A method and system for low-temperature charging control of electric light trucks

Abstract

This invention discloses a low-temperature charging control method and system for electric light trucks. After the charging pile is connected, the BMS wakes up and detects the lowest cell temperature Tmin, ambient temperature, voltage, current, and SOC. It determines whether the current lowest cell temperature Tmin is less than a preset low-temperature charging threshold T2. When Tmin < T2, it enters a multi-stage adaptive heating charging mode, which includes an ultra-low temperature processing sub-mode and a low-temperature rechargeable sub-mode. When Tmin ≥ T2, it enters standard charging. This invention achieves an optimal balance between charging time and energy consumption in low-temperature environments by combining multi-stage adaptive heating with current regulation control logic, while ensuring battery safety.

Description

Technical Field

[0001] This invention relates to a low-temperature charging control method and system for electric light trucks, belonging to the field of electric vehicle charging control technology. Background Technology

[0002] With the rapid development of the new energy vehicle industry, electric light trucks, as an important tool for urban logistics and distribution, have seen continuous growth in market share and are widely used in intercity delivery and logistics scenarios in cold northern regions. However, the charging problem of electric light trucks in low-temperature environments has always been one of the key technical bottlenecks restricting their widespread adoption.

[0003] The performance degradation of power batteries under low-temperature conditions is the core reason affecting the low-temperature charging efficiency of electric light trucks. Taking lithium iron phosphate batteries as an example, when the minimum battery temperature is below 0°C, the conductivity of the battery electrolyte decreases significantly, and the diffusion rate of lithium ions on the negative electrode surface slows down. If the battery is directly charged with a large current at this time, lithium deposition is very likely to occur on the negative electrode surface, forming lithium dendrites. Lithium dendrites will continue to grow during repeated charge and discharge processes, which may puncture the separator, causing a short circuit between the positive and negative electrodes, leading to serious safety accidents such as internal short circuits or even thermal runaway. Therefore, the battery must be fully preheated before charging in low-temperature environments.

[0004] In existing technologies, various solutions have been proposed for low-temperature charging of electric vehicles. For example, some solutions employ a single preheating-before-charging strategy, which involves heating the battery without charging until the temperature reaches a preset threshold, and then starting charging once the temperature is reached. While this method offers high safety, the heating process completely occupies the charging time, resulting in an excessively long overall charging time and a poor user experience. Other solutions employ a simultaneous heating and charging strategy, allowing low-current charging while heating. However, these solutions typically use fixed heating power and fixed charging current, lacking dynamic response capabilities to changes in battery state, making it difficult to achieve an optimal balance between charging efficiency and battery safety. Furthermore, existing technologies include solutions that use a stepped activation of the heating module, such as gradually activating the heating module by increasing the power in stages during the low-temperature charging heating process. However, these solutions typically only consider the stepped increase in heating power, without coordinating the heating process with the adjustment of the charging current, or considering the impact of the battery's state of charge (SOC) on the heating and charging strategies, resulting in high energy consumption and room for improvement in charging efficiency.

[0005] In summary, existing low-temperature charging control methods for electric light trucks have the following shortcomings: (1) The heating strategy is simple and fails to adapt the heating power in stages according to the changes in battery temperature. It has high energy consumption and long charging time. (2) Charging with fixed current while heating has poor adaptability and cannot cope with different degrees of low temperature; (3) Simple PID heating control, with no coordinated regulation of charging current; (4) Lack of refined coordinated control over battery status and ambient temperature. Summary of the Invention

[0006] Aiming at the technical problems existing in the low-temperature charging of electric light trucks in the prior art, such as long charging time, high heating energy consumption, and lack of collaborative optimization between heating and charging processes, the present invention provides a low-temperature charging control method for electric light trucks. Through the control logic combining multi-stage adaptive heating and current regulation, the optimal balance between charging time and energy consumption in low-temperature environments is achieved on the premise of ensuring battery safety.

[0007] The object of the present invention is achieved through the following technical solutions: A low-temperature charging control method for an electric light truck, comprising the following steps: Step S1, charging wake-up and initial detection, After the charging pile is connected, the BMS wakes up and detects the minimum cell temperature Tmin, ambient temperature, voltage, current and SOC; Step S2, determining whether the current minimum cell temperature Tmin is less than a preset low-temperature charging threshold T2, when Tmin < T2, proceed to step S3; when Tmin ≥ T2, proceed to step S4; Step S3, entering a multi-stage adaptive heating charging mode, wherein the multi-stage adaptive heating charging mode includes an extreme low-temperature processing sub-mode and a low-temperature chargeable sub-mode, the extreme low-temperature processing sub-mode is: determining whether Tmin is less than or equal to a preset extreme low-temperature charging threshold T1, wherein T1 < T2; if yes, first use the current maximum available power to purely heat the battery without outputting charging current to the battery until Tmin rises above T1, then adopt an alternating heating-pulse charging mode; the low-temperature chargeable sub-mode is: when T1 < Tmin < T2, start the heating circuit and the charging circuit simultaneously, and dynamically adjust the heating power and charging current according to the real-time temperature of the battery; Step S4, standard charging, Perform CC-CV charging according to the optimal charging MAP recommended by the battery manufacturer until the charging is completed; Step S5, during the charging process, monitor the voltage, temperature and current parameters of the battery in real time, and execute a protection action when any parameter exceeds the corresponding safety threshold.

[0008] Furthermore, the heating-pulse charging alternating mode is as follows: heating is paused after a certain period of time; then the battery is charged with a small pulse current, and after charging, it is left to stand for a certain period of time before heating again; the above cycle is repeated, and Tmin is detected after each cycle until Tmin≥T2.

[0009] Furthermore, the heating-pulse charging alternating mode specifically refers to: Heat for 30-35 seconds, then pause heating. Charge with a 0.01–0.05C pulse for 20–30 seconds, then let stand for 10–20 seconds; Repeat the above cycle, and check Tmin after each cycle until Tmin ≥ T2.

[0010] Furthermore, the cryogenic fillable sub-mode specifically refers to: Set the initial heating power and initial charging current, and use the initial heating power and initial charging current to simultaneously heat and charge the battery; After charging for a certain period of time, the temperature rise rate dT / dt is calculated, and the heating power and charging current are dynamically adjusted based on the temperature rise rate.

[0011] Furthermore, the initial heating power is 50% to 60% of the rated power; the initial charging current is 0.05 to 0.1C.

[0012] Furthermore, the temperature rise rate dT / dt is calculated every 30–50 seconds, and the heating power and charging current are adjusted in a closed loop based on the temperature rise rate. Specifically, this includes: When dT / dt < 0.5℃ / min, the heating power increases by 5% to 10% in steps, and the final increase does not exceed 100%, while the charging current remains unchanged. When dT / dt > 2.0℃ / min, the charging current decreases by 0.02C step by step but is not lower than 0.05C, while the heating power remains unchanged; When 0.5 ≤ dT / dt ≤ 2.0, maintain the current parameters; When T_min≥T2, heating is turned off and standard CC-CV charging is switched to start.

[0013] Furthermore, the low-temperature charging threshold T2 is 5℃~10℃; the ultra-low-temperature charging threshold T1 is -8℃~-10℃.

[0014] A low-temperature charging control system for electric light trucks includes a power battery, a battery management system, a vehicle controller, an on-board water heater, and a charging control unit. The battery management system and the vehicle controller are used to execute the aforementioned low-temperature charging control method for electric light trucks.

[0015] Compared with the prior art, the present invention has the following advantages: (1) Interval fine control: This invention adopts a multi-stage adaptive heating strategy and uses different heating power in different temperature ranges. This avoids damage to the battery caused by excessive heating power in the low temperature start-up stage and reduces the risk of lithium plating. It also rapidly increases the heating power when the temperature conditions allow. Compared with a single heating power scheme, it can significantly shorten the battery preheating time and thus shorten the overall charging time. (2) Heating energy consumption optimization: The present invention adaptively adjusts the heating power of each stage according to the battery SOC and real-time temperature, avoiding the waste of heating power and minimizing heating energy consumption while ensuring charging efficiency. (3) Improved charging safety: In the heating and charging mode, the present invention adopts a temperature-based segmented heating power and charging current adjustment strategy. The charging current gradually increases with the increase of battery temperature, which effectively avoids the risk of lithium plating caused by high current charging under low temperature conditions and ensures the charging safety of the battery. (4) Optimal balance between charging time and energy consumption: This invention achieves global optimization of charging time and heating energy consumption by using a combination of multi-stage heating and dynamic current regulation and different heating-charging combination strategies at different temperature stages. This has significant advantages over the existing technologies that separate or simply superimpose the heating and charging processes. (5) Wide range of applications: The control logic of this invention is clear and easy to be embedded in BMS. It is applicable to various low-temperature scenarios of electric light trucks. It is not only applicable to lithium iron phosphate battery system, but can also be applied to low-temperature charging control of other types of power batteries such as ternary lithium batteries. It has good versatility and promotion value.

[0016] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein: Figure 1 This is an overall flowchart of the low-temperature charging control method for electric light trucks of the present invention; Figure 2 This is a schematic diagram of the temperature-power relationship for the low-temperature charging control of the electric light truck of the present invention; Figure 3 This is a graph showing the change of charging current with temperature in the low-temperature rechargeable sub-mode of the present invention. Figure 4 This is a structural block diagram of the low-temperature charging control system for electric light trucks of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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. Example 1

[0019] This embodiment provides a low-temperature charging control method for electric light trucks, applied to electric light truck logistics vehicles equipped with lithium iron phosphate battery packs. The battery pack has a rated voltage of 540V and a rated capacity of 180Ah. The battery pack contains multiple battery cells, and the voltage, temperature, and other status parameters of each cell are monitored in real time by a battery management system (BMS).

[0020] like Figures 1-2 As shown, the low-temperature charging control method of this embodiment includes the following steps: Step S1, Charging preparation, When the charging gun is inserted into the vehicle's charging port, the charging station detects the connection signal and initiates low-voltage auxiliary power-on, activating the Battery Management System (BMS) and Vehicle Control Unit (VCU). After power-on, the BMS is awakened and detects the lowest cell temperature Tmin, as well as ambient temperature, voltage, and SOC.

[0021] The BMS sends a charging request to the VCU. After the VCU confirms the charging request from the BMS, it sends a command to the BMS to activate the main negative relay. The BMS closes the main negative relay and the pre-charge relay. After completing the pre-charge process, it closes the main positive relay. After a preset delay, it disconnects the pre-charge relay to complete the high-voltage power-on.

[0022] Step S2: Temperature determination. The BMS determines whether the current lowest cell temperature Tmin is less than or equal to the preset low-temperature charging threshold T2. In this embodiment, T2 is set to 5°C.

[0023] If Tmin≥5℃, it indicates that the battery temperature is within the safe charging range. Directly use standard charging, that is, perform CC-CV charging according to the optimal charging MAP recommended by the battery manufacturer until charging is complete.

[0024] If Tmin < 5℃, it indicates that the battery temperature is too low and preheating is required before entering a multi-stage adaptive heating mode.

[0025] Step S3: Multi-stage adaptive heating In this embodiment, T1 = -10℃, T2 = 5℃, and the specific control of each heating stage is as follows: When Tmin≤-10°C, the ultra-low temperature processing sub-mode is adopted, and the BMS controls the WPTC water heater to start heating at the current maximum available power. The VCU controls the battery water pump to start, so that the heated coolant circulates in the battery pack to uniformly heat the battery. The BMS continuously monitors the minimum cell temperature of the battery. When Tmin reaches -10°C, it automatically switches to the heating-pulse charging cycle; the heating-pulse charging cycle is specifically: heating for 30 seconds, pausing heating, performing pulse charging at 0.05C for 20 seconds, standing for 10 seconds, repeating this cycle, detecting Tmin after each cycle until T_min≥T2, and adopting standard CC-CV charging.

[0026] In the ultra-low temperature processing sub-mode, the safety of the low-temperature startup phase can be guaranteed, and the optimization of heating time is realized.

[0027] When -10°C<Tmin≤5°C, the low-temperature chargeable sub-mode is adopted. The BMS controls the WPTC to start heating at the initial heating power P0, where P0 is 60% of the rated power, and charging is performed at a current of 0.1C simultaneously. In this embodiment, Prated =5kW. After adaptive adjustment according to the current SOC and temperature, P0 is approximately 3kW. After 30S of heating + charging, the temperature rise rate dT / dt is calculated once, where dT / dt =ΔT / Δt, ΔT is the temperature change amount; Δt is the time change amount.

[0028] Closed-loop adjustment of heating power and charging current is performed through the temperature rise rate: If dT / dt<0.5°C / min, the heating power is increased by 10% step by step, and the final increment does not exceed 100%; If dT / dt>2.0°C / min, the charging current is decreased by 0.02C step by step, and the final decrement is not lower than 0.05C; If dT / dt is within the range of 0.5≤dT / dt≤2.0, the current parameters are maintained; When Tmin≥T2, heating is turned off and the process switches to standard CC-CV charging.

[0029] When dT / dt exceeds the preset safe temperature rise rate threshold dT / dt_safe, a protection action is performed, and the protection action includes reducing the heating power or stopping heating. The safe temperature rise rate threshold dT / dt_safe is set to 3-5°C / min.

[0030] As Figure 3 shown, in the low-temperature chargeable sub-mode, the charging current increases stepwise with the increase of battery temperature, realizing the matching of charging current and battery temperature. Moreover, the BMS continuously monitors the voltage and temperature of each battery cell to ensure that all parameters are always within the safe range.

[0031] Step S4: Security Monitoring and Protection Throughout the charging process, the BMS monitors the battery's voltage, temperature, and current parameters in real time and performs the following safety checks: When the voltage of any single battery cell exceeds the charging cutoff voltage (e.g., 3-5V), reduce the charging current or stop charging. When the temperature of any single battery cell exceeds the safe temperature threshold (e.g., 50-55℃), charging will stop and the fan will start cooling. When the charging current exceeds the set maximum value, a current adjustment request is sent to the charging pile via the CAN bus to reduce the charging current. When an abnormality is detected in the communication between the battery management system and the charging station, the main positive relay and the main negative relay are immediately disconnected to stop charging. Example 2

[0032] The difference between this embodiment and Embodiment 1 lies in the setting of the low-temperature charging threshold T0 and the various temperature thresholds. In this embodiment, T1 = -8℃ and T2 = 10℃. This set of thresholds is suitable for battery systems with good low-temperature tolerance or applications with extremely low ambient temperatures.

[0033] When Tmin≤-8℃, it enters the multi-stage adaptive heating mode, and the rest of the control logic is the same as in Example 1. Example 3

[0034] This embodiment provides an electric light truck, the structure of which is as follows: Figure 4 As shown, it includes: Power battery: Composed of multiple lithium iron phosphate battery cells connected in series, providing driving energy for the vehicle; Battery Management System (BMS): Connected to each individual battery cell, it is used to collect voltage and temperature data of each cell in real time, calculate state parameters such as SOC and SOH, and execute charging control strategies. Vehicle Control Unit (VCU): Communicates with the BMS via the CAN bus and is responsible for the energy management and coordinated control of the entire vehicle; Onboard Water Heater (WPTC): Connected to the coolant circulation system of the battery pack, it is used to heat the coolant under low temperature conditions and heat the battery pack through coolant circulation; Charging control unit: Communicates with BMS and charging pile, and requests the corresponding charging current from the charging pile according to the instructions of BMS.

[0035] The BMS and VCU work together to execute the low-temperature charging control method for electric light trucks as described in Example 1.

[0036] The low-temperature charging control method for electric light trucks provided by this invention can be widely applied to the battery management and charging control systems of various types of electric light trucks, electric logistics vehicles, and other electric commercial vehicles. This method is implemented through software algorithms, requiring no additional hardware costs, and thus exhibits good economic efficiency and feasibility. Real-vehicle testing has verified that the charging time for electric light trucks using this method at an ambient temperature of -20℃ is reduced by approximately 40% compared to traditional methods, and heating energy consumption is reduced by approximately 30%, demonstrating significant practical value and economic significance.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments without departing from the technical solution of the present invention and based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for controlling low-temperature charging of an electric light truck, characterized in that, Comprising the following steps: Step S1: charging wake-up and initial detection, after the charging pile is connected, the BMS wakes up and detects the minimum cell temperature Tmin, ambient temperature, voltage, current and SOC; Step S2: determining whether the current minimum cell temperature Tmin is less than a preset low-temperature charging threshold T2, when Tmin < T2, proceed to step S3; when Tmin ≥ T2, proceed to step S4; Step S3: entering a multi-stage adaptive heating charging mode, wherein the multi-stage adaptive heating charging mode comprises an extreme low temperature processing sub-mode and a low-temperature chargeable sub-mode, the extreme low temperature processing sub-mode is: determining whether Tmin is less than or equal to a preset extreme low temperature charging threshold T1, wherein T1<T2; if yes, firstly heating the battery purely by using the current maximum available power without outputting charging current to the battery until Tmin rises to be greater than T1, and then adopting a heating-pulse charging alternating mode; the low-temperature chargeable sub-mode is: when T1<Tmin<T2, starting a heating circuit and a charging circuit simultaneously, and dynamically adjusting the heating power and the charging current according to the real-time temperature of the battery; Step S4: standard charging, performing CC-CV charging according to the optimal charging MAP recommended by the battery manufacturer until the charging is completed; Step S5: monitoring voltage, temperature and current parameters of the battery in real time during the charging process, and executing a protection action when any parameter exceeds the corresponding safety threshold.

2. The low-temperature charging control method for electric light trucks according to claim 1, characterized in that, the heating-pulse charging alternating mode is: stopping heating after heating for a certain period of time; then charging the battery with a small pulse current, and then heating again after standing for a certain period of time after charging; repeating the above cycle, and detecting Tmin after each cycle until Tmin≥T2.

3. The low-temperature charging control method for electric light trucks according to claim 2, characterized in that, the heating-pulse charging alternating mode is specifically: heating for 30 to 35 seconds, then stopping heating; charging with a 0.01 to 0.05C pulse for 20 to 30 seconds, then standing for 10 to 20 seconds; repeating the above cycle, and detecting Tmin after each cycle until Tmin≥T2.

4. The low-temperature charging control method for electric light trucks according to claim 1, characterized in that, the low-temperature chargeable sub-mode is specifically: setting an initial heating power and an initial charging current, and performing synchronous heating and charging on the battery with the initial heating power and the initial charging current; after charging for a certain period of time, calculating a temperature rise rate dT / dt, and dynamically adjusting the heating power and the charging current through the temperature rise rate.

5. The low-temperature charging control method for electric light trucks according to claim 4, characterized in that, the initial heating power is 50% to 60% of the rated power; and the initial charging current is 0.05 to 0.1C.

6. The low-temperature charging control method for electric light trucks according to claim 5, characterized in that, calculating the temperature rise rate dT / dt every 30 to 50 seconds, and performing closed-loop adjustment on the heating power and the charging current through the temperature rise rate, which specifically comprises: when dT / dt < 0.5°C / min, increasing the heating power by 5% to 10% step by step, with the final increment not exceeding 100%, and keeping the charging current unchanged; when dT / dt > 2.0°C / min, decreasing the charging current by 0.02C step by step and keeping it not lower than 0.05C, and keeping the heating power unchanged; when 0.5 ≤ dT / dt ≤ 2.0, maintaining current parameters; when Tmin ≥ T2, turning off heating and switching to standard CC-CV charging.

7. The low-temperature charging control method for electric light trucks according to any one of claims 1-6, characterized in that, The low-temperature charging threshold T2 is 5℃~10℃; the ultra-low-temperature charging threshold T1 is -8℃~-10℃.

8. A low-temperature charging control system for electric light trucks, characterized in that, It includes a power battery, a battery management system, a vehicle controller, an on-board water heater, and a charging control unit, wherein the battery management system and the vehicle controller are used to execute the low-temperature charging control method for electric light trucks as described in any one of claims 1 to 7.

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