CN114043901A - Protection method for lithium battery and lithium battery - Google Patents
Protection method for lithium battery and lithium battery Download PDFInfo
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- CN114043901A CN114043901A CN202111322351.0A CN202111322351A CN114043901A CN 114043901 A CN114043901 A CN 114043901A CN 202111322351 A CN202111322351 A CN 202111322351A CN 114043901 A CN114043901 A CN 114043901A
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000012544 monitoring process Methods 0.000 claims abstract description 41
- 230000002159 abnormal effect Effects 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims description 67
- 238000007599 discharging Methods 0.000 claims description 60
- 238000012937 correction Methods 0.000 claims description 36
- 238000004891 communication Methods 0.000 claims description 13
- 239000000178 monomer Substances 0.000 claims description 7
- 238000005070 sampling Methods 0.000 claims description 6
- 230000007547 defect Effects 0.000 abstract description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 5
- 239000012528 membrane Substances 0.000 description 4
- 238000001514 detection method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/12—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries responding to state of charge [SoC]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
- B60L3/0023—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
- B60L3/0046—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train relating to electric energy storage systems, e.g. batteries or capacitors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/40—Drive Train control parameters
- B60L2240/54—Drive Train control parameters related to batteries
- B60L2240/545—Temperature
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/40—Drive Train control parameters
- B60L2240/54—Drive Train control parameters related to batteries
- B60L2240/547—Voltage
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Secondary Cells (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
A protection method for a lithium battery and a lithium battery, comprising: the sub-monitoring system detects a state value of each independent battery pack, wherein the state value comprises battery cell voltage, battery cell temperature and current data of the battery pack during working, and meanwhile, the sub-control system sends the data to the main control system; calculating a protection threshold value of the abnormal state of the battery according to the battery state data received and collected by the sub-control system; establishing a voltage U protection condition according to the calculated protection threshold value; and establishing a temperature T protection condition according to the calculated protection threshold value. The invention overcomes the defects of the prior art, and ensures the real-time performance and the effectiveness of the protection threshold value by adopting the protection threshold value calculation scheme. And the fault judgment triggering calculation scheme is adopted, so that the stability of system operation is ensured, and misjudgment caused by external interference is avoided.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a protection method for a lithium battery and the lithium battery.
Background
The power source of the industrial vehicle is 'trending' in the global scope when the traditional energy is transformed to the new energy, and the electric industrial vehicle in China in the future will take the market leading position from the increasing speed of the new energy forklift in recent years. Meanwhile, as an important branch of industrial vehicles, lithium batteries of power supplies of the airport tractors can obtain new opportunities. The power supply vehicle of the airplane is a very important airport special vehicle. With the great improvement of the performance of the lithium battery, the application range is expanded from the civil consumption field to the aerospace field.
In order to build green airports, the use of airport-related equipment in new energy is enhanced, and the most important is to realize the full electric operation of airport ground vehicles. The special lithium iron phosphate battery of airport tractor brings cleanness, green, environmental protection, wisdom into airport design, and the lithium iron phosphate battery has huge advantage in the aspect of good performance, fabulous cycle life, quick charge, low cost etc. when high efficiency is exported, high temperature, can satisfy the high requirement of power battery system application to safety function such as electric, machinery, heat, electromagnetic compatibility, environment. The method is characterized in that a special lithium iron phosphate battery is customized and developed for airport equipment, complete matching is realized, and 'oil-to-electricity' of airport ground vehicles is promoted.
Due to the complex airport use environment, compared with the use condition of the traditional industrial vehicle, the reliability of the lithium iron phosphate battery special for the airport tractor is higher. In short, when a certain electricity-saving core monomer of the lithium battery breaks down, the system can be positioned in time, and meanwhile, a part of battery string groups can be cut off actively without influencing the normal work of other battery packs, so that the airport tractor can be ensured to be used continuously.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a protection method for a lithium battery and the lithium battery, which overcome the defects of the prior art, not only can accurately position a fault source of the lithium battery, but also can put the use reliability of a battery pack to the first place, and can cut off part of battery loops while accurately positioning the fault source, thereby ensuring the safety of a system.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a protection method for a lithium battery includes the following steps:
step S1: the sub-monitoring system detects a state value of each independent battery pack, wherein the state value comprises battery cell voltage, battery cell temperature and current data of the battery pack during working, and meanwhile, the sub-control system sends the data to the main control system;
step S2: according to each single voltage value U of the sub-battery packCELLCalculating the average monomer voltage value U of the sub-battery packAVG(ii) a According to the temperature value T of each single body of the sub-battery packCELLElectronic calculatorAverage monomer temperature value T of pool bagAVG；
Step S3: calculating a protection threshold value of the abnormal state of the battery according to the battery state data received and collected by the sub-control system;
step S4: establishing a voltage U protection condition according to the calculated protection threshold value;
step S5: and establishing a temperature T protection condition according to the calculated protection threshold value.
Preferably, the step S3 of calculating the protection threshold of the abnormal state of the battery specifically includes:
voltage protection threshold function U:
U＝Up*(1+Ua+Ub)
wherein U ispA basic threshold value for cell voltage protection;
wherein U isa＝(UCELL/UAVG-1) × a, which represents the correction of the voltage protection threshold value under the condition of different cell average voltages, wherein when the voltage value of the battery pack has small discreteness, the voltage protection threshold value correction value is reduced, and when the discreteness is increased, the protection threshold value correction value is increased, and a is the multiplication value of the correction coefficient;
wherein U isb＝(IpB) represents the correction of the protection threshold in the case of different discharge currents, I)pThe correction value of the voltage protection threshold is a current basic threshold during the voltage protection of the battery cell, when the discharge current is closer to the current basic threshold, the correction value of the voltage protection threshold is reduced, when the discharge current is farther away from the current basic threshold, the correction value of the voltage protection threshold is increased, and b is a correction coefficient multiplied value;
temperature protection threshold function T:
T＝Tp*(1+Ta)
wherein T ispBasic threshold value for battery core temperature protection
Wherein T isa＝(TCELL/TAVG-1) × c, which represents the correction of the temperature protection threshold value under the condition of different average cell temperatures, when the dispersion of the temperature value of the battery pack is not large, the correction value of the temperature protection threshold value is reduced, when the dispersion is increased, the correction value of the temperature protection threshold value is increased, and c is a correction systemA number times the value.
Preferably, the establishing of the voltage U protection condition in step S4 is specifically:
wherein t is the unit time interval of the lowest sampling period;
wherein U ismaxAnd UminCalculating an upper limit protection threshold value and a lower limit protection threshold value for the voltage protection threshold value function U;
wherein U (k) is the accumulated value of the cell voltage exceeding the upper threshold value in unit time, U (n) is the accumulated value of the cell voltage below the lower threshold value in unit time, and when the accumulated value of U (k) is greater than the protection accumulated threshold value U (k) in unit time TmaxThe system will trigger the over-voltage protection, and the same U (n) accumulated value is larger than the protection accumulated threshold value U (n) in the unit time TminThe system will trigger an under voltage protection.
Preferably, the establishing of the temperature T protection condition in step S5 is specifically:
wherein t is the unit time interval of the lowest sampling period;
wherein T ismaxAnd TminCalculating an upper limit protection threshold value and a lower limit protection threshold value for the temperature protection threshold value function T;
wherein T (k) is an accumulated value of the cell temperature exceeding an upper threshold value in unit time, T (N) is an accumulated value of the cell temperature below a lower threshold value in unit time, and when the accumulated value of T (k) is greater than a protection accumulated threshold value T (k) in unit time N)maxThe system will trigger the over-voltage protection, when the accumulated value of T (N) is larger than the protection accumulated threshold value T (N) in the same unit time NminThe system will trigger an under voltage protection.
The invention also discloses a lithium battery applied to the protection method, which comprises the following steps: the system comprises at least two sub-battery packs and a main monitoring system, wherein the sub-battery packs are connected in parallel; each sub-battery pack comprises a sub-monitoring system, a battery pack and a control unit, and the sub-monitoring system, the battery pack and the control unit operate independently; the word monitoring system is used for detecting the current, the temperature and the voltage of the battery pack corresponding to the word monitoring system, and the control unit is used for controlling the current on-off of the battery pack corresponding to the word monitoring system and external equipment parts; the main monitoring system is in communication connection with the sub-monitoring systems;
the positive output end and the negative output end of the sub-battery pack are respectively connected in parallel to form a discharging positive electrode and a discharging negative electrode; the positive pole that discharges, the negative pole that discharges appear in pairs and can have a plurality ofly, still parallelly mounted has first discharge current sensor, second discharge current sensor between the positive pole that discharges, the negative pole that discharges, first discharge current sensor, second discharge current sensor are used for surveying the current when the positive pole that discharges, the negative pole that discharges outwards discharges, and with the main monitored control system BMS of probing result input.
Preferably, a first discharging relay and a second discharging relay are respectively connected in series on a line of each discharging anode, and the first discharging relay and the second discharging relay are respectively used for controlling the on-off of the current of the circuit connected in series with the first discharging relay and the second discharging relay, so that the on-off of the current released by each discharging anode is controlled.
Preferably, the positive discharging line and the negative discharging line are respectively and electrically connected with the positive charging line and the negative charging line, the positive charging line is sequentially connected with a charging fuse and a charging relay in series, and the charging fuse plays a role in overload fusing; the charging relay is used for controlling the on-off of the current of the charging anode circuit, and is in a closed state in an initial state; and the control end of the charging relay is in communication connection with the signal end of the main monitoring system.
Preferably, the sub-battery pack comprises a battery pack, a battery management unit and a current sensor, wherein the battery management unit is used for detecting the voltage and the temperature of the battery pack; a current sensor is connected in series on a power supply line of the battery pack and is used for detecting the current supplied by the battery pack to the outside and transmitting a signal to a battery management unit, an output relay is connected in series on the line supplied by the battery pack to the outside, and the output relay is in a closed state in an initial state and is used for cutting off a circuit for outputting current to the outside of the battery pack; the control end of the output relay is in communication connection with the signal end of the battery management unit; the battery management unit collects and analyzes the running state of the battery pack in real time and sends the state data to the main control system.
Preferably, a fuse is further connected in series on a line for supplying power to the battery pack, and the fuse is blown in an overload mode.
Preferably, a heating film is installed in the sub-battery pack, and heat is released after the heating film is electrified; the heating film is powered by the battery pack, a power supply circuit of the heating film is connected with a heating film relay in series, the heating film relay is used for controlling the on-off of the current of the heating film, and the heating film relay is in an off state in an initial state; the control end of the heating film relay is in communication connection with the signal end of the battery management;
the current access end of the heating film relay is also electrically connected with the output end of the first discharging relay and the output end of the second discharging relay respectively, so that the heating film relay can be powered when any one of the output end of the first discharging relay and the second discharging relay is closed;
the positive electrode of the heating film is electrically connected with the output end of the heating relay, and the input end of the heating relay is directly or indirectly electrically connected with the charging positive electrode; the access end of the heating relay is connected with the heating fuse in series and then is electrically connected with the charging anode.
The invention provides a protection method for a lithium battery and the lithium battery. The method has the following beneficial effects: by adopting the protection threshold value calculation scheme, the real-time performance and the effectiveness of the protection threshold value are ensured. And the fault judgment triggering calculation scheme is adopted, so that the stability of system operation is ensured, and misjudgment caused by external interference is avoided.
And the independent BMU is adopted to collect and control each sub-battery pack, and the independent controllable relay is used for cutting off the sub-battery pack, if the single sub-battery pack is abnormal, the sub-battery pack can be cut off independently, and the other sub-battery packs can still continue to operate.
The heating system under the battery working mode of adopting independent BMU control can independently carry out temperature judgement and heating, guarantees the temperature maintenance of battery package in the use, guarantees the life of battery. The invention adopts different heating control strategies under the charging mode and the discharging mode, thereby fully ensuring the reliability and the efficiency of battery heating. And a double-current sensor mode is adopted in a discharge loop, so that the current collection precision and the overcurrent capacity of electric connection are ensured, and an independent current collection mode is respectively adopted in each sub-battery pack, so that the system can be ensured to accurately collect the running current of each battery pack, and the system safety is ensured.
Drawings
In order to more clearly illustrate the present invention or the prior art solutions, the drawings that are needed in the description of the prior art will be briefly described below.
FIG. 1 is a system framework diagram of the present invention.
Fig. 2 is a schematic diagram of a battery architecture according to the present invention.
Fig. 3 is a schematic diagram of a sub-battery pack system according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings.
Example one
A protection method for a lithium battery includes the following steps:
step S1: the sub-monitoring system detects a state value of each independent battery pack, wherein the state value comprises battery cell voltage, battery cell temperature and current data of the battery pack during working, and meanwhile, the sub-control system sends the data to the main control system; the battery pack comprises a battery pack, a battery core, a battery pack and a battery pack, wherein the battery core voltage value is a real-time data acquisition value, the battery core temperature is a real-time data acquisition value, and the battery pack discharge current value is a real-time data acquisition value.
Step S2: according to each single voltage value U of the sub-battery packCELLCalculating the average monomer voltage value U of the sub-battery packAVG(ii) a According to the temperature value T of each single body of the sub-battery packCELLCalculating the average monomer temperature value T of the sub-battery packAVG；
Step S3: calculating a protection threshold value of the abnormal state of the battery according to the battery state data received and collected by the sub-control system;
step S4: establishing a voltage U protection condition according to the calculated protection threshold value;
step S5: and establishing a temperature T protection condition according to the calculated protection threshold value.
The sub-control system automatically cuts off the output of the sub-battery pack control unit according to the operation state of the sub-battery pack under the condition that the battery pack is abnormal or has a fault, so that the sub-battery pack is in an open circuit state, and the safety of the battery pack is fully ensured on the premise of not influencing the operation of the whole battery pack.
Specifically, the step S3 of calculating the protection threshold of the abnormal state of the battery specifically includes:
voltage protection threshold function U:
U＝Up*(1+Ua+Ub)
wherein U ispA basic threshold value for cell voltage protection;
wherein U isa＝(UCELL/UAVG-1) × a, which represents the correction of the voltage protection threshold value under the condition of different cell average voltages, wherein when the voltage value of the battery pack has small discreteness, the voltage protection threshold value correction value is reduced, and when the discreteness is increased, the protection threshold value correction value is increased, and a is the multiplication value of the correction coefficient;
wherein U isb＝(IpB) represents the correction of the protection threshold in the case of different discharge currents, I)pFor the current basic threshold value of the cell voltage protection, when the discharge current is closer to the current basic threshold value, the corrected value of the voltage protection threshold value is reducedWhen the discharge current is farther away from the current basic threshold, the corrected value of the voltage protection threshold is increased, and b is the multiplied value of the correction coefficient;
temperature protection threshold function T:
T＝Tp*(1+Ta)
wherein T ispBasic threshold value for battery core temperature protection
Wherein T isa＝(TCELL/TAVGAnd-1) × c, which represents the correction of the temperature protection threshold value under the condition of different average cell temperatures, wherein when the discreteness of the temperature value of the battery pack is not large, the correction value of the temperature protection threshold value is reduced, when the discreteness is increased, the correction value of the temperature protection threshold value is increased, and c is the multiplication value of the correction coefficient.
Specifically, the establishing voltage U protection condition in step S4 is specifically:
wherein t is the unit time interval of the lowest sampling period;
wherein U ismaxAnd UminCalculating an upper limit protection threshold value and a lower limit protection threshold value for the voltage protection threshold value function U;
wherein U (k) is the accumulated value of the cell voltage exceeding the upper threshold value in unit time, U (n) is the accumulated value of the cell voltage below the lower threshold value in unit time, and when the accumulated value of U (k) is greater than the protection accumulated threshold value U (k) in unit time TmaxThe system will trigger the over-voltage protection, and the same U (n) accumulated value is larger than the protection accumulated threshold value U (n) in the unit time TminThe system will trigger an under voltage protection.
Specifically, the establishing of the temperature T protection condition in step S5 specifically includes:
wherein t is the unit time interval of the lowest sampling period;
wherein T ismaxAnd TminCalculating an upper limit protection threshold value and a lower limit protection threshold value for the temperature protection threshold value function T;
wherein T (k) is an accumulated value of the cell temperature exceeding an upper threshold value in unit time, T (N) is an accumulated value of the cell temperature below a lower threshold value in unit time, and when the accumulated value of T (k) is greater than a protection accumulated threshold value T (k) in unit time N)maxThe system will trigger the over-voltage protection, when the accumulated value of T (N) is larger than the protection accumulated threshold value T (N) in the same unit time NminThe system will trigger an under voltage protection.
In the practical application of the embodiment, an 80V912Ah lithium iron phosphate battery is adopted, and the battery pack is formed by combining 4 independent 80V228Ah sub-battery packs in parallel. Actually simulating fault working condition generation: when 1 independent sub-battery pack is abnormal, the control system where the independent sub-battery pack is located actively cuts off the control unit corresponding to the output, the rest 3 sub-batteries continue to work, the target tractor is smoothly moved to the designated area, and the running and the use of the vehicle are not influenced in the whole process. Compared with the traditional battery pack scheme, the whole battery pack output is switched when a fault occurs, and the reliability of the vehicle in the using process can be greatly improved by adopting the new system architecture scheme.
The protection method adopts the protection threshold value calculation scheme, so that the real-time performance and the effectiveness of the protection threshold value are ensured. And the fault judgment triggering calculation scheme is adopted, so that the stability of system operation is ensured, and misjudgment caused by external interference is avoided.
Example two
As shown in fig. 1 to 3, the present invention also discloses a lithium battery applied to the protection method, including: the system comprises a plurality of sub-battery packs with the same voltage and a main monitoring system BMS, wherein the sub-battery packs are connected in parallel; each sub-battery pack comprises a sub-monitoring system, a battery pack and a control unit, and the sub-monitoring system, the battery pack and the control unit operate independently; the word monitoring system is used for detecting the current, the temperature and the voltage of the battery pack corresponding to the word monitoring system, and the control unit is used for controlling the current on-off of the battery pack corresponding to the word monitoring system and external equipment parts;
the main monitoring system BMS is in communication connection with the sub-monitoring systems; the sub monitoring system and the main monitoring system BMS form a complete battery control construction; if the sub monitoring system finds that the corresponding detected battery pack is abnormal, the corresponding output control unit is cut off and the main monitoring system is informed; after the output control unit of the independent battery pack is cut off, the rest battery packs can continue to work, and the use safety and continuity of the equipment are ensured.
In this embodiment, the slave battery pack system has a certain logic control autonomy, and when the occurrence of a fault condition is detected, the battery management unit BMU actively turns off the output relay K1 to cut off the output of the slave battery pack. Meanwhile, the sub-battery pack system is provided with an independent heating control system, the battery management unit BMU detects and calculates according to real-time temperature, and when the sub-battery pack system has a heating requirement, the heating film relay K2 is closed to heat the sub-battery pack system.
Referring to fig. 2, the whole battery comprises 4 sub-battery PACKs PACK01-04, and the positive output end and the negative output end of the four sub-battery PACKs PACK01-04 are respectively connected in parallel to form a discharging positive electrode and a discharging negative electrode; the discharging positive electrodes and the discharging negative electrodes are in pairs and can be multiple, a first discharging relay K5 and a second discharging relay K6 are respectively connected in series on a circuit of each discharging positive electrode, and the first discharging relay K5 and the second discharging relay K6 are respectively used for controlling the on-off of current of a circuit connected in series with the first discharging relay K5 and the second discharging relay K6, so that the on-off of current released outwards by each discharging positive electrode is controlled.
The circuit of the discharging anode and the circuit of the discharging cathode are also electrically connected with the circuit of the charging anode and the circuit of the charging cathode respectively, a charging fuse F2 and a charging relay K3 are also sequentially connected in series on the circuit of the charging anode, and the charging fuse F2 plays a role in overload fusing; the charging relay K3 is used for controlling the on-off of the current of the charging anode circuit, and the initial state of the charging relay K3 is a closed state; the control end of the charging relay K3 is in communication connection with the signal end of the main monitoring system BSM, so that the on-off of the charging relay K3 can be controlled through the main monitoring system BSM, the on-off of the charging current of the sub-battery pack is controlled, and overcharging is prevented.
A first discharging current sensor S2 and a second discharging current sensor S3 are further installed between the discharging anode and the discharging cathode in parallel, the first discharging current sensor S2 and the second discharging current sensor S3 are used for detecting currents when the discharging anode and the discharging cathode discharge outwards, and detection results are input into a main monitoring system BMS; the main monitoring system BMS adds the detection results of the first discharging current sensor S2 and the second discharging current sensor S3 to obtain an overall discharging current value, which is mainly used to improve the detection accuracy; and then, the discharge current of each sub-battery pack is combined, so that the current loss of the whole line and the battery pack with abnormal current are judged.
Referring to fig. 3, the sub-battery pack includes a battery pack CELL, a battery management unit BMU for detecting a voltage and a temperature of the battery pack CELL, and a current sensor S1; a current sensor S1 is also connected in series on a power supply line of the battery pack CELL, the current sensor S1 is used for detecting the current of the battery pack CELL for supplying power outwards and transmitting a signal to a battery management unit BMU, an output relay K1 and a fuse F1 are also connected in series on the circuit of the battery pack CELL for supplying power outwards in sequence, and the output relay K1 is in a closed state in an initial state and is used for cutting off the circuit of the battery pack CELL for outputting current outwards; the fuse F1 is used for preventing current overload, and the fuse is fused when the current is overloaded, so that the battery pack CELL is protected; the control terminal of the output relay K1 is connected in communication with the signal terminal of the battery management unit BMU, so that the battery management unit BMU can control the on/off of the output relay K1. The battery management unit BMU collects and analyzes the running state of the battery pack CELL in real time and sends state data to the main control system BMS.
Preferably, a heating film R1 is installed in the sub-battery pack, and the heating film R1 releases heat after being electrified, so that the battery pack CELL and corresponding parts are heated, and the attenuation caused by the overcooling of the battery pack CELL is ensured. The heating film R1 is powered by a battery pack CELL, a power supply circuit of the heating film R1 is connected with a heating film relay K2 in series, the heating film relay K2 is used for controlling the on-off of the current of the heating film R1, and the heating film relay K2 is in an off state in an initial state; the control end of the heating film relay K2 is in communication connection with the signal end of the battery management unit BMU, so that the heating film relay K2 can be controlled to be opened and closed by the battery management unit BMU. When the battery pack heating device is used, once the temperature of the battery pack CELL is lower than a preset threshold value, the battery management unit BMU controls the heating film relay K2 to be closed, and the heating film R1 is electrified, so that the sub battery pack is heated, namely the battery pack CELL is heated, and the normal operation of the battery pack CELL is ensured.
Preferably, the current incoming end of the heating membrane relay is also respectively connected with the outgoing end of the first discharging relay K5 and the outgoing end of the second discharging relay K6, so that when any one of the outgoing end of the first discharging relay K5 and the second discharging relay K6 is closed, the heating membrane relay can be powered, and the current and the voltage output by the whole battery can be utilized to power the heating membrane, so that the heating membrane works.
More preferably, the positive electrode of the heating film is electrically connected with the terminal or the terminal of the heating film relay is electrically connected with the terminal of the heating relay K4, and the terminal of the heating relay K4 is electrically connected with the charging positive electrode after being connected with the heating fuse F3 in series. In the charging state, the heating relay K4 is closed to directly supply the heating film with the charging current to realize heating, mainly in order to keep the battery pack in a proper temperature range, thereby improving the charging efficiency. The heating fuse F3 is used for fusing when the current is overloaded, and plays a role in protection. The control terminal of the heating relay K4 is connected in communication with the signal terminal of the main monitoring system BMS, so that the closing of the heating relay K4 can be controlled by the main monitoring system BMS.
In actual use, the main monitoring system BMS may directly transmit a control command to the battery management unit BMU, thereby controlling the corresponding operation of the sub battery pack.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A protection method for a lithium battery is characterized by comprising the following steps:
step S1: the sub-monitoring system detects a state value of each independent battery pack, wherein the state value comprises battery cell voltage, battery cell temperature and current data of the battery pack during working, and meanwhile, the sub-control system sends the data to the main control system;
step S2: according to each single voltage value U of the sub-battery packCELLCalculating the average monomer voltage value U of the sub-battery packAVG(ii) a According to the temperature value T of each single body of the sub-battery packCELLCalculating the average monomer temperature value T of the sub-battery packAVG；
Step S3: calculating a protection threshold value of the abnormal state of the battery according to the battery state data received and collected by the sub-control system;
step S4: establishing a voltage U protection condition according to the calculated protection threshold value;
step S5: and establishing a temperature T protection condition according to the calculated protection threshold value.
2. The method according to claim 1, wherein the step of calculating the protection threshold for the abnormal state of the battery in step S3 specifically includes:
voltage protection threshold function U:
U＝Up*(1+Ua+Ub)
wherein U ispA basic threshold value for cell voltage protection;
wherein U isa＝(UCELL/UAVG-1) a, representing the correction of the voltage protection threshold for different average cell voltages, when the battery pack is chargedWhen the pressure value discreteness is not large, the voltage protection threshold value correction value is reduced, when the discreteness is increased, the protection threshold value correction value is increased, and a is a correction coefficient multiplied value;
wherein U isb＝(IpB) represents the correction of the protection threshold in the case of different discharge currents, I)pThe correction value of the voltage protection threshold is a current basic threshold during the voltage protection of the battery cell, when the discharge current is closer to the current basic threshold, the correction value of the voltage protection threshold is reduced, when the discharge current is farther away from the current basic threshold, the correction value of the voltage protection threshold is increased, and b is a correction coefficient multiplied value;
temperature protection threshold function T:
T＝Tp*(1+Ta)
wherein T ispBasic threshold value for battery core temperature protection
Wherein T isa＝(TCELL/TAVGAnd-1) × c, which represents the correction of the temperature protection threshold value under the condition of different average cell temperatures, wherein when the discreteness of the temperature value of the battery pack is not large, the correction value of the temperature protection threshold value is reduced, when the discreteness is increased, the correction value of the temperature protection threshold value is increased, and c is the multiplication value of the correction coefficient.
3. A method of protecting a lithium battery as claimed in claim 1, characterized in that: the establishing of the voltage U protection condition in step S4 specifically includes:
wherein t is the unit time interval of the lowest sampling period;
wherein U ismaxAnd UminCalculating an upper limit protection threshold value and a lower limit protection threshold value for the voltage protection threshold value function U;
wherein U (k) is the accumulated value of the cell voltage exceeding the upper limit threshold value in unit timeU (n) is the accumulated value of the cell voltage lower than the lower threshold value in unit time, and when the accumulated value of U (k) is greater than the protection accumulated threshold value U (k) in unit time TmaxThe system will trigger the over-voltage protection, and the same U (n) accumulated value is larger than the protection accumulated threshold value U (n) in the unit time TminThe system will trigger an under voltage protection.
4. A method of protecting a lithium battery as claimed in claim 1, characterized in that: the establishing of the temperature T protection condition in step S5 specifically includes:
wherein t is the unit time interval of the lowest sampling period;
wherein T ismaxAnd TminCalculating an upper limit protection threshold value and a lower limit protection threshold value for the temperature protection threshold value function T;
wherein T (k) is an accumulated value of the cell temperature exceeding an upper threshold value in unit time, T (N) is an accumulated value of the cell temperature below a lower threshold value in unit time, and when the accumulated value of T (k) is greater than a protection accumulated threshold value T (k) in unit time N)maxThe system will trigger the over-voltage protection, when the accumulated value of T (N) is larger than the protection accumulated threshold value T (N) in the same unit time NminThe system will trigger an under voltage protection.
5. A lithium battery to be used in the protection method according to any one of claims 1 to 4, characterized in that: the method comprises the following steps: the system comprises at least two sub-battery packs and a main monitoring system, wherein the sub-battery packs are connected in parallel; each sub-battery pack comprises a sub-monitoring system, a battery pack and a control unit, and the sub-monitoring system, the battery pack and the control unit operate independently; the word monitoring system is used for detecting the current, the temperature and the voltage of the battery pack corresponding to the word monitoring system, and the control unit is used for controlling the current on-off of the battery pack corresponding to the word monitoring system and external equipment parts; the main monitoring system is in communication connection with the sub-monitoring systems;
the positive output end and the negative output end of the sub-battery pack are respectively connected in parallel to form a discharging positive electrode and a discharging negative electrode; the positive pole that discharges, the negative pole that discharges appear in pairs and can have a plurality ofly, still parallelly mounted has first discharge current sensor, second discharge current sensor between the positive pole that discharges, the negative pole that discharges, first discharge current sensor, second discharge current sensor are used for surveying the current when the positive pole that discharges, the negative pole that discharges outwards discharges, and with the main monitored control system BMS of probing result input.
6. The method of claim 5, further comprising the step of: and a first discharging relay and a second discharging relay are respectively connected in series on the circuit of each discharging anode and are respectively used for controlling the current on-off of the circuit connected in series with the first discharging relay and the second discharging relay so as to control the on-off of the current released by each discharging anode outwards.
7. The method of claim 5, further comprising the step of: the circuit of the discharging anode and the circuit of the discharging cathode are respectively and electrically connected with the circuit of the charging anode and the circuit of the charging cathode, a charging fuse and a charging relay are sequentially connected in series on the circuit of the charging anode, and the charging fuse plays a role in overload fusing; the charging relay is used for controlling the on-off of the current of the charging anode circuit, and is in a closed state in an initial state; and the control end of the charging relay is in communication connection with the signal end of the main monitoring system.
8. The method of claim 5, further comprising the step of: the sub-battery pack comprises a battery pack, a battery management unit and a current sensor, wherein the battery management unit is used for detecting the voltage and the temperature of the battery pack; a current sensor is connected in series on a power supply line of the battery pack and is used for detecting the current supplied by the battery pack to the outside and transmitting a signal to a battery management unit, an output relay is connected in series on the line supplied by the battery pack to the outside, and the output relay is in a closed state in an initial state and is used for cutting off a circuit for outputting current to the outside of the battery pack; the control end of the output relay is in communication connection with the signal end of the battery management unit; the battery management unit collects and analyzes the running state of the battery pack in real time and sends the state data to the main control system.
9. A method of protecting a lithium battery as claimed in claim 8, characterized in that: and a fuse is also connected in series on a circuit for supplying power to the battery pack, and the fuse is fused in an overload manner.
10. A method of protecting a lithium battery as claimed in claim 8, characterized in that: a heating film is arranged in the sub-battery pack, and heat is released after the heating film is electrified; the heating film is powered by the battery pack, a power supply circuit of the heating film is connected with a heating film relay in series, the heating film relay is used for controlling the on-off of the current of the heating film, and the heating film relay is in an off state in an initial state; the control end of the heating film relay is in communication connection with the signal end of the battery management;
the current access end of the heating film relay is also electrically connected with the output end of the first discharging relay and the output end of the second discharging relay respectively, so that the heating film relay can be powered when any one of the output end of the first discharging relay and the second discharging relay is closed;
the positive electrode of the heating film is electrically connected with the output end of the heating relay, and the input end of the heating relay is directly or indirectly electrically connected with the charging positive electrode; the access end of the heating relay is connected with the heating fuse in series and then is electrically connected with the charging anode.
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