Battery capacity self-correction method, battery management system and energy storage power supply

Abstract

The application relates to a battery capacity self-correction method, a battery management system and an energy storage power supply. The battery management system comprises a control unit, an independent protection module and a switching unit. The independent protection module directly drives the switching unit and is not in communication connection with the control unit, and an analog front-end chip for collecting the voltage of a single battery cell is not arranged. The control unit switches between a calibration mode and a normal mode according to a preset flag. In the calibration mode, the electrical parameter meets the full discharge condition, the accumulated discharge capacity is in a valid interval, and the temperature is higher than a threshold value, and the calibration capacity is written. In the normal mode, the battery pack empty electricity is determined, and the original SOC is obtained. If the original SOC is lower than a preset jump threshold value, the SOC is set to zero. If the original SOC is not lower than the jump threshold value and is in an allowed correction state, the capacity calibration is carried out according to the calibration capacity. Therefore, the SOC estimation accuracy is long-term maintained through the capacity and temperature double-checking and the jump triggering decrement correction without the AFE hardware.

Description

Technical Field

[0001] This invention relates to the field of battery capacity calibration technology, and in particular to a battery capacity self-calibration method, a battery management system, and an energy storage power source. Background Technology

[0002] With the rapid development of new energy storage technologies, energy storage power supplies (such as portable energy storage power stations, home energy storage systems, and industrial backup power supplies) have been widely used in daily life and industrial production. As a core component of energy storage power supplies, the Battery Management System (BMS) is responsible for accurately estimating the battery's remaining charge (SOC) and remaining capacity, providing crucial information for charge / discharge control, safety protection, and lifespan management of the energy storage power supply.

[0003] In traditional BMS architectures, the analog front-end chip (AFE) is a core component. Its main function is to collect the voltage and temperature of individual battery cells, achieve equalization control and overvoltage / undervoltage protection for each cell, and upload the collected parameters to the control module (MCU) for calculating the remaining battery power and capacity. However, the high-integration AFE with multiple cells connected in series has a high hardware cost, which is detrimental to cost control of energy storage power supplies. Furthermore, the AFE chip needs to communicate with the MCU (e.g., via I2C or SPI protocols) and requires additional peripheral components such as sampling resistors and equalization circuits, increasing PCB design complexity, wiring difficulty, and hardware failure rate. In addition, the operation of the AFE chip and its peripheral circuits consumes additional power, reducing the overall energy efficiency of the energy storage power supply and resulting in a lower battery life for portable energy storage power supplies.

[0004] To address these issues, a "no AFE chip" BMS architecture has gradually emerged in the industry. This architecture uses an MCU to directly collect global parameters such as the total voltage, total current, and ambient temperature of the battery pack, replacing the single-cell parameter acquisition function of the AFE chip. However, in the no-AFE chip architecture, the MCU cannot collect the voltage and temperature of individual cells and can only rely on the total voltage of the battery pack to reflect the overall state. But the total voltage of the battery pack is greatly affected by factors such as charging and discharging current, temperature, and cycle count, and cannot accurately reflect the true state of individual cells (e.g., the total voltage may still be within the normal range when some cells are overcharged / undercharged), resulting in large errors in the estimation of remaining battery capacity. At the same time, existing no-AFE chip solutions usually only use a fixed rated capacity and ampere-hour integration to calculate the capacity, lacking an active capacity correction mechanism. This makes it unable to adapt to the capacity decay caused by battery aging, and the SOC estimation deviation increases significantly after long-term use. Furthermore, when the total voltage of the battery pack drops rapidly due to nonlinear characteristics (i.e., a jump in capacity), existing solutions can only force the SOC to zero and cannot simultaneously correct the calibrated capacity, resulting in continuous errors in the capacity estimation after the jump. Therefore, under the triple hardware constraints of not configuring an analog front-end chip, being unable to obtain the voltage of a single cell, and having no communication connection between the control unit and the independent protection module, how to achieve accurate self-calibration of the calibrated capacity by relying solely on global parameters such as the total voltage, total current, and temperature of the battery pack, in order to solve the problems of ampere-hour integral cumulative error, misjudgment of full discharge caused by the nonlinearity of the total voltage, and the inability to correct the capacity after the power jump, has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of this, in order to at least partially improve the above-mentioned problems, the present invention provides a battery capacity self-calibration method, a battery management system, and an energy storage power source.

[0006] This invention provides a battery capacity self-calibration method applied to a battery management system connected to a battery pack. The battery management system includes a control unit, a switching unit, an independent protection module, and a memory electrically connected to the control unit. The battery management system does not have an analog front-end chip for acquiring the voltage of individual cells in the battery pack, and the control unit does not acquire the voltage of individual cells in the battery pack. The control unit acquires the operating parameters of the battery pack and calculates the remaining state of charge (SOC) of the battery based on the calibrated capacity stored in the memory. The operating parameters include at least electrical parameters and temperature parameters. The switching unit controls the charging and discharging circuit of the battery pack and is controlled by the independent protection module in the battery management system. There is no signal interaction between the control unit and the independent protection module. The method includes: The control unit controls the battery management system to switch between calibration mode and normal mode according to a preset flag bit; During the discharge phase of the calibration mode, when the electrical parameters meet the preset full discharge conditions, the current cumulative discharge capacity and the temperature parameters are obtained; when the cumulative discharge capacity and the temperature parameters meet the preset correction conditions, the cumulative discharge capacity is written to the calibration capacity, and the system switches to the normal mode; otherwise, the calibration capacity is not updated, the cumulative discharge capacity is cleared, and the system switches back to the charging phase of the calibration mode. During the discharge phase of the normal mode, when the electrical parameters meet the preset full discharge condition, it is determined that the battery pack is in an empty state, and the remaining battery charge SOC at the corresponding time is obtained as the original SOC. If the original SOC is lower than the preset jump threshold, it is determined to be a normal empty battery, the capacity self-correction is not triggered, and the current remaining battery SOC is forcibly set to zero. If the original SOC is not lower than the preset jump threshold, and it is determined to be in the allowable correction state according to the preset flag bit, then the capacity self-correction is triggered: update the calibrated capacity according to the calibrated capacity and the preset correction coefficient, update the preset flag bit, and force the current remaining battery SOC to be set to zero. If the original SOC is not lower than the preset jump threshold, and it is determined according to the preset flag that it is not in the allowed correction state, then the calibrated capacity will not be updated, and the current remaining battery SOC will be forcibly set to zero.

[0007] Preferably, the operating parameters include the total voltage and total current of the battery pack; the control unit performs ampere-hour integration on the total current to obtain the cumulative discharge capacity, and calculates the remaining battery charge (SOC) based on the cumulative discharge capacity and the rated capacity; The switching unit includes a charging MOSFET and a discharging MOSFET connected in reverse series to the charging and discharging circuit. The on / off states of the charging MOSFET and the discharging MOSFET are directly driven by the independent protection module.

[0008] Preferably, the step of writing the accumulated discharge capacity into the calibration capacity when the accumulated discharge capacity and the temperature parameter meet the preset correction conditions includes: Determine whether the accumulated discharge capacity satisfies the condition of being greater than a preset effective lower limit value and not greater than a preset effective upper limit value; Determine whether the temperature parameter is higher than a preset temperature threshold; When the cumulative discharge capacity is greater than the preset effective lower limit and not greater than the preset effective upper limit, and the temperature parameter is higher than the preset temperature threshold, it is determined that the preset correction condition is met, and the cumulative discharge capacity is written into the calibration capacity.

[0009] Preferably, the preset flag bit has multiple state values ​​representing the system state, and the method further includes: During the charging phase of the calibration mode, when the electrical parameters meet the preset full charge conditions, the preset flag bit is updated to a state value representing the calibration discharge phase, the charging is stopped and the accumulated discharge capacity is cleared, and the discharge phase of the calibration mode is entered. During the charging phase of the normal mode, when the electrical parameters meet the preset full charge conditions, the preset flag is updated to a state value representing the normal discharge phase, the accumulated discharge capacity is cleared, and the normal mode discharge phase begins.

[0010] As a preferred option, it also includes: Determine whether the preset flag bit is currently the state value representing the normal discharge stage; If so, it is determined that the state is in the allowable correction state, and after the trigger capacity self-correction is performed, the preset flag is updated to a state value indicating that the state is not correctable.

[0011] Preferably, updating the calibration capacity based on the calibration capacity and the preset correction coefficient includes: Based on the current calibration capacity, the preset attenuation scaling ratio, and the preset compensation value, the updated calibration capacity is calculated. The preset attenuation scaling ratio is determined based on the preset depth of discharge coefficient, and the preset compensation value is a fixed compensation value or zero.

[0012] Preferably, during the discharge phase of the calibration mode, the control unit also acquires the total current in real time and calculates the rate of change of the total current between adjacent sampling periods. When the rate of decrease of the total current within a preset sampling period exceeds a preset sudden change threshold, the control unit determines that the independent protection module has forcibly cut off the charging and discharging circuit due to hardware protection conditions, sets the accumulated discharge capacity to invalid and clears it to zero, exits the discharge phase of the calibration mode, switches back to the charging phase of the calibration mode, and does not update the calibration capacity.

[0013] As a preferred option, it also includes: During the discharge phase of the normal mode, when it is determined that the battery pack is in a depleted state and the original SOC is lower than a preset lower limit, the number of consecutive times that the condition is met is accumulated. When the number of consecutive satisfactions reaches a preset threshold, the calibration capacity is increased according to a preset recovery coefficient, and the number of consecutive satisfactions is reset to zero. and / or When the preset recalibration conditions are met, the preset flag bit is updated to a state value indicating the charging stage of entering the calibration mode. The preset recalibration conditions include at least one of the following: the cumulative number of charge-discharge cycles reaches a preset cycle threshold, the attenuation ratio of the calibrated capacity relative to the rated capacity of the battery pack reaches a preset attenuation threshold, and the battery pack is detected to have been replaced.

[0014] The present invention also provides a battery management system, including a memory, a control unit, an independent protection module, and a switching unit for controlling the charging and discharging circuit of the battery pack; The memory is electrically connected to the control unit and is used to store computer programs; The control unit is used to be electrically connected to the battery pack to obtain the operating parameters of the battery pack; The switching unit is used to connect in series to the charging and discharging circuit of the battery pack; The independent protection module is electrically connected to the switching unit and is used to directly drive the switching unit to turn on and off, and there is no signal interaction between the independent protection module and the control unit; The memory stores a computer program, which, when executed by the control unit, implements the steps of the battery capacity self-calibration method as described in any of the preceding claims.

[0015] The present invention also provides an energy storage power supply, including a battery pack and a battery management system as described above, wherein the battery management system is electrically connected to the battery pack.

[0016] Beneficial effects: Compared with existing battery management solutions that have analog front-end chips, this invention eliminates the need for analog front-end chips and peripheral communication interfaces, significantly reducing the hardware cost and wiring complexity of the battery management system. Furthermore, the independent protection module independently controls the MOSFET, and the design eliminates communication between the MCU and the protection chip, effectively avoiding safety hazards caused by software failures and improving system reliability. Compared with existing simplified solutions without analog front-end chips, this invention no longer relies on a fixed rated capacity. Instead, it automatically enters calibration mode upon first power-on using a calibration flag state machine, obtaining the true initial calibrated capacity through a complete charge-discharge cycle. This overcomes the shortcomings of existing solutions that cannot adapt to battery aging and long-term capacity reference drift. In calibration mode, this invention effectively filters out invalid discharge data caused by abnormal interruptions or low-temperature nonlinearity through dual verification of cumulative discharge capacity range and ambient temperature threshold, ensuring the accuracy of the initial calibrated capacity. During normal discharge, continuous preset cycle monitoring of total voltage is used to filter out instantaneous voltage drops caused by load fluctuations, avoiding false triggering of the empty state. At the same time, the original SOC value is used as the judgment basis, and capacity self-correction is triggered only when the original SOC value is higher than the preset threshold. Each time the jump correction is triggered, the calibrated capacity is slightly reduced, so that the calibrated capacity gradually decreases with the increase of charge and discharge cycles, which is consistent with the actual usable capacity decay trend caused by battery aging. Compared with the existing solution that only forces the SOC to zero without correcting the calibrated capacity when the power jump occurs, this invention synchronously corrects the capacity benchmark when the power jump occurs, fundamentally eliminating the cumulative error of ampere-hour integration, and maintaining a high SOC estimation accuracy for a long time without the hardware limitation of AFE chip. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic flowchart of a battery capacity self-calibration method according to an embodiment of the present invention.

[0018] Figure 2 This is a block diagram of a battery management system in which the battery capacity self-calibration method of one embodiment of the present invention is applied.

[0019] Figure 3 This is a block diagram of an energy storage power supply according to an embodiment of the present invention. Detailed Implementation

[0020] The terms "first," "second," and "third," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish different objects and not to describe a specific order. Furthermore, the term "comprising," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include steps or modules not listed, or may optionally include other steps or modules inherent to these processes, methods, products, or apparatuses.

[0021] Please see Figure 1-3 One embodiment of the present invention provides a battery capacity self-calibration method, which is applied to a battery management system without a dedicated analog front-end (AFE) chip. The battery management system is connected to a battery pack and mainly includes a control unit, a switching unit and an independent protection module. The control unit can be a microcontroller (MCU), such as an STM32F030 microcontroller. This MCU is connected to the battery pack and is used to acquire the operating parameters of the battery pack. The operating parameters include at least electrical parameters, specifically the total voltage of the battery pack acquired through a total voltage divider network and the total current acquired through a current differential amplifier and a sampling resistor. It also includes temperature parameters, specifically the ambient temperature acquired through an NTC temperature sampling circuit. The calibrated capacity is stored in the memory, and the current remaining battery power is calculated in real time based on the calibrated capacity and the ampere-hour integration (coulomb counting method) of the total current during charging and discharging.

[0022] The switching unit controls the charging and discharging circuit of the battery pack, including a charging MOSFET (QCHG) and a discharging MOSFET (QDSG) connected in reverse series to the charging and discharging circuit. The independent protection module is an independent hardware protection chip. The on / off states of the charging and discharging MOSFETs are directly driven and controlled by this independent protection module, and there is no communication connection between this independent protection module and the MCU. Thus, the MCU is only responsible for capacity calculation and software state machine scheduling, and does not directly control the charging and discharging MOSFETs; the on / off state of the charging and discharging MOSFETs is autonomously controlled by the independent protection module based on hardware voltage / current conditions. The independent protection module is a dedicated lithium battery protection chip that directly drives the on / off state of the charging and discharging MOSFETs based solely on hardware voltage / current thresholds. It does not collect the voltage of individual cells in the battery pack, does not perform cell balancing, and does not communicate with the control unit.

[0023] The control unit has a preset calibration flag for scheduling logic. By changing the state value of this preset flag, the battery management system switches between calibration mode and normal mode. Both modes include corresponding charging and discharging phases. For example, the preset flag can be defined as a state machine with values ​​of 0, 1, 2, and 3. When the system is first powered on and there are no historical parameters, the flag is set to 2, entering the charging phase of calibration mode. When the charging phase of calibration mode reaches full charge, the system sets the flag to 3, entering the discharging phase of calibration mode. When the system is running in normal mode, the flag is between 0 and 1, where 0 represents the charging phase of normal mode, and the flag is set to 1 after full charge.

[0024] In addition, to distinguish between the two semantics of "normal charging phase" and "corrected / uncorrectable", a state value 4 is set to represent the uncorrectable state.

[0025] The method includes: S1. The control unit controls the battery management system to switch between calibration mode and normal mode according to a preset flag bit; S2. During the discharge phase of the calibration mode, when the electrical parameters meet the preset full discharge conditions, the current cumulative discharge capacity and the temperature parameters are obtained; when the cumulative discharge capacity and the temperature parameters meet the preset correction conditions, the cumulative discharge capacity is written to the calibration capacity, and the system switches to the normal mode; otherwise, the calibration capacity is not updated, the cumulative discharge capacity is cleared, and the system switches back to the charging phase of the calibration mode. S3. During the discharge phase of the normal mode, when the electrical parameters meet the preset full discharge condition, it is determined that the battery pack is in an empty state, and the remaining battery charge SOC at the corresponding time is obtained as the original SOC. S4. If the original SOC is lower than the preset jump threshold, it is determined to be a normal empty battery, the capacity self-correction is not triggered, and the current remaining battery SOC is forcibly set to zero. S5. If the original SOC is not lower than the preset jump threshold, and it is determined to be in the allowable correction state according to the preset flag bit, then the capacity self-correction is triggered: update the calibrated capacity according to the calibrated capacity and the preset correction coefficient, update the preset flag bit, and force the current remaining battery SOC to zero. S6. If the original SOC is not lower than the preset jump threshold, and it is determined according to the preset flag that it is not in the allowed correction state, then the calibration capacity is not updated, and the current remaining battery SOC is forcibly set to zero.

[0026] As mentioned above, since no AFE chip is configured in this embodiment, the MCU cannot directly collect the voltage of a single cell and can only estimate the battery state based on the total voltage and current of the battery pack. To address the estimation error caused by this hardware limitation, this embodiment implements capacity self-calibration according to the following logic: the cumulative discharge capacity is calculated based on the integral of the total voltage and current. When the electrical parameters reach the preset full discharge conditions, the cumulative discharge capacity and temperature parameters are checked to see if they meet the preset calibration conditions. Only when both conditions are met is the cumulative capacity written to the calibration capacity; otherwise, the update is abandoned, the data is cleared, and the process returns to the calibration charging stage to ensure the accuracy of the initial reference capacity.

[0027] During the discharge phase in normal mode, electrical parameters are continuously monitored. If the electrical parameters reach the preset full discharge condition (e.g., the total voltage is continuously at a low level as determined by filtering and anti-shake), it is confirmed that the battery pack is discharged, and the current battery remaining capacity SOC is obtained as the original SOC. Using this original SOC as the detection anchor point, it is determined whether it is lower than the preset jump threshold. If the original SOC is very low, i.e., lower than the preset jump threshold, it indicates that the ampere-hour integration has not drifted significantly and is considered normal empty charge. In this case, the battery remaining capacity SOC is simply forced to zero. If the original SOC is high, i.e., not lower than the preset jump threshold, it indicates that the integration error has caused the calculated capacity to be falsely high. In this case, after determining that correction is allowed based on the flag bit, the calibrated capacity is attenuated and corrected using the preset correction coefficient. After the correction is completed, it is forced to zero.

[0028] Through the above method, this embodiment, without the hardware limitations of an AFE chip, does not require complex monitoring of individual cells. It can accurately distinguish between normal discharge and capacity fluctuations simply by using the total voltage and current. When a fluctuation occurs, the calibrated capacity can be automatically adjusted to effectively offset the cumulative drift caused by long-term operation of the ampere-hour integral, reducing errors and improving the accuracy of battery capacity estimation while reducing hardware costs.

[0029] Furthermore, the preset jump threshold is a pre-stored value determined by ambient temperature and discharge current. Lithium batteries experience a significant increase in internal resistance at low temperatures and a greater polarization voltage drop during high-current discharge. Both of these factors cause the total battery pack voltage to momentarily drop to near the full discharge threshold while the battery still has remaining charge. If a fixed preset jump threshold is used, this momentary drop caused by polarization may be misjudged as a capacity jump due to battery aging, leading to an incorrect reduction in the rated capacity based on the correction factor.

[0030] To this end, the control unit pre-stores the correspondence between ambient temperature, discharge current, and the preset jump threshold (e.g., a two-dimensional mapping table or fitting relationship). When the ambient temperature is low or the discharge current is high, the control unit correspondingly increases the preset jump threshold (e.g., from 15 corresponding to the original SOC range at room temperature to 35 under low-temperature, high-current conditions). In this way, only when the original SOC is still higher than the increased jump threshold after eliminating polarization factors such as low temperature and high current is it determined to be a true capacity jump and trigger capacity self-calibration, thereby avoiding erroneous attenuation correction of the calibrated capacity under harsh operating conditions.

[0031] Furthermore, in the calibration mode, the control unit does not write the cumulative discharge capacity into the calibration capacity immediately after a single discharge meets the preset correction condition. Instead, it records the cumulative discharge capacity that meets the preset correction condition multiple times consecutively. When the number of consecutive meets reaches a preset calibration count threshold, the statistical result of the recorded cumulative discharge capacity is written into the calibration capacity. If any discharge does not meet the preset correction condition, the number of consecutive meets is cleared and the counting restarts.

[0032] As described above, to avoid deviations in the calibration capacity benchmark caused by a single accidental factor, this embodiment does not use a one-time pass-through writing method. Instead, when each calibration discharge meets the preset correction conditions (i.e., the cumulative discharge capacity falls within the effective range and the temperature is higher than the threshold), the calibration capacity is not immediately written. Instead, the cumulative discharge capacity is recorded and the consecutive fulfillment count is incremented. When the consecutive fulfillment count reaches the preset calibration count threshold (e.g., three times), the control unit writes the statistical result of the recorded multiple cumulative discharge capacities (e.g., the average or median) into the calibration capacity. If any discharge fails to meet the preset correction conditions due to abnormal interruption, excessively low temperature, or exceeding the capacity range limit during the accumulation of consecutive fulfillment counts, the consecutive fulfillment count is reset to zero, the recorded historical cumulative discharge capacity is cleared, and the continuous counting restarts. This ensures that the writing of the calibration capacity is statistically confirmed through multiple complete charge-discharge cycles, further suppressing the occasional impact of a single abnormal discharge on the calibration benchmark.

[0033] In one embodiment, the operating parameters include the total voltage and total current of the battery pack; the control unit performs ampere-hour integration on the total current to obtain the cumulative discharge capacity, and calculates the remaining battery charge (SOC) based on the cumulative discharge capacity and the calibrated capacity; the switching unit includes a charging MOSFET and a discharging MOSFET connected in reverse series to the charging and discharging circuit, and the on / off state of the charging MOSFET and the discharging MOSFET is directly driven by the independent protection module.

[0034] As described above, the MCU acquires the total voltage and total current of the battery pack in real time through its built-in ADC module. During charging and discharging, the MCU performs ampere-hour integration (i.e., coulomb counting) on ​​the acquired total current and calculates the current remaining battery capacity (SOC) by comparing the integration result with the rated capacity.

[0035] In another embodiment, for situations where there is no communication connection between the independent protection module and the control unit, and the control unit cannot directly know the protection action of the independent protection module, in the discharge phase of the calibration mode, when the independent protection module forcibly shuts down the charging MOS transistor or the discharging MOS transistor due to hardware protection conditions, since there is no signal interaction between the control unit and the independent protection module, the control unit cannot directly know the occurrence of the protection action; if the discharge capacity continues to accumulate at this time, an incomplete discharge interrupted by hardware abnormality will be misjudged as a complete discharge, thereby causing a deviation in the written calibration capacity.

[0036] Based on this, during the discharge phase of the calibration mode, the control unit, while acquiring the accumulated discharge capacity, also detects the rate of change of the total current in real time. Specifically, the control unit continuously samples the total current according to a preset sampling period (e.g., every 10ms) and calculates the current difference between adjacent sampling periods to determine whether the rate of decrease of the total current is abnormal. If the rate of decrease of the total current within the preset sampling period is detected to exceed a preset sudden change threshold, the control unit determines that the independent protection module has forcibly disconnected the charging and discharging circuit due to hardware protection conditions (e.g., overcurrent protection or undervoltage protection). At this time, since the current discharge process is abnormally interrupted by hardware and is not a complete discharge, its accumulated discharge capacity has no reference value. The control unit invalidates and clears the accumulated discharge capacity, exits the discharge phase of the calibration mode, switches back to the charging phase of the calibration mode, does not update the calibration capacity, and waits for the next complete charge and discharge cycle. Therefore, under hardware conditions without communication connection, the control unit can identify the discharge interruption caused by hardware protection based solely on the total current, avoiding mistaking an incomplete discharge process as a complete discharge and writing it into the calibration capacity accordingly, which would cause a deviation in the calibration capacity reference.

[0037] Furthermore, after the control unit determines that the rate of decrease of the total current exceeds the preset sudden change threshold, the control unit continues to monitor the total current within a preset time window; if the total current recovers to the discharge current range within the preset time window, it is determined that the current interruption is an instantaneous disconnection on the load side rather than a hardware cutoff by the independent protection module, and the accumulated discharge capacity is retained and continues to accumulate; if the total current remains lower than the preset judgment current within the preset time window, it is determined that the independent protection module has been hardware cutoff, and the accumulated discharge capacity is set to invalid and cleared to zero.

[0038] As described above, considering that the instantaneous drop in total current may be caused not only by the hardware protection action of the independent protection module, but also by non-protection reasons such as the instantaneous removal of the user-side load or the instantaneous jitter of the contact, in order to avoid misjudging the brief current interruption caused by non-protection reasons as a discharge process that is forcibly interrupted by hardware protection, and thus incorrectly determining the current accumulated discharge capacity as invalid data, this embodiment does not immediately determine the current accumulated discharge capacity as invalid data after detecting that the rate of decrease in total current exceeds the preset sudden change threshold, but instead enters a short discrimination time window.

[0039] Within this time window (e.g., several hundred milliseconds), the control unit continuously monitors the total current: if the total current quickly recovers to the normal discharge current range, it indicates that the previous current drop was caused by a momentary disconnection on the load side, and the discharge process itself was not hardware-interrupted. The control unit retains the accumulated discharge capacity and continues to integrate. If the total current remains below the preset judgment current within this time window, it is confirmed that the discharge circuit has indeed been hardware-interrupted by the independent protection module. Only then is the accumulated discharge capacity invalidated and cleared to zero, returning to the charging phase of the calibration mode. This further reduces the deviation of non-protection-type momentary interruptions from the calibration capacity benchmark.

[0040] During the discharge phase of the normal mode, when the electrical parameters meet the preset full discharge condition, it is determined that the battery pack is in an empty state, including: detecting whether the total voltage drops below the preset full discharge threshold; if the total voltage drops below the preset full discharge threshold and does not exceed the preset full discharge threshold within a continuous preset sampling period or a continuous preset time, it is determined that the preset full discharge condition is met, and the battery pack is determined to be in an empty state.

[0041] As mentioned above, because the voltage of a single battery cell cannot be obtained without an AFE chip, and the MCU can only obtain the total voltage, but the total voltage fluctuates due to instantaneous load surges, this embodiment does not determine whether the battery is depleted based on a single total voltage reading. Instead, it periodically obtains the total voltage of the battery pack according to a preset sampling period (e.g., every 10ms). First, the MCU compares the currently detected total voltage with a pre-stored full-discharge threshold to determine whether the total voltage has dropped below the full-discharge threshold. If the total voltage has dropped below the full-discharge threshold, the MCU does not immediately determine that the battery pack is depleted, but enters the anti-jitter confirmation stage. Specifically, the MCU continues to monitor the total voltage within the sampling period. If, in subsequent consecutive sampling periods (e.g., once every 10ms, for 200 consecutive sampling periods, equivalent to approximately 2 seconds), the total voltage is consistently not higher than the full-discharge threshold, the MCU confirms that the voltage drop was indeed caused by the battery being depleted, rather than a misjudgment caused by instantaneous load fluctuations. Only after confirming that the above conditions are met is the battery pack determined to be depleted.

[0042] In one embodiment, during the discharge phase of the normal mode, when the electrical parameters meet the preset full discharge condition and it is determined that the battery pack is in an empty state, the control unit sets a forced empty flag. During the period when the forced depletion flag is in position, the control unit ignores the subsequent voltage rise of the total battery pack due to the depolarization effect and maintains the state of prohibiting discharge; The condition for releasing the forced power-off flag is: the charging power supply is detected, and the current continuous charging capacity obtained by integrating the charging current in ampere-hours is greater than the preset unlocking capacity threshold. The power-off state will not be lifted by the recovery of the total voltage before the forced power-off flag is released.

[0043] As mentioned above, considering that after a lithium iron phosphate battery discharges to the full discharge threshold, once the load is disconnected, the battery's terminal voltage will significantly rebound from the full discharge threshold within several seconds to tens of seconds due to the depolarization effect (e.g., from 16.5V to above 18V). Without an AFE chip and without the independent protection module reporting its protection action to the control unit, the control unit can only determine the depletion state based on the total battery pack voltage. Without constraint, when the total voltage rebounds above the full discharge threshold due to depolarization, the control unit may mistakenly believe the battery has recovered its charge and deactivate the depletion state, allowing continued discharge. This results in repeated switching phenomena (i.e., discharge oscillation) of depletion cutoff, voltage rebound, discharge permission, and subsequent cutoff.

[0044] To eliminate this phenomenon, in this embodiment, after confirming that the battery pack is in a depleted state, the control unit sets the forced depletion flag. During the period this flag is set, regardless of the total voltage's rebound value due to depolarization, the control unit does not release the depletion state based on this, nor does it allow the discharge circuit to enter the discharge state. The release of the forced depletion flag does not depend on the total voltage, but only on the cumulative charging capacity during the charging process: when the charging power supply is detected, the control unit performs ampere-hour integration on the charging current. Only when the current continuous charging capacity exceeds the preset unlocking capacity threshold (e.g., 5% of the battery pack's rated capacity) is the forced depletion flag released, and the system resumes normal charging and discharging scheduling. Thus, under hardware conditions without AFE and individual cell hysteresis signals, the discharge oscillation caused by voltage rebound is completely avoided solely by relying on the software criterion of cumulative charging ampere-hours.

[0045] In one embodiment, after confirming that the battery pack has reached the full discharge threshold, the MCU verifies whether the data from this discharge is genuine and valid, thereby deciding whether to write the accumulated discharge capacity into the calibrated capacity. Specifically: Because the battery may interrupt discharge due to abnormal undervoltage protection before it is fully discharged, or because the charge accumulation is incomplete due to the system just being powered on, the accumulated discharge capacity is often small in both cases. Therefore, this embodiment sets a preset effective capacity range for the accumulated discharge capacity. For example, it determines whether the current accumulated discharge capacity is greater than a preset effective lower limit (e.g., greater than 5Ah) and not greater than a preset effective upper limit (e.g., not greater than 15Ah). Only when the accumulated discharge capacity is within this range is the current discharge considered a complete discharge process.

[0046] In addition, due to the significant increase in internal resistance of the battery at low temperatures, the total voltage exhibits a non-linear and rapid downward trend. Using the total voltage to determine full discharge under these conditions can easily lead to misjudgments and affect the accuracy of the calibrated capacity. Therefore, this embodiment sets a preset temperature threshold (e.g., -5℃). While determining the capacity range, the MCU also acquires the current ambient temperature and compares it with the preset temperature threshold to determine if the temperature is higher than the threshold. Only when both conditions are met simultaneously (i.e., the accumulated discharge capacity is within the valid range, and the current ambient temperature is higher than the preset temperature threshold) does the MCU determine that the discharge data is valid and meets the preset correction conditions. The accumulated discharge capacity is then written into the calibrated capacity stored in the memory, completing the capacity calibration.

[0047] If either of the above two conditions is not met, the MCU will determine that the current full discharge is invalid, will not update the calibration capacity, will directly clear the accumulated discharge capacity of this discharge, and will control the battery management system to return to the charging stage of calibration mode, waiting for the next complete charge and discharge cycle to obtain valid capacity data again.

[0048] In cases where the discharge process is abnormally interrupted due to hardware protection conditions (such as overcurrent protection or undervoltage protection), the cumulative discharge capacity is usually lower than the effective lower limit because the discharge is not complete. This capacity will also be filtered by the capacity range verification mentioned above, thus avoiding writing invalid capacity into the calibrated capacity.

[0049] In one embodiment, the method further includes: During the charging phase of the calibration mode, when the electrical parameters meet the preset full charge conditions, the preset flag bit is updated to a state value representing the calibration discharge phase, the charging is stopped and the accumulated discharge capacity is cleared, and the discharge phase of the calibration mode is entered. During the charging phase of the normal mode, when the electrical parameters meet the preset full charge conditions, the preset flag is updated to a state value representing the normal discharge phase, the accumulated discharge capacity is cleared, and the normal mode discharge phase begins.

[0050] Furthermore, it also includes: Determine whether the preset flag bit is currently the state value representing the normal discharge stage; If so, it is determined that the state is in the allowable correction state, and after the trigger capacity self-correction is performed, the preset flag is updated to a state value indicating that the state is not correctable.

[0051] As described above, during the charging phase of the calibration mode, the MCU continuously monitors the electrical parameters of the battery pack. When the electrical parameters meet the preset full-charge conditions, the MCU determines that the system is fully charged. At this time, the MCU updates the preset flag from the state value representing the calibration charging phase (e.g., state value 2) to the state value representing the calibration discharging phase (e.g., state value 3), and simultaneously controls the charging to stop (e.g., the MCU controls the charging relay in the charging circuit to close, thus disconnecting the charging circuit), and clears the currently accumulated discharge capacity to zero. Thus, the system enters the discharging phase of the calibration mode, waiting for the battery pack to begin discharging.

[0052] During the charging phase in the normal mode, the MCU continuously monitors the electrical parameters. When the electrical parameters meet the preset full charge condition, the MCU updates the preset flag from the state value representing the normal charging phase (e.g., state value 0) to the state value representing the normal discharging phase (e.g., state value 1), while clearing the accumulated discharge capacity and entering the discharging phase in the normal mode.

[0053] Furthermore, during the discharge phase of the normal mode, after the MCU determines that capacity self-calibration needs to be triggered according to the aforementioned step S5, it needs to further confirm whether calibration is currently allowed. Specifically, the MCU first determines whether the preset flag bit is currently the state value representing the normal discharge phase (i.e., whether the flag bit is 1). Only when the flag bit is 1 does it indicate that the system is currently in a calibration-allowed state, and the MCU will then execute the subsequent capacity self-calibration steps. After performing capacity self-calibration (i.e., updating the calibrated capacity), the MCU updates the preset flag bit to a state value representing an uncalibrable state (e.g., state value 4), thereby preventing calibration from being triggered again due to voltage fluctuations or other factors within the same discharge cycle, and then forcibly resets the remaining battery charge (SOC) to zero.

[0054] In one embodiment, updating the calibration capacity based on the calibration capacity and a preset correction coefficient includes: Based on the current calibration capacity, the preset attenuation scaling ratio, and the preset compensation value, the updated calibration capacity is calculated. The preset attenuation scaling ratio is determined based on the preset depth of discharge coefficient, and the preset compensation value is a fixed compensation value or zero.

[0055] As mentioned above, the attenuation scaling ratio refers to the reduction ratio calculated based on a preset depth of discharge coefficient. Because the battery pack cannot fully utilize its nominal capacity when actually discharged to the cutoff voltage due to the effects of protection circuit hardware action and current sampling errors, a certain safety margin needs to be reserved to make the corrected capacity closer to the actual usable capacity. For example, the depth of discharge coefficient is set to 97, corresponding to a scaling ratio of 97% (i.e., 97 / 100). In addition to scaling proportionally, this embodiment also subtracts a preset fixed compensation value. This compensation value is used for secondary fine-tuning of the proportionally scaled capacity, further improving its accuracy. This compensation value can be preset according to the total nominal capacity of the battery pack. For example, when the nominal capacity of the battery pack is 20Ah, the compensation value can be set to 10mAh; when the nominal capacity of the battery pack is 100Ah, the compensation value can be set to 20mAh. If this additional correction is not required in actual applications, the compensation value can also be set directly to zero. The MCU first multiplies the current calibrated capacity by the scaling ratio, and then subtracts the fixed compensation value. After the calculation is complete, the MCU writes the calculated new capacity into the storage unit, replacing the original calibrated capacity, and finally forces the remaining battery power SOC to zero, completing this capacity self-calibration.

[0056] In one embodiment, before the MCU controls the battery management system to enter calibration mode or normal mode according to preset flag bits, the system first performs an initialization process to ensure that the capacity parameters and flag bit states stored in the memory are correct and valid. First, after the MCU powers on, it reads the previously saved initial calibration capacity and initial flag bit states from the backup register or FLASH memory. Then, it determines whether the initial calibration capacity is zero or less than a preset abnormal value (for example, if data is lost due to a system power failure or first power-on, the read value may be 0 or a very small value; this abnormal value is usually set to be much smaller than the default capacity). If the determination result is "yes," meaning the capacity is invalid, the MCU forcibly initializes the current calibration capacity to a default nominal capacity (for example, the battery's factory rated capacity) and simultaneously clears the accumulated discharge capacity to zero, using this as the initial reference for capacity calculation.

[0057] Next, the MCU checks the validity of the read initial flag state. If the flag state is determined to be "no valid historical state stored" (for example, the flag was never written to the FLASH during the first power-on, and the read value is invalid), the MCU sets the preset flag to an initial state value. For example, this initial state value is set to 2 (i.e., representing the charging phase of calibration mode), thereby instructing the system to directly enter the charging phase of calibration mode after startup, and begin a complete charge-discharge calibration cycle of the battery to obtain the true initial calibration capacity.

[0058] In one embodiment, the method further includes two steps: rise correction and recalibration. Specifically: Recovery Correction: During the discharge phase of the normal mode, when it is determined that the battery pack is in a depleted state and the initial SOC is lower than a preset lower limit, the control unit accumulates the number of consecutive satisfactions. When the number of consecutive satisfactions reaches a preset threshold, the calibrated capacity is increased according to a preset recovery coefficient, and the number of consecutive satisfactions is reset to zero. Therefore, when the calibrated capacity is persistently low due to occasional false triggering, the system can automatically restore it to a reasonable range after multiple consecutive normal depletions, preventing the calibrated capacity from remaining persistently low.

[0059] Recalibration: When preset recalibration conditions are met, the control unit updates the preset flag bit to a state value indicating the charging phase of entering the calibration mode, and re-executes a complete charge-discharge calibration cycle. The preset recalibration conditions include at least one of the following three: the cumulative number of charge-discharge cycles reaches a preset cycle threshold, the degradation ratio of the calibrated capacity relative to the rated capacity of the battery pack reaches a preset degradation threshold, and the battery pack is detected to have been replaced.

[0060] Through the above-mentioned recovery correction and capacity reduction correction in normal mode, the calibrated capacity automatically recovers when it is too low and automatically decreases when it is too high, converges bidirectionally with charge and discharge cycles, and is recalibrated when the battery ages or is replaced, thereby realizing dynamic maintenance of the calibrated capacity throughout its entire life cycle.

[0061] In one embodiment, the above method is applied to a 6-cell lithium iron phosphate battery pack with a nominal capacity of 15Ah, and the MCU used is an STM32F030 microcontroller. The battery pack has a preset full charge threshold of 21V, a full discharge threshold of 16.5V, an empty-charge delay of 2 seconds, and a depth of discharge (DOD) of 97.

[0062] When the system is first powered on, the MCU cannot read valid historical capacity and flag records from the memory. Therefore, the MCU sets the preset flag to "2" and directly enters the charging phase of calibration mode. During charging, when the MCU detects that the total voltage of the battery pack reaches 21V, it determines that the full charge condition is met, and the system stops charging (for example, the MCU controls the charging relay to turn off). At the same time, the flag is updated from "2" to "3", the accumulated discharge capacity is cleared, and the system officially enters the discharge phase of calibration mode.

[0063] During discharge, the battery pack voltage gradually decreases. When the total voltage drops to 16.5V or below, and remains at this low voltage for approximately 2 seconds, the MCU begins to verify the validity of the discharge data. First, the MCU checks if the current accumulated discharge capacity is within the valid range of 5Ah to 15Ah (for example, an accumulated discharge of 4.2Ah is considered invalid, while 13.8Ah is considered valid). Simultaneously, the MCU checks if the current ambient temperature is higher than the preset -5℃ temperature threshold. When both capacity and temperature conditions are met, the MCU determines that the full discharge is genuine and valid, writes the accumulated discharge capacity (e.g., 13.8Ah) to the calibration capacity, updates the flag bit to "0", and the system enters normal mode. If either the capacity or temperature condition is not met, the calibration is abandoned, the accumulated discharge capacity is cleared, the flag bit is reset to "2", and the calibration cycle restarts.

[0064] After entering normal mode, the MCU checks the total battery pack voltage every 10ms during the discharge phase. When the total voltage does not exceed the full discharge threshold of 16.5V for 200 consecutive sampling cycles (approximately 2 seconds), the MCU confirms that the battery pack is depleted and obtains the calculated remaining battery capacity SOC as the initial SOC. The MCU determines whether this initial SOC is less than 15 (original range 0~1000, corresponding to 1.5%). If the initial SOC is less than 15, it is considered normally depleted, and capacity correction is not triggered; the remaining battery capacity SOC is directly forced to zero. If the initial SOC is equal to or greater than 15, and the current flag is in the normal discharge phase, a capacity jump is detected, triggering capacity self-correction. The system multiplies the current calibrated capacity by 0.97 and subtracts the preset compensation value to obtain the updated calibrated capacity. After the update is completed, the flag is updated to an uncorrectable state, and finally, the remaining battery capacity SOC is forced to zero, ending the current correction process.

[0065] It is understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0066] Based on the same inventive concept, embodiments of the present invention also provide a method for implementing the battery management system described above. The solution provided by this system is similar to the solution described in the above method; therefore, specific limitations in one or more system embodiments provided below can be found in the limitations of the method described above, and will not be repeated here.

[0067] In one embodiment, the battery management system includes a memory, a control unit, an independent protection module, and a switching unit for controlling the charging and discharging circuit of the battery pack. The memory is electrically connected to the control unit and is used to store computer programs; The control unit is used to be electrically connected to the battery pack to obtain the operating parameters of the battery pack; The switching unit is used to connect in series to the charging and discharging circuit of the battery pack; The independent protection module is electrically connected to the switching unit and is used to directly drive the switching unit to turn on and off, and there is no signal interaction between the independent protection module and the control unit; The memory stores a computer program, which, when executed by the control unit, implements the steps of the battery capacity self-calibration method as described in any of the preceding claims.

[0068] The present invention also provides an energy storage power supply, including a battery pack and a battery management system as described above, wherein the battery management system is electrically connected to the battery pack.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery capacity self-calibration method, characterized in that, A battery management system connected to a battery pack is provided. The battery management system includes a control unit, a switching unit, an independent protection module, and a memory electrically connected to the control unit. The battery management system does not have an analog front-end chip for acquiring the voltage of individual cells in the battery pack, and the control unit does not acquire the voltage of individual cells in the battery pack. The control unit acquires the operating parameters of the battery pack and calculates the remaining state of charge (SOC) of the battery based on the calibrated capacity stored in the memory. The operating parameters include at least electrical parameters and temperature parameters. The switching unit controls the charging and discharging circuit of the battery pack and is controlled by the independent protection module in the battery management system. There is no signal interaction between the control unit and the independent protection module. The method includes: The control unit controls the battery management system to switch between calibration mode and normal mode according to a preset flag bit; During the discharge phase of the calibration mode, when the electrical parameters meet the preset full discharge conditions, the current cumulative discharge capacity and the temperature parameters are obtained; when the cumulative discharge capacity and the temperature parameters meet the preset correction conditions, the cumulative discharge capacity is written to the calibration capacity, and the system switches to the normal mode; otherwise, the calibration capacity is not updated, the cumulative discharge capacity is cleared, and the system switches back to the charging phase of the calibration mode. During the discharge phase of the normal mode, when the electrical parameters meet the preset full discharge condition, it is determined that the battery pack is in an empty state, and the remaining battery charge SOC at the corresponding time is obtained as the original SOC. If the original SOC is lower than the preset jump threshold, it is determined to be a normal empty battery, the capacity self-correction is not triggered, and the current remaining battery SOC is forcibly set to zero. If the original SOC is not lower than the preset jump threshold, and it is determined to be in the allowable correction state according to the preset flag bit, then the capacity self-correction is triggered: update the calibrated capacity according to the calibrated capacity and the preset correction coefficient, update the preset flag bit, and force the current remaining battery SOC to be set to zero. If the original SOC is not lower than the preset jump threshold, and it is determined according to the preset flag that it is not in the allowed correction state, then the calibrated capacity will not be updated, and the current remaining battery SOC will be forcibly set to zero.

2. The battery capacity self-calibration method according to claim 1, characterized in that, The operating parameters include the total voltage and total current of the battery pack; the control unit performs ampere-hour integration on the total current to obtain the cumulative discharge capacity, and calculates the remaining battery charge (SOC) based on the cumulative discharge capacity and the rated capacity; The switching unit includes a charging MOSFET and a discharging MOSFET connected in reverse series to the charging and discharging circuit. The on / off states of the charging MOSFET and the discharging MOSFET are directly driven by the independent protection module.

3. The battery capacity self-calibration method according to claim 1, characterized in that, The step of writing the accumulated discharge capacity into the calibrated capacity when the accumulated discharge capacity and the temperature parameter meet the preset correction conditions includes: Determine whether the accumulated discharge capacity satisfies the condition of being greater than a preset effective lower limit value and not greater than a preset effective upper limit value; Determine whether the temperature parameter is higher than a preset temperature threshold; When the cumulative discharge capacity is greater than the preset effective lower limit and not greater than the preset effective upper limit, and the temperature parameter is higher than the preset temperature threshold, it is determined that the preset correction condition is met, and the cumulative discharge capacity is written into the calibration capacity.

4. The battery capacity self-calibration method according to claim 1, characterized in that, The preset flag bit has multiple state values ​​representing the system state, and the method further includes: During the charging phase of the calibration mode, when the electrical parameters meet the preset full charge conditions, the preset flag bit is updated to a state value representing the calibration discharge phase, the charging is stopped and the accumulated discharge capacity is cleared, and the discharge phase of the calibration mode is entered. During the charging phase of the normal mode, when the electrical parameters meet the preset full charge conditions, the preset flag is updated to a state value representing the normal discharge phase, the accumulated discharge capacity is cleared, and the normal mode discharge phase begins.

5. The battery capacity self-calibration method according to claim 4, characterized in that, Also includes: Determine whether the preset flag bit is currently the state value representing the normal discharge stage; If so, it is determined that the state is in the allowable correction state, and after the trigger capacity self-correction is performed, the preset flag is updated to a state value indicating that the state is not correctable.

6. The battery capacity self-calibration method according to claim 1, characterized in that, The step of updating the calibration capacity based on the calibration capacity and the preset correction coefficient includes: Based on the current calibration capacity, the preset attenuation scaling ratio, and the preset compensation value, the updated calibration capacity is calculated. The preset attenuation scaling ratio is determined based on the preset depth of discharge coefficient, and the preset compensation value is a fixed compensation value or zero.

7. The battery capacity self-calibration method according to claim 2, characterized in that, During the discharge phase of the calibration mode, the control unit also acquires the total current in real time and calculates the rate of change of the total current between adjacent sampling periods. When the rate of decrease of the total current within a preset sampling period exceeds a preset sudden change threshold, the control unit determines that the independent protection module has forcibly cut off the charging and discharging circuit due to hardware protection conditions, sets the accumulated discharge capacity to invalid and clears it to zero, exits the discharge phase of the calibration mode, switches back to the charging phase of the calibration mode, and does not update the calibration capacity.

8. The battery capacity self-calibration method according to claim 1, characterized in that, Also includes: During the discharge phase of the normal mode, when it is determined that the battery pack is in a depleted state and the original SOC is lower than a preset lower limit, the number of consecutive times that the condition is met is accumulated. When the number of consecutive satisfactions reaches a preset threshold, the calibration capacity is increased according to a preset recovery coefficient, and the number of consecutive satisfactions is reset to zero. and / or When the preset recalibration conditions are met, the preset flag bit is updated to a state value indicating the charging stage of entering the calibration mode. The preset recalibration conditions include at least one of the following: the cumulative number of charge-discharge cycles reaches a preset cycle threshold, the attenuation ratio of the calibrated capacity relative to the rated capacity of the battery pack reaches a preset attenuation threshold, and the battery pack is detected to have been replaced.

9. A battery management system, characterized in that, It includes a memory, a control unit, an independent protection module, and a switching unit for controlling the charging and discharging circuit of the battery pack; The memory is electrically connected to the control unit and is used to store computer programs; The control unit is used to be electrically connected to the battery pack to obtain the operating parameters of the battery pack; The switching unit is used to connect in series to the charging and discharging circuit of the battery pack; The independent protection module is electrically connected to the switching unit and is used to directly drive the switching unit to turn on and off, and there is no signal interaction between the independent protection module and the control unit; The memory stores a computer program, which, when executed by the control unit, implements the steps of the battery capacity self-calibration method as described in any one of claims 1 to 8.

10. An energy storage power source, characterized in that, It includes a battery pack and a battery management system as described in claim 9, wherein the battery management system is electrically connected to the battery pack.

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