A self-powered circuit for a power battery system and an over-discharge protection method

Abstract

The present invention discloses a self-powered circuit and an over-discharge protection method for a power battery system, which belongs to the field of electronic technology. The circuit for implementing the method includes: a battery management system, a discharge fuse, a first relay, a second relay, a third relay, a first Hall sensor, a second Hall sensor, a pre-charge resistor, a fourth relay, a power supply, a charger, a battery module, and a battery switch. The battery management system includes a BMS slave control and a BMS master control, one end of the BMS master control is connected to one end of the BMS slave control, and the other end of the BMS slave control is connected to the battery module. The present invention provides a self-powered circuit and an over-discharge protection method for a power battery system, which solves the problem that the battery switch is in a closed state for a long time, and the battery management system itself continues to consume the power of the lithium battery pack, which will cause the lithium battery to be deeply under-voltage or even zero-voltage, causing the lithium battery to be damaged or even scrapped, thereby improving the service life and reliability of the power battery system.

Description

Technical Field

[0001] The present invention belongs to the field of electronic technology, and in particular, relates to a self-powered circuit of a power battery system and an over-discharge protection method. Background Art

[0002] Power battery systems usually require a battery management system (BMS) to monitor and manage the charging and discharging of the battery pack. Traditional power battery systems usually use 12V / 24V external lead-acid batteries to provide low-voltage power for the battery management system. The battery management system controls the power output of the battery pack to the external high-voltage load. The 12V / 24V lead-acid battery alone powers the battery management system to ensure the reliable operation of the battery management system. With the development of power batteries and market demand, the battery pack itself is used to power the battery management system to save the 12V / 24V lead-acid battery. The lithium battery self-powered circuit usually consists of a lithium battery module, a battery management system, a DC / DC power supply, a relay, and an external battery switch. When the voltage of the power battery pack is too low, the management system controls the lithium battery pack to stop supplying power to the high-voltage load to prevent the lithium battery pack from over-discharging. However, for electric vehicles, electric vehicles, UPS power supplies and other products that use lithium battery packs to power the battery management system, after the management system controls the lithium battery pack to stop supplying power to the load, if the battery switch is in a closed state for a long time, the battery management system itself continues to consume the power of the lithium battery pack, which will cause the lithium battery to be deeply under-voltage or even zero voltage, causing damage to the lithium battery or even scrapping.

[0003] Currently, no effective solution to the above problems has been found. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a self-powered circuit and over-discharge protection method for a power battery system in view of the above shortcomings, which solves the problem that the battery switch is in a closed state for a long time, and the battery management system itself continues to consume the power of the lithium battery pack, which will cause the lithium battery to be deeply under-voltage or even zero-voltage, causing the lithium battery to be damaged or even scrapped, thereby improving the service life and reliability of the power battery system.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A power battery system self-powered circuit and over-discharge protection method, comprising the following steps:

[0007] Step S1, the battery switch is closed, the BMS voltage is powered on, and then proceed to step 2;

[0008] Step S2, BMS self-checks whether there is a system fault, if yes, proceeds to step S4, otherwise proceeds to step S3;

[0009] Step S3, BMS controls the fourth relay and the third relay to close, and after 3 seconds, the second relay is closed and the third relay is disconnected, and the process goes to step 5;

[0010] Step S4, the BMS sends a fault signal. When sending the fault signal, the voltage of the battery module cannot be output externally. The battery switch is always in the on state. The BMS will continue to consume the power of the battery module. It is necessary to continue to detect the battery module status and enter step S41;

[0011] Step S41, the BMS determines whether the voltage of the battery module is ≤2.0V and the current detected by the second Hall sensor is ≤0.5A. If yes, it proceeds to step S42, otherwise, it continues to determine the voltage of the battery module and the current detected by the second Hall sensor;

[0012] Step S42, the BMS continuously sends a sleep instruction to the DCDC power supply, and then proceeds to step S43;

[0013] Step S43, the DCDC power supply receives the sleep command more than 3 times, enters the sleep mode and cuts off the 24V external output port, and then enters step S44;

[0014] Step S44, the BMS enters the shutdown state. The BMS stops working without 24V power supply, no longer consumes the power of the battery module, and enters the extreme over-discharge protection state, and ends;

[0015] Step S5, when the minimum voltage of the battery module is ≤2.5V, proceed to step S6;

[0016] Step S6, disconnect the second relay and the fourth relay, cut off the external output of the battery module, the battery switch 14 is continuously closed, the battery module power and voltage will drop rapidly, and enter step S7;

[0017] Step S7, determining whether the battery module voltage detected by the BMS is ≤2.0V and the second Hall sensor detection current is ≤0.5A, if yes, proceeding to step S8, otherwise, continuing to detect the battery module voltage and the second Hall sensor detection current;

[0018] Step S8, the BMS continues to send a sleep instruction to the DCDC power supply, and then proceeds to step S9;

[0019] Step S9, the DCDC power supply receives the sleep command more than 3 times, enters the sleep mode and cuts off the 24V external output port, and then enters step S10;

[0020] Step S10, the BMS enters the shutdown state. The BMS will stop working without 24V power supply and will no longer consume the power of the battery module. The battery module enters the extreme over-discharge protection state and ends.

[0021] Furthermore, a self-powered circuit of a power battery system that implements the above-mentioned protection method includes: a battery management system, a discharge fuse, a first relay, a second relay, a third relay, a first Hall sensor, a second Hall sensor, a pre-charging resistor, a fourth relay, a power supply, a charger, a battery module, and a battery switch. The battery management system includes a BMS slave control and a BMS master control, one end of the BMS master control is connected to one end of the BMS slave control, and the other end of the BMS slave control is connected to the battery module.

[0022] Furthermore, the positive electrode of the battery module is connected to the K4- port of the first relay, the K1+ port of the second relay, the K3+ port of the third relay, and the switch input interface.

[0023] The K3-port of the third relay is connected to the input end of the pre-charging resistor, and the output end of the pre-charging resistor is connected to the K1-port and the output positive interface of the second relay.

[0024] The K1- port of the second relay is also connected to the output positive interface.

[0025] Furthermore, the K4+ port of the first relay is connected to the V0+ interface of the charger.

[0026] The input end of the charger is connected to the input AC L interface and the input AC N interface respectively.

[0027] Furthermore, the negative electrode of the battery module is connected to the input end of the discharge fuse, and the output end of the discharge fuse is connected to the K2-interface of the fourth relay, the VO-port of the charger, and the input-port of the DC / DC power supply in sequence.

[0028] Furthermore, the second Hall sensor and the first Hall sensor are connected to the BMS main control.

[0029] Furthermore, the second Hall sensor is arranged between the first relay and the charger.

[0030] The first Hall sensor is disposed between the discharge fuse and the fourth relay.

[0031] Furthermore, the 24V+ port of the BMS master is connected to the output 24V+ port of the DC / DC power supply, the 24V- port of the BMS master is connected to the output 24V- port of the DC / DC power supply, the X1 port of the BMS master is connected to the X3 port of the DC / DC power supply, and the X2 port of the BMS master is connected to the X4 port of the DC / DC power supply; the input + interface of the DC / DC power supply is connected to the switch output interface.

[0032] The present invention adopts the above technical solution, and has the following advantages compared with the prior art:

[0033] (1) The second Hall sensor is set between the first relay and the charger. The BMS can control the first relay to close and open, and further control the charger to output and cut off the battery module. At the same time, the second Hall sensor can detect the working current of the charger and determine the working status of the charger.

[0034] (2) The DCDC power supply has a CAN interface and enters a sleep state after receiving the BMS sleep command more than three times through the CAN interface, thereby improving the accuracy of the BMS sleep command.

[0035] (3) After the conventional over-discharge protection, the BMS can be controlled to shut down to prevent the BMS from consuming the battery module power, thus playing the role of extreme over-discharge protection of the battery module, extending the life of the power battery and improving reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of the over-discharge protection method of the self-powered circuit of the power battery system of the present invention;

[0037] Figure 2 It is a schematic diagram of the self-powered circuit of the power battery system of the present invention.

[0038] In the figure: 1-BMS slave control, 2-BMS master control, 3-discharge fuse, 4-first relay, 5-second relay, 6-third relay, 7-first Hall sensor, 8-second Hall sensor, 9-pre-charging resistor, 10-fourth relay, 11-power supply, 12-charger, 13-battery module, 14-battery switch. DETAILED DESCRIPTION

[0039] The present invention is further described below. Those skilled in the art should be able to understand from the following examples that the examples are not intended to limit the technical solutions of the present invention, but are merely intended to fully illustrate how to implement the invention.

[0040] The core process of the control method of the present invention is that after the second Hall sensor 8 does not detect the charging current and the single cell voltage is lower than the limit over-discharge protection threshold, the battery management system (BMS) controls the subsequent use logic of the execution. After the conventional over-discharge protection, the BMS cuts off the external output, and the battery module 13 itself has a very low power. At this time, the battery module 13 should be charged in time or the battery switch 14 should be turned off. If the battery switch 14 is continuously closed, the battery module 13 power and voltage will drop rapidly. If there is no further protection measure, the battery module 13 is very easy to over-discharge or even become zero voltage.

[0041] In the present invention, after the second Hall sensor 8 does not detect the charging current and the single cell voltage is lower than the limit over-discharge protection threshold, the BMS will actively and continuously send sleep instructions to the DCDC power supply 11. After receiving the instruction three times, the DCDC power supply 11 will enter the sleep low-power mode (the condition of increasing the number of instruction judgment times is to prevent the DCDC power supply 11 from erroneously receiving the instruction and entering the sleep mode to affect the normal operation of the battery system). When the 24V output is cut off, the BMS will also stop working and enter the shutdown state, thereby protecting the battery from over-discharge.

[0042] Examples, such as Figure 1 As shown, a method for protecting a power battery system from over-discharge due to self-power supply comprises the following steps:

[0043] Step S1, the battery switch 14 is closed, the BMS voltage is powered on, and the process goes to step 2;

[0044] Step S2, BMS self-checks whether there is a system fault, otherwise proceeds to step S3, if yes, proceeds to step S4;

[0045] Step S3, BMS controls the fourth relay 10 and the third relay 6 to close, and 3 seconds later the second relay 5 is closed and the third relay 6 is disconnected, and the process goes to step 5;

[0046] Step S4, the BMS sends a fault signal. When sending the fault signal, the voltage of the battery module 13 cannot be output externally, the battery switch 14 is always in the on state, and the BMS will continue to consume the power of the battery module 13. It is necessary to continue to detect the state of the battery module 13, and enter step S41;

[0047] Step S41, the BMS determines whether the voltage of the battery module 13 is ≤2.0V and the current detected by the second Hall sensor 8 is ≤0.5A. If yes, the process proceeds to step S42, otherwise, the BMS continues to determine the voltage of the battery module 13 and the current detected by the second Hall sensor 8;

[0048] Step S42, the BMS continues to send a sleep instruction to the DCDC power supply 11, and then proceeds to step S43;

[0049] Step S43, the DCDC power supply 11 receives the sleep command more than 3 times, enters the sleep mode and cuts off the 24V external output port, and then enters step S44;

[0050] Step S44, the BMS enters the shutdown state. The BMS stops working without 24V power supply, no longer consumes the power of the battery module 13, and enters the extreme over-discharge protection state, and ends;

[0051] Step S5, when the minimum voltage of the battery module 13 is ≤2.5V, proceed to step S6;

[0052] Step S6, disconnect the second relay 5 and the fourth relay 10, cut off the external output of the battery module 13, the battery switch 14 is continuously closed, the power and voltage of the battery module 13 will drop rapidly, and enter step S7;

[0053] Step S7, determining whether the voltage of the battery module 13 detected by the BMS is ≤2.0V and the current detected by the second Hall sensor 8 is ≤0.5A, if yes, proceeding to step S8, otherwise, continuing to detect the voltage of the battery module 13 and the current detected by the second Hall sensor 8;

[0054] Step S8, the BMS continues to send a sleep instruction to the DCDC power supply 11, and then proceeds to step S9;

[0055] Step S9, the DCDC power supply 11 receives the sleep command more than 3 times, enters the sleep mode and cuts off the 24V external output port, and then enters step S10;

[0056] Step S10, the BMS enters the shutdown state. The BMS stops working without 24V power supply and no longer consumes the power of the battery module 13. The battery module 13 enters the extreme over-discharge protection state, and ends;

[0057] like Figure 2 As shown, the self-powered circuit of the power battery system implementing this method includes: a battery management system, a discharge fuse 3, a first relay 4, a second relay 5, a third relay 6, a first Hall sensor 7, a second Hall sensor 8, a pre-charging resistor 9, a fourth relay 10, a power supply 11, a charger 12, a battery module 13, and a battery switch 14.

[0058] The battery management system includes a BMS slave control 1 and a BMS master control 2, one end of the BMS master control 2 is connected to one end of the BMS slave control 1, and the other end of the BMS slave control 1 is connected to the battery module 13, the positive electrode of the battery module 13 is connected to the K4-port of the first relay 4, the K1+port of the second relay 5, the K3+port of the third relay 6, and the switch input interface; the K3-port of the third relay 6 is connected to the input end of the pre-charging resistor 9, and the output end of the pre-charging resistor 9 is connected to the K1-port of the second relay 5 and the output positive interface; the K1-port of the second relay 5 is connected to the output positive interface; the K4+port of the first relay 4 is connected to the V0+ interface of the charger 12, and the input end of the charger 12 is respectively connected to the input AC L interface and the input AC N interface.

[0059] The negative pole of the battery module 13 is connected to the input end of the discharge fuse 3 , and the output end of the discharge fuse 3 is connected to the K2-interface of the fourth relay 10 , the VO-port of the charger 12 , and the input-port of the DC / DC power supply 11 in sequence.

[0060] The second Hall sensor 8 and the first Hall sensor 7 are connected to the BMS main control 2 .

[0061] The second Hall sensor 8 is disposed between the first relay 4 and the charger 12 and is used to detect the operating current of the charger and determine the operating state of the charger.

[0062] The first Hall sensor 7 is provided between the discharge fuse 3 and the fourth relay 10 .

[0063] The 24V+ port of the BMS main control 2 is connected to the output 24V+ port of the DC / DC power supply 11, the 24V- port of the BMS main control 2 is connected to the output 24V- port of the DC / DC power supply 11, the X1 port of the BMS main control 2 is connected to the X3 port of the DC / DC power supply 11, and the X2 port of the BMS main control 2 is connected to the X4 port of the DC / DC power supply 11; the 11 input + interface of the DC / DC power supply is connected to the switch output interface.

[0064] The battery management system (BMS) is a conventional model, including 1 BMS master control + 1 BMS slave control. The BMS master control model is CR-BMU80-24V-B, and the BMS slave control model is CR-BSU80-24V-48S16T.

[0065] The battery module 13 is high voltage, and the management system power supply is generally low voltage 24V. The high voltage of the battery module 13 needs to be converted to 24V low voltage through the DCDC power supply 11 to power the BMS, so that the BMS can work normally.

[0066] When the battery module 13 supplies power to the BMS: connect the positive pole of the battery module 13 to the switch input interface, connect the switch output interface to the positive pole of the DC / DC power supply 11 input, connect the negative pole of the battery module 13 to the negative pole of the DC / DC power supply 11 input, and connect the DC24V positive / negative output of the DC / DC power supply 11 to the BMS main control power supply. When the battery switch 14 is closed, the battery module 13 provides high-voltage direct current to the DC / DC power supply 11, and the DC / DC power supply 11 outputs a constant voltage DC24V to power the BMS. Therefore, the closing / opening of the battery switch 14 can control the operation / shutdown of the BMS.

[0067] When the battery module 13 outputs externally, the positive / negative poles of the battery module 13 are connected to the output positive / negative interfaces. The second relay 5 and the fourth relay 10 can control the output and cutoff of the battery module 13 .

[0068] When the battery module 13 is charged: the input AC L / N interface is connected to the charger 12, the VO+ port of the charger 12 is connected to the K4+ port of the first relay 4, the K4- port of the first relay 4 is connected to the positive electrode of the battery module 13, and the output VO- port of the charger 12 is connected to the negative electrode of the battery module 13. When the charger 12 has AC220V input, the BMS can control the closing and opening of the first relay 4 when the battery module 13 is charged, and further control the output and disconnection of the charger 12 to the battery module 13. At the same time, the second Hall sensor 8 can detect the working current of the charger 12 and determine the working state of the charger 12.

[0069] During the electrical design process, a CAN communication interface will be added to the DC / DC power supply 11 and the CAN communication sleep function will be provided. One CAN communication channel of the BMS main control 2 is connected to the DC / DC power supply 11 CAN interface for information exchange, and a second Hall sensor 8 is added to the charging circuit to detect the charging current. When the battery switch 14 is in a long-term closed state, the BMS detects that the voltage of the battery module 13 or the single cell voltage is too low and the charger 12 does not charge the battery module 13, the BMS main control 2 will send a sleep command to the DC / DC power supply 11. The DC / DC power supply 11 will enter a sleep low-power state after receiving the command more than 3 times, and the 24V voltage output will be cut off. The BMS will enter shutdown to prevent the BMS from consuming the power of the battery module 13, thereby playing the role of protecting the battery module from over-discharge, extending the life of the power battery and improving reliability.

[0070] The above is an example of the best implementation of the present invention, and the parts not described in detail are common knowledge of ordinary technicians in the field. The protection scope of the present invention shall be based on the content of the claims, and any equivalent transformation based on the technical enlightenment of the present invention is also within the protection scope of the present invention.

Claims

1. A self-powered circuit and over-discharge protection method for a power battery system, characterized in that: The following steps are involved: Step S1, the battery switch (14) is closed, the BMS voltage is powered on, and then the process goes to step 2; Step S2, BMS self-checks whether there is a system fault, if yes, proceeds to step S4, otherwise proceeds to step S3; Step S3, the BMS controls the fourth relay (10) and the third relay (6) to close, and 3 seconds later the second relay (5) is closed and the third relay (6) is disconnected, and the process proceeds to step 5; Step S4, the BMS sends a fault signal. When sending the fault signal, the voltage of the battery module (13) cannot be output externally, the battery switch (14) is always in the on state, and the BMS will continue to consume the power of the battery module (13). It is necessary to continue to detect the state of the battery module (13), and enter step S41; Step S41, the BMS determines whether the voltage of the battery module (13) is ≤2.0V and the current detected by the second Hall sensor (8) is ≤0.5A. If yes, the process proceeds to step S42; otherwise, the process continues to determine the voltage of the battery module (13) and the current detected by the second Hall sensor (8); Step S42, the BMS continuously sends a sleep instruction to the DCDC power supply (11), and then proceeds to step S43; Step S43, the DCDC power supply (11) receives the sleep command more than three times, enters the sleep mode and cuts off the 24V external output port, and then enters step S44; Step S44, the BMS enters a shutdown state. The BMS stops working when there is no 24V power supply, and no longer consumes the power of the battery module (13). The BMS enters a limit over-discharge protection state, and ends. Step S5, when the minimum voltage of the battery module (13) is ≤2.5V, proceed to step S6; Step S6, disconnecting the second relay (5) and the fourth relay (10), cutting off the external output of the battery module (13), the battery switch (14) continues to be closed, the power and voltage of the battery module (13) will drop rapidly, and then proceeding to step S7; Step S7, determining whether the voltage of the battery module (13) detected by the BMS is ≤2.0V and the current detected by the second Hall sensor (8) is ≤0.5A, if yes, proceeding to step S8, otherwise continuing to detect the voltage of the battery module (13) and the current detected by the second Hall sensor (8); Step S8, the BMS continuously sends a sleep instruction to the DCDC power supply (11), and then proceeds to step S9; Step S9, the DCDC power supply (11) receives the sleep command more than three times, enters the sleep mode and cuts off the 24V external output port, and then enters step S10; Step S10, the BMS enters a shutdown state. The BMS stops working without a 24V power supply and no longer consumes power from the battery module (13). The battery module (13) enters a limit over-discharge protection state and ends.

2. A power battery system self-powered circuit for implementing the protection method according to claim 1, comprising: A battery management system, a discharge fuse (3), a first relay (4), a second relay (5), a third relay (6), a first Hall sensor (7), a second Hall sensor (8), a pre-charging resistor (9), a fourth relay (10), a power source (11), a charger (12), a battery module (13), and a battery switch (14), characterized in that: The battery management system comprises a BMS slave control (1) and a BMS master control (2), one end of the BMS master control (2) is connected to one end of the BMS slave control (1), and the other end of the BMS slave control (1) is connected to a battery module (13).

3. The power battery system self-powered circuit according to claim 2, characterized in that: The positive electrode of the battery module (13) is connected to the K4- port of the first relay (4), the K1+ port of the second relay (5), the K3+ port of the third relay (6), and the switch input interface; The K3-port of the third relay (6) is connected to the input end of the pre-charging resistor (9), and the output end of the pre-charging resistor (9) is connected to the K1-port and the output positive interface of the second relay (5); The K1-port of the second relay (5) is also connected to the output positive interface.

4. The power battery system self-powered circuit according to claim 2, characterized in that: The K4+ port of the first relay (4) is connected to the V0+ port of the charger (12); The input end of the charger (12) is connected to the input AC L interface and the input AC N interface respectively.

5. The power battery system self-powered circuit according to claim 2, characterized in that: The negative electrode of the battery module (13) is connected to the input end of the discharge fuse (3), and the output end of the discharge fuse (3) is connected in sequence to the K2-interface of the fourth relay (10), the VO-port of the charger (12), and the input-port of the DC / DC power supply (11).

6. The power battery system self-powered circuit according to claim 2, characterized in that: The second Hall sensor (8) and the first Hall sensor (7) are connected to the BMS main control (2).

7. The power battery system self-powered circuit according to claim 2, characterized in that: The second Hall sensor (8) is arranged between the first relay (4) and the charger (12); The first Hall sensor (7) is arranged between the discharge fuse (3) and the fourth relay (10).

8. The power battery system self-powered circuit according to claim 2, characterized in that: The 24V+ port of the BMS main control (2) is connected to the output 24V+ port of the DC / DC power supply (11), the 24V- port of the BMS main control (2) is connected to the output 24V- port of the DC / DC power supply (11), the X1 port of the BMS main control (2) is connected to the X3 port of the DC / DC power supply (11), and the X2 port of the BMS main control (2) is connected to the X4 port of the DC / DC power supply (11); the input + interface of the DC / DC power supply (11) is connected to the switch output interface.

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