A battery pack safety protection method and device with passive branch self-detection fusing

Abstract

The application discloses a battery group safety protection method and device with passive branch self-detection fusing, and belongs to the technical field of battery safety protection. Passive execution units are independently configured for each parallel branch, the thermal equilibrium state of the branch is taken as a dynamic reference to sense the temperature rise deviation, an alloy solid-state phase change material is used to realize physical fusing, and a charge temporary storage circuit is used to complete power-off coding and reporting. The method and device are not dependent on external power supply, master control chips, software algorithms and communication instructions, can independently detect the branch, respond in milliseconds, accurately locate and independently isolate, and have nearly zero power consumption during normal operation. The unified fusing of all branches ensures that the battery pack is completely electrically disconnected during disassembly, and the risk of combustion and explosion caused by residual electricity is eliminated. The method and device are compatible with various battery cells and group structures, can be directly embedded into an existing battery system, and realize passive bottom-up safety protection in the whole life cycle.

Description

Technical Field

[0001] This invention belongs to the field of battery safety protection technology, specifically relating to a battery pack safety protection method and device that does not rely on external power supply, main control chip and communication link, and features self-detection, self-triggered fuse, fault code location and full life cycle safety protection. It is applicable to vehicle power batteries, stationary energy storage stations, battery swapping chassis power systems and various multi-cell combined power supply equipment. Background Technology

[0002] Currently, power batteries and energy storage batteries generally use multiple cells connected in series and parallel to form a power supply. The number of cells in a battery pack ranges from dozens to thousands. If any cell experiences an internal micro-short circuit, poor contact of the tabs, abnormal increase in internal resistance, or local overheating, it may develop into thermal runaway within seconds to minutes, ultimately leading to fire or explosion.

[0003] Existing safety protection solutions heavily rely on the battery management system, which achieves pack-wide power failure control through voltage sampling, current sampling, temperature sampling, and communication links. This approach has the following unavoidable drawbacks.

[0004] First, the protection function relies on external power supply, main control chip, and communication link. When the battery system loses power due to collision, water ingress, aging wiring, or main control failure, the battery management system also fails simultaneously, leaving the battery pack unprotected and without any backup capability.

[0005] Second, it can only achieve a complete power outage of the entire package and cannot independently isolate faulty branches. If a single branch or a single cell malfunctions, the entire package will stop supplying power, causing the vehicle to lose power midway and the energy storage system to disconnect from the grid, which seriously affects the system's continuous operation capability and emergency safety.

[0006] Third, there is an inherent delay of tens to hundreds of milliseconds from the occurrence of an anomaly to sampling, computation, communication, and execution. When the fault current rises sharply or the local temperature rise rate is extremely high, traditional solutions cannot complete the blocking in the early stage of thermal runaway.

[0007] Fourth, the fault location accuracy is extremely low. The system can only report voltage or current abnormalities and cannot directly pinpoint the specific faulty branch or cell location. During maintenance, a complete disassembly and inspection is required, resulting in extremely high operation and maintenance costs.

[0008] Fifth, traditional monitoring and execution devices require continuous power consumption, increasing the ineffective power consumption of batteries and shortening the effective battery life and energy storage time.

[0009] Sixth, retired battery packs still contain residual charge during disassembly. Mechanical cutting and separation can easily cause short circuits between the positive and negative terminals, generating electric arcs or sparks, which directly threaten the lives of recycling personnel.

[0010] There is currently a lack of a comprehensive safety solution that covers the entire lifecycle from vehicle installation and service to decommissioning and dismantling, without relying on external conditions and with independent protection at the branch level. Summary of the Invention

[0011] (a) Purpose of the invention This invention provides a battery pack safety protection method and device with passive branch self-detection and fuse breaking, aiming to achieve the following objectives: independent of external power supply and main control system, each branch independently and autonomously completes anomaly detection and fuse breaking isolation; millisecond-level response after an anomaly occurs, blocking the faulty branch in the early stage of thermal runaway; near-zero power consumption during normal operation, without affecting battery life; faulty branch is located by physical coding, eliminating the need for disassembly of each pack during maintenance; during decommissioning and dismantling, electrical circuit is broken by unified fuse breaking of all branches, eliminating the risk of combustion and explosion caused by residual charge.

[0012] (II) Core Principles This invention establishes a fundamental principle in its design: safety protection devices must not introduce additional failure modes exceeding the failure rate of the protected object itself. Any active chip, software algorithm, or communication protocol can introduce new failure points such as system crashes, program malfunctions, data errors, and power fluctuations. Therefore, all sensing, judgment, and execution actions of the method and device described in this invention are based on the inherent physical properties of the materials and the intrinsic behavior of the circuit.

[0013] This invention constructs a complete passive closed-loop protection logic based on the following three independent yet complementary underlying principles.

[0014] First, the principle of detecting deviations from thermodynamic equilibrium.

[0015] When each working branch operates under rated current for a long period of time, a thermal equilibrium is reached between the Joule heating of the conductor and the heat dissipation to the environment. The surface temperature of the conductor stabilizes at a certain value, which is uniquely determined by the branch resistance, current and heat dissipation conditions. This is a physical fact and does not depend on any storage or calculation.

[0016] When an abnormality occurs within a branch circuit, the abnormal current or increased local contact resistance leads to increased Joule heating, disrupting the original thermal equilibrium and causing a sharp rise in conductor temperature relative to its steady-state operating point. This invention uses "whether the branch deviates from its thermal equilibrium state" rather than "whether it exceeds a preset absolute temperature value" as the criterion for temperature-related faults. When the overall ambient temperature of the battery pack rises, each branch changes synchronously and slowly, remaining in a state of thermal equilibrium and not triggering protection; however, a temperature rise caused by a defect within a single branch is abrupt and localized, and will inevitably be detected and trigger a fuse.

[0017] Second, the principle of self-triggered execution of solid-state phase change.

[0018] This invention employs an alloy material that undergoes a solid-state phase transition at a specific temperature as the actuator. Within its normal operating temperature range, this alloy exhibits a stable, low-resistance crystal structure with extremely low on-resistance. When its temperature reaches a preset phase transition point, the crystal structure within the alloy undergoes reorganization, transforming from a conductive phase to a high-resistance or insulating phase. The resistance jumps by several orders of magnitude in a very short time, and the branch is physically severed.

[0019] This phase transition behavior is an intrinsic physical behavior of materials at a specific temperature, belonging to the same physical property laws as the boiling of water and the melting of ice, and does not depend on any chip judgment, software decision, or external instructions. The phase transition temperature is precisely controlled by the metallurgical ratio of the alloy composition, which can achieve consistency in mass production in engineering.

[0020] Third, the principle of charge temporary storage and autonomous reporting.

[0021] When a branch circuit blows, the main circuit disconnects, the current drops to zero, and the branch is in a power-off state. If there is no backup energy, the fault location information will be lost with the power outage. This invention incorporates a miniature charge storage circuit in each branch. During the branch's normal conduction period, this circuit uses an induction circuit to pick up the weak electrical energy in the branch and continuously replenish the energy storage element, storing the energy in it. The impact of this power extraction process on the branch's transmission efficiency is negligible.

[0022] When a branch circuit blows and the main circuit loses power, the charge storage circuit releases the stored charge, providing transient operating energy to the encoding and identification unit. This drives the unit to output the hardware-defined encoded signal for that branch, completing the final fault report. After reporting, the circuit is completely de-energized. The entire process does not rely on an external power source, a backup battery, or continuous power from the communication line.

[0023] The three principles described above form a complete closed-loop logic: the thermodynamic equilibrium deviation detection principle is responsible for sensing anomalies; the solid-state phase change self-triggered execution principle is responsible for executing the cut-off; and the charge temporary storage autonomous reporting principle is responsible for completing information reporting after the cut-off. Together, these three constitute a fully passive safety protection chain from "sensing—execution—reporting".

[0024] (III) Technical Solution This invention provides a battery pack safety protection method with passive branch self-detection and fuse breaking, comprising the following steps: The first step is to configure independent passive detection and execution units for each of the multiple parallel current branches in the battery pack module, so that each branch can independently complete the abnormality detection and fuse action.

[0025] The second step involves using the thermal equilibrium state of each branch under normal steady-state operation as a dynamic temperature reference, and continuously monitoring the deviation of the conductor temperature from this reference.

[0026] The third step involves simultaneously monitoring whether the current in each branch exceeds a preset multiple of the rated current and whether the internal resistance exceeds a preset multiple of the initial value.

[0027] Fourth, when any parameter of branch current, temperature rise deviation or internal resistance sudden change reaches the preset trigger threshold, the execution unit completes the irreversible physical melting of the branch within the preset time window.

[0028] The fifth step involves storing a unique code in hardware and drawing power for energy storage during normal branch conduction via a charge storage circuit.

[0029] The sixth step is that when a branch is melted, the charge storage circuit releases the stored energy and drives the coding point identification unit to output the hardware coding signal of that branch.

[0030] The seventh step involves aggregating the coded signals of each branch through a convergence acquisition unit and communicating with an external system to provide information on the location of the faulty branch.

[0031] Step 8: When the battery pack is retired and enters the recycling and dismantling process, the entire branch circuit is sent to the busbar acquisition unit to make all branches melt simultaneously, thereby achieving an overall electrical circuit break for the battery pack.

[0032] This invention also provides a passive branch self-detection fuse-type battery pack safety protection device for implementing the above method. The device includes: The battery pack module consists of multiple cells connected in series and parallel to form multiple independent current branches; Multiple passive fuse actuators are connected in series in a current branch. Each actuator is internally set with a main current circuit and an induction circuit connected in parallel. The main current circuit is made of phase change alloy material. The induction circuit is used to collect branch current, conductor temperature and internal resistance changes. Multiple coding point identification units are connected one-to-one with a branch passive fuse execution unit. The unique code is fixed in hardware. The internal charge storage circuit is integrated. During the normal conduction of the branch, the charge storage circuit picks up the weak electrical energy in the branch through the induction circuit to replenish the energy storage element. The cascade acquisition unit connects to all coding point identification units to aggregate fault coding signals and communicate with external systems. It also has the function of forwarding fuse-breaking commands for all branches.

[0033] The main current conduction circuit and the sensing circuit are physically connected in parallel and independent in terms of power consumption, allowing high current conduction and low power induction to coexist. The energy storage capacity of the charge storage circuit is designed to match the operating voltage and duration required for the coded point identification unit to complete one full fault signal reporting.

[0034] The device does not contain a continuously powered active computing or control semiconductor chip, and does not rely on external power supply, software algorithms, or communication commands to complete protection actions.

[0035] (iv) Beneficial effects First, it provides passive backup protection under all operating conditions. Completely independent of external power supply and main control system, it relies on the energy of its own branch circuit to complete detection and execution, and can still independently trigger protection under extreme conditions such as vehicle power failure, BMS failure, and communication interruption.

[0036] Second, branch-level independent isolation ensures uninterrupted normal power supply. Only the faulty branch is disconnected, while the remaining normal branches maintain conductive output, allowing vehicles to maintain safe driving capabilities and the energy storage system to continue grid-connected operation.

[0037] Third, millisecond-level response. The entire process is physical, with no software computation or transmission delay, completing the blocking in the early stages of thermal runaway.

[0038] Fourth, near-zero additional power consumption. In normal conduction mode, it is a low-impedance path, the power consumption of the sensing circuit is negligible, and there is no continuous standby power consumption.

[0039] Fifth, physical dynamic benchmark, error-free triggering across the entire temperature range. Based on the thermal equilibrium state of the branch circuit itself, it is unaffected by ambient temperature and the overall temperature rise of the battery pack, ensuring error-free triggering at high temperatures and no failure to operate at low temperatures.

[0040] Sixth, unique hardware coding enables precise fault location. Each branch corresponds to an independent, fixed code, and the fault location is directly reported upon triggering, eliminating the need for disassembling and troubleshooting each package individually.

[0041] Seventh, high compatibility across all scenarios. It is not limited by cell type, assembly method, or chassis structure, and can be directly embedded into existing battery modules and slave control boards.

[0042] Eighth, end-to-end terminal safety. During decommissioning and dismantling, a unified fuse across all branches can be triggered, eliminating the risk of combustion and explosion caused by residual electrical charge. Detailed Implementation

[0043] Example 1: Vehicle-mounted power lithium iron phosphate battery pack A certain vehicle-mounted power battery pack adopts a multi-series, multi-parallel structure, forming multiple parallel branches. Each branch is connected in series to a passive fuse actuator, which is correspondingly connected to an coded point identification unit. Each branch has an independent and unique code. The actuator has a preset overcurrent trigger threshold of a preset multiple of the rated current (e.g., 1.5 times), a temperature rise threshold of a preset temperature difference based on the branch's steady-state thermal equilibrium temperature (e.g., 25°C), an internal resistance change threshold of a preset multiple of the initial internal resistance (e.g., 1.5 times), and a response time no greater than a preset duration (e.g., 5ms).

[0044] During normal operation, each branch execution unit maintains low-resistance conduction. When a micro-short circuit occurs in a branch, causing the current to surge above the threshold, the sensing circuit directly detects the current over-limit. Within a preset time window, the alloy material of the main current-carrying circuit undergoes a solid-state phase transition, resistance jumps, and the branch is physically disconnected. The remaining branches maintain normal power supply. At the moment of circuit break, the charge storage circuit releases the stored charge, driving the coding point identification unit to output the coded signal of that branch to the bus acquisition unit. The bus unit reports to the vehicle BMS, and maintenance personnel directly locate and replace the faulty branch.

[0045] Example 2 Large-scale energy storage battery cluster A certain energy storage battery cluster adopts a multi-series, multi-parallel structure, forming multiple parallel branches. Each branch is equipped with a passive fuse actuator and a unique coding unit, with independent partitioned wiring connecting to a current acquisition unit, which in turn connects to the energy storage management system. The trigger threshold is set according to preset multiples of rated current, preset temperature difference, and preset multiples of internal resistance, and the response time does not exceed a preset duration. The system operates continuously without error triggering or missed actions; in the event of a single branch failure, the remaining branches continue to charge and discharge normally.

[0046] Example 3: Safe Application of Retired Battery Disassembly Once the battery pack containing this device reaches the retirement standard, it enters the official recycling and dismantling process. Dismantling line operators send a full-branch fuse-breaking command via the busbar acquisition unit. All branch execution units simultaneously trigger the fuses, and the entire battery pack enters a permanent electrical open-circuit state within a preset time window, with all individual cells insulated from each other. Subsequently, mechanical dismantling equipment safely performs operations such as casing opening, cell separation, and material sorting, with no risk of short circuits, electric arcs, or explosions throughout the entire process.

Claims

1. A battery pack safety protection method with passive branch self-detection and fuse breaking, characterized in that, Includes the following steps: Each of the multiple parallel current branches in the battery pack module is configured with an independent passive detection and execution unit, and each branch independently completes the abnormality detection and fuse action. Each branch uses its own thermal equilibrium state during normal steady-state operation as a dynamic temperature reference, and continuously monitors the deviation of the conductor temperature from this reference. Each branch simultaneously monitors whether the current exceeds a preset multiple of the rated current and whether the internal resistance exceeds a preset multiple of the initial value; When any parameter of branch current, temperature rise deviation or internal resistance sudden change reaches the preset trigger threshold, the execution unit completes the irreversible physical melting of the branch within the preset time window. Each branch stores a unique code in a hardware-based fixed manner, and draws power to store energy during the normal conduction period of the branch through a charge temporary storage circuit. When a branch is melted, the charge storage circuit releases the stored energy, driving the coding point identification unit to output the hardware coding signal of that branch. The combined acquisition unit aggregates the coded signals of each branch and communicates with the external system. When the battery pack is retired and enters the recycling and dismantling process, the busbar acquisition unit sends a full branch circuit blow-off command to make all branches blow-off simultaneously, thereby achieving an overall electrical circuit break for the battery pack.

2. The method according to claim 1, characterized in that, The dynamic temperature reference is the thermal equilibrium temperature of the conductor surface formed by the steady-state operation of the branch. The establishment and maintenance of this reference does not require external power supply, but is determined solely by the branch's own Joule heating and heat dissipation conditions.

3. The method according to claim 1, characterized in that, Phase change alloys are used as the fuse actuators. The alloys are low-resistance conductive phases under normal conditions. After being heated to a preset phase change point, they spontaneously transform into high-resistance or insulating phases. Passive cut-off is achieved by relying on the intrinsic properties of the material, without the need for external control signals.

4. The method according to claim 1, characterized in that, The charge storage circuit relies on the induction circuit to pick up the weak electrical energy of the branch to complete the energy storage. The power taken does not affect the normal current carrying capacity of the branch. The energy storage capacity matches the energy consumption required for a single fault code reporting.

5. The method according to claim 1, characterized in that, The entire process of detection, judgment, circuit breaking, encoding and reporting is carried out without the intervention of active computing chips, relying entirely on the electrical energy and material physical properties of the branch circuit itself.

6. A passive branch self-detection fuse-type battery pack safety protection device, characterized in that, include: The battery pack module consists of multiple cells connected in series and parallel to form multiple independent current branches; Multiple passive fuse actuators are provided, each actuator is connected in series in a current branch, and internally there are parallel main current loops and sensing circuits. The main current loops are made of phase change alloy material, and the sensing circuits are used to collect branch current, conductor temperature and internal resistance changes. Multiple coding point identification units, each coding point identification unit is connected to a branch passive fuse execution unit, and the unique code is fixed in hardware. The internal charge storage circuit is integrated. The convergence acquisition unit is connected to all coding point identification units to summarize fault coding signals and communicate with external systems. It also has the function of forwarding fuse-breaking instructions for all branches.

7. The apparatus according to claim 6, characterized in that, The main current-carrying circuit and the sensing circuit are physically connected in parallel and have independent power consumption. The high current-carrying and low power signal acquisition operate synchronously without interfering with each other.

8. The apparatus according to claim 6, characterized in that, The charge storage circuit is electrically connected to the induction circuit. When the branch is working normally, it picks up the weak electrical energy of the branch and stores it. After the branch is blown, it releases the electrical energy to drive the coding point identification unit to output the fault point signal.

9. The apparatus according to claim 6, characterized in that, Each coding point identification unit is connected to the bus acquisition unit by independent partition wiring. The transmission of each fault signal is isolated and free from crosstalk, and it is compatible with synchronous identification of multiple branches.

10. The apparatus according to claim 6, characterized in that, The device does not contain continuously powered active computing or control semiconductor chips, and protection triggering and fault reporting do not rely on external power sources, software programs, or communication commands.