Electric two-wheeled vehicle lithium battery pack thermal runaway protection device and method

Abstract

This invention belongs to the field of battery thermal runaway monitoring technology, specifically relating to a thermal runaway protection device and method for lithium battery packs in electric two-wheeled vehicles. The device includes a first protection circuit and a second protection circuit connected in series between the negative terminal and the interface of the battery pack, and a BMS main control chip connected to both. The first protection circuit includes a discharge MOSFET and a charging MOSFET connected in common drain configuration, used to cut off the charging and discharging circuit according to a first control signal. The second protection circuit includes an active isolation element connected in series between the negative terminal of the battery pack and the first protection circuit, and its trigger circuit. After the main control chip detects that the voltage or temperature exceeds a first threshold and outputs a first control signal, if it detects that the voltage or temperature reaches a second threshold, it outputs a second control signal to the trigger circuit, driving the active isolation element to a permanently disconnected state, achieving permanent physical isolation of the battery circuit.

Description

Technical Field

[0001] This invention belongs to the field of battery thermal runaway monitoring technology, specifically relating to a thermal runaway protection device and method for lithium battery packs in electric two-wheeled vehicles. Background Technology

[0002] Electric two-wheelers (including electric bicycles and electric motorcycles) are an important personal transportation tool, and their market size continues to expand. Lithium-ion battery packs have become the mainstream power source due to their high energy density and long cycle life. However, compared with electric vehicles, the battery packs of electric two-wheelers are usually more compact, have limited heat dissipation conditions, and are used in complex and variable environments. These factors significantly increase the risk of thermal runaway in battery packs. Once thermal runaway occurs, if it cannot be effectively contained and physically isolated in a very short time, it can easily cause a fire or even an explosion in the confined battery compartment, posing a serious threat to the life and property safety of users. Therefore, developing a thermal runaway protection device that is fast-responding, reliable, and can achieve ultimate physical isolation for the specific application scenario of electric two-wheelers is an urgent need to improve product safety levels and ensure the healthy development of the industry.

[0003] The prior art, disclosed in CN111907331A, provides a thermal runaway early warning system for an electric vehicle battery pack, comprising a pressure detection module, a control module, a wake-up module, a wake-up feedback module, a signal modulation module, and a battery management module. Its core working principle is as follows: the pressure detection module, deployed inside the battery pack, senses changes in the internal pressure; the control module determines whether a thermal runaway fault has occurred based on the pressure data; if so, it issues an early warning signal and outputs status information; subsequently, the wake-up module wakes up the battery management module (BMS), and the signal modulation module sends the status information to the BMS.

[0004] While the aforementioned existing technologies provide a framework for thermal runaway early warning, they have significant shortcomings when applied to electric two-wheeled vehicle scenarios.

[0005] First, the solution comprises multiple independent modules (such as independent signal modulation modules and multi-feedback modules), resulting in a relatively complex system architecture. This presents challenges in terms of integration, reliability, and cost control for cost-sensitive and space-constrained electric two-wheeler battery packs.

[0006] Secondly, the core functionality of this solution is limited to "early warning" and "status reporting" to the BMS. On electric two-wheelers, the BMS's computing power and response priority may be limited. There is a significant delay between the issuance of an early warning and the BMS's decision-making process, followed by the control of traditional MOS switches to execute a power-off. During the critical window of rapid thermal runaway development, this delay can lead to delayed protection actions.

[0007] Finally, the solution does not integrate any active, irreversible hardware fuse protection mechanism. For electric two-wheelers, when the main circuit switch (such as a MOSFET) fails to disconnect due to sticking, breakdown, or control failure, or when thermal runaway develops too rapidly, the system lacks a last line of defense that can force a physical circuit break, thus failing to prevent catastrophic consequences. Summary of the Invention

[0008] The purpose of this invention is to provide a thermal runaway protection device and method for lithium battery packs in electric two-wheeled vehicles, so as to solve the technical problems of existing thermal runaway protection schemes for lithium battery packs in electric two-wheeled vehicles, such as delayed response, lack of active physical isolation means, low circuit integration, and difficulty in adapting to compact space requirements.

[0009] The present invention achieves the above objectives through the following technical solutions: In a first aspect, the present invention proposes a thermal runaway protection device for lithium battery packs of electric two-wheeled vehicles, including a first protection circuit and a second protection circuit connected in series between the negative terminal of the battery pack and the load / charger interface, and a battery management system main control chip connected to the first protection circuit and the second protection circuit. The first protection circuit includes a discharge control MOSFET Q1 and a charge control MOSFET Q2 connected by a common drain, used to cut off the charging and discharging circuit according to the first control signal output by the main control chip; The second protection circuit includes an active isolation element and its trigger circuit connected in series between the negative terminal of the battery pack and the first protection circuit; the main control chip is configured to: after detecting that the battery pack voltage or temperature exceeds a first preset threshold and outputting the first control signal, if the battery pack voltage or temperature rises to a second preset threshold, output a second control signal to the trigger circuit to drive the active isolation element from a conducting state to a permanently disconnected state, thereby achieving permanent physical isolation of the battery circuit.

[0010] Furthermore, the active isolation element is a three-terminal fuse, which includes a main path pin and a heating element pin; the trigger circuit is electrically connected to the heating element pin and is used to apply a driving voltage to the heating element pin so that the heating element inside the three-terminal fuse heats up and melts the main path pin.

[0011] Furthermore, the trigger circuit includes a switching transistor Q4, a driving MOSFET Q3, and an isolation diode D2; The second control signal output by the main control chip is connected to the base of the switching transistor Q4 to control the switching transistor Q4 on and off. The collector of the switching transistor Q4 is connected to the gate of the driving MOS transistor Q3, and the emitter of the switching transistor Q4 is grounded. The drain of the driving MOSFET Q3 is connected to the heating element pin of the three-terminal fuse via the isolation diode D2, and the source of the driving MOSFET is connected to the positive terminal of the battery pack.

[0012] Furthermore, the trigger circuit also includes a first resistor R3 and a second resistor R4; The second control signal is connected to the base of the switching transistor Q4 via the first resistor R3, and the first resistor R3 is used to limit the base current; The second resistor R4 is connected between the base of the switching transistor Q4 and ground, and is used to provide a pull-down bias to the base when the second control signal is not enabled, so as to keep the switching transistor Q4 reliably turned off; When the second control signal is at a valid high level, the switching transistor Q4 is driven to turn on, so that the positive voltage of the battery pack is applied between the gate and source of the driving MOSFET Q3 after being divided by the first resistor R3 and the second resistor R4, thereby driving the driving MOSFET Q3 to turn on.

[0013] Furthermore, both the discharge control MOS transistor Q1 and the charge control MOS transistor Q2 are NMOS transistors, and their drains are interconnected to form a common drain node. The source of the discharge control MOS transistor Q1 is connected to one end of the active isolation element, and the other end of the active isolation element is connected to the negative terminal of the battery pack. The source of the charging control MOSFET Q2 is connected to the negative terminal of the load / charger interface.

[0014] Furthermore, the first control signal output by the main control chip includes a discharge enable signal and a charge enable signal. The discharge enable signal is used to control the on / off state of the discharge control MOS transistor Q1, and the charge enable signal is used to control the on / off state of the charge control MOS transistor Q2.

[0015] Furthermore, the discharge control MOSFET, the charge control MOSFET, and the active isolation element are all connected in series in the negative electrode single-side circuit of the battery pack.

[0016] Secondly, the present invention proposes a method for thermal runaway protection of lithium battery packs in electric two-wheeled vehicles, applied to the aforementioned device, comprising the following steps: The battery management system's main control chip monitors the battery pack's voltage and temperature; When the battery pack voltage or temperature is detected to exceed the first preset threshold, the first control signal is output to turn off the corresponding MOS transistor in the first protection circuit. After outputting the first control signal, the battery pack voltage and temperature are continuously monitored. When the battery pack voltage or temperature reaches or exceeds the second preset threshold, the second control signal is output to the trigger circuit to drive the active isolation element to change from the on state to the permanent off state.

[0017] Furthermore, the active isolation element is a three-terminal fuse; the step of driving the active isolation element from a conducting state to a permanently disconnected state includes: The second control signal controls the switching transistor Q4 in the trigger circuit to turn on, thereby driving the driving MOSFET Q3 in the trigger circuit to turn on; The positive voltage of the battery pack is applied to the heating element pin of the three-terminal fuse through the conducting drive MOSFET Q3, causing the internal heating element to heat up and melt the main circuit of the three-terminal fuse.

[0018] Furthermore, the first preset threshold is a voltage threshold or temperature threshold that triggers the first-level protection action, and the first-level protection action is to turn off the discharge control MOSFET Q1 or the charging control MOSFET Q2; the second preset threshold is the voltage or temperature value corresponding to when the battery pack voltage or temperature continues to rise or fails to fall after the first-level protection action.

[0019] The beneficial effects of this invention are as follows: (1) This invention combines a two-stage progressive protection mechanism that combines the rapid turn-off of the first-stage MOS transistor with the permanent melting of the second-stage active isolation element. When a reversible abnormality occurs in the battery, the circuit is cut off at a speed of milliseconds, and irreversible physical isolation is provided when the abnormality continues to deteriorate. This solves the defects of existing solutions, such as long response chains and lack of ultimate protection measures.

[0020] (2) The present invention uses an active-triggerable isolation element, which is actively controlled by the BMS main control chip to blow according to the real-time monitoring results of voltage or temperature parameters. This avoids the disadvantage of traditional fuses that can only passively respond to current over-limit, and ensures that the circuit can still be completely cut off when the MOS tube sticks or breaks down.

[0021] (3) The present invention arranges the discharge control MOS transistor, the charging control MOS transistor and the active isolation element in series in the single-side circuit of the negative electrode of the battery pack. Compared with the traditional scheme of arranging switching devices on both the positive and negative electrodes, it significantly reduces the number of power devices and the PCB trace area, effectively reduces the size of the protection board, reduces material costs, and improves circuit integration. It is particularly suitable for battery packs of electric two-wheeled vehicles with compact space. Attached Figure Description

[0022] Figure 1 This is a system block diagram of a battery pack thermal runaway protection device in an embodiment of the present invention; Figure 2 This is a schematic diagram of a battery pack thermal runaway protection device in an embodiment of the present invention; Figure 3 This is a flowchart of a battery pack thermal runaway protection method in an embodiment of the present invention. Detailed Implementation

[0023] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0024] This disclosure provides a thermal runaway protection device and method for lithium battery packs in electric two-wheeled vehicles. Please refer to [link / reference]. Figure 1 and Figure 2 The device can be integrated into the battery management system (BMS) protection board of an electric two-wheeler's lithium battery pack. This embodiment takes the application of the device in a compact electric two-wheeler lithium battery pack with limited heat dissipation as an example, and elaborates on its circuit structure and workflow. The device executes two-stage progressive protection actions under the control of the same battery management system main control chip to effectively curb and ultimately physically isolate the battery's thermal runaway from initial abnormality to continuous deterioration. The following will combine... Figure 2 The circuit schematic and Figure 3 The protection flowchart shown provides a detailed explanation of the specific implementation of the thermal runaway protection device and method for the lithium battery pack used in electric two-wheeled vehicles.

[0025] Example 1

[0026] A preferred embodiment of the present invention proposes a thermal runaway protection device for lithium battery packs of electric two-wheelers. This device is specifically designed for the characteristics of electric two-wheeler battery packs, such as compact space, limited heat dissipation conditions, and complex and variable operating environments. It mainly improves the safety performance of the battery pack by taking corresponding containment and isolation measures at different stages of thermal runaway development through a two-stage progressive protection mechanism.

[0027] like Figure 1 and Figure 2 As shown, the protection device in this embodiment mainly includes a first protection circuit and a second protection circuit connected in series between the negative terminal (BATT-) of the battery pack and the load / charger interface (PACK-), as well as a battery management system (BMS) main control chip connected to the first protection circuit and the second protection circuit. The BMS main control chip is responsible for collecting key parameters of the battery pack such as voltage and temperature in real time, and outputting corresponding control signals according to preset logic.

[0028] The first protection circuit includes a discharge control MOSFET Q1 and a charge control MOSFET Q2 connected by a common drain. Specifically, both Q1 and Q2 are NMOS transistors, and their drains are directly connected to form a common drain node. The source of Q1 is connected to one end of the active isolation element in the second protection circuit, and the other end of the active isolation element is connected to the negative terminal of the battery pack (BATT-). The source of Q2 is connected to the negative terminal of the load / charger interface (PACK-). The advantage of using a common drain connection is that by independently controlling the gates of Q1 and Q2, the discharge circuit and the charging circuit can be cut off separately or simultaneously, achieving flexible control of bidirectional current.

[0029] Under normal operating conditions, the first control signal output by the BMS main control chip (including the discharge enable signal DSG_EN and the charging enable signal CHG_EN) is at an effective level, keeping Q1 and Q2 on.

[0030] During discharge, the current path is: negative terminal of the battery pack (BATT-) Active isolation element Q1 source Q1 drain common drain node The body diode of Q2 (or through its channel when Q2 is on). The load / charger interface negative terminal (PACK-) eventually returns to the battery pack positive terminal (BATT+) to form a complete circuit.

[0031] During charging, the current path is: charger negative terminal (PACK-) Q2 source Q2 drain common drain node The body diode of Q1 (or through its channel when Q1 is on). Active isolation element Battery pack negative terminal (BATT-).

[0032] The second protection circuit includes an active isolation element and its triggering circuit connected in series between the negative terminal (BATT-) of the battery pack and the first protection circuit. In a preferred embodiment, this active isolation element is a three-terminal fuse F1. The three-terminal fuse F1 not only possesses the passive fusing capability of a conventional fuse based on rated current / voltage, but its unique feature is that it includes an independent heating element pin (such as...). Figure 2 Pin 2) and two main path pins (such as Figure 2(Pin 1 and pin 3). The main circuit pins are connected in series in the main circuit, while the heating element pins are used to receive external trigger signals, causing the main circuit to melt through the internal heating element. This design allows the protection system to actively and accurately control the fuse to blow based on the BMS algorithm, rather than relying solely on passive blowing due to current over-limit. This avoids the drawback of traditional single-circuit fuses that cannot operate when the fault current has not yet reached the melting value but the risk of thermal runaway is extremely high.

[0033] The trigger circuit is used to provide a driving voltage to the heating element pin of the three-terminal fuse F1 when the main control chip outputs the second control signal. Specifically, the trigger circuit includes a switching transistor Q4, a driving MOSFET Q3, an isolation diode D2, a first resistor R3, and a second resistor R4.

[0034] The connection relationships and functions of each component are as follows: The second control signal (FUSE_EN) output by the main control chip is connected to the base of the switching transistor Q4 via the first resistor R3. The first resistor R3 is a current-limiting resistor, used to limit the current flowing into the base of Q4 and protect Q4 from damage by excessive base current.

[0035] The second resistor R4 is connected between the base of the switching transistor Q4 and ground (GND), serving as a pull-down bias. When the second control signal (FUSE_EN) is not enabled (i.e., low level or floating), R4 reliably pulls the base potential of Q4 to ground, preventing Q4 from being mis-turned on due to electromagnetic interference or a floating state, thereby ensuring that the trigger circuit will not malfunction.

[0036] The emitter of the switching transistor Q4 is grounded (GND), and its collector is connected to the gate of the driving MOSFET Q3.

[0037] The source of the driving MOSFET Q3 is connected to the positive terminal of the battery pack (BATT+), and the drain is connected to the heating element pin (pin 2) of the three-terminal fuse F1 via the isolation diode D2. The isolation diode D2 is used for unidirectional power supply and isolation, preventing the voltage of the F1 terminal or other networks in the main circuit from accidentally flowing into the control network on the positive side of Q3 and the battery, ensuring the unidirectionality of the trigger signal and the stability of the circuit operation.

[0038] The BMS main control chip is configured to execute two-level progressive protection logic: Level 1 Protection (Fast Shutdown): The BMS main control chip monitors the battery pack's voltage and temperature in real time. When any parameter exceeds a preset first threshold (safety threshold), the BMS determines that the battery is in a reversible abnormal operating state and immediately sets the corresponding first control signal (DSG_EN or CHG_EN) to an invalid level. For example, if overcharging causes the voltage to exceed the threshold, CHG_EN is set to a low level, shutting down the charging control MOSFET Q2; if over-discharge or a short circuit causes excessive current and a sudden temperature rise, DSG_EN is set to a low level, shutting down the discharging control MOSFET Q1. This action has a millisecond-level response, which can quickly cut off the charging and discharging current that exacerbates thermal runaway and handle most reversible faults.

[0039] Second-level protection (ultimate physical isolation): After the first-level protection is activated (i.e., Q1 or Q2 is turned off), the BMS main control chip continuously monitors the voltage and temperature status of the battery pack. If the voltage or temperature parameter does not decrease after the first-level protection is activated, but instead continues to rise and reaches or exceeds the second preset threshold (critical value), the BMS determines that the risk of thermal runaway continues to develop inside the battery, and the first-level protection is no longer sufficient to curb the deterioration of the risk, and ultimate protection must be activated. At this time, the BMS main control chip outputs a second control signal (FUSE_EN) to the trigger circuit. Specifically, the FUSE_EN signal is set to a valid high level.

[0040] The specific triggering process for Level 2 protection is as follows: When FUSE_EN is high, it drives the switching transistor Q4 to conduct after being current-limited by the first resistor R3.

[0041] After Q4 is turned on, its collector potential is pulled down to near ground potential, causing the positive voltage of the battery pack (BATT+) to form a positive voltage between the gate and source (Vgs) of the driving MOSFET Q3 after being divided by the first resistor R3 and the second resistor R4. For example, assuming BATT+ is 48V, the resistance ratio of R3 and R4 is designed so that Vgs of Q3 reaches the threshold voltage (e.g., 10V) required for its full conduction, thus enabling Q3 to conduct reliably.

[0042] After Q3 is turned on, the voltage at the positive terminal (BATT+) of the battery pack is applied to the heating element pin (pin 2) of the three-terminal fuse F1 through the drain-source terminal of Q3 and the isolation diode D2.

[0043] Since pin 3 of the three-terminal fuse F1 is directly connected to the negative terminal (BATT-) of the battery pack, a voltage difference is formed between pin 2 and pin 3, which drives the internal heating element to heat up rapidly.

[0044] The heat generated by the heating element melts the main circuit of the fuse (i.e., the connection between pin 1 and pin 3) in a very short time (usually milliseconds). Once the main circuit is broken, all connections between the negative terminal (BATT-) of the battery pack and the external circuit are permanently and physically severed. Even if the upstream MOS switches Q1 and Q2 fail completely due to faults such as sticking or breakdown, the battery pack can be absolutely isolated, fundamentally curbing the spread of thermal runaway.

[0045] As an illustrative example and not a limitation thereof, a typical ternary lithium-ion battery pack (e.g., 13 cells in series, nominal voltage 48V) can be used as an example. Its protection thresholds can be set as follows: In the first preset threshold (safety threshold), the overcharge protection voltage can be set to 4.25V ± 0.05V per cell, the over-discharge protection voltage can be set to 2.7V ± 0.1V per cell, the charging over-temperature protection temperature can be set to 55℃ ± 3℃, and the discharging over-temperature protection temperature can be set to 65℃ ± 3℃. When the BMS main control chip detects that any parameter exceeds the corresponding first preset threshold, it determines that the battery is in a reversible abnormal operating state and outputs a first control signal to turn off the corresponding MOSFET.

[0046] The second preset threshold (critical threshold) is set to a more stringent value than the first preset threshold. For example, the overcharge secondary protection voltage can be set to 4.35V±0.05V per cell, the charging secondary over-temperature protection temperature can be set to 65℃±3℃, and the discharging secondary over-temperature protection temperature can be set to 75℃±3℃. After the first protection action (MOSFET turn-off), if the BMS main control chip continuously monitors that the battery pack voltage or temperature not only does not decrease but continues to rise and reaches or exceeds the above-mentioned second preset threshold, it is determined that the risk of thermal runaway continues to deteriorate inside the battery, and the first-level protection is no longer sufficient to contain it. Then, a second control signal is output to initiate the final physical isolation.

[0047] The specific values ​​of the above thresholds can be adjusted and calibrated according to the actual lithium-ion battery chemistry system used (such as lithium iron phosphate, ternary lithium, lithium manganese oxide, etc.), cell specifications, and the safety strategies of vehicle manufacturers. Those skilled in the art can set them reasonably according to the teachings of this invention.

[0048] As a key structural feature of this embodiment, the discharge control MOSFET Q1, the charge control MOSFET Q2, and the active isolation element F1 are all connected in series in the negative terminal circuit of the battery pack. Compared to the traditional approach of arranging switching devices on both the positive and negative terminals of the battery, this single-sided protection topology significantly reduces the number of power devices, drive circuits, and PCB traces. This design directly brings three benefits: first, it greatly reduces the size of the protection circuit board (PCB), making it very suitable for the battery packs of electric two-wheelers where space is extremely limited; second, it effectively reduces system material costs; and third, it improves circuit integration and manufacturing consistency.

[0049] Example 2

[0050] Another preferred embodiment of the present invention proposes a method for thermal runaway protection of a lithium battery pack for an electric two-wheeled vehicle, which can be applied to the device described in Embodiment 1. Figure 3 As shown, the method includes the following steps: S1. The BMS main control chip monitors the voltage and temperature parameters of the battery pack in real time.

[0051] S2. When the battery pack voltage or temperature exceeds the first preset threshold, the BMS main control chip outputs a first control signal to turn off the corresponding MOSFET (Q1 or Q2) in the first protection circuit. The first preset threshold is the voltage or temperature threshold that triggers the first-level protection action, representing the safety boundary for the battery to reach a reversible abnormal state.

[0052] S3. After outputting the first control signal, the BMS main control chip continuously monitors the battery pack voltage and temperature. It determines whether the monitored voltage or temperature reaches or exceeds a second preset threshold. The second preset threshold is the voltage or temperature value corresponding to the battery pack voltage or temperature continuing to rise or failing to decrease after the first-level protection action, representing a critical state where the risk of battery thermal runaway continues to develop and the first protection action has failed to effectively contain it.

[0053] S4. When the battery pack voltage or temperature is detected to reach or exceed the second preset threshold, the BMS main control chip outputs the second control signal (FUSE_EN) to the trigger circuit, driving the active isolation element to change from the on state to the permanent off state, thereby achieving permanent physical isolation of the battery circuit.

[0054] In the preferred embodiment where a three-terminal fuse F1 is used as the active isolation element, step S4 specifically includes: The second control signal (FUSE_EN) first controls the switching transistor Q4 in the trigger circuit to turn on; after Q4 turns on, it drives the driving MOSFET Q3 in the trigger circuit to turn on; the battery pack positive terminal (BATT+) voltage is applied to the heating element pin (pin 2) of the three-terminal fuse F1 through the turned-on Q3, causing the internal heating element to heat up and melt the main path of the three-terminal fuse F1 (between pin 1 and pin 3) in a very short time.

[0055] At this point, the connection between the battery pack and the external circuit is permanently and physically severed, achieving ultimate protection against thermal runaway.

[0056] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present invention are generated.

[0057] The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can access, or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)).

[0058] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0059] In addition, the functional modules in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0060] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A thermal runaway protection device for lithium battery packs in electric two-wheeled vehicles, characterized in that, It includes a first protection circuit and a second protection circuit connected in series between the negative terminal of the battery pack and the load / charger interface, and a battery management system main control chip connected to the first protection circuit and the second protection circuit. The first protection circuit includes a discharge control MOSFET Q1 and a charge control MOSFET Q2 connected by a common drain, used to cut off the charging and discharging circuit according to the first control signal output by the main control chip; The second protection circuit includes an active isolation element and its trigger circuit connected in series between the negative terminal of the battery pack and the first protection circuit; the main control chip is configured to: after detecting that the battery pack voltage or temperature exceeds a first preset threshold and outputting the first control signal, if the battery pack voltage or temperature rises to a second preset threshold, output a second control signal to the trigger circuit to drive the active isolation element from a conducting state to a permanently disconnected state, thereby achieving permanent physical isolation of the battery circuit.

2. The thermal runaway protection device for lithium battery packs of electric two-wheeled vehicles according to claim 1, characterized in that, The active isolation element is a three-terminal fuse, which includes a main path pin and a heating element pin. The trigger circuit is electrically connected to the heating element pin and is used to apply a driving voltage to the heating element pin so that the heating element inside the three-terminal fuse heats up and melts the main path pin.

3. The thermal runaway protection device for lithium battery packs of electric two-wheeled vehicles according to claim 2, characterized in that, The trigger circuit includes a switching transistor Q4, a driving MOSFET Q3, and an isolation diode D2; The second control signal output by the main control chip is connected to the base of the switching transistor Q4 to control the switching transistor Q4 on and off. The collector of the switching transistor Q4 is connected to the gate of the driving MOS transistor Q3, and the emitter of the switching transistor Q4 is grounded. The drain of the driving MOSFET Q3 is connected to the heating element pin of the three-terminal fuse via the isolation diode D2, and the source of the driving MOSFET is connected to the positive terminal of the battery pack.

4. The thermal runaway protection device for lithium battery packs of electric two-wheeled vehicles according to claim 3, characterized in that, The trigger circuit also includes a first resistor R3 and a second resistor R4; The second control signal is connected to the base of the switching transistor Q4 via the first resistor R3, and the first resistor R3 is used to limit the base current; The second resistor R4 is connected between the base of the switching transistor Q4 and ground, and is used to provide a pull-down bias to the base when the second control signal is not enabled, so as to keep the switching transistor Q4 reliably turned off; When the second control signal is at a valid high level, the switching transistor Q4 is driven to turn on, so that the positive voltage of the battery pack is applied between the gate and source of the driving MOSFET Q3 after being divided by the first resistor R3 and the second resistor R4, thereby driving the driving MOSFET Q3 to turn on.

5. The thermal runaway protection device for lithium battery packs of electric two-wheeled vehicles according to claim 1, characterized in that, Both the discharge control MOS transistor Q1 and the charge control MOS transistor Q2 are NMOS transistors, and their drains are connected to form a common drain node. The source of the discharge control MOS transistor Q1 is connected to one end of the active isolation element, and the other end of the active isolation element is connected to the negative terminal of the battery pack. The source of the charging control MOSFET Q2 is connected to the negative terminal of the load / charger interface.

6. The thermal runaway protection device for lithium battery packs of electric two-wheeled vehicles according to claim 5, characterized in that, The first control signal output by the main control chip includes a discharge enable signal and a charge enable signal. The discharge enable signal is used to control the on / off state of the discharge control MOS transistor Q1, and the charge enable signal is used to control the on / off state of the charge control MOS transistor Q2.

7. The thermal runaway protection device for lithium battery packs of electric two-wheeled vehicles according to claim 1, characterized in that, The discharge control MOSFET, the charge control MOSFET, and the active isolation element are all connected in series in the negative electrode single-side circuit of the battery pack.

8. A method for thermal runaway protection of lithium battery packs in electric two-wheeled vehicles, applied to the device according to any one of claims 1-7, characterized in that, Includes the following steps: The battery management system's main control chip monitors the battery pack's voltage and temperature; When the battery pack voltage or temperature is detected to exceed the first preset threshold, the first control signal is output to turn off the corresponding MOS transistor in the first protection circuit. After outputting the first control signal, the battery pack voltage and temperature are continuously monitored. When the battery pack voltage or temperature reaches or exceeds the second preset threshold, the second control signal is output to the trigger circuit to drive the active isolation element to change from the on state to the permanent off state.

9. The method for thermal runaway protection of lithium battery packs for electric two-wheeled vehicles according to claim 8, characterized in that, The active isolation element is a three-terminal fuse; the step of driving the active isolation element from a conducting state to a permanently disconnected state includes: The second control signal controls the switching transistor Q4 in the trigger circuit to turn on, thereby driving the driving MOSFET Q3 in the trigger circuit to turn on; The positive voltage of the battery pack is applied to the heating element pin of the three-terminal fuse through the conducting drive MOSFET Q3, causing the internal heating element to heat up and melt the main circuit of the three-terminal fuse.

10. The method for thermal runaway protection of lithium battery packs for electric two-wheeled vehicles according to claim 8, characterized in that, The first preset threshold is a voltage or temperature threshold that triggers the first-level protection action, which is to turn off the discharge control MOSFET Q1 or the charging control MOSFET Q2; the second preset threshold is the voltage or temperature value corresponding to when the battery pack voltage or temperature continues to rise or fails to fall after the first-level protection action.

Images