Charging and discharging control early warning method for series structure retired battery module

Abstract

The invention provides a charge and discharge control early warning method for a series structure decommissioned battery module. The series structure decommissioned battery module comprises a plurality of decommissioned batteries, a switching control circuit and a control unit, the switching control circuit comprises a series electronic switch group and a charging and discharging electronic switch group; the series electronic switch group comprises m-1 electronic switches which are respectively arranged between the positive electrodes and the negative electrodes of the adjacent retired batteries and are used for connecting the adjacent retired batteries in series; in the charging and discharging process, the series-connected decommissioned batteries are sequentially charged based on the charge states and voltages of the decommissioned batteries, and the low-charge decommissioned batteries exit discharging during discharging, so that the phenomenon of unbalanced charging and discharging is prevented, irreversible damage to the decommissioned batteries is avoided, the service life of the decommissioned batteries is prolonged, and the service life of the decommissioned batteries is prolonged. And potential safety hazards are reduced.

Description

Technical Field

[0001] The present invention relates to a battery management control method, and in particular to a charge and discharge control early warning method for retired battery modules with a series structure. Background Art

[0002] With the increasing popularity of electric vehicles, power battery packs, as one of the core components of electric vehicles, are also being used more and more. When the power battery packs reach certain conditions, they cannot meet the needs of electric vehicles, thus forming retired batteries. Although the retired batteries cannot meet the power needs of electric vehicles, they can still meet other scenarios.

[0003] When retired batteries are used in other application scenarios, multiple retired batteries are often connected in series to supply power to subsequent electrical devices, such as directly supplying electrical devices or supplying power to subsequent circuits through DC-DC conversion circuits. In the prior art, retired batteries are directly connected in series through wires or the like, and are directly charged or discharged at the same time during charging and discharging. Although the retired batteries are subjected to corresponding health tests or consistency tests when they are reused, in subsequent use, after the retired batteries are discharged once, their charge states and voltages are different when they are charged again. If they are directly and arbitrarily charged or discharged at the same time, it is easy to cause imbalance in the charging and discharging of the retired batteries in series, causing great irreversible damage to the batteries, and thus posing serious safety hazards.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a charge and discharge control and early warning method for retired battery modules with a series structure, by connecting retired batteries in series through a switching control circuit, and sequentially charging the retired batteries in series based on the charge state and voltage of the retired batteries during the charging and discharging process, so that the low-charged retired batteries are allowed to exit discharge during discharge, thereby preventing the occurrence of charge and discharge imbalance, avoiding irreversible damage to the retired batteries, extending the service life of the retired batteries, and reducing safety hazards.

[0006] The present invention provides a charge and discharge control and early warning method for a retired battery module of a series structure, comprising a plurality of retired batteries, a switching control circuit and a control unit;

[0007] The switching control circuit includes a series electronic switch group and a charge and discharge electronic switch group;

[0008] The series electronic switch group includes m-1 electronic switches and is respectively arranged between the positive electrodes and negative electrodes of adjacent retired batteries and connects the adjacent retired batteries in series;

[0009] The charging and discharging electronic switch group includes a plurality of electronic switches, the positive electrode of each retired battery is connected to the charging DC bus through an electronic switch, the negative electrode of the retired battery at the end of the series connection is connected to the negative electrode of the charging output port through an electronic switch, and the charging DC bus is connected to the positive electrode of the charging output port through the charging master switch QZ1; the charging DC bus is connected to the negative electrode of the back-end circuit through an electronic switch;

[0010] The positive electrode of each retired battery is connected to the discharge DC bus through an electronic switch, and the discharge DC bus is connected to the positive electrode of the back-end circuit through the discharge master switch QZ2. The negative electrode of the retired battery at the end of the series connection is connected to the negative electrode of the back-end circuit through an electronic switch; the discharge DC bus is connected to the negative electrode of the charging output port through an electronic switch;

[0011] The control input ends of the electronic switches of the series electronic switch group and the charge-discharge electronic switch group are connected to a control unit. The control unit controls the on and off of each electronic switch according to the charge state and voltage of the retired battery, thereby realizing the charging and discharging of the retired battery, and the control unit issues an alarm according to the charge state and voltage of the retired battery.

[0012] Furthermore, the electronic switch is an NMOS tube.

[0013] Further, the control unit controls the switching control circuit to make the retired battery enter the charging state according to the following method:

[0014] SA1. The control unit obtains the status information of each retired battery, the status information includes the current state of charge SOC and voltage of each retired battery module; and the control unit controls the main discharge switch QZ2 to always be in the off state

[0015] SA2. The control unit calculates the difference in the state of charge SOC of any two retired batteries and determines whether the difference in the state of charge SOC of any two retired batteries is less than a set threshold value. If so, the process proceeds to step SA5, and if not, the process proceeds to step SA3;

[0016] SA3. The control unit sorts the retired batteries according to the state of charge SOC from small to large, and the control unit determines the charging priority of each retired battery, the priority being that the smaller the state of charge SOC, the higher the charging priority;

[0017] SA4. The control unit first controls the electronic switch corresponding to the retired battery with the smallest state of charge SOC to turn on and the retired battery enters the charging state, and obtains the battery voltage of the retired battery module. When the voltage of the retired battery module with the smallest state of charge SOC reaches the battery voltage with the second smallest state of charge SOC among the retired batteries, the control unit controls the electronic switch corresponding to the retired battery module with the second smallest state of charge SOC to turn on, and so on, until all retired battery modules enter the charging state.

[0018] SA5. The control unit controls the electronic switches corresponding to each retired battery and the main charging switch QZ1 to enter the on state, and each retired battery enters the charging state.

[0019] Further, the control unit switches the control circuit to operate in the following manner to make the retired battery enter a discharge state:

[0020] SB1. The control unit obtains the state of charge SOC and voltage of each retired battery at the initial discharge, and the control unit controls the charging main switch QZ1 to always be in the off state;

[0021] SB2. The control unit controls all retired batteries to enter the discharge state. After the set discharge time, the control unit obtains the state of charge (SOC) and voltage of each retired battery module again. When the difference between the current state of charge (SOC) value of any retired battery and the average state of charge (SOC) value of all retired batteries at the current moment is greater than the set value, or when the difference between the current voltage value of any retired battery and the average voltage value of all retired batteries is greater than the set value, the control unit controls the electronic switch corresponding to the current retired battery to turn off, and the electronic switches corresponding to other retired batteries to turn on and be in the discharge state.

[0022] SB3. Return to step S2 until the set discharge time is reached or the power provided by the remaining retired battery modules cannot meet the needs of the electrical devices.

[0023] Furthermore, the control unit issues an alarm according to the state of charge and voltage of the retired battery, specifically including:

[0024] The control unit calculates the state of charge consistency and voltage consistency of the retired battery according to the state of charge SOC and voltage at the beginning of the discharge of the retired battery and the state of charge SOC and voltage after the set discharge time, where the state of charge consistency is:

[0025] Among them, CON SOC is the charge state consistency, η SOC is the rate of change of state of charge, is the average rate of change of state of charge of all retired battery modules, SOC0 is the state of charge value of the retired battery module at the initial discharge time after charging, and SOC1 is the state of charge value of the retired battery module after the set discharge time;

[0026] The voltage consistency is:

[0027]

[0028] Among them: CON V is the voltage consistency, η V is the voltage change rate, is the average voltage change rate of all retired battery modules, V0 is the voltage value of the retired battery module at the initial discharge time after charging, and V1 is the voltage value of the retired battery module after the set discharge time;

[0029] When any retired battery module has a charge state consistency value greater than a set value or a voltage consistency value greater than a set value during N consecutive discharges, the control unit issues a fault alarm through the alarm connected thereto.

[0030] The beneficial effects of the present invention are as follows: through the present invention, retired batteries are connected in series by switching the control circuit, and the retired batteries in series are charged sequentially based on the charge state and voltage of the retired batteries during the charging and discharging process, so that the retired batteries with low charge are allowed to exit the discharge during discharge, thereby preventing the occurrence of charge and discharge imbalance, avoiding irreversible damage to the retired batteries, extending the service life of the retired batteries, and reducing safety hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0032] Figure 1 It is a schematic diagram of the structure of the switching control circuit of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below:

[0034] The present invention provides a charge and discharge control and early warning method for a retired battery module of a series structure, comprising a plurality of retired batteries, a switching control circuit and a control unit;

[0035] The switching control circuit includes a series electronic switch group and a charge and discharge electronic switch group;

[0036] The series electronic switch group includes m-1 electronic switches and is respectively arranged between the positive electrodes and negative electrodes of adjacent retired batteries and connects the adjacent retired batteries in series;

[0037] The charging and discharging electronic switch group includes a plurality of electronic switches, the positive electrode of each retired battery is connected to the charging DC bus through an electronic switch, the negative electrode of the retired battery at the end of the series connection is connected to the negative electrode of the charging output port through an electronic switch, and the charging DC bus is connected to the positive electrode of the charging output port through the charging master switch QZ1; the charging DC bus is connected to the negative electrode of the back-end circuit through an electronic switch;

[0038] The positive electrode of each retired battery is connected to the discharge DC bus through an electronic switch, and the discharge DC bus is connected to the positive electrode of the back-end circuit through the discharge master switch QZ2. The negative electrode of the retired battery at the end of the series connection is connected to the negative electrode of the back-end circuit through an electronic switch; the discharge DC bus is connected to the negative electrode of the charging output port through an electronic switch;

[0039] The control input end of the electronic switch of the series electronic switch group and the charge-discharge electronic switch group is connected to the control unit, and the control unit controls the conduction and disconnection of each electronic switch according to the charge state and voltage of the retired battery, thereby realizing the charging and discharging of the retired battery, and the control unit alarms according to the charge state and voltage of the retired battery. Among them, the back-end circuit can be an electrical device, or a DC-DC conversion circuit, etc., wherein the control unit adopts an existing controller. For example: STM32 series single-chip microcomputer. Through the above method, the retired batteries are connected in series by switching the control circuit, and the retired batteries in series are sequentially charged based on the charge state and voltage of the retired batteries during the charging and discharging process, and the retired batteries with low charge are made to exit the discharge during the discharge, thereby preventing the occurrence of charge and discharge imbalance, avoiding irreversible damage to the retired batteries, extending the service life of the retired batteries, and reducing safety hazards.

[0040] like Figure 1 As shown: Figure 1 The dotted lines in the figure indicate that the middle battery and the corresponding electronic switch are omitted. Q1 to Qm-1 represent series electronic switches used to connect retired battery modules in series, while QC1-QCn+1 and QD1-QDn+1 represent charging and discharging electronic switches, and BAT represents retired batteries.

[0041] In this embodiment, the electronic switch is an NMOS tube; because after the NMOS tube is turned on, its current has bidirectionality between the gate and source of the NMOS tube, that is, it can flow from the drain to the source and from the source to the drain, so that the loop during switching control can be ensured to be a complete loop, and the NMOS tube has a faster response speed, strong impact resistance and good stability.

[0042] In this embodiment, the control unit controls the switching control circuit to operate so that the retired battery enters the charging state according to the following method:

[0043] SA1. The control unit obtains the status information of each retired battery, the status information includes the current state of charge SOC and voltage of each retired battery module; and the control unit controls the main discharge switch QZ2 to always be in the off state

[0044] SA2. The control unit calculates the difference in the state of charge SOC of any two retired batteries and determines whether the difference in the state of charge SOC of any two retired batteries is less than a set threshold value. If so, the process proceeds to step SA5, and if not, the process proceeds to step SA3;

[0045] SA3. The control unit sorts the retired batteries according to the state of charge SOC from small to large, and the control unit determines the charging priority of each retired battery, the priority being that the smaller the state of charge SOC, the higher the charging priority;

[0046] SA4. The control unit first controls the electronic switch corresponding to the retired battery with the smallest state of charge SOC to turn on and the retired battery enters the charging state, and obtains the battery voltage of the retired battery module. When the voltage of the retired battery module with the smallest state of charge SOC reaches the battery voltage with the second smallest state of charge SOC among the retired batteries, the control unit controls the electronic switch corresponding to the retired battery module with the second smallest state of charge SOC to turn on, and so on, until all retired battery modules enter the charging state.

[0047] SA5. The control unit controls the electronic switches corresponding to each retired battery and the main charging switch QZ1 to enter the on state, and each retired battery enters the charging state. Control the corresponding electronic switch to be turned on. When charging, Qz2 and QCn+1 must be turned off. Assuming that BAT1 is charged first, then at this time, Qz1, QC2 and QC1 are turned on, and the other electronic switches are turned off. When BAT1 is charged to a certain extent, assuming that BATm should be charged, then at this time, QZ1, QCn, QDn-1, QD2, and QC1 are turned on, and the other electronic devices are turned off. Assuming that BATm needs to be charged, then at this time, QZ1, QCn, QDn-1, and QDn+1 are turned on, and all other electronic switches are turned off, thereby completing the charging. Of course, other combinations are analogous to the above examples. In actual control, when the retired battery module is determined and the structure of the switching control circuit is also determined, the corresponding conduction control table is formulated. As long as the control unit determines the charging order according to the above steps, it directly calls the serial number of the turned-on electronic switch in the conduction control table of the corresponding electronic switch to achieve charging control. Of course, if sorting is not required, the control unit controls the electronic switches corresponding to all retired battery modules to be turned on, and all retired battery modules are directly charged at the same time, that is, Qz1, Q1-Qm-1, and QC1 are turned on, and the remaining electronic switches are all turned off; for QCn+1, it is always turned off during charging, and when discharging, as long as BAT1 at the end of the series connection participates in the discharge, QCn+1 remains turned off, otherwise it remains turned on and QD1 is turned off; for QDn+1, the situation is the opposite. When discharging, it is always turned off, and when charging, as long as BAT1 participates in the charging, it remains turned off, otherwise it remains turned on and QC1 remains turned off. Based on the above, during the charging process, it is determined whether each retired battery is charged sequentially or simultaneously according to the SOC state, thereby avoiding charging imbalance.

[0048] In this embodiment, the control unit switches the control circuit to operate in the following manner to make the retired battery enter the discharge state:

[0049] SB1. The control unit obtains the state of charge SOC and voltage of each retired battery at the initial discharge, and the control unit controls the charging main switch QZ1 to always be in the off state;

[0050] SB2. The control unit controls all retired batteries to enter the discharge state. After the set discharge time, the control unit obtains the state of charge (SOC) and voltage of each retired battery module again. When the difference between the current state of charge (SOC) value of any retired battery and the average state of charge (SOC) value of all retired batteries at the current moment is greater than the set value, or when the difference between the current voltage value of any retired battery and the average voltage value of all retired batteries is greater than the set value, the control unit controls the electronic switch corresponding to the current retired battery to turn off, and the electronic switches corresponding to other retired batteries to turn on and be in the discharge state.

[0051] SB3. Return to step S2 until the set discharge time is reached or the power provided by the remaining retired battery modules cannot meet the needs of electrical devices. Through the above method, during the discharge process, it is prevented that the retired battery has a low charge state after being discharged for a period of time, and continues to discharge to cause discharge imbalance, causing the retired battery to be over-discharged, thereby avoiding the consequences of over-discharge.

[0052] During the initial discharge, QZ2, Q1-Qm-1, and QD1 are all turned on, and the rest are all turned off. All batteries enter the discharge state. After a certain period of time, assuming that BAT1 reaches the stop discharge state mentioned above first, then at this time, QD1 and Q1 enter the cut-off state, while QCn+1 and QC3, which were originally turned off, enter the conduction state, and the rest of the electronic switches remain turned off. At this time, after BAT1 exits, the overall output voltage will decrease. At this time, the control unit also needs to adjust the duty cycle of the PWM signal according to the current output voltage, so that the DC-DC maintains the original output; when the voltage input to the DC-DC conversion circuit still cannot meet the power demand after conversion, the overall discharge is stopped. Of course, other combinations are analogous to the above examples. Like charging, in actual control, when the retired battery module is determined, the structure of the switching control circuit is also determined, and the corresponding conduction control table is formulated. As long as the control unit determines the exited battery according to the above steps, it directly calls the serial number of the turned-on electronic switch in the conduction control table of the corresponding electronic switch, and discharge control can be achieved.

[0053] In this embodiment, the control unit generates an alarm according to the state of charge and voltage of the retired battery, specifically including:

[0054] The control unit calculates the state of charge consistency and voltage consistency of the retired battery according to the state of charge SOC and voltage at the beginning of the discharge of the retired battery and the state of charge SOC and voltage after the set discharge time, where the state of charge consistency is:

[0055] Among them, CON SOC is the charge state consistency, η SOC is the rate of change of state of charge, is the average rate of change of state of charge of all retired battery modules, SOC0 is the state of charge value of the retired battery module at the initial discharge time after charging, and SOC1 is the state of charge value of the retired battery module after the set discharge time;

[0056] The voltage consistency is:

[0057]

[0058] Among them: CON V is the voltage consistency, η V is the voltage change rate, is the average voltage change rate of all retired battery modules, V0 is the voltage value of the retired battery module at the initial discharge time after charging, and V1 is the voltage value of the retired battery module after the set discharge time;

[0059] When the state of charge consistency value of any retired battery module is greater than the set value or the voltage consistency value is greater than the set value during N consecutive discharges, the control unit will issue a fault alarm through the alarm connected to it. In fact, in practice, it is normal that the state of charge consistency and voltage consistency do not meet the conditions due to a certain discharge imbalance. If the above phenomenon occurs after N consecutive discharges, maintenance is required, such as replacing the retired battery module to avoid safety hazards. This N times is generally set at 3 times.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A charge and discharge control and early warning method for retired battery modules in series structure, characterized in that: including a plurality of retired batteries, a switching control circuit and a control unit; The switching control circuit includes a series electronic switch group and a charge and discharge electronic switch group; The series electronic switch group includes m-1 electronic switches and is respectively arranged between the positive electrodes and negative electrodes of adjacent retired batteries and connects the adjacent retired batteries in series; The charging and discharging electronic switch group includes a plurality of electronic switches, the positive electrode of each retired battery is connected to the charging DC bus through an electronic switch, the negative electrode of the retired battery at the end of the series connection is connected to the negative electrode of the charging output port through an electronic switch, and the charging DC bus is connected to the positive electrode of the charging output port through the charging master switch QZ1; the charging DC bus is connected to the negative electrode of the back-end circuit through an electronic switch; The positive electrode of each retired battery is connected to the discharge DC bus through an electronic switch, and the discharge DC bus is connected to the positive electrode of the back-end circuit through the discharge master switch QZ2. The negative electrode of the retired battery at the end of the series connection is connected to the negative electrode of the back-end circuit through an electronic switch; the discharge DC bus is connected to the negative electrode of the charging output port through an electronic switch; The control input ends of the electronic switches of the series electronic switch group and the charge-discharge electronic switch group are connected to a control unit. The control unit controls the on and off of each electronic switch according to the charge state and voltage of the retired battery, thereby realizing the charging and discharging of the retired battery, and the control unit issues an alarm according to the charge state and voltage of the retired battery.

2. According to claim 1, the charge and discharge control and early warning method for retired battery modules of series structure is characterized by: The electronic switch is an NMOS tube.

3. According to claim 1, the charge and discharge control and early warning method for retired battery modules of series structure is characterized by: The control unit controls the switching control circuit to make the retired battery enter the charging state according to the following method: SA1. The control unit obtains the status information of each retired battery, the status information includes the current state of charge SOC and voltage of each retired battery module; and the control unit controls the main discharge switch QZ2 to always be in the off state SA2. The control unit calculates the difference in the state of charge SOC of any two retired batteries and determines whether the difference in the state of charge SOC of any two retired batteries is less than a set threshold value. If so, the process proceeds to step SA5, and if not, the process proceeds to step SA3; SA3. The control unit sorts the retired batteries according to the state of charge SOC from small to large, and the control unit determines the charging priority of each retired battery, the priority being that the smaller the state of charge SOC, the higher the charging priority; SA4. The control unit first controls the electronic switch corresponding to the retired battery with the smallest state of charge SOC to turn on and the retired battery enters the charging state, and obtains the battery voltage of the retired battery module. When the voltage of the retired battery module with the smallest state of charge SOC reaches the battery voltage with the second smallest state of charge SOC among the retired batteries, the control unit controls the electronic switch corresponding to the retired battery module with the second smallest state of charge SOC to turn on, and so on, until all retired battery modules enter the charging state. SA5. The control unit controls the electronic switches corresponding to each retired battery and the main charging switch QZ1 to enter the on state, and each retired battery enters the charging state.

4. According to claim 1, the charge and discharge control and early warning method for retired battery modules of series structure is characterized by: The control unit switches the control circuit to operate in the following manner to make the retired battery enter a discharge state: SB1. The control unit obtains the state of charge SOC and voltage of each retired battery at the initial discharge, and the control unit controls the charging main switch QZ1 to always be in the off state; SB2. The control unit controls all retired batteries to enter the discharge state. After the set discharge time, the control unit obtains the state of charge (SOC) and voltage of each retired battery module again. When the difference between the current state of charge (SOC) value of any retired battery and the average state of charge (SOC) value of all retired batteries at the current moment is greater than the set value, or when the difference between the current voltage value of any retired battery and the average voltage value of all retired batteries is greater than the set value, the control unit controls the electronic switch corresponding to the current retired battery to turn off, and the electronic switches corresponding to other retired batteries to turn on and be in the discharge state. SB3. Return to step S2 until the set discharge time is reached or the power provided by the remaining retired battery modules cannot meet the needs of the electrical devices.

5. According to claim 1, the charge and discharge control and early warning method for retired battery modules of series structure is characterized by: The control unit issues an alarm based on the state of charge and voltage of the retired battery, including: The control unit calculates the state of charge consistency and voltage consistency of the retired battery according to the state of charge SOC and voltage at the beginning of the discharge of the retired battery and the state of charge SOC and voltage after the set discharge time, where the state of charge consistency is: Among them, CON SOC is the charge state consistency, η SOC is the rate of change of state of charge, is the average rate of change of state of charge of all retired battery modules, SOC0 is the state of charge value of the retired battery module at the initial discharge time after charging, and SOC1 is the state of charge value of the retired battery module after the set discharge time; The voltage consistency is: Among them: CON V is the voltage consistency, η V is the voltage change rate, is the average voltage change rate of all retired battery modules, V0 is the voltage value of the retired battery module at the initial discharge time after charging, and V1 is the voltage value of the retired battery module after the set discharge time; When any retired battery module has a charge state consistency value greater than a set value or a voltage consistency value greater than a set value during N consecutive discharges, the control unit issues a fault alarm through the alarm connected thereto.

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