Rapid charging method and system for battery pack

Abstract

The invention relates to a quick charging method and system for a battery pack, and belongs to the technical field of power supply charging. Constructing an equivalent circuit model according to the internal structure of the battery; solving the residual electric quantity of the battery based on the equivalent circuit model; constructing a heat exchange model of the battery according to the temperature between the battery and the environment; constructing a charging loss model according to the charging process of the battery; solving the current state of the battery by using the residual electric quantity of the battery, the heat exchange model and the charging loss model; constructing a target function according to the state of the battery; and solving the objective function to obtain an optimal charging strategy of the battery. According to the method, the SOC, the battery temperature, the energy loss and other multi-dimensional information are integrated into the objective function, the optimal charging strategy is solved through the optimization algorithm, and the safety and the service life can be both considered on the premise that the charging speed of the battery is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of power supply charging technology, and in particular to a method and system for fast charging of battery packs. Background Technology

[0002] With the rapid development of new energy technologies, battery packs, as core components for energy storage and supply, are widely used in electric vehicles, portable electronic devices, energy storage systems, and other fields. How to achieve efficient, fast, and safe charging of battery packs has become a research hotspot in the field of Battery Management Systems (BMS).

[0003] Currently, common battery charging methods mainly include constant current charging, constant voltage charging, and pulse charging control strategies. These methods typically focus on a single aspect of charging speed, charging efficiency, or charging safety, making it difficult to balance multiple performance indicators. In practical applications, due to the complex internal structure of batteries, the thermal effects accompanying charging and discharging processes, and energy losses during charging, batteries generate heat during electrochemical reactions. If heat cannot be dissipated in time, it can easily lead to battery overheating, thereby accelerating aging and even causing safety accidents. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a method and system for fast charging of battery packs.

[0005] A method for fast charging a battery pack, comprising:

[0006] Step 1: Disassemble the battery pack into individual cells;

[0007] Step 2: Construct an equivalent circuit model based on the battery's internal structure;

[0008] Step 3: Solve for the remaining battery capacity based on the equivalent circuit model;

[0009] In step 3, the remaining battery capacity is calculated using a first-order RC equivalent circuit model; the formula for calculating the remaining battery capacity is as follows:

[0010]

[0011] Among them, U oc U represents open-circuit voltage, I represents current, and U represents open-circuit voltage. t R0 represents the terminal voltage, and U represents the internal resistance in ohms. p R represents the voltage across the polarization resistor and polarization capacitor. p C represents the polarization resistance. p C represents the polarization capacitance, SOC represents the remaining charge at time t, SOC0 represents the remaining charge at time t0, and Cn The rated capacity of the battery is represented by I(t), the charging current at time t is represented by η, and the charging and discharging efficiency of the battery is represented by η.

[0012] Step 4: Construct a heat exchange model for the battery based on the temperature between the battery and the environment;

[0013] Step 5: Construct a charging loss model based on the battery charging process;

[0014] Step 6: Solve for the current state of the battery using the remaining battery capacity, heat exchange model, and charging loss model;

[0015] Step 7: Construct the objective function based on the battery state;

[0016] Step 8: Solve the objective function to obtain the optimal charging strategy for the battery.

[0017] Preferably, step 4: constructing a heat exchange model for the battery based on the temperature between the battery and the environment, includes:

[0018] Step 4.1: Calculate the heat generation of the battery based on its internal ohmic resistance; the formula for calculating the heat generation of the battery is:

[0019] Q gen (t)=R0 2 I0T'

[0020] Among them, Q gen (t) represents the heat generated by the battery, R0 represents the internal resistance of the ohms, I0 represents the current passing through the internal resistance of the ohms, and T′ represents the charging time.

[0021] Step 4.2: Calculate the heat exchange of the battery based on the difference between the battery and the environment;

[0022] Step 4.3: Construct a heat exchange model of the battery using the heat generated and the heat exchanged by the battery.

[0023] Preferably, in step 4.3, the heat exchange model of the battery is:

[0024]

[0025] Where m represents the mass of the battery, c d The specific heat capacity of the battery is represented by S, the surface area of ​​the battery is represented by h, and the heat transfer coefficient of the battery is represented by T. amb (t) represents the ambient temperature, Q exc (t) represents the heat exchanged by the battery, T cell (t) represents the battery temperature.

[0026] Preferably, step 5: constructing a charging loss model based on the battery charging process includes:

[0027] Step 5.1: Calculate the lithium plating difference potential based on the lithium plating reaction that occurs during battery charging; the formula for calculating the lithium plating difference potential is:

[0028]

[0029] Where, φ s φ represents the solid-state potential. e η represents the liquid phase potential. Li Indicates the lithium plating differential potential. Let j represent the equilibrium potential of lithium plating, j represent the main reaction current density, F represent the Faraday constant, and R represent the equilibrium potential of lithium plating. SEI Indicates the resistance of the solid electrolyte layer;

[0030] Step 5.2: Calculate the current density in the lithium plating reaction based on the lithium plating differential potential;

[0031]

[0032] Where, j Li Expressed as the lithium plating reaction current density, i Li α represents the exchange current density. Li T represents the cathode transfer coefficient of lithium-ion battery plating, R represents the gas constant, and T represents the cathode transfer coefficient of lithium-ion battery plating. cell (t) represents the battery temperature, η Li Indicates overpotential;

[0033] Step 5.3: Construct a charging loss model based on current density.

[0034] Preferably, in step 5.3, the charging loss model is:

[0035]

[0036] Among them, Q Li L represents charging loss. n a represents the thickness of the negative electrode plate. s ε represents the specific surface area, A represents the electrode reaction area, and ε represents the specific surface area. s,n C represents the volume fraction of solids. s θ represents the solid-phase lithium intercalation concentration. maxn, θ represents the maximum proportion of lithium intercalation in the electrode. min,n This indicates the minimum proportion of lithium intercalation in the electrode.

[0037] Preferably, step 7: constructing an objective function based on the battery state includes:

[0038] Step 7.1: Discretize the battery state to construct a charging state matrix; wherein, the charging state matrix is:

[0039]

[0040] Where x(k)=[SOC,U t ,T cell ,η Li Q Li ] represents the battery state at time k, I(k) represents the charging current at time k, x(k+1) represents the battery state at time k+1, A represents the first discretization parameter, and B represents the second discretization parameter.

[0041] Step 7.2: Construct constraints and objective function based on the charging state matrix.

[0042] Preferably, in step 7.2, the constraints and objective function are as follows:

[0043]

[0044] minJ = Q Li

[0045] Among them, T min T represents the minimum operating temperature of the battery. cell (k) represents the temperature of the battery at time k, T max I(k) represents the maximum operating temperature of the battery, and I(k) represents the current at time k. max U(k) represents the maximum charging current, and U(k) represents the terminal voltage at time k. max This indicates the maximum charging voltage.

[0046] The present invention also provides a battery pack fast charging system, comprising:

[0047] Battery splitting module, used to split the battery pack into individual cells;

[0048] The equivalent circuit model building module is used to build an equivalent circuit model based on the internal structure of the battery.

[0049] In the equivalent circuit model construction module, a first-order RC equivalent circuit model is used to solve for the remaining battery capacity; the formula for calculating the remaining battery capacity is as follows:

[0050]

[0051] Among them, U oc U represents open-circuit voltage, I represents current, and U represents open-circuit voltage. t R0 represents the terminal voltage, and U represents the internal resistance in ohms. p R represents the voltage across the polarization resistor and polarization capacitor. p C represents the polarization resistance. pC represents the polarization capacitance, SOC represents the remaining charge at time t, SOC0 represents the remaining charge at time t0, and C n The rated capacity of the battery is represented by I(t), the charging current at time t is represented by η, and the charging and discharging efficiency of the battery is represented by η.

[0052] The remaining battery capacity calculation module is used to calculate the remaining battery capacity based on the equivalent circuit model.

[0053] The heat exchange model building module is used to build a heat exchange model of the battery based on the temperature between the battery and the environment.

[0054] The charging loss model building module is used to build a charging loss model based on the battery charging process.

[0055] The battery state solution module is used to solve the current battery state using the remaining battery capacity, heat exchange model, and charging loss model.

[0056] The objective function construction module is used to construct the objective function based on the battery state.

[0057] The optimal charging strategy determination module is used to solve the objective function to obtain the optimal charging strategy for the battery.

[0058] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0059] This invention relates to a fast charging method for battery packs. Compared with the prior art, this invention integrates multi-dimensional information such as SOC, battery temperature, and energy loss into an objective function, and obtains the optimal charging strategy through an optimization algorithm. This method can ensure battery charging speed while taking into account safety and lifespan.

[0060] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 A flowchart of a battery pack fast charging method provided by the present invention;

[0063] Figure 2 A schematic diagram of an equivalent circuit model provided by the present invention. Detailed Implementation

[0064] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0065] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0066] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0067] Please see Figure 1 A method for fast charging a battery pack, comprising:

[0068] Step 1: Disassemble the battery pack into individual cells;

[0069] Step 2: Construct an equivalent circuit model based on the battery's internal structure;

[0070] Step 3: Solve for the remaining battery capacity based on the equivalent circuit model;

[0071] like Figure 2 As shown, in step 3, the remaining battery capacity is calculated using a first-order RC equivalent circuit model; the formula for calculating the remaining battery capacity is:

[0072]

[0073] Among them, U oc U represents open-circuit voltage, I represents current, and U represents open-circuit voltage. t U represents the terminal voltage, R0 represents the internal resistance in ohms, and U represents the internal resistance in ohms.p R represents the voltage across the polarization resistor and polarization capacitor. p C represents the polarization resistance. p C represents the polarization capacitance, SOC represents the remaining charge at time t, SOC0 represents the remaining charge at time t0, and C n The rated capacity of the battery is represented by I(t), the charging current at time t is represented by η, and the charging and discharging efficiency of the battery is represented by η.

[0074] Step 4: Construct a heat exchange model for the battery based on the temperature between the battery and the environment;

[0075] Further, step 4: Construct a heat exchange model for the battery based on the temperature between the battery and the environment, including:

[0076] Step 4.1: Calculate the heat generation of the battery based on its internal ohmic resistance; the formula for calculating the heat generation of the battery is:

[0077] Q gen (t)=R0 2 I0T'

[0078] Among them, Q gen (t) represents the heat generated by the battery, R0 represents the internal resistance of the ohms, I0 represents the current passing through the internal resistance of the ohms, and T′ represents the charging time.

[0079] Step 4.2: Calculate the heat exchange of the battery based on the difference between the battery and the environment;

[0080] Step 4.3: Construct a heat exchange model for the battery using its heat generation and heat exchange.

[0081] In step 4.3, the heat exchange model of the battery is as follows:

[0082]

[0083] Where m represents the mass of the battery, c d The specific heat capacity of the battery is represented by S, the surface area of ​​the battery is represented by h, and the heat transfer coefficient of the battery is represented by T. amb (t) represents the ambient temperature, Q exc (t) represents the heat exchanged by the battery, T cell (t) represents the battery temperature.

[0084] Step 5: Construct a charging loss model based on the battery charging process;

[0085] Furthermore, step 5 includes:

[0086] The deposited lithium metal reacts with solvents or salts to form insoluble products, leading to lithium consumption. During charging, when the local potential difference at the interface between the anode current collector and the separator falls below the equilibrium potential of the lithium plating reaction, the lithium plating reaction is triggered.

[0087] Step 5.1: Calculate the lithium plating difference potential based on the lithium plating reaction that occurs during battery charging; the formula for calculating the lithium plating difference potential is:

[0088]

[0089] Where, φ s φ represents the solid-state potential. e η represents the liquid phase potential. Li Indicates the lithium plating differential potential. Let j represent the equilibrium potential of lithium plating, j represent the main reaction current density, F represent the Faraday constant, and R represent the equilibrium potential of lithium plating. SEI Indicates the resistance of the solid electrolyte layer;

[0090] Step 5.2: Calculate the current density in the lithium plating reaction based on the lithium plating differential potential;

[0091]

[0092] Where, j Li Expressed as the lithium plating reaction current density, i Li α represents the exchange current density. Li T represents the cathode transfer coefficient of lithium-ion battery plating, R represents the gas constant, and T represents the cathode transfer coefficient of lithium-ion battery plating. cell (t) represents the battery temperature, η Li Indicates overpotential;

[0093] Step 5.3: Construct a charging loss model based on current density;

[0094] In step 5.3, the charging loss model is as follows:

[0095]

[0096] Among them, Q Li L represents charging loss. n a represents the thickness of the negative electrode plate. s ε represents the specific surface area, A represents the electrode reaction area, and ε represents the specific surface area. s,n C represents the volume fraction of solids. s θ represents the solid-phase lithium intercalation concentration. maxn, θ represents the maximum proportion of lithium intercalation in the electrode. min,n This indicates the minimum proportion of lithium intercalation in the electrode.

[0097] Step 6: Solve for the current state of the battery using the remaining battery capacity, heat exchange model, and charging loss model;

[0098] Step 7: Construct the objective function based on the battery state;

[0099] Step 7 includes:

[0100] Step 7.1: Discretize the battery state to construct a charging state matrix; wherein, the charging state matrix is:

[0101]

[0102] Where x(k)=[SOC,U t ,T cell ,η Li Q Li ] represents the battery state at time k, I(k) represents the charging current at time k, x(k+1) represents the battery state at time k+1, A represents the first discretization parameter, and B represents the second discretization parameter.

[0103] Step 7.2: Construct constraints and objective function based on the charging state matrix. The constraints and objective function are as follows:

[0104]

[0105] minJ = Q Li

[0106] Among them, T min T represents the minimum operating temperature of the battery. cell (k) represents the temperature of the battery at time k, T max I(k) represents the maximum operating temperature of the battery, and I(k) represents the current at time k. max U(k) represents the maximum charging current, and U(k) represents the terminal voltage at time k. max This indicates the maximum charging voltage.

[0107] Step 8: Solve the objective function to obtain the optimal charging strategy for the battery.

[0108] This invention integrates multi-dimensional information such as SOC, battery temperature, and energy loss into an objective function, and obtains the optimal charging strategy through an optimization algorithm. This approach can ensure both battery charging speed and safety and lifespan.

[0109] The present invention also provides a battery pack fast charging system, comprising:

[0110] Battery splitting module, used to split the battery pack into individual cells;

[0111] The equivalent circuit model building module is used to build an equivalent circuit model based on the internal structure of the battery.

[0112] In the equivalent circuit model construction module, a first-order RC equivalent circuit model is used to solve for the remaining battery capacity; the formula for calculating the remaining battery capacity is as follows:

[0113]

[0114] Among them, U oc U represents open-circuit voltage, I represents current, and U represents open-circuit voltage. t R0 represents the terminal voltage, and U represents the internal resistance in ohms. p R represents the voltage across the polarization resistor and polarization capacitor. p C represents the polarization resistance. p C represents the polarization capacitance, SOC represents the remaining charge at time t, SOC0 represents the remaining charge at time t0, and C n The rated capacity of the battery is represented by I(t), the charging current at time t is represented by η, and the charging and discharging efficiency of the battery is represented by η.

[0115] The remaining battery capacity calculation module is used to calculate the remaining battery capacity based on the equivalent circuit model.

[0116] The heat exchange model building module is used to build a heat exchange model of the battery based on the temperature between the battery and the environment.

[0117] The charging loss model building module is used to build a charging loss model based on the battery charging process.

[0118] The battery state solution module is used to solve the current battery state using the remaining battery capacity, heat exchange model, and charging loss model.

[0119] The objective function construction module is used to construct the objective function based on the battery state.

[0120] The optimal charging strategy determination module is used to solve the objective function to obtain the optimal charging strategy for the battery.

[0121] Compared with the prior art, the beneficial effects of the battery pack fast charging system provided by the present invention are the same as those of the battery pack fast charging method described in the above technical solution, and will not be repeated here.

[0122] The present invention also provides an electronic device, including a bus, a transceiver, a memory, a processor, and a computer program stored in the memory and executable on the processor. The transceiver, the memory, and the processor are connected via the bus. When the computer program is executed by the processor, it implements the steps of the aforementioned battery pack fast charging method. Compared with the prior art, the beneficial effects of the electronic device provided by the present invention are the same as those of the battery pack fast charging method described above, and will not be repeated here.

[0123] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for fast charging a battery pack, characterized in that, include: Step 1: Disassemble the battery pack into individual cells; Step 2: Construct an equivalent circuit model based on the battery's internal structure; Step 3: Solve for the remaining battery capacity based on the equivalent circuit model; In step 3, the remaining battery capacity is calculated using a first-order RC equivalent circuit model; the formula for calculating the remaining battery capacity is as follows: Among them, U oc U represents open-circuit voltage, I represents current, and U represents open-circuit voltage. t U represents the terminal voltage, R0 represents the internal resistance in ohms, and U represents the internal resistance in ohms. p R represents the voltage across the polarization resistor and polarization capacitor. p C represents the polarization resistance. p C represents the polarization capacitance, SOC represents the remaining charge at time t, SOC0 represents the remaining charge at time t0, and C n The rated capacity of the battery is represented by I(t), the charging current at time t is represented by η, and the charging and discharging efficiency of the battery is represented by η. Step 4: Construct a heat exchange model for the battery based on the temperature between the battery and the environment; Step 5: Construct a charging loss model based on the battery charging process; Step 6: Solve for the current state of the battery using the remaining battery capacity, heat exchange model, and charging loss model; Step 7: Construct the objective function based on the battery state; Step 8: Solve the objective function to obtain the optimal charging strategy for the battery.

2. The method for fast charging a battery pack according to claim 1, characterized in that, Step 4: Constructing a heat exchange model for the battery based on the temperature between the battery and the environment, including: Step 4.1: Calculate the heat generation of the battery based on its internal ohmic resistance; the formula for calculating the heat generation of the battery is: Q gen (t)=R0 2 I0T′ Among them, Q gen (t) represents the heat generated by the battery, R0 represents the internal resistance of the ohms, I0 represents the current passing through the internal resistance of the ohms, and T′ represents the charging time. Step 4.2: Calculate the heat exchange of the battery based on the difference between the battery and the environment; Step 4.3: Construct a heat exchange model of the battery using the heat generated and the heat exchanged by the battery.

3. The method for fast charging a battery pack according to claim 2, characterized in that, In step 4.3, the heat exchange model of the battery is as follows: Where m represents the mass of the battery, c d The specific heat capacity of the battery is represented by S, the surface area of ​​the battery is represented by h, and the heat transfer coefficient of the battery is represented by T. amb (t) represents the ambient temperature, Q exc (t) represents the heat exchanged by the battery, T cell (t) represents the battery temperature.

4. A method for fast charging a battery pack according to claim 3, characterized in that, Step 5: Constructing a charging loss model based on the battery charging process, including: Step 5.1: Calculate the lithium plating difference potential based on the lithium plating reaction that occurs during battery charging; the formula for calculating the lithium plating difference potential is: Where, φ s φ represents the solid-state potential. e η represents the liquid phase potential. Li Indicates the lithium plating differential potential. Let j represent the equilibrium potential of lithium plating, j represent the main reaction current density, F represent the Faraday constant, and R represent the equilibrium potential of lithium plating. SEI Indicates the resistance of the solid electrolyte layer; Step 5.2: Calculate the current density in the lithium plating reaction based on the lithium plating differential potential; Where, j Li Expressed as the lithium plating reaction current density, i Li α represents the exchange current density. Li T represents the cathode transfer coefficient of lithium-ion battery plating, R represents the gas constant, and T represents the cathode transfer coefficient of lithium-ion battery plating. cell (t) represents the battery temperature, η Li Indicates overpotential; Step 5.3: Construct a charging loss model based on current density.

5. A method for fast charging a battery pack according to claim 4, characterized in that, In step 5.3, the charging loss model is as follows: Among them, Q Li L represents charging loss. n a represents the thickness of the negative electrode plate. s ε represents the specific surface area, A represents the electrode reaction area, and ε represents the specific surface area. s,n C represents the volume fraction of solids. s θ represents the solid-phase lithium intercalation concentration. maxn, θ represents the maximum proportion of lithium intercalation in the electrode. min,n This indicates the minimum proportion of lithium intercalation in the electrode.

6. A method for fast charging a battery pack according to any one of claims 5, characterized in that, Step 7: Constructing an objective function based on the battery state, including: Step 7.1: Discretize the battery state to construct a charging state matrix; wherein, the charging state matrix is: Where x(k)=[SOC,U t ,T cell ,η Li Q Li ] represents the battery state at time k, I(k) represents the charging current at time k, x(k+1) represents the battery state at time k+1, A represents the first discretization parameter, and B represents the second discretization parameter. Step 7.2: Construct constraints and objective function based on the charging state matrix.

7. A method for fast charging a battery pack according to any one of claims 6, characterized in that, In step 7.2, the constraints and objective function are as follows: Among them, T min T represents the minimum operating temperature of the battery. cell (k) represents the temperature of the battery at time k, T max I(k) represents the maximum operating temperature of the battery, and I(k) represents the current at time k. max U(k) represents the maximum charging current, and U(k) represents the terminal voltage at time k. max This indicates the maximum charging voltage.

8. A battery pack fast charging system, characterized in that, include: Battery splitting module, used to split the battery pack into individual cells; The equivalent circuit model building module is used to build an equivalent circuit model based on the internal structure of the battery. In the equivalent circuit model construction module, a first-order RC equivalent circuit model is used to solve for the remaining battery capacity; the formula for calculating the remaining battery capacity is as follows: Among them, U oc U represents open-circuit voltage, I represents current, and U represents open-circuit voltage. t U represents the terminal voltage, R0 represents the internal resistance in ohms, and U represents the internal resistance in ohms. p R represents the voltage across the polarization resistor and polarization capacitor. p C represents the polarization resistance. p C represents the polarization capacitance, SOC represents the remaining charge at time t, SOC0 represents the remaining charge at time t0, and C n The rated capacity of the battery is represented by I(t), the charging current at time t is represented by η, and the charging and discharging efficiency of the battery is represented by η. The remaining battery capacity calculation module is used to calculate the remaining battery capacity based on the equivalent circuit model. The heat exchange model building module is used to build a heat exchange model of the battery based on the temperature between the battery and the environment. The charging loss model building module is used to build a charging loss model based on the battery charging process. The battery state solution module is used to solve the current battery state using the remaining battery capacity, heat exchange model, and charging loss model. The objective function construction module is used to construct the objective function based on the battery state. The optimal charging strategy determination module is used to solve the objective function to obtain the optimal charging strategy for the battery.

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