Battery management system

Abstract

A battery management system has an arithmetic processing device that selects a replacement battery for replacement of a mounted battery mounted on an apparatus from among a plurality of candidate batteries. The arithmetic processing device calculates a supposed maximum current rate of a candidate battery when used in the apparatus, based on a current rate history of the mounted battery and a capacity of the candidate battery that takes into account a deterioration amount of the candidate battery. The arithmetic processing device selects, from among the plurality of candidate batteries, a battery whose calculated supposed maximum current rate of the candidate battery is equal to or lower than a predetermined current rate, as the replacement battery.

Description

Technical Field

[0001] This disclosure relates to battery management systems. Background Technology

[0002] Various studies have been conducted on battery management systems related to battery replacement.

[0003] Japanese Patent Application Publication No. 2016-139572 discloses a secondary battery management system capable of replacing secondary batteries that takes temperature load into account. Summary of the Invention

[0004] When a battery is used at a predetermined current rate (C-rate), its resistance increases significantly. Therefore, when replacing the battery, it is possible that the most suitable battery cannot be replaced based solely on temperature load and the user's operating environment.

[0005] This disclosure provides a battery management system that can replace the battery with the one most suitable for the user when replacing the battery.

[0006] The battery management system disclosed herein includes a processing unit for selecting a replacement battery from a plurality of candidate batteries for replacing a battery mounted in a device. The processing unit calculates a predetermined maximum current rate for the candidate battery when used in the device, based on the current rate history of the battery mounted in the device and the capacity of the candidate battery taking into account the degradation of the candidate battery. From among the plurality of candidate batteries, the processing unit selects the battery whose calculated predetermined maximum current rate is below a predetermined current rate as the replacement battery.

[0007] In the battery management system disclosed herein, the computing device may also calculate the intended maximum current rate of the backup battery when used in the device based on the current rate history of the battery, the capacity of the backup battery considering the degradation amount of the backup battery calculated based on the usage history of the battery, and the intended usage period of the backup battery.

[0008] This disclosure provides a battery management system that can replace the battery with the one most suitable for the user when replacing the battery. Attached Figure Description

[0009] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and wherein:

[0010] Figure 1This is a graph illustrating an example of the relationship between current rate (C-rate) and resistance value in an all-solid-state battery that uses lithium titanate (LTO) as the negative electrode active material.

[0011] Figure 2 It is a graph showing the relationship between battery temperature T and degradation rate.

[0012] Figure 3 This is a graph showing an example of the charging time at various temperatures under a predetermined SOC of the battery.

[0013] Figure 4 This is a flowchart illustrating an example of a method for selecting a replacement battery performed by the battery management system of this disclosure. Detailed Implementation

[0014] The following describes the embodiments involved in this disclosure. Furthermore, matters not specifically mentioned in this specification but necessary for the implementation of this disclosure (e.g., the general structure and manufacturing process of a battery management system without additional features to this disclosure) can be grasped based on related technologies in the art. This disclosure can also be implemented based on the content disclosed in this specification and common technical knowledge in the art.

[0015] This disclosure discloses a battery management system that selects a replacement battery from a plurality of candidate batteries for use with a battery mounted in a device. The battery management system calculates the intended maximum current rate of the candidate battery when used in the device, based on the current rate history of the mounted battery and the capacity of the candidate battery taking into account the degradation of the candidate battery. From among the plurality of candidate batteries, the battery management system selects the battery whose calculated intended maximum current rate is below a predetermined current rate as the replacement battery.

[0016] Figure 1 This is a graph illustrating an example of the relationship between current rate (C-rate) and resistance in an all-solid-state battery using lithium titanate (LTO) as the negative electrode active material. (Example) Figure 1As shown, in the case of an all-solid-state battery using an LTO negative electrode, the resistance value increases sharply above 40C. Regardless of the capacity of the all-solid-state battery, the resistance value increases sharply around 40C. When selecting a replacement battery without considering the current rate of the user's battery, the performance degradation of the replacement battery is sometimes accelerated. This disclosure calculates the rate distribution of the battery at various current rates when replacing the battery and the replacement battery, based on the usage history related to the current rate of the battery to be replaced. This takes into account the user's battery usage environment. Furthermore, based on the capacity of the candidate battery, taking into account the degradation level (degradation state) of the candidate battery used as a replacement battery, the envisioned maximum current rate of the candidate battery when used in the device is calculated. A battery whose envisioned maximum current rate is below a predetermined current rate is selected as the replacement battery. Therefore, the battery can be replaced with the most suitable battery for the user. As a result, performance degradation of the replaced battery can be suppressed.

[0017] [Usage History]

[0018] In this disclosure, the battery's usage history can also be its current rate history, temperature history, SOC history, and charging history. The definitions of current rate history, temperature history, SOC history, and charging history are as follows: Current rate history: The history of the current rate at which the battery was used before the current (replacement point). Temperature history: The history of the temperature experienced by the battery before the current (replacement point) (the duration of exposure at each temperature). SOC history: The history of the SOC experienced by the battery before the current (replacement point) (the duration of residence at each SOC). Charging history: The history of the current flowing through the battery before the current (replacement point) (the duration of current flow at each current value). In this disclosure, the State of Charge (SOC) represents the ratio of the battery's charged capacity to its fully charged capacity. Full charge capacity is SOC 100%.

[0019] [Imagine maximum current ratio]

[0020] In this disclosure, the intended maximum current rate of the candidate battery when used in the device is calculated based on the current rate history of the battery and the capacity of the candidate battery considering the degradation of the candidate battery. The current rate history can also be extracted from the battery's usage history. The capacity of the candidate battery considering the degradation of the candidate battery can be, for example, the current capacity of the candidate battery or the intended capacity when using the candidate battery in the device. The current capacity of the candidate battery can also be calculated, for example, by first calculating the degradation of the candidate battery and then correcting the initial capacity of the candidate battery based on the degradation of the candidate battery. The degradation of the candidate battery can be, for example, the current degradation of the candidate battery, the intended degradation when using the candidate battery in the device, or a degradation including both. The degradation of the candidate battery can also be calculated based on the usage history of at least one of the batteries, including the battery and the candidate battery. The assumed degradation of the backup battery is the estimated degradation expected when the backup battery is installed in the device. This can be calculated based on the battery's usage history or by considering the assumed service life. The assumed capacity of the backup battery can also be calculated based on its assumed degradation. Alternatively, the maximum current value can be calculated based on historical current rates, and the assumed maximum current rate can be calculated using this maximum current value and the backup battery's capacity after accounting for degradation.

[0021] In this disclosure, the intended maximum current rate of the backup battery when used in the device can also be calculated based on the current rate history of the battery, the capacity of the backup battery considering the degradation amount calculated based on the usage history of the battery, and the intended service life of the backup battery. In this case, the intended maximum current rate is calculated based on the capacity reduction of the backup battery due to the degradation amount added to the intended service life of the backup battery. The degradation amount added to the intended service life of the backup battery can be calculated based on the usage history of the battery or the intended degradation amount mentioned above. In this disclosure, the intended service life can be a predetermined value, a intended service life of the backup battery, an expected period such as how much future use the battery will take the user's expectations, or a period that takes into account the user's expected battery replacement costs, etc.

[0022] [Current Ratio History]

[0023] The current rate distribution of the battery at various current rates can be calculated based on the current rate history extracted from the battery's usage history. A predetermined current rate can also be set based on the calculated rate distribution. Furthermore, the maximum current value can be calculated based on the current rate history. In this disclosure, the predetermined current rate varies depending on the user's battery usage environment, battery type, and materials used in the battery, and can therefore be appropriately set.

[0024] [Deterioration level]

[0025] The amount of battery degradation can also be calculated based on the usage history of the original battery and the backup battery. The projected degradation amount of the backup battery can also be calculated based on the usage history of the original battery. The definition of degradation amount is as follows: Degradation amount: Defined as the rate of increase in resistance (%) of the battery's resistance value (mΩ) or the current resistance value of the battery compared to its factory resistance value. Associated with an increase in battery degradation amount, the battery capacity decreases.

[0026] [Calculation method for degradation]

[0027] The degradation amount is calculated as follows. Based on the degradation rate at each temperature and at each State of Charge (SOC) (during equipment placement / operation), and the temperature history, SOC history, and power-on history, the degradation amount at each temperature is calculated. The power-on history is converted into total power-on time. The total degradation amount of the battery is calculated by summing the calculated degradation amounts at each temperature.

[0028] Figure 2 This is a graph showing the relationship between the battery temperature T and the degradation rate. The degradation rate can be calculated using the following equation (1).

[0029] Deterioration rate [% / √h] = α × EXP(β × temperature T) ... Equation (1)

[0030] Based on the temperature and the degradation rate per state of charge (SOC), α (intercept) and β (slope) are calculated. The degradation rate can also be obtained beforehand as a degradation rate data set through experiments, etc. Furthermore, in the case of equipment being a vehicle, equipment operation implies vehicle movement. Therefore, regarding equipment operation, in... Figure 2 The example shown is of the vehicle in motion.

[0031] Figure 3 This is a graph showing an example of the charging time at various temperatures under a predetermined SOC of the battery. Figure 3 This shows how long the battery is exposed at each temperature under a predetermined SOC. The predetermined temperature T1 and the amount of degradation at the predetermined SOC can be calculated using the following formula (2).

[0032] (T 1_SOC1 (deterioration rate)2 ×(in T) 1_SOC1 Exposure time h1) = (at T 1_SOC1 Deterioration at exposure (C1) 2 …Formula (2)

[0033] The degradation C1 to C at each temperature and per state of charge (SOC) can be calculated using the above equation (2). xx In the case of a vehicle, the amount of degradation can also be calculated under the conditions of the vehicle being placed and the vehicle being driven. The total amount of degradation can be calculated according to the following formula (3).

[0034] Total degradation C total =√{(Deterioration amount C1)} 2 +(Deterioration amount C2) 2 +…(Deterioration C) xx ) 2 Equation (3)

[0035] Total degradation C total This involves considering the temperature and the degradation amount C1 to C per state of charge (SOC). xx The sum can be calculated according to the above formula (3).

[0036] [Diagnosis of Replacement Battery Degradation]

[0037] The degradation level and capacity of candidate batteries (whether used or new) in the replacement candidate list can also be diagnosed in advance. Furthermore, a rating can be assigned to the candidate batteries based on this degradation level and capacity. For example, diagnostic information can be listed as shown in Table 1 below. The obtained diagnostic information can also be aggregated on a server, and the control unit described later receives the diagnostic information. The control unit can also use the received diagnostic information for selecting candidate batteries. The capacity of the candidate battery can also be determined by including the degradation level and manufacturing deviation of the candidate battery. In Table 1, the assumed maximum current ratio (1) is a value calculated as follows. The maximum current value of the battery is calculated based on the current ratio history of the battery. The assumed maximum current ratio (1) is calculated based on the calculated maximum current value of the battery and the capacity of the candidate battery (capacity at the replacement time). In Table 1, the assumed maximum current ratio (2) is a value calculated based on the maximum current value of the battery and the capacity of the candidate battery (capacity considering the assumed degradation level after replacement). The capacity of the backup battery is calculated based on the capacity reduction of the backup battery due to the degradation of the backup battery during the intended use period. Depending on the capacity reduction of the backup battery, the intended maximum current ratio (2) can also be greater than the intended maximum current ratio (1).

[0038] [Battery Replacement Options]

[0039] The battery management system selects a replacement battery from a plurality of candidate batteries for replacing the battery mounted in the device. Among the candidate batteries, the battery management system selects the battery whose calculated maximum current rate is below a predetermined current rate as the replacement battery. At least two candidate batteries are required, with no particular upper limit. If no battery has a current rate below the predetermined current rate, the predetermined current rate setting can be changed, or the battery with the maximum current rate closest to the predetermined current rate can be selected. If there are two or more candidate batteries with current rates below the predetermined current rate, the battery with the highest capacity among the two or more candidate batteries can be selected as the replacement battery.

[0040] Table 1

[0041] backup battery Deterioration capacity grade Imagine the maximum current multiplier (1) Imagine the maximum current multiplier (2) Battery 1 Small Small C 44C 48C Battery 2 big Small B 40C 44C Battery 3 Small big A 36C 40C

[0042] Figure 4 This is a flowchart illustrating an example of the process of selecting a replacement battery performed by the battery management system of this disclosure. SP1. Analyze the current load based on the user's battery usage history, obtain the current rate history, and set a predetermined current rate. SP2. Calculate the capacity of the candidate battery, taking into account the degradation of the candidate battery, based on the usage history of at least one of the batteries, the battery and the candidate battery. SP3. Calculate the intended maximum current rate of the candidate battery, taking into account the current rate history of the battery, the capacity of the candidate battery, the degradation of the candidate battery, and the intended usage period of the candidate battery as needed. Here, multiple candidate batteries as replacement candidates can also be assigned grades and listed. SP4. Among the multiple candidate batteries, select the battery whose intended maximum current rate is below the predetermined current rate as the replacement battery. As shown in Table 1, for example, when the predetermined current rate is set to 40C, sometimes the most suitable battery is mistakenly selected when selecting a candidate battery based solely on the intended maximum current rate (1). Furthermore, here the current rate (current C rate) refers to the magnitude of the current when charging and discharging the battery. "1C" refers to the current value of a battery that is fully charged (SOC 100%) and then fully discharged (SOC 0%) in 1 hour. On the other hand, by calculating and using the envisioned maximum current rate (2), it is possible to select a more suitable battery.

[0043] In this disclosure, the device is not particularly limited. For example, it can also be a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a battery electric vehicle (BEV), a gasoline vehicle, a diesel vehicle, or other vehicles, as well as other mobile bodies (such as railways, ships, and aircraft), electrical products such as information processing devices, etc.

[0044] In this disclosure, the battery can be either a primary battery or a secondary battery. The battery can also be an aqueous battery, a non-aqueous battery, or an all-solid-state battery. An all-solid-state battery can also have at least one unit cell consisting of a positive electrode having a positive current collector and a positive electrode layer, a solid electrolyte layer, and a negative electrode having a negative current collector and a negative electrode layer. The materials used in the battery are not particularly limited, and various materials can be used. The negative electrode active material can also be lithium titanate (LTO). Lithium titanate is, for example, Li₄Ti₅O₂. 12 wait.

[0045] The battery management system disclosed herein may also include a detection unit, a control unit, and a calculation unit. The detection unit may detect the usage history of batteries such as the mounted battery and candidate batteries. The calculation unit may calculate the rate distribution and maximum current value based on the current rate history of the mounted battery. The calculation unit may also calculate the degradation amount of batteries such as the mounted battery and candidate batteries based on the usage history. The calculation unit may also calculate the capacity of candidate batteries considering the degradation amount. The calculation unit may also calculate the intended maximum current rate of candidate batteries when used in the device based on the current rate history of the mounted battery and the capacity of candidate batteries considering the degradation amount. The control unit may also select batteries whose calculated intended maximum current rate is below a predetermined current rate from among multiple candidate batteries as replacement batteries. The control unit may also update the battery usage history based on the usage history detected by the detection unit. The control unit may also prepare diagnostic information in advance, including the degradation amount of candidate batteries to be replaced, the capacity of candidate batteries considering the degradation amount, and the intended maximum current rate of candidate batteries.

[0046] The battery management system, which includes a detection unit, a control unit, and a computing unit, physically includes, for example, a computing processing unit such as a CPU (central processing unit), a storage unit such as a ROM (read-only memory) that stores control programs and control data processed by the CPU, a RAM (random access memory) that is mainly used for various operating areas for control processing, and an input / output interface.

Claims

1. A battery management system, characterized in that, The device includes a processing unit that selects a replacement battery from a plurality of candidate batteries for replacement with the battery mounted on the device. The processing unit is configured as follows: The maximum current value is calculated based on the historical current rate of the battery. Based on the maximum current value and the capacity of the candidate battery that takes into account the degradation of the candidate battery, the intended maximum current rate of the candidate battery when used in the device is calculated. as well as Among the candidate batteries, the battery whose calculated maximum current ratio is below a predetermined current ratio is selected as the replacement battery.

2. The battery management system according to claim 1, characterized in that, The processing unit calculates the intended maximum current rate of the candidate battery when used in the device, based on the current rate history of the battery, the capacity of the candidate battery considering the degradation amount of the candidate battery calculated based on the usage history of the battery, and the capacity reduction of the candidate battery due to the degradation amount during the intended use period of the candidate battery.

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