Battery monitoring system, radio communication program, and radio communication method

Abstract

A battery monitoring system (100) transmits / receives battery information by radio communication and thereby monitors a battery unit (20), said system comprising: radio devices (30, 40) for using a communication channel selected from among a plurality of communication channels to transmit / receive information by radio communication; and a storage device (44) for storing a channel map in which the availability of the plurality of communication channels is set. The radio devices are configured to update the channel map on the basis of communication results during radio communication, and store the updated channel map in the storage device. At the start of the radio communication, the radio device acquires the updated channel map stored in the storage device, and refers to the updated channel map to select the communication channel.

Description

Battery monitoring system, wireless communication program, and wireless communication method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-174396 filed on October 6, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a battery monitoring system, a wireless communication program for the battery monitoring system, and a wireless communication method for the battery monitoring system.

[0003] Conventionally, there are battery systems that transmit and receive battery information using wireless communication. In such battery systems, a communication channel is selected from multiple communication channels according to a predetermined selection pattern to perform data communication. Some battery systems change the selection pattern based on the communication results so that an appropriate communication channel can be selected depending on the surrounding environment. Such a battery system is described, for example, in Patent Document 1.

[0004] Patent No. 6514694

[0005] However, even when the selection pattern is changed based on the communication result, the selection pattern of the communication channel is predetermined at the start of communication, so for a while after the start of communication, it is not possible to select an appropriate communication channel according to the surrounding environment, which tends to result in an increase in communication errors.

[0006] The present disclosure has been made in consideration of the above circumstances, and its main purpose is to provide a battery monitoring system, a wireless communication program, and a wireless communication method that can reduce communication errors.

[0007] A first means for solving the above problem is a battery monitoring system that monitors a battery unit by transmitting and receiving battery information via wireless communication, comprising: a wireless device that transmits and receives information via wireless communication using a communication channel selected from a plurality of communication channels; and a storage device that stores a channel map in which the availability of the plurality of communication channels is set; the wireless device is configured to update the channel map based on the communication result during wireless communication and store the updated channel map in the storage device; and when the wireless communication starts, obtain the updated channel map stored in the storage device and select the communication channel by referring to the updated channel map.

[0008] According to this, when starting communication, an updated channel map is acquired and a communication channel is selected by referring to the updated channel map. Therefore, when starting communication, a channel map that reflects the communication result of the previous wireless communication can be referred to, and an appropriate communication channel can be selected, thereby reducing communication errors.

[0009] A second means for solving the above problem comprises a wireless device that transmits and receives information via wireless communication using a communication channel selected from a plurality of communication channels, and a storage device that stores a channel map in which the availability of the plurality of communication channels is set, and the wireless communication program that is executed by the wireless device of a battery monitoring system that transmits and receives battery information via the wireless communication and monitors a battery unit, includes an update process that updates the channel map based on the communication results during wireless communication, a storage process that stores the updated channel map updated by the update process in the storage device, an acquisition process that acquires the updated channel map stored in the storage device at the start of wireless communication, and a selection process that selects a communication channel by referring to the updated channel map acquired in the acquisition process.

[0010] According to this, when starting communication, an updated channel map is acquired and a communication channel is selected by referring to the updated channel map. Therefore, when starting communication, a channel map that reflects the communication result of the previous wireless communication can be referred to, and an appropriate communication channel can be selected, thereby reducing communication errors.

[0011] A third means for solving the above problem is a battery monitoring system comprising a wireless device that transmits and receives information wirelessly using a communication channel selected from a plurality of communication channels, and a storage device that stores a channel map in which the availability of the plurality of communication channels is set, and in the wireless communication method implemented by the wireless device, which transmits and receives battery information via the wireless communication and monitors a battery unit, the method includes an update process that updates the channel map based on the communication results during wireless communication, a storage process that stores the updated channel map updated by the update process in the storage device, an acquisition process that acquires the updated channel map stored in the storage device at the start of wireless communication, and a selection process that selects a communication channel by referring to the updated channel map acquired in the acquisition process.

[0012] According to this, when starting communication, an updated channel map is acquired and a communication channel is selected by referring to the updated channel map. Therefore, when starting communication, a channel map that reflects the communication result of the previous wireless communication can be referred to, and an appropriate communication channel can be selected, thereby reducing communication errors.

[0013] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a block diagram showing a schematic configuration of a vehicle, Fig. 2 is a block diagram showing a configuration of a battery pack, Fig. 3 is a perspective view showing a schematic configuration of the battery pack, Fig. 4 is a flowchart showing a data communication flow, Fig. 5 is a flowchart showing a data communication flow, Fig. 6 is a flowchart showing a connection process flow, Fig. 7 is a diagram showing frequency bands of communication channels, Fig. 8 is a diagram showing a data flow when a connection is established, Fig. 9 is a diagram showing an example of a channel map, Fig. 10 is a flowchart showing a release process flow, Fig. 11 is a flowchart showing a release process flow of a second embodiment, Fig. 12 is a flowchart showing a release process flow of a third embodiment, Fig. 13 is a flowchart showing a release process flow of a fourth embodiment, Fig. 14 is a flowchart showing a connection process flow of a fifth embodiment, Fig. 15 is a flowchart showing a data communication flow of the fifth embodiment, and Fig. 16 is a flowchart showing a connection process flow of a sixth embodiment.

[0014] Hereinafter, embodiments of a battery monitoring system, a wireless communication program, and a wireless communication method according to the present disclosure will be described in detail with reference to the drawings. Note that, between the embodiments and modifications, the same or equivalent parts in the drawings are designated by the same reference numerals, and their descriptions will not be repeated in principle. Below, we will describe the application to a vehicle, but the present disclosure can also be applied to applications other than vehicles, such as drones and other flying objects, ships, construction machinery, agricultural machinery, etc.

[0015] (First embodiment) <Vehicle> Fig. 1 is a diagram that shows a schematic configuration of a vehicle 10. The vehicle 10 is an electrically powered vehicle such as an electric vehicle (EV), a hybrid vehicle (HV), or a plug-in hybrid vehicle (PHV). The vehicle 10 includes a battery pack 11 (shown as "Battery" in Fig. 1), a power control unit (hereinafter referred to as "PCU") 12 as a power conversion device, a motor 13 (shown as "MG" in Fig. 1) as an electric load, and a vehicle ECU 14 (shown as "ECU" in Fig. 1). Note that PCU is an abbreviation for "Power Control Unit," MG is an abbreviation for "Motor Generator," and ECU is an abbreviation for "Electronic Control Unit."

[0016] The battery pack 11 is mounted on the vehicle 10 as a driving power source for the vehicle 10. In Fig. 1, the battery pack 11 is disposed, for example, in a front compartment. However, the battery pack 11 may also be disposed in a rear compartment, under a seat, under the floor, or the like.

[0017] The battery pack 11 is a chargeable and dischargeable DC voltage source that includes a battery pack 20 (described later). The battery pack 11 supplies power to the electrical loads of the vehicle 10. The battery pack 11 also converts power via the PCU 12 and supplies the power to the motor 13. The battery pack 11 is also charged via the PCU 12.

[0018] The PCU 12 performs bidirectional power conversion between the battery pack 11 and the motor 13 in accordance with a control signal from the vehicle ECU 14. The PCU 12 includes, for example, an inverter that converts DC voltage from the battery pack 11 into AC voltage to drive the motor 13, and a converter that boosts the DC voltage supplied to the inverter to a voltage equal to or higher than the output voltage of the battery pack 11.

[0019] The motor 13 is an AC rotating electric machine, such as a three-phase AC synchronous motor with a permanent magnet embedded in the rotor. The motor 13 is driven by the PCU 12 to generate rotational driving force, which is transmitted to the drive wheels. Meanwhile, when braking the vehicle 10, the motor 13 operates as a generator and performs regenerative power generation. The electric power generated by the motor 13 is supplied to the battery pack 11 via the PCU 12 and stored in the battery pack 20.

[0020] The vehicle ECU 14 includes a CPU, ROM, RAM, input / output ports for inputting and outputting various signals, etc. The CPU loads a program stored in the ROM into the RAM and executes it. The program stored in the ROM describes the processing of the vehicle ECU 14. As an example of the main processing of the vehicle ECU 14, the vehicle ECU 14 receives information such as the voltage, current, SOC (State of Charge), and SOH (State of Health) of the battery pack 20 from the battery pack 11, and controls the PCU 12 to instruct the driving of the motor 13 and the charging and discharging of the battery pack 11.

[0021] <Battery Pack> The battery pack 11 will be described in detail. FIG. 2 is a block diagram showing the configuration of the battery pack 11, and FIG. 3 is a perspective view showing a schematic configuration of the battery pack 11. The battery pack 11 includes a battery pack 20, a battery monitoring system 100, and a housing 50 (shown by a dashed line) that houses them. The battery monitoring system 100 is a system that monitors and manages the battery pack 20 using wireless communication. The battery monitoring system 100 includes multiple battery monitoring devices 30a to 30h and a battery control device 40, and wireless communication is performed between these devices. This wireless communication uses frequency bands used for short-range communication, such as the 2.4 GHz band or the 5 GHz band. Hereinafter, the battery monitoring devices 30a to 30h may be referred to as battery monitoring devices 30. The battery monitoring devices 30 and the battery control device 40 each correspond to a wireless device.

[0022] In this embodiment, the battery pack 20, the battery monitoring device 30, and the battery control device 40 are housed inside the housing 50 (battery housing space), but they may also be arranged outside the housing 50. Alternatively, the housing 50 may not be provided, and the battery pack 20 and the battery monitoring system 100 may be directly attached to a battery housing space provided in a vehicle body frame or the like. In other words, the vehicle body frame may replace the housing 50.

[0023] <Battery Assembly> The battery assembly 20 includes a plurality of battery blocks 21 (sometimes referred to as battery stacks or battery modules). The battery assembly 20 is configured by connecting these battery blocks 21 in series and / or in parallel. Each battery block 21 includes a plurality of battery cells 22. Each battery cell 22 is configured by a lithium-ion secondary battery, a nickel-metal hydride secondary battery, or the like. Note that a lithium-ion secondary battery is a secondary battery that uses lithium as a charge carrier, and may include not only a typical lithium-ion secondary battery with a liquid electrolyte but also a so-called all-solid-state battery that uses a solid electrolyte. The battery block 21 is configured by connecting these battery cells 22 in series and / or in parallel. Note that the presence of a battery block 21 is optional, and the battery assembly 20 may be configured by connecting multiple battery cells 22 in series and / or in parallel. In this embodiment, the battery assembly 20, the battery block 21, or the battery cells 22 corresponds to the battery section.

[0024] <Battery Monitoring Device> The battery monitoring device 30 will now be described. Note that each battery monitoring device 30 has a common configuration. The battery monitoring device 30 is also called a satellite battery module (SBM), and is provided for each battery block 21, i.e., for each of a plurality of battery cells 22. As shown in FIG. 2 , each battery monitoring device 30 includes a monitoring IC 31, a slave device-side wireless IC 32, and a slave device-side wireless antenna 33. The slave device-side wireless IC 32 is connected to the monitoring IC 31 by a wire. The slave device-side wireless IC 32 is also connected to the slave device-side wireless antenna 33 by a wire.

[0025] The monitoring IC 31, also called a cell monitoring circuit, acquires (senses) battery information of each battery cell 22 constituting the battery block 21 via a physical quantity detection sensor (not shown) or the like. The physical quantity detection sensor is, for example, a voltage sensor, a temperature sensor, a current sensor, or the like, and the battery information includes, for example, voltage information, temperature information, current information, and the like of each battery cell 22. The object monitored by the battery monitoring device 30 may be the battery block 21 or the entire battery pack 20, and may be changed as desired.

[0026] When the monitoring IC 31 receives data (control data as control information) requesting acquisition and transmission of battery information, it acquires the battery information and transmits monitoring data (control results) including at least the battery information. Note that the monitoring IC 31 may have a function of performing a fault diagnosis (self-diagnosis) of the circuitry of the battery monitoring device 30, including itself, and transmitting the monitoring data including the diagnosis results together with the acquired battery information.

[0027] The handset-side wireless IC 32 includes an RF circuit, a microcomputer, a front-end circuit, and other components (not shown) for wirelessly transmitting and receiving data. The handset-side wireless IC 32 has a transmission function that modulates data and oscillates at the frequency of an RF signal. At the same time, the handset-side wireless IC 32 has a reception function that demodulates received data. RF is an abbreviation for "radio frequency."

[0028] The slave-side wireless IC 32 modulates the monitoring data including the battery information received from the monitoring IC 31 and transmits it to the battery control device 40 via the slave-side wireless antenna 33. At this time, the slave-side wireless IC 32 adds data necessary for wireless communication, such as communication control information, to the monitoring data including the battery information and transmits it. Examples of data necessary for wireless communication include an identification number (ID) and an error detection code. The slave-side wireless IC 32 also has functions such as determining the data size, communication format, and schedule of communication between the battery monitoring device 30 and the battery control device 40, and detecting errors.

[0029] The handset-side wireless IC 32 also receives and demodulates data wirelessly transmitted from the battery control device 40 via the handset-side wireless antenna 33. When the handset-side wireless IC 32 receives control data including a request to acquire and transmit battery information, for example, the handset-side wireless IC 32 transmits (transfers) the control data via a wired connection to the monitoring IC 31. When the handset-side wireless IC 32 receives monitoring data including battery information from the monitoring IC 31 in response to the request, the handset-side wireless IC 32 modulates the monitoring data and wirelessly transmits it to the battery control device 40 via the handset-side wireless antenna 33.

[0030] The handset side wireless antenna 33 converts the RF signal, which is an electrical signal, into radio waves and radiates it into space, and also receives the radio waves propagating through space and converts them into an electrical signal.

[0031] The slave-side wireless IC 32 includes a cache memory 32a that can temporarily store various data. The cache memory 32a is used to store data and commands that are frequently accessed when transmitting and receiving data or executing programs. The various data include, for example, data requesting the acquisition and transmission of battery information, data required for wireless communication, and monitoring data including battery information. Normally, the contents of the cache memory 32a are lost when the battery monitoring device 30 is in a stopped state (including a sleep state).

[0032] <Battery Control Device> The battery control device 40 is also called a battery ECU or a BMU (Battery Management Unit). The battery control device 40 is configured to be able to wirelessly communicate with each battery monitoring device 30.

[0033] 2, the battery control device 40 includes a battery control MCU 41, a base unit wireless IC 42, a base unit wireless antenna 43, and a main memory 44. The base unit wireless IC 42 is connected to the battery control MCU 41 by a wire. The base unit wireless IC 42 is also connected to the base unit wireless antenna 43 by a wire. The main memory 44 is also connected to at least the base unit wireless IC 42 by a wire.

[0034] The battery control MCU 41 is composed of a microcontroller unit (microcontroller unit) including a CPU, ROM, RAM, input / output interface, etc. The CPU of the battery control MCU 41 loads a program stored in the ROM into the RAM and executes it. The program stored in the ROM contains processes related to battery control, etc.

[0035] As an example of its main processing, the battery control MCU 41 transmits control data to the battery monitoring device 30 requesting the acquisition and transmission of battery information. Furthermore, the battery control MCU 41 performs various processes related to monitoring the battery pack 20, battery block 21, and battery cells 22 based on monitoring data including battery information received from the battery monitoring device 30. For example, the battery control MCU 41 may transmit monitoring results (monitoring data) to the vehicle ECU 14, which is a higher-level ECU. In this case, the battery control MCU 41 may calculate the SOC and / or SOH based on the battery information and transmit battery information including the calculated SOC and SOH to the vehicle ECU 14. Furthermore, the battery control MCU 41 controls relay switches that switch the energized and de-energized states of the battery pack 20, the PCU 12, and the motor 13 based on the monitoring results. Furthermore, the battery control MCU 41 may transmit an equalization signal to equalize the voltages of the battery cells 22. In this embodiment, the vehicle ECU 14 issues instructions to the PCU 12 to control the charging and discharging of the battery pack 20, but the battery control MCU 41 may also be configured to perform this function. As described above, the battery control MCU 41 monitors and manages the battery pack 20, the battery block 21, and the battery cells 22.

[0036] The master-side wireless IC 42 includes an RF circuit, a microcomputer, a front-end circuit, and the like (not shown) for wirelessly transmitting and receiving data, similar to the slave-side wireless IC 32. The master-side wireless IC 42 has a transmission function and a reception function, similar to the slave-side wireless IC 32.

[0037] The base unit side wireless IC 42 demodulates the received monitoring data including battery information via the base unit side wireless antenna 43 and transmits the demodulated data to the battery control MCU 41. The base unit side wireless IC 42 also modulates the control data received from the battery control MCU 41 with data necessary for wireless communication, such as communication control information, and transmits the modulated data to the battery monitoring device 30 via the base unit side wireless antenna 43. The data necessary for wireless communication includes, for example, an identification number (ID) and an error detection code. The base unit side wireless IC 42 also has functions such as determining the data size, communication format, and schedule of communication between the battery monitoring device 30 and the battery control device 40, and detecting errors.

[0038] The base unit side wireless antenna 43 has the same configuration and function as the slave unit side wireless antenna 33. That is, the base unit side wireless antenna 43 converts an RF signal, which is an electrical signal, into a radio wave and radiates it into space, and also receives the radio wave propagating through space and converts it into an electrical signal.

[0039] The master-side wireless IC 42 has a cache memory 42a that can temporarily store data, similar to the slave-side wireless IC 32. As with the cache memory 32a, the contents stored in the cache memory 42a are usually lost when the battery control device 40 is in a stopped state (including a sleep state).

[0040] The battery control device 40 also includes a main memory 44, which serves as a primary storage device and is configured using a DRAM or the like. The main memory 44 may be shared with the battery control MCU 41 as a storage device (such as a ROM) in which wireless communication programs and the like are stored, or may be provided separately. Unlike the cache memories 32a and 42a, the main memory 44 is configured so that its stored contents are not erased even when the battery control device 40 is in a stopped state (including a sleep state). The main memory 44 stores various programs, various histories (such as histories related to battery information), various control information (such as information related to communication control, such as an ID), and the like.

[0041] <Housing> The housing 50 is made of a conductive material such as metal. In this embodiment, the housing 50 is formed in the shape of a metal box, and has a substantially rectangular parallelepiped shape. Note that the housing 50 may be partially or entirely made of a non-conductive material such as resin. The housing 50 houses the battery pack 20, the battery monitoring device 30, and the battery control device 40.

[0042] Here, the arrangement of the battery pack 20, battery monitoring device 30, and battery control device 40 will be briefly described with reference to Figure 3. The bottom surface of the housing 50 is the mounting surface for the vehicle 10. As shown in Figure 3, inside the substantially rectangular parallelepiped housing 50, multiple battery blocks 21 that make up the battery pack 20 are arranged side by side in the longitudinal direction (X direction in Figure 3). In each battery block 21, the battery cells 22 that make up the battery block 21 are arranged so as to be stacked in the lateral direction of the housing 50 (Y direction in Figure 3).

[0043] The battery monitoring device 30 and bus bars 23 are disposed on the top surface of each battery block 21 (the surface on the +Z direction side in FIG. 3 ) and secured in place with screws or the like. The battery control device 40 is disposed at the very end in the longitudinal direction (X direction). It is attached to the side of one of the battery blocks 21 (the battery block 21 at the end in the X direction in this embodiment) so that the circuit board on which the battery control device 40 is disposed is vertical. It is desirable that the parent-side wireless antenna 43 be disposed so that it protrudes above the top surface of the battery block 21. The arrangement of the battery pack 20, battery monitoring device 30, and battery control device 40 shown in FIG. 3 is merely an example and may be changed as desired.

[0044] <Wireless Communication> Next, wireless communication (wireless communication method) between the battery monitoring device 30 and the battery control device 40 will be described with reference to Figures 4 to 6. Figures 4 and 5 are diagrams showing an example of a communication sequence for data communication between the battery monitoring device 30 and the battery control device 40. This communication sequence is repeated at predetermined intervals or according to a determined communication schedule after the battery monitoring system 100 is started up until it transitions to a stopped state. Each process is carried out by the battery monitoring device 30 and the battery control device 40 executing a wireless communication program stored in their respective storage devices (ROM, etc.).

[0045] 4 to 6 explain wireless communication between one battery monitoring device 30 and a battery control device 40. The battery monitoring device 30 that will communicate is determined by a communication schedule or the like. In FIGS. 4 to 6, the monitoring IC 31 is indicated as MIC31, the slave device side wireless IC 32 is indicated as WIC32, the battery control MCU 41 is indicated as MCU41, and the master device side wireless IC 42 is indicated as WIC42. FIG. 6 is a diagram showing an example of the connection process (step S10) shown in FIG. 4.

[0046] As shown in FIG. 4, after startup, the slave-side wireless IC 32 of the battery monitoring device 30 and the master-side wireless IC 42 of the battery control device 40 execute a connection process to establish a connection (step S10).

[0047] This connection process is executed, for example, when the battery monitoring system 100 is started. Startup refers to, for example, when operating power is supplied. It may also be when a startup signal, such as an IG signal output when the ignition switch is turned on, is input. For example, startup occurs when the ignition switch is switched from off to on by a user operation. Furthermore, when predetermined conditions are met, the battery monitoring device 30 and the battery control device 40 transition to a sleep state (standby mode), but are activated intermittently during the sleep state. In other words, they may be activated spontaneously to equalize the voltages of the battery cells 22 or monitor the voltages. The connection process may also be executed during this startup.

[0048] At the time of startup, processing related to this connection processing is executed between the battery control device 40 and all of the battery monitoring devices 30 that are targets for connection with the battery control device 40 via wireless communication.

[0049] The connection process of step S10 will now be described with reference to Fig. 6. As shown in Fig. 6, the master-side wireless IC 42 of the battery control device 40 executes a scanning operation (a slave-side detection operation) (step S11), and the slave-side wireless IC 32 executes an advertising operation (a connection information transmission operation) (step S12). The scanning operation may start earlier than or at approximately the same timing as the advertising operation. It may also start later than the advertising operation.

[0050] The advertising operation is an operation in which the slave-side wireless IC 32 transmits an advertisement packet (ADV_PKT) by broadcast communication to notify the master-side wireless IC 42 of its own existence. The advertisement packet corresponds to communication, and includes ID information (identification number) of the slave-side wireless IC 32 itself (the battery monitoring device 30) and the battery control device 40.

[0051] In this advertising operation, a communication channel for establishing a connection (for advertising) is used among the multiple communication channels. The communication channel is a frequency band used in short-range communication, for example, a 2.4 GHz band, divided by a predetermined bandwidth (for example, 2 MHz), and in this embodiment, as shown in FIG. 7, it is divided into 40 channels, 0ch to 39ch. The communication channel for establishing a connection is a predetermined communication channel (for example, 37ch to 39ch) among the 40 channels. Meanwhile, the channels other than the communication channel for establishing a connection (for example, 0ch to 36ch) among the multiple communication channels are communication channels for transmitting data, which will be described later.

[0052] In the advertising operation, as shown in Fig. 8, advertisement packets are transmitted at predetermined intervals using multiple (three in this embodiment) communication channels for connection establishment. As a result, even if communication failure occurs in one of the communication channels for connection establishment, communication can be performed using the other communication channels for connection establishment. For this reason, the three communication channels for connection establishment are set with frequency bands as far apart as possible to prevent interference with each other (see Fig. 7). In addition, it is desirable that the communication channels for connection establishment be set so as not to overlap with frequency bands used by other devices, etc.

[0053] Returning to the explanation of the connection process, as shown in Fig. 6, when the master-side wireless IC 42 of the battery control device 40 detects an advertisement packet, i.e., the slave-side wireless IC 32, by a scanning operation, it transmits a connection request signal (CONNECT_REQ) to the detected slave-side wireless IC 32 (step S13).

[0054] While transmitting the connection request signal, the master-side wireless IC 42 also reads and acquires the channel map stored in the main memory 44 from the main memory 44 (step S14). The process of step S14 and the channel map will be described later.

[0055] When the slave-side wireless IC 32 receives the connection request signal, a connection, i.e., a wireless communication path connection, is established between one battery monitoring device 30 and the battery control device 40 (step S15). Once the connection is established, the slave-side wireless IC 32 of the battery monitoring device 30 stops transmitting advertisement packets. The slave-side wireless IC 32 periodically transmits advertisement packets until the connection is established.

[0056] Note that when the battery monitoring device 30 and the battery control device 40 are disconnected (the connection state is severed) even when the battery monitoring system 100 is not transitioning to a stopped state (including transitioning to a sleep state), they again execute the connection process (step S10). That is, they execute reconnection. The battery control device 40 executes reconnection (establishment of connection) with the disconnected battery monitoring device 30 while continuing data communication with the remaining battery monitoring devices 30 with which connections have been established. For example, if the connection is disconnected due to a deterioration in the communication environment, the battery control device 40 executes reconnection.

[0057] Furthermore, once a wireless communication connection is established, the connection process is skipped and subsequent processes are performed unless the connection is released, in principle. In other words, once a connection is established in step S10, the battery monitoring system 100 stops, and therefore the battery control device 40 periodically performs data communication (processing of steps S20 to S35) with the battery monitoring device 30 unless a release process (described later) is performed to release the connection.

[0058] The processing from step S20 onward will be described in detail. As shown in FIG. 4 , after the connection processing is performed and the connection is established, the battery control MCU 41 of the battery control device 40 selects a battery monitoring device 30 to be the communication partner (step S20). The battery monitoring device 30 to be the communication partner is selected from among the battery monitoring devices 30 with which the connection has been established. In this embodiment, the communication partner is selected in a pre-scheduled order, but the selection method may be changed as desired. Furthermore, although the battery control MCU 41 selects the communication partner, the parent-side wireless IC 42 may also select the communication partner.

[0059] Next, the battery control MCU 41 of the battery control device 40 transmits control data (control information) including a request to acquire and a request to transmit monitoring data including battery information to the battery monitoring device 30, which is the communication partner (step S21).

[0060] When the base unit wireless IC 42 receives the control data, it generates transmission data by adding data necessary for wireless communication, such as communication control information, to the control data (step S22). In step S22, the base unit wireless IC 42 designates the battery monitoring device 30 to be the communication partner, and adds data necessary for wireless communication, such as communication control information, to the control data.

[0061] At the same time, the base unit wireless IC 42 selects one of the communication channels for data transmission (e.g., ch0 to ch36) (step S23). At this time, as shown in Fig. 9, the base unit wireless IC 42 refers to a channel map in which the status (state) of each communication channel is set as usable (selectable, the same applies below) or unusable (unselectable, the same applies below), and selects a communication channel from the usable communication channels for data transmission. Note that a channel map is provided for each communication partner (slave unit wireless IC 32), i.e., for each battery monitoring device 30a to 30h. In Fig. 9, usable channels are indicated by blank spaces, and unusable channels are indicated by "x".

[0062] Then, the base station side wireless IC 42 wirelessly transmits the transmission data to the slave station side wireless IC 32 via the base station side wireless antenna 43 (step S24). At this time, the base station side wireless IC 42 wirelessly transmits the data to the slave station side wireless IC 32 using the selected communication channel for data transmission.

[0063] When the slave-side wireless IC 32 of the battery monitoring device 30 selected as the destination (communication partner) receives the transmission data via the slave-side wireless antenna 33, it determines whether the communication quality of the communication channel used to transmit the transmission data was good (step S25).

[0064] In step S25, the slave-side wireless IC 32 may determine that the communication quality is poor (not good) if, for example, the received signal strength (RSSI: Received Signal Strength Indicator) is equal to or lower than a predetermined strength threshold. The slave-side wireless IC 32 may also determine the communication quality using, for example, a CRC (Cyclic Redundancy Check). The slave-side wireless IC 32 may also determine the communication quality based on, for example, whether a packet error rate is equal to or lower than a predetermined error rate. The slave-side wireless IC 32 may also determine the communication quality based on the communication time from when the master-side wireless IC 42 transmits data to when the slave-side wireless IC 32 receives data. When transmitting data divided into packets, the slave-side wireless IC 32 may also determine the communication quality based on the variation in the interval between when one packet arrives and when the next packet arrives. The communication quality may also be determined based on the SNR (Signal-to-Noise Ratio). Other well-known methods may also be employed, or a combination of these methods may be used to determine the communication quality based on the results of these determinations.

[0065] After determining the communication quality, the slave wireless IC 32 transmits the control data included in the received transmission data to the monitor IC 31 (step S26). Upon receiving the control data, the monitor IC 31 acquires (senses) battery information in accordance with the control data (step S27). The monitor IC 31 may also perform circuit fault diagnosis.

[0066] Next, the monitoring IC 31 transmits monitoring data including the battery information to the slave wireless IC 32 in accordance with the control data (step S28). At this time, the monitoring data including the diagnosis result may be transmitted together with the battery information.

[0067] Upon receiving the monitoring data from the monitoring IC 31, the slave-side wireless IC 32 generates transmission data including the monitoring data, i.e., response data, and wirelessly transmits (responses) the transmission data to the master-side wireless IC 42 via the slave-side wireless antenna 33 (step S29). At this time, the response data includes data necessary for wireless communication, such as communication control information, as in the processing of the master-side wireless IC 42 in step S22. The response data also includes communication quality data (the processing result of step S25). The slave-side wireless IC 32 selects the same communication channel as the communication channel used when receiving the transmission data transmitted by the master-side wireless IC 42, and wirelessly transmits the data to the master-side wireless IC 42. That is, the slave-side wireless IC 32 transmits the data using the data transmission communication channel selected in step S23. Therefore, the data transmission communication channel corresponds to the battery information transmission communication channel for transmitting and receiving battery information.

[0068] Note that even if the communication quality is determined to be poor in step S25, if the control data included in the transmission data can be read, the processing of steps S26 to S29 is executed. On the other hand, if the control data cannot be read, the processing of steps S26 to S29 is terminated without being executed. Also, if the transmission data cannot be received, the processing of steps S26 to S29 is terminated without being executed.

[0069] 5, after transmitting the transmission data in step S24, the base unit wireless IC 42 determines whether or not response data has been returned from the communication partner, the slave unit wireless IC 32 (step S30). Specifically, after transmitting the transmission data in step S24, the base unit wireless IC 42 determines whether or not response data has been received within a predetermined time period.

[0070] If the result of this determination is negative, that is, if the response data cannot be received normally and it is determined that the communication quality is poor, the base unit side wireless IC 42 updates the channel map to reflect this (step S31).

[0071] Here, the channel map and the updating of the channel map in step S31 will be described. A channel map is provided for each of the battery monitoring devices 30a to 30h that will be communicating with each other, and is stored in the main memory 44 of the battery control device 40. Specifically, the channel map is stored in the main memory 44 in association with the identification number (ID) of each of the battery monitoring devices 30a to 30h.

[0072] As described above, the channel map is read in step S14 of the connection process and stored in the cache memory 42a of the master-side wireless IC 42. At this time, the channel map is associated with the identification number (ID) of each battery monitoring device 30a-30h and managed for each battery monitoring device 30a-30h (see FIG. 9). Then, in step S31, the channel map stored in the cache memory 42a is updated.

[0073] In step S31, the base-side wireless IC 42 first identifies the channel map associated with the identification number of the battery monitoring device 30, the communication partner selected in step S20. The base-side wireless IC 42 then changes the status of the communication channel selected in step S23 to unavailable in the channel map. For example, if the communication partner selected in step S20 is the battery monitoring device 30a and the communication channel for data transmission selected in step S23 is communication channel ch1, the base-side wireless IC 42 updates communication channel ch1 in the channel map associated with the identification number of the battery monitoring device 30a to unavailable in step S31. In FIG. 9 , unavailable communication channel ch1 is indicated by an "x" and available communication channel ch1 is indicated by a blank. As a result, communication channel ch1 will not be selected in the next step S23. The base-side wireless IC 42 then terminates data communication for that period.

[0074] If the determination result in step S30 is positive, i.e., if response data has been returned, the base unit wireless IC 42 determines whether the communication quality of the communication channel used to return the response data was good (step S32). In step S32, the base unit wireless IC 42 determines the communication quality of the used communication channel by performing the same process as in step S25. At the same time, the base unit wireless IC 42 determines the communication quality based on the communication quality determination result included in the response data (the determination result of step S25). If the communication quality is determined to be poor based on either the transmission data or the response data, the communication quality is determined to be poor. However, if the communication quality is determined not to be poor based on either the transmission data or the response data, the communication quality is determined to be good.

[0075] Then, the base-side wireless IC 42 updates the channel map (step S33), similarly to step S31. That is, if it is determined in step S32 that the communication quality is poor, the base-side wireless IC 42 first identifies the channel map associated with the identification number of the battery monitoring device 30, the communication partner selected in step S20. Then, the base-side wireless IC 42 changes the state (status) of the communication channel selected in step S23 in the channel map to unavailable. On the other hand, if it is determined in step S32 that the communication quality is good, the processing of step S33 ends without updating the channel map.

[0076] After step S33 is completed, the base unit wireless IC 42 transmits the monitoring data included in the received response data to the battery control MCU 41 (step S34). The battery control MCU 41 executes a predetermined process based on the monitoring data (step S35). The base unit wireless IC 42 then terminates data communication for that period. Note that if the monitoring data cannot be read correctly due to poor communication quality, the base unit wireless IC 42 terminates data communication without executing step S34.

[0077] The battery control device 40 periodically performs the above-described data communication with the battery monitoring device 30 with which a connection has been established until the battery monitoring system 100 transitions to a stopped state (including a sleep state).

[0078] As described above, the channel map stored in the cache memory 42a continues to be updated based on the communication results, i.e., the communication quality judgment results, while the battery monitoring system 100 is running. This makes it possible to select a communication channel that is suitable for the environment along the radio wave propagation path.

[0079] Incidentally, the external environment of the battery pack 11 may change frequently as the vehicle 10 travels, but the internal environment of the battery pack 11 does not change unless maintenance or the like is performed on the vehicle 10. In other words, the arrangement of the battery monitoring device 30 and the battery control device 40, the shape of the housing 50, the arrangement of various components inside the housing 50 (such as wiring including the bus bar 23), and the like are usually not changed even when the battery monitoring system 100 is stopped. In addition, because the housing 50 is made of a conductor, it is less susceptible to influences from outside the battery pack 11 (such as electromagnetic noise).

[0080] Therefore, it is believed that the propagation path of radio waves used for wireless communication within the battery pack 11 does not change significantly even when the battery monitoring system 100 is stopped. Nevertheless, when the battery monitoring system 100 is started up, if a communication channel is selected by referring to an initial (i.e., unupdated) channel map, the same number of communication errors occurs every time the battery monitoring system 100 is started up. Therefore, in this embodiment, the following configuration is adopted.

[0081] First, the process when wireless communication is terminated will be described. When a connection is established and data communication is being performed and the battery monitoring system 100 transitions to a stopped state (including a sleep state, the same applies below), the master-side wireless IC 42 of the battery control device 40 executes the release process shown in Fig. 10 in order to terminate wireless communication. The release process is performed at any timing during data communication after the connection process is completed. For example, the release process may be performed at predetermined intervals or at predetermined timings (when the voltage drops or when a connection release request signal is input from outside), etc.

[0082] When the disconnection process is performed, the master-side wireless IC 42 determines whether a disconnection request signal has been input (step S50). The disconnection request signal is input, for example, from an external device (such as the vehicle ECU 14) or the battery control MCU 41 when the battery monitoring system 100 transitions to a stopped state. Specifically, the disconnection request signal is input when the ignition switch is turned off. For example, the disconnection request signal is input when the vehicle 10 comes to a complete stop with the brake pedal depressed, a predetermined time has passed, and it is determined that the vehicle 10 will transition to a sleep state. The disconnection request signal may also be input when the power supply voltage falls below a predetermined operating threshold or when some abnormality or malfunction, such as a communication abnormality, occurs. If the determination result is negative, the disconnection process is terminated.

[0083] On the other hand, if the determination result in step S50 is positive, the base-side wireless IC 42 stores the updated channel map stored in the cache memory 42a in the main memory 44 (step S51). At this time, the base-side wireless IC 42 reads the updated channel map for each of the battery monitoring devices 30a to 30h and stores the updated channel map for each of the battery monitoring devices 30a to 30h. In other words, the updated channel map is stored in the main memory 44 in association with the identification number (ID) of each of the battery monitoring devices 30a to 30h.

[0084] Furthermore, the base station wireless IC 42 reads information required for the next wireless communication from the cache memory 42a and stores it in the main memory 44 (step S52). For example, if the cache memory 42a stores information required for wireless communication (such as a communication schedule or ID) or a battery information history, the information is stored in the main memory 44.

[0085] Next, the base unit side wireless IC 42 transmits a release signal to each of the slave unit side wireless ICs 32 (step S53). Upon receiving the release signal, the slave unit side wireless IC 32 performs processing required for disconnecting the connection on the slave unit side wireless IC 32 side, and then transmits a release acknowledgement signal to the base unit side wireless IC 42. After transmitting the release acknowledgement signal, the slave unit side wireless IC 32 determines that the connection has been disconnected on the slave unit side.

[0086] Meanwhile, the base unit side wireless IC 42 determines whether or not it has received the release acknowledgement signals from all of the slave unit side wireless ICs 32 (step S54). If the determination result of step S54 is positive, it determines that the connection has been released on the base unit side (step S55). On the other hand, if the determination result of step S54 is negative, the base unit side wireless IC 42 waits for a predetermined time and then performs the process of step S54 again.

[0087] Based on the above explanation, the processing content when the next connection processing is performed after the end of the release processing will be described with reference to Fig. 6. The processing from steps S11 to S13 is the same as that described above, and therefore will not be described here. As shown in Fig. 6, the master-side wireless IC 42 of the battery control device 40 transmits a connection request signal (CONNECT_REQ) in step S13, and then reads and acquires the channel map stored in the main memory 44 from the main memory 44 (step S14).

[0088] As described above, the main memory 44 stores an updated channel map for each slave unit (i.e., for each identification number of the battery monitoring devices 30a to 30h). Therefore, the master unit wireless IC 42 stores the channel map read from the main memory 44 in the cache memory 42a for each slave unit. In other words, the channel map is stored in the cache memory 42a in association with the identification number of each battery monitoring device 30a to 30h. Thereafter, a connection is established as described above, and the connection process ends.

[0089] If an updated channel map is not stored in the main memory 44, the base unit wireless IC 42 reads out an initialized channel map that was originally stored and saved in the main memory 44, and stores it in the cache memory 42a. An example of a case in which an updated channel map is not stored is when the initial connection process is executed after the battery pack 11 is manufactured, or when the channel map is not saved correctly for some reason during the disconnection process. The initialized channel map may be in any state for each communication channel, but may be, for example, a channel map in which all communication channels are available.

[0090] Thereafter, when performing the processing of step S23 in data communication, the base station side wireless IC 42 reads out the channel map stored in the cache memory 42a that corresponds to the identification number of the battery monitoring device 30a to 30h selected as the communication partner in step S20, and selects a communication channel by referring to the channel map.

[0091] After the channel map stored in the cache memory 42a is saved in step S14 of the connection process, it continues to be updated based on the communication results (good or bad communication quality) in steps S31 and S33 unless the release process is executed. On the other hand, the channel map stored in the main memory 44 is not updated unless the release process step S51 is executed.

[0092] In the first embodiment described above, steps S31 and S33 correspond to the channel map update process, step S14 corresponds to the channel map acquisition process, step S51 corresponds to the channel map saving process, and step S23 corresponds to the communication channel selection process.

[0093] According to the above embodiment, the following effects can be obtained.

[0094] At the start of communication, the base station wireless IC 42 acquires an updated channel map that reflects the communication results of the previous wireless communication (data communication) and selects a communication channel by referring to the updated channel map. Therefore, at the start of data communication, the base station wireless IC 42 can appropriately select a communication channel by referring to the channel map that reflects the communication results of the previous data communication, thereby reducing communication errors. In particular, because the internal radio wave propagation path of the battery pack 11 does not change, communication errors can be effectively reduced by referring to the channel map that reflects the communication results of the previous data communication.

[0095] Between the start of the connection process and before the start of data communication, specifically before the process of step S20, the base station wireless IC 42 acquires the updated channel map stored in the main memory 44. This allows the updated channel map to be acquired before the start of data communication, thereby reducing communication errors at the start of data communication and ensuring reliable acquisition of battery information from the start of communication.

[0096] In the connection process, when a connection request signal is transmitted and received, the communication partner is identified and a connection is established. Therefore, by obtaining a channel map after the connection request signal is transmitted and received (after step S13) and before step S15 when the connection is established, i.e., at the timing of step S14, it is possible to avoid a situation in which the obtained channel map is wasted without being used.

[0097] The updated channel map is saved in main memory 44 between the time when the disconnection request signal is received and the time when the connection is released in the disconnection process (up to step S55), specifically in step S51. In other words, the updated channel map is saved in a state where no further data communication is being performed (a state where no new communication results are being generated). This makes it possible to save a channel map that reflects the latest communication results.

[0098] The channel map is provided for each battery monitoring device 30a-30h, updated for each battery monitoring device 30a-30h, saved in the main memory 44 for each battery monitoring device 30a-30h during the release process, and read out for each battery monitoring device 30a-30h during the connection process. This allows an appropriate communication channel to be selected at the start of communication depending on the environment of each battery monitoring device 30a-30h.

[0099] The master-side wireless IC 42 starts wireless communication when the battery monitoring system 100 is started (including when operating power is supplied, when a start-up signal is input, and when the battery monitoring system 100 is started spontaneously from a sleep state). Then, in the connection process executed when wireless communication starts, the master-side wireless IC 42 reads the updated channel map from the main memory 44. Thereafter, the channel map is not read from the main memory 44 until the battery monitoring system 100 is stopped. This reduces the frequency with which the channel map is obtained from the main memory 44.

[0100] Furthermore, when the battery monitoring system 100 is stopped during wireless communication (including when the supply of operating power is stopped, when a stop signal is input, or when the system transitions to a sleep state), the master-side wireless IC 42 terminates wireless communication. Then, in a release process executed when the wireless communication is terminated, the master-side wireless IC 42 saves the updated channel map in the main memory 44. This reduces the frequency with which the channel map needs to be saved in the main memory 44.

[0101] When wireless communication starts, the base station wireless IC 42 stores the updated channel map it has read in its cache memory 42a. During wireless communication, the base station wireless IC 42 updates the channel map based on the communication results while referring to the channel map stored in the cache memory 42a. When wireless communication ends, the base station wireless IC 42 stores the updated channel map stored in the cache memory 42a in the main memory 44. This allows the channel map to be stored and maintained even during a shutdown. Temporarily storing the channel map in the cache memory 42a reduces the frequency with which the channel map is read from and saved in the main memory 44, thereby improving the speed at which it is referenced and updated.

[0102] (Modification of First Embodiment) Hereinafter, a modification of the battery monitoring system 100 in the first embodiment will be described.

[0103] In the first embodiment, a channel map is provided for each of the battery monitoring devices 30a to 30h. However, there may be only one common channel map.

[0104] In the connection process ( FIG. 6 ) of the first embodiment, the roles of the master-side wireless IC 42 and the slave-side wireless IC 32 may be reversed. For example, the master-side wireless IC 42 makes the connection request (step S13), but the slave-side wireless IC 32 may make the connection request instead. Alternatively, the slave-side wireless IC 32 may perform the scanning operation (step S11), and the master-side wireless IC 42 may perform the advertising operation (step S12).

[0105] In the channel map of the first embodiment, the status of a communication channel that has become unavailable may be changed to available at a predetermined timing. For example, after a certain period of time has passed, the status of the communication channel that has become unavailable may be changed to available. Furthermore, for example, after a certain period of time has passed, data (test data, etc.) may be sent and received using the communication channel that has become unavailable, the communication quality may be determined, and if the communication quality is good, the status may be changed to available.

[0106] In the channel map of the first embodiment, if the communication quality is poor, the communication channel with poor communication quality is made unusable. However, the communication channel may be made unusable if the communication quality is poor for a predetermined number of times or a predetermined number of consecutive times.

[0107] In the first embodiment, a plurality of communication channels may be used in one data transmission.

[0108] In step S14 of the first embodiment, if the channel map is not properly stored in the main memory 44, an initialized channel map may be acquired.

[0109] In the first embodiment, an identification number is assigned to each of the battery monitoring devices 30a to 30h, but it may be assigned to each of the slave-side wireless ICs 32. In other words, if one battery monitoring device 30 has multiple slave-side wireless ICs 32, it is necessary to manage each of the slave-side wireless ICs 32 with an identification number. Similarly, although an identification number is assigned to the battery control device 40, it may be assigned to the master-side wireless IC 42.

[0110] In the first embodiment, the battery control device 40 has the main memory 44 as a storage device for storing the updated channel map, but the main memory 44 may be provided outside the battery control device 40. Also, the storage device for storing the updated channel map may be provided in the battery monitoring device 30.

[0111] In the first embodiment, when wireless communication is terminated, specifically during the cancellation process, the updated channel map is stored in the main memory 44. However, the channel map in the main memory 44 may be overwritten and stored each time the channel map is updated.

[0112] Second Embodiment A second embodiment will be described in which the configuration of the battery monitoring system 100 of the first embodiment is partially modified.

[0113] If a communication abnormality occurs during data communication, it may become difficult to continue wireless communication, and the connection may be forcibly terminated. For example, a communication abnormality may occur due to unstable power supply to the master wireless IC 42 or the slave wireless IC 32, or due to the influence of strong external electromagnetic noise. In such a situation, if the channel map is updated based on the communication results, the number of unusable communication channels may increase. Therefore, in the termination process of the second embodiment, if the connection is terminated due to a communication abnormality, the updated channel map is not saved. The termination process of the second embodiment will be described below with reference to FIG. 11 .

[0114] In the second embodiment, when the release process is performed, the base station wireless IC 42 determines whether a communication abnormality has occurred (step S150). A known method may be used to determine the communication abnormality. For example, if data communication has not been performed successfully multiple times (if the determination result in step S30 is negative consecutively, or if the communication quality is poor consecutively in step S32), the base station wireless IC 42 determines that a communication abnormality has occurred. Alternatively, the base station wireless IC 42 may determine that a communication abnormality has occurred if the power supply becomes unstable or if external electromagnetic noise becomes large.

[0115] If the determination result is negative, the base station wireless IC 42 performs the processing from step S50 onward. The processing from step S50 onward is the same as that in the first embodiment, and therefore will not be described further. On the other hand, if the determination result in step S150 is positive, the base station wireless IC 42 does not save the updated channel map in the main memory 44, but instead initializes the channel map and stores it in the main memory 44 (step S151). Next, the base station wireless IC 42 performs processing necessary to disconnect communication and processing to notify the user that a communication abnormality has occurred (step S152). The processing necessary to disconnect communication includes, as in step S52, reading information necessary for the next wireless communication from the cache memory 42a and storing it in the main memory 44. Then, the base station wireless IC 42 forcibly (unilaterally) disconnects the connection (step S153) and terminates the processing.

[0116] The effects of the second embodiment will be described.

[0117] When a communication abnormality occurs, it is highly likely that an abnormality also occurs in the communication result, and if the channel map is updated based on such a communication result, it is highly likely that the channel map has not been properly updated. Therefore, if communication is performed according to such a channel map, it is highly likely that a communication error will occur or that a normal communication channel will not be able to be selected. Therefore, when a communication abnormality occurs, the updated channel map will not be saved and will not be used in the next wireless communication.

[0118] Referencing the channel map that was referenced at the start of the previous communication may cause a communication error to occur again or may reduce the number of selectable communication channels. Therefore, in the second embodiment, if a communication error occurs, an initialized channel map is used in the next wireless communication. This reduces the possibility of such an error occurring.

[0119] (Modification of Second Embodiment) Hereinafter, a modification of the battery monitoring system 100 in the second embodiment will be described.

[0120] In the second embodiment, the channel map stored in the main memory 44 (the channel map to be loaded in the next connection process) is initialized, but initialization is not necessary. In other words, it is possible to simply not overwrite the updated channel map in the main memory 44. This makes it possible to refer to the updated channel map that was updated in a wireless communication performed before the wireless communication in which the communication abnormality occurred.

[0121] In the second embodiment, the channel map stored in the main memory 44 (the channel map to be loaded in the next connection process) is initialized, but it is also possible to simply not save it. Then, the initialized channel map can be loaded in the next connection process. In other words, if the connection is terminated due to a communication abnormality, this fact can be stored, and if it is stored that the connection was terminated due to a communication abnormality, the initialized channel map can be loaded in the connection process.

[0122] Third Embodiment A third embodiment will be described in which the configuration of the battery monitoring system 100 of the first embodiment is partially modified.

[0123] When a channel map is updated in a noisy external environment, communication quality tends to deteriorate, and the number of communication channels that are usable in a quiet external environment tends to increase. Also, if the number of usable communication channels is so small that there is no choice, and a channel map is referred to from the start of communication, it may be difficult to continue wireless communication.

[0124] Therefore, in the cancellation process of the third embodiment, if the number of available communication channels in the updated channel map falls below a predetermined threshold, the updated channel map is not saved. In other words, the updated channel map is not carried over to the next or subsequent connection processes. The cancellation process of the third embodiment will be described below with reference to FIG. 12.

[0125] In the third embodiment, when the disconnection process is performed, the base station wireless IC 42 determines whether a disconnection request signal has been input, as in the first embodiment (step S50). If the determination result is positive, the base station wireless IC 42 determines whether any channel map stored in the cache memory 42a has a number of available communication channels equal to or less than a threshold (step S250). In step S250, the determination is made for each of the battery monitoring devices 30a to 30h, i.e., for each channel map associated with an identification number.

[0126] If the determination result of step S250 is positive, the base-side wireless IC 42 initializes the channel map identified in step S250 and stores it in the main memory 44, and stores channel maps other than the channel map identified in step S250 in association with their identification numbers in the main memory 44 (step S251). Then, the base-side wireless IC 42 performs the processes from step S52 onward, as in the first embodiment. Note that if the determination result of step S250 is negative, the base-side wireless IC 42 proceeds to the process of step S51.

[0127] The effects of the third embodiment will be described.

[0128] During data communication processing, if there is an updated channel map in which the number of available communication channels is equal to or less than a predetermined threshold, the base station wireless IC 42 does not store the channel map in the main memory 44. This prevents a situation in which there are so few available communication channels that there is no choice and, conversely, an appropriate communication channel cannot be selected.

[0129] The use of a channel map referenced during the previous communication may result in a decrease in the number of available communication channels. Therefore, in the third embodiment, when the number of available communication channels falls below a predetermined threshold, the channel map that falls below the threshold is initialized, and the initialized channel map is used in the next wireless communication. This reduces the possibility of such a problem occurring.

[0130] (Modification of the Third Embodiment) Hereinafter, a modification of the battery monitoring system 100 in the third embodiment will be described.

[0131] In the third embodiment, when the number of available communication channels falls below a predetermined threshold, the channel map (the channel map to be loaded in the next connection process) is initialized. However, initialization is not necessary. In other words, it is also possible to simply not overwrite the updated channel map in the main memory 44. This allows the updated channel map that was updated in the previous wireless communication to be used in subsequent wireless communications.

[0132] In the second embodiment, the channel map is initialized when the number of available communication channels falls below a predetermined threshold. However, it is also possible to simply not save the channel map. The initialized channel map can then be loaded during the next connection process. In other words, if a channel map in which the number of available communication channels falls below a predetermined threshold is loaded from the main memory 44 at the start of communication, the channel map can be initialized during the connection process.

[0133] Fourth Embodiment A fourth embodiment will be described in which the configuration of the battery monitoring system 100 of the first embodiment is partially modified.

[0134] The type (frequency) and amount of electromagnetic noise may vary depending on the external environment. That is, the communication channel with good communication quality may vary depending on the external environment. Furthermore, when the vehicle 10 is traveling, the external environment changes rapidly, and communication channels with good (or poor) communication quality tend to change frequently. For this reason, even if an updated channel map is referred to in the next wireless communication while the vehicle 10 is traveling, it may not be very useful due to the difference in the external environment.

[0135] On the other hand, when the vehicle 10 is stopped, it is expected that there will be little change in the external environment, and the channel map is updated mainly to reflect the internal environment of the battery pack 11. Therefore, if the channel map updated to reflect the internal environment of the battery pack 11, which is unlikely to change, is referenced in subsequent wireless communications, it is expected that communication errors will be reduced. Therefore, the fourth embodiment is configured as follows.

[0136] 13 , in the fourth embodiment, when the disconnection process is performed, the master wireless IC 42 determines whether a disconnection request signal has been input (step S50), as in the first embodiment. If the determination result is positive, the master wireless IC 42 determines whether the vehicle 10 was stopped from the time the battery monitoring system 100 started to be activated until the time the disconnection request signal was input (step S350). Specifically, the master wireless IC 42 receives information from an external device, such as the vehicle ECU 14, regarding whether the vehicle 10 was stopped from the time the battery monitoring system 100 started to be activated until the time the disconnection request signal was input, and makes the determination based on that information. Whether the vehicle 10 was stopped may be determined by a well-known method, such as by determining the vehicle speed obtained from a vehicle speed sensor.

[0137] If the determination result in step S350 is positive, the base station wireless IC 42 performs the processes from step S51 onward. On the other hand, if the determination result in step S350 is negative, the base station wireless IC 42 does not save the updated channel map in the main memory 44, but instead initializes the channel map and stores it in the main memory 44 (step S351). Then, it performs the processes from step S52 onward.

[0138] The effects of the fourth embodiment will be described below.

[0139] The master wireless IC 42 stores in the main memory 44 only the channel map that has been updated while the vehicle 10 is stopped. This allows a channel map that reflects the internal environment of the vehicle to be created and stored, regardless of the external environment. Therefore, a channel map that is valid to a certain extent can be created not only when the vehicle 10 is stopped, but also when the vehicle 10 is moving, regardless of the state of the external environment of the vehicle 10.

[0140] (Modification of Fourth Embodiment) Hereinafter, a modification of the battery monitoring system 100 in the fourth embodiment will be described.

[0141] In the fourth embodiment, the battery control MCU 41 or the base unit wireless IC 42 may receive vehicle speed information or the like to determine whether the vehicle 10 is stopped.

[0142] In the fourth embodiment, if the determination result in step S350 is negative, the channel map is initialized. However, the process of step S51 may simply be skipped. In other words, the channel map stored in the main memory 44 may be used in the next wireless communication without being overwritten.

[0143] In the fourth embodiment, only the channel map updated during the sleep state or when the ignition switch is off may be stored in the main memory 44 and may be carried over to the next and subsequent wireless communication.

[0144] In the fourth embodiment, the communication quality of all communication channels may be determined while the vehicle 10 is stopped, and a channel map that sets whether each communication channel is available or not based on the determination results may be stored in the main memory 44.

[0145] Fifth Embodiment A fifth embodiment will be described in which the configuration of the battery monitoring system 100 of the first embodiment is partially modified.

[0146] In the first embodiment, the channel map is referenced only on the side of the master-side wireless IC 42, but in the fifth embodiment, the channel map is also referenced on the side of the slave-side wireless IC 32. This will be described in detail below.

[0147] First, the connection process in the fifth embodiment will be described with reference to FIG. 14. Steps S11 to S15 of the connection process are performed in the same manner as in the first embodiment, and a connection is established. After the connection is established, the master wireless IC 42 distributes the updated channel map stored in the cache memory 42a in step S14 to each of the battery monitoring devices 30a to 30h based on the associated identification number (step S16).

[0148] When the slave-side wireless IC 32 of each of the battery monitoring devices 30a to 30h receives the channel map, it stores it in its own cache memory 32a (step S17), and then ends the connection process.

[0149] In data communication according to the fifth embodiment, as shown in FIG. 15 , upon receiving the monitoring data transmitted from the monitoring IC 31 in step S28, the slave-side wireless IC 32 refers to the channel map stored in the cache memory 32a and selects one of the communication channels (e.g., channels 0 to 36) for data transmission (step S401). In step S401, a communication channel is selected from available communication channels. Note that a communication channel different from the communication channel selected by the master-side wireless IC 42 in step S23 may be selected. Furthermore, if the communication quality is determined to be poor in step S25, it is desirable to select a communication channel different from the communication channel selected by the master-side wireless IC 42 in step S23.

[0150] The slave-side wireless IC 32 proceeds to step S29, and similarly to the first embodiment, generates response data and wirelessly transmits (responses) the response data to the master-side wireless IC 42 via the slave-side wireless antenna 33 (step S29). At this time, the response data is transmitted using the communication channel selected in step S401.

[0151] Then, the base station wireless IC 42 performs the process of step S30, as in the first embodiment. If the determination result of step S30 is negative, the base station wireless IC 42 ends the process without updating the channel map, unlike the first embodiment. This is because the communication channel used to transmit the transmission data may differ from the communication channel used to transmit the response data, making it impossible to determine which communication channel was used to successfully transmit the data.

[0152] On the other hand, if the judgment result of step S30 is positive, the parent device side wireless IC 42 judges the communication quality of the communication channel selected in step S23 (the communication channel at the time of transmission) and the communication quality of the communication channel used to return the response data (the communication channel at the time of return) (step S402).

[0153] The communication quality of the communication channel selected in step S23 is determined based on the communication quality determination result included in the response data (the determination result of step S25). On the other hand, the communication quality of the communication channel used to return the response data is determined by performing the same process as step S25.

[0154] Next, based on the determination result of step S402, the base unit wireless IC 42 updates the channel map associated with the identification number of the battery monitoring device 30, the communication partner selected in step S20 (step S403). Specifically, if the processing of step S402 determines that the communication quality of the communication channel selected in step S23 is poor, the base unit wireless IC 42 changes the status of the communication channel to unusable. Also, if the processing of step S402 determines that the communication quality of the communication channel used to return the response data is poor, the base unit wireless IC 42 changes the status of the communication channel to unusable. Note that if the communication quality is good, the channel map is not updated.

[0155] When the channel map is updated, the master-side wireless IC 42 transmits the updated channel map to the slave-side wireless IC 32 of the battery monitoring device 30a to 30h identified by the identification number associated with the updated channel map. Although not shown, when the slave-side wireless IC 32 receives this updated channel map, it overwrites and saves the channel map stored in its own cache memory 32a.

[0156] Then, the base station side wireless IC 42 performs the processes from step S34 onwards, similarly to the first embodiment.

[0157] According to the fifth embodiment, the following effects are achieved.

[0158] The master-side wireless IC 42 is configured to store updated channel maps in the main memory 44, and during connection processing (i.e., at the start of wireless communication), it reads the updated channel maps stored in the main memory 44 and transmits the read updated channel maps to the slave-side wireless IC 32. In this way, the master-side wireless IC 42 collectively manages the channel maps, thereby reducing the number and storage capacity of the main memories 44. Furthermore, it is possible to avoid problems such as differences in the contents of the updated channel maps between the master-side wireless IC 42 and the slave-side wireless IC 32.

[0159] When wireless communication starts, the slave-side wireless IC 32 stores the channel map received from the master-side wireless IC 42 in the cache memory 32 a, and when transmitting (replying) response data, selects a communication channel by referring to the channel map stored in the cache memory 32 a. This allows the response data to be returned using a different communication quality when the communication quality of the communication channel at the time of transmission is poor.

[0160] Furthermore, in one data communication, the communication qualities of different communication channels can be obtained on the parent device side wireless IC 42 side and the child device side wireless IC 32 side, thereby improving the update speed of the channel map.

[0161] (Modification of Fifth Embodiment) Hereinafter, a modification of the battery monitoring system 100 in the fifth embodiment will be described.

[0162] In the fifth embodiment, when the channel map is updated in step S402, the updated channel map is transmitted to the slave-side wireless IC 32, and the channel map in the cache memory 32a in the slave-side wireless IC 32 is also updated. However, the timing of the update may be changed as desired. Also, the channel map in the cache memory 32a in the slave-side wireless IC 32 does not have to be updated.

[0163] In the fifth embodiment, if the result of the determination in step S30 is negative (if response data is not received), the channel map is not updated, but the channel map may be updated. In this case, the communication quality of both the communication channel at the time of sending and the communication channel at the time of replying can be determined to be poor, and the communication channels can be made unusable.

[0164] In the fifth embodiment, the slave-side wireless IC 32 of the battery monitoring device 30 may update the channel map stored in the cache memory 32a based on the result of step S25. In this case, since there is a possibility that the channel map stored in the cache memory 42a of the master-side wireless IC 42 and the channel map stored in the cache memory 32a of the slave-side wireless IC 32 may differ in content, it is desirable to align the content at some point. When aligning the content, for example, if there is an unusable communication channel in either channel map, it is sufficient to set the channel to unusable in both channel maps. Alternatively, if there is an usable communication channel in either channel map, it is sufficient to set the channel to usable in both channel maps.

[0165] Sixth Embodiment A sixth embodiment will be described in which the configuration of the battery monitoring system 100 of the first embodiment is partially modified.

[0166] If the placement of the battery control device 40 or the battery monitoring device 30 is changed, or if the size, number, shape, or placement of the battery cells 22, battery block 21, or assembled battery 20 is changed, or if the shape of the housing 50 is changed, the radio wave propagation path, including the radio wave reflection angle and reflection position, is likely to change. If the radio wave propagation path is changed, the communication quality of each communication channel is also likely to change. Therefore, if the internal environment of the battery pack 11 changes, the previous channel map is likely to become useless. Therefore, in the connection process of the sixth embodiment, it is determined whether the internal environment of the battery pack 11 has changed, and then it is determined whether to acquire an updated channel map. The connection process of the sixth embodiment will be described in detail below with reference to FIG. 16 .

[0167] In the connection process of the sixth embodiment, after transmitting a connection request signal (after step S13) and before reading the channel map from the main memory 44 (before step S14), the base unit wireless IC 42 determines whether there has been a change in the internal environment of the battery pack 11 (step S500). Specifically, if the number or arrangement of the slave unit wireless ICs 32 with which the battery pack 11 communicates is changed, or if one of the slave unit wireless ICs 32 is replaced with another slave unit wireless IC 32, information indicating that the internal environment has changed is stored in the main memory 44 or the like. Therefore, the base unit wireless IC 42 reads whether or not there has been a change from the main memory 44 or the like, and performs the determination of step S500. If the determination result is positive (if there has been no change), the base unit wireless IC 42 performs the process of step S14, as in the first embodiment. If the determination result is negative (if there has been a change), the base unit wireless IC 42 initializes the channel map and stores it in the cache memory 42a (step S501). Then, the base unit wireless IC 42 proceeds to the process of step S15.

[0168] According to the sixth embodiment, the following effects are achieved.

[0169] When the internal environment of the battery pack 11 has changed and it is highly likely that the previous channel map is no longer useful, the channel map is initialized. This prevents communication channels that should have good communication quality in the current internal environment from being made unusable. It also prevents communication channels that should have poor communication quality in the current internal environment from being made unusable.

[0170] (Modification of Sixth Embodiment) A modification of the battery monitoring system 100 in the sixth embodiment will now be described.

[0171] In the sixth embodiment, a list of identification numbers of the handset-side wireless ICs 32 that are to be communication partners may be stored (managed) in the main memory 44 or the like, and if there is a change in the list, the determination result of step S500 may be denied (determined that there has been a change).

[0172] In the sixth embodiment, a list of identification numbers of the handset-side wireless ICs 32 that were the communication partners in the previous data communication may be stored (managed) in the main memory 44, etc., and if a request for connection establishment is made from a handset-side wireless IC 32 with an identification number that is not stored in the main memory 44, it may be determined that a change has occurred.

[0173] In the sixth embodiment, if there is a change in the configuration related to the internal environment, such as the casing 50 or the battery pack 20, the main memory 44 may store information indicating that the internal environment has been changed.

[0174] (Other Modifications) In the above embodiments and modifications, wireless communication may be performed at a predetermined timing, and the channel map updated based on the results of the wireless communication may be stored as an initialized channel map. The predetermined timing is preferably a timing in an environment free of external noise, such as during factory production or shipping. In this way, a channel map updated to reflect the internal environment of the battery pack 11 can be used.

[0175] In the above embodiments and modifications, wireless communication may be performed at a predetermined timing, and the channel map updated based on the results of the wireless communication may be stored as an updated channel map for use in the next wireless communication. The predetermined timing is preferably a timing when the external noise is constant or low, such as during factory production or when the vehicle is parked for a long period of time. In this way, the channel map updated to reflect the internal environment of the battery pack 11 can be used in the next wireless communication.

[0176] In each of the above embodiments and modifications, the communication quality of a communication channel for establishing a connection may be determined, and a channel map that sets whether or not the communication channel is usable may be stored.

[0177] The above-described embodiments and their modifications may be combined within the scope of possible combinations. For example, the first embodiment (and its modifications, the same applies hereinafter) may be combined with any two or more of the second embodiment (and its modifications, the same applies hereinafter) to the sixth embodiment (and its modifications, the same applies hereinafter), or all of the embodiments may be combined.

[0178] The following describes characteristic configurations extracted from the above-described embodiments.

[0179] [Configuration 1] A battery monitoring system (100) that monitors a battery unit (20, 21, 22) by transmitting and receiving battery information via wireless communication, comprising: a wireless device (30, 40) that transmits and receives information via wireless communication using a communication channel selected from a plurality of communication channels; and a storage device (44) that stores a channel map that sets whether or not the plurality of communication channels are usable, wherein the wireless device is configured to update the channel map based on a communication result during wireless communication and store the updated channel map in the storage device, and when the wireless communication starts, obtain the updated channel map stored in the storage device and select the communication channel by referring to the updated channel map.

[0180] [Configuration 2] The wireless device executes a connection process to establish a connection before starting the wireless communication, performs data communication to send and receive data related to battery information during the wireless communication, and executes a release process to release the established connection when terminating the wireless communication, and the wireless device acquires the updated channel map stored in the storage device between the start of the connection process and before the start of the data communication. This is the battery monitoring system described in Configuration 1.

[0181] [Configuration 3] In the connection process, one of the plurality of wireless devices, a slave device (30) and a master device (40), transmits a connection request signal to the other, and when the connection request signal is transmitted and received, a connection is established between the master device and the slave device, and in the connection process, the wireless device acquires the updated channel map stored in the storage device between the time the connection request signal is transmitted and received and the time the connection establishment is completed. This is the battery monitoring system described in Configuration 2.

[0182] [Configuration 4] The battery monitoring system of Configuration 2, wherein the wireless device is configured to terminate the data communication and start the release process when it receives a disconnection request signal during the data communication, and the updated channel map is stored in the storage device after receiving the disconnection request signal and before the connection is released in the release process.

[0183] [Configuration 5] The battery monitoring system according to any one of configurations 1 to 4, wherein if a communication abnormality occurs during the wireless communication, the channel map updated during the wireless communication is not saved in the storage device.

[0184] [Configuration 6] The battery monitoring system according to any one of configurations 1 to 5, wherein the wireless device does not store the updated channel map during the wireless communication in the storage device if the number of available communication channels in the updated channel map during the wireless communication falls below a predetermined threshold.

[0185] [Configuration 7] A battery monitoring system according to any one of configurations 1 to 6, wherein the wireless device refers to an initialized channel map in the next wireless communication if a communication abnormality occurs during the wireless communication, or if the number of available communication channels in the updated channel map falls below a predetermined threshold, or if an updated channel map is not stored in the storage device.

[0186] [Configuration 8] The battery monitoring system according to any one of Configurations 1 to 7, wherein the battery monitoring system is mounted on a vehicle (10), and the wireless device stores in the storage device only channel maps that are updated while the vehicle is stopped.

[0187] [Configuration 9] A battery monitoring system according to any one of configurations 1 to 8, wherein a parent device among the plurality of wireless devices is configured to store the updated channel map in the storage device, and when the wireless communication starts, reads the updated channel map stored in the storage device and transmits the read updated channel map to a child device among the plurality of wireless devices.

[0188] [Configuration 10] The battery monitoring system according to Configuration 9, wherein the channel map is provided for each of the plurality of child devices, and the parent device updates the channel map for each of the plurality of child devices and stores the updated channel map separately for each of the plurality of child devices.

[0189] [Configuration 11] The battery monitoring system according to any one of configurations 1 to 10, wherein the wireless device starts the wireless communication when the battery monitoring system is started, and ends the wireless communication when the battery monitoring system is stopped during the wireless communication.

[0190] [Configuration 12] A battery monitoring system according to any one of configurations 1 to 11, wherein the storage device is a main storage device (44) that can store and retain the saved channel map even when the battery monitoring system is stopped, and the wireless device has a cache memory (32a, 42a) that can store data temporarily, and when the wireless communication starts, the read updated channel map is saved in the cache memory, and during the wireless communication, the channel map stored in the cache memory is updated based on the communication result while referring to the channel map, and when the wireless communication ends, the updated channel map updated in the cache memory is stored in the main storage device.

[0191] [Configuration 13] A battery monitoring system according to any one of configurations 1 to 12, wherein when the number or arrangement of the wireless devices is changed, or when one of the wireless devices is replaced with another wireless device, the communication channel is selected by referring to an initialized channel map at the start of the wireless communication.

[0192] [Configuration 14] A battery monitoring system (100) comprising: a wireless device (30, 40) that transmits and receives information by wireless communication using a communication channel selected from a plurality of communication channels; and a storage device (44) that stores a channel map that sets whether the plurality of communication channels are usable; the wireless communication program to be executed by the wireless device includes: an update process that updates the channel map based on a communication result during wireless communication; a storage process that stores the updated channel map updated by the update process in the storage device; an acquisition process that acquires the updated channel map stored in the storage device at the start of the wireless communication; and a selection process that selects a communication channel by referring to the updated channel map acquired in the acquisition process.

[0193] [Configuration 15] A wireless communication method implemented by the wireless device of a battery monitoring system (100) that monitors a battery unit (20, 21, 22) by transmitting and receiving battery information via the wireless communication, the wireless device comprising: a wireless device (30, 40) that transmits and receives information via wireless communication using a communication channel selected from a plurality of communication channels; and a storage device (44) that stores a channel map that sets whether the plurality of communication channels are usable or not, the wireless communication method comprising: an update process that updates the channel map based on a communication result during wireless communication; a storage process that stores the updated channel map updated by the update process in the storage device; an acquisition process that acquires the updated channel map stored in the storage device at the start of the wireless communication; and a selection process that selects a communication channel by referring to the updated channel map acquired in the acquisition process.

[0194] The controller and methods described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the controller and methods described herein may be implemented by a special-purpose computer configured with a processor configured with one or more dedicated hardware logic circuits. Alternatively, the controller and methods described herein may be implemented by one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory storage medium.

[0195] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A battery monitoring system (100) that transmits and receives battery information via wireless communication to monitor a battery unit (20, 21, 22), comprising: a wireless device (30, 40) that transmits and receives information via wireless communication using a communication channel selected from a plurality of communication channels; and a storage device (44) that stores a channel map in which the availability of the plurality of communication channels is set, wherein the wireless device is configured to update the channel map based on a communication result during wireless communication and store the updated channel map in the storage device, and at the start of the wireless communication, obtain the updated channel map stored in the storage device and select the communication channel by referring to the updated channel map.

2. The battery monitoring system of claim 1, wherein the wireless device executes a connection process to establish a connection before the start of the wireless communication, performs data communication to send and receive data related to battery information during the wireless communication, and executes a release process to release the established connection when the wireless communication is terminated, and the wireless device acquires the updated channel map stored in the storage device between the start of the connection process and before the start of the data communication.

3. The battery monitoring system of claim 2, wherein in the connection process, one of the multiple wireless devices, a child device (30) and a parent device (40), transmits a connection request signal to the other, and when the connection request signal is transmitted and received, a connection is established between the parent device and the child device, and the wireless device acquires the updated channel map stored in the storage device during the connection process from the time the connection request signal is transmitted and received until the establishment of the connection is completed.

4. The battery monitoring system of claim 2, wherein the wireless device is configured to terminate the data communication and initiate the release process when a disconnection request signal is received during the data communication, and the updated channel map is stored in the storage device between the time when the disconnection request signal is received and the time when the connection is released in the release process.

5. A battery monitoring system as claimed in any one of claims 1 to 4, wherein if a communication abnormality occurs during the wireless communication, the channel map updated during the wireless communication is not stored in the storage device.

6. A battery monitoring system as described in any one of claims 1 to 4, wherein the wireless device does not store in the memory device an updated channel map during wireless communication if the number of available communication channels in the updated channel map during the wireless communication falls below a predetermined threshold.

7. A battery monitoring system as described in any one of claims 1 to 4, wherein the wireless device refers to an initialized channel map in the next wireless communication if a communication abnormality occurs during the wireless communication, or if the number of available communication channels in the updated channel map falls below a predetermined threshold, or if the updated channel map is not stored in the memory device.

8. A battery monitoring system as described in any one of claims 1 to 4, wherein the battery monitoring system is mounted on a vehicle (10), and the wireless device stores in the storage device only channel maps that are updated while the vehicle is stopped.

9. A battery monitoring system as described in any one of claims 1 to 4, wherein a parent unit among the plurality of wireless devices is configured to store the updated channel map in the storage device, and at the start of the wireless communication, reads the updated channel map stored in the storage device and transmits the read updated channel map to a child unit among the plurality of wireless devices.

10. The battery monitoring system of claim 9, wherein the channel map is provided for each of the plurality of child units, and the parent unit updates the channel map for each of the plurality of child units and stores the updated channel map separately for each of the plurality of child units.

11. A battery monitoring system as described in any one of claims 1 to 4, wherein the wireless device initiates the wireless communication when the battery monitoring system is started up, and terminates the wireless communication when the battery monitoring system is stopped during the wireless communication.

12. A battery monitoring system as described in any one of claims 1 to 4, wherein the storage device is a main storage device (44) capable of storing and holding the saved channel map even when the battery monitoring system is stopped, and the wireless device has a cache memory (32a, 42a) capable of temporary storage, and when the wireless communication starts, the read updated channel map is saved in the cache memory, and during the wireless communication, the channel map stored in the cache memory is referenced and updated based on the communication results, and when the wireless communication is terminated, the updated channel map updated in the cache memory is stored in the main storage device.

13. A battery monitoring system as described in any one of claims 1 to 4, wherein when the number or arrangement of the wireless devices is changed, or when any of the multiple wireless devices is replaced with another wireless device, the communication channel is selected by referring to an initialized channel map at the start of the wireless communication.

14. A battery monitoring system (100) comprising a wireless device (30, 40) that transmits and receives information via wireless communication using a communication channel selected from a plurality of communication channels, and a storage device (44) that stores a channel map in which the use of the plurality of communication channels is set, the system comprising: a wireless communication program to be executed by the wireless device; an update process to update the channel map based on communication results during wireless communication; a storage process to store an updated channel map updated by the update process in the storage device; an acquisition process to acquire the updated channel map stored in the storage device at the start of the wireless communication; and a selection process to select a communication channel by referring to the updated channel map acquired in the acquisition process.

15. A wireless communication method implemented by a wireless device of a battery monitoring system (100) comprising: a wireless device (30, 40) that transmits and receives information via wireless communication using a communication channel selected from a plurality of communication channels; and a storage device (44) that stores a channel map in which the availability of the plurality of communication channels is set; the wireless communication method including: an update process for updating the channel map based on a communication result during wireless communication; a storage process for saving an updated channel map updated by the update process in the storage device; an acquisition process for acquiring the updated channel map saved in the storage device at the start of the wireless communication; and a selection process for selecting a communication channel by referring to the updated channel map acquired in the acquisition process.

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