Predictive detection system, predictive detection method, and predictive detection program

Abstract

In this indication detection system, a battery data acquisition unit acquires battery data including current data obtained by periodically measuring the current flowing through a battery pack. If there is included, in the current data for a period in which the battery pack is being charged from a charger, an interval where a current value temporarily becomes zero, and an accumulated current value of the charging period including the interval where the current value temporarily becomes zero is more than at least one of accumulated current values of a discharging period directly before or a discharging period directly after the charging period, a determination unit determines that the occurrence of the interval where the current value is zero is an indication that the battery pack will become unusable.

Description

Technical Field

[0001] The present disclosure relates to a prediction detection system, a prediction detection method, and a prediction detection program for detecting signs of abnormal occurrences such as battery heat generation and ignition.

Background Art

[0002] Electric vehicles (EVs) have been spreading mainly for commercial vehicles such as delivery vehicles. In recent years, an environment has been gradually built where EV driving data (such as battery information and vehicle control information) is stored on the cloud and can be utilized in various fields.

[0003] When a lithium-ion battery deteriorates, lithium metal may precipitate dendritically and penetrate the separator, causing an internal short circuit between the positive electrode and the negative electrode. This short circuit path is instantaneously blown when current flows, and the insulation between the positive electrode and the negative electrode is restored. As the deterioration of the lithium-ion battery progresses, the occurrence frequency of instantaneous short circuits due to metal precipitation increases, and ultimately the battery becomes unusable. In addition, the frequency of instantaneous short circuits due to metal precipitation increases the risk of ignition.

[0004] A method has been proposed for detecting an instantaneous short circuit due to metal precipitation based on an instantaneous decrease in battery voltage (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] However, voltage fluctuations due to instantaneous short circuits caused by metal deposition are on the order of milliseconds, and their fluctuation range is only a few tens of millivolts. Therefore, if the voltage is not monitored with high-speed sampling, detection is likely to be missed. High-precision monitoring of voltage fluctuations with high-speed sampling requires a high-spec measurement system, large-capacity memory, and high-speed communication. In that case, cost and power consumption will increase.

[0007] This disclosure is made in light of these circumstances, and its purpose is to provide a technology for detecting signs of battery failure at low cost and with high accuracy.

[0008] To solve the above problems, a predictive detection system according to one embodiment of the present disclosure includes: an acquisition unit that acquires battery data including current data obtained by periodically measuring the current flowing through the battery pack; and a determination unit that determines that the occurrence of a period in which the current value is zero is a predictive sign that the battery pack will become unusable, when the current data for the period in which the battery pack is being charged by the charger includes a period in which the current value is temporarily zero, and the integrated current value for the charging period including the period in which the current value is temporarily zero is greater than at least one of the integrated current values ​​for the discharge period immediately before or immediately after the charging period.

[0009] Furthermore, any combination of the above components, as well as any conversion of the expressions of this disclosure between devices, systems, methods, computer programs, recording media on which computer programs are recorded, etc., are also valid as aspects of this disclosure.

[0010] According to this disclosure, signs of battery failure can be detected at low cost and with high accuracy. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram illustrating the general outline of the predictive maintenance system according to the embodiment. [Figure 2] This figure shows an example of a charger and electric vehicle configuration. [Figure 3] This figure shows an example configuration of the predictive maintenance system according to the embodiment. [Figure 4] This figure shows a specific example of three days' worth of battery data for a certain electric vehicle. [Figure 5] This is a diagram illustrating how to set the pre-charge discharge period. [Figure 6] This flowchart shows the flow of a first processing example in which the predictive detection system according to the embodiment detects signs that the battery pack is about to become unusable. [Figure 7] This flowchart shows the flow of a second processing example in which the predictive detection system according to the embodiment detects signs that the battery pack is about to become unusable. [Figure 8] This flowchart shows the flow of a third processing example in which the predictive detection system according to the embodiment detects signs that the battery pack is about to become unusable. [Figure 9] This flowchart shows the flow of a fourth processing example in which the predictive detection system according to the embodiment detects signs that the battery pack is about to become unusable. [Figure 10] This flowchart shows the flow of a fifth processing example in which the predictive detection system according to the embodiment detects signs that the battery pack is about to become unusable. [Figure 11] This figure shows an example of the changes in current data and voltage data, including the protective operation period of the charger. [Modes for carrying out the invention]

[0012] Figure 1 is a diagram illustrating the outline of the predictive detection system 1 according to the embodiment. The predictive detection system 1 according to the embodiment is a system for detecting signs that the battery pack 31 (see Figure 2) mounted on the electric vehicle 3 will become unusable. Unusable states of the battery pack 31 include unusable states due to abnormal occurrences such as overheating, ignition, or wire breakage, and unusable states due to the end of life. Signs that the battery pack 31 will become unusable include frequent instantaneous short circuits due to metal deposition, and poor contact due to corrosion or loosening of fastening parts (bus bars and screws). If the current path is eliminated due to corrosion or detachment of fastening parts, there is a risk of arc discharge.

[0013] Figure 1 shows an example of a delivery company using the predictive maintenance system 1. The predictive maintenance system 1 may be built, for example, on a server installed in the company's own facilities or data center of a service provider that provides operation management support services for electric vehicles 3. Alternatively, the predictive maintenance system 1 may be built on a cloud server used under a cloud service contract. Furthermore, the predictive maintenance system 1 may be built on multiple servers distributed across multiple locations (data centers, company facilities). These multiple servers may be a combination of multiple company servers, multiple cloud servers, or a combination of company servers and cloud servers.

[0014] Each delivery company owns multiple electric vehicles 3 and at least one charger 4, and has a delivery base for parking the multiple electric vehicles 3. The electric vehicles 3 are connected to the charger 4 by a charging cable 5, and the battery packs 31 installed in the electric vehicles 3 are charged from the charger 4 via the charging cable 5.

[0015] A fleet management terminal device 7 is installed at the delivery base of the delivery company. The fleet management terminal device 7 is, for example, composed of a PC. The fleet management terminal device 7 is used to manage multiple electric vehicles 3 belonging to the delivery base. The fleet manager of the delivery company can use the fleet management terminal device 7 to create delivery plans and charging plans for multiple electric vehicles 3. The fleet management terminal device 7 can access the predictive maintenance system 1 via the network 2.

[0016] Network 2 is a general term for communication channels such as the Internet, dedicated lines, and VPN (Virtual Private Network), regardless of the communication medium or protocol. As the communication medium, for example, a mobile phone network (cellular network), wireless LAN, wired LAN, optical fiber network, ADSL network, CATV network, etc. can be used. As the communication protocol, for example, TCP (Transmission Control Protocol) / IP (Internet Protocol), UDP (User Datagram Protocol) / IP, Ethernet (registered trademark), etc. can be used.

[0017] Figure 2 is a diagram showing a configuration example of the charger 4 and the electric vehicle 3. The charger 4 includes a rectifier circuit 41, a PFC (Power Factor Correction) circuit 42, a DC / DC converter 43, a control unit 44, a current sensor 45, a voltage sensor 46, and an output relay 47. In the embodiment, a rapid charger compliant with CHAdeMO (registered trademark) is assumed.

[0018] The rectifier circuit 41 full-wave rectifies the AC voltage (for example, three-phase AC 200V) supplied from the commercial power system 6. The PFC circuit 42 improves the power factor of the full-wave rectified power. The DC / DC converter 43 is an isolated DC / DC converter and controls the current or voltage of the DC power supplied from the PFC circuit 42. The current sensor 45 detects the output current of the DC / DC converter 43 and outputs it to the control unit 44. The voltage sensor 46 detects the output voltage of the DC / DC converter 43 and outputs it to the control unit 44.

[0019] The control unit 44 controls the output current or output voltage of the DC / DC converter 43 based on the output current detected by the current sensor 45 and the output voltage detected by the voltage sensor 46. The control unit 44 includes a microcontroller, a communication controller, and a non-volatile memory (for example, EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory).

[0020] In CHAdeMO and ChaoJi, CAN (Controller Area Network) is adopted as the communication method between the charger 4 and the electric vehicle 3 via the charging cable 5. In Combo, PLC (Power Line Telecommunication) is adopted. The charging cable 5 compliant with CHAdeMO includes a CAN communication line. The control unit 44 includes a CAN controller as a communication controller for controlling communication with the vehicle control unit 36 in the electric vehicle 3.

[0021] Generally, for charging the battery pack 31, constant current (CC)-constant voltage (CV) charging is used. The target current value during the constant current charging period may be a constant value or may be switched step by step.

[0022] During constant current charging control, the control unit 44 controls the DC / DC converter 43 so that the output current detected by the current sensor 45 maintains the target current value. Specifically, when the detected output current is higher than the target current value, the control unit 44 generates a current command value for decreasing the output current of the DC / DC converter 43, and when the detected output current is lower than the target current value, the control unit 44 generates a current command value for increasing the output current of the DC / DC converter 43. The DC / DC converter 43 performs a switching operation according to the drive signal based on the generated current command value.

[0023] During constant current charging control, when the deviation between the output current detected by the current sensor 45 and the target current value becomes equal to or greater than a predetermined value (for example, 5 to 20%), the control unit 44 determines that an overcurrent has occurred and activates a protection operation to stop charging. As a protection operation, the control unit 44 stops the operation of the DC / DC converter 43 and controls the output relay 47 to the off state (open state). After stopping charging, the control unit 44 executes a restart sequence to resume charging the battery pack 31. The restart sequence usually takes about several tens of seconds for safety reasons.

[0024] For example, if contact resistance increases due to poor contact caused by corrosion or loosening of the fastening part as described above, the output current of the charger 4 will drop and will not be able to maintain the target current value. Also, if the fastening part comes undone, the output current of the charger 4 will become zero.

[0025] Furthermore, if the output current detected by the current sensor 45 exceeds the overcurrent threshold, the control unit 44 activates a protection operation and stops charging. In this case as well, after stopping charging, the control unit 44 executes a restart sequence to resume charging the battery pack 31. For example, if an instantaneous short circuit occurs due to the metal deposition described above, a large current flows instantaneously through the short circuit path, causing the output current of the charger 4 to exceed the overcurrent threshold.

[0026] The electric vehicle 3 includes a battery pack 31, a battery control unit 32, a current sensor 33, a voltage sensor 34, a temperature sensor 35, a vehicle control unit 36, a motor 37, an inverter 38, a first relay 39, a second relay 310, an onboard charger 311, a vehicle speed sensor 313, a wireless communication unit 314, and an antenna 315.

[0027] The battery pack 31 includes multiple cells connected in series or in series-parallel. These cells can be lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, etc. Hereinafter, this specification assumes the use of lithium-ion battery cells (nominal voltage: 3.6-3.7V).

[0028] The current sensor 33 detects the current flowing through the battery pack 31 and outputs it to the battery control unit 32. The voltage sensor 34 detects the voltage of the battery pack 31 and outputs it to the battery control unit 32. Although not shown in the diagram, the voltage sensor 34 can also detect the voltage of each of the multiple series-connected cells included in the battery pack 31. The temperature sensor 35 detects the temperature of the battery pack 31 and outputs it to the battery control unit 32. The temperature sensor 35 may be installed at multiple locations on the battery pack 31.

[0029] The battery control unit 32 (also referred to as BMU or BMS) includes a microcontroller, a communication controller, and non-volatile memory. The battery control unit 32 and the vehicle control unit 36 ​​are connected via an in-vehicle network (e.g., CAN or LIN (Local Interconnect Network)). The communication controller controls communication with the vehicle control unit 36.

[0030] The battery control unit 32 estimates the State of Charge (SOC), Full Charge Capacity (FCC), and State of Health (SOH) of each of the multiple cells contained in the battery pack 31.

[0031] The battery control unit 32 estimates the State of Charge (SOC) by combining the Open Circuit Voltage (OCV) method and the current integration method. The OCV method estimates the SOC based on the OCV of the cell and the SOC-OCV curve of the cell. The SOC-OCV curve of the cell is created in advance based on characteristic tests conducted by the battery manufacturer and is registered in the internal memory of the microcontroller at the time of shipment.

[0032] The current integration method is a method for estimating the state of charge (SOC) based on the OCV at the start of charging and discharging of the cell and the integrated value of the current flowing through the cell. With the current integration method, current measurement errors accumulate as the charging and discharging time increases. Therefore, it is preferable to correct the SOC estimated by the current integration method using the SOC estimated by the OCV method.

[0033] The battery control unit 32 can estimate the FCC by dividing the integrated current value from the start to the end of charging and discharging by the change in SOC during that period. The SOC at the start and end of charging and discharging can be determined from the measured OCV and SOC-OCV curve, respectively. SOH is defined as the ratio of the current FCC to the initial FCC, and a lower value (closer to 0%) indicates that degradation is progressing.

[0034] The battery control unit 32 transmits the voltage, current, temperature, SOC, FCC, and SOH of the battery pack 31 and each cell to the vehicle control unit 36 ​​via the in-vehicle network.

[0035] The vehicle control unit 36 ​​is a vehicle ECU (Electronic Control Unit) that controls the entire electric vehicle 3, and may be composed of, for example, an integrated VCM (Vehicle Control Module). The vehicle control unit 36 ​​includes a communication controller for connecting to an in-vehicle network and a communication controller (e.g., a CAN controller) for communicating with the control unit 44 of the charger 4 via the charging cable 5.

[0036] The electric vehicle 3 is equipped with a three-phase AC motor as the drive motor 37. During acceleration, the inverter 38 converts the DC power supplied from the battery pack 31 into AC power and supplies it to the motor 37. During regeneration, it converts the AC power supplied from the motor 37 into DC power and supplies it to the battery pack 31. During acceleration, the motor 37 rotates in accordance with the AC power supplied from the inverter 38. During regeneration, it converts the rotational energy due to deceleration into AC power and supplies it to the inverter 38.

[0037] The first relay 39 is a contactor inserted into the wiring connecting the battery pack 31 and the inverter 38. When the vehicle is running, the vehicle control unit 36 ​​controls the first relay 39 to the ON state (closed state), electrically connecting the battery pack 31 and the inverter 38. When the vehicle is not running, the vehicle control unit 36 ​​controls the first relay 39 to the OFF state (open state), electrically disconnecting the battery pack 31 and the inverter 38.

[0038] The second relay 310 is a relay inserted into the DC wiring connecting the battery pack 31 and the inlet into which the charging cable 5 is plugged. The battery control unit 32 controls the second relay 310 to the ON state when charging from the charger 4, and controls the second relay 310 to the OFF state after charging is complete.

[0039] The onboard charger 311 is used when charging with AC power by plugging an AC plug cable into a standard charger or general-purpose AC outlet. The onboard charger 311 full-wave rectifies the AC voltage supplied via the AC plug cable, improves the power factor of the full-wave rectified power, and controls the current or voltage of the DC power with the improved power factor before supplying it to the battery pack 31.

[0040] The onboard charger 311 essentially has the same functions as the charger 4. During constant current charging control, if the deviation between the detected charging current and the target current value exceeds a predetermined value (for example, 5-20%), the onboard charger 311 determines that there is a current abnormality and activates a protection operation to stop charging. After stopping charging, the onboard charger 311 executes a restart sequence to resume charging the battery pack 31. The same applies when overcurrent is detected.

[0041] The vehicle speed sensor 313 generates a pulse signal proportional to the rotation speed of the axle and transmits the generated pulse signal to the vehicle control unit 36. The vehicle control unit 36 ​​detects the speed of the electric vehicle 3 based on the pulse signal received from the vehicle speed sensor 313.

[0042] The wireless communication unit 314 performs signal processing for wireless connection to network 2 via antenna 315. As wireless communication networks to which the electric vehicle 3 can wirelessly connect, for example, a mobile phone network (cellular network), wireless LAN, V2I (Vehicle to Infrastructure), V2V (Vehicle to Vehicle), ETC system (Electronic Toll Collection System), DSRC (Dedicated Short Range Communications), etc. can be used.

[0043] While the electric vehicle 3 is in motion, the vehicle control unit 36 ​​can transmit driving data, including battery data, to the predictive detection system 1 in real time using the wireless communication unit 314. The driving data includes at least the vehicle speed of the electric vehicle 3. The battery data includes the voltage, current, temperature, state of charge (SOC), and state of health (SOH) of the battery pack 31 and multiple cells. The vehicle control unit 36 ​​samples this data periodically (for example, at 10-second intervals) and transmits it to the predictive detection system 1 each time.

[0044] The vehicle control unit 36 ​​may store the driving data of the electric vehicle 3 in its internal memory and transmit the stored driving data in a batch at a predetermined timing. For example, the vehicle control unit 36 ​​may transmit the stored driving data to the operation management terminal device 7 in a batch after the end of business for the day. The operation management terminal device 7 transmits the driving data of multiple electric vehicles 3 to the predictive detection system 1 at a predetermined timing.

[0045] Furthermore, when charging from a charger 4 equipped with network communication functionality, the vehicle control unit 30 may transmit the driving data stored in its memory to the charger 4 in a single batch via the charging cable 5. The charger 4 then transmits the received driving data to the predictive detection system 1. This example is effective when the charger 4 is equipped with network communication functionality and the electric vehicle 3 is not equipped with wireless communication functionality.

[0046] Even when the electric vehicle 3 is parked, the vehicle control unit 36 ​​periodically samples battery data (for example, at 10-second intervals) and stores it in its internal memory. When the battery pack 31 is charged from the charger 4 while the electric vehicle 3 is parked, the battery data includes the charging start time and charging end time. The charging start time and charging end time can be determined from the communication log between the charger 4 and the electric vehicle 3. The vehicle control unit 30 transmits the battery data stored in memory to the predictive detection system 1 at a predetermined timing (for example, at the start of driving).

[0047] Figure 3 shows an example configuration of the predictive detection system 1 according to an embodiment. The predictive detection system 1 comprises a processing unit 11, a storage unit 12, and a communication unit 13. The communication unit 13 is a communication interface for connecting to the network 2 by wire or wireless.

[0048] The processing unit 11 includes a battery data acquisition unit 111, a determination unit 112, and a notification unit 113. The functions of the processing unit 11 can be realized through the cooperation of hardware and software resources, or solely through hardware resources. Hardware resources that can be used include a CPU, ROM, RAM, GPU (Graphics Processing Unit), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), and other LSIs. Software resources that can be used include operating systems, applications, and other programs.

[0049] The storage unit 12 includes a battery data storage unit 121. The storage unit 12 includes a non-volatile recording medium such as an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various types of data.

[0050] The battery data acquisition unit 111 acquires driving data (including battery data) of the electric vehicle 3 when it is running, or battery data when it is parked, via the network 2, and stores the acquired battery data in the battery data storage unit 121. Driving data other than battery data may be stored together in the battery data storage unit 121, or may be stored in a separate driving data storage unit (not shown).

[0051] The determination unit 112 periodically (for example, once a month) checks whether there are any signs that the battery pack 31 installed in the electric vehicle 3 is about to become unusable. When performing a periodic inspection, the determination unit 112 reads the battery data of the target battery pack 31 stored in the battery data storage unit 121 from the battery data storage unit 121.

[0052] The determination unit 112 determines whether the current data for the period during which the battery pack 31 is being charged from the charger 4 (hereinafter referred to as the charging period) includes a section in the battery data where the current value is temporarily zero (hereinafter referred to as the zero current section). In this specification, the charging period is defined as the period during which the battery pack 31 is being charged from the commercial power grid 6 using the charger 4 (hereinafter referred to as the concept including the onboard charger 311). This charging period does not include the regenerative charging period from the motor 37.

[0053] If the current data for the charging period includes a zero-current interval, the determination unit 112 determines that the occurrence of the zero-current interval is a sign that the battery pack 31 will become unusable, or that there is a possibility of such a sign.

[0054] The zero-current interval during the charging period essentially indicates a period in which charging is stopped due to the protection function of charger 4. The duration of the zero-current interval corresponds to the period from when charging stops due to the protection function of charger 4 until it resumes (approximately several tens of seconds in the example above). For example, if the sampling interval of the current data is 10 seconds, the zero-current interval will be 1 to several sampling intervals.

[0055] In reality, even if the current data for the charging period includes a zero-current data interval, this zero-current interval may have occurred due to a malfunction in the measurement system including the current sensor 33, data loss during transmission, data modification, etc. Therefore, it is conceivable to add a method to increase the certainty that the zero-current interval during the charging period is data generated by the activation of the protection function of the charger 4.

[0056] First, one possible method is to consider the frequency with which zero-current intervals occur during the charging period. In this first method that considers the frequency of occurrence, the determination unit 112 determines that the occurrence of a zero-current interval is a sign that the battery pack 31 will become unusable if the current data for the charging period includes a zero-current interval and the interval between zero-current intervals is shorter than the previous one. The interval between zero-current intervals is detected by the period between zero-current intervals or by the number of occurrences per predetermined period of the charging period.

[0057] In the second method, which takes into account the frequency of occurrence, the determination unit 112 determines that the occurrence of a zero current section is a sign that the battery pack 31 will become unusable if the current data for the charging period includes a zero current section and the zero current section occurs multiple times during one charging period or a predetermined period within a pre-set charging period. One charging period refers to the period during which one charge cycle continues from the start to the end of charging, and represents the period from the start of charging to the State of Charge (SOC) set for the end of charging, or until charging is forcibly terminated. The predetermined period within the charging period is a fixed period set in advance, or a predetermined period set based on multiple current data stored on the server.

[0058] Normally, lithium metal deposits grow in a dendritic pattern, causing momentary short circuits at multiple points. As the deposits progress, the intervals between momentary short circuits shorten. Also, as corrosion of the fastening parts progresses, the period of increased resistance increases, and the number of times the charger 4 is unable to maintain constant current control increases. Therefore, if the interval between zero-current data occurrences is shorter than the previous time, it can be estimated that lithium metal deposits are progressing or that corrosion of the fastening parts is progressing. If zero-current intervals occur multiple times during a single charge, it can be estimated that the deposits or corrosion are progressing and the battery pack 31 is close to being unusable.

[0059] Next, as a way to increase the certainty that the zero-current interval during the charging period is data generated due to the activation of the protection function of the charger 4, a method of considering energy loss can be considered. The determination unit 112 determines that the occurrence of the zero-current interval is a sign that the battery pack 31 will become unusable if the current data for the charging period includes a zero-current interval, and the integrated current value of the charging period including the zero-current interval is greater than (a) the integrated current value of the discharge period immediately preceding the charging period, (b) the integrated current value of the discharge period immediately following the charging period, or (c) the integrated current values ​​of both discharge periods. Any of the conditions (a)-(c) may be used.

[0060] In the case of the battery pack 31 installed in the electric vehicle 3, it is common practice not to charge it to SOC=100% and not to discharge it to SOC=0%. Therefore, it is necessary to determine the start and end times of the charging period and the discharge period based on various data.

[0061] Figure 4 shows a specific example of battery data for a certain electric vehicle 3 over three days. The upper figure plots current data, and the lower figure plots State of Charge (SOC) data. In the current data shown in Figure 4, positive values ​​represent discharge current, and negative values ​​represent charging current. In the example shown in Figure 4, the battery pack 31 is charged by charger 4 using constant current-constant voltage charging, where the charging current decreases in stages. The other irregular charging currents are due to regenerative charging. In addition, there is a period of inactivity of about 12 hours within the day.

[0062] If the battery data includes a communication log between the charger 4 and the electric vehicle 3, the determination unit 112 can identify the charging start time and charging end time from the communication log. In the example shown in Figure 4, the SOC at the start of charging is 24%, and the SOC at the end of charging is 96%.

[0063] The determination unit 112 sets the end time of the discharge period immediately preceding the charging period including the zero-current section (hereinafter referred to as the pre-charge discharge period) as the start time of the charging period. The determination unit 112 sets the start time of the pre-charge discharge period as the time of the nearest State of Charge (SOC) corresponding to the SOC of the end time of the charging period.

[0064] Figure 5 is a diagram illustrating the method for setting the pre-charge / discharge period. In the example shown in Figure 5, the determination unit 112 sets the time of the most recent State of Charge (SOC) of the battery pack 31, when it is at the SOC of the end of the charging period including the zero-current interval (=96%), as the start time of the pre-charge / discharge period, and sets the start time of that charging period as the end time of the pre-charge / discharge period.

[0065] The determination unit 112 calculates the total charging capacity [Ah] for the charging period by integrating the current values ​​during that charging period. The determination unit 112 also calculates the total discharge capacity [Ah] for the pre-charging discharge period by integrating the current values ​​during that pre-charging discharge period.

[0066] The total discharge capacity during the pre-charge discharge period is calculated by subtracting the integrated regenerative charging current value from the integrated discharge current value during the pre-charge discharge period. The integrated discharge current value during the pre-charge discharge period includes not only the discharge current supplied to the motor 37, but also the discharge current supplied to auxiliary equipment (not shown) within the electric vehicle 3.

[0067] The total charging capacity during the charging period and the total discharge capacity during the pre-charging discharge period are essentially the same. That is, the charge / discharge efficiency (= total charging capacity during the charging period / total discharge capacity during the pre-charging discharge period) = 1.

[0068] If a momentary short circuit occurs during the charging period due to the deposition of lithium metal, the current flowing through the short-circuit path will not be charged into the battery pack 31, resulting in energy loss. Furthermore, if contact resistance increases due to corrosion or loosening of the fastening parts, the energy consumed by the contact resistance without being charged into the battery pack 31 will also increase. Therefore, if the charging period includes a zero-current section, the total charging capacity will exceed the total discharge capacity by the amount of energy loss during that zero-current section.

[0069] The determination unit 112 can determine that the occurrence of the zero-current period is a sign that the battery pack 31 will become unusable if the total charge capacity during the charging period including the zero-current period is greater than the total discharge capacity during the pre-charge discharge period.

[0070] If there is a standby current that is not measured by the current sensor 33 (for example, the power consumption of the sensor or microcontroller, or the self-discharge of the cell), the determination unit 112 estimates the cumulative value of the standby current for the pre-charge period based on the estimated standby current for the driving period by temperature, the estimated standby current for the parking period (rest time) by temperature, the cumulative driving time during the pre-charge period, the cumulative parking time during the pre-charge period, and the temperature data for each period. Note that the method for estimating the cumulative value of the standby current is just one example, and it can be estimated in various other ways.

[0071] The determination unit 112 adds the estimated integrated value of the standby current during the pre-charge / discharge period to the total discharge capacity during the pre-charge / discharge period, or subtracts it from the total charge capacity during the charge period. Alternatively, the determination unit 112 may correct the determination value to a value less than 1 based on the estimated integrated value of the standby current during the pre-charge / discharge period.

[0072] The determination unit 112 sets the start time of the discharge period immediately following the charging period including the zero-current section (hereinafter referred to as the post-charge-discharge period) to the end time of the charging period. The determination unit 112 sets the end time of the post-charge-discharge period to the time of the state of charge (SOC) immediately following the SOC of the charging start time of the charging period. If the total charging capacity of the charging period including the zero-current section is greater than the total discharge capacity of the post-charge-discharge period, the determination unit 112 can determine that the occurrence of the zero-current section is a sign that the battery pack 31 will become unusable.

[0073] The determination unit 112 calculates the total charging capacity [Ah] for the charging period by integrating the current values ​​during that charging period. The determination unit 112 also calculates the total discharge capacity [Ah] for the post-charge discharge period by integrating the current values ​​during that period. If the total charging capacity of the charging period, including the zero-current section, is greater than the total discharge capacity of the post-charge discharge period, the determination unit 112 can determine that the occurrence of the zero-current section is a sign that the battery pack 31 is about to become unusable.

[0074] The determination unit 112 can also set the end time of the post-charge-discharge period to a State of Charge (SOC) time higher than the SOC of the start time of the charge period. In that case, the determination unit 112 sets the start time of the charge period to a SOC time corresponding to the SOC of the end time of the post-charge-discharge period. Note that a zero-current section must be included within the shortened charge period.

[0075] Furthermore, if the total charging capacity during the charging period including the zero-current section is greater than the total discharge capacity during the pre-charging discharge period, and the zero-current section is greater than the total discharge capacity during the pre-charging discharge period, the determination unit 112 may determine that the occurrence of the zero-current section is a sign that the battery pack 31 will become unusable.

[0076] Next, as a way to increase the certainty that the zero-current interval during the charging period is data generated due to the activation of the protection function of the charger 4, a method of considering the temperature rise can be considered. Even if the current data for the charging period includes a zero-current interval, the determination unit 112 will not determine the occurrence of the zero-current interval as a sign that the battery pack 31 will become unusable if the temperature data for the zero-current interval has not risen by a predetermined value or more compared to the temperature data for the previous period. The predetermined value is determined based on data obtained from experiments and simulations, the designer's knowledge, etc.

[0077] Normally, overcurrent due to instantaneous short circuits and increased resistance due to poor contact are accompanied by an increase in Joule heat. Therefore, a zero-current section without a temperature rise is likely to have occurred due to another factor, such as a malfunction in the measurement system. In that case, the determination unit 112 does not determine that the occurrence of a zero-current section is a sign that the battery pack 31 is about to become unusable. The method of considering temperature rise is more effective when used in combination with the method of considering the frequency of zero-current sections or the method of considering energy loss described above.

[0078] The notification unit 113 sends an alert to the electric vehicle 3 equipped with the battery pack 31 that has been detected as showing signs of impending failure, or to the operation management terminal device 7 managing the electric vehicle 3, indicating that the battery pack 31 is about to become unusable.

[0079] Figure 6 is a flowchart showing the flow of a first processing example in which the predictive detection system 1 according to the embodiment detects signs that the battery pack 31 is about to become unusable. The determination unit 112 reads the battery data of the battery pack 31 to be inspected, which is stored in the battery data holding unit 121, from the battery data holding unit 121 (S10). The determination unit 112 identifies the current data for the charging period from the read battery data (S11).

[0080] The determination unit 112 determines whether or not a zero current interval is included in the current data for the charging period (S12). If a zero current interval is not included (N in S12), the determination unit 112 terminates the inspection of the battery pack 31. If a zero current interval is included (Y in S12), the determination unit 112 calculates the following (Equation 1) (S13).

[0081] Rt = (Period from the previous zero-current interval to the current zero-current interval) / (Period from the zero-current interval two intervals ago to the previous zero-current interval) ... (Equation 1) The determination unit 112 compares the period ratio Rt with a set value (a value less than 1) (S14). The set value is determined based on data obtained from experiments or simulations, the designer's knowledge, etc. For example, it may be set to 0.5.

[0082] If the period ratio Rt is greater than or equal to the set value (N in S14), the determination unit 112 terminates the inspection of the battery pack 31. If the period ratio Rt is less than the set value (Y in S14), the determination unit 112 determines that the occurrence of the zero-current section is a sign that the battery pack 31 is about to become unusable. The notification unit 113 sends an alert via the network 2 to the electric vehicle 3 on which the battery pack 31 is installed, or to the operation management terminal device 7 that manages the electric vehicle 3, indicating that the battery pack 31 is about to become unusable (S15).

[0083] Figure 7 is a flowchart showing the flow of a second processing example in which the predictive detection system 1 according to the embodiment detects a precursor to the battery pack 31 becoming unusable. The second processing example is an example in which the processing of step S14a is added to the first processing example. If the period ratio Rt is smaller than the set value (Y in S14), the determination unit 112 determines whether the temperature data of the zero current section has risen by a predetermined value or more compared to the temperature data of the previous period (S14a). If the temperature data of the zero current section has not risen by a predetermined value or more (N in S14a), the determination unit 112 terminates the inspection of the battery pack 31. If the temperature data of the zero current section has risen by a predetermined value or more (Y in S14a), the determination unit 112 determines that the occurrence of the zero current section is a precursor to the battery pack 31 becoming unusable. The notification unit 113 transmits the above alert (S15).

[0084] Figure 8 is a flowchart showing the flow of a third processing example in which the predictive detection system 1 according to the embodiment detects signs of the battery pack 31 becoming unusable. The processing in steps S20-S22 of the third processing example is the same as the processing in steps S10-S12 of the first processing example. If the current data for the charging period includes a zero current section (Y in S22), the determination unit 112 determines whether or not multiple zero current sections occurred during the charging period (1 charging period) (S23). If multiple zero current sections did not occur (N in S23), the determination unit 112 terminates the inspection of the battery pack 31. If multiple zero current sections occurred (Y in S23), the determination unit 112 determines that the occurrence of the zero current section is a sign that the battery pack 31 will become unusable. The notification unit 113 sends the above alert (S24). As in the second processing example, a condition may be added to check whether or not the zero current section is accompanied by a temperature rise.

[0085] Figure 9 is a flowchart showing the flow of a fourth processing example in which the predictive detection system 1 according to the embodiment detects a precursor to the battery pack 31 becoming unusable. The processing in steps S30-S32 of the fourth processing example is the same as the processing in steps S10-S12 of the first processing example. If the current data for the charging period includes a zero current interval (Y in S32), the determination unit 112 calculates the total charging capacity B for the charging period, the total discharge capacity A for the pre-charge discharge period, and the total discharge capacity C for the post-charge discharge period (S33). The determination unit 112 determines whether the conditions (total charging capacity B / total discharge capacity A) > 1 and (total discharge capacity C / total charging capacity B) < 1 are met (S34). If these conditions are not met (N in S34), the determination unit 112 terminates the inspection of the battery pack 31. If the conditions are met (Y in S34), the determination unit 112 determines that the occurrence of the zero current interval is a sign that the battery pack 31 is about to become unusable. The notification unit 113 sends the above alert (S35).

[0086] Figure 10 is a flowchart showing the flow of a fifth processing example in which the predictive detection system 1 according to the embodiment detects a precursor to the battery pack 31 becoming unusable. The fifth processing example is an example in which the processing of step S34a is added to the fourth processing example. If the conditions of step S34 are met (Y in S34), the determination unit 112 determines whether the temperature data of the zero current section has risen by a predetermined value or more compared to the temperature data of the previous period (S34a). If the temperature data of the zero current section has not risen by a predetermined value or more (N in S34a), the determination unit 112 terminates the inspection of the battery pack 31. If the temperature data of the zero current section has risen by a predetermined value or more (Y in S34a), the determination unit 112 determines that the occurrence of the zero current section is a precursor to the battery pack 31 becoming unusable. The notification unit 113 transmits the above alert (S35).

[0087] As described above, this embodiment makes it possible to detect signs that the battery pack 31 is about to become unusable at low cost and with high accuracy. As mentioned above, the zero-current interval included in the current data during the charging period of the battery pack 31 occurs based on the protective operation of the charger 4 due to overcurrent detection or failure of constant current control. For safety reasons, many chargers 4 set the recharge sequence time from the stop of charging due to overcurrent detection or failure of constant current control to the resumption of charging to several tens of seconds to about one minute. Control that gradually increases the current value during this restart sequence is often performed.

[0088] Furthermore, it is known that the occurrence of zero-current intervals due to the protective operation of the charger 4 occurs frequently towards the end of the cell's lifespan. In this embodiment, the occurrence of zero-current intervals due to the protective operation of the charger 4 can be detected, and warning signs of malfunctions such as overheating or ignition can be detected before they occur.

[0089] Figure 11 shows an example of the changes in current and voltage data, including the protective operation period of charger 4. In the example shown in Figure 11, the current changes from 80A → 0A → 80A, and the voltage changes from 3.97V → 3.93V → 3.97V, with the protective operation period of charger 4 in between. During this period, the current includes a 100% fluctuation, but the voltage includes only a fluctuation of about 1%. When considering the fluctuation of the pack voltage, it is even smaller than the fluctuation of the cell voltage.

[0090] To detect signs of battery pack 31 failure based on voltage changes, it is necessary to constantly monitor and record the voltage at high-speed sampling rates ranging from microseconds to milliseconds. Therefore, expensive memory with high capacity and high-speed access is required. In addition, the power consumption of the measurement system will increase.

[0091] On the other hand, when detecting the warning sign based on current changes, it is possible to detect the warning sign with higher accuracy compared to detecting it based on minute voltage fluctuations by utilizing the existing observation system and detecting 100% of the current fluctuation. By taking advantage of the fast response of the protection operation of charger 4 and the fact that the recharging sequence takes several tens of seconds to about one minute, it is sufficient to monitor and record the current with low-speed sampling. Expensive memory and additional sensors are not required, so additional hardware costs are basically zero. Detection is possible using only existing cloud-stored data. In addition, the power consumption of the measurement system does not increase.

[0092] Furthermore, by considering the frequency of zero-current intervals, energy loss, and temperature rise, it is possible to accurately distinguish whether the occurrence of a zero-current interval is due to cell degradation or abnormalities in the current path, or to other accidental abnormalities (noise factors). This makes it possible to detect signs that the battery pack 31 is about to become unusable with higher accuracy.

[0093] According to this embodiment, by notifying the user in advance of signs of the battery pack 31 becoming unusable, the user can replace the battery pack 31 at the optimal timing as a predictive maintenance measure. This allows the user to minimize downtime while pursuing economic rationality.

[0094] The present disclosure has been described above based on embodiments. The embodiments are illustrative, and it will be readily apparent to those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure.

[0095] The above-described predictive detection system may be implemented in the battery control unit 32 within the electric vehicle 3. In particular, the process of detecting a precursor to the battery pack 31 becoming unusable based on whether or not zero current intervals occur multiple times during one charging period is suitable for implementation in the battery control unit 32. The occurrence of zero current intervals multiple times during one charging period suggests that deposition and corrosion are progressing and the battery pack 31 is close to becoming unusable. If zero current intervals occur multiple times during one charging period, the battery control unit 32 may treat the battery pack 31 as unusable at that point.

[0096] Furthermore, in the above embodiment, the electric vehicle 3 is assumed to be a four-wheeled electric vehicle. However, it may also be an electric motorcycle (electric scooter), electric bicycle, or electric kick scooter. In addition, electric vehicles include not only full-size electric vehicles but also low-speed electric vehicles such as golf carts and land cars used in shopping malls and entertainment facilities. Moreover, the battery pack 31 is not limited to electric vehicle 3. For example, it can also be used on electric mobile devices such as electric boats, railway vehicles, and multicopters (drones).

[0097] The embodiments may be specified by the following items.

[0098] [Item 1] An acquisition unit (111) acquires battery data including current data obtained by periodically measuring the current flowing through the battery pack (31), If the current data during the period when the battery pack (31) is being charged by the charger (4) includes a section in which the current value is temporarily zero, and the integrated current value of the charging period including the section in which the current value is temporarily zero is greater than at least one of the integrated current values ​​of the discharge period immediately before or after the charging period, the determination unit (112) determines that the occurrence of the section in which the current value is zero is a sign that the battery pack (31) will become unusable. A predictive detection system (1) characterized by comprising the following:

[0099] According to this method, by using current data and considering energy loss, it is possible to detect signs that the battery pack (31) is about to become unusable at low cost and with high accuracy.

[0100] [Item 2] The aforementioned battery data further includes SOC data obtained by periodically measuring the SOC (State of Charge) of the battery pack (31), The predictive detection system (1) according to item 1, characterized in that when the determination unit (112) calculates the integrated current value of the discharge period immediately preceding the charging period, it sets the time of the most recent SOC corresponding to the SOC at the end of the charging period to the start time of the discharge period.

[0101] According to this, it is possible to appropriately set the range of the discharge period immediately preceding the charging period, which should be compared with the range of the charging period.

[0102] [Item 3] The battery data further includes temperature data obtained by periodically measuring the temperature of the battery pack (31), The predictive detection system (1) according to any one of items 1 to 3, characterized in that even if the current data during the period in which the charger (4) is charging the battery pack (31) includes a period in which the current value is temporarily zero, if the temperature data during the period in which the current value is temporarily zero has not risen by a predetermined value or more compared to the temperature data of the preceding period, the determination unit (112) does not determine that the occurrence of the period in which the current value is zero is a sign that the battery pack (31) will become unusable.

[0103] According to this, by taking temperature rise into consideration, it is possible to detect with even greater accuracy the signs that the battery pack (31) is about to become unusable.

[0104] [Item 4] The predictive detection system (1) according to item 1 or 2, characterized in that the period during which the current value temporarily becomes zero corresponds to the period from when charging stops due to the protection function of the charger (4) until it resumes.

[0105] According to this, by utilizing the protection function of the charger (4), it becomes unnecessary to change the observation system of the battery pack (31).

[0106] [Item 5] Driving data from multiple electric mobile units (3) equipped with the aforementioned battery pack (31) is stored in the server (12). The predictive detection system (1) according to any one of items 1 to 4, characterized in that the determination unit (112) uses the current data included in the driving data to determine a section in which the current value is zero, which serves as a criterion for determining a precursor to the battery pack (31) becoming unusable.

[0107] According to this, a cloud service can be realized that detects and provides information about signs that the battery pack (31) mounted on the electric mobile unit (3) is about to become unusable, based on driving data accumulated on the server (12).

[0108] [Item 6] A step of acquiring battery data including current data obtained by periodically measuring the current flowing through the battery pack (31), If the current data during the period in which the charger (4) is charging the battery pack (31) includes a section in which the current value is temporarily zero, and the integrated current value of the charging period including the section in which the current value is temporarily zero is greater than the integrated current value of the discharge period immediately before or after the charging period, the occurrence of the section in which the current value is zero is determined to be a sign that the battery pack (31) will become unusable. A method for detecting an anomaly, characterized by having the following features.

[0109] According to this method, by using current data and considering energy loss, it is possible to detect signs that the battery pack (31) is about to become unusable at low cost and with high accuracy.

[0110] [Item 7] A process to acquire battery data including current data obtained by periodically measuring the current flowing through the battery pack (31), If the current data during the period when the battery pack (31) is being charged by the charger (4) includes a section in which the current value is temporarily zero, and the integrated current value for the charging period including the section in which the current value is temporarily zero is greater than the integrated current value for the discharge period immediately before or after the charging period, the occurrence of the section in which the current value is zero is determined to be a sign that the battery pack (31) is about to become unusable. A predictive animation program characterized by having a computer execute a command.

[0111] According to this method, by using current data and considering energy loss, it is possible to detect signs that the battery pack (31) is about to become unusable at low cost and with high accuracy. [Explanation of Symbols]

[0112] 1 Predictive detection system, 2 Network, 3 Electric vehicle, 4 Charger, 5 Charging cable, 6 Commercial power grid, 7 Operation management terminal device, 11 Processing unit, 111 Battery data acquisition unit, 112 Judgment unit, 113 Notification unit, 12 Storage unit, 121 Battery data holding unit, 31 Battery pack, 32 Battery control unit, 33 Current sensor, 34 Voltage sensor, 35 Temperature sensor, 36 Vehicle control unit, 37 Motor, 38 Inverter, 39 First relay, 310 Second relay, 311 Onboard charger, 313 Vehicle speed sensor, 314 Wireless communication unit, 315 Antenna, 41 Rectifier circuit, 42 PFC circuit, 43 DC / DC converter, 44 Control unit, 45 Current sensor, 46 Voltage sensor, 47 Output relay.

Claims

1. An acquisition unit that acquires battery data including current data obtained by periodically measuring the current flowing through the battery pack, A determination unit determines that if the current data during the period in which the battery pack is being charged by the charger includes a section in which the current value is temporarily zero, and the integrated current value of the charging period including the section in which the current value is temporarily zero is greater than at least one of the integrated current values ​​of the discharge period immediately before or after the charging period, the occurrence of the section in which the current value is zero is a sign that the battery pack is about to become unusable. A predictive detection system characterized by comprising the following features.

2. The aforementioned battery data further includes SOC data obtained by periodically measuring the SOC (State of Charge) of the battery pack. The predictive detection system according to claim 1, characterized in that when the determination unit calculates the integrated current value of the discharge period immediately preceding the charging period, it sets the time of the most recent SOC corresponding to the SOC at the end of the charging period as the start time of the discharge period.

3. The aforementioned battery data further includes temperature data obtained by periodically measuring the temperature of the battery pack. The predictive detection system according to claim 1 or 2, characterized in that even if the current data during the period in which the charger is charging the battery pack includes a period in which the current value is temporarily zero, if the temperature data during the period in which the current value is temporarily zero has not risen by a predetermined value or more compared to the temperature data of the preceding period, the determination unit does not determine that the occurrence of the period in which the current value is zero is a sign that the battery pack will become unusable.

4. The predictive detection system according to claim 1 or 2, characterized in that the period during which the current value temporarily becomes zero corresponds to the period from when charging stops due to the protection function of the charger until it resumes.

5. The driving data of multiple electric mobile units equipped with the aforementioned battery pack is stored in a server. The predictive detection system according to claim 1 or 2, characterized in that the determination unit uses the current data included in the driving data to determine a section in which the current value, which serves as a criterion for determining an indication that the battery pack will become unusable, is zero.

6. A step of acquiring battery data, including current data obtained by periodically measuring the current flowing through the battery pack, If the current data during the period in which the battery pack is being charged by the charger includes a section in which the current value is temporarily zero, and the integrated current value for the charging period including the section in which the current value is temporarily zero is greater than the integrated current value for the discharge period immediately preceding or following the charging period, the occurrence of the section in which the current value is zero is determined to be a sign that the battery pack is about to become unusable. A method for detecting an anomaly, characterized by having the following features.

7. A process to acquire battery data, including current data obtained by periodically measuring the current flowing through the battery pack, If the current data during the period in which the battery pack is being charged by the charger includes a section in which the current value is temporarily zero, and the integrated current value for the charging period including the section in which the current value is temporarily zero is greater than the integrated current value for the discharge period immediately preceding or following the charging period, the occurrence of the section in which the current value is zero is determined to be a sign that the battery pack is about to become unusable. A predictive animation program characterized by having a computer execute a command.

Images