WO2024108401A1 - Battery pack parallel connection method, battery management system, battery pack, and electrical device - Google Patents

Abstract

Embodiments of the present application relate to the technical field of batteries, and relate, for example, to a battery pack parallel connection method, a battery management system, a battery pack, an electrical device, and a storage medium. The battery pack parallel connection method comprises: in response to a first battery pack satisfying a first parallel connection condition and being in a charge state, controlling a switch on a discharge loop to be opened, and the first battery pack to perform parallel charging; or, in response to the first battery pack satisfying the first parallel connection condition and being in a discharge state, controlling a switch on a charge loop to be opened, and the first battery pack to perform parallel discharging. In the embodiments of the present application, when battery packs are charged, the discharge loop is disconnected, and when battery packs are discharged, the charge loop is disconnected. In this way, circulating currents generated between the battery packs through the discharge loop during charging can be reduced, and circulating currents generated through the charge loop during discharging can also be reduced, thereby reducing circulating currents between the battery packs, and improving the safety of the battery packs.

Description

A battery pack parallel connection method, battery management system, battery pack and electrical equipment Technical Field

The embodiments of the present application relate to the field of battery technology, and in particular to a battery pack parallel connection method, a battery management system, a battery pack, an electrical device, and a storage medium.

Background technique

When supplying power to electrical equipment, battery packs can be connected in parallel to increase the capacity of the battery, which can increase the use time of the electrical equipment. For example, a two-wheeled vehicle powered by batteries can use parallel battery packs to increase the vehicle's mileage.

Due to the differences in the charging and discharging process of each battery pack, as well as the differences in the leakage current of the battery cells when they are stationary, the voltages of the battery packs may be inconsistent, so when the battery packs are connected in parallel, it is easy to generate circulating current. Excessive circulating current may cause a battery pack to have too much current, thus causing current limiting protection, and even damaging the battery pack.

In the current battery pack parallel connection scheme, it is easy to generate large circulating current between the battery packs, causing the battery pack to overcurrent.

Summary of the invention

Embodiments of the present application provide a battery pack parallel connection method, a battery management system, a battery pack, an electrical device, and a storage medium, which can reduce the circulation current between battery packs.

In a first aspect, an embodiment of the present application provides a battery pack parallel connection method, the method comprising, in response to the first battery pack satisfying the first parallel connection condition and the first battery pack being in a charging state, controlling the switch on the discharge circuit to be in an off state, and the first battery pack performs charging parallel connection. Alternatively, in response to the first battery pack satisfying the first parallel connection condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit to be in an off state, and the first battery pack performs discharging parallel connection. The first parallel connection condition may include that the operating data of the first battery pack satisfies the parallel connection condition, and the operating data includes at least one of voltage data, current data, SOC data, temperature data, and communication status.

In some embodiments, the first parallel condition includes at least one of the following:

(1) The voltage difference between the voltage of the first battery pack and the first voltage is within a first voltage difference range. When the first battery pack is in a charging state, the first voltage is the minimum voltage among the battery packs; when the first battery pack is in a discharging state, the first voltage is the maximum voltage among the battery packs.

(2) The difference between the SOC of the first battery pack and the first SOC is within a first SOC range, wherein when the first battery pack is in a charging state, the first SOC is the minimum SOC among the battery packs; when the first battery pack is in a discharging state, the first SOC is the maximum SOC among the battery packs.

(3) The temperature of the first battery pack is within a first temperature range.

(4) The first charging current rate is within a first current rate range, or the first discharging current rate is within a second current rate range. The first charging current rate is the maximum charging current rate of the battery packs connected in parallel, and the first discharging current rate is the maximum discharging current rate of the battery packs connected in parallel.

(5) Communication status of the first battery pack. The communication status of the first battery pack is used to indicate that the first battery pack has successfully communicated with at least one of the parallel-connected battery packs.

In some embodiments, controlling the switch on the discharge circuit to be in an off state, and the first battery pack performs parallel charging, includes: controlling the switch on the discharge circuit of the first battery pack and/or each parallel battery pack to be in an off state, and the first battery pack performs parallel charging.

Controlling the first battery pack and/or controlling the switches on the discharge circuits of each parallel-connected battery pack to be in an off state can cut off the discharge parallel connection between the first battery pack and the parallel-connected battery packs, thereby reducing the circulating current generated between the battery packs through the discharge circuit during charging.

In some embodiments, controlling the switch on the charging circuit to be in an off state, and the first battery pack performs discharge in parallel, includes: controlling the switch on the charging circuit of the first battery pack and/or each parallel battery pack to be in an off state, and the first battery pack performs discharge in parallel.

Controlling the switches on the charging circuits of the first battery pack and/or each parallel-connected battery pack to be in an off state can cut off the parallel charging connection between the first battery pack and the parallel-connected battery packs, thereby reducing the circulating current generated between the battery packs through the charging circuit during discharge.

In some embodiments, in response to the first battery pack satisfying the first parallel condition and the first battery pack being in a charging state, controlling the switch on the discharge circuit to be in an open state, and the first battery pack performing charging in parallel, includes: in response to the first battery pack satisfying the first parallel condition, the first battery pack sends a parallel request instruction. In response to the first battery pack being in a charging state, disconnecting the switch on the discharge circuit of the first battery pack, and closing the charging switch on the charging circuit of the first battery pack.

In some embodiments, in response to the first battery pack satisfying the first parallel condition and the first battery pack being in a charging state, controlling the switch on the discharge circuit to be in an off state, and the first battery pack performing charging in parallel, includes: in response to the first battery pack satisfying the first parallel condition and the first battery pack being in a charging state, controlling the switch on the discharge circuit to be in an off state, and the first battery pack performing charging in parallel, including: in response to the first battery pack satisfying the first parallel condition, the first battery pack sends a parallel request instruction. The switch on the discharge circuit of the first battery pack is in an off state, and in response to the first battery pack being in a charging state, the charging switch on the charging circuit of the first battery pack is closed.

In some embodiments, in response to the first battery pack satisfying the first parallel connection condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit to be in an off state, and the first battery pack performing a discharge parallel connection, includes: in response to the first battery pack satisfying the first parallel connection condition, the first battery pack sends a parallel connection request instruction. In response to the first battery pack being in a discharging state, disconnecting the switch on the charging circuit of the first battery pack, and closing the discharge switch on the discharge circuit of the first battery pack.

In some embodiments, in response to the first battery pack satisfying the first parallel condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit to be in an off state, and the first battery pack performing a discharge parallel connection, includes: in response to the first battery pack satisfying the first parallel condition, the first battery pack sends a parallel connection request instruction. The switch on the charging circuit of the first battery pack is in an off state, and in response to the first battery pack being in a discharging state, closing the discharge switch on the discharge circuit of the first battery pack.

The parallel request instruction is used to notify other battery packs to be incorporated into the electrical equipment, so that the first battery pack and other battery packs can be roughly synchronized and connected in parallel. After receiving the parallel request instruction sent by other battery packs, the battery pack can also execute the parallel judgment logic. Then, the battery pack can periodically execute the parallel judgment logic at a longer interval, which can reduce the amount of calculation of the battery pack. On the other hand, the parallel request instruction can also carry information used to indicate the charging and discharging status of the electrical equipment. Even if the battery pack cannot receive the charging signal sent by the charger, it can still correct the working status through the parallel request instruction, which can reduce the battery pack's misjudgment of the working status.

In some embodiments, the battery pack parallel connection method further includes: in response to the second battery pack receiving a parallel connection request instruction, disconnecting a discharge switch on a charging circuit of the second battery pack, the second battery pack being a parallel connected battery pack. Disconnecting the discharge switch on the charging circuit of the parallel connected battery pack can disconnect the circulation path of the parallel connected battery pack, thereby reducing the circulation current.

In some embodiments, closing the charging switch on the charging circuit of the first battery pack includes: closing the charging switch in response to receiving first information. The first information is used to indicate that the discharge switch on the charging circuit of the second battery pack is in an open state, and the second battery pack is a parallel-connected battery pack. The first information can ensure that the first battery pack performs the operation of closing the charging switch on the charging circuit only after the circulation path on the charging circuit of the parallel-connected battery pack is disconnected, thereby reducing the circulating current.

In some embodiments, in response to the first battery pack satisfying the first condition, the discharge switch on the charging circuit of the first battery pack is closed, and/or, in response to the second battery pack satisfying the first condition, the discharge switch on the charging circuit of the second battery pack is closed. The first condition includes at least one of the following:

(1) The charging current of the battery pack is greater than or equal to the first current threshold.

(2) The charging current of the battery pack is less than the first current threshold, and the voltage difference between the sum of the voltage of the battery pack and the second voltage is within a second voltage difference range.

The second voltage is the minimum voltage in each battery pack. Setting the first condition can limit the circulation, and the circulation path is closed only when the risk of a large circulation is small.

In some embodiments, the battery pack parallel connection method further includes: in response to the first battery pack satisfying the first circulation condition, disconnecting the charging switch and the discharging switch on the charging circuit of the first battery pack. The first circulation condition includes that the absolute value of the difference between the current rate of the first battery pack and the first current rate is greater than or equal to the first current rate threshold. The first current rate is the maximum charging current rate among all the battery packs connected in parallel, and the current rate of the first battery pack includes a charging current rate or a discharging current rate, the charging current rate is a positive value, and the discharging current rate is a negative value.

After the charging switch and the discharging switch on the battery pack charging circuit are closed, the circulating current risk is also judged, which can reduce the circulating current risk.

In some embodiments, the battery pack parallel connection method further includes: in response to the second battery pack receiving a parallel connection request instruction, disconnecting a charging switch on a discharge circuit of the second battery pack. The second battery pack is a battery pack that has been connected in parallel. Disconnecting the charging switch on the discharge circuit of the battery pack that has been connected in parallel can disconnect the circulation path of the battery pack that has been connected in parallel, thereby reducing the circulation current.

In some embodiments, closing the discharge switch on the discharge loop of the first battery pack includes: closing the discharge switch in response to receiving second information. The second information is used to indicate that the charging switch on the discharge loop of the second battery pack is in an open state, and the second battery pack is a parallel-connected battery pack. The second information can ensure that the first battery pack performs the operation of closing the discharge switch on the discharge loop only after the circulation path on the discharge loop of the parallel-connected battery pack is disconnected, so as to reduce the circulating current.

In some embodiments, in response to the first battery pack satisfying the first parallel condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit of the first battery pack to be in an off state, and the first battery pack performing discharge parallel connection, further comprising: in response to the first battery pack satisfying the second condition, closing the charging switch on the discharging circuit of the first battery pack, and/or, in response to the second battery pack satisfying the second condition, closing the charging switch on the charging circuit of the second battery pack. The second condition includes at least one of the following:

(1) The discharge current of the battery pack is greater than or equal to the second current threshold;

(2) The discharge current of the battery pack is less than the second current threshold, and the voltage difference between the voltage of the battery pack and the third voltage is within the third voltage difference range.

The third voltage is the maximum voltage of each battery pack. Setting the second condition can limit the circulation, and the circulation path is closed only when the risk of a large circulation is small.

In some embodiments, in response to the first battery pack satisfying the first parallel condition and the first battery pack being in a discharging state, the switch on the charging circuit of the first battery pack is controlled to be in an off state, and the first battery pack performs discharge parallel connection, and further includes: in response to the first battery pack satisfying the second circulating current condition, the charging switch and the discharging switch on the discharging circuit of the first battery pack are disconnected. The second circulating current condition includes that the absolute value of the difference between the current rate of the first battery pack and the second current rate is greater than or equal to the second current rate threshold. The second current rate is the maximum discharge current rate among the battery packs that have been connected in parallel, and the current rate of the first battery pack includes a charging current rate or a discharging current rate, the charging current rate is a positive value, and the discharging current rate is a negative value.

After the charging switch and the discharging switch on the battery pack discharge circuit are closed, the circulating current risk is also judged, which can reduce the circulating current risk.

In some embodiments, the battery pack parallel connection method further includes: detecting the on-off state of the charging switch and/or the discharging switch on the charging circuit of the battery pack, and sending a third information; and/or detecting the on-off state of the charging switch and/or the discharging switch on the discharging circuit of the battery pack, and sending a fourth information. The third information is used to indicate the on-off state of the charging switch and/or the discharging switch on the charging circuit, and the fourth information is used to indicate the on-off state of the charging switch and/or the discharging switch on the discharging circuit. The third information and the fourth information can be referred to as back-check information. By sending the back-check information through the back-check switch, the parallel connection time of the battery pack can be accelerated as a whole, and the parallel connection process can be simplified.

In some embodiments, the battery pack parallel connection method further includes: the switch on the discharge circuit responds to the control signal and extends the first time to perform on-off, and the switch on the charging circuit responds to the control signal and extends the second time to perform on-off. After receiving the control signal, the switch on the charge and discharge circuit extends a period of time before performing on-off or off, which can ensure that the switch is normally closed or opened, making the parallel connection of the battery pack more stable.

In a second aspect, an embodiment of the present application also provides a battery management system, comprising at least one processor and a memory, wherein the memory is communicatively connected to the at least one processor, and the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the above method.

In a third aspect, an embodiment of the present application further provides a battery pack, comprising the above-mentioned battery management system.

In a fourth aspect, an embodiment of the present application further provides an electrical device, including a load and the above-mentioned battery pack, wherein the battery pack is used to supply power to the load.

In a fifth aspect, an embodiment of the present application further provides a storage medium, which stores computer-executable instructions. When the computer-executable instructions are executed by a machine, the machine executes the above-mentioned method.

Compared with the prior art, the embodiment of the present application disconnects the discharge circuit when the battery pack is charging, and disconnects the charging circuit when the battery pack is discharging. This can reduce the circulating current generated between the battery packs through the discharge circuit during charging, and the circulating current generated through the charging circuit during discharging, thereby reducing the circulating current between the battery packs and improving the safety of the battery pack. When the battery pack is discharging, the switch on the charging circuit is controlled to be in the disconnected state, which can reduce the voltage at the charging port, and when the charging circuits of the first battery pack and the battery packs that have been connected in parallel are disconnected, the charging port can be de-energized. Thereby, the safety of the charging port is improved, and the risk of electric shock from contacting the charging port is reduced.

In addition, when the electric device changes from the discharge state to the charging state, the present embodiment can directly control the switch on the discharge circuit to be in the disconnected state to perform charging in parallel. When the electric device changes from the charging state to the discharge state, the present embodiment can directly control the switch on the charging circuit to be in the disconnected state to perform discharging in parallel. The working state can be easily switched without shutting down and restarting, or each battery pack exiting the parallel connection and then reconnecting the parallel connection, and the process is relatively simple.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are exemplarily described by the figures in the accompanying drawings, which are not intended to limit the embodiments. Elements with the same reference numerals in the drawings represent similar elements.

Figures 1a to 1c are schematic diagrams of the structure of electrical equipment according to an embodiment of the present application;

FIG. 2a-FIG. 2c and FIG. 3 are schematic diagrams of the structure of a battery pack according to an embodiment of the present application;

4a-4c are working state diagrams of the discharge circuit of the battery pack according to the embodiment of the present application;

5a-5c are working state diagrams of the charging circuit of the battery pack according to the embodiment of the present application;

6a-6d are schematic diagrams of the switch structure of the charge and discharge control part of the BMS according to the embodiment of the present application;

FIG7 is a schematic diagram of the hardware structure of the controller in the BMS of the embodiment of the present application;

FIG8 is a flow chart of an embodiment of a method for connecting battery packs in parallel according to the present invention;

FIG9 is a schematic diagram of the switch structure of the charge and discharge control part of the BMS according to an embodiment of the present application;

FIG10 is a flow chart of charging in one embodiment of the battery pack parallel connection method of the present application;

FIG11 is a flow chart of discharging in one embodiment of the battery pack parallel connection method of the present application;

12a-12d are schematic diagrams of working states at various stages during charging in one embodiment of a battery pack parallel connection method of the present application;

FIG13 is a schematic diagram of an interactive process of charging a battery pack in parallel according to an embodiment of the present application;

14a-14d are schematic diagrams of working states at various stages during charging in one embodiment of a battery pack parallel connection method of the present application;

FIG15 is a schematic diagram of an interactive process when discharging a battery pack in parallel according to an embodiment of the present application;

FIG. 16 is a schematic diagram of the interactive process when charging the battery packs in parallel according to an embodiment of the present application.

Detailed ways

In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and in detail below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. The technical features involved in the various embodiments of the present application described below do not conflict with each other and can be combined with each other.

Furthermore, although the device schematic diagram is divided into functional modules and the flowchart shows a logical order, in some cases, the steps may be divided into modules different from those in the device or may be executed in an order different from that shown in the flowchart.

When an element is referred to as being “connected to” another element, it can be directly connected to the other element, or one or more intervening elements may be present therebetween.

In some electrical devices, the use of parallel connected battery packs can increase the capacity of the battery, thereby increasing the use time of the electrical device. Figure 1a shows the structure of the battery-related part of the electrical device 1000, which includes N parallel connected battery packs 100, namely battery pack 1 to battery pack N, where N is a natural number ≥ 2, and each battery pack 100 can be used as an energy module of the electrical device.

The electrical equipment 1000 may be an electric vehicle, or other equipment that can be powered by a parallel battery pack, such as an electric two-wheeler, an electric three-wheeler, etc.

The power-consuming device 1000 may include a charging and discharging port, through which the battery pack 100 of the power-consuming device 1000 may be charged and discharged. In one embodiment of the present application, the charging and discharging ports of the power-consuming device 1000 may adopt a different port scheme, and the charging and discharging different port scheme may be understood as the charging port and the discharging port being different ports. In a specific implementation, the charging and discharging ports may be different connection ports on a connector.

As shown in FIG1a, each battery pack shares a negative electrode port, that is, the negative electrode charging port C- and the negative electrode discharging port P- of the electric device 1000 are the same connection port on the connector, while the positive electrode charging port C+ and the positive electrode discharging port P+ of the electric device 1000 are different connection ports on the connector. It can be understood that, in the scheme shown in FIG1a, the negative electrode charging port C- and the negative electrode discharging port P- are the same port, and the positive electrode charging port C+ and the positive electrode discharging port P+ are different ports.

1b, the discharge port of the electric device 1000 is used to electrically connect the load 200 of the electric device 1000 to supply power to the load 200. In which, taking the electric device as an electric vehicle as an example, the load may be an electric device on the electric vehicle, such as a motor, an instrument, a vehicle controller, etc.

The charging port of the electric device 1000 is used to electrically connect to the charger 2000, and the charger is used to connect to an external power source to charge the electric device 1000, specifically the battery pack 100.

The battery pack 100 may be provided with corresponding electrical connection terminals (e.g., connectors or connection harnesses) for respectively electrically connecting to the charging and discharging ports of the power-consuming device 1000. In the embodiment where the power-consuming device 1000 has a port C+, a port P+, and a port P-(C-), correspondingly, please refer to FIG. 2a, the battery pack 100 has a C+ terminal, a P+ terminal, and a P-(C-) terminal, respectively, for respectively electrically connecting to the port C+, the port P+, and the port P-(C-) of the power-consuming device 1000.

In other embodiments of the electric device 1000 with different charging and discharging ports, each battery pack may also share a common positive electrode and a common positive electrode port P+ (C+). The positive charging port C+ and the positive discharging port P+ of the electric device 1000 are the same connection port on the connector, while the negative charging port C- and the negative discharging port P- of the electric device 1000 are different connection ports on the connector.

In the embodiment where the power-consuming device 1000 has a port P+(C+), a port C- and a port P-, correspondingly, please refer to FIG. 2b , the battery pack 100 respectively has a P+(C+) terminal, a C- terminal and a P- terminal, which are used to electrically connect to the port P+(C+), the port C- and the port P- of the power-consuming device 1000 respectively.

In other embodiments with different charging and discharging ports, the battery packs may not share ports, the charging port includes port C+ and port C-, and the discharging port includes port P+ and port P-.

In the embodiment where the electrical device 1000 has port C+, port C-, port P+ and port P-, correspondingly, please refer to Figure 2c, the battery pack 100 respectively has a C+ terminal, a C- terminal, a P+ terminal and a P- terminal, which are used to electrically connect the corresponding ports C+, C-, P+ and P- of the electrical device.

Those skilled in the art will appreciate that the above is merely an example of the connection relationship between the battery pack and the charging port and the discharging port of the electrical device. In other embodiments, other connection methods may also be used. For example, the battery pack has a C+ terminal, a C- terminal, a P+ terminal, and a P- terminal as shown in FIG2c. The C+ terminal may be electrically connected to the port C+, the P+ terminal may be electrically connected to the port P+, and the C- terminal and the P- terminal may be electrically connected to the port P-(C-). For another example, the battery pack has a C+ terminal, a P+ terminal, and a P-(C-) terminal as shown in FIG2a. The C+ terminal may be electrically connected to the port C+, the P+ terminal may be electrically connected to the port P+, and the P-(C-) terminal may be electrically connected to the port C- and the port P-, respectively.

The charging port and/or the discharging port may be provided in the form of a connection port or a connector. In other embodiments, since the discharging port does not need to be connected to an external device but only needs to be connected to a load inside the electrical device, there is no need to provide a connection port or a connector, and the battery pack may be directly electrically connected to the corresponding load using a connection harness.

Please refer to FIG. 1 c , FIG. 2 a - FIG. 2 c , and FIG. 3 , each battery pack 100 includes a battery management system (BMS) 10 and an energy module 20 (eg, a battery cell module).

The energy module 20 includes a plurality of cells for storing and providing electric energy. The plurality of cells can be connected in series, in parallel or in a mixed connection. The mixed connection of the plurality of cells means that the electrical connection of the cells includes both series connection and parallel connection. The BMS 10 is used to detect, manage, control and/or protect the energy module 20. For example, the BMS 10 can detect the operating data of the energy module 20 and/or the communication status of the battery pack, such as voltage data, current data, temperature data, capacity (State of Charge, SOC) data, etc.

The BMS10 on each battery pack 100 can be communicatively connected to each other. For example, as shown in FIG. 1c , each BMS10 is communicatively connected via a communication bus 300 . Through the communication bus 300 , each battery pack 100 can exchange instructions and data (such as the above-mentioned operating data).

In some embodiments, the charger may also be communicatively connected to the BMS10 of each battery pack, for example, by being communicatively connected to the BMS10 of each battery pack through a communication bus, and sending a charging signal to each battery pack, and the charging signal may be used to instruct the battery pack to perform a charging operation.

Among them, the communication bus 300 is such as a CAN communication bus, an RS485 communication bus, etc. In addition, each BMS10 and the charger and the BMS10 can also be communicated and connected through other wired or wireless methods, such as through Wi-Fi communication, mobile communication technology or Bluetooth communication technology.

The energy modules 20 of each battery pack 100 may be electrically connected in parallel to supply power to the power-consuming device 1000 , so as to increase the battery capacity of the power-consuming device 1000 .

In some embodiments, the energy module 20 can be connected in parallel with other energy modules through the BMS 10. Electrical connection terminals for connecting the charging and discharging ports of electrical equipment (such as the C+ terminal, P+ terminal and P-(C-) terminal in Figure 2a) can be set on the BMS 10, one end of the electrical connection terminal is used to connect the energy module 20, and the other end is used to connect the charging and discharging port. By connecting the electrical connection terminal on the BMS 10 with the corresponding charging and discharging port, the parallel connection between the energy modules 20 is realized.

The C+ terminal, P+ terminal and P+(C+) terminal of the electrical connection terminal are used to connect the positive electrode of the energy module 20, and the C- terminal, P- terminal and P-(C-) terminal are used to connect the negative electrode of the energy module 20. The electrical connection terminal can be configured as a connection port or a connector, or can also be a section of a connection harness.

In some specific implementations of the present application, the BMS 10 may be presented in the form of a printed circuit board, and a switch may be further provided on the BMS 10 circuit board, for example, provided between the energy module 20 and the electrical connection end, and the BMS 10 may control the switch to incorporate the energy module 20 into the electrical device 1000 or to cut out the electrical device 1000. When the BMS 10 controls the switch to establish a connection between the energy module 20 and the electrical connection end, the energy module 20 is incorporated into the electrical device 1000, and when the BMS 10 controls the switch to disconnect the connection between the energy module 20 and the electrical connection end, the energy module 20 is cut out of the electrical device 1000.

For the convenience of description below, the energy module 20 is integrated into or disconnected from the electrical equipment, which is called the battery pack is integrated into or disconnected from the electrical equipment, and the energy modules 20 are connected in parallel, which is called the battery pack is connected in parallel.

In the charging and discharging scheme, different circuits can be used to charge and discharge the battery pack 100, using the charging circuit to charge the battery pack 100 and the discharging circuit to discharge the battery pack 100. The charging circuit is electrically connected to the charging port of the electrical device, and the discharging circuit is electrically connected to the discharging port of the electrical device.

Switches may be provided on the charging circuit and the discharging circuit respectively. For example, at least one switch may be provided on the charging circuit to control the on and off of the charging circuit, and at least one switch may be provided on the discharging circuit to control the on and off of the discharging circuit.

By closing or opening the switch on the BMS 10, the battery pack 100 is connected to or disconnected from the electrical equipment 1000. When the BMS 10 controls the switch to turn on the charging circuit, the battery pack is connected to the electrical equipment, and the battery pack is "charged in parallel". When the BMS 10 controls the switch to turn on the discharging circuit, the battery pack is connected to the electrical equipment, and the battery pack is "discharged in parallel".

When the BMS10 controls the switch to disconnect the charging circuit, the "charging parallel" of the battery pack is disconnected, and the connection between the battery pack and the charging port is disconnected. When the BMS10 controls the switch to disconnect the discharging circuit, the "discharging parallel" of the battery pack is disconnected, and the connection between the battery pack and the discharging port is disconnected.

Fig. 3 shows a structure of the charge and discharge control part of the BMS 10. It can be understood that the figure only shows the switch structure of the charge and discharge control part of the BMS, and does not show other structures such as the main control part and the detection part.

In the embodiment shown in FIG3 , the discharge circuit of the BMS10 includes a charging switch CHG1 and a discharging switch DSG1 connected in series. As a specific implementation, the charging switch CHG1 and the discharging switch DSG1 may be field effect transistors, the charging switch CHG1 includes a body diode D1, and the discharging switch DSG1 includes a body diode D2. In some other implementations, the charging switch CHG1 is connected in parallel with a diode D1, and the discharging switch DSG1 is connected in parallel with a diode D2, and the diode D1 and the diode D2 share a common cathode. The charging switch CHG1, the discharging switch DSG1, the diode D1, and the diode D2 may be used as part of the discharge circuit, and the charging switch CHG1 and the discharging switch DSG1 are used to control the working state of the discharge circuit.

Please refer to Figure 4a, when the discharge switch DSG1 is closed and the charging switch CHG1 is opened, the discharge path of the energy module 20 is turned on, and the energy module 20 can discharge to the load through the discharge path and the discharge ports P+ and P-(C-). The current direction is: the positive electrode of the energy module 20 → the diode D1 → the discharge switch DSG1 → P+ → the load (not shown) → P-(C-) → the negative electrode of the energy module 20.

Please refer to Figure 4b, when the discharge switch DSG1 is turned off and the charging switch CHG1 is turned on, the circulation path of the energy module 20 is turned on, and when the energy module 20 is connected in parallel with other energy modules and the voltage of other energy modules is higher than that of the energy module 20, other energy modules 20 can charge the energy module 20 through the circulation path and the discharge ports P+ and P-(C-). The current direction is: positive electrode of other energy modules → P+ → diode D2 → charging switch CHG1 → positive electrode of energy module 20 → negative electrode of energy module 2020 → P-(C-) → negative electrode of other energy modules.

Referring to FIG. 4 c , when the discharge switch DSG1 and the charge switch CHG1 are both closed, the discharge path and the circulation path are both turned on, and the current can flow in two directions.

When the discharge switch DSG1 and the charge switch CHG1 are both turned off, the discharge path and the circulation path are both disconnected, and no current flows in the circuit.

The charging circuit of BMS10 may include a charging switch CHG2 and a discharging switch DSG2 connected in series. As a specific embodiment, the charging switch CHG2 and the discharging switch DSG2 may be field effect transistors, the charging switch CHG2 includes a body diode D3, and the discharging switch DSG2 includes a body diode D4. In some other embodiments, the charging switch CHG2 is connected in parallel with a diode D3, and the discharging switch DSG2 is connected in parallel with a diode D4, and the diode D3 and the diode D4 share a common cathode. The charging switch CHG2, the discharging switch DSG2, the diode D3, and the diode D4 may be used as part of the charging circuit, and the charging switch CHG2 and the discharging switch DSG2 are used to control the working state of the charging circuit.

Please refer to Figure 5a, when the charging switch CHG2 is closed and the discharging switch DSG2 is opened, the charging path of the energy module 20 is turned on, and the external power supply can charge the energy module 20 through the charging path and the charging ports C+ and P-(C-). The current direction is: the positive electrode of the external power supply → C+ → the diode D4 → the charging switch CHG2 → the positive electrode of the energy module 20 → the negative electrode of the energy module 2020 → P-(C-) → the negative electrode of the external power supply.

Please refer to Figure 5b, when the charging switch CHG2 is turned off and the discharging switch DSG2 is turned on, the circulation path of the energy module 20 is turned on. When the energy module 20 is connected in parallel with other energy modules and the voltage of other energy modules is lower than that of the energy module 20, the energy module 20 can discharge to other energy modules through the circulation path and the charging ports C+ and P-(C-). The current direction is: positive electrode of energy module 20 → diode D3 → discharging switch DSG2 → C+ → positive electrode of other energy modules → negative electrode of other energy modules → P-(C-) → negative electrode of energy module 20.

Referring to FIG. 5 c , when the charging switch CHG2 and the discharging switch DSG2 are both closed, the charging path and the circulating path are both turned on, and the current can flow in two directions.

When the discharge switch DSG2 and the charge switch CHG2 are both turned off, the charging path and the circulating current path are both disconnected, and no current flows in the circuit.

FIG6a and FIG6b take two battery packs as an example to exemplarily illustrate the switch structure of the charge and discharge control part when the battery packs share a negative electrode, and FIG6c and FIG6d take two battery packs as an example to exemplarily illustrate the switch structure of the charge and discharge control part when the battery packs share a positive electrode. For the convenience of description, the following embodiments are all described by taking the battery packs sharing a negative electrode as an example.

In some embodiments, referring to FIG. 6b and FIG. 6d , the BMS 10 may further include a pre-discharge switch (PDSG1, PDSG2) and a current limiting resistor (R1, R2), and the pre-discharge switch is connected in series with the current limiting resistor. As a specific implementation, the pre-discharge switch may be a field effect transistor, and the pre-discharge switch may include a body diode (D9, D10). In some other embodiments, the pre-discharge switch is connected in parallel with a diode (D9, D10).

The current limiting resistor can limit the discharge current. When the battery pack is ready to discharge, if the discharge switch in the discharge loop is directly closed, a large discharge current will be formed, and the large current has the risk of damaging the discharge switch and the charging switch. Therefore, when the battery pack is ready to discharge, the BMS10 can control the pre-discharge switch to be closed first, and keep the discharge switch in the open state, so that the discharge current flows through the current limiting resistor and decreases, thereby reducing the risk of damage to the discharge switch and the charging switch. After discharging for a period of time, the discharge switch is closed again and the pre-discharge switch is disconnected.

Those skilled in the art will appreciate that the above is merely an example of the structure of the charge and discharge control part of the BMS. In other embodiments, the charge and discharge control part may also adopt other switch structures, such as including only one switch in the charging circuit and/or only one switch in the discharging circuit.

In other embodiments, more than one charging switch and/or more than one discharging switch may be provided on the charging circuit. More than one charging switch and/or more than one discharging switch may be provided on the discharging circuit.

The above-mentioned charging switch and/or discharging switch can be one of a triode, a field effect transistor, a signal relay, an insulated gate bipolar transistor (IGBT), or other controllable switches that can control the conduction or shutdown of the circuit.

The BMS 10 may further include a switch driving circuit and at least one controller for controlling the closing and opening operations of the above switches to execute the steps in any method embodiment of the present application.

FIG7 schematically shows the hardware structure of the controller. As shown in FIG7 , the controller includes a processor 11 and a memory 12 .

The memory 12 is a non-volatile computer-readable storage medium that can be used to store non-volatile software programs and non-volatile computer-executable program instructions. The memory 12 may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required for at least one function; and the data storage area may store data created according to the use of the BMS 10, etc.

In addition, the memory 12 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 12 may optionally include a memory remotely arranged relative to the processor 11, and these remote memories may be connected to the BMS 10 via a network.

Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network and combinations thereof.

The processor 11 uses various interfaces and lines to connect various parts of the entire BMS 10, and executes various functions of the BMS 10 and processes data by running or executing software programs stored in the memory 12 and calling data stored in the memory 12, such as implementing the method described in any embodiment of the present application.

The processor 11 may include a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) device, etc. The processor 11 may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration.

Those skilled in the art can understand that in FIG7, one processor 11 and one memory 12 are used as examples. When the BMS 10 includes a multi-level management unit, or when multiple processors need to work together, the BMS 10 can also include multiple processors, and the method described in any embodiment of the present application can be implemented by multiple processors working together. Similarly, the memory can also be one or more, and the processor 11 and the memory 12 can be connected through a bus or other means. In the embodiment shown in FIG7, the processor 11 and the memory 12 are connected through a bus.

The embodiments of the present application also provide a battery pack parallel connection method, which can be applied to the BMS in any of the above embodiments, wherein "battery pack parallel connection" and "battery pack parallel operation" can mean that the battery pack is integrated into an electrical device.

Referring to FIG. 8 , the battery pack parallel connection method includes:

101: In response to the first battery pack satisfying the first parallel condition and the first battery pack being in a charging state, controlling the switch on the discharge circuit to be in an off state, and the first battery pack performs parallel charging.

and / or,

102: In response to the first battery pack satisfying the first parallel connection condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit to be in an off state, so that the first battery pack performs a discharging parallel connection.

When battery packs are connected in parallel, if there are certain differences between the battery packs, such as voltage difference, SOC difference, etc., the current will flow from one battery pack to another through the connecting line, causing a circulation current. Excessive circulation current may cause excessive current in one battery pack, which may cause an overcurrent fault or even damage the battery pack.

In the embodiment of the present application, when the battery pack is charged, the switch on the discharge circuit is controlled to be in an off state, so that the discharge circuit is in an off state, the "discharge parallel connection" between the battery pack and other battery packs can be cut off, and the circulating current generated by the discharge circuit between the battery packs during charging can be reduced. When the battery pack is discharged, the switch on the charging circuit is controlled to be in an off state, so that the charging circuit is in an off state, the "charge parallel connection" between the battery pack and other battery packs can be cut off, and the circulating current generated by the charging circuit during discharge can be reduced.

Moreover, when the electrical equipment changes from a discharge state to a charge state, some embodiments of the present application can directly control the switch on the discharge circuit to be in an off state to perform charging in parallel. When the electrical equipment changes from a charge state to a discharge state, some embodiments of the present application can directly control the switch on the charging circuit to be in an off state to perform discharging in parallel. The working state of the battery pack can be easily converted without shutting down and restarting, or all battery packs are withdrawn from parallel connection and then reconnected, and the process is simpler.

The following takes the first battery pack as an example to explain that when the first battery pack is charged, the switch on the discharge circuit is controlled to be in an off state, the purpose of which is to disconnect the "discharge parallel connection" formed by the first battery pack and other battery packs through the discharge circuit. Therefore, controlling the switch on the discharge circuit to be in an off state may be controlling the switch on the discharge circuit of the first battery pack to be in an off state.

For the first battery pack, the BMS of the first battery pack puts its discharge circuit in a disconnected state. For other battery packs, when the other battery packs meet the first parallel condition and are in a charging state, the BMS of other battery packs can also put their discharge circuits in a disconnected state. Then, the discharge circuits of all the battery packs in parallel charging are in a disconnected state, and the "discharge parallel" between the battery packs is cut off, which can reduce the circulating current generated by the discharge circuit.

Please refer to Figure 9. When the discharge circuits of battery pack BT1 and battery pack BT2 are in a disconnected state, the "discharge in parallel" of battery pack BT1 and battery pack BT2 is disconnected, and battery pack BT1 cannot receive the circulating current of battery pack BT2 through the discharge circuit, or output the circulating current to battery pack BT2 through the discharge circuit.

In other embodiments, when the first battery pack is charged, the switch on the discharge circuit is controlled to be in an open state, and the switches on the discharge circuits of each parallel battery pack can also be controlled to be in an open state. When the discharge circuits of each parallel battery pack are in an open state, the "discharge parallel" formed by the first battery pack and the parallel battery packs through the discharge circuit is disconnected, which can reduce the circulating current generated by the discharge circuit. The "parallel battery pack" here can be "a battery pack whose switch on the discharge circuit is closed and has been incorporated into the electrical device."

As a specific implementation manner, when the first battery pack is charged, a control instruction may be transmitted to the BMS of each parallel-connected battery pack, instructing the BMS of each parallel-connected battery pack to control the switch on its discharge circuit to be in an off state.

Please refer to the embodiment shown in Figure 9. When the discharge circuit of the battery pack BT2 is in a disconnected state, the "discharge parallel" of the battery pack BT1 and the battery pack BT2 is disconnected, and the battery pack BT1 cannot receive the circulating current of the battery pack BT2 through the discharge circuit, or output the circulating current to the battery pack BT2 through the discharge circuit.

Of course, when the first battery pack is charged, the switch on the discharge circuit is controlled to be in an off state, or the switches on the discharge circuits of the first battery pack and each battery pack connected in parallel are controlled to be in an off state. Alternatively, when each battery pack in the electrical device determines that it is in a charging state, the switch on its own discharge circuit is controlled to be in an off state, so as to achieve the effect that the switches on the discharge circuits of each battery pack in the electrical device are all in an off state.

When the first battery pack is discharging, the switch on the charging circuit is controlled to be in an off state, the purpose of which is to disconnect the "charging parallel connection" formed by the first battery pack and other battery packs through the charging circuit. Therefore, controlling the switch on the charging circuit to be in an off state may be controlling the switch on the charging circuit of the first battery pack to be in an off state.

For the first battery pack, the BMS of the first battery pack puts its charging circuit in a disconnected state. For other battery packs, when the other battery packs meet the first parallel condition and are in a discharging state, the BMS of other battery packs can also put their charging circuits in a disconnected state. Then, the charging circuits of all the battery packs in discharge parallel can be in a disconnected state, and the "charging parallel" between the battery packs can be cut off, which can reduce the circulating current generated by the charging circuit.

Please refer to Figure 9. When the charging circuits of battery pack BT1 and battery pack BT2 are in a disconnected state, the "charging in parallel" of battery pack BT1 and battery pack BT2 is disconnected, and battery pack BT1 cannot receive the circulating current of battery pack BT2 through the charging circuit, or output the circulating current to battery pack BT2 through the charging circuit.

Moreover, when the charging circuit is in the disconnected state, the connection between the battery pack and the charging port is disconnected, so that the charging port is not charged, which improves the safety of the charging port and reduces the risk of electric shock caused by contact with the charging port.

In other embodiments, when the first battery pack is discharged, the switch on the charging circuit is controlled to be in an off state, and the switches on the charging circuits of the parallel-connected battery packs may also be controlled to be in an off state. When the charging circuits of the parallel-connected battery packs are in an off state, the "charging parallel" formed by the first battery pack and the parallel-connected battery packs through the charging circuit is disconnected, which can reduce the circulating current generated by the charging circuit.

Moreover, the connection between the parallel-connected battery pack and the charging port is disconnected, which can reduce the voltage at the charging port, improve the safety of the charging port, and reduce the risk of electric shock when touching the charging port. The "parallel-connected battery pack" here can be "a battery pack whose switch on the charging circuit is closed and has been connected to the power-consuming device".

As a specific implementation manner, when the first battery pack is discharging, a control instruction may be transmitted to the BMS of each parallel-connected battery pack, instructing the BMS of each parallel-connected battery pack to control the switch on its charging circuit to be in an off state.

Please refer to Figure 9. When the charging circuit of the battery pack BT2 is in a disconnected state, the "charging in parallel" of the battery pack BT1 and the battery pack BT2 is disconnected, and the battery pack BT1 cannot receive the circulating current of the battery pack BT2 through the charging circuit, or output the circulating current to the battery pack BT2 through the charging circuit.

Of course, when the first battery pack is discharging, the switch on the charging circuit is controlled to be in the off state. It is also possible to control the switches on the charging circuits of the first battery pack and each parallel-connected battery pack to be in the off state. Alternatively, when each battery pack in the electrical equipment determines that it is in a discharging state, the switch on its own charging circuit is controlled to be in the off state, so as to achieve the effect that the switches on the charging circuits of each battery pack in the electrical equipment are in the off state.

It can be understood that controlling the switch on the battery pack discharge circuit to be in an off state may be controlling each switch on the battery pack discharge circuit to be in an off state. For example, when the discharge circuit includes a switch, the switch is controlled to be in an off state. In the embodiment shown in FIG3 , the charging switch CHG1 and the discharging switch DSG1 are controlled to be in an off state.

Controlling the switch on the battery pack charging circuit to be in an off state may be controlling each switch on the battery pack charging circuit to be in an off state. For example, when the charging circuit includes a switch, the switch is controlled to be in an off state. In the embodiment shown in FIG3 , the charging switch CHG2 and the discharging switch DSG2 are controlled to be in an off state.

In some embodiments, in order to improve the safety of the battery pack when it is integrated into the electrical equipment, it is detected whether the operating data of the battery pack meets the parallel connection condition, and the battery pack is only integrated when the battery pack meets the first parallel connection condition. The operating data includes at least one of voltage data, current data, SOC data, temperature data, and communication status.

Specifically, in some embodiments, the first parallel connection condition includes at least one of the following:

(1) A voltage difference between the voltage of the first battery pack and the first voltage is within a first voltage difference range.

When the voltage difference between the battery packs is large, the circulating current formed between the battery packs is correspondingly large, and when the voltage difference between the battery packs is small, the circulating current formed between the battery packs is correspondingly small. Keeping the voltage difference between the voltage of the first battery pack and the first voltage within a certain voltage difference range can further reduce the circulating current between the battery packs.

The first voltage may be an average voltage of each battery pack, or a maximum voltage or a minimum voltage of each battery pack. In some embodiments, when the first battery pack is in a charging state, the first voltage is the minimum voltage of each battery pack, and when the first battery pack is in a discharging state, the first voltage is the maximum voltage of each battery pack.

The value of the first voltage distinguishes the charging and discharging states. In the charging state, the first voltage is the minimum voltage, and in the discharging state, the first voltage is the maximum voltage, which can further reduce the circulating current between the battery packs.

If the battery pack is in charging parallel operation, if the voltage difference between the battery pack and the battery pack with the smallest voltage is small, the charging current and discharging current between the battery packs can be well limited, thereby limiting the circulating current between the battery packs. If the battery pack is in discharging parallel operation, if the voltage difference between the battery pack and the battery pack with the largest voltage is small, the charging current and discharging current between the battery packs can be well limited, thereby limiting the circulating current between the battery packs. The charging current and discharging current between battery packs means that when two battery packs are in parallel operation, the battery pack with a higher voltage will discharge the battery pack with a lower voltage to form a discharge current, and the battery pack with a lower voltage will be charged by the battery pack with a higher voltage to form a charging current.

The battery packs may be all the battery packs in the electrical device, or may be battery packs connected in parallel.

(2) A difference between the SOC of the first battery pack and the first SOC is within a first SOC range.

When the SOC difference between the battery packs is large, the circulating current formed between the battery packs is correspondingly large, and when the SOC difference between the battery packs is small, the circulating current between the battery packs is correspondingly small. Keeping the SOC difference between the first battery pack and the first SOC within a certain SOC range can further reduce the circulating current between the battery packs.

The first SOC may be the average SOC of each battery pack, or the maximum SOC or minimum SOC of each battery pack. In some embodiments, when the first battery pack is in a charging state, the first SOC is the minimum SOC of each battery pack, and when the first battery pack is in a discharging state, the first SOC is the maximum SOC of each battery pack.

The value of the first SOC distinguishes the charging and discharging states. In the charging state, the first SOC is the minimum SOC, and in the discharging state, the first SOC is the maximum SOC, which can further reduce the circulating current between the battery packs.

If the battery pack is in the process of charging and parallel operation, if the SOC difference between the battery pack and the battery pack with the smallest SOC value is small, the charging current and discharging current between the battery packs can be well limited, thereby limiting the circulating current between the battery packs. If the battery pack is in the process of discharging and parallel operation, if the SOC difference between the battery pack and the battery pack with the largest SOC value is small, the charging current and discharging current between the battery packs can be well limited, thereby limiting the circulating current between the battery packs.

The battery packs may be all the battery packs in the electrical equipment, or may be battery packs connected in parallel.

(3) The temperature of the first battery pack is within the first temperature range.

Limiting the temperature of the first battery pack to within the first temperature range can reduce damage to other battery packs due to excessively high or low temperatures, or reduce the risk of thermal runaway caused by parallel operation.

(4) The first charging current rate is within a first current rate range, or the first discharging current rate is within a second current rate range. The first charging current rate is the maximum charging current rate of the battery packs connected in parallel, and the first discharging current rate is the maximum discharging current rate of the battery packs connected in parallel.

When the first battery pack is to be connected to an electrical device, if there is a large charging current or a large discharging current in the parallel-connected battery pack, a large circulating current may flow into the first battery pack, damaging the switch device in the first battery pack. Moreover, due to the large charging current or discharging current, the voltage, power and other detection values of the battery pack may be affected by the load and the detection may be inaccurate. At this time, parallel connection may also have certain risks.

To improve the safety of the first battery pack, during discharge, the maximum discharge current rate of each battery pack connected in parallel is obtained. If the maximum discharge current rate exceeds the second current rate range, the first battery pack is not integrated. During charging, the maximum charge current rate of each battery pack connected in parallel is obtained. If the maximum charge current rate exceeds the first current rate range, the first battery pack is not integrated.

In other embodiments, it is also possible to determine whether to perform the parallel operation on the first battery pack by the charging current value or the discharging current value. That is, the first parallel condition includes that the first charging current is within the first current range, or the first discharging current is within the second current range. The first charging current is the maximum charging current of the battery packs that have been connected in parallel, and the first discharging current is the maximum discharging current of the battery packs that have been connected in parallel.

The first battery pack can obtain the charging current rate or discharging current rate, charging current value or discharging current value of other battery packs by communication, for example, through a communication bus.

(5) Communication status of the first battery pack.

The communication status of the first battery pack is used to indicate that the first battery pack has successfully communicated with at least one of the battery packs. As a specific implementation, when the first battery pack receives a message from any other battery pack, it can be considered that the first battery pack has successfully communicated with any of the battery packs, and the merging operation (including determining whether the first parallel condition is met, etc.) can be performed.

In some embodiments, when the first battery pack does not receive a message from any battery pack, the first battery pack does not determine whether the first battery pack meets the first parallel condition, but is directly integrated into the power-consuming device and works as a single battery pack.

It is understandable that the first parallel connection condition may include one of the above conditions, or include at least two of the above conditions at the same time. When the first parallel connection condition includes at least two of the above conditions, the first battery pack must meet at least two conditions at the same time before the first battery pack can perform the incorporation operation.

The first pressure difference range, the first SOC range, the first temperature range, the first current rate range, and the second current rate range can be set according to specific application conditions, for example, according to the applicability of the battery pack, including: the characteristics of the battery cells in the battery pack (including the maximum allowable charge and discharge rate and/or time of the battery cells), the overcurrent capacity of the connector or connecting harness, the withstand voltage and overcurrent capacity of the electrical equipment, the performance of components in the battery pack (such as switches), and other settings.

In some of the embodiments, the first pressure difference range can be set according to the internal resistance of the battery pack and the ability to withstand the maximum circulating current. The pressure difference range can be roughly the product of the tolerable circulating current size and the internal resistance of the battery pack. For example, the first pressure difference range can be [-1V, 1V], [-0.5V, 0.5V], etc. The first pressure difference range is not intended to limit the present application.

The SOC difference between the battery packs can affect the circulation time between the battery packs. The greater the SOC difference between the two battery packs, the longer the circulation time will be after the two battery packs are connected in parallel. Therefore, the SOC range can be set according to the circulation time that the battery pack can withstand. In a specific implementation, the first SOC range can be set to [-5%, 5%].

In a specific implementation, the first temperature range may be set to [-10, 50°C], the first current multiplier range may be set to 0.2-0.3°C, and the second current multiplier range may be set to 2-3°C.

Among them, when the electric device is connected to the charger, it can be considered that the electric device and the battery pack are in a charging state. When the electric device is not connected to the charger, it can be considered that the electric device and the battery pack are in a discharging state. The discharge can include discharging the electronic components in the BMS (for example, powering the MCU on the BMS circuit board) and discharging the load of the electric device (for example, discharging the load such as the motor of the electric vehicle). The discharge state of the battery pack includes the standby state and the working state.

The battery pack can confirm that it is in a charging state through a charging signal. In one implementation, when the charger is connected to the charging port, the charger sends a charging signal to the battery pack through data communication. After the battery pack receives the charging signal, it can be confirmed that the battery pack is in a charging state.

In another implementation, a hardware detection circuit may be provided on the BMS to detect whether a charger is plugged into the charging port. Before and after the charger is plugged in, the hardware detection circuit outputs different level signals. After the controller on the BMS detects that the level signal is flipped, it can be determined that the charger has been plugged into the charging port and the electrical device and the battery pack are in a charging state.

If no charging signal is received, for example, if no charging signal is received within a preset time, it can be considered that the electrical device and the battery pack are in a discharging state.

In some embodiments, in order to make the battery packs that meet the parallel connection conditions roughly synchronized and connected, a parallel connection request instruction is also sent when the battery pack is connected to the electrical equipment.

FIG. 10 shows an embodiment of a method for connecting battery packs in parallel during charging, the method comprising:

101a: In response to the first battery pack satisfying the first parallel connection condition, the first battery pack sends a parallel connection request instruction.

101b: In response to the first battery pack being in a charging state, opening a switch on a discharge circuit of the first battery pack, and closing a charging switch on a charging circuit of the first battery pack.

As a specific implementation, the first battery pack executes parallel judgment logic (including judging whether the battery pack meets the first parallel condition), and when the first battery pack meets the first parallel condition, the first battery pack sends a parallel request instruction. When the first battery pack is in a charging state, the switch on the discharge circuit of the first battery pack is disconnected, so that the discharge circuit is in an open state, and the charging switch on the charging circuit of the first battery pack is closed, so that the charging path of the charging circuit is turned on, and the first battery pack can be charged through the charging path.

It can be understood that when the electrical equipment is just turned on, the switches on the charging circuit and the discharging circuit of the first battery pack are in the disconnected state. At this time, the microcontroller of the BMS10 of the first battery pack does not need to send an instruction to disconnect the switch on the discharge circuit. In this scenario, 101b may also include: in response to the first battery pack being in the charging state, closing the charging switch on the charging circuit of the first battery pack.

9 is used as an example to illustrate that in response to the first battery pack BT1 meeting the first parallel condition, the first battery pack BT1 sends a parallel request instruction. In response to the first battery pack BT1 being in a charging state, the charging switch CHG1 and the discharging switch DSG1 are opened, and the charging switch CHG2 is closed.

FIG. 11 shows an embodiment of a method for connecting battery packs in parallel during discharge, the method comprising:

102a: In response to the first battery pack satisfying the first parallel connection condition, the first battery pack sends a parallel connection request instruction.

102b: In response to the first battery pack being in a discharging state, opening a switch on a charging circuit of the first battery pack, and closing a discharging switch on a discharging circuit of the first battery pack.

As a specific implementation, the first battery pack executes parallel judgment logic, and when the first battery pack meets the first parallel condition, the first battery pack sends a parallel request instruction. When the first battery pack is in a discharging state, the switch on the charging circuit of the first battery pack is disconnected, so that the charging circuit is in a disconnected state, and the discharge switch on the discharge circuit of the first battery pack is closed, so that the discharge path of the discharge circuit is turned on, and the first battery pack can discharge through the discharge path.

It is understandable that when the electrical equipment is just turned on, the switches on the charging circuit and the discharging circuit of the first battery pack are both in the disconnected state. At this time, the microcontroller of the BMS10 of the first battery pack may not send an instruction to disconnect the switch on the charging circuit. In this scenario, 102b may also include: in response to the first battery pack being in the discharging state, closing the discharge switch on the discharge circuit of the first battery pack.

Taking the embodiment shown in FIG9 as an example, in response to the first battery pack meeting the first parallel condition, the first battery pack sends a parallel request instruction. In response to the first battery pack being in a discharging state, the charging switch CHG2 and the discharging switch DSG2 are opened, and the discharging switch DSG1 is closed.

The parallel connection request instruction can be used to notify other battery packs to be connected to the power-consuming device. When other battery packs also meet the first parallel connection condition, the other battery packs are also connected to the power-consuming device, so that the first battery pack and other battery packs are roughly synchronously connected to each other.

In some embodiments, the battery pack in the electrical device can periodically execute the parallel judgment logic at a certain interval (e.g., 1S, 2S, etc.), and the battery pack will also execute the parallel judgment logic after receiving the parallel request instruction sent by other battery packs. Since the parallel request instruction will form an event trigger, triggering the battery pack to execute the parallel judgment logic, the battery pack can periodically execute the parallel judgment logic at a longer interval, which can reduce the amount of calculation of the battery pack.

On the other hand, the parallel request instruction can also carry information used to indicate the charging and discharging status of the electrical equipment. The battery pack may misjudge the charging and discharging status. For example, battery pack A is still in the discharging state because it has not received the charging signal sent by the charger. If battery pack A can receive the parallel request instruction sent by other battery packs, the working state of battery pack A can be corrected and changed to the charging state. In other words, the parallel request instruction can reduce the battery pack's misjudgment of the working state.

The following describes the parallel charging and parallel discharging methods of the battery packs, that is, the control of the charging circuit when the battery pack is charged, and the control of the discharging circuit when the battery pack is discharged.

In some embodiments, the first battery pack performs parallel charging, including: closing a charging switch on a charging circuit of the first battery pack. Alternatively, it includes: closing a charging switch and a discharging switch on a charging circuit of the first battery pack. When there are other battery packs connected in parallel, the other battery packs may transmit circulating current to the first battery pack through the circulating current paths of the other battery packs.

Please refer to FIG. 9 , when the battery pack BT1 is not connected in parallel and the battery pack BT2 is connected in parallel, if the voltage of BT2 is higher than that of BT1, a circulating current may be transmitted to BT1 through the circulating current path.

In other embodiments, in order to reduce the circulating current, the battery packs performing parallel charging also include operating the circulating current path. Taking the embodiment shown in FIG9 as an example, the electric device is in the charging state, the battery pack BT1 is not incorporated (the battery pack BT1 can represent an uncharged parallel battery pack), and the battery pack BT2 is incorporated (the battery pack BT2 can represent one or more charged parallel battery packs). Please refer to FIG12a for the status of the battery packs BT1 and BT2.

The battery pack BT1 can be charged in parallel in the following four stages:

Phase 1: Disconnect the circulation path of BT2.

The conduction and disconnection of the circulation path in the charging circuit can be controlled by the discharge switch. Disconnecting the circulation path can be by disconnecting the discharge switch in the charging circuit. Taking the embodiment shown in Figure 9 as an example, disconnecting the circulation path of BT2 includes disconnecting the discharge switch DSG4 of BT2. Before closing the switch on the charging circuit of the battery pack BT1, the battery pack BT2 can be cut off from transmitting the circulation current to the battery pack BT1 through the circulation path. Please refer to Figure 12b.

As a specific implementation manner, the battery pack BT2 disconnects the discharge switch on the charging circuit of the battery pack BT2 in response to receiving a parallel request instruction (in this embodiment, receiving a parallel request instruction sent by BT1).

In this embodiment, BT2 is in a charged parallel state. In order to reduce the circulation between the first battery pack BT1 and the second battery pack BT2, the circulation path of BT2 is first disconnected, and then the charging path of BT1 is closed. In other embodiments, when the electrical equipment is just turned on, the charging circuit and the discharging circuit of each battery pack are in a disconnected state, and the circulation path of each battery pack is in a disconnected state. This stage 1 can be omitted, and stage 1 can be directly skipped to execute stage 2. In some other embodiments of the present application, the circulation path of the second battery pack BT2 can be disconnected by executing the operation of stage 1.

Phase 2: Turn on the charging path of BT1.

The on and off of the charging path in the charging circuit can be controlled by the charging switch, and the on charging path can be the charging switch in the closed charging circuit. Taking the embodiment shown in FIG9 as an example, the charging path of BT1 includes closing the charging switch CHG2 of BT1. The battery pack BT1 can be charged through the charging path, please refer to FIG12c.

In some embodiments, in order to confirm that the circulation path of the parallel battery pack is in a disconnected state and reduce the circulation, the battery pack BT1 closes the charging switch on the charging circuit in response to receiving the first information. The first information is used to indicate that the circulation path of the battery pack BT2 has been disconnected. In this embodiment of the present application, it can be that the discharge switch on the charging circuit of the battery pack BT2 is in a disconnected state.

Phase 3: Turn on the circulation path of BT1 and BT2.

The conducting loop current path can be achieved by closing the discharge switch in the charging loop. Taking the embodiment shown in FIG. 9 as an example, the conducting loop current path of BT1 includes closing the discharge switch DSG2, and the conducting loop current path of BT2 includes closing the discharge switch DSG4 of BT2, please refer to FIG. 12d.

To limit the circulating current, in some embodiments, stage 3 further includes: in response to the operating data of the battery pack BT1 satisfying the first condition, closing the discharge switch on the charging circuit of the battery pack BT1, and/or, in response to the operating data of the battery pack BT2 satisfying the first condition, closing the discharge switch on the charging circuit of the battery pack BT2. The first condition is used to indicate the condition for limiting the circulating current, and may include at least one of the following conditions:

(1) The charging current of the battery pack is greater than or equal to the first current threshold.

(2) The charging current of the battery pack is less than the first current threshold, and the voltage difference between the voltage of the battery pack and the second voltage is within a second voltage difference range.

Taking the battery pack BT1 as an example, according to I=V/R, if the internal resistance remains unchanged, the larger the current I, the larger the voltage V. When the battery pack BT1 is in the charging state, the internal resistance of the battery pack is considered to be roughly the same. Then, the larger the charging current, the larger the voltage difference between the battery pack BT1 and the charger, and the smaller the battery pack voltage.

If the charging current of the battery pack BT1 is greater than or equal to the first current threshold, the voltage difference between the battery pack and the charger is large, the voltage of the battery pack is small, and the battery pack with a small voltage needs to be charged first. Because charging the battery pack with a small voltage first can reduce the voltage difference between the battery packs, it can be considered that the battery pack BT1 meets the circulation limit conditions.

If the charging current of battery pack BT1 is less than the first current threshold, the voltage difference between the battery pack and the charger is small, the voltage of the battery pack is large, and the voltage of the battery pack is closer to the charger. Battery pack BT1 may discharge to other battery packs (i.e., a circulation occurs). At this time, it can be further combined with other operating data to determine whether battery pack BT1 has a circulation risk.

Therefore, when the charging current of the battery pack BT1 is greater than or equal to the first current threshold, it can be considered that the first battery pack meets the circulation restriction condition, its circulation path can be turned on, and the discharge switch on the charging circuit of the battery pack BT1 is closed.

When the charging current of the battery pack BT1 is less than the first current threshold, it can be further determined whether the voltage difference between the battery pack BT1 and the second voltage is within the second voltage difference range. If the voltage difference is within the second voltage difference range, the voltage difference between the battery packs is small, and the risk of large circulation is small. The circulation path can be turned on and the discharge switch on the charging circuit of the battery pack BT1 can be closed.

Among them, those skilled in the art can understand that "large circulation current" means that the circulation current value between the battery pack BT1 and other battery packs is larger, and conversely, "small circulation current" means that the circulation current value between the battery pack BT1 and other battery packs is smaller.

If the charging current of the battery pack BT1 is less than the first current threshold, and the voltage difference between the voltage of BT1 and the second voltage exceeds the second voltage difference range, the discharge switch on the charging circuit is not closed. In some embodiments, the judgment may be made again after a period of time.

The second voltage may be an average voltage of each battery pack, or a maximum voltage or a minimum voltage of each battery pack. In some embodiments, the second voltage is the minimum voltage of each battery pack.

The second pressure difference range can be set according to specific application conditions, for example, according to the applicability of the battery pack, the performance of components (such as switches) in the battery pack, etc. The second pressure difference range and the first pressure difference range can be the same or different. In some embodiments, the second pressure difference range is within the first pressure difference range, and the second pressure difference range is smaller than the first pressure difference range.

The first current threshold can be set according to the specific application, for example, according to the maximum charging current and/or time allowed by the battery cells in the battery pack, the model and specification of the charger, the overcurrent capacity of the connector or connecting harness, the withstand voltage and overcurrent capacity of the electrical equipment, and the performance of the components (such as switches) in the battery pack. In a specific implementation of the present application, the first current threshold can be 2A.

Phase 4: If there is a risk of circulating current, disconnect the charging circuit of BT1 or only disconnect the circulating current path. If there is no risk of circulating current, complete the charging and parallel operation.

To further reduce the circulating current, after the charging switch and the discharging switch on the charging circuit of the battery pack BT1 are closed, a step of further judging the circulating current risk is included. If there is a circulating current risk, the discharging switch and the charging switch on the charging circuit of the battery pack BT1 are disconnected, or only the discharging switch on the charging circuit of the battery pack BT1 can be disconnected. If there is no circulating current risk, the circulating current path of the battery pack BT1 is kept open. In other embodiments, the battery pack charging in parallel may not include stage 4.

Whether there is a circulation risk between battery packs can be determined by determining whether the battery pack meets a first circulation condition, wherein the first circulation condition includes that the absolute value of the difference between the current rate of the first battery pack and the first current rate is greater than or equal to a first current rate threshold.

The first current rate is the maximum charging current rate of each battery pack connected in parallel. As a specific implementation method, the charging current of each battery pack connected in parallel can be obtained, and then the maximum charging current rate is selected as the first current rate.

When the current directions of the two battery packs are opposite, for example, the current of one battery pack is positive and the current of the other battery pack is negative, it can be considered that one battery pack is charging and the other battery pack is discharging, and the risk of circulation between the battery packs is relatively high. When the currents of the two battery packs are both positive or both negative, but the values differ greatly, the risk of circulation between the battery packs is also relatively high. The embodiment of the present application uses the maximum charging current rate (i.e., the first current rate) of each battery pack connected in parallel as a benchmark, and uses the absolute value of the difference between the current rate of the first battery pack and the first current rate as a judgment condition, which can well identify the risk of circulation.

For example, the discharge current can be specified as negative and the charge current as positive. When the current of the battery pack BT1 is the discharge current, the current multiplier of the battery pack BT1 is negative, the first current multiplier is positive, and the absolute value of the difference between the two is large. When the current of the battery pack BT1 is the charging current, the current multiplier of the battery pack BT1 and the first current multiplier are both positive. If the current multiplier of the battery pack BT1 differs greatly from the first current multiplier, the absolute value of the difference between the two is also large. In some other embodiments, the discharge current can also be specified as positive and the charge current can be specified as negative.

In other embodiments, the presence of a circulating current risk may also be determined by the charging current value. The first circulating current condition may also include: the absolute value of the difference between the current of the first battery pack and the first current is greater than or equal to the first current threshold. The first current is the maximum charging current of each battery pack connected in parallel.

The first current rate threshold can be set according to the specific application situation, for example, it can be determined according to the maximum charging current and/or time allowed by the battery cells in the battery pack, the model and specifications of the charger, the overcurrent capacity of the connector or connecting harness, the voltage resistance and overcurrent capacity of the electrical equipment, and the performance of components in the battery pack (such as switches).

FIG. 13 shows a flow chart of a specific embodiment of parallel charging of battery packs.

In some embodiments, the first battery pack performs discharge in parallel, including: closing a discharge switch on a discharge loop of the first battery pack. Alternatively, including: closing a charge switch and a discharge switch on a discharge loop of the first battery pack. When there are other battery packs connected in parallel, the first battery pack may transmit circulating current to the other battery packs through the circulating current paths of the other battery packs.

Please refer to FIG. 9 , when the battery pack BT1 is not connected in parallel and the battery pack BT2 is connected in parallel, if the voltage of BT1 is higher than that of BT2, a circulating current may be transmitted to BT2 through the circulating current path.

In other embodiments, in order to reduce the circulating current, the battery pack performs discharge parallel connection and also includes the operation of the circulating current path. Taking the embodiment shown in FIG9 as an example, the electric device is in the discharge state, the battery pack BT1 is not incorporated (the battery pack BT1 can represent a battery pack that is not discharged in parallel), and the battery pack BT2 is incorporated (the battery pack BT2 can represent one or more battery packs that are discharged in parallel). Please refer to FIG14a for the status of the battery packs BT1 and BT2.

The battery pack BT1 can perform discharge parallel connection in the following four stages:

Phase 1: Disconnect the circulation path of BT2.

The conduction and disconnection of the circulation path in the discharge circuit can be controlled by the charging switch. Disconnecting the circulation path can be disconnecting the charging switch in the discharge circuit. Taking the embodiment shown in Figure 9 as an example, disconnecting the circulation path of BT2 includes disconnecting the charging switch CHG3 of BT2, so that the battery pack BT1 cannot transmit the circulation current to the battery pack BT2 through the circulation path, and the circulation current can be further reduced. Please refer to Figure 14b.

As a specific implementation manner, the battery pack BT2 disconnects the charging switch on the discharge circuit of the battery pack BT2 in response to receiving a parallel request instruction (in this embodiment, receiving a parallel request instruction sent by BT1).

In this embodiment, BT2 is in a state of being discharged in parallel. In order to reduce the circulation between the first battery pack BT1 and the second battery pack BT2, the circulation path of BT2 is first disconnected, and then the discharge path of BT1 is turned on. In other embodiments, when the electrical equipment is just turned on, the switches on the charging circuit and the discharging circuit of each battery pack can be considered to be in a disconnected state, and the circulation path of each battery pack is in a disconnected state. Then, stage 1 can be omitted, and stage 1 can be directly skipped to execute stage 2. In some other embodiments of the present application, the circulation path of the second battery pack BT2 can be disconnected by executing the operation of stage 1.

Phase 2: Turn on the discharge path of BT1.

The conduction and disconnection of the discharge path in the discharge circuit can be controlled by the discharge switch, and the conduction discharge path can be the discharge switch in the closed discharge circuit. Taking the embodiment shown in FIG9 as an example, the discharge path of conducting BT1 includes closing the discharge switch DSG1 of BT1. The battery pack BT1 can be charged through the discharge path, please refer to FIG14c.

In an embodiment including a pre-discharge switch, such as the embodiment shown in FIG. 6 b and FIG. 6 d , before closing the discharge switch, the pre-discharge switch may be closed first, and then the pre-discharge switch may be opened after a certain time interval, and the discharge switch may be closed.

In some embodiments, in order to confirm that the circulation path of the parallel battery pack is in a disconnected state and reduce the circulation, the battery pack BT1 closes the discharge switch on the discharge loop in response to receiving the second information. The second information is used to indicate that the circulation path of the battery pack BT2 has been disconnected. In this embodiment of the present application, it may be that the charging switch on the discharge loop of the battery pack BT2 is in a disconnected state.

Phase 3: Turn on the circulation path of BT1 and BT2.

The conducting circulation path can be realized by closing the charging switch in the discharge loop. Taking the embodiment shown in FIG. 9 as an example, the conducting circulation path of BT1 includes closing the charging switch CHG1, and the conducting circulation path of BT2 includes closing the charging switch CHG3 of BT2, please refer to FIG. 14d.

To limit the circulating current, in some specific embodiments, stage 3 may also include: in response to the operating data of the battery pack BT1 satisfying the second condition, closing the charging switch on the discharge circuit of the battery pack BT1, and/or, in response to the operating data of the battery pack BT2 satisfying the second condition, closing the charging switch on the discharge circuit of the battery pack BT2. The second condition is used to indicate the condition for limiting the circulating current, and may include at least one of the following conditions:

(1) The discharge current of the battery pack is greater than or equal to the second current threshold.

(2) The discharge current of the battery pack is less than the second current threshold, and the voltage difference between the voltage of the battery pack and the third voltage is within the third voltage difference range.

Taking the battery pack BT1 as an example, according to I=V/R, if the internal resistance remains unchanged, the larger the current I, the larger the voltage V. When the battery pack BT1 is in a discharging state, the internal resistance of the battery pack is considered to be roughly the same. Then, the larger the discharge current, the larger the voltage difference between the battery pack BT1 and the load, and the larger the battery pack voltage.

If the discharge current of the battery pack BT1 is greater than or equal to the second current threshold, the voltage difference between the battery pack and the load is large, and the voltage of the battery pack is large. The battery pack with a large voltage needs to be discharged first, because discharging the battery pack with a large voltage first can reduce the voltage difference between the battery packs. Therefore, it can be considered that the battery pack BT1 meets the circulation limit conditions.

If the discharge current of battery pack BT1 is less than the second current threshold, the voltage difference between the battery pack and the load is small, the voltage of the battery pack is small, and the voltage of the battery pack is closer to the load. Other battery packs may discharge to battery pack BT1 (i.e., circulating current occurs), and at this time, further judgment can be made in combination with other electrical parameters.

Therefore, when the discharge current of the battery pack BT1 is greater than or equal to the second current threshold, it can be considered that the first battery pack meets the circulation restriction condition, and its circulation path can be turned on to close the charging switch on the discharge loop.

When the discharge current of the battery pack BT1 is less than the second current threshold, it can be further determined whether the voltage difference between the battery pack BT1 and the third voltage is within the third voltage difference range. If the voltage difference is within the third voltage difference range, the voltage difference between the battery packs is small, and the risk of large circulation is small. The circulation path can be turned on and the charging switch on the discharge circuit of the battery pack BT1 can be closed.

Among them, those skilled in the art can understand that "large circulation current" means that the circulation current value between the battery pack BT1 and other battery packs is larger, and conversely, "small circulation current" means that the circulation current value between the battery pack BT1 and other battery packs is smaller.

If the discharge current of the battery pack BT1 is less than the second current threshold, and the voltage difference between the voltage of BT1 and the third voltage exceeds the third voltage difference range, the charging switch on the discharge loop is not closed. In some embodiments, the judgment may be made again after a period of time.

The third voltage may be an average voltage of each battery pack, or a maximum voltage or a minimum voltage of each battery pack. In some embodiments, the third voltage is the maximum voltage of each battery pack.

The third pressure difference range can be set according to specific application conditions, for example, according to the maximum charging current and/or time allowed for the battery cells in the battery pack, the model and specifications of the charger, the overcurrent capacity of the connector or connecting harness, the withstand voltage and overcurrent capacity of the electrical equipment, and the performance of the components (such as switches) in the battery pack. The third pressure difference range and the first pressure difference range can be the same or different. In some embodiments, the third pressure difference range is within the first pressure difference range, and the range of the third pressure difference range is smaller than the first pressure difference range.

The second current threshold can be set according to the specific application, for example, according to the maximum charging current and/or time allowed by the battery cells in the battery pack, the model and specification of the charger, the overcurrent capacity of the connector or connecting harness, the withstand voltage and overcurrent capacity of the electrical equipment, and the performance of the components (such as switches) in the battery pack. In a specific implementation of the present application, the second current threshold can be 2A.

Phase 4: If there is a risk of circulating current, disconnect the discharge circuit of BT1, or just disconnect the circulating current path. If there is no risk of circulating current, complete the charging and parallel operation.

To further reduce the circulating current, after the charging switch and the discharging switch on the discharge circuit of the battery pack BT1 are closed, a step of judging the circulating current risk is also included. If there is a circulating current risk, the charging switch and the discharging switch on the discharge circuit of the battery pack BT1 are disconnected, or only the charging switch can be disconnected. If there is no circulating current risk, the circulating current path of the battery pack BT1 is kept open. In other embodiments, the battery pack discharge in parallel may not include stage 4.

Whether there is a circulation risk between battery packs can be determined by determining whether the battery pack meets a second circulation condition, wherein the second circulation condition includes that the absolute value of the difference between the current rate of the first battery pack and the second current rate is greater than or equal to a second current rate threshold.

The second current rate is the maximum discharge current rate among the battery packs connected in parallel. As a specific implementation, the discharge currents of the battery packs connected in parallel can be obtained, and then the maximum discharge current rate is selected as the second current rate.

When the current directions of the two battery packs are opposite, for example, the current of one battery pack is positive and the current of the other battery pack is negative, it can be considered that one battery pack is charging and the other battery pack is discharging, and the risk of circulation between the battery packs is relatively high. When the currents of the two battery packs are both positive or both negative, but the values differ greatly, the risk of circulation between the battery packs is also relatively high. The embodiment of the present application uses the maximum discharge current rate (i.e., the second current rate) in each battery pack connected in parallel as a benchmark, and uses the absolute value of the difference between the current rate of the first battery pack and the second current rate as a judgment condition, which can well identify situations where there is a risk of large circulation.

For example, the discharge current can be set as negative and the charge current as positive. When the current of the battery pack BT1 is the charge current, the current magnification of the battery pack BT1 is positive, the second current magnification is negative, and the absolute value of the difference between the two is large. When the current of the battery pack BT1 is the discharge current, the current magnification of the battery pack BT1 and the first current magnification are both negative. If the current magnification of the battery pack BT1 differs greatly from the first current magnification, the absolute value of the difference between the two is also large.

In some other implementations, the discharge current may be positive and the charge current may be negative.

In some other embodiments, the presence of a circulating current risk may also be determined by the discharge current value. The first circulating current condition may also include: the absolute value of the difference between the current of the first battery pack and the second current is greater than or equal to the second current threshold. The second current is the maximum discharge current of each battery pack connected in parallel.

The second current threshold can be set according to specific application conditions, for example, according to the large circulating current tolerance of the battery pack.

FIG. 15 shows a flow chart of a specific embodiment of parallel charging of battery packs.

In some embodiments, the battery pack parallel connection method also includes detecting the on/off state of a charging switch and/or a discharging switch on a charging circuit of the battery pack and sending a third message, and/or detecting the on/off state of a charging switch and/or a discharging switch on a discharging circuit of the battery pack and sending a fourth message.

The third information is used to indicate the on/off state of the charging switch and/or the discharging switch on the charging circuit, and the fourth information is used to indicate the on/off state of the charging switch and/or the discharging switch on the discharging circuit. In some embodiments of the present application, the third information and the fourth information may be referred to as checkback information.

As a specific implementation method, after sending a closing or opening signal to the charging switch or the discharging switch, the BMS will detect the on-off state of the charging switch or the discharging switch, and send the on-off state to other battery packs. By receiving the third information or the fourth information indicating the on-off state of the switch, other battery packs can know the on-off state of the switch of the battery pack that sent the information, clarify the specific stage of the battery pack in the parallel process, and provide a reference for the next stage of operation.

For example, taking the embodiment in which charging in parallel includes four stages, when the discharge switches on the charging circuits of battery pack BT1 and battery pack BT2 are in the disconnected state, the parallel process is in the first stage. Each battery pack can identify the current stage as the first stage through the received feedback information and can enter the second stage (closing the charging switch on the BT1 charging circuit).

When the charging switches on the charging circuits of battery pack BT1 and battery pack BT2 are in the closed state and the discharging switches are in the open state, the parallel process is in the second stage. Each battery pack can identify the current stage as the second stage through the received feedback information and can enter the third stage (closing the discharging switches on the charging circuits of BT1 and BT2).

When the charging switches on the charging circuits of battery pack BT1 and battery pack BT2 are in a closed state and the discharging switches are in a closed state, the parallel process is in the third stage. Each battery pack can identify the current stage as the third stage through the received feedback information and can enter the fourth stage.

In some embodiments of the present application, there is no step of detecting the on/off check information of the charging switch and/or the discharging switch during the parallel connection of the battery pack. Instead, a delay time is set for the on/off of the charging switch and/or the discharging switch. For example, after the BMS sends a control signal to disconnect or close the charging switch and/or the discharging switch, a period of time (for example, 1s) is extended to ensure that the switch is normally closed or disconnected. It can be understood that in the embodiment of the present application where there is a detection of the on/off of the charging switch and/or the discharging switch, it is not necessary to set a delay time, which is beneficial to shorten the parallel connection time of the battery pack. In addition, when the parallel connection process encounters a problem, a reset method is often used to restart the parallel connection process. The use of the back-check switch and the sending of back-check information can ensure the status of each stage, thereby ensuring to a certain extent that the predetermined parallel connection process can be executed and the parallel connection can be completed.

FIG16 takes charging as an example and shows a flow chart of an embodiment of a battery pack parallel connection method including a backcheck step. The switch backcheck operation during discharge can be referred to FIG16 and will not be described in detail here.

An embodiment of the present application also provides a storage medium storing computer executable instructions, which are executed by one or more processors, such as a processor 11 in Figure 7, so that the one or more processors can execute the battery pack parallel connection method in any of the above method embodiments, for example, execute method steps 101 and 102 in Figure 8 described above.

The embodiment of the present application also provides a computer program product, the computer program product includes a computer program stored on a non-volatile computer-readable storage medium, the computer program includes program instructions, when the program instructions are executed by a machine (such as a BMS), the machine executes the above-mentioned battery pack parallel connection method. For example, execute the method steps 101 and 102 in Figure 8 described above.

The above description is only an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them. Under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order. It should be understood by ordinary technicians in this field that they can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims (19)

A battery pack parallel connection method, characterized in that: In response to the first battery pack satisfying the first parallel condition and the first battery pack being in a charging state, controlling the switch on the discharge circuit to be in an off state, so that the first battery pack performs charging in parallel; or, In response to the first battery pack satisfying the first parallel connection condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit to be in an off state, so that the first battery pack performs a discharging parallel connection; Among them, the first parallel condition includes that the operating data of the first battery pack meets the parallel condition, and the operating data includes at least one of voltage data, current data, SOC data, temperature data, and communication status. The battery pack parallel connection method according to claim 1, characterized in that: The first parallel connection condition includes at least one of the following: A voltage difference between the voltage of the first battery pack and the first voltage is within a first voltage difference range; The difference between the SOC of the first battery pack and the first SOC is within a first SOC range; The temperature of the first battery pack is within a first temperature range; The first charging current rate is within a first current rate range, or the first discharging current rate is within a second current rate range; a communication status of the first battery pack; Among them, when the first battery pack is in a charging state, the first voltage is the minimum voltage among all battery packs, and the first SOC is the minimum SOC among all battery packs; when the first battery pack is in a discharging state, the first voltage is the maximum voltage among all battery packs, and the first SOC is the maximum SOC among all battery packs; the first charging current ratio is the maximum charging current ratio among the battery packs connected in parallel, and the first discharging current ratio is the maximum discharging current ratio among the battery packs connected in parallel, and the communication status of the first battery pack is used to indicate that the first battery pack has successfully communicated with at least one of the battery packs. The battery pack parallel connection method according to claim 1, characterized in that: The controlling the switch on the discharge circuit to be in an off state, and the first battery pack to perform parallel charging, comprises: controlling the switch on the discharge circuit of the first battery pack and/or each parallel-connected battery pack to be in an off state, and the first battery pack to perform parallel charging; The controlling of the switch on the charging circuit to be in an off state, and the first battery pack performing discharge in parallel, includes: controlling the switch on the charging circuit of the first battery pack and/or each parallel-connected battery pack to be in an off state, and the first battery pack performing discharge in parallel. The battery pack parallel connection method according to any one of claims 1 to 3, characterized in that: In response to the first battery pack satisfying the first parallel condition and the first battery pack being in a charging state, controlling the switch on the discharge circuit to be in an off state, and the first battery pack performing charging in parallel, comprises: in response to the first battery pack satisfying the first parallel condition, the first battery pack sending a parallel request instruction; In response to the first battery pack being in a charging state, opening a switch on a discharge circuit of the first battery pack and closing a charging switch on a charging circuit of the first battery pack; or, The switch on the discharging circuit of the first battery pack is in an open state, and in response to the first battery pack being in a charging state, the charging switch on the charging circuit of the first battery pack is closed. The battery pack parallel connection method according to claim 4 is characterized in that: The closing of the charging switch on the charging circuit of the first battery pack includes: closing the charging switch in response to receiving first information, wherein the first information is used to indicate that the discharge switch on the charging circuit of the second battery pack is in an open state, and the second battery pack is a battery pack connected in parallel. The battery pack parallel connection method according to claim 4 is characterized in that: In response to the second battery pack receiving the parallel connection request instruction, the discharge switch on the charging circuit of the second battery pack is disconnected, and the second battery pack is a parallel connected battery pack. The battery pack parallel connection method according to any one of claim 4, characterized in that: In response to the first battery pack satisfying the first parallel condition and the first battery pack being in a charging state, controlling the switch on the discharge circuit of the first battery pack to be in an open state, and the first battery pack performing charging in parallel, further comprising: in response to the first battery pack satisfying the first condition, closing the discharge switch on the charging circuit of the first battery pack, and/or, in response to the second battery pack satisfying the first condition, closing the discharge switch on the charging circuit of the second battery pack, the second battery pack being a parallel-connected battery pack; The first condition includes at least one of the following: The charging current of the battery pack is greater than or equal to the first current threshold; The charging current of the battery pack is less than the first current threshold, and the voltage difference between the voltage of the battery pack and the second voltage is within a second voltage difference range, and the second voltage is the minimum voltage of each battery pack. The battery pack parallel connection method according to claim 7, characterized in that: The battery pack parallel connection method further includes: in response to the first battery pack satisfying a first circulation condition, disconnecting a charging switch and a discharging switch on a charging circuit of the first battery pack; Among them, the first circulation condition includes that the absolute value of the difference between the current rate of the first battery pack and the first current rate is greater than or equal to the first current rate threshold; the first current rate is the maximum charging current rate of all battery packs connected in parallel, and the current rate of the first battery pack includes a charging current rate or a discharging current rate, the charging current rate is a positive value, and the discharging current rate is a negative value. The battery pack parallel connection method according to any one of claims 1 to 3, characterized in that: In response to the first battery pack satisfying the first parallel connection condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit to be in an off state, so that the first battery pack performs discharge parallel connection, comprising: in response to the first battery pack satisfying the first parallel connection condition, the first battery pack sending a parallel connection request instruction; In response to the first battery pack being in a discharging state, opening a switch on a charging circuit of the first battery pack and closing a discharging switch on a discharging circuit of the first battery pack; or, The switch on the charging circuit of the first battery pack is in an open state, and in response to the first battery pack being in a discharging state, the discharge switch on the discharging circuit of the first battery pack is closed. The battery pack parallel connection method according to claim 9 is characterized in that: The closing of the discharge switch on the discharge loop of the first battery pack includes: closing the discharge switch in response to receiving second information, wherein the second information is used to indicate that the charging switch on the discharge loop of the second battery pack is in an open state, and the second battery pack is a battery pack connected in parallel. The battery pack parallel connection method according to claim 9, characterized in that it also includes: In response to the second battery pack receiving the parallel connection request instruction, the charging switch on the discharge circuit of the second battery pack is disconnected, and the second battery pack is a parallel connected battery pack. The battery pack parallel connection method according to any one of claim 9, characterized in that: In response to the first battery pack satisfying the first parallel connection condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit of the first battery pack to be in an off state, so that the first battery pack performs a discharging parallel connection, further comprising: In response to the first battery pack satisfying a second condition, closing a charging switch on a discharge circuit of the first battery pack, and/or, in response to the second battery pack satisfying a second condition, closing a charging switch on a charging circuit of the second battery pack, the second battery pack being a parallel-connected battery pack; The second condition includes at least one of the following: The discharge current of the battery pack is greater than or equal to the second current threshold; The discharge current of the battery pack is less than the second current threshold, and a voltage difference between the voltage of the battery pack and a third voltage is within a third voltage difference range, and the third voltage is a maximum voltage in each battery pack. The battery pack parallel connection method according to claim 12, characterized in that: In response to the first battery pack satisfying the first parallel connection condition and the first battery pack being in a discharging state, controlling the switch on the charging circuit of the first battery pack to be in an off state, and the first battery pack performing a discharging parallel connection, further comprising: In response to the first battery pack satisfying a second circulation condition, disconnecting a charging switch and a discharging switch on a discharging circuit of the first battery pack; Among them, the second circulating current condition includes that the absolute value of the difference between the current rate of the first battery pack and the second current rate is greater than or equal to the second current rate threshold, wherein the second current rate is the maximum discharge current rate of each battery pack connected in parallel, and the current rate of the first battery pack includes a charging current rate or a discharging current rate, the charging current rate is a positive value, and the discharging current rate is a negative value. The battery pack parallel connection method according to claim 1, characterized in that it also includes: Detecting the on/off status of a charging switch and/or a discharging switch on a charging circuit of a battery pack, and sending third information, wherein the third information is used to indicate the on/off status of the charging switch and/or the discharging switch on the charging circuit; and / or, Detect the on/off status of the charging switch and/or the discharging switch on the discharge circuit of the battery pack, and send fourth information, where the fourth information is used to indicate the on/off status of the charging switch and/or the discharging switch on the discharge circuit. The battery pack parallel connection method according to claim 1, characterized in that: The switch on the discharge circuit responds to the control signal and prolongs the first time to perform on-off. The switch on the charging circuit responds to the control signal and prolongs the second time to perform on-off. A battery management system, characterized in that it includes at least one processor, and A memory, wherein the memory is communicatively connected to the at least one processor, the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method described in any one of claims 1 to 15. A battery pack, comprising: a battery management system as claimed in claim 16. An electrical device, characterized in that it comprises: load; and The battery pack as claimed in claim 17, wherein the battery pack is used to power the load. A storage medium, characterized in that the storage medium stores computer executable instructions, and when the computer executable instructions are executed by a machine, the machine executes the method according to any one of claims 1 to 15.

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