Control system and method for parallel operation charging of multiple battery boxes

Abstract

The invention relates to a control system and method for parallel charging of multiple battery boxes, belongs to the technical field of battery charging control, and solves the problems of poor stability and low efficiency during parallel charging of the multiple battery boxes in the prior art. The control system comprises a control box and a plurality of battery boxes; the control box comprises a first BMS, a charger and a charging relay; the first BMS is used for collecting the online state quantity of the charger in real time and controlling the switching value of the charging relay. Each battery box comprises a second BMS, a third BMS, a heating loop, a battery module and a charging and discharging loop; the third BMS is used for collecting the temperature of the battery module and the voltage of each battery string monomer in real time, and sending the collected information to the second BMS in real time; and the second BMS is used for sending the received information to the first BMS in real time, and is also used for controlling the on-off of the heating loop and the charging and discharging loop according to the control instruction. And the stability and the efficiency of parallel charging of a plurality of battery boxes are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery charging control, and in particular to a control system and method for charging multiple battery boxes in parallel. Background Art

[0002] In electric vehicles, the battery system is one of its core components, and the charging efficiency, stability and safety of the battery system are very high. The use of multiple battery boxes for parallel charging can effectively improve the charging speed and efficiency of the battery system and shorten the charging time on the basis of ensuring the capacity and energy density of the battery system. At the same time, it can also keep the voltage between each battery box roughly equal, ensuring the stability and life of the battery system. Therefore, the multi-battery box parallel charging technology of the battery system has broad application prospects and development space.

[0003] The prior art involves a multi-battery box parallel charging technical solution that uses an energy storage inverter to achieve charging and discharging control. Although this method preliminarily solves the problem of parallel connection of energy storage units, it does not explain the parallel charging and discharging strategy and how to deal with a failure in a certain energy storage unit, resulting in poor stability and low efficiency during parallel charging. At the same time, a special energy storage inverter needs to be added, which increases the difficulty of maintaining the battery system.

[0004] Therefore, there is an urgent need for a solution for controlling the parallel charging of multiple battery boxes. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a control system and method for charging multiple battery boxes in parallel, so as to solve the problems of poor stability and low efficiency when charging multiple battery boxes in parallel in the prior art.

[0006] On the one hand, an embodiment of the present invention provides a control system for charging multiple battery boxes in parallel, the control system comprising a control box and multiple battery boxes; the multiple battery boxes are connected in parallel to a bus bar;

[0007] The control box includes a first BMS, a charger and a charging relay; the first BMS is used to collect the online status of the charger in real time and to control the switching value of the charging relay;

[0008] Each battery box includes a second BMS, a third BMS, a heating circuit, a battery module and a charge-discharge circuit; the heating circuit and the charge-discharge circuit of each battery box are connected to the busbar, and the busbar is connected to the charger through a charging relay; the battery module is formed by a plurality of battery string monomers connected in series, and each battery string monomer is composed of a plurality of battery cells connected in parallel;

[0009] The third BMS is used to collect the temperature of the battery module and the voltage of each battery string monomer in real time, and send the collected information to the second BMS in real time; the second BMS is used to send the received information to the first BMS in real time, and the second BMS is also used to receive the control instructions sent by the first BMS in real time, and the second BMS controls the on and off of the heating circuit and the charging and discharging circuit according to the control instructions.

[0010] Based on the further improvement of the above control system, the control box also includes a charging fuse;

[0011] One end of the charging relay is connected to the busbar, the other end of the charging relay is connected to one end of the charging fuse, the other end of the charging fuse is connected to the output end of the charger, and the input end of the charger is connected to the mains.

[0012] Based on the further improvement of the above control system, the heating circuit includes a heating relay, a heating fuse and a heating film; the charging and discharging circuit includes a charging and discharging relay and a main circuit fuse;

[0013] One end of the heating fuse is connected to the busbar, the other end of the heating fuse is connected to one end of the heating relay, and the other end of the heating relay is connected to one end of the heating film; the heating film is arranged on the periphery of the battery module;

[0014] One end of the main circuit fuse is connected to the busbar, the other end of the main circuit fuse is connected to one end of the charge-discharge relay, and the other end of the charge-discharge relay is connected to the positive electrode of the battery module;

[0015] The second BMS is used to control the switching values ​​of the heating relay and the charging and discharging relay according to the control instruction received from the first BMS.

[0016] Based on the further improvement of the above control system, the charge and discharge circuit also includes a pre-charge relay and a pre-charge resistor;

[0017] One end of the pre-charge relay is connected to the positive electrode of the battery module, the other end of the pre-charge relay is connected to one end of the pre-charge resistor, and the other end of the pre-charge resistor is connected to the other end of the main circuit fuse;

[0018] The second BMS is further used to control the switching value of the pre-charging relay according to the control instruction received from the first BMS.

[0019] Based on the further improvement of the above control system, the control system further includes a temperature sensor and a plurality of voltage sensors, and the third BMS is connected to the temperature sensor and the plurality of voltage sensors respectively;

[0020] The temperature sensor is arranged around the battery module to collect the temperature of the battery module in real time; each voltage sensor is arranged at both ends of each battery string monomer to collect the voltage of the battery string monomer in real time.

[0021] On the other hand, an embodiment of the present invention provides a control method for parallel charging of multiple battery boxes, the control method comprising:

[0022] The first BMS determines whether there is an abnormality in the control system based on the received switching values ​​of each relay and the information of the battery module. If there is an abnormality, the first BMS performs fault inspection and repair until the control system is fault-free.

[0023] The first BMS determines whether the temperatures of all battery boxes have reached the charging temperature threshold according to the temperatures of the battery boxes. If there is a battery box whose temperature has not reached the charging temperature threshold, the battery box is heated until its temperature reaches the charging temperature threshold.

[0024] The first BMS determines the number of rechargeable battery boxes according to the highest voltage of the battery string monomers of each battery box; if the number of rechargeable battery boxes does not reach the first number threshold, the parallel charging is stopped and the status of the charger is set to offline; otherwise, it is determined whether the voltage of each rechargeable battery box is within the first bus voltage difference range; if the voltage of each battery box is not within the first bus voltage difference range, the voltage of each battery box is adjusted so that the voltage of each rechargeable battery box is within the first bus voltage difference range;

[0025] The first BMS controls the switch of the charging relay and sets the status of the charger to online, and sends a control instruction to the second BMS of the rechargeable battery box. The second BMS controls the switch of the charging and discharging relay to close according to the control instruction; the first BMS sends normal charging parameters to the charger, and the charger starts to charge the rechargeable battery box normally and enters the normal charging process.

[0026] Based on the further improvement of the above control method, if there is a battery box whose temperature does not reach the charging temperature threshold, heating the battery box includes:

[0027] The first BMS controls the switch of the charging relay to close and sets the status of the charger to be online, and sends a heating instruction to the second BMS of the battery box that has not reached the charging temperature threshold, and the second BMS controls the switch of the heating relay to close according to the heating instruction;

[0028] The first BMS sends a heating parameter to the charger, and the charger starts heating the battery box that has not reached the charging temperature threshold;

[0029] The first BMS continuously determines whether the temperatures of all battery boxes have reached the charging temperature threshold; when all have reached it, the switches of the charging relay and the heating relay are controlled to be disconnected.

[0030] Based on the further improvement of the above control method, the control method further includes:

[0031] During normal charging, the first BMS determines whether there is a battery box that reaches the first voltage parameter threshold according to the highest voltage of the battery string monomers of each rechargeable battery box; if not, normal charging continues; otherwise, the overcharge protection process is entered;

[0032] During the overcharge protection process, the first BMS continuously determines whether each rechargeable battery box meets the reduced current charging conditions; if not, normal charging continues until all rechargeable battery boxes are charged and disconnected, and parallel charging is stopped; otherwise, the reduced current charging process is entered;

[0033] During the reduced current charging process, the first BMS continuously determines whether each rechargeable battery box meets the end charging condition; if not, the reduced current charging continues; otherwise, the parallel charging is stopped.

[0034] Based on the further improvement of the above control method, the first BMS continuously determines whether each rechargeable battery box meets the current reduction charging condition, including:

[0035] Determine whether there is a battery box that is disconnected from charging among the rechargeable battery boxes; if so, control the switch of the charging and discharging relay of the battery box to be disconnected, and update the state of the battery box to non-rechargeable;

[0036] Determining whether the number of each rechargeable battery box reaches a second number threshold;

[0037] Determine whether there is a battery box in which the voltage difference between any two battery string monomers reaches a voltage difference threshold in the rechargeable battery box;

[0038] When any one of the rechargeable battery boxes is disconnected from charging, and the number of rechargeable battery boxes reaches a second number threshold, and at the same time the voltage difference between any two battery string cells in the rechargeable battery box reaches a voltage difference threshold, the reduced current charging condition is met.

[0039] Based on the further improvement of the above control method, the first BMS continuously determines whether each rechargeable battery box meets the charging termination condition, including:

[0040] Determining whether the highest voltage of the battery string monomers of each rechargeable battery box reaches a second voltage parameter threshold;

[0041] Determine whether the voltage difference between each rechargeable battery box reaches the second bus voltage difference;

[0042] When the highest voltage of the battery string monomers of each rechargeable battery box reaches the second voltage parameter threshold, and the voltage difference between each rechargeable battery box reaches the second bus voltage difference, the charging termination condition is met.

[0043] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0044] 1. The control system of the present invention includes a control box and multiple battery boxes. The control box includes a first BMS, a charger and a charging relay. Each battery box includes a second BMS, a third BMS, a heating circuit, a battery module and a charging and discharging circuit. The temperature information and voltage information of the battery box are obtained by real-time monitoring through the third BMS, and the information obtained by the third BMS is sent to the first BMS in real time through the second BMS. The charging parameters of the battery box are controlled by the first BMS, so that the stability is good during parallel charging.

[0045] 2. Through the first BMS, charger and charging relay included in the control box, and the second BMS, third BMS, heating circuit, battery module and charging and discharging circuit included in each battery box, the first BMS can monitor the status of the relays and chargers in the entire control system, making the entire control system more convenient to maintain.

[0046] 3. During the parallel charging process, the temperature judgment of each battery box, the maximum voltage judgment of the battery string monomer, the judgment of whether the voltage is within the first bus voltage difference range, and the reasonable setting of the current reduction charging conditions and the charging end conditions are set, so that the efficiency is significantly improved when multiple battery boxes are charged in parallel.

[0047] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0049] Figure 1 A schematic diagram of the structure of a control system for parallel charging of multiple battery boxes provided in an embodiment of the present invention;

[0050] Figure 2 One of the flow charts of the control method for parallel charging of multiple battery boxes provided in an embodiment of the present invention;

[0051] Figure 3 The second flowchart of the control method for parallel charging of multiple battery boxes provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0053] BMS (Battery Management System) is a control system that protects the safety of power batteries. In a narrow sense, BMS includes battery management unit (BMU), cell management unit (CMU), sensors, wiring harnesses, etc.; in a broad sense, BMS also includes high-voltage safety management system, high-voltage power distribution system, thermal management system, etc.

[0054] In order to increase the system capacity and charge and discharge rate in the battery system, multiple battery boxes are connected in parallel based on the series-parallel cells inside a single battery box. The process of charging the entire machine after the battery boxes are connected in parallel is called parallel charging.

[0055] A specific embodiment of the present invention discloses a control system for charging multiple battery boxes in parallel, such as Figure 1 shown.

[0056] The control system comprises a control box and a plurality of battery boxes; the plurality of battery boxes are connected in parallel to the busbar;

[0057] The control box includes a first BMS, a charger and a charging relay; the first BMS is used to collect the online status of the charger in real time and to control the switching value of the charging relay;

[0058] Each battery box includes a second BMS, a third BMS, a heating circuit, a battery module and a charge-discharge circuit; the heating circuit and the charge-discharge circuit of each battery box are connected to the busbar, and the busbar is connected to the charger through a charging relay; the battery module is formed by a plurality of battery string monomers connected in series, and each battery string monomer is composed of a plurality of battery cells connected in parallel;

[0059] The third BMS is used to collect the temperature of the battery module and the voltage of each battery string monomer in real time, and send the collected information to the second BMS in real time; the second BMS is used to send the received information to the first BMS in real time, and the second BMS is also used to receive the control instructions sent by the first BMS in real time, and the second BMS controls the on and off of the heating circuit and the charging and discharging circuit according to the control instructions.

[0060] Specifically, Figure 1 As shown, the control system includes N battery boxes and a control box, and the N battery boxes include battery box No. 1, battery box No. 2, and battery box No. N. The N battery boxes are connected to the control box in parallel through busbars to form a control system for parallel charging of multiple battery boxes.

[0061] Specifically, the charger includes two states, one is an online state, whose online state quantity is 1, and the other is an offline state, whose online state quantity is 0. The first BMS is used to collect the online state quantity of the charger in real time, so that the first BMS can know the status of the charger in real time. The charging relay includes two states: open and closed. When the charging relay is open, its switch quantity is 0; when the charging relay is closed, its switch quantity is 1; the first BMS is also used to control the switch quantity of the charging relay so that the charging relay is open or closed.

[0062] When the online state of the charger is 1 and the switch value of the charger is 1, the first BMS sends a charging parameter or a heating parameter to the charger. The charging parameter or the heating parameter can be current, voltage or power. After receiving the parameter, the charger will output the current, voltage or power to the bus according to the current, voltage or power specified by the parameter. It can be understood that the mains power is only used as an example to provide the original energy for the charger.

[0063] Specifically, the battery module is formed by connecting multiple battery string monomers in series, and each battery string monomer can be composed of multiple battery cells connected in parallel. It is worth noting that the battery cell described in the embodiment of the present invention can be a battery cell of a lithium iron phosphate battery, or a battery cell of a ternary lithium battery, etc.

[0064] Preferably, the control box further comprises a charging fuse;

[0065] One end of the charging relay is connected to the busbar, the other end of the charging relay is connected to one end of the charging fuse, the other end of the charging fuse is connected to the output end of the charger, and the input end of the charger is connected to the mains.

[0066] Specifically, Figure 1 As shown, the control box also includes a charging fuse, which is located between the charging relay and the charger. When the BMS system is powered on abnormally or the current in the circuit is abnormal, the charging fuse protects the charger by fusing.

[0067] Specifically, Figure 1 As shown, each battery box includes a second BMS, a third BMS, a heating circuit, a battery module and a charge and discharge circuit. The heating circuit and the charge and discharge circuit of each battery box are connected to the bus, and the bus is connected to the charger through a charging relay.

[0068] The third BMS is used to collect the temperature of the battery module and the voltage of each battery string monomer in real time. It is worth noting that the sum of the voltages of all battery string monomers in each battery box is the voltage of each battery box. The second BMS is used to send the received information to the first BMS in real time, and the second BMS is also used to receive the control instructions sent by the first BMS in real time. The second BMS controls the on and off of the heating circuit and the charging and discharging circuit according to the control instructions. It is worth noting that the control instructions sent by the first BMS to the second BMS can be used to control the on and off and closing of the heating circuit or the charging and discharging circuit in the battery box.

[0069] Preferably, the heating circuit includes a heating relay, a heating fuse and a heating film; the charging and discharging circuit includes a charging and discharging relay and a main circuit fuse;

[0070] One end of the heating fuse is connected to the busbar, the other end of the heating fuse is connected to one end of the heating relay, and the other end of the heating relay is connected to one end of the heating film; the heating film is arranged on the periphery of the battery module;

[0071] One end of the main circuit fuse is connected to the busbar, the other end of the main circuit fuse is connected to one end of the charge-discharge relay, and the other end of the charge-discharge relay is connected to the positive electrode of the battery module;

[0072] The second BMS is used to control the switching values ​​of the heating relay and the charging and discharging relay according to the control instruction received from the first BMS.

[0073] Specifically, Figure 1 As shown, the heating circuit includes a heating relay, a heating fuse and a heating film; one end of the heating circuit is connected to the busbar for receiving current, voltage, etc. sent by the charger. It is understandable that the other end of the heating circuit is grounded. The heating film surrounds the battery module and is used to heat the battery module.

[0074] Specifically, Figure 1 As shown, the charge and discharge circuit includes a charge and discharge relay and a main circuit fuse. One end of the charge and discharge circuit is connected to the busbar, and the other end is connected to the positive electrode of the battery module. When the battery module is short of power and needs to be charged, the charge and discharge circuit is used to charge the battery module. When the battery module needs to supply power to the load, it can output to the load through the charge and discharge circuit.

[0075] Preferably, if Figure 1 As shown, the charge and discharge circuit also includes a pre-charge relay and a pre-charge resistor;

[0076] One end of the pre-charge relay is connected to the positive electrode of the battery module, the other end of the pre-charge relay is connected to one end of the pre-charge resistor, and the other end of the pre-charge resistor is connected to the other end of the main circuit fuse;

[0077] The second BMS is further used to control the switching value of the pre-charging relay according to the control instruction received from the first BMS.

[0078] It is worth noting that the main circuit fuse included in the charge and discharge circuit is used to protect the charge and discharge circuit to prevent abnormal current from causing damage to the charge and discharge circuit. The heating fuse included in the heating circuit is used to protect the heating circuit to prevent abnormal current from causing damage to the heating circuit.

[0079] Preferably, if Figure 1 As shown, the control system further includes a temperature sensor and a plurality of voltage sensors, and the third BMS is connected to the temperature sensor and the plurality of voltage sensors respectively;

[0080] The temperature sensor is arranged around the battery module to collect the temperature of the battery module in real time; each voltage sensor is arranged at both ends of each battery string monomer to collect the voltage of the battery string monomer in real time.

[0081] It can be understood that the temperature sensor is arranged around the battery module, and the collected temperature information is used to characterize the real-time temperature of the battery module; the voltage sensor is used to collect the voltage at both ends of the corresponding battery string monomer, and the sum of all voltage sensors in the battery box is used to characterize the voltage of the battery box.

[0082] It is worth noting that the voltage of the battery string monomer in each battery box is relatively small, and a precision voltage sensor can be used to collect the voltage of the battery string monomer.

[0083] A specific embodiment of the present invention discloses a control method for charging multiple battery boxes in parallel. Figure 2 As shown, the control method includes:

[0084] Step S1: The first BMS determines whether there is an abnormality in the control system based on the received switching values ​​of each relay and the information of the battery module. If there is an abnormality, the first BMS performs fault inspection and repair until the control system is fault-free.

[0085] Step S2: the first BMS determines whether the temperatures of all battery boxes have reached the charging temperature threshold according to the temperatures of the battery boxes. If there is a battery box whose temperature has not reached the charging temperature threshold, the battery box is heated until its temperature reaches the charging temperature threshold.

[0086] Step S3: The first BMS determines the number of rechargeable battery boxes according to the highest voltage of the battery string monomers of each battery box; if the number of rechargeable battery boxes does not reach the first number threshold, the parallel charging is stopped and the status of the charger is set to offline; otherwise, it is determined whether the voltage of each rechargeable battery box is within the first bus voltage difference range; if the voltage of each battery box is not within the first bus voltage difference range, the voltage of each battery box is adjusted so that the voltage of each rechargeable battery box is within the first bus voltage difference range;

[0087] Step S4: the first BMS controls the switch of the charging relay and sets the status of the charger to online, and sends a control instruction to the second BMS of the rechargeable battery box. The second BMS controls the switch of the charging and discharging relay to close according to the control instruction; the first BMS sends normal charging parameters to the charger, and the charger starts to charge the rechargeable battery box normally and enters the normal charging process.

[0088] Specifically, Figure 2 As shown, in step S1, when multiple battery boxes need to be charged in parallel, the BMS system is powered on, and the BMS system includes a first BMS, a second BMS, and a third BMS. After the BMS system is powered on, the first BMS can receive the online status of the charger in the battery box and the switching value of the charging relay; at the same time, the first BMS can receive the switching value of the charging and discharging relays and heating relays inside each battery box, the temperature information of the battery module, and the voltage information of the battery string monomer collected by the third BMS through the second BMS. The first BMS compares the above received and collected information with the corresponding standard value to determine whether there is an abnormality in the control system. If there is an abnormality, fault inspection and repair are performed until the control system is fault-free.

[0089] Specifically, Figure 2 As shown, in step S2, when the control system is fault-free, the first BMS determines whether the temperature of all battery boxes has reached the charging temperature threshold based on the temperature of each battery box. It is worth noting that the battery modules composed of different cells have different charging temperature thresholds for the battery boxes. For example, when the battery cell is a lithium iron phosphate battery, the charging temperature threshold set here is 5°C. If the temperature of the battery box is less than 5°C, the charging efficiency of the battery module composed of lithium iron phosphate batteries is very low, and it will cause irreversible damage to the life of the lithium iron phosphate battery.

[0090] Specifically, Figure 1 As shown, among the N battery boxes, if there is a battery box whose temperature is lower than the charging temperature threshold, the battery box needs to be heated until its temperature reaches the charging temperature threshold.

[0091] Preferably, if there is a battery box whose temperature does not reach the charging temperature threshold, heating the battery box comprises:

[0092] The first BMS controls the switch of the charging relay to close and sets the status of the charger to be online, and sends a heating instruction to the second BMS of the battery box that has not reached the charging temperature threshold, and the second BMS controls the switch of the heating relay to close according to the heating instruction;

[0093] The first BMS sends a heating parameter to the charger, and the charger starts heating the battery box that has not reached the charging temperature threshold;

[0094] The first BMS continuously determines whether the temperatures of all battery boxes have reached the charging temperature threshold; when all have reached it, the switches of the charging relay and the heating relay are controlled to be disconnected.

[0095] Exemplarily, the heating parameters include current and voltage, the current is 5A, and the voltage is 250V.

[0096] Specifically, if the temperature of battery box No. 1 is lower than the set charging temperature threshold, the first BMS needs to control the switch of the charging relay to close, set the status of the charger to online, and send a heating instruction to the second BMS of battery box No. 1. The second BMS of battery box No. 1 controls the switch of the heating relay of battery box No. 1 to close according to the heating instruction.

[0097] Specifically, after the second BMS of the No. 1 battery box executes the above control instruction, the first BMS starts to send heating parameters to the charger according to the switch state of the heating relay of the No. 1 battery box sent by the No. 1 battery box, and the charger starts to heat the No. 1 battery box; during the heating process of the No. 1 battery box, the first BMS continues to receive the temperature information of the No. 1 battery box, and can determine whether the temperature of the No. 1 battery box reaches the set charging temperature threshold. When the temperature of the No. 1 battery box reaches the charging temperature threshold, the first BMS controls the charging relay and the switch of the heating relay of the No. 1 battery box to be disconnected, and the heating process of the No. 1 battery box is stopped.

[0098] When the temperatures of the N battery boxes included in the control system all reach the charging temperature threshold, the heating process ends.

[0099] Specifically, Figure 2As shown, in step S3, after the temperatures of the N battery boxes included in the control system reach the charging temperature threshold, the first BMS first determines the number of rechargeable battery boxes according to the highest voltage of the battery string monomers of each battery box. It can be understood that if the highest voltage of the battery string monomer of each battery box exceeds the set highest voltage parameter, the battery string monomer cannot be charged, that is, the battery box cannot be charged, and the battery box is a non-rechargeable battery box.

[0100] It is worth noting that the maximum voltage parameter settings of the battery string monomers formed by battery modules composed of different cells are different. For example, when the battery cell is a lithium iron phosphate battery, the maximum voltage parameter is set to 3.63V. When the maximum voltage of the battery string monomers in the battery box exceeds the maximum voltage parameter, it means that the battery box has sufficient power and does not need to be charged.

[0101] The number of rechargeable battery boxes is determined by the highest voltage of the battery string monomers of each battery box. If the number of rechargeable battery boxes does not reach the first number threshold, parallel charging is stopped and the status of the charger is set to offline. It is worth noting that for parallel charging of multiple battery boxes, if the number of rechargeable battery boxes is small, the parallel charging efficiency is low, and the parallel charging method is not suitable.

[0102] Specifically, Figure 2 As shown, in step S3, when the number of rechargeable battery boxes reaches the set first quantity threshold, the first BMS receives the voltage of each battery string monomer of each rechargeable battery box, takes the sum of the voltages of all battery string monomers inside the battery box as the voltage of the battery box, takes the average value of the voltage of each battery box as the standard value, and obtains the first bus voltage difference range according to the standard value; determines whether the voltage of each battery box is within the first bus voltage difference range; if the voltage of each battery box is not within the first bus voltage difference range, adjusts the voltage of each battery box so that the voltage of each battery box is within the first bus voltage difference range. Exemplarily, the first bus voltage difference range is (standard value-floating amount, standard value+floating amount), and when the battery cell is lithium iron phosphate, the floating amount is 1V.

[0103] It is worth noting that when the voltage of each battery needs to be adjusted, the first BMS controls the switch of the charging relay to be disconnected, and at the same time, the second BMS of each rechargeable battery box closes the switch of the charging and discharging relay of each battery box, so that each rechargeable battery box can achieve voltage balance, and finally the voltage of all rechargeable battery boxes is within the first bus voltage difference range.

[0104] Specifically, Figure 2As shown, in step S4, after entering the normal charging process, the first BMS needs to control the switch of the charging relay and set the status of the charger to online, and send a control instruction to the second BMS of the rechargeable battery box. The second BMS of the rechargeable battery box controls the switch of the charging and discharging relay to close according to the control instruction; the first BMS sends normal charging parameters to the charger, and the charger starts to charge the rechargeable battery box normally.

[0105] Preferably, the control method further includes:

[0106] During normal charging, the first BMS determines whether there is a battery box that reaches the first voltage parameter threshold according to the highest voltage of the battery string monomers of each rechargeable battery box; if not, normal charging continues; otherwise, the overcharge protection process is entered;

[0107] During the overcharge protection process, the first BMS continuously determines whether each rechargeable battery box meets the reduced current charging conditions; if not, normal charging continues until all rechargeable battery boxes are charged and disconnected, and parallel charging is stopped; otherwise, the reduced current charging process is entered;

[0108] During the reduced current charging process, the first BMS continuously determines whether each rechargeable battery box meets the end charging condition; if not, the reduced current charging continues; otherwise, the parallel charging is stopped.

[0109] Preferably, the first BMS continuously determines whether each rechargeable battery box meets the current reduction charging condition, including:

[0110] Determine whether there is a battery box that is disconnected from charging among the rechargeable battery boxes; if so, control the switch of the charging and discharging relay of the battery box to be disconnected, and update the state of the battery box to non-rechargeable;

[0111] Determining whether the number of each rechargeable battery box reaches a second number threshold;

[0112] Determine whether there is a battery box in which the voltage difference between any two battery string monomers reaches a voltage difference threshold in the rechargeable battery box;

[0113] When any one of the rechargeable battery boxes is disconnected from charging, and the number of rechargeable battery boxes reaches a second number threshold, and at the same time the voltage difference between any two battery string cells in the rechargeable battery box reaches a voltage difference threshold, the reduced current charging condition is met.

[0114] Preferably, the first BMS continuously determines whether each rechargeable battery box meets the charging termination condition, including:

[0115] Determining whether the highest voltage of the battery string monomers of each rechargeable battery box reaches a second voltage parameter threshold;

[0116] Determine whether the voltage difference between each rechargeable battery box reaches the second bus voltage difference;

[0117] When the highest voltage of the battery string monomers of each rechargeable battery box reaches the second voltage parameter threshold, and the voltage difference between each rechargeable battery box reaches the second bus voltage difference, the charging termination condition is met.

[0118] Specifically, Figure 3 As shown, after the control system enters the normal charging process, the charger continues to output according to the instructions of the first BMS to charge the rechargeable battery box. As the normal charging time becomes longer and longer, the maximum voltage of the battery string monomers of each rechargeable battery box continues to rise. When the maximum voltage of the battery string monomers of any battery box in the rechargeable battery box is greater than the set first voltage parameter threshold, the overcharge protection process is entered. It is worth noting that the first voltage parameter threshold sets different parameters according to different battery cells. For example, when the battery cell is lithium iron phosphate, the first voltage parameter threshold is 3.55V.

[0119] Specifically, Figure 3 As shown, during the overcharge protection process, the first BMS continuously determines whether each rechargeable battery box meets the reduced current charging conditions; if not, normal charging continues until all rechargeable battery boxes are charged and disconnected, and parallel charging is stopped; otherwise, the reduced current charging process is entered.

[0120] It is worth noting that when any one of the rechargeable battery boxes is disconnected from charging, and the number of rechargeable battery boxes reaches the second number threshold, and the voltage difference between any two battery string monomers in the rechargeable battery box reaches the voltage difference threshold, the reduced current charging condition is met. When the reduced current charging condition is met, it means that the voltage difference between the battery string monomers in the rechargeable battery box is large. At this time, by reducing the current charging, such as charging with a current of 0.6A, the influence of the voltage difference between the battery string monomers can be reduced, the consistency of each battery box can be increased, and the power storage performance of the battery system can be improved.

[0121] It can be understood that when the voltage difference between any two battery string monomers in the battery box reaches the voltage difference threshold, it means that the difference between the highest voltage and the lowest voltage of the battery string monomers in the battery box reaches the voltage difference threshold.

[0122] Specifically, the voltage difference threshold is set with different parameters according to different battery cells. For example, when the battery cell is lithium iron phosphate, the voltage difference threshold is 250mv.

[0123] It can be understood that the first quantity threshold and the second quantity threshold are comprehensively determined based on the actual number of battery boxes connected in parallel. For example, the N battery boxes in the embodiment of the present invention are 5 battery boxes, and the combined parallel output of at least 3 battery boxes is required to meet the power consumption requirement of the load, then the first quantity threshold and the second quantity threshold can both be set to 3.

[0124] Specifically, Figure 3 As shown, during the reduced current charging process, the first BMS continuously determines whether each rechargeable battery box meets the charging termination condition; if not, the reduced current charging continues; otherwise, the parallel charging is stopped.

[0125] It is worth noting that when the highest voltage of the battery string monomers of each rechargeable battery box reaches the second voltage parameter threshold, and the voltage difference between each rechargeable battery box reaches the second bus voltage difference, it means that the battery string monomers have been charged and the charging end conditions are met.

[0126] Specifically, the second voltage parameter threshold is set with different parameters according to different battery cells. For example, when the battery cell is lithium iron phosphate, the second voltage parameter threshold is 3.6V.

[0127] Specifically, different parameters of the second bus voltage difference are set according to different battery cells. For example, when the battery cell is lithium iron phosphate, the second bus voltage difference is 0.1V.

[0128] Compared with the prior art, the control system and method for parallel charging of multiple battery boxes provided in this embodiment include a control box and multiple battery boxes, the control box includes a first BMS, a charger and a charging relay, and each battery box includes a second BMS, a third BMS, a heating circuit, a battery module and a charging and discharging circuit; the temperature information and voltage information of the battery box are obtained by real-time monitoring through the third BMS, and the information obtained by the third BMS is sent to the first BMS in real time through the second BMS, and the charging parameters of the battery box are controlled by the first BMS, so that the stability during parallel charging is good; at the same time, through the first BMS, the charger and the charging relay included in the control box, and the second BMS, the third BMS, the heating circuit, the battery module and the charging and discharging circuit included in each battery box, the first BMS can monitor the status of the relay and the charger in the entire control system, so that the entire control system is more convenient to maintain; in addition, during the parallel charging process, by setting the temperature judgment of each battery box, the maximum voltage judgment of the battery string monomer, the judgment of whether the voltage is within the first bus voltage difference range, and reasonably setting the current reduction charging condition and the charging end condition, the efficiency is significantly improved when multiple battery boxes are charged in parallel.

[0129] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0130] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A control system for charging multiple battery boxes in parallel, characterized in that: The control system includes a control box and a plurality of battery boxes; the plurality of battery boxes are connected in parallel to the busbar; The control box includes a first BMS, a charger, and a charging relay; the first BMS is used to collect the online status of the charger in real time and to control the switching value of the charging relay; Each battery box includes a second BMS, a third BMS, a heating circuit, a battery module, and a charge-discharge circuit. The heating circuit and the charge-discharge circuit of each battery box are connected to the busbar, which is connected to the charger through a charging relay. The battery module is formed by multiple battery string monomers connected in series, and each battery string monomer is composed of multiple battery cells connected in parallel; The third BMS is used to collect the temperature of the battery module and the voltage of each battery string cell in real time, and send the collected information to the second BMS in real time; The second BMS is used to send the received information to the first BMS in real time, and the second BMS is also used to receive the control instructions sent by the first BMS in real time. The second BMS controls the on and off of the heating circuit and the charging and discharging circuit according to the control instructions.

2. The control system according to claim 1, characterized in that: The control box also includes charging fuses; One end of the charging relay is connected to the busbar, the other end of the charging relay is connected to one end of the charging fuse, the other end of the charging fuse is connected to the output end of the charger, and the input end of the charger is connected to the mains.

3. The control system according to claim 2, characterized in that: The heating circuit includes a heating relay, a heating fuse and a heating film; the charging and discharging circuit includes a charging and discharging relay and a main circuit fuse; One end of the heating fuse is connected to the busbar, the other end of the heating fuse is connected to one end of the heating relay, and the other end of the heating relay is connected to one end of the heating film; the heating film is arranged on the periphery of the battery module; One end of the main circuit fuse is connected to the busbar, the other end of the main circuit fuse is connected to one end of the charge and discharge relay, and the other end of the charge and discharge relay is connected to the positive electrode of the battery module; The second BMS is used to control the switching values ​​of the heating relay and the charging and discharging relay according to the control instruction received from the first BMS.

4. The control system according to claim 3, characterized in that: The charge and discharge circuit also includes a pre-charge relay and a pre-charge resistor; One end of the pre-charge relay is connected to the positive terminal of the battery module, the other end of the pre-charge relay is connected to one end of the pre-charge resistor, and the other end of the pre-charge resistor is connected to the other end of the main circuit fuse; The second BMS is further configured to control the switching value of the pre-charging relay according to the control instruction received from the first BMS.

5. The control system according to claim 1, characterized in that: The control system further includes a temperature sensor and a plurality of voltage sensors, and the third BMS is connected to the temperature sensor and the plurality of voltage sensors respectively; The temperature sensor is arranged around the battery module to collect the temperature of the battery module in real time; each voltage sensor is arranged at both ends of each battery string monomer to collect the voltage of the battery string monomer in real time.

6. A control method for parallel charging of multiple battery boxes based on the control system according to any one of claims 1 to 5, characterized in that: The control method includes: The first BMS determines whether there is any abnormality in the control system based on the received switching values ​​of each relay and the information of the battery module. If there is any abnormality, the first BMS performs fault inspection and repair until the control system is fault-free. The first BMS determines whether the temperatures of all battery boxes have reached the charging temperature threshold based on the temperatures of the battery boxes. If there is a battery box whose temperature has not reached the charging temperature threshold, the battery box is heated until its temperature reaches the charging temperature threshold. The first BMS determines the number of rechargeable battery boxes based on the highest voltage of the battery string monomers of each battery box; if the number of rechargeable battery boxes does not reach a first quantity threshold, parallel charging is stopped and the charger status is set to offline; otherwise, it is determined whether the voltage of each rechargeable battery box is within a first busbar voltage differential range; if the voltage of each battery box is not within the first busbar voltage differential range, the voltage of each battery box is adjusted so that the voltage of each rechargeable battery box is within the first busbar voltage differential range; The first BMS controls the switch of the charging relay and sets the status of the charger to online, and sends a control instruction to the second BMS of the rechargeable battery box. The second BMS controls the switch of the charging and discharging relay according to the control instruction; the first BMS sends normal charging parameters to the charger, and the charger starts to charge the rechargeable battery box normally, entering the normal charging process.

7. The control method according to claim 6, characterized in that: If there is a battery box whose temperature does not reach the charging temperature threshold, heating the battery box includes: The first BMS controls the switch of the charging relay to close and sets the status of the charger to online, and sends a heating instruction to the second BMS of the battery box that has not reached the charging temperature threshold. The second BMS controls the switch of the heating relay to close according to the heating instruction; The first BMS sends heating parameters to the charger, and the charger starts heating the battery packs that have not reached the charging temperature threshold; The first BMS continuously determines whether the temperatures of all battery boxes have reached the charging temperature threshold; when all have reached it, it controls the switches of the charging relay and the heating relay to be disconnected.

8. The control method according to claim 6, characterized in that: The control method further includes: During normal charging, the first BMS determines whether there is a battery box that reaches the first voltage parameter threshold based on the highest voltage of the battery string monomers of each rechargeable battery box; if not, normal charging continues; otherwise, the overcharge protection process is entered; During the overcharge protection process, the first BMS continuously determines whether each rechargeable battery box meets the reduced current charging conditions; if not, normal charging continues until all rechargeable battery boxes are charged and disconnected, and parallel charging is stopped; otherwise, the reduced current charging process is entered; During the reduced current charging process, the first BMS continuously determines whether each rechargeable battery box meets the end charging condition; if not, the reduced current charging continues; otherwise, the parallel charging is stopped.

9. The control method according to claim 8, characterized in that: The first BMS continuously determines whether each rechargeable battery box meets the reduced current charging conditions, including: Determine whether there is a battery box with charging disconnected among the rechargeable battery boxes; if so, control the switch of the charge and discharge relay of the battery box to be disconnected, and update the status of the battery box to non-rechargeable; Determining whether the number of each rechargeable battery box reaches a second number threshold; Determine whether there is a battery box in which the voltage difference between any two battery string cells reaches a voltage difference threshold in the rechargeable battery box; When any one of the rechargeable battery boxes is disconnected from charging, and the number of rechargeable battery boxes reaches the second number threshold, and the voltage difference between any two battery string cells in the rechargeable battery box reaches the voltage difference threshold, the reduced current charging condition is met.

10. The control method according to claim 9, characterized in that: The first BMS continuously determines whether each rechargeable battery box meets the charging termination condition, including: Determining whether the highest voltage of the battery string monomers of each rechargeable battery box reaches a second voltage parameter threshold; Determining whether the voltage difference between each rechargeable battery box reaches the second bus voltage difference; When the highest voltage of the battery string monomers of each rechargeable battery box reaches the second voltage parameter threshold, and the voltage difference between each rechargeable battery box reaches the second bus voltage difference, the charging end condition is met.

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