Method for solving power-off load throwing problem of lithium battery

Abstract

The invention discloses a method for solving the problem of power-off load throwing of a lithium battery. The method comprises the following steps: S1, connecting a super-capacitor absorption circuit between a negative terminal of a storage battery and a negative terminal of a battery management system (BMS); s2, when the negative terminal of the storage battery is disconnected, the super-capacitor absorption circuit is utilized to instantaneously absorb a voltage peak generated by load throwing; s3, through a capacitor discharge path connected in parallel with the super-capacitor absorption circuit, releasing residual charges in the super-capacitor unit after peak absorption is completed; and S4, when the storage battery recovers normal connection or the system is in a non-load-throwing state, maintaining the connection state of the super-capacitor absorption circuit and the capacitor discharge path so as to immediately respond when the next load throwing occurs. According to the invention, the problem that the vehicle-mounted electric appliance and the control system are impacted by the voltage spike generated by the disconnection of the negative binding post in the operation process of the lithium battery is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery power supply and protection control technology, specifically relating to a method for solving the problem of load dumping when a lithium battery loses power. Background Technology

[0002] In vehicle electrical systems, lithium batteries are widely used in trucks, construction vehicles, and other equipment requiring high-power supply for energy storage and stable power delivery. However, during actual operation, the negative terminal of the lithium battery may suddenly disconnect due to vibration, improper maintenance, poor contact, or human error. When such a power outage occurs, the vehicle's alternator continues to operate and supply power to the system. The sudden change in system load causes a momentary voltage spike, a phenomenon commonly known as "load dump."

[0003] Load dumping generates high-amplitude voltage spikes in circuits, especially in the presence of inductive components. The rapid rate of voltage change and high peak value can easily impact onboard electrical components, control modules, and sensors, leading to insulation breakdown, electronic device malfunctions, or shortened lifespan. Existing technologies attempt to mitigate such impacts through control logic or delayed switching; however, in most trucks and some engineering vehicles, there is a lack of effective communication interfaces between the onboard system and the battery management system (BMS), hindering rapid control responses during power outages. Furthermore, some solutions rely on large absorption devices or complex control circuits, which are not only costly and complex to install but may also introduce additional power consumption and maintenance issues.

[0004] Therefore, how to absorb the voltage spikes caused by load dumping in a timely manner when the lithium battery is powered off, and release the residual charge in the absorption device without affecting the normal operation of the system, has become an important technical problem for improving the safety and stability of vehicle electrical systems. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a method for resolving the load dumping problem caused by lithium battery power failure. This method effectively solves the problem of voltage spikes caused by the disconnection of the negative terminal of the lithium battery during operation, which can impact vehicle electrical appliances and control systems.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows:

[0007] A method for solving the problem of lithium battery power loss and load dumping includes the following steps:

[0008] S1: Connect a supercapacitor absorption circuit between the negative terminal of the battery and the negative terminal of the battery management system (BMS).

[0009] S2: When the negative terminal of the battery is disconnected, the supercapacitor absorption circuit instantly absorbs the voltage spike caused by load dump.

[0010] S3: After the peak absorption is completed, the residual charge inside the supercapacitor unit is released through the capacitor discharge path connected in parallel with the supercapacitor absorption circuit.

[0011] S4: When the battery is restored to normal connection or the system is in a non-load-discharge state, maintain the connection state of the supercapacitor absorption circuit and the capacitor discharge path so as to respond immediately when the next load discharge occurs.

[0012] Preferably, the supercapacitor absorption circuit includes at least one supercapacitor unit with a rated voltage of not less than 3V and a capacity of 10F to 30F, and is connected to the negative terminal of the battery and the negative terminal of the BMS through a diode.

[0013] Preferably, the capacitor discharge path includes a discharge resistor connected in parallel with both ends of the supercapacitor unit, the discharge resistor having a resistance of 5kΩ to 50kΩ, used to slowly release the residual charge of the supercapacitor unit under non-load-discharge conditions.

[0014] Preferably, the supercapacitor absorption circuit and the capacitor discharge path are connected by a preset terminal block, with the positive lead connected to the B- terminal of the BMS and the negative lead connected to the C- terminal of the BMS.

[0015] Preferably, the supercapacitor absorption circuit is composed of multiple supercapacitor units connected in parallel or series to achieve the required total capacity and withstand voltage.

[0016] Preferably, during the charging process of the generator of the truck lithium battery system, when the negative terminal of the battery is disconnected, the supercapacitor absorption circuit is executed to absorb voltage spikes and release residual charge through the capacitor discharge path, so as to reduce the impact of load dumping on the electrical components at the rear end of the vehicle.

[0017] This invention features a novel structure, ingenious design, and simple and convenient operation, offering the following advantages compared to existing technologies:

[0018] 1. This invention establishes a supercapacitor absorption circuit between the negative terminal of the battery and the negative terminal of the BMS, consisting of at least one supercapacitor unit with a rated voltage of not less than 3V and a capacity of 10F to 30F. Unidirectional conduction control is achieved via a diode, enabling the supercapacitor to instantly absorb high-amplitude voltage spikes generated by load dumping when the battery negative terminal is suddenly disconnected. This structure achieves rapid response through physical characteristics, without relying on control chips or logic judgments. It features a short response time, stable suppression effect, and effectively prevents instantaneous impacts from high-voltage spikes on the vehicle control module and sensors.

[0019] 2. A discharge resistor with a resistance of 5kΩ to 50kΩ is connected in parallel across the supercapacitor absorption circuit to form a capacitor discharge path, enabling the supercapacitor to automatically release residual charge after peak absorption. This discharge path design avoids interference and safety hazards caused by high potential remaining in the capacitor during subsequent operation, ensuring that the system still has sufficient absorption capacity when the next load dump occurs. This achieves a cyclical working characteristic of absorption-release-reabsorption, thereby maintaining long-term stable protection performance.

[0020] 3. The access terminal of this invention uses a pre-set terminal block connection. The positive lead connects to the B- terminal of the BMS, and the negative lead connects to the C- terminal of the BMS. Installation requires no changes to the existing vehicle wiring or the addition of complex adapter circuits. This standardized access method not only lowers the installation threshold but also facilitates rapid deployment in lithium battery systems of different models of trucks or engineering vehicles. Its compact structure and strong adaptability reduce manual modification costs and improve the convenience of maintenance and replacement. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system principle of a method for solving the problem of load dumping when a lithium battery is powered off, according to the present invention.

[0022] In the attached diagram: 1-Battery; 2-Negative terminal; 3-Battery Management System (BMS); 4-B-terminal; 5-C-terminal; 6-Supercapacitor unit; 7-Diode; 8-Discharge resistor; 9-Positive lead; 10-Negative lead; 11-Supercapacitor absorption circuit; 12-Capacitor discharge path. Detailed Implementation

[0023] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0024] like Figure 1 As shown, this invention relates to a method for solving the problem of lithium battery power failure and load dumping. Its overall structure includes a battery 1, a battery management system (BMS) 3, a supercapacitor absorption circuit 11, and a capacitor discharge path 12 connected in parallel with it. The battery 1 is a vehicle power battery or an energy storage lithium battery, externally equipped with a negative terminal 2 and a positive terminal. The positive terminal is connected to the input terminal of the BMS 3 via a positive lead 9, and the negative terminal 2 is connected to the B-terminal 4 of the BMS 3 via a negative lead 10. The BMS 3 internally has a C-terminal 5, which is electrically connected to the external supercapacitor absorption circuit 11 to achieve shunt absorption of transient high voltages.

[0025] The supercapacitor absorption circuit 11 consists of at least one supercapacitor unit 6 and a diode 7 connected in series with it. The supercapacitor unit 6 is preferably an electrochemical double-layer capacitor or a hybrid supercapacitor with a rated voltage of not less than 3V and a capacitance of 10F to 30F. Multiple units can be connected in parallel or in series to achieve the required total capacitance and voltage rating, depending on the system's withstand voltage and energy absorption requirements. The anode of the diode 7 is connected to the C-terminal 5 of the BMS 3, and the cathode is connected to the anode of the supercapacitor unit 6, enabling unidirectional conduction. This ensures that the supercapacitor unit 6 only rapidly charges and absorbs peak voltages during load dumping, and does not discharge backwards to the system during normal operation. The other end of the supercapacitor unit 6 is connected back to the B-terminal 4 of the BMS 3 via a wire, forming a complete absorption circuit.

[0026] To prevent the supercapacitor unit 6 from remaining charged for an extended period after peak absorption, which could affect safety and subsequent operation, this invention incorporates a capacitor discharge path 12 connected in parallel across the supercapacitor absorption circuit 11. The capacitor discharge path 12 primarily includes a discharge resistor 8, with its two ends connected to the positive and negative terminals of the supercapacitor unit 6, respectively. Its resistance is preferably 5kΩ to 50kΩ, ensuring a high discharge speed while preventing excessive energy waste or component overheating. When the system is in a non-load-discharge state, this path can slowly and steadily release the residual charge in the supercapacitor unit 6, ensuring that the supercapacitor unit 6 is in an unloaded and usable state when the next load discharge occurs.

[0027] In terms of working principle, when the battery 1 is momentarily disconnected from the system due to some reason during vehicle operation (such as accidental disconnection of the negative terminal 2, maintenance work, loose connectors, etc.), the current output by the vehicle's generator will generate a high-amplitude voltage spike due to the sudden decrease in load. If this spike is directly applied to the BMS 3 and the vehicle's electrical equipment, it can easily cause problems such as semiconductor device breakdown, relay contact burning, and control system reset. This invention connects a supercapacitor absorption circuit 11 in parallel between the B-terminal 4 and C-terminal 5 of the BMS 3. At the moment the voltage spike occurs, the diode 7 conducts, and the supercapacitor unit 6 quickly charges and absorbs the excess energy, suppressing the spike within a safe range, thereby effectively protecting the downstream electrical components.

[0028] After the spike is eliminated, the charge stored in the supercapacitor unit 6 is gradually released through the discharge resistor 8 and the capacitor discharge path 12, preventing the residual voltage from causing a secondary impact when the system is switched on or off again. Since the supercapacitor absorption circuit 11 and the capacitor discharge path 12 remain connected to the system under normal conditions, no additional control switch or delay circuit is needed. It can respond instantly when a load dump occurs. The structure is simple and highly reliable, making it suitable for widespread application in trucks, buses, and other vehicles or equipment that use lithium battery energy storage.

[0029] This invention not only solves the voltage spike problem of lithium batteries under power outage and load dumping conditions, but also plays a buffering role in scenarios such as vehicle generator charging, system switching, and sudden power failure, extending the service life of BMS and electrical equipment.

[0030] During installation, battery 1 can be fixedly installed in the vehicle's battery compartment or battery tray. The negative terminal 2 and positive terminal can use a copper alloy bolt-type structure, treated with an anti-corrosion coating to improve conductivity and durability. The positive lead 9 is made of high-temperature resistant silicone-insulated soft copper wire with a cross-sectional area of ​​not less than 35mm². One end is fixed to the positive terminal of battery 1 via a crimped copper lug, and the other end is connected to the positive input terminal of the battery management system (BMS) 3 via a similar copper lug, with an insulating sheath to prevent short circuits. The negative lead 10 also uses the same specification wire material, with one end fixed to the negative terminal 2 of battery 1 and the other end connected to the B-terminal 4 of the BMS 3.

[0031] The BMS 3 can be encapsulated in an aluminum alloy or flame-retardant plastic shell, with the internal circuit board sealed with waterproof potting compound to withstand long-term vehicle vibration and humid environments. C-terminal 5 is a dedicated control negative interface within the BMS 3, soldered to the PCB board via a tin-plated copper sheet, with a terminal lead extending out for connection to the external supercapacitor absorption circuit 11. The supercapacitor absorption circuit 11 can be fabricated as a separate mounting module, with a flame-retardant ABS or aluminum alloy small shell. The supercapacitor unit 6 and diode 7 are fixed inside. Wiring terminals are pre-drilled at both ends of the shell, labeled with wiring markings corresponding to the B-terminal 4 and C-terminal 5 of the BMS, to prevent reverse connection during installation.

[0032] The selection of supercapacitor unit 6 needs to be determined based on the potential voltage spikes and energy absorption from the vehicle's generator. If higher voltage withstand is required, multiple supercapacitor units can be connected in series, with a voltage-equalizing resistor (200kΩ~500kΩ) connected in parallel across each unit to ensure voltage balance. If higher capacity is required, a parallel connection can be used to increase the total energy storage. Diode 7 should preferably be a Schottky diode or a fast recovery diode. Its rated reverse voltage withstand must be higher than the system's highest peak voltage (a margin of at least 50% is recommended), and its forward current must be sufficient to handle the large current surge during peak absorption.

[0033] The discharge resistor 8 is preferably a metal film or cement resistor. The power is calculated based on the energy of the discharge process, and a specification of 2W to 10W is usually selected. The resistance value is in the range of 5kΩ to 50kΩ, and the discharge speed and heat dissipation are adjusted as needed. The discharge resistor 8 is connected in parallel to the two ends of the supercapacitor unit 6 through a high-temperature resistant silicone wire, and sufficient creepage distance and insulation groove are left on the circuit board to avoid leakage in high humidity or dusty environments.

[0034] During the production and assembly process, the supercapacitor unit 6, diode 7, and discharge resistor 8 can be soldered together on a double-sided fiberglass epoxy PCB board using wave soldering or manual soldering processes, and coated with conformal coating to prevent moisture and salt spray corrosion. The PCB board is installed inside a small housing and fixed to the housing base plate with screws. A waterproof connector is added to the outside of the housing to connect the leads. The entire module can be bolted to the vehicle's battery compartment near BMS 3 to shorten the lead length and reduce impedance.

[0035] To facilitate subsequent maintenance and replacement, the wiring terminals of the supercapacitor absorption circuit 11 and the capacitor discharge path 12 are all connected using pluggable terminals or anti-loosening bolt terminals, and the terminals are all equipped with color differentiation and polarity markings. All wires must be encased in wear-resistant corrugated tubing and secured to the vehicle frame or wiring harness bracket with cable ties to prevent short circuits or wire breaks caused by vibration and wear during driving.

[0036] Through the above-mentioned structural layout and manufacturing process, the present invention not only ensures instantaneous response and voltage spike absorption capability under power failure and load dump conditions, but also enables the entire device to be quickly installed and easily replaced through modular and maintainable design, making it suitable for direct integration into existing lithium battery management systems in mass production.

[0037] In practical applications, the method of this invention has been tested in lithium battery power supply systems for various vehicle types, including heavy-duty trucks, large buses, and some construction machinery vehicles. The test environment covers typical operating conditions such as high-speed driving, low-speed heavy load, idling power generation, and frequent start-stop operations, aiming to comprehensively verify the load dump protection capability and stability of this invention under different operating conditions.

[0038] Taking a heavy-duty truck equipped with a 48V lithium battery system as an example, when the vehicle was traveling at high speed (90km / h), the negative terminal 2 was manually disconnected. The recorded instantaneous peak voltage at the generator output terminal dropped from approximately 78V without this device to approximately 53V after installation, representing a peak suppression of approximately 32%, effectively preventing insulation shock to the vehicle's electrical equipment. In the same test, the supercapacitor unit 6 absorbed approximately 15A of peak surge current at the moment of power failure and released the stored energy to below the safe voltage through the discharge resistor 8 within approximately 2.8 seconds after power failure. The entire process did not adversely affect the BMS 3 or the downstream load.

[0039] In a test on a large bus equipped with a 24V lithium battery system, a negative terminal disconnection experiment was conducted at idle speed (engine speed approximately 800 rpm) with the air conditioning and lighting operating at full load. The results showed that without this device installed, the system voltage spiked to 41V instantaneously, causing the air conditioning control module to malfunction. After installing the device, the peak voltage was limited to below 28.7V, and the air conditioning, lighting, and other equipment operated without interruption, verifying the device's protective effect under low-speed, high-load conditions.

[0040] Furthermore, the present invention also demonstrates a stable suppression effect in some construction machinery (such as large excavators and concrete pump trucks). Test data shows that when the engine is running at high speed (2100 rpm) driving a high-power hydraulic pump, the voltage change rate (dV / dt) at the moment the negative electrode is disconnected decreases from 3.2V per millisecond to 1.1V per millisecond, significantly reducing the probability of the control module being impacted by sudden voltage changes.

[0041] Long-term operation tests show that after 50 consecutive simulated power outage load dumps, the energy absorption performance of the supercapacitor absorption circuit 11 and capacitor discharge path 12 decreased by less than 3%, and there was no obvious abnormal temperature rise or insulation damage to the internal components, proving that the device has good durability and reusability. During the test, no delay or efficiency reduction in the normal charging and discharging process was found due to the connection of this device, verifying its compatibility with the original electrical system.

[0042] In summary, this invention can significantly suppress peak voltages and transient inrush currents caused by power failure and load dumping under various vehicle models and complex operating conditions, effectively protecting on-board electronic equipment and control systems from damage. It also has comprehensive advantages such as fast response speed, stable suppression effect, modular structure, and easy installation and maintenance, making it suitable for widespread application in existing and new lithium battery vehicle electrical systems.

[0043] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for solving the problem of lithium battery load dumping when power is off, characterized in that, Includes the following steps: S1: Connect a supercapacitor absorption circuit (11) between the negative terminal (2) of the battery (1) and the negative terminal of the battery management system (BMS) (3). S2: When the negative terminal (2) of the battery (1) is disconnected, the supercapacitor absorption circuit (11) is used to absorb the voltage spike caused by the load dump in an instant. S3: After the peak absorption is completed, the residual charge inside the supercapacitor unit (6) is released through the capacitor discharge path (12) connected in parallel with the supercapacitor absorption circuit (11). S4: When the battery (1) is restored to normal connection or the system is in a non-load-discharge state, maintain the connection state of the supercapacitor absorption circuit (11) and the capacitor discharge path (12) so as to respond immediately when the next load discharge occurs.

2. The method for solving the problem of load dumping when a lithium battery is powered off, as described in claim 1, is characterized in that... The supercapacitor absorption circuit (11) includes at least one supercapacitor unit (6) with a rated voltage of not less than 3V and a capacity of 10F to 30F, and is connected to the negative terminal of the battery (2) and the negative terminal of the BMS through a diode (7).

3. The method for solving the problem of load dumping when a lithium battery is powered off, as described in claim 1, is characterized in that... The capacitor discharge path (12) includes a discharge resistor (8) connected in parallel with the two ends of the supercapacitor unit (6). The discharge resistor (8) has a resistance of 5kΩ to 50kΩ and is used to slowly release the residual charge of the supercapacitor unit (6) under non-load-discharge conditions.

4. The method for solving the problem of load dumping when a lithium battery is powered off, as described in claim 1, is characterized in that... The supercapacitor absorption circuit (11) and the capacitor discharge path (12) are connected by a preset terminal block. The positive lead (9) is connected to the B- terminal (4) of the BMS, and the negative lead (10) is connected to the C- terminal (5) of the BMS.

5. The method for solving the problem of load dumping when a lithium battery is powered off, as described in claim 1, is characterized in that... The supercapacitor absorption circuit (11) is composed of multiple supercapacitor units (6) connected in parallel or in series to achieve the required total capacity and withstand voltage.

6. The method for solving the problem of load dumping when a lithium battery is powered off, as described in claim 1, is characterized in that... During the generator charging process of the truck lithium battery system, when the negative terminal (2) of the battery is disconnected, the supercapacitor absorption circuit (11) absorbs the voltage spike and releases the residual charge through the capacitor discharge path (12) to reduce the impact of load dumping on the electrical components at the rear end of the vehicle.

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