Battery parallel capacity expansion circuit, control method and energy storage device

Abstract

The invention provides a battery parallel capacity expansion circuit, a control method and an energy storage device, and relates to the technical field of batteries, and the battery parallel capacity expansion circuit comprises a first control unit and a second control unit which are respectively used for carrying out discharge control on a first battery pack and a second battery pack; the battery management system is used for detecting the voltage of the first battery pack and the second battery pack in real time, and when the voltage difference value of the two is larger than a first preset voltage threshold value, the switch element in the control unit corresponding to the high-voltage battery pack is closed, and the switch element in the control unit corresponding to the low-voltage battery pack is disconnected. The high-voltage battery pack independently supplies power to the load; and when the voltage difference value is smaller than a first preset voltage threshold value, all switching elements in the first control unit and the second control unit are closed and are connected in parallel to supply power to a load. By implementing the technical scheme provided by the invention, the safety effect of improving the capacity expansion of the battery is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery parallel expansion circuit, a control method and an energy storage device. BACKGROUND

[0002] With the increasing demand for battery capacity of electric vehicles, portable energy storage devices and the like, increasing the total capacity of the battery pack by parallel connection has become a possible technical path. However, due to the characteristics of small internal resistance and high activity of power batteries, there are inherent technical difficulties in direct parallel connection. In the prior art, if multiple power battery packs are simply connected in parallel, due to the inevitable differences in voltage and other parameters between the battery packs, a significant circulating current (current backflow) will be formed between the battery packs, which will cause mutual charging and discharging between the battery packs, not only causing energy loss and system efficiency reduction, but also causing battery pack overheating, rapid life decay, and even a major risk of thermal runaway leading to safety accidents. For this reason, in the existing technical practice, power batteries usually avoid using parallel connection for capacity expansion due to safety considerations, which greatly limits the improvement of the total capacity of the battery system and is difficult to meet the market demand for long-range, large-capacity power supply systems. How to safely and intelligently realize multi-battery capacity expansion is a technical problem to be solved in the field. SUMMARY

[0003] In order to solve the above technical problems, the present application provides a battery parallel expansion circuit, a control method and an energy storage device.

[0004] In a first aspect, the application provides a battery parallel expansion circuit, comprising: a first battery pack, a second battery pack, a first control unit, a second control unit, and a battery management system, wherein the first control unit is connected in series between the first battery pack and an external interface, the second control unit is connected in series between the second battery pack and the external interface, the first control unit and the second control unit are respectively used for discharging control of the first battery pack and the second battery pack; the battery management system is connected with the first battery pack, the second battery pack, the first control unit and the second control unit, respectively, and is used for real-time detection of voltages of the first battery pack and the second battery pack, and performing the following control according to the voltage detection result: when an absolute value of a difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than a first preset voltage threshold, and the voltage of the first battery pack is greater than the voltage of the second battery pack, closing a switching element in the first control unit and opening a switching element in the second control unit, so that the first battery pack supplies power to a load through the external interface; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is less than the voltage of the second battery pack, closing the switching element in the second control unit and opening the switching element in the first control unit, so that the second battery pack supplies power to the load through the external interface; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, closing all switching elements in the first control unit and the second control unit, so that the first battery pack and the second battery pack are connected in parallel to supply power to the load.

[0005] By adopting the above technical solution, the voltages of the first battery pack and the second battery pack can be detected in real time, the on-off of the switching elements in the first control unit and the second control unit is automatically controlled according to the voltage difference, the circulating current generated when the battery packs are directly connected in parallel is avoided, the safety of battery expansion is improved, the problems of energy loss, system efficiency reduction, battery pack overheating, service life attenuation, safety accidents and the like are solved, safe and intelligent expansion of multiple batteries is realized, and the demand of the market for long endurance and large capacity power supply systems is met.

[0006] Optionally, the first control unit comprises a first switch element, a second switch element, a first diode and a second diode, the first switch element and the second switch element are connected in series between the positive pole of the first battery pack and the first end of the external interface, the negative pole of the first battery pack is electrically connected with the second end of the external interface, the first diode is connected in parallel with the first switch element, the second diode is connected in parallel with the second switch element, the anode of the first diode is electrically connected with the positive pole of the first battery pack, the anode of the second diode is electrically connected with the first end of the external interface, and the cathode of the first diode is electrically connected with the cathode of the second diode; the second control unit comprises a third switch element, a fourth switch element, a third diode and a fourth diode, the third switch element and the fourth switch element are connected in series between the positive pole of the second battery pack and the first end of the external interface, the negative pole of the second battery pack is electrically connected with the second end of the external interface, the third diode is connected in parallel with the third switch element, the fourth diode is connected in parallel with the fourth switch element, the anode of the third diode is electrically connected with the positive pole of the second battery pack, the anode of the fourth diode is electrically connected with the first end of the external interface, and the cathode of the third diode is electrically connected with the cathode of the fourth diode.

[0007] By adopting the above technical scheme, in the battery parallel expansion circuit, the first control unit and the second control unit are respectively provided with switch elements and diodes, the switch elements are connected in series between the positive poles of the battery packs and the external interface, and the diodes are connected in parallel with the switch elements, so that the discharge control of the first battery pack and the second battery pack can be realized, the current backflow can be prevented, the mutual charge and discharge between the battery packs can be avoided, the energy loss can be reduced, the system efficiency can be improved, the problems such as overheating and service life attenuation of the battery packs can be prevented, and the switch elements can be controlled according to the voltage conditions of the battery packs to realize the separate power supply or parallel power supply of different battery packs, thereby meeting the power demand of the load.

[0008] Optionally, when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is greater than the voltage of the second battery pack, the first switch element and the second switch element are closed, and the third switch element is disconnected; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is less than the voltage of the second battery pack, the third switch element and the fourth switch element are closed, and the first switch element is disconnected; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, the first switch element, the second switch element, the third switch element and the fourth switch element are closed.

[0009] By adopting the technical scheme, the on-off of the first switch element, the second switch element, the third switch element and the fourth switch element is accurately controlled according to the voltage difference between the first battery pack and the second battery pack, the circulating current caused by the voltage difference between the battery packs can be effectively avoided, the energy loss and the overheating of the battery packs are prevented, the service life of the battery packs is prolonged, the safety of power utilization is ensured, and the single battery pack power supply or the parallel power supply of the two battery packs can be flexibly selected according to the voltage, the total capacity of the battery system is improved to meet the load demand.

[0010] Optionally, the first switch element, the second switch element, the third switch element and the fourth switch element are MOS tubes, and the gate of each MOS tube is electrically connected with the battery management system.

[0011] By adopting the technical scheme, the first switch element, the second switch element, the third switch element and the fourth switch element are MOS tubes, and the gate of each MOS tube is electrically connected with the battery management system, the conduction and disconnection of the MOS tubes can be accurately controlled by the battery management system, and then the discharging of the first battery pack and the second battery pack is accurately controlled, the circulating current caused by the difference in voltage and other parameters when the multiple power battery packs are directly connected in parallel is avoided, the energy loss, the system efficiency reduction caused by the mutual charging and discharging between the battery packs are prevented, the overheating, the rapid service life decay and the safety accidents caused by the thermal runaway of the battery packs are avoided, and the safe and intelligent multi-battery expansion is realized.

[0012] Optionally, the first diode, the second diode, the third diode and the fourth diode are body diodes integrated with the corresponding switch elements, or are independent diodes connected in parallel outside the corresponding switch elements.

[0013] By adopting the technical scheme, the diodes in the first control unit and the second control unit can be body diodes integrated with the corresponding switch elements or independent diodes connected in parallel outside the corresponding switch elements, the flexibility of the circuit design is improved, different application requirements are met, the discharging control of the first battery pack and the second battery pack is realized by using the one-way conductivity of the diodes and cooperating with the switch elements, the circulating current between the battery packs is avoided, the energy loss is reduced, the system efficiency is improved, and the safe and stable operation of the battery parallel expansion circuit is ensured.

[0014] Optionally, the first control unit and the second control unit are integrated and packaged as an independent intelligent parallel module, the intelligent parallel module is provided with a battery interface for connecting the battery packs, an external interface and a communication port for connecting the battery management system, and the intelligent parallel module includes at least two battery interfaces for connecting the first battery pack and the second battery pack.

[0015] By adopting the technical scheme, the first control unit and the second control unit are integrated and packaged as an independent intelligent parallel module, so that the circuit structure can be simplified, and the integration and reliability of the circuit can be improved; the intelligent parallel module is provided with a battery interface, an external interface and a communication port, so that the intelligent parallel module is convenient to connect with a battery pack, a load and a battery management system; the at least two battery interfaces can be connected with the first battery pack and the second battery pack respectively, so that parallel expansion of the battery pack can be conveniently realized.

[0016] Optionally, the battery parallel expansion circuit further comprises a state indication unit, the state indication unit being electrically connected with the battery management system; the battery management system controls the state indication unit to display different state information according to a current working mode, the state information at least including only the first battery pack for power supply, only the second battery pack for power supply or the two battery packs in parallel for power supply.

[0017] By adopting the technical scheme, the battery parallel expansion circuit is additionally provided with the state indication unit and is electrically connected with the battery management system, the battery management system can control the state indication unit to display different state information according to a current working mode, such as only the first battery pack for power supply, only the second battery pack for power supply or the two battery packs in parallel for power supply, so that a user can intuitively know the working state of the battery parallel expansion circuit.

[0018] Optionally, the battery management system is further used for performing charging control when the external interface accesses a charging power supply, the charging control including: when an absolute value of a difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than a second preset voltage threshold, the battery management system closes the switching element in the control unit corresponding to the battery pack with a lower voltage and opens the switching element in the control unit corresponding to the battery pack with a higher voltage, so as to preferentially charge the battery pack with the lower voltage; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the second preset voltage threshold, the battery management system closes all the switching elements in the first control unit and the second control unit, so as to perform parallel charging on the two battery packs.

[0019] By adopting the technical scheme, when the external interface accesses the charging power supply, the battery management system can perform charging control according to the voltage difference between the first battery pack and the second battery pack. When the absolute value of the voltage difference is greater than the second preset voltage threshold, the battery pack with the lower voltage is preferentially charged, so that the electric quantity of the two battery packs can be more balanced, and the service life of the battery pack can be avoided from being affected due to too large electric quantity difference; when the absolute value of the voltage difference is less than or equal to the second preset voltage threshold, the two battery packs are parallel charged, so that the charging efficiency can be improved, and safe and intelligent multi-battery charging expansion can be realized.

[0020] Optionally, the battery management system is configured with a voltage slope adaptive algorithm, which is executed based on the real-time voltage relationship between the first battery pack and the second battery pack: the battery management system calculates the voltage drop slope of the main power supply unit in real time; when the voltage drop slope of the main power supply unit is greater than or equal to a preset slope threshold, it is determined that the load demand is large, causing the voltage of the main power supply unit to drop sharply, and the battery management system controls the switch element corresponding to the standby power supply unit to be partially conductive, with a conduction duty ratio of 30%-50%, realizing the pre-access of the standby power supply unit group, wherein the main power supply unit is the battery pack with higher voltage in the first battery pack and the second battery pack, and the standby power supply unit is the battery pack with lower voltage in the first battery pack and the second battery pack; after the pre-access of the standby power supply unit group, the battery management system continuously detects the voltage difference between the main power supply unit and the standby power supply unit, and when the voltage difference is less than or equal to a first preset voltage threshold, controls the switch element corresponding to the standby power supply unit to be completely closed, and the two battery packs are in parallel power supply; when the voltage drop slope of the main power supply unit is less than the preset slope threshold, the switch element corresponding to the standby power supply unit is kept open until the voltage difference between the main power supply unit and the standby power supply unit is less than or equal to the first preset voltage threshold, and then the switch element corresponding to the standby power supply unit is closed.

[0021] By using the above technical solution, the voltage slope adaptive algorithm is used to calculate the voltage drop slope of the main power supply unit in real time, and when the voltage drop slope of the main power supply unit is greater than or equal to the preset slope threshold, the switch element corresponding to the standby power supply unit is controlled to be partially conductive for pre-access, which can avoid the large current impact caused by directly accessing the standby power supply unit when the voltage of the main power supply unit drops sharply due to large load demand, and realize smooth transition to parallel power supply of the two battery packs; when the voltage drop slope of the main power supply unit is less than the preset slope threshold, the switch element corresponding to the standby power supply unit is kept open until the voltage difference meets the condition and the switch element is closed, ensuring that the battery packs are connected in parallel at the right time, reducing circulating current, reducing energy loss, improving system efficiency, prolonging the service life of the battery packs, and ensuring the safe and stable operation of the battery system.

[0022] Optionally, the battery parallel expansion circuit further comprises: a multi-mode load identification module connected with the battery management system, used for identifying the load type; the battery management system dynamically adjusts the conduction strategy according to the identified load type in combination with the on-off logic of the switching elements in the first control unit and the second control unit; specifically including: when the load type is an inductive load, a soft conduction mode is adopted, the soft conduction mode is used to represent that the duty cycle of the switching element of the corresponding control unit is gradually increased from 10% to 100% through the PWM signal, and the increase duration is 0.5s-1s; when the load type is a capacitive load, a segmented conduction mode is adopted, the segmented conduction mode is used to represent that the switching element of the corresponding control unit is first turned on at a duty cycle of 50% for 0.3s-0.5s, and then increased to 100% for complete conduction; when the load type is a resistive load, a direct conduction mode is adopted, the direct conduction mode is used to represent that the switching element of the corresponding control unit is directly and completely closed.

[0023] By adopting the above technical solution, the multi-mode load identification module can identify the load type, and the battery management system dynamically adjusts the conduction strategy according to the load type in combination with the on-off logic of the switching elements. For an inductive load, a soft conduction mode is adopted, which can avoid the impact of current mutation on the circuit. For a capacitive load, a segmented conduction mode is adopted, which can prevent the damage of instantaneous large current to the circuit and the battery pack. For a resistive load, a direct conduction mode is adopted, which can realize rapid power supply, improve the adaptability and stability of the circuit, and optimize the performance of the battery parallel expansion circuit.

[0024] In the second aspect of the present application, a control method of a battery parallel expansion circuit is also provided, which is applied to any one of the battery parallel expansion circuits described above, and includes: detecting the voltages of the first battery pack and the second battery pack in real time; comparing the voltage of the first battery pack with the voltage of the second battery pack to obtain a comparison result; and controlling the on-off state of the switching elements in the first control unit and the second control unit based on the comparison result: when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than a first preset voltage threshold, and the voltage of the first battery pack is greater than the voltage of the second battery pack, the switching elements in the first control unit are closed, and the switching elements in the second control unit are disconnected, so that the first battery pack supplies power to the load through the external interface; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is less than the voltage of the second battery pack, the switching elements in the second control unit are closed, and the switching elements in the first control unit are disconnected, so that the second battery pack supplies power to the load through the external interface; and when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, all the switching elements in the first control unit and the second control unit are closed, so that the first battery pack and the second battery pack are connected in parallel to supply power to the load.

[0025] In the third aspect of the present application, a power storage device is also provided, which comprises the battery parallel expansion circuit of any one of the preceding aspects.

[0026] In summary, the one or more technical solutions provided in the present application have at least the following technical effects or advantages: 1. The voltage of the first battery pack and the second battery pack can be detected in real time, and the on-off of the switching elements in the first control unit and the second control unit is automatically controlled according to the voltage difference, thereby avoiding the circulation current generated when the battery packs are directly connected in parallel, improving the safety of battery expansion, and solving the problems of energy loss, system efficiency reduction, battery pack overheating, service life attenuation, safety accidents and the like, realizing safe and intelligent expansion of multiple batteries, and meeting the market demand for long endurance and large-capacity power supply systems. 2. The first control unit and the second control unit are integrated and packaged as an independent intelligent parallel module, which can simplify the circuit structure, improve the integration and reliability of the circuit, and the intelligent parallel module is provided with a battery interface, an external interface and a communication port, which facilitates connection with the battery pack, the load and the battery management system; and at least two battery interfaces can be connected with the first battery pack and the second battery pack respectively, thereby facilitating parallel expansion of the battery packs. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a framework diagram of a battery parallel expansion circuit provided by an embodiment of the present application; Figure 2 is a principle schematic diagram of a battery parallel expansion circuit provided by an embodiment of the present application; Figure 3 is a schematic diagram of an intelligent parallel module provided by an embodiment of the present application; Figure 4 is a control method flowchart of a battery parallel expansion circuit provided by an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order for those skilled in the art to better understand the technical solutions in the present specification, the technical solutions in the present specification will be described in detail below in conjunction with the drawings in the embodiments of the present specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0029] In the description of the embodiments of the present application, the words such as "for example" or "for instance" are used to represent an example, illustration or description. Any embodiment or design scheme described as "for example" or "for instance" in the embodiments of the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the words such as "for example" or "for instance" are intended to present the relevant concept in a specific manner.

[0030] In the description of the embodiments of the present application, the term "a plurality of" means two or more. In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and cannot be construed as indicating or implying relative importance or implying the indicated technical features. Therefore, the features defined as "first", "second", etc. can be explicitly or implicitly included one or more features. The terms "include", "contain", "have" and their variants mean "include but not limited to", unless otherwise specifically emphasized.

[0031] The accompanying drawings are described below in conjunction with the Figure 1 - The accompanying drawings are described below in conjunction with the Figure 4 The embodiments of the present application are described in detail.

[0032] The present application provides a battery parallel expansion circuit, Figure 1 is a framework diagram of a battery parallel expansion circuit provided by the embodiments of the present application, the circuit comprising: a first battery pack, a second battery pack, a first control unit, a second control unit and a battery management system, wherein, The first control unit is connected in series between the first battery pack and the external interface, the second control unit is connected in series between the second battery pack and the external interface, and the first control unit and the second control unit are respectively used for discharging control of the first battery pack and the second battery pack; The battery management system is connected with the first battery pack, the second battery pack, the first control unit and the second control unit respectively, and the battery management system is used for real-time detection of voltages of the first battery pack and the second battery pack, and performing the following control according to the voltage detection result: When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than a first preset voltage threshold, and the voltage of the first battery pack is greater than the voltage of the second battery pack, the switch element in the first control unit is closed, and the switch element in the second control unit is opened, so that the first battery pack supplies power to the load through the external interface; When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than a first preset voltage threshold, and the voltage of the first battery pack is less than the voltage of the second battery pack, the switch element in the second control unit is closed, and the switch element in the first control unit is opened, so that the second battery pack supplies power to the load through the external interface; When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, all the switch elements in the first control unit and the second control unit are closed, so that the first battery pack and the second battery pack are connected in parallel to supply power to the load.

[0033] In the above embodiment, the voltage of the first battery pack and the second battery pack can be detected in real time, and the on-off of the switching elements in the first control unit and the second control unit is automatically controlled according to the voltage difference, thereby avoiding the generation of circulating current when the battery packs are directly connected in parallel, improving the safety of battery expansion, and solving the problems of energy loss, system efficiency reduction, battery overheating, service life attenuation, safety accidents and the like, realizing the safe and intelligent expansion of multiple batteries, and meeting the market demand for long endurance and large-capacity power supply systems.

[0034] The battery parallel expansion circuit of the embodiment realizes the safe parallel expansion of multiple battery packs through the cooperative mechanism of voltage detection and switching control, adopts a series topology of "battery pack-control unit-external interface" in hardware, each battery pack (first and second battery packs) corresponds to an independent control unit, and all control units are in communication connection with a battery management system (BMS); in terms of specific control logic: the battery management system collects the voltages of the two battery packs in real time, and controls the on-off of the switching elements of the corresponding control units according to the comparison result of the voltage difference and the first preset voltage threshold: when the voltage difference is greater than the threshold and the voltage of the first battery pack is higher, only the switching elements of the first control unit are closed and the switching elements of the second control unit are disconnected, and the first battery pack is powered alone; when the voltage difference is greater than the first preset voltage threshold and the voltage of the second battery pack is higher, only the switching elements of the second control unit are closed and the switching elements of the first control unit are disconnected, and the second battery pack is powered alone; when the voltage difference is less than or equal to the first preset voltage threshold, the switching elements of the two control units are closed, and the two battery packs are connected in parallel to supply power. The scheme of the embodiment is to cut off the path of the battery pack with lower voltage when the voltage difference may cause harmful circulating current, so that the battery pack exits parallel connection; only when the voltages are close is parallel connection allowed, thereby converting the "hard connection" of traditional continuous parallel connection into "intelligent soft parallel connection". In related technologies, when multiple batteries are directly connected in parallel, circulating current may be generated due to the voltage parameter difference between the battery packs, thereby causing many problems such as energy loss and efficiency reduction, battery overheating and service life attenuation, thermal runaway safety risk, and ultimately leading to the inability of the power battery to be expanded by parallel connection. The embodiment accurately controls the voltage difference threshold, fundamentally avoids the generation of large circulating current, eliminates the risk of overheating and thermal runaway during parallel connection, and ensures the safe operation of the battery system; when the voltage difference is large, the battery pack is powered alone, thereby avoiding the invalid charging and discharging between the battery packs, reducing energy loss, and improving the overall energy utilization efficiency of the battery system; when the voltage difference is small, the battery packs are allowed to be connected in parallel to supply power, thereby realizing the parallel expansion of the power battery and meeting the demand for large-capacity power supply systems in electric vehicles, portable energy storage devices and the like; relying on the real-time detection and automatic control of the battery management system, manual intervention is not required, the adaptive switching of the parallel / single power supply mode of the battery packs is realized, and the intelligent level of the system is improved.

[0035] In an alternative embodiment, the first control unit comprises a first switch element, a second switch element, a first diode and a second diode, the first switch element and the second switch element are connected in series between the positive pole of the first battery pack and the first end of the external interface, the negative pole of the first battery pack is electrically connected to the second end of the external interface, the first diode is connected in parallel with the first switch element, the second diode is connected in parallel with the second switch element, the anode of the first diode is electrically connected to the positive pole of the first battery pack, the anode of the second diode is electrically connected to the first end of the external interface, and the cathode of the first diode is electrically connected to the cathode of the second diode; the second control unit comprises a third switch element, a fourth switch element, a third diode and a fourth diode, the third switch element and the fourth switch element are connected in series between the positive pole of the second battery pack and the first end of the external interface, the negative pole of the second battery pack is electrically connected to the second end of the external interface, the third diode is connected in parallel with the third switch element, the fourth diode is connected in parallel with the fourth switch element, the anode of the third diode is electrically connected to the positive pole of the second battery pack, the anode of the fourth diode is electrically connected to the first end of the external interface, and the cathode of the third diode is electrically connected to the cathode of the fourth diode.

[0036] As shown in Figure 2 Figure 2 S1, S2, S3 and S4 are respectively the first switch element, the second switch element, the third switch element and the fourth switch element, D1, D2, D3 and D4 are respectively the first diode, the second diode, the third diode and the fourth diode, and B1 and B2 are respectively the first battery pack and the second battery pack. In the above embodiment, in the battery parallel expansion circuit, the first control unit and the second control unit are respectively provided with switch elements and diodes, the switch elements are connected in series between the positive pole of the battery pack and the external interface, and the diodes are connected in parallel with the switch elements, which can realize the discharge control of the first battery pack and the second battery pack, prevent the current from flowing back, avoid the mutual charge and discharge between the battery packs, reduce the energy loss, improve the system efficiency, prevent the problems such as overheating and life attenuation of the battery packs, and also can control the on-off of the switch elements according to the voltage of the battery packs, realize the separate power supply or parallel power supply of different battery packs, and meet the power demand of the load.

[0037] ​The embodiment realizes reliable on-off control and reverse current blocking through the combination circuit of the switching element and the diode. Each control unit includes two series-connected switching elements, such as the first / second switching element and the third / fourth switching element, and a diode in one-to-one parallel connection with the two switching elements, such as the first / second diode and the third / fourth diode; the switching elements are connected in series between the positive electrode of the battery pack and the first end of the external interface, and the negative electrode of the battery pack is directly connected to the second end of the external interface; the intelligent control of the battery pack discharge circuit is realized by controlling the conduction and turn-off of the two series-connected switching elements; when the switching elements are turned off, the directions of the two parallel diodes make it impossible to form a current path for the reverse current flowing from the outside or another battery pack into the battery pack, thereby physically preventing the formation of circulating current, for example, when the first switching element and the second switching element are turned off, the first diode and the second diode can prevent the external current from flowing to the battery pack. The on-off of the switching elements follows the voltage difference control logic of the aforementioned battery management system, and the diodes block the reverse current between the battery pack and the external interface and between the battery packs when the switching elements are turned off, thereby avoiding the reverse current. The design of the double-switching-element series connection improves the on-off reliability of the control unit and reduces the safety hazards caused by the failure of a single switch.

[0038] In an optional embodiment, when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is greater than the voltage of the second battery pack, the first switching element and the second switching element are closed, and the third switching element is turned off; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is less than the voltage of the second battery pack, the third switching element and the fourth switching element are closed, and the first switching element is turned off; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, the first switching element, the second switching element, the third switching element and the fourth switching element are closed.

[0039] In the above embodiment, the on-off of the first switching element, the second switching element, the third switching element and the fourth switching element is accurately controlled according to the voltage difference between the first battery pack and the second battery pack, which can effectively avoid the circulating current generated between the battery packs due to the voltage difference, prevent energy loss and overheating of the battery packs, prolong the service life of the battery packs, ensure the safety of power use, and flexibly select single battery pack power supply or two battery packs parallel power supply according to the voltage, thereby improving the total capacity of the battery system to meet the load demand.

[0040] The battery management system takes the comparison between the voltage difference of the two battery packs and the first preset voltage threshold as the judgment basis, and executes differentiated on-off instructions for the two series switch elements in the control unit: when the voltage difference is greater than the first preset voltage threshold and the first battery pack voltage is higher, the two switch elements (first and second switch elements) of the first control unit are closed, and the third switch element in the second control unit is disconnected, which can prevent the first battery pack from charging the second battery pack; optionally, the third switch element and the fourth switch element in the second control unit can also be disconnected; similarly, when the voltage difference is greater than the first preset voltage threshold and the second battery pack voltage is higher, the two switch elements (third and fourth switch elements) of the second control unit are closed, and the first switch element in the first control unit is disconnected, which can prevent the second battery pack from charging the first battery pack; optionally, the first switch element and the second switch element in the first control unit can also be disconnected; when the voltage difference is less than or equal to the first preset voltage threshold, all four switch elements of the two control units are closed, realizing parallel power supply of the two battery packs. The above-mentioned first preset voltage threshold can be 0.1V (or 0.2V, or other values).

[0041] Figure 2 The battery parallel expansion circuit shown has three working modes: Mode one: the first battery pack B1 voltage > the second power supply B2 voltage; ① Let the first battery pack B1 be the main power supply (because the voltage is higher), and the second battery pack B2 is on standby or weakly involved (to avoid reverse current).

[0042] ② The two branch switches in the first battery pack B1 are all closed (to make the first battery pack B1 batteries parallel, releasing high voltage); when the switch is in the closed state (forward bias), the current passes through S1 / S2, at which time S1 / S2 has low impedance (usually in the on state). If the switch is open (reverse bias), the diode forms a high impedance (blocking state) due to the reverse voltage, at which time the circuit is equivalent to being disconnected.

[0043] ③ S3 in the second battery pack B2 is disconnected (because the voltage is low, if it is closed, the first battery pack B1 will charge the second battery pack B2 in reverse; ④ If there is a "cross-pack control" (not explicitly shown in the figure, additional logic is required), the active path of the second battery pack B2 to the load is preferentially cut off, and only the first battery pack B1 is used for power supply.

[0044] Mode two: the first battery pack B1 voltage < the second battery pack B2 voltage; ① Let the second battery pack B2 be the main power supply (the voltage is higher), and the first battery pack B1 is on standby.

[0045] ② The two branch switches in the second battery pack B2 are all closed (the second battery pack B2 batteries are parallel, releasing high voltage); ③ S1 in the first battery pack B1 is disconnected (to avoid the second battery pack B2 charging the first battery pack B1 in reverse); ④ Similarly, if there is cross-group control, the active path of the first battery pack B1 to the load is preferentially cut off, and the second battery pack B2 is relied on for power supply.

[0046] Mode three: the voltage of the first battery pack B1 = the voltage of the second battery pack B2; ① The two battery packs are connected in parallel to supply power to the load (to improve the total capacity).

[0047] ② All branch switches in the first battery pack B1 and the second battery pack B2 are closed (the two groups are connected in parallel, and then the whole is connected in parallel to the load).

[0048] The BMS is used to detect the voltage of the battery pack; the BMS controls the on-off of the switch tube according to the voltage difference to realize balanced discharge; after the discharge is completed, all switch tubes are disconnected to prevent current from flowing back.

[0049] In an optional embodiment, the first switch element, the second switch element, the third switch element, and the fourth switch element are all MOS tubes, and the gates of each MOS tube are respectively electrically connected with the battery management system.

[0050] In the above embodiment, the first switch element, the second switch element, the third switch element, and the fourth switch element are all set as MOS tubes, and the gates of each MOS tube are respectively electrically connected with the battery management system, so that the conduction and disconnection of the MOS tube can be accurately controlled by the battery management system, and the discharge of the first battery pack and the second battery pack can be accurately controlled, thereby avoiding the formation of circulating current due to the difference in voltage and other parameters when multiple power battery packs are directly connected in parallel, preventing energy loss, system efficiency reduction caused by mutual charging and discharging between battery packs, avoiding battery pack overheating, rapid life decay, and safety accidents caused by thermal runaway, and realizing safe and intelligent multi-battery expansion.

[0051] The switch element can be a relay, a contactor, a MOS tube, or an IGBT, etc. Taking the MOS tube as an example, the BMS can accurately, quickly, and independently control the conduction and disconnection of each switch by directly outputting a specific control voltage signal to the gate of the MOS tube. The nanosecond-level on-off characteristic of the MOS tube can realize instantaneous switching of the switch state, avoid circulating current in the voltage difference window period caused by switch delay, and further improve the safety of parallel expansion. The gate is directly controlled by the BMS, the control signal transmission path is short, the on-off instruction corresponding to the voltage difference threshold can be accurately executed, the probability of switch misoperation is reduced, and the control stability of the system is improved. The MOS tube can directly adapt to the weak electric control signal of the BMS, without additional driving or conversion circuit, which simplifies the hardware structure of the control unit and reduces the volume, weight, and manufacturing cost of the system.

[0052] In an optional embodiment, the first diode, the second diode, the third diode, and the fourth diode are all body diodes integrated with the corresponding switching elements, or are all independent diodes connected in parallel outside the corresponding switching elements.

[0053] In the above embodiments, the diodes in the first control unit and the second control unit can be body diodes integrated with the corresponding switching elements or independent diodes connected in parallel outside the corresponding switching elements, which can improve the flexibility of circuit design, meet different application requirements, and realize discharge control of the first battery pack and the second battery pack by using the unidirectional conductivity of the diodes and cooperating with the switching elements, thereby avoiding circulating current between the battery packs, reducing energy loss, improving system efficiency, and ensuring safe and stable operation of the battery parallel expansion circuit.

[0054] The first to fourth diodes are explicitly defined as two implementation paths, one is a body diode (parasitic PN junction) provided by a MOS tube or other switching element, and the other is an independent diode (such as a Schottky diode or a super-fast recovery diode) connected in parallel with the switching element. Both forms meet the connection requirement of being connected in parallel with the corresponding switching element, and maintain the connection relationship between the anode and the cathode of the diode in the original topology, thereby ensuring the effective reverse blocking function. Whether a body diode or an independent diode is used, the diode cooperates with the on-off action of the switching element and follows the voltage difference control strategy to block circulating current when a single battery pack is powered. The diode has the advantages of flexible selection and performance optimization. For cost-sensitive, space-constrained, and moderately performance-demanding applications, the body diode solution can maximize the advantages of the invention (safe and intelligent parallel connection) while maintaining a minimalist hardware structure. When a larger current needs to be withstood, a faster reverse recovery characteristic is required, or the switching element itself does not have a suitable body diode, a more optimal independent diode can be selected to ensure the feasibility of the solution in high-performance and special application scenarios.

[0055] In an optional embodiment, the first control unit and the second control unit are integrated and packaged as an independent intelligent parallel connection module, and the intelligent parallel connection module is provided with a battery interface for connecting the battery pack, an external interface, and a communication port for connecting a battery management system. The intelligent parallel connection module includes at least two battery interfaces for connecting the first battery pack and the second battery pack, respectively.

[0056] In the above embodiments, the first control unit and the second control unit are integrated and packaged as an independent intelligent parallel connection module, which can simplify the circuit structure and improve the integration and reliability of the circuit. The intelligent parallel connection module is provided with a battery interface, an external interface, and a communication port, which facilitates connection with the battery pack, the load, and the battery management system. The at least two battery interfaces can be connected to the first battery pack and the second battery pack, respectively, thereby facilitating parallel expansion of the battery pack.

[0057] Figure 3This is a schematic diagram of the intelligent parallel module provided in this application embodiment. The first and second control units (including core components such as switches and diodes) are integrated and packaged into an independent intelligent parallel module. The module has three types of interfaces: at least two battery interfaces for connecting the first / second battery packs, an external interface for external power supply, and a communication port for communication with the BMS. The function and connection object of each interface are clearly defined. In this way, multiple battery packs can be directly connected to the intelligent parallel module through the battery interfaces, and the BMS can be connected to the intelligent parallel module through the communication interface. When the battery discharges to the load, the external interface is used to connect to the load; when the battery needs to be charged, the external interface is used to connect to an external power source or charger. The BMS still outputs commands through the communication port to control the on / off of the switching elements within the intelligent parallel module, realizing the switching between single-group power supply and two-group parallel power supply. The standardized interface design allows the module to quickly connect to battery packs, loads, and the BMS without additional customized wiring, improving engineering adaptability. This solution, through pre-integration and packaging, completes and tests the complex internal wiring and processes in the factory. Users only need to connect the battery, load, and signal lines, greatly reducing the technical threshold, error probability, and debugging time for on-site installation.

[0058] In an optional embodiment, the battery parallel expansion circuit further includes: a status indicator unit, which is electrically connected to the battery management system; the battery management system controls the status indicator unit to display different status information according to the current operating mode, and the status information includes at least: only the first battery pack is powered, only the second battery pack is powered, or the two battery packs are powered in parallel.

[0059] In the above embodiments, the battery parallel expansion circuit is equipped with a status indicator unit and electrically connected to the battery management system. The battery management system can control the status indicator unit to display different status information according to the current working mode, such as only the first battery pack is powered, only the second battery pack is powered, or the two battery packs are powered in parallel, so that the user can intuitively understand the working status of the battery parallel expansion circuit.

[0060] A new status indicator unit is added to the circuit and electrically connected to the BMS. This unit can use LED lights, digital tubes, LCDs, or other display devices to intuitively output the system's power supply status. The BMS collects data such as the voltage of the first / second battery pack and the on / off status of switching elements in real time to determine the current operating mode (power supply from the first battery pack only, power supply from the second battery pack only, or both battery packs in parallel), and outputs control signals to drive the status indicator unit to display the corresponding status information. The display content of the status indicator unit is bound to the operating mode, ensuring that users or maintenance personnel can quickly identify the current power supply status of the system, forming a closed-loop status visualization mechanism of "status acquisition - mode judgment - indicator output". On-site, the power supply mode can be quickly identified through the status indicator unit without connecting to a host computer or dedicated equipment, significantly reducing the time and cost of inspection and maintenance, and adapting to the needs of rapid on-site operation and maintenance. The intuitive status display can effectively avoid risks such as live operation and accidental power failure caused by misjudging the power supply mode, reduce safety hazards such as electric arcs and circulating currents, and ensure the safety of personnel and equipment.

[0061] In an optional embodiment, the battery management system is further configured to perform charging control when a charging power source is connected to an external interface. The charging control includes: when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than a second preset voltage threshold, the battery management system closes the switching element in the control unit corresponding to the lower voltage battery pack and opens the switching element in the control unit corresponding to the higher voltage battery pack, so as to prioritize charging the lower voltage battery pack; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the second preset voltage threshold, the battery management system closes all switching elements in the first control unit and the second control unit, so as to charge the two battery packs in parallel.

[0062] In the above embodiments, when a charging power source is connected to the external interface, the battery management system can perform charging control based on the voltage difference between the first battery pack and the second battery pack. When the absolute value of the voltage difference is greater than a second preset voltage threshold, the battery pack with the lower voltage is charged first, which can make the charge of the two battery packs more balanced and avoid affecting the service life of the battery packs due to excessive charge difference; when the absolute value of the voltage difference is less than or equal to the second preset voltage threshold, the two battery packs are charged in parallel, which can improve charging efficiency and realize safe and intelligent multi-battery charging capacity expansion.

[0063] When the system detects that the external interface is connected to a charging power source (not a load), the Battery Management System (BMS) also initiates voltage difference comparison logic. When the voltage difference is greater than a second preset voltage threshold, a "selective charging" strategy is adopted, closing only the switch of the branch containing the lower voltage battery pack, allowing it to receive charging first, thereby quickly increasing its voltage and actively narrowing the gap with the higher voltage battery pack. When the voltage difference is less than or equal to the second preset voltage threshold, a "parallel equalization charging" strategy is adopted. All switches are closed, allowing the two battery packs to be connected in parallel and charged simultaneously. The aforementioned second preset voltage threshold is less than 0.5V, for example, it could be 0.1V (or 0.2V, or other values). Similar to discharging, if the voltage difference is significant in the early stages of charging, even with an external charger connected, internal circulating currents may still form between the battery packs (the higher voltage pack discharging to the lower voltage pack). The "selective charging" mode of this solution physically cuts off the circulating current path, eliminating energy loss and thermal risks during charging. By prioritizing the charging of lower-voltage groups, the system systematically and proactively corrects the differences in state of charge (SOC) between battery packs. Compared to passive or unbalanced solutions, this approach more effectively maintains long-term consistency among battery packs, thereby extending the cycle life of the entire battery system. It avoids the potential overcharging risk of high-SOC battery packs, which is crucial, especially in fast-charging scenarios. The priority charging strategy allows the system to reach an overall balanced state more quickly, potentially enabling full-power parallel charging in subsequent stages. Theoretically, this can shorten the total charging time and improve charging efficiency.

[0064] In an optional embodiment, the battery management system is configured with a voltage slope adaptive algorithm, which is executed based on the real-time voltage relationship between the first battery pack and the second battery pack: the battery management system calculates the voltage drop slope of the main power supply unit in real time; when the voltage drop slope of the main power supply unit is greater than or equal to a preset slope threshold, it is determined that the large load demand has caused a sudden drop in the voltage of the main power supply unit, and the battery management system controls the corresponding switching element of the unit to be powered to partially conduct, with a conduction duty cycle of 30%-50%, to realize the pre-connection of the unit group to be powered, wherein the main power supply unit is the one with a higher voltage between the first battery pack and the second battery pack. The battery pack has a high voltage, and the unit to be powered is the battery pack with the lower voltage between the first battery pack and the second battery pack. After the unit to be powered is pre-connected, the battery management system continuously monitors the voltage difference between the main power supply unit and the unit to be powered. When the voltage difference is less than or equal to the first preset voltage threshold, the system controls the switch element corresponding to the unit to be powered to be fully closed, and the two battery packs are connected in parallel to supply power. When the voltage drop slope of the main power supply unit is less than the preset slope threshold, the system keeps the switch element corresponding to the unit to be powered open until the voltage difference between the main power supply unit and the unit to be powered is less than or equal to the first preset voltage threshold, at which point the switch element corresponding to the unit to be powered is closed.

[0065] In the above embodiments, an adaptive voltage slope algorithm is used to calculate the voltage drop slope of the main power supply unit in real time. When the voltage drop slope of the main power supply unit is greater than or equal to a preset slope threshold, the corresponding switching element of the unit to be powered is partially turned on for pre-connection. This avoids the large current surge caused by directly connecting the unit to be powered when the voltage of the main power supply unit drops sharply due to high load demand, thus achieving a smooth transition to parallel power supply of the two battery packs. When the voltage drop slope of the main power supply unit is less than the preset slope threshold, the corresponding switching element of the unit to be powered is kept open until the voltage difference meets the condition before the switching element is closed. This ensures that the battery packs are connected in parallel at the appropriate time, reducing circulating current generation, reducing energy loss, improving system efficiency, extending battery pack life, and ensuring the safe and stable operation of the battery system.

[0066] Furthermore, the BMS uses a voltage slope adaptive algorithm to achieve dynamic power supply switching for the parallel expansion circuit of the battery pack, forming a three-level control logic of "slope prediction - pre-connection buffer - full parallel connection". The BMS calculates the voltage drop slope of the main power supply unit (the first / second battery pack with higher voltage) in real time, while monitoring the voltage difference between the main and the standby power supply units (the battery packs with lower voltage). A preset slope threshold is set. When the voltage drop slope is greater than or equal to the preset slope threshold, it is determined that a surge in load demand has caused a sudden drop in the voltage of the main power supply unit. At this time, the corresponding switching element of the standby power supply unit is partially turned on (conduction duty cycle 30%-50%) to achieve pre-connection of the standby power supply unit and avoid the large circulating current impact caused by direct full conduction. After pre-connection, the voltage difference is continuously monitored. When the voltage difference is less than or equal to the first preset voltage threshold, the switch of the standby power supply unit is fully closed, and the two battery packs are connected in parallel for power supply; if the voltage drop slope is less than the preset slope threshold, the switch of the standby power supply unit is kept open until the voltage difference meets the condition before closing. This algorithm can automatically adjust the switching strategy according to dynamic load changes, adapting to power supply demands under different load surge intensities. It solves the problems of large circulating currents and surges caused by direct parallel connection during load spikes; direct full-conduction of the unit to be powered leads to sudden power surges in the system, affecting the stability of the load power supply. This solution uses a partially-conducted pre-access mode to smoothly transition power allocation. In this embodiment, the duty cycle control during the pre-access phase limits instantaneous current, avoiding large circulating currents generated by direct parallel connection, protecting switching components and battery packs, and reducing safety hazards such as short circuits and thermal runaway. Three-level control logic achieves a smooth transition in power supply switching, reducing the impact of power surges on the load, ensuring power supply continuity, and adapting to scenarios with high power supply stability requirements, such as automotive and energy storage applications. Voltage slope prediction can identify load surges in advance, shortening the switching response time compared to control schemes relying solely on voltage differences, and preventing voltage collapse of the main power supply unit due to overload.

[0067] For example, with a preset slope threshold of 0.05V / s (or 0.1V / s, or other values) and a duty cycle of 30% (or 50%, or other values), taking the electric bicycle climbing a hill (sudden increase in load power) as an example, the voltage of the main power supply unit (such as the first battery pack B1) drops rapidly from 48.8V, and the voltage slope reaches 0.15V / s (exceeding the preset threshold of 0.1V / s). The BMS immediately outputs a PWM signal with a duty cycle of 40% to the switching elements S3 / S4 of the unit to be powered (such as the second battery pack B2). B2 is pre-connected to the circuit through "pulse conduction" to shunt 8A of the total current of 20A. The voltage drop rate of B1 drops to 0.08V / s. After the voltage difference between B1 and B2 is ≤0.3V, the BMS increases the PWM duty cycle of S3 / S4 to 100% (fully closed), and the two battery packs are connected in parallel to supply power at full load.

[0068] In an optional embodiment, the battery parallel expansion circuit further includes: a multi-mode load identification module connected to the battery management system for identifying load types; the battery management system dynamically adjusts the conduction strategy based on the identified load type and the on / off logic of the switching elements in the first control unit and the second control unit; specifically including: when the load type is an inductive load, a soft conduction mode is adopted, which means that the duty cycle of the switching element of the corresponding control unit is gradually increased from 10% to 100% through the PWM signal, with an increase time of 0.5s-1s; when the load type is a capacitive load, a segmented conduction mode is adopted, which means that the switching element of the corresponding control unit is controlled to conduct with a 50% duty cycle for 0.3s-0.5s, and then increased to 100% full conduction; when the load type is a resistive load, a direct conduction mode is adopted, which means that the switching element of the corresponding control unit is directly and completely closed.

[0069] In the above embodiments, the multi-mode load identification module can identify the load type. The battery management system, in conjunction with the switching logic of the switching elements, dynamically adjusts the conduction strategy according to the load type. For inductive loads, a soft conduction mode is adopted to avoid the impact of sudden current changes on the circuit. For capacitive loads, a segmented conduction mode is adopted to prevent damage to the circuit and battery pack from instantaneous large currents. For resistive loads, a direct conduction mode is adopted to achieve fast power supply, improve the adaptability and stability of the circuit, and optimize the performance of the battery parallel expansion circuit.

[0070] This embodiment adds a multi-mode load identification module connected to the BMS. This module can detect the electrical characteristics of the load (such as impedance, phase difference, etc.) in real time and identify the load type as inductive, capacitive, or resistive. Based on the load identification result and combined with the voltage difference control logic in the previous embodiment, the BMS dynamically matches differentiated conduction strategies for the switching elements of the corresponding control unit. Inductive loads (such as motors and transformers): a soft conduction mode is adopted, and the duty cycle of the switch is gradually increased from 10% to 100% through the PWM signal, with the increase time controlled within 0.5s-1s; Capacitive loads (such as capacitor banks and filter circuits): a segmented conduction mode is adopted, and the switch is first turned on with a 50% duty cycle for 0.3s-0.5s, and then increased to 100% for full conduction; Resistive loads (such as resistance heaters and incandescent lamps): a direct conduction mode is adopted, and the switch is directly and completely closed. The load identification, voltage difference judgment, and conduction strategy execution are linked together to ensure the anti-circulating current requirements of the parallel battery pack and to adapt to the access characteristics of different loads. Differentiated conduction strategies for inductive and capacitive loads effectively suppress current spikes and inrush currents upon connection, reducing battery pack internal resistance losses and overcurrent risks to switching components, ensuring safe circuit operation. It avoids sudden voltage drops in the battery pack due to load surges, prevents BMS misjudgments caused by voltage fluctuations (such as false triggering of parallel / single power supply switching), and ensures the continuity and stability of load power supply. It is adaptable to diverse load scenarios (such as electric vehicle drive motors, energy storage system filter capacitors, and resistive loads in portable devices), broadening the circuit's application range.

[0071] This application also provides a control method for a battery parallel capacity expansion circuit, applicable to the battery parallel capacity expansion circuit of any of the foregoing embodiments. Figure 4 This is a flowchart of a control method for a battery parallel capacity expansion circuit provided in an embodiment of this application. The process includes: S401, real-time detection of the voltage of the first and second battery packs; S402, compare the voltage of the first battery pack with the voltage of the second battery pack to obtain the comparison result; S403, based on the comparison result, control the on / off state of the switching elements in the first control unit and the second control unit: when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than a first preset voltage threshold and the voltage of the first battery pack is greater than the voltage of the second battery pack, close the switching element in the first control unit and open the switching element in the second control unit so that the first battery pack supplies power to the load through the external interface; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold and the voltage of the first battery pack is less than the voltage of the second battery pack, close the switching element in the second control unit and open the switching element in the first control unit so that the second battery pack supplies power to the load through the external interface; when the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, close all the switching elements in the first control unit and the second control unit so that the first battery pack and the second battery pack are connected in parallel to supply power to the load.

[0072] Through the above steps, the Battery Management System (BMS) collects voltage data of the first and second battery packs in real time, providing a basis for subsequent control decisions. The BMS calculates the voltage difference between the two battery packs and obtains a comparison result of the absolute value of the voltage difference. Based on the comparison result of the absolute value of the voltage difference and the first preset voltage threshold, the switching element is controlled to switch on and off under three operating conditions: when the voltage difference is greater than the first preset voltage threshold and the voltage of the first battery pack is higher, the switching element in the first control unit is closed and the switching element in the second control unit is opened, and the first battery pack supplies power alone; when the voltage difference is greater than the first preset voltage threshold and the voltage of the second battery pack is higher, the switching element in the second control unit is closed and the switching element in the first control unit is opened, and the second battery pack supplies power alone; when the voltage difference is less than or equal to the first preset voltage threshold, all switches in the two control units are closed, realizing parallel power supply of the two battery packs.

[0073] The control method of this implementation can detect and compare the voltages of the first and second battery packs in real time, and control the on / off state of the switching elements in the first and second control units based on the comparison results. This avoids circulating currents caused by voltage differences between battery packs, prevents mutual charging and discharging between battery packs, reduces energy loss, improves system efficiency, avoids safety accidents such as battery pack overheating, lifespan degradation, and thermal runaway, and enables safe parallel expansion of battery packs to power the load, meeting the market demand for high-capacity power systems.

[0074] It should be noted that the system and method embodiments provided in the above embodiments belong to the same concept. Other method embodiments correspond to the aforementioned system embodiments. Other technical features can be found in the previous embodiments and will not be repeated here.

[0075] Through the embodiments of this application, 1) multiple batteries can be safely connected in parallel, increasing the total capacity and extending the device's battery life; 2) the role of the BMS: with the BMS, multiple batteries can be stably connected in parallel, preventing damage under short circuits and abnormal conditions, and improving safety; 3) the mechanism for parallel discharge: each battery is connected to the outside through a control switch, which controls the discharge channel, allowing only the battery to discharge to the outside and preventing reverse current; 4) the battery voltage matching mechanism: the battery with the higher voltage will discharge first until the voltage of other batteries is close, and then other batteries will gradually be connected to the discharge circuit, ultimately achieving synchronous discharge of multiple batteries; 5) the automatic connection mechanism: when the voltages of multiple batteries are consistent, all switches are automatically closed, and the battery pack as a whole discharges to the outside; if the voltages are inconsistent, the higher voltage battery discharges first, and then all batteries are connected after the voltages are consistent; 6) capacity expansion application scenarios: when it is necessary to extend the battery life, new batteries can be directly connected in parallel on the basis of the original batteries without replacing the original system, which is convenient and flexible.

[0076] The embodiments of this application have at least the following technical effects: they solve the problem of current backflow when multiple batteries are connected in parallel, thus improving system safety; they achieve automatic battery discharge balancing, thus extending battery life; and they lower the threshold for battery capacity expansion through low-cost design.

[0077] This application also provides an energy storage device, including the battery parallel expansion circuit of any of the foregoing embodiments.

[0078] The energy storage device includes the battery parallel expansion circuit in any of the aforementioned embodiments. This circuit, as the core power management module of the energy storage device, undertakes functions such as parallel control of multiple battery packs, anti-circulating current protection, and charge / discharge management. The energy storage device fully reuses the core control strategy of this circuit. The BMS detects the voltage difference of the battery packs in real time and controls the switching of the corresponding control unit based on the comparison result of the voltage difference with a first preset voltage threshold, realizing adaptive switching between "single-pack power supply / parallel power supply". The hardware optimization scheme of this circuit (such as intelligent parallel module, status indicator unit, integrated charge / discharge control) can be flexibly selected according to the application scenario of the energy storage device (portable energy storage, household energy storage, etc.) to ensure the performance and practicality of the energy storage device. It can safely and intelligently realize multi-battery expansion, avoid the formation of circulating current when multiple power battery packs are directly connected in parallel, prevent energy loss and system efficiency reduction caused by mutual charging and discharging between battery packs, avoid safety issues such as battery pack overheating and lifespan degradation, and meet the market demand for long-range, high-capacity power systems.

[0079] The above description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Other embodiments of this disclosure will be readily apparent to those skilled in the art upon consideration of the disclosure herein.

[0080] This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art that are not described in this disclosure.

Claims

1. A battery parallel capacity expansion circuit, characterized in that, include: The battery pack comprises a first battery pack, a second battery pack, a first control unit, a second control unit, and a battery management system, wherein... The first control unit is connected in series between the first battery pack and the external interface, and the second control unit is connected in series between the second battery pack and the external interface. The first control unit and the second control unit are respectively used to control the discharge of the first battery pack and the second battery pack. The battery management system is connected to the first battery pack, the second battery pack, the first control unit, and the second control unit, respectively. The battery management system is used to detect the voltage of the first battery pack and the second battery pack in real time, and to perform the following control based on the voltage detection results: When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than a first preset voltage threshold, and the voltage of the first battery pack is greater than the voltage of the second battery pack, the switching element in the first control unit is closed, and the switching element in the second control unit is opened, so that the first battery pack supplies power to the load through the external interface; When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold and the voltage of the first battery pack is less than the voltage of the second battery pack, the switching element in the second control unit is closed and the switching element in the first control unit is opened, so that the second battery pack supplies power to the load through the external interface; When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, all switching elements in the first control unit and the second control unit are closed, so that the first battery pack and the second battery pack are connected in parallel to supply power to the load.

2. The battery parallel capacity expansion circuit according to claim 1, characterized in that, The first control unit includes a first switching element, a second switching element, a first diode, and a second diode. The first switching element and the second switching element are connected in series between the positive terminal of the first battery pack and the first terminal of the external interface. The negative terminal of the first battery pack is electrically connected to the second terminal of the external interface. The first diode is connected in parallel with the first switching element, and the second diode is connected in parallel with the second switching element. The anode of the first diode is electrically connected to the positive terminal of the first battery pack, the anode of the second diode is electrically connected to the first terminal of the external interface, and the cathode of the first diode is electrically connected to the cathode of the second diode. The second control unit includes a third switching element, a fourth switching element, a third diode, and a fourth diode. The third switching element and the fourth switching element are connected in series between the positive terminal of the second battery pack and the first terminal of the external interface. The negative terminal of the second battery pack is electrically connected to the second terminal of the external interface. The third diode is connected in parallel with the third switching element, and the fourth diode is connected in parallel with the fourth switching element. The anode of the third diode is electrically connected to the positive terminal of the second battery pack, the anode of the fourth diode is electrically connected to the first terminal of the external interface, and the cathode of the third diode is electrically connected to the cathode of the fourth diode.

3. The battery parallel capacity expansion circuit according to claim 2, characterized in that, When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is greater than the voltage of the second battery pack, the first switch element and the second switch element are closed, and the third switch element is opened at the same time. When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is less than the voltage of the second battery pack, the third switch element and the fourth switch element are closed, and the first switch element is opened at the same time. When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, the first switching element, the second switching element, the third switching element and the fourth switching element are closed.

4. The battery parallel capacity expansion circuit according to claim 2, characterized in that, The first switching element, the second switching element, the third switching element, and the fourth switching element are all MOSFETs, and the gate of each MOSFET is electrically connected to the battery management system.

5. The battery parallel capacity expansion circuit according to claim 2, characterized in that, The first diode, the second diode, the third diode, and the fourth diode are all body diodes integrated with the corresponding switching element, or are independent diodes connected in parallel outside the corresponding switching element.

6. The battery parallel capacity expansion circuit according to claim 1, characterized in that, The first control unit and the second control unit are integrated and packaged into an independent intelligent parallel module. The intelligent parallel module is provided with a battery interface for connecting the battery pack, the external interface, and a communication port for connecting the battery management system. The intelligent parallel module includes at least two battery interfaces, which are respectively used to connect the first battery pack and the second battery pack.

7. The battery parallel capacity expansion circuit according to claim 1, characterized in that, The battery parallel capacity expansion circuit further includes: a status indicator unit, which is electrically connected to the battery management system; The battery management system controls the status indicator unit to display different status information according to the current working mode. The status information includes at least: only the first battery pack is powered, only the second battery pack is powered, or the two battery packs are connected in parallel to provide power.

8. The battery parallel capacity expansion circuit according to claim 1, characterized in that, The battery management system is also used to perform charging control when a charging power source is connected to the external interface, the charging control including: When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the second preset voltage threshold, the battery management system closes the switching element in the control unit corresponding to the battery pack with lower voltage and opens the switching element in the control unit corresponding to the battery pack with higher voltage, so as to give priority to charging the battery pack with lower voltage. When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the second preset voltage threshold, the battery management system closes all switching elements in the first control unit and the second control unit to charge the two battery packs in parallel.

9. A control method for a battery parallel capacity expansion circuit, characterized in that, Applied to the battery parallel capacity expansion circuit according to any one of claims 1 to 8, comprising: Real-time monitoring of the voltages of the first and second battery packs; The voltage of the first battery pack is compared with the voltage of the second battery pack to obtain the comparison result; Based on the comparison results, the on / off states of the switching elements in the first control unit and the second control unit are controlled: When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold, and the voltage of the first battery pack is greater than the voltage of the second battery pack, the switching element in the first control unit is closed, and the switching element in the second control unit is opened, so that the first battery pack supplies power to the load through the external interface; When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is greater than the first preset voltage threshold and the voltage of the first battery pack is less than the voltage of the second battery pack, the switching element in the second control unit is closed and the switching element in the first control unit is opened, so that the second battery pack supplies power to the load through the external interface; When the absolute value of the difference between the voltage of the first battery pack and the voltage of the second battery pack is less than or equal to the first preset voltage threshold, all switching elements in the first control unit and the second control unit are closed, so that the first battery pack and the second battery pack are connected in parallel to supply power to the load.

10. An energy storage device, characterized in that, Includes the battery parallel capacity expansion circuit according to any one of claims 1 to 8.

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