviation of the voltage of each of the lithium ion secondary batteries.

4. The charging rate measuring device according to any one of claims 1 to 3, The predetermined charging rate is set between 20% and 50% of the fully charged charging rate.

5. The charging rate measuring device according to any one of claims 1 to 4, The battery includes a discharge prohibition unit that prohibits discharging of the lithium ion secondary battery when the charging rate acquired by the charging rate acquisition unit is below a charging rate lower limit value.

6. The charging rate measuring device according to any one of claims 1 to 5, the lithium ion secondary battery connected to the charging rate measuring device; A battery pack equipped with

7. The battery pack according to claim 6; a motor that receives power from the battery pack; a wheel driven by the motor; A saddle-type vehicle equipped with a

8. A charging rate measurement program that causes a computer provided in a charging rate measurement device connected to a lithium ion secondary battery to perform an operation of measuring a charging rate of the lithium ion secondary battery, The charging rate measurement program a voltage measurement function for measuring a battery voltage of the lithium ion secondary battery; a characteristic storage function for storing voltage-charging rate characteristics representing the characteristics of the lithium ion secondary battery; a charging rate acquisition function that acquires the charging rate of the lithium ion secondary battery from the battery voltage measured by the voltage measurement function, by referring to the voltage-charging rate characteristics; a history storage function for storing a starting charging rate, which is a charging rate at the start of past charging of the lithium ion secondary battery; A deterioration degree acquisition function for acquiring a deterioration degree of the lithium ion secondary battery is realized, As the charging rate acquisition function, if the initial charging rate at the start of the immediately preceding multiple chargings is higher than a predetermined charging rate, the charging rate of the lithium ion secondary battery is acquired by referring to a lithium corrected characteristic in which the charging rate index in a specific voltage range of the voltage-charging rate characteristic is increased for the lithium ion secondary battery, and if the deterioration progress of the lithium ion secondary battery is greater than a reference progress, the increase in the charging rate index in the lithium corrected characteristic is reduced compared to when the deterioration progress is small.

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