Quick charging method for electrically assisted bicycles

Abstract

This application relates to a fast charging method for an electric-assist bicycle, comprising: after the charger is powered on, first controlling the power conversion unit to have no output, interacting with the battery management system to obtain battery pack identity information and determine the upper limit of charging current; the battery management system periodically acquiring multiple real-time status parameters, fusing them to determine the target charging current value and issuing a current request command; in the next PWM cycle after receiving the command, the charger adjusts the duty cycle of the PWM control signal to the target duty cycle and outputs the charging current, samples the actual charging current of the output circuit, and corrects the duty cycle according to the difference between the actual current and the target current so that the actual current follows the target current; when the target current is a reduced current value, the same process is still executed; when the charging termination condition is met, the PWM control signal is turned off. This application uses a semi-solid-state battery module, thereby significantly improving thermal stability and safety.

Description

Technical Field

[0001] This application relates to the field of battery charging technology, specifically to a fast charging method for electric-assisted bicycles. Background Technology

[0002] With the successive implementation of new national standards such as GB 43854-2024 "Safety Technical Specification for Lithium-ion Batteries for Electric Bicycles" and GB / T 36972—2026 "Performance Technical Specification for Lithium-ion Batteries for Electric Bicycles", clear and strict requirements have been put forward for the battery performance and safety of electric bicycles.

[0003] Currently, most mainstream e-bikes on the market use liquid lithium batteries as their energy storage core. However, due to limitations in the characteristics of liquid battery materials, structural stability, and safety thresholds, the industry standard charging current is generally 2A–5A, and charging time typically ranges from 4 to 8 hours. This results in slow charging speeds and low energy replenishment efficiency, failing to meet users' needs for rapid energy replenishment for emergency travel and frequent short-distance rides. Furthermore, most e-bike batteries on the market do not support charging at sub-zero temperatures, thus failing to address the travel needs of users in winter or cold regions.

[0004] Meanwhile, existing electric bicycle charging systems are all designed to be compatible with low-current liquid batteries. The charger output current is limited and the charging circuit of the whole vehicle has weak voltage and current carrying capacity. Even if a large-capacity battery is replaced, it is impossible to achieve high-current fast charging. Problems such as charging heat, circuit overload, battery bulging, and accelerated service life degradation are very likely to occur. Summary of the Invention

[0005] To overcome the above-mentioned defects, this application provides a fast charging method for electric-assisted bicycles, which uses a semi-solid battery module to significantly improve thermal stability and safety, and effectively suppress the risks of lithium plating and thermal runaway.

[0006] The technical solution adopted by this application to solve its technical problem is:

[0007] A fast charging method for an electric-assist bicycle is disclosed, applied to a fast charging system for the electric-assist bicycle. The fast charging system includes a charger and a battery pack, wherein the battery pack is a semi-solid-state battery module. The charger includes a power conversion unit, a current sampling unit, a communication interface for communicating with the battery management system of the battery pack, and a control unit. The method includes the following steps:

[0008] In response to the charger being powered on, the control unit controls the power conversion unit to be in a state with no charging current output;

[0009] The control unit sends an identity query command to the battery management system through the communication interface, and receives the identity information of the battery pack returned by the battery management system in response to the identity query command;

[0010] If the identity information does not meet the preset allowed charging conditions, the control unit controls the power conversion unit to maintain the state of no charging current output.

[0011] If the identity information meets the preset allowed charging conditions, the control unit determines the upper limit of the charging current of the battery pack based on the identity information. When the battery pack supports a preset fast charging current, the upper limit of the charging current is the fast charging current. When the battery pack does not support the fast charging current, the upper limit of the charging current is a reduced current value less than the fast charging current.

[0012] The battery management system periodically acquires various real-time status parameters of the battery pack to determine the target charging current value that the battery pack can safely withstand at present, and sends a current request command carrying the target charging current value to the charger through the communication interface.

[0013] When the target charging current value is greater than the upper limit of the charging current, the control unit limits the target charging current value to the upper limit of the charging current.

[0014] In the next PWM cycle after receiving the current request command, the control unit adjusts the duty cycle of the PWM control signal output to the power conversion unit to the target duty cycle, and the power conversion unit outputs the charging current to the battery pack.

[0015] The control unit samples the actual charging current output by the power conversion unit through the current sampling unit to obtain the actual charging current value, and corrects the duty cycle according to the difference between the target charging current value and the actual charging current value, so that the deviation between the actual charging current value and the target charging current value is less than a preset deviation threshold.

[0016] The above process is repeated periodically, and when the target charging current value is the current reduction value, the same process is still executed to output the charging current corresponding to the current reduction value.

[0017] When the preset charging termination condition is met, the control unit shuts off the PWM control signal, causing the power conversion unit to stop outputting charging current.

[0018] Optionally, the identity information includes at least one of the following: battery pack model, rated voltage, rated capacity, cell type, and maximum allowable charging current; the control unit determines that the battery pack supports the fast charging current when the maximum allowable charging current is greater than or equal to the fast charging current; the fast charging current is 10A, and the current reduction current is 2A to 5A.

[0019] Optionally, the real-time status parameters include parameters directly collected by the battery management system and parameters calculated from the collected parameters. The real-time status parameters include at least two of the following: battery temperature, battery voltage, battery polarization, current state of charge, battery health status, and voltage change trend. The battery management system integrates the multiple real-time status parameters to determine the target charging current value that the battery pack can safely withstand.

[0020] Optionally, the parameters directly collected by the battery management system include the individual cell voltage, the total voltage of the battery pack, the charging current, the temperature values ​​collected by multiple temperature sampling points distributed on the surface and inside of the battery cells, and the internal resistance of the battery pack; the current state of charge is determined by the battery management system through ampere-hour integration combined with open-circuit voltage calibration; the battery health status is determined by the battery management system based on the ratio of the actual capacity to the rated capacity of the battery pack and / or the growth rate of the battery internal resistance relative to the initial internal resistance; the degree of battery polarization is determined by at least one of polarization voltage, the rate of change of battery voltage, and the change in battery internal resistance; and the voltage change trend is determined by the rate of change of battery voltage within a preset time window.

[0021] Optionally, the battery management system fuses the various real-time state parameters to determine the target charging current value, including any of the following methods:

[0022] For each of the real-time state parameters, a corresponding candidate charging current value is determined, and the minimum value among the multiple candidate charging current values ​​is determined as the target charging current value.

[0023] The target charging current value is determined by querying a preset current mapping table based on the various real-time status parameters.

[0024] For each of the real-time status parameters, a corresponding derating factor is determined, and the minimum value of the product of each derating factor and the fast charging current is determined as the target charging current value.

[0025] The target charging current value is obtained by weighting each of the real-time state parameters and then calculating the weighted average.

[0026] Optionally, the battery management system encapsulates the target charging current value into an instruction frame and sends the current request instruction through the communication interface. The instruction frame includes an instruction type field, a target current value field, an instruction sequence number field, and a checksum field. The target current value field carries the target charging current value in amperes, and the resolution of the target current value field is 0.1A. The communication interface is a UART interface or a CAN interface, and the battery management system sends the current request instruction in a period of 1s to 5s.

[0027] Optionally, after receiving the current request command, the control unit parses the target charging current value and calculates the duty cycle adjustment of the PWM control signal based on the difference between the target charging current value and the actual charging current value using a proportional-integral-derivative (PID) algorithm. In the next PWM cycle, the control unit updates the duty cycle according to the duty cycle adjustment and performs amplitude limiting on the updated duty cycle to ensure it does not exceed a preset maximum duty cycle. The entire response time from receiving the current request command to the actual charging current value stabilizing at the target charging current value is less than or equal to 200ms. The next PWM cycle refers to the first complete PWM switching cycle after receiving the current request command, and the switching frequency of the PWM control signal is 65kHz to 100kHz.

[0028] Optionally, the control unit transmits the actual charging current value back to the battery management system via the communication interface; after sending the current request command, the battery management system compares the transmitted actual charging current value with the target charging current value after a preset comparison delay to obtain the current execution deviation; when the absolute value of the current execution deviation is less than or equal to a preset deviation ratio threshold, it is determined that the charger has correctly executed the current request command and continues to send the current request command; the comparison delay is greater than or equal to the entire process response time, and the preset deviation ratio threshold is ±5% of the target charging current value.

[0029] Optionally, the control unit monitors the duration of the absence of the current request command, and determines that the communication interface is abnormal when the duration exceeds a preset duration; the preset duration is greater than the transmission period and is 2 to 5 times the transmission period.

[0030] When the communication interface is determined to be abnormal, the control unit first reduces the target charging current value to a preset safe charging current and maintains it for a first predetermined duration. If the current request command that has passed verification is not received within the first predetermined duration, the output charging current is reduced step by step from the safe charging current to zero, the PWM control signal is turned off, and the power circuit between the power conversion unit and the battery pack is disconnected. The safe charging current is less than the current reduction value. When the current request command that has passed verification is received again before the charging current is reduced to zero, the timing of the duration is cleared and the output charging current is restored according to the newly received target charging current value.

[0031] Optionally, the preset charging termination conditions include charging completion conditions and abnormal termination conditions;

[0032] The charging completion conditions include at least one of the following: the battery voltage of the battery pack reaches a preset charging cutoff voltage, the actual charging current value drops below a preset cutoff current, and the current state of charge reaches a preset full charge threshold; the preset full charge threshold is 95-100%, and the preset cutoff current is 0.5A;

[0033] The abnormal termination conditions include at least one of the following: the voltage of any single cell is greater than or equal to the overcharge protection threshold; the battery temperature is greater than or equal to the temperature protection threshold; the control unit does not receive the current request command within a preset time and is determined to be in communication abnormality; the charger triggers hardware protection, the hardware protection including at least one of over-temperature protection, output overcurrent protection and short-circuit protection; the overcharge protection threshold is 4.225V to 4.275V, and the temperature protection threshold is 55℃;

[0034] When the abnormal termination condition is met, the control unit or the battery management system also outputs an alarm signal. The alarm signal includes at least one of the following: an audible and visual alarm signal output by an indicator light and / or a buzzer installed on the charger, and an alarm message sent to the host system through the communication interface or wireless communication module. The alarm message includes an exception code indicating the type of exception.

[0035] The beneficial effects of this application are:

[0036] (1) Compared with traditional liquid lithium batteries, the semi-solid battery in this application has a solid-liquid coexistence state of electrolyte, which greatly improves thermal stability and safety, effectively suppresses the risk of lithium plating and thermal runaway, and is not easy to catch fire or explode even when punctured; at the same time, the system significantly extends the cycle life to more than 1200 times, improves low-temperature discharge performance, maintains high capacity at -20℃, and supports higher fast charging rates without excessive life loss; in addition, the higher energy density helps to make the battery pack lighter. These characteristics together constitute the technical basis for the semi-solid battery to support 10A high-current fast charging, making fast, safe and long-life charging solutions possible for electric bicycles. In terms of charging speed, the charging time of batteries of the same capacity can be shortened by more than 60%, effectively solving the defects of slow energy replenishment and inability to be used in emergencies in traditional technologies, and adapting to high-frequency travel and temporary energy replenishment scenarios.

[0037] (2) In this application, after the charger is powered on, it first controls the power conversion unit to be in a state of no charging current output. Before completing the identity query with the battery management system and confirming that the identity information meets the allowed charging conditions, it does not output any charging current to the battery pack. When fast charging is confirmed to be supported, the fast charging current is used as the upper limit of the charging current; when it is not supported, a smaller charging current is used as the upper limit of the charging current. When the target charging current value issued by the battery management system exceeds the upper limit, the charger limits it to the upper limit before execution. Therefore, even if a third-party battery pack that does not support high current or an aging battery pack is mistakenly connected, or if the battery management system mistakenly issues an over-limit current request due to a malfunction, the charger will not blindly follow the output, thus avoiding the risk of battery overcurrent, excessive temperature rise, or even thermal runaway from the source. This achieves inherent safety after power-on and avoids the risks of mischarging and non-standard batteries.

[0038] (3) In this application, within the next PWM cycle after receiving the current request command sent by the battery management system, the charger adjusts the duty cycle of the PWM control signal to the target duty cycle, so that the output current quickly approaches the target value from the current value. Subsequently, the actual output current is sampled by the current sampling unit connected in series in the output circuit of the secondary rectifier filter output unit, and the duty cycle is corrected by the difference between the target current value and the actual current value, so that the deviation between the actual charging current and the target charging current is less than the preset deviation threshold. Since the sampling point is located in the output circuit rather than the primary side, the errors caused by factors such as transformer loss, leakage inductance, rectified voltage drop and temperature drift are incorporated into the closed loop, and the current control accuracy is significantly improved. Feedforward ensures a microsecond-level response after the command arrives, and the closed loop eliminates steady-state error. The response time from receiving the command to the current stabilizing at the target value does not exceed 200ms, achieving a combination of speed and accuracy. Attached Figure Description

[0039] Figure 1 This is a simplified diagram of the fast charging method in this application. Detailed Implementation

[0040] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the embodiments described in this application are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0041] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of the terms can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0042] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0043] A fast charging method for an electric-assist bicycle is applied to a fast charging system for an electric-assist bicycle. The fast charging system includes a charger and a battery pack. The battery pack is a semi-solid-state battery module. The charger includes a power conversion unit, a current sampling unit, a communication interface for communicating with the battery management system (BMS) of the battery pack, and a control unit. The power conversion unit is used to convert the input DC bus voltage into a DC charging current and output it to the battery pack under the control of the PWM control signal output by the control unit.

[0044] The method includes the following steps:

[0045] In response to the charger being powered on, the control unit controls the power conversion unit to be in a state of no charging current output; so that the charger does not output charging current to the battery pack.

[0046] The control unit sends an identity query command to the battery management system through the communication interface, and receives the identity information of the battery pack returned by the battery management system in response to the identity query command;

[0047] If the identity information does not meet the preset allowed charging conditions, the control unit controls the power conversion unit to maintain the state of no charging current output.

[0048] If the identity information meets the preset allowed charging conditions, the control unit determines the upper limit of the charging current of the battery pack based on the identity information. When the battery pack supports a preset fast charging current, the upper limit of the charging current is the fast charging current. When the battery pack does not support the fast charging current, the upper limit of the charging current is a reduced current value less than the fast charging current.

[0049] The battery management system periodically acquires various real-time status parameters of the battery pack to determine the target charging current value that the battery pack can safely withstand at present, and sends a current request command carrying the target charging current value to the charger through the communication interface.

[0050] When the target charging current value is greater than the upper limit of the charging current, the control unit limits the target charging current value to the upper limit of the charging current.

[0051] In the next PWM cycle after receiving the current request command, the control unit adjusts the duty cycle of the PWM control signal output to the power conversion unit to the target duty cycle, and the power conversion unit outputs the charging current to the battery pack.

[0052] The control unit samples the actual charging current output by the power conversion unit through the current sampling unit to obtain the actual charging current value, and corrects the duty cycle according to the difference between the target charging current value and the actual charging current value, so that the deviation between the actual charging current value and the target charging current value is less than a preset deviation threshold.

[0053] The above process is repeated periodically, and when the target charging current value is the current reduction value, the same process is still executed to output the charging current corresponding to the current reduction value.

[0054] When the preset charging termination condition is met, the control unit shuts off the PWM control signal, causing the power conversion unit to stop outputting charging current.

[0055] Compared to traditional liquid lithium batteries, the semi-solid-state battery in this application exhibits a solid-liquid coexistence state in its electrolyte, significantly improving thermal stability and safety. It effectively suppresses the risks of lithium plating and thermal runaway, and is less prone to fire and explosion even when punctured. Simultaneously, this system significantly extends cycle life to over 1200 cycles, improves low-temperature discharge performance, maintains high capacity even at -20°C, and supports higher fast charging rates without excessive lifespan loss. Furthermore, its higher energy density contributes to lighter battery packs. These characteristics collectively form the technological foundation for the semi-solid-state battery to support 10A high-current fast charging, making a fast, safe, and long-life charging solution possible for e-bikes. In terms of charging speed, it can reduce the charging time of batteries of the same capacity by more than 60%, effectively solving the shortcomings of traditional technologies such as slow recharging and inability to be used in emergencies, making it suitable for high-frequency travel and temporary recharging scenarios.

[0056] In this application, after the charger is powered on, it first controls the power conversion unit to a state with no charging current output. Before completing an identity query with the battery management system and confirming that the identity information meets the allowed charging conditions, it does not output any charging current to the battery pack. If fast charging is confirmed, the fast charging current is used as the upper limit of the charging current; if not, a smaller charging current is used as the upper limit. Furthermore, if the target charging current value issued by the battery management system exceeds this upper limit, the charger limits it to the upper limit before execution. Therefore, even if a third-party battery pack that does not support high current is mistakenly connected, an aging battery pack is used, or the battery management system malfunctions and mistakenly issues an over-limit current request, the charger will not blindly follow the output, thus avoiding the risks of battery overcurrent, excessive temperature rise, and even thermal runaway from the source. This achieves inherent safety after power-on and avoids the risks of mischarging and non-standard batteries.

[0057] In this application, the charger adjusts the duty cycle of the PWM control signal to the target duty cycle in the next PWM cycle after receiving the current request command from the battery management system, causing the output current to rapidly approach the target value from the current value. Subsequently, the actual output current is sampled by a current sampling unit connected in series in the output circuit of the secondary rectifier filter output unit, and the duty cycle is corrected by the difference between the target current value and the actual current value, so that the deviation between the actual charging current and the target charging current is less than a preset deviation threshold. Since the sampling point is located in the output circuit rather than the primary side, errors caused by factors such as transformer losses, leakage inductance, rectified voltage drop, and temperature drift are incorporated into the closed loop, significantly improving the current control accuracy. Feedforward ensures a microsecond-level response after the command arrives, and the closed loop eliminates steady-state errors. The entire response time from receiving the command to the current stabilizing at the target value does not exceed 200ms, achieving a combination of speed and accuracy.

[0058] This application addresses the technical challenges of small battery pack size, limited heat dissipation, and inability to withstand continuous high-current charging in electric-assist bicycles. Through a complete technology chain including identification, current upper limit limitation, multi-parameter fusion decision-making, next PWM cycle duty cycle feedforward adjustment, output-side sampling closed-loop correction, communication reliability assurance, dual closed-loop execution confirmation, and graded termination protection, it significantly improves charging speed while controlling battery temperature, polarization, overcharging, and communication failure risks within a safe range, achieving a synergistic unity between fast charging and safe charging.

[0059] The identity information includes at least one of the following: battery pack model, rated voltage, rated capacity, cell type, and maximum allowable charging current. The control unit determines that the battery pack supports the fast charging current when the maximum allowable charging current is greater than or equal to the fast charging current. The fast charging current is 10A, meaning the charger is a 10A fast charger, and the current reduction value is 2A to 5A. Optionally, the current reduction value is 5A. The current reduction value covers two scenarios: one is limited current reduction, where the upper limit of the charging current is limited to a smaller current reduction value when the battery pack does not support the fast charging current; the other is dynamic current reduction, where the target charging current value decreases from the fast charging current to the current reduction value during fast charging due to changes in parameters such as battery temperature, polarization, and state of charge.

[0060] When the real-time status parameters of the battery pack trigger current reduction, the target charging current value decreases from the fast charging current to the reduced current value. The charger still executes the same process of "receiving instructions - adjusting the duty cycle in the next PWM cycle - inversion - isolation coupling - rectification and filtering output - output side sampling - difference correction", outputting a charging current corresponding to the reduced current value. Therefore, both 10A fast charging and the reduced current 5A are executed under the same closed-loop control, avoiding the response lag caused by the passive attenuation or slow communication adjustment during the constant voltage stage in conventional solutions. This significantly reduces the risk of lithium plating and thermal runaway under high charge and high temperature conditions.

[0061] This application uses a semi-solid cell adapted for 10A continuous fast charging, adopts a solid-liquid composite electrolyte structure, optimizes electrode conductivity, breaks through the traditional liquid battery charging current limit of 2A-5A, and has the characteristics of anti-polarization, low heat generation, not easy to bulge, and non-explosive under needle puncture. It can stably carry a large current input of 10A and can also accept small current charging below zero degrees. At the same time, it is equipped with a BMS circuit board with a cell balancing algorithm to ensure the balanced working state of each cell under high current charging.

[0062] The real-time status parameters include parameters directly collected by the battery management system and parameters calculated from the collected parameters. The real-time status parameters include at least two of the following: battery temperature, battery voltage, battery polarization degree, current state of charge, battery health status, and voltage change trend. The battery management system integrates the multiple real-time status parameters to determine the target charging current value that the battery pack can safely withstand.

[0063] The parameters directly collected by the battery management system include the individual cell voltage, the total voltage of the battery pack, the charging current, the temperature values ​​collected by multiple temperature sampling points distributed on the surface and inside of the battery cells, and the internal resistance of the battery pack. The current state of charge is determined by the battery management system through ampere-hour integration combined with open-circuit voltage calibration. The battery health status is determined by the battery management system based on the ratio of the actual capacity to the rated capacity of the battery pack and / or the growth rate of the battery internal resistance relative to the initial internal resistance. The degree of battery polarization is determined by at least one of polarization voltage, the rate of change of battery voltage, and the change in battery internal resistance. The voltage change trend is determined by the rate of change of battery voltage within a preset time window. The battery management system samples the cell voltage, the total voltage, and the charging current at a frequency greater than or equal to 10 Hz, and samples the temperature value at a frequency greater than or equal to 1 Hz, with the sampling frequency of the temperature value being less than the sampling frequency of the cell voltage. The battery management system determines the maximum value among the temperature values ​​collected at each of the temperature sampling points as the battery temperature, and determines the maximum value among the cell voltages as the cell voltage to be compared with the overcharge protection threshold.

[0064] The battery management system determines the target charging current value by fusing the various real-time status parameters, including any of the following methods:

[0065] For each of the real-time state parameters, a corresponding candidate charging current value is determined, and the minimum value among the multiple candidate charging current values ​​is determined as the target charging current value.

[0066] The target charging current value is determined by querying a preset current mapping table based on the various real-time status parameters.

[0067] For each of the real-time status parameters, a corresponding derating factor is determined, and the minimum value of the product of each derating factor and the fast charging current is determined as the target charging current value.

[0068] The target charging current value is obtained by weighting each of the real-time state parameters and then calculating the weighted average.

[0069] The battery management system reduces the target charging current value when at least one of the following conditions is met, and takes the minimum value among the reduction results when multiple conditions are met simultaneously:

[0070] The battery temperature is greater than or equal to a preset high temperature threshold, or less than or equal to a preset low temperature threshold; the battery polarization degree is greater than or equal to a preset polarization threshold.

[0071] The current state of charge is greater than a preset state of charge threshold;

[0072] The battery health status is less than a preset health threshold.

[0073] The voltage change rate characterized by the voltage change trend is greater than or equal to a preset rate threshold.

[0074] Specifically, when the battery temperature is less than or equal to the preset low-temperature threshold, the battery management system first outputs a preheating request to instruct the battery pack to be preheated, and then sends the current request command after the battery temperature rises to the allowable charging temperature. Because of this function, even at temperatures between -10°C and 0°C, users can charge the battery without affecting its lifespan.

[0075] The battery management system encapsulates the target charging current value into an instruction frame and sends the current request instruction through the communication interface. The instruction frame includes an instruction type field, a target current value field, an instruction sequence number field, and a checksum field. The target current value field carries the target charging current value in amperes, and the resolution of the target current value field is 0.1A. The communication interface is a UART interface or a CAN interface, and the battery management system sends the current request instruction every 1 to 5 seconds. After receiving the current request instruction, the control unit verifies the current request instruction according to the checksum field. If the verification passes, the control unit updates the target charging current value according to the target current value field. If the verification fails, or if the instruction sequence number field is not continuous with the previously received instruction sequence number, the control unit discards the current request instruction and maintains the target charging current value as the previously verified target charging current value.

[0076] After receiving the current request command, the control unit parses the target charging current value and calculates the duty cycle adjustment of the PWM control signal based on the difference between the target charging current value and the actual charging current value using a proportional-integral-derivative (PID) algorithm. In the next PWM cycle, the control unit updates the duty cycle according to the adjustment and limits the updated duty cycle to ensure it does not exceed a preset maximum duty cycle. The entire response time from receiving the current request command to the actual charging current value stabilizing at the target charging current value is less than or equal to 200ms. The next PWM cycle refers to the first complete PWM switching cycle after receiving the current request command, and the switching frequency of the PWM control signal is 65kHz to 100kHz.

[0077] The control unit transmits the actual charging current value back to the battery management system via the communication interface. After sending the current request command, the battery management system compares the transmitted actual charging current value with the target charging current value after a preset comparison delay to obtain the current execution deviation. When the absolute value of the current execution deviation is less than or equal to a preset deviation ratio threshold, it is determined that the charger has correctly executed the current request command and continues to send the current request command. The comparison delay is greater than or equal to the overall response time, and the preset deviation ratio threshold is ±5% of the target charging current value. When the absolute value of the current execution deviation is greater than the preset deviation ratio threshold, the battery management system accumulates one execution abnormality. When the number of consecutive execution abnormalities reaches a preset number threshold, the battery management system determines that the charger has not correctly executed the current request command and sends a stop-charging command to the charger via the communication interface. The control unit immediately shuts down the PWM control signal in response to the stop-charging command. The preset number threshold is 2 to 5 times.

[0078] This mechanism is independent of the charger's internal control closed loop. Even if the charger's internal control fails, communication is interfered with, or a non-standard charger that does not follow the protocol is used, the battery management system can still actively detect and terminate charging. The comparison delay and continuous counting design avoid misjudgment during the dynamic adjustment of current and will not stop charging due to normal step process.

[0079] The control unit monitors the duration of the absence of the current request command, and determines that the communication interface is abnormal when the duration exceeds a preset duration; the preset duration is greater than the transmission period and is 2 to 5 times the transmission period.

[0080] When the communication interface is determined to be abnormal, the control unit first reduces the target charging current value to a preset safe charging current and maintains it for a first predetermined duration. If the current request command that has passed verification is not received within the first predetermined duration, the output charging current is reduced step by step from the safe charging current to zero, the PWM control signal is turned off, and the power circuit between the power conversion unit and the battery pack is disconnected. The safe charging current is less than the current reduction value. When the current request command that has passed verification is received again before the charging current is reduced to zero, the timing of the duration is cleared and the output charging current is restored according to the newly received target charging current value.

[0081] The preset charging termination conditions include charging completion conditions and abnormal termination conditions.

[0082] The charging completion conditions include at least one of the following: the battery voltage of the battery pack reaches a preset charging cutoff voltage, the actual charging current value drops below a preset cutoff current, and the current state of charge reaches a preset full charge threshold; the preset full charge threshold is 95-100%, and the preset cutoff current is 0.5A;

[0083] The abnormal termination conditions include at least one of the following: the voltage of any single cell is greater than or equal to the overcharge protection threshold; the battery temperature is greater than or equal to the temperature protection threshold; the control unit does not receive the current request command within a preset time and is determined to be in communication abnormality; the charger triggers hardware protection, the hardware protection including at least one of over-temperature protection, output overcurrent protection and short-circuit protection; the overcharge protection threshold is 4.225V to 4.275V, and the temperature protection threshold is 55℃;

[0084] When the abnormal termination condition is met, the control unit or the battery management system also outputs an alarm signal. The alarm signal includes at least one of the following: an audible and visual alarm signal output by an indicator light and / or a buzzer on the charger; and an alarm message sent to the host system via the communication interface or wireless communication module. The alarm message includes an exception code indicating the type of exception. The charger also includes an EMI filter unit and a power frequency rectification filter unit connected between the mains input terminal and the power conversion unit. These units are used to perform electromagnetic interference filtering, power frequency rectification, and filtering on the mains power, and output a DC bus voltage to the power conversion unit.

[0085] This application optimizes the vehicle charging system to accommodate 10A high-current charging conditions. This includes replacing the high-temperature resistant, high-current-carrying wiring harness and the high-conductivity charging interface, and replacing the original 10A fuse on the charging cable with a 15A fuse. It also addresses the requirements for high-current charging signal transmission and real-time monitoring. The system employs an intelligent safety protection mechanism, collecting real-time data on charging current, voltage, battery and wiring harness temperatures. In abnormal conditions, it can quickly disconnect the charging circuit. It integrates multiple protection functions including overcurrent, overvoltage, overheat, and short circuit protection to mitigate risks such as overheating, overload, and component damage caused by high-current charging. At temperatures between -10℃ and 0℃, the charger outputs approximately 1A of current based on the physical characteristics of the semi-solid-state battery cells, preventing internal crystallization at low temperatures that could puncture the cells.

[0086] like Figure 1 As shown, the charger in this embodiment includes a power conversion unit, a current sampling unit, a communication interface, a control unit, an EMI filtering unit, and a power frequency rectification and filtering unit. The power conversion unit includes a PWM high-frequency inverter control unit, a high-frequency isolation transformer, and a secondary rectification and filtering output unit connected in sequence.

[0087] The system includes: an EMI filter unit with its input connected to AC mains power; a power frequency rectifier filter unit connected to the output of the EMI filter unit for outputting DC bus voltage; a PWM high-frequency inverter control unit connected to the output of the power frequency rectifier filter unit, comprising a digital power controller and a power switch, for inverting the DC bus voltage into a high-frequency AC square wave voltage in response to a PWM control signal, wherein the duty cycle of the PWM control signal is adjustable and the switching frequency is 65kHz to 100kHz; a high-frequency isolation transformer connected to the primary side of the PWM high-frequency inverter control unit for coupling the high-frequency AC square wave voltage to the secondary side; a secondary rectifier filter output unit connected to the secondary side of the high-frequency isolation transformer for outputting DC charging current to the battery pack; a current sampling unit connected in series in the output circuit of the secondary rectifier filter output unit for sampling the actual output charging current; a communication interface for communicating with the battery management system of the battery pack; and a control unit connected to the PWM high-frequency inverter control unit, the current sampling unit, and the communication interface, respectively.

[0088] Specifically: the mains power is filtered by EMI and then rectified by power frequency to obtain the DC bus voltage; the PWM high-frequency inverter control unit inverts the DC bus voltage into a high-frequency AC square wave voltage (switching frequency 65kHz~100kHz) under the action of the PWM control signal; the high-frequency isolation transformer couples it to the secondary side to achieve electrical isolation between the primary and secondary sides; the secondary rectifier and filter output unit rectifies and filters the output DC charging current to the battery pack.

[0089] The PWM high-frequency inverter control unit includes a digital power controller and power switching transistors. The digital power controller generates the PWM control signal and outputs it to the control terminal of the power switching transistors. The power switching transistors alternately turn on and off in response to the PWM control signal, chopping the DC bus voltage into a high-frequency AC square wave voltage. The power switching transistors constitute a full-bridge inverter circuit, a half-bridge inverter circuit, or a push-pull inverter circuit. The digital power controller is the control unit, or a dedicated digital power control chip independent of the control unit but communicatively connected to it. Preferably, the power switching transistors are gallium nitride devices to achieve higher switching frequencies and lower conduction losses.

[0090] The control unit is also used to detect the operating parameters of the charger, including the temperature of the power conversion unit, the actual charging current value, and the output impedance of the secondary rectifier filter output unit; when the operating parameters trigger the hardware protection, the control unit immediately shuts off the PWM control signal. Figure 1 The multi-protection unit includes at least one of an over-temperature protection circuit, an output overcurrent protection circuit, and a short-circuit protection circuit. That is, the multi-protection unit is used to implement over-temperature protection, output overcurrent protection, and short-circuit protection. The multi-protection unit is connected to the power conversion unit and the control unit, and is used to output a protection action signal to cut off the output when the operating parameters of the charger trigger hardware protection.

[0091] Example 1: A fast charging method for an electric-assisted bicycle, applied to a fast charging system for electric-assisted bicycles. The fast charging system includes a charger and a battery pack, wherein the battery pack is a semi-solid-state battery module, and the charger is a 10A fast charger. Figure 1 As shown, the method includes:

[0092] Step 1: The charger receives the mains power input, filters the mains power for electromagnetic interference through the EMI filter unit, and then performs power frequency rectification and filtering on the filtered mains power through the power frequency rectification and filtering unit to obtain the DC bus voltage;

[0093] Step 2: After the charger is powered on, it does not immediately output power. The control unit first performs a handshake interaction with the battery management system (BMS) of the battery pack through the communication interface.

[0094] Step 3: The control unit sends an identity query command to the battery management system through the communication interface. The identity information includes parameters such as battery type code (distinguishing between semi-solid batteries and ordinary liquid lithium batteries), nominal voltage, nominal capacity, maximum allowable charging current, current state of charge (SOC), and battery temperature. If the control unit cannot establish communication with the BMS, for example, if a non-smart battery is connected, the charger disconnects its output to avoid conflict with national standards.

[0095] Step 4: After successfully reading the battery parameters, the control unit makes a comprehensive judgment based on the battery parameters. The judgment criteria include: whether the battery type is a semi-solid-state battery that supports 10A fast charging, whether the battery's nominal voltage matches the charger's output voltage, whether the battery's maximum allowable charging current reaches or exceeds 10A, and whether the battery's current temperature is within the allowable fast charging range, preferably 5℃ to 45℃. If all the above conditions are met, the fast charging mode is entered; if any condition is not met, the current reduction mode is entered. This judgment node setting ensures the charger's adaptive compatibility with different types of batteries.

[0096] Step 5: Once the fast charging conditions are met, the charger enters fast charging mode, sets the target charging current to 10A, and enters a high-current fast charging preparation state. At this time, the charger does not immediately output 10A current, but waits for the BMS to send further specific current request instructions before executing the output according to the instructions. The function of this node is to enable the fast charging mode and set the initial target current.

[0097] Step 6: The PWM high-frequency inverter control unit responds to the current request command from the BMS and completes the duty cycle adjustment in the next PWM cycle after receiving the command, so that the output current quickly approaches the desired value. The input terminal of the PWM high-frequency inverter control unit is connected to the DC bus to invert the DC bus voltage into a high-frequency AC square wave. The switching frequency of the PWM control signal is preferably 65kHz to 100kHz. This unit achieves precise control of the output power by adjusting the duty cycle of the PWM signal: when the output current needs to be increased, the control chip increases the duty cycle; when the output current needs to be decreased, the duty cycle decreases. The key components of this unit include a digital power controller and a power switching transistor, wherein the power switching transistor is preferably a gallium nitride device to achieve a higher switching frequency and lower conduction loss.

[0098] Step 7: Throughout the charging process, the BMS continuously collects the battery pack's status parameters. Monitored parameters include: individual cell voltage, total battery pack voltage, charging current, temperature values ​​at multiple temperature sampling points distributed on and inside the cells, state of charge (SOC), state of health (SOH), and battery internal resistance (impedance). The sampling frequency for voltage and current is no less than 10Hz, and the temperature sampling frequency is no less than 1Hz. All monitored data is aggregated and sent to the BMS calculation stage as the basis for dynamically adjusting the charging current. This node also serves as the communication initiation point, through which the BMS establishes a bidirectional data link with the charger.

[0099] Step 8: The BMS comprehensively evaluates the maximum charging current that the battery can safely withstand based on various parameters acquired through real-time monitoring. The calculation is based on, but is not limited to: the current temperature of the battery (current limiting is applied if the temperature is too high, and current limiting or preheating is triggered if the temperature is too low), the degree of battery polarization (judged by voltage change rate or internal resistance change; severe polarization triggers active current reduction), the current state of charge (automatic current reduction in high SOC ranges to protect the battery), the battery health status (reducing the maximum allowable current threshold for batteries with high aging levels), and the voltage change trend (preventing voltage overshoot). The BMS integrates the above multi-parameter information and calculates the optimal target current value under the current state using built-in safety thresholds and control algorithms.

[0100] Step 9: The BMS encapsulates the calculated target current value into a command frame and sends it to the charger's control unit via the communication link. The communication protocol is preferably based on UART or CAN bus, using a custom application layer protocol. The BMS sends current request commands preferably once every 1 to 5 seconds to achieve dynamic adjustment of the charging current. The command frame content includes at least the target current value (in amperes, with an accuracy of 0.1A), the command sequence number, and a checksum to ensure the reliability and integrity of the communication.

[0101] Step 10: The charger's control unit receives the current request command from the BMS, parses the target current value, calculates the required PWM duty cycle adjustment using the built-in PID algorithm, and immediately executes the duty cycle adjustment. The entire response time, from receiving the command to the output current stabilizing at the target value, does not exceed 200ms. Furthermore, the charger has an internal communication timeout monitoring mechanism: if no new command is received from the BMS for more than a preset time (preferably 5 seconds), the communication link is deemed abnormal, triggering a protection mechanism that gradually reduces the output current until it is completely shut down.

[0102] Step 11: The charger transmits the current actual output current value back to the BMS via the communication link, forming a closed-loop confirmation. The BMS compares the transmitted actual current value with the previously sent target current value: if the deviation is within the allowable range (preferably within ±5%), it is determined that the charger has correctly executed the instruction, and the charging process continues normally; if the deviation exceeds the allowable range, the BMS determines that the charger has not correctly executed the instruction (possibly caused by communication interference or charger hardware failure), immediately triggers the protection mechanism, sends a stop charging instruction to the charger, and forcibly terminates the charging process.

[0103] Step 12: Charging process termination includes two scenarios: normal termination and abnormal termination. The normal termination condition is as follows: when the BMS detects that the state of charge has reached 100% and the charging current has dropped below a preset threshold (preferably 0.5A), the BMS sends a stop charging command to the charger. After receiving the command, the charger turns off the PWM output, cuts off the power circuit, and the charging process ends normally.

[0104] Abnormal termination conditions include: the BMS detecting that the voltage of any single cell exceeds the overcharge protection threshold, preferably 4.25V±0.025V; the battery temperature exceeds the temperature protection threshold, preferably 55℃; the communication interruption between the charger and the BMS exceeds a preset time, preferably 5 seconds; or any one of the following is triggered by the charger's hardware protection (including over-temperature protection, output over-current protection, short-circuit protection, etc.). After abnormal termination is triggered, the charger immediately shuts off the PWM output, cuts off the power circuit, and sends an alarm signal to the upper-level system via audible and visual means or communication.

[0105] It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this patent application shall be determined by the appended claims.

Claims

1. A fast charging method for an electric-assisted bicycle, applied to a fast charging system for electric-assisted bicycles, characterized in that: The fast charging system includes a charger and a battery pack, wherein the battery pack is a semi-solid-state battery module, and the charger includes a power conversion unit, a current sampling unit, a communication interface for communicating with the battery management system of the battery pack, and a control unit. The method includes the following steps: In response to the charger being powered on, the control unit controls the power conversion unit to be in a state with no charging current output; The control unit sends an identity query command to the battery management system through the communication interface, and receives the identity information of the battery pack returned by the battery management system in response to the identity query command; If the identity information does not meet the preset allowed charging conditions, the control unit controls the power conversion unit to maintain the state of no charging current output. If the identity information meets the preset allowed charging conditions, the control unit determines the upper limit of the charging current of the battery pack based on the identity information. When the battery pack supports a preset fast charging current, the upper limit of the charging current is the fast charging current. When the battery pack does not support the fast charging current, the upper limit of the charging current is a reduced current value less than the fast charging current. The battery management system periodically acquires various real-time status parameters of the battery pack to determine the target charging current value that the battery pack can safely withstand at present, and sends a current request command carrying the target charging current value to the charger through the communication interface. When the target charging current value is greater than the upper limit of the charging current, the control unit limits the target charging current value to the upper limit of the charging current. In the next PWM cycle after receiving the current request command, the control unit adjusts the duty cycle of the PWM control signal output to the power conversion unit to the target duty cycle, and the power conversion unit outputs the charging current to the battery pack. The control unit samples the actual charging current output by the power conversion unit through the current sampling unit to obtain the actual charging current value, and corrects the duty cycle according to the difference between the target charging current value and the actual charging current value, so that the deviation between the actual charging current value and the target charging current value is less than a preset deviation threshold. The above process is repeated periodically, and when the target charging current value is the current reduction value, the same process is still executed to output the charging current corresponding to the current reduction value. When the preset charging termination condition is met, the control unit shuts off the PWM control signal, causing the power conversion unit to stop outputting charging current.

2. The fast charging method for an electric-assisted bicycle according to claim 1, characterized in that: The identity information includes at least one of the following: battery pack model, rated voltage, rated capacity, cell type, and maximum allowable charging current; the control unit determines that the battery pack supports the fast charging current when the maximum allowable charging current is greater than or equal to the fast charging current; the fast charging current is 10A, and the current reduction current is 2A to 5A.

3. The fast charging method for an electric-assisted bicycle according to claim 1, characterized in that: The real-time status parameters include parameters directly collected by the battery management system and parameters calculated from the collected parameters. The real-time status parameters include at least two of the following: battery temperature, battery voltage, battery polarization degree, current state of charge, battery health status, and voltage change trend. The battery management system integrates the various real-time status parameters to determine the target charging current value that the battery pack can safely withstand.

4. The fast charging method for an electric-assisted bicycle according to claim 3, characterized in that: The parameters directly collected by the battery management system include the individual cell voltage, the total voltage of the battery pack, the charging current, the temperature values ​​collected by multiple temperature sampling points distributed on the surface and inside of the battery cells, and the internal resistance of the battery pack. The current state of charge is determined by the battery management system through ampere-hour integration combined with open-circuit voltage calibration. The battery health status is determined by the battery management system based on the ratio of the actual capacity to the rated capacity of the battery pack and / or the growth rate of the battery internal resistance relative to the initial internal resistance. The degree of battery polarization is determined by at least one of polarization voltage, the rate of change of battery voltage, and the change in battery internal resistance. The voltage change trend is determined by the rate of change of battery voltage within a preset time window.

5. The fast charging method for an electric-assisted bicycle according to claim 3, characterized in that: The battery management system determines the target charging current value by fusing the various real-time status parameters, including any of the following methods: For each of the real-time state parameters, a corresponding candidate charging current value is determined, and the minimum value among the multiple candidate charging current values ​​is determined as the target charging current value. The target charging current value is determined by querying a preset current mapping table based on the various real-time status parameters. For each of the real-time status parameters, a corresponding derating factor is determined, and the minimum value of the product of each derating factor and the fast charging current is determined as the target charging current value. The target charging current value is obtained by weighting each of the real-time state parameters and then calculating the weighted average.

6. The fast charging method for an electric-assisted bicycle according to claim 1, characterized in that: The battery management system encapsulates the target charging current value into an instruction frame and sends the current request instruction through the communication interface. The instruction frame includes an instruction type field, a target current value field, an instruction sequence number field, and a checksum field. The target current value field carries the target charging current value in amperes, and the resolution of the target current value field is 0.1A. The communication interface is a UART interface or a CAN interface, and the battery management system sends the current request instruction every 1 to 5 seconds.

7. The fast charging method for an electric-assisted bicycle according to claim 1, characterized in that: After receiving the current request command, the control unit parses the target charging current value and calculates the duty cycle adjustment of the PWM control signal based on the difference between the target charging current value and the actual charging current value using a proportional-integral-derivative (PID) algorithm. In the next PWM cycle, the duty cycle is updated according to the duty cycle adjustment and the updated duty cycle is limited to ensure that the updated duty cycle does not exceed the preset maximum duty cycle. The entire response time from receiving the current request command to the actual charging current value stabilizing at the target charging current value is less than or equal to 200ms; the next PWM cycle refers to the first complete PWM switching cycle after receiving the current request command, and the switching frequency of the PWM control signal is 65kHz to 100kHz.

8. The fast charging method for an electric-assisted bicycle according to claim 1, characterized in that: The control unit transmits the actual charging current value back to the battery management system through the communication interface; after sending the current request command, the battery management system compares the transmitted actual charging current value with the target charging current value after a preset comparison delay to obtain the current execution deviation; when the absolute value of the current execution deviation is less than or equal to a preset deviation ratio threshold, it is determined that the charger has correctly executed the current request command and continues to send the current request command; the comparison delay is greater than or equal to the entire process response time, and the preset deviation ratio threshold is ±5% of the target charging current value.

9. The fast charging method for an electric-assisted bicycle according to claim 1, characterized in that: The control unit monitors the duration for which the current request command is not received, and determines that the communication interface is abnormal when the duration exceeds a preset duration. The preset duration is longer than the transmission period, and is 2 to 5 times the transmission period; When the communication interface is determined to be abnormal, the control unit first reduces the target charging current value to a preset safe charging current and maintains it for a first predetermined time. If the current request command that has passed verification is not received within the first predetermined time period, the output charging current will be reduced step by step from the safe charging current to zero, the PWM control signal will be turned off, and the power circuit between the power conversion unit and the battery pack will be cut off; wherein, the safe charging current is less than the current reduction value; and when the current request command that has passed verification is received again before the charging current is reduced to zero, the timing of the duration will be cleared and the output charging current will be restored according to the target charging current value received again.

10. The fast charging method for an electric-assisted bicycle according to claim 4, characterized in that: The preset charging termination conditions include charging completion conditions and abnormal termination conditions. The charging completion conditions include at least one of the following: the battery voltage of the battery pack reaches a preset charging cutoff voltage, the actual charging current value drops below a preset cutoff current, and the current state of charge reaches a preset full charge threshold; the preset full charge threshold is 95-100%, and the preset cutoff current is 0.5A; The abnormal termination conditions include at least one of the following: the voltage of any single cell is greater than or equal to the overcharge protection threshold; the battery temperature is greater than or equal to the temperature protection threshold; the control unit does not receive the current request command within a preset time and is determined to be in communication abnormality; the charger triggers hardware protection, the hardware protection including at least one of over-temperature protection, output overcurrent protection and short-circuit protection; the overcharge protection threshold is 4.225V to 4.275V, and the temperature protection threshold is 55℃; When the abnormal termination condition is met, the control unit or the battery management system also outputs an alarm signal. The alarm signal includes at least one of the following: an audible and visual alarm signal output by an indicator light and / or a buzzer installed on the charger, and an alarm message sent to the host system through the communication interface or wireless communication module. The alarm message includes an exception code indicating the type of exception.

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