Battery management system

Abstract

This battery management system can improve the accuracy of detecting temporary over-discharge and degradation of on-board batteries by taking into account actual vehicle data trends in the market. [Solution] A battery management system that determines the state of an on-board battery based on the starting voltage of the on-board battery at the time of vehicle startup and a predetermined voltage threshold, comprising: a collection unit that collects vehicle data, including the starting voltage, from multiple vehicles in the market; and an update unit that updates the voltage threshold based on the vehicle data collected from vehicles in the market.

Description

Technical Field

[0001] The present disclosure relates to a system for managing a battery mounted on a vehicle.

Background Art

[0002] Patent Document 1 discloses a battery management system that detects the state of an in-vehicle battery by using both the voltage of the in-vehicle battery and the charge / discharge amount of the in-vehicle battery when the vehicle starts. In this battery management system, it is possible to accurately detect the state of the in-vehicle battery such as temporary over-discharge and deterioration by suppressing the error effects of the voltage and charge / discharge amount in the in-vehicle battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the battery management system described in Patent Document 1 above, the threshold values used for determining temporary over-discharge and deterioration of the in-vehicle battery are set by a pre-prepared data map or the like, and do not take into account the actual data trends of vehicles in the market. Therefore, there are still problems in terms of determination accuracy in the method for determining temporary over-discharge and deterioration of the in-vehicle battery described in Patent Document 1.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a battery management system capable of improving the determination accuracy of temporary over-discharge and deterioration of an in-vehicle battery in consideration of the actual data trends of vehicles in the market.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the disclosed technology is a battery management system that determines the state of an on-board battery based on the starting voltage of the on-board battery and a predetermined voltage threshold when the vehicle is started, and comprises a collection unit that collects vehicle data, including the starting voltage, from multiple vehicles in the market, and an update unit that updates the voltage threshold based on the vehicle data collected from the vehicles in the market. [Effects of the Invention]

[0007] According to the battery management system described herein, the voltage threshold for determining the state of the vehicle battery takes into account actual data trends of vehicles in the market, thereby improving the accuracy of determining temporary over-discharge and degradation of the vehicle battery. [Brief explanation of the drawing]

[0008] [Figure 1] Schematic diagram of a battery management system according to one embodiment of the present disclosure. [Figure 2A] Flowchart of the voltage threshold update control process performed by the battery management system [Figure 2B] Flowchart of the voltage threshold update control process performed by the battery management system [Figure 3] Image diagram of the data frequency distribution of the correction startup voltage. [Figure 4] A diagram illustrating a method for updating the voltage threshold using the quartile method. [Modes for carrying out the invention]

[0009] The logic for detecting factors such as temporary over-discharge and degradation that cause vehicle battery failure uses changes in the vehicle's startup voltage to make a determination. However, the voltage threshold used for this determination varies depending on the vehicle's hardware configuration (ECU system, battery mounting location, wiring configuration, etc.), and therefore needs to be set for each vehicle model. Furthermore, it is difficult to determine the exact value of this voltage threshold through theoretical calculations due to the vehicle's complex hardware configuration, and it is desirable to set it based on actual vehicle data. Therefore, the battery management system disclosed herein proposes logic for automatically setting an accurate voltage threshold on a server by eliminating voltage fluctuation factors, noise, and bias. The embodiments of this disclosure will be described in detail below with reference to the drawings.

[0010] <Embodiment> [composition] Figure 1 is a block diagram showing a schematic configuration of a vehicle communication system 100 including a battery management system 122 according to one embodiment of the present disclosure. The vehicle communication system 100 illustrated in Figure 1 includes a vehicle 110 and a center 120.

[0011] (1) Vehicle Vehicle 110 is connected to the center 120 in a communicative manner. This vehicle 110 is, for example, an automobile and is equipped with at least a battery 111, a data acquisition unit 112, and a data transmission unit 113. Although only one vehicle 110 connected to the center 120 in a communicative manner is shown in the example in Figure 1, in reality, multiple vehicles 110 are each connected to the center 120 in a communicative manner.

[0012] Battery 111 is a rechargeable secondary battery, such as a lithium-ion battery or a lead-acid battery. An example of battery 111 is an on-board battery such as an auxiliary battery. This battery 111 is charged by a generator such as an alternator (not shown) and can supply (discharge) the power it stores to accessories and equipment (not shown) mounted on the vehicle 110.

[0013] The data acquisition unit 112 is configured to acquire vehicle data when the vehicle 110 is started with the ignition turned ON. This vehicle data includes information about the vehicle 110 (hereinafter referred to as "vehicle information") and information about the battery 111 (hereinafter referred to as "battery information"). The vehicle information includes at least the vehicle 110's mileage (ODO) and parking time (the time from when the ignition is continuously OFF until it is started). The battery information includes at least the voltage of the battery 111 when the vehicle 110 is started (hereinafter referred to as "startup voltage"), current, temperature, and state of charge (SOC).

[0014] The data transmission unit 113 has a configuration that controls communication between the vehicle 110 and the center 120. The data transmission unit 113 transmits the vehicle data acquired by the data acquisition unit 112 to the center 120. Typically, the data transmission unit 113 transmits its own vehicle data to the center 120 when the vehicle 110 is started (when the ignition is turned ON and the trip starts). This data transmission unit 113 is implemented, for example, by a data communication module (DCM).

[0015] (2) Center The center 120 is connected to the vehicle 110 in a communicative manner. This center 120 is, for example, a server on the cloud and comprises at least a data receiving unit 121, a battery management system 122, a battery determination unit 125, and a notification unit 126.

[0016] The data receiving unit 121 has a function to control communication between the center 120 and multiple vehicles 110. This data receiving unit 121 can receive multiple vehicle data transmitted from each of the multiple vehicles 110. The vehicle data received by the data receiving unit 121 each time is stored in, for example, a storage unit (not shown).

[0017] The battery management system 122 is a system for managing the battery 111 mounted on the vehicle 110. Characteristically, the battery management system 122 of this embodiment performs a process of updating a voltage threshold value for determining a specific state such as a temporary over-discharge state or a deterioration state of the battery 111, which is a factor for battery overheating. This battery management system 122 includes a data collection unit 123 and a threshold value update unit 124.

[0018] The data collection unit 123 collects vehicle data of the vehicle 110 to be controlled for each trip among the plurality of vehicle data acquired by the data reception unit 121. The vehicle 110 to be controlled is a vehicle 110 for which the same voltage threshold value can be applied for determining a specific state of the battery 111, and as an example, it can be a vehicle 110 of the same vehicle type equipped with the same battery 111. Then, the data collection unit 123 accumulates the starting voltage included in the collected vehicle data of the vehicle 110 to be controlled until the stage where the voltage threshold value is updated according to a predetermined condition (sufficient vehicle data is collected). The processes related to the collection and accumulation performed by this data collection unit 123 will be described later.

[0019] The threshold value update unit 124 updates (corrects) the voltage threshold value used for determining the specific state of the battery 111 based on the information of the starting voltage accumulated by the data collection unit 123. In order to set the voltage threshold value for determining the specific state of this battery 111, information on the starting voltage applied to the ECU system (main ECU, etc.) is required. However, since the starting voltage of this ECU system depends on the specifications of the ECU system, the shunt with a plurality of vehicle loads and after-installed equipment mounted on the vehicle 110, and the wiring structure between the battery 111 and the ECU system, it is difficult to accurately calculate the starting voltage by on-board calculation. Therefore, the threshold value update unit 124 automatically updates the voltage threshold value used for determining the specific state of the battery 111 based on the vehicle data considering the variations including the actual after-installed equipment acquired from the vehicle 110 actually used in the market. The voltage threshold value update process performed by this threshold value update unit 124 will be described later.

[0020] The battery determination unit 125 is configured to determine the state of the battery 111 using the voltage threshold updated by the threshold update unit 124 or the previous voltage threshold. Examples of the state of the battery 111 determined by this battery determination unit 125 include specific states such as a state where the battery 111 is temporarily overdischarged and a state where the battery 111 is deteriorated due to aging or the like.

[0021] The notification unit 126 is configured to perform an appropriate notification according to the state of the battery 111 determined by the battery determination unit 125. This notification is preferably performed when the battery 111 is in a temporarily overdischarged state or when the battery 111 is in a deteriorated state. Examples of the notification destination include the vehicle 110 and a portable terminal such as the user or driver of the vehicle 110.

[0022] [Control] Next, referring further to FIGS. 2A and 2B, the control performed by the battery management system 122 according to the present embodiment will be described. FIGS. 2A and 2B are flowcharts for explaining the processing procedure of the voltage threshold update control executed by each component of the battery management system 122. The processing in FIG. 2A and the processing in FIG. 2B are connected by a connector X.

[0023] The voltage threshold update control shown in FIGS. 2A and 2B is started, for example, when the vehicle 110 is shipped (line-off) to the market.

[0024] (Step S201) The data collection unit 123 determines whether there is vehicle data of the vehicle type to be controlled among the plurality of vehicle data received by the data reception unit 121 from the plurality of vehicles 110. This determination may be made each time the data reception unit 121 receives new vehicle data from the vehicle 110, or may be made at a predetermined interval.

[0025] If the data acquisition unit 123 determines that the data received by the data reception unit 121 contains vehicle data for the vehicle type to be controlled (step S201, yes), the process proceeds to step S202.

[0026] (Step S202) The data acquisition unit 123 acquires vehicle information and battery information for the vehicle to be controlled from the vehicle data. Specifically, the data acquisition unit 123 acquires mileage (ODO) and parking time as vehicle information, and startup voltage, current, temperature, and state of charge (SOC) as battery information. The state of charge can be calculated based on the open circuit voltage (OCV), which is the voltage of the battery 111 under no load, and the integrated current value. If the state of charge can be directly obtained from an SOC sensor or the like, that value may be used.

[0027] Once the data acquisition unit 123 acquires vehicle information and battery information for the vehicle to be controlled, the process proceeds to step S203.

[0028] (Step S203) The data acquisition unit 123 determines whether the startup voltage acquired in step S202 above satisfies predetermined conditions (hereinafter referred to as "collection conditions") for collecting statistical data. These collection conditions are determined as follows, based on the vehicle's mileage (ODO) and parking time, and the battery's state of charge (SOC).

[0029] The first collection condition is that the vehicle 110's mileage (ODO) is within a predetermined range. This first collection condition is set to exclude the effect of battery 111 degradation, which is one of the factors that cause fluctuations in the starting voltage. Since battery 111 degradation progresses over a relatively long period, the degradation state is eliminated by acquiring vehicle data immediately after delivery. Therefore, the predetermined range can be set to, for example, 10km < mileage < 1000km.

[0030] A second collection condition is that the vehicle 110 is parked for a predetermined time or longer. This second collection condition is set to eliminate the effect of polarization of the battery 111, which is one of the factors that cause fluctuations in the starting voltage. The starting voltage immediately after charging or discharging the battery 111 is affected by polarization due to the concentration distribution inside the battery 111. Since the effect of this polarization gradually mitigates with the length of time the vehicle is left idle, the polarized state is eliminated by increasing the parking time until just before the vehicle 110 starts up. Therefore, the predetermined time can be set to, for example, a parking time > 12 hours.

[0031] A third collection condition is that the state of charge (SOC) of the battery 111 is above a predetermined value. This third collection condition is set up to eliminate the influence of the battery 111's SOC, which is one of the factors that cause fluctuations in the startup voltage. The startup voltage is affected by the SOC because the resistance and open-circuit voltage (OCV) change depending on the SOC of the battery 111. Also, normally, the auxiliary battery of a vehicle 110 is defined as being maintained in a high SOC state by continuous charging. Therefore, by using the startup voltage when the battery 111 has a high SOC, the influence of the SOC is eliminated. Thus, the predetermined value can be set to, for example, a SOC ≥ 80%.

[0032] Furthermore, in order to account for the effect of resistance that changes with temperature, the state of charge (SOC) of the battery 111 obtained from the vehicle 110 may be corrected by the following formula [1]. Here, resistance (25°C) is the resistance value at 25°C in the wiring path from the battery 111 to the ECU system, and the temperature-resistance ratio is a ratio used to determine the resistance fluctuation due to the actual temperature in the vehicle 110. Corrected storage rate = Storage rate (OCV) - Current x Temperature resistance ratio x Resistance (25℃) …[1]

[0033] If the data acquisition unit 123 satisfies all of the first, second, and third acquisition conditions, it determines that the acquisition conditions for the startup voltage are satisfied (step S203, yes), and proceeds to step S204. On the other hand, if the data acquisition unit 123 does not satisfy any one of the first, second, and third acquisition conditions, it determines that the acquisition conditions for the startup voltage are not satisfied (step S203, no), and proceeds to step S201.

[0034] (Step S204) The data acquisition unit 123 corrects the startup voltage acquired in step S202 based on the temperature of the battery 111. This correction is performed to eliminate the effect of temperature, which is one of the factors that cause fluctuations in the startup voltage. Since wiring resistance and other factors change with temperature, the startup voltage is affected by temperature. Therefore, the effect of temperature is eliminated by correcting the startup voltage using the temperature information of the battery 111, which is acquired simultaneously with the startup voltage. The corrected startup voltage (hereinafter referred to as "corrected startup voltage") can be calculated, for example, by the following formula [2] based on the (pre-correction) startup voltage, current, and temperature of the battery 111 acquired in step S202, and the constants resistance (25°C) and temperature-resistance ratio mentioned above. Corrected startup voltage = Open-circuit voltage - Current × Temperature-to-resistance ratio × Resistance (25°C) …[2]

[0035] The aforementioned resistance (25°C) is a fixed value determined during the design of the vehicle 110. Therefore, the data acquisition unit 123 may pre-store the resistance (25°C) for each vehicle type in a storage unit (not shown), or each vehicle 110 may include it in the vehicle data and transmit it to the center 120. Furthermore, the aforementioned temperature-resistance ratio information can be exemplified by the data acquisition unit 123 pre-keeping the temperature-resistance ratio for each vehicle type in a storage unit in the form of a data map or the like.

[0036] Once the startup voltage is corrected by the data acquisition unit 123 based on the temperature of the battery 111, the process proceeds to step S205.

[0037] (Step S205) The data acquisition unit 123 creates a frequency distribution of the corrected startup voltage obtained by the correction in step S204 above. More specifically, the data acquisition unit 123 cumulatively counts the corrected startup voltage as one data point. Figure 3 shows an image of the data frequency distribution accumulated by the cumulative counting of the corrected startup voltage. The voltage range to be counted can be any range width (for example, 0.1V or 0.5V). For example, if the corrected startup voltage is 12.6V, the number of data points in the 12.5V to 13.0V voltage range will be incremented by one.

[0038] Once the correction startup voltage is cumulatively counted by the data acquisition unit 123, the process proceeds to step S206.

[0039] (Step S206) The data acquisition unit 123 updates the elapsed days and the number of vehicles. The elapsed days are the number of days that have elapsed since the time when vehicle data was first acquired from vehicle 110 in step S201 (service start). The number of vehicles is the total number of vehicles 110 from which vehicle data satisfying the startup voltage acquisition conditions has been acquired in step S203. The elapsed days can be measured using a clock function (not shown) of the data acquisition unit 123. The number of vehicles is incremented by one each time the corrected startup voltage is counted in step S205.

[0040] Once the data collection unit 123 updates the elapsed days and the number of vehicles, the process proceeds to step S207.

[0041] If multiple vehicle data for the target vehicle type are obtained during the processing in step S201, the processing in steps S202 to S206 will be performed for each of the multiple vehicle data.

[0042] (Step S207) The threshold update unit 124 determines whether the elapsed days and the number of vehicles updated in step S206 above satisfy the predetermined conditions (hereinafter referred to as "update conditions") for updating the voltage threshold. These update conditions are determined as follows, based on the elapsed days and the number of vehicles.

[0043] The first update condition is that the number of elapsed days is equal to or greater than a predetermined number. The second update condition is that the number of vehicles is equal to or greater than a predetermined number. These first and second update conditions are set up to eliminate the influence of data noise caused by noise and bias in the collected startup voltage, which is one of the factors that causes fluctuations in the startup voltage. After collecting a sufficient number of startup voltages in the normal state of vehicle 110, the quartile deviation method described later is applied, and the median is obtained to obtain a reference voltage value from which noise and bias have been removed and data noise is eliminated. The elapsed days and number of vehicles used to determine a sufficient number can be set to values ​​such as elapsed days ≥ 20 days and number of vehicles ≥ 200 units, or elapsed days ≥ 60 days and number of vehicles ≥ 30 units.

[0044] If the threshold update unit 124 satisfies all of the first and second update conditions, it determines that the voltage threshold update conditions are satisfied (step S207, yes), and proceeds to step S208. On the other hand, if the threshold update unit 124 fails to satisfy either the first or second update conditions, it determines that the voltage threshold update conditions are not satisfied (step S207, no), and proceeds to step S201.

[0045] (Step S208) The threshold update unit 124, based on the corrected startup voltages accumulated in step S205, creates a stacked probability line by stacking the ratios of the number of data points in each category to the total number of data points in order of voltage, with the total number of data points for the corrected startup voltages set to 100%. An image of this stacked probability line is shown in Figure 4(b). The threshold update unit 124 then derives the corrected startup voltage with a 25% probability (25% voltage) and the corrected startup voltage with a 75% probability (75% voltage) on this stacked probability line. An image of these 25% and 75% voltages of the corrected startup voltage (white circles in the figure) is shown in Figure 4(b).

[0046] Once the threshold update unit 124 derives the 25% voltage and 75% voltage of the corrected startup voltage in the stacked probability line, the process proceeds to step S209.

[0047] (Step S209) The threshold update unit 124 derives the upper control limit (UCL) and lower control limit (LCL) of the corrected startup voltage based on the 25% and 75% voltages of the corrected startup voltage derived in step S208. The upper control limit (UCL) and lower control limit (LCL) are calculated using the quartile deviation (QD) based on the quartile method by the following equations [3], [4], and [5]. An image of the upper control limit (UCL) and lower control limit (LCL) (white squares in the figure) is shown in Figure 4(a). Interquartile deviation QD = (25th percentile voltage + 75th percentile voltage) / 2 …[3] Upper control limit UCL = 75% voltage + 3 × interquartile deviation QD …[4] Lower control limit LCL = 25% voltage - 3 × interquartile deviation QD …[5]

[0048] Once the threshold update unit 124 derives the upper limit control limit UCL and the lower limit control limit LCL, the process proceeds to step S210.

[0049] (Step S210) The threshold update unit 124 calculates the average probability of the upper control limit UCL and the lower control limit LCL derived in step S209. This average probability is the average of the cumulative probability corresponding to the upper control limit UCL and the cumulative probability corresponding to the lower control limit LCL. Figure 4(b) shows an image of the cumulative probability corresponding to the upper control limit UCL and the cumulative probability corresponding to the lower control limit LCL (black circles in the figure), and an image of the average probability (dotted line in the figure).

[0050] Once the threshold update unit 124 calculates the probability mean of the upper control limit UCL and the lower control limit LCL, the process proceeds to step S211.

[0051] (Step S211) The threshold update unit 124 calculates the median voltage of the corrected startup voltage based on the probability mean values ​​of the upper control limit UCL and the lower control limit LCL calculated in step S210. This median voltage is the value of the corrected startup voltage corresponding to the probability mean value, and is the voltage value at which the dashed line of the probability mean value and the stacked probability line (solid line) intersect in Figure 4(b).

[0052] Once the threshold update unit 124 calculates the median voltage of the correction startup voltage, the process proceeds to step S212.

[0053] (Step S212) The threshold update unit 124 calculates and sets a new voltage threshold based on the median voltage of the corrected startup voltage calculated in step S211. This voltage threshold is a voltage value that serves as the reference value for determining a specific state of the battery 111, and is calculated by adding a predetermined margin to the median voltage. This margin is set to improve the efficiency and accuracy of the determination, such as preventing the battery determination unit 125 from excessively determining a specific state of the battery 111. For example, the voltage threshold can be set by multiplying the median voltage by a predetermined coefficient (e.g., 0.3), or by subtracting a predetermined constant (e.g., 0.3V) from the median voltage.

[0054] The voltage threshold setting process by the threshold update unit 124 (steps S208-S212) described above is executed only once after the data acquisition process by the data acquisition unit 123 (steps S201-S207) is completed.

[0055] When the threshold update unit 124 calculates and sets a new voltage threshold, this voltage threshold update control ends.

[0056] This threshold update unit 124 process removes startup voltages in the region above the upper limit UCL and startup voltages in the region below the lower limit LCL, respectively. Furthermore, by calculating a reference value for determining a specific state of the battery 111 from the median voltage, the influence of data bias can be reduced.

[0057] [Application Examples] If an unexpected bias occurs in the multiple startup voltages obtained from the vehicle 110, it is conceivable to set a fail-safe value as the voltage threshold for the startup voltage. In this case, the fail-safe value should be a low voltage value such that the logic of the battery determination unit 125 does not determine specific states such as temporary over-discharge and deterioration of the battery 111. The following contents in the data frequency distribution of the corrected startup voltage can be exemplified as processing conditions (fail-safe processing conditions) for setting this low voltage value.

[0058] • The data ratio of the maximum voltage in the distribution is greater than or equal to a predetermined value P1 (e.g., 5%). • The data ratio of the minimum voltage in the distribution is greater than or equal to a predetermined value P1 (e.g., 5%). • The data ratio in the region above the upper limit control level (UCL) is greater than or equal to a predetermined value P2 (e.g., 10%). • The percentage of data in the region below the lower control limit (LCL) is greater than or equal to a predetermined value P2 (e.g., 10%). • The upper limit control level (UCL) is greater than the maximum voltage (UCL > Vmax). • The lower control limit LCL is less than the minimum voltage (LCL <Vmin) • The quartile deviation (QD) is greater than the maximum possible value (QD > QDmax).

[0059] In addition to the methods described above, fail-safe processing may also be performed using indicators that represent the distribution shape, such as kurtosis or skewness.

[0060] <Effects and Actions> As described above, in the battery management system 122 according to one embodiment of this disclosure, considering that it is desirable to set the voltage threshold for the startup voltage based on actual vehicle data, a voltage threshold (hypothetical number) is set based on hardware specifications and limited vehicle data before the vehicle 110 rolls off the line (LO), and after the vehicle 110 rolls off the line, the voltage threshold is automatically adjusted from market data.

[0061] This process makes it possible to set the correct voltage threshold in the logic for determining the specific state of the battery 111, taking into account the actual data trends of vehicles 110 in the market, thereby improving the accuracy of determining temporary over-discharge and degradation of the battery 111.

[0062] Furthermore, since the battery management system 122 automatically sets (adjusts) the voltage threshold based on vehicle data, the amount of work required for operators to manually update the voltage threshold can be reduced.

[0063] Furthermore, by obtaining a normal startup voltage that excludes factors that cause fluctuations in the startup voltage in market data after the vehicle 110 rolls off the production line (temperature, state of charge (SOC) status, degradation status, polarization after charging / discharging, variations in battery performance and aftermarket equipment, and data noise), it is possible to update the correct voltage threshold setting. [Industrial applicability]

[0064] The battery management system described herein can be used, for example, to estimate the discharge rate of a battery installed in a vehicle. [Explanation of symbols]

[0065] 100 Vehicle Communication Systems 110 vehicles 111 Battery 112 Data Acquisition Unit 113 Data transmission unit 120 Center 121 Data receiving unit 122 Battery Management System 123 Data Collection Unit 124 Threshold update section 125 Battery detection unit 126 Notification Department

Claims

1. A battery management system that determines the state of an onboard battery based on the starting voltage of the onboard battery and a predetermined voltage threshold when the vehicle is started, A collection unit that collects vehicle data, including the startup voltage, from multiple of the aforementioned vehicles in the market, The system includes an update unit that updates the voltage threshold based on vehicle data collected from the aforementioned vehicles in the market, Battery management system.

2. The vehicle data further includes the vehicle's mileage, the parking time from the vehicle's stop to its start, and the charge level of the vehicle's battery. The collection unit stores the startup voltage when the driving distance, parking time, and charge level each satisfy predetermined conditions. The battery management system according to claim 1.

3. The vehicle data further includes the temperature of the onboard battery, The collection unit corrects the startup voltage based on the temperature. The battery management system according to claim 2.

4. The update unit updates the voltage threshold based on the accumulated startup voltage when the number of days elapsed since the collection unit started collecting the vehicle data and the number of vehicles for which vehicle data has been collected satisfy predetermined conditions. The battery management system according to claim 3.

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