A vehicle-mounted lithium battery adaptive management and control method based on constant temperature calibration and dynamic filtering

Abstract

The application provides a vehicle-mounted lithium battery adaptive control method based on constant temperature calibration and dynamic filtering. The first allowable current is constrained by a physical limit voltage and a physical limit current, and basic protection can be formed when serious overcurrent or single battery voltage is too low. The second allowable current can limit the current before the end voltage breaks the safety bottom line by feedforward calculation and dynamic correction of voltage drop risk. The third allowable current is constrained based on the heat accumulation state, which can inhibit the internal temperature rise in the continuous starting process. Finally, the minimum value of the three is taken as the current maximum allowable discharge current, so that the output current is limited by the physical limit, voltage safety and thermal management conditions, thereby balancing the starting capacity and battery safety, and improving the adaptability in low temperature starting, aged battery and continuous starting scenarios.

Description

Technical Field

[0001] This application relates to the field of vehicle battery management, specifically to an adaptive control method for vehicle lithium batteries based on constant temperature calibration and dynamic filtering. Background Technology

[0002] Lithium-ion batteries for vehicle starting are primarily used to provide a large instantaneous current to the starting load during vehicle startup. Unlike ordinary energy storage or low-rate discharge scenarios, vehicle startup is characterized by large discharge current, short duration, rapid current rise, and significant changes in ambient temperature. In low-temperature environments, during repeated starts, in battery aging scenarios, or in applications involving the reuse of cells, the battery's discharge capacity will change significantly with variations in open-circuit voltage, equivalent internal resistance, temperature state, and the consistency of individual cells in each string.

[0003] Existing automotive lithium battery management systems typically employ fixed current and voltage thresholds for protection. When a vehicle starts and generates a large current, the battery terminal voltage drops rapidly due to ohmic voltage drop, transient voltage drop, and polarization voltage drop. If the battery management system relies solely on a fixed undervoltage threshold to determine whether to cut off the output, it may misinterpret normal transient voltage drops during startup as undervoltage faults, leading to premature output cutoff and impacting startup success rate. Conversely, reducing undervoltage protection sensitivity to minimize false alarms may result in insufficient protection when the actual cell voltage is too low, internal resistance is increased, or connections are abnormal, increasing the risk of cell over-discharge and damage.

[0004] Meanwhile, when a vehicle's starting lithium battery is started multiple times in a short period, heat gradually accumulates inside the cell. Existing methods mostly rely on external temperature sampling or simple temperature thresholds for protection, which are difficult to accurately reflect the equivalent temperature rise inside the cell. Especially after a high-current pulse discharge, there is a lag between the internal temperature of the cell and the externally sampled temperature. If the heat accumulation state cannot be recursively judged by combining the discharge current and equivalent internal resistance, it is easy to encounter a situation where the internal temperature rise is already high but the system has not yet limited the current, thereby affecting the cell's lifespan and operational safety.

[0005] Furthermore, as the usage time of automotive lithium batteries increases, the open-circuit voltage and equivalent internal resistance of the cells will change with the degree of aging, state of charge, and temperature conditions. For cells used in secondary applications, the differences in equivalent internal resistance and remaining discharge capacity between different cells are even more pronounced. If fixed factory parameters and uniform thresholds are still used for control, it is difficult to take into account the differences between cells in each string, which may result in situations where strong cells still have a margin of safety while weak cells are already close to the risk threshold. Summary of the Invention

[0006] In view of the above problems, this application provides an adaptive control method for vehicle lithium batteries based on constant temperature calibration and dynamic filtering, so as to solve the problems of existing vehicle lithium battery management methods relying on fixed thresholds, which are prone to false start-up protection, insufficient undervoltage protection and uncontrolled heat accumulation.

[0007] To achieve the above objectives, the inventors provide an adaptive control method for vehicle-mounted lithium batteries based on isothermal calibration and dynamic filtering, comprising:

[0008] The calibration parameters of the vehicle lithium battery under different ambient temperatures are obtained, and the open circuit voltage parameters and equivalent internal resistance of the battery are updated by dynamic filtering after the charging and discharging are completed.

[0009] The real-time terminal voltage of each cell in the string of the vehicle lithium battery and the real-time discharge current of the battery are collected. Based on the real-time terminal voltage and real-time discharge current, and constrained by the physical limit voltage and physical limit current, the first allowable current is obtained.

[0010] Based on the open-circuit voltage parameters, the equivalent internal resistance, and the calibration parameters, feedforward calculation is performed with the goal of ensuring that the real-time terminal voltage is not lower than the preset safety voltage floor. The preset voltage drop safety margin is dynamically corrected based on the real-time terminal voltage and the real-time discharge current to obtain the second allowable current.

[0011] Based on the real-time discharge current, the equivalent internal resistance, and the calibration parameters, and with the constraint that the battery thermal accumulation state does not exceed the preset thermal management conditions, a third allowable current is obtained.

[0012] The minimum value among the first allowable current, the second allowable current, and the third allowable current is determined as the current maximum allowable discharge current, and the output of the vehicle lithium battery is controlled according to the current maximum allowable discharge current.

[0013] Unlike existing technologies, the above-mentioned solution first obtains the calibration parameters of the vehicle-mounted lithium battery under different ambient temperatures. After charging and discharging, it updates the battery's open-circuit voltage parameters and equivalent internal resistance through dynamic filtering. This allows subsequent current control to no longer rely on fixed factory thresholds, but instead to make judgments based on the current cell charge status, aging status, and temperature conditions. When the cell's equivalent internal resistance increases or its open-circuit voltage decreases due to low temperature, aging, or a decrease in charge, the system can adjust the allowable discharge current accordingly based on the updated parameters. This reduces the problems of insufficient undervoltage protection or false protection activation that are prone to occur under fixed threshold control.

[0014] This invention obtains a first allowable current, a second allowable current, and a third allowable current during the start-up discharge process, and takes the minimum of these three as the current maximum allowable discharge current. The first allowable current is constrained by the physical limit voltage and the physical limit current, enabling timely limitation or disconnection of the output in cases of severe overcurrent or when the voltage of any single cell in the string falls below the physical limit voltage. The second allowable current aims to ensure that the real-time terminal voltage does not fall below a preset safety voltage floor, actively constraining voltage drop risk through feedforward calculation and dynamic correction. The third allowable current is constrained by ensuring that the battery's thermal accumulation does not exceed preset thermal management conditions, limiting heat accumulation during continuous start-up. Therefore, this invention can jointly constrain the output current of the vehicle-mounted lithium battery from three aspects: physical limits, voltage safety, and thermal management, improving safety and adaptability in vehicle start-up scenarios.

[0015] When determining the second allowable current, this invention performs feedforward calculations based on open-circuit voltage parameters, equivalent internal resistance, and calibration parameters. This allows for the pre-determining of a current range that meets voltage safety targets before the terminal voltage actually drops below the safety boundary. Simultaneously, it dynamically corrects the preset voltage drop safety margin based on real-time terminal voltage and real-time discharge current. When contact resistance changes, terminals become loose, sampling deviations occur, or the cell condition deviates from calibration conditions, the allowable current can be further adjusted according to the actual voltage drop state. Therefore, this invention can reduce false start-up cutoffs caused by simply fixing the undervoltage threshold and also reduce the risk of cell over-discharge due to undetected abnormal voltage drops.

[0016] This invention determines the battery's thermal accumulation state based on real-time discharge current, equivalent internal resistance, and calibration parameters when determining the third permissible current. This allows thermal management to no longer rely solely on external temperature thresholds but to incorporate constraints based on the actual heat generation during the discharge process. When a vehicle is started continuously within a short period, the heat inside the battery accumulates with multiple discharge processes. This invention can limit the current maximum permissible discharge current based on the thermal accumulation state, thereby reducing the risk of thermal damage caused by lag in internal cell temperature rise. This is beneficial for improving the lifespan of automotive lithium batteries and the reliability of continuous starting.

[0017] In summary, this invention, through the combination of constant temperature calibration, dynamic filtering, physical limit constraints, voltage feedforward and dynamic correction constraints, and thermal accumulation constraints, enables the output control of on-board lithium batteries to adapt to changes in ambient temperature, cell aging, charge status, and real-time discharge status, taking into account both start-up output capability and safety protection. It is especially suitable for complex on-board application scenarios such as low-temperature start-up, continuous start-up, aging cells, and cascade utilization cells. Attached Figure Description

[0018] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of the present invention and other related contents, and should not be considered as limitations on this application.

[0019] In the accompanying drawings of the instruction manual:

[0020] Figure 1 This is a flowchart of an adaptive control method for vehicle-mounted lithium batteries based on isothermal calibration and dynamic filtering, as shown in the embodiment. Detailed Implementation

[0021] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0022] An adaptive control method for vehicle-mounted lithium batteries based on isothermal calibration and dynamic filtering includes:

[0023] The calibration parameters of the vehicle lithium battery under different ambient temperatures are obtained, and the open circuit voltage parameters and equivalent internal resistance of the battery are updated by dynamic filtering after the charging and discharging are completed.

[0024] The real-time terminal voltage of each cell in the string of the vehicle lithium battery and the real-time discharge current of the battery are collected. Based on the real-time terminal voltage and real-time discharge current, and constrained by the physical limit voltage and physical limit current, the first allowable current is obtained.

[0025] Based on the open-circuit voltage parameters, the equivalent internal resistance, and the calibration parameters, feedforward calculation is performed with the goal of ensuring that the real-time terminal voltage is not lower than the preset safety voltage floor. The preset voltage drop safety margin is dynamically corrected based on the real-time terminal voltage and the real-time discharge current to obtain the second allowable current.

[0026] Based on the real-time discharge current, the equivalent internal resistance, and the calibration parameters, and with the constraint that the battery thermal accumulation state does not exceed the preset thermal management conditions, a third allowable current is obtained.

[0027] The minimum value among the first allowable current, the second allowable current, and the third allowable current is determined as the current maximum allowable discharge current, and the output of the vehicle lithium battery is controlled according to the current maximum allowable discharge current.

[0028] As described above, by using calibration parameters, open-circuit voltage parameters obtained through dynamic filtering, and equivalent internal resistance as the basis for current control, the output control of the vehicle lithium battery no longer relies on fixed factory thresholds but can instead make judgments based on current temperature, charge status, and aging status. The first allowable current is constrained by the physical limit voltage and physical limit current, providing basic protection against severe overcurrent or low cell voltage. The second allowable current, through feedforward calculation and dynamic correction of voltage drop risk, proactively limits the current before the terminal voltage falls below the safety threshold. The third allowable current is constrained based on the thermal accumulation state, suppressing internal temperature rise during continuous startup. Finally, the minimum value among these three is taken as the current maximum allowable discharge current, ensuring that the output current is simultaneously limited by physical limits, voltage safety, and thermal management conditions. This balances startup capability and battery safety, improving adaptability in low-temperature startup, aged cells, and continuous startup scenarios.

[0029] In some embodiments, obtaining the calibration parameters of the vehicle-mounted lithium battery under different ambient temperatures includes:

[0030] The vehicle lithium battery is placed at multiple preset ambient temperature levels and kept at a constant temperature until thermal equilibrium is reached.

[0031] A pulsed discharge current simulating vehicle startup conditions is applied at each of the aforementioned ambient temperature settings;

[0032] The voltage, current, and temperature changes under the action of the pulsed discharge current are collected.

[0033] Based on the voltage, current, and temperature changes, determine the voltage compensation parameters, thermal management parameters, and safety threshold parameters for the corresponding ambient temperature setting, and store these parameters as calibration parameters.

[0034] As described above, by calibrating the vehicle lithium battery under constant temperature and pulse discharge conditions at multiple ambient temperature levels, the calibration parameters can cover the voltage, current, and temperature variations under different temperatures. Since the battery discharge capacity during vehicle startup is significantly affected by ambient temperature—internal resistance increases and polarization intensifies at low temperatures, while thermal safety margin decreases at high temperatures—using only ambient temperature parameters can easily lead to judgment errors. Therefore, by simulating vehicle startup conditions at each ambient temperature level, voltage compensation parameters, thermal management parameters, and safety threshold parameters that more closely reflect the actual startup process can be obtained.

[0035] Specifically, the voltage compensation parameters include a first compensation parameter for characterizing the transient voltage drop caused by current changes, and a second compensation parameter for characterizing the voltage drop change caused by temperature changes;

[0036] The feedforward calculation includes:

[0037] The first compensation parameter and the second compensation parameter are determined from the voltage compensation parameters based on the current ambient temperature.

[0038] The first compensation parameter characterizes the transient voltage drop caused by the change in current, and the second compensation parameter characterizes the voltage drop caused by the change in temperature.

[0039] The dynamic voltage drop compensation amount is determined based on the first compensation parameter and the second compensation parameter;

[0040] Based on the open-circuit voltage parameters, the equivalent internal resistance, the dynamic voltage drop compensation, and the preset safety voltage floor, the feedforward allowable current that meets the voltage safety target is calculated.

[0041] As described above, the voltage compensation parameters are further defined as a first compensation parameter and a second compensation parameter. The first compensation parameter characterizes the transient voltage drop caused by current changes, while the second compensation parameter characterizes the voltage drop caused by temperature changes. During vehicle startup, the current rises rapidly, and the voltage drop is not solely caused by the equivalent internal resistance but is also affected by transient voltage drops, polarization changes, and temperature variations. By determining the first and second compensation parameters based on the current ambient temperature and obtaining the dynamic voltage drop compensation amount accordingly, the feedforward calculation can more closely approximate the voltage changes during actual discharge. Furthermore, by back-calculating the allowable feedforward current based on the open-circuit voltage parameter, equivalent internal resistance, dynamic voltage drop compensation amount, and preset safe voltage floor, the safe current range can be determined in advance before the actual discharge current becomes excessive. This reduces the risk of the voltage dropping below the safe floor at startup and minimizes false tripping or protection lag caused by fixed undervoltage protection.

[0042] Preferably, the step of dynamically correcting the preset voltage drop safety margin based on the real-time terminal voltage and real-time discharge current to obtain the second allowable current includes:

[0043] The voltage drop evaluation value is determined based on the open-circuit voltage parameters, the equivalent internal resistance, the real-time discharge current, and the dynamic voltage drop compensation.

[0044] Compare the voltage drop assessment value with the preset voltage drop safety margin;

[0045] If the voltage drop assessment value is higher than the preset voltage drop safety margin, then the feedforward allowable current is used as the second allowable current;

[0046] Otherwise, the feedforward allowable current is reduced according to the degree of deviation of the voltage drop assessment value from the preset voltage drop safety margin to obtain the second allowable current.

[0047] As described above, a dynamic correction process based on the voltage drop assessment value is added to the feedforward calculation. The allowable feedforward current is mainly calculated based on the open-circuit voltage parameters, equivalent internal resistance, and calibration parameters. However, in actual vehicle use, there may be situations such as loose connectors, sudden increases in contact resistance, sampling errors, or cell conditions exceeding the calibration range. Relying solely on feedforward calculation may not be sufficient to cover all anomalies in a timely manner. By determining the voltage drop assessment value based on the open-circuit voltage parameters, equivalent internal resistance, real-time discharge current, and dynamic voltage drop compensation, and comparing it with the preset voltage drop safety margin, the system can determine in real time whether the current voltage drop status is still within the safe range. When the voltage drop assessment value is insufficient, the system reduces the allowable feedforward current according to the degree of deviation, allowing the second allowable current to dynamically change with the actual voltage drop risk. This improves the robustness of voltage safety constraints and avoids excessively low terminal voltage caused by model deviations or connection abnormalities.

[0048] And, reducing the feedforward allowable current according to the degree of deviation of the voltage drop assessment value from the preset voltage drop safety margin includes:

[0049] The voltage drop assessment value is compared with the preset voltage drop safety margin to obtain the voltage drop margin deviation;

[0050] The current reduction amount is determined based on the voltage drop margin deviation.

[0051] Based on the current reduction amount, the second allowable current of the previous control cycle is reduced to obtain the second allowable current of the current control cycle;

[0052] When the voltage drop assessment value meets the preset voltage drop safety margin again, the reduction of the second allowable current is stopped.

[0053] As described above, the method for adjusting the second allowable current is further defined. First, the voltage drop margin deviation is obtained; then, the current reduction amount is determined based on the voltage drop margin deviation; and finally, the second allowable current of the previous control cycle is reduced based on this current reduction amount. This method ensures that the adjustment of the second allowable current is no longer a simple fixed-step process, but rather matches the current voltage drop risk level. When the voltage drop assessment value is significantly lower than the preset voltage drop safety margin, the voltage drop margin deviation is large, and the system can correspondingly increase the current reduction amount to bring the battery terminal voltage back to the safe range as quickly as possible. When the deviation is small, the reduction amount is small, which can avoid excessive current reduction affecting the starting capability. Simultaneously, stopping the reduction of the second allowable current when the voltage drop assessment value again meets the preset voltage drop safety margin can prevent the continuous current drop from causing an unnecessary reduction in output capability, thus achieving a better balance between safety protection and starting output.

[0054] In some implementations, obtaining the third allowable current based on the real-time discharge current, the equivalent internal resistance, and the calibration parameters, with the battery thermal accumulation state not exceeding preset thermal management conditions, includes:

[0055] The heat generated in the current control cycle is calculated based on the real-time discharge current collected during the current control cycle and the equivalent internal resistance.

[0056] Based on the thermal management parameters in the calibration parameters, the heat generated is recursively processed with heat dissipation attenuation to obtain the battery thermal accumulation state.

[0057] The equivalent internal temperature of the battery is determined based on the battery thermal accumulation state and the ambient temperature.

[0058] When the equivalent internal temperature of the battery reaches the preset thermal management soft threshold, the third allowable current of the previous control cycle is reduced in a stepwise manner to obtain the third allowable current of the current control cycle.

[0059] When the equivalent internal temperature of the battery reaches the preset thermal management upper limit, the third allowable current of the current control cycle is set to zero.

[0060] As described above, the heat generated in the current control cycle is calculated using real-time discharge current and equivalent internal resistance. This heat is then recursively processed with heat dissipation attenuation, combining the thermal management parameters from the calibration parameters. This allows the system to obtain a reflection of the battery's thermal accumulation state during continuous startup. Although the on-board starting current has a short duration, its peak value is high. If the interval between multiple startups is short, the heat generated by the previous startup may not be fully dissipated, leading to further heat accumulation in subsequent startups. By determining the battery's equivalent internal temperature based on the thermal accumulation state and ambient temperature, the system can more accurately approximate the internal thermal state of the cell than relying solely on external temperature sampling. When the equivalent internal temperature reaches a preset thermal management soft threshold, the third allowable current is gradually reduced to decrease the heat generation intensity. When the preset thermal management upper limit is reached, the third allowable current is set to zero to promptly prevent further discharge, reducing thermal damage and safety risks.

[0061] Specifically, the thermal management parameters include heat dissipation time parameters during the heating phase and heat dissipation time parameters during the cooling phase;

[0062] When the vehicle lithium battery is in the start-up discharge state, the heat dissipation time parameter of the heating stage is used to recursively calculate the battery thermal accumulation state.

[0063] When the vehicle-mounted lithium battery is in a static or cooling state after discharge, the heat dissipation time parameter of the cooling stage is used to recursively calculate the battery thermal accumulation state.

[0064] As described above, thermal management parameters are categorized into heat dissipation time parameters for the heating phase and heat dissipation time parameters for the cooling phase. Different parameters are selected based on the state of the on-board lithium battery to recursively deduce the battery's thermal accumulation state. During battery start-up discharge, the battery undergoes a heating process involving both heat generation and dissipation. After discharge, the static or cooling state primarily reflects heat diffusion outwards, and the rates of heat change differ between the two states. Using a single heat dissipation parameter can easily underestimate or overestimate the internal temperature of the cell during continuous startup. By using heat dissipation time parameters for the heating phase during start-up discharge and heat dissipation time parameters for the cooling phase during static or cooling states, the heat accumulation and decay process can be described more accurately. This makes the calculated equivalent internal temperature of the battery more consistent with actual thermal changes, thereby improving the accuracy of the third allowable current step adjustment and recovery judgment, and reducing thermal management lag or excessive current limiting issues.

[0065] Preferably, the step of obtaining the third allowable current by constraining the battery thermal accumulation state to not exceed a preset thermal management condition further includes:

[0066] When the equivalent internal temperature of the battery is lower than the preset thermal management soft threshold, the third allowable current is maintained or gradually restored.

[0067] When the equivalent internal temperature of the battery reaches the preset thermal management soft threshold and is lower than the preset thermal management upper limit, the third allowable current is reduced in a stepwise manner.

[0068] When the equivalent internal temperature of the battery reaches the preset thermal management upper limit, the third allowable current is set to zero, and the output of the vehicle lithium battery is cut off.

[0069] As described above, the control method for the third allowable current is limited across different temperature ranges. When the battery's equivalent internal temperature is below the preset thermal management soft threshold, maintaining or gradually restoring the third allowable current ensures good start-up output capability when the battery is thermally safe. When the battery's equivalent internal temperature reaches the preset thermal management soft threshold but is below the preset thermal management upper limit, reducing the third allowable current in a stepped manner allows for a smooth decrease in discharge capability, avoiding sudden changes in usage caused by directly cutting off the output, while also reducing subsequent heat generation. When the battery's equivalent internal temperature reaches the preset thermal management upper limit, setting the third allowable current to zero and cutting off the output establishes a thermal safety protection boundary. This tiered approach ensures that thermal management is neither simply unrestricted nor immediately cut off upon reaching the soft threshold, but rather intervenes gradually based on the degree of thermal risk, thus balancing continuous start-up capability and thermal safety.

[0070] In some implementations, updating the battery's open-circuit voltage parameters and equivalent internal resistance through dynamic filtering after charging and discharging includes:

[0071] After charging and discharging are completed, allow the device to stand for a preset time.

[0072] Multiple voltage sampling points are collected during the resting process, and outlier values ​​are removed and averaged sequentially for the multiple voltage sampling points to obtain the open circuit voltage parameters.

[0073] During this charging and discharging process, multiple current change events are selected. The initial internal resistance value is calculated based on the voltage change and current change corresponding to each current change event. The multiple initial internal resistance values ​​are then filtered to obtain the equivalent internal resistance.

[0074] As described above, by allowing the battery to rest for a preset time after charging and discharging, and by removing outliers and averaging multiple voltage sampling points during the resting process, the acquisition of open-circuit voltage parameters can reduce the impact of polarization recovery and sampling noise. Since the instantaneous voltage after the start-up discharge does not accurately reflect the battery's stable state, directly using this instantaneous voltage for subsequent calculations can easily lead to an overestimation or underestimation of the feedforward allowable current. This embodiment also calculates the initial internal resistance value through multiple current change events and filters these initial internal resistance values ​​to obtain the equivalent internal resistance, avoiding distortion in internal resistance estimation caused by single current disturbances or sampling anomalies. By continuously updating the open-circuit voltage parameters and equivalent internal resistance, the system can adjust the current limit according to cell aging, charge changes, and temperature changes, improving the reliability of the calculation of the second and third allowable currents.

[0075] In some implementations, obtaining the first allowable current based on the real-time terminal voltage and real-time discharge current, constrained by the physical limit voltage and physical limit current, includes:

[0076] The real-time discharge current is compared with the physical limit current, and the real-time terminal voltage of any single cell in the string is compared with the physical limit voltage.

[0077] When the real-time discharge current exceeds the physical limit current, or when the real-time terminal voltage of any single cell in the string is lower than the physical limit voltage, the first allowable current is set to zero, and the output of the vehicle lithium battery is cut off.

[0078] When the real-time discharge current does not exceed the physical limit current, and the real-time terminal voltage of each individual cell in the string is not lower than the physical limit voltage, the first allowable current is determined as the physical limit current.

[0079] As described above, the method for determining the first allowable current is specifically defined, making the physical limit protection logic more explicit. By comparing the real-time discharge current with the physical limit current and comparing the real-time terminal voltage of any cell in a string with the physical limit voltage, both high-risk conditions such as severe overcurrent and severe undervoltage of a cell can be covered simultaneously. When the real-time discharge current exceeds the physical limit current, or the real-time terminal voltage of any cell in a string is lower than the physical limit voltage, the first allowable current is set to zero and the output is cut off, preventing the battery from continuing to discharge beyond the physical safety boundary. When neither the real-time discharge current nor the real-time terminal voltage of any cell in a string triggers the limit condition, the first allowable current is set as the physical limit current, allowing subsequent current control to be further constrained by the second and third allowable currents. This design uses physical limit protection as a basic safety boundary, ensuring that the system can stop output promptly under abnormal operating conditions.

[0080] Example 1:

[0081] Please refer to Figure 1 An adaptive control method for vehicle-mounted lithium batteries based on constant temperature calibration and dynamic filtering is proposed. In this embodiment, the vehicle-mounted lithium battery is a vehicle-mounted starting lithium battery composed of multiple strings of individual cells. The battery management system can collect the real-time terminal voltage of each string of individual cells, the real-time discharge current of the battery, and the ambient temperature, and can store the calibration parameters under different ambient temperatures.

[0082] For ease of explanation, the open-circuit voltage parameter of the nth individual unit is denoted as... The equivalent internal resistance of the nth monomer is denoted as . The real-time terminal voltage of the nth individual unit is denoted as The real-time discharge current of the battery is denoted as I, and the ambient temperature is denoted as... The equivalent internal temperature of the nth cell in the battery string is denoted as . The dynamic pressure drop compensation amount is recorded as The first permissible current is denoted as The second allowable current is denoted as The third permissible current is denoted as The current maximum allowable discharge current is denoted as .

[0083] S100 acquires the calibration parameters of the vehicle lithium battery under different ambient temperatures, and updates the open circuit voltage parameters and equivalent internal resistance of the battery through dynamic filtering after charging and discharging.

[0084] In this step, the calibration parameters of the vehicle lithium battery under different ambient temperatures are first obtained. The calibration parameters include voltage compensation parameters, thermal management parameters, and safety threshold parameters. At the same time, after each charge and discharge cycle, the open circuit voltage parameters and equivalent internal resistance of the vehicle lithium battery are updated by dynamic filtering, so that subsequent current control can be calculated based on the current battery state.

[0085] S110, the vehicle lithium battery is placed at multiple preset ambient temperature levels and kept at a constant temperature until thermal equilibrium is reached;

[0086] In some implementations, the vehicle-mounted lithium battery is placed in a constant temperature chamber with multiple preset ambient temperature settings, such as -10℃, 0℃, 10℃, 25℃, 35℃, and 45℃. At each ambient temperature setting, the vehicle-mounted lithium battery is kept at a constant temperature until thermal equilibrium is reached. Thermal equilibrium can be understood as the difference between the internal temperature of the battery cell, the temperature of the casing, and the ambient temperature being within a preset range, such as not exceeding 0.5℃.

[0087] S120 applies a pulsed discharge current simulating vehicle startup conditions at each ambient temperature setting;

[0088] At each ambient temperature setting, a pulsed discharge current simulating vehicle startup conditions is applied to the on-board lithium battery. This pulsed discharge current can include discharge pulses of different amplitudes, durations, and current change rates to simulate vehicle startup conditions such as low-temperature startup, normal-temperature startup, high-temperature startup, and continuous startup.

[0089] S130 collects voltage, current and temperature changes under pulsed discharge current and determines calibration parameters;

[0090] During pulse discharge, the terminal voltage, battery circuit current, ambient temperature, cell casing temperature, and cell core temperature of each cell in the string are collected. Based on the collected voltage, current, and temperature changes, the voltage compensation parameters, thermal management parameters, and safety threshold parameters for the corresponding ambient temperature settings are determined and stored as calibration parameters.

[0091] The voltage compensation parameters include a first compensation parameter and a second compensation parameter. The first compensation parameter characterizes the transient voltage drop caused by current changes, and the second compensation parameter characterizes the voltage drop caused by temperature changes.

[0092] S140, after charging and discharging are completed, is left to stand for a preset time and multiple voltage sampling points are collected;

[0093] After the vehicle-mounted lithium battery completes one charge or discharge cycle, it is allowed to rest for a preset time to reduce the impact of polarization voltage on the sampling results. During the resting period, multiple voltage sampling points are collected for each cell in each string, and outlier values ​​are sequentially removed and averaged to obtain the open-circuit voltage parameters of the corresponding cells in the string.

[0094] The open-circuit voltage parameter of the nth individual unit can be expressed as:

[0095]

[0096] in, Let L represent the iii-th voltage sampling point acquired by the nth individual unit during the resting phase, where L represents the number of valid sampling points. This represents the voltage value after median filtering of the voltage values ​​within the sampling window.

[0097] S150, selects multiple current change events during this charge and discharge process and calculates the equivalent internal resistance;

[0098] During this charge-discharge process, multiple current change events are selected, and the initial internal resistance value is calculated based on the voltage and current changes corresponding to each current change event. The initial internal resistance value of the nth cell in the j-th current change event can be expressed as:

[0099]

[0100] in, This represents the voltage change of the nth individual cell during the j-th current change event. This represents the amount of current change in the j-th current change event.

[0101] After obtaining multiple initial internal resistance values, outliers can be removed, and the equivalent internal resistance of the nth unit can be obtained by median filtering or recursive averaging.

[0102]

[0103] Where m represents the number of effective current change events. Through the above dynamic filtering process, the open-circuit voltage parameters and equivalent internal resistance can be updated as the battery's state of charge, aging state, and temperature state change.

[0104] S200 collects the real-time terminal voltage of each cell in the string of the vehicle lithium battery and the real-time discharge current of the battery. Based on the real-time terminal voltage and real-time discharge current, and constrained by the physical limit voltage and physical limit current, the first allowable current is obtained.

[0105] In this step, the first allowable current is used to characterize the allowable discharge current under physical limit constraints. The physical limit voltage and physical limit current can be determined based on cell specifications, power device capabilities, and battery pack safety design.

[0106] S210 compares the real-time discharge current with the physical limit current and compares the real-time terminal voltage of any single cell in the string with the physical limit voltage.

[0107] During each control cycle, the real-time discharge current I of the battery is acquired, and the real-time terminal voltage of each cell in the string is also acquired. The real-time discharge current I is compared with the physical limiting current. Compare the values ​​and simultaneously set the real-time terminal voltage of any individual unit in the string. With physical limit voltage Compare them.

[0108] S220, when the physical limit condition is triggered, sets the first allowable current to zero and cuts off the output.

[0109] When the real-time discharge current exceeds the physical limit current, or the real-time terminal voltage of any single cell in the string is lower than the physical limit voltage, the first allowable current is set to zero, and the output of the vehicle lithium battery is cut off.

[0110]

[0111] This method enables output cutoff to be triggered by severe overcurrent and severe undervoltage of individual cells, thus forming basic safety protection.

[0112] S230, when the physical limit condition is not triggered, the first allowable current is determined as the physical limit current.

[0113] When the real-time discharge current does not exceed the physical limit current, and the real-time terminal voltage of each individual cell in the string is not lower than the physical limit voltage, the first allowable current is determined as the physical limit current.

[0114]

[0115] At this point, the first allowable current serves as the upper limit at the physical limit level, while the second and third allowable currents further constrain voltage safety and thermal management.

[0116] S300 performs feedforward calculations based on open-circuit voltage parameters, equivalent internal resistance, and calibration parameters, with the goal of ensuring that the real-time terminal voltage is not lower than the preset safety voltage floor. It also dynamically corrects the preset voltage drop safety margin based on the real-time terminal voltage and real-time discharge current to obtain the second allowable current.

[0117] In this step, the second allowable current is used to characterize the allowable discharge current under voltage safety constraints. The second allowable current includes two parts: feedforward calculation and dynamic correction. The feedforward calculation is used to estimate the current range that meets the voltage safety target in advance, and the dynamic correction is used to correct the feedforward result based on the actual voltage drop state.

[0118] S310, determine the first compensation parameter and the second compensation parameter from the voltage compensation parameters based on the current ambient temperature;

[0119] Based on the current ambient temperature Determine the first compensation parameter from the voltage compensation parameters in the calibration parameters. and the second compensation parameter The first compensation parameter characterizes the transient voltage drop caused by the change in current, and the second compensation parameter characterizes the voltage drop caused by the change in temperature.

[0120] S320 determines the dynamic pressure drop compensation amount based on the first compensation parameter and the second compensation parameter.

[0121] Based on the first compensation parameter, the second compensation parameter, the real-time discharge current change rate, and the battery's equivalent internal temperature change rate, determine the dynamic voltage drop compensation amount corresponding to the nth cell in the string:

[0122]

[0123] in, This represents the rate of change of the real-time discharge current. This represents the rate of change of the equivalent internal temperature of the nth cell in the battery.

[0124] S330, based on open-circuit voltage parameters, equivalent internal resistance, dynamic voltage drop compensation, and preset safety voltage floor, calculates the allowable feedforward current.

[0125] Based on the open-circuit voltage parameters of the nth individual unit Equivalent internal resistance Dynamic pressure drop compensation and preset safety voltage floor By reverse calculation, the allowable feedforward current corresponding to the nth individual unit is obtained:

[0126]

[0127] For multiple strings of individual cells, calculate the feedforward allowable current for each individual cell in each string, and take the minimum value as the feedforward allowable current for the entire vehicle lithium battery pack:

[0128]

[0129] This feedforward calculation allows us to determine the discharge current range that meets the voltage safety target under the current operating conditions before the terminal voltage actually drops below the safety boundary.

[0130] S340 determines the voltage drop evaluation value based on open-circuit voltage parameters, equivalent internal resistance, real-time discharge current, and dynamic voltage drop compensation.

[0131] During the start-up discharge process, the voltage drop evaluation value of the nth cell is determined based on the open-circuit voltage parameters, equivalent internal resistance, real-time discharge current, and dynamic voltage drop compensation.

[0132]

[0133] This voltage drop assessment value is used to reflect the remaining voltage state of the nth cell after deducting the internal resistance voltage drop and dynamic voltage drop under the current real-time discharge current.

[0134] S350 compares the voltage drop assessment value with the preset voltage drop safety margin;

[0135] The assessed voltage drop value is compared with the preset voltage drop safety margin. The safety judgment condition can be expressed as:

[0136]

[0137] in, This indicates the preset pressure drop safety margin related to ambient temperature.

[0138] S360: When the voltage drop assessment value meets the preset voltage drop safety margin, the feedforward allowable current is used as the second allowable current;

[0139] If the voltage drop assessment values ​​of each individual cell in the string all meet the above safety judgment conditions, it indicates that the current voltage drop state has a sufficient safety margin, and the feedforward allowable current can be used as the second allowable current.

[0140]

[0141] S370: When the voltage drop assessment value does not meet the preset voltage drop safety margin, the feedforward allowable current is dynamically corrected.

[0142] If the voltage drop assessment value of any individual cell in the string does not meet the above safety judgment conditions, the feedforward allowable current is reduced according to the degree of deviation of the voltage drop assessment value from the preset voltage drop safety margin. For the k-th control cycle, the feedback correction current limit value can be updated as follows:

[0143]

[0144] in, This represents the feedback correction current limiting value for the k-th control cycle. This represents the voltage drop assessment value for the k-th control cycle. The further it deviates from the safety boundary, the higher the voltage drop assessment value becomes. The smaller the value, the faster the corresponding feedback correction current limit value decreases.

[0145] Specifically, a preset voltage drop safety margin is provided. The values ​​can be referenced in the table below:

[0146]

[0147] Furthermore, the second allowable current can be the smaller value between the feedforward allowable current and the feedback correction current limit value:

[0148]

[0149] When the voltage drop assessment value meets the preset voltage drop safety margin again, the adjustment of the second allowable current can be stopped.

[0150] S400, based on real-time discharge current, equivalent internal resistance and calibration parameters, and constrained by the battery thermal accumulation state not exceeding the preset thermal management conditions, obtains the third allowable current.

[0151] In this step, the third allowable current is used to characterize the allowable discharge current under thermal management constraints. By calculating the heat generation using the real-time discharge current and equivalent internal resistance, and combining this with thermal management parameters for recursive processing with heat dissipation attenuation, the battery's thermal accumulation state can be obtained, and the battery's equivalent internal temperature can be further determined.

[0152] S410, calculate the heat generated in the current control cycle based on the real-time discharge current and equivalent internal resistance collected during the current control cycle;

[0153] For the nth single unit, the heat generation in the current control cycle can be expressed as:

[0154]

[0155] in, This represents the heat generated by the nth monomer in the current control cycle. Indicates the duration of the control cycle.

[0156] S420, based on the thermal management parameters in the calibration parameters, performs a recursive process on the heat generation with heat dissipation attenuation to obtain the battery thermal accumulation state;

[0157] Thermal management parameters include heat dissipation time parameters during the heating phase. and cooling phase heat dissipation time parameters .

[0158] When the vehicle-mounted lithium battery is in the start-up discharge state, the heat dissipation time parameter during the temperature rise stage is used to recursively estimate the battery's thermal accumulation state:

[0159]

[0160] When the vehicle-mounted lithium battery is in a static or cooling state after discharge, the battery's thermal accumulation state is recursively deduced using the heat dissipation time parameter during the cooling phase:

[0161]

[0162] in, This represents the battery thermal accumulation state of the nth cell in the kth control cycle.

[0163] S430 determines the equivalent internal temperature of the battery based on the battery's thermal accumulation state and ambient temperature.

[0164] Based on the battery thermal accumulation state, ambient temperature, and heat generation temperature rise conversion parameters, determine the equivalent internal temperature of the nth cell in the string:

[0165]

[0166] in, This represents the heat generation temperature rise conversion parameter related to ambient temperature.

[0167] In some implementations, the heat generation temperature rise conversion parameters can be obtained through factory temperature calibration:

[0168]

[0169] in, This represents the core temperature of the nth single-cell assembly measured during the calibration process.

[0170] During the cooling phase, a first-order cooling model can also be used to describe the decrease in the equivalent internal temperature of the battery:

[0171]

[0172] in, The value represents the equivalent internal temperature of the battery at the start of cooling, and t represents the cooling time.

[0173] The table below shows the safe temperature versus current limiting coefficient comparison:

[0174]

[0175] S440: When the battery's equivalent internal temperature is lower than the preset thermal management soft threshold, the third allowable current is maintained or gradually restored.

[0176] When the battery's equivalent internal temperature is lower than the preset thermal management soft threshold, it indicates that the current thermal accumulation state has not reached the level requiring current reduction, and the third allowable current can be maintained or gradually restored.

[0177] S450: When the battery's equivalent internal temperature reaches the preset thermal management soft threshold and is lower than the preset thermal management upper limit, the third allowable current is reduced in a stepwise manner.

[0178] When the battery's equivalent internal temperature reaches the preset thermal management soft threshold but is below the preset thermal management upper limit, the third allowable current of the previous control cycle is reduced in a stepwise manner.

[0179] The recursive control of the third allowable current can be expressed as:

[0180]

[0181] in, Indicates the step size of the descent. Indicates the restoration of step size. This indicates the temperature hysteresis range.

[0182] Furthermore, the recovery step size can be smaller than the current reduction step size to reduce frequent fluctuations of the third allowable current near the threshold during continuous startup:

[0183]

[0184] in, The recovery rate coefficient is, and ＜1 .

[0185] The upper limit of the third permissible current can be determined based on the physical limit current and the second permissible current:

[0186]

[0187] S460: When the battery's equivalent internal temperature reaches the preset thermal management upper limit, the third allowable current is set to zero.

[0188] When the battery's equivalent internal temperature reaches the preset thermal management upper limit, the third allowable current is set to zero, and the output of the vehicle's lithium battery is cut off.

[0189]

[0190] Through the thermal management processes of S410 to S460 described above, the third allowable current can be gradually reduced or restored according to the battery's thermal accumulation state, thereby actively constraining the internal temperature rise during continuous startup.

[0191] S500 determines the minimum value among the first allowable current, the second allowable current, and the third allowable current as the current maximum allowable discharge current, and controls the output of the vehicle lithium battery according to the current maximum allowable discharge current;

[0192] In this step, the minimum value among the first allowable current, the second allowable current, and the third allowable current is determined as the current maximum allowable discharge current:

[0193]

[0194] In some implementations, for multiple strings of individual cells, the maximum allowable discharge current for each individual cell in a string can be determined separately:

[0195]

[0196] Then, the minimum value among the individual cells in each string is taken as the current maximum allowable discharge current of the entire vehicle lithium battery pack:

[0197]

[0198] Subsequently, the output of the vehicle-mounted lithium battery is controlled according to the current maximum allowable discharge current, ensuring that the actual output current of the vehicle-mounted lithium battery does not exceed the current maximum allowable discharge current. When the current maximum allowable discharge current is zero, the output of the vehicle-mounted lithium battery is cut off.

[0199] After this initial discharge cycle, the vehicle's lithium battery returns to the resting phase and executes the dynamic filtering update of open-circuit voltage parameters and equivalent internal resistance in step S100 again. The updated open-circuit voltage parameters and equivalent internal resistance are stored and used to redetermine the first, second, and third allowable currents during the next initial discharge cycle.

[0200] Through the processes described above (S100 to S500), the output current of the vehicle-mounted lithium battery can be simultaneously constrained by physical limits, voltage safety, and thermal management conditions. Furthermore, it can be dynamically adjusted according to changes in ambient temperature, open-circuit voltage parameters, equivalent internal resistance, real-time terminal voltage, real-time discharge current, and thermal accumulation state, thereby achieving adaptive control in vehicle startup scenarios.

[0201] Example 2:

[0202] Based on Example 1, the open-circuit voltage parameters and equivalent internal resistance of the vehicle-mounted lithium battery have been updated through dynamic filtering after charging and discharging. Taking one of the cells in a string as an example, the open-circuit voltage parameters of this string of cells are:

[0203] .

[0204] The equivalent internal resistance obtained by dynamic filtering is:

[0205] .

[0206] The preset safe voltage floor is:

[0207] .

[0208] During the discharge initiation process, the dynamic voltage drop compensation amount can be determined based on the calibration parameters corresponding to the current ambient temperature.

[0209]

[0210] In this embodiment, the dynamic voltage drop compensation amount is:

[0211] .

[0212] The battery management system first performs feedforward calculations based on open-circuit voltage parameters, equivalent internal resistance, dynamic voltage drop compensation, and a preset safe voltage floor to obtain the allowable feedforward current that meets the voltage safety target:

[0213]

[0214] Since the equivalent internal resistance of the dynamic filter record is 2.1mΩ at this time, the feedforward calculation is still based on this equivalent internal resistance to determine the allowable feedforward current.

[0215] However, during vehicle startup, a connector became loose, causing an additional 1.0mΩ increase in contact resistance, resulting in the equivalent resistance of the actual circuit becoming:

[0216] .

[0217] When the real-time discharge current is:

[0218] I=200A.

[0219] The actual terminal voltage is:

[0220] 。

[0221] Since the sum of the preset safety voltage floor and the preset voltage drop safety margin is:

[0222]

[0223] The actual terminal voltage satisfies:

[0224] 2.12V < 2.40V.

[0225] This indicates that the current voltage drop condition no longer meets the preset voltage drop safety margin. At this point, the battery management system determines the voltage drop assessment value based on open-circuit voltage parameters, equivalent internal resistance, real-time discharge current, and dynamic voltage drop compensation.

[0226]

[0227] The feedforward allowable current is dynamically corrected based on the voltage drop assessment value. The feedback correction current limit value is updated according to the following formula:

[0228]

[0229] Substituting the voltage drop state from this embodiment, we get:

[0230]

[0231] Therefore, when poor contact leads to an increase in the actual voltage drop, the feedback correction current limit will be adjusted downwards according to the ratio between the voltage drop assessment value and the safety boundary. The second allowable current is the smaller value between the feedforward allowable current and the feedback correction current limit.

[0232]

[0233] Through the above process, even if the feedforward calculation fails to cover the anomaly of sudden increase in contact resistance, the battery management system can still dynamically correct the voltage drop safety margin based on the real-time terminal voltage and real-time discharge current, so that the second allowable current drops to a safe range, thereby preventing the single-cell terminal voltage from continuing to drop to the dangerous range.

[0234] Example 3:

[0235] Based on Example 1, the vehicle performs multiple start-up discharges consecutively within a short period. The battery management system collects the real-time discharge current during each control cycle and calculates the heat generation for the current control cycle using the equivalent internal resistance obtained through dynamic filtering. For any given cell in a string, the heat generation for the current control cycle is:

[0236]

[0237] Where I represents the real-time discharge current, and R represents the equivalent internal resistance. Indicates the duration of the control cycle.

[0238] During the initial discharge phase, the battery management system uses the heat dissipation time parameter from the calibration parameters to perform a recursive processing on the generated heat with heat dissipation attenuation, thus obtaining the battery's thermal accumulation state:

[0239]

[0240] in, This indicates the battery thermal accumulation state during the k-th control cycle. This indicates the heat dissipation time parameter during the heating phase.

[0241] After discharge, in the static or cooling state, the battery thermal accumulation state is recursively deduced using the heat dissipation time parameter during the cooling phase:

[0242]

[0243] in, This indicates the heat dissipation time parameter during the cooling phase.

[0244] Furthermore, based on the battery's thermal accumulation state and ambient temperature, the battery's equivalent internal temperature is determined:

[0245]

[0246] in, This represents the heat generation temperature rise conversion parameter corresponding to the ambient temperature.

[0247] After the first start-up, the battery's thermal state increases, and the battery's equivalent internal temperature reaches:

[0248] .

[0249] At this point, the preset thermal management soft threshold has not yet been reached, and the third allowable current remains unchanged.

[0250] After a second start-up shortly afterward, the heat generated during the first start-up has not yet fully dissipated, and the heat generated during the second start-up continues to accumulate, causing the battery's equivalent internal temperature to reach:

[0251] .

[0252] If the preset thermal management soft threshold at the current ambient temperature is:

[0253] .

[0254] Therefore, due to:

[0255] 54℃ > 50℃.

[0256] The battery management system determines that the battery's thermal accumulation state has reached the preset thermal management conditions, and therefore the third allowable current needs to be reduced in stages.

[0257] In this embodiment, the third allowable current can be gradually reduced from 400A according to a preset current reduction step size, for example:

[0258] 400A→395A→390A.

[0259] During the third startup, because the battery's thermal accumulation state is still at a high level, the third allowable current can be further limited to:

[0260] .

[0261] This reduces the heat generated during the startup process.

[0262] The recursive control of the third allowable current can be expressed as:

[0263]

[0264] After continuous startup ends and the battery is left to stand for a period of time, the battery's thermal accumulation gradually decreases according to the heat dissipation time parameters of the cooling phase, and the battery's equivalent internal temperature drops. At this time, the third allowable current can gradually recover at a recovery rate lower than the current reduction rate, for example:

[0265]

[0266] in:

[0267]

[0268] Through the above process, the on-board lithium battery can calculate the battery's thermal accumulation state based on real-time discharge current, equivalent internal resistance, and calibration parameters during continuous startup, and adjust the third allowable current in a step-wise manner or gradually restore it based on the battery's equivalent internal temperature. This avoids continuous heat accumulation inside the cell due to continuous startup, and also prevents the output from being immediately cut off when the thermal management soft threshold is reached, thus balancing startup availability and thermal safety.

[0269] Example 4:

[0270] A terminal includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of the adaptive control method for vehicle-mounted lithium batteries based on constant temperature calibration and dynamic filtering in Embodiment 1.

[0271] The processor described in the embodiments of this application can be implemented by hardware, firmware, software, or a combination thereof. It can be a circuit, one or more of an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field-programmable gate array (FPGA), a central processing unit (CPU), a controller, a microcontroller, or a microprocessor. It also includes other physical, biological, or chemical structures that can implement the same or equivalent functions as the processors listed above, such as biological neurons, quantum computing units, DNA computing units, etc., so that the processor can execute some or all of the steps in the computer program or method involved in the various embodiments of this application, or any combination of the steps mentioned therein.

[0272] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A method for adaptive control of vehicle-mounted lithium batteries based on isothermal calibration and dynamic filtering, characterized in that, include: The calibration parameters of the vehicle lithium battery under different ambient temperatures are obtained, and the open circuit voltage parameters and equivalent internal resistance of the battery are updated by dynamic filtering after the charging and discharging are completed. The real-time terminal voltage of each cell in the string of the vehicle lithium battery and the real-time discharge current of the battery are collected. Based on the real-time terminal voltage and real-time discharge current, and constrained by the physical limit voltage and physical limit current, the first allowable current is obtained. Based on the open-circuit voltage parameters, the equivalent internal resistance, and the calibration parameters, feedforward calculation is performed with the goal of ensuring that the real-time terminal voltage is not lower than the preset safety voltage floor. The preset voltage drop safety margin is dynamically corrected based on the real-time terminal voltage and the real-time discharge current to obtain the second allowable current. Based on the real-time discharge current, the equivalent internal resistance, and the calibration parameters, and with the constraint that the battery thermal accumulation state does not exceed the preset thermal management conditions, a third allowable current is obtained. The minimum value among the first allowable current, the second allowable current, and the third allowable current is determined as the current maximum allowable discharge current, and the output of the vehicle lithium battery is controlled according to the current maximum allowable discharge current.

2. The adaptive control method for vehicle-mounted lithium batteries according to claim 1, characterized in that, The process of obtaining calibration parameters for the vehicle-mounted lithium battery under different ambient temperatures includes: The vehicle lithium battery is placed at multiple preset ambient temperature levels and kept at a constant temperature until thermal equilibrium is reached. A pulsed discharge current simulating vehicle startup conditions is applied at each of the aforementioned ambient temperature settings; The voltage, current, and temperature changes under the action of the pulsed discharge current are collected. Based on the voltage, current, and temperature changes, determine the voltage compensation parameters, thermal management parameters, and safety threshold parameters for the corresponding ambient temperature setting, and store these parameters as calibration parameters.

3. The adaptive control method for vehicle-mounted lithium batteries according to claim 2, characterized in that, The voltage compensation parameters include a first compensation parameter for characterizing the transient voltage drop caused by current changes, and a second compensation parameter for characterizing the voltage drop change caused by temperature changes. The feedforward calculation includes: The first compensation parameter and the second compensation parameter are determined from the voltage compensation parameters based on the current ambient temperature. The first compensation parameter characterizes the transient voltage drop caused by the change in current, and the second compensation parameter characterizes the voltage drop caused by the change in temperature. The dynamic voltage drop compensation amount is determined based on the first compensation parameter and the second compensation parameter; Based on the open-circuit voltage parameters, the equivalent internal resistance, the dynamic voltage drop compensation, and the preset safety voltage floor, the feedforward allowable current that meets the voltage safety target is calculated.

4. The adaptive control method for vehicle-mounted lithium batteries according to claim 3, characterized in that, The dynamic pressure drop compensation amount is calculated according to the following formula: in, This is the dynamic pressure drop compensation amount; As the first compensation parameter, This is the second compensation parameter; The ambient temperature; This represents the rate of change of the real-time discharge current. This represents the equivalent internal temperature change rate of the nth cell in the battery. The allowable feedforward current is calculated according to the following formula: This is the allowable feedforward current corresponding to the nth individual unit; The open-circuit voltage parameter of the nth individual unit; Let be the equivalent internal resistance of the nth unit; To pre-set a safe voltage floor; This is the allowable feedforward current for the entire vehicle-mounted lithium battery pack.

5. The adaptive control method for vehicle-mounted lithium batteries according to claim 4, characterized in that, The step of dynamically correcting the preset voltage drop safety margin based on the real-time terminal voltage and real-time discharge current to obtain the second allowable current includes: The voltage drop evaluation value is determined based on the open-circuit voltage parameters, the equivalent internal resistance, the real-time discharge current, and the dynamic voltage drop compensation. Compare the voltage drop assessment value with the preset voltage drop safety margin; If the voltage drop assessment value is higher than the preset voltage drop safety margin, then the feedforward allowable current is used as the second allowable current; Otherwise, the feedforward allowable current is reduced according to the degree of deviation of the voltage drop assessment value from the preset voltage drop safety margin to obtain the second allowable current.

6. The adaptive control method for vehicle-mounted lithium batteries according to claim 5, characterized in that, The pressure drop assessment value is calculated according to the following formula: In the formula, This is the voltage drop assessment value for the nth monomer string; I This is the real-time discharge current of the battery; The voltage drop assessment value is compared with the preset voltage drop safety margin according to the following formula: In the formula, This indicates the preset voltage drop safety margin related to ambient temperature; If the voltage drop assessment value is higher than the preset voltage drop safety margin, then the feedforward allowable current is used as the second allowable current, as shown below: This indicates the second permissible current.

7. The adaptive control method for vehicle-mounted lithium batteries according to claim 6, characterized in that, Reducing the feedforward allowable current according to the degree of deviation of the voltage drop assessment value from the preset voltage drop safety margin includes: The voltage drop assessment value is compared with the preset voltage drop safety margin to obtain the voltage drop margin deviation; The current reduction amount is determined based on the voltage drop margin deviation. Based on the aforementioned current reduction amount, the second allowable current of the previous control cycle is reduced to obtain the second allowable current of the current control cycle, according to the following formula: In the formula, This represents the feedback correction current limiting value for the (k+1)th control cycle; This represents the feedback correction current limiting value for the k-th control cycle. This represents the pressure drop assessment value for the k-th control cycle; This is to allow for a preset voltage drop safety margin; When the voltage drop assessment value meets the preset voltage drop safety margin again, the reduction of the second allowable current is stopped.

8. The adaptive control method for vehicle-mounted lithium batteries according to claim 1, characterized in that, The process of obtaining a third allowable current based on the real-time discharge current, the equivalent internal resistance, and the calibration parameters, with the constraint that the battery thermal accumulation state does not exceed preset thermal management conditions, includes: The heat generated in the current control cycle is calculated based on the real-time discharge current collected during the current control cycle and the equivalent internal resistance. Based on the thermal management parameters in the calibration parameters, the heat generated is recursively processed with heat dissipation attenuation to obtain the battery thermal accumulation state. The equivalent internal temperature of the battery is determined based on the battery thermal accumulation state and the ambient temperature. When the equivalent internal temperature of the battery reaches the preset thermal management soft threshold, the third allowable current of the previous control cycle is reduced in a stepwise manner to obtain the third allowable current of the current control cycle. When the equivalent internal temperature of the battery reaches the preset thermal management upper limit, the third allowable current of the current control cycle is set to zero.

9. The adaptive control method for vehicle-mounted lithium batteries according to claim 8, characterized in that, The thermal management parameters include heat dissipation time parameters during the heating phase and heat dissipation time parameters during the cooling phase; When the vehicle lithium battery is in the start-up discharge state, the heat dissipation time parameter of the heating stage is used to recursively calculate the battery thermal accumulation state. When the vehicle-mounted lithium battery is in a static or cooling state after discharge, the heat dissipation time parameter of the cooling stage is used to recursively calculate the battery thermal accumulation state.

10. The adaptive control method for vehicle-mounted lithium batteries according to claim 8, characterized in that, The method of obtaining the third allowable current by constraining the battery thermal accumulation state from not exceeding preset thermal management conditions also includes: When the equivalent internal temperature of the battery is lower than the preset thermal management soft threshold, the third allowable current is maintained or gradually restored. When the equivalent internal temperature of the battery reaches the preset thermal management soft threshold and is lower than the preset thermal management upper limit, the third allowable current is reduced in a stepwise manner. When the equivalent internal temperature of the battery reaches the preset thermal management upper limit, the third allowable current is set to zero, and the output of the vehicle lithium battery is cut off.

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