CN214623352U - Communication circuit of battery management system and terminal equipment - Google Patents

Abstract

The application provides a communication circuit and terminal equipment of a battery management system, wherein the communication circuit of the battery management system comprises a central control module, a first communication module, a Bluetooth communication module and a battery module, the first communication module is respectively connected with the central control module and the battery module, and the Bluetooth communication module is respectively connected with the central control module and the battery module; the Bluetooth communication module is used for providing communication connection for the central control module and the battery module when the first communication module is abnormal in communication, and the first communication module comprises an RS485 communication module or a CAN communication module. Under the condition that a large capacity is used in a plurality of parallel or a plurality of strings of traditional lithium batteries, a wireless Bluetooth communication mode CAN be adopted when a wired CAN communication module or an RS485 communication module is unstable or is disconnected, the communication stability of a battery system is greatly improved, and the probability of communication faults is reduced.

Description

Communication circuit of battery management system and terminal equipment

Technical Field

The application belongs to the technical field of battery management system communication, and particularly relates to a communication circuit of a battery management system and terminal equipment.

Background

At present, lithium batteries have become the first choice for Power supply batteries in the industries of energy storage, communication and Uninterruptible Power Supply (UPS) because of the obvious advantages of safety, energy density, applicable temperature range, service life, environmental protection and the like, and the cooperation with an intelligent battery management System.

Generally, a lithium battery needs to be equipped with a Battery Management System (BMS), and the battery management system has the functions of monitoring, managing and protecting the state of a battery array, so that the storage capacity of the battery is fully utilized and the service life of the battery is prolonged on the premise of ensuring safe use of the battery, thereby achieving the purpose of efficient use of the battery.

The battery management system of the traditional lithium battery generally adopts a Controller Area Network (CAN) or RS485 as a communication mode, but when the capacity of the lithium battery is large and a large capacity is needed to be realized in a multi-string or multi-string manner, because CAN or RS485 has limited transmission data, signals of the CAN or RS485 are easy to be unstable or drop along with the increase of communication data, and then the stability of the system is influenced.

SUMMERY OF THE UTILITY MODEL

The application aims to provide a communication circuit and terminal equipment of a battery management system, and aims to solve the problem that a CAN signal or an RS485 signal is unstable or disconnected easily along with the increase of communication data in the conventional battery management system.

In order to achieve the above object, in a first aspect, an embodiment of the present application provides a communication circuit of a battery management system, including a central control module, a first communication module, a bluetooth communication module, and a battery module, where the first communication module is connected to the central control module and the battery module, respectively, and the bluetooth communication module is connected to the central control module and the battery module, respectively;

the Bluetooth communication module is used for providing communication connection for the central control module and the battery module when the first communication module is abnormal in communication;

the first communication module comprises an RS485 communication module or a CAN communication module.

In a possible implementation manner of the first aspect, the bluetooth module includes a first chip U1, a seventh pin of the first chip U1 is electrically connected to a BLE-INT pin of the central control module, a third pin of the first chip U1 is electrically connected to a BLE-TX pin of the central control module, a second pin of the first chip U1 is electrically connected to a BLE-RX pin of the central control module, and a fourth pin of the first chip U1 is electrically connected to a BLE-wait pin of the central control module.

In another possible implementation manner of the first aspect, the RS485 communication module includes an RS485 communication unit and an RS485 selection unit, the RS485 communication unit is connected to the RS485 selection unit, and the RS485 selection unit is configured to select the RS485 communication unit as a communication medium between the central control module and the battery module.

In another possible implementation manner of the first aspect, a VIA pin of the RS485 communication unit is connected to a 485TX pin of the central control module, a VOB pin of the RS485 communication unit is connected to a 485RX pin of the central control module, and a 485TE1 pin of the RS485 communication unit is connected to a 485TE1 pin of the central control module.

In another possible implementation manner of the first aspect, an RS485SEC pin of the RS485 selection unit is connected to an RS485SEC pin of the central control module, the RS485 selection unit includes a first relay S1, a sixth pin of the first relay S1 is connected to a pin B of the battery module, and a third pin of the first relay S1 is connected to a pin a of the battery module.

In another possible implementation manner of the first aspect, the CAN communication module includes a CAN communication unit and a CAN selection unit, the CAN communication unit is connected to the CAN selection unit, and the CAN selection unit is configured to select the CAN communication unit as a communication intermediary between the central control module and the battery module.

In another possible implementation manner of the first aspect, a VIB pin of the CAN communication unit is connected to a CANTX pin of the central control module, and a VOA pin of the CAN selection unit is connected to a CANRX pin of the central control module.

In another possible implementation manner of the first aspect, the CAN SEC pin of the CAN selection unit is connected to the CAN SEC pin of the central control module, the CAN selection unit includes a second relay S2, the third pin of the second relay S2 is connected to the CAN-H pin of the battery module, and the sixth pin of the second relay S2 is connected to the CAN-L pin of the battery module.

In a second aspect, an embodiment of the present application provides a battery management system, which includes a system control module, a sampling module, and the communication circuit, where the sampling module is connected to the system control module and the communication circuit;

the sampling module is used for identifying when the communication circuit is abnormal and sending the identified abnormal information to the system control module, and the system control module is used for switching the communication module in the communication circuit according to the abnormal information.

In a third aspect, an embodiment of the present application provides a terminal device, including the battery management system.

Compared with the prior art, the embodiment of the utility model beneficial effect who exists is: the communication circuit of the battery management system is mainly communicated through the traditional RS485 communication module or the CAN communication module, and the Bluetooth module is used for standby communication.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a communication circuit of a battery management system according to an embodiment of the present disclosure;

fig. 2 is a circuit diagram of a communication circuit of a battery management system according to an embodiment of the present disclosure;

fig. 3 is a schematic structural diagram of a battery management system according to an embodiment of the present application.

Wherein, in the figures, the respective reference numerals:

1-a central control module, 2-a first communication module, 21-an RS485 communication module, 211-an RS485 communication unit, 212-an RS485 selection unit, 22-a CAN communication module, 221-a CAN communication unit, 222-a CAN selection unit, 3-a Bluetooth module, 4-a battery module, 51-a system control module and 52-a sampling module.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, refer to an orientation or positional relationship illustrated in the drawings for convenience in describing the present application and to simplify description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

Fig. 1 shows a schematic structural diagram of a communication circuit of a battery management system according to an embodiment of the present application, and for convenience of description, only the parts related to the embodiment are shown, which are detailed as follows: the Bluetooth communication device comprises a central control module 1, a first communication module 2, a Bluetooth communication module 3 and a battery module 4, wherein the first communication module 2 is respectively connected with the central control module 1 and the battery module 4, and the Bluetooth communication module 3 is respectively connected with the central control module 1 and the battery module 4;

the bluetooth communication module 3 is used for providing communication connection for the central control module 1 and the battery module 4 when the first communication module 2 has communication abnormality;

the first communication module 2 comprises an RS485 communication module 21 or a CAN communication module 22.

In this embodiment of the application, when the first communication module 2 (i.e., the RS485 communication module 21 or the CAN communication module 22) is in an unstable or offline communication abnormal condition, the abnormal communication condition is identified by the sampling module in the battery management system and the abnormal communication information is sent to the central control module 1, the central control module 1 sends a signal switching instruction to the first communication module 2 and the bluetooth module 3 according to the abnormal communication information, the first communication module 2 is cut off, the bluetooth module 3 is turned on, and therefore the communication function of the battery module 4 is continuously realized through the standby bluetooth module 3.

Fig. 2 is a circuit diagram illustrating a communication circuit of a battery management system according to another embodiment of the present disclosure, in which the bluetooth module 3 includes a first chip U1, a thirteenth pin of the first chip U1 is sequentially connected in series with a first resistor R1 and a first LED lamp D1 and then connected to a power supply VDD, a ninth pin of the first chip U1 is connected in parallel with the power supply VDD and one end of a first capacitor C1, and the fifteenth pin, the sixteenth pin, the tenth pin of the first chip U1 and the other end of the first capacitor C1 are all grounded; the seventh pin of the first chip U1 is connected in parallel with one end of a fourth resistor R4 and a BLE-INT pin of the central control module 1, the third pin of the first chip U1 is electrically connected with a BLE-TX pin of the central control module 1, the second pin of the first chip U1 is electrically connected with a BLE-RX pin of the central control module 1, the fourth pin of the first chip U1 is connected in parallel with one end of a fifth resistor R5 and a BLE-wait pin of the central control module 1, and the other end of the fourth resistor R4 and the other end of the fifth resistor R5 are both electrically connected with a power supply VDD.

In the embodiment of the application, the model of the first chip U1 is HY-40R204P, the first chip is a bluetooth 4.2BLE data transmission module, data transmission inside the battery is realized in a standby mode through a bluetooth module 3, and the bluetooth module inside each battery has a unique address to distinguish serial or parallel use of a plurality of batteries; the RS485 communication module and the CAN communication module CAN self-define the sequence of each module according to the serial communication line, and the RS485 communication module, the CAN communication module and the Bluetooth module are unique in definition and are matched with each other.

The RS485 communication module 21 comprises an RS485 communication unit 211 and an RS485 selection unit 212, the RS485 communication unit 211 is connected with the RS485 selection unit 212, and the RS485 selection unit 212 is used for selecting the RS485 communication unit 211 as a communication medium of the central control module 1 and the battery module 4.

In the embodiment of the application, the RS485 communication module 21 or the CAN communication module 22 is used as a communication mode to provide communication connection for the central control module 1 and the battery module 4. When the communication connection between the central control module 1 and the battery module 4 is realized by the RS485 communication module 21, the RS485 selection unit 212 selects the RS485 communication unit 211 to connect the battery module 4 in a wired manner, so that data information between the battery module 4 and the central control module 1 is transmitted in a wired manner through the RS485 communication unit 211.

The RS485 communication unit 211 includes a fifth chip U5, a ninth chip U9, and an eleventh chip U11, the eighth pin of the fifth chip U5 is serially connected to the seventh capacitor C7 and then grounded, the seventh pin of the fifth chip U5 is electrically connected to the 485TX pin of the central control module 1, the sixth pin of the fifth chip U5 is electrically connected to the 485RX pin of the central control module 1, the fifth pin of the fifth chip U5 is grounded, the fourth pin of the fifth chip U5 is electrically connected with the negative pole of 485V voltage, the third pin of the fifth chip U5 is electrically connected to the first pin of the ninth chip U9, the second pin of the fifth chip U5 is electrically connected to the fourth pin of the ninth chip U9, the first pin of the fifth chip U5 is connected in parallel with one end of a ninth capacitor C9, one end of an eleventh capacitor C11 and the anode of 485V voltage, the other end of the ninth capacitor C9 and the other end of the eleventh capacitor C11 are both electrically connected with the negative pole of 485V voltage;

a second pin and a third pin of the ninth chip U9 are both electrically connected to a third pin of an eleventh chip U11, a fifth pin of the ninth chip U9 is connected in parallel to one end of a seventeenth resistor R17, a third pin of a second electrostatic protection diode ZD2 and a negative electrode of 485V voltage, a sixth pin of the ninth chip U9 is connected in parallel to one end of a sixteenth resistor R16 and one end of a thirteenth resistor R13, the other end of the thirteenth resistor R13 is electrically connected to a second pin of the second electrostatic protection diode ZD2, a seventh pin of the ninth chip U9 is connected in parallel to the other end of a seventeenth resistor R17 and one end of a twelfth resistor R12, the other end of the twelfth resistor R12 is electrically connected to a first pin of the second electrostatic protection diode ZD2, and the eighth pin of the ninth chip U9 and the other end of the sixteenth resistor R16 are both electrically connected to a positive electrode of 485V voltage;

the first pin of the eleventh chip U11 is connected with the power supply VDD after being connected with the third resistor R3 in series, the second pin of the eleventh chip U11 is electrically connected with the 485TE1 pin of the central control module 1, the third pin of the eleventh chip U11 is connected with the negative electrode of 485V voltage after being connected with the twentieth resistor R20 in series, and the fourth pin of the eleventh chip U11 is electrically connected with the positive electrode of 485V voltage.

In the embodiment of the application, the hardware model of the fifth chip U5 is NSI8121, which is a digital isolation chip, and is used for transmitting signals while isolating high-voltage signals, the hardware model of the ninth chip U9 is SP485REN, which is a transceiver chip, which is used for transceiving data of a battery module, and the hardware model of the eleventh chip U11 is TLV357T/C, which is a photocoupler, which provides signal isolation, high noise suppression capability, and system protection.

The RS485 selection unit 212 includes a first relay S1, a seventh pin of the first relay S1 is electrically connected to a first pin of a second electrostatic protection diode ZD2, a second pin of the first relay S1 is electrically connected to a second pin of the second electrostatic protection diode ZD2, an eighth pin of the first relay S1 is connected to a collector of a first triode Q1 after being connected to a twenty-second resistor R22 in series, a base of the first triode Q1 is connected to an RS485SEC pin of the central control module 1 after being connected to a nineteenth resistor R19 in series, an emitter of the first triode Q1 is grounded, a sixth pin of the first relay S1 is electrically connected to a pin B of the battery module 4, and a third pin of the first relay S1 is electrically connected to a pin a of the battery module 4.

In the embodiment of the present application, the first relay S1 is an electromagnetic relay, and is configured to receive the selection instruction of the central control module 1 and select the RS485 communication unit 211, so that the data information of the battery module 4 is transmitted through the RS485 communication unit 211.

The CAN communication module 22 includes a CAN communication unit 221 and a CAN selection unit 222, the CAN communication unit 221 is connected to the CAN selection unit 222, and the CAN selection unit 222 is used for selecting the CAN communication unit 221 as a communication medium between the central control module 1 and the battery module 4.

In the embodiment of the present application, when the CAN communication module 22 is used to realize the communication connection between the central control module 1 and the battery module 4, the CAN selection unit 222 selects the CAN communication unit 221 to connect the battery module 4 through a wire, so that the data information between the battery module 4 and the central control module 1 is transmitted through the CAN communication unit 221 through a wire.

The CAN communication unit 221 includes a third chip U3 and a seventh chip U7, a first pin of the third chip U3 is connected to a power supply VDD, the second pin of the third chip U3 is electrically connected to the CANRX pin of the central control module 1, the third pin of the third chip U3 is electrically connected to the CANTX pin of the central control module 1, the fourth pin of the third chip U3 is grounded, the fifth pin of the third chip U3 is connected in parallel with the negative pole of 485V voltage, one end of a fifth capacitor C5, one end of a fourth capacitor C4 and the second pin of the seventh chip U7, the sixth pin of the third chip U3 is electrically connected to the first pin of the seventh chip U7, the seventh pin of the third chip U3 is electrically connected to the fourth pin of the seventh chip U7, the eighth pin of the third chip U3 is connected in parallel with the 485V positive electrode, the other end of the fifth capacitor C5, the other end of the fourth capacitor C4 and the third pin of the seventh chip U7;

the eighth pin of the seventh chip U7 is electrically connected to the negative electrode of 485V, the sixth pin of the seventh chip U7 is connected in parallel to one end of a fourth semiconductor discharge tube TV4, one end of a fifth semiconductor discharge tube TV5 and one end of an eighth resistor R8, the seventh pin of the seventh chip U7 is connected in parallel to the other end of a fifth semiconductor discharge tube TV5 and one end of a sixth semiconductor discharge tube TV6, and the other end of the fourth semiconductor discharge tube TV4 and the other end of a sixth semiconductor discharge tube TV6 are both electrically connected to the negative electrode of 485V.

In the embodiment of the application, the hardware model of the third chip U3 is NSI8121, which is a digital isolation chip, and is used for transmitting signals while isolating high-voltage signals, and the hardware model of the seventh chip U7 is TJA1051, which is a high-speed CAN transceiver, which provides an interface between a Controller Area Network (CAN) protocol controller and a physical two-wire CAN bus, and is used for transceiving data of a battery module. The semiconductor discharge tube is an overvoltage protection device, is manufactured by using a thyristor principle, triggers the device to conduct discharge by depending on breakdown current of a PN junction, and can flow large surge current or pulse current. The range of breakdown voltage constitutes the range of overvoltage protection.

The CAN selection unit 222 includes a second relay S2, a seventh pin of the second relay S2 is electrically connected to the other end of an eighth resistor R8, a second pin of the second relay S2 is electrically connected to the other end of a ninth resistor R9, an eighth pin of the second relay S2 is connected to a collector of a second transistor Q2 after being connected to a twenty-third resistor R23 in series, a base of the second transistor Q2 is connected to a CANSEC pin of the central control module 1 after being connected to a twenty-first resistor R21 in series, an emitter of the second transistor Q2 is grounded, a third pin of the second relay S2 is connected to a CAN-H pin of the battery module 4, and a sixth pin of the second relay S2 is connected to a CAN-L pin of the battery module 4.

In the embodiment of the present application, the second relay S2 is an electromagnetic relay, and is configured to receive a selection instruction from the central control module 1 to select the CAN communication unit 221, so as to transmit information of the battery module 4 through the CAN communication unit 221.

The specific using method comprises the following steps: installing a battery system: installing the battery system according to a conventional method; communication connection: connecting the communication cable according to a conventional method; the Bluetooth mobile phone software is installed, so that the traditional RS485 communication module or the CAN communication module is used as main communication, and the Bluetooth module is used as standby communication.

It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

Fig. 3 is a schematic diagram of a battery management system according to an embodiment of the present application. As shown in fig. 3, the battery management system of this embodiment includes: the system comprises a system control module 51, a sampling module 52 and the communication circuit, wherein the sampling module 52 is connected with the system control module 51 and the communication circuit;

the sampling module 52 is configured to identify when the communication circuit is abnormal, and send the identified abnormal information to the system control module 51, where the system control module 51 is configured to switch the communication module in the communication circuit according to the abnormal information.

In the embodiment of the application, the communication condition of the communication circuit is collected in real time through the sampling module 52, when the abnormal condition of the communication circuit is detected, the abnormal information is sent to the system control module 51, and the system control module 51 interrupts the existing communication module according to the abnormal information, namely interrupts the RS485 communication module or the CAN communication module, and then switches to adopt the bluetooth communication module.

The application is also provided with a terminal device which comprises the battery management system and realizes all functions of the battery management system.

It will be understood by those skilled in the art that fig. 3 is merely an example of a battery management system, and is not intended to be limiting, and may include more or fewer components than those shown, or some components may be combined, or different components, for example, the battery management system may further include a power-on self-test module and an interrupt module, etc.

The system control module 51 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA) or other Programmable logic device, a discrete Gate or transistor logic device, a discrete hardware component, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-mentioned division of the functional units and modules is illustrated, and in practical applications, the above-mentioned function distribution may be performed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-mentioned functions. Each functional unit and module in the embodiments may be integrated in one processing unit, or each unit may exist alone physically, or two or more units are integrated in one unit, and the integrated unit may be implemented in a form of hardware, or in a form of software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working processes of the units and modules in the system may refer to the corresponding processes in the foregoing embodiments, and are not described herein again.

In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to the related descriptions of other embodiments for parts that are not described or illustrated in a certain embodiment.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

In the embodiments provided in the present application, it should be understood that the disclosed battery management system may be implemented in other manners. For example, the above-described battery management system embodiments are merely illustrative, and for example, the division of the modules or units is only one logical functional division, and there may be other divisions when actually implemented, for example, a plurality of units or components may be combined or may be integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims (10)

1. The communication circuit of the battery management system is characterized by comprising a central control module (1), a first communication module (2), a Bluetooth communication module (3) and a battery module (4), wherein the first communication module (2) is respectively connected with the central control module (1) and the battery module (4), and the Bluetooth communication module (3) is respectively connected with the central control module (1) and the battery module (4);

the Bluetooth communication module (3) is used for providing communication connection for the central control module (1) and the battery module (4) when the first communication module (2) is abnormal in communication;

the first communication module (2) comprises an RS485 communication module (21) or a CAN communication module (22).

2. The communication circuit according to claim 1, wherein the bluetooth communication module (3) comprises a first chip U1, the seventh pin of the first chip U1 is electrically connected to the BLE-INT pin of the central control module (1), the third pin of the first chip U1 is electrically connected to the BLE-TX pin of the central control module (1), the second pin of the first chip U1 is electrically connected to the BLE-RX pin of the central control module (1), and the fourth pin of the first chip U1 is electrically connected to the BLE-wait pin of the central control module (1).

3. The communication circuit according to claim 1 or 2, wherein the RS485 communication module (21) comprises an RS485 communication unit (211) and an RS485 selection unit (212), the RS485 communication unit (211) is connected to the RS485 selection unit (212), and the RS485 selection unit (212) is configured to select the RS485 communication unit (211) as a communication medium between the central control module (1) and the battery module (4).

4. The communication circuit according to claim 3, wherein the VIA pin of the RS485 communication unit (211) is connected to the 485TX pin of the central control module (1), the VOB pin of the RS485 communication unit (211) is connected to the 485RX pin of the central control module (1), and the 485TE1 pin of the RS485 communication unit (211) is connected to the 485TE1 pin of the central control module (1).

5. The communication circuit according to claim 4, wherein the RS485SEC pin of the RS485 selection unit (212) is connected to the RS485SEC pin of the central control module (1), the RS485 selection unit (212) comprises a first relay S1, the sixth pin of the first relay S1 is connected to the B pin of the battery module (4), and the third pin of the first relay S1 is connected to the A pin of the battery module (4).

6. The communication circuit according to claim 3, wherein the CAN communication module (22) comprises a CAN communication unit (221) and a CAN selection unit (222), the CAN communication unit (221) is connected to the CAN selection unit (222), and the CAN selection unit (222) is configured to select the CAN communication unit (221) as a communication medium between the central control module (1) and the battery module (4).

7. The communication circuit according to claim 6, wherein the VIB pin of the CAN communication unit (221) is connected to the CANTX pin of the central control module (1), and the VOA pin of the CAN selection unit (222) is connected to the CANRX pin of the central control module (1).

8. The communication circuit according to claim 7, wherein the CAN SEC pin of the CAN selection unit (222) is connected to the CAN SEC pin of the central control module (1), the CAN selection unit (222) comprises a second relay S2, the third pin of the second relay S2 is connected to the CAN-H pin of the battery module (4), and the sixth pin of the second relay S2 is connected to the CAN-L pin of the battery module (4).

9. A battery management system, comprising a system control module (51), a sampling module (52) and the communication circuit of any one of claims 1 to 8, wherein the sampling module (52) connects the system control module (51) and the communication circuit;

the sampling module (52) is used for identifying when the communication circuit is abnormal and sending the identified abnormal information to the system control module (51), and the system control module (51) is used for switching the communication module in the communication circuit according to the abnormal information.

10. A terminal device characterized by comprising the battery management system of claim 9.

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