A Discharge Control Method and a Charge Control Method for a Battery Pack Control System

Abstract

The present application provides a discharge control method and a charging control method of a battery pack control system, wherein the battery pack control system includes a master battery management unit and multiple slave battery management units, wherein the master battery management unit is used to control the slave battery management units, and the slave battery management units are used to control the battery pack to access a working circuit or disconnect from the working circuit. The discharge control method and the charging control method provided in the present application predict the circulating current value generated by the battery pack incorporation in advance each time before the slave battery management unit controls the battery pack to access the working circuit, and control the battery pack to access the working circuit within a safe circulating current value range. The control method does not rely on equalizing resistance, avoids energy loss, and effectively protects the battery cells and relays of the battery pack connected to the circuit from being damaged by the impact of the circulating current.

Description

Technical Field

[0001] This application relates to the technical field of charge and discharge control of energy storage systems. Specifically, it relates to a discharge control method and a charge control method for a battery pack control system. Background Art

[0002] Currently, most of the lithium battery packs in energy storage systems and electric vehicles adopt the form of multiple battery packs in parallel to meet the capacity and performance requirements of energy storage systems and electric vehicles. As the system scale increases, more and more battery packs are connected in parallel. Due to differences in parameters such as battery voltage, internal resistance, and self-discharge rate among the parallel battery packs, current imbalance will occur. In severe cases, current circulation will occur, affecting the life and performance of the energy storage system and posing potential safety hazards.

[0003] When multiple battery packs are connected in parallel, there is a pressure difference between the branches where the multiple battery packs are located. If directly closed, if the pressure difference between the branches is too large, the circulation current generated by the pressure difference will impact the relay, resulting in adhesion, shortened lifespan, or damage to the battery cells. During the charging process, there is a pressure difference between the branches where the multiple battery packs are located. If the branches with too large a pressure difference are not closed, some branches will not be able to charge. If the charging is carried out in a time-sharing closing manner, the charging time will be long; during the discharging process, similarly, when the pressure difference between the branches where the multiple battery packs are located is too large during discharging, if the branches with too large a pressure difference are not closed, the output power will be limited, the cruising range will be reduced, and the problem of uneven use of the battery packs in the multi-branch system will occur.

[0004] The prior art usually uses an equalizing resistor to control the equalizing current of the parallel battery packs. However, due to the use of the equalizing resistor, which is a lossy device, it will consume the energy of the system, resulting in energy waste. Summary of the Invention

[0005] The purpose of the embodiments of this application is to provide a discharge control method and a charge control method for a battery pack control system to solve the technical defect that it is difficult to reasonably close and connect the branches into the working circuit due to the too large pressure difference between the branches where multiple battery packs are located during the charge and discharge processes in the prior art. Moreover, in the technical solution provided by this application, when closing the parallel battery packs, the original scheme of using an equalizing resistor is abandoned, and the technical defect of energy waste is also avoided.

[0006] A discharge control method for a battery pack control system provided by the embodiments of this application. The battery pack control system includes a main battery management unit and N slave battery management units for controlling N parallel battery packs; among them, the slave battery management unit is used to control the battery pack to be connected to or disconnected from the working circuit. The slave battery management unit is communicatively connected to the main battery management unit, and N is a positive integer greater than or equal to 2;

[0007] The discharge control method is applied to the main battery management unit, and the discharge control method includes:

[0008] At a first moment, first voltage values of N battery packs connected in parallel are obtained, a first battery pack having a maximum first voltage value is determined, and a control instruction for connecting the first battery pack to a working circuit is sent to a slave battery management unit corresponding to the first battery pack;

[0009] At the i-th moment, obtain the i-th voltage value of the N-i+1 battery packs that are not connected to the working circuit, and the i-th sampled voltage, where the i-th sampled voltage is the voltage of the i-1 battery packs that are connected to the working circuit in parallel; subtract all i-th voltage values from the i-th sampled voltage to obtain N-i+1 differences; obtain Mi differences that are less than the corresponding voltage difference threshold among the N-i+1 differences, determine the i-th battery pack with the largest voltage among the Mi battery packs corresponding to the Mi differences, and send a control instruction to connect the i-th battery pack to the working circuit to the slave battery management unit corresponding to the i-th battery pack; wherein i is a positive integer greater than or equal to 2, and Mi is an integer greater than or equal to 0;

[0010] Until Mi=0, a command to allow discharge is output.

[0011] In the above technical solution, the battery pack control system includes a main battery management unit and multiple slave battery management units. The main battery management unit is used to control the slave battery management units, and the slave battery management units are used to control the battery pack to access the working circuit or disconnect from the working circuit. Each time before the slave battery management unit controls the battery pack to access the working circuit, it predicts in advance the circulating current value generated by the battery pack, and controls the battery pack to access the working circuit within a safe circulating current value range. This control method does not rely on balancing resistance, avoids energy loss, and effectively protects the battery cells and relays of the battery pack connected to the circuit (the function of the relay is to connect the battery pack to the working circuit or disconnect it from the working circuit by opening and closing the relay) from being damaged by the impact of the circulating current.

[0012] In some optional implementations, the step of obtaining Mi difference values among N-i+1 difference values that are smaller than the corresponding pressure difference threshold value includes:

[0013] The voltage difference threshold is obtained according to the allowable discharge current of each battery pack in the N-i+1 battery packs not connected to the working circuit and the internal resistance of the corresponding battery pack.

[0014] In the above technical solution, each pressure difference threshold corresponding to the N-i+1 difference values is a threshold that changes dynamically in real time. The pressure difference threshold is obtained based on the allowable discharge current and internal resistance of each battery pack, wherein the allowable discharge current of the battery pack is the allowable discharge current under the temperature and SOC value of the battery pack at the current moment or the maximum circulating current value of the relay closure.

[0015] In some alternative embodiments, it further includes:

[0016] After receiving an instruction indicating that the (i - 1)-th battery pack is connected to the working circuit, it is determined as the i-th moment; wherein, the instruction indicating that the (i - 1)-th battery pack is connected to the working circuit is sent by the slave battery management unit corresponding to the (i - 1)-th battery pack.

[0017] In the above technical solution, after the master battery management unit sends an instruction to connect the (i - 1)-th battery pack to the working circuit to the slave battery management unit corresponding to the (i - 1)-th battery pack, the slave battery management unit corresponding to the (i - 1)-th battery pack will perform an open - circuit diagnosis on the relay of the (i - 1)-th battery pack. If there is no open - circuit fault, the slave battery management unit corresponding to the (i - 1)-th battery pack confirms that the relay of the (i - 1)-th battery pack is closed and sends an instruction indicating that the (i - 1)-th battery pack is connected to the working circuit to the master battery management unit. After the master battery management unit receives this instruction, it is determined as the i-th moment. During the discharge control process, each time the relay of the battery pack is closed, an open - circuit diagnosis is performed to ensure the smooth progress of the subsequent control process.

[0018] In some alternative embodiments, the discharge control method further includes:

[0019] Obtain the sampled voltage, sampled current, and the voltage of the battery packs not connected to the working circuit, and send a control instruction to connect the battery packs to the working circuit to the slave battery management units corresponding to the battery packs that meet the first condition; wherein, the first condition includes: taking the difference between the voltage of the battery packs not connected to the working circuit and the sampled voltage. When the difference is within the corresponding pressure - difference range, it is determined that the sampled current is less than the set threshold and lasts for a preset time.

[0020] Wherein, the pressure - difference range of the difference between the voltage VBatVolt of the battery packs not connected to the working circuit and the sampled voltage VLINK is ΔVmin < (VBatVolt - VLINK) < ΔVmax; ΔVmin = ΔV - U0, ΔVmax = ΔV + U0, ΔV = the product of the maximum circulating current value and the internal resistance, and U0 is the threshold tolerance of the set sampling error and over - current judgment standard.

[0021] In the above technical solution, after the high - voltage is completed during the discharge control, when the electric vehicle or other electrical equipment is running, the master battery management unit monitors the change of the sampled voltage in real time, predicts the timing of connecting the remaining battery packs not connected to the working circuit to the working circuit, and sends a control instruction to connect the battery packs to the working circuit to the slave battery management units corresponding to these battery packs at this timing, which can connect all the battery packs with a large pressure - difference to the working circuit, avoiding the problems of insufficient output power and shortened driving range caused by the inability of some battery packs to discharge due to the pressure - difference.

[0022] In some alternative embodiments, the discharge control method further includes:

[0023] Obtain the sampled voltage, the sampled current, and the voltage of the battery pack not connected to the working circuit, and send a control instruction to the battery pack that meets the second condition to connect the battery pack to the working circuit; wherein, the second condition includes: taking the difference between the voltage of the battery pack not connected to the working circuit and the sampled voltage, when the difference is within the voltage difference range, reducing the sampled current by controlling the output power, determining that the sampled current is less than the set threshold and lasting for a preset time.

[0024] In the above technical solution, after the high voltage is completed in the discharge control, during the operation of the electric vehicle or other electrical equipment, the main battery management unit monitors the change of the sampled voltage in real time, predicts and controls the timing of connecting the remaining battery packs not connected to the working circuit to the working circuit, and sends a control instruction to the slave battery management unit corresponding to the battery pack to connect the battery pack to the working circuit at this timing, avoiding further widening of the voltage difference between the battery packs, improving the consistency of the battery cells, enabling all battery packs with a large voltage difference to be connected to the working circuit, and avoiding problems such as insufficient output power and shortened driving range caused by the voltage difference resulting in some battery packs being unable to discharge.

[0025] In some alternative embodiments, the discharge control method further includes:

[0026] Dynamically adjust the allowable discharge power until the discharge current of the battery pack already connected to the working circuit drops to a level that does not damage the capacitive life of the relay, and then send an instruction to the slave battery management unit corresponding to the battery pack to disconnect the battery pack from the working circuit;

[0027] After receiving the instruction indicating that the disconnection of the battery pack from the working circuit is completed, re-request the allowable discharge power according to all the battery packs already connected to the working circuit.

[0028] In the above technical solution, during the discharge process, before disconnecting the battery pack from the working circuit, the current is reduced by dynamically adjusting the allowable discharge power until the current drops to a level that does not damage the capacitive life of the relay, and then the relay is controlled to disconnect to disconnect the battery pack from the working circuit, protecting the relay from being damaged when the battery pack is disconnected from the working circuit.

[0029] A charging control method for a battery pack control system provided by an embodiment of the present application, the charging control method is applied to the main battery management unit, and the charging control method includes:

[0030] At a first moment, obtain the first voltage value of N parallel-connected battery packs, determine the first battery pack with the smallest first voltage value, and send a control instruction to the slave battery management unit corresponding to the first battery pack to connect the first battery pack to the working circuit; wherein, N is a positive integer greater than or equal to 2;

[0031] At the j-th moment, obtain the j-th voltage value of N - j + 1 battery packs not connected to the working circuit, and the j-th sampled voltage, where the j-th sampled voltage is the voltage of the j - 1 battery packs connected in parallel in the working circuit; subtract each of the j-th voltage values from the j-th sampled voltage respectively to obtain N - j + 1 differences; obtain Pj differences among the N - j + 1 differences that are less than the corresponding differential voltage threshold, determine the j-th battery pack with the lowest voltage among the Pj battery packs corresponding to the Pj differences, and send a control instruction to the slave battery management unit corresponding to the j-th battery pack to connect the j-th battery pack to the working circuit; where j is a positive integer greater than or equal to 2, and Pj is an integer greater than or equal to 0;

[0032] Until Pj = 0, output an instruction allowing charging.

[0033] In the above technical solution, the battery pack control system includes a master battery management unit and multiple slave battery management units. The master battery management unit is used to control the slave battery management units, and the slave battery management units are used to control the connection or disconnection of the battery packs to the working circuit. During the charging control process, each time before the slave battery management unit controls a battery pack to be connected to the working circuit, the circulating current value generated by the connection of the battery pack is predicted in advance, and the battery pack is controlled to be connected to the working circuit within a safe circulating current value range. This control method does not rely on a balancing resistor, avoids energy loss, and effectively protects the battery cells and relays of the battery packs connected to the circuit (the function of the relay is: to realize the connection or disconnection of the battery pack to the working circuit through the opening and closing of the relay) from being damaged by the impact generated by the circulating current.

[0034] In some alternative embodiments, the step of obtaining Pj differences among the N - j + 1 differences that are less than the corresponding differential voltage threshold includes:

[0035] Obtain the differential voltage threshold according to the allowable charging current of each of the N - j + 1 battery packs not connected to the working circuit and the internal resistance of the corresponding battery pack.

[0036] In the above technical solution, each differential voltage threshold corresponding to the N - j + 1 differences is a real-time dynamic change threshold, which is obtained according to the allowable charging current and internal resistance of each battery pack. Among them, the allowable charging current of the battery pack is the allowable charging current at the temperature and SOC value of the battery pack at the current moment or the maximum circulating current value when the relay is closed.

[0037] In some alternative embodiments, it further includes:

[0038] After receiving an instruction indicating that the connection of the (j - 1)-th battery pack to the working circuit is completed, it is determined as the j-th moment; where the instruction indicating that the connection of the (j - 1)-th battery pack to the working circuit is completed is sent by the slave battery management unit corresponding to the (j - 1)-th battery pack.

[0039] In the above technical solution, after the main battery management unit sends an instruction to the slave battery management unit corresponding to the (j - 1)-th battery pack to connect the (j - 1)-th battery pack to the working circuit, the slave battery management unit corresponding to the (j - 1)-th battery pack will perform an open-circuit diagnosis on the relay of the (j - 1)-th battery pack. If there is no open-circuit fault, the slave battery management unit corresponding to the (j - 1)-th battery pack will confirm that the relay of the (j - 1)-th battery pack is closed and send an instruction to the main battery management unit to indicate that the (j - 1)-th battery pack is connected to the working circuit. After the main battery management unit receives this instruction, it is determined as the j-th moment. During the charging control process, each time the relay of the battery pack is closed, an open-circuit diagnosis is performed to ensure the smooth progress of the subsequent control process.

[0040] In some optional embodiments, the sampling voltage, sampling current, and the voltage of the battery pack not connected to the working circuit are obtained, and a control instruction to connect the battery pack to the working circuit is sent to the slave battery management unit corresponding to the battery pack that meets the third condition; wherein, the third condition includes: subtracting the voltage of the battery pack not connected to the working circuit from the sampling voltage, and when the difference is within the corresponding voltage difference range, perform a reduced-charging-rate control on all the battery packs already connected to the working circuit until the charging rate drops to the target value.

[0041] In the above technical solution, after the high-voltage charging control is completed, multiple parallel-connected battery packs already connected to the working circuit start charging. During the charging process, the main battery management unit monitors the change of the sampling voltage in real time, predicts and controls the timing of connecting the remaining battery packs not connected to the working circuit to the working circuit, and sends a control instruction to the slave battery management unit corresponding to the battery pack at this timing, avoiding overcurrent charging caused by circulating current generated when the battery pack is incorporated during the charging process, enabling all battery packs with a large voltage difference to be connected to the working circuit, solving the problem that battery packs with too large a voltage difference cannot be charged, and effectively improving the battery availability.

[0042] In some optional embodiments, performing a reduced-charging-rate control on all the battery packs already connected to the working circuit until the charging rate drops to the target value includes:

[0043] When the difference between the voltage VBatVolt of the battery pack not connected to the working circuit and the sampling voltage VLINK is within the voltage difference range ΔVmin < (VBatVolt - VLINK) < ΔVmax, charge at a charging rate σi which is the current charging rate looked up in the table multiplied by the gradient coefficient φi. When the sampling voltage is charged to VLINK = ΔV + VBatVolt and the stable time is τs, switch to the next gradient coefficient; where, ΔVmin = ΔV - U0, ΔVmax = ΔV + U0; ΔV = the product of the maximum circulating current value and the internal resistance, and U0 is the threshold tolerance for the set sampling error and overcurrent judgment standard;

[0044] Repeat the above steps until σi = 0.1C, charge the sampling voltage to VLINK = ΔV + VBatVolt and stabilize for a time τs.

[0045] In some alternative embodiments, the charging control method further includes:

[0046] Dynamically adjust the allowed charging power until the charging current of the battery pack connected to the working circuit drops to a level that does not damage the capacitive life of the relay, and then send an instruction to disconnect the battery pack from the working circuit to the slave battery management unit corresponding to the battery pack;

[0047] After receiving the instruction indicating that the disconnection of the battery pack from the working circuit is completed, re-request the allowed charging power according to all the battery packs connected to the working circuit.

[0048] In the above technical solution, during the charging process, before disconnecting the battery pack from the working circuit, the current is reduced by dynamically adjusting the allowed charging power until the current drops to a level that does not damage the capacitive life of the relay, and then the relay is controlled to disconnect to disconnect the battery pack from the working circuit, protecting the relay from being damaged when the battery pack is disconnected from the working circuit.

[0049] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the following specifically gives the specific embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0051] Figure 1 It is a schematic structural diagram of a battery pack control system provided by an embodiment of the present application;

[0052] Figure 2 It is a flowchart of the steps of a discharge control method of a battery pack control system provided by an embodiment of the present application;

[0053] Figure 3 It is an open-circuit diagnostic flowchart provided by an embodiment of the present application;

[0054] Figure 4 It is a flowchart of the steps of a charging control method of a battery pack control system provided by an embodiment of the present application;

[0055] Figure 5 The flowchart of open - circuit diagnosis provided for another embodiment of this application. Specific implementation manners

[0056] Next, embodiments of the technical solution of this application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of this application more clearly, so they are only examples and cannot be used to limit the protection scope of this application.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above - mentioned drawings are intended to cover non - exclusive inclusion.

[0058] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary - secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means more than two, unless otherwise specifically defined.

[0059] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0060] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after. In the description of the embodiments of this application, the term "a plurality of" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0061] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0062] At present, most lithium battery packs in energy storage systems and electric vehicles adopt the form of multiple battery packs in parallel to meet the capacity and performance requirements of energy storage systems and electric vehicles. However, there is a voltage difference between the multiple voltages of multiple battery packs. If the relays in the battery packs are directly closed to achieve parallel connection, the circulating current generated by the excessive voltage difference will impact the relays and cause adhesion, shortening the life or causing damage to the battery cells. When charging, the voltage difference is too large, which will cause some battery packs to fail to charge; when discharging, the voltage difference is too large, which will cause some battery packs to fail to discharge, limiting the output power and reducing the driving range.

[0063] In order to solve the problem that some battery packs in parallel cannot be charged or discharged due to voltage difference, the applicant has found through research that balancing resistors can be used to control the balancing current of parallel battery packs, but the current balancing capacity is limited, and the balancing resistors used are lossy devices that will consume energy of the system.

[0064] Based on the above considerations, in order to solve the problem of energy loss caused by the use of balancing resistors, the inventors have conducted in-depth research and designed a discharge control method and a charging control method for a battery pack control system. Each time before the battery management unit controls the battery pack to connect to the working circuit, the circulating current value generated by the battery pack is predicted in advance, and the battery pack is controlled to connect to the working circuit within a safe circulating current value range. This control method does not rely on balancing resistors and avoids energy loss.

[0065] The discharge control method and the charging control method disclosed in the embodiments of the present application are applicable to the control of the charging or discharging process of multiple parallel battery packs when multiple battery packs are connected in parallel. Multiple parallel battery packs can be used in but not limited to mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft and other electrical devices. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles and spacecraft, etc.

[0066] For the convenience of description, the following embodiments are described by taking an electric vehicle as an example of an electric device in one embodiment of the present application.

[0067] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a battery pack control system provided by an embodiment of the present application. The battery pack control system includes a main battery management unit and N slave battery management units, and is used to control N parallel-connected battery packs. The slave battery management unit controls the on / off of the relay in the battery pack to control the battery pack to be connected to or disconnected from the working circuit. The slave battery management unit is communicatively connected to the main battery management unit, and N is a positive integer greater than or equal to 2.

[0068] In some embodiments of the present application, the slave battery management unit can be implemented by using the battery management system (Battery Mannagement Sysytem, BMS) of the corresponding battery pack; the main battery management unit can be implemented by the control module of the battery disconnect unit (Battery Disconnect Unit, BDU), or can be implemented by the battery management system of one of the battery packs.

[0069] Please refer to Figure 2 , Figure 2 which is a step flowchart of a discharge control method for a battery pack control system. The discharge control method is applied to the main battery management unit, and the discharge control method includes Step 100 - Step 300.

[0070] Step 100: At a first moment, obtain the first voltage values of N parallel-connected battery packs, determine the first battery pack with the largest first voltage value, and send a control instruction to the slave battery management unit corresponding to the first battery pack to connect the first battery pack to the working circuit.

[0071] Step 200: At the i-th moment, obtain the i-th voltage values of N - i + 1 battery packs not connected to the working circuit, and the i-th sampling voltage, where the i-th sampling voltage is the voltage of the i - 1 battery packs connected in parallel that have been connected to the working circuit; subtract each of the i-th voltage values from the i-th sampling voltage to obtain N - i + 1 differences; obtain Mi differences that are less than the corresponding pressure difference thresholds among the N - i + 1 differences, determine the i-th battery pack with the largest voltage among the Mi battery packs corresponding to the Mi differences, and send a control instruction to the slave battery management unit corresponding to the i-th battery pack to connect the i-th battery pack to the working circuit; where i is a positive integer greater than or equal to 2, and Mi is an integer greater than or equal to 0.

[0072] Step 300: Until Mi = 0, output an instruction to allow discharge.

[0073] Among them, the first moment in step 100, that is, after the BMS of the battery pack completes the self-test, the high-voltage instruction of the vehicle control unit (VCU) is obtained. The BMS self-test of the battery pack includes initialization and fault judgment. The main battery management unit can send a signal to the slave battery management unit to instruct the BMS self-test. After the BMS self-test of all battery packs is completed, the main battery management unit will receive the high-voltage instruction of the vehicle controller. After the main battery management unit receives the high-voltage instruction, that is, at the first moment, the first battery pack with the largest battery pack voltage is connected to the working circuit. The battery pack voltage can be the cumulative sum of the single cell voltages in the battery pack, or it can be the battery pack terminal voltage collected by the high-voltage acquisition unit. After the first battery pack is connected to the working circuit, enter step 200: at each moment (i=2, 3, 4, ...), respectively determine the Mi battery packs whose voltage value of the battery pack that is not connected to the working circuit at the current moment and the sampled voltage at the current moment are less than the corresponding voltage difference threshold, and connect the i-th battery pack with the largest voltage among the Mi battery packs to the working circuit. At each moment (i=2, 3, 4, ...), step 200 is repeated until: step 300, when Mi=0, it indicates that at the current moment there is no battery pack that can satisfy the condition that the difference between the battery pack voltage value and the sampled voltage is less than the corresponding voltage difference threshold, that is, at the current moment there is no battery pack that can be connected to the working circuit. At this time, these battery packs that are not connected to the working circuit remain disconnected from the working circuit, and the main battery management unit feedbacks the high voltage completion instruction on the system. The main battery management unit requests permission to discharge power and outputs power for discharge according to the number of battery packs connected to the working circuit.

[0074] During the high-voltage process of the discharge control of the embodiment of the present application, each time before the battery management unit controls the battery pack to access the working circuit, it is determined whether there is a battery pack that meets the condition: the difference between the battery pack voltage value and the sampled voltage is less than the corresponding pressure difference threshold. The pressure difference threshold is set as follows: the circulating current value corresponding to the pressure difference threshold is within a safe circulating current value range. Then, if a battery pack meets this condition, it can be predicted that the circulating current value generated by the incorporation of the battery pack is also within a safe circulating current value range. The control method of this embodiment ensures that the battery pack is controlled to access the working circuit within a safe circulating current value range, and avoids the impact of excessive circulating current values generated by the incorporation of the battery pack on the relay, resulting in adhesion, shortened life or damage to the battery cell, and effectively protects the battery cells and relays of the battery pack connected to the circuit. In addition, the control method does not rely on the balancing resistor, avoiding energy loss. Among them, the function of the relay is to connect the battery pack to the working circuit or disconnect it from the working circuit by opening and closing the relay.

[0075] In some embodiments of the present application, in the step of obtaining Mi difference values among N-i+1 difference values that are smaller than the corresponding pressure difference threshold, the pressure difference threshold ΔV is:

[0076] ΔV = (Ri + Rj) × Ix

[0077] Ix = Min(y(x)map, F(x)map)

[0078] Wherein, Ri and Rj are respectively the internal resistance of the battery pack connected to the working circuit and the internal resistance of the battery pack not connected to the working circuit. The calculation of the internal resistance is R = f(x) = (αT, βSOC, δSOH), that is, the internal resistance of the battery pack is calculated in real time through the mathematical model of temperature T, SOC (the ratio of available capacity to actual capacity), and SOH (the remaining ratio of available performance). Ix is the allowable discharge current of the battery pack, which takes the smaller value of y(x)map and F(x)map. y(x)map is the allowable discharge current at the current temperature and SOC value obtained from the discharge current map of the battery management unit, and F(x)map is the maximum circulating current value that allows the relay to close without damaging the capacitive life of the relay. Therefore, by obtaining the maximum safe circulating current value generated by the allowable parallel battery pack in real time through Ix, the differential pressure threshold ΔV of the allowable parallel battery pack can be calculated.

[0079] In the embodiment of the present application, each differential pressure threshold corresponding to the N - i + 1 differences is a real - time dynamic change threshold, and this differential pressure threshold is obtained according to the allowable discharge current and internal resistance of each battery pack. Among them, the allowable discharge current of the battery pack is the allowable discharge current at the current temperature and SOC value of the battery pack or the maximum safe circulating current value when the relay closes. Therefore, the differential pressure threshold calculated according to the maximum safe circulating current value enables the battery pack to be allowed to be incorporated into the working circuit as much as possible on the premise of generating a safe circulating current value when incorporated into the working circuit, reducing the number of battery packs that cannot be incorporated into the working circuit.

[0080] In some alternative embodiments, the discharge control method further includes:

[0081] After receiving the instruction indicating that the connection of the (i - 1)th battery pack to the working circuit is completed, it is determined as the i - th moment; wherein, the instruction indicating that the connection of the (i - 1)th battery pack to the working circuit is issued by the slave battery management unit corresponding to the (i - 1)th battery pack.

[0082] Please refer to Figure 3 , Figure 3This is the open - circuit diagnosis workflow diagram provided by the embodiments of the present application. After the main battery management unit sends an instruction to the slave battery management unit corresponding to the (i - 1)-th battery pack to connect the (i - 1)-th battery pack to the working circuit, the slave battery management unit corresponding to the (i - 1)-th battery pack will perform an open - circuit diagnosis on the relay of the (i - 1)-th battery pack. If there is no open - circuit fault, the slave battery management unit corresponding to the (i - 1)-th battery pack will confirm that the relay of the (i - 1)-th battery pack is closed, and send an instruction to the main battery management unit indicating that the (i - 1)-th battery pack is connected to the working circuit. After the main battery management unit receives this instruction, it is determined as the i - th moment. During the discharge control process, each time the relay of the battery pack is controlled to close, an open - circuit diagnosis is performed to ensure the smooth progress of the subsequent control process.

[0083] In some alternative embodiments, after the high - voltage application is completed during the discharge control process, when the electric vehicle is running, as the battery packs connected to the working circuit discharge, their voltages decrease, and gradually approach the voltages of the battery packs not connected to the working circuit. At this time, the discharge control method further includes: obtaining the sampled voltage, sampled current, and the voltage of the battery packs not connected to the working circuit, and sending a control instruction to the slave battery management unit corresponding to the battery pack that meets the first condition to connect the battery pack to the working circuit; wherein, the first condition includes: taking the difference between the voltage of the battery pack not connected to the working circuit and the sampled voltage, and when the difference is within the corresponding voltage difference range, it is determined that the sampled current is less than the set threshold and lasts for a preset time. The voltage difference range of the difference between the voltage VBatVolt of the battery pack not connected to the working circuit and the sampled voltage VLINK is ΔVmin < (VBatVolt - VLINK) < ΔVmax; ΔVmin = ΔV - U0, ΔVmax = ΔV + U0, ΔV = the product of the maximum circulating current value and the internal resistance, and U0 is the threshold tolerance of the set sampling error and over - current judgment standard.

[0084] In the embodiments of the present application, after the high - voltage application is completed during the discharge control process, when the electric vehicle is running, the main battery management unit monitors the change of the sampled voltage in real time and predicts the timing of connecting the battery packs not yet connected to the working circuit to the working circuit. Among them, this timing in this embodiment is: the difference between the voltage of the battery pack not connected to the working circuit and the sampled voltage is within the voltage difference range, and the sampled current is less than the set threshold. At this timing, sending a control instruction to the slave battery management unit corresponding to this battery pack to connect the battery pack to the working circuit can connect all the battery packs with a large voltage difference to the working circuit, avoiding problems such as insufficient output power and shortened cruising range caused by the voltage difference resulting in some battery packs being unable to discharge.

[0085] In some alternative embodiments, after the high voltage is applied during the discharge control process, during the operation of the electric vehicle, as the battery pack connected to the working circuit discharges, its voltage drops and gradually approaches the voltage of the battery pack not connected to the working circuit. At this time, the discharge control method further includes: obtaining the sampled voltage, sampled current, and the voltage of the battery pack not connected to the working circuit, and sending a control instruction to the battery pack that meets the second condition to connect the battery pack to the working circuit; wherein, the second condition includes: taking the difference between the voltage of the battery pack not connected to the working circuit and the sampled voltage, when the difference is within the voltage difference range, reducing the sampled current by controlling the output power, and determining that the sampled current is less than the set threshold θA and lasts for a preset time. The setting of the value of θA mainly considers the following aspects: 1) The driving condition of the electric vehicle, that is, giving priority to ensuring the safe driving of the vehicle; 2) The polarization internal resistance generated by the cell due to the output current. That is:

[0086] θ = min(I_safety, I_Resistance), where I_safety refers to the current at the safe vehicle speed; I_Resistance refers to the current at the maximum allowable polarization voltage during dynamic regulation.

[0087] In the above technical solution, after the high voltage is applied during the discharge control process, during the driving and discharging process of the electric vehicle, the main battery management unit monitors the change of the sampled voltage in real time and predicts the timing of connecting the battery pack not connected to the working circuit to the working circuit. Among them, the timing in this embodiment is: when the difference between the voltage of the battery pack not connected to the working circuit and the sampled voltage is within the voltage difference range, dynamically control the output power to reduce the sampled current, and then control the sampled current to be less than the set threshold. At this timing, a control instruction to connect the battery pack to the working circuit is sent to the slave battery management unit corresponding to the battery pack, avoiding further widening of the voltage difference between the battery packs, improving the consistency of the cells, enabling all battery packs with a large voltage difference to be connected to the working circuit, and avoiding problems such as insufficient output power and shortened driving range caused by the inability of some battery packs to discharge due to a large voltage difference.

[0088] In some alternative embodiments, during the discharge process, if a certain battery pack fails and the relay of the battery pack needs to be disconnected, at this time, the discharge control method further includes: dynamically adjusting the allowable discharge power until the discharge current of the battery pack connected to the working circuit drops to a level that does not damage the capacitive life of the relay, and then sending an instruction to disconnect the battery pack from the working circuit to the slave battery management unit corresponding to the battery pack; after receiving the instruction indicating that the disconnection of the battery pack from the working circuit is completed, re-request the allowable discharge power according to all the battery packs connected to the working circuit.

[0089] During the discharging process of the embodiments of the present application, before the battery pack is disconnected from the working circuit, the current is reduced by dynamically adjusting the allowable discharging power until the current drops to a level that does not damage the capacitive life of the relay. Then, the relay is controlled to disconnect, so that the battery pack is disconnected from the working circuit, protecting the relay from being damaged when the battery pack is disconnected from the working circuit.

[0090] Please refer to Figure 4 , Figure 4 which is a flowchart of the steps of a charging control method for a battery pack control system provided by the embodiments of the present application. The charging control method is applied to the main battery management unit, and the charging control method includes steps 400 to 600.

[0091] Step 400: At the first moment, obtain the first voltage values of N parallel-connected battery packs, determine the first battery pack with the smallest first voltage value, and send a control instruction to the slave battery management unit corresponding to the first battery pack to connect the first battery pack to the working circuit; where N is a positive integer greater than or equal to 2.

[0092] Step 500: At the j-th moment, obtain the j-th voltage values of N - j + 1 battery packs not connected to the working circuit, and the j-th sampled voltage, where the j-th sampled voltage is the voltage of the j - 1 battery packs connected in parallel that are already connected to the working circuit; subtract each of the j-th voltage values from the j-th sampled voltage to obtain N - j + 1 differences; obtain Pj differences among the N - j + 1 differences that are less than the corresponding pressure difference thresholds, determine the j-th battery pack with the smallest voltage among the Pj battery packs corresponding to the Pj differences, and send a control instruction to the slave battery management unit corresponding to the j-th battery pack to connect the j-th battery pack to the working circuit; where j is a positive integer greater than or equal to 2, and Pj is an integer greater than or equal to 0.

[0093] Step 600: Until Pj = 0, output an instruction to allow charging.

[0094] Among them, the first moment in step 400, that is, when a charging request is received. At the first moment, the first battery pack with the lowest battery pack voltage is connected to the working circuit. After the first battery pack is connected to the working circuit, step 500 is entered: at each moment when (j = 2, 3, 4,...), the voltage values of the battery packs not connected to the working circuit at the current moment are respectively judged to be less than the corresponding pressure difference thresholds of the Pj battery packs with the sampling voltage difference at the current moment, and the jth battery pack with the lowest voltage among the Pj battery packs is connected to the working circuit. At each moment when (j = 2, 3, 4,...), step 500 is repeatedly executed until: step 600, when Pj = 0, it means that there is no battery pack that can satisfy the condition that the battery pack voltage value is less than the corresponding pressure difference threshold with the sampling voltage at the current moment, that is, there is no battery pack that can be connected to the working circuit at the current moment. At this time, these battery packs not connected to the working circuit remain in a disconnected state from the working circuit, and the main battery management unit feeds back a high-voltage completion instruction to the system, and the main battery management unit requests the allowed charging power according to the number of battery packs connected to the working circuit.

[0095] In the charging control of the embodiment of the present application during the high-voltage process, each time before the battery management unit controls the battery pack to be connected to the working circuit, it is judged whether there is a battery pack that satisfies the condition: the difference between the battery pack voltage value and the sampling voltage is less than the corresponding pressure difference threshold. The pressure difference threshold is set as follows: the circulating current value corresponding to the pressure difference threshold is within the safe circulating current value range. Then, if there is a battery pack that satisfies this condition, it can be predicted that the circulating current value generated by the connection of this battery pack is also within the safe circulating current value range. The control method of this embodiment ensures that the battery pack is connected to the working circuit within the safe circulating current value range, avoids the impact of excessive circulating current value generated by the connection of the battery pack on the relay, resulting in adhesion, shortened life or damage to the battery core, effectively protects the battery core and relay of the battery pack connected to the circuit, and moreover, this control method does not rely on the balancing resistor, avoiding energy loss. Among them, the role of the relay is: to realize the connection of the battery pack to the working circuit or the disconnection from the working circuit through the opening and closing of the relay.

[0096] In some alternative embodiments, for the step of obtaining Pj differences less than the corresponding pressure difference thresholds among the N - j + 1 differences, the pressure difference threshold:

[0097] ΔV = (Ri + Rj) × Ix

[0098] Ix = Min(Y(x)map,F(x)map)

[0099] Among them, Ri and Rj are respectively the internal resistance of the battery pack already connected to the working circuit and the internal resistance of the battery pack not connected to the working circuit. The calculation of the internal resistance is R = f(x) = (αT, βSOC, δSOH), that is, the internal resistance of the battery pack is obtained by real-time calculation through the mathematical model of temperature T, SOC (the ratio of available capacity to actual capacity), and SOH (the remaining proportion of available performance). Ix is the allowable charging current of the battery pack, which takes the smaller value in Y(x)map and F(x)map. Y(x)map is the allowable charging current obtained from the charging current map of the battery management unit at the current temperature and SOC value, and F(x)map is the maximum circulating current value that allows the relay to close without damaging the capacitive life of the relay. Therefore, by obtaining the maximum safe circulating current value allowed to be incorporated into the battery pack in real time through Ix, the differential pressure threshold ΔV allowed to be incorporated into the battery pack can be calculated.

[0100] In the embodiment of the present application, each differential pressure threshold corresponding to the N - j + 1 differences is a real-time dynamic change threshold, and this differential pressure threshold is obtained according to the allowable charging current and internal resistance of each battery pack. Among them, the allowable charging current of the battery pack is the allowable charging current at the current temperature and SOC value of the battery pack or the maximum safe circulating current value when the relay is closed. Therefore, the differential pressure threshold calculated according to the maximum safe circulating current value enables the battery pack to be allowed to be incorporated into the working circuit as much as possible on the premise of generating a safe circulating current value when incorporated into the working circuit, reducing the number of battery packs that cannot be incorporated into the working circuit.

[0101] In some alternative embodiments, the charging control method further includes:

[0102] After receiving the instruction indicating that the connection of the (j - 1)th battery pack to the working circuit is completed, it is judged as the jth moment; among them, the instruction indicating that the connection of the (j - 1)th battery pack to the working circuit is sent by the slave battery management unit corresponding to the (j - 1)th battery pack.

[0103] Please refer to Figure 5 , Figure 5 , which is the open - circuit diagnosis work flow chart provided by the embodiment of the present application. After the master battery management unit sends an instruction to the slave battery management unit corresponding to the (j - 1)th battery pack to connect the (j - 1)th battery pack to the working circuit, the slave battery management unit corresponding to the (j - 1)th battery pack will perform an open - circuit diagnosis on the relay of the (j - 1)th battery pack. If there is no open - circuit fault, the slave battery management unit corresponding to the (j - 1)th battery pack confirms that the relay of the (j - 1)th battery pack is closed and sends an instruction indicating that the connection of the (j - 1)th battery pack to the working circuit is completed to the master battery management unit. After the master battery management unit receives this instruction, it is judged as the jth moment. During the charging control process, each time the relay of the battery pack is controlled to close, an open - circuit diagnosis is performed to ensure the smooth progress of the subsequent control process.

[0104] In some optional embodiments, after the high voltage is applied in the charging control and during the charging process of multiple parallel-connected battery packs, the voltage of the battery packs already connected to the working circuit gradually rises. At this time, the charging control method further includes: obtaining the sampled voltage, sampled current, and the voltage of the battery packs not connected to the working circuit, and sending a control instruction to the slave battery management unit corresponding to the battery packs that meet the third condition to connect the battery packs to the working circuit; wherein, the third condition includes: subtracting the voltage of the battery packs not connected to the working circuit from the sampled voltage, and when the difference is within the corresponding voltage difference range, performing a charging rate reduction control on all the battery packs already connected to the working circuit until the charging rate drops to the target value.

[0105] In the embodiments of the present application, after the high voltage is applied in the charging control, multiple parallel-connected battery packs already connected to the working circuit start charging. During the charging process, the main battery management unit monitors the change of the sampled voltage in real time and predicts the timing of connecting the remaining battery packs not connected to the working circuit to the working circuit. Among them, the timing in this embodiment is: when the difference between the voltage of the battery packs not connected to the working circuit and the sampled voltage is within the voltage difference range, perform a charging rate reduction control on all the battery packs already connected to the working circuit until the charging rate drops to the target value. At this timing, send a control instruction to the slave battery management unit corresponding to the battery pack to connect the battery pack to the working circuit, avoiding overcurrent charging caused by circulating current generated when the battery pack is incorporated during the charging process, enabling all battery packs with a large voltage difference to be connected to the working circuit, solving the problem that battery packs with too large a voltage difference cannot be charged, and effectively improving battery availability.

[0106] In some optional embodiments, performing a charging rate reduction control on all the battery packs already connected to the working circuit until the charging rate drops to the target value includes:

[0107] When the difference between the voltage VBatVolt of the battery packs not connected to the working circuit and the sampled voltage VLINK is within the voltage difference range ΔVmin < (VBatVolt - VLINK) < ΔVmax, charge at a charging rate σi which is the current charging rate looked up in the table multiplied by the gradient coefficient φi. When the sampled voltage is charged to VLINK = ΔV + VBatVolt and stabilized for a time τs, switch to the next gradient coefficient; wherein, ΔVmin = ΔV – U0, ΔVmax = ΔV + U0; ΔV = the product of the maximum circulating current value and the internal resistance, and U0 is the threshold tolerance set for the sampling error and overcurrent judgment standard;

[0108] Repeat the above steps until σi = 0.1C, and the sampled voltage is charged to VLINK = ΔV + VBatVolt and stabilized for a time τs.

[0109] In the embodiment of the present application, during the charging control with a decreasing charging rate, a gradient descent charging control with a decreasing charging rate is adopted, which improves the overall charging efficiency compared with the method of directly reducing the charging rate to the target value.

[0110] In some alternative embodiments, during the charging process, if a certain battery pack fails and the relay of the battery pack needs to be disconnected, at this time, the charging control method further includes: dynamically adjusting the allowed charging power until the charging current of the battery packs already connected to the working circuit drops to a level that does not damage the capacitive life of the relay, and then sending an instruction to disconnect the battery pack from the working circuit to the slave battery management unit corresponding to the battery pack; after receiving the instruction indicating that the disconnection of the battery pack from the working circuit is completed, re-requesting the allowed charging power according to all the battery packs already connected to the working circuit.

[0111] In the embodiment of the present application, during the charging process, before the battery pack is disconnected from the working circuit, the current is reduced by dynamically adjusting the allowed charging power until the current drops to a level that does not damage the capacitive life of the relay, and then the relay is controlled to disconnect to make the battery pack disconnect from the working circuit, protecting the relay from being damaged when the battery pack is disconnected from the working circuit.

[0112] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only illustrative. For example, the division of the units is only a logical function division, and there may be other division methods in actual implementation. For another example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some communication interfaces, and the indirect couplings or communication connections of the devices or units can be in electrical, mechanical or other forms.

[0113] In addition, the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0114] Furthermore, in each embodiment of the present application, the various functional modules can be integrated together to form an independent part, or each module can exist alone, or two or more modules can be integrated to form an independent part.

[0115] In this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present application, and they should all be covered by the scope of the claims and the specification of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A discharge control method for a battery pack control system, characterized in that, The battery pack control system includes a main battery management unit and N slave battery management units, and is used to control N parallel-connected battery packs; wherein, the slave battery management unit is used to control the battery pack to access the working circuit or disconnect from the working circuit, the slave battery management unit is communicatively connected to the main battery management unit, and N is a positive integer greater than or equal to 2; The discharge control method is applied to the main battery management unit, and the discharge control method includes: At the first moment, obtain the first voltage values of the N parallel-connected battery packs, determine the first battery pack with the largest first voltage value, and send a control instruction to the slave battery management unit corresponding to the first battery pack to connect the first battery pack to the working circuit; At the i-th moment, obtain the i-th voltage values of the N - i + 1 battery packs not connected to the working circuit, and the i-th sampling voltage, where the i-th sampling voltage is the voltage of the i - 1 battery packs connected in parallel that have been connected to the working circuit; subtract each of the i-th voltage values from the i-th sampling voltage to obtain N - i + 1 differences; obtain Mi differences among the N - i + 1 differences that are less than the corresponding pressure difference threshold, determine the i-th battery pack with the largest voltage among the Mi battery packs corresponding to the Mi differences, and send a control instruction to the slave battery management unit corresponding to the i-th battery pack to connect the i-th battery pack to the working circuit; wherein, i is a positive integer greater than or equal to 2, and Mi is an integer greater than or equal to 0; Until Mi = 0, output an instruction to allow discharge; The step of obtaining Mi differences among the N - i + 1 differences that are less than the corresponding pressure difference threshold includes: According to the allowable discharge current of each of the N - i + 1 battery packs not connected to the working circuit and the internal resistance of the corresponding battery pack, obtain the pressure difference threshold through the following formula: ΔV=(Ri+Rj)×Ix,Ix=Min(y(x)map,F(x)map) Wherein, Ri represents the internal resistance of the battery pack connected to the working circuit, Rj represents the internal resistance of the battery pack not connected to the working circuit, Ix is the allowable discharge current of the battery pack, y(x)map is the allowable discharge current obtained from the discharge current of the slave battery management unit under the current temperature and the ratio of the available capacity to the actual capacity, and F(x)map is the maximum circulating current value that allows the relay to close without damaging the capacitive life of the relay.

2. The discharge control method according to claim 1, wherein It further includes: After receiving the instruction indicating that the (i - 1)-th battery pack is connected to the working circuit, determine it as the i-th moment; wherein, the instruction indicating that the (i - 1)-th battery pack is connected to the working circuit is sent by the slave battery management unit corresponding to the (i - 1)-th battery pack.

3. The discharge control method according to claim 1, wherein The discharge control method further includes: Obtain the sampled voltage, sampled current, and the voltage of the battery pack not connected to the working circuit, and send a control command to the slave battery management unit corresponding to the battery pack that meets the first condition to connect the battery pack to the working circuit; wherein, the first condition includes: taking the difference between the voltage of the battery pack not connected to the working circuit and the sampled voltage, when the difference is within the corresponding voltage difference range, determine that the sampled current is less than the set threshold and lasts for a preset time, and the sampled current is the current of the battery pack already connected to the working circuit; Among them, the voltage V of the battery pack not connected to the working circuit BatVolt and the voltage difference between the sampling voltage V LINK is within the range of ∆V min < (V BatVolt - V LINK ) < ∆V max ; ∆V min = ∆V – U0, ∆V max = ∆V + U0, ∆V is the product of the maximum circulating current value and the internal resistance, and U0 is the threshold tolerance of the set sampling error and overcurrent judgment standard.

4. The discharge control method according to claim 1, wherein The discharge control method further includes: Obtain the sampled voltage, sampled current, and the voltage of the battery pack not connected to the working circuit, and send a control command to the battery pack that meets the second condition to connect the battery pack to the working circuit; wherein, the second condition includes: taking the difference between the voltage of the battery pack not connected to the working circuit and the sampled voltage, when the difference is within the voltage difference range, reduce the sampled current by controlling the output power, determine that the sampled current is less than the set threshold and lasts for a preset time, and the sampled current is the current of the battery pack already connected to the working circuit.

5. The discharge control method according to claim 1, wherein, The discharge control method further includes: Perform dynamic adjustment of the allowed discharge power until the discharge current of the battery pack already connected to the working circuit drops to a level that does not damage the capacitive life of the relay, and then send a command to the slave battery management unit corresponding to the battery pack to disconnect the battery pack from the working circuit; After receiving the command indicating that the disconnection of the battery pack from the working circuit is completed, re-request the allowed discharge power according to all the battery packs already connected to the working circuit.

6. A charging control method for a battery pack control system, characterized in that, The charging control method is applied to the master battery management unit, and the charging control method includes: At the first moment, obtain the first voltage value of N parallel-connected battery packs, determine the first battery pack with the smallest first voltage value, and send a control command to the slave battery management unit corresponding to the first battery pack to connect the first battery pack to the working circuit; wherein, N is a positive integer greater than or equal to 2; At the j-th moment, obtain the j-th voltage value of N - j + 1 battery packs not connected to the working circuit, and the j-th sampled voltage, where the j-th sampled voltage is the voltage of j - 1 battery packs connected in parallel already connected to the working circuit; take the difference between each of the N - j + 1 j-th voltage values and the j-th sampled voltage to obtain N - j + 1 differences; obtain Pj differences among the N - j + 1 differences that are less than the corresponding voltage difference threshold, determine the j-th battery pack with the smallest voltage among the Pj battery packs corresponding to the Pj differences, and send a control command to the slave battery management unit corresponding to the j-th battery pack to connect the j-th battery pack to the working circuit; wherein, j is a positive integer greater than or equal to 2, and Pj is an integer greater than or equal to 0; Until Pj = 0, output an instruction to allow charging; The step of obtaining Pj differences among the N - j + 1 differences that are less than the corresponding voltage difference threshold includes: According to the allowed charging current of each of the N - j + 1 battery packs not connected to the working circuit and the internal resistance of the corresponding battery pack, obtain the voltage difference threshold: ΔV = (Ri + Rj) × Ix, Ix = Min(y(x)map,F(x)map) Wherein, Ri represents the internal resistance of the battery pack connected to the working circuit, Rj represents the internal resistance of the battery pack not connected to the working circuit, Ix is the allowable discharge current of the battery pack, y(x)map is the allowable discharge current at the current temperature and the ratio of the available capacity to the actual capacity obtained from the discharge current of the battery management unit, and F(x)map is the maximum circulating current value that allows the relay to close without damaging the capacitive life of the relay.

7. The charging control method according to claim 6, wherein It further includes: After receiving the instruction indicating that the connection of the (j - 1)th battery pack to the working circuit is completed, it is determined as the jth moment; wherein, the instruction for indicating the completion of the connection of the (j - 1)th battery pack to the working circuit is sent by the slave battery management unit corresponding to the (j - 1)th battery pack.

8. The charging control method according to claim 6, characterized in that, It further includes: Obtain the sampled voltage, sampled current, and the voltage of the battery pack not connected to the working circuit, and send a control instruction to the slave battery management unit corresponding to the battery pack that meets the third condition to connect the battery pack to the working circuit; wherein, the third condition includes: subtracting the voltage of the battery pack not connected to the working circuit from the sampled voltage, and when the difference is within the corresponding pressure difference range, perform a charge rate reduction control on all the battery packs already connected to the working circuit until the charge rate drops to the target value, and the sampled current is the current of the battery pack already connected to the working circuit.

9. The charging control method according to claim 8, wherein Performing the charge rate reduction control on all the battery packs already connected to the working circuit until the charge rate drops to the target value includes: The voltage V of the battery pack not connected to the working circuit BatVolt The difference from the sampled voltage V LINK is within the differential voltage range ∆V min <(V BatVolt -V LINK ) < ∆V max When this occurs, charge at the charging rate σi which is the current charging rate looked up in the table multiplied by the gradient coefficient φi until the sampled voltage is charged to V LINK = ∆V + V BatVolt and reaches the stable time τs, then switch to the next gradient coefficient; where ∆V min = ∆V – U0, ∆V max = ∆V + U0; ∆V is the product of the maximum circulating current value and the internal resistance, and U0 is the threshold tolerance for the set sampling error and overcurrent judgment standard; Repeat the above steps until σi = 0.1C, and charge the sampling voltage to V LINK = ∆V + V BatVolt Stable time τs.

10. The charging control method according to claim 6, characterized in that, The charge control method further includes: Dynamically adjust the allowable charging power until the charging current of the battery pack already connected to the working circuit drops to a value that does not damage the capacitive life of the relay, and then send an instruction to the slave battery management unit corresponding to the battery pack to disconnect the battery pack from the working circuit; After receiving the instruction indicating the completion of the disconnection of the battery pack from the working circuit, re-request the allowable charging power according to all the battery packs already connected to the working circuit.

Images