Battery module equalization device and method

Abstract

A battery module equalization device comprises a sampling module, an equalization module and a microcontroller, and the equalization module comprises more than two equalization units; the first equalization unit is used for being connected with the microcontroller and the positive electrode of the first battery module, and the second equalization unit of the equalization module is used for being connected with the microcontroller and the positive electrode of the second battery module. The positive electrode of the first battery module and the positive electrode of the second battery module are electrically connected through the first equalization unit and the second equalization unit respectively; the sampling module is used for collecting a first equalizing current signal from the first battery module, collecting a second equalizing current signal from the second battery module, and electrically connecting the negative electrode of the first battery module with the negative electrode of the second battery module; and the microcontroller controls the on-off of the controllable switch according to the first equalizing current signal or the second equalizing current signal, so that the positive electrode of the first battery module and the positive electrode of the second battery module are connected or disconnected. And the security is improved while the equalization rate is improved.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a battery module balancing device and method. Background Technology

[0002] Battery packs are a crucial component of energy storage devices, typically comprising multiple battery modules and a battery management system. Each battery module consists of multiple individual cells, a supporting structure, and a casing. Due to individual differences among the cells, their capacity and voltage can vary during use. Battery balancing technology is commonly used to address these inconsistencies after battery pack assembly.

[0003] Most existing battery balancing methods are implemented through battery management systems during the charging and discharging process. For example, active balancing circuits or software algorithms can be used to divert voltage-high cells at the end of charging or the beginning of discharging. However, these methods are only applicable when the battery is in operation and depend on the external charging and discharging environment. They are not suitable for batteries that are not in operation or are in a static state, leading to the long-term accumulation of inconsistencies within the battery, which affects the overall battery capacity and safety during use. Summary of the Invention

[0004] In view of this, the present application provides a battery module balancing device and method to solve at least one problem existing in the background art.

[0005] In a first aspect, one embodiment of this application provides a battery module equalization device for equalizing two or more battery modules, comprising: a sampling module, an equalization module, and a microcontroller, wherein the equalization module includes two or more equalization units; Each of the equalization units is used to electrically connect to the positive electrode of different battery modules, so that the positive electrode of each battery module is electrically connected through different equalization units; each of the equalization units includes an equalization resistor and a controllable switch connected in series. The sampling module is used to connect to the negative electrode of different battery modules respectively, to collect the balanced current signal of different battery modules and output it to the microcontroller, and to connect the negative electrode of each battery module. The microcontroller is electrically connected to each equalization unit and is used to control the on / off state of the controllable switch according to the equalization current signal, so that the positive terminals of each battery module remain connected or disconnected.

[0006] In this aspect, by adopting an active balancing method, the battery modules are connected in parallel, enabling automatic charging and discharging among the battery modules to achieve mutual balancing. The current flows from the high-voltage battery module to the low-voltage battery module, improving the balancing rate. Furthermore, the controllable switches of the corresponding balancing units are turned on and off according to the balancing current. In the case of excessive balancing current, the battery module with excessive balancing current is disconnected, improving both the balancing rate and safety.

[0007] By connecting different equalization units to the positive terminals of each battery module, the positive terminals of multiple battery modules are connected together. When selecting some battery modules for equalization, it is only necessary to control the equalization unit directly connected to the target battery module to conduct, without the need to connect other equalization circuits or equalization units. This simplifies the circuit structure, shortens the equalization path, reduces the error rate in the control process, makes it easier to select and control multiple battery modules, improves the flexibility of control when equalizing multiple battery modules, and improves equalization efficiency.

[0008] In conjunction with the first aspect of this application, in an optional embodiment, the microcontroller is configured to be electrically connected to each battery module to obtain multiple voltage values ​​of each battery module, and to control whether each battery module is balanced and / or the conduction sequence between the positive terminals of each battery module according to the multiple voltage values.

[0009] In this implementation, the voltage difference between battery modules is determined based on their voltage values. If the difference is too large, equalization is not performed, thereby improving the safety of the equalization process. By obtaining the voltage values ​​of each battery module, the battery module with the largest voltage difference is preferentially selected for equalization, further improving the equalization rate.

[0010] In conjunction with the first aspect of this application, in an optional embodiment, the equalization unit includes at least two parallel branches, each branch including an equalization resistor and a controllable switch connected in series, and the microcontroller further controls the on / off state of the controllable switch according to the equalization current signal to control the on / off state of the parallel branches.

[0011] In this embodiment, by setting at least two parallel branches in the equalization unit, when the equalization current is too low, the parallel branches are closed at the same time to increase the equalization current and further improve the equalization rate.

[0012] In conjunction with the first aspect of this application, in an optional embodiment, the sampling module includes two or more sampling units, each of which is used to collect the equalization current signal of different battery modules and to electrically connect the negative terminals of different battery modules.

[0013] In this implementation, the negative terminals of each battery module are connected together via a sampling unit, simplifying the parallel connection of the battery modules. In controlling the conduction of the battery modules, only the positive terminals need to be controlled, simplifying the circuit structure. By using different sampling units to collect the equalization current of each battery module, the microcontroller can determine whether the equalization current of each battery module is too high, improving the control sensitivity and response speed, and further enhancing the safety of the equalization process.

[0014] In conjunction with the first aspect of this application, in an optional embodiment, the sampling unit includes a sampling circuit, an amplification circuit, and a reference circuit; the amplification circuit is connected to the sampling circuit and the microcontroller respectively, and is used to amplify the equalization current signal collected by the sampling circuit and output the amplified signal to the microcontroller; the reference circuit is used to provide a reference voltage signal to the amplification circuit.

[0015] In this implementation, the uncertain direction of the equalization current results in both positive and negative sampling signals, making data processing inconvenient. By using a reference circuit to uniformly convert the sampling signals into a predetermined data range greater than or equal to zero or less than or equal to zero, data processing becomes easier and the accuracy of data calculations is improved.

[0016] In conjunction with the first aspect of this application, in an optional embodiment, the controllable switch includes a transistor and a relay. The base of the transistor is connected to the microcontroller for receiving control signals. The emitter of the transistor is connected to the ground terminal, and the collector of the transistor is connected to the power supply. The control terminal of the relay is connected between the collector of the transistor and the power supply. The two pull-in terminals of the relay are respectively connected to the common terminal and the equalizing resistor.

[0017] In this embodiment, by employing a circuit structure combining transistors and relays, rapid and flexible control of multiple equalization units and multiple branch switching is achieved, thereby improving response speed, safety, and equalization rate.

[0018] Secondly, embodiments of this application provide a battery module balancing method for balancing multiple battery modules, comprising the following steps: S10: Dynamically acquire the voltage of each battery module to be balanced, and obtain multiple voltage values; S30, connect the battery modules corresponding to the maximum and minimum voltage values ​​among the multiple voltage values ​​in parallel to achieve balancing; S50, determine whether the voltage difference of the battery modules in the equalization is less than or equal to the second voltage threshold. If so, disconnect the battery modules in the equalization. S70, repeat steps S10 to S50 until the voltage difference between any two battery modules is less than or equal to the second voltage threshold, and complete the initial equalization. S90, connect the multiple battery modules after the initial equalization in parallel simultaneously for secondary equalization, and end the equalization process if the equalization termination condition is met.

[0019] In this aspect, during the initial equalization stage, the conduction sequence of the battery modules to be equalized is optimized. Each time, the battery modules with the largest voltage difference are selected for equalization, prioritizing those with the largest voltage difference. This ensures that equalization is performed with the maximum equalization current each time, thereby maximizing the equalization rate and shortening the equalization time. During the secondary equalization stage, multiple battery modules are connected in parallel simultaneously to increase the equalization current, ensuring thorough equalization and improving equalization efficiency. By employing both primary and secondary equalization stages and maximizing the equalization current in each stage, the overall equalization efficiency is significantly improved, and the equalization time is shortened.

[0020] In conjunction with a second aspect of this application, in an optional embodiment, step S30 further includes: S20, determine whether the voltage difference between the maximum and minimum voltage values ​​among the plurality of voltage values ​​is greater than the first voltage threshold. If not, proceed to step S30. If the first voltage threshold is greater than the second voltage threshold, exclude the battery module corresponding to the minimum voltage value from the battery modules to be balanced, and proceed to step S10.

[0021] In this aspect, by determining whether the voltage difference between the maximum and minimum voltage values ​​of multiple battery modules is greater than a first voltage threshold, battery modules with abnormal power or voltage are excluded, thus improving the safety of battery balancing.

[0022] In conjunction with a second aspect of this application, in an optional embodiment, step S30 further includes: S31, obtain the equalization current of each battery module during the equalization process; S32, determine whether any of the multiple equalization currents is greater than the first current threshold. If so, stop equalization and proceed to step S10.

[0023] In this regard, by determining whether the balancing current is greater than the first current threshold, the balancing unit is disconnected and balancing is stopped when the balancing current is too large, which improves the safety of the balancing process. Moreover, since the balancing current of different battery modules may be different at the same time, by collecting and judging each balancing current, the sensitivity and response speed of the control are improved, which further enhances the safety.

[0024] In conjunction with the second aspect of this application, in an optional embodiment, the battery modules are connected in parallel through two or more parallel balancing branches, and step S30 and / or S90 further includes: S81, obtain the equalization current of each battery module during the equalization process; S82, determine whether the equalization current of each battery module is less than the third current threshold. If so, close the parallel branch in the equalization unit connected to the corresponding battery module at the same time. The third current threshold is less than the first current threshold.

[0025] In this aspect, by determining whether the balancing current is less than the third current threshold, when the balancing current is too small, the parallel branches in the balancing unit connected to the battery module are closed at the same time to increase the balancing current and further improve the balancing rate.

[0026] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 Schematic diagram of a battery module balancing device provided in an embodiment of this application Figure 1 ; Figure 2 The circuit of the equalization unit in one embodiment of this application Figure 1 ; Figure 3 The circuit of the equalization unit in one embodiment of this application Figure 2 ; Figure 4 Schematic diagram of a battery module balancing device provided in an embodiment of this application Figure 2 ; Figure 5 This is a circuit diagram of a sampling unit in one embodiment of this application; Figure 6 This is a schematic diagram of a battery module balancing method provided in an embodiment of this application. Detailed Implementation

[0028] To make the technical solutions and beneficial effects of this application more apparent and understandable, the technical solutions in the embodiments of this application are clearly and completely described below by listing specific examples. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0030] It should be noted that the terms "first," "second," etc., used in this application may be used to describe various elements, but these elements are not limited by these terms. These terms are used only to distinguish one element from another, and not to describe a specific order or sequence. The terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, not excluding the presence or addition of one or more other features.

[0031] refer to Figure 1 This application provides a battery module equalization device 10 for equalizing two or more battery modules, including a sampling module 20, an equalization module 30, and a microcontroller (MCU) 40. The equalization module 30 includes two or more equalization units 31, 32...3n. Each equalization unit is used to electrically connect to the positive electrode of a different battery module, so that the positive electrode of each battery module is electrically connected through a different equalization unit.

[0032] The first equalization unit 31 is connected to the positive terminals of the microcontroller 40 and the first battery module 11, respectively. The second equalization unit 32 is connected to the positive terminals of the microcontroller 40 and the second battery module 12, respectively, and so on. The nth equalization unit 3n is connected to the positive terminals of the microcontroller 40 and the nth battery module 1n, respectively, so that the positive terminals of the first battery module 1, the second battery module 2, ... the nth battery module 1n are electrically connected through the first equalization unit, the second equalization unit, and so on, up to the nth equalization unit, and are all connected to the common terminal CON+. Wherein, n is a natural number greater than or equal to 2.

[0033] Each balancing unit includes a balancing resistor and a controllable switch connected in series. The balancing resistor limits the balancing current to prevent excessive current from impacting the battery module and damaging it. Figure 2 As shown, the balancing resistors include at least one set of resistors R16 and R17 connected in parallel. Using parallel resistors can improve overcurrent capability while avoiding large current surges. A controllable switch is used to control the on / off state of each balancing unit according to the control signal from the microcontroller 40, thereby controlling the on / off state of the electrical connection between the positive terminals of each battery module.

[0034] Sampling module 20 is used to electrically connect to the negative terminals of different battery modules, collect the equalization current signals of different battery modules and output them to microcontroller 40, and electrically connect the negative terminals of each battery module to the ground terminal AGND. Sampling module 30 is used to collect the first equalization current signal from the first battery module 11, the second equalization current signal from the second battery module 12, ..., the nth equalization current from the nth battery module 1n, and electrically connect the negative terminals of the first battery module 1, the second battery module 12, ..., and the nth battery module 1n. Sampling module 20 includes sampling resistors, and the negative terminals of each battery module are electrically connected through the sampling resistors and connected to the ground terminal AGND. By sampling from the negative terminals of the battery modules, the sampling voltage can be reduced, the sampling circuit can be protected, and the sampling safety can be improved.

[0035] The microcontroller 40 is electrically connected to each balancing unit and controls the on / off state of the controllable switches based on the collected balancing current signals to keep the positive terminals of each battery module connected or disconnected. Different balancing current signals represent the balancing current flowing through each battery module. The microcontroller 40 checks whether each of the n balancing current signals is greater than a first current threshold. If so, the microcontroller 40 disconnects the balancing unit of the battery module corresponding to that balancing current signal. If the balancing current is not greater than the first current threshold, the microcontroller 40 controls or keeps the controllable switches of each balancing unit closed, turning on the corresponding balancing unit and connecting the corresponding battery modules in parallel for balancing. This active balancing method connects the battery modules in parallel, enabling automatic charging and discharging between the battery modules. Current flows from the high-voltage battery module to the low-voltage battery module, increasing the balancing current and thus improving the balancing rate.

[0036] If a certain balancing current exceeds a first current threshold, it indicates that the balancing current of the battery module is too high, posing a safety risk such as burnt-out circuits or components. At this point, the microcontroller 40 controls the controllable switch of the balancing unit directly connected to the battery module to disconnect, thus stopping the balancing process. This improves both the balancing speed and the safety of the balancing process. Furthermore, since the balancing current of different battery modules may differ at the same time, by separately collecting the balancing current of each battery module and judging it one by one, if a certain balancing current becomes too high, the balancing of that battery module is immediately disconnected, thereby improving the control sensitivity and response speed.

[0037] The microcontroller 40 is also used to control the on / off state of the controllable switches of the equalization units according to the equalization termination conditions. When the equalization termination conditions are met, the controllable switches of each equalization unit are disconnected, and the equalization ends. The equalization termination conditions include: determining whether the equalization has ended based on the equalization time. The longer the equalization time, the more thorough the equalization. If the equalization time exceeds a certain predetermined value, it is considered that the battery modules have been sufficiently equalized, and the equalization can end. At this time, the microcontroller 40 controls the controllable switches to disconnect, and the equalization ends.

[0038] Optionally, the balancing termination condition also includes: determining whether balancing has ended based on the balancing current. When sufficient balancing has been achieved between battery modules, the balancing current between battery modules will become very small. If the balancing current signal is less than the second current threshold, it is considered that sufficient balancing has been achieved between battery modules, and balancing can be terminated. At this time, the microcontroller 40 controls the controllable switches of each balancing unit to open, and balancing ends. The second current threshold is less than the first current threshold.

[0039] Optionally, the equalization termination condition also includes determining whether equalization has ended based on the voltage difference between each battery module. The microcontroller 40 is also electrically connected to each battery module to obtain the voltage value of each battery module and determine whether equalization has ended based on the voltage difference between the battery modules. The more thorough the equalization, the smaller the voltage difference between the battery modules. When the voltage difference between the first battery module 11 and the second battery module 12 is less than a predetermined value, it indicates that the voltage values ​​between the two battery modules are equal or approximately equal, and equalization can end. At this time, the microcontroller 40 controls the controllable switch to open, and equalization ends. Optionally, the microcontroller 40 is connected to the battery modules via a CAN bus or daisy-chain method to obtain the voltage value of each battery module. Since the negative terminals of each battery module are electrically connected and all are connected to the ground terminal, the obtained voltage values ​​of the battery modules are the voltage values ​​of the positive terminals of each battery module relative to ground.

[0040] like Figure 2 The diagram illustrates possible implementations of each equalization unit, including equalization resistors connected in series and controllable switches. The equalization resistors include at least one set of first resistors R16 and second resistors R17 connected in parallel. Using parallel resistors as equalization resistors improves the overcurrent capability. Figure 3 The diagram illustrates a configuration using three sets of balancing resistors connected in series, each set including a parallel resistor. The number of balancing resistor sets is not limited to three and can be increased or decreased. By employing multiple sets of balancing resistors connected in series, each set including a parallel resistor, the overcurrent capability is improved while simultaneously enhancing current limiting capability.

[0041] The controllable switch includes a third transistor Q3 and a third relay RE3. The control terminal CN4 of transistor Q3 is connected to the microcontroller 40 to receive control signals. The emitter of transistor Q3 is connected to ground, and the collector of transistor Q3 is connected to the first voltage VCC1. The control terminals 1 and 2 of relay RE3 are connected between the collector of transistor Q3 and the power supply VCC1. The two pull-in terminals 3 and 4 of relay RE3 are connected to the equalizing resistor and the common terminal CON+, respectively. A third current-limiting resistor R15 is connected between the base of transistor Q3 and the control terminal CN4. J6 is the positive terminal of the battery module. J5 is the power supply terminal of power supply 60. F2 is a fuse, which provides current-limiting protection.

[0042] When the controllable switch control terminal CN4 receives a high-level control signal output by the microcontroller 40, the transistor Q3 turns on, and current flows through the control terminal of the relay RE3 connected to the collector of the transistor Q3. The relay RE3 energizing terminals 3 and 4 are energized, and equalization begins. The positive terminals of each battery module are connected together through the equalization resistor, and the negative terminals of each battery module are connected together through the sampling resistor, forming a closed loop. The equalization current flows out from the high-voltage battery module, through the equalization resistor and the controllable switch, and flows to the low-voltage battery module. With the positive terminal J6 of the battery module connected to the positive terminal of the high-voltage battery module, and the common terminal CON+ connected to the positive terminal of the low-voltage battery module, the balancing current flows in from terminal J6, passes through the balancing resistor and the controllable switch, and then flows out through the common terminal CON+ to reach the positive terminal of the low-voltage battery module. With the positive terminal J6 of the battery module connected to the positive terminal of the low-voltage battery module, and the common terminal CON+ connected to the positive terminal of the high-voltage battery module, the balancing current flows in from the common terminal CON+, passes through the controllable switch and the balancing resistor, and then flows out through terminal J6 to reach the negative terminal of the high-voltage battery module.

[0043] For cases where there are three or more battery modules requiring equalization, taking three as an example, the positive terminals of the first battery module 11, the second battery module 12, and the third battery module 1n are electrically connected via the first equalization unit 31, the second equalization unit 32, and the third equalization unit 3n, respectively, and are all connected to the common terminal CON+. The negative terminals of the first battery module 11, the second battery module 12, and the third battery module 13 are connected to the ground terminal via the sampling resistor of the sampling module 20. When equalization begins, the microcontroller 40 outputs a high-level control signal to the controllable switch of each equalization unit. The transistor Q1 of each equalization unit is turned on, the relay RE1 is energized, the positive terminals of each battery module are connected together via the equalization resistor, and the negative terminals of each battery module are connected together via the sampling resistor, all connected to the ground terminal, forming a closed loop. The equalization current flows out from the high-voltage battery module, through the equalization resistor, and to the low-voltage battery module.

[0044] The microcontroller 40 sequentially checks whether each of the n equalization current signals collected from the three battery modules exceeds a first current threshold. If a certain equalization current exceeds the first current threshold, the microcontroller 40 disconnects the equalization unit of the battery module corresponding to that equalization current signal, and the remaining two battery modules undergo equalization. Assuming the first equalization current signal exceeds the first current threshold, the microcontroller 40 outputs a low-level control signal to the transistor of the first equalization unit 31, causing the relay in the first equalization unit 31 to disconnect, thus disconnecting the equalization circuit of the first battery module 11. At this time, the remaining battery modules undergo equalization. If only two battery modules undergo equalization, then the equalization process ends.

[0045] The working principle of the battery module equalization device 10 in this embodiment is as follows: First, disconnect the interconnection of two or more battery modules that need to be equalized. Connect the negative terminal of each battery module to the sampling terminal of the sampling module 20, and connect the positive terminal of each battery module to the access terminal of each equalization unit. Connect the negative terminals of each battery module to be equalized together, and connect the positive terminals of each battery module to be equalized to the common terminal through the corresponding equalization unit. Before equalization begins, the controllable switches of each equalization unit are turned off.

[0046] The microcontroller 40 controls the controllable switches of each equalization unit to close, and equalization begins. The positive terminals of each battery module to be equalized are connected through equalization resistors, while the negative terminals of each battery module to be equalized are electrically connected through sampling module 20, all of which are connected to the ground terminal. At this time, the battery modules to be equalized are connected in parallel with each other, and the equalization current flows from the high-voltage battery module to the low-voltage battery module. After waiting for a period of time, the microcontroller determines whether the equalization end condition is met. If so, it disconnects the controllable switches of each equalization unit, and equalization is completed.

[0047] The battery module balancing device in this embodiment adopts an active balancing method, connecting the battery modules in parallel to enable automatic charging and discharging and mutual balancing among them. Current flows from the high-voltage battery module to the low-voltage battery module. Since the battery modules have relatively high voltages, typically ranging from 20V to 400V, the balancing current after parallel connection is also large, reaching a maximum of 20A, thus improving the balancing rate. It does not rely on a battery management system and requires no external power supply, overcoming the shortcomings of traditional balancing methods that rely on a battery management system and external power supply, such as low balancing current, slow balancing rate, and long cycle time. Compared to passive balancing methods, it reduces unnecessary energy loss.

[0048] Because the equalization current may be too high during the equalization process, there is a risk of circuit and component burnout. Therefore, the microcontroller 40 determines whether the collected equalization current signals exceed a first current threshold. If the equalization current signal of a certain battery module exceeds the first current threshold, it indicates that the equalization current of that battery module is too high. The microcontroller then controls the controllable switch of the corresponding equalization unit (or directly connected) to that battery module to disconnect, cutting off the equalization circuit and stopping the equalization of that battery module, thus achieving the purpose of protection. This improves both the equalization rate and safety. Furthermore, since the equalization current of different battery modules may differ at the same time, by collecting the equalization current of different battery modules separately and judging them one by one, the sensitivity and response speed of the control are improved.

[0049] By using multiple equalization units connected to the positive terminals of each battery module, the positive terminals of multiple battery modules are connected together. When selecting some battery modules for equalization, it is only necessary to control the equalization unit directly connected to the target battery module to conduct, without the need to connect other equalization circuits or equalization units. This simplifies the circuit structure, shortens the equalization path, reduces the error rate in the control process, makes it easier to select and control multiple battery modules, improves the flexibility of control when equalizing multiple battery modules, and improves equalization efficiency.

[0050] The battery module balancing device of this application solves the problem of inconsistent energy levels among battery modules caused by self-discharge during transportation, storage, and other applications. This device can increase the number of battery modules to be balanced, is highly scalable, plug-and-play, flexible in use, and does not rely on a battery management system or external power supply. Its balancing scenarios are not limited, improving ease of use and expanding its application scope.

[0051] In possible embodiments, such as Figure 3 As shown, the balancing unit includes at least two parallel branches, each branch including a balancing resistor and a controllable switch connected in series. The microcontroller also controls the on / off state of the controllable switches based on the balancing current signal to control the on / off state of the parallel branches. The microcontroller 40 controls the on / off state of each branch in the balancing unit connected to the positive terminal of the battery module corresponding to the obtained balancing current signal. Each balancing current signal represents the balancing current of each battery module. The microcontroller 40 determines whether a certain balancing current is less than a third balancing current threshold, wherein the third current threshold is less than a first current threshold and greater than a second current threshold. If so, it indicates that the balancing current of the battery module is too low. At this time, the microcontroller 40 controls the controllable switches of each branch in the balancing unit directly connected to the positive terminal of the battery module to close simultaneously to increase the balancing current and further improve the balancing rate.

[0052] Figure 3The diagram shows that the balancing unit includes two parallel branches, each branch employing three sets of series-connected balancing resistors. It is understood that the number of balancing branches is not limited to two, and the number of series resistors in each balancing branch is not limited to three sets; they can be adjusted as needed.

[0053] The first parallel branch includes three sets of equalizing resistors and controllable switches connected in series. The first set of equalizing resistors includes the third resistor R2 and the fourth resistor R5 connected in parallel; the second set of resistors includes the fifth resistor R3 and the sixth resistor R6 connected in parallel; and the third set of resistors includes the seventh resistor R4 and the eighth resistor R7 connected in parallel.

[0054] The controllable switch of the first parallel branch includes a first transistor Q1 and a first relay RE1. The first control terminal CN4 of the first transistor Q1 is connected to the microcontroller 40 to receive control signals. The emitter of the first transistor Q1 is connected to the ground terminal, and the collector of the first transistor Q1 is connected to the first voltage VCC1. The control terminals 1 and 2 of the first relay RE1 are connected between the collector of the first transistor Q1 and the first voltage VCC1. The two pull-in terminals 3 and 4 of the first relay RE1 are connected to the equalizing resistor and the common terminal CON+, respectively. A first current-limiting resistor R1 is connected between the base of the first transistor Q1 and the first control terminal CN4. J3 is the positive terminal of the battery module. J2 is the power supply terminal of the power supply 60. F1 is a fuse, which serves as a current-limiting protection.

[0055] The second parallel branch includes three sets of resistors and controllable switches connected in series. The fourth set of resistors includes the ninth resistor R8 and the tenth resistor R11 connected in parallel; the fifth set of resistors includes the eleventh resistor R9 and the twelfth resistor R12 connected in parallel; and the sixth set of resistors includes the thirteenth resistor R10 and the fourteenth resistor R13 connected in parallel.

[0056] The controllable switch in the second parallel branch includes a second transistor Q2 and a second relay RE2. The second control terminal CN1 of the second transistor Q2 is connected to the microcontroller 40 to receive control signals. The emitter of the second transistor Q2 is connected to ground, and the collector of the second transistor Q2 is connected to the first voltage VCC1. The control terminals 1 and 2 of the second relay RE2 are connected between the collector of the second transistor Q2 and the first voltage VCC1. The two pull-in terminals 3 and 4 of the second relay RE2 are connected to the equalizing resistor and the common terminal CON+, respectively. A second current-limiting resistor R14 is connected between the base of the second transistor Q2 and the second control terminal CN1. D1, D2, and D3 are freewheeling diodes for the relay.

[0057] During balancing, the microcontroller 40 first selects one of the two parallel branches to conduct. When the controllable switch control terminal CN1 or CN4 receives a high-level control signal output from the microcontroller 40, Q1 or Q3 conducts, current flows through the control terminal of relay RE1 or RE2, and the energizing terminals 3 and 4 of relay RE1 or RE2 are energized, balancing begins. The positive terminals of each battery module are connected together through the balancing unit and connected to the common terminal CON+. The negative terminals of each battery module are connected to the ground terminal through the sampling resistor, forming a closed loop. The balancing current flows out from the positive terminal of the high-voltage battery module, through the conducting balancing unit, and to the low-voltage battery module. The sampling module 20 collects the balancing current signal of each battery module during balancing and outputs it to the microcontroller 40. The microcontroller 40 determines whether the balancing current is less than the third current threshold. If it is less, it controls the parallel branches in the conducting balancing unit to conduct simultaneously. A balancing current less than the second current threshold indicates that the balancing current is too small. By controlling the parallel branches of the conducting balancing unit to conduct simultaneously, the balancing current is increased, further improving the balancing rate.

[0058] Optionally, in the above embodiments, field-effect transistors are used instead of bipolar transistors, and the device connection method is adjusted accordingly. The controllable switch can also be a thyristor or an IGBT.

[0059] In another embodiment, there are three or more battery modules to be balanced. A microcontroller 40 is electrically connected to each battery module to obtain multiple voltage values ​​for each module, and controls whether each battery module is balanced and / or the conduction sequence between the positive terminals of each module based on these multiple voltage values. Since the negative terminals of each battery module are electrically connected to ground, the obtained voltage values ​​for each battery module are the voltage values ​​of the positive terminal relative to the negative terminal. Multiple battery modules are sampled simultaneously each time, with each module corresponding to one voltage value, resulting in multiple voltage values. The microcontroller 40 selects the maximum and minimum voltage values ​​from the multiple voltage values, calculates the voltage difference, and determines whether the voltage difference between the maximum and minimum voltage values ​​is greater than a first voltage threshold. If so, the battery module corresponding to the minimum voltage value is excluded from the battery modules to be balanced, and balancing of that battery module is temporarily suspended. This allows abnormal battery modules to be excluded, improving the safety of the balancing process.

[0060] If the voltage difference between the maximum and minimum voltage values ​​among multiple voltage values ​​is not greater than a first voltage threshold, then the battery modules to be balanced are balanced. The balancing process consists of two stages: initial balancing and secondary balancing. In the initial balancing stage, the microcontroller 40 dynamically acquires the voltage of each battery module to be balanced, obtaining multiple voltage values. The battery modules corresponding to the maximum and minimum voltage values ​​are connected in parallel for balancing. By prioritizing the balancing of the battery modules corresponding to the maximum and minimum voltage values ​​among multiple battery modules, and prioritizing the balancing of the battery modules with the largest voltage difference (the larger the voltage difference, the larger the balancing current), the balancing rate is improved and the balancing time is shortened.

[0061] Next, the microprocessor acquires the voltage of each battery module to be balanced again and updates multiple voltage values. Throughout the battery module balancing process, the number of battery modules to be balanced and their voltages change; therefore, it is necessary to dynamically acquire the number of battery modules to be balanced and update their voltage values ​​to accurately determine the maximum and minimum voltage values.

[0062] Repeat the above equalization process until the voltage difference between any two battery modules to be equalized is less than or equal to the second voltage threshold, completing the initial equalization. During the initial equalization phase, by optimizing the conduction sequence of the battery modules to be equalized, the battery modules corresponding to the maximum and minimum voltage values ​​are selected for equalization each time. That is, the battery module with the largest voltage difference is prioritized for equalization, ensuring that equalization is performed with the maximum equalization current each time, thereby maximizing the equalization rate and shortening the equalization time.

[0063] Multiple battery modules to be balanced after the initial equalization are connected in parallel simultaneously for a second equalization. The equalization process ends when the conditions for termination are met. The microcontroller 40 simultaneously closes the controllable switches of the equalization units connected to the positive terminals of the multiple battery modules to be balanced, thus connecting them in parallel simultaneously, increasing the equalization current, ensuring sufficient equalization, and improving equalization efficiency. By employing two stages—initial and secondary equalization—and maximizing the equalization current in each stage, the overall equalization efficiency is significantly improved, and the equalization time is shortened.

[0064] During the initial and secondary equalization processes, the sampling module 20 collects the equalization current of each battery module in real time and outputs it to the microcontroller 40. The microcontroller 40 further determines whether the equalization current is less than a third current threshold and greater than a second current threshold, wherein the third current threshold is greater than the second current threshold and less than the first current threshold. If so, it indicates that the equalization current is too low. At this time, the parallel branches in the equalization unit corresponding to the battery module in the equalization process are simultaneously turned on to increase the equalization current. In this way, the equalization rate is further improved and the equalization time is shortened.

[0065] During the initial and secondary equalization processes, the microcontroller 40 also determines whether the equalization current exceeds the first current threshold. If so, it indicates that the equalization current of the battery module is too high, posing a safety risk such as burnout of circuits or components. In this case, the microcontroller 40 controls the controllable switch of the equalization unit directly connected to the battery module to disconnect, thus stopping the equalization process. In this way, the equalization speed is increased while the safety of the equalization process is improved.

[0066] During the initial and secondary equalization processes, the microcontroller 40 also controls the on / off state of the controllable switches of the equalization units according to the equalization termination conditions. When the equalization termination conditions are met, the controllable switches of the corresponding equalization units are disconnected, ending the equalization process. The equalization termination conditions include: determining whether equalization has ended based on the equalization time, the equalization current, or the voltage difference between the battery modules. For detailed descriptions of other embodiments, please refer to the relevant descriptions; they will not be repeated here.

[0067] The sampling module 20 in this embodiment includes two or more sampling units, each used to collect the equalization current signal of different battery modules and to electrically connect the negative terminals of different battery modules. Figure 4 As shown, the sampling module 20 includes a first sampling unit 21, a second sampling unit 22, ..., an nth sampling unit 2n. The first sampling unit 21 is connected to the negative terminal of the first battery module 11 to collect the second equalization current signal of the first battery module 11. The second sampling unit 22 is connected to the negative terminal of the second battery module 12 to collect the second equalization current signal of the second battery module 12, ..., the nth sampling unit 2n is connected to the negative terminal of the nth battery module 1n to collect the nth equalization current signal of the nth battery module 1n. Each sampling unit includes a sampling resistor for electrically connecting the negative terminal of the battery module to which it is connected, and all are connected to the ground terminal AGND. By sampling from the negative terminal of the battery module, the sampling voltage can be reduced, the sampling circuit can be protected, and the sampling safety can be improved. The sampling module 30 is connected to the microcontroller 40 and is used to output the collected equalization current signal to the microcontroller 40. Since the equalization current of different battery modules may be different at the same time, the equalization current of each battery module is collected by different sampling units so that the microcontroller 40 can determine whether the equalization current of each battery module is too large, thereby improving the control sensitivity and response speed and further improving the safety of equalization.

[0068] Figure 5The diagram illustrates a possible implementation of a sampling unit, comprising a sampling circuit 203, an amplifier circuit 202, and a reference circuit 203. The amplifier circuit 202 is connected to both the sampling circuit 301 and the microcontroller 40, amplifying the equalization current signal acquired by the sampling circuit 302 and outputting the amplified signal to the microcontroller 40. The reference circuit 201 provides a reference voltage signal VCC3 to the amplifier circuit 202, enabling the amplifier circuit 202 to transform the acquired current signal to a predetermined range. During the equalization process of each battery module, the direction of the equalization current is uncertain, resulting in acquired current signals that can be positive or negative, for example, -2V to 2V. By using the reference circuit to provide a reference signal, such as 2.5V, to the amplifier circuit 302, the amplifier circuit 302 transforms both the reference signal and the acquired current signal into a positive or negative range, facilitating processing by the microprocessor 40 and improving the accuracy of data processing. The transformation method can be a summation operation, for example, transforming the acquired current range of -2V to 2V to 0.5V to 4.5V.

[0069] The reference circuit 201 includes a first chip U1. The power input pin IN and the ground pin GND of U1 are connected to the second voltage VCC2 and the ground terminal AGND, respectively. The voltage output terminal VOUT of U1 outputs the reference voltage VCC3 to the amplifier circuit 202. A fourth capacitor C4 is connected between the power input pin IN and the ground pin GND of U1. The VOUT pin is grounded to AGND through an eighth capacitor C8.

[0070] Amplifier circuit 202 includes a second chip U2, whose reference pin REF is connected to the voltage output pin VOUT of reference circuit 201 to receive reference voltage VCC3. The signal output pin OUT is connected to microcontroller 40 to output the acquired equalization current signal TIO to microcontroller 40. The signal output pin OUT is also connected to ground terminal AGND via a first filter capacitor C1 and a second filter capacitor C2 connected in parallel. The power supply pin V+ and the ground pin GND of U2 are connected to the second voltage VCC2 and the ground terminal AGND, respectively. A third capacitor C3 and a ninth capacitor C9 are connected between the REF pin and the GND pin, and between the GND pin and the V+ pin, respectively. C1-C4, C8, and C9 are filter capacitors.

[0071] The sampling circuit 203 includes a first sampling resistor R18 and a second sampling resistor R19 connected in parallel between the sampling port J7 and the ground terminal AGND. The sampling port J7 is used to connect to the negative terminal of the battery module. Positive and negative sampling signals are respectively led out from the two ends of the sampling resistors; the positive sampling signal is led out from the ground terminal AGND side, and the negative sampling signal is led out from the sampling port J7 side. The negative terminal of the battery module is connected to the ground terminal AGND via the parallel first sampling resistor R18 and the second sampling resistor R19. The sampling circuit 203 also includes a filtering circuit, including a first filtering resistor R20, a second filtering resistor R21 connected in parallel, and a sixth capacitor C6 connected between R20 and R21. One end of R20 is connected to port J7, and the other end is connected to the negative signal input terminal IN- of U2. The negative sampling signal enters the negative signal input terminal IN- of U2 through the first filtering resistor R20. One end of R21 is connected to the ground terminal AGND, and the other end is connected to the positive signal input terminal IN+ of U2. The positive sampling signal enters the positive signal input terminal IN+ of U2 through the second filtering resistor R21. C6, R20, and R21 form a π-type filter circuit, which improves the filtering effect.

[0072] In the embodiments of this application, the battery module equalization device 10 further includes a power supply 60, which is connected to any battery module, the sampling module 20, the equalization module 30, and the microcontroller 40, respectively, for drawing power from any battery module and supplying power to the sampling module 20, the equalization module 30, and the microcontroller 40. The power supply 60 draws power through port J2 or J5 connected to the positive terminal of the battery module. Optionally, the power supply 60 uses a DC-DC power supply to convert the voltage output by the battery module into the voltage required by each power-consuming unit, providing a first voltage VCC1 to the equalization module 30 and a second voltage VCC2 to the sampling module 20. The battery module equalization device 10 also includes a display unit 50, connected to the microcontroller 40, for displaying information such as equalization current, battery module voltage, and temperature.

[0073] like Figure 6 As shown in the figure, this application embodiment also provides a battery module balancing method for balancing multiple battery modules, including the following steps: S10: Dynamically acquire the voltage of each battery module to be balanced, obtaining multiple voltage values. The microcontroller 40 is electrically connected to each battery module to obtain multiple voltage values ​​for each module, with one voltage value corresponding to each battery module. Since the negative terminal of the battery module is grounded, the obtained voltage value is the voltage of the positive terminal of the battery module relative to ground. Optionally, the microcontroller and each battery module are connected via a CAN bus or daisy chain. During the entire battery module balancing process, the number of battery modules to be balanced and their voltages change; therefore, it is necessary to dynamically acquire the number of battery modules to be balanced and update their voltage values ​​to accurately determine the maximum and minimum voltage values.

[0074] S30, the battery modules corresponding to the highest and lowest voltage values ​​obtained in step S10 are connected in parallel for balancing. For example... Figure 1 , Figure 4 As shown, the negative terminal of each battery module is grounded, and the positive terminals are connected through an balancing unit. The microcontroller 40 selects the maximum and minimum voltage values ​​from multiple voltage values ​​and controls the controllable switch in the balancing unit connected to the battery module corresponding to the maximum and minimum voltage values ​​to close, thus connecting the battery modules corresponding to the maximum and minimum voltage values ​​in parallel. At this time, the balancing current flows from the positive terminal of the battery module with the maximum voltage value, through the balancing unit to the positive terminal of the battery module with the minimum voltage value, and then returns to the negative terminal of the battery module with the higher voltage value through the ground terminal, forming a closed loop for balancing. By prioritizing the balancing of the battery modules corresponding to the maximum and minimum voltage values ​​among multiple battery modules, and prioritizing the battery modules with the largest voltage difference for balancing, the larger the voltage difference, the larger the balancing current, thereby improving the balancing rate.

[0075] In a possible implementation, the following steps are included before step S30: S20: Determine whether the voltage difference between the maximum and minimum voltage values ​​among the multiple voltage values ​​in step S10 is greater than a first voltage threshold. If not, proceed to step S30. If yes, exclude the battery module corresponding to the minimum voltage value from the battery modules to be balanced, and proceed to step S10. When the voltage difference between the maximum and minimum voltage values ​​is greater than the first voltage threshold, it indicates that the voltage difference between battery modules is too large. Therefore, battery module balancing is not performed, and the battery module corresponding to the minimum voltage value is excluded from the battery modules to be balanced. This excludes battery modules with abnormal power or voltage, improving the safety of the balancing process.

[0076] Optionally, the microcontroller 40 sorts the obtained multiple voltage values ​​to obtain the maximum and minimum voltage values, as well as the battery modules corresponding to each voltage value.

[0077] In a possible implementation, step S30 further includes: S31, acquire the equalization current of each battery module during the equalization process. The sampling module 20 acquires the equalization current of each battery module during the equalization process and outputs it to the microcontroller 40. The sampling module 20 includes two or more sampling units, which are used to acquire the equalization current signal of each battery module and output it to the microcontroller 40.

[0078] S32, determine if the balancing current exceeds the first current threshold. If so, stop the balancing of the battery module and proceed to step S10. The microcontroller 40 determines if each balancing current exceeds the first current threshold. If so, it indicates that the balancing current of the battery module is too high, posing a safety risk such as burnt-out circuits or components. In this case, the microcontroller 40 controls the controllable switch of the balancing unit directly connected to the battery module to disconnect, stopping the balancing of the battery module. This improves the safety of the balancing process.

[0079] S50: Determine if the voltage difference between the battery modules during equalization is less than or equal to a second voltage threshold. If so, disconnect the battery modules during equalization. The second voltage threshold is less than the first voltage threshold. The longer the equalization time between battery modules, the smaller the voltage difference and the closer the voltage values. If the voltage difference between the battery modules during equalization is less than or equal to the second voltage threshold, it indicates that the equalization between the battery modules is nearly complete. Microcontroller 40: Determine if the voltage difference is less than or equal to the second voltage threshold. If so, control the controllable switch of the corresponding equalization unit to disconnect and stop equalization; otherwise, continue equalization.

[0080] S70, repeat steps S10 to S50 until the voltage difference between any two battery modules is less than or equal to the second voltage threshold, completing the initial equalization. The battery modules with the highest and lowest voltage values ​​are selected sequentially from among multiple battery modules for equalization. After this equalization is completed, the voltage of each battery module to be equalized is dynamically acquired and updated. In the next equalization, the battery modules with the highest and lowest voltage values ​​are reselected from among multiple voltage values ​​for equalization. This ensures that equalization is performed with the maximum current each time, maximizing the equalization rate and shortening the equalization time.

[0081] S90: Multiple battery modules, after the initial equalization, are simultaneously connected in parallel for secondary equalization. The equalization process ends when the equalization termination condition is met. After the initial equalization, the microcontroller 40 controls the equalization units corresponding to each battery module to close simultaneously, connecting the multiple battery modules in parallel for secondary equalization. This increases the equalization current and further shortens the equalization time. The equalization termination condition includes: determining whether equalization has ended based on the equalization time; or, determining whether equalization has ended based on the equalization current, where the equalization current signal is less than a second current threshold, indicating that the battery modules have been sufficiently equalized and the equalization can be terminated; or, determining whether equalization has ended based on the voltage difference between the battery modules. A description of the equalization termination condition can be found in other embodiments and will not be repeated here.

[0082] In a possible implementation, the battery modules are connected in parallel through two or more parallel balancing branches, and steps S30 and / or S90 further include: S81, acquire the equalization current of each battery module during the equalization process. The sampling module 20 includes two or more sampling units, which are used to acquire the equalization current signal of each battery module and output it to the microcontroller 40.

[0083] S82, determine whether the balancing current of each battery module is less than the third current threshold. If so, simultaneously close the parallel branches in the balancing unit corresponding to (directly connected to) that battery module. The third current threshold is less than the first current threshold and greater than the second current threshold. Microcontroller 40 determines whether the balancing current signal collected from each battery module in step S81 is less than the third balancing current threshold. If so, it indicates that the balancing current of that battery module is too low. In this case, simultaneously close the parallel branches in the balancing unit corresponding to (directly connected to) that battery module to increase the balancing current and further improve the balancing rate.

[0084] In the initial equalization stage, by optimizing the conduction sequence of the battery modules to be equalized, the battery modules with the largest and smallest voltage values ​​are selected for equalization each time. That is, the battery modules with the largest voltage difference are prioritized for equalization, ensuring that equalization is performed with the maximum equalization current each time, thereby maximizing the equalization rate and shortening the equalization time. In the secondary equalization stage, multiple battery modules are connected in parallel simultaneously to increase the equalization current, ensuring thorough equalization and improving equalization efficiency. By employing both the initial and secondary equalization stages, the overall equalization efficiency is significantly improved, and the equalization time is shortened.

[0085] The battery module in this application includes various types of secondary batteries, such as lithium batteries, lead-acid batteries, nickel-metal hydride batteries, sodium-sulfur batteries, nickel-metal hydride batteries, flow batteries, and sodium-ion batteries. In this application, n is a natural number greater than or equal to 2.

[0086] The relevant content of each unit in this embodiment can be referred to the relevant content of the units with the same reference numerals in any of the foregoing embodiments, and will not be repeated here.

[0087] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0088] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A battery module balancing device for balancing two or more battery modules, characterized in that, It includes a sampling module, an equalization module, and a microcontroller, wherein the equalization module includes two or more equalization units; Each of the equalization units is used to electrically connect to the positive electrode of different battery modules, so that the positive electrode of each battery module is electrically connected through different equalization units; each of the equalization units includes an equalization resistor and a controllable switch connected in series. The sampling module is used to connect to the negative electrode of different battery modules respectively, to collect the balanced current signal of different battery modules and output it to the microcontroller, and to connect the negative electrode of each battery module. The microcontroller is electrically connected to each equalization unit and is used to control the on / off state of the controllable switch according to the equalization current signal, so that the positive terminals of each battery module remain connected or disconnected.

2. The battery module balancing device according to claim 1, characterized in that, The microcontroller is used to electrically connect to each battery module to obtain multiple voltage values ​​of each battery module, and to control whether each battery module is balanced and / or the conduction sequence between the positive terminals of each battery module according to the multiple voltage values.

3. The battery module balancing device according to claim 1, characterized in that, The equalization unit includes at least two parallel branches, each of which includes an equalization resistor and a controllable switch connected in series. The microcontroller also controls the on / off state of the controllable switch according to the equalization current signal to control the on / off state of the parallel branches.

4. The battery module balancing device according to claim 1, characterized in that, The sampling module includes two or more sampling units, each of which is used to collect the equalization current signal of different battery modules and to electrically connect the negative terminals of different battery modules.

5. The battery module balancing device according to claim 1, characterized in that, The sampling unit includes a sampling circuit, an amplification circuit, and a reference circuit. The amplification circuit is connected to the sampling circuit and the microcontroller, respectively, and is used to amplify the equalized current signal collected by the sampling circuit and output the amplified signal to the microcontroller. The reference circuit is used to provide a reference voltage signal to the amplification circuit.

6. The battery module balancing device according to claim 5, characterized in that, The controllable switch includes a transistor and a relay. The base of the transistor is connected to the microcontroller to receive control signals. The emitter of the transistor is connected to the ground terminal, and the collector of the transistor is connected to the power supply. The control terminal of the relay is connected between the collector of the transistor and the power supply. The two pull-in terminals of the relay are respectively connected to the common terminal and the equalization resistor.

7. A battery module balancing method for balancing multiple battery modules, comprising the following steps: S10: Dynamically acquire the voltage of each battery module to be balanced, and obtain multiple voltage values; S30, connect the battery modules corresponding to the maximum and minimum voltage values ​​among the multiple voltage values ​​in parallel to achieve balancing; S50, determine whether the voltage difference of the battery modules in the equalization is less than or equal to the second voltage threshold. If so, disconnect the battery modules in the equalization. S70, repeat steps S10 to S50 until the voltage difference between any two battery modules is less than or equal to the second voltage threshold, and complete the initial equalization. S90, connect the multiple battery modules after the initial equalization in parallel simultaneously for secondary equalization, and end the equalization process if the equalization termination condition is met.

8. The battery module balancing method according to claim 7, further comprising the following steps before step S30: S20, determine whether the voltage difference between the maximum and minimum voltage values ​​among the plurality of voltage values ​​is greater than a first voltage threshold. If not, proceed to step S30, where the first voltage threshold is greater than the second voltage threshold. If yes, exclude the battery module corresponding to the minimum voltage value from the battery modules to be balanced, and proceed to step S10.

9. The battery module balancing method according to claim 7, characterized in that, Step S30 further includes: S31, obtain the equalization current of each battery module during the equalization process; S32, determine whether the balancing current is greater than the first current threshold. If so, stop the balancing of the battery module and proceed to step S10.

10. The battery module balancing method according to claim 9, wherein the balancing unit comprises two or more parallel branches, and step S30 and / or S90 further comprises: S81, obtain the equalization current of each battery module during the equalization process; S82, determine whether the equalization current of each battery module is less than the third current threshold. If so, close the parallel branch in the equalization unit connected to the corresponding battery module at the same time. The third current threshold is less than the first current threshold.

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