A parallel structure of lithium battery packs with the same voltage specification but different capacities and its working method

Abstract

A parallel structure of lithium battery packs with the same voltage specification but different capacities includes at least two battery packs, a charging module and a control circuit module: the positive ends of each battery pack are connected to each other to form a DC bus positive end, and the negative end of each battery pack is connected to a current control circuit; the current control circuit includes a first control MOS tube, a second control MOS tube and a current sampling resistor, the source of the first control MOS tube is connected to the source of the second control MOS tube, and the gate of the first control MOS tube and the gate of the second control MOS tube are connected to the control port of the control circuit module. The purpose of automatically completing the charging and discharging of multiple lithium battery packs with the same voltage specification but different capacities is achieved, avoiding the trouble of manually charging the battery packs one by one in the past.

Description

Technical Field

[0001] The present invention relates to the field of electronic circuits, and in particular to a parallel structure of lithium battery packs with the same voltage specification but different capacities and a working method thereof. Background Art

[0002] At present, the main types of lithium battery cells and lead-acid battery packs that are connected in parallel on the market are those with the same voltage and capacity. For lithium battery packs with the same voltage but different capacities, the parallel connection is limited to two battery packs. For multiple lithium battery packs with the same voltage but different capacities, the main method is to connect them in series.

[0003] The technology of connecting only two battery packs in parallel limits the number of lithium battery packs, and the total output power of the battery pack is very limited. For general users, they usually have multiple lithium battery packs with the same voltage specifications but different capacities. This method can only be combined in pairs, and the total output power can be doubled at most. In some special loads, such as inductive and nonlinear loads, it does not play a big role and is very inconvenient.

[0004] There are two main drawbacks to the series connection of lithium battery packs: 1. If any one of the lithium battery packs in the series circuit is damaged or open, the battery pack cannot output; 2. The discharge capacity of the lithium battery pack depends on the weakest one, which greatly reduces the discharge capacity of the battery pack. In addition, the series connection method will cause the voltage to increase exponentially, and the equipment originally suitable for a single battery pack can no longer be used and needs to be replaced with equipment with a higher voltage level. Summary of the invention

[0005] The present invention aims to solve the following problems in view of the deficiencies in the prior art:

[0006] 1. The number of lithium battery packs: Theoretically, this method is not limited by the number of battery packs, but in view of the convenience of user use and the actual system cost, volume, weight, etc., it can generally meet the parallel connection of 3 to 5 battery packs with the same voltage specification.

[0007] 2. During use, each battery pack can be replaced or increased or decreased at any time, which will not affect the operation of the battery parallel system, but will only affect the total output power;

[0008] 3. Open circuit or short circuit of any battery pack will not affect the operation of the battery parallel system.

[0009] 4. Multiple small-capacity lithium battery packs can be connected in parallel to form a large-capacity lithium battery, and the user does not need to replace the load equipment to meet the user's needs for high-power output applications.

[0010] Therefore, a parallel structure of lithium battery packs with the same voltage specification but different capacities and a working method thereof are proposed:

[0011] Among them, a specific technical solution of a parallel structure of lithium battery packs with the same voltage specification but different capacities is as follows: A parallel structure of lithium battery packs with the same voltage specification but different capacities, characterized in that: it includes at least two battery packs, a charging module and a control circuit module:

[0012] The positive ends of each battery pack are connected to each other to form a DC bus positive end, and the negative end of each battery pack is connected to a current control circuit respectively;

[0013] The current control circuit comprises a first control MOS tube, a second control MOS tube and a current sampling resistor, the source of the first control MOS tube is connected to the source of the second control MOS tube, and the gate of the first control MOS tube and the gate of the second control MOS tube are connected to the control port of the control circuit module;

[0014] The drain of the first control MOS tube is connected to the negative end of the corresponding battery pack, the drain of the second control MOS tube is connected to one end of the current sampling resistor, the other end of the current sampling resistor is connected to the negative end of the DC bus, and the two ends of the current sampling resistor are respectively connected to the two sampling ports of the control circuit module.

[0015] Among them, a working method of a parallel structure of lithium battery packs with the same voltage specification but different capacities is characterized by:

[0016] It includes a first battery pack, a second battery pack, a third battery pack, a control circuit module and a charging module:

[0017] The positive ends of the first battery group, the second battery group and the third battery group are connected together to form a DC bus positive end;

[0018] The input port of the charging module is connected to the AC input port, and the charging signal port of the charging module is connected to the signal acquisition port of the control circuit module;

[0019] The negative end of the first battery pack is connected to the drain of the control MOSFET Q1, the source of the control MOSFET Q1 is connected to the source of the control MOSFET Q4, the drain of the control MOSFET Q4 is connected to one end of the current sampling resistor R1, and the other end of the current sampling resistor R1 is connected to the negative end of the DC bus;

[0020] The two ends of the current sampling resistor R1 are respectively connected to the first sampling port and the second sampling port of the control circuit module;

[0021] The gates of the control MOS tube Q1 and the control MOS tube Q4 are connected to the first control port and the fourth control port of the control circuit module respectively;

[0022] The negative end of the second battery pack is connected to the drain of the control MOSFET Q2, the source of the control MOSFET Q2 is connected to the source of the control MOSFET Q5, the drain of the control MOSFET Q5 is connected to one end of the current sampling resistor R2, and the other end of the current sampling resistor R2 is connected to the negative end of the DC bus;

[0023] The two ends of the current sampling resistor R2 are respectively connected to the third sampling port and the fourth sampling port of the control circuit module;

[0024] The gates of the control MOS tube Q2 and the control MOS tube Q5 are connected to the first control port and the fourth control port of the control circuit module respectively;

[0025] The negative end of the third battery pack is connected to the drain of the control MOSFET Q3, the source of the control MOSFET Q3 is connected to the source of the control MOSFET Q6, the drain of the control MOSFET Q6 is connected to one end of the current sampling resistor R3, and the other end of the current sampling resistor R3 is connected to the negative end of the DC bus;

[0026] The two ends of the current sampling resistor R3 are respectively connected to the fifth sampling port and the sixth sampling port of the control circuit module;

[0027] The gates of the control MOS tube Q3 and the control MOS tube Q6 are connected to the first control port and the fourth control port of the control circuit module respectively;

[0028] The discharge working process of the present invention comprises the following steps:

[0029] S1: When the battery pack is discharging, if the control circuit module does not detect the signal of the charging module working, the system will enter the discharge mode, assuming that the voltage of lithium battery pack 3 is the highest, battery pack 2 is the second highest, and battery pack 1 is the lowest;

[0030] S2: The control circuit module first detects the information of the battery pack, which includes voltage, temperature, and remaining power, and will give priority to releasing the power of the third battery pack, so the control circuit module turns on the MOS tube Q6;

[0031] The current passes through the positive end of the third battery pack, the positive end of the DC bus, the load, the negative end of the DC bus, the resistor R3, the MOS tube Q6, and the parasitic diode of the MOS tube Q3, and returns to the negative end of the third battery pack to form a discharge loop;

[0032] The discharge process of each battery pack is similar;

[0033] S3: During the discharge process of the third battery pack, the current sampling resistor R3 detects the forward current and converts the current into a positive voltage and transmits it to the control circuit module. The control circuit module turns on the MOS tube Q3, and the current passes through Q3 instead of the parasitic diode, thus achieving the discharge function;

[0034] S4: Since the voltages of the first battery group and the second battery group are low, the third battery group tends to charge the first battery group and the second battery group;

[0035] Assuming that the second battery pack is charged, the current passes through the positive end of the third battery pack, the positive end of the DC bus, the positive end of the second battery pack, the negative end of the second battery pack, the control MOSFET Q2, the control MOSFET Q5, the current sampling resistor R2, the negative end of the DC bus, the current sampling resistor R3, the MOSFET Q6 and the MOSFET Q3, and returns to the negative end of the battery pack 3, forming a current loop;

[0036] In this current loop, since both MOSFET Q3 and MOSFET Q6 are turned on, the current sampling resistor R2 detects a negative current. Meanwhile, the control circuit module does not detect a working signal of the charging module. The control circuit module determines that it is a discharge between battery packs, and immediately turns off the control MOSFET Q2 of battery pack 2, thereby blocking the above current loop and preventing battery pack 3 from charging battery pack 2.

[0037] For the charging process of the first battery pack, the same procedure applies;

[0038] S5: During the discharge process, the voltage of the third battery pack continues to decrease. When the voltage approaches the voltage of the second battery pack, the second battery pack and the third battery pack discharge simultaneously. The current sampling resistor R2 detects the forward current, and the control circuit module turns on the MOS tube Q2.

[0039] Since the third battery pack and the second battery pack have different capacities and different voltage drop speeds, the system will always detect the current direction of the resistors R3 and R2. Once a negative current appears, it means that the high-voltage battery pack is charging the low-voltage battery pack. The control module turns off the charging control MOS tube corresponding to the low-voltage battery pack to prevent the high-voltage battery pack from charging the low-voltage battery pack.

[0040] During the discharge process, the voltage of the third battery pack and the second battery pack decreases alternately and gradually approaches the voltage of the first battery pack. Then, all three battery packs begin to discharge. The sampling resistor R1 detects the forward current and the control module turns on the MOS tube Q1.

[0041] S6: If the three battery packs have different voltage changes due to different capacities, the control circuit module continuously controls MOS tubes Q1 to Q6 according to the current direction of the current sampling resistors R1, R2 and R3, the battery voltage and the above control method to ensure that the battery pack with high voltage is discharged, and the battery pack with low voltage is not charged, so that all discharge is completed.

[0042] To better implement the present invention, the charging process may further include the following steps:

[0043] S1: When the system detects the signal that the charging module is working, the system will enter the charging mode. If the charging process does not allow the battery pack to discharge, it will enter S2, otherwise, it will enter S4;

[0044] S2: When the charging module is working, the control circuit module detects the charging module working signal, firstly turns off all MOSFETs Q1 to Q6, and then turns on the charging control MOSFET Q1 or control MOSFET Q2 or control MOSFET Q3 corresponding to the battery pack with the lowest voltage, until the corresponding MOSFET is turned off after it is fully charged;

[0045] S3: If the system is suddenly loaded during the charging process, since the MOSFETs Q4, MOSFET Q5, and MOSFET Q6 of each battery pack are all turned off, all battery packs will not discharge. Since the load is directly connected to the DC bus, it is equivalent to the charging module directly supplying power to the load. If there is surplus current, the battery pack with the lowest voltage will continue to be charged.

[0046] S4: When the charging module works, the control circuit module detects the charging module working signal, firstly turns off all MOS tubes Q1 to Q6, then turns on the charging control MOS tube Q1 or MOS tube Q2 or MOS tube Q3 and the discharge control MOS tube Q4 or MOS tube Q5 or MOS tube Q6 corresponding to the battery pack with the lowest voltage, until the two MOS tubes are turned off after full charge;

[0047] S5: If the system is suddenly loaded during the charging process, since the load is directly connected to the DC bus, it is equivalent to the charging module directly supplying power to the load:

[0048] S51: If the load is less than the output power of the charging module, the surplus current continues to charge the battery pack with the lowest voltage;

[0049] S52: If the load is greater than the output power of the charging module, the battery pack with the highest voltage starts discharging.

[0050] Further: When the battery is abnormal, the work includes the following processing procedures:

[0051] S1: Assuming that a short circuit or abnormal voltage occurs inside the first battery pack, if it is in the charging state, the process is performed according to S2, and if it is in the discharging state, the process is performed according to step S3;

[0052] S2: If the charging module is charging the first battery pack, the current passes through the positive terminal of the charging module, the battery pack 1, the MOSFET Q1, the MOSFET Q4, the current sampling resistor R1, the PGND, and then returns to the negative terminal of the charging module.

[0053] In this case, the current through the sampling resistor R1 is negative and very large, and the control module immediately turns off the MOSFET Q1 and MOSFET Q4. The battery pack 1 is disconnected from the system, and the system will not turn on the control MOSFET Q1 and MOSFET Q4 before the correct information of the battery pack is detected;

[0054] When other battery packs are being charged, in this case, the control MOSFET Q1 and MOSFET Q4 corresponding to the first battery pack are originally in a closed state, which has no effect on the system. Before detecting the correct information of the battery pack, the system will not turn on the control MOSFET Q1 and MOSFET Q4.

[0055] S3: In the discharge state, if the first battery pack is discharging and has no output due to an internal short circuit, the control circuit module will detect that the battery pack voltage is abnormal, and immediately turn off MOSFET Q1 and MOSFET Q4, opening the battery pack from the system to prevent other battery packs from discharging through battery pack 1.

[0056] If other battery packs are discharging, since the control MOSFET Q1 and the control MOSFET Q4 corresponding to the first battery pack are originally in the closed state, the first battery pack is not connected to the system and has no impact on the system. If the MOSFET Q1 and the MOSFET Q4 are turned on due to some abnormalities, the other battery packs will discharge through the first battery pack, and the current collection resistor R1 will detect an overcurrent signal and immediately turn off the MOSFET Q1 and the MOSFET Q4 to open the first battery pack from the system.

[0057] Before detecting the correct information of the first battery pack, the system will not turn on the control MOSFET Q1 and MOSFET Q4.

[0058] The beneficial effects of the present invention are as follows: first, the purpose of enabling the end user to connect multiple lithium battery packs with the same voltage specification but different capacities in parallel to form a large-capacity battery pack system is achieved;

[0059] Second, it realizes the purpose of automatically completing the charging and discharging of multiple lithium battery packs with the same voltage specifications and different capacities, avoiding the trouble of manually charging the battery packs one by one in the past;

[0060] Third, it solves the problem of mutual charging and discharging between battery packs, which wastes power, and improves the utilization rate of battery pack power;

[0061] Fourth, avoid system safety issues and battery pack damage caused by uncontrollable charging and discharging between battery packs;

[0062] Fifth, it solves the problem that when battery packs are used in parallel, individual or part of the battery packs are damaged, causing the system to not work or even cause safety hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is the overall structure diagram of the present invention. DETAILED DESCRIPTION

[0064] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0065] like Figure 1 As shown: A parallel structure of lithium battery packs with the same voltage specification but different capacities, including a first battery pack, a second battery pack, a third battery pack, a control circuit module and a charging module:

[0066] The positive terminals of the first battery group, the second battery group and the third battery group are connected together to form a DC bus positive terminal BAT+;

[0067] The input port of the charging module is connected to the AC input port, and the charging signal port of the charging module is connected to the signal acquisition port of the control circuit module;

[0068] The negative end of the first battery pack is connected to the drain of the control MOSFET Q1, the source of the control MOSFET Q1 is connected to the source of the control MOSFET Q4, the drain of the control MOSFET Q4 is connected to one end of the current sampling resistor R1, and the other end of the current sampling resistor R1 is connected to the negative end PGND of the DC bus;

[0069] The two ends of the current sampling resistor R1 are respectively connected to the first sampling port and the second sampling port of the control circuit module;

[0070] The gates of the control MOS tube Q1 and the control MOS tube Q4 are connected to the first control port and the fourth control port of the control circuit module respectively;

[0071] The negative end of the second battery pack is connected to the drain of the control MOSFET Q2, the source of the control MOSFET Q2 is connected to the source of the control MOSFET Q5, the drain of the control MOSFET Q5 is connected to one end of the current sampling resistor R2, and the other end of the current sampling resistor R2 is connected to the negative end PGND of the DC bus;

[0072] The two ends of the current sampling resistor R2 are respectively connected to the third sampling port and the fourth sampling port of the control circuit module;

[0073] The gates of the control MOS tube Q2 and the control MOS tube Q5 are connected to the first control port and the fourth control port of the control circuit module respectively;

[0074] The negative end of the third battery pack is connected to the drain of the control MOSFET Q3, the source of the control MOSFET Q3 is connected to the source of the control MOSFET Q6, the drain of the control MOSFET Q6 is connected to one end of the current sampling resistor R3, and the other end of the current sampling resistor R3 is connected to the negative end PGND of the DC bus;

[0075] The two ends of the current sampling resistor R3 are respectively connected to the fifth sampling port and the sixth sampling port of the control circuit module;

[0076] The gates of the control MOS tube Q3 and the control MOS tube Q6 are connected to the first control port and the fourth control port of the control circuit module respectively.

[0077] Among them, MOS tube Q1, MOS tube Q2 and MOS tube Q3 are charging control tubes, and MOS tube Q4, MOS tube Q5 and MOS tube Q6 are discharging control tubes.

[0078] In the present invention, the first battery pack, the second battery pack and the third battery pack correspond to Figure 1 Among battery packs 1, 2 and 3, the negative terminal of the first battery pack, the negative terminal of the second battery pack and the negative terminal of the third battery pack correspond to Figure 1 PGND_BAT1-, PGND_BAT2-, PGND_BAT3-, the positive end of the DC bus is Figure 1 BAT+, negative end of DC bus, i.e. Figure 1 The corresponding PGND, Figure 1 DC+_OUT and DC-_OUT are the input and output ends of the load.

[0079] The lithium battery packs connected in parallel must be of the same voltage level. Lithium battery packs of different voltage levels are not allowed to be connected in parallel.

[0080] In the present invention, it is assumed that the discharge current direction of each battery pack is positive, such as Figure 1 As shown by the arrow in the middle, that is, the direction in which the current flows from right to left relative to the resistance, the current direction opposite to the discharge current of the battery pack is set as the negative phase.

[0081] The present invention describes the working methods of a lithium battery pack in three modes: discharge, charge and battery pack failure.

[0082] The discharge working process of the present invention comprises the following steps:

[0083] S1: When the battery pack is discharging, if the control circuit module does not detect the signal that the charging module is working, the system enters the discharge mode, assuming that the voltage of the third battery pack is the highest, the voltage of the second battery pack is the second highest, and the voltage of the first battery pack is the lowest;

[0084] S2: The control circuit module first detects the information of the battery pack, which includes voltage, temperature, and remaining power, and will give priority to releasing the power of the third battery pack, so the control circuit module turns on the MOS tube Q6;

[0085] The current passes through the positive end of the third battery pack, the positive end of the DC bus, the load, the negative end of the DC bus, the resistor R3, the MOS tube Q6, and the parasitic diode of the MOS tube Q3, and returns to the negative end of the third battery pack to form a discharge loop;

[0086] The discharge process of each battery pack is similar;

[0087] S3: During the discharge process of the third battery pack, the current sampling resistor R3 detects the forward current and converts the current into a positive voltage and transmits it to the control circuit module. The control circuit module turns on the MOS tube Q3, and the current passes through Q3 instead of the parasitic diode, thus achieving the discharge function;

[0088] S4: Since the voltages of the first battery group and the second battery group are low, the third battery group tends to charge the first battery group and the second battery group;

[0089] Assuming that the second battery pack is charged, the current passes through the positive end of the third battery pack, the positive end of the DC bus, the positive end of the second battery pack, the negative end of the second battery pack, the control MOSFET Q2, the control MOSFET Q5, the current sampling resistor R2, the negative end of the DC bus, the current sampling resistor R3, the MOSFET Q6 and the MOSFET Q3, and returns to the negative end of the battery pack 3, forming a current loop;

[0090] In this current loop, since both MOSFET Q3 and MOSFET Q6 are turned on, the current sampling resistor R2 detects a negative current. Meanwhile, the control circuit module does not detect a working signal of the charging module. The control circuit module determines that it is a discharge between battery packs, and immediately turns off the control MOSFET Q2 of battery pack 2, thereby blocking the above current loop and preventing battery pack 3 from charging battery pack 2.

[0091] For the charging process of the first battery pack, the same procedure applies;

[0092] S5: During the discharge process, the voltage of the third battery pack continues to decrease. When the voltage approaches the voltage of the second battery pack, the second battery pack and the third battery pack discharge simultaneously. The current sampling resistor R2 detects the forward current, and the control circuit module turns on the MOS tube Q2.

[0093] Since the third battery pack and the second battery pack have different capacities and different voltage drop speeds, the system will always detect the current direction of the resistors R3 and R2. Once a negative current appears, it means that the high-voltage battery pack is charging the low-voltage battery pack. The control module turns off the charging control MOS tube corresponding to the low-voltage battery pack to prevent the high-voltage battery pack from charging the low-voltage battery pack.

[0094] During the discharge process, the voltage of the third battery pack and the second battery pack decreases alternately and gradually approaches the voltage of the first battery pack. Then, all three battery packs begin to discharge. The sampling resistor R1 detects the forward current and the control module turns on the MOS tube Q1.

[0095] S6: If the three battery packs have different voltage changes due to different capacities, the control circuit module continuously controls MOS tubes Q1 to Q6 according to the current direction of the current sampling resistors R1, R2 and R3, the battery voltage and the above control method to ensure that the battery pack with high voltage is discharged, and the battery pack with low voltage is not charged, so that all discharge is completed.

[0096] S7: In the above discharge process, when the current is detected to exceed the design requirements, the control circuit module can turn off the load. At the same time, the battery pack has its own BMS management circuit, which will limit the battery pack temperature and discharge current to prevent various hazards caused by continuous overcurrent in the discharge circuit.

[0097] S8: If the working condition of the load is not controlled by the control circuit module and the discharge current needs to be precisely controlled, the control circuit module controls the three discharge control MOS tubes respectively by adjusting the duty cycle of the PWM drive waveform to achieve precise control of the discharge current.

[0098] The charging process of the present invention comprises the following steps:

[0099] S1: When the system detects the signal that the charging module is working, the system will enter the charging mode. If the charging process does not allow the battery pack to discharge, it will enter S2, otherwise, it will enter S4;

[0100] S2: When the charging module is working, the control circuit module detects the charging module working signal, and first turns off all MOS tubes Q1 to Q6, and then turns on the charging control MOS tube Q1 or control MOS tube Q2 or control MOS tube Q3 corresponding to the battery pack with the lowest voltage, until the corresponding MOS tube is turned off after it is fully charged.

[0101] Here, assuming that charging the battery pack 1 is taken as an example, the system will turn on the MOS tube Q1 and turn off Q1 after the battery pack 1 is fully charged.

[0102] The charging process of battery pack 2 and battery pack 3 is similar.

[0103] S3: If the system is suddenly loaded during the charging process, all battery packs will not discharge because the discharge control MOSFETs, MOSFETs Q4, MOSFETs Q5, and MOSFETs Q6 of each battery pack are all turned off. Since the load is directly connected to the DC bus, it is equivalent to the charging module directly supplying power to the load. If there is surplus current, the battery pack with the lowest voltage will continue to be charged.

[0104] S4: When the charging module works, the control circuit module detects the charging module working signal, and first turns off all MOS tubes Q1 to MOS tube Q6, and then turns on the charging control MOS tube Q1 or MOS tube Q2 or MOS tube Q3 and the discharge control MOS tube Q4 or MOS tube Q5 or MOS tube Q6 corresponding to the battery pack with the lowest voltage, until the two MOS tubes are turned off after full charge.

[0105] Here, specifically, charging of battery pack 1 is taken as an example: the system will turn on MOS tube Q1 and MOS tube Q4, and then turn off MOS tube Q1 and MOS tube Q4 after battery pack 1 is fully charged. The charging process of the geothermal battery pack and the third battery pack is similar.

[0106] S5: If the system is suddenly loaded during the charging process, since the load is directly connected to the DC bus, it is equivalent to the charging module directly supplying power to the load:

[0107] S51: If the load is less than the output power of the charging module, the surplus current continues to charge the battery pack with the lowest voltage.

[0108] S52: If the load is greater than the output power of the charging module, the battery pack with the highest voltage starts discharging.

[0109] The work when the battery is abnormal includes the following processing procedures:

[0110] Battery pack damage refers to damage to the battery pack in non-hazardous ways such as combustion, explosion, liquid leakage, etc., generally referring to internal short circuit, internal open circuit or abnormal voltage.

[0111] If the battery has an open circuit inside, it is equivalent to not adding the battery pack to the system, and there is no impact on system safety. Here we only analyze the internal short circuit situation. The following analysis is carried out under the conditions of charging and discharging the battery pack.

[0112] S1: Assuming that a short circuit or abnormal voltage occurs inside the first battery pack, if it is in the charging state, the process is performed according to S2, and if it is in the discharging state, the process is performed according to step S3;

[0113] S2: If the charging module is charging the first battery pack, the current passes through the positive terminal of the charging module, the battery pack 1, the MOSFET Q1, the MOSFET Q4, the current sampling resistor R1, the PGND, and then returns to the negative terminal of the charging module.

[0114] In this case, the current through the sampling resistor R1 is negative and very large, and the control module immediately turns off the MOSFET Q1 and MOSFET Q4. The battery pack 1 is disconnected from the system, and the system will not turn on the control MOSFET Q1 and MOSFET Q4 before the correct information of the battery pack is detected;

[0115] When other battery packs are being charged, in this case, the control MOSFET Q1 and MOSFET Q4 corresponding to the first battery pack are originally in a closed state, which has no effect on the system. Before detecting the correct information of the battery pack, the system will not turn on the control MOSFET Q1 and MOSFET Q4.

[0116] S3: In the discharge state, if the first battery pack is discharging and has no output due to an internal short circuit, the control circuit module will detect that the battery pack voltage is abnormal, and immediately turn off MOSFET Q1 and MOSFET Q4, opening the battery pack from the system to prevent other battery packs from discharging through battery pack 1.

[0117] If other battery packs are discharging, since the control MOSFET Q1 and the control MOSFET Q4 corresponding to the first battery pack are originally in the closed state, the first battery pack is not connected to the system and has no impact on the system. If the MOSFET Q1 and the MOSFET Q4 are turned on due to some abnormalities, the other battery packs will discharge through the first battery pack, and the current collection resistor R1 will detect an overcurrent signal and immediately turn off the MOSFET Q1 and the MOSFET Q4 to open the first battery pack from the system.

[0118] Before detecting the correct information of the first battery pack, the system will not turn on the control MOSFET Q1 and MOSFET Q4.

Claims

1. A method for operating a parallel structure of lithium battery packs with the same voltage specification but different capacities, characterized in that: Includes at least two battery packs, a charging module and a control circuit module: The positive ends of each battery pack are connected to each other to form a DC bus positive end, and the negative end of each battery pack is respectively connected to a current control circuit; the current control circuit includes a first control MOSFET, a second control MOSFET and a current sampling resistor, the source of the first control MOSFET is connected to the source of the second control MOSFET, and the gate of the first control MOSFET and the gate of the second control MOSFET are connected to the control port of the control circuit module; The drain of the first control MOS tube is connected to the negative end of the corresponding battery pack, the drain of the second control MOS tube is connected to one end of the current sampling resistor, the other end of the current sampling resistor is connected to the negative end of the DC bus, and the two ends of the current sampling resistor are respectively connected to the two sampling ports of the control circuit module; The positive end of the DC bus is also connected to the positive end of the charging module, and the communication port of the charging module is connected to the communication port of the control circuit module; It includes a first battery pack, a second battery pack, a third battery pack, a control circuit module and a charging module: The positive ends of the first battery group, the second battery group and the third battery group are connected together to form a DC bus positive end; The input port of the charging module is connected to the AC input port, and the charging signal port of the charging module is connected to the signal acquisition port of the control circuit module; The negative end of the first battery pack is connected to the drain of the control MOSFET Q1, the source of the control MOSFET Q1 is connected to the source of the control MOSFET Q4, the drain of the control MOSFET Q4 is connected to one end of the current sampling resistor R1, and the other end of the current sampling resistor R1 is connected to the negative end of the DC bus; The two ends of the current sampling resistor R1 are respectively connected to the first sampling port and the second sampling port of the control circuit module; The gates of the control MOS tube Q1 and the control MOS tube Q4 are connected to the first control port and the fourth control port of the control circuit module respectively; The negative end of the second battery pack is connected to the drain of the control MOSFET Q2, the source of the control MOSFET Q2 is connected to the source of the control MOSFET Q5, the drain of the control MOSFET Q5 is connected to one end of the current sampling resistor R2, and the other end of the current sampling resistor R2 is connected to the negative end of the DC bus; The two ends of the current sampling resistor R2 are respectively connected to the third sampling port and the fourth sampling port of the control circuit module; The gates of the control MOS tube Q2 and the control MOS tube Q5 are connected to the first control port and the fourth control port of the control circuit module respectively; The negative end of the third battery pack is connected to the drain of the control MOSFET Q3, the source of the control MOSFET Q3 is connected to the source of the control MOSFET Q6, the drain of the control MOSFET Q6 is connected to one end of the current sampling resistor R3, and the other end of the current sampling resistor R3 is connected to the negative end of the DC bus; The two ends of the current sampling resistor R3 are respectively connected to the fifth sampling port and the sixth sampling port of the control circuit module; The gates of the control MOS tube Q3 and the control MOS tube Q6 are connected to the first control port and the fourth control port of the control circuit module respectively; The discharge process includes the following steps: S1: When the battery pack is discharging, if the control circuit module does not detect the signal of the charging module working, the system enters the discharge mode, assuming that the voltage of the third lithium battery pack is the highest, the second battery pack is the second highest, and the first battery pack is the lowest; S2: The control circuit module first detects the information of the battery pack, which includes voltage, temperature, and remaining power, and will give priority to releasing the power of the third battery pack, so the control circuit module turns on the MOS tube Q6; The current passes through the positive end of the third battery pack, the positive end of the DC bus, the load, the negative end of the DC bus, the resistor R3, the MOS tube Q6, and the parasitic diode of the MOS tube Q3, and returns to the negative end of the third battery pack to form a discharge loop; The discharge process of each battery pack is similar. S3: During the discharge process of the third battery pack, the current sampling resistor R3 detects the forward current and converts the current into a positive voltage and transmits it to the control circuit module. The control circuit module turns on the MOS tube Q3, and the current passes through Q3 instead of the parasitic diode, thereby realizing the discharge function. S4: Since the voltages of the first battery group and the second battery group are low, the third battery group tends to charge the first battery group and the second battery group; Assuming that the second battery pack is charged, the current passes through the positive end of the third battery pack, the positive end of the DC bus, the positive end of the second battery pack, the negative end of the second battery pack, the control MOSFET Q2, the control MOSFET Q5, the current sampling resistor R2, the negative end of the DC bus, the current sampling resistor R3, the MOSFET Q6 and the MOSFET Q3, and returns to the negative end of the third battery pack to form a current loop; In this current loop, since both MOSFET Q3 and MOSFET Q6 are turned on, the current sampling resistor R2 detects a negative current. Meanwhile, the control circuit module does not detect a working signal of the charging module. The control circuit module determines that it is a discharge between battery packs, and immediately turns off the control MOSFET Q2 of the second battery pack, thereby blocking the above current loop and preventing the third battery pack from charging the second battery pack. For the charging process of the first battery pack, the same procedure applies; S5: During the discharge process, the voltage of the third battery pack continues to decrease. When the voltage approaches the voltage of the second battery pack, the second battery pack and the third battery pack discharge simultaneously. The current sampling resistor R2 detects the forward current, and the control circuit module turns on the MOS tube Q2. Since the third battery pack and the second battery pack have different capacities and different voltage drop speeds, the system will always sample the current direction of the resistors R3 and R2. Once a negative current appears, it means that the battery pack with a high voltage is charging the battery pack with a low voltage. The control module turns off the charging control MOS tube corresponding to the low voltage battery pack to prevent the high voltage battery pack from charging the low voltage battery pack. During the discharge process, the voltage of the third battery pack and the second battery pack decreases alternately and gradually approaches the voltage of the first battery pack. Then, all three battery packs begin to discharge. The sampling resistor R1 detects the forward current and the control module turns on the MOS tube Q1. S6: If the voltage of the three battery packs changes at different speeds due to different capacities of the battery packs, the control circuit module continuously controls MOSFETs Q1 to Q6 according to the current directions of the current sampling resistors R1, R2 and R3, the battery voltage and the above control steps to ensure that the battery pack with a high voltage is discharged and the battery pack with a low voltage is not charged, so that all discharge is completed eventually; The charging process includes the following steps: S1: When the system detects the signal that the charging module is working, the system will enter the charging mode. If the charging process does not allow the battery pack to discharge, it will enter S2, otherwise, it will enter S4; S2: When the charging module is working, the control circuit module detects the charging module working signal, firstly turns off all MOSFETs Q1 to Q6, and then turns on the charging control MOSFET Q1 or control MOSFET Q2 or control MOSFET Q3 corresponding to the battery pack with the lowest voltage, until the corresponding MOSFET is turned off after it is fully charged; S3: If the system is suddenly loaded during the charging process, since the MOSFET Q4, MOSFET Q5, and MOSFET Q6 of each battery pack are all turned off, all battery packs will not discharge. Since the load is directly connected to the DC bus, it is equivalent to the charging module directly supplying power to the load. If there is surplus current, the battery pack with the lowest voltage will continue to be charged. S4: When the charging module works, the control circuit module detects the charging module working signal, firstly turns off all MOS tubes Q1 to Q6, then turns on the charging control MOS tube Q1 or MOS tube Q2 or MOS tube Q3 and the discharge control MOS tube Q4 or MOS tube Q5 or MOS tube Q6 corresponding to the battery pack with the lowest voltage, until the two MOS tubes are turned off after full charge; S5: If the system is suddenly loaded during the charging process, since the load is directly connected to the DC bus, it is equivalent to the charging module directly supplying power to the load: S51: If the load is less than the output power of the charging module, the surplus current continues to charge the battery pack with the lowest voltage; S52: If the load is greater than the output power of the charging module, the battery pack with the highest voltage starts discharging.

2. According to claim 1, a working method for a parallel structure of lithium battery packs with the same voltage specification but different capacities, characterized in that: The work when the battery is abnormal includes the following processing procedures: S1: Assuming that a short circuit or abnormal voltage occurs inside the first battery pack, if it is in the charging state, the process is performed according to S2, and if it is in the discharging state, the process is performed according to step S3; S2: If the charging module is charging the first battery pack, the current passes through the positive terminal of the charging module, the battery pack 1, the MOS tube Q1, the MOS tube Q4, the current sampling resistor R1, PGND, and then returns to the negative terminal of the charging module; In this case, the current through the sampling resistor R1 is negative and very large, and the control module immediately turns off the MOSFET Q1 and MOSFET Q4, and disconnects the battery pack 1 from the system. Before detecting the correct information of the battery pack, the system will not turn on the control MOSFET Q1 and the control MOSFET Q4. When charging other battery packs, in this case, the control MOSFET Q1 and MOSFET Q4 corresponding to the first battery pack are originally in the off state, which has no effect on the system. Before detecting the correct information of the battery pack, the system will not turn on the control MOSFET Q1 and MOSFET Q4; S3: In the case of discharge, if the first battery pack is discharging and has no output due to an internal short circuit, the control circuit module will detect that the battery pack voltage is abnormal, and immediately turn off the MOS tube Q1 and the MOS tube Q4, and open the battery pack from the system to prevent other battery packs from discharging through the battery pack 1; If other battery packs are discharging, since the control MOSFET Q1 and the control MOSFET Q4 corresponding to the first battery pack are originally in the closed state, the first battery pack is not connected to the system and has no impact on the system. If the MOSFET Q1 and the MOSFET Q4 are already turned on due to some abnormality, the other battery packs will discharge through the first battery pack, and the current collection resistor R1 will detect the overcurrent signal and immediately turn off the MOSFET Q1 and the MOSFET Q4 to open the circuit of the first battery pack from the system. Before detecting the correct information of the first battery pack, the system will not turn on the control MOSFET Q1 and MOSFET Q4.

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