Battery management system, management device, cycle setting method, and program

Abstract

Provided are a battery management system, a management device, a cycle setting method, and a program capable of automatically setting a voltage measurement time even if the number of connected monitoring devices changes. The battery management system is provided with a plurality of monitoring devices that measure the voltage of each of a plurality of secondary batteries, and a management device that manages the plurality of monitoring devices, wherein the management device acquires, from each monitoring device, a voltage measurement time indicating the time required to measure the voltage of the corresponding secondary battery, and unifies the voltage measurement time of each monitoring device on the basis of the acquired voltage measurement times.

Description

Battery management system, management device, period setting method and program

[0001] The present disclosure relates to a battery management system, a management device, a period setting method, and a program.

[0002] Conventionally, a battery management system has been known in which a secondary battery is used as a charging system, and a plurality of monitoring devices, which are slave devices, are connected to a management device, which is a master device (see, for example, Patent Document 1).

[0003] In the battery management system, a secondary battery is connected to each of multiple monitoring devices. Each monitoring device measures the voltage of the connected secondary battery and transmits the measurement results to a management device. The management device manages the monitoring devices and secondary batteries based on the measurement results received from the multiple monitoring devices.

[0004] The management device synchronizes the measurement periods of the secondary batteries by the multiple monitoring devices and sets a predetermined voltage measurement time for each monitoring device. Here, if the voltage measurement times of the respective monitoring devices are different, the voltage measurement time is set to match the longest voltage measurement time.

[0005] On the other hand, the voltage measurement time in a monitoring device depends on the measurement performance of a monitoring integrated circuit (IC) installed in the monitoring device, and therefore the voltage measurement time in a battery management system is set based on the measurement performance of the monitoring IC installed in each monitoring device.

[0006] JP 2010-142040 A

[0007] However, when the number of monitoring devices connected to the management device is changed, the voltage measurement time is reset taking into consideration the number of connections and the measurement performance of the monitoring ICs used. Since this voltage measurement time is usually set manually by an operator, the operator must redesign the voltage measurement time of the monitoring devices.

[0008] Furthermore, when a monitoring device is added to a battery management system, the added monitoring device is not synchronized with the other monitoring devices, which causes a discrepancy in the timing of measurements of the secondary battery by the monitoring device, so an operator must synchronize the added monitoring device with the other monitoring devices.

[0009] Furthermore, even if the number of monitoring devices connected to the management device remains the same, if the monitoring IC installed in the monitoring device is changed, the voltage measurement time, which is the measurement performance of the monitoring IC, will change, and in this case, it will be necessary to redesign the voltage measurement time.

[0010] An object of the present disclosure is to provide a battery management system, a management device, a period setting method, and a program that can automatically set the voltage measurement time even if there is a change in the number of connected monitoring devices.

[0011] The battery management system according to the present disclosure comprises a plurality of monitoring devices that measure the voltage of each of a plurality of secondary batteries, and a management device that manages the plurality of monitoring devices, wherein the management device acquires a voltage measurement time indicating the time required to measure the voltage of the secondary battery from each of the monitoring devices, and unifies the voltage measurement time in each of the monitoring devices based on the acquired voltage measurement time.

[0012] In addition, the management device according to the present disclosure is a management device that manages a plurality of monitoring devices that measure the voltage of each of a plurality of secondary batteries, and has a processing unit that acquires a voltage measurement time indicating the time required to measure the voltage of each of the secondary batteries from each of the monitoring devices, and unifies the voltage measurement time in each of the monitoring devices based on the acquired voltage measurement time.

[0013] Furthermore, the period setting method according to the present disclosure is a period setting method for a battery management system including a plurality of secondary batteries, a plurality of monitoring devices that measure the voltage of each of the plurality of secondary batteries, and a management device that manages the plurality of monitoring devices, and includes obtaining voltage measurement times indicating the time required to measure the voltage of the secondary batteries from the plurality of monitoring devices, and unifying the voltage measurement times in each of the monitoring devices based on the obtained voltage measurement times.

[0014] Furthermore, a program according to the present disclosure causes a computer to execute the above-described period setting method.

[0015] According to the present disclosure, even if there is a change in the number of connected monitoring devices, the voltage measurement time can be automatically set.

[0016] FIG. 1 is a schematic diagram showing an example of the configuration of a battery management system according to the present embodiment. FIG. 2 is a schematic diagram for explaining setting of a voltage measurement time in a period setting process according to the present embodiment. FIG. 3 is a schematic diagram for explaining setting of a voltage measurement time in a period setting process according to the present embodiment. FIG. 4 is a schematic diagram for explaining setting of a voltage measurement time in a period setting process according to the present embodiment. FIG. 5 is a schematic diagram for explaining setting of a voltage measurement time in a period setting process according to the present embodiment. FIG. 6 is a sequence diagram showing an example of the flow of a period setting process performed by the battery management system according to the present embodiment. FIG. 7 is a sequence diagram showing an example of the flow of a period setting process performed by the battery management system according to the present embodiment. FIG. 8 is a schematic diagram showing an example of the configuration of a battery management system according to a modified example of the present embodiment.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications are possible without departing from the spirit of the present disclosure. Furthermore, the present disclosure includes all possible combinations of the configurations shown in the following embodiments. In addition, in each drawing, components with the same reference numerals are the same or equivalent, and this is common throughout the entire specification.

[0018] [Configuration of Battery Management System 1] Fig. 1 is a schematic diagram showing an example of the configuration of a battery management system 1 according to this embodiment. The battery management system (hereinafter abbreviated as "BMS (Battery Management System)") 1 stores power supplied from an external power source (not shown) and supplies the stored power to a power supply target (not shown). As shown in Fig. 1, the BMS 1 includes a management device 10 which is a master device, multiple monitoring devices 20 which are slave devices, and multiple secondary batteries 30. The management device 10 and the multiple monitoring devices 20 are connected to a bus 2.

[0019] (Management Device 10) The management device 10 controls and manages the multiple monitoring devices 20 and the multiple secondary batteries 30. The management device 10 communicates with each monitoring device 20 via a bus 2 using a communication protocol such as CAN (Controller Area Network), and exchanges instruction information and battery information.

[0020] The battery information is information relating to the secondary battery, such as the voltage of the secondary battery 30. The instruction information is information for instructing the monitoring device 20, including a request for the measurement value of the voltage of the secondary battery 30.

[0021] In this embodiment, the management device 10 transmits voltage requests to the plurality of monitoring devices 20 and sequentially receives measurement results of the voltage of the secondary battery 30 as battery information from each of the plurality of monitoring devices 20 within a preset master measurement time. The master measurement time is the time required for the management device 10 to receive measurement results from all of the monitoring devices 20 connected to the management device 10.

[0022] The management device 10 has a master microcomputer 11. The master microcomputer 11 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (none of which are shown). The CPU reads a program corresponding to the processing content from the ROM, loads it into the RAM, and works with the loaded program to centrally control the operation of the management device 10. The master microcomputer 11 corresponds to the "processing unit" in this disclosure.

[0023] In this embodiment, the master microcomputer 11 sets a voltage measurement time for the monitoring device 20. The voltage measurement time is the time required for the monitoring device 20 to measure the voltage of the secondary battery 30. In this embodiment, the master microcomputer 11 sets a unified voltage measurement time for each of the multiple monitoring devices 20 during the cycle setting process described below.

[0024] (Monitoring device 20) The monitoring device 20 controls and monitors the secondary battery 30. For example, the monitoring device 20 monitors the voltage of the secondary battery 30 based on detection results from various sensors (not shown). The monitoring device 20 has a slave-side microcomputer 21 and a monitoring IC 22.

[0025] The slave microcomputer 21 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. (none of which are shown in the figure). The CPU reads a program corresponding to the processing content from the ROM, loads it into the RAM, and performs centralized control of the operation of the power storage device 1 in cooperation with the loaded program.

[0026] In this embodiment, the slave-side microcomputer 21 transmits, based on a pre-calculated voltage acquisition period, an instruction to measure the voltage and the like of the connected secondary battery 30 to the monitoring IC 22. Then, the slave-side microcomputer 21 acquires battery information including the voltage and the like of the secondary battery 30 from the monitoring IC 22.

[0027] Furthermore, the slave microcomputer 21 receives the voltage measurement time from the master microcomputer 11 and sets the received voltage measurement time as the voltage measurement time of the monitoring device 20 .

[0028] The monitoring IC 22 monitors the secondary battery 30 and acquires information about the secondary battery 30. For example, the monitoring IC 22 measures the cell voltage, which is the voltage of each of the multiple battery cells that make up the secondary battery 30, as the information about the secondary battery 30.

[0029] A predetermined voltage measurement time is specified in advance for the monitoring IC 22. This voltage measurement time is an inherent characteristic that is specified, for example, depending on the type of monitoring IC 22. Therefore, the voltage measurement time in the monitoring device 20 varies depending on the type of monitoring IC 22 used. Furthermore, the monitoring device 20 is configured not to be able to measure the voltage of the secondary battery 30 in a time shorter than the voltage measurement time specified for the monitoring IC 22.

[0030] (Secondary battery 30) The secondary battery 30 is composed of one or more battery cells. When the secondary battery 30 is composed of multiple battery cells, the battery cells are connected in series. The secondary battery 30 is, for example, a nickel-metal hydride secondary battery. Note that the type of the secondary battery 30 is not limited to this example, and it may be a secondary battery other than a nickel-metal hydride secondary battery, such as a lithium-ion secondary battery.

[0031] [Measurement Period Setting Operation of BMS 1] A description will be given of the measurement period setting operation of the BMS 1 having the above configuration. Conventionally, when measuring the cell voltage of the secondary battery 30 mounted on the BMS 1, the cell voltage of the secondary battery 30 is measured with the voltage measurement periods of the multiple monitoring devices 20 synchronized.

[0032] On the other hand, the voltage measurement period depends on the voltage measurement time, which is a characteristic of the monitoring IC 22 mounted on the monitoring device 20. Therefore, when multiple monitoring devices 20 are synchronized, the voltage measurement times by the monitoring IC 22 of each monitoring device 20 are set to be uniform. In such a BMS 1, if the number of monitoring devices 20 or the monitoring ICs 22 mounted on the monitoring devices 20 is changed, the voltage measurement times may no longer be uniform.

[0033] Therefore, in this embodiment, a period setting process is performed to automatically set the voltage measurement time to a unified value based on the voltage measurement time by the monitoring IC 22 of each monitoring device 20. In the period setting process, a slave synchronization process and a master measurement period setting process are performed.

[0034] The slave synchronization process is a process for unifying the voltage measurement times of the multiple monitoring devices 20, which are slave devices, and synchronizing the multiple monitoring devices 20. The master measurement period setting process is a process for setting a master measurement period that indicates the period at which the management device 10, which is the master device, acquires measurement values ​​from all the monitoring devices 20.

[0035] 2 to 5 are schematic diagrams for explaining the setting of the voltage measurement time in the period setting process according to this embodiment. In the example shown in Fig. 2 to 5, seven monitoring devices 20A to 20G are connected to the management device 10.

[0036] In this example, the voltage measurement times are set as follows for each of the monitoring devices 20A to 20G. As shown in FIG. 2 , the voltage measurement time by the monitoring IC 22 of the monitoring device 20A (monitoring device #1) and the monitoring device 20F (monitoring device #6) is 10 ms. The voltage measurement time by the monitoring IC 22 of the monitoring device 20B (monitoring device #2) is 25 ms. The voltage measurement time by the monitoring IC 22 of the monitoring device 20C (monitoring device #3) and the monitoring device 20E (monitoring device #5) is 20 ms. The voltage measurement time by the monitoring IC 22 of the monitoring device 20D (monitoring device #4) and the monitoring device 20G (monitoring device #7) is 15 ms.

[0037] 3, in the slave synchronization process, the monitoring devices 20A to 20G first transmit voltage measurement times to the management device 10 based on a voltage request from the management device 10. As a result, the management device 10 acquires the voltage measurement times from the monitoring devices 20A to 20G.

[0038] Next, when the management device 10 acquires the voltage measurement times from all of the monitoring devices 20A to 20G, it sets the voltage measurement times of the monitoring devices 20A to 20G to be uniform.

[0039] Here, when measuring the cell voltage of the secondary battery 30, the monitoring device 20 cannot measure the cell voltage in a time shorter than the voltage measurement time specified for the monitoring IC 22. Therefore, the voltage measurement time that is standardized across the multiple monitoring devices 20A to 20G needs to be set to the longest time among the voltage measurement times set in these monitoring devices 20A to 20G.

[0040] Therefore, the management device 10 extracts the voltage measurement time with the maximum value from the acquired voltage measurement times as the maximum voltage measurement time, as shown in Fig. 4. In this example, the voltage measurement time (25 ms) acquired from the monitoring device 20B is the longest, so the management device 10 extracts the voltage measurement time acquired from the monitoring device 20B as the maximum voltage measurement time.

[0041] 5, the management device 10 notifies each of the monitoring devices 20A to 20G of the extracted maximum voltage measurement time. Upon receiving the notification, each of the monitoring devices 20A to 20G sets the received maximum voltage measurement time as its voltage measurement time.

[0042] In this way, the slave synchronization process automatically unifies the voltage measurement times of all monitoring devices 20A to 20G connected to the management device 10. This allows the voltage measurements of the secondary batteries 30 in the monitoring devices 20A to 20G to be synchronized even if the number of monitoring devices 20 or the monitoring ICs 22 are changed.

[0043] (Master Measurement Period Setting Process) The master measurement period setting process is performed when the slave synchronization process is completed and the management device 10 receives the cell voltages of the secondary batteries 30 from all of the monitoring devices 20A to 20G.

[0044] When the management device 10 receives measurement results from all of the monitoring devices 20A to 20G, it checks the number of connected monitoring devices 20. In this case, the management device 10 checks the number of connected monitoring devices 20, for example, based on the number of monitoring devices 20 from which it received voltage measurement times in the slave synchronization process. In this example, seven monitoring devices 20A to 20G are connected to the management device 10, and responses are received from each of the monitoring devices 20A to 20G, so the number of connections is "7."

[0045] After confirming the number of connected monitoring devices 20, the management device 10 calculates the voltage acquisition period of the monitoring devices 20. The voltage acquisition period is the period for acquiring information indicating the voltage of the secondary battery 30 from each monitoring device 20, and specifically includes a voltage measurement time and a voltage acquisition time. The voltage acquisition time is the time required for the management device 10 to receive the cell voltage of the secondary battery 30 from the monitoring device 20. The voltage acquisition time is determined by the communication protocol and communication speed used between the management device and the monitoring device 20, etc.

[0046] Next, the management device 10 calculates the master measurement period based on the number of connected monitoring devices 20 and the calculated voltage acquisition period. Specifically, the management device 10 calculates the master measurement period by multiplying the calculated voltage acquisition period by the number of connected monitoring devices 20. This is because, if the number of cells of the secondary battery 30 to be measured and the communication protocol and communication speed when communicating with the management device 10 are the same for each of the monitoring devices 20A to 20G, the voltage acquisition time included in the voltage acquisition period can be considered to be the same.

[0047] The management device 10 is not limited to this example, and may, for example, calculate the master measurement period by calculating the voltage acquisition period of each of the monitoring devices 20A to 20G and then accumulating the calculated values. If the voltage acquisition times of the monitoring devices 20A to 20G are different, the management device 10 can calculate the master measurement period more accurately by performing the calculation in this manner.

[0048] After calculating the master measurement period, the management device 10 compares the calculated master measurement period with the current setting value (default value) of the preset master measurement period. If the comparison shows that the calculated master measurement period is greater than the setting value, the management device 10 sets the calculated master measurement period as the new setting value. Also, if the calculated master measurement period is equal to or less than the setting value, the management device 10 sets the calculated master measurement period as the new setting value. Note that this is not a limitation, and if the calculated master measurement period is equal to or less than the setting value, the management device 10 may maintain the preset setting value.

[0049] In this way, in the master measurement period setting process, the master measurement period is set according to the number of monitoring devices 20 connected to the management device 10 and the voltage acquisition period. Therefore, even if the number of monitoring devices 20 connected to the management device 10 is changed, the management device 10 can acquire battery information about the secondary battery at an appropriate time.

[0050] (Period Setting Process) Figures 6 and 7 are sequence diagrams showing an example of the flow of a period setting process by the battery management system 1 according to this embodiment. Note that this example illustrates the process performed between the management device 10 and a specific monitoring device 20 out of multiple monitoring devices 20 connected to the management device 10. In an actual period setting process, the management device 10 performs similar processes with other monitoring devices 20 not shown. Also, in Figures 6 and 7, symbols A to C indicate that the process moves to the corresponding symbol.

[0051] First, when the voltage acquisition period expires, the slave microcomputer 21 of the monitoring device 20 transmits a voltage measurement instruction to the monitoring IC 22 (sequence SEQ1).

[0052] When the monitoring IC 22 receives the voltage measurement instruction, in step S1 it starts measuring the cell voltages of the secondary battery 30 connected to the monitoring device 20. When the monitoring IC 22 has measured the cell voltages of all the battery cells that make up the secondary battery 30, in step S2 it ends measuring the cell voltages of the secondary battery 30. Then, the monitoring IC 22 transmits the measurement results, that is, the cell voltages of all the battery cells, to the slave-side microcomputer 21 (sequence SEQ2).

[0053] When the slave-side microcomputer 21 receives the cell voltage, it acquires the voltage measurement time in step S3. The voltage measurement time is the time elapsed from the time when the voltage measurement instruction is sent to the monitoring IC 22 in sequence SEQ1 to the time when the cell voltage is received from the monitoring IC 22.

[0054] On the other hand, the master microcomputer 11 transmits a voltage request to the slave microcomputer 21 to receive the cell voltage (sequence SEQ3).

[0055] When the slave microcomputer 21 receives the voltage request from the master microcomputer 11, it transmits the voltage measurement time acquired in step S3 to the master microcomputer 11 (sequence SEQ4).

[0056] Furthermore, in response to a voltage request from the master microcomputer 11, the slave microcomputer 21 transmits the cell voltage acquired from the monitoring IC 22 to the master microcomputer 11 (sequences SEQ5-1 to SEQ5-4).

[0057] For example, if CAN is used as the communication protocol, the number of frames and data size that can be handled in one transmission / reception are fixed. Therefore, if the data size for all cell voltages is larger than the specified size, the cell voltage data must be divided and transmitted using multiple frames. In this example, the slave microcomputer 21 divides all cell voltage data into four parts and transmits the cell voltage data to the master microcomputer 11 in four separate transmissions.

[0058] Note that the transmission and reception of cell voltages is not limited to this example. For example, if the data size that can be handled in one transmission and reception is larger than the data size of all the cell voltages, the slave-side microcomputer 21 may transmit all the cell voltages at once to the master-side microcomputer 11. In other words, the slave-side microcomputer 21 only needs to transmit the cell voltages in accordance with the regulations of the communication protocol between the management device 10 and the monitoring device 20.

[0059] In this cycle setting process, the processes from sequence SEQ1 to sequence SEQ5-4 are repeated a predetermined number of times, for example, five times, in order to suppress errors due to variations in voltage measurement time in the process of step S4 described later.

[0060] Next, in step S4, the master microcomputer 11 extracts the maximum voltage measurement time from the received voltage measurement times after receiving the voltage measurement times and cell voltages from all monitoring devices 20. Then, the master microcomputer 11 transmits to the slave microcomputer 21 a voltage measurement time setting instruction for setting the extracted maximum voltage measurement time as the voltage measurement time, and the maximum voltage measurement time (sequence SEQ6).

[0061] When the slave microcomputer 21 receives the voltage measurement time setting instruction, in step S5, it sets the received maximum voltage measurement time as the voltage measurement time.

[0062] In step S6, the master microcomputer 11 calculates the voltage acquisition period by adding the voltage measurement time and the voltage acquisition time. The voltage measurement time at this time is the maximum voltage measurement time extracted in step S4. The voltage acquisition time is the time it takes to receive the voltage measurement time and cell voltage from the slave microcomputer 21. Specifically, the voltage acquisition time is the time from receiving the voltage measurement time in sequence SEQ4 to receiving the cell voltage in sequence SEQ5-4.

[0063] Next, in step S7, the master microcomputer 11 calculates the master measurement period by multiplying the voltage acquisition period calculated in step S6 by the number of monitoring devices 20 connected to the management device 10.

[0064] Then, in step S8, the master-side microcomputer 11 compares the calculated master measurement period with the current preset value of the master measurement period, and sets the master measurement period based on the comparison result. For example, if the calculated master measurement period is greater than the preset value, the master-side microcomputer 11 sets the calculated master measurement period as the new preset value. Also, if the calculated master measurement period is equal to or less than the preset value, the master-side microcomputer 11 sets the calculated master measurement period as the new set value. Note that this example is not limiting, and if the calculated master measurement period is equal to or less than the set value, the management device 10 may maintain the preset set value.

[0065] As described above, in the BMS 1 according to the present embodiment, the management device 10 that manages the multiple monitoring devices 20 acquires, from each monitoring device 20, a voltage measurement time indicating the time required to measure the voltage of the secondary battery 30. Then, the management device 10 unifies the voltage measurement times of the respective monitoring devices based on the acquired voltage measurement times. This allows the BMS 1 to automatically set the voltage measurement time even if there is a change in the number of monitoring devices 20 connected to the management device 10.

[0066] [Modification] A battery management system according to a modification of the present embodiment will be described. In the above-described BMS 1, it is assumed that the management device 10, the monitoring device 20, and the secondary battery 30 are arranged in a common device. In contrast, for example, the management device 10 can be configured separately from the monitoring device 20 and the secondary battery 30, and the management device 10 can remotely control and manage the monitoring device 20 and the secondary battery 30.

[0067] 8 is a schematic diagram showing an example of the configuration of a battery management system 1A according to a modification of the present embodiment. As shown in Fig. 8, the BMS 1A includes a management device 10 as a master device, multiple monitoring devices 20 as slave devices, and multiple secondary batteries 30. In this modification, the management device 10 is connected to the multiple monitoring devices 20 via a network 3 such as the Internet or an intranet.

[0068] 8 , various types of information can be exchanged between the management device 10 and the monitoring devices 20 via the network 3. Therefore, the management device 10 can perform the above-described period setting process with the multiple monitoring devices 20 connected via the network 3.

[0069] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2023-203101, filed on November 30, 2023, are incorporated herein by reference in their entirety.

[0070] REFERENCE SIGNS LIST 1, 1A Battery management system 2 Bus 3 Network 10 Management device 11 Master side microcomputer 20, 20A, 20B, 20C, 20D, 20E, 20F, 20G Monitoring device 21 Slave side microcomputer 22 Monitoring IC 30 Secondary battery

Claims

1. A battery management system comprising a plurality of monitoring devices which measure the voltage of a plurality of secondary batteries, and a management device which manages the plurality of monitoring devices, wherein the management device acquires from each of the monitoring devices a voltage measurement time indicating the time required to measure the voltage of the secondary battery, and unifies the voltage measurement time in each of the monitoring devices based on the acquired voltage measurement time.

2. The battery management system of claim 1, wherein the management device extracts a maximum value from the multiple voltage measurement times received from each of the monitoring devices, and sets the extracted maximum value as a new voltage measurement time for each of the monitoring devices.

3. A battery management system as described in claim 2, wherein the monitoring device measures the voltage measurement time a predetermined number of times, and the management device extracts the maximum voltage measurement time from the multiple voltage measurement times measured by each of the monitoring devices.

4. A battery management system as described in claim 2, wherein the management device calculates a voltage acquisition period based on the voltage measurement times set in all of the monitoring devices and the voltage acquisition times by each of the monitoring devices, and determines a master measurement period based on the voltage acquisition period.

5. The battery management system according to claim 1, wherein the monitoring device has a monitoring IC that measures the voltage of the secondary battery during the voltage measurement time.

6. A management device that manages a plurality of monitoring devices that measure the voltage of each of a plurality of secondary batteries, the management device having a processing unit that acquires a voltage measurement time indicating the time required to measure the voltage of the secondary battery from each of the monitoring devices, and unifies the voltage measurement time in each of the monitoring devices based on the acquired voltage measurement time.

7. A period setting method for a battery management system comprising a plurality of secondary batteries, a plurality of monitoring devices that measure the voltage of each of the plurality of secondary batteries, and a management device that manages the plurality of monitoring devices, the period setting method comprising: acquiring a voltage measurement time indicating the time required to measure the voltage of the secondary batteries from the plurality of monitoring devices; and unifying the voltage measurement time in each of the monitoring devices based on the acquired voltage measurement time.

8. A program for causing a computer to execute the cycle setting method according to claim 7.

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