CN112072733A - Charging equalization system and method for liquid metal battery - Google Patents
Charging equalization system and method for liquid metal battery Download PDFInfo
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- CN112072733A CN112072733A CN202010884771.7A CN202010884771A CN112072733A CN 112072733 A CN112072733 A CN 112072733A CN 202010884771 A CN202010884771 A CN 202010884771A CN 112072733 A CN112072733 A CN 112072733A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4207—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells for several batteries or cells simultaneously or sequentially
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
- H01M10/441—Methods for charging or discharging for several batteries or cells simultaneously or sequentially
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0016—Circuits for equalisation of charge between batteries using shunting, discharge or bypass circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00302—Overcharge protection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00306—Overdischarge protection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/0031—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
- H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
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- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- General Chemical & Material Sciences (AREA)
- Microelectronics & Electronic Packaging (AREA)
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Abstract
The invention provides a charging equalization system and a charging equalization method for a liquid metal battery, which comprise the liquid metal battery, a passive equalization circuit and a battery monitoring system; the passive equalization circuit is characterized in that SiC nonlinear resistors are connected in parallel to the two ends of the positive electrode and the negative electrode of the liquid metal battery monomer and used for shunting the charging current of the liquid metal battery monomer after the voltage of the liquid metal battery monomer reaches a certain value and slowing down the charging rate of the liquid metal battery monomer; the battery monitoring system is used for measuring the voltage of the liquid metal monocell, determining the charge state of the battery according to the voltage of the battery, controlling the charge and discharge processes of the battery and realizing the protection of the battery equalization circuit and the battery. The invention has simple structure and high reliability, and can effectively carry out charge equalization and discharge protection aiming at the characteristics of the liquid metal battery.
Description
Technical Field
The invention belongs to the technical field of battery equalization, and particularly relates to a charge equalization system and method for a liquid metal battery.
Background
At present, a large-scale battery energy storage system is widely applied to the scenes of new energy grid connection, power grid peak-valley regulation and the like, and is an important component of an energy system. However, the existing energy storage modes such as lead-acid batteries and lithium ion batteries cannot meet the requirements of low cost, large capacity and long service life of large-scale energy storage, and are difficult to realize large-scale application. The liquid metal battery is a novel energy storage battery, and the characteristics of long service life and large capacity make the battery very suitable for being applied to a large-scale energy storage system. However, since the liquid metal battery cell has a low voltage and a charge cut-off voltage of only 1.2V, the battery cells are connected in series to be used in a group. Therefore, a new problem is caused simultaneously, namely that overcharge or overdischarge of some single cells is easily caused when the battery pack is charged and discharged in series, and further, the service life and the safety and reliability of the battery pack are damaged. Therefore, balancing measures are necessary to balance the cells of the battery pack.
The existing equalizing circuit mainly faces to the traditional battery, and because the voltage of a single battery of the traditional battery is generally 2V (lead-acid battery) or 3.7V (lithium battery), power electronic devices in the equalizing circuit can be normally switched on and off; in addition, the traditional batteries work at room temperature, so that the problem of high-temperature adaptability does not exist; meanwhile, as the manufacturing process of the batteries is stable, the difference between the batteries is small, and the equalizing current is not required to be very large. However, these are problems of liquid metal batteries, the working voltage of the liquid metal battery is about 1V, and most of power electronic devices are just in an amplification working state, so that the balanced power consumption of the devices is high, and the switching-on stability is poor; the liquid metal battery works at a high temperature of 500 ℃, so that the temperature is the environment temperature at which ordinary power electronic devices cannot work, and therefore the balancing circuit cannot be connected to the battery nearby; the battery manufacturing process causes the consistency of the battery to be larger than that of the traditional battery, and meanwhile, the difference of the charge state of the battery in the early stage of charging and discharging is difficult to observe, and the equalization cannot be carried out in advance, so that the requirements on the equalization time in the later stage of charging and discharging are short, and the requirements on the equalization current are large. In conclusion, the existing battery equalization circuit and system cannot meet the equalization requirements of low voltage, high temperature and large current of the liquid metal battery at all.
Disclosure of Invention
The invention aims to provide a charge equalization system and a charge equalization method for a liquid metal battery, which have the advantages of simple structure and high reliability and can effectively perform charge equalization and discharge protection aiming at the characteristics of the liquid metal battery.
The invention provides the following technical scheme:
a charge equalization system of a liquid metal battery comprises the liquid metal battery, a passive equalization circuit and a battery monitoring system;
the passive equalization circuit is characterized in that SiC nonlinear resistors are connected in parallel to the two ends of the positive electrode and the negative electrode of the liquid metal battery monomer and used for shunting the charging current of the liquid metal battery monomer after the voltage of the liquid metal battery monomer reaches a certain value and slowing down the charging rate of the liquid metal battery monomer;
the battery monitoring system is used for measuring the voltage of the liquid metal monocell, determining the charge state of the battery according to the voltage of the battery, controlling the charge and discharge processes of the battery and realizing the protection of the battery equalization circuit and the battery.
Preferably, the SiC nonlinear resistor is welded by high-temperature solder and packaged into a TO220 type two-terminal resistor with a radiating fin, the two-terminal resistor can work at 500 ℃, the resistor is in a constant-voltage conducting state when the applied voltage is higher than 1.3V at 500 ℃, the resistor is basically maintained in a cut-off state when the applied voltage is smaller than 1.1V, and the resistor is in a transition state from cut-off TO conduction in the middle of 1.1V TO 1.2V.
Preferably, the battery monitoring system adopts an isolation type single battery voltage detection circuit to detect the voltage of each battery in the liquid metal batteries, determines the charge state of the batteries in the charging process through voltage detection, ensures that the working time of the equalization circuit does not exceed the equalization time allowed by the SiC nonlinear resistor, determines the charge state of the batteries according to the voltage in the discharging process, and ensures that when the charge state of one battery in series connection is less than 0.1, the discharging of the whole battery group is stopped, and the overdischarge of the battery is avoided.
Preferably, the isolated single cell voltage detection circuit comprises a voltage acquisition circuit, a multi-way switch, a CPLD chip and an ARM chip; each single battery is provided with a voltage acquisition circuit, the voltage acquisition circuit comprises an optical coupling isolator, a subtracter and an inverter which are sequentially connected, and voltage information of each battery is input into an analog-to-digital converter of an electric ARM chip to carry out voltage measurement; eight I/O ports PF0-PF7 of the ARM chip determine address data, after the address data is decoded by the CPLD chip, an optical coupler isolator of the voltage acquisition circuit is driven and a multi-way switch is gated, so that only one path of voltage signal is transmitted to a PC0(ADC123_ IN10) port of the ARM chip for analog-to-digital conversion, the other paths of acquisition circuits are guaranteed not to work, and the influence on the voltage of the series main loop battery is reduced.
A charge equalization method of a liquid metal battery comprises the following steps:
the passive equalization is adopted to directly connect the nonlinear resistor of the high-temperature-resistant SiC material in parallel at two ends of each liquid metal battery at high temperature, and after the voltage of a single liquid metal battery reaches a certain value, the charging current of the liquid metal battery can be shunted, so that the charging rate of the liquid metal battery can be reduced;
the battery monitoring system is adopted to measure the voltage of the monocell, the state of charge of the battery is determined according to the voltage of the battery, the charging and discharging process of the battery is controlled, and the battery equalization circuit and the battery are protected.
Preferably, when the nonlinear resistance of the SiC material is at 500 ℃, the resistance value is rapidly reduced when the voltage of two ends is increased to 1.1V, so that partial charging current of the battery is shunted, the current flowing through the liquid metal battery is reduced, the charging rate of a battery monomer with higher capacity is reduced, and the purpose of automatic equalization is achieved.
Preferably, in the charging process, the battery monitoring system automatically measures the voltage and the charging current of each battery in the battery pack, calculates the charge state of the battery according to the voltage and the charging current of the single battery by using a standard charging charge state and voltage current curve, judges whether the equalizing circuit is started or not according to the voltage measurement data of the battery, determines whether the charging process of the battery pack is stopped or not according to the current value, and sends a charging stopping command to the battery charging and discharging system through a network; during discharging, the battery monitoring system automatically measures the voltage and the discharge current of each battery in the battery pack, calculates the charge state of the battery according to the voltage and the discharge current of a single battery by using a standard discharge charge state and voltage current curve, determines whether to stop the discharge process of the battery pack according to the charge state of the battery, and sends a discharge stopping command to the battery charge-discharge system through a network.
Preferably, the battery monitoring system firstly sets the positive and negative current and the numerical value to determine whether charging or discharging is carried out, then determines whether the stored voltage and SoC data need to be initialized, and then carries out data processing and calculates the SoC of the battery through the voltage data acquired by the sampling circuit in real time; if the charging is carried out, judging which single battery voltage in the battery pack exceeds 1.3V, starting the non-linear resistor equalization at the moment, starting timing, and disconnecting a power supply loop if the set time is exceeded, so as to avoid the resistor damage caused by overheating; and during discharging, if the SoC of a certain battery is calculated to be less than 0.1, the discharging loop is disconnected to avoid over-discharging of the battery.
The invention has the beneficial effects that: aiming at the special balance requirements of low working voltage, high environmental temperature and large balance current of the liquid metal battery, the high-temperature SiC nonlinear resistor is invented, and the voltage and current characteristics of the high-temperature SiC nonlinear resistor are utilized, so that the automatic balance of monocells in the battery pack at high temperature during charging is realized, and the problem of overcharging of the battery is avoided; through the battery detection system, the full observation of the battery charge state of the monocell under the charging and discharging is realized, the charging and discharging process is controlled through the actual calculation of the SoC state in the charging and discharging process, and the automatic equalization of the battery pack charging process and the battery protection in the discharging process are realized.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a diagram of the parallel connection of the passive equalization resistor and the battery according to the present invention;
FIG. 2 is a graph of the voltage across the SiC non-linear resistor of the present invention versus the current through the resistor;
FIG. 3 is a voltage acquisition circuit of the present invention;
FIG. 4 is a circuit diagram of a battery monitoring system of the present invention;
fig. 5 is a control flow chart of the battery monitoring system of the present invention.
Detailed Description
A charge equalization system of a liquid metal battery comprises the liquid metal battery, a passive equalization circuit and a battery monitoring system; the scheme adopts the passive equilibrium to use the nonlinear resistor of the SiC material which can resist high temperature and is directly connected in parallel at the two ends of each liquid metal battery at high temperature, and the nonlinear resistor is specially developed for the high temperature application and has the following special properties: the SiC material is a special material which can resist the high temperature of more than 700 ℃, the high temperature nonlinear resistor is prepared on a high temperature substrate material by utilizing the high temperature characteristic of the material through high temperature growth, in order TO lead out leads at two ends of the resistor, high temperature solder is adopted for welding, and finally the TO220 type two-end resistor with the radiating fin is packaged. The resistor can work at 500 ℃ and has the characteristic similar to a diode, and the resistor is in a constant-voltage on-state when an applied voltage is higher than 1.3V at 500 ℃ by adjusting the thickness of a growing material, while the resistor is basically maintained in an off-state when the applied voltage is less than 1.1V, and is in a transition state from the off-state to the on-state between 1.1V and 1.2V. The characteristic can ensure that the batteries connected in parallel do not exceed the upper limit voltage all the time when being charged, and can ensure that the batteries cannot be overcharged after each battery is connected in parallel. Meanwhile, a battery detection system is developed in the scheme, the system detects the voltage of each battery in the liquid metal battery through a special isolated single battery voltage detection circuit, determines the charge state of the battery in the charging process through voltage detection, ensures that the working time of an equalization circuit does not exceed the equalization time allowed by the nonlinear resistance of the SiC material, determines the charge state of the battery according to the voltage in the discharging process, ensures that when the charge state of one battery in series connection is less than 0.1, the whole battery stops discharging, ensures that the battery does not over-discharge, and improves the safety of the battery pack.
The specific process is as follows: in the passive equalization circuit, a nonlinear resistor made of high-temperature-resistant SiC material is connected in parallel between the positive electrode and the negative electrode of each liquid metal battery, and when the voltage of the two ends of the nonlinear resistor is increased to 1.1V at 500 ℃, the resistance value is rapidly reduced, so that partial charging current of the battery is shunted, the current flowing through the liquid metal battery is reduced, the charging rate of a battery monomer with higher capacity is reduced, and the aim of automatic equalization is fulfilled. In the charging process, the battery detection system automatically measures the voltage and the charging current of each battery in the battery pack, calculates the charge state of the battery according to the voltage and the charging current of a single battery by using a charge state and voltage current curve in standard charging, judges whether the equalizing circuit is started or not according to the measurement data of the voltage of the battery, determines whether the charging process of the battery pack is stopped or not according to the current value, and sends a charging stopping command to the battery charging and discharging system through a network; during discharging, the battery detection system automatically measures the voltage and the discharge current of each battery in the battery pack, calculates the charge state of the battery according to the voltage and the discharge current of a single battery by using a standard discharge charge state and voltage current curve, determines whether to stop the discharge process of the battery pack according to the charge state of the battery, and sends a discharge stopping command to the battery charge-discharge system through a network.
A charge equalization method of a liquid metal battery comprises a passive equalization circuit and a battery monitoring system; the passive equalization circuit is characterized in that a nonlinear resistor is connected in parallel with the two ends of the positive electrode and the negative electrode of the liquid metal battery, and after the voltage of the liquid metal battery reaches a certain value, the charging current of the liquid metal battery can be shunted, so that the charging rate of the liquid metal battery can be slowed down; the battery monitoring system measures the voltage of the monocell, determines the charge state of the battery according to the voltage of the battery, controls the charge and discharge process of the battery and realizes the protection of the battery equalization circuit and the battery.
The method comprises the following specific implementation steps:
as shown in fig. 1, the liquid metal battery case 21 is a positive electrode, the cylindrical inner layer protruding from the middle is a negative electrode 22, and the cylindrical outer layer is an insulating ceramic tube 221 for isolating the positive electrode and the negative electrode of the battery. The nonlinear resistor 1 is respectively connected with the anode and the cathode of the battery in a welding mode.
As shown in fig. 2, when the voltage of the liquid metal battery reaches UA, the charging capacity can reach more than 95% of the rated capacity, at this time, the nonlinear resistor starts to be turned on, the resistor branch starts to shunt, and the resistance value rapidly decreases as the voltage continues to increase. The non-linear resistor can flow through the nominal charging current IN of the battery when the voltage reaches UB.
As shown in fig. 3, each cell in the battery pack is provided with a voltage acquisition circuit, which is composed of an optical coupling isolator, a subtractor and an inverter, and voltage information of each cell is input into an ARM chip analog-to-digital converter of the battery conversion system for voltage measurement.
As shown IN fig. 4, eight I/O ports PF0-PF7 of the ARM chip are used to determine address data, and after decoding by the CPLD chip, the address data drives the light barrier of the acquisition circuit and gates the multi-way switch, so that only one voltage signal is sent to the PC0(ADC123_ IN10) port of the ARM chip for analog-to-digital conversion, thereby ensuring that other acquisition circuits do not work and reducing the influence on the voltage of the battery of the main circuit connected IN series.
As shown in fig. 5, when the program starts, the positive and negative current and the value are set to determine whether charging or discharging is performed, and then whether the stored voltage and SoC data need to be initialized is determined, and then the voltage data collected in real time by the sampling circuit is used for data processing and calculating the SoC of the battery. Firstly, if the charging is carried out, judging which single battery voltage in the battery pack exceeds 1.3V, starting the nonlinear resistor equalization at the moment, starting timing, and disconnecting a power supply loop if the set time is exceeded, so as to avoid the resistor damage caused by overheating; secondly, when the battery pack discharges, if the SoC of a certain battery is calculated to be less than 0.1, the discharging loop is disconnected to avoid the over-discharge of the battery.
The scheme adopts a balance scheme that the nonlinear resistor of the SiC material which can endure high temperature is connected with the battery in parallel for balancing, and a battery detection system is combined to control the charging and discharging process. According to the scheme, almost no current flows through the nonlinear resistor when the voltage at two ends of the nonlinear resistor is smaller than a certain value, the voltage can be rapidly increased when the battery is nearly fully charged, the resistance value of the nonlinear resistor is rapidly reduced, most of charging current flows through the high-temperature resistor branch, the charging rate of the high-capacity liquid metal battery is slowed down, and therefore automatic equalization is achieved, the nonlinear resistor can bear the high temperature of 500 ℃, the most important high-temperature environment adaptability problem of liquid metal battery equalization is solved, and meanwhile the resistance and voltage characteristics of the resistor enable the battery to be capable of achieving automatic equalization and protection of charging of the battery when the battery is charged. Meanwhile, the battery monitoring system is adopted to test the voltage of each single battery in the battery pack, so that the nonlinear resistor is prevented from being damaged due to overheating caused by overlong equalization time during charging, the single batteries are protected during discharging, and the over-discharging of the battery is avoided.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The charge equalization system of the liquid metal battery is characterized by comprising the liquid metal battery, a passive equalization circuit and a battery monitoring system;
the passive equalization circuit is characterized in that SiC nonlinear resistors are connected in parallel to the two ends of the positive electrode and the negative electrode of the liquid metal battery monomer and used for shunting the charging current of the liquid metal battery monomer after the voltage of the liquid metal battery monomer reaches a certain value and slowing down the charging rate of the liquid metal battery monomer;
the battery monitoring system is used for measuring the voltage of the liquid metal monocell, determining the charge state of the battery according to the voltage of the battery, controlling the charge and discharge processes of the battery and realizing the protection of the battery equalization circuit and the battery.
2. The system for equalizing charge of liquid metal batteries according TO claim 1, wherein said SiC non-linear resistor is soldered with high temperature solder and packaged as a TO220 type two-terminal resistor with heat sink, said two-terminal resistor being capable of operating at 500 ℃ and 500 ℃, which is in constant voltage on state when applied voltage is higher than 1.3V, and the resistor less than 1.1V is substantially maintained in off state and in transition state from off TO on state between 1.1V and 1.2V.
3. The system for charge equalization of a liquid metal battery according to claim 1, wherein the battery monitoring system employs an isolated cell voltage detection circuit to detect each cell voltage in the liquid metal battery, determine the state of charge of the battery during charging through voltage detection, and ensure that the operating time of the equalization circuit does not exceed the equalization time allowed by the SiC nonlinear resistor, determine the state of charge of the battery during discharging according to the voltage, and ensure that when the state of charge of one battery in series is less than 0.1, the discharge of the whole battery pack is stopped, and the overdischarge of the battery is avoided.
4. The charge equalization system of a liquid metal battery according to claim 3, wherein the isolated cell voltage detection circuit comprises a voltage acquisition circuit, a multi-way switch, a CPLD chip and an ARM chip; each single battery is provided with a voltage acquisition circuit, the voltage acquisition circuit comprises an optical coupling isolator, a subtracter and an inverter which are sequentially connected, and voltage information of each battery is input into an analog-to-digital converter of an electric ARM chip to carry out voltage measurement; the address data is determined by eight I/O ports PF0-PF7 of the ARM chip, after the address data is decoded by the CPLD chip, an optical coupler isolator of the voltage acquisition circuit is driven, and a multi-way switch is gated, so that only one path of voltage signal is sent to a PC0 port of the ARM chip to perform analog-to-digital conversion, the fact that other paths of acquisition circuits do not work is guaranteed, and the influence on the voltage of a battery of a main circuit connected in series is reduced.
5. A charge equalization method for a liquid metal battery is characterized by comprising the following steps:
the passive equalization is adopted to directly connect the nonlinear resistor of the high-temperature-resistant SiC material in parallel at two ends of each liquid metal battery at high temperature, and after the voltage of a single liquid metal battery reaches a certain value, the charging current of the liquid metal battery can be shunted, so that the charging rate of the liquid metal battery can be reduced;
the battery monitoring system is adopted to measure the voltage of the monocell, the state of charge of the battery is determined according to the voltage of the battery, the charging and discharging process of the battery is controlled, and the battery equalization circuit and the battery are protected.
6. The charge equalization method for liquid metal batteries according to claim 5, characterized in that the non-linear resistance of the SiC material is rapidly reduced when the voltage across the terminals rises to 1.1V at 500 ℃, so that part of the charging current of the battery is shunted, the current flowing through the liquid metal battery is reduced, the charging rate of the battery cell with higher capacity is reduced, and the purpose of automatic equalization is achieved.
7. The charge equalization method for the liquid metal battery according to claim 5, characterized in that in the charging process, the battery monitoring system automatically measures the voltage and the charging current of each battery in the battery pack, calculates the state of charge of the battery according to the cell voltage and the charging current by using a standard charging state and voltage current curve, judges whether the equalization circuit is started according to the battery voltage measurement data, determines whether to stop the battery pack charging process according to the current value, and sends a command of stopping the charging to the battery charging and discharging system through the network; during discharging, the battery monitoring system automatically measures the voltage and the discharge current of each battery in the battery pack, calculates the charge state of the battery according to the voltage and the discharge current of a single battery by using a standard discharge charge state and voltage current curve, determines whether to stop the discharge process of the battery pack according to the charge state of the battery, and sends a discharge stopping command to the battery charge-discharge system through a network.
8. The charge equalization method for the liquid metal battery according to claim 5, wherein the battery monitoring system firstly sets the positive and negative current and the numerical value to determine whether charging or discharging is performed, then determines whether the stored voltage and SoC data need to be initialized, and then performs data processing and calculates the SoC of the battery through the voltage data acquired by the sampling circuit in real time; if the charging is carried out, judging which single battery voltage in the battery pack exceeds 1.3V, starting the non-linear resistor equalization at the moment, starting timing, and disconnecting a power supply loop if the set time is exceeded, so as to avoid the resistor damage caused by overheating; and during discharging, if the SoC of a certain battery is calculated to be less than 0.1, the discharging loop is disconnected to avoid over-discharging of the battery.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105141004A (en) * | 2015-09-29 | 2015-12-09 | 西安交通大学 | Equalizing charging system for liquid state metal battery |
| CN208044035U (en) * | 2018-04-04 | 2018-11-02 | 骆驼集团武汉光谷研发中心有限公司 | A kind of battery pack battery core voltage sampling circuit |
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| CN105141004A (en) * | 2015-09-29 | 2015-12-09 | 西安交通大学 | Equalizing charging system for liquid state metal battery |
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Application publication date: 20201211 |