Parallel Circuit of Multiple Battery Modules and Control Method

Abstract

The present invention discloses a parallel circuit and a control method for multiple battery modules, relating to the technical field of battery parallel connection. Among them, the parallel circuit includes multiple battery modules, and each battery module includes a battery pack, a battery management system, a discharge switch, a charging switch, and a current limiting circuit. The battery management systems of multiple battery modules are communicatively connected to each other. When the absolute value of the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, the battery packs B1 and B2 are controlled to discharge externally simultaneously when battery module 2 is incorporated into battery module 1; when the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, battery pack B1 is controlled to charge battery pack B2 with current limiting; when the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, battery pack B2 is controlled to charge battery pack B1 with current limiting. The purpose of the present invention is to improve the efficiency and safety of parallel connection of multiple battery modules.

Description

Technical Field

[0001] The present invention relates to the technical field of battery parallel connection, and particularly relates to a parallel circuit and a control method for multiple battery modules. Background Art

[0002] At present, since parallel connection of multiple batteries has the advantages of increasing the total charge capacity and increasing the power output, battery parallel connection technology has received increasing attention.

[0003] However, existing battery parallel connection technologies are generally implemented by a waiting method or a probing method. For example, when two battery modules are connected in parallel, the waiting method means that the two battery modules periodically send each other the battery voltages of their respective modules, and when it is determined that the absolute value of the difference between the battery voltages of each other is lower than the parallel voltage value, they are connected in parallel. The disadvantage is that the waiting time for parallel connection is long. The probing method means that the two battery modules periodically conduct parallel connection probing, and when it is detected that the circuit current during parallel connection probing is less than the maximum charging current value of the battery module, they are connected in parallel. The disadvantage is that the instantaneous current in the circuit during parallel connection probing is likely to be too large, resulting in damage to the internal components of the battery module. Summary of the Invention

[0004] The main object of the present invention is to provide a parallel circuit for multiple battery modules, aiming to improve the efficiency and safety of parallel connection.

[0005] To achieve the above object, the parallel circuit for multiple battery modules proposed by the present invention includes multiple battery modules, and each battery module includes a battery pack, a battery management system, a discharge switch, a charging switch, and a current limiting switch;

[0006] Among them, the discharge switch is used to control the discharge of the battery pack; the charging switch is used to control the charging of the battery pack; the current limiting switch circuit is used to limit the charging current of the battery pack; the battery management system is used to control the closing / opening of the discharge switch and the charging switch, and to control the working state of the current limiting switch circuit when the battery pack is charging;

[0007] Among them, the first ends of the multiple battery modules are electrically connected to each other, and the second ends of the multiple battery modules are electrically connected to each other; the battery management systems of the multiple battery modules are communicatively connected to each other;

[0008] When the absolute value of the difference between the total voltages of battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, control battery pack B1 and battery pack B2 to discharge externally simultaneously;

[0009] When the absolute value of the difference between the total voltages of battery pack B1 and battery pack B2 is greater than the parallel voltage value, control battery pack B1 to charge battery pack B2 with current limiting;

[0010] When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, control battery pack B2 to charge battery pack B1 with current limiting.

[0011] In one embodiment, each battery module further includes a sampling resistor, an inductor, and a diode.

[0012] Wherein, the positive electrode of the battery pack, the first power supply terminal of the battery management system, the negative electrode of the diode, and the first terminal of the battery module are electrically connected; the negative electrode of the battery pack, the second power supply terminal of the battery management system, the first terminal of the sampling resistor, and the first detection terminal of the battery management system are electrically connected; the second terminal of the sampling resistor, the second detection terminal of the battery management system, and the first terminal of the discharge switch are electrically connected; the second terminal of the discharge switch, the first terminal of the charging switch, and the first terminal of the inductor are electrically connected; the second terminal of the inductor, the first terminal of the current limiting switch, and the positive electrode of the diode are electrically connected; the second terminal of the current limiting switch, the second terminal of the charging switch, and the second terminal of the battery module are electrically connected; the battery management system is further electrically connected to the controlled terminal of the battery pack, the controlled terminal of the discharge switch, the controlled terminal of the charging switch, and the controlled terminal of the current limiting switch respectively.

[0013] In one embodiment, the battery management system M1 is used to obtain the total voltage of battery pack B1 and send the total voltage of battery pack B1 to the battery management system M2; the battery management system M2 is used to obtain the total voltage of battery pack M2 and send the total voltage of battery pack M2 to the battery management system M1.

[0014] The battery management system M1 is further used for:

[0015] When the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, control the discharge switch Q11 to close, the charging switch Q12 to close, and the current limiting switch Q13 to open until the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value; or,

[0016] When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, control the discharge switch Q11 to close and the charging switch Q12 to open until the total voltage difference between battery pack B2 and battery pack B1 is less than or equal to the parallel voltage value; or,

[0017] When the absolute value of the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, control the discharge switch Q11 to close, the charging switch Q12 to close, and the current limiting switch Q13 to open.

[0018] The battery management system M2 is further used for:

[0019] When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, control the discharge switch Q21 to close, the charge switch Q22 to close, and the current-limiting switch Q23 to open until the total voltage difference between battery pack B2 and battery pack B1 is less than or equal to the parallel voltage value; or,

[0020] When the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, control the discharge switch Q21 to close and the charge switch Q22 to open until the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value; or,

[0021] When the absolute value of the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, control the discharge switch Q21 to close, the charge switch Q22 to close, and the current-limiting switch Q23 to open.

[0022] In one embodiment, the battery management system M1 is further configured to, when the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, control the closing / opening frequency of the current-limiting switch Q13 according to the voltage value across the sampling resistor R1 to control the charging current of battery pack B1.

[0023] In one embodiment, the battery management system M2 is further configured to, when the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, control the closing / opening frequency of the current-limiting switch Q23 according to the voltage value across the sampling resistor R2 to control the charging current of battery pack B2.

[0024] In one embodiment, each battery management system includes a control circuit, an analog front-end circuit, a communication circuit, a first drive circuit, and a second drive circuit;

[0025] Among them, the analog front-end circuit is electrically connected to the battery pack, the sampling resistor, the first drive circuit, and the control circuit respectively. The analog front-end circuit is configured to convert the input analog signal into a digital signal and input it to the control circuit, and to convert the digital signal output by the control circuit into an analog signal for output;

[0026] The first drive circuit is configured to drive the closing / opening of the discharge switch and the charge switch;

[0027] The second drive circuit is electrically connected to the control circuit, and the second drive circuit is configured to drive the closing / opening of the current-limiting switch;

[0028] The communication circuit is electrically connected to the control circuit, and the communication circuit is configured to send / receive communication data;

[0029] The control circuit is configured to control the operation of the analog front-end circuit, the first drive circuit, the second drive circuit, and the communication circuit.

[0030] In one embodiment, each battery management system further includes:

[0031] A first voltage conversion circuit, which is electrically connected to the battery pack and the analog front-end circuit respectively. The first voltage conversion circuit is used to convert the output voltage of the battery pack into a first voltage to supply power to the analog front-end circuit;

[0032] A second voltage conversion circuit, which is electrically connected to the battery pack and the control circuit respectively. The second voltage conversion circuit is used to convert the output voltage of the battery pack into a second voltage to supply power to the control circuit.

[0033] In one embodiment, the discharge switch, the charge switch and the current-limiting switch are all MOS transistors.

[0034] The present invention also provides a control method, which is applied to a parallel circuit of multiple battery modules;

[0035] Wherein, the parallel circuit of multiple battery modules includes multiple battery modules. Each battery module includes a battery pack, a battery management system, a sampling resistor, a discharge switch, a charge switch, a current-limiting switch, an inductor and a diode. The positive electrode of the battery pack, the first power supply terminal of the battery management system, and the negative electrode of the diode are electrically connected to the first end of the battery module. The negative electrode of the battery pack, the second power supply terminal of the battery management system, and the first end of the sampling resistor are electrically connected to the first detection terminal of the battery management system. The second end of the sampling resistor, the second detection terminal of the battery management system, and the first end of the discharge switch are electrically connected. The second end of the discharge switch, the first end of the charge switch, and the first end of the inductor are electrically connected. The second end of the inductor, the first end of the current-limiting switch, and the positive electrode of the diode are electrically connected. The second end of the current-limiting switch, the second end of the charge switch, and the second end of the battery module are electrically connected. The battery management system is also electrically connected to the controlled terminal of the battery pack, the controlled terminal of the discharge switch, the controlled terminal of the charge switch, and the controlled terminal of the current-limiting switch respectively. The first ends of multiple battery modules are electrically connected to each other, and the second ends of multiple battery modules are electrically connected to each other. The battery management systems of multiple battery modules are communicatively connected to each other;

[0036] The control method includes:

[0037] S1: The battery management system M1 obtains the total voltage of the battery pack B1 and sends it to the battery management system M2. The battery management system M2 obtains the total voltage of the battery pack B2 and sends it to the battery management system M1;

[0038] S2: When the absolute value of the difference between the total voltages of the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, the battery management system M1 controls the discharge switch Q11 to close, the charge switch Q12 to close, and the current-limiting switch Q13 to open. The battery management system M2 controls the discharge switch Q21 to close, the charge switch Q22 to close, and the current-limiting switch Q23 to open;

[0039] S3: When the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, battery management system M1 controls discharge switch Q11 to close, charge switch Q12 to close, and current-limiting switch Q13 to open; and, battery management system M2 controls discharge switch Q21 to close and charge switch Q22 to open, until the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, then return to step S2;

[0040] S4: When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, battery management system M2 controls discharge switch Q21 to close, charge switch Q22 to close, and current-limiting switch Q23 to open; and, battery management system M1 controls discharge switch Q11 to close and charge switch Q12 to open, until the total voltage difference between battery pack B2 and battery pack B1 is less than or equal to the parallel voltage value, then return to step S2.

[0041] In an embodiment, step S3 further includes: when the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, controlling the closing / opening frequency of current-limiting switch Q23 according to the voltage value across sampling resistor R2, so as to control the charging current of battery pack B2;

[0042] Step S4 further includes: when the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, controlling the closing / opening frequency of current-limiting switch Q13 according to the voltage value across sampling resistor R1, so as to control the charging current of battery pack B1.

[0043] The technical solution of the present invention adopts a parallel circuit of multiple battery modules, including multiple battery modules. Each battery module includes a battery pack, a battery management system, a discharge switch, a charging switch, and a current limiting circuit. Among them, when battery module 2 is incorporated into battery module 1, the battery management system M1 can obtain the total voltage value of the battery pack B1 and send it to the battery management system M2; the battery management system M2 can obtain the total voltage value of the battery pack B2 and send it to the battery management system M1. The battery management system M1 and the battery management system M2 compare the total voltages of the battery pack B1 and the battery pack B2. When the absolute value of the difference between the total voltages of the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, the battery pack B1 and the battery pack B2 can be controlled to discharge externally simultaneously. When the difference between the total voltages of the battery pack B1 and the battery pack B2 is greater than the parallel voltage value, the battery pack B1 can be controlled to charge the battery pack B2 with current limiting. When the difference between the total voltages of the battery pack B2 and the battery pack B1 is greater than the parallel voltage value, the battery pack B2 can be controlled to charge the battery pack B1 with current limiting. Thus, compared with the waiting method, the waiting time for parallel connection in the present invention is short. Compared with the probing method, parallel connection is only performed when the absolute value of the difference between the total voltages of the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value. The loop current generated during parallel connection is less than or equal to the maximum charging current value of the battery module, and the induced inductive voltage is small. Thus, the present invention improves the efficiency and safety of parallel connection of multiple battery modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0045] Figure 1 Schematic structural diagram of an embodiment of the parallel circuit of multiple battery modules provided by the present invention;

[0046] Figure 2 Schematic structural diagram of multiple parallel states of another embodiment of the parallel circuit of multiple battery modules provided by the present invention;

[0047] Figure 3 Schematic structural diagram of another embodiment of the parallel circuit of multiple battery modules provided by the present invention;

[0048] Figure 4 Schematic flowchart of an embodiment of the control method provided by the present invention.

[0049] Explanation of the reference numerals in the drawings:

[0050] 1. Battery module 1; 2. Battery module 2;

[0051] B1. Battery pack B1; M1. Battery management system M1; R1. Sampling resistor R1; Q11. Discharge switch Q11; Q12. Charging switch Q12; Q13. Current limiting switch Q13; L1. Inductor L1; D1. Diode D1;

[0052] B2. Battery pack B2; M2. Battery management system M2; R2. Sampling resistor R2; Q21. Discharge switch Q21; Q22. Charging switch Q22; Q23. Current limiting switch Q23; L2. Inductor L2; D2. Diode D2.

[0053] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0054] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0055] It should be noted that all the directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0056] In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions appears to be contradictory or unable to be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0057] It should be noted that when two battery modules are connected in parallel, if the voltages of the battery packs of the two battery modules are different, the battery pack with a higher voltage will tend to provide more current than the battery pack with a lower voltage, which can easily lead to over-discharge of the battery pack with a higher voltage, while the battery pack with a lower voltage may be charged or under-discharged, which can easily cause damage to the two battery packs and shorten their service life. Moreover, when the voltage difference between the battery packs of the two battery modules is too large, parallel connection can easily cause a large current to flow, which can cause battery overheating and lead to safety issues such as battery swelling, leakage, or even explosion.

[0058] It should be noted that in the existing battery parallel connection technology, a maximum charging current value can generally be defined, that is, the maximum charging current value allowed for safe charging of the battery module.

[0059] It should be noted that the existing battery parallel connection technology generally performs battery parallel connection through a waiting mode or a trial mode. For example, when two battery modules are connected in parallel, the waiting mode is that the two battery modules periodically send the battery voltages of their respective modules to each other, and when the absolute value of the difference between the battery voltages is determined to be lower than the parallel voltage value, they are connected in parallel. The disadvantage is that the waiting time for parallel connection is long. The trial mode is that the two battery modules periodically conduct parallel connection trials, and when the circuit current is less than the maximum charging current value of the battery module during the parallel connection trial, they are connected in parallel. The disadvantage is that the charging switch needs to be frequently switched during the parallel connection trial, and the instantaneous current of the circuit is easily too large, resulting in the generated inductive induced voltage may be extremely high, which is easy to exceed the tolerance range of the circuit components, and there is a risk of damaging the circuit components.

[0060] The present invention provides a parallel circuit of multiple battery modules, including multiple battery modules, each battery module including a battery pack, a battery management system, a discharge switch, a charge switch and a current limiting switch;

[0061] Among them, the discharge switch is used to control the discharge of the battery pack; the charging switch is used to control the charging of the battery pack; the current limiting switch circuit is used to limit the charging current of the battery pack; the battery management system is used to control the closing / opening of the discharge switch and the charging switch, and control the working state of the current limiting switch circuit when the battery pack is charging;

[0062] The first ends of the plurality of battery modules are electrically connected to each other, and the second ends of the plurality of battery modules are electrically connected to each other; the battery management systems of the plurality of battery modules are communicatively connected to each other;

[0063] When the absolute value of the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, the battery pack B1 and the battery pack B2 are controlled to discharge simultaneously;

[0064] When the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, control battery pack B1 to charge battery pack B2 with current limiting.

[0065] When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, control battery pack B2 to charge battery pack B1 with current limiting.

[0066] It should be noted that battery module 1 and battery module 2 can be any two different battery modules among multiple battery modules. Battery module 1 includes battery pack B1, battery management system M1, discharge switch Q11, charging switch Q12 and current limiting switch Q13, and battery module 2 includes battery pack B2, battery management system M2, discharge switch Q21, charging switch Q22 and current limiting switch Q23.

[0067] It should be noted that the specific value of the parallel voltage value can be set according to the specific value of the maximum charging current value of the battery module, for example, it can be a value less than or equal to the first voltage value. Among them,

[0068] The first voltage value = maximum charging current value * equivalent resistance of the charging circuit;

[0069] Among them, the equivalent resistance of the charging circuit represents the equivalent resistance of the charging circuit when battery module 1 charges battery module 2, and the minimum value can be taken when the equivalent resistance of the charging circuit fluctuates.

[0070] In this embodiment, when battery module 1 and battery module 2 are connected in parallel, battery management system M1 can obtain the total voltage value of battery pack B1 and send it to battery management system M2; battery management system M2 can obtain the total voltage value of battery pack B2 and send it to battery management system M1. Battery management system M1 and battery management system M2 compare the total voltages of battery pack B1 and battery pack B2. When the absolute value of the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, battery pack B1 and battery pack B2 can be controlled to discharge externally at the same time. When the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, battery pack B1 can be controlled to charge battery pack B2 with current limiting. When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, battery pack B2 can be controlled to charge battery pack B1 with current limiting. Thus, compared with the waiting method, the time for parallel connection in this embodiment is short, and compared with the probing method, parallel connection is only performed when the absolute value of the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, and the loop current generated during parallel connection is less than or equal to the maximum charging current. Thus, this embodiment improves the efficiency and safety of parallel connection of multiple battery modules.

[0071] It should be noted that after the battery module 1 and the battery module 2 are connected in parallel to form a battery module, the battery module 1 and the battery module 2 can be used as synchronous battery modules and connected in parallel with the next battery module, that is, the battery module 1, the battery module 2 and the next battery module discharge synchronously, or the battery module 1 and the battery module 2 charge the next battery module synchronously, or the next battery module charges the battery module 1 and the battery module 2 synchronously, so as to realize the parallel connection of the battery module 1, the battery module 2 and the next battery module, and so on, until the parallel connection of multiple battery modules is realized. In this way, multiple battery modules can be connected in parallel in this embodiment.

[0072] In the present invention, when the battery module 1 and the battery module 2 are connected in parallel, the battery management system M1 can obtain the total voltage value of the battery pack B1 and send it to the battery management system M2; the battery management system M2 can obtain the total voltage value of the battery pack B2 and send it to the battery management system M1. The battery management system M1 and the battery management system M2 compare the total voltages of the battery pack B1 and the battery pack B2. When the absolute value of the difference between the total voltages of the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, the battery pack B1 and the battery pack B2 can be controlled to discharge externally at the same time. When the difference between the total voltages of the battery pack B1 and the battery pack B2 is greater than the parallel voltage value, the battery pack B1 can be controlled to charge the battery pack B2 with current limiting. When the difference between the total voltages of the battery pack B2 and the battery pack B1 is greater than the parallel voltage value, the battery pack B2 can be controlled to charge the battery pack B1 with current limiting. In this way, compared with the waiting method, the present invention has a shorter parallel connection time. Compared with the probing method, parallel connection is only carried out when the absolute value of the difference between the total voltages of the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, and the loop current generated during parallel connection is less than or equal to the maximum charging current. In this way, the present invention improves the efficiency and safety of parallel connection of multiple battery modules.

[0073] Please refer to Figure 1 and Figure 3 , in an embodiment of the present invention, the current limiting switch circuit includes a sampling resistor, a current limiting switch, an inductor and a diode;

[0074] Among them, the positive electrode of the battery pack, the first power supply terminal of the battery management system, and the negative electrode of the diode are electrically connected to the first end of the battery module; the negative electrode of the battery pack, the second power supply terminal of the battery management system, and the first end of the sampling resistor are electrically connected to the first detection terminal of the battery management system; the second end of the sampling resistor and the second detection terminal of the battery management system are electrically connected to the first end of the discharge switch; the second end of the discharge switch and the first end of the charging switch are electrically connected to the first end of the inductor; the second end of the inductor and the first end of the current limiting switch are electrically connected to the positive electrode of the diode; the second end of the current limiting switch and the second end of the charging switch are electrically connected to the second end of the battery module; the battery management system is also respectively electrically connected to the controlled terminal of the battery pack, the controlled terminal of the discharge switch, the controlled terminal of the charging switch, and the controlled terminal of the current limiting switch.

[0075] In this embodiment, the voltage difference across the sampling resistor can reflect the actual current magnitude. Furthermore, the battery management system can precisely control the charging and discharging states of the battery pack based on the sampling signal, avoiding damage to the battery pack caused by overcurrent. The introduction of the inductor helps to smooth the current, reduce the impact of current fluctuations on the battery pack and other circuit components, and improve the stability and efficiency of the battery module. During the charging process, the circuit composed of the inductor and the diode can provide an energy buffering path when the charging switch operates, avoiding voltage spikes and protecting the battery and other circuit components. The battery management system is electrically connected to each controlled terminal, enabling highly flexible charging and discharging strategies, that is, it can adjust the charging / discharging speed according to different working conditions to meet the requirements of different usage scenarios and extend the battery life. By continuously monitoring the voltage across the sampling resistor, the battery management system can also detect abnormal conditions in the circuit in advance and send early warning information about line faults.

[0076] Please refer to Figure 1 and Figure 2 , in an embodiment of the present invention, the battery management system M1 is used to obtain the total voltage of the battery pack B1 and send the total voltage of the battery pack B1 to the battery management system M2; the battery management system M2 is used to obtain the total voltage of the battery pack M2 and send the total voltage of the battery pack M2 to the battery management system M1;

[0077] The battery management system M1 is further used for:

[0078] When the voltage difference between the battery pack B1 and the battery pack B2 is greater than the parallel voltage value, controlling the discharge switch Q11 to close, the charging switch Q12 to close, and the current limiting switch Q13 to open until the voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value; or,

[0079] When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, control the discharge switch Q11 to close and the charging switch Q12 to open until the total voltage difference between battery pack B2 and battery pack B1 is less than or equal to the parallel voltage value; or,

[0080] When the absolute value of the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, control the discharge switch Q11 to close, the charging switch Q12 to close, and the current-limiting switch Q13 to open;

[0081] The battery management system M2 is further configured to:

[0082] When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, control the discharge switch Q21 to close, the charging switch Q22 to close, and the current-limiting switch Q23 to open until the total voltage difference between battery pack B2 and battery pack B1 is less than or equal to the parallel voltage value; or,

[0083] When the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, control the discharge switch Q21 to close and the charging switch Q22 to open until the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value; or,

[0084] When the absolute value of the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, control the discharge switch Q21 to close, the charging switch Q22 to close, and the current-limiting switch Q23 to open.

[0085] In this embodiment, when the battery modules are connected in parallel, the battery management system M1 can obtain the total voltage value of battery pack B1 and send it to the battery management system M2; the battery management system M2 can obtain the total voltage value of battery pack B2 and send it to the battery management system M1. The battery management systems M1 and M2 compare the total voltages of battery packs B1 and B2.

[0086] When the absolute value of the total voltage difference between battery packs B1 and B2 is less than or equal to the parallel voltage value, battery packs B1 and B2 can be controlled to discharge externally simultaneously. At this time, battery packs B1 and B2 are in a discharging state. The battery management system M1 controls the discharge switch Q11 to close, the charging switch Q12 to close, and the current-limiting switch Q13 to open, and the battery management system M2 controls the discharge switch Q21 to close, the charging switch Q22 to close, and the current-limiting switch Q23 to open.

[0087] When the total voltage difference between battery pack B1 and battery pack B2 is greater than the parallel voltage value, battery pack B1 is in the discharging state and battery pack B2 is in the charging state. The battery management system M1 controls the closing of the discharging switch Q11, the closing of the charging switch Q12, and the opening of the current-limiting switch Q13, and the battery management system M2 controls the closing of the discharging switch Q21 and the opening of the charging switch Q22 until the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value.

[0088] When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, battery pack B2 is in the discharging state and battery pack B1 is in the charging state. The battery management system M1 controls the closing of the discharging switch Q21, the closing of the charging switch Q22, and the opening of the current-limiting switch Q23, and the battery management system M2 controls the closing of the discharging switch Q21, the closing of the charging switch Q22, and the opening of the current-limiting switch Q23 until the total voltage difference between battery pack B2 and battery pack B1 is less than or equal to the parallel voltage value.

[0089] In this way, in this embodiment, by controlling the closing / opening of the discharging switch, the charging switch, and the current-limiting switch, the parallel connection of battery module 1 and battery module 2 can be performed when the absolute value of the total voltage difference between battery pack B1 and battery pack B2 is less than or equal to the parallel voltage value, and the loop current generated during parallel connection is less than or equal to the maximum charging current value of the battery module, and the inductive voltage generated is small. In this way, this embodiment can improve the efficiency and safety of parallel connection of multiple battery modules.

[0090] Please refer to Figure 2 , in an embodiment of the present invention, the battery management system M1 is further configured to, when the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, control the closing / opening frequency of the current-limiting switch Q13 according to the voltage value across the sampling resistor R1 to control the charging current of battery pack B1.

[0091] In this embodiment, when the current-limiting switch Q13 is closed, a charging loop of battery module 2, the positive electrode of battery pack B1, the negative electrode of battery pack B1, the sampling resistor R1, the discharging switch Q11, the inductor L1, and the current-limiting switch Q13 to battery module 2 is formed, and at this time, the inductor L1 stores energy. When the current-limiting switch Q13 is opened, a charging loop of the inductor L1, the diode D1, the positive electrode of battery pack B1, the negative electrode of battery pack B1, the sampling resistor R1, and the discharging switch Q11 to the inductor L1 is formed, and at this time, the energy stored in the inductor L1 is released. The battery management system M1 can adjust the average output power by changing the duty cycle of the control signal of the current-limiting switch (i.e., the ratio of the closing time to the total cycle time in one cycle). In this way, in this embodiment, when battery pack B2 discharges to battery pack B1, the charging current for charging battery pack B1 can be limited to avoid the charging current being greater than the maximum charging current and damaging the circuit.

[0092] Please refer to Figure 2 In an embodiment of the present invention, the battery management system M2 is further configured to control the closing / opening frequency of the current-limiting switch Q23 according to the voltage value across the sampling resistor R2 when the total voltage difference between the battery pack B1 and the battery pack B2 is greater than the parallel voltage value, so as to control the charging current of the battery pack B2.

[0093] In this embodiment, when the current-limiting switch Q23 is closed, a charging circuit of the battery module 1, the positive electrode of the battery pack B2, the negative electrode of the battery pack B2, the sampling resistor R2, the discharge switch Q21, the inductor L2, and the current-limiting switch Q23 to the battery module 1 is formed, and at this time, the inductor L2 stores energy. When the current-limiting switch Q23 is opened, a charging circuit of the inductor L2, the diode D2, the positive electrode of the battery pack B2, the negative electrode of the battery pack B2, the sampling resistor R2, and the discharge switch Q21 to the inductor L2 is formed, and at this time, the energy stored in the inductor L2 is released. The battery management system M2 can adjust the average output power by changing the duty cycle of the control signal of the current-limiting switch (i.e., the ratio of the closing time to the total cycle time in one cycle). Thus, in this embodiment, when the battery pack B1 discharges to the battery pack B2, the charging current of the battery pack B2 can be limited to avoid the charging current being greater than the maximum charging current and damaging the circuit.

[0094] Please refer to Figure 3 In an embodiment of the present invention, each battery management system includes a control circuit, an analog front-end circuit, a communication circuit, a first driving circuit, and a second driving circuit;

[0095] Among them, the analog front-end circuit is electrically connected to the battery pack, the sampling resistor, the first driving circuit, and the control circuit respectively. The analog front-end circuit is configured to convert the input analog signal into a digital signal and input it to the control circuit, and to convert the digital signal output by the control circuit into an analog signal for output;

[0096] The first driving circuit is configured to drive the closing / opening of the discharge switch and the charging switch;

[0097] The second driving circuit is electrically connected to the control circuit, and the second driving circuit is configured to drive the closing / opening of the current-limiting switch;

[0098] The communication circuit is electrically connected to the control circuit, and the communication circuit is configured to send / receive communication data;

[0099] The control circuit is configured to control the operation of the analog front-end circuit, the first driving circuit, the second driving circuit, and the communication circuit.

[0100] In this embodiment, each battery management system integrates multiple core functional modules such as control, analog signal processing, drive control, and communication, which facilitates system maintenance and upgrade and can meet diverse requirements. Among them, the analog front-end circuit, as a bridge for the control circuit to interact with the battery pack, can convert the analog signals of the battery state and sampling information (such as voltage and current) into digital signals for the control circuit to process. The control circuit can output a first control signal, which is converted into an analog signal by the analog front-end circuit and output to the first drive circuit. The first drive circuit can control the closing / opening of the discharge switch and the charging switch to control the discharge / charging of the battery pack. The control circuit can output a second control signal to control the closing / opening frequency of the current-limiting switch, which can effectively adjust the magnitude of the charging current and prevent damage caused by overcurrent. The communication circuit enables communication connections between the battery management systems of different battery modules. Thus, in this embodiment, the parallel control of multiple battery modules can be achieved through the control circuit, analog front-end circuit, communication circuit, first drive circuit, and second drive circuit.

[0101] Please refer to Figure 3 , in an embodiment of the present invention, each battery management system further includes:

[0102] A first voltage conversion circuit, which is electrically connected to the battery pack and the analog front-end circuit respectively. The first voltage conversion circuit is used to convert the output voltage of the battery pack into a first voltage to supply power to the analog front-end circuit;

[0103] A second voltage conversion circuit, which is electrically connected to the battery pack and the control circuit respectively. The second voltage conversion circuit is used to convert the output voltage of the battery pack into a second voltage to supply power to the control circuit.

[0104] In this embodiment, the first voltage conversion circuit can convert the output voltage of the battery pack into a first voltage to supply power to the analog front-end circuit, and the second voltage conversion circuit can convert the output voltage of the battery pack into a second voltage to supply power to the control circuit.

[0105] In an embodiment of the present invention, the discharge switch, the charging switch, and the current-limiting switch are all MOS transistors.

[0106] In this embodiment, due to its characteristics such as low on-resistance, high-speed switching ability, easy integration and control, and strong breakdown voltage ability, the MOS transistor is suitable for being used as the discharge switch, the charging switch, and the current-limiting switch of the battery module.

[0107] Please refer to Figure 3 , and the working principle of the present invention will be specifically described below in conjunction with Figure 3 as follows:

[0108] It should be noted that the present invention aims to solve the disadvantages of the waiting method and the probing method in the battery parallel connection technology, and achieve the purpose of improving the efficiency and safety of parallel connection of multiple battery modules. Taking the Figure 3 circuit as an example, when battery module 1 and battery module 2 are connected in parallel:

[0109] In the waiting method, P1+ of battery module 1 is connected to P2+ of battery module 2, P1- of battery module 1 is connected to P2- of battery module 2, and the communication circuits of battery module 1 and battery module 2 are connected. The control circuit in battery module 1 can read the total voltage V1 of battery pack B1 in this battery module, and the control circuit in battery module 2 reads the total voltage V2 of battery pack B2 in this battery module. The total voltage of this battery module is sent to the other party through their respective communication circuits. The control circuit of battery module 1 compares the magnitudes of V1 and V2, and the control circuit of battery module 2 also compares the magnitudes of V1 and V2. If V1 > V2 and (V1 - V2) is greater than the parallel connection voltage value, the control circuit of battery module 1 closes discharge switch Q11, closes charge switch Q12, and opens current limiting switch Q13, and battery module 1 discharges. The discharge switch 21, charge switch Q22, and current limiting switch Q23 of battery module 2 remain open, and battery module 2 does not discharge. When V1 > V2 and (V1 - V2) is less than the parallel connection voltage value, battery module 2 closes discharge switch 21 and charge switch Q22. At this time, battery module 1 and battery module 2 are connected in parallel. This method requires a long time to wait for parallel connection, and the response speed is slow.

[0110] In the trial mode, P1+ of battery module 1 is connected to P2+ of battery module 2, P1- of battery module 1 is connected to P2- of battery module 2, and then the communication circuit of battery module 1 is connected to the communication circuit of battery module 2. The control circuit in battery module 1 reads the total voltage V1 of battery group B1 in this battery module, and the control circuit in battery module 2 reads the total voltage V2 of battery group B1 in this battery module. The total voltage of this battery module is sent to each other through their respective communication circuits. The control circuit of battery module 1 compares the sizes of V1 and V2, and the control circuit of battery module 2 also compares the sizes of V1 and V2. If V1>V2, and (V1-V2) is greater than the parallel voltage value, battery module 1 can send a notification to battery module 2 through the communication circuit, declaring that battery module 1 is the main package and battery module 2 is the secondary package. If V1 <V2,并且(V2-V1)大于并联电压值。电池模块2就通过通信电路向电池模块1发送通知,声明电池模块2为主包,电池模块1为副包。以V1> V2, and (V1-V2) is greater than the parallel voltage value, that is, battery module 1 is the main package and battery module 2 is the secondary package for illustration. At this time, a parallel test is performed, that is, battery module 1 controls the discharge switch Q11 to be closed, the charging switch Q12 to be closed, and the current limiting switch Q13 to be disconnected, and battery module 2 controls the discharge switch Q21 to be closed, the charging switch Q22 to be closed, and the current limiting switch Q23 to be disconnected, and the loop current during the parallel test is calculated by detecting the voltage of the sampling resistor R2. If the loop current during the parallel test is greater than the maximum charging current, the discharge switch Q21 of the battery module 2 is closed, the charging switch Q22 is disconnected, and the current limiting switch Q23 is closed, and the battery module 1 charges the battery module 2. A parallel test is performed every time T, that is, the charging switch Q22 is controlled to be closed once, the current limiting switch Q23 is controlled to be disconnected once, and the loop current during the parallel test is calculated by detecting the voltage of R2. Until the loop current during the parallel test is less than or equal to the maximum charging current, the control circuit of the battery module 2 controls the charging switch Q22 to close and controls the current limiting switch Q23 to open, so that the battery module 1 and the battery module 2 are connected in parallel. However, due to the inductance effect of the circuit element, when the inductance value of the circuit element is L0, according to the inductance induced voltage formula Um=L0*di / dt, before and after the process of controlling the charging switch Q22 to close and the current limiting switch Q23 to open at intervals of T, since the loop current during the parallel test is greater than the maximum charging current, the time for controlling the charging switch Q22 to close / open is very short, at the microsecond level, and the di / dt is very large. In this way, the inductance induced voltage Um of the circuit element will be very large, which is easy to exceed its own withstand voltage value and cause damage. That is, when the parallel connection is performed in a trial manner, the inductance induced voltage is very large, which is easy to cause damage to the circuit components.

[0111] In the present invention, to solve the above problems and achieve the purpose of improving the efficiency and safety of parallel connection of multiple battery modules, a novel parallel circuit for multiple battery modules is proposed. Specifically:

[0112] Taking Figure 3 the circuit as an example, when battery module 1 and battery module 2 are connected in parallel, connect P1+ of battery module 1 and P2+ of battery module 2, connect P1- of battery module 1 and P2- of battery module 2, and connect the communication circuits of battery module 1 and battery module 2. The control circuit in battery module 1 can read the total voltage V1 of battery pack B1 of this battery module, and the control circuit in battery module 2 can read the total voltage V2 of battery B2 in this battery pack. The total voltage of this battery pack can be sent to the other party through their respective communication circuits. The control circuit of battery module 1 can compare the magnitudes of V1 and V2, and the control circuit of battery module 2 can also compare the magnitudes of V1 and V2. If V1 > V2 and (V1 - V2) is greater than the parallel voltage value, battery module 1 can send a notification to battery module 2 through the communication circuit, declaring that battery module 1 is the main pack and battery module 2 is the secondary pack. If V1 < V2 and (V2 - V1) is greater than the parallel voltage value, battery module 2 can send a notification to battery module 1 through the communication circuit, declaring that battery module 2 is the main pack and battery module 1 is the secondary pack.

[0113] Taking V1 > V2 and (V1 - V2) being greater than the parallel voltage value, that is, battery module 1 is the main pack and battery pack 2 is the secondary pack as an example for illustration. At this time, the control circuit of battery module 1 controls the discharge switch Q11 to close, the charging switch Q12 to close, and the current-limiting switch Q13 to open. The control circuit of battery module 2 controls the discharge switch Q21 to close and the charging switch Q22 to open, and the control circuit of battery module 2 controls the closing / opening frequency of the current-limiting switch Q23 according to the voltage value across the sampling resistor R2 to control the charging current of battery pack B2, so as to achieve current-limiting charging of battery module 2. Specifically:

[0114] When the current-limiting switch Q23 is closed, the current flow direction is: P1+ of battery module 1, P2+ of battery module 2, battery pack B2, sampling resistor R2, discharge switch Q21, inductor L2, current-limiting switch Q23, P2- of battery module 2, P1- of battery module 1, charging switch Q12, discharge switch Q11, sampling resistor R1, battery pack B1 until P1+ of battery module 1. When the current-limiting switch Q23 is open, the current flow direction is: inductor L2, diode D2, P2+ of battery module 2, battery pack B2, sampling resistor R2, discharge switch Q21 until inductor L2.

[0115] During this process, battery module 1 is discharging and battery module 2 is charging. Therefore, V1 is decreasing and V2 is increasing. The control circuit of battery module 1 sends the total voltage V1 of battery pack B1 to battery module 2 through the communication circuit. The control circuit of battery module 2 can read the total voltage V2 of battery module 2 and compare it with V1. If V1 > V2 and (V1 - V2) is greater than the parallel voltage value, the current-limiting charging process continues. If V1 > V2 and (V1 - V2) is less than or equal to the parallel voltage value, then control battery pack B1 and battery pack B2 to discharge externally at the same time, and the parallel connection of battery module 1 and battery module 2 can be completed.

[0116] At this time, since the parallel voltage value is less than or equal to the first voltage value, and the first voltage value = maximum charging current value * equivalent resistance of the charging circuit. Among them, the equivalent resistance of the charging circuit represents the equivalent resistance of the charging circuit when battery module 1 charges battery module 2, specifically the impedance sum of all devices and traces in P1+ of battery module 1, P2+ of battery module 2, battery pack B2, sampling resistor R2, discharge switch Q21, inductor L2, current-limiting switch Q23, P2- of battery module 2, P1- of battery module 1, charging switch Q12, discharge switch Q11, sampling resistor R1, battery pack B1 and P1+ of battery module 1. That is, it can satisfy that the loop current when battery module 1 and battery module 2 are in parallel is less than or equal to the maximum charging current value. When the inductance value of the circuit element is L0, according to the inductance induced voltage formula Um = L0 * di / dt, when V1 > V2 and (V1 - V2) is less than or equal to the parallel voltage value, since during current-limiting charging, the charging switch is always in the off state and the loop current during parallel connection is less than or equal to the maximum charging current value, that is, di / dt is also relatively small, generally only dozens of amperes, then the inductance induced voltage Um is also very small and will not cause damage to the circuit elements. In summary, the present invention achieves the purpose of improving the efficiency and safety of parallel connection of multiple battery modules.

[0117] Please refer to Figure 1 and Figure 4 , the present invention also proposes a control method, and the control method is applied to a parallel circuit of multiple battery modules;

[0118] Among them, the parallel circuit of multiple battery modules includes multiple battery modules, and each battery module includes a battery pack, a battery management system, a sampling resistor, a discharge switch, a charging switch, a current limiting switch, an inductor and a diode; the positive electrode of the battery pack, the first power supply terminal of the battery management system, the negative electrode of the diode are electrically connected to the first end of the battery module; the negative electrode of the battery pack, the second power supply terminal of the battery management system, the first end of the sampling resistor are electrically connected to the first detection terminal of the battery management system; the second end of the sampling resistor, the second detection terminal of the battery management system are electrically connected to the first end of the discharge switch; the second end of the discharge switch, the first end of the charging switch are electrically connected to the first end of the inductor; the second end of the inductor, the first end of the current limiting switch are electrically connected to the positive electrode of the diode; the second end of the current limiting switch, the second end of the charging switch are electrically connected to the second end of the battery module; the battery management system is also respectively electrically connected to the controlled terminal of the battery pack, the controlled terminal of the discharge switch, the controlled terminal of the charging switch and the controlled terminal of the current limiting switch; the first ends of multiple battery modules are electrically connected to each other, and the second ends of multiple battery modules are electrically connected to each other; the battery management systems of multiple battery modules are communicatively connected to each other;

[0119] The steps of the control method include:

[0120] Step S1, the battery management system M1 obtains the total voltage of the battery pack B1 and sends it to the battery management system M2; the battery management system M2 obtains the total voltage of the battery pack B2 and sends it to the battery management system M1;

[0121] Step S2, when the absolute value of the difference between the total voltages of the battery packs B1 and B2 is less than or equal to the parallel voltage value, the battery management system M1 controls the discharge switch Q11 to close, the charging switch Q12 to close and the current limiting switch Q13 to open; the battery management system M2 controls the discharge switch Q21 to close and the charging switch Q22 to close and the current limiting switch Q23 to open;

[0122] Step S3, when the difference between the total voltages of the battery packs B1 and B2 is greater than the parallel voltage value, the battery management system M1 controls the discharge switch Q11 to close, the charging switch Q12 to close and the current limiting switch Q13 to open; and, the battery management system M2 controls the discharge switch Q21 to close and the charging switch Q22 to open until the difference between the total voltages of the battery packs B1 and B2 is less than or equal to the parallel voltage value, then return to Step S2;

[0123] Step S4, when the difference between the total voltages of the battery packs B2 and B1 is greater than the parallel voltage value, the battery management system M2 controls the discharge switch Q21 to close, the charging switch Q22 to close and the current limiting switch Q23 to open; and, the battery management system M1 controls the discharge switch Q11 to close and the charging switch Q12 to open until the difference between the total voltages of the battery packs B2 and B1 is less than or equal to the parallel voltage value, then return to Step S2.

[0124] In this embodiment, by controlling the discharge switch Q11, the charging switch Q12, and the current-limiting switch Q13 through the battery management system M1, and by controlling the discharge switch Q21, the charging switch Q22, and the current-limiting switch Q23 through the battery management system M2, the parallel connection process of the battery module 1 and the battery module 2 can be controlled. Compared with the waiting method, the parallel connection time of this embodiment is short. Compared with the probing method, parallel connection is performed only when the absolute value of the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel connection voltage value. The current in the parallel connection loop is less than or equal to the maximum charging current, and the induced inductance voltage generated is small, which can improve the efficiency and safety of the parallel connection of multiple battery modules.

[0125] In an embodiment of the present invention, step S3 further includes: when the total voltage difference between the battery pack B1 and the battery pack B2 is greater than the parallel connection voltage value, controlling the closing / opening frequency of the current-limiting switch Q23 according to the voltage value across the sampling resistor R2 to control the charging current of the battery pack B2;

[0126] Step S4 further includes: when the total voltage difference between the battery pack B2 and the battery pack B1 is greater than the parallel connection voltage value, controlling the closing / opening frequency of the current-limiting switch Q13 according to the voltage value across the sampling resistor R1 to control the charging current of the battery pack B1.

[0127] In this embodiment, when the total voltage difference between the battery pack B1 and the battery pack B2 is greater than the parallel connection voltage value, the battery management system M1 controls the discharge switch Q11 to close, the charging switch Q12 to close, and the current-limiting switch Q13 to open. The battery management system M2 controls the discharge switch Q21 to close and the charging switch Q22 to open, and controls the closing / opening frequency of the current-limiting switch Q23 according to the voltage value across the sampling resistor R2 to control the charging current of the battery pack B2, which can limit the charging current of the battery pack and avoid damage to the battery module caused by excessive charging current. Until the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel connection voltage value, return to step S2.

[0128] When the total voltage difference between the battery pack B2 and the battery pack B1 is greater than the parallel connection voltage value, the battery management system M2 controls the discharge switch Q21 to close, the charging switch Q22 to close, and the current-limiting switch Q23 to open. The battery management system M1 controls the discharge switch Q11 to close and the charging switch Q12 to open, and controls the closing / opening frequency of the current-limiting switch Q13 according to the voltage value across the sampling resistor R1 to control the charging current of the battery pack B1, which can limit the charging current of the battery pack and avoid damage to the battery module caused by excessive charging current. Until the total voltage difference between the battery pack B2 and the battery pack B1 is less than or equal to the parallel connection voltage value, return to step S2.

[0129] The above are only exemplary embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A parallel circuit of multiple battery modules, characterized in that: It includes multiple battery modules, each of which includes a battery pack, a battery management system, a discharge switch, a charge switch and a current limiting switch circuit; Among them, the discharge switch is used to control the discharge of the battery pack; the charging switch is used to control the charging of the battery pack; the current limiting switch circuit is used to limit the charging current of the battery pack; the battery management system is used to control the closing / opening of the discharge switch and the charging switch, and control the working state of the current limiting switch circuit when the battery pack is charging; The first ends of the plurality of battery modules are electrically connected to each other, and the second ends of the plurality of battery modules are electrically connected to each other; the battery management systems of the plurality of battery modules are communicatively connected to each other; When the absolute value of the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, the battery pack B1 and the battery pack B2 are controlled to discharge simultaneously; When the total voltage difference between the battery group B1 and the battery group B2 is greater than the parallel voltage value, the battery group B1 is controlled to charge the battery group B2 with limited current; When the total voltage difference between the battery group B2 and the battery group B1 is greater than the parallel voltage value, the battery group B2 is controlled to charge the battery group B1 with limited current; The current limiting switch circuit includes a sampling resistor, a current limiting switch, an inductor and a diode; Among them, the positive electrode of the battery pack, the first power supply end of the battery management system, and the negative electrode of the diode are electrically connected to the first end of the battery module; the negative electrode of the battery pack, the second power supply end of the battery management system, and the first end of the sampling resistor are electrically connected to the first detection end of the battery management system; the second end of the sampling resistor and the second detection end of the battery management system are electrically connected to the first end of the discharge switch; the second end of the discharge switch and the first end of the charging switch are electrically connected to the first end of the inductor; the second end of the inductor and the first end of the current limiting switch are electrically connected to the positive electrode of the diode; the second end of the current limiting switch and the second end of the charging switch are electrically connected to the second end of the battery module; the battery management system is also electrically connected to the controlled end of the battery pack, the controlled end of the discharge switch, the controlled end of the charging switch, and the controlled end of the current limiting switch respectively; The battery management system M1 is used to obtain the total voltage of the battery group B1, and send the total voltage of the battery group B1 to the battery management system M2; the battery management system M2 is used to obtain the total voltage of the battery group M2, and send the total voltage of the battery group M2 to the battery management system M1; The battery management system M1 is also used for: When the total voltage difference between the battery pack B1 and the battery pack B2 is greater than the parallel voltage value, the discharge switch Q11 is controlled to be closed, the charging switch Q12 is controlled to be closed, and the current limiting switch Q13 is disconnected until the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value; When the total voltage difference between the battery pack B2 and the battery pack B1 is greater than the parallel voltage value, the discharge switch Q11 is controlled to be closed and the charging switch Q12 is disconnected, and the closing / disconnecting frequency of the current limiting switch Q13 is controlled according to the voltage value across the sampling resistor R1 to control the charging current of the battery pack B1 until the total voltage difference between the battery pack B2 and the battery pack B1 is less than or equal to the parallel voltage value; When the absolute value of the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, the discharge switch Q11 is controlled to be closed, the charge switch Q12 is controlled to be closed, and the current limiting switch Q13 is disconnected; The battery management system M2 is also used for: When the total voltage difference between the battery pack B2 and the battery pack B1 is greater than the parallel voltage value, the discharge switch Q21 is controlled to be closed, the charge switch Q22 is controlled to be closed, and the current limiting switch Q23 is disconnected until the total voltage difference between the battery pack B2 and the battery pack B1 is less than or equal to the parallel voltage value; When the total voltage difference between the battery pack B1 and the battery pack B2 is greater than the parallel voltage value, the discharge switch Q21 is controlled to be closed and the charging switch Q22 is disconnected, and the closing / disconnecting frequency of the current limiting switch Q23 is controlled according to the voltage value across the sampling resistor R2 to control the charging current of the battery pack B2 until the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value; When the absolute value of the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, the discharge switch Q21 is controlled to be closed, the charge switch Q22 is controlled to be closed, and the current limiting switch Q23 is disconnected; Among them, battery module 1 and battery module 2 are any two different battery modules among multiple battery modules, battery module 1 includes battery pack B1, battery management system M1, discharge switch Q11, charging switch Q12 and current limiting switch Q13, battery module 2 includes battery pack B2, battery management system M2, discharge switch Q21, charging switch Q22 and current limiting switch Q23.

2. The parallel circuit of multiple battery modules according to claim 1, characterized in that: Each battery management system includes a control circuit, an analog front-end circuit, a communication circuit, a first drive circuit and a second drive circuit; The analog front-end circuit is electrically connected to the battery pack, the sampling resistor, the first drive circuit and the control circuit respectively. The analog front-end circuit is used to convert the input analog signal into a digital signal and then input it to the control circuit, and to convert the digital signal output by the control circuit into an analog signal for output; The first driving circuit is used to drive the discharge switch and the charging switch to close / open; The second drive circuit is electrically connected to the control circuit, and the second drive circuit is used to drive the current limiting switch to close / open; The communication circuit is electrically connected to the control circuit, and the communication circuit is used to send / receive communication data; The control circuit is used to control the operation of the analog front-end circuit, the first drive circuit, the second drive circuit and the communication circuit.

3. The parallel circuit of multiple battery modules according to claim 2, characterized in that: Each battery management system also includes: A first voltage conversion circuit, the first voltage conversion circuit is electrically connected to the battery pack and the analog front-end circuit respectively, and the first voltage conversion circuit is used to convert the output voltage of the battery pack into a first voltage to power the analog front-end circuit; The second voltage conversion circuit is electrically connected to the battery pack and the control circuit respectively, and is used for converting the output voltage of the battery pack into a second voltage to supply power to the control circuit.

4. The parallel circuit of multiple battery modules according to claim 1, characterized in that: The discharge switch, charge switch and current limiting switch are all MOS tubes.

5. A method for controlling a parallel circuit of multiple battery modules, characterized in that: The control method of the parallel circuit of multiple battery modules is applied to the parallel circuit of multiple battery modules; Among them, the parallel circuit of multiple battery modules includes multiple battery modules, each battery module includes a battery pack, a battery management system, a sampling resistor, a discharge switch, a charging switch, a current limiting switch, an inductor and a diode; the positive electrode of the battery pack, the first power supply end of the battery management system, and the negative electrode of the diode are electrically connected to the first end of the battery module; the negative electrode of the battery pack, the second power supply end of the battery management system, and the first end of the sampling resistor are electrically connected to the first detection end of the battery management system; the second end of the sampling resistor and the second detection end of the battery management system are electrically connected to the first end of the discharge switch; the second end of the discharge switch and the first end of the charging switch are electrically connected to the first end of the inductor; the second end of the inductor and the first end of the current limiting switch are electrically connected to the positive electrode of the diode; the second end of the current limiting switch and the second end of the charging switch are electrically connected to the second end of the battery module; the battery management system is also electrically connected to the controlled end of the battery pack, the controlled end of the discharge switch, the controlled end of the charging switch, and the controlled end of the current limiting switch respectively; the first ends of the multiple battery modules are electrically connected to each other, and the second ends of the multiple battery modules are electrically connected to each other; the battery management systems of the multiple battery modules are communicatively connected to each other; Wherein, the battery module 1 and the battery module 2 are any two different battery modules among the plurality of battery modules, the battery module 1 includes a battery pack B1, a battery management system M1, a discharge switch Q11, a charging switch Q12 and a current limiting switch Q13, and the battery module 2 includes a battery pack B2, a battery management system M2, a discharge switch Q21, a charging switch Q22 and a current limiting switch Q23; The steps of the control method include: S1: The battery management system M1 obtains the total voltage of the battery pack B1 and sends it to the battery management system M2; the battery management system M2 obtains the total voltage of the battery pack B2 and sends it to the battery management system M1; S2: When the absolute value of the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, the battery management system M1 controls the discharge switch Q11 to close, the charging switch Q12 to close, and the current limiting switch Q13 to open; the battery management system M2 controls the discharge switch Q21 to close, the charging switch Q22 to close, and the current limiting switch Q23 to open; S3: When the total voltage difference between the battery pack B1 and the battery pack B2 is greater than the parallel voltage value, the battery management system M1 controls the discharge switch Q11 to be closed, the charging switch Q12 to be closed, and the current limiting switch Q13 to be disconnected; and the battery management system M2 controls the discharge switch Q21 to be closed and the charging switch Q22 to be disconnected, and controls the closing / disconnecting frequency of the current limiting switch Q23 according to the voltage value across the sampling resistor R2, so as to control the charging current of the battery pack B2, until the total voltage difference between the battery pack B1 and the battery pack B2 is less than or equal to the parallel voltage value, and then returns to step S2; S4: When the total voltage difference between battery pack B2 and battery pack B1 is greater than the parallel voltage value, the battery management system M2 controls the discharge switch Q21 to close, the charging switch Q22 to close, and the current limiting switch Q23 to open; and the battery management system M1 controls the discharge switch Q11 to close and the charging switch Q12 to open, and controls the frequency of closing / opening the current limiting switch Q13 according to the voltage value across the sampling resistor R1 to control the charging current of the battery pack B1, until the total voltage difference between battery pack B2 and battery pack B1 is less than or equal to the parallel voltage value, and then returns to step S2.

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