Energy storage system and equalization control method

Abstract

The embodiment of the invention relates to an energy storage system and a balance control method, the energy storage system comprises a battery control unit BCU and a plurality of battery packs, each battery pack comprises a battery management unit BMU, and the BCU is in communication connection with each BMU. The BMU sends the target battery electric quantity to the BCU, the BCU determines whether a preset starting condition is met according to the target battery electric quantity, if yes, a target battery pack is determined according to the target battery electric quantity, and an equalization instruction is sent to the target battery pack, so that a target BMU in the target battery pack responds to the equalization instruction to control the target battery pack to discharge or charge, the battery electric quantity of any battery pack is greater than the first preset threshold value. According to the energy storage system, the to-be-balanced battery packs are discharged or charged, so that the battery electric quantity of the to-be-balanced battery packs is adjusted, balance is achieved, the energy storage system achieves balance between the battery packs through electric quantity transfer, energy dissipation is little, generated heat is little, and safety is high.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of battery technology, and in particular to an energy storage system and a balancing control method. Background Art

[0002] As the wave of new energy is being promoted, the photovoltaic energy storage industry is developing rapidly, and the application scenarios of energy storage batteries are becoming more and more diverse. Due to the limitations of battery production technology and the limitations of usage scenarios, battery clusters are generally composed of multiple battery packs connected in series and parallel to expand the available capacity. As the frequency of use increases, imbalances between battery packs begin to appear, that is, the voltages between battery packs will have relatively large differences, which can easily lead to the "short board effect". In the long run, this vicious cycle will greatly weaken the charging and discharging capabilities and application performance of the battery pack, and may even cause major safety accidents. Therefore, battery balancing is an important part of the battery management system.

[0003] The existing balancing control method is generally the energy dissipation method, which achieves balance by consuming unbalanced energy, but it is easy to generate a lot of heat in the process, which is not conducive to battery thermal management and has low safety. Summary of the invention

[0004] The embodiments of the present application provide an energy storage system and a balancing control method, which can balance the battery power of each battery pack in a safer manner, thereby improving the charging and discharging capabilities of the battery pack and the battery life.

[0005] In a first aspect, an embodiment of the present application provides an energy storage system, a battery control unit BCU and a plurality of battery packs, each of the battery packs includes a battery management unit BMU, and the BCU is communicatively connected with each of the BMUs;

[0006] The BMU is used to send a target battery power to the BCU, wherein the target battery power is the battery power at the end of charging, wherein the end of charging refers to the time when any one of the battery packs has a full charge event and is reported to the BCU, and the BCU stops charging each of the battery packs;

[0007] The BCU is used to determine whether a preset start-up condition is reached according to the target battery power, and if reached, determine a target battery pack according to the target battery power, and send a balancing instruction to the target battery pack, so that the target BMU in the target battery pack responds to the balancing instruction to control the target battery pack to discharge or charge until the battery power of any one of the battery packs is greater than a first preset threshold;

[0008] The preset start-up condition is that the power level of any one of the target batteries is less than or equal to the first preset threshold, and the target battery pack is a battery pack to be balanced.

[0009] In some embodiments, each of the battery packs includes a plurality of single cells, and the BMU is specifically used for:

[0010] Detecting the voltage of each of the single cells;

[0011] When the voltage of any of the single cells reaches the charging cut-off voltage, it is determined that a full charging event occurs in the battery pack where the BMU is located.

[0012] In some embodiments, the BMU is specifically used for:

[0013] When a full charge event occurs in the battery pack where the BMU is located, the full charge event is reported to the BCU, so that the BCU stops charging each of the battery packs and broadcasts a charging end event to each of the BMUs.

[0014] In some embodiments, the BMU is specifically used for:

[0015] Collecting the open circuit voltage of each of the single cells for a first time period before a receiving time, wherein the receiving time is the time when the BMU receives the charging end event;

[0016] Determine the average open circuit voltage of each of the single cells at each acquisition moment;

[0017] The maximum open circuit voltage average is determined as the target open circuit voltage, wherein the target open circuit voltage is the average open circuit voltage of each of the single cells at the end of charging.

[0018] In some embodiments, the BMU is specifically used for:

[0019] Obtain a mapping curve between battery power and the open circuit voltage of a single cell;

[0020] The target battery power corresponding to the target open circuit voltage is queried on the mapping curve using a linear interpolation method.

[0021] In some embodiments, before obtaining a mapping curve of battery power and open circuit voltage of a single battery, the BMU is specifically used to:

[0022] Acquire a first charging current of the battery pack where the BMU is located and an average temperature of each of the single cells at the end of charging;

[0023] Acquire a second charging current of the battery pack for a second time period before the charging end time;

[0024] Determining whether the first charging current, the second charging current, and the average temperature meet a preset query condition;

[0025] If yes, then start the step of obtaining the mapping curve between the battery power and the open circuit voltage of the single cell;

[0026] The preset query condition is that the first charging current meets a first preset interval, each of the second charging currents meets a second preset interval, and each of the average temperatures is greater than or equal to a preset temperature.

[0027] In some embodiments, each of the battery packs includes a DC / DC balancing unit, the DC / DC balancing unit is electrically connected to the corresponding BMU, and each of the battery packs is electrically connected in parallel through a first power line, and the BCU is specifically used for:

[0028] Determine a first battery pack and a second battery pack according to the target battery power, wherein the first battery pack is a battery pack with the largest power among the target battery power, and the second battery pack is a battery pack with the smallest power among the target battery power;

[0029] Sending a first balancing instruction to the first battery pack, so that a first DC / DC balancing unit in the first battery pack controls the first battery pack to discharge toward the first power line in response to the first balancing instruction;

[0030] Sending a second balancing instruction to the second battery pack, so that a second DC / DC balancing unit in the second battery pack controls the second battery pack to be charged through the first power line in response to the second balancing instruction;

[0031] When the discharge amount of the first battery pack or the charge amount of the second battery pack reaches a preset shutdown condition, a shutdown instruction is sent to the first battery pack so that the first DC / DC balancing unit controls the first battery pack to stop discharging in response to the shutdown instruction, and the shutdown instruction is sent to the second battery pack so that the second DC / DC balancing unit controls the second battery pack to stop charging in response to the shutdown instruction;

[0032] Controlling each of the battery packs to recharge;

[0033] When a full charge event occurs again in any one of the battery packs, the process starts again from the step of determining whether the preset start-up condition is reached according to the target battery power, until the battery power of any one of the battery packs is greater than the first preset threshold.

[0034] In some embodiments, the preset shutdown condition is that the discharge capacity of the first battery pack or the charge capacity of the second battery pack reaches a first ratio of the rated capacity of the first battery pack.

[0035] In a second aspect, an embodiment of the present application provides a balancing control method, which is applied to the energy storage system as described above, and the method includes:

[0036] The BMU sends a target battery power to the BCU, wherein the target battery power is the battery power at the end of charging, and the end of charging refers to the time when any one of the battery packs has a full charge event and is reported to the BCU, and the BCU stops charging each of the battery packs;

[0037] The BCU determines whether a preset start-up condition is met according to the target battery power, and if so, determines a target battery pack according to the target battery power, and sends a balancing instruction to the target battery pack, so that the target BMU in the target battery pack responds to the balancing instruction to control the target battery pack to discharge or charge, until the battery power of any one of the battery packs is greater than a first preset threshold;

[0038] The preset start-up condition is that the power level of any one of the target batteries is less than or equal to the first preset threshold, and the target battery pack is a battery pack to be balanced.

[0039] In some embodiments, each of the battery packs includes a plurality of single cells, and the method further includes:

[0040] The BMU detects the voltage of each of the single cells;

[0041] When the voltage of any of the single cells reaches the charge cut-off voltage, the BMU determines that a full charge event occurs in the battery pack where the battery is located.

[0042] In some embodiments, when the BMU detects that a full charge event occurs in the battery pack in which the BMU is located, the BMU reports the full charge event to the BCU;

[0043] The BCU stops charging of each of the battery packs and broadcasts a charging end event to each of the BMUs.

[0044] In some embodiments, the method further comprises:

[0045] The BMU collects the open circuit voltage of each of the single cells for a first time period before a receiving time, wherein the receiving time is the time when the BMU receives the charging end event;

[0046] The BMU determines the average open circuit voltage of each of the single cells at each acquisition moment;

[0047] The BMU determines the maximum open circuit voltage average as the target open circuit voltage, wherein the target open circuit voltage is the average open circuit voltage of each of the single cells at the end of charging.

[0048] In some embodiments, the method further comprises:

[0049] The BMU obtains a mapping curve between battery power and open circuit voltage of a single cell;

[0050] The BMU uses a linear interpolation method to query the target battery power corresponding to the target open circuit voltage on the mapping curve.

[0051] In some embodiments, before the BMU acquires a mapping curve between battery power and an open circuit voltage of a single cell, the method further includes:

[0052] When the BMU acquires the first charging current of the battery pack where the BMU is located and the average temperature of each of the single cells at the charging end time;

[0053] The BMU acquires a second charging current of the battery pack for a second time period before the charging end time;

[0054] The BMU determines whether the first charging current, the second charging current, and the average temperature meet a preset query condition;

[0055] If it is in compliance, the BMU starts the step of obtaining a mapping curve between battery power and the open circuit voltage of a single cell;

[0056] The preset query condition is that the first charging current meets a first preset interval, each of the second charging currents meets a second preset interval, and each of the average temperatures is greater than or equal to a preset temperature.

[0057] In some embodiments, each of the battery packs includes a DC / DC balancing unit, the DC / DC balancing unit is electrically connected to the corresponding BMU, and each of the battery packs is electrically connected in parallel through a first power line, the BCU determines a target battery pack according to the target battery power, and sends a balancing instruction to the target battery pack, so that the target BMU in the target battery pack responds to the balancing instruction to control the target battery pack to discharge or charge until the capacity of any of the battery packs is greater than a first preset threshold, including:

[0058] The BCU determines the first battery pack and the second battery pack according to the target battery power, wherein the first battery pack is the battery pack with the largest capacity in the target battery power, and the second battery pack is the battery pack with the smallest capacity in the target battery power;

[0059] The BCU sends a first balancing instruction to the first battery pack, so that a first DC / DC balancing unit in the first battery pack controls the first battery pack to discharge to the first power line in response to the first balancing instruction;

[0060] The BCU sends a second balancing instruction to the second battery pack, so that the second DC / DC balancing unit in the second battery pack controls the second battery pack to be charged through the first power line in response to the second balancing instruction;

[0061] When the discharge amount of the first battery pack or the charge amount of the second battery pack reaches a preset shutdown condition, the BCU sends a shutdown instruction to the first battery pack and the second battery pack, so that the first DC / DC balancing unit controls the first battery pack to stop discharging in response to the shutdown instruction, and the BCU sends the shutdown instruction to the second battery pack, so that the second DC / DC balancing unit controls the second battery pack to stop charging in response to the shutdown instruction;

[0062] The BCU controls each of the battery packs to recharge;

[0063] When a full charge event occurs again in any one of the battery packs, the BCU starts the cycle again from the step of determining whether the preset start-up condition is met according to the target battery power until the battery power of any one of the battery packs is greater than the first preset threshold.

[0064] In some embodiments, the preset shutdown condition is that the discharge capacity of the first battery pack or the charge capacity of the second battery pack reaches a first ratio of the rated capacity of the first battery pack.

[0065] Compared with the prior art, the energy storage system of the embodiment of the present application includes a battery control unit BCU and multiple battery packs, each battery pack includes a battery management unit BMU, and the BCU is communicatively connected with each BMU. The BMU sends the target battery power to the BCU, and the BCU determines whether the preset start-up condition is reached according to the target battery power. If reached, the target battery pack is determined according to the target battery power, and a balancing instruction is sent to the target battery pack, so that the target BMU in the target battery pack responds to the balancing instruction to control the target battery pack to discharge or charge, until the battery power of any battery pack is greater than the first preset threshold, wherein the preset start-up condition is that the battery power of any target battery pack is less than or equal to the first preset threshold, and the target battery pack is the battery pack to be balanced. Therefore, the energy storage system can discharge or charge the battery pack to be balanced to adjust the battery power of the battery pack to be balanced, so that the battery power of each battery pack is consistent, to achieve balance, and then improve the charge and discharge capacity of the battery pack and the battery life, and the energy storage system achieves balance between battery packs through power transfer, with less energy dissipation, less heat generation, and high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] One or more embodiments are exemplarily described by the figures in the corresponding drawings, and these exemplary descriptions are not intended to limit the embodiments. Elements with the same reference numerals in the drawings represent similar elements.

[0067] Figure 1 is a structural schematic diagram of one of the energy storage systems provided in the embodiments of the present application;

[0068] Figure 2 This is a flow chart of a balancing control method provided in an embodiment of the present application;

[0069] Figure 3 This is a flow chart of a balancing control method provided in an embodiment of the present application;

[0070] Figure 4 This is a flow chart of a balancing control method provided in an embodiment of the present application;

[0071] Figure 5 yes Figure 2 Schematic diagram of the process of step S102. DETAILED DESCRIPTION

[0072] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and in detail in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0073] In the present application, when an element is expressed as being “connected to” another element, it may be directly connected to the other element, or one or more intervening elements may be present therebetween.

[0074] In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as there is no structural conflict between them.

[0075] See also Figure 1 , Figure 1 is a schematic diagram of the structure of an energy storage system provided in an embodiment of the present application, such as Figure 1 As shown, the energy storage system includes a battery management unit (Battery Control Unit, BCU for short) and a battery cluster 20. The battery cluster 20 includes n battery packs, where n is an integer greater than or equal to 2, and can be three, four or more battery packs. The specific number of battery packs can be set as needed and is not limited here.

[0076] Each battery pack is connected in parallel through a first power line and in series through a second power line. The second power line is also connected to an external power source through a current switch (not shown in the figure). When each battery pack needs to be charged, the BCU 10 controls the current switch on the second power line to close, and the external power source charges each battery pack. When charging, a current sensor 30 can be used to collect the charging current, and the charging current is transmitted to the BCU 10.

[0077] If charging is stopped, the BCU 10 controls the current switch on the second power line to be turned off, and each battery pack stops charging. If internal balancing is required between the battery packs within the energy storage system, the battery packs to be balanced are charged or discharged through the first power line to adjust the battery power of the battery packs to be balanced until the battery power reaches consistency.

[0078] Each battery pack includes a battery management unit (BMU) and a battery cell, wherein the battery cell includes multiple single cells connected in parallel, series or mixed, for storing and providing electric energy, and mixed connection includes series and parallel connection. The battery cell is electrically connected to the BMU, and the BMU can collect information such as the temperature and voltage of the corresponding battery cell, such as the voltage of each single cell, the temperature of each single cell, etc.

[0079] BCU10 and each BMU constitute a battery management system. BCU10 is in communication connection with each BMU. BCU10 can obtain the information of each battery unit by exchanging data with each BMU. For example, BMU reports the voltage, temperature, battery charge of each single battery and other information to BCU10. BCU10 generates various control commands based on the information reported by BMU and sends them to BMU to control the charging or discharging of the battery pack where the BMU is located.

[0080] In some embodiments, the BMUs of each battery pack are also cascaded in communication with the BCU 10, and each BMU from the first-level BMU to the last-level BMU is communicatively connected to the BCU 10. In some embodiments, the first-level BMU or the last-level BMU is communicatively connected to the BCU 10, the BCU 10 can exchange data with the first-level BMU or the last-level BMU, and the remaining BMUs can exchange data with the BCU through the first-level BMU or the last-level BMU. Figure 1 In the figure, it is taken as an example that BCU 10 is in communication connection with each BMU.

[0081] It should be understood that the communication connection in the embodiments of the present application may include a wired connection and a wireless connection, and similarly the communication cascade may also include a wired cascade and a wireless cascade. Figure 1 The dotted line in the figure represents a communication connection, so that data can be exchanged between two devices in the communication connection, and the communication connection using the CAN bus is shown as an example. Figure 1 The solid line in the figure represents an electrical connection, so that electrical energy can be transmitted between the two electrically connected devices.

[0082] Battery capacity refers to the battery's SOC (State of Charge), which is the percentage of the battery's current remaining capacity, and is used to describe the battery's state of charge from fully discharged to fully charged. SOC is a value between 0% (fully discharged) and 100% (fully charged), which provides a visual representation of the battery's current capacity.

[0083] When charging each battery pack, when the single cell in any battery pack reaches the charge cut-off voltage, it is determined that the battery pack has a full charge event. The charge cut-off voltage refers to the maximum voltage that a single cell can reach. For example, for lithium iron phosphate batteries, the allowable voltage range is generally 2.5 to 3.65V. Discharge is not allowed below 2.5V, and charging is not allowed above 3.65V. Therefore, 3.65V is the charge cut-off voltage, which is the maximum voltage that a single cell can reach.

[0084] There is a communication delay between BCU10 and BMU, so the time of full charge event, charge end event and each BMU receiving the charge end event broadcast is different. Specifically, when BMU detects that the battery pack where it is located has a full charge event, it will report the full charge event to BCU10. After receiving the full charge event, BCU10 will immediately stop charging (control the current switch to turn off). The moment of stopping charging is the moment of charging end. BCU10 will also broadcast the charge end event to each BMU.

[0085] After each BMU receives the charging end event, it will query the charging end time and the data of the battery pack where the BMU is located, such as the battery power, the temperature of the single cell, and the voltage of the single cell. First, calculate the battery power corresponding to the battery pack where the BMU is located at the charging end time. If the time when the BMU receives the charging end event is called the receiving time, then due to a certain delay in communication, the receiving time of each BMU will lag behind the charging end time. For example, if the BMU receives the charging end event 2s after stopping charging, the receiving time of the BMU will lag behind the charging end time by 2s.

[0086] First, the target battery power at the end of charging needs to be determined and reported to the BCU 10. After charging is completed, the battery pack is in a state of stopping charging or discharging. Therefore, at the end of charging, the open circuit voltage of the single cell of the battery pack is the maximum. The end of charging is determined by determining the time when the open circuit voltage of the single cell is the maximum.

[0087] Specifically, the open circuit voltage of each single cell in the first time period before the receiving moment is collected, and then the average open circuit voltage of each single cell at each collection moment is determined, and finally the maximum open circuit voltage average is determined as the target open circuit voltage.

[0088] For example, if the first time duration is 5 seconds and the number of single cells is 16, then the voltage of each single cell 5 seconds before the receiving time is queried, and the average voltage of each single cell at each time is obtained by formula (1):

[0089]

[0090] Where i represents the number of the single cell, i is an integer from 0 to 15, t represents the time, t is an integer from 0 to 4, cell_num represents the number of single cells, avg t It represents the average voltage of each single cell at time t.

[0091] Then, the maximum mean among all the means is obtained by formula (2):

[0092]

[0093] Among them, y aim Indicates the target open circuit voltage.

[0094] y aim The corresponding time is the charging end time, and the BMU reports the battery power corresponding to the charging end time to the BCU 10 , which receives and processes it.

[0095] Thus, the charging end time is determined by the voltage average of each single cell, and the open circuit voltage average of each single cell corresponding to the charging end time is determined as the target open circuit voltage. The BMU then obtains the target battery power at the charging end time through the mapping curve between battery power and single cell open circuit voltage.

[0096] Specifically, the BMU obtains a mapping curve between the battery power and the open circuit voltage of the single battery, and uses a linear interpolation method to query the target battery power corresponding to the target open circuit voltage on the mapping curve.

[0097] The mapping curve of battery capacity and open circuit voltage of single cell is SOC-OCV curve. Under the condition of stable temperature and battery aging, it has a one-to-one mapping relationship. This mapping relationship is related to the battery material itself and is the characteristic of the battery itself. This curve can be obtained through calibration. The SOC-OCV curve obtained after calibration is stored in BMU, and BMU can directly obtain it when needed.

[0098] Since the SOC-OCV curve is obtained by fitting each discrete point, if the target battery capacity corresponding to the target open circuit voltage is directly obtained from the SOC-OCV curve, the error is large and the accuracy of the target battery capacity is low. Therefore, in the embodiment of the present application, a linear interpolation method is used to query the target battery capacity corresponding to the target open circuit voltage on the SOC-OCV curve.

[0099] For example, first obtain the values ​​of two known data points on the SOC-OCV curve, namely (OCV1, SOC1) and (OCV2, SOC2), and then determine the target battery power by formula (3):

[0100]

[0101] Among them, SOC is the target battery capacity, and OCV is the target open circuit voltage.

[0102] Through the linear interpolation method, the target battery power can be accurately obtained, the error can be reduced, and the balancing accuracy can be improved.

[0103] Since the SOC-OCV curve is greatly affected by the discharge rate, temperature and charging current, when calibrating the SOC-OCV curve, the SOC-OCV curve will be calibrated when the charging current fluctuates slightly and the temperature is relatively suitable (such as around 25 degrees). Therefore, in actual use, the SOC-OCV curve can only be queried to obtain the corresponding battery power when the charging current fluctuates slightly and the temperature is relatively suitable. Otherwise, the queried battery power will have a large error and low accuracy, which will affect the subsequent balancing effect.

[0104] Therefore, before obtaining the mapping curve of battery capacity and open circuit voltage of a single cell, it is necessary to confirm whether the charging current of the battery pack is stable and whether the temperature of the battery pack is appropriate. Only when the charging current of the battery pack is stable and the temperature of the battery pack is appropriate can the SOC-OCV curve be used to query the battery capacity.

[0105] Specifically, the BMU obtains the first charging current of the battery pack where the BMU is located and the average temperature of each single cell when charging ends, and then obtains the second charging current of the battery pack for a second period of time before charging ends, and determines whether the first charging current, the second charging current and the average temperature meet the preset query conditions. If so, a mapping curve of the battery power and the open circuit voltage of the single cell is obtained, wherein the preset query conditions are that the first charging current meets the first preset interval, each second charging current meets the second preset interval, and each average temperature is greater than or equal to the preset temperature.

[0106] Among them, the second duration, the first preset interval, the second preset interval and the preset temperature can be set as needed. In the embodiment of the present application, the second duration is 1 min, the first preset interval is [5A, 12A], the second preset interval is [5A, 12A], and the preset temperature is 10°C.

[0107] After the end of charging, each battery pack stops charging. First, obtain the first charging current of the battery pack at the end of charging, and determine whether it is within the range of [5A, 12A]. If so, obtain the second charging current 1 minute before the end of charging. The number of second charging currents is related to the sampling frequency. If the second charging current is obtained once every 1s, the number of second charging currents is 60, that is, obtain the second charging current every second before the end of charging, obtain 60, and determine whether the 60 second charging currents are all within the range of [5A, 12A]. If so, obtain the average temperature of each single cell at the end of charging, and determine whether each average temperature is greater than or equal to 10°C. If so, determine that the first charging current, the second charging current and the average temperature of each single cell meet the preset query conditions, and then determine the battery capacity at the end of charging through the SOC-OCV curve.

[0108] The BMU reports the target battery power at the end of charging to the BCU10. The BCU10 determines the target battery pack according to the target battery power. The target battery pack is the battery pack to be balanced. The number of the target battery packs can be two, three or more, and the number of target battery packs is less than or equal to the total number of battery packs. The target battery pack is determined according to the number of battery packs that need to be balanced.

[0109] After BCU10 determines the target battery pack, it balances the target battery pack and controls the battery pack with higher battery charge in the target battery pack to discharge to the battery pack with lower battery charge, so as to achieve balanced charge of each battery pack. When BCU10 balances the target battery pack, it can balance the charge of each battery pack in the target battery pack through multiple cycles of balancing process. In a single balancing process, only the battery pack with the largest battery charge and the battery pack with the smallest battery charge in the target battery pack are balanced. After the single balancing is completed, each battery pack is charged again. When a battery pack is fully charged, the single balancing process is triggered again, and so on, until the battery charge of each battery pack is greater than the first preset threshold, it is considered that the battery charge of each battery pack is consistent, and the active balancing process ends.

[0110] The charging or discharging of the battery pack is achieved by the DC / DC balancing unit. Figure 2 Each battery pack includes a DC / DC balancing unit, which is electrically connected to the corresponding BMU. The DC / DC balancing unit includes a charging MOS and a discharging MOS. By controlling the working states of the charging MOS and the discharging MOS, the charging and discharging of the battery pack where the DC / DC balancing unit is located can be controlled, thereby adjusting the electrical energy between the battery pack where the DC / DC balancing unit is located and other battery packs.

[0111] BCU10 determines the first battery pack and the second battery pack according to the target battery power, wherein the first battery pack is the battery pack with the largest power in the target battery power, and the second battery pack is the battery pack with the smallest power in the target battery power. BCU10 can sort the target battery power reported by the BMU to determine the first battery pack and the second battery pack, wherein the DC / DC balancing unit in the first battery pack is the first DC / DC balancing unit, and the DC / DC balancing unit in the second battery pack is the second DC / DC balancing unit.

[0112] BCU10 sends a first balancing instruction to the BMU in the first battery pack, and the BMU in the first battery pack sends the first balancing instruction to the first DC / DC balancing unit. The first DC / DC balancing unit responds to the first balancing instruction and controls the discharge MOS to turn on, so that the first battery pack discharges to the first power line.

[0113] And BCU10 sends a second balancing instruction to the BMU in the second battery pack, and the BMU in the second battery pack sends the second balancing instruction to the second DC / DC balancing unit. The second DC / DC balancing unit responds to the second balancing instruction and controls the charging MOS to be turned on, so that the second battery pack is charged through the first power line.

[0114] Therefore, the electricity discharged from the first battery pack is transferred to the second battery pack through the first power line to charge the second battery pack, thereby realizing energy transfer.

[0115] When the discharge amount of the first battery pack or the charge amount of the second battery pack reaches the preset shutdown condition, the BCU10 sends a shutdown instruction to the first battery pack and the second battery pack respectively, and the BMU of the first battery pack sends the shutdown instruction to the first DC / DC balancing unit, and the first DC / DC balancing unit responds to the shutdown instruction and controls the discharge MOS to be cut off, so that the first battery pack stops discharging. Similarly, the BMU of the second battery pack sends the shutdown instruction to the second DC / DC balancing unit, and the second DC / DC balancing unit responds to the shutdown instruction and controls the charge MOS to be cut off, so that the second battery pack stops charging, and the single balancing process ends.

[0116] The preset shutdown condition can be set as needed. In the embodiment of the present application, the preset shutdown condition can be that the discharge capacity of the first battery pack or the charge capacity of the second battery pack reaches a first ratio of the rated capacity of the first battery pack. For example, the discharge capacity of the first battery pack or the charge capacity of the second battery pack reaches 0.5% of the rated capacity of the first battery pack. In other embodiments, the preset shutdown condition can also be that the discharge capacity of the first battery pack reaches a preset power threshold. For example, the discharge capacity of the first battery pack reaches 500mAh.

[0117] After a single balancing process is completed, any battery pack is not fully charged, allowing the external power supply to recharge each battery pack. Specifically, the BCU 10 controls the current switch on the second power line to close, so that the external power supply recharges each battery pack, thereby realizing energy replenishment for each battery pack.

[0118] Each battery pack is charged again until any battery pack is fully charged again, which triggers a single balancing process again. The BMU sends the target battery power to the BCU10 again, and the BCU10 determines whether the preset start-up condition is met based on the target battery power. If so, the BCU10 determines the target battery pack based on the target battery power again to adjust the power between the target battery packs and realize power transfer.

[0119] Similarly, when BCU10 adjusts the power between the target battery packs again, it will first find the first battery pack with the highest power and the second battery pack with the lowest power, and transfer the power of the first battery pack to the second battery pack, thereby transferring power from the battery pack with the highest power to the battery pack with the lowest power, until the transferred power meets the preset shutdown condition, and the single balancing process ends again.

[0120] The external power source charges each battery pack again. If the BCU10 determines that the battery power of any battery pack is greater than the first preset threshold after a full charge event occurs again, it indicates that the battery power of each battery pack is approximately the same, and the battery power of each battery pack is balanced. If the BCU10 determines that the battery power of any battery pack is less than or equal to the first preset threshold after a full charge event occurs, the single balancing process is cycled again, and so on, until the battery power of any battery pack is greater than the first preset threshold.

[0121] The first preset threshold can be set as needed, and in the embodiment of the present application, it can be 99%. If the battery power of each battery pack is greater than the first preset threshold, it is determined that the battery power of each battery pack is consistent and balanced.

[0122] Therefore, the balancing process of the energy storage system can be described as follows: If a full charge event occurs in one of the battery packs, the BMU in the battery pack reports the full charge event to BCU10, and BCU10 controls the current switch to be disconnected, and each battery pack stops charging. BCU10 determines the target battery pack and sends a balancing instruction to the target BMU in the target battery pack, so that the DC / DC balancing unit in the target BMU responds to the balancing instruction and controls the target battery pack to discharge or charge through the first power line to achieve a single balancing. After the single balancing is completed, BCU10 controls the current switch to be closed again, and the external power supply charges each battery pack again. When a full charge event occurs again, BCU10 again determines whether to start a single balancing process, and so on, and the balancing is cyclic until the battery power of each battery pack reaches the same level.

[0123] In summary, the energy storage system can discharge or charge the battery pack to be balanced to adjust the battery power of the battery pack to be balanced, so that the battery power of each battery pack is consistent and balanced, thereby improving the charge and discharge capacity of the battery pack and the battery life. The energy storage system achieves balance between battery packs through power transfer, with less energy dissipation, less heat generation and high safety.

[0124] See also Figure 2 , Figure 2A consumption reduction control method provided in an embodiment of the present application is applied to an energy storage system, wherein the energy storage system includes a battery control unit BCU and multiple battery packs, each of which includes a battery management unit BMU. The specific structure and specific connection relationship of the energy storage system are as follows Figure 1 As shown, the consumption reduction control method S100 includes:

[0125] S101: The BMU is used to send a target battery power to the BCU, wherein the target battery power is the battery power at the end of charging, wherein the end of charging refers to the time when any one of the battery packs has a full charge event and is reported to the BCU, and the BCU stops charging each of the battery packs;

[0126] S102: The BCU determines whether a preset start-up condition is met according to the target battery power. If so, a target battery pack is determined according to the target battery power, and a balancing instruction is sent to the target battery pack, so that the target BMU in the target battery pack controls the target battery pack to discharge or charge in response to the balancing instruction until the battery power of any one of the battery packs is greater than a first preset threshold value;

[0127] The preset start-up condition is that the power level of any one of the target batteries is less than or equal to the first preset threshold, and the target battery pack is a battery pack to be balanced.

[0128] In an embodiment of the present application, when the preset start-up conditions are met, the BCU determines the battery pack to be balanced based on the target battery power sent by each BMU, and then sends a balancing instruction to the BMU in the target battery pack, so that the target BMU responds to the balancing instruction to control the target battery pack to discharge or charge, and then adjusts the battery power between the target battery packs to achieve balancing.

[0129] In some embodiments, each of the battery packs includes a plurality of single cells, and the method further includes:

[0130] The BMU detects the voltage of each of the single cells;

[0131] When the voltage of any of the single cells reaches the charge cut-off voltage, the BMU determines that a full charge event occurs in the battery pack where the battery is located.

[0132] In some embodiments, when a full charge event is detected in the battery pack where the BMU is located, the full charge event is reported to the BCU so that the BCU stops charging each of the battery packs and broadcasts a charging end event to each of the BMUs.

[0133] In some embodiments, Figure 3 As shown, the method S100 also includes:

[0134] S103: collecting the open circuit voltage of each of the single cells for a first time period before a receiving time, wherein the receiving time is the time when the BMU receives the charging end event;

[0135] S104: The BMU determines the average open circuit voltage of each of the single cells at each collection moment;

[0136] S105: The BMU determines the maximum open circuit voltage average as the target open circuit voltage, wherein the target open circuit voltage is the average open circuit voltage of each of the single cells at the end of charging.

[0137] After the charging end time, each battery pack stops charging or discharging. Therefore, at the charging end time, the average voltage of each single battery is the largest. Therefore, the average voltage of each single battery in the period before the charging end event is received is queried, and the time corresponding to the maximum voltage average is determined as the charging end time.

[0138] In some embodiments, the method S100 further includes:

[0139] The BMU obtains a mapping curve between battery power and open circuit voltage of a single cell;

[0140] The BMU uses a linear interpolation method to query the target battery power corresponding to the target open circuit voltage on the mapping curve.

[0141] When the BMU receives the charging end event sent by the BCU, it will query the data of the battery pack where the BMU is located at the time of charging end, such as the battery power, temperature of the single battery, and voltage of the single battery, so as to send the data of the battery pack where the BMU is located at the time of charging end to the BCU.

[0142] The BMU can directly collect the temperature and voltage of a single cell, but it needs to query the battery capacity through the mapping curve of the battery capacity and the open circuit voltage of the single cell (SOC-OCV curve). The mapping curve can be obtained through calibration fitting, and the mapping curve obtained by calibration fitting is stored in the BMU.

[0143] The BMU queries the target battery capacity corresponding to the target open circuit voltage on the SOC-OCV mapping curve, or uses a linear interpolation method to query the target battery capacity corresponding to the target open circuit voltage on the SOC-OCV mapping curve, which can reduce errors and improve the accuracy of the target battery capacity.

[0144] In some embodiments, before the BMU obtains a mapping curve between battery power and the open circuit voltage of a single cell, Figure 4 As shown, the method S100 also includes:

[0145] S106: The BMU acquires a first charging current of the battery pack where the BMU is located and an average temperature of each of the single cells when charging ends;

[0146] S107: The BMU acquires a second charging current of the battery pack for a second period of time before the charging end time;

[0147] S108: The BMU determines whether the first charging current, the second charging current, and the average temperature meet a preset query condition;

[0148] S109: If the conditions are met, the BMU starts the step of obtaining a mapping curve between battery power and the open circuit voltage of a single cell;

[0149] The preset query condition is that the first charging current meets a first preset interval, each of the second charging currents meets a second preset interval, and each of the average temperatures is greater than or equal to a preset temperature.

[0150] Since the SOC-OCV mapping curve is calibrated when the charging current of the battery pack does not fluctuate much and the temperature of the single cells of the battery pack is appropriate, and the SOC-OCV curve is easily affected by temperature and current, the SOC-OCV curve can only be used to query the target battery power to reduce the error of the target battery power when the charging current of the battery pack fluctuates little and the temperature of the single cells is appropriate.

[0151] If the first charging current, the second charging current and the average temperature of each single cell meet the preset query conditions, indicating that the charging current fluctuation of the battery pack where the BMU is located is small and the temperature of the single cell is relatively suitable, the SOC-OCV curve is allowed to be used to query the target battery power with high accuracy.

[0152] In some embodiments, each of the battery packs includes a DC / DC balancing unit, the DC / DC balancing unit is electrically connected to the corresponding BMU, and each of the battery packs is electrically connected in parallel via a first power line, such as Figure 5 As shown, step S102 includes:

[0153] S1021: The BCU determines the first battery pack and the second battery pack according to the target battery power, wherein the first battery pack is the battery pack with the largest capacity in the target battery power, and the second battery pack is the battery pack with the smallest capacity in the target battery power;

[0154] S1022: The BCU sends a first balancing instruction to the first battery pack, so that a first DC / DC balancing unit in the first battery pack controls the first battery pack to discharge toward the first power line in response to the first balancing instruction;

[0155] S1023: The BCU sends a second balancing instruction to the second battery pack, so that the second DC / DC balancing unit in the second battery pack controls the second battery pack to be charged through the first power line in response to the second balancing instruction;

[0156] S1024: When the discharge amount of the first battery pack or the charge amount of the second battery pack reaches a preset shutdown condition, the BCU sends a shutdown instruction to the first battery pack and the second battery pack, so that the first DC / DC balancing unit controls the first battery pack to stop discharging in response to the shutdown instruction, and the BCU sends the shutdown instruction to the second battery pack, so that the second DC / DC balancing unit controls the second battery pack to stop charging in response to the shutdown instruction;

[0157] S1025: The BCU controls each of the battery packs to charge again;

[0158] S1026: When a full charge event occurs again in any one of the battery packs, the BCU starts the cycle again from the step of determining whether the preset start-up condition is met according to the target battery power, until the battery power of any one of the battery packs is greater than the first preset threshold.

[0159] In some embodiments, the preset shutdown condition is that the discharge capacity of the first battery pack or the charge capacity of the second battery pack reaches a first ratio of the rated capacity of the first battery pack.

[0160] Through the above method, during a single balancing process, the battery pack with the highest battery power is controlled to discharge to the battery pack with the lowest battery power, and the power between the battery packs is adjusted. After the single balancing is completed, each battery pack is charged. When a full charging event occurs again, the single balancing process is repeated, and the cycle is repeated in sequence until the battery power of any battery pack is greater than the first preset threshold.

[0161] In summary, the energy storage system can discharge or charge the battery pack to be balanced to adjust the battery power of the battery pack to be balanced, so that the battery power of each battery pack is consistent and balanced, thereby improving the charge and discharge capacity of the battery pack and the battery life. The energy storage system achieves balance between battery packs through power transfer, with less energy dissipation, less heat generation and high safety.

[0162] It should be noted that, in each of the above-mentioned embodiments, there is not necessarily a certain order between the above-mentioned steps. A person skilled in the art can understand, based on the description of the embodiments of the present application, that in different embodiments, the above-mentioned steps may have different execution orders, that is, they may be executed in parallel, may be executed interchangeably, and so on.

[0163] As another aspect of the embodiment of the present application, the embodiment of the present application provides a consumption reduction control device, which is applied to the above-mentioned first controller. The consumption reduction control device can be a software module, and the software module includes a number of instructions, which are stored in a memory. The processor can access the memory and call the instructions for execution to complete the consumption reduction control method described in each of the above-mentioned embodiments.

[0164] In some embodiments, the consumption reduction control device can also be constructed by hardware devices, for example, the consumption reduction control device can be constructed by one or more chips, and each chip can work in coordination with each other to complete the consumption reduction control method described in each of the above embodiments. For another example, the consumption reduction control device can also be constructed by various logic devices, such as a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a single-chip microcomputer, an ARM (Acorn RISC Machine) or other programmable logic device, a discrete gate or transistor logic, a discrete hardware component, or any combination of these components.

[0165] It should be noted that, since the consumption reduction control device and the consumption reduction control method in the above embodiment are based on the same inventive concept, the corresponding contents in the above method embodiment are also applicable to the device embodiment and will not be described in detail here.

[0166] An embodiment of the present invention also provides a non-transitory computer-readable storage medium, which stores computer-executable instructions. The computer-executable instructions are executed by one or more processors, so that the one or more processors can execute the power consumption reduction control method in any of the above method embodiments.

[0167] An embodiment of the present invention further provides a non-volatile computer storage medium, which stores computer executable instructions. The computer executable instructions are executed by one or more processors, so that the one or more processors can execute the power consumption reduction control method in any of the above method embodiments.

[0168] An embodiment of the present invention further provides a computer program product, which includes a computer program stored on a non-volatile computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a controller, the controller executes any one of the power consumption reduction control methods.

[0169] Through the description of the above implementation methods, ordinary technicians in this field can clearly understand that each implementation method can be implemented by means of software plus a general hardware platform, and of course, it can also be implemented by hardware. Ordinary technicians in this field can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing related hardware through a computer program in a computer program product. The computer program can be stored in a non-transitory computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a drone, the drone can execute the processes of the embodiments of the above-mentioned methods. Among them, the storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0170] The above descriptions are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

[0171] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them. Under the idea of ​​the present application, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order. It should be understood by ordinary technicians in this field that they can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An energy storage system, characterized in that: include: A battery control unit BCU and a plurality of battery packs, each of which includes a battery management unit BMU, and the BCU is in communication connection with each of the BMUs; The BMU is used to send a target battery power to the BCU, wherein the target battery power is the battery power at the end of charging, wherein the end of charging refers to the time when any one of the battery packs has a full charge event and is reported to the BCU, and the BCU stops charging each of the battery packs; The BCU is used to determine whether a preset start-up condition is reached according to the target battery power, and if reached, determine a target battery pack according to the target battery power, and send a balancing instruction to the target battery pack, so that the target BMU in the target battery pack responds to the balancing instruction to control the target battery pack to discharge or charge until the battery power of any one of the battery packs is greater than a first preset threshold; The preset start-up condition is that the power level of any one of the target batteries is less than or equal to the first preset threshold, and the target battery pack is a battery pack to be balanced.

2. The energy storage system according to claim 1, characterized in that: Each of the battery packs includes a plurality of single cells, and the BMU is specifically used for: Detecting the voltage of each of the single cells; When the voltage of any of the single cells reaches the charging cut-off voltage, it is determined that a full charging event occurs in the battery pack where the BMU is located.

3. The energy storage system according to claim 2, characterized in that: The BMU is specifically used for: When a full charge event occurs in the battery pack where the BMU is located, the full charge event is reported to the BCU, so that the BCU stops charging each of the battery packs and broadcasts a charging end event to each of the BMUs.

4. The energy storage system according to claim 3, characterized in that: The BMU is specifically used for: Collecting the open circuit voltage of each of the single cells for a first time period before a receiving time, wherein the receiving time is the time when the BMU receives the charging end event; Determine the average open circuit voltage of each of the single cells at each acquisition moment; The maximum open circuit voltage average is determined as the target open circuit voltage, wherein the target open circuit voltage is the average open circuit voltage of each of the single cells at the end of charging.

5. The energy storage system according to claim 4, characterized in that: The BMU is specifically used for: Obtain a mapping curve between battery power and the open circuit voltage of a single cell; The target battery power corresponding to the target open circuit voltage is queried on the mapping curve using a linear interpolation method.

6. The energy storage system according to claim 5, characterized in that: Before obtaining the mapping curve between the battery power and the open circuit voltage of the single cell, the BMU is specifically used for: Acquire a first charging current of the battery pack where the BMU is located and an average temperature of each of the single cells at the end of charging; Acquire a second charging current of the battery pack for a second time period before the charging end time; Determining whether the first charging current, the second charging current, and the average temperature meet a preset query condition; If yes, then start the step of obtaining the mapping curve between the battery power and the open circuit voltage of the single cell; The preset query condition is that the first charging current meets a first preset interval, each of the second charging currents meets a second preset interval, and each of the average temperatures is greater than or equal to a preset temperature.

7. The energy storage system according to claim 1, characterized in that: Each of the battery packs includes a DC / DC balancing unit, the DC / DC balancing unit is electrically connected to the corresponding BMU, and each of the battery packs is electrically connected in parallel through a first power line, and the BCU is specifically used for: Determine a first battery pack and a second battery pack according to the target battery power, wherein the first battery pack is a battery pack with the largest power among the target battery power, and the second battery pack is a battery pack with the smallest power among the target battery power; Sending a first balancing instruction to the first battery pack, so that a first DC / DC balancing unit in the first battery pack controls the first battery pack to discharge toward the first power line in response to the first balancing instruction; Sending a second balancing instruction to the second battery pack, so that a second DC / DC balancing unit in the second battery pack controls the second battery pack to be charged through the first power line in response to the second balancing instruction; When the discharge amount of the first battery pack or the charge amount of the second battery pack reaches a preset shutdown condition, a shutdown instruction is sent to the first battery pack so that the first DC / DC balancing unit controls the first battery pack to stop discharging in response to the shutdown instruction, and the shutdown instruction is sent to the second battery pack so that the second DC / DC balancing unit controls the second battery pack to stop charging in response to the shutdown instruction; Controlling each of the battery packs to recharge; When a full charge event occurs again in any one of the battery packs, the process starts again from the step of determining whether the preset start-up condition is reached according to the target battery power, until the battery power of any one of the battery packs is greater than the first preset threshold.

8. The energy storage system according to claim 7, characterized in that: The preset shutdown condition is that the discharge capacity of the first battery pack or the charge capacity of the second battery pack reaches a first ratio of the rated capacity of the first battery pack.

9. A balancing control method, characterized in that: Applied to the energy storage system according to any one of claims 1 to 8, the method comprises: The BMU sends a target battery power to the BCU, wherein the target battery power is the battery power at the end of charging, and the end of charging refers to the time when any one of the battery packs has a full charge event and is reported to the BCU, and the BCU stops charging each of the battery packs; The BCU determines whether a preset start-up condition is met according to the target battery power, and if so, determines a target battery pack according to the target battery power, and sends a balancing instruction to the target battery pack, so that the target BMU in the target battery pack responds to the balancing instruction to control the target battery pack to discharge or charge, until the battery power of any one of the battery packs is greater than a first preset threshold; The preset start-up condition is that the power level of any one of the target batteries is less than or equal to the first preset threshold, and the target battery pack is a battery pack to be balanced.

10. The method according to claim 9, characterized in that Each of the battery packs includes a plurality of single cells, and the method further includes: The BMU detects the voltage of each of the single cells; When the voltage of any of the single cells reaches the charge cut-off voltage, the BMU determines that a full charge event occurs in the battery pack where the battery is located.

11. The method according to claim 10, characterized in that When the BMU detects that a full charge event occurs in the battery pack where the BMU is located, the BMU reports the full charge event to the BCU; The BCU stops charging of each of the battery packs and broadcasts a charging end event to each of the BMUs.

12. The method according to claim 11, characterized in that The method further comprises: The BMU collects the open circuit voltage of each of the single cells for a first time period before a receiving time, wherein the receiving time is the time when the BMU receives the charging end event; The BMU determines the average open circuit voltage of each of the single cells at each acquisition moment; The BMU determines the maximum open circuit voltage average as the target open circuit voltage, wherein the target open circuit voltage is the average open circuit voltage of each of the single cells at the end of charging.

13. The method according to claim 12, characterized in that The method further comprises: The BMU obtains a mapping curve between battery power and open circuit voltage of a single cell; The BMU uses a linear interpolation method to query the target battery power corresponding to the target open circuit voltage on the mapping curve.

14. The method according to claim 13, characterized in that Before the BMU obtains a mapping curve between battery power and an open circuit voltage of a single cell, the method further includes: When the BMU acquires the first charging current of the battery pack where the BMU is located and the average temperature of each of the single cells at the charging end time; The BMU acquires a second charging current of the battery pack for a second time period before the charging end time; The BMU determines whether the first charging current, the second charging current, and the average temperature meet a preset query condition; If it is in compliance, the BMU starts the step of obtaining a mapping curve between battery power and the open circuit voltage of a single cell; The preset query condition is that the first charging current meets a first preset interval, each of the second charging currents meets a second preset interval, and each of the average temperatures is greater than or equal to a preset temperature.

15. The method according to claim 9, characterized in that Each of the battery packs includes a DC / DC balancing unit, the DC / DC balancing unit is electrically connected to the corresponding BMU, and each of the battery packs is electrically connected in parallel through a first power line, the BCU determines a target battery pack according to the target battery power, and sends a balancing instruction to the target battery pack, so that the target BMU in the target battery pack responds to the balancing instruction to control the target battery pack to discharge or charge until the capacity of any of the battery packs is greater than a first preset threshold, including: The BCU determines the first battery pack and the second battery pack according to the target battery power, wherein the first battery pack is the battery pack with the largest capacity in the target battery power, and the second battery pack is the battery pack with the smallest capacity in the target battery power; The BCU sends a first balancing instruction to the first battery pack, so that a first DC / DC balancing unit in the first battery pack controls the first battery pack to discharge to the first power line in response to the first balancing instruction; The BCU sends a second balancing instruction to the second battery pack, so that the second DC / DC balancing unit in the second battery pack controls the second battery pack to be charged through the first power line in response to the second balancing instruction; When the discharge amount of the first battery pack or the charge amount of the second battery pack reaches a preset shutdown condition, the BCU sends a shutdown instruction to the first battery pack and the second battery pack, so that the first DC / DC balancing unit controls the first battery pack to stop discharging in response to the shutdown instruction, and the BCU sends the shutdown instruction to the second battery pack, so that the second DC / DC balancing unit controls the second battery pack to stop charging in response to the shutdown instruction; The BCU controls each of the battery packs to recharge; When a full charge event occurs again in any one of the battery packs, the BCU starts the cycle again from the step of determining whether the preset start-up condition is met according to the target battery power until the battery power of any one of the battery packs is greater than the first preset threshold.

16. The method according to claim 15, characterized in that The preset shutdown condition is that the discharge capacity of the first battery pack or the charge capacity of the second battery pack reaches a first ratio of the rated capacity of the first battery pack.

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