Method and system for prolonging low-power endurance of lithium battery of low-voltage new energy vehicle

Abstract

The invention discloses a low-power endurance prolonging method and system for a lithium battery of a low-voltage new energy vehicle. The method comprises the following steps that original operation data such as voltage, current and temperature of the lithium battery are collected through a single-chip microcomputer; when the residual electric quantity of the lithium battery is smaller than or equal to 30%, a power generation quantity grading power controller is triggered: when SOC is larger than or equal to 15% and smaller than or equal to 30%, a control signal that the starting current slope is smaller than or equal to 30 A / ms and the operation power gradually changes to 50% is generated; when SOC is smaller than 15%, a control signal with the forced starting current slope smaller than or equal to 20 A / ms and 50% of power locked is generated; dynamically increasing an under-voltage protection threshold compensation coefficient in a power limiting period, wherein the compensation amount is + 0.5 V; a power control signal generated by the electric quantity grading controller is transmitted to the motor through a motor driving instruction, and the actual output power of the motor is changed. The method can solve the problem of false power-lack shutdown, greatly improves the utilization rate of residual electric quantity, solves the problem of sudden reduction of endurance in case of low electric quantity, and prolongs the service life of the lithium battery.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle control technology, specifically to a method and system for extending the driving range of low-voltage new energy vehicle lithium batteries when the battery is low. Background Technology

[0002] In the field of low-voltage new energy vehicles, lithium batteries serve as the core power source, and their performance directly affects the overall operation of the vehicle. With the rapid development of the new energy vehicle market, users have increasingly stringent requirements for vehicle range, especially range performance when the battery is low, which has become a key indicator of a vehicle's practicality and reliability. However, currently, low-voltage new energy vehicle lithium batteries face many problems that urgently need to be addressed when operating at low battery levels.

[0003] First, there are frequent instances of false power depletion causing vehicle shutdowns. When a lithium battery is in a low-charge state (i.e., SOC < 30%), the high-current start-up of the vehicle causes a sudden drop in battery voltage, often exceeding 20%. This voltage drop easily triggers the vehicle's undervoltage protection mechanism, resulting in 15%-20% of the battery's remaining charge being unusable. For example, in some real-world driving scenarios, a vehicle attempts to start when the battery is low but is forced to shut down due to the sudden voltage drop. Even if there is still some charge remaining in the battery, it cannot support continued driving, severely impacting the user's travel experience. Secondly, the problem of drastically reduced driving range is prominent. Traditional battery management solutions allow the vehicle to output 100% power even when the lithium battery is low. This causes the battery to be depleted rapidly in a short time, significantly shortening the vehicle's driving range. Taking urban driving as an example, when the vehicle's battery is low, if it continues to operate at normal power output, its actual driving range will be significantly reduced compared to when the battery is high, causing great inconvenience to users' travel planning. Third, severe battery damage occurs. When lithium batteries operate under high current in the deep discharge region, their aging process is accelerated, not only reducing battery lifespan but also causing gradual capacity decay, thus affecting the vehicle's overall range and performance. Lithium batteries operating under this condition for extended periods will gradually experience increased internal resistance and reduced charging / discharging efficiency, potentially requiring premature battery replacement and increasing user costs. Summary of the Invention

[0004] In view of the above situation and to overcome the defects of the prior art, the present invention provides a method and system for extending the driving range of low-voltage new energy vehicle lithium batteries when the battery is low, which at least partially solves the problems mentioned in the background art.

[0005] The technical solution adopted in this invention is as follows: In a first aspect, the present invention provides a method for extending the driving range of a low-voltage new energy vehicle lithium battery when the battery is low, the method comprising: S1. Collect raw operating data such as voltage, current, and temperature of the lithium battery through a microcontroller (MCU); S2. Determine if the remaining charge (SOC) of the lithium battery meets the preset conditions: When the remaining charge (SOC) of the lithium battery is less than or equal to 30%, the power controller with tiered charge level is triggered. When 15%≤SOC≤30%, a control signal is generated with a starting current slope ≤30A / ms and the operating power gradually changes to 50%. When SOC < 15%, a control signal is generated with a forced start current slope ≤ 20A / ms and 50% power is locked. During power limitation, the undervoltage protection threshold compensation coefficient is dynamically increased by +0.5V.

[0006] S3: The power control signal generated by the power level controller is transmitted to the motor through the motor drive command, changing the actual output power of the motor.

[0007] Furthermore, in step S2, when the remaining charge (SOC) of the lithium battery is less than or equal to 30%, a safety coordination mechanism is triggered: Soft start should be activated immediately when the vehicle is running; When the vehicle is not running, the runtime power gradually changes. Both soft start and running power gradients meet the requirement that instantaneous power is prohibited from being greater than 50%, so as to achieve voltage fluctuations of less than 10%.

[0008] As a preferred technical solution, the power gradient in S2 is achieved through linear adjustment of the PWM duty cycle, and the adjustment method is as follows: Duty_new=Duty_old×(1-0.05×t) Where Duty_old is the initial PWM duty cycle before adjustment, Duty_new is the target duty cycle after adjustment, t is time, and 0≤t≤10s.

[0009] Furthermore, when the vehicle's gradient is greater than 8%, the power limit will be temporarily lifted to 70%. The power limit will be automatically reset once the slope returns to normal.

[0010] As a preferred technical solution, the microcontroller in step S1 is the MCU XMC1302 model.

[0011] The XMC1302 MCU features efficient data processing capabilities and real-time response performance, enabling it to meet the system's real-time acquisition and calculation requirements for parameters such as lithium battery voltage, current, and slope. It also provides hardware support for the stable operation of modules such as the dynamic SOC calculation engine and power curve optimization engine.

[0012] Secondly, the present invention provides a system for extending the driving range of low-voltage new energy vehicle lithium batteries when the battery is low, the system comprising: A. Lithium batteries, as the energy source of the entire system, are used to provide the electrical energy required for the power output of low-voltage new energy vehicles; B. The MCU XMG1302 is used to collect raw operating data such as voltage, current, and temperature of the lithium battery in real time, and to issue instructions and control the status of the downstream engine through the built-in communication and computing modules. C. Dynamic SOC calculation engine: Combining real-time current and temperature data transmitted by the MCU, it uses a dynamic correction algorithm to eliminate the interference of voltage fluctuations on SOC calculation under low battery conditions, and accurately outputs the actual remaining battery power. D. Power curve optimization engine, used to build a power output model in the low power range and generate power limiting instructions based on the real-time power data output by the dynamic SOC calculation engine; E. Hierarchical power controller, used to convert the power limiting instructions generated by the power curve optimization engine into specific hardware control signals; F. Motor drive command, used to transmit the power control signal generated by the graded power controller to the motor.

[0013] Furthermore, when the remaining charge (SOC) of the lithium battery is less than or equal to 30%, the graded power controller performs the following control: When 15%≤SOC≤30%, output a control signal with a starting current slope ≤30A / ms and a running power gradually increasing to 50%; When SOC < 15%, output a control signal with a forced start current slope ≤ 20A / ms and lock 50% power.

[0014] In a further implementation, the graded power controller dynamically increases the undervoltage protection threshold compensation coefficient by +0.5V during power limiting.

[0015] In a further implementation, the graded power controller temporarily releases the power limit to 70% when the vehicle's driving gradient is greater than 8%; and automatically resets the power limit when the gradient returns to normal.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: By using a dynamic SOC calculation engine to accurately sense the actual remaining battery power, and combined with the limitation of high current output by a graded power controller, it can avoid voltage drop caused by high current startup when the battery is low (SOC<30%), thereby preventing the undervoltage protection mechanism from being falsely triggered, effectively solving the problem of false power depletion shutdown, and significantly improving the utilization rate of residual power.

[0017] By using a power curve optimization engine, a corresponding power limit curve is generated based on the SOC gradient in the low battery range, replacing the traditional solution that allows 100% power output. At the same time, the power gradient achieved by linear adjustment of PWM duty cycle ensures a smooth transition in power output, further reducing unnecessary power loss and effectively improving the problem of sudden reduction in battery life when the battery is low.

[0018] By employing a graded power controller to strictly control current output in the deep discharge region, especially in the low SOC range, the impact of high current operation on the battery is avoided. Meanwhile, a dynamic soft-start strategy reduces current fluctuations during the startup phase, minimizing cycle damage to the lithium battery under deep discharge conditions. The combined effect of these two strategies effectively mitigates battery aging issues caused by high current operation in the deep discharge region, extending the lifespan of the lithium battery.

[0019] Functional enhancements are achieved through software algorithm optimization and coordinated control with existing hardware architecture, without incurring additional hardware costs, thus overcoming the low-battery range bottleneck at zero cost. Furthermore, its architecture design does not rely on a complex Battery Management System (BMS), making it particularly suitable for low-voltage electric vehicles without a BMS, such as those used in mountainous logistics vehicles, sanitation vehicles, and elderly mobility scooters. It provides a practical solution for improving the range performance of these vehicles, demonstrating high practical value and promising market application prospects. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the graded power limiting strategy in an embodiment of the present invention; Figure 2 This is a schematic diagram of the low-voltage new energy vehicle lithium battery low-power range extension system architecture in an embodiment of the present invention; Figure 3 This is a schematic diagram of the security collaboration mechanism proposed in an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] When a lithium battery is low in charge, a high-current start-up of the vehicle causes a sudden drop in battery voltage, often exceeding 20%. This voltage drop easily triggers the vehicle's undervoltage protection mechanism, leaving 15%-20% of the battery's remaining charge unusable. Even with a sudden reduction in range, the vehicle is still allowed to output 100% power. This causes the battery to be depleted rapidly in a short time, significantly shortening the vehicle's driving range. When a lithium battery operates under high current in the deep discharge region, it accelerates its aging process, reducing not only its lifespan but also its capacity, thus affecting the vehicle's overall range and performance. Lithium batteries operating under this condition for extended periods experience increased internal resistance and reduced charging / discharging efficiency, potentially requiring premature battery replacement and increasing user costs.

[0026] Recognizing the above problems, this application proposes and discloses a method and system for extending the driving range of low-voltage new energy vehicle lithium batteries when the battery is low, in order to solve the problem of false power depletion and shutdown, significantly improve the utilization rate of residual power, improve the problem of sudden reduction in driving range when the battery is low, and extend the service life of lithium batteries.

[0027] See Figure 1 In a first aspect, this embodiment provides a method for extending the driving range of a low-voltage new energy vehicle lithium battery when the battery is low, the method comprising: S1. Collect raw operating data such as voltage, current, and temperature of the lithium battery using the MCUXMC1302 microcontroller; S2. Determine whether the remaining battery charge (SOC) meets the preset conditions: When the remaining charge (SOC) of the lithium battery is less than or equal to 30%, the power controller with tiered charge level is triggered. When 15%≤SOC≤30%, a control signal is generated with a starting current slope ≤30A / ms and the operating power gradually changes to 50%. When SOC < 15%, a control signal is generated with a forced start current slope ≤ 20A / ms and 50% power is locked. During power limitation, the undervoltage protection threshold compensation coefficient is dynamically increased by +0.5V.

[0028] S3: The power control signal generated by the power level controller is transmitted to the motor through the motor drive command, changing the actual output power of the motor.

[0029] For example, in the operation procedure of a 48V system: Scene 1: - When the dynamic SOC calculation engine detects SOC = 25%, immediately: - The startup current slope is limited to 30A / ms (original value 50A / ms). - Power decreases linearly from 100% to 50% (over 10 seconds) -Result: Voltage dropped from 40V to 38.5V (38V protection not triggered) Scene 2: -When the dynamic SOC calculation engine obtains SOC = 12%: - Coercive measures: - All startup event slopes ≤ 20A / ms - Maximum power permanently locked at 50% - Effect: - Voltage stabilized at 37.2-38.1V - Range increased by 7km (to SOC=5%) Through comparative testing, the traditional solution offers a low-battery range of 19km, 3.2 undervoltage protection false triggers per vehicle, and a battery cycle life of 500 cycles. In contrast, this invention offers a low-battery range of 26km, 0 undervoltage protection false triggers, and a battery cycle life of 500 cycles. This significantly improves the low-battery range of lithium batteries, reduces the frequency of undervoltage protection triggers due to voltage drops, and extends battery lifespan.

[0030] In one specific implementation, in step S2, when the remaining charge (SOC) of the lithium battery is less than or equal to 30%, a safety coordination mechanism is triggered: Soft start is activated immediately when the vehicle is running; When the vehicle is not running, the runtime power gradually changes. Both soft start and running power gradients meet the requirement that instantaneous power is prohibited from being greater than 50%, so as to achieve voltage fluctuations of less than 10%.

[0031] For details, please refer to Figure 3 The triggering logic for the security collaboration mechanism is as follows: A [Power level detected: SOC ≤ 30%] --> B {Is it running?} B --> | Yes | C [Enable soft boot immediately] B -->|No| D[Power Gradual Change During Runtime] C & D --> E [Instantaneous power > 50% prohibited] E --> F [Voltage fluctuation < 10%] Its core logic is that, in low battery scenarios (SOC≤30%), depending on whether the vehicle is running, the power output is limited by either "soft start" or "gradual power change during operation" (prohibiting instantaneous power >50%), ultimately achieving the control target of voltage fluctuation <10%.

[0032] For example, in the operation procedure of a 48V system: With a SOC of 25% during startup, the traditional solution triggers protection when the voltage drops by 18V. This invention, through soft start and gradual power change, reduces the voltage drop to ≤8V, preventing the vehicle from stopping accidentally and releasing 12% of the power. At SOC=15% ramp-up, in traditional solutions, high current causes a rapid drop in voltage. This invention stabilizes the voltage above 40V by locking in 50% power, increasing the range by 7km. In low temperature and low power conditions (-10℃), traditional solutions result in a 40% reduction in battery capacity. This invention, through power limiting and temperature compensation coordinated control, achieves a 28% improvement in actual power utilization.

[0033] In one specific implementation, the power gradient in S2 is achieved through linear adjustment of the PWM duty cycle, and the adjustment formula is as follows: Duty_new = Duty_old × (1 - 0.05 × t) (t is time, 0 ≤ t ≤ 10 s).

[0034] PWM (Pulse Width Modulation) is a technique that adjusts output voltage or power by changing the duty cycle of a pulse signal. In the field of electronic control, it is widely used to precisely control the output intensity of equipment such as motors and power supplies. The higher the duty cycle, the more energy is output per unit time, and the greater the power output of the corresponding equipment; conversely, the lower the duty cycle, the lower the power output.

[0035] In this method, the linear adjustment of PWM duty cycle can achieve a smooth power transition under low power conditions, avoiding the impact of power sudden changes on battery and vehicle operation.

[0036] In the above formula, Duty_old represents the initial PWM duty cycle before adjustment, and Duty_new is the target duty cycle after adjustment. As time t increases from 0 seconds to 10 seconds, the coefficient of (1-0.05×t) linearly decreases from 1 to 0.5, meaning that the duty cycle decreases uniformly at a rate of 5% per second within 10 seconds, eventually dropping to 50% of its initial value. This linear change directly translates into a linear decrease in motor power.

[0037] For example, when the initial power corresponds to a duty cycle of 80% (i.e., Duty_old=80%), the duty cycle changes to 76% after 1 second (the power synchronously drops to 76%), and stabilizes at 40% after 10 seconds, achieving a smooth transition of power from 80% to 40%.

[0038] This adjustment method avoids the sudden power drops caused by the "step-down" power reduction in traditional power limiting, ensuring smooth driving. Furthermore, by gradually reducing power, the battery voltage adapts to load changes at low charge levels, reducing voltage fluctuations caused by sudden power drops and further mitigating the risk of false power depletion shutdowns. Simultaneously, during linear adjustment, the current intensity decreases smoothly and synchronously with the power, reducing the impact of large current surges on the lithium battery. Combined with graded power control logic, this more effectively protects the battery's safety in the deep discharge region.

[0039] In one specific implementation, when the vehicle's gradient is greater than 8%, the power limit is temporarily lifted to 70%. The power limit will be automatically reset once the slope returns to normal.

[0040] In this embodiment, the 70% temporary power limit is still lower than the 100% power output of the traditional solution, and it is only triggered when the slope is greater than 8%. This can reduce the damage to the battery caused by continuous high current output, balancing power demand and battery protection. On the other hand, the "automatic reset" mechanism ensures that the system can quickly return to the low power limit state after the vehicle leaves the climbing scenario, avoiding excessive power consumption due to lack of human intervention. This improves the vehicle's passability while ensuring battery safety and range.

[0041] See Figure 2 Secondly, this embodiment provides a low-voltage new energy vehicle lithium battery low-charge range extension system, the system comprising: A. Lithium batteries, as the energy source of the entire system, are used to provide the electrical energy required for the power output of low-voltage new energy vehicles.

[0042] B. The MCU XMG1302 is used to collect raw operating data such as voltage, current, and temperature of the lithium battery in real time. It uses the built-in communication and computing modules to issue commands and control the status of downstream engines.

[0043] As the core control and data processing hub, the MCU XMG1302 provides real-time support for dynamic SOC calculation and power optimization with its efficient data processing capabilities, ensuring that the response latency of the entire system is controlled at the millisecond level, and meeting the real-time adjustment requirements of the vehicle during dynamic operation.

[0044] C. Dynamic SOC calculation engine: Combining real-time current and temperature data transmitted by the MCU, it eliminates the interference of voltage fluctuations on SOC calculation under low power through dynamic correction algorithm, accurately outputs the actual remaining power of the battery, provides a reliable basis for subsequent power control, and avoids false triggering of protection mechanisms due to misjudgment of power.

[0045] D. Power curve optimization engine, used to construct a power output model for low power range and generate power limiting instructions based on real-time power data output by the dynamic SOC calculation engine.

[0046] When the State of Charge (SOC) is less than 30%, the engine automatically generates a corresponding power limiting curve based on the battery level gradient. For example, it allows 80% of the rated power output when the SOC is between 20% and 30%, and limits it to 50% of the rated power when the SOC is between 10% and 20%. This tiered control avoids the sudden power drain caused by 100% power output in traditional solutions. Simultaneously, the engine also combines historical discharge data to predict the remaining driving range, providing a quantitative reference for power adjustment.

[0047] E. Tiered power controller, used to convert the power limiting instructions generated by the power curve optimization engine into specific hardware control signals.

[0048] The tiered power controller achieves tiered control of output power by adjusting the current threshold of the motor drive circuit: when high power demand is detected, such as during rapid acceleration, if the current is in a low-battery range, the controller will automatically reduce the output current to within a safe threshold to avoid voltage drops caused by high current; while in low-power scenarios such as smooth driving, the restrictions are appropriately relaxed to ensure basic power needs. This dynamic tiered control not only solves the problem of false power depletion shutdown but also reduces the impact of high current in the deep discharge region.

[0049] F. The motor drive command is the connection node between the system and the execution terminal. The power control signal generated by the hierarchical power controller is transmitted to the motor through this command, directly determining the motor's actual output power. Through dynamic adjustment of the command, the motor can ultimately operate smoothly under low battery conditions, achieving the dual goals of extended range and battery protection.

[0050] In the low-voltage new energy vehicle lithium battery low-charge range extension system of the present invention, each core module forms a complete control link through orderly data transmission and command interaction. The specific architecture process can be further explained as follows: The system uses a lithium battery (A) as its energy source, and its real-time operating data, such as voltage, current, and temperature, is first transmitted to the MCU XMC1302 (B). As the core control hub, the MCU XMC1302 performs preliminary processing on the raw data and then synchronizes it to the dynamic SOC calculation engine (C). The dynamic SOC calculation engine eliminates voltage fluctuation interference under low battery conditions through a dynamic correction algorithm, accurately outputs the real-time battery power information, and transmits this data to the power curve optimization engine (D).

[0051] The power curve optimization engine constructs hierarchical control logic based on real-time battery power data, generates targeted power limiting commands, and sends them to the hierarchical power controller (E). The core control strategies of the hierarchical power controller include: when the battery's remaining SOC is detected to be ≤30%, a soft-slope power adjustment mode is immediately activated to limit power output through a smooth transition; when SOC <15%, a mandatory measure is triggered to permanently lock the maximum power to 50% to prevent rapid depletion of battery power in the deep discharge zone.

[0052] Ultimately, the tiered power controller translates the aforementioned control strategy into specific hardware drive signals, which are then transmitted to the motor via motor drive commands (F) to achieve dynamic regulation of the motor's output power. This architecture embodies the closed-loop logic of "data acquisition - precise perception - intelligent decision-making - execution control," and through the differentiated strategies of the tiered power controller, it ensures extended driving range when the battery is low while also considering battery safety and smooth vehicle operation.

[0053] For example, in a scenario where the SOC is 25%, after the dynamic SOC calculation engine outputs the real-time power, the power curve optimization engine triggers the soft ramp adjustment of the graded power controller. Through linear adjustment of the PWM duty cycle (Duty_new=Duty_old×(1-0.05×t)), a smooth power transition is achieved. When the SOC drops to 12%, the graded power controller automatically switches to the 50% power lock-in mode. Combined with undervoltage protection threshold compensation (+0.5V), it ensures that the voltage is stable in the range of 37.2-38.1V, ultimately achieving the dual goals of extended battery life and battery protection.

[0054] It should be noted that, in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0055] Although embodiments have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.

[0056] The embodiments have been described above, and such description is not restrictive. The figures shown are only one embodiment, and the actual structure is not limited to this. In short, if a person skilled in the art is inspired by this description and designs a similar structure and embodiment without departing from the inventive spirit, such design should fall within the scope of protection.

Claims

1. A method for extending the driving range of a low-voltage new energy vehicle lithium battery when the battery is low, characterized in that, The method includes: S1. Collect raw operating data such as voltage, current, and temperature of the lithium battery through a microcontroller (MCU); S2. Determine if the remaining charge (SOC) of the lithium battery meets the preset conditions: When the remaining charge (SOC) of the lithium battery is less than or equal to 30%, the power controller with tiered charge level is triggered. When 15%≤SOC≤30%, a control signal is generated with a starting current slope ≤30A / ms and the operating power gradually changes to 50%. When SOC < 15%, a control signal is generated with a forced start current slope ≤ 20A / ms and 50% power is locked. During power limiting, the undervoltage protection threshold compensation coefficient is dynamically increased by +0.5V. S3: The power control signal generated by the power level controller is transmitted to the motor through the motor drive command, changing the actual output power of the motor.

2. The method for extending the driving range of a low-voltage new energy vehicle lithium battery when the battery is low, as described in claim 1, is characterized in that... In step S2, when the remaining charge (SOC) of the lithium battery is less than or equal to 30%, the safety coordination mechanism is triggered: Soft start should be activated immediately when the vehicle is running; When the vehicle is not running, the runtime power gradually changes. Both soft start and running power gradients meet the requirement that instantaneous power is prohibited from being greater than 50%, so as to achieve voltage fluctuations of less than 10%.

3. The method for extending the driving range of a low-voltage new energy vehicle lithium battery when the battery is low, as described in claim 1, is characterized in that... The power gradual change in step S2 is achieved by linear adjustment of the PWM duty cycle, and the adjustment formula is: Duty_new=Duty_old×(1-0.05×t) Where Duty_old is the initial PWM duty cycle before adjustment, Duty_new is the target duty cycle after adjustment, t is time, and 0≤t≤10s.

4. The method for extending the driving range of a low-voltage new energy vehicle lithium battery when the battery is low, as described in claim 1, is characterized in that... Also includes: When the vehicle's gradient is greater than 8%, the power limit will be temporarily lifted to 70%. The power limit will be automatically reset once the slope returns to normal.

5. A low-voltage new energy vehicle lithium battery low-charge range extension system, characterized in that, include: Lithium batteries are used to provide the electrical energy required for power output in low-voltage new energy vehicles. The XMG1302 MCU is used to collect raw operating data such as voltage, current, and temperature of lithium batteries in real time, and to issue commands and control the status of downstream engines. The dynamic SOC calculation engine is used to combine real-time current and temperature data transmitted by the microcontroller to accurately output the actual remaining power of the battery. The power curve optimization engine is used to build a power output model for low power range and generate power limiting instructions based on real-time power data output by the dynamic SOC calculation engine. A graded power controller is used to translate the power limiting instructions generated by the power curve optimization engine into specific hardware control signals; Motor drive commands are used to transmit power control signals generated by the graded power controller to the motor.

6. The low-voltage new energy vehicle lithium battery low-charge range extension system according to claim 5, characterized in that, When the remaining charge (SOC) of the lithium battery is less than or equal to 30%, the graded power controller performs the following control: When 15%≤SOC≤30%, output a control signal with a starting current slope ≤30A / ms and a running power gradually increasing to 50%; When SOC < 15%, output a control signal with a forced start current slope ≤ 20A / ms and lock 50% power.

7. The low-voltage new energy vehicle lithium battery low-charge range extension system according to claim 5, characterized in that, During power limiting periods, the graded power controller dynamically increases the undervoltage protection threshold compensation coefficient by +0.5V.

8. The low-voltage new energy vehicle lithium battery low-charge range extension system according to claim 5, characterized in that, When the vehicle's gradient is greater than 8%, the graded power controller temporarily releases the power limit to 70%; when the gradient returns to normal, it automatically resets the power limit.

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