Multi-stage charging optimization method based on adaptive identification battery

Abstract

The invention relates to the technical field of charging optimization, and discloses a multi-stage charging optimization method based on adaptive identification of a battery, and the method comprises the following steps: S101, in-situ detection and battery type identification; step S102, applying a current step and collecting a voltage response; s103, predicting the change of the terminal voltage along with time; step S104, determining a safe amplitude limiting current; step S105, determining a pre-deceleration factor; and step S106, judging full power, generating a quota recovery instruction, and returning to the step S104 for redistribution. Battery individual parameters are obtained through in-situ detection and micro-pulse identification, current quotas are dynamically distributed based on a constant voltage proportion, a safe target current is determined by combining voltage and power amplitude limiting, current distribution unbalance is avoided, the bus current utilization rate is maximized, voltage overshoot is inhibited by means of a first-order following strategy and a pre-deceleration factor, and the safety of a battery is improved. And stable switching is ensured by matching with constant-voltage inlet current clamping.

Description

Technical Field

[0001] This invention relates to the field of charging optimization technology, and more specifically, to a multi-stage charging optimization method based on adaptive battery identification. Background Technology

[0002] With the development of energy storage systems, electric vehicles and other fields, parallel charging of multiple battery modules has become the mainstream configuration. Its core requirement is to improve charging efficiency while ensuring safety. However, in actual applications, individual differences of battery modules objectively exist and change dynamically, directly causing a series of technical problems.

[0003] Individual differences in battery modules stem from deviations in capacity and internal resistance at the time of manufacture, as well as parameter differentiation caused by different cycle counts and aging levels during use. Specifically, key characteristic parameters such as equivalent instantaneous internal resistance, polarization internal resistance, and polarization time constant are inconsistent. Existing charging methods do not accurately identify these individual characteristics and generally adopt uniform charging parameters and fixed current quota schemes.

[0004] When some modules reach full charge prematurely, the system needs to reduce the overall charging current or stop charging to avoid overcharging. At this time, the modules that are not fully charged cannot fully utilize the bus current resources, leading to a significant decrease in overall charging efficiency. When switching from the constant current stage to the constant voltage stage, existing methods lack a targeted current slope constraint mechanism. Due to lag in control loop response or rigid parameter settings, voltage overshoot can easily occur, exceeding the battery voltage limit and damaging the cells. Simultaneously, current quota allocation is not linked to the real-time battery status, and the quota holding period does not match the battery polarization decay rhythm, further exacerbating current distribution imbalance and charging fluctuations. This reduces bus current utilization and introduces safety risks. These problems become increasingly prominent with the increase in the number of modules and the extension of usage time, becoming the core bottleneck restricting the performance of multi-module charging systems. Summary of the Invention

[0005] This invention provides a multi-stage charging optimization method based on adaptive battery identification, which solves the technical problems mentioned in the background.

[0006] This invention provides a multi-stage charging optimization method based on adaptive battery identification, comprising the following steps: Step S101: By performing in-situ detection and battery type identification, obtain the voltage upper limit, rated capacity, temperature and pressure safety range, Joule heating power upper limit, initial state of charge, and bus current budget. Step S102: During the pre-charge stage, a current step is applied to the battery and the voltage response is collected. The equivalent instantaneous internal resistance, polarization internal resistance, polarization time constant, and DC internal resistance are calculated. Step S103: Under a given constant current, predict the change of the terminal voltage over time to obtain the switching time from constant current to constant voltage, and determine the constant voltage start current, cut-off current, constant voltage tail duration and constant voltage percentage. In step S104, the main module generates the quota current according to the constant voltage ratio and the bus current budget, calculates the voltage limiting current and the power limiting current, takes the minimum value as the safety limiting current, sends it as the target current, and sets the quota holding time as the constant voltage tail segment duration. Step S105: The module adopts a first-order following strategy to the target current. The pre-deceleration factor is determined according to the constant current to constant voltage switching time. When the actual terminal voltage reaches the upper voltage limit, the constant voltage is switched to constant voltage, and the constant voltage inlet current is clamped with the constant voltage starting current. In step S106, during the constant voltage stage, the system determines that the battery is fully charged based on the cutoff current and polarization time constant, generates a quota recovery instruction, and returns to step S104 for redistribution.

[0007] Furthermore, the terminal voltage at the moment the battery is powered on is collected, and the open-circuit voltage corresponding to the battery type and the inverse function of the state of charge function are input to obtain the initial state of charge of the battery. The bus current budget is received from the main module through a half-duplex bus.

[0008] Further, step S102 includes the following steps: Step S201: The difference between the battery terminal voltage at any time after the current step is applied and the battery terminal voltage at the instant the current step is applied is the first voltage change; the difference between the battery terminal voltage at the sampling time at the end of the micro-pulse identification window and the battery terminal voltage at the instant the current step is applied is the second voltage change. Step S202: Divide the difference between the battery terminal voltage at the instant the current step is applied and the battery terminal voltage before the current step is applied by the magnitude of the current step to obtain the equivalent instantaneous internal resistance. Step S203: Divide the second voltage change by the amplitude of the current step to obtain the polarization resistance. Step S204: Take the negative of the difference between the two sampling times as the numerator, divide the difference between the second voltage change and the first voltage change at the second sampling time by the difference between the second voltage change and the first voltage change at the first sampling time, and take the natural logarithm of the resulting ratio as the denominator. Divide the numerator by the denominator to obtain the polarization time constant. Step S205: The difference between the battery terminal voltage at the second sampling time and the battery terminal voltage at the first sampling time is divided by the amplitude of the current step to obtain the DC internal resistance.

[0009] Furthermore, the initial state of charge is first added to the product of the provisional constant current and time, divided by the rated capacity, and used as the input to the open-circuit voltage and state of charge function to obtain the first term; the product of the provisional constant current and the equivalent instantaneous internal resistance is calculated to obtain the second term; the product of the provisional constant current and the polarization internal resistance is calculated, and then this product is multiplied by 1 and subtracted from the difference between the negative time of the natural exponent and the polarization time constant to obtain the third term. The three terms are added together to obtain the terminal voltage at any time, and the time when the terminal voltage equals the upper voltage limit is obtained. This time is used as the constant current to constant voltage switching time.

[0010] Further, the constant voltage start current, cutoff current, constant voltage tail duration, and constant voltage percentage are determined, including the following steps: Step S301: The initial state of charge is added to the product of the provisional constant current and the constant current to constant voltage switching time, and then divided by the rated capacity to obtain the state of charge at the constant current to constant voltage switching time. Step S302: Subtract the terminal voltage under charged state at the moment of constant current to constant voltage switching from the upper voltage limit to obtain the voltage difference. Then divide the voltage difference by the sum of the equivalent instantaneous internal resistance and the polarization internal resistance to obtain the constant voltage starting current. Step S303: Multiply the constant voltage starting current by the value of the natural exponent negative one to obtain the cutoff current. Step S304: Set the value of the constant voltage tail segment duration to be the same as the value of the polarization time constant to obtain the constant voltage tail segment duration. Step S305: Divide the constant voltage tail segment duration by the sum of the constant current to constant voltage switching time and the constant voltage tail segment duration to obtain the constant voltage ratio.

[0011] Further, step S104 includes the following steps: Step S401: Subtract the constant voltage ratio of each slave module from 1 to obtain the quota weight of each slave module; Step S402: For each slave module, the bus current budget is multiplied by the ratio of the slave module's quota weight to the sum of the quota weights of all slave modules to obtain the quota current of that slave module. Step S403: For each slave module, subtract the current terminal voltage of the slave module from the upper voltage limit, and then divide the difference by the sum of the equivalent instantaneous internal resistance and polarization internal resistance of the slave module to obtain the voltage limiting current of the slave module. Step S404: For each slave module, divide the upper limit of the Joule heating power of the slave module by the DC internal resistance of the slave module, and then calculate the square root of the quotient to obtain the power limiting current of the slave module. Step S405: For each slave module, select the minimum value from the quota current, voltage limiting current and power limiting current of the slave module, take the minimum value as the safe limiting current of the slave module, and set it as the target current to be sent to the corresponding slave module. Step S406: For each slave module, set the quota holding time of the slave module to be the same as the constant voltage tail duration of the slave module, and the constant voltage tail duration is the same as the polarization time constant of the slave module.

[0012] Furthermore, the first-order following strategy involves real-time acquisition of the current actual current from the module, adding the current actual current to the quotient of the sampling interval of the control cycle divided by the polarization time constant, and then multiplying it by the difference between the target current and the current actual current to obtain the actual current for the next control cycle.

[0013] Furthermore, subtract the cumulative time of the constant current stage from 1 and divide it by the quotient of the constant current to constant voltage switching moment. If the result is less than 0, take 0 to obtain the pre-deceleration factor. Set the upper limit of the current change slope. The upper limit value is the pre-deceleration factor multiplied by the difference between the upper limit of voltage and the current terminal voltage, and then divided by the product of the equivalent instantaneous internal resistance and the polarization time constant.

[0014] Furthermore, when the current terminal voltage is detected to be greater than or equal to the upper voltage limit, the module's charging control mode will be immediately switched from constant current control to constant voltage control; the actual current at the moment before switching to constant voltage control will be recorded, and the minimum value between the actual current at the moment before switching and the constant voltage starting current will be taken as the constant voltage input current.

[0015] Further, the cutoff current of the slave module is obtained by multiplying the constant voltage starting current by the natural exponent -1; a starting point of a continuous detection window is selected, and the maximum value of the actual current during the time period from the starting point to the sum of the starting point and the polarization time constant is calculated; if the maximum value is less than or equal to the cutoff current, the slave module is determined to be fully charged; when it is determined to be fully charged, the target current of the slave module is set to 0, and the current quota originally allocated to the slave module is recovered to the bus current budget, waiting for reallocation; the time of the previous quota issuance is recorded, and the quota holding time of the slave module is obtained, which is the same as the constant voltage tail duration of the slave module and the same as the polarization time constant of the slave module; when the current time is greater than or equal to the sum of the time of the previous quota issuance and the quota holding time, the process returns to step S104, and the process returns to the online monitoring stage.

[0016] The beneficial effects of this invention are as follows: This invention acquires individual battery parameters through in-situ detection and micro-pulse identification, providing a precise basis for regulation; then, based on constant voltage ratio, it dynamically allocates current quotas, combining voltage and power limiting to determine a safe target current, avoiding current distribution imbalance and maximizing bus current utilization; during the constant current to constant voltage transition phase, it uses a first-order following strategy and pre-deceleration factor to suppress voltage overshoot, and coordinates constant voltage inlet current clamping to ensure stable switching; the full-charge criterion combines cutoff current and polarization time constant to accurately determine the full-charge state and recover quota for redistribution. The overall process adapts to changes in individual battery characteristics, avoiding safety risks such as overvoltage and overheating, and significantly improving the overall throughput efficiency of multi-module charging systems. Attached Figure Description

[0017] Figure 1 This is a flowchart of a multi-stage charging optimization method based on adaptive battery identification according to the present invention. Detailed Implementation

[0018] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0019] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of the present invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in one or more embodiments of the present invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" indicate that the element or object preceding the term encompasses the elements or objects listed following the term and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] like Figure 1 As shown, a multi-stage charging optimization method based on adaptive battery identification includes the following steps: Step S101: By performing in-situ detection and battery type identification, obtain the voltage upper limit, rated capacity, temperature and pressure safety range, Joule heating power upper limit, initial state of charge, and bus current budget. Step S102: During the pre-charge stage, a current step is applied to the battery and the voltage response is collected. The equivalent instantaneous internal resistance, polarization internal resistance, polarization time constant, and DC internal resistance are calculated. Step S103: Under a given constant current, predict the change of the terminal voltage over time to obtain the switching time from constant current to constant voltage, and determine the constant voltage start current, cut-off current, constant voltage tail duration and constant voltage percentage. In step S104, the main module generates the quota current according to the constant voltage ratio and the bus current budget, calculates the voltage limiting current and the power limiting current, takes the minimum value as the safety limiting current, sends it as the target current, and sets the quota holding time as the constant voltage tail segment duration. Step S105: The module adopts a first-order following strategy to the target current. The pre-deceleration factor is determined according to the constant current to constant voltage switching time. When the actual terminal voltage reaches the upper voltage limit, the constant voltage is switched to constant voltage, and the constant voltage inlet current is clamped with the constant voltage starting current. In step S106, during the constant voltage stage, the system determines that the battery is fully charged based on the cutoff current and polarization time constant, generates a quota recovery instruction, and returns to step S104 for redistribution.

[0021] It should be noted that, through in-situ detection and battery type identification, the upper limit of voltage, rated capacity, temperature and pressure safety range, and upper limit of Joule heating power are obtained. In-situ detection is achieved through hardware interface detection, such as monitoring the change of specific pin levels at the connection interface between the battery and the charging system. When the battery is connected, the pin level changes according to a preset pattern, and the system determines that the battery is in place. Battery type identification is achieved by reading the battery's built-in identification information, such as the type code recorded in the battery's internal storage chip. The system reads this code through the communication interface and matches it with a preset type library to determine the battery type. The upper limit of voltage indicates the highest voltage that the battery is allowed to reach during charging. Exceeding this voltage will damage the battery. Rated capacity indicates the standard capacity specified in the battery design, that is, the amount of electricity that the battery can release after being fully charged under standard conditions. The temperature and pressure safety range indicates the temperature and voltage range that the battery is allowed to operate normally. Exceeding this temperature or voltage range will affect the battery's safety or lifespan. The upper limit of Joule heating power indicates the maximum heat output that the battery is allowed to generate during charging, which is determined by the battery's heat tolerance. Exceeding this power will lead to excessively high temperatures.

[0022] It should be noted that the master module is the module responsible for overall management in the charging system. Its functions include communicating with the host computer, monitoring system status, allocating current to each slave module, and coordinating the work of each slave module. The slave module is the module that connects to a single battery. Its functions include executing charging commands issued by the master module, collecting the status of the connected battery (such as voltage, current, and temperature), and feeding back battery information to the master module. The master-slave module design can improve system management efficiency and enhance system scalability. When it is necessary to increase the number of battery charging units, only the corresponding slave module needs to be added and connected to the half-duplex bus of the master module. There is no need to modify the core management logic of the master module. This design can flexibly adapt to scenarios where multiple batteries are charged at the same time without reconstructing the overall system architecture.

[0023] In one embodiment of the present invention, the terminal voltage at the moment of battery power-on is collected, the open-circuit voltage corresponding to the battery type and the inverse function of the state of charge function are input to obtain the initial state of charge of the battery, and the bus current budget is received from the main module through a half-duplex bus.

[0024] It should be noted that the open-circuit voltage and state-of-charge (POC) function corresponding to the battery type are derived from experimental testing. Multiple charge-discharge experiments were conducted on this type of battery, and it was left to rest for a sufficient time under different POC states to eliminate polarization. The open-circuit voltage at this time was measured, and the POC function was fitted to the corresponding open-circuit voltage to obtain their functional relationship. The terminal voltage at the moment of battery power-on is known, meaning the battery is approximately in an open-circuit state at this time; the terminal voltage can be considered as the open-circuit voltage. The POC corresponding to this open-circuit voltage is calculated using the inverse function of the above function. The initial POC represents the proportion of remaining charge to the rated capacity at the moment of battery power-on. A half-duplex bus indicates that only unidirectional data transmission can occur at any given time; either the master module sends information to the slave module, or the slave module sends information to the master module. The bus current budget is the total current that the master module can allocate to all slave modules based on factors such as the total power of the power supply system and the current power consumption of other loads.

[0025] It should be noted that, assuming the total power of the charging system's power supply is 10 kilowatts and the charging bus voltage is 500 volts, the maximum total current that the power supply can provide is the total power divided by the bus voltage, which is 20 amps. If, in addition to the charging module, there are auxiliary loads such as cooling fans in the system, and their total current requirement is 2 amps, then the main module will determine the remaining current available for charging as the bus current budget, that is, 20 amps minus 2 amps equals 18 amps. At this time, 18 amps is the total current quota subsequently allocated to each slave module.

[0026] In one embodiment of the present invention, step S102 includes the following steps: Step S201: The difference between the battery terminal voltage at any time after the current step is applied and the battery terminal voltage at the instant the current step is applied is the first voltage change; the difference between the battery terminal voltage at the sampling time at the end of the micro-pulse identification window and the battery terminal voltage at the instant the current step is applied is the second voltage change. Step S202: Divide the difference between the battery terminal voltage at the instant the current step is applied and the battery terminal voltage before the current step is applied by the magnitude of the current step to obtain the equivalent instantaneous internal resistance. Step S203: Divide the second voltage change by the amplitude of the current step to obtain the polarization internal resistance; Step S204: Take the negative of the difference between the two sampling times as the numerator, divide the difference between the second voltage change and the first voltage change at the second sampling time by the difference between the second voltage change and the first voltage change at the first sampling time, and take the natural logarithm of the resulting ratio as the denominator. Divide the numerator by the denominator to obtain the polarization time constant. Step S205: The difference between the battery terminal voltage at the second sampling time and the battery terminal voltage at the first sampling time is divided by the amplitude of the current step to obtain the DC internal resistance.

[0027] Specifically, polarization time constant The calculation formula is as follows: ,in This represents the second voltage change. and These represent the first voltage change at the first sampling time and the second sampling time, respectively.

[0028] It should be noted that when applying a small current step to the battery during the pre-charging phase, the amplitude of this current step and the duration of the micro-pulse identification need to be set. The amplitude of the current step should be determined based on the battery's rated capacity, typically 0.05 to 0.1 times the rated capacity. For example, for a battery with a rated capacity of 10 amp-hours, the current step amplitude can be set to 0.5 to 1 amp-hour. This range ensures accurate voltage response acquisition without causing damage to the battery due to excessive current. The micro-pulse identification duration needs to be matched to the polarization rate of the battery type. For batteries with faster polarization establishment, such as ternary lithium batteries... The time interval can be set from 50 milliseconds to 200 milliseconds; for batteries with slow polarization establishment, such as lithium iron phosphate batteries, it can be set from 200 milliseconds to 500 milliseconds to ensure that the polarization voltage can approach its steady-state value within this time period, so as to accurately calculate the second voltage change; the battery terminal voltage before the current step is applied is collected, and the battery terminal voltage at the instant the current step is applied is collected; within the set micropulse identification time period, two sampling times are selected, and the two sampling times satisfy that the first sampling time is earlier than the second sampling time and both are within the micropulse identification time period, and the battery terminal voltage within this micropulse identification time period is continuously collected.

[0029] It should be noted that the first voltage change reflects the increment of the battery polarization voltage, the second voltage change reflects the increment of the battery polarization voltage after it reaches a steady state; the equivalent instantaneous internal resistance reflects the ohmic internal resistance of the battery, including the instantaneous resistance of the electrodes, electrolyte, etc.; the polarization internal resistance reflects the equivalent resistance of the battery's electrochemical polarization and concentration polarization; the polarization time constant reflects the time scale of the exponential change of the polarization voltage over time; and the DC internal resistance reflects the equivalent DC resistance of the battery within the time window.

[0030] In one embodiment of the present invention, the initial state of charge is first calculated by adding the product of the provisional constant current and time to the rated capacity, and this product is used as the input to the open-circuit voltage and the state of charge function to obtain the first term. The product of the provisional constant current and the equivalent instantaneous internal resistance is calculated to obtain the second term. The product of the provisional constant current and the polarization internal resistance is calculated, and this product is multiplied by 1 and then subtracted from the difference between the negative time of the natural exponent and the polarization time constant to obtain the third term. The three terms are added together to obtain the terminal voltage at any time. The time when the terminal voltage is equal to the upper voltage limit is obtained, and this time is used as the constant current to constant voltage switching time.

[0031] Specifically, the formula for calculating the battery terminal voltage at time t is as follows: Where OCV represents the open-circuit voltage versus state-of-charge function, Indicates the initial state of charge. This indicates a provisional constant current. This represents the equivalent instantaneous internal resistance. Indicates polarization internal resistance. represents the polarization time constant, and e represents the natural constant.

[0032] It should be noted that the provisional constant current is a constant charging current value assumed during the terminal voltage prediction stage. It is used to simulate the current state during constant current charging and is not the final current during actual charging. It is typically taken as 0.1 to 0.5 times the battery's rated capacity. For example, for a battery with a rated capacity of 10 amp-hours, the provisional constant current can be set to 1 to 5 amp-hours. This range aligns with the typical constant current charging current range of most batteries, avoiding inaccurate predictions due to excessive deviation between the assumed current and actual operating conditions. It also ensures that the predicted switching time, constant voltage initiation current, and other parameters have engineering reference value. The first item reflects the open-circuit voltage changing over time. As charging time increases, the battery's state of charge... As the open-circuit voltage increases, it changes accordingly, forming the fundamental component of the terminal voltage. The second term reflects the ohmic voltage drop during constant current charging. Current passing through the battery's equivalent instantaneous internal resistance (e.g., electrode and electrolyte resistance) generates a fixed voltage drop, which is proportional to the current and remains constant during the constant current phase. The third term reflects the polarization voltage drop over time. During charging, the battery undergoes electrochemical polarization and concentration polarization, and the polarization voltage drop gradually increases over time and approaches a steady state (determined by the polarization time constant). This term accurately simulates this dynamic process. Therefore, the actual terminal voltage of the battery consists of three parts: open-circuit voltage, ohmic voltage drop, and polarization voltage drop, enabling the prediction of the terminal voltage's change over time.

[0033] In one embodiment of the present invention, determining the constant voltage start current, cutoff current, constant voltage tail duration, and constant voltage percentage includes the following steps: Step S301: The initial state of charge is added to the product of the provisional constant current and the constant current to constant voltage switching time, and then divided by the rated capacity to obtain the state of charge at the constant current to constant voltage switching time. Step S302: Subtract the terminal voltage under charged state at the moment of constant current to constant voltage switching from the upper voltage limit to obtain the voltage difference. Then divide the voltage difference by the sum of the equivalent instantaneous internal resistance and the polarization internal resistance to obtain the constant voltage starting current. Step S303: Multiply the constant voltage starting current by the value of the natural exponent negative one to obtain the cutoff current. Step S304: Set the value of the constant voltage tail segment duration to be the same as the value of the polarization time constant to obtain the constant voltage tail segment duration. Step S305: Divide the constant voltage tail segment duration by the sum of the constant current to constant voltage switching time and the constant voltage tail segment duration to obtain the constant voltage ratio.

[0034] It should be noted that the terminal voltage under state of charge at the moment of switching from constant current to constant voltage is obtained through the open-circuit voltage and the state of charge function; the constant voltage starting current represents the initial charging current value set when the battery switches from the constant current stage to the constant voltage stage. Its magnitude is determined by the difference between the open-circuit voltage and the upper voltage limit at the moment of switching, the sum of the equivalent instantaneous internal resistance and the polarization internal resistance, and is used to ensure that the current does not change abruptly when switching to the constant voltage stage, thus maintaining a stable charging process; the cutoff current is the current threshold for determining whether the battery is fully charged in the constant voltage stage. When the charging current in the constant voltage stage drops to... This value indicates that the battery's remaining capacity is close to full charge. The constant voltage tail duration represents the expected duration of the constant voltage phase, and its value is equal to the polarization time constant. Because the polarization time constant reflects the rate of polarization voltage decay, the current decay law in the constant voltage phase is consistent with the polarization decay law. Therefore, using the polarization time constant as the constant voltage tail duration can reasonably estimate the duration of the constant voltage phase. The constant voltage percentage represents the proportion of time in the constant voltage phase during the entire charging process. The smaller the percentage, the shorter the battery time in the constant voltage phase, and the more current quota can be obtained first.

[0035] In one embodiment of the present invention, step S104 includes the following steps: Step S401: Subtract the constant voltage ratio of each slave module from 1 to obtain the quota weight of each slave module; Step S402: For each slave module, the bus current budget is multiplied by the ratio of the slave module's quota weight to the sum of the quota weights of all slave modules to obtain the quota current of that slave module. Step S403: For each slave module, subtract the current terminal voltage of the slave module from the upper voltage limit, and then divide the difference by the sum of the equivalent instantaneous internal resistance and polarization internal resistance of the slave module to obtain the voltage limiting current of the slave module. Step S404: For each slave module, divide the upper limit of the Joule heating power of the slave module by the DC internal resistance of the slave module, and then calculate the square root of the quotient to obtain the power limiting current of the slave module. Step S405: For each slave module, select the minimum value from the quota current, voltage limiting current and power limiting current of the slave module, take the minimum value as the safe limiting current of the slave module, and set it as the target current to be sent to the corresponding slave module. Step S406: For each slave module, set the quota holding time of the slave module to be the same as the constant voltage tail duration of the slave module, and the constant voltage tail duration is the same as the polarization time constant of the slave module.

[0036] It should be noted that the quota weight represents the priority used for allocating bus current; the higher the quota weight, the higher the proportion of current obtained in the current allocation. The quota current represents the initial current quota allocated to each slave module, and the sum of the quota currents of all slave modules shall not exceed the bus current budget. The voltage limiting current is the maximum allowable current set to prevent the battery terminal voltage from exceeding the voltage limit, ensuring that the battery terminal voltage does not exceed the safe range under this current. The power limiting current is the maximum allowable current set to prevent the battery Joule heating power from exceeding the allowable limit, ensuring that the battery heating power does not exceed the safe tolerance range under this current.

[0037] It should be noted that the quota current only considers the current allocation ratio and does not involve safety constraints; the voltage limiting current only ensures voltage safety, and the power limiting current only ensures thermal safety. Taking the minimum of the three can simultaneously meet the requirements of current allocation, voltage safety, and thermal safety, avoiding battery overvoltage or overheating damage due to considering only a single factor; in addition, the quota holding time is determined based on the battery's own polarization characteristics (polarization time constant), which can ensure that the battery's charging state (e.g., polarization degree, terminal voltage change) is relatively stable within this period, avoiding charging current fluctuations caused by excessively frequent quota allocation, which would affect charging efficiency and battery life; at the same time, using the duration of the constant voltage tail section as a benchmark, the quota holding time is matched with the duration of the subsequent constant voltage stage, improving the coordination of the entire charging process.

[0038] In one embodiment of the present invention, the first-order following strategy is to collect the current actual current of the slave module in real time, add the current actual current to the quotient of the sampling interval of the control cycle divided by the polarization time constant, and then multiply it by the difference between the target current and the current actual current to obtain the actual current of the next control cycle.

[0039] Specifically, the actual current in the next control cycle The calculation formula is as follows: ,in Indicates the current actual current. Indicates the sampling interval of the control cycle. Indicates the target current from the module. This represents the polarization time constant.

[0040] In one embodiment of the present invention, the quotient of the constant current stage cumulative time divided by the constant current to constant voltage switching time is subtracted from 1. If the result is less than 0, it is taken as 0 to obtain the pre-deceleration factor. The upper limit of the current change slope is set. The upper limit value is the pre-deceleration factor multiplied by the difference between the voltage upper limit and the current terminal voltage, and then divided by the product of the equivalent instantaneous internal resistance and the polarization time constant.

[0041] Specifically, to suppress voltage overshoot during the transition from constant current to constant voltage, an upper limit constraint is applied to the current change slope using a pre-deceleration factor, the calculation formula of which is as follows: ,in Represents the absolute value of the rate of change of current. Indicates the pre-deceleration factor. Indicates the upper limit of voltage. Indicates the current terminal voltage. This represents the equivalent instantaneous internal resistance. This represents the polarization time constant.

[0042] It should be noted that the sampling interval of the control cycle needs to be determined in conjunction with the battery's dynamic response speed and hardware processing capabilities, and is usually set to 10 to 100 milliseconds. The polarization time constant reflects the battery's dynamic response characteristics. Adjusting it proportionally based on this constant current allows the actual current to gradually approach the target current, avoiding drastic fluctuations in battery terminal voltage caused by sudden current changes. The pre-deceleration factor is a coefficient that changes with the cumulative time of the constant current stage. Its value is initially 1, and as the cumulative time of the constant current stage gradually approaches the moment of switching from constant current to constant voltage, the value gradually decreases to 0, intuitively reflecting the control logic that the closer to the switching moment, the stronger the current deceleration. The purpose of setting the upper limit of the current change slope is to limit the rate of current rise and fall. That is, in the early stage of the constant current stage, the pre-deceleration factor is 1, and the upper limit of the slope is relatively large, so the current can track the target current relatively quickly. As time approaches the switching moment (the terminal voltage gradually approaches the upper limit of the voltage), the pre-deceleration factor decreases, the upper limit of the slope decreases accordingly, and the rate of current change slows down, avoiding the terminal voltage from suddenly exceeding the upper limit of the voltage due to excessively rapid current changes, thereby suppressing voltage overshoot and ensuring that the battery is not damaged by overvoltage.

[0043] In one embodiment of the present invention, when the current terminal voltage is detected to be greater than or equal to the upper voltage limit, the charging control mode of the module is immediately switched from constant current control to constant voltage control; the actual current at the moment before switching to constant voltage control is recorded, and the minimum value between the actual current at the moment before switching and the constant voltage starting current is taken as the constant voltage inlet current.

[0044] It should be noted that when the battery terminal voltage reaches the safe upper limit, the charging control mode should be immediately switched from constant current to constant voltage to prevent the terminal voltage from continuing to rise and avoid overvoltage damage to the battery. The constant voltage inlet current is the initial charging current value set when the battery switches from the constant current stage to the constant voltage stage. This ensures that the current will not overshoot in the early stage of the constant voltage stage and maintains the stability of the charging process. The minimum value is taken from the actual current at the moment before the switch and the constant voltage inlet current. This avoids the current from exceeding the actual current before the switch at the moment of switch, prevents voltage fluctuations caused by sudden current changes, and also avoids the current from exceeding the constant voltage inlet current calculated based on the battery characteristics (which meets the current tolerance capability of the battery in the constant voltage stage).

[0045] In one embodiment of the present invention, the cutoff current of the slave module is obtained by multiplying the constant voltage starting current by the natural exponent -1; a starting point of a continuous detection window is selected, and the maximum value of the actual current during the time period from the starting point to the sum of the starting point and the polarization time constant is calculated; if the maximum value is less than or equal to the cutoff current, the slave module is determined to be fully charged.

[0046] It should be noted that the cutoff current is the current threshold used to determine whether the battery is close to full charge during the constant voltage stage. This value matches the battery's polarization characteristics and reflects the critical value when the current decays to a reasonably low level during the constant voltage stage. The starting point of the continuous detection window can be selected from the moment the current first drops to near the cutoff current during the constant voltage stage, avoiding misjudgment due to selecting the starting point too early. The duration of the window is fixed to the polarization time constant, because the polarization time constant reflects the time scale of battery polarization decay. Using this duration ensures that the window can cover the complete cycle of the current being stable at a low level, avoiding misjudgment of full charge due to occasional current fluctuations caused by an excessively short window. The charging current during the constant voltage stage will gradually decrease as the battery's state of charge increases. When the maximum value of the actual current is less than or equal to the cutoff current during the time period from the starting point to the starting point plus the polarization time constant, it indicates that the current has stabilized at a low level and no longer shows significant fluctuations or rebounds. This means that the remaining battery capacity is close to full charge, and the polarization has basically decayed. Continuing to charge will have limited capacity improvement and may increase the risk of overcharging. Therefore, at this point, the battery is judged to be fully charged, which is in line with the battery's electrochemical characteristics and safe charging requirements.

[0047] In one embodiment of the present invention, when it is determined that the module is fully charged, the target current of the slave module is set to 0, and the original current quota allocated to the slave module is recovered to the bus current budget and awaits reallocation; the time of the previous quota issuance is recorded, and the quota holding time of the slave module is obtained, which is the same as the constant voltage tail duration of the slave module and the same as the polarization time constant of the slave module; when the current time is greater than or equal to the sum of the time of the previous quota issuance and the quota holding time, the process returns to step S104, and the process returns to the online monitoring stage.

[0048] It's important to note that setting the target current to 0 is to stop charging fully charged batteries, preventing overcharging that could damage battery life or cause safety issues. Reclaiming the originally allocated current quota from the bus current budget allows this idle current to be reallocated back into the system's allocable resources. This allows the master module to allocate it to other slave modules that are not fully charged in subsequent quota allocations, improving bus current utilization, preventing current waste, and ultimately enhancing the overall charging throughput efficiency of the charging system.

[0049] It should be noted that the three values ​​of quota holding time, constant voltage tail duration, and polarization time constant are the same because they are all determined based on the polarization characteristics of the battery. The polarization time constant comes from the micro-pulse identification in step S102 and reflects the time scale of battery polarization establishment and decay. The constant voltage tail duration comes from step S103 and is set based on the polarization time constant to match the current decay period in the constant voltage stage. The quota holding time comes from step S104 and is set based on the constant voltage tail duration to ensure that the effective period of the quota matches the duration of the battery charging stage (especially the constant voltage stage), avoiding frequent quota adjustments caused by the mismatch between the quota period and the battery state change period, and maintaining the stability of the charging process.

[0050] It should be noted that when the current time reaches or exceeds the deadline, regardless of whether the module is fully charged, the system must return to the online monitoring stage. That is, the online monitoring stage will re-detect key information such as the battery's presence status, current terminal voltage, and state of charge to confirm whether the battery status has changed (e.g., whether it is still in place or whether an anomaly has occurred). Based on the updated battery status, the main module will trigger the next round of quota calculation and distribution in step S104 to ensure that the quota allocation can adapt to the dynamic changes in battery status and maintain the rationality and safety of the entire charging system scheduling.

[0051] It should be noted that the interval and threshold sizes are set for ease of comparison. The size of the threshold depends on the amount of sample data and the base number set by those skilled in the art for each set of sample data, as long as it does not affect the proportional relationship between the parameter and the quantized value. Furthermore, the above formulas are all dimensionless calculations, and the formulas are derived from software simulations using a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0052] The embodiments of this example have been described above. However, this example is not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms based on the guidance of this example, and all of them are within the protection scope of this example.

Claims

1. A multi-stage charging optimization method based on adaptive battery identification, characterized in that, Includes the following steps: Step S101: By performing in-situ detection and battery type identification, obtain the voltage upper limit, rated capacity, temperature and pressure safety range, Joule heating power upper limit, initial state of charge, and bus current budget. Step S102: During the pre-charge stage, a current step is applied to the battery and the voltage response is collected. The equivalent instantaneous internal resistance, polarization internal resistance, polarization time constant, and DC internal resistance are calculated. Step S103: Under a given constant current, predict the change of the terminal voltage over time to obtain the switching time from constant current to constant voltage, and determine the constant voltage start current, cut-off current, constant voltage tail duration and constant voltage percentage. In step S104, the main module generates the quota current according to the constant voltage ratio and the bus current budget, calculates the voltage limiting current and the power limiting current, takes the minimum value as the safety limiting current, sends it as the target current, and sets the quota holding time as the constant voltage tail segment duration. Step S105: The module adopts a first-order following strategy to the target current. The pre-deceleration factor is determined according to the constant current to constant voltage switching time. When the actual terminal voltage reaches the upper voltage limit, the constant voltage is switched to constant voltage, and the constant voltage inlet current is clamped with the constant voltage starting current. In step S106, during the constant voltage stage, the system determines that the battery is fully charged based on the cutoff current and polarization time constant, generates a quota recovery instruction, and returns to step S104 for redistribution.

2. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, The system acquires the terminal voltage at the moment the battery is powered on, inputs the open-circuit voltage corresponding to the battery type and the inverse function of the state of charge function to obtain the initial state of charge of the battery, and receives the bus current budget from the main module through a half-duplex bus.

3. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, Step S102 includes the following steps: Step S201: The difference between the battery terminal voltage at any time after the current step is applied and the battery terminal voltage at the instant the current step is applied is the first voltage change; the difference between the battery terminal voltage at the sampling time at the end of the micro-pulse identification window and the battery terminal voltage at the instant the current step is applied is the second voltage change. Step S202: Divide the difference between the battery terminal voltage at the instant the current step is applied and the battery terminal voltage before the current step is applied by the magnitude of the current step to obtain the equivalent instantaneous internal resistance. Step S203: Divide the second voltage change by the amplitude of the current step to obtain the polarization internal resistance; Step S204: Take the negative of the difference between the two sampling times as the numerator, divide the difference between the second voltage change and the first voltage change at the second sampling time by the difference between the second voltage change and the first voltage change at the first sampling time, and take the natural logarithm of the resulting ratio as the denominator. Divide the numerator by the denominator to obtain the polarization time constant. Step S205: Divide the difference between the battery terminal voltage at the second sampling time and the battery terminal voltage at the first sampling time by the amplitude of the current step to obtain the DC internal resistance.

4. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, First, the initial state of charge is added to the product of the provisional constant current and time, divided by the rated capacity, and used as the input to the open-circuit voltage and state of charge function to obtain the first term. The product of the provisional constant current and the equivalent instantaneous internal resistance is calculated to obtain the second term. The product of the provisional constant current and the polarization internal resistance is calculated, and then this product is multiplied by 1 and the difference between the negative time of the natural exponent and the polarization time constant is subtracted to obtain the third term. The three terms are added together to obtain the terminal voltage at any time. The time when the terminal voltage equals the upper voltage limit is obtained, and this time is used as the constant current to constant voltage switching time.

5. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, Determining the constant voltage start current, cutoff current, constant voltage tail duration, and constant voltage percentage includes the following steps: Step S301: The initial state of charge is added to the product of the provisional constant current and the constant current to constant voltage switching time, and then divided by the rated capacity to obtain the state of charge at the constant current to constant voltage switching time. Step S302: Subtract the terminal voltage under charged state at the moment of constant current to constant voltage switching from the upper voltage limit to obtain the voltage difference. Then divide the voltage difference by the sum of the equivalent instantaneous internal resistance and the polarization internal resistance to obtain the constant voltage starting current. Step S303: Multiply the constant voltage starting current by the value of the natural exponent negative one to obtain the cutoff current. Step S304: Set the value of the constant voltage tail segment duration to be the same as the value of the polarization time constant to obtain the constant voltage tail segment duration. Step S305: Divide the constant voltage tail segment duration by the sum of the constant current to constant voltage switching time and the constant voltage tail segment duration to obtain the constant voltage ratio.

6. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, Step S104 includes the following steps: Step S401: Subtract the constant voltage ratio of each slave module from 1 to obtain the quota weight of each slave module; Step S402: For each slave module, the bus current budget is multiplied by the ratio of the slave module's quota weight to the sum of the quota weights of all slave modules to obtain the quota current of that slave module. Step S403: For each slave module, subtract the current terminal voltage of the slave module from the upper voltage limit, and then divide the difference by the sum of the equivalent instantaneous internal resistance and polarization internal resistance of the slave module to obtain the voltage limiting current of the slave module. Step S404: For each slave module, divide the upper limit of the Joule heating power of the slave module by the DC internal resistance of the slave module, and then calculate the square root of the quotient to obtain the power limiting current of the slave module. Step S405: For each slave module, select the minimum value from the quota current, voltage limiting current and power limiting current of the slave module, take the minimum value as the safe limiting current of the slave module, and set it as the target current to be sent to the corresponding slave module. Step S406: For each slave module, set the quota holding time of the slave module to be the same as the constant voltage tail duration of the slave module, and the constant voltage tail duration is the same as the polarization time constant of the slave module.

7. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, The first-order following strategy involves real-time acquisition of the current actual current from the module, adding the current actual current to the quotient of the sampling interval of the control cycle divided by the polarization time constant, and then multiplying it by the difference between the target current and the current actual current to obtain the actual current for the next control cycle.

8. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, Subtract the cumulative time of the constant current stage from 1 and divide by the quotient of the constant current to constant voltage switching time. If the result is less than 0, take 0 to obtain the pre-deceleration factor. Set an upper limit for the slope of the current change. The upper limit is the pre-deceleration factor multiplied by the difference between the upper limit of the voltage and the current terminal voltage, and then divided by the product of the equivalent instantaneous internal resistance and the polarization time constant.

9. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, When the current terminal voltage is detected to be greater than or equal to the upper voltage limit, the charging control mode of the module will be immediately switched from constant current control to constant voltage control. The actual current at the moment before switching to constant voltage control is recorded, and the minimum value between the actual current at the moment before switching and the constant voltage starting current is taken as the constant voltage input current.

10. The multi-stage charging optimization method based on adaptive battery identification according to claim 1, characterized in that, Obtain the cutoff current of the slave module, which is obtained by multiplying the constant voltage starting current by the natural exponent -1; select the starting point of a continuous detection window, and calculate the maximum value of the actual current in the time period from the starting point to the sum of the starting point and the polarization time constant; if the maximum value is less than or equal to the cutoff current, the slave module is determined to be fully charged. Once the module is determined to be fully charged, the target current of the slave module is set to 0, and the original current quota allocated to the slave module is recovered to the bus current budget, awaiting reallocation; the time of the previous quota issuance is recorded, and the quota holding time of the slave module is obtained, which is the same as the constant voltage tail duration of the slave module and the same as the polarization time constant of the slave module; when the current time is greater than or equal to the sum of the time of the previous quota issuance and the quota holding time, the process returns to step S104, and the process returns to the online monitoring stage.

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