Inter-cell active equalization control method and device, battery management system and battery pack

Abstract

The invention relates to an inter-cell active equalization control method and device, a battery management system and a battery pack. The method comprises the following steps: acquiring state information of each cell in the battery pack according to a preset time interval; judging whether the battery pack meets an active equalization starting condition or not according to the state information; wherein the active equalization starting conditions comprise that the battery pack is not in a fault state, the battery pack is not in a protection state, the voltage difference between battery cells is greater than a preset voltage threshold value, the charge state difference between the battery cells is greater than a preset charge state threshold value, and the temperature of the battery cells is in a normal working range of the battery cells; the charging current is in a normal working range and the battery pack is not in a discharging state; and under the condition that the active equalization starting condition is met, active equalization is automatically started. According to the method, multiple groups of active equalization starting conditions are judged before active equalization is started, so that the safety of active equalization control among the battery cells can be effectively guaranteed, and active equalization among the battery cells can be realized in time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage control, in particular to a method and device for active balancing control between battery cells, a battery management system and a battery pack. BACKGROUND

[0002] After a certain length of time of use, the battery often has the problem of poor voltage consistency between battery cells, which is caused by different voltage attenuation degrees of each battery cell during the battery aging process, resulting in differences in voltage difference between battery cells.

[0003] Most of the existing control schemes for actively balancing between batteries are between batteries, and there are few schemes for actively balancing control between battery cells, which cannot effectively achieve voltage balancing between battery cells in a single battery and has low safety. SUMMARY

[0004] Therefore, it is necessary to provide a method and device for active balancing control between battery cells, a battery management system and a battery pack, which can actively achieve battery balancing between battery cells in a single battery under the condition of ensuring safety.

[0005] In a first aspect, the present application provides a method for active balancing control between battery cells, comprising:

[0006] acquiring state information of each battery cell in the battery pack at a preset time interval, the state information including voltage, current, temperature and state of charge of each battery cell;

[0007] determining whether the battery pack meets an active balancing start condition according to the state information, wherein the active balancing start condition includes that the battery pack is not in a fault state, the battery pack is not in a protection state, the voltage difference between battery cells is greater than a preset voltage threshold, the state of charge difference between battery cells is greater than a preset state of charge threshold, the temperature of the battery cell is in a normal working range of the battery cell, the charging current is in a normal working range and the battery pack is not in a discharging state;

[0008] automatically starting active balancing to adjust the voltage difference between the battery cells to be balanced according to a target balancing current when the active balancing start condition is met.

[0009] In one embodiment, the automatic starting of active balancing comprises:

[0010] acquiring the positions of the highest voltage battery cell and the lowest voltage battery cell;

[0011] determining whether to start active balancing in a forward direction or a reverse direction according to the positions of the highest voltage battery cell and the lowest voltage battery cell.

[0012] In one of the embodiments, the current values of the equalization currents in the forward active equalization and the reverse active equalization are different, and the current values of the equalization currents are dynamically adjusted according to the position difference between the highest voltage cell and the lowest voltage cell.

[0013] In one of the embodiments, the method further comprises:

[0014] In the active equalization process, a target duty cycle of a voltage sampling time, an active equalization start time and a static time is set, and the active equalization is realized according to the target duty cycle; wherein the active equalization is turned off in the voltage sampling time, and the voltage is collected after the cell voltage is stabilized.

[0015] In one of the embodiments, the method further comprises:

[0016] receiving a communication signal sent by a preset communication terminal, wherein the communication signal comprises equalization control parameters, and the equalization control parameters comprise an equalization direction, a cell to be equalized and an equalization time;

[0017] determining whether the battery pack satisfies the active equalization start condition in real time according to the communication signal;

[0018] in the case that the active equalization start condition is satisfied and the battery pack is not in the active equalization state, starting the active equalization according to the equalization control parameters.

[0019] In one of the embodiments, after the active equalization is started, the method further comprises:

[0020] monitoring state information of each cell in the battery pack;

[0021] in the case that the state information does not satisfy the active equalization start condition, turning off the active equalization.

[0022] In one of the embodiments, before the communication signal sent by the preset communication terminal is received, the method further comprises:

[0023] sending the state information to the preset communication terminal, so that the preset communication terminal determines a sampling information error and a battery charge and discharge capacity according to the state information, and generates and sends the communication signal in the case that the sampling information error is greater than a preset error threshold or the battery charge and discharge capacity decreases to a preset threshold.

[0024] In a second aspect, the application further provides an active equalization control device between cells, comprising:

[0025] a state information acquisition module, configured to acquire state information of each cell in the battery pack at a preset time interval, and the state information comprises voltage, current, temperature and state of charge of each cell.

[0026] The equalization condition determining module is configured to determine whether the battery pack satisfies an active equalization starting condition according to the state information, wherein the active equalization starting condition comprises that the battery pack is not in a fault state, the battery pack is not in a protection state, a voltage difference between the battery cells is greater than a preset voltage threshold, a state of charge difference between the battery cells is greater than a preset state of charge threshold, a temperature of the battery cell is in a normal working range of the battery cell, a charging current is in a normal working range, and the battery pack is not in a discharging state.

[0027] The active equalization control module is configured to automatically start the active equalization to adjust the equalization current between the battery cells to be equalized when the active equalization starting condition is satisfied.

[0028] In a third aspect, the application further provides a battery management system, comprising a front-end sampling unit, a control unit and a temperature unit, wherein the front-end sampling unit is configured to sample the voltage and the current of the battery cell, the temperature unit is configured to sample the temperature of the battery cell and the ambient temperature, and the control unit is configured to execute the inter-battery-cell active equalization control method of the first aspect.

[0029] In a fourth aspect, the application further provides a lithium battery pack, comprising a plurality of battery cells connected in series or in parallel and the battery management system of the third aspect.

[0030] In summary, the application provides an inter-battery-cell active equalization control method, device, battery management system and battery pack, comprising: obtaining state information of each battery cell in a battery pack at a preset time interval; determining whether the battery pack satisfies an active equalization starting condition according to the state information; wherein the active equalization starting condition comprises that the battery pack is not in a fault state, the battery pack is not in a protection state, a voltage difference between the battery cells is greater than a preset voltage threshold, a state of charge difference between the battery cells is greater than a preset state of charge threshold, a temperature of the battery cell is in a normal working range of the battery cell, a charging current is in a normal working range, and the battery pack is not in a discharging state; and automatically starting the active equalization when the active equalization starting condition is satisfied. The application can effectively guarantee the safety of the inter-battery-cell active equalization control and timely realize the inter-battery-cell active equalization by determining a plurality of active equalization starting conditions before starting the active equalization. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 FIG. 1 is a structural block diagram of a battery management system in one embodiment;

[0032] Figure 2 FIG. 2 is a flowchart of an inter-battery-cell active equalization control method in one embodiment;

[0033] Figure 3 FIG. 3 is a flowchart of an inter-battery-cell active equalization control method in another embodiment;

[0034] Figure 4 A flowchart of a method for active inter-cell equalization control in another embodiment;

[0035] Figure 5 A block diagram of an active inter-cell equalization control device in an embodiment;

[0036] Figure 6 An internal structure diagram of a computer device in an embodiment. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the present application clearer, further detailed description will be made to the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0038] In the related art, lithium batteries are widely used in energy storage, new energy vehicles and other fields due to their high energy density and long cycle life. However, a lithium battery pack is composed of multiple cells in series or parallel. Due to the differences in cell manufacturing process, different use environments and inconsistent aging levels, the voltage and state of charge (SOC) between cells are prone to inconsistency, especially at the end of charging and discharging, the pressure difference will increase significantly. This inconsistency will lead to a decrease in the charging and discharging capacity of the battery pack, a shortening of the cycle life, and even cause safety hazards such as overcharging and overdischarging.

[0039] In the related art, battery equalization methods are mainly divided into passive equalization and active equalization. Passive equalization consumes the energy of high-voltage cells through resistance to achieve equalization, but its efficiency is low and energy loss is large, and it is only suitable for small-capacity battery systems. Active equalization achieves equalization through energy transfer (such as charging from high-voltage cells to low-voltage cells), which is more efficient and suitable for large-capacity battery systems.

[0040] However, the existing active equalization technology has the following shortcomings: first, the equalization start condition is single, only based on voltage difference, without considering key parameters such as SOC and temperature, which is prone to false triggering or delayed equalization. Second, the voltage sampling in the equalization process is greatly affected by current fluctuations, with low collection accuracy, affecting the equalization effect. Third, there is a lack of flexible control mode, which cannot adapt to complex scenarios such as cell aging and sampling error. Fourth, the safety design is insufficient, and there is no protection mechanism for risks such as temperature rise and current abnormalities during equalization.

[0041] To solve the problems of low equalization accuracy, poor adaptability and insufficient safety in existing active equalization technology, the present application provides an active inter-cell equalization control method based on lithium batteries, which improves the consistency of cells and the reliability of battery packs through multi-parameter judgment, timing optimization and flexible control mode.

[0042] In one embodiment, as shown in FIG. 1, a battery management system (BMS) is provided, which includes a front-end sampling unit 110, a control unit 120 and a temperature unit 130. The control unit 120 is connected to the front-end sampling unit 110 and the temperature unit 130, respectively. Figure 1

[0043] In this embodiment, the front-end sampling unit 110 is configured to sample the voltage and current of the battery cell. The front-end sampling unit 110 can use an active front end (AFE) unit to sample the voltage and current of the battery cell. It should be noted that the specific chip composition and related circuit of the AFE unit are not limited in this embodiment, and the chip composition and related circuit of the AFE unit can be determined according to the type of the battery pack and the specific circuit structure of the battery cell in the actual application scenario.

[0044] In this embodiment, the temperature unit 130 is configured to sample the temperature of the battery cell and the ambient temperature. The temperature unit 130 can use a negative temperature coefficient thermistor (NTC thermistor) or a positive temperature coefficient thermistor (PTC thermistor) and configure a corresponding temperature acquisition circuit to sample the temperature of each battery cell and the ambient temperature of the environment where the battery cell is located. It should be noted that after the temperature unit 130 acquires the temperature data, the temperature data will be sent to the control unit 120, so that the control unit 120 can determine the temperature state of the battery cell according to the temperature data. For example, the temperature unit 130 can use a NTC thermistor with a sampling range of -40-80 degrees Celsius (℃) and an accuracy of ±1℃ as a temperature data sampling element. The control unit 120 determines whether the current battery cell is in a normal temperature state or an overheating state according to the temperature data returned by the temperature data sampling element. It should be noted that the temperature state of the battery cell includes an overcooling state, a normal temperature state and an overheating state, and the temperature threshold related to the temperature state of the battery cell can be defined according to the actual application needs, so that the control unit 120 can determine the temperature state of the battery cell in real time according to the battery cell temperature detected by the temperature unit 130, thereby monitoring the temperature abnormality.

[0045] ​In the embodiment, the control unit 120 includes a microcontroller unit (MCU) and related control circuit. In an embodiment, an STM32 series single-chip microcomputer can be used as the MCU to execute the equalization strategy logic of the inter-cell active equalization control method in the embodiment, including state judgment, timing control, communication interaction, etc. In the embodiment, the battery management system further includes an equalization circuit, wherein the equalization circuit is connected with the control unit 120, and the equalization circuit can use a bidirectional DC / DC converter to support a 0.5-2A adjustable current to realize energy transfer from a high-voltage cell to a low-voltage cell. In actual application, the actual circuit structure of the equalization circuit can be configured according to the connection mode of the battery pack and the cells in the actual application scenario. In an embodiment, the equalization circuit includes a boost circuit and a buck circuit to realize forward equalization and reverse equalization.

[0046] Based on the above steps, the embodiment provides a battery management system capable of monitoring the state information of each cell in the battery pack, and by presetting the equalization strategy logic of the inter-cell active equalization control method in the control unit 120, the battery management system can realize higher safety, higher equalization accuracy, and better adaptability.

[0047] In an embodiment, as shown in Figure 2 , an inter-cell active equalization control method is provided, which is applied to the battery management system in Figure 1 for example, including the following steps:

[0048] S201, acquiring the state information of each cell in the battery pack according to a preset time interval, the state information including voltage, current, temperature, and state of charge of each cell.

[0049] In the embodiment, the preset time interval can be 200 ms, and by acquiring the state information of each cell in the battery pack at a regular time interval, the attenuation degree of each cell in the battery pack can be monitored in real time. It should be noted that the preset time interval can also be configured to be any time such as 150 ms-300 ms according to actual application needs, and the embodiment does not limit the preset time interval.

[0050] In the embodiment, the state information of the cell is mainly acquired by the front-end sampling unit and the temperature unit in the battery management system. It should be noted that the method of acquiring each state information includes two steps, i.e., acquiring the current and voltage by the front-end sampling unit and acquiring the temperature by the temperature unit, and then determining the SOC of the cell based on the current, voltage, and temperature after acquiring the current, voltage, and temperature.

[0051] It should be noted that in this embodiment, the control unit acquires the cell status information before activating active balancing. When acquiring the current, the control power supply can first perform zero-point current calibration, and then acquire the current after confirming that the zero-point current calibration is complete. SOC represents the percentage of the current remaining charge relative to the total battery capacity, and the calculation formula is:

[0052]

[0053] The remaining charge indicates the amount of charge the battery can actually use, and can be estimated using methods such as current integration and open-circuit voltage method. The rated capacity indicates the maximum amount of charge the battery can release under standard conditions (such as specific temperature and discharge rate), usually expressed in ampere-hours (AH). ) or wattage ( The unit is (). In this embodiment, when calculating the current remaining current of the battery cell, the estimation result can be corrected based on the cell's attenuation factor and temperature factor to ensure that an accurate SOC value is obtained.

[0054] S202, determine whether the battery pack meets the active balancing start conditions based on the status information; wherein, the active balancing start conditions include the battery pack not being in a fault state, the battery pack not being in a protection state, the voltage difference between cells being greater than a preset voltage threshold, the state of charge difference between cells being greater than a preset state of charge threshold, the cell temperature being within the normal operating range of the cell, the charging current being within the normal operating range and the battery pack not being in a discharging state.

[0055] In this embodiment, the safety status of the battery pack is determined by judging multiple sets of active balancing activation conditions. Specifically, active balancing automatically activates when the battery pack simultaneously meets the following active balancing activation conditions:

[0056] 1. The battery management system determines whether the battery pack is in a fault-free or protected state.

[0057] 2. The voltage difference between cells is greater than the preset voltage threshold, where the preset voltage threshold is, for example, 30mV.

[0058] 3. The SOC difference between cells is greater than the preset SOC threshold, where the preset SOC threshold is, for example, 5%.

[0059] 4. The cell temperature is within the normal operating range of the cell.

[0060] 5. The charging current is within the normal range and the device is not in a discharging state.

[0061] In the embodiment, the battery management system BMS continuously monitors the state of the battery pack through the built-in self-checking program and sensor data. The fault types that the battery management system can detect include electrical faults, thermal faults, and communication faults. Among them, the electrical faults include overvoltage, undervoltage, overcurrent, short circuit, etc. The thermal faults include that the temperature of the battery cell exceeds the safe range, and the heat dissipation system fails. The communication faults include that the BMS interrupts the communication with the slave unit or the upper computer.

[0062] In the embodiment, the protection state includes charging protection and discharging protection. The charging protection includes charging interruption triggered by overvoltage, overcurrent, etc. The discharging protection includes discharging interruption triggered by undervoltage, overtemperature, etc. In actual application, both the fault state and the protection state can be marked by internal state registers or fault codes. The BMS determines that the battery pack is in a fault state or a protection state when any corresponding flag bit is activated. In the case where none of the fault flag bits is activated, it is determined that the battery pack is not in a fault state or a protection state.

[0063] In the embodiment, the inter-cell voltage difference refers to the difference between the maximum cell voltage and the minimum cell voltage. Assuming that the maximum cell voltage is V_max and the minimum cell voltage is V_min, the inter-cell voltage difference is ΔV = V_max - V_min. In actual application, all cell voltages can be synchronously collected by using an AFE unit or a high-precision analogue-to-digital conversion circuit (ADC). In the embodiment, assuming that the preset voltage threshold is 30 mV, when ΔV > 30 mV and the duration is ≥1 s (to avoid transient interference), it is determined that the second active equalization condition is met. It should be known that the preset voltage threshold and the duration can be configured according to the needs of the actual application scenario.

[0064] In the embodiment, the inter-cell SOC difference refers to the difference between the maximum cell SOC and the minimum cell SOC. Assuming that the maximum cell SOC is SOC_max and the minimum cell SOC is SOC_min, the inter-cell SOC difference is ΔSOC = SOC_max - SOC_min. In actual application, the SOC values of the cells can be calculated by using the extended Kalman filter (EKF) or the ampere-hour integration combined with the open circuit voltage (OCV) algorithm. When calculating the SOC values of the cells, the SOC calculation time stamps of all the cells are synchronized to ensure consistency. In the embodiment, assuming that the preset SOC threshold is 5%, if it is determined that ΔSOC > 5% and the duration is ≥10 s, it is determined that the third active equalization condition is met. It should be known that the preset SOC threshold and the duration can be configured according to the needs of the actual application scenario.

[0065] In the embodiment, the temperature of each battery cell can be collected by arranging NTC temperature sensors (temperature units) in each battery cell to obtain the working temperature of each battery cell. Assuming that the normal working temperature range is 0℃≤T≤45℃, the fourth active balancing condition is determined to be met when the minimum temperature of each battery cell is greater than or equal to 0℃ and the maximum temperature is less than or equal to 45℃. If the temperature of any battery cell exceeds the range, the BMS triggers the thermal management (such as starting the fan or heating) and suspends the balancing. It should be noted that the manner in which the BMS performs thermal management can be configured according to the needs of the actual application scenario, which is not limited here.

[0066] In the embodiment, the current direction can be determined by the current sensor (such as a Hall sensor) arranged in the AFE unit, and the charging and discharging state can be determined by the relationship between the current direction and the charging and discharging state. For example, the current is positive during charging and negative during discharging. In some embodiments, a state machine can also be used to distinguish between charging, discharging and resting states to avoid misjudgment due to current fluctuations. Assuming that the normal charging current range is 0A<I_charge≤I_max_allow (where I_max_allow is the maximum allowed charging current of the battery), the current value is monitored in real time, and if I_charge is within the normal charging current range and the discharging current I_discharge=0, the fifth active balancing condition is met.

[0067] In the embodiment, the determination of the fault state and the protection state is to ensure that the active balancing works in a safe environment. For example, after the AFE chip is damaged (the battery pack is in a fault state), the actual situation of the battery cell is uncertain, and after the active balancing is started, there is current in the loop, which may cause safety hazards to the battery pack.

[0068] In the embodiment, the BMS collects the voltage of each battery cell, and when the voltage is too low, the active balancing is not allowed to be started again, because the active balancing consumes more power and prevents the battery cell from being discharged. Similarly, the BMS collects the charging and discharging current of the battery to prevent the temperature from rising too fast and the current from damaging the active balancing chip.

[0069] In one embodiment, the active balancing can also be automatically started when the first, second, fourth and fifth active balancing start conditions or the first, third, fourth and fifth active balancing start conditions are met. It should be noted that at the end of charging and discharging, the voltage fluctuates greatly, and it is more accurate to use SOC to determine whether the battery pack is in a safe state.

[0070] S203, automatically starting the active balancing under the condition that the active balancing start condition is met, to adjust the voltage difference between the battery cells to be balanced according to the target balancing current.

[0071] In the embodiment, the SOC difference between the to-be-balanced cells is greater than a preset SOC threshold, and the voltage difference between the cells is greater than a preset voltage threshold. The preset SOC threshold and the preset voltage threshold can be configured according to the actual application scenario.

[0072] In the case where the active balancing start condition in the foregoing embodiment is met, the BMS automatically starts the active balancing, controls the high-capacity cell to charge the low-capacity cell according to the target balancing current, so as to adjust the voltage difference between the to-be-balanced cells. The target balancing current can be determined according to the positions of the highest-voltage cell and the lowest-voltage cell.

[0073] In summary, the embodiment provides an active balancing control method between cells. The state information of each individual cell in the battery pack is monitored, and a plurality of active balancing start conditions are judged. In the case where the active balancing start condition is met, the active balancing control is started, which can effectively guarantee the consistency of the cells in the battery pack, improve the working life of the battery pack, guarantee the reliability and safety of the battery pack in performing the active balancing, and avoid safety hazards or equipment failures of the battery pack caused by the active balancing control.

[0074] In one of the embodiments, as shown in FIG. 1, the active balancing is automatically started, including: Figure 3

[0075] S301, obtaining the positions of the highest-voltage cell and the lowest-voltage cell.

[0076] S302, determining the forward or reverse start of the active balancing according to the positions of the highest-voltage cell and the lowest-voltage cell.

[0077] In the embodiment, in the active balancing process, the positions of the highest-voltage cell and the lowest-voltage cell, i.e., the positions of the cell with the highest capacity and the cell with the lowest capacity, are obtained first. The balancing direction refers to two different active balancing modes, i.e., discharging through a step-down circuit (discharging from a low string to a high string) and discharging through a step-up circuit (discharging from a high string to a low string). The balancing currents of different active balancing modes are different. Specifically, the balancing currents of the forward start of the active balancing and the reverse start of the active balancing are different in current value, and the current value of the balancing current is dynamically adjusted according to the position difference between the highest-voltage cell and the lowest-voltage cell.

[0078] ​In the embodiment, the position difference refers to the physical interval of the highest voltage cell (H) and the lowest voltage cell (L) in the battery pack. In an actual application scenario, the cells can be divided into adjacent cells, near-interval cells and far-interval cells according to the position difference, wherein the H and the L of the adjacent cells are directly adjacent (with an interval of 0 cells), the H and the L of the near-interval cells are spaced apart by 1-3 cells, and the H and the L of the far-interval cells are spaced apart by more than 3 cells or are located in different modules. In the forward equalization process, i.e., the discharging process, a Buck circuit can be used to realize discharging from a low string to a high string. In the reverse equalization process, i.e., the charging process, a Boost circuit can be used to realize discharging from a high string to a low string.

[0079] In the embodiment, the equalization current increases with the increase of the position difference, so as to quickly equalize the far-interval cells by a larger current. It should be noted that, in a feasible embodiment, for the adjacent cells, the near-interval cells and the far-interval cells, a stepped incremental equalization voltage adjustment can be used. For example, for the equalization current of the adjacent cells, the equalization current is 2A in the forward equalization and 1A in the reverse equalization. For the equalization current of the near-interval cells, the equalization current is 3A in the forward equalization and 1.5A in the reverse equalization. For the far-interval cells, the equalization current is 4A in the forward equalization and 2A in the reverse equalization.

[0080] In an embodiment, by continuously monitoring the position difference and the cell state, the equalization current is updated once every interval, so as to be adaptively adjusted based on the position difference between the highest voltage cell and the lowest voltage cell, so that the highest voltage cell can stably provide power to the lowest voltage cell, thereby ensuring the consistency of the capacity between the cells in the battery pack and improving the charging and discharging capacity of the battery pack.

[0081] Based on the above steps, the active equalization control method between cells provided in the embodiment can dynamically adjust the discharging mode of the equalization circuit according to the actual state of the cells in the battery pack, realize bidirectional active equalization, and greatly improve the flexibility of active equalization control.

[0082] In an embodiment, the active equalization control method between cells further comprises:

[0083] In the active equalization process, the target duty cycle of the voltage sampling time, the active equalization start time and the standby time is set, and the active equalization is realized according to the target duty cycle; wherein the active equalization is closed in the voltage sampling time, and the voltage is collected after the cell voltage is stable.

[0084] In the embodiment, by setting a proper target duty cycle, the timing of the active balancing can be effectively optimized. For example, the voltage sampling time: active balancing on time: resting time = 1:3:2 (which can be adjusted according to the performance of the battery cell) is set, and the active balancing is turned off during the voltage sampling process in the voltage sampling time, so as to effectively ensure the voltage sampling accuracy, and thus the accurate voltage adjustment during the active balancing process can be ensured. In the case of ensuring safety and reliability, the longer the balancing time is, the higher the active balancing efficiency between the battery cells is.

[0085] In actual application, the battery cell is different from the battery. When the energy of the battery cell is transferred, the voltage of the battery cell is unstable. After the active balancing is started, the voltage of the battery cell is sampled to obtain the actual voltage of the battery cell. During the sampling process, the active balancing is not performed. After the energy is stabilized, the voltage of the battery cell is collected, so as to ensure that the real voltage of the battery cell is collected. It should be noted that the active balancing on time is used to represent the time for performing the active balancing. In fact, when the voltage sampling time starts, the BMS has automatically started the active balancing. The resting time is set to stabilize the energy of the battery cell.

[0086] Based on the above steps, by setting the active balancing duty cycle, the time for the active balancing can be as long as possible under the premise that the real voltage of each battery cell can be collected, and the longer the active balancing time is, so that the energy of each battery cell in the battery is balanced to a balanced state more quickly. The active balancing control method between the battery cells provided in the embodiment can be applied to the case where the consistency between the battery cells in the battery is very poor. In the case where the sampling information error is greater than a preset error threshold or the battery charge and discharge capacity decreases to a preset threshold, it is indicated that the consistency between the battery cells is very poor. The sampling information error refers to the error between the voltage collected by the TFE chip and the real voltage of the battery cell, and the battery charge and discharge capacity refers to the charge and discharge capacity of the battery pack composed of the battery cells.

[0087] In one of the embodiments, as shown in Figure 4 the active balancing control method between the battery cells further includes:

[0088] S401, receiving a communication signal sent by a preset communication terminal, wherein the communication signal includes balancing control parameters, and the balancing control parameters include a balancing direction, a battery cell to be balanced, and a balancing time;

[0089] S402, judging whether the battery pack satisfies an active balancing start condition in real time according to the communication signal;

[0090] S403, starting the active balancing according to the balancing control parameters in the case where the active balancing start condition is satisfied and the battery pack is not in the active balancing state.

[0091] In the embodiment, the inter-cell active balancing control method further provides a forced opening mode, and the opening / closing of the active balancing is controlled through a communication instruction, which is suitable for a scenario where the sampling error is large or the consistency of the cells is poor.

[0092] In the embodiment, the preset communication terminal generates a communication signal including a balancing direction, a cell to be balanced, and a balancing time when determining that the sampling error of the sensor in the battery pack is large or the consistency of the cells is poor. The balancing direction is used to indicate forward balancing (discharge from a low string to a high string) or reverse balancing (discharge from a high string to a low string). The cell to be balanced is used to indicate the identification (such as a cell number) of a high-voltage cell (H) and a low-voltage cell (L) that needs to participate in balancing. The balancing time is a preset balancing duration.

[0093] After receiving the communication signal sent by the preset communication terminal, the BMS analyzes the balancing control parameters in the communication signal and determines the five active balancing conditions in the foregoing embodiments in real time. In the case where all the active balancing conditions are met, the active balancing is started. In the case where any of the active balancing conditions is not met, the active balancing is stopped.

[0094] In a feasible embodiment, the priority of the balancing control parameters (such as the cell to be balanced) in the communication signal can be set to be higher than the parameters detected by the BMS automatically. For example, if the communication signal specifies that the cell A is H, but the BMS detects that the voltage of the cell B is higher, the communication signal is used as the criterion.

[0095] In the embodiment, the preset communication terminal can be any terminal that communicates with the BMS of the battery pack, such as a personal computer, a notebook computer, a smart phone, a tablet computer, an Internet of Things device, and a portable wearable device.

[0096] It should be noted that the specific implementation of steps S402-S403 in the embodiment can refer to the specific implementation of the foregoing embodiments, which will not be described herein. In the embodiment, the active balancing is still started in the case where the active balancing is started in advance, and whether the active balancing starting condition is met is determined to ensure the reliability and safety of the active balancing of the battery pack.

[0097] Based on the foregoing steps, the embodiment combines the real-time monitoring of the BMS and the communication instruction to ensure that the balancing process is controllable. The balancing parameters are dynamically adjusted through the communication signal, which can adapt to different working conditions (such as fast charging and low temperature) of the battery pack.

[0098] In one of the embodiments, before receiving the communication signal sent by the preset communication terminal, the method further includes:

[0099] The state information is sent to the preset communication terminal, so that the preset communication terminal determines the sampling information error and the battery charge and discharge capacity according to the state information, and generates and sends a communication signal in the case that the sampling information error is greater than a preset error threshold or the battery charge and discharge capacity decreases to a preset threshold.

[0100] In this embodiment, the preset terminal generates and sends a communication signal to the BMS in the case that the sampling error is large or the consistency between the battery cells is poor. The sampling information error greater than the preset error threshold indicates that the sampling error is large, and the battery charge and discharge capacity decreasing to the preset threshold indicates that the consistency between the battery cells is poor. The preset error threshold and the preset threshold can be customized according to the actual application scenario.

[0101] In this embodiment, the voltage and temperature data of the same battery cell are synchronously collected by the TFE unit and the temperature unit, and the reference comparison method or the cross-validation method is used to determine whether the sampling information has a large error. For example, when the battery is at rest (current = 0A) and the temperature is stable, the theoretical voltage should be close to the open circuit voltage (OCV). The reference comparison method compares the sampling voltage with the OCV, and if the difference between the sampling voltage and the OCV exceeds the threshold (such as ±20mV), it is determined that the sampling information has a large error. The cross-validation method compares the sampling values of different sensors of the same battery cell or the voltage difference between adjacent battery cells to determine whether the sampling information has a large error. For example, the voltage of battery cell 1 (sensor A) is 3.80V, and the voltage of battery cell 2 (sensor B) is 3.75V. If the actual states of the two battery cells are consistent, the theoretical voltage difference should be ≤10mV, and the actual difference is 50mV, it is determined that the sampling information of sensor A or B has a large error.

[0102] In this embodiment, the battery charge and discharge capacity is reflected by the state of charge (SOC) and the state of health (SOH). In actual application, the range or variance of SOC can be calculated, and the consistency between the battery cells can be determined according to the corresponding analysis rules. For example, the difference (ΔSOC) between the maximum and minimum values of the SOC of the battery cells is calculated, and it is determined that the consistency between the battery cells is poor when the ΔSOC is greater than or equal to the preset threshold. Assuming that the preset threshold is 8%, SOC_max=85% and SOC_min=75% in the battery cell group, ΔSOC=10% (poor consistency). Alternatively, the variance of the SOC of all battery cells is calculated, and the greater the variance, the poorer the consistency between the battery cells.

[0103] In one embodiment, after the active balancing is started, the active balancing control method between the battery cells further includes:

[0104] The state information of each battery cell in the battery pack is monitored.

[0105] In the case that the state information does not satisfy the active balancing start condition, the active balancing is closed.

[0106] In the embodiment, by monitoring the state of the battery cell in real time, if the state exceeds the balancing start condition range, the active balancing is automatically closed to ensure the safety of the battery pack. For example, the BMS collects the voltage of each battery cell, and when the voltage is too low, the active balancing is not allowed to be started again, because the active balancing consumes more power, prevents the battery cell from being discharged, and thus damages the battery. The BMS collects the charging and discharging current of the battery to prevent the temperature from rising too fast and the current from damaging the active balancing chip.

[0107] In the embodiment, the state information includes charging and discharging current, battery cell temperature, SOC, SOH, fault flag, communication state, balancing efficiency and chip state, time parameter, etc. It is known that the monitoring of the state information is related to the active balancing start condition judgment process in the foregoing embodiment. The BMS can realize safe and efficient active balancing control by comprehensively monitoring the above-mentioned state information, and ensure the stable operation of the battery pack under complex working conditions.

[0108] For example, the time length from starting balancing to the current time of the battery cell to be balanced can be monitored, and the state information is verified whether it still satisfies the balancing condition regularly (for example, every 10 minutes). The start and stop of the active balancing can also be realized by monitoring whether the actual output balancing current of the balancing circuit reaches the target value (for example, 4A) or the working temperature of the balancing chip (such as Buck / Boost circuit), or the power consumption of the system in the balancing process (for example, whether it exceeds the rated power of the chip).

[0109] In summary, the embodiment provides a kind of active balancing control method between battery cell, judges by comprehensively voltage, SOC, temperature and other parameters, avoids false balancing, can improve balancing accuracy. By timing optimization (duty cycle setting) reduces voltage sampling error, can effectively improve balancing precision. Support automatic / forced start active balancing dual mode, adapt to different use scenarios, strong flexibility. Built-in safety protection mechanism, prevent battery cell from overcharging, overdischarging or temperature rise anomaly in balancing process, improve system safety. Can significantly reduce the voltage difference and SOC difference between battery cells by flexible active balancing control, prolong the cycle life of battery pack, improve energy utilization efficiency.

[0110] In a more detailed embodiment, the execution process of the control mode of automatically starting active balancing is as follows:

[0111] First, the BMS (battery management system) collects the voltage and current of each battery cell through the AFE chip every 200 ms, collects the battery cell temperature and environmental temperature through the temperature module, and calculates the SOC of each battery cell through the MCU.

[0112] Second, determine whether to meet the active balancing open condition. Assuming that a lithium battery pack contains 12 cells, and after detection, each cell in the lithium battery pack meets the following conditions: no overvoltage, overcurrent, high temperature and other faults; the voltage of cell 1 is 3.75V, the voltage of cell 6 is 3.71V, the voltage difference is 40mV (> 30mV); the SOC of cell 1 is 85%, the SOC of cell 6 is 78%, the SOC difference is 7% (> 5%); the cell temperature is 25℃ (in the normal working range of 20-40℃); the charging current is 1A (in the normal range of 0.5-2A), and it is not in the discharging state. Based on the above judgment result, it is determined that the cell meets all the active balancing open conditions.

[0113] Third, determine that the highest voltage cell is cell 1 and the lowest is cell 6. Since cell 1 is located in front of cell 6, active balancing is opened in the forward direction, and the balancing current is set to 0.8A.

[0114] Fourth, timing control, set every 6ms as an active balancing period, wherein 1ms is used for closing the balance and sampling the voltage, 3ms is used for opening the balance (cell 1 charging to cell 6), and 2ms is used for static (voltage stabilization).

[0115] Fifth, balance termination, after 30 minutes of continuous balancing, the voltage difference between cell 1 and cell 6 is reduced to 20mV, and the SOC difference is reduced to 4%, which is lower than the preset threshold, and the active balancing is automatically closed.

[0116] In another more detailed embodiment, the execution process of forced opening of active balancing is as follows:

[0117] First, when the AFE chip has sampling error (such as the actual voltage difference is 40mV, but the sampling shows 25mV), or the cell consistency is poor (after long-term use, the voltage difference of part of the cells is continuously > 50mV), the user can send a forced opening instruction through CAN communication.

[0118] Second, after the BMS receives the instruction, it first verifies whether the active balancing open condition (safety condition) is met.

[0119] Third, when the active balancing open condition is met, the active balancing is forced to open, the balancing current is increased to 1.0A, and the timing duty cycle is adjusted to 1:4:1 (the balancing time is prolonged).

[0120] Fourth, during the forced balancing process, the BMS checks the cell state every 100ms, and if the temperature rises suddenly (such as > 5℃ / min), the balance is immediately closed and an alarm is given.

[0121] The application solves the problems of low precision, poor adaptability and insufficient safety in the existing active balancing technology by multi-parameter fusion judgment, time sequence optimization and dual-mode control, significantly improves the consistency and reliability of the lithium battery pack, and can be widely applied to lithium battery management systems in the fields of electric vehicles and energy storage power stations.

[0122] It should be understood that, although each step in the flowchart involved in each embodiment as described above is displayed in sequence according to the arrow, these steps are not necessarily executed in the order indicated by the arrow. Unless otherwise specified herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other orders. Moreover, at least part of the steps in the flowchart involved in each embodiment as described above can include multiple steps or stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least part of other steps or steps or stages in other steps.

[0123] Based on the same inventive concept, the embodiments of the present application also provide an inter-cell active balancing control device for implementing the above-mentioned inter-cell active balancing control method. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme described in the above method, so the specific limitations in one or more inter-cell active balancing control device embodiments provided below can refer to the limitations of the inter-cell active balancing control method in the above text, and will not be repeated here.

[0124] In one embodiment, as shown in Figure 5 An inter-cell active balancing control device 500 is provided, comprising: a state information acquisition module 510, an equalization condition determination module 520 and an active balancing control module 530, wherein:

[0125] The state information acquisition module 510 is configured to acquire the state information of each cell in the battery pack at a preset time interval, and the state information includes voltage, current, temperature and state of charge of each cell;

[0126] The equalization condition determination module 520 is configured to determine whether the battery pack satisfies the active balancing start condition according to the state information; wherein the active balancing start condition includes that the battery pack is not in a fault state, the battery pack is not in a protection state, the voltage difference between the cells is greater than a preset voltage threshold, the state of charge difference between the cells is greater than a preset state of charge threshold, the temperature of the cell is in a normal working range of the cell, the charging current is in a normal working range and the battery pack is not in a discharging state;

[0127] The active balancing control module 530 is configured to automatically start the active balancing to adjust the balancing current among the to-be-balanced battery cells when the active balancing start condition is met.

[0128] The active balancing control module 530 is specifically configured to obtain the positions of the highest-voltage battery cell and the lowest-voltage battery cell, and determine whether to start the active balancing in a forward direction or a reverse direction according to the positions of the highest-voltage battery cell and the lowest-voltage battery cell.

[0129] The active balancing control module 530 is specifically configured to receive a communication signal sent by a preset communication terminal, wherein the communication signal comprises balancing control parameters, the balancing control parameters comprise a balancing direction, to-be-balanced battery cells, and a balancing time, and the active balancing control module 530 is specifically configured to determine whether the battery pack meets the active balancing start condition in real time according to the communication signal, and start the active balancing according to the balancing control parameters when the active balancing start condition is met and the battery pack is not in the active balancing state.

[0130] The active balancing control module 530 is specifically configured to monitor state information of each battery cell in the battery pack, and stop the active balancing when the state information does not meet the active balancing start condition.

[0131] The active balancing control module 530 is specifically configured to send the state information to the preset communication terminal, so that the preset communication terminal determines a sampling information error and a battery charge and discharge capacity according to the state information, and generates and sends the communication signal when the sampling information error is greater than a preset error threshold or the battery charge and discharge capacity decreases to a preset threshold.

[0132] To sum up, the embodiment provides an active balancing control device among battery cells, which comprehensively judges multiple parameters such as voltage, SOC, and temperature, avoids false balancing, and can improve balancing accuracy. The voltage sampling error is reduced through timing optimization (duty cycle setting), which can effectively improve the balancing accuracy. The active balancing control device supports automatic / forced start active balancing dual mode, adapts to different use scenarios, and has strong flexibility. The active balancing control device has a built-in safety protection mechanism to prevent overcharging, overdischarging, or abnormal temperature rise of the battery cells during the balancing process, and improves system safety. The active balancing control device can significantly reduce the voltage difference and SOC difference among the battery cells through flexible active balancing control, prolong the cycle life of the battery pack, and improve the energy utilization efficiency.

[0133] Each module in the active balancing control device among battery cells described above can be realized by software, hardware, or a combination thereof, in whole or in part. Each module described above can be embedded in or independent of a processor in a computer device in hardware form, or can be stored in a memory in a computer device in software form, so as to be called and executed by a processor to perform the operations corresponding to each module.

[0134] In one embodiment, a lithium battery pack is also provided, which comprises a plurality of battery cells connected in series or parallel and the battery management system in the foregoing embodiment.

[0135] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 6 As shown, the computer device includes a processor, memory, input / output interface, communication interface, display unit, and input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The input / output interface is used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements an active cell balancing control method. The display unit is used to form a visually visible image and can be a display screen, projection device, or virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of the computer device can be a touch layer covering the display screen, or buttons, trackballs, or touchpads set on the casing of the computer device, or external keyboards, touchpads, or mice, etc.

[0136] Those skilled in the art will understand that Figure 6 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0137] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0138] The status information of each cell in the battery pack is acquired at preset time intervals. The status information includes voltage, current, temperature and the state of charge of each cell.

[0139] determining whether the battery pack meets an active balancing start condition according to the state information; wherein the active balancing start condition comprises that the battery pack is not in a fault state, the battery pack is not in a protection state, a voltage difference between the battery cells is greater than a preset voltage threshold, a state of charge difference between the battery cells is greater than a preset state of charge threshold, a temperature of the battery cell is in a normal working range of the battery cell, a charging current is in a normal working range, and the battery pack is not in a discharging state;

[0140] in a case where the active balancing start condition is met, automatically starting the active balancing to adjust the voltage difference between the battery cells to be balanced according to a target balancing current.

[0141] In one embodiment, a computer readable storage medium is provided, and a computer program is stored on the computer readable storage medium, and the computer program is executed by a processor to implement the following steps:

[0142] acquiring state information of each battery cell in the battery pack at a preset time interval, the state information comprising voltage, current, temperature, and state of charge of each battery cell;

[0143] determining whether the battery pack meets an active balancing start condition according to the state information; wherein the active balancing start condition comprises that the battery pack is not in a fault state, the battery pack is not in a protection state, a voltage difference between the battery cells is greater than a preset voltage threshold, a state of charge difference between the battery cells is greater than a preset state of charge threshold, a temperature of the battery cell is in a normal working range of the battery cell, a charging current is in a normal working range, and the battery pack is not in a discharging state;

[0144] in a case where the active balancing start condition is met, automatically starting the active balancing to adjust the voltage difference between the battery cells to be balanced according to a target balancing current.

[0145] In one embodiment, a computer program product is provided, and the computer program product comprises a computer program, and the computer program is executed by a processor to implement the following steps:

[0146] acquiring state information of each battery cell in the battery pack at a preset time interval, the state information comprising voltage, current, temperature, and state of charge of each battery cell;

[0147] determining whether the battery pack meets an active balancing start condition according to the state information; wherein the active balancing start condition comprises that the battery pack is not in a fault state, the battery pack is not in a protection state, a voltage difference between the battery cells is greater than a preset voltage threshold, a state of charge difference between the battery cells is greater than a preset state of charge threshold, a temperature of the battery cell is in a normal working range of the battery cell, a charging current is in a normal working range, and the battery pack is not in a discharging state;

[0148] in a case where the active balancing start condition is met, automatically starting the active balancing to adjust the voltage difference between the battery cells to be balanced according to a target balancing current.

[0149] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when the computer program is executed, the processes of the above-mentioned embodiments of the methods can be included. Any reference to memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The database involved in the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., without being limited thereto. The processor involved in the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., without being limited thereto.

[0150] Any combination of the technical features of the above embodiments can be made. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist, it should be considered as the scope of the present application.

[0151] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for active inter-cell equalization control, characterized in that, The method comprises: acquiring state information of each battery cell in the battery pack at preset time intervals, the state information including voltage, current, temperature, and state of charge of each battery cell; determining whether the battery pack meets a condition for starting active balancing according to the state information, wherein the condition for starting active balancing includes that the battery pack is not in a fault state, the battery pack is not in a protection state, a voltage difference between battery cells is greater than a preset voltage threshold, a state of charge difference between battery cells is greater than a preset state of charge threshold, a temperature of a battery cell is in a normal working range of the battery cell, a charging current is in a normal working range, and the battery pack is not in a discharging state; in a case where the condition for starting active balancing is met, automatically starting active balancing to adjust a voltage difference between battery cells to be balanced according to a target balancing current.

2. The method of claim 1, wherein, The automatic starting of active balancing comprises: acquiring positions of a battery cell with the highest voltage and a battery cell with the lowest voltage; determining whether to start active balancing in a forward direction or a reverse direction according to the positions of the battery cell with the highest voltage and the battery cell with the lowest voltage.

3. The method of claim 2, wherein, The balancing current in the forward direction and the balancing current in the reverse direction have different current values, and the current values of the balancing currents are dynamically adjusted according to a position difference between the battery cell with the highest voltage and the battery cell with the lowest voltage.

4. The method of claim 1, wherein, The method further comprises: during the active balancing process, setting a target duty cycle of a voltage sampling time, a starting time of active balancing, and a standing time, and achieving the active balancing according to the target duty cycle; wherein the active balancing is turned off during the voltage sampling time, and voltage is collected after the voltage of the battery cell is stabilized.

5. The method of claim 1, wherein, The method further comprises: receiving a communication signal sent by a preset communication terminal, wherein the communication signal includes balancing control parameters, and the balancing control parameters include a balancing direction, battery cells to be balanced, and a balancing time; determining whether the battery pack meets the condition for starting active balancing in real time according to the communication signal; in a case where the condition for starting active balancing is met and the battery pack is not in an active balancing state, starting active balancing according to the balancing control parameters.

6. The method according to any one of claims 1 to 5, characterized in that, After the active balancing is started, the method further comprises: monitoring state information of each battery cell in the battery pack; in a case where the state information does not meet the condition for starting active balancing, turning off the active balancing.

7. The method of claim 5, wherein, Before the receiving of the communication signal sent by the preset communication terminal, the method further comprises: sending the state information to the preset communication terminal, so that the preset communication terminal determines a sampling information error and a battery charging and discharging capacity according to the state information, and generates and sends the communication signal in a case where the sampling information error is greater than a preset error threshold or the battery charging and discharging capacity decreases to a preset threshold.

8. An active inter-cell equalization control device, characterized by comprising: The method comprises: a state information acquisition module configured to acquire state information of each battery cell in the battery pack at preset time intervals, the state information including voltage, current, temperature, and state of charge of each battery cell; An equalization condition determining module is configured to determine whether the battery pack satisfies an active equalization starting condition according to the state information; wherein the active equalization starting condition includes that the battery pack is not in a fault state, the battery pack is not in a protection state, a voltage difference between the battery cells is greater than a preset voltage threshold, a state of charge difference between the battery cells is greater than a preset state of charge threshold, a temperature of the battery cell is in a normal working range, a charging current is in a normal working range, and the battery pack is not in a discharging state; An active equalization control module is configured to automatically start the active equalization to adjust an equalization current between the battery cells to be equalized when the active equalization starting condition is satisfied.

9. A battery management system, characterized by, The battery management system comprises a front-end sampling unit, a control unit and a temperature unit, wherein the front-end sampling unit is configured to sample a voltage and a current of the battery cell, the temperature unit is configured to sample a temperature of the battery cell and an ambient temperature, and the control unit is configured to execute the inter-battery cell active equalization control method according to any one of claims 1-7.

10. A lithium battery pack characterized by, The battery management system comprises a plurality of battery cells connected in series or in parallel and the battery management system according to claim 9.

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