BATTERY MANAGEMENT DEVICE AND BATTERY MANAGEMENT SYSTEM

Abstract

A battery management device according to the present disclosure comprises: a high-frequency signal supply unit that supplies a high-frequency signal of 0.1 MHz or higher to a lithium-ion secondary battery; an impedance sensing unit that detects a value of a real part of an AC impedance from the lithium-ion secondary battery to which the high-frequency signal is supplied; a calculation unit that calculates a Li deposition quantity in the lithium-ion secondary battery from the detected value of the real part of the AC impedance; and a control unit that reduces a permissible charging power for the lithium-ion secondary battery if the calculated Li deposition quantity is greater.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present disclosure relates to a battery management device and a battery management system. 2. Description of the state of the art

[0002] To prevent the performance degradation of a lithium-ion secondary battery, it is desirable to limit the deposition (hereinafter referred to as Li deposition) of lithium (Li) metal in the lithium-ion secondary battery. However, no method is currently known for detecting Li deposition in the lithium-ion secondary battery in a non-destructive manner.

[0003] In response, as disclosed in Japanese unpublished patent application No. 2022-108602 (JP 2022-108602 A), the inventors have developed a method by which the real part of the AC impedance of the lithium-ion secondary battery is detected using a high-frequency signal and the amount of Li deposited in the lithium-ion secondary battery is calculated based on the difference between the real part of the AC impedance in the current value and in the initial value. OVERVIEW OF THE INVENTION

[0004] Lithium deposition progresses with increasing charging power, which is why, from the perspective of limiting lithium deposition, a permissible charging power is defined for each product type of lithium-ion secondary battery. Regarding the rate of lithium deposition in the lithium-ion secondary battery, there is a variation (for example, a standard deviation σ) depending on the individual product, even within the same product type. For example, in conventional lithium-ion secondary batteries, for products within a range of ±6σ, the permissible charging power for each product type is set (fixed) at a value that is too low, so that lithium deposition does not progress, resulting in a long charging time.

[0005] The present disclosure was made taking into account the above circumstances and aims to provide a battery management device and a battery management system that enable efficient charging of the lithium-ion secondary battery.

[0006] A battery management device according to the present disclosure comprises: a high-frequency signal supply unit that supplies a high-frequency signal of 0.1 MHz or higher to a lithium-ion secondary battery; an impedance sensing unit that detects a value of a real part of an AC impedance from the lithium-ion secondary battery to which the high-frequency signal is supplied; a calculation unit that calculates a Li deposition quantity in the lithium-ion secondary battery from the detected value of the real part of the AC impedance; and a control unit that reduces a permissible charging power for the lithium-ion secondary battery if the calculated Li deposition quantity is greater.The battery management device according to the present disclosure calculates the amount of Li deposition in the lithium-ion secondary battery from the value of the real part of the AC impedance detected by the lithium-ion secondary battery and performs feedback control of the permissible charging power for the lithium-ion secondary battery based on the calculated amount of Li deposition.This allows the battery management device, according to the present disclosure, to adjust the permissible charging power for the lithium-ion secondary battery to a suitable value depending on the amount of Li deposited, instead of setting it to a value that is too low, and thus to achieve efficient charging of the lithium-ion secondary battery.

[0007] With the present disclosure, it is possible to provide a battery management device and a battery management system that make it possible to achieve efficient charging of the lithium-ion secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Features, advantages and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which the same symbols denote the same elements, wherein Fig. 1 is a block diagram showing an exemplary configuration of a battery management system according to embodiment 1; Fig. 2 is a diagram showing the relationship between the SOH of a secondary battery and the rate of change of a real part Z of an AC impedance when a 1 MHz high-frequency signal is supplied to the secondary battery; Fig. 3 is a diagram showing the relationship between a frequency of an alternating current signal supplied to the secondary battery and the real part of the alternating current impedance detected by the secondary battery; Fig. Figure 4 is a diagram showing the relationship between the frequency of an alternating current signal supplied to the secondary battery and the real part of the alternating current impedance detected by the secondary battery; Fig. 5 is a flowchart showing the operation of a battery management device according to embodiment 1; and Fig. Figure 6 is a block diagram showing an exemplary configuration of a battery management system according to embodiment 2. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0009] Specific embodiments to which the present invention is applied are described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. Furthermore, the following description and the drawings have been simplified accordingly for clarity. Design 1

[0010] Fig. Figure 1 is a block diagram showing an exemplary configuration of a battery management system according to embodiment 1. As shown in Fig. As shown in Figure 1, a battery management system 1 comprises a battery management device 10 and a secondary battery 20 which is managed by the battery management device 10.

[0011] The secondary battery 20 is a lithium-ion secondary battery and is formed by a cell stack in which a large number of battery cells are layered, and a housing that accommodates the cell stack.

[0012] Each battery cell comprises a positive electrode, a negative electrode, and an ionically conductive medium that conducts carrier ions between the positive and negative electrodes. A separator may also be provided between the positive and negative electrodes. Polyethylene or polypropylene, for example, is used for the separator.

[0013] For example, a sulfide containing a transition metal element or an oxide containing lithium and a transition metal element is used as the positive electrode active material. In particular, a lithium-manganese compound oxide with a basic composition formula of Li is used as the positive electrode active material. (1-x) MnO2 (0 < x < 1), Li (1-x) Mn2O4 or the like, a lithium-cobalt compound oxide with a basic composition of the formula Li (1-x )CoO2 or the like, a lithium-nickel composite oxide with a basic composition of the formula Li (1-x) NiO2 or the like, a lithium-nickel-cobalt-manganese composite oxide with a basic composition formula of Li (1-x) Ni a Co b Mn cO2 (a + b + c = 1) or the like, or others, may be used. For the positive electrode active material, a substance containing another element in the basic composition formula above may be used. For example, aluminum (Al) is used for a current collector of the positive electrode.

[0014] For a negative electrode active material, a lithium-containing composite oxide or a carbon material is used, for example. Specifically, the negative electrode active material can be an inorganic compound such as lithium, a lithium alloy, a tin compound, a carbon material capable of storing and releasing lithium ions, a composite oxide containing a variety of elements, a conductive polymer, or other materials. Carbon materials used for the negative electrode active material include coke, glassy carbon, graphite, non-graphitizable carbon, pyrolytic carbon, carbon fiber, and the like, with graphite, such as synthetic and natural graphite, being preferred. Composite oxides used for the negative electrode active material include lithium-titanium composite oxides, lithium-vanadium composite oxides, and the like.For example, copper (Cu) is used for the current collector of the negative electrode.

[0015] The ionically conductive medium is used as an electrolyte solution, for example, by dissolving a carrier salt. Lithium salts such as LiPF6 and LiBF4 are used as carrier salts. Solvents for the electrolyte solution include carbonates, esters, ethers, nitriles, furans, sulfolanes, dioxolanes, or mixtures of these. Examples of carbonates used include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinyl carbonate, butyl carbonate, and chloroethyl carbonate, as well as chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl n-butyl carbonate, methyl tert-butyl carbonate, dipropyl carbonate, and tert-butyl propyl carbonate.Alternatively, a solid ion-conducting polymer, an inorganic solid electrolyte, a mixture of an organic polymer electrolyte and an inorganic solid electrolyte, inorganic solid powders bound by an organic binder, or the like can be used for the ion-conducting medium.

[0016] The battery management device 10 performs charge management for the secondary battery 20, which is a management object. For example, the battery management device 10 non-destructively detects the amount of Li deposited in the secondary battery 20 and, based on the detection result, performs feedback control of a permissible charging power (an upper limit of the charging power) Pa for the secondary battery 20.

[0017] The battery management device 10 comprises a high-frequency signal supply unit 11, an impedance detection unit 12, a calculation unit 13, a control unit 14 and a storage unit 15.

[0018] The high-frequency signal supply unit 11 delivers a high-frequency signal to the secondary battery 20. The impedance detection unit 12 detects a value of a real part Z of an AC impedance from the secondary battery 20, to which the high-frequency signal is supplied.

[0019] In the secondary battery 20, lithium metal is deposited on an electrode surface of each battery cell through repeated charging. Lithium deposition progresses with increasing charging power to increase the charging speed and deteriorates the state of health (SOH) of the secondary battery 20. The SOH of the secondary battery 20 is the ratio of the current capacity of the secondary battery 20 when the initial capacity is 100%. Accordingly, it is desirable to define a maximum permissible charging power (Pa) for the secondary battery 20 that enables efficient charging in the shortest possible charging time while simultaneously limiting lithium deposition.

[0020] In the event that a high-frequency signal with such a high frequency that the diffusion, reaction, and movement of lithium ions in each cell of the secondary battery 20 cannot be tracked, the electric current for the high-frequency signal flows along the edges of the electrical conductors of each battery cell due to a skin effect. In other words, the electric current for the high-frequency signal flows on an electrode surface of each battery cell due to the skin effect, where lithium can easily be deposited. Furthermore, even in the case where the lithium metal is electrically separated from the negative electrode and enters a float state after lithium deposition, an electric current also flows due to an inductive connection and an electric field connection on the lithium metal.Accordingly, for example, with a smaller amount of lithium deposited, the electrical conductivity of the electrode surface of each battery cell is lower, and therefore the value of the real part Z of the AC impedance is larger. The larger the amount of lithium deposited, the higher the electrical conductivity of the electrode surface of each battery cell, and the smaller the value of the real part Z of the AC impedance. A large amount of electric current is concentrated on the highly electrically conductive lithium metal, causing the magnetic field to change around a lithium deposited area and generating eddy currents. The eddy current causes losses at a current-collecting foil and an electrically conductive section of the electrode, but reduces the overall battery loss. Consequently, the change in the magnetic field is greater the larger the amount of lithium deposited, and therefore the eddy current is higher, resulting in a smaller value of the real part Z.Therefore, the amount of Li deposited in the secondary battery 20 can be calculated from the value of the real part Z of the AC impedance measured by the secondary battery 20 to which the high-frequency signal is supplied. Once the amount of Li deposited has been determined, the state of health (SOH) of the secondary battery 20 can also be estimated.

[0021] Fig. Figure 2 is a diagram showing the relationship between the state of health (SOH) of secondary battery 20 and the rate of change (the difference between the sensing value and the initial value) of the real part Z of the AC impedance when a 1 MHz high-frequency signal is applied to secondary battery 20. As indicated by the triangle markings in Fig. As shown in Figure 2, with normal charging at low charging power, the amount of Li deposited is small even with repeated charging, so the rate of change of the real part Z of the AC impedance remains small even with progressive deterioration of the SOH due to other causes (i.e., the detection value of the real part Z of the AC impedance is kept at a high value). On the other hand, as shown by the circles in Figure 2, Fig. Figure 2 shows that in the case of fast charging with high charging power, the amount of lithium deposits is large with repeated charging, and consequently the state of health (SOH) deteriorates, resulting in a large change in the real part Z of the AC impedance (i.e., the measured value of the real part Z of the AC impedance is low). If the battery deteriorates primarily due to lithium deposits, which are one of the causes of battery deterioration, the amount of lithium deposits can be derived from the SOH. Alternatively, the SOH can be derived from the amount of lithium deposits.

[0022] Fig. 3 and Fig. Figure 4 are each diagram showing the relationship between a frequency of the AC signal supplied to the secondary battery 20 and the real part of the AC impedance detected from the secondary battery 20. Fig. Figure 3 shows the value of the real part Z of the AC impedance when AC signals of 1 kHz to 100 kHz are supplied to the secondary battery 20. Fig. Figure 4 shows the value of the real part Z of the AC impedance when AC signals of 100 kHz to 100 MHz are supplied to the secondary battery 20.

[0023] As in Fig. As shown in Figure 3, when the AC signal is supplied to the secondary battery 20 at approximately 1 kHz, the value of the real part Z of the AC impedance becomes minimal. In this case, one impedance component is an ohmic resistance component. As shown in Fig. 3 and Fig. As shown in Figure 4, the current flow concentrates on the electrode surface of each cell due to the skin effect, the higher the frequency of the alternating current signal supplied to the secondary battery 20, and therefore the value of the rear part Z of the alternating current impedance is greater.

[0024] Thus, the high-frequency signal supply unit 11 delivers an AC signal (i.e., a high-frequency signal) to the secondary battery 20 at a high frequency sufficient to detect the value of the real part Z of the AC impedance, which is sufficiently higher than the ohmic resistance component. For example, the high-frequency signal supply unit 11 delivers a high-frequency signal of 0.1 MHz or higher to the secondary battery 20. Alternatively, the high-frequency signal supply unit 11 delivers a high-frequency signal to the secondary battery 20 at such a frequency that, due to the skin effect, the determined value of the real part Z of the AC impedance is at least ten times the value of the real part Z of an AC impedance obtained when a 1 kHz AC signal is applied to the secondary battery 20. In the examples in Fig. 3 and Fig. 4 The high-frequency signal supply unit 11 delivers a high-frequency signal of 0.5 MHz or higher to the secondary battery 20. As a result, the electric current for the high-frequency signal flows due to the skin effect on the electrode surface (Li deposition area) of each battery cell of the secondary battery 20. This allows the impedance detection unit 12 to detect the real part Z of the AC impedance corresponding to the amount of Li deposition.

[0025] The calculation unit 13 calculates the amount of lithium deposited in the secondary battery 20 from the value of the real part Z of the AC impedance, which is detected by the impedance detection unit 12. More precisely, the calculation unit 13 calculates the amount of lithium deposited in the secondary battery 20 based on the difference between the current value of the real part Z of the AC impedance, detected by the impedance detection unit 12, and the initial value of the real part Z of the AC impedance of the secondary battery 20. Information about the initial value of the real part Z of the AC impedance of the secondary battery 20, which is the management object, is stored, for example, in the storage unit 15.

[0026] For example, the calculation unit 13 calculates the Li deposition quantity in such a way that the value of the Li deposition quantity is smaller the larger the determined value of the real part Z of the AC impedance is, and in such a way that the value of the Li deposition quantity is larger the smaller the determined value of the real part Z of the AC impedance is.

[0027] Storage unit 15 can store information about the initial value of the real part Z of the secondary battery's AC impedance for each product type. Furthermore, storage unit 15 can store map information that specifies the relationship between the difference (change amount) between the current value (acquisition value) and the initial value of the real part Z of the secondary battery's AC impedance for each product type, and the amount of lithium deposited. This mapping information is information previously obtained, for example, through experiments, and can be updated as needed with information acquired from the secondary battery 20, which is the management object. In this case, computation unit 13 extracts the amount of lithium deposited, corresponding to the value of the real part Z of the AC impedance acquired by impedance acquisition unit 12, from the map information stored in storage unit 15.

[0028] The control unit 14 regulates a permissible charging power Pa for the secondary battery 20 based on the amount of lithium deposition calculated by the calculation unit 13. For example, if the calculated amount of lithium deposition is small, the progress of lithium deposition is inhibited, and therefore the control unit 14 adjusts the permissible charging power Pa to maintain or increase the current value. Since the calculated amount of lithium deposition is larger, the progress of lithium deposition must be limited, and therefore the control unit 14 adjusts the permissible charging power Pa to decrease it. For example, the control unit 14 can switch the permissible charging power Pa in steps from 100% as an initial value to 95%, 90%, or other values ​​depending on the calculated amount of lithium deposition.

[0029] This allows the battery management device 10, according to the present disclosure, to set the highest possible permissible charging power Pa for the secondary battery 20, enabling efficient charging in the shortest possible charging time while limiting lithium deposition. That is, the battery management device 10, according to the present disclosure, can adjust the permissible charging power Pa for the secondary battery 20 to a suitable value depending on the amount of lithium deposition, instead of setting it to a value that is too low, thus enabling efficient charging of the secondary battery 20. Function of the battery management device 10

[0030] The functionality of the battery management device 10 will then be explained using the following examples: Fig. 5 described. Fig. Figure 5 is a flowchart showing the operation of the battery management device 10.

[0031] First, the battery management device 10 supplies a high-frequency signal to the secondary battery 20 at a frequency so high that the diffusion, reaction, and movement of lithium ions in each battery cell cannot be tracked (step S101). For example, the battery management device 10 supplies a high-frequency signal of 0.1 MHz or higher to the secondary battery 20. Then, the battery management device 10 detects the value of the real part Z of the AC impedance of the secondary battery 20 to which the high-frequency signal is supplied (step S102).

[0032] The battery management device 10 then calculates the amount of lithium deposited in the secondary battery 20 from the determined value of the real part Z of the AC impedance (step S103). For example, the battery management device 10 extracts the amount of lithium deposited, corresponding to the detected value of the real part Z of the AC impedance, from the map information stored in the storage unit 15. In general, the battery management device 10 calculates the amount of lithium deposited such that the value of the amount of lithium deposited is smaller the larger the determined value of the real part Z of the AC impedance, and the value of the amount of lithium deposited is larger the smaller the determined value of the real part Z of the AC impedance.

[0033] Subsequently, the battery management device 10 controls the permissible charging power Pa for the secondary battery 20 based on the calculated amount of Li deposition (step S104). For example, if the calculated amount of Li deposition is small, the progress of Li deposition is inhibited, and therefore the battery management device 10 controls the permissible charging power Pa to maintain or increase it. Since the calculated amount of Li deposition is larger, the progress of Li deposition must be limited, and therefore the battery management device 10 reduces the permissible charging power Pa.

[0034] In this way, the battery management device 10 according to the present disclosure can set a maximum permissible charging power Pa for the secondary battery 20, enabling efficient charging in the shortest possible charging time while simultaneously limiting lithium deposition. That is, the battery management device 10 according to the present disclosure can adjust the permissible charging power Pa for the secondary battery 20 to a suitable value depending on the amount of lithium deposition, instead of setting it to a value that is too low, thus enabling efficient charging of the secondary battery 20.

[0035] An example has been described in which the impedance detection unit 12 detects the value of the real part Z of the AC impedance from the secondary battery 20 at any given time, and the calculation unit 13 calculates the amount of Li deposited in the secondary battery 20 based on the value of the real part Z of the AC impedance detected at that given time, but the present disclosure is not limited to this.

[0036] For example, the impedance sensing unit 12 can periodically acquire the value of the real part Z of the AC impedance from the secondary battery 20 at a measurement interval T1 specified by the control unit 14 or the like, and the calculation unit 13 can acquire the rate of change of the Li-ion deposition during the measurement interval T1 of the AC, based on the value of the real part Z of the AC, which is periodically acquired during the measurement interval T1. In this case, the control unit 14 performs such a control that the permissible charging power Pa for the secondary battery 20 is reduced if the rate of change of the Li-ion deposition during the measurement interval T1 is greater. The control unit 14 can be configured to change the measurement interval T1 to any desired length.For example, the control unit 14 shortens the measurement interval T1 in an environment where Li deposition is light, such as in an environment where fast charging is performed, and lengthens the measurement interval T1 in an environment where Li deposition is heavy, such as in an environment where charging is performed with an electrical power that is sufficiently lower than the permissible charging power.

[0037] When the amount of lithium deposited in the secondary battery 20 reaches a first predetermined amount, the control unit 14 can release the deposited lithium by forcibly discharging the secondary battery 20. In this case, the control unit 14 can, for example, maintain the permissible charging power Pa at its current value if the amount of lithium deposited in the secondary battery 20 after the release of the deposited lithium is less than or equal to a second predetermined amount that is less than the first predetermined amount, and implement control measures such that the permissible charging power Pa is reduced if the amount of deposited lithium is greater than the second predetermined amount.

[0038] Furthermore, if the secondary battery 20 is mounted on a hybrid vehicle, for example a hybrid electric vehicle (HEV) and a plug-in hybrid electric vehicle (PHEV), and if the control unit 14 releases the deposited lithium by forcibly discharging the secondary battery 20, the control unit 14 can switch the hybrid vehicle from propulsion with the secondary battery 20 to propulsion with gasoline. Design 2

[0039] Fig.Figure 6 is a block diagram showing an exemplary configuration of a battery management system 100 according to embodiment 2. The battery management system 100 comprises n (n is an integer of 2 or more) battery management devices 10, which are configured to correspond to n secondary batteries 20, a control device 40, and a network 50. The n battery management devices 10 and the control device 40 are configured to communicate with each other via the network 50. Hereinafter, the n secondary batteries 20 are further referred to as secondary batteries 20_1 to 20_n, and the n battery management devices 10 are further referred to as battery management devices 10_1 to 10_n.

[0040] The secondary batteries 20_1 to 20_n are each mounted on the vehicles 30_1 to 30_n. Furthermore, the battery management devices 10_1 to 10_n are mounted on the vehicles 30_1 to 30_n together with the secondary batteries 20_1 to 20_n. Each of the vehicles 30_1 to 30_n is a battery electric vehicle or a hybrid vehicle powered by a secondary battery.

[0041] The control device 40 learns the permissible charging power setting defined for each of the secondary batteries 20_1 to 20_n managed by the battery management devices 10_1 to 10_n and updates the permissible charging power setting for each of the secondary batteries 20_1 to 20_n based on the learning result. In other words, the control device 40 updates the permissible charging power setting defined for each of the secondary batteries 20_1 to 20_n using a relearning model generated by machine learning, which utilizes the permissible charging power setting.

[0042] For example, if the permissible charging power, which is lower than expected, is set after a predetermined service life for a predetermined number or more secondary batteries 20 managed by a predetermined number or more battery management devices 10 (10_1 to 10_n), it is possible that the initial permissible charging power is too high. In such a case, the control device 40 performs a control such that the permissible charging power is reduced for all secondary batteries 20_1 to 20_n managed by the battery management devices 10_1 to 10_n. This limits the lithium deposition in each of the secondary batteries 20_1 to 20_n.The control device 40 can set the initial value of the permissible charging power, which is set for the newly delivered secondary battery 20, to a low value, similar to the secondary batteries 20_1 to 20_n.

[0043] In the present disclosure, some or all processes of the battery management device 10 can be realized by a central processing unit (CPU) executing a computer program.

[0044] The program described above comprises instructions (or software code) that cause a computer to perform one or more of the functions described in the embodiments when the computer reads the program described above. The program may be stored on a non-volatile, computer-readable medium or a tangible storage medium. By way of example, and not as a limitation, the computer-readable medium or the tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, a solid-state drive (SSD), other storage technologies, a CD-ROM, a digital versatile disc (DVD), a Blu-ray disc (registered trademark), other optical storage media, a magnetic cartridge, a magnetic tape, a magnetic disk storage device, or other magnetic storage devices.The program can be transmitted on a transient computer-readable medium or communication medium. By way of example, which is not a limitation, the transient computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagation signals.

[0045] The present disclosure has been described with reference to the embodiments. The present disclosure is not limited to the embodiments described above. Various modifications to the configurations and details of the present disclosure, which are understandable to a person skilled in the art, may be made within the scope of this disclosure. Furthermore, each embodiment may optionally be combined with another embodiment. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-108602 A

[0003]

Claims

[1] Battery management device, with a high-frequency signal supply unit that delivers a high-frequency signal of 0.1 MHz or higher to a lithium-ion secondary battery, an impedance detection unit that detects a value of a real part of an AC impedance from the lithium-ion secondary battery to which the high-frequency signal is supplied, a calculation unit that calculates a Li deposition quantity in the lithium-ion secondary battery from the recorded value of the real part of the AC impedance, and a control unit that reduces the permissible charging power for the lithium-ion secondary battery when the calculated amount of Li deposition is larger. [2] Battery management device according to claim 1, wherein the high-frequency signal supply unit provides the high-frequency signal at a frequency such that the detected value of the real part of the AC impedance due to a skin effect is ten times or more than the value of a real part of an AC impedance detected when an AC signal of 1 kHz is supplied to the lithium-ion secondary battery. [3] Battery management device according to claim 1, wherein The impedance measurement unit records the value of the real part of the AC impedance of the lithium-ion secondary battery at a defined measurement interval. The calculation unit calculates a change in the Li deposition quantity during the specified measurement interval based on the value of the real part of the AC impedance recorded in the specified measurement interval, and The control unit reduces the permissible charging power for the lithium-ion secondary battery if the increase in the amount of Li-ion deposition during the specified measurement interval is greater. [4] Battery management device according to claim 1, wherein the control unit releases the deposited Li by forcibly discharging the lithium-ion secondary battery when the amount of Li deposited in the lithium-ion secondary battery reaches a first predetermined amount, and does not reduce and maintain the permissible charging power for the lithium-ion secondary battery when the amount of Li deposited in the lithium-ion secondary battery after the release of the Li is less than or equal to a second predetermined amount. [5] Battery management system with several battery management devices according to claim 1, wherein the battery management devices manage a plurality of lithium-ion secondary batteries, each mounted on a plurality of vehicles, and a control device that learns a setting content of the permissible charging power set for each of the lithium-ion secondary batteries and updates the setting content of the permissible charging power for each of the lithium-ion secondary batteries based on a learning result.

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