Battery life prediction method and energy storage system

Abstract

Providing technology for accurately calculating the degradation of storage batteries during storage and storage periods. [Solution] The energy storage system of this embodiment has a function to calculate calendar degradation (degradation during non-operation) that progresses over time during the inventory period from manufacturing to the start of operation and the period of inactivity from the stop of operation to the restart of operation, and a function to predict the lifespan of the storage battery by calculating cycle degradation (degradation during operation) that progresses with charging and discharging during the operating period from the start of operation to the stop of operation. During non-operation, the microcontroller on the board connected to the storage battery is maintained in a sleep state or shutdown state, but starts up at regular intervals and calculates the degradation during non-operation based on the temperature. During operation, the microcontroller on the board that controls charging and discharging calculates the degradation during operation based on the current and temperature at regular intervals. According to the energy storage system of this embodiment, degradation is calculated at regular intervals even during non-operation, so the accuracy of degradation calculation and, consequently, lifespan prediction can be improved.

Description

Technical Field

[0001] The present invention relates to a method for predicting the service life of a storage battery, and particularly relates to a method for calculating deterioration of a storage battery during a stock period and a standing period, and a power storage system to which the method is applied.

Background Art

[0002] In a power storage system that supplies electric power stored in a storage battery to a device, there are cases where a substrate having a function of calculating deterioration of the storage battery and predicting the service life thereof is connected to the storage battery. For example, in Patent Document 1, a current sensor, a temperature sensor, and a voltage sensor provided in a battery pack are connected to a battery life prediction system, and on the system side, the discharge amount, discharge rate, and discharge temperature of the battery pack detected by the current sensor and the temperature sensor, as well as the standing time, state of charge, and standing temperature of the battery pack are measured, these histories are recorded, and the current amount of deterioration of the battery pack is calculated based on the recorded data. This is disclosed in the document.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the aforementioned prior art, the cumulative storage period of the battery pack from the start of use to the present, the average charge state during the storage period, and the average temperature during the storage period are calculated, and the amount of degradation during the storage period is calculated based on these values. However, since battery degradation is easily affected by temperature, using the average temperature during the storage period for calculation may result in a result that differs significantly from the actual degradation situation. In addition, batteries also degrade during the storage period from shipment to the start of use, so in order to accurately calculate degradation, it is necessary to consider temperature changes during the storage period as well.

[0005] Therefore, the present invention aims to provide a technology for appropriately calculating the degradation of storage batteries during storage and storage periods. [Means for solving the problem]

[0006] To solve the above problems, the battery life prediction method of the present invention includes a first calculation step of calculating the degradation of the battery during the non-operation period using the power of the battery in a predetermined first cycle, during the non-operation period from when the battery is manufactured until it is incorporated into equipment and starts operating, and from when it stops operating until it restarts; and a second calculation step of calculating the degradation of the battery during operation in a predetermined second cycle during the operating period from when the battery starts operating until it stops operating.

[0007] Furthermore, the energy storage system of the present invention comprises a battery, a first calculation unit that uses the power of the battery to calculate the degradation of the battery during the non-operation period in a predetermined first cycle, from the time the battery is manufactured until it is incorporated into the equipment and starts operating, and from the time it stops operating until it restarts, and a second calculation unit that calculates the degradation of the battery during operation in a predetermined second cycle, from the time the battery starts operating until it stops operating. [Effects of the Invention]

[0008] According to the present invention, since the degradation of the storage battery is calculated at regular intervals even during non-operational periods (storage periods and periods of inactivity), temperature changes, which can greatly affect degradation, are accurately reflected in the degradation calculation results. This improves the accuracy of degradation calculations compared to cases where degradation during non-operational periods is not calculated or where fixed values ​​or average values ​​are applied to the temperature to calculate degradation during non-operational periods, making it possible to predict the lifespan of the storage battery more accurately. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows the operating cycle of an energy storage system. [Figure 2] This is a block diagram showing the configuration of the energy storage system 1 of the first embodiment. [Figure 3] This flowchart shows an example of the procedure for processing performed in energy storage system 1. [Figure 4] This diagram illustrates the concept of battery degradation calculation in energy storage system 1. [Figure 5] This is a block diagram showing the configuration of the energy storage system 2 of the second embodiment. [Figure 6] This flowchart shows an example of the procedure for processing performed in the energy storage system 2. [Figure 7] This is a block diagram showing the configuration of the energy storage system 3 of the third embodiment. [Figure 8] This flowchart shows an example of the processing steps performed in the energy storage system 3. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. The following embodiments are preferred examples of the battery life prediction method and energy storage system of the present invention, and the present invention is not limited to these examples.

[0011] [Operation cycle of energy storage system] Figure 1 shows the operation cycle of the energy storage system of the embodiment. The energy storage system of this embodiment includes a battery, a configuration for controlling the charging and discharging of the battery, and a configuration for calculating the degradation of the battery and predicting its lifespan. The specific configuration of the energy storage system will be described in detail later with reference to separate drawings.

[0012] After manufacturing (completion of the product), the energy storage system is stored as inventory at the manufacturer, then packaged and shipped, and after a period of storage at the customer's location, it is incorporated into equipment and devices that use the battery as a backup power source (hereinafter referred to as the "higher-level system") and begins operation. When the operation of the higher-level system is suspended or terminated (the energy storage system is removed from the higher-level system), the operation of the energy storage system stops accordingly. When the operation of the higher-level system resumes, the operation of the energy storage system resumes accordingly.

[0013] The period from manufacturing to the start of operation is considered the storage period for the battery, the period from the start of operation to the end of operation is considered the operating period for the battery, and the period from the end of operation to the restart of operation is considered the storage period for the battery. The storage period and the storage period can be considered as the non-operating period for the battery. During the non-operating period, the battery undergoes calendar degradation as time passes, while during the operating period, it undergoes cycle degradation due to charging and discharging. The energy storage system of this embodiment has a function to calculate both the calendar degradation and charge / discharge degradation of the battery using parameters such as temperature, charge / discharge current, and number of charge / discharge cycles. During the storage period and the storage period, it calculates the degradation during non-operating periods at regular intervals, and during the operating period, it calculates the degradation during operating periods at regular intervals, and predicts the lifespan based on the degradation during non-operating and operating periods.

[0014] [First Embodiment] Figure 2 is a block diagram showing the configuration of the energy storage system 1 according to the first embodiment. The energy storage system 1 includes a battery backup unit (hereinafter abbreviated as "BBU") 10, which is housed together with the battery and contains a configuration for controlling the charging and discharging of the battery and a configuration for calculating the degradation of the battery and predicting its lifespan.

[0015] In the BBU 10, a substrate is connected to an unillustrated nickel-metal hydride battery, and a microcomputer 11 is mounted on this substrate. The microcomputer 11 is implemented with software necessary for processing executed when the storage battery is in operation and non-operation, thereby having a charge / discharge control unit 12a and a calculation unit 12b, and the CPU 12 serves as the operating entity for these functional units 12a and 12b. An ammeter 17 is installed in the charge / discharge circuit, and a thermometer 18 is installed near the storage battery. The storage battery is shipped in a state charged to a certain level, and the elements mounted on the substrate operate with power from the storage battery.

[0016] The BBU 10 is incorporated into a host system US via an interface (I / F). While the host system US is in operation, the BBU 10 is in an operating state and the microcomputer 11 is always in an activated state; in contrast, when the host system US is stopped or not connected to the host system US, the BBU 10 is in a non-operating state and the microcomputer 11 enters a sleep state.

[0017] While the microcomputer 11 is activated, the charge / discharge control unit 12a appropriately controls charging and discharging of the storage battery, and the calculation unit 12b, triggered by an interrupt from the fixed-cycle timer 13 at fixed intervals, measures current with the ammeter 17 while measuring temperature with the thermometer 18, calculates degradation of the storage battery during operation, and performs life prediction. On the other hand, while the microcomputer 11 is in sleep, the RTC 14 functions as a timer, and the microcomputer 11 is activated for a short period of time at fixed intervals by an interrupt from the RTC 14. During this period, the calculation unit 12b measures the temperature with the thermometer 18 and calculates degradation of the storage battery during non-operation (during storage in inventory, during left standing). Information such as degradation calculated by the calculation unit 12b is accumulated in the non-volatile memory 15.

[0018] An application 80 corresponding to the BBU 10 is installed in the host system US. A BBU information reading unit 81 reads out information related to degradation and life calculated by the calculation unit 12b via the I / F. A BBU information display unit 82 can display the state of health (SOH) of the storage battery, a life alarm and the like based on the information read out by the BBU information reading unit 81.

[0019] In the illustrated example, the RTC 14 and non-volatile memory 15 are built into the microcontroller 11, but an external timer IC connected to the microcontroller may be used instead of the built-in RTC, or an external non-volatile memory may be used instead of the built-in non-volatile memory.

[0020] Figure 3 shows an example of the processing steps performed in the energy storage system 1. Of these, (A) is a flowchart showing an example of the RTC interrupt processing step that is performed in the BBU 10 at regular intervals (for example, every hour) while the microcontroller 11 is in sleep mode. The following will explain the procedure according to this example.

[0021] In RTC interrupt handling, first, the microcontroller 11 prepares to start up in response to an interrupt from the RTC 14 (step S11). When the microcontroller 11 starts up, the calculation unit 12b counts the period of inactivity since the last execution of the RTC interrupt processing (step S12), measures the current temperature (step S13), calculates the degradation during the inactivity period based on the temperature, specifically the degradation during the inactivity period counted in step 12 (step S14), and appends the calculated degradation during inactivity and the inactivity period to the non-volatile memory 15 for storage (step S15). Once the calculation unit 12b completes a series of processes (steps S12 to S15), the microcontroller 11 terminates its operation (step S16). As a result, the microcontroller 11 returns to sleep mode.

[0022] Furthermore, (B) is a flowchart showing an example of the procedure for a periodic timer interrupt processing that is executed at regular intervals (for example, every minute) while the microcontroller 11 is starting up in the BBU 10. The procedure will be explained below in accordance with this example.

[0023] In the periodic timer interrupt processing, the calculation unit 12b counts the operating period since the last execution of the RTC interrupt processing (step S21), measures the current current and temperature (step S22), calculates the degradation during operation, specifically the degradation during the operating period counted in step S21, based on the current and temperature (step S23), appends the calculated degradation during operation and operating period to the non-volatile memory 15 for storage (step S24), and executes the lifespan calculation process (step S25). In the lifespan calculation process, the calculation unit 12b sums the degradation during operation and the degradation during non-operation stored in the non-volatile memory, and calculates the predicted period until the end of life based on the slope of degradation during the operating period.

[0024] Figure 4 illustrates the concept of battery degradation calculation in energy storage system 1. We will examine the degradation of a battery in the following scenario, for example, as shown in Figure 4(A): it goes through an inventory period SP from completion to the start of operation, operates for an operation period OP1, then stops, undergoes a storage period PP1, resumes operation, operates for an operation period OP2, stops again, undergoes a storage period PP2, and has reached the present.

[0025] In this case, as shown in Figure 4(B), the period obtained by adding the inventory period SP and the idle periods PP1 and PP2 constitutes the non-operation period, and the period obtained by adding the operating periods OP1 and OP2 constitutes the cumulative operating period. Degradation that progresses during the non-operation period is calculated in the RTC interrupt processing (Figure 3(A)) described above as degradation during non-operation (more precisely, degradation during inventory and idle periods). Degradation that progresses during the operating period is calculated in the fixed-period timer interrupt processing (Figure 3(B)) described above as degradation during operation. Furthermore, the remaining lifespan is predicted based on the assumption that the degradation to progress from here on will proceed along the slope of degradation during the operating period shown by the dashed line in the figure.

[0026] In energy storage systems where the microcontroller remains shut down during non-operation, degradation calculations for storage or idle periods are not performed, making it impossible to accurately calculate battery degradation. In contrast, with energy storage system 1, even when discharge ends or the system is removed from the higher-level system US, the microcontroller 11 in the BBU 10 starts up at regular intervals, and degradation calculations for non-operation periods are performed based on the temperature at that time. This improves the accuracy of degradation calculations and, consequently, the accuracy of lifespan predictions compared to systems where degradation calculations are not performed during non-operation periods. Furthermore, since the microcontroller 11 is maintained in a sleep state when the BBU 10 is non-operational, degradation calculations during non-operation periods can be performed with low power consumption, enabling long-term operation using the battery's capacity.

[0027] [Second Embodiment] Figure 5 is a block diagram showing the configuration of the energy storage system 2 of the second embodiment. The energy storage system 2 has the same functions as the energy storage system 1 of the first embodiment described above as a whole system, but differs from the energy storage system 1 in that the battery unit (hereinafter abbreviated as "BTU") 20 that supplies power and the battery control unit (hereinafter abbreviated as "BCU") 40 that controls the BTU 20 are provided as separate components. Details common to both the energy storage system 2 and the energy storage system 1 will be omitted from the explanation as appropriate.

[0028] In energy storage system 2, the BTU20 and BCU40 are shipped separately, and after the BTU20 and BCU40 are connected via an interface, the BCU40 is integrated into the higher-level system US via the interface.

[0029] The operation / stopping of BCU40 is linked to the higher-level system US. BTU20 operates in conjunction with the operation of BCU40, keeping the microcontroller 21 constantly active, while BTU20 becomes inactive when BCU40 stops, putting the microcontroller 21 into sleep mode.

[0030] The BTU20 consists of a nickel-metal hydride battery (not shown) connected to a circuit board, on which a microcontroller 21 is mounted. The microcontroller 21 has a non-operating calculation unit 22b and a communication reception unit 23b, with software necessary for processing to be executed when the battery is not in operation implemented on it, and the CPU 22 is the main operator of these functional units 22b and 22c. A thermometer 28 is installed near the battery.

[0031] While the microcontroller 21 is in sleep mode (when the BTU 20 is not in operation), the microcontroller 21 is briefly activated at regular intervals by interrupts from the RTC 24. During this time, the non-operation calculation unit 22b calculates the degradation of the battery while it is not in operation based on the measurements taken by the thermometer 28, and stores the calculation results in the non-volatile memory 25. On the other hand, while the microcontroller 21 is running (when the BTU 20 is in operation), the communication reception unit 22c responds to requests received from the BCU 40 via the I / F at regular intervals by interrupts from the fixed-period timer 13 (requests for measuring the current temperature, requests for reading information about degradation while in operation stored in the non-volatile memory 25).

[0032] The BCU40 consists of a microcontroller 41 mounted on a circuit board. The microcontroller 41 has software implemented for processing related to the control of the BTU20, and includes a charge / discharge control unit 42a, an operational calculation unit 42b, and a BTU information reading unit 42c, with the CPU 42 being the main operator of these functional units 42a, 42b, and 42c. An ammeter 47 is installed in the charge / discharge circuit. The charge / discharge control unit 42a appropriately controls the charging and discharging of the battery provided by the BTU20. The operational calculation unit 42b, at regular intervals triggered by interrupts from the fixed-period timer 43, measures the current using the ammeter 47 and acquires the temperature measured by the thermometer 28, calculates the degradation of the battery during operation, predicts its lifespan, and stores the calculation results in the non-volatile memory 45. The BTU information reading unit 42c acquires information necessary for calculations by the operational calculation unit 42b (current temperature, information on degradation during non-operation) from the BTU20 via an interface.

[0033] The higher-level system US has an application 90 implemented that corresponds to the BCU 40. The BCU information reading unit 91 reads out information about degradation and lifespan calculated by the operational calculation unit 42b via the I / F. The BCU information display unit 92 can display the battery degradation level (SOH) and lifespan alarms based on the information read out by the BCU information reading unit 91.

[0034] Alternatively, an external timer IC may be used instead of the RTC24 built into the microcontroller, or an external non-volatile memory may be used instead of the non-volatile memory 25 and 45 built into the microcontroller.

[0035] Figure 6 shows an example of the processing procedure performed in the energy storage system 2. Of these, (A) is a flowchart showing an example of the RTC interrupt processing procedure that is performed at regular intervals (for example, every hour) when the BTU 20 is not in operation (when the microcontroller 21 is in sleep mode). Except for the fact that this RTC interrupt processing is performed in the BTU 20, the procedure is the same as the RTC interrupt processing in the energy storage system 1 described above (Figure 3 (A)).

[0036] Furthermore, (B) is a flowchart showing an example of the procedure for a periodic timer interrupt processing that is executed at regular intervals (for example, every minute) in the BCU40 while the BTU20 is in operation. While the overall flow of this periodic timer interrupt processing is generally the same as the periodic timer interrupt processing in the energy storage system 1 described above (Figure 3 (B)), the details of the processing are slightly different. The procedure will be explained below according to the example.

[0037] In this periodic timer interrupt processing, the operational calculation unit 42b counts the operational period since the last execution of the periodic timer interrupt processing (step S41), measures the current current with the ammeter 47 (step S42), and obtains the current temperature, non-operational degradation, and non-operational period from the BTU 20 (step S43). Then, the operational calculation unit 42b calculates the operational degradation based on the current and temperature (step S44), appends the calculated operational degradation and operational period to the non-volatile memory 45 for storage (step S45), and executes the lifespan calculation processing (step S46).

[0038] The energy storage system 2 configured in this way can achieve the same effects as the energy storage system 1 described above.

[0039] [Third Embodiment] Figure 7 is a block diagram showing the configuration of the energy storage system 3 of the third embodiment. The energy storage system 3 includes a BTU 30 that supplies power and a BCU 50 that controls the BTU 30. It is similar to the energy storage system 2 of the second embodiment described above in that it is composed of separate BTU and BCU components, but it differs from the energy storage system 2 in that the microcontroller is shut down when the BTU is not in operation. In the following, explanations of aspects of the energy storage system 3 that are common to the energy storage system 2 will be omitted as appropriate.

[0040] In energy storage system 3, the BTU30 and BCU50 are shipped separately, and after the BTU30 and BCU50 are connected via an interface, the BCU50 is integrated into the higher-level system US via the interface. The operation / stopping of the BCU50 is linked to the higher-level system US.

[0041] In the BTU30, the timer IC34 and non-volatile memory 35 are externally connected to the microcontroller 31, and power is supplied to them directly from the battery. When the BTU30 is not connected to the BCU50, it is in a shut-down state, and the microcontroller 31 is started up for a short time at regular intervals by the timer IC34. During this time, the non-operational calculation unit 32b calculates the degradation of the storage battery while it is not in operation, based on the measurement value from the thermometer 38, and stores the calculation result in the non-volatile memory 35. On the other hand, when the BTU30 is connected to the BCU50, the BCU50 disables the start signal of the timer IC34 via the I / F, and as a result the microcontroller 31 does not start up. The thermometer 38 and non-volatile memory 35 are then directly accessed from the BCU50 via the I / F.

[0042] Figure 8 shows an example of the processing steps performed in the energy storage system 3. Of these, (A) is a flowchart showing an example of the microcontroller startup process that is performed at regular intervals (for example, every hour) while the BTU30 is not connected to the BCU50. The following explanation will follow this example.

[0043] In the microcontroller startup process, first, the microcontroller 31 is started and initialized by the timer IC 34 (step S51). When the microcontroller 31 starts up, the non-operation calculation unit 32b reads the degradation during non-operation and the non-operation period from the non-volatile memory 35 (step S52), counts the non-operation period since the last execution of the microcontroller startup process (step S53), measures the current temperature (step S54), calculates the degradation during non-operation based on the temperature (step S55), and appends the calculated degradation during non-operation and the non-operation period to the non-volatile memory for storage (step S56). Once the series of processes performed by the non-operating calculation unit 32b (steps S52 to S56) are completed, the microcontroller 31 shuts down.

[0044] Furthermore, (B) is a flowchart showing an example of the procedure for a periodic timer interrupt processing that is executed at regular intervals (for example, every minute) while the BCU50 is connected to the BTU30. The procedure will be explained below in accordance with this example.

[0045] In this periodic timer interrupt processing, the operational calculation unit 52b counts the operational period since the last execution of the periodic timer interrupt processing (step S61), measures the current current with the ammeter 57, measures the current temperature with the thermometer 38 inside the BTU 30 (step S62), and obtains the degradation and non-operation period from the non-volatile memory 35 inside the BTU 30 (step S63). Then, the operational calculation unit 52b calculates the degradation during operation based on the current and temperature (step S64), appends the calculated degradation and operational period to the non-volatile memory 55 for storage (step S65), and executes the prediction calculation process (step S66).

[0046] The energy storage system 3 configured in this way can achieve the same effects as the energy storage systems 1 and 2 described above. Furthermore, the shutdown-type BTU 30 in the energy storage system 3 can suppress the power consumption during non-operation compared to the sleep-type BTU 20 in the energy storage system 2 described above.

[0047] As described above, according to the energy storage systems 1, 2, and 3 of the embodiments, degradation calculations are performed periodically even during the inventory period and storage period of the BBU and BTU while they are not in operation. This improves the accuracy of battery degradation calculations and makes it possible to predict the lifespan more accurately.

[0048] The present invention is not limited to the embodiments described above and can be implemented in various modified forms. In the embodiments described above, nickel-metal hydride batteries are installed in the energy storage system, but other secondary batteries (for example, lithium-ion batteries) may be installed instead. The content of the degradation calculation needs to be changed depending on the type of battery, but the configuration of calculating degradation during non-operation at regular intervals during the storage period and the storage period, and calculating degradation during operation at regular intervals during the operating period, remains unchanged.

[0049] In the embodiments described above, the execution cycle for the RTC interrupt processing performed when BBU10 or BTU20 is inactive, and the microcontroller startup processing performed when BTU30 is inactive, is set to 1 hour. However, these processes may be executed at shorter intervals. The inventors' verification has confirmed that even if they are executed at intervals of minutes, power consumption increases only slightly, without a significant impact. By shortening the execution cycle, temperature changes can be reflected more precisely, thereby further improving the accuracy of degradation calculations and life predictions. [Explanation of symbols]

[0050] 1,2,3 Energy storage system 10 BBU 12b Calculation part (1st calculation part, 2nd calculation part) 20 BTU 22b Non-operational computing unit (First computing unit) 30 BTU 32b Non-operational computing unit (First computing unit) 40 BCU 42b Operating Computing Unit (Second Computing Unit) 50 BCU 52b Operating Computing Unit (Second Computing Unit)

Claims

1. A first calculation step is performed to calculate the degradation of the battery during the non-operation period, using the power of the battery, in a predetermined first cycle, from the time the battery is manufactured until it is incorporated into the equipment and starts operating, and from the time the operation stops until it is restarted. A second calculation step is performed to calculate the degradation of the battery during operation in a predetermined second cycle during the operating period from when the battery starts to when it stops. A method for predicting the lifespan of a storage battery, including [specific details omitted].

2. Storage batteries and A first calculation unit calculates the degradation of the battery during the period from when the battery is manufactured until it is incorporated into the equipment and starts operating, and during the period from when the battery stops operating until it restarts, using the power of the battery in a predetermined first cycle. A second calculation unit calculates the degradation of the battery during operation in a predetermined second cycle during the operating period from the start of operation to the stop of operation of the battery. A well-equipped energy storage system.

3. In the energy storage system according to claim 2, A microcontroller mounted on a circuit board connected to the aforementioned battery enters a sleep state or shutdown state during the non-operational period, A timer that starts the microcontroller in the first cycle during the aforementioned non-operation period. Furthermore, The first calculation unit is implemented in the microcontroller, and the energy storage system is characterized in that it calculates the degradation during non-operation while the microcontroller is running.

4. In the energy storage system described in claim 3, The second calculation unit is implemented in the microcontroller, A power storage system characterized in that the battery and the circuit board on which the microcontroller is mounted are housed in the same enclosure.

5. In the energy storage system described in claim 3, The board further includes a control microcontroller mounted on a separate board from the aforementioned board. The second calculation unit is implemented in the control microcontroller, The energy storage system is characterized by comprising a battery unit that supplies power, which includes a battery and a circuit board on which the microcontroller is mounted, and a battery control unit that controls the battery unit, which includes another circuit board.

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