Battery heating system, method, power supply system and electrical device

Abstract

A battery heating system, method, power supply system, and electrical device are disclosed. The battery heating system (100) includes: a voltage conversion unit (110) electrically connected to a power supply (200) and a battery (300) to be heated, receiving a first voltage input from the power supply (200) or a second voltage input from the battery to be heated; and a control unit (120) for acquiring the charging and discharging frequency of the voltage conversion unit (110), determining the charge transfer impedance of the battery to be heated based on the charging and discharging frequency, calculating the safe amplitude current of the battery to be heated based on the charge transfer impedance, and sending a control signal to the voltage conversion unit (110) based on the charging and discharging frequency and the safe amplitude current, so that the voltage conversion unit (110) performs boosting or bucking processing on the first voltage or the second voltage according to the control signal.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a battery heating system, method, power supply system, and electrical device. Background Technology

[0002] Energy conservation and emission reduction are key to the sustainable development of the automotive industry, and electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of this sustainable development. For electric vehicles, battery technology is a crucial factor in their development.

[0003] With the widespread use of batteries, improving battery performance has become an increasingly urgent problem to be solved in the development of battery technology. The inventors of this application have discovered that temperature has a particularly serious impact on battery performance, especially at low temperatures, where the usable capacity of the battery will decrease significantly, leading to a situation where the battery cannot discharge or charge under low-temperature conditions, severely limiting the performance of the battery. Summary of the Invention

[0004] This application provides a battery heating system, method, power supply system, and electrical device to solve the aforementioned problems in the prior art.

[0005] On one hand, this application proposes a battery heating system, including: a voltage conversion unit electrically connected to a power source and a battery to be heated, receiving a first voltage input from the power source or a second voltage input from the battery to be heated; and a control unit configured to acquire the charging and discharging frequency of the voltage conversion unit, determine the charge transfer impedance of the battery to be heated based on the charging and discharging frequency, calculate the safe amplitude current of the battery to be heated based on the charge transfer impedance, and send a control signal to the voltage conversion unit based on the charging and discharging frequency and the safe amplitude current, so that the voltage conversion unit boosts or bucks the first voltage or the second voltage according to the control signal.

[0006] The embodiments described above in this application determine the safe amplitude current based on the charging and discharging frequency and charge transfer impedance of the voltage conversion unit, and send a control signal to the voltage conversion unit based on the charging and discharging frequency and the safe amplitude current, so that the voltage conversion unit can boost or buck the first voltage or the second voltage according to the control signal, which greatly improves the heating effect of the battery and increases the heating efficiency.

[0007] In some embodiments, a temperature monitoring unit is included; the temperature monitoring unit is used to monitor the temperature of the battery to be heated and send the temperature to the control unit; the control unit determines the charge transfer impedance of the battery to be heated based on the temperature and the charging and discharging frequency of the voltage conversion unit.

[0008] This method allows for real-time monitoring of the battery's condition and correction of the charging and discharging voltage, ensuring the battery is always in optimal heating condition and significantly improving heating efficiency.

[0009] In some embodiments, the control unit is further configured to determine the charge transfer impedance of the battery to be heated based on the state of charge of the battery to be heated, the temperature, and the charge / discharge frequency; the control unit is further configured to calculate the safe amplitude current of the battery to be heated based on the lithium plating potential of the battery to be heated and the charge transfer impedance.

[0010] The embodiments of this application obtain a safe amplitude current based on the equilibrium potential and charge transfer impedance of the graphite negative electrode. This does not depend on the charging cutoff voltage and open circuit voltage set by the manufacturer, and can reflect the true state of the battery to be charged to the greatest extent. This breaks through the limitation of the cutoff voltage set by the manufacturer and greatly improves the heating efficiency.

[0011] In some embodiments, the control unit pre-stores a mapping table of the state of charge, temperature, charge / discharge frequency, and safe amplitude current of the battery to be heated; the control unit is also used to query the safe amplitude current mapping table based on the state of charge, temperature, and charge / discharge frequency of the battery to be heated, and determine the safe amplitude current of the battery to be heated in the current state.

[0012] By setting a mapping table between the state of charge of the battery to be heated, the temperature, the charging and discharging frequency, and the safe amplitude current, the safe amplitude current for charging and discharging can be obtained quickly, thus improving heating efficiency.

[0013] In some embodiments, the voltage conversion unit is used to boost or buck the first voltage or the second voltage within a first time period, so that the charging current received by the battery to be heated is less than the safe amplitude current.

[0014] In some embodiments, the voltage conversion unit is used to boost or buck the first voltage or the second voltage in a second time period so that the discharge current output by the battery to be heated is less than the safe amplitude current.

[0015] In some embodiments, the control unit is further configured to send a control signal to the voltage conversion unit when the temperature is less than a first preset threshold, and to stop outputting the control signal when the temperature is greater than or equal to the first preset threshold.

[0016] By monitoring the temperature of the battery to be heated in real time, the heating process can be controlled in a timely manner according to the condition of the battery. When the heating effect is not good, the heating process can be terminated in time to save energy.

[0017] In some embodiments, the system includes an external heating source; the control unit is configured to activate the external heating source to heat the battery to be heated when the temperature is less than the second preset threshold; and to deactivate the external heating source when the temperature is greater than or equal to the second preset threshold, wherein the first preset threshold is less than the second preset threshold.

[0018] By combining the rapid heating mode with the mode of heating from an external heating source, the heating effect on the battery to be heated is improved, and the heating efficiency is increased.

[0019] On the other hand, this application also proposes a battery heating method, wherein the battery to be heated is electrically connected to a power source through a voltage conversion unit. The method includes: obtaining the charging and discharging frequency of the voltage conversion unit; determining the charge transfer impedance of the battery to be heated based on the charging and discharging frequency; calculating the safe amplitude current of the battery to be heated based on the charge transfer impedance; and sending a control signal to the voltage conversion unit based on the safe amplitude current and the charging and discharging frequency, so that the unit adjusts the first voltage input to the battery to be heated or the second voltage input to the power source according to the control signal.

[0020] The embodiments described above in this application determine the safe amplitude current based on the charging and discharging frequency and charge transfer impedance of the voltage conversion unit, and send a control signal to the voltage conversion unit based on the charging and discharging frequency and the safe amplitude current, so that the voltage conversion unit can boost or buck the first voltage or the second voltage according to the control signal, which greatly improves the heating effect of the battery and increases the heating efficiency.

[0021] In some embodiments, determining the charge transfer impedance of the battery to be heated based on the charge / discharge frequency includes: obtaining the temperature of the battery to be heated, and determining the charge transfer impedance of the battery to be heated based on the temperature and the charge / discharge frequency.

[0022] This method allows for real-time monitoring of the battery's condition and correction of the charging and discharging voltage, ensuring the battery is always in optimal heating condition and significantly improving heating efficiency.

[0023] In some embodiments, determining the charge transfer impedance of the battery to be heated based on the charge / discharge frequency includes: determining the charge transfer impedance of the battery to be heated based on the state of charge of the battery to be heated, the temperature, and the charge / discharge frequency; calculating the safe amplitude current of the battery to be heated based on the charge transfer impedance includes: calculating the safe amplitude current of the battery to be heated based on the lithium plating potential of the battery to be heated and the charge transfer impedance.

[0024] The embodiments of this application obtain a safe amplitude current based on the equilibrium potential and charge transfer impedance of the graphite negative electrode. This does not depend on the charging cutoff voltage and open circuit voltage set by the manufacturer, and can reflect the true state of the battery to be charged to the greatest extent. This breaks through the limitation of the cutoff voltage set by the manufacturer and greatly improves the heating efficiency.

[0025] In some embodiments, calculating the safe amplitude current of the battery to be heated based on charge transfer impedance includes: pre-storing a mapping table of the state of charge, temperature, charge / discharge frequency, and safe amplitude current of the battery to be heated; and querying the safe amplitude current mapping table based on the state of charge, temperature, and charge / discharge frequency of the battery to be heated to determine the safe amplitude current of the battery to be heated in the current state.

[0026] By setting a mapping table between the state of charge of the battery to be heated, the temperature, the charging and discharging frequency, and the safe amplitude current, the safe amplitude current for charging and discharging can be obtained quickly, thus improving heating efficiency.

[0027] In some embodiments, adjusting the first voltage input to the battery to be heated or the second voltage input to the power supply according to the control signal includes: boosting or bucking the first voltage or the second voltage within a first time period so that the charging current received by the battery to be heated is less than the safe amplitude current.

[0028] In some embodiments, adjusting the first voltage input to the battery to be heated or the second voltage input to the power supply according to the control signal includes: boosting or bucking the first voltage or the second voltage within a second time period so that the discharge current output by the battery to be heated is less than the safe amplitude current.

[0029] In some embodiments, the method further includes: adjusting a first voltage input to the battery to be heated or a second voltage input to the power supply when the temperature is less than a first preset threshold; and stopping the adjustment of the first voltage input to the battery to be heated or the second voltage input to the power supply when the temperature is greater than or equal to the first preset threshold.

[0030] By monitoring the temperature of the battery to be heated in real time, the heating process can be controlled in a timely manner according to the condition of the battery. When the heating effect is not good, the heating process can be terminated in time to save energy.

[0031] In some embodiments, the method further includes: when the temperature is less than the second preset threshold, activating an external heating source to heat the battery to be heated; when the temperature is greater than or equal to the second preset threshold, turning off the external heating source, wherein the first preset threshold is less than the second preset threshold.

[0032] By combining the rapid heating mode with the mode of heating from an external heating source, the heating effect on the battery to be heated is improved, and the heating efficiency is increased.

[0033] In another aspect of the embodiments of this application, a power supply system is also proposed, including the battery heating system proposed in the above embodiments. The battery heating system is used to heat the battery to be heated, and the battery to be heated is used to provide power.

[0034] In another aspect of the embodiments of this application, an electrical device is also proposed, including the power supply system described above, which is used to provide power.

[0035] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0037] Figure 1 A schematic diagram of an electrical device according to an embodiment of this application is shown;

[0038] Figure 2 A schematic diagram of the heating system of the electrical device proposed in the embodiments of this application is shown;

[0039] Figure 3 A schematic diagram of the battery heating system proposed in an embodiment of this application is shown;

[0040] Figure 4 A schematic diagram of the equivalent circuit of the battery internal resistance proposed in an embodiment of this application is shown;

[0041] Figure 5 This paper illustrates a schematic diagram showing the relationship between the battery's internal impedance and charge / discharge frequency according to an embodiment of this application.

[0042] Figure 6 A schematic diagram illustrating the relationship between battery temperature and safe current as proposed in an embodiment of this application is shown.

[0043] Figure 7 A schematic diagram of the forward charging and discharging of the battery heating system proposed in an embodiment of this application is shown;

[0044] Figure 8 A schematic diagram of reverse charging and discharging of the battery heating system proposed in an embodiment of this application is shown;

[0045] Figure 9 A diagram of the low-voltage battery heating topology proposed in an embodiment of this application is shown;

[0046] Figure 10 The diagram shows the heating topology of the high-voltage battery and the low-voltage battery proposed in the embodiments of this application;

[0047] Figure 11 The diagram shows the heating topology of the OBC, high-voltage battery, and low-voltage battery proposed in the embodiments of this application.

[0048] Figure 12 The diagram shows the OBC and low-voltage battery heating topology proposed in the embodiments of this application;

[0049] Figure 13 The diagram shows the topology of the battery heating system and external heat source proposed in the embodiments of this application;

[0050] Figure 14 A schematic diagram of the battery heating method proposed in an embodiment of this application is shown. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0053] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0054] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" 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 direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0055] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three possibilities: A exists, A and B exist simultaneously, and B exists. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0056] In this application, "multiple" refers to two or more (including two), and similarly, "multiple groups" refers to two or more (including two), and "multiple pieces" refers to two or more (including two).

[0057] In this application, the battery cell may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and the embodiments of this application are not limited to these. The battery cell may be cylindrical, flat, cuboid, or other shapes, etc., and the embodiments of this application are not limited to these. Battery cells are generally divided into three types according to their packaging method: cylindrical battery cells, cuboid / square battery cells, and pouch battery cells, and the embodiments of this application are not limited to these.

[0058] Currently, with technological advancements, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively applied in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As the application areas of power batteries continue to expand, the market demand is also constantly increasing.

[0059] The inventors of this application have noted that existing electrical devices using battery technology as a power source, such as electric vehicles, use batteries to power these devices and also to supply power to low-voltage systems, such as dashboards, headlights, and radar equipment. Currently, most batteries use lithium-ion batteries for energy storage. The inventors of this application have discovered that because lithium-ion batteries primarily rely on the movement of lithium ions between the positive and negative electrodes to convert chemical energy into electrical energy, the mobility of lithium ions in the electrolyte is significantly reduced at low temperatures. Therefore, the performance of lithium-ion batteries is greatly affected by temperature, especially at low temperatures, where the usable capacity of the battery decreases drastically. This results in lithium batteries being unable to discharge or charge at low temperatures, and their rate capability is severely degraded, greatly limiting the performance of lithium batteries. Furthermore, under low-temperature charging conditions, due to the low battery activity, lithium plating reactions are very likely to occur, leading to internal short circuits and causing serious safety risks. Therefore, under low-temperature conditions, lithium batteries need to be heated to a suitable temperature before use.

[0060] Currently, to ensure the performance of lithium-ion batteries, external heating sources are typically used to heat the batteries. Examples include heating films or PTC hydrothermal systems. Both methods involve heat transfer through contact with the battery surface, offering advantages such as simple heating structures and mature technology. However, this approach requires additional heating devices and a separate power or heat source, resulting in a complex structure and high cost. Furthermore, external heating sources result in a slow temperature rise rate, typically between 0.2 and 0.6°C / min, leading to uneven heating between cells and large temperature differences between the inside and outside of the cells. Additionally, because external heating sources rely on heat conduction, heat is easily dissipated, resulting in low energy utilization.

[0061] Based on the above considerations, and to address the problems of low heating efficiency and complex structure in existing battery heating technologies, this application proposes a battery heating system and method. This system utilizes the principle that batteries generate heat during charging and discharging, and leverages the characteristic that batteries have high internal resistance and are prone to heating at low temperatures. Frequent charging and discharging between battery packs creates mutual loads between them. A control unit controls a voltage conversion unit to periodically adjust the input and output voltages of different battery packs, generating high-frequency alternating current in the entire battery circuit. When this alternating current passes through the low-temperature battery, it directly heats the battery from within due to the high impedance formed at low temperatures. This achieves rapid heating of the battery, allowing it to directly heat itself using its own generated heat, eliminating the need for additional heating devices, resulting in high energy utilization and fast heating speed.

[0062] The battery heating system, method, and power supply system disclosed in this application can be applied to a battery management system as part of the battery management system. This battery management system can be applied to, but is not limited to, electrical devices such as vehicles, ships, or aircraft, which is beneficial for quickly heating the battery and improving battery performance.

[0063] This application provides an electrical device that uses a battery incorporating the battery heating system proposed in this application as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0064] For ease of explanation, the following embodiments will be described using an embodiment of this application with an electrical device, specifically a vehicle 1000.

[0065] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the vehicle structure provided in an embodiment of this application. The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 2000 is installed inside the vehicle, and the battery 2000 can be located at the bottom, front, or rear of the vehicle. The battery 2000 can be used to supply power to the vehicle; for example, the battery 2000 can serve as the vehicle's operating power source. The vehicle also includes a battery management system 1000 and a motor 3000. The battery management system 1000 controls the battery 2000 to supply power to the motor 3000, for example, to meet the power needs of the vehicle during starting, navigation, and driving.

[0066] In some embodiments of this application, the battery 2000 can not only serve as the operating power source for the vehicle, but also as the driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0067] The battery 2000 mentioned in this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery 2000 mentioned in this application may include a battery module or a battery pack. There may be multiple battery cells, which can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple battery cells are connected in both series and parallel. Multiple battery cells can be directly connected in series, parallel, or a combination thereof, and then the entire assembly of the multiple battery cells is housed in a casing. Alternatively, multiple battery cells can first be connected in series, parallel, or a combination thereof to form a battery module, and then the multiple battery modules can be connected in series, parallel, or a combination thereof to form a whole, which is then housed in a casing. The battery 2000 may also include other structures; for example, the battery 2000 may also include a busbar component for realizing electrical connection between multiple battery cells. Each battery cell may be a lithium-ion secondary battery, a lithium-ion primary battery, a lithium-sulfur battery, a sodium-lithium-ion battery, or a magnesium-ion battery, but is not limited to these. Battery cells may be cylindrical, flat, cuboid, or other shapes.

[0068] The battery management system 1000 is a system that manages the battery and is the core of the battery. The battery management system collects and calculates parameters such as voltage, current, temperature, and SOC to control the charging and discharging process of the battery, thereby protecting the battery and improving its overall performance. It is a crucial link between the vehicle's power battery and the electric vehicle. The battery heating system 100 proposed in this application embodiment is a component of the battery management system 1000, such as... Figure 2 The diagram shown is a schematic representation of the application structure of the battery heating system 100 proposed in this application. The electrical device typically includes a high-voltage battery 500 and a low-voltage battery 700. The high-voltage battery 500 charges the low-voltage battery 700 after being stepped down by a voltage conversion unit, and together with the low-voltage battery 700, supplies power to the vehicle's low-voltage system. The low-voltage battery 700 primarily provides power to the low-voltage loads of the electrical device, such as instruments, lights, and radar. The low-voltage battery 700 is directly connected to the low-voltage load 600.

[0069] The battery heating system 100 proposed in this application includes a control unit 120 and a voltage conversion unit 110. Under normal operating conditions, the voltage conversion unit 110 is responsible for voltage conversion. When the battery needs to be heated, the voltage conversion unit 110, under the control of the control unit 120, performs voltage boosting or bucking on the battery to be heated, thereby rapidly heating the battery 300.

[0070] Specifically, the battery heating system 100 proposed in this application embodiment, such as Figure 3As shown, the device includes a voltage conversion unit 110 and a control unit 120. The voltage conversion unit 110 is electrically connected to a power supply 200 and a battery 300 to be heated, respectively, and receives a first voltage input from the power supply 200 or a second voltage input from the battery 300 to be heated. The control unit 120 is used to acquire the charging and discharging frequency of the voltage conversion unit 110, determine the charge transfer impedance of the battery 300 to be heated based on the charging and discharging frequency, calculate the safe amplitude current of the battery 300 to be heated based on the charge transfer impedance, and send a control signal to the voltage conversion unit 110 based on the charging and discharging frequency and the safe amplitude current, so that the voltage conversion unit 110 can boost or buck the first voltage or the second voltage according to the control signal.

[0071] like Figure 3 The diagram shows the structure of the battery heating system 100 proposed in this application embodiment. The control unit 120 is electrically connected to the voltage conversion unit 110 and is used to control the voltage conversion unit 110. The two ends of the voltage conversion unit 110 are respectively connected to the power supply 200 and the battery 300 to be heated, and are used to convert the voltage output by the power supply 200, or to convert the voltage output by the battery 300 to be heated.

[0072] The power source 200 is a carrier that provides input to the battery 300 to be heated. It can be a high-voltage battery 500 that is already installed in the electrical device, an additional low-voltage battery 700, or an external power source, etc. Its purpose is to provide voltage input to the battery 300 to be heated.

[0073] The battery to be heated 300 is a battery that needs to be heated and is part of the electrical device itself. It can be a low-voltage battery 700 or a high-voltage battery 500. This battery to be heated 300 is typically a lithium battery. At low temperatures, the usable capacity of this battery will significantly decrease; it will neither discharge nor charge, and its rate performance will severely degrade. Furthermore, under low-temperature charging conditions, this battery is prone to lithium plating, which can lead to internal short circuits and pose a serious safety risk. During charging, lithium ions are extracted from the positive electrode and inserted into the negative electrode. However, in some situations, such as charging at low temperatures, lithium ions extracted from the positive electrode cannot insert into the negative electrode and can only deposit on the surface of the negative electrode. This phenomenon is called lithium plating. When lithium plating occurs in a lithium battery, it can cause an internal short circuit, resulting in a serious safety risk.

[0074] In this embodiment, to heat the battery 300 under low-temperature conditions, the battery 300 is periodically charged and discharged. Taking advantage of the high impedance of the battery 300 at low temperatures, it generates its own heat for self-heating. During frequent charging and discharging of the battery 300, a higher charging and discharging current and frequency result in more heat generation and a faster temperature rise. However, lithium plating is prone to occur when charging and discharging lithium batteries at low temperatures. Therefore, a balance must be struck between charging / discharging frequency, safe current amplitude, and heating efficiency to ensure rapid heating of the battery 300 while preventing lithium plating during the heating process.

[0075] like Figure 4 The diagram shows the equivalent circuit diagram of the internal resistance of a lithium-ion battery. The equivalent circuit consists of three parts: Z1, Z2, and Z3. Z1 represents the ohmic resistance of the battery's internal current collector, active material, and electrolyte; Z2 represents the impedance of the solid electrolyte interphase (SEI) film, including Q... SEI and R SEI Z3 represents the charge transfer impedance at the solid-liquid interface of the active substance, including Q. dl and R CT .

[0076] Q SEI Q dl This belongs to the category of constant phase element (CPE). A constant phase element is described by the CPE coefficient Q and the CPE exponent n, and its impedance expression is:

[0077]

[0078] Where Q is the CPE coefficient, n is the CPE exponent, and j is the imaginary unit.

[0079] The real part of the resistance of the equivalent circuit of this lithium-ion battery is expressed as follows:

[0080]

[0081] Among them, Q SEI With n SEI The CPE index and CPE coefficient of the constant phase angle element in the Z2 section are respectively, Q dl With n dl R1 and R2 are the CPE index and CPE coefficient of the constant phase angle element in section Z3, respectively; R0 is the ohmic impedance of section Z1 in the equivalent circuit, R...SEI R is the internal resistance of the SEI film. CT ω represents the charge transfer impedance. ω represents the angular frequency of battery charging and discharging, and j represents the imaginary part of the impedance. It should be noted that all of the above parameters are temperature-sensitive and need to be calibrated at different temperatures. All of the above parameters can be obtained by fitting the electrochemical spectrum (EIS) of a lithium-ion battery.

[0082] As can be seen from the above, the real part of the impedance Z of a lithium-ion battery RE Frequency-related, such as Figure 5 The diagram shown is a simplified electrochemical spectrum analysis of a lithium battery, based on the calculation of its internal resistance. It illustrates the impedance of the lithium-ion battery at different charge / discharge frequencies. The horizontal axis represents the real impedance of the battery, and the vertical axis represents the imaginary impedance. The electrochemical spectrum can be divided into charge transfer and mass transfer regions, with a mixed region between them.

[0083] Within the charge transfer region, the higher the charge / discharge frequency, the more charge transfer occurs during charging and discharging, without mass diffusion, meaning lithium plating does not occur. In the extremely high frequency region, the battery exhibits purely resistive characteristics, and its impedance can be expressed as Z = R0. In the mass transfer region, the charge / discharge frequency is lower, and both charge and mass transfer occur, meaning lithium plating will occur in this region. The charge / discharge frequency in the mass transfer region is lower than that in the charge transfer region. In the mixed region, the lithium-ion battery transitions from charge transfer to mass transfer; both occur within this range. Therefore, to avoid lithium plating during charging and discharging, the charge / discharge frequency should be as high as possible. There is no uniform standard for the values ​​of high and low frequencies mentioned above; a general rule of thumb is: high frequency range 1kHz-10kHz; mid-low frequency range 0.001Hz-1kHz. It should be noted that these frequency ranges are not fixed and will vary depending on battery temperature and battery state.

[0084] It should be noted that, theoretically, in the charge transfer region, a higher charge / discharge frequency makes the battery less prone to lithium plating, and a higher charge / discharge frequency is preferable to ensure optimal battery performance. However, in practice, battery charge / discharge control is achieved through a voltage conversion unit 110, which switches between charging and discharging processes. The time required for switching makes faster switching between charge and discharge cycles very difficult. Therefore, the switching frequency of the voltage conversion unit 110 becomes a key factor limiting the improvement of the charge / discharge frequency. Thus, in this application, to reduce the complexity of the battery heating system 100 and improve charge / discharge efficiency, the inventors propose directly using the maximum switching frequency of the voltage conversion unit 110 as the charge / discharge frequency in the battery heating system 100.

[0085] As mentioned above, when charging and discharging a lithium-ion battery, it is necessary to comprehensively consider the balance between the charging / discharging frequency, the safe amplitude current, and the heating efficiency. This involves quickly charging the battery 300 to be heated while preventing lithium plating. Once the charging / discharging frequency is determined, the safe amplitude current of the battery heating system 100 under specific temperature conditions needs to be determined based on this frequency.

[0086] Continue to refer to Figure 4 The schematic diagram of the equivalent circuit of the battery internal resistance shows that, in order to avoid lithium plating at the negative electrode of a lithium-ion battery, the potential difference between the solid and liquid phases on the surface of the negative electrode particles must be greater than the equilibrium potential for lithium plating, that is:

[0087] φ s -φ l >U e，2 ;

[0088] Where, φ s and φ l U represents the potential of the negative electrode particles on both sides of the solid-liquid interface. e，2 To balance the potential, it is usually considered to be 0V.

[0089] When lithium plating occurs, lithium ions need to gain electrons to be reduced to lithium metal. It is generally believed that the lithium plating reaction initially occurs on the surface of graphite particles, that is, inside the solid electrolyte intercalation (SEI) film. The overpotential for the lithium intercalation reaction inside the SEI film is:

[0090] η=φ s -φ l -U e，1 ;

[0091] Among them, U e，1 This represents the equilibrium potential of the graphite negative electrode under a specific state of charge (SOC) of the battery.

[0092] Based on the derivation of the lithium-ion battery impedance spectrum, and through the linearization of the Butler-Volmer equation, the overpotential of the lithium intercalation reaction inside the SEI film can be approximated as:

[0093] η≈i ct R ct ;

[0094] Among them, i ct R is the Faraday current. CT As the charge transfer impedance, i ct The value is negative, meaning the equivalent circuit corresponding to the negative electrode of graphite is:

[0095] i ct R ct =-V3;

[0096] Where V3 is the charge transfer impedance R CT The voltage across the two ends, i.e. Figure 4 The voltage across section Z3 in the battery internal resistance equivalent circuit shown.

[0097] Since the equilibrium potential of the graphite anode at a specific state of charge (SOC) is U e，1 Therefore, to avoid lithium plating on the negative electrode surface, the charge transfer impedance R CT The voltage V3 across the terminals must satisfy:

[0098] V3<U e，1 (1);

[0099] exist Figure 4 In the battery internal resistance equivalent circuit shown, the relationship between the overall impedance of section Z3 and the charging / discharging frequency is as follows:

[0100]

[0101] When an AC excitation is applied to the lithium-ion battery, the voltage amplitude across Z3 is:

[0102] |V3|=I ac |Z3| (2);

[0103] Where |Z3| is the impedance value of the Z3 part in the equivalent circuit of the battery's internal resistance, and it is related to the frequency; I ac The amplitude of the applied alternating current.

[0104] From the above formulas (1) and (2), the condition under which lithium-ion batteries do not undergo lithium plating under AC excitation is:

[0105] I ac |Z3|<U e，1 ;

[0106] In order to avoid lithium plating, at a specific state of charge (SOC) of the battery, the voltage amplitude across the Z3 portion is always less than the equilibrium potential of the graphite anode.

[0107] As can be seen from the above, in this embodiment of the application, when the maximum switching frequency of the battery conversion unit is used as the charging and discharging frequency in the battery heating system 100, at this charging and discharging frequency, the battery heating system 100 is heated by the battery switching unit. Figure 5 It can be seen that the resistance of the Z3 section is equal to the charge transfer impedance R of the lithium battery. CT ,Right now:

[0108]

[0109] Therefore, the safe amplitude current at the above charging and discharging frequencies can be determined as follows: In other words, during the charging and discharging process of the battery to be heated, the charging current must be less than [a certain value].

[0110] Through the above process, the charge / discharge frequency for the battery 300 to be heated is determined, and the charge transfer impedance is determined based on the charge / discharge frequency. Then, the safe amplitude current for charging and discharging is determined based on the charge transfer impedance. It should be noted that the above-mentioned charge transfer impedance and corresponding safe amplitude current are closely related to temperature and the battery's state of charge (SOC), and are not static, but will change continuously with temperature changes. The charge transfer impedance and its corresponding safe amplitude current at a specific temperature and a specific SOC can be obtained by querying the electrochemical spectrum (EIS) of the battery to be charged. This EIS can be pre-set in the control unit 120, and the control unit 120 can obtain it under specific conditions. The specific query method will not be elaborated here.

[0111] In existing technology, for the battery 300 to be heated, the battery manufacturer sets a charging cutoff voltage V when the battery leaves the factory. max Different charging currents are set according to the charging cutoff voltage, resulting in different charging capacities at the cutoff voltage. This charging cutoff voltage is generally a conservative value and is typically applicable to DC conditions. Under AC conditions, it does not accurately reflect the battery's actual condition. For example, when the State of Charge (SOC) is low, the open-circuit voltage V at that SOC will be... ocv If it is relatively small, it will cause Excessive current can cause lithium plating in the battery. When the state of charge (SOC) is high, the open-circuit voltage V at that SOC will increase. ocv It is relatively large, causing The current is too low, resulting in low battery heating efficiency and greatly weakening the heating effect.

[0112] In this embodiment of the application, the equilibrium potential U of the graphite negative electrode of the lithium battery is used... e，1 and charge transfer impedance R CT Determining a safe current amplitude, independent of set charging cutoff and open-circuit voltages, allows for a more accurate reflection of the battery's true state, overcoming the limitations of manufacturer-set cutoff voltages and significantly improving heating efficiency. For example... Figure 6 As shown, under the solution proposed in this embodiment, the battery to be heated 300 can be rapidly heated in a short time, and the safe amplitude current gradually increases, which greatly improves the heating effect of the battery to be heated 300.

[0113] After determining the charging and discharging frequency and safe amplitude current of the battery 300 to be heated, the control unit 120 sends a control signal to the voltage conversion unit 110 based on the charging and discharging frequency and safe amplitude current. The voltage conversion unit 110 then boosts or bucks the first or second voltage of the power supply and the battery to be heated according to the control signal. The charging and discharging frequency is set as the maximum charging and discharging frequency, and the safe amplitude current is set as the maximum charging and discharging current.

[0114] The control unit 120 sends a control signal to the voltage conversion unit 110 within a first time period based on the charging / discharging frequency and the safe amplitude current, causing the first voltage output by the power supply 200 to be higher than the second voltage of the battery 300 to be heated, thereby performing forward charging of the battery. Within a second time period, the control unit 120 sends a control signal to the voltage conversion unit 110, causing the first voltage of the power supply 200 to be lower than the second voltage of the battery 300 to be heated, thereby putting the battery 300 in a discharging state. During the first and second time periods, when boosting or deflating the first voltage, the voltage difference between the first and second voltages needs to be maintained within a certain range so that the maximum charging / discharging current of the battery 300 in the charging state is less than the determined safe amplitude current.

[0115] Therefore, as can be seen from the above, in this embodiment of the application, the control unit 120 determines the safe amplitude current based on the charging and discharging frequency and charge transfer impedance of the voltage conversion unit 110, and sends a control signal to the voltage conversion unit 110 based on the charging and discharging frequency and the safe amplitude current, so that the voltage conversion unit 110 performs voltage boosting or voltage bucking processing on the first voltage or the second voltage according to the control signal, which greatly improves the heating effect of the battery and improves the heating efficiency.

[0116] In some embodiments, the battery heating system 100 further includes a temperature monitoring unit 130, which monitors the temperature of the battery 300 to be heated and sends the temperature to the control unit 120. The control unit 120 determines the charge transfer impedance of the battery 300 to be heated based on the temperature and the charging and discharging frequency of the voltage conversion unit 110.

[0117] like Figure 7 As shown, the battery heating system 100 proposed in this application embodiment also includes a temperature monitoring unit 130. The temperature monitoring unit 130 is connected to the battery 300 to be heated and is used to monitor the temperature of the battery 300 to be heated and send the monitored temperature information to the control unit 120 so that the control unit 120 can control the charging and discharging frequency and charging and discharging current of the voltage conversion unit 110 according to the temperature information of the battery to be heated.

[0118] The temperature monitoring unit 130 can be a temperature sensor, which may include a thermocouple, a negative temperature coefficient temperature sensor, or an infrared sensor, etc., and is usually placed around or on the surface of the battery 300 to be heated, so as to accurately monitor the temperature of the battery 300. The temperature monitoring unit 130 periodically acquires the temperature information of the battery 300 to be heated and sends the temperature information to the control unit 120. The control unit 120 periodically determines the safe amplitude current based on the temperature information, the state of charge (SOC) of the battery 300 to be heated, and the charging and discharging frequency of the voltage conversion unit 110, and adjusts the charging and discharging voltage of the power supply 200 and the battery 300 to be heated according to the safe amplitude current.

[0119] This method allows for real-time monitoring of the state of the battery 300 to be heated and correction of the charging and discharging voltage, ensuring that the battery 300 is always in optimal heating condition and greatly improving heating efficiency.

[0120] In some embodiments, the control unit 120 is further configured to determine the charge transfer impedance of the battery 300 to be heated based on the state of charge (SOC), temperature, and charge / discharge frequency of the battery 300 to be heated; the control unit 120 is further configured to calculate the safe amplitude current of the battery 300 to be heated based on the lithium plating potential of the battery 300 to be heated and the charge transfer impedance.

[0121] The control unit 120 pre-acquires the state of charge (SOC) of the battery 300 to be heated. This SOC can be obtained in several ways. One method is that the manufacturer calibrates the SOC at the factory, specifying the SOC at a particular temperature and voltage. Another method is to calculate the SOC using ampere-hour integration, where the battery management system records the current flowing through the battery and then calculates the current SOC over time. A combination of these two methods can also be used. Of course, there are other methods for obtaining SOC, which will not be elaborated upon here.

[0122] After acquiring the state of charge (SOC) of the battery to be heated 300, the control unit 120 determines the charge transfer impedance R of the battery to be heated 300 based on the temperature information acquired by the temperature monitoring unit 130 and the charge / discharge frequency, using the electrochemical spectrum (EIS) of the battery to be heated 300. CT .

[0123] The control unit 120 also acquires the lithium plating potential of the battery to be heated 300, wherein the lithium plating potential is the equilibrium potential U of the graphite negative electrode of the battery to be heated 300 at a specific state of charge (SOC). e，1 To avoid lithium plating on the graphite anode surface, the charge transfer impedance R CT The voltage V3 across the terminals must satisfy:

[0124] V3<U e，1 ;

[0125] exist Figure 4 In the battery internal resistance equivalent circuit shown, the relationship between the overall impedance of section Z3 and the charging / discharging frequency is as follows:

[0126]

[0127] When an AC excitation is applied to the lithium-ion battery, the voltage amplitude across Z3 is:

[0128] |V3|=I ac |Z3|;

[0129] Where |Z3| is the impedance value of the Z3 part in the equivalent circuit of the battery's internal resistance, and it is related to the frequency; I ac The amplitude of the applied alternating current.

[0130] The conditions under which lithium-ion batteries do not undergo lithium plating under alternating current excitation are:

[0131] I ac |Z3|<U e，1 ;

[0132] In the equivalent circuit of the graphite anode of a lithium-ion battery, under a specific state of charge (SOC) of the battery, the voltage amplitude across the Z3 section is always less than the equilibrium potential of the graphite anode.

[0133] In this embodiment, the maximum switching frequency of the battery conversion unit is used as the charging and discharging frequency in the battery heating system 100. At this charging and discharging frequency, [the system operates as follows:] Figure 5 It can be seen that the resistance of the Z3 section is equal to the charge transfer impedance R of the lithium battery. CT ,Right now:

[0134]

[0135] The safe amplitude current at the above charging and discharging frequencies can be determined as follows:

[0136] By obtaining a safe amplitude current based on the equilibrium potential and charge transfer impedance of the graphite negative electrode, without relying on the set charging cutoff voltage and open circuit voltage, it can reflect the true state of the rechargeable battery to the greatest extent, breaking through the limitation of the cutoff voltage set by the manufacturer, and greatly improving the heating efficiency of the battery to be heated.

[0137] In some embodiments, in order to improve battery heating efficiency, the control unit 120 pre-stores a mapping table of the state of charge, temperature, charge / discharge frequency and safe amplitude current of the battery to be heated 300; the control unit 120 is also used to query the safe amplitude current mapping table according to the state of charge, temperature and charge / discharge frequency of the battery to be heated 300 to determine the safe amplitude current of the battery to be heated 300 in the current state.

[0138] According to the electrochemical spectrum (EIS) of the battery to be heated 300, the safe amplitude current of the battery is determined at a specific temperature, charge / discharge frequency, and state of charge. Therefore, the control unit 120 can pre-store the mapping table of state of charge, temperature, charge / discharge frequency, and safe amplitude current of the battery to be heated 300. During the heating process, the corresponding safe amplitude current is determined in real time based on the acquired state of charge and temperature of the battery to be heated 300. Table 1 shows a schematic table of the mapping table of state of charge, temperature, charge / discharge frequency, and safe amplitude current of the battery to be heated 300.

[0139] Table 1

[0140]

[0141] During the heating process of the battery 300 to be heated, when the charging and discharging frequency, temperature and state of charge are determined, the safe amplitude current can be obtained in a timely manner by querying the mapping table.

[0142] As shown in Table 1, under specific frequency (XHz) and temperature conditions, the lower the state of charge (SOC), the higher the allowable safe amplitude current, and the better the heating effect. Under specific frequency (XHz) and SOC conditions, the allowable safe amplitude current also increases with increasing temperature. When a certain temperature condition is reached, the allowable safe amplitude current remains stable.

[0143] In some embodiments, the voltage conversion unit 110 is used to boost or buck the first voltage or the second voltage within a first time period, so that the charging current received by the battery to be heated 300 is less than the safe amplitude current. The voltage conversion unit 110 is also used to boost or buck the first voltage or the second voltage within a second time period, so that the discharging current output by the battery to be heated 300 is less than the safe amplitude current.

[0144] Such as 7 and Figure 8 The diagram shows a topology in which the voltage conversion unit 110, under the control of the control unit 120, heats the battery 300 to be heated via the power supply 200. The control unit 120 and the voltage conversion unit 110 can communicate via a CAN bus or other buses.

[0145] Figure 7 This diagram illustrates the operating mode in which the power supply 200 discharges while the battery 300 to be heated is forward-charged during the first time period. Under initial conditions, the control unit 120 first determines the charging / discharging frequency K1 and the safe amplitude current I1 of the voltage conversion unit 110 based on the state of charge (SOC) of the battery 300. At this time, the power supply 200 discharges, and the battery 300 to be heated is charged. The output voltage of the power supply 200 is Ua, and the voltage of the battery 300 to be heated is Ub. The voltage conversion unit 110 boosts the voltage Ua output by the power supply 200, resulting in Ua1. Therefore, I1 = (Ua1 - Ub) / R, where R is the equivalent resistance of the battery heating system 100. Ua1 needs to be determined by the control unit based on the safe amplitude current I1 to ensure that the charging current of the battery 300 to be heated is less than the safe amplitude current, thus preventing lithium plating while charging the battery 300.

[0146] Figure 8 This diagram illustrates a working mode in which the voltage conversion unit 110, under the control of the control unit 120, discharges the battery 300 to charge the power supply 200 during the second time period. Figure 7 Compared to forward discharge, Figure 8The discharge is reversed, with both directions opposite. The output voltage of the battery to be heated 300 is Ub, and the voltage of the power supply 200 is Ua. The control unit 120 controls the voltage conversion unit 110 to step down Ua. After being stepped down by the voltage conversion unit 110, Ua becomes Ua2. I1 = (Ub - Ua2) / R, where R is the equivalent resistance of the battery heating system 100. The discharge current output by the battery to be heated 300 is less than the safe amplitude current.

[0147] The aforementioned switching cycle between forward charging and reverse discharging is the charging / discharging frequency K1, meaning that the battery 300 to be heated and the power supply 200 are in a charging state for half the time and a discharging state for the other half, switching between charging and discharging. According to the heating formula for resistance:

[0148] P = I 2 Rt;

[0149] It is known that the higher the current, the better the heat generation effect. Since the control unit 120 continuously adjusts the safe amplitude current as the battery is charged and discharged, the heating effect on the battery will become better and better as the charging and discharging process continues.

[0150] The battery heating method proposed in this application can be applied to various electrical devices, such as electric vehicles. Since electrical devices typically include a high-voltage battery 500 and a low-voltage battery 700, the high-voltage battery 500 generally provides power to the electrical device, and the low-voltage battery 700 generally provides power 200 to the low-voltage components of the electrical device. To heat the battery 300 to be heated, various methods can be used as the power source 200 to provide heating power to the battery 300. For ease of explanation, the following description uses an electric vehicle as an example.

[0151] like Figure 9 As shown, the electrical device includes a high-voltage battery 500, a first voltage conversion unit 111, a first low-voltage battery 301, and a low-voltage load 600. The high-voltage battery 500 provides power to the electrical device and also charges the first low-voltage battery 301 through the first voltage conversion unit 111. The first low-voltage battery 301 provides power to the low-voltage load 600. To rapidly heat the first low-voltage battery 301, the electrical device includes a second low-voltage battery 302, a second voltage conversion unit 112, a control unit 120, and a temperature monitoring unit 130.

[0152] Under normal operating conditions, the high-voltage battery 500 charges the first low-voltage battery 301 through the first voltage conversion unit 111, and the first low-voltage battery 301 provides power 200 to the low-voltage load 600. When the temperature monitoring unit 130 detects that the temperature of the first low-voltage battery 301 is below a certain threshold, the performance of the first low-voltage battery 301 is significantly affected, and it needs to be heated first. The control unit 120 then sends a control signal to the second voltage conversion unit 112, controlling the second voltage conversion unit 112 to continuously charge and discharge the first low-voltage battery 301 and the second low-voltage battery 302 according to a determined charging and discharging frequency and safe amplitude current, so that the temperature of the first low-voltage battery 301 gradually increases, thereby achieving rapid heating of the first low-voltage battery 301.

[0153] Figure 10 Another battery heating topology is shown, including a high-voltage battery 500, a first voltage conversion unit 111, a first low-voltage battery 301, a low-voltage load 600, a control unit 120, and a temperature monitoring unit 130. The control unit 120 is connected to the first voltage conversion unit 111 and is used to control the first voltage conversion unit 111 to heat the first low-voltage battery 301. In this topology, the battery heating system 100 and the high-voltage battery 500 of the electrical device share a voltage conversion unit. By modifying the original voltage conversion unit, it is made capable of high-frequency interaction between the high-voltage battery and the low-voltage battery.

[0154] Under normal operating conditions, the high-voltage battery 500 provides power to the electrical device, and simultaneously charges the first low-voltage battery 301 through the first voltage conversion unit 111. The first low-voltage battery 301 then provides power to the low-voltage load 600. When the temperature monitoring unit 130 detects that the temperature of the first low-voltage battery 301 is below a certain threshold, its performance is significantly affected, requiring initial heating. The control unit 120 then sends a control signal to the first voltage conversion unit 111, controlling it to continuously charge and discharge the first low-voltage battery 301 and the high-voltage battery 500 according to a predetermined charging and discharging frequency and safe current amplitude. This gradually increases the temperature of the first low-voltage battery 301, achieving rapid heating. In this way, the high-voltage and low-voltage batteries share a single voltage conversion unit, simplifying the structure and reducing the complexity of the electrical device.

[0155] Figure 11 Another battery heating topology is shown, integrating the battery heating system 100, the high-voltage battery 500, and the on-board charger (OBC) of the electrical device. Figure 11As shown, the on-board charging system (OBC) includes an AC socket 803, a compensation unit 801, an AC / DC voltage conversion unit 802, and a first voltage conversion unit 111. Figure 11 In this system, the high-voltage battery 500, the on-board charging system (OBC), and the battery heating system share a first voltage conversion unit 111. When heating of the first low-voltage battery 301 is required, the high-voltage battery 500 or the on-board charging system (OBC) can be used as a power source to provide heating power to the first low-voltage battery 301.

[0156] When the first low-voltage battery 301 is heated by the on-board charging system (OBC), under normal operating conditions, the high-voltage battery 500 charges the first low-voltage battery 301 through the first voltage conversion unit 111, and the first low-voltage battery 301 provides power to the low-voltage load 600. When the temperature monitoring unit 130 detects that the temperature of the first low-voltage battery 301 is below a certain threshold, the performance of the first low-voltage battery 301 is significantly affected, and it needs to be heated first. The on-board charging system (OBC) is connected to the first voltage conversion unit 111, and the control unit 120 sends a control signal to the first voltage conversion unit 111 to control the first voltage conversion unit 111 to continuously charge and discharge the first low-voltage battery 301 and the on-board charging system (OBC) according to a determined charging and discharging frequency and safe amplitude current, so that the temperature of the first low-voltage battery 301 gradually increases, thereby achieving rapid heating of the first low-voltage battery 301. In this way, the on-board charger (OBC) is used to heat the low-voltage battery, and the OBC, high-voltage battery, and low-voltage battery share a single voltage conversion unit, which simplifies the structure and reduces the complexity of the electrical device.

[0157] Figure 12 Another battery heating topology is shown, integrating the battery heating system 100 of the electrical device with the on-board charging system (OBC). For example... Figure 12 As shown, the high-voltage battery 500 charges the first low-voltage battery 301 through the first voltage conversion unit 111. The on-board charging system (OBC) includes an AC socket 803, a compensation unit 801, an AC / DC voltage conversion unit 802, and a second voltage conversion unit 112. Figure 12 In this system, the on-board charging system (OBC) and the heating system share a second voltage conversion unit 112, which can use the on-board charging system (OBC) as a power source to provide heating power to the first low-voltage battery 301. The control unit 120 is connected to the second voltage conversion unit 112.

[0158] Under normal operating conditions, the high-voltage battery 500 charges the first low-voltage battery 301 through the first voltage conversion unit 111, and the first low-voltage battery 301 provides power to the low-voltage load 600. When the temperature monitoring unit 130 detects that the temperature of the first low-voltage battery 301 is below a certain threshold, the performance of the first low-voltage battery 301 is significantly affected, requiring it to be heated first. The control unit 120 sends a control signal to the second voltage conversion unit 112, controlling the second voltage conversion unit 112 to continuously charge and discharge the first low-voltage battery 301 and the on-board charger (OBC) system according to a determined charging and discharging frequency and safe amplitude current, thereby gradually increasing the temperature of the first low-voltage battery 301 and achieving rapid heating. In this way, the on-board charger (OBC) is used to heat the low-voltage battery, and the OBC and the low-voltage battery share a single voltage conversion unit, simplifying the structure and reducing the complexity of the electrical device.

[0159] In some embodiments, the control unit 120 is further configured to send a control signal to the voltage conversion unit when the temperature is less than a first preset threshold, and to stop outputting the control signal when the temperature is greater than or equal to the first preset threshold.

[0160] The temperature monitoring unit 130 monitors the temperature. When the temperature of the battery to be heated 300 is greater than or equal to the first preset threshold, it indicates that the temperature of the battery to be heated 300 is sufficient to ensure the normal operation of the battery. Then the control unit 120 stops outputting control signals and stops heating the battery to be heated 300.

[0161] Of course, since the internal resistance of a lithium battery becomes relatively large at low temperatures, heating the battery in this way at low temperatures is quite effective. However, once the lithium battery temperature reaches a certain threshold, the internal resistance of the battery has decreased significantly. At this point, further heating through the battery heating system will be much less effective. Therefore, the control unit 120 can stop outputting control signals and stop heating the battery 300.

[0162] By monitoring the temperature of the battery 300 to be heated in real time, the heating process can be controlled in a timely manner according to the condition of the battery 300. When the heating effect is not good, the heating process can be terminated in time to save energy.

[0163] In some embodiments, the battery heating system 100 includes an external heating source 400, and the control unit 120 is used to activate the external heating source 400 to heat the battery 300 when the temperature is less than the second preset threshold; and to turn off the external heating source 400 when the temperature is greater than or equal to the second preset threshold, wherein the first preset threshold is less than the second preset threshold.

[0164] like Figure 12 As shown, the battery heating system 100 also includes an external heating source 400, which includes heating film heating or PTC hydrothermal heating. Both heating film and PTC hydrothermal heating involve heat transfer through contact with the battery surface, and their main advantages are simple heating structure and mature technology. This application embodiment combines the characteristics of lithium batteries by combining the two heating methods.

[0165] When the temperature is below the first preset threshold, the control unit 120 controls the voltage conversion unit to heat the battery 300 while simultaneously activating the external heating source 400 to heat the battery 300. When the temperature is greater than or equal to the first preset threshold, the internal resistance of the battery has been significantly reduced, and the effect of heating through frequent charging and discharging is greatly reduced. At this time, the battery heating system stops heating the battery. However, since the temperature of the battery 300 has not yet reached the preset second threshold, the external heating source 400 continues to heat the battery 300 until the temperature of the battery 300 reaches the preset second threshold. At this point, the temperature of the battery 300 is sufficient for normal use, and the external heating source 400 can be turned off.

[0166] This application embodiment combines the battery's self-heating mode with the traditional external heating source mode, thereby improving the heating effect and efficiency of the battery.

[0167] In summary, the battery heating system proposed in this application greatly improves the heating effect and efficiency of the battery by having the control unit determine the safe amplitude current based on the charging and discharging frequency and charge transfer impedance of the voltage conversion unit, and sending a control signal to the voltage conversion unit based on the charging and discharging frequency and safe amplitude current.

[0168] Another aspect of this application embodiment provides a battery heating method, applied to the battery heating system proposed in the above embodiments, specifically as follows: Figure 14 As shown. The battery heating method proposed in this application includes:

[0169] Step 1401: Obtain the charging and discharging frequency of the voltage conversion unit;

[0170] Step 1402: Determine the charge transfer impedance of the battery 300 to be heated based on the charge and discharge frequency;

[0171] Step 1403: Calculate the safe amplitude current of the battery 300 to be heated based on the charge transfer impedance;

[0172] Step 1404: Send a control signal to the voltage conversion unit according to the safe amplitude current and the charging and discharging frequency, so that the unit can adjust the first voltage input to the battery to be heated 300 or the second voltage input to the power supply 200 according to the control signal.

[0173] The battery to be heated is electrically connected to a power source through a voltage conversion unit. This power source can take many forms, such as a high-voltage battery or a low-voltage battery in the electrical device, or a power source provided after voltage conversion through an on-board charging system.

[0174] The embodiments described above in this application determine the safe amplitude current based on the charging and discharging frequency and charge transfer impedance of the voltage conversion unit, and send a control signal to the voltage conversion unit based on the charging and discharging frequency and the safe amplitude current, so that the voltage conversion unit can boost or buck the first voltage or the second voltage according to the control signal, which greatly improves the heating effect of the battery and increases the heating efficiency.

[0175] In some embodiments, determining the charge transfer impedance of the battery to be heated based on the charge / discharge frequency includes: obtaining the temperature of the battery to be heated, and determining the charge transfer impedance of the battery to be heated based on the temperature and the charge / discharge frequency.

[0176] This method allows for real-time monitoring of the battery's condition and correction of the charging and discharging voltage, ensuring the battery is always in optimal heating condition and significantly improving heating efficiency.

[0177] In some embodiments, determining the charge transfer impedance of the battery to be heated based on the charge / discharge frequency includes: determining the charge transfer impedance of the battery to be heated based on the state of charge of the battery to be heated, the temperature, and the charge / discharge frequency; calculating the safe amplitude current of the battery to be heated based on the charge transfer impedance includes: calculating the safe amplitude current of the battery to be heated based on the lithium plating potential of the battery to be heated and the charge transfer impedance.

[0178] The embodiments of this application obtain a safe amplitude current based on the equilibrium potential and charge transfer impedance of the graphite negative electrode. This does not depend on the charging cutoff voltage and open circuit voltage set by the manufacturer, and can reflect the true state of the battery to be charged to the greatest extent. This breaks through the limitation of the cutoff voltage set by the manufacturer and greatly improves the heating efficiency.

[0179] In some embodiments, calculating the safe amplitude current of the battery to be heated based on charge transfer impedance includes: pre-storing a mapping table of the state of charge, temperature, charge / discharge frequency, and safe amplitude current of the battery to be heated; querying the safe amplitude current mapping table based on the state of charge, temperature, and charge / discharge frequency of the battery to be heated to determine the safe amplitude current of the battery to be heated in the current state.

[0180] By setting a mapping table between the state of charge of the battery to be heated, the temperature, the charging and discharging frequency, and the safe amplitude current, the safe amplitude current for charging and discharging can be obtained quickly, thus improving heating efficiency.

[0181] In some embodiments, adjusting the first voltage input to the battery to be heated or the second voltage input to the power supply according to the control signal includes: boosting or bucking the first voltage or the second voltage within a first time period so that the charging current received by the battery to be heated is less than the safe amplitude current.

[0182] In some embodiments, adjusting the first voltage input to the battery to be heated or the second voltage input to the power supply according to the control signal includes: boosting or bucking the first voltage or the second voltage within a second time period so that the discharge current output by the battery to be heated is less than the safe amplitude current.

[0183] In some embodiments, the method further includes: adjusting a first voltage input to the battery to be heated or a second voltage input to the power supply when the temperature is less than a first preset threshold; and stopping the adjustment of the first voltage input to the battery to be heated or the second voltage input to the power supply when the temperature is greater than or equal to the first preset threshold.

[0184] The above method monitors the temperature of the battery to be heated in real time, and can control the heating process in a timely manner according to the condition of the battery. When the heating effect is not good, the heating process can be terminated in time to save energy.

[0185] In some embodiments, the method further includes: when the temperature is less than the second preset threshold, activating an external heating source to heat the battery to be heated; when the temperature is greater than or equal to the second preset threshold, turning off the external heating source, wherein the first preset threshold is less than the second preset threshold.

[0186] This application embodiment improves the heating effect and heating efficiency of the battery by combining a rapid heating mode with a mode of heating by an external heating source.

[0187] In another aspect of the embodiments of this application, a power supply system is also proposed, including the battery heating system proposed in the above embodiments. The battery heating system is used to heat the battery to be heated, and the battery to be heated is used to provide power.

[0188] Another aspect of this application embodiment also proposes an electrical device including the aforementioned power supply system, which is used to provide power. This electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0189] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A battery heating system, characterized in that, include: The voltage conversion unit is electrically connected to the power supply and the battery to be heated, respectively, and receives a first voltage input from the power supply or a second voltage input from the battery to be heated. The control unit is configured to acquire the charging and discharging frequency of the voltage conversion unit, determine the charge transfer impedance of the battery to be heated based on the charging and discharging frequency, calculate the safe amplitude current of the battery to be heated based on the charge transfer impedance, and send a control signal to the voltage conversion unit based on the charging and discharging frequency and the safe amplitude current, so that the voltage conversion unit can boost or buck the first voltage or the second voltage according to the control signal.

2. The battery heating system according to claim 1, characterized in that, Includes a temperature monitoring unit; The temperature monitoring unit is used to monitor the temperature of the battery to be heated and send the temperature to the control unit. The control unit determines the charge transfer impedance of the battery to be heated based on the temperature and the charging and discharging frequency of the voltage conversion unit.

3. The battery heating system according to claim 2, characterized in that, The control unit is also configured to determine the charge transfer impedance of the battery to be heated based on the state of charge of the battery to be heated, the temperature, and the charge / discharge frequency; The control unit is also used to calculate the safe amplitude current of the battery to be heated based on the lithium plating potential of the battery to be heated and the charge transfer impedance.

4. The battery heating system according to claim 2, characterized in that, The control unit has a pre-stored mapping table of the state of charge, temperature, charge and discharge frequency and safe amplitude current of the battery to be heated; The control unit is also used to query the safe amplitude current mapping table based on the state of charge of the battery to be heated, the temperature, and the charging and discharging frequency to determine the safe amplitude current of the battery to be heated in the current state.

5. The battery heating system according to any one of claims 1-4, characterized in that, The voltage conversion unit is used to boost or buck the first voltage or the second voltage within a first time period, so that the charging current received by the battery to be heated is less than the safe amplitude current.

6. The battery heating system according to any one of claims 1-4, characterized in that, The voltage conversion unit is used to boost or buck the first voltage or the second voltage in the second time period so that the discharge current output by the battery to be heated is less than the safe amplitude current.

7. The battery heating system according to any one of claims 2-4, characterized in that, The control unit is also configured to send a control signal to the voltage conversion unit when the temperature is less than a first preset threshold, and to stop outputting the control signal when the temperature is greater than or equal to the first preset threshold.

8. The battery heating system according to claim 7, characterized in that, Including external heating sources; The control unit is used to activate the external heating source to heat the battery to be heated when the temperature is less than the second preset threshold; and to turn off the external heating source when the temperature is greater than or equal to the second preset threshold, wherein the first preset threshold is less than the second preset threshold.

9. A battery heating method, wherein the battery to be heated is electrically connected to a power source via a voltage conversion unit, characterized in that, include: Obtain the charging and discharging frequency of the voltage conversion unit; The charge transfer impedance of the battery to be heated is determined based on the charge and discharge frequency. Calculate the safe amplitude current of the battery to be heated based on the charge transfer impedance; The voltage conversion unit is sent a control signal according to the safe amplitude current and the charging / discharging frequency, so that it adjusts the first voltage input to the battery to be heated or the second voltage input to the power supply according to the control signal.

10. The battery heating method according to claim 9, characterized in that, Determining the charge transfer impedance of the battery to be heated based on the charge / discharge frequency includes: The temperature of the battery to be heated is obtained, and the charge transfer impedance of the battery to be heated is determined based on the temperature and the charge / discharge frequency.

11. The battery heating method according to claim 10, characterized in that, Determining the charge transfer impedance of the battery to be heated based on the charge / discharge frequency includes: The charge transfer impedance of the battery to be heated is determined based on the state of charge of the battery to be heated, the temperature, and the charge / discharge frequency. The calculation of the safe amplitude current of the battery to be heated based on the charge transfer impedance includes: The safe amplitude current of the battery to be heated is calculated based on the lithium plating potential and the charge transfer impedance.

12. The battery heating method according to claim 10, characterized in that, The calculation of the safe amplitude current of the battery to be heated based on the charge transfer impedance includes: A pre-stored mapping table of the state of charge, temperature, charge / discharge frequency, and safe amplitude current of the battery to be heated; The safe amplitude current of the battery under the current state is determined by querying the safe amplitude current mapping table based on the state of charge of the battery to be heated, the temperature, and the charge / discharge frequency.

13. The battery heating method according to any one of claims 9-12, characterized in that, The adjustment of the first voltage input to the battery to be heated or the second voltage input to the power supply according to the control signal includes: The first voltage or the second voltage is boosted or bucked within a first time period so that the charging current received by the battery to be heated is less than the safe amplitude current.

14. The battery heating method according to any one of claims 9-12, characterized in that, The adjustment of the first voltage input to the battery to be heated or the second voltage input to the power supply according to the control signal includes: In the second time period, the first voltage or the second voltage is boosted or bucked so that the discharge current output by the battery to be heated is less than the safe amplitude current.

15. The battery heating method according to any one of claims 9-12, characterized in that, The method further includes: When the temperature is less than a first preset threshold, the first voltage input to the battery to be heated or the second voltage input to the power supply is adjusted; when the temperature is greater than or equal to the first preset threshold, the adjustment of the first voltage input to the battery to be heated or the second voltage input to the power supply is stopped.

16. The battery heating method according to claim 15, characterized in that, The method further includes: When the temperature is less than the second preset threshold, the external heating source is activated to heat the battery to be heated; when the temperature is greater than or equal to the second preset threshold, the external heating source is turned off, and the first preset threshold is less than the second preset threshold.

17. A power supply system, characterized in that, Includes the battery heating system as described in any one of claims 1-8; The battery heating system is used to heat the battery to be heated; The battery to be heated is used to provide power.

18. An electrical appliance, characterized in that, Includes the power supply system as described in claim 17, wherein the power supply system is used to provide power.

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