Calibration method and device for maximum continuous charging current, vehicle and medium

Abstract

The invention relates to the technical field of new energy vehicles, and discloses a maximum continuous charging current calibration method and device, a vehicle and a medium, and the method comprises the steps: obtaining an aging coefficient of a sodium battery sample, the aging coefficient being used for representing the aging degree of the sodium battery sample relative to a brand new state; determining a theoretical maximum charging current value according to a preset battery charge state and a preset battery core temperature of the sodium battery sample; and amplifying the theoretical maximum charging current value based on the aging coefficient to obtain a preset battery charge state, a preset cell temperature condition and a corrected maximum charging current under the current aging condition. According to the invention, the low-temperature charging safety of the sodium battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a maximum continuous charging current calibration method, device, vehicle and medium. Background Art

[0002] Sodium batteries are currently being increasingly adopted in the low-voltage power supply systems of new energy vehicles due to their low cost, excellent low-temperature performance, ability to support high-power discharge, and excellent safety. However, sodium batteries also present some challenges. Charging a sodium battery in a low-temperature environment (generally defined as below 0°C) causes sodium metal to precipitate on the surface of the positive electrode inside the battery, and this process is irreversible. The precipitated sodium metal can permanently damage the sodium battery, severely reducing its safety. In high-temperature environments, sodium batteries are prone to rapid temperature rise during charging, posing a risk of fire. To address this, some technologies use a protection current method to charge sodium batteries. By calibrating the protection current, the charging current of the sodium battery does not exceed the protection current, thereby preventing sodium precipitation or overheating. However, with the use of new energy vehicles, this charging protection method often leads to charging failure. Therefore, it is crucial to simultaneously address both charging protection and failure issues. Summary of the Invention

[0003] In view of this, the present invention provides a maximum continuous charging current calibration method, device, vehicle and medium to solve the problem that the charging protection effect and normal charging of sodium batteries cannot be taken into account at the same time.

[0004] In a first aspect, the present invention provides a method for calibrating a maximum continuous charging current, the method comprising: obtaining an aging coefficient of a sodium battery sample, the aging coefficient being used to represent the degree of aging of the sodium battery sample relative to a brand-new state; determining a theoretical maximum charging current value based on a preset battery state of charge and a preset cell temperature of the sodium battery sample; and amplifying the theoretical maximum charging current value based on the aging coefficient to obtain a corrected maximum charging current under a preset battery state of charge, a preset cell temperature, and current aging conditions.

[0005] According to the above technical means, when the battery ages, the degree of battery aging is indicated by obtaining the battery aging coefficient. When the battery is severely aged and thus difficult to charge, the theoretical maximum charging current value used to protect the battery is linearly amplified based on the aging coefficient, and the adjusted corrected maximum charging current is used as the new protection current, which ensures that charging proceeds normally while achieving the purpose of battery protection, achieving the technical effect of taking into account both charging protection and normal charging.

[0006] In one possible embodiment, when the theoretical maximum charging current value is a current limit value at which sodium batteries do not precipitate sodium under preset low-temperature charging conditions, determining the theoretical maximum charging current value based on a preset battery state of charge and a preset cell temperature of the sodium battery samples includes: fully charging multiple sodium battery samples under preset normal temperature conditions, and discharging the sodium battery samples to a preset battery state of charge, wherein the preset normal temperature condition is greater than a preset temperature threshold, and the preset temperature threshold is used to indicate a boundary between low-temperature and non-low-temperature scenarios; allowing the discharged sodium battery samples to rest for a first preset time at a preset cell temperature, wherein the preset cell temperature is less than or equal to the preset temperature threshold; charging the rested sodium battery samples with different test charging currents, and dissecting each sodium battery sample when fully charged; obtaining a first target sodium battery sample without sodium precipitation based on whether metallic sodium precipitates from each sodium battery sample; and determining the theoretical maximum charging current value at the preset battery state of charge and the preset cell temperature based on the maximum test charging current among the first target sodium battery samples.

[0007] Based on the above technical means, a complete calibration method for the theoretical maximum charging current value is provided. First, battery samples are subjected to a predetermined low temperature and state of charge by charging at room temperature and discharging at low temperature. The battery samples are then charged with different test charging currents. By dissecting the batteries and observing them, all battery samples that do not precipitate metallic sodium are identified. The maximum test charging current is then determined as the theoretical maximum charging current value. This allows the theoretical maximum charging current value of the sodium battery to be determined under any temperature and state of charge, creating a lookup table for the theoretical maximum charging current value. During the subsequent actual charging of the sodium battery, the control strategy can query the optimal theoretical maximum charging current value based on the actual temperature conditions and the battery's actual state of charge. As charging progresses, the theoretical maximum charging current value can also be updated in real time based on the data in the table, synchronizing the charging voltage of the sodium battery and ensuring that the charging strategy fully balances charging speed and safety.

[0008] In one possible implementation, the amplifying the theoretical maximum charging current value based on the aging coefficient to obtain a corrected maximum charging current under a preset battery state of charge, a preset cell temperature condition, and a current aging condition includes: calculating a ratio of the theoretical maximum charging current value to the aging coefficient to obtain an initial value of the corrected current, where the aging coefficient is the health state of the sodium battery; fully charging a sodium battery sample under a preset normal temperature condition, and discharging the sodium battery sample to a preset battery state of charge; allowing the discharged sodium battery sample to rest for a first preset time at a preset cell temperature; charging the rested sodium battery sample using the initial value of the corrected current, and discharging the battery when the battery is fully charged. dissecting a sodium battery sample; adjusting the initial value of the correction current by a preset step size according to whether metallic sodium is precipitated from the sodium battery sample to obtain an adjusted value of the correction current; wherein the initial value of the correction current is reduced when metallic sodium is precipitated, and the initial value of the correction current is increased when metallic sodium is not precipitated; using the adjusted value of the correction current as the initial value of the correction current, returning to the step of charging the sodium battery sample after standing using the initial value of the correction current, and dissecting the sodium battery sample when the battery is fully charged; until a maximum adjusted value of the correction current is obtained when no metallic sodium is precipitated, and using the maximum adjusted value of the correction current when no metallic sodium is precipitated as the corrected maximum charging current.

[0009] According to the above technical means, the aging coefficient is determined based on the health status of the battery, and the initial value of the correction current is obtained by the ratio of the theoretical maximum charging current value to the aging coefficient. To further ensure that the protection current can achieve the protection effect, the initial value of the correction current is used as the current test value to repeat the above-mentioned calibration process of the theoretical current value, and then the initial value of the correction current is fine-tuned according to whether sodium precipitation occurs to obtain the corrected maximum charging current. Compared with the solution of customizing multiple current test values and then determining which current test value can be used under aging conditions, the correction maximum charging current calibration method provided by the present invention only requires fine-tuning based on the initial value of the correction current, and does not require repeated experiments on a large number of test currents. The calibration efficiency is faster and more accurate.

[0010] In one possible implementation, when the theoretical maximum charging current value is a current limit value at which the temperature rise of the sodium battery does not exceed a temperature warning value under preset high-temperature charging conditions, determining the theoretical maximum charging current value based on a preset battery state of charge and a preset cell temperature of the sodium battery samples includes: fully charging a plurality of sodium battery samples under preset normal temperature conditions, and discharging the sodium battery samples to a preset battery state of charge, wherein the preset normal temperature condition is greater than a preset temperature threshold, and the preset temperature threshold is used to indicate a boundary between low-temperature and non-low-temperature scenarios; allowing the discharged sodium battery samples to rest at a preset cell temperature for a second preset time period, wherein the preset cell temperature is greater than the preset normal temperature condition; charging the rested sodium battery samples with different test charging currents, and detecting whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to the temperature warning value during the charging process, wherein the test charging current is greater than 1C; obtaining a second target sodium battery sample whose temperature or the temperature of the sodium battery management system rises to the preset temperature warning value; and determining the theoretical maximum charging current value at the preset battery state of charge and the preset cell temperature based on the minimum test charging current among the second target sodium battery samples.

[0011] Based on the above technical means, a complete calibration method for the theoretical maximum charging current value in high-temperature scenarios is also provided. First, by charging at room temperature and discharging at preset high-temperature conditions, the battery samples are placed in a specified state of preset high temperature and preset state of charge. Then, the battery samples are charged with different test charging currents. By measuring the battery temperature rise, all battery samples with temperatures exceeding the warning line are found, and the minimum charging current is determined as the theoretical maximum charging current value. The theoretical maximum charging current value of the sodium battery can be determined under any temperature condition and any state of charge, forming a query table for the theoretical maximum charging current value. During the subsequent actual charging process of the sodium battery, the control strategy can query the optimal theoretical maximum charging current value based on the actual temperature conditions and the actual state of charge of the battery. As charging progresses, the theoretical maximum charging current value can also be updated in real time based on the data in the table, so that the charging strategy of the sodium battery fully takes into account both charging speed and high-temperature protection.

[0012] In one possible embodiment, amplifying the theoretical maximum charging current value based on the aging coefficient to obtain a corrected maximum charging current under a preset battery state of charge, a preset cell temperature condition, and a current aging condition includes: calculating a ratio of the theoretical maximum charging current value to the aging coefficient to obtain an initial correction current value, where the aging coefficient is the health state of the sodium battery; fully charging a sodium battery sample under a preset normal temperature condition, and discharging the sodium battery sample to a preset battery state of charge; allowing the discharged sodium battery sample to rest at a preset cell temperature for a second preset time; charging the rested sodium battery sample using the initial correction current value, and detecting whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to the preset temperature warning value during the charging process; and determining whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to the preset temperature warning value based on whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to the preset temperature warning value. phenomenon, adjusting the initial value of the correction current by a preset step size to obtain a correction current adjustment value; wherein the initial value of the correction current is adjusted down when the temperature reaches the preset temperature warning value, and is adjusted up when the temperature does not reach the preset temperature warning value; using the correction current adjustment value as the initial value of the correction current, returning to the step of charging the sodium battery sample after standing by using the initial value of the correction current, and detecting whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system reaches the preset temperature warning value during the charging process; until the maximum correction current adjustment value is obtained when the internal temperature of the sodium battery or the internal temperature of the sodium battery management system does not reach the preset temperature warning value, and using the maximum correction current adjustment value when the temperature does not reach the preset temperature warning value as the corrected maximum charging current.

[0013] According to the above technical means, the aging coefficient is determined based on the health status of the battery, and the initial value of the correction current is obtained by the ratio of the theoretical maximum charging current value and the aging coefficient. Although the initial value of the correction current has been amplified according to the aging degree of the battery, it is a theoretically feasible protection current. In order to further ensure that the protection current can definitely play a protective role, the initial value of the correction current is used as the test value of the current to repeat the calibration process of the above-mentioned theoretical current value, and then the initial value of the correction current is fine-tuned according to whether the temperature alarm occurs to obtain the corrected maximum charging current. Compared with the solution of customizing multiple current test values and then determining which current test value can be used under aging conditions, the correction maximum charging current calibration method provided by the present invention only needs to be fine-tuned based on the initial value of the correction current, and does not need to repeat the experiment on a large number of test currents. The calibration efficiency is faster and more accurate.

[0014] In a possible implementation, the method further includes: obtaining a current temperature, a current state of charge, a current aging coefficient, and a terminal voltage of a target sodium battery; querying a corresponding target corrected maximum charging current based on the current temperature, the current state of charge, and the current aging coefficient; and adjusting the charging voltage of the target sodium battery within a charging protection interval, wherein the charging protection interval is a voltage interval greater than the terminal voltage and less than or equal to a target voltage, and the target voltage is a voltage value corresponding to the target corrected maximum charging current.

[0015] According to the above technical approach, a target rectified maximum charging current is pre-calibrated to prevent sodium battery metal precipitation or temperature alarms. The target rectified maximum charging current is then used to determine the maximum allowable charging voltage for the sodium battery, i.e., the target voltage. To ensure normal charging of the sodium battery, the minimum charging voltage must not be less than the battery's terminal voltage. After determining the charging protection range based on the battery's terminal voltage and the target voltage, the charging voltage is adaptively adjusted when the sodium battery is charged at low or high temperatures. This not only ensures normal charging but also provides safety protection, preventing sodium metal precipitation during low-temperature charging and temperature alarms during high-temperature charging, thereby improving charging safety. Furthermore, because the calibrated current takes into account the effects of battery aging, it balances normal charging with battery protection.

[0016] In one possible implementation, adjusting the charging voltage of the sodium battery in the charging protection interval includes: determining whether the current charging current is less than the target corrected maximum charging current; if the current charging current is less than the target corrected maximum charging current and lasts for a third preset time, increasing the charging voltage by a first step; if the current charging current is greater than or equal to the target corrected maximum charging current and lasts for a fourth preset time, decreasing the charging voltage by a second step; determining whether the charging voltage is less than or equal to the terminal voltage; if the charging voltage is less than or equal to the terminal voltage and lasts for a fifth preset time, increasing the charging voltage by a third step; determining whether the charging voltage is greater than the sum of the terminal voltage and a preset voltage threshold; if the charging voltage is greater than the sum of the terminal voltage and the preset voltage threshold and lasts for a sixth preset time, decreasing the charging voltage by a fourth step.

[0017] Based on the above technical means, the present invention implements a dynamic voltage regulation method within the charging protection range. As long as the charging voltage is less than the terminal voltage, the charging voltage is immediately increased. If the charging voltage exceeds the terminal voltage by too much, the charging voltage is slowly reduced to ensure charging stability and protect battery life. If the current charging current is less than the target rectified maximum charging current, it means that there is room for improvement in the charging voltage. The charging voltage can be slowly increased to make the current charging current approach the target rectified maximum charging current, thereby increasing the charging speed. If the current charging current is greater than or equal to the target rectified maximum charging current, to ensure that the sodium battery does not precipitate metallic sodium or does not trigger a temperature alarm, the charging voltage needs to be reduced to reduce the current charging current to a level lower than the target rectified maximum charging current. Through the above dynamic adjustment, the charging voltage of the sodium battery can ultimately be in an optimal state that ensures the fastest charging speed without causing safety issues.

[0018] In a second aspect, the present invention provides a device for calibrating a maximum continuous charging current, the device comprising: an aging module for obtaining an aging coefficient of a sodium battery sample, the aging coefficient being used to indicate the degree of aging of the sodium battery sample relative to a brand-new state; a theoretical protection current acquisition module for determining a theoretical maximum charging current value based on a preset battery state of charge and a preset cell temperature of the sodium battery sample; and a correction protection current module for amplifying the theoretical maximum charging current value based on the aging coefficient to obtain a corrected maximum charging current under a preset battery state of charge, a preset cell temperature, and current aging conditions.

[0019] In a third aspect, the present invention provides a vehicle comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the method of the first aspect or any corresponding embodiment thereof by executing the computer instructions.

[0020] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the method of the first aspect or any corresponding embodiment thereof.

[0021] In a fifth aspect, the present invention provides a computer program product comprising computer instructions for causing a computer to execute the method of the first aspect or any corresponding embodiment thereof.

[0022] The technical solution provided by the present invention has the following advantages:

[0023] (1) According to the above technical means, when the battery ages, the degree of battery aging is indicated by obtaining the battery aging coefficient. When the battery is severely aged and thus difficult to charge, the theoretical maximum charging current value for protecting the battery is linearly amplified based on the aging coefficient, and the adjusted corrected maximum charging current is used as the new protection current, thereby ensuring that charging proceeds normally and achieving the purpose of battery protection, thereby achieving the technical effect of taking into account both charging protection and normal charging.

[0024] (2) Based on the above technical means, a complete calibration method for the theoretical maximum charging current value is provided. First, the battery sample is placed in a specified state of a preset low temperature and a preset state of charge by charging at room temperature and discharging at low temperature. Then, the battery sample is charged with different test charging currents. By dissecting the battery and observing, all battery samples that do not precipitate metallic sodium are found, and the maximum test charging current is determined as the theoretical maximum charging current value. The theoretical maximum charging current value of the sodium battery can be determined under any temperature condition and any state of charge, forming a query table for the theoretical maximum charging current value. In the subsequent actual charging process of the sodium battery, the control strategy can query the optimal theoretical maximum charging current value based on the actual temperature conditions and the actual state of charge of the battery. As charging proceeds, the theoretical maximum charging current value can also be updated in real time according to the data in the table, so that the charging voltage of the sodium battery changes synchronously, so that the charging strategy fully takes into account both charging speed and safety.

[0025] (3) According to the above technical means, the aging coefficient is determined based on the health status of the battery, and the initial value of the correction current is obtained by the ratio of the theoretical maximum charging current value and the aging coefficient. In order to further ensure that the protection current can definitely play a protective role, the initial value of the correction current is used as the test value of the current to repeat the calibration process of the above current theoretical value, and then the initial value of the correction current is fine-tuned according to whether sodium precipitation occurs to obtain the corrected maximum charging current. Compared with the solution of customizing multiple current test values and then determining which current test value can be used under aging conditions, the correction maximum charging current calibration method provided by the present invention only needs to be fine-tuned based on the initial value of the correction current, and does not need to repeat the experiment on a large number of test currents. The calibration efficiency is faster and more accurate.

[0026] (4) Based on the above technical means, a complete calibration method for the theoretical maximum charging current value under high temperature scenarios is also provided. First, the battery sample is placed in a specified state of preset high temperature and preset charge state through the operations of normal temperature charging and preset high temperature condition discharge. Then, the battery sample is charged with different test charging currents respectively. By measuring the battery temperature rise, all battery samples whose temperature exceeds the warning line are found, and the minimum charging current is determined as the theoretical maximum charging current value. The theoretical maximum charging current value of the sodium battery can be determined under any temperature condition and any charge state, forming a query table for the theoretical maximum charging current value. In the subsequent actual charging process of the sodium battery, the control strategy can query the optimal theoretical maximum charging current value according to the actual temperature conditions and the actual charge state of the battery. As the charging progresses, the theoretical maximum charging current value can also be updated in real time according to the data in the table, so that the charging strategy of the sodium battery fully takes into account both the charging speed and the high temperature protection effects.

[0027] (5) According to the above technical means, the aging coefficient is determined based on the health status of the battery, and the initial value of the correction current is obtained by the ratio of the theoretical maximum charging current value and the aging coefficient. Although the initial value of the correction current has been amplified according to the aging degree of the battery, it is a theoretically feasible protection current. In order to further ensure that the protection current can definitely play a protective role, the initial value of the correction current is used as the test value of the current to repeat the calibration process of the above-mentioned theoretical current value, and then the initial value of the correction current is fine-tuned according to whether the temperature alarm occurs to obtain the corrected maximum charging current. Compared with the solution of customizing multiple current test values and then determining which current test value can be used under aging conditions, the correction maximum charging current calibration method provided by the present invention only needs to be fine-tuned based on the initial value of the correction current, and does not need to repeat the experiment on a large number of test currents. The calibration efficiency is faster and more accurate.

[0028] (6) According to the above technical means, the target corrected maximum charging current that can prevent the sodium battery from precipitating metallic sodium or temperature alarm is pre-calibrated. Therefore, the maximum charging voltage allowed by the sodium battery, that is, the target voltage, is determined based on the target corrected maximum charging current. Because it is necessary to ensure that the sodium battery can be charged normally, the minimum charging voltage cannot be less than the terminal voltage of the sodium battery. After the charging protection interval is determined according to the terminal voltage and the target voltage of the sodium battery, when the sodium battery is in low-temperature or high-temperature charging conditions, the charging protection interval is enabled to adaptively adjust the charging voltage of the sodium battery, which not only allows the sodium battery to charge normally, but also plays a safety protection role, avoiding the problem of metallic sodium precipitation in the sodium battery during low-temperature charging, and avoiding the problem of temperature alarm when the sodium battery is charged at high temperature, thereby improving the safety of sodium battery charging. And because the calibrated current takes into account the influence of battery aging, it takes into account both normal charging and battery protection.

[0029] (7) According to the above technical means, the present invention implements a dynamic voltage regulation method within the charging protection range. As long as the charging voltage is less than the terminal voltage, the charging voltage is increased immediately; if the charging voltage is too much greater than the terminal voltage, in order to ensure charging stability and protect battery life, the charging voltage is slowly reduced; if the current charging current is less than the target corrected maximum charging current, it means that there is still room for improvement in the charging voltage, and the charging voltage can be slowly increased, thereby making the current charging current approach the target corrected maximum charging current and increasing the charging speed; if the current charging current is greater than or equal to the target corrected maximum charging current, in order to ensure that the sodium battery does not precipitate metallic sodium or does not issue a temperature alarm, the charging voltage needs to be reduced so that the current charging current drops below the target corrected maximum charging current. Through the above dynamic adjustment, the charging voltage of the sodium battery can finally be in an optimal state that can ensure the fastest charging speed without causing safety problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 is a flow chart of a method for calibrating a maximum continuous charging current according to an embodiment of the present invention;

[0032] Figure 2 2 is a schematic structural diagram of a maximum continuous charging current calibration device according to an embodiment of the present invention;

[0033] Figure 3 is a schematic structural diagram of a vehicle according to an embodiment of the present invention;

[0034] Figure 4 4 is a structural block diagram of the electrical connection relationship of a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0036] As the configuration of new energy vehicles continues to increase, the capacity of high-voltage batteries (mainly used to drive electric motors to make the vehicle move) increases, the demand for thermal management also increases, the rated power of water pumps, oil pumps, and cooling fans increases, and the duty cycle during operation is also close to full state, resulting in an increase in vehicle power demand and an increase in the voltage drop of the wiring harness circuit.

[0037] The low-voltage system widely used in new energy vehicles (the battery system used to power low-voltage components such as doors, lights, and audio) has a mainstream voltage level of 12V. The DC converter module of the high-voltage to 12V system supports a maximum power of approximately 4kW for the low-voltage system. If the power exceeds this, the cost will increase exponentially. However, due to the aforementioned increasing power demand of new energy vehicles, the power of the vehicle's low-voltage system may exceed 4kW under extreme operating conditions, which may affect the performance of the vehicle.

[0038] To accommodate similar extreme operating conditions, some automakers have upgraded their low-voltage systems from 12V to 48V or other voltage levels to accommodate increasing power demands. Sodium batteries, due to their low cost, excellent low-temperature performance, high-power discharge capability, and safety, hold great promise for their application in the 48V low-voltage systems of new energy vehicles.

[0039] However, sodium batteries also have some problems. In particular, charging sodium batteries in a low-temperature environment (generally defined as below 0°C) will cause sodium metal to precipitate on the surface of the positive electrode inside the sodium battery, and this process is irreversible. The precipitated sodium metal will cause permanent damage to the sodium battery and seriously reduce the safety of the sodium battery. Similarly, when the battery is in a high-temperature environment (for example, above 40°C), it is easy to overheat during the battery charging process due to too rapid a temperature rise, which is not conducive to battery safety. To address similar problems, the method often used in related technologies is to set a protection current that is less than the rated charging current of the sodium battery. The protection current can prevent the sodium battery from precipitating sodium or overheating, thereby limiting the charging current of the sodium battery through protection current control, thereby achieving the purpose of safe charging of the sodium battery.

[0040] As the battery is used, it will age. The calibrated current is the theoretical value when the battery is not aged. Therefore, the calibrated protection current will become inaccurate during the use of the battery, resulting in problems such as difficulty in protection and inability to charge the battery. Therefore, it is necessary to develop a method that can take into account the technical effects of charging protection and normal charging.

[0041] According to an embodiment of the present invention, an embodiment of a method for calibrating a maximum continuous charging current is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0042] In this embodiment, a method for calibrating the maximum continuous charging current is provided. Figure 1 FIG. 1 is a flow chart of a method for calibrating a maximum continuous charging current according to an embodiment of the present invention, the flow comprising the following steps:

[0043] Step S101, obtaining an aging coefficient of a sodium battery sample, where the aging coefficient is used to indicate the aging degree of the sodium battery sample relative to a brand new state;

[0044] Step S102, determining a theoretical maximum charging current value according to a preset battery state of charge and a preset battery cell temperature of the sodium battery sample;

[0045] Step S103 : amplifying the theoretical maximum charging current value based on the aging coefficient to obtain a corrected maximum charging current under a preset battery state of charge, a preset cell temperature condition, and a current aging condition.

[0046] Specifically, as vehicle batteries are used for longer and longer periods of time, they will begin to age, often accompanied by changes in battery performance parameters. Therefore, recalibrating the battery's protection current based on battery aging is a problem that needs to be addressed. Generally, as the battery ages, related technologies will reduce the rated charging current of the battery to extend the battery's service life. However, this aging treatment method is not applicable to the battery's protection current. Because in low-temperature and high-temperature environments, in order to prevent sodium deposition in sodium batteries and to prevent sodium batteries from overheating, the battery's protection charging current will be reduced based on the rated current, thereby achieving a protective purpose. Because the protection charging current itself is already relatively small, and the aging of the sodium battery will weaken the sodium battery's ability to accept electrical energy, further reducing the protection current will result in the battery being unable to charge. Based on this, the recalibration method provided in the embodiment of the present invention needs to simultaneously take into account both protecting the battery and maintaining the battery's charging capacity.

[0047] First, the aging coefficient of the battery is obtained. The aging coefficient is used to represent the degree of aging of the sodium battery sample relative to a brand new state. In some optional embodiments, the aging coefficient of the battery can be represented based on the battery's state of health (SOH). Of course, it can also be represented by other calculation methods. This embodiment is only used as an example and is not limited to this. Afterwards, the theoretical maximum charging current value of the sodium battery sample is determined by looking up the table at a preset battery state of charge and a preset cell temperature. The theoretical maximum charging current value refers to the most ideal protection current of the sodium battery under non-aging conditions. The calibration process of the theoretical maximum charging current value can refer to the existing technology and will not be repeated here. For example, it can be calibrated by simulation.

[0048] This embodiment then amplifies the theoretical maximum charging current value using the aging factor. In other words, the aging factor represents the degree of aging of the sodium battery. Therefore, the smaller the degree of aging, the smaller the amplification of the theoretical maximum charging current value, while the larger the degree of aging, the greater the amplification of the theoretical maximum charging current value. By amplifying the theoretical maximum charging current value, the battery can maintain its ability to receive charging energy despite aging. Because the theoretical maximum charging current value is amplified strictly based on the aging factor and the amplification is not high, still less than the rated charging current of the sodium battery, the amplified corrected maximum charging current still provides battery protection.

[0049] Finally, the theoretical maximum charge current value is corrected for each preset battery state of charge, preset cell temperature condition, and aging condition to obtain the corrected maximum charge current for each preset battery state of charge, preset cell temperature condition, and aging condition. By saving the corrected maximum charge current under various conditions as a lookup table, the most appropriate target corrected maximum charge current can be adaptively found over time based on the degree of battery aging during vehicle use. This target corrected maximum charge current can then be used to limit battery charging, achieving the desired balance between battery protection and normal charging.

[0050] In some optional embodiments, when the theoretical maximum charging current value is a current limit value at which the sodium battery does not precipitate sodium under a preset low-temperature charging condition, the step S102 includes:

[0051] Step a1: fully charge a plurality of sodium battery samples under a preset normal temperature condition, and discharge the sodium battery samples to a preset battery state of charge, wherein the preset normal temperature condition is greater than a preset temperature threshold, and the preset temperature threshold is used to indicate the boundary between low temperature and non-low temperature scenarios;

[0052] Step a2, leaving the discharged sodium battery sample at a preset cell temperature for a first preset time, wherein the preset cell temperature is less than or equal to a preset temperature threshold;

[0053] Step a3, charging the sodium battery samples after standing at rest with different test charging currents, and dissecting each sodium battery sample when the battery is fully charged;

[0054] Step a4, obtaining a first target sodium battery sample without precipitation of metallic sodium based on whether metallic sodium is precipitated in each sodium battery sample;

[0055] Step a5: determining a theoretical maximum charging current value at a preset battery state of charge and a preset battery cell temperature according to the maximum tested charging current of the first target sodium battery sample.

[0056] Specifically, the present embodiment compares the acquired cell temperature with a preset temperature threshold. If the cell temperature is less than or equal to the preset temperature threshold, the sodium battery is determined to be in a low-temperature charging environment, posing a risk of sodium metal precipitation. Therefore, the risk of sodium metal precipitation needs to be brought to a manageable level by adjusting the charging voltage. If the cell temperature is greater than the preset temperature threshold, the sodium battery is not in a low-temperature charging environment and will not precipitate sodium metal. Therefore, the sodium battery can be charged at the rated voltage normally set by the sodium battery manufacturer.

[0057] It should be noted that the embodiment of the present invention compares the obtained battery cell temperature with a preset temperature threshold. Specifically, the battery cell temperature of each battery cell in the sodium battery is compared with the preset temperature threshold. Only when all battery cell temperatures are greater than the preset temperature threshold is it considered that the sodium battery is being charged in a non-low-temperature charging environment. As long as at least one battery cell temperature is less than the preset temperature threshold, it is determined that the sodium battery is being charged in a low-temperature charging environment and voltage adjustment is required.

[0058] In the embodiments of the present invention, the preset temperature threshold is used to measure whether the current charging environment is a low-temperature charging environment or a non-low-temperature charging environment. The preset temperature threshold can be adjusted according to the actual application scenario and geographical environment. For example, based on the differences between the north and the south, the preset temperature threshold can be 0°C, 5°C, -2°C, etc. This is only an example and does not specifically limit the specific value of the preset temperature threshold. Based on automobile manufacturing experience, 0°C is more often used as the preset temperature threshold. To facilitate the description and understanding of the technical solution, the following examples will use the preset temperature threshold as 0°C.

[0059] When it is determined that the sodium battery is currently in a low-temperature charging environment and there is a risk of metallic sodium precipitation, voltage regulation is required. The embodiment of the present invention obtains a theoretical maximum charging current value. Because in a low-temperature environment, a higher charging current is more likely to cause metallic sodium to precipitate in the battery, when the charging current is weakened to a certain level, the precipitation of metallic sodium is likely to be suppressed, thereby protecting the battery. The theoretical maximum charging current value is a pre-calibrated current value that indicates the maximum charging current that will prevent the sodium battery from precipitating metallic sodium under the current temperature conditions. In other words, when the charging current of the sodium battery does not exceed the theoretical maximum charging current value, the sodium battery is unlikely to precipitate metallic sodium even when charging in a low-temperature charging environment.

[0060] In an embodiment of the present invention, the method of calibrating the theoretical maximum charging current value can be implemented through the above-mentioned steps a1 to a5. Specifically, before calibrating the theoretical maximum charging current value, it is necessary to accurately measure the battery state to determine the temperature and battery state of charge (SOC) of the sodium battery. First, obtain sodium battery samples of the same batch and the same model to ensure the rationality of the calibration data. Then, under preset normal temperature conditions (for example, 25°C is regarded as normal temperature), multiple sodium battery samples are fully charged, that is, charged to 100% SOC state. Thereafter, the sodium battery samples are discharged to a preset battery state of charge, where the preset battery state of charge includes but is not limited to 90% SOC, 80% SOC, 70% SOC, 60% SOC..., thereby calibrating the battery state of charge used to measure the theoretical maximum charging current value. Afterwards, the discharged sodium battery samples are left to stand at a preset cell temperature (the preset cell temperature in this embodiment refers to a preset low temperature condition) for a first preset time period. For example, each discharged sodium battery sample is left to stand at preset low temperature conditions such as 0°C, -10°C, -20°C, and -30°C for 12 hours, thereby calibrating the cell temperature used to measure the theoretical maximum charging current value.

[0061] Through the above preparation process, a large number of sodium battery samples were obtained. Since different sodium battery samples can be discharged to different states of charge, and battery samples with different states of charge can also be left stationary under different temperature conditions, each sodium battery sample covers a variety of state of charge test scenarios such as 90% SOC, 80% SOC, 70% SOC, and 60% SOC. In addition, each state of charge also covers a variety of different temperature scenarios such as 0℃, -10℃, -20℃, and -30℃.

[0062] Afterwards, the sodium battery samples prepared in the above steps are charged with different test charging currents. For example, each 48V sodium battery sample is fully charged with different test charging currents such as 0.1C, 0.2C, 0.3C..., 1C, 1.2C, and 1.5C. Then, each sodium battery sample is dissected to observe whether metallic sodium is precipitated in each sample, and the first target sodium battery sample without metallic sodium precipitation is screened out.

[0063] The first target sodium battery samples that do not precipitate sodium metal should cover all state-of-charge test scenarios and all temperature scenarios. Because higher currents increase the likelihood of sodium metal precipitation, multiple first target sodium battery samples meeting the requirements under the same state-of-charge and temperature scenarios may exist. For example, at -10°C and 70% SOC, multiple first target sodium battery samples that do not precipitate sodium metal may exist. Furthermore, this embodiment determines the maximum charging current to be used from the first target sodium battery samples. For example, the first target sodium battery samples that do not precipitate sodium metal include battery samples with test charging currents ranging from 0.1C to 0.8C, with the maximum test charging current without sodium metal precipitation being 0.8C. Finally, the maximum test charging current among the first target sodium battery samples is determined to be the theoretical maximum charging current value at a preset battery state-of-charge and preset low temperature conditions. For example, 0.8C is used as the theoretical maximum charging current value for a sodium battery at -10°C and 70% SOC.

[0064] The above calibration method for the theoretical maximum charging current value can be used to determine the theoretical maximum charging current value for sodium batteries at any temperature and any state of charge. By organizing the obtained data, a theoretical maximum charging current value lookup table can be generated as shown below. For each temperature and each state of charge test scenario, a corresponding theoretical maximum charging current value can be found.

[0065] Table 1. Lookup table of theoretical maximum charging current value under low temperature conditions

[0066]

[0067] The calibration method provided by the embodiments of the present invention obtains the theoretical maximum charging current values corresponding to any temperature and state of charge, thereby forming a lookup table for the theoretical maximum charging current values. During the subsequent actual charging of the sodium battery, if battery aging is temporarily disregarded, the control strategy can query the optimal theoretical maximum charging current value based on the actual temperature conditions and the battery's actual state of charge. As charging progresses, if the temperature and battery state of charge change, the theoretical maximum charging current value used can also be updated in real time based on the data in the table. Furthermore, when adjusting the sodium battery's charging voltage, the charging voltage will also change with changes in the theoretical maximum charging current value, further enhancing the dynamic performance of the charging voltage adjustment. This not only ensures that the sodium battery does not precipitate metallic sodium during charging, but also allows the battery to be quickly fully charged at the optimal charging speed, ensuring that the sodium battery charging strategy fully balances charging speed and safety.

[0068] In addition, in an alternative embodiment, due to variations in the consistency of sodium battery production processes and secondary materials, the SOC learning may have some deviation. Generally, the SOC accuracy deviation is within 5%. This results in some deviation in the maximum continuous charge current at different SOCs and temperatures. Therefore, based on the detected sodium battery SOC, this embodiment can further correct the ±5% deviation based on different experimental conditions to ensure the accuracy of the calibration conditions.

[0069] In some optional implementations, in a low-temperature charging scenario, step S103 includes:

[0070] Step b1, calculating the ratio of the theoretical maximum charging current value to the aging coefficient to obtain the initial value of the correction current, where the aging coefficient is the health state of the sodium battery;

[0071] Step b2, fully charging the sodium battery sample under a preset room temperature condition, and discharging the sodium battery sample to a preset battery state of charge;

[0072] Step b3, allowing the discharged sodium battery sample to stand at a preset cell temperature for a first preset time;

[0073] Step b4, charging the sodium battery sample after standing still using the initial value of the rectified current, and dissecting the sodium battery sample when the battery is fully charged;

[0074] Step b5, adjusting the initial value of the correction current by a preset step size according to whether metallic sodium is deposited in the sodium battery sample to obtain an adjusted value of the correction current; wherein the initial value of the correction current is adjusted to a lower value when metallic sodium is deposited, and the initial value of the correction current is adjusted to a higher value when metallic sodium is not deposited;

[0075] Step b6, using the adjusted correction current value as the initial correction current value, returning to the step of charging the sodium battery sample after standing using the initial correction current value, and dissecting the sodium battery sample when the battery is fully charged;

[0076] Step b7, until the maximum correction current adjustment value when no metallic sodium is precipitated is obtained, and the maximum correction current adjustment value when no metallic sodium is precipitated is used as the correction maximum charging current.

[0077] Specifically, this embodiment determines the aging coefficient based on the battery's health status, thereby obtaining the initial value of the correction current by taking the ratio of the theoretical maximum charging current value to the aging coefficient. This allows for linear aging correction of the theoretical maximum charging current value using an aging coefficient less than 1. Although the initial value of the correction current calculated using the aging coefficient can amplify the protection current, the core requirement of this embodiment of the present invention is that the battery cannot deposit sodium. Therefore, whether the corrected protection current will cause sodium deposition in the battery still requires verification and fine-tuning to ensure the maximum accuracy of the corrected protection current.

[0078] To further ensure that the protective current can achieve a protective effect, the initial value of the correction current is used as the test value of the current and the above-mentioned calibration process of the theoretical current value is repeated (i.e., steps b2 to b6, which is equivalent to using the initial value of the correction current as the test charging current and repeating the above-mentioned steps a1 to a5). Then, the initial value of the correction current is fine-tuned according to whether sodium precipitation occurs to obtain the corrected maximum charging current. Among them, the preset step size for fine-tuning can be defined based on the experience of R&D personnel. When the initial value of the correction current is used to precipitate metallic sodium during charging of the sodium battery sample, the initial value of the correction current is adjusted to a smaller value. When no metallic sodium is precipitated, the initial value of the correction current is adjusted to a larger value. Finally, after several steps of fine-tuning, the final correction current adjustment value is obtained, i.e., the corrected maximum charging current in step S103.

[0079] Compared to traditional calibration methods, which require customizing a large number of different current test values and conducting extensive experiments before determining which current test value is suitable for use under aging conditions, the solution provided by this embodiment only requires fine-tuning the initial correction current value, eliminating the need for repeated experiments for a large number of test currents. Because the calibration solution has a standard reference value, it is more efficient and accurate.

[0080] In some optional embodiments, when the theoretical maximum charging current value is a current limit value at which the sodium battery does not overheat under a preset high temperature charging condition, step S102 includes:

[0081] Step c1, fully charging a plurality of sodium battery samples under a preset normal temperature condition, and discharging the sodium battery samples to a preset battery state of charge, wherein the preset normal temperature condition is greater than a preset temperature threshold, and the preset temperature threshold is used to indicate the boundary between low temperature and non-low temperature scenes;

[0082] Step c2, leaving the discharged sodium battery sample at a preset cell temperature for a second preset time, wherein the preset cell temperature is greater than a preset normal temperature condition;

[0083] Step c3, charging the rested sodium battery samples with different test charging currents, and detecting during the charging process whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to a temperature warning value, wherein the test charging current is greater than 1C;

[0084] Step c4, obtaining a second target sodium battery sample whose sodium battery temperature or the temperature of the sodium battery management system rises to a preset temperature warning value;

[0085] Step c5: determining a theoretical maximum charging current value at a preset battery state of charge and a preset battery cell temperature based on the minimum tested charging current of the second target sodium battery sample.

[0086] Specifically, when charging in an environment where the cell temperature is greater than a preset temperature threshold (not a low temperature), for example, when the cell temperature is above 0°C, there will be no problem of metallic sodium precipitation. However, there may be safety issues caused by excessive battery temperature or excessive battery management system temperature, such as fire. Based on this, the technical solution provided by the present invention also calibrates the current at which the battery temperature rises too high. The calibrated theoretical maximum charging current value is used to represent the maximum current value that can prevent the temperature of the sodium battery and the sodium battery management system from rising by more than a preset temperature warning value during the charging process. For example, as long as the charging current of the sodium battery does not exceed the theoretical maximum charging current value, the temperature of the sodium battery and the sodium battery management system will not exceed the preset temperature warning value of 65°C.

[0087] Similar to the calibration principle in a low-temperature environment, before calibrating the theoretical maximum charging current value, the battery state needs to be accurately measured to determine the temperature and battery state of charge of the sodium battery. First, sodium battery samples of the same batch and model are obtained to ensure the rationality of the calibration data. Then, multiple sodium battery samples are fully charged under preset normal temperature conditions (for example, 25°C is considered normal temperature), that is, charged to 100% SOC state. Then, the sodium battery samples are discharged to a preset battery state of charge, where the preset battery state of charge includes but is not limited to 90% SOC, 80% SOC, 70% SOC, 60% SOC..., thereby calibrating the battery state of charge used to measure the theoretical maximum charging current value. Then, the discharged sodium battery samples are left to stand for a second preset time under preset high temperature conditions, for example, each discharged sodium battery sample is left to stand for more than 12 hours under preset high temperature conditions such as 10°C, 40°C, and 60°C, thereby calibrating the battery cell temperature test scenario used to measure the theoretical maximum charging current value.

[0088] Through the above preparation process, a large number of sodium battery samples were obtained. Since different sodium battery samples can be discharged to different states of charge, and battery samples with different states of charge can also be left stationary under different temperature conditions, each sodium battery sample covers a variety of state of charge test scenarios such as 90% SOC, 80% SOC, 70% SOC, and 60% SOC. In addition, each state of charge also covers a variety of different high temperature scenarios such as 10°C, 40°C, and 60°C.

[0089] Based on the prepared samples, the prepared sodium battery samples were charged with different test charging currents. For example, each 48V sodium battery sample was fully charged with different test charging currents, such as 1.5C, 2.0C, 2.5C, etc. Since sodium metal will not be precipitated when charging sodium batteries under normal temperature and high temperature conditions, the test can be performed starting from a charging current of 1C or above, and there is no need to test scenarios less than 1C. During the charging process, the internal temperature of each sodium battery sample and the corresponding battery management system is measured to determine whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system has risen to a preset temperature warning value (e.g., 65°C).

[0090] By measuring the battery temperature rise, all sodium battery samples whose temperatures have exceeded a preset temperature warning value are found as the second target sodium battery samples.

[0091] The second target sodium battery samples whose temperatures exceed the preset temperature warning value should cover all state-of-charge test scenarios and all temperature scenarios, and all of them should fail the temperature rise test. Because higher currents are more likely to cause battery temperature rise, multiple second target sodium battery samples may fail the temperature rise test under the same state-of-charge and temperature scenario. For example, at 10°C and 70% SOC, multiple second target sodium battery samples may experience a temperature rise exceeding 65°C. Furthermore, this embodiment determines the minimum charging current to be used from the second target sodium battery samples. For example, each second target sodium battery sample includes battery samples charged with currents ranging from 3C to 5C. The minimum charging current at which excessive temperature rise occurs is 3C. Furthermore, if the charging current is less than 3C, excessive temperature rise will not occur. Finally, the minimum charging current among the second target sodium battery samples is determined to be the theoretical maximum charging current value under the preset battery state-of-charge and preset low temperature conditions. For example, 3C is set as the theoretical maximum charging current value for a sodium battery under 10°C and 70% SOC conditions. In other words, at 10°C and 70% SOC, if the charging current does not exceed 3C, there will be no problem of excessive temperature rise.

[0092] The above calibration method for the theoretical maximum charging current value can be used to determine the theoretical maximum charging current value for sodium batteries at any temperature and any state of charge. By organizing the obtained data, a theoretical maximum charging current value lookup table can be generated as shown below. For each temperature and each state of charge test scenario, a corresponding theoretical maximum charging current value can be found.

[0093] Table 2. Lookup table of theoretical maximum charging current values in high temperature scenarios

[0094]

[0095] The calibration method provided by the embodiments of the present invention obtains the theoretical maximum charging current values corresponding to any temperature conditions and any state of charge, thereby forming a lookup table for the theoretical maximum charging current values. During the subsequent actual charging process of the sodium battery, the control strategy can query the optimal theoretical maximum charging current value based on the actual temperature conditions and the battery's actual state of charge. As charging progresses, if the temperature and battery state of charge change, the adopted theoretical maximum charging current value can also be updated in real time based on the data in the table. Furthermore, when adjusting the sodium battery's charging voltage, the upper limit of the charging voltage changes with the theoretical maximum charging current value, and the actual charging voltage also changes with the theoretical maximum charging current value. This further enhances the dynamic performance of the charging voltage adjustment, not only ensuring that the sodium battery's charging temperature rise does not trigger an alarm, but also enabling the battery to be quickly fully charged at the optimal charging speed, enabling the sodium battery charging strategy to fully balance charging speed and safety.

[0096] In some optional implementations, when the theoretical maximum charging current value is a protection current in a high temperature scenario, step S103 includes:

[0097] Step d1, calculating the ratio of the theoretical maximum charging current value to the aging coefficient to obtain the initial value of the correction current, where the aging coefficient is the health state of the sodium battery;

[0098] Step d2, fully charging the sodium battery sample under a preset normal temperature condition, and discharging the sodium battery sample to a preset battery state of charge;

[0099] Step d3, allowing the discharged sodium battery sample to stand at a preset cell temperature for a second preset time;

[0100] Step d4, charging the rested sodium battery sample using the initial value of the corrected current, and detecting during the charging process whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to a preset temperature warning value;

[0101] Step d5, adjusting the initial value of the correction current by a preset step size according to whether the temperature reaches the preset temperature warning value to obtain an adjusted value of the correction current; wherein the initial value of the correction current is reduced when the temperature reaches the preset temperature warning value, and is increased when the temperature does not reach the preset temperature warning value;

[0102] Step d6, using the adjusted correction current value as the initial correction current value, returning to the step of charging the rested sodium battery sample using the initial correction current value, and detecting during the charging process whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system has risen to a preset temperature warning value;

[0103] Step d7, until the maximum correction current adjustment value when the internal temperature of the sodium battery or the internal temperature of the sodium battery management system does not rise to the preset temperature warning value is obtained, and the maximum correction current adjustment value when it does not rise to the preset temperature warning value is used as the correction maximum charging current.

[0104] Specifically, the embodiment of the present invention determines the aging coefficient based on the health status of the battery, and thus obtains the initial value of the correction current by the ratio of the theoretical maximum charging current value to the aging coefficient. Although the initial value of the correction current has been amplified according to the degree of aging of the battery and is a theoretically feasible protection current, it cannot necessarily be determined that the initial value of the correction current will not cause an overtemperature alarm. In order to further ensure that the protection current can definitely play a protective role, the initial value of the correction current is used as the test value of the current to repeat the calibration process of the above-mentioned theoretical current value, and then the initial value of the correction current is fine-tuned according to whether the temperature alarm occurs to obtain the corrected maximum charging current. Compared with the solution of customizing multiple current test values and then determining which current test value can be used under aging conditions, the correction maximum charging current calibration method provided by the present invention only needs to be fine-tuned based on the initial value of the correction current, and does not require repeated experiments on a large number of test currents. The calibration efficiency is faster and more accurate.

[0105] In some optional embodiments, the method provided by the present invention further comprises:

[0106] Step e1, obtaining the current temperature, current state of charge, current aging coefficient and terminal voltage of the target sodium battery;

[0107] Step e2, querying the corresponding target corrected maximum charging current based on the current temperature, the current state of charge, and the current aging coefficient;

[0108] Step e3, adjusting the charging voltage of the target sodium battery to be within the charging protection interval, the charging protection interval being a voltage interval greater than the terminal voltage and less than or equal to the target voltage, the target voltage being the voltage value corresponding to the target corrected maximum charging current.

[0109] Specifically, the above steps e1 to e3 are specific charging schemes for sodium batteries, which are implemented based on the corrected maximum charging current generated in the above steps. First, the embodiment of the present invention solves the problem of sodium metal precipitation and high temperature alarm during low-temperature charging of sodium batteries by regulating the charging voltage of the sodium battery. First, when the vehicle is charging the sodium battery, it is necessary to collect the cell temperature and terminal voltage of the sodium battery. Among them, the sodium battery often contains multiple cells. In this embodiment, collecting the cell temperature of the sodium battery specifically refers to collecting the temperature of each cell of the sodium battery. The terminal voltage of the sodium battery refers to the voltage of the sodium battery itself. This parameter is a key parameter for adjusting the charging voltage. If the sodium battery is to be charged, it is necessary to ensure that the charging voltage is greater than the terminal voltage of the sodium battery to form a voltage difference so that the charging function can be performed normally.

[0110] As an example, sodium battery charging scenarios include charging while the vehicle is powered on and charging while the vehicle is powered off. When the vehicle is powered on, the high-voltage battery used to drive the electric motor can charge the sodium battery, ensuring that the battery has sufficient power to drive the vehicle's low-voltage components. When the vehicle is powered off, the high-voltage battery can also charge the sodium battery based on an intelligent charging strategy, or the vehicle can be connected to an external charging station to charge the sodium battery.

[0111] After obtaining the terminal voltage and target rectified maximum charging current, this embodiment calculates the corresponding target voltage based on the target rectified maximum charging current. The target voltage represents the charging voltage value corresponding to when the charging current reaches the target rectified maximum charging current, where the target voltage is greater than the terminal voltage of the sodium battery. When the sodium battery is in a low or high temperature state, the low-voltage system controller limits the input voltage to the power battery, restricting the output charging voltage to a charging protection range greater than the terminal voltage and less than or equal to the target voltage.

[0112] On the one hand, the charging voltage is greater than the terminal voltage, creating a voltage difference that ensures that electrical energy can flow into the sodium battery. On the other hand, the charging current corresponding to the charging voltage does not exceed the pre-calibrated target rectified maximum charging current, thereby preventing metallic sodium precipitation during the charging process, avoiding short-circuiting issues or high-temperature alarms. The above-described technical solution provides a method for improving sodium battery charging safety without disconnecting the charging circuit, which can be applied during the sodium battery charging process. Furthermore, a relatively accurate upper current limit (target rectified maximum charging current) is obtained for the sodium battery charging current based on a calibration method. Based on this target rectified maximum charging current, the charging voltage can be accurately controlled, fully accounting for the battery's SOC, temperature, and aging. Even after extended vehicle use, the rectified maximum charging current used to protect the battery will adaptively change based on the aging factor. Due to the accurate control upper limit, compared to fuzzy control methods, there is no need to adjust the battery temperature while reducing the charging current, thus saving equipment costs. The technical solution provided by the present invention combines the advantages of high charging efficiency, high battery safety, and low equipment cost.

[0113] In some optional implementations, step e3 includes:

[0114] Step f1, determining whether the current charging current is less than the target corrected maximum charging current;

[0115] Step f2: If the current charging current is less than the target rectified maximum charging current and lasts for a third predetermined time period, then the charging voltage is increased by the first step;

[0116] Step f3: If the current charging current is greater than or equal to the target rectified maximum charging current and lasts for a fourth predetermined time period, then reducing the charging voltage by a second step size;

[0117] Step f4, determining whether the charging voltage is less than or equal to the terminal voltage;

[0118] Step f5: if the charging voltage is less than or equal to the terminal voltage and lasts for a fifth predetermined time period, then increase the charging voltage by a third step length;

[0119] Step f6, determining whether the charging voltage is greater than the sum of the terminal voltage and a preset voltage threshold;

[0120] In step f7, if the charging voltage is greater than the sum of the terminal voltage and the preset voltage threshold and lasts for a sixth preset time period, the charging voltage is reduced by a fourth step.

[0121] Specifically, the aforementioned embodiments have proposed adjusting the charging voltage to prevent the precipitation of metallic sodium during low-temperature charging of sodium batteries and to avoid high-temperature alarms. This embodiment of the present invention further provides a dynamic voltage adjustment method. The charging voltage is not a fixed value within the charging protection range, but rather dynamically changes according to rules to increase the charging rate of the sodium battery.

[0122] At the initial stage of sodium battery charging, the initial charging voltage is often set slightly higher than the battery's terminal voltage. For example, for a 48V sodium battery, the initial charging voltage can be set to 48V + 0.1V to ensure that the initial charging voltage is sufficient for charging the sodium battery. Subsequently, the current charging current is periodically checked to see if it is less than the target rectified maximum charging current. If this occurs for a third preset duration (e.g., 5 seconds), this embodiment increases the charging voltage by a first step (e.g., setting the first step to 0.3V). Because a higher charging current results in a faster charging speed, assuming the sodium battery does not precipitate metallic sodium or trigger a high-temperature alarm, the charging voltage is increased as much as possible to bring the corresponding actual charging current close to the target rectified maximum charging current, further improving the sodium battery's charging speed. If the current charging current is greater than or equal to the target rectified maximum charging current and persists for a fourth preset duration (e.g., 3 seconds), the sodium battery is at risk of metallic sodium precipitation. In this embodiment, the charging voltage is immediately reduced by a second step (e.g., 0.1V), thereby reducing the actual charging current until it is less than the target rectified maximum charging current, ensuring the battery's charging reliability.

[0123] Specifically, the initial charging voltage can be set to 48V+0.1V to ensure that the initial charging voltage is sufficient to charge the sodium battery. Furthermore, it is necessary to periodically check whether the actual charging voltage is less than or equal to the terminal voltage. If the charging voltage is less than or equal to the terminal voltage and persists for a fifth predetermined time period (e.g., 5 seconds), normal charging cannot occur. Therefore, in this embodiment, the charging voltage is increased in third steps (e.g., 0.3V) until the charging voltage exceeds the terminal voltage.

[0124] In addition, this embodiment periodically detects whether the actual charging voltage is greater than the sum of the terminal voltage and a preset voltage threshold (e.g., 0.8V), thereby determining whether the actual charging voltage exceeds the terminal voltage by a significant amount. If the charging voltage exceeds the terminal voltage by a significant amount and persists for a sixth preset duration (e.g., 5 seconds), it is determined that prolonged charging at a high voltage is detrimental to the lifespan of the sodium battery, and the charging voltage is reduced by a fourth step (e.g., 0.1V).

[0125] Through the above four logics, the charging voltage is continuously and dynamically adjusted, so that the charging voltage fluctuates within the charging protection range according to the actual charging situation, and finally stabilizes near a more reasonable voltage value. This not only ensures that the sodium battery does not precipitate metallic sodium and does not trigger high-temperature alarms, but also increases the charging speed and extends the battery life, achieving the technical effect of comprehensively improving the reliability of the sodium battery.

[0126] The examples involving specific numerical values in the above embodiments are all empirical example values. In actual application scenarios, they can be adjusted according to the actual needs of users, and the present invention does not make specific limitations on this.

[0127] This embodiment provides a device for calibrating the maximum continuous charging current. Figure 2 As shown, the device includes:

[0128] An aging module 201 is used to obtain an aging coefficient of a sodium battery sample, where the aging coefficient is used to indicate the degree of aging of the sodium battery sample relative to a brand new state;

[0129] Theoretical protection current acquisition module 202 is used to determine the theoretical maximum charging current value according to the preset battery state of charge and the preset battery cell temperature of the sodium battery sample;

[0130] The correction protection current module 203 is used to amplify the theoretical maximum charging current value based on the aging coefficient to obtain the corrected maximum charging current under the preset battery state of charge, preset battery cell temperature condition and current aging condition.

[0131] An embodiment of the present invention also provides a vehicle having a sodium battery of a low-voltage system and a vehicle controller, wherein the vehicle controller includes a memory and a processor, the memory stores the program of the charging voltage control method provided by the aforementioned method embodiment, and the processor is used to execute the method program.

[0132] In some optional embodiments, such as Figure 3 As shown, the vehicle provided by the present invention also includes a body domain controller 1, a power battery to sodium battery DC module 2, a vehicle controller 3, a battery 4, a battery management system 5, a sodium battery to battery DC module 6, a power battery 7, a power battery management system 8, a sodium battery management system 10, and other controllers 11.

[0133] The vehicle domain controller 1 integrates a gateway controller, which allocates network segments to facilitate unified management of various components by the vehicle domain controller 1. The sodium battery 9, sodium battery management system 10, power battery to sodium battery DC module 2, and vehicle controller 3 are allocated on the first network segment. The sodium battery 9 is typically 48V. The sodium battery management system 10 monitors the status of the sodium battery 9, such as voltage, current, temperature, and SOC, and performs power management. The power battery to sodium battery DC module 2 converts the power battery 7 to the voltage level of the sodium battery 9, such as a high-voltage to 48V DC-DC module. This voltage conversion is used by the sodium battery 9 low-voltage system and the sodium battery 9. The vehicle controller 3 controls the output voltage of the power battery to sodium battery DC module 2 and the sodium battery to battery DC module 6.

[0134] Battery 4, battery management system 5, and sodium battery to battery DC module 6 are allocated on the second network segment. Battery 4 is often 12V or lower. The battery management system 5 mainly monitors the status of battery 4, such as voltage, current, temperature, and SOC, and performs power management. Sodium battery to battery DC module 6 is responsible for converting the power of sodium battery 9 to the voltage level of battery 4, such as a 48V to 12V DC-DC module. Through voltage conversion, the power is supplied to the low-voltage system of battery 4 and battery 4.

[0135] The power battery 7, power battery management system 8, and other controllers 11 are allocated on the third network segment. The power battery 7 is the battery that drives the vehicle's electric motor to make the vehicle move. Its voltage range is generally between 300V and 600V. The main function of the power battery management system 8 is to monitor the status of the power battery 7 and perform power management on it. Other controllers 11 include cockpit domain control, chassis wire control, intelligent driving system, etc. For example, it includes a 48V controller for controlling high-power electrical appliances such as the chassis system, window system, and air suspension system, and also includes a 12V controller for controlling the cockpit system, intelligent driving system, etc.

[0136] like Figure 4 As shown, the present invention provides a vehicle electrical schematic diagram. After power battery 7 undergoes voltage conversion via power battery-to-sodium battery DC module 2, the high voltage of hundreds of volts is converted to the low voltage level of sodium battery 9. The sodium battery 9 and power battery-to-sodium battery DC module 2 are connected in parallel. The outputs of the sodium battery 9 and power battery-to-sodium battery DC module 2 are connected to other controllers 11 and the sodium battery-to-storage battery DC module 6. The output of the sodium battery-to-storage battery DC module 6 is connected to the storage battery 4 and other controllers 11. In the low-voltage system of the sodium battery 9, for cost considerations, some loads supported by the voltage level of the storage battery 4 can be retained. For example, in a 48V low-voltage system, some 12V low-voltage loads can be retained.

[0137] With the vehicle provided by the present invention, the sodium battery management system 10 determines the cell temperature of the sodium battery 9 when the vehicle is powered on. For example, in one embodiment, the sodium battery 9 includes 17 cells connected in series, each of which requires a temperature sensor for temperature monitoring.

[0138] If the sodium battery management system 10 monitors that the temperature of any cell of the sodium battery 9 is lower than a preset temperature threshold (e.g., 0°C), it is necessary to adjust the charging voltage output by the power battery-to-sodium battery DC module 2. The adjustment process is similar to the aforementioned method embodiment. The theoretical maximum charging current value lookup table used when adjusting the charging voltage is stored in the vehicle controller 3. Based on the cell temperature monitored by the sodium battery management system 10 and the terminal voltage of the sodium battery 9, interpolation processing is performed through the lookup table.

[0139] If the sodium battery management system 10 monitors that the temperature of all cells of the sodium battery 9 is greater than the preset temperature threshold, the output voltage of the power battery to sodium battery DC module 2 is mainly adjusted according to the terminal voltage of the sodium battery 9, and the theoretical maximum charging current value lookup table used for voltage regulation is placed in the vehicle controller 3.

[0140] Under the premise that the vehicle is powered off, the vehicle controller 3 determines whether the vehicle is in intelligent charging or the charging pile is performing fast charging or slow charging function on the vehicle;

[0141] When performing the above functions, the sodium battery management system 10 monitors the sodium battery 9. If the temperature of any cell is lower than a preset temperature threshold, the output voltage of the power battery to sodium battery DC module 2 needs to be adjusted. The adjustment process is described in the aforementioned method embodiment. The theoretical maximum charging current value lookup table used when adjusting the charging voltage is placed in the vehicle controller 3. Based on the cell temperature monitored by the sodium battery management system 10 and the terminal voltage of the sodium battery 9, interpolation processing is performed through the lookup table;

[0142] If the sodium battery management system 10 monitors that the temperature of all cells of the sodium battery 9 is greater than the preset temperature threshold, the output voltage of the power battery to sodium battery DC module 2 is mainly adjusted according to the terminal voltage of the sodium battery 9, and the theoretical maximum charging current value lookup table used for voltage regulation is placed in the vehicle controller 3.

[0143] The embodiment of the present invention also provides a computer-readable storage medium. The above-mentioned method according to the embodiment of the present invention can be implemented in hardware, firmware, or implemented as a computer code that can be recorded in a storage medium, or implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and downloaded through a network and will be stored in a local storage medium, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state drive, etc.; further, the storage medium can also include a combination of the above-mentioned types of memory. It can be understood that a computer, a processor, a microprocessor controller or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor or hardware, the method shown in the above embodiment is implemented.

[0144] A portion of the present invention may be applied as a computer program product, such as a computer program instruction, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. Those skilled in the art should understand that the form in which the computer program instruction exists in a computer-readable medium includes, but is not limited to, a source file, an executable file, an installation package file, etc. Accordingly, the way in which the computer program instruction is executed by the computer includes, but is not limited to: the computer directly executes the instruction, or the computer compiles the instruction and then executes the corresponding compiled program, or the computer reads and executes the instruction, or the computer reads and installs the instruction and then executes the corresponding installed program. Here, the computer-readable medium may be any available computer-readable storage medium or communication medium that can be accessed by the computer.

[0145] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for calibrating the maximum continuous charging current, characterized in that: The method comprises: obtaining an aging coefficient of a sodium battery sample, wherein the aging coefficient is used to indicate an aging degree of the sodium battery sample relative to a brand-new state; Determine a theoretical maximum charging current value according to a preset battery state of charge and a preset cell temperature of the sodium battery sample; The theoretical maximum charging current value is amplified based on the aging coefficient to obtain a corrected maximum charging current under a preset battery state of charge, a preset battery cell temperature condition and a current aging condition.

2. The method according to claim 1, characterized in that When the theoretical maximum charging current value is a current limit value at which the sodium battery does not precipitate sodium under a preset low-temperature charging condition, determining the theoretical maximum charging current value according to a preset battery state of charge and a preset cell temperature of the sodium battery sample includes: Fully charging a plurality of sodium battery samples under a preset normal temperature condition, and discharging the sodium battery samples to a preset battery state of charge, wherein the preset normal temperature condition is greater than a preset temperature threshold, and the preset temperature threshold is used to indicate a boundary between low temperature and non-low temperature scenarios; The discharged sodium battery sample is left standing for a first preset time at a preset battery cell temperature, wherein the preset battery cell temperature is less than or equal to the preset temperature threshold; The sodium battery samples were charged with different test charging currents after being left at rest, and each sodium battery sample was dissected when fully charged; According to the phenomenon of whether metallic sodium is precipitated in each sodium battery sample, a first target sodium battery sample without metallic sodium precipitation is obtained; The theoretical maximum charging current value at the preset battery state of charge and the preset battery cell temperature is determined according to the maximum tested charging current of the first target sodium battery sample.

3. The method according to claim 2, characterized in that The amplifying the theoretical maximum charging current value based on the aging coefficient to obtain a corrected maximum charging current under a preset battery state of charge, a preset battery cell temperature condition, and a current aging condition includes: Calculating a ratio of the theoretical maximum charging current value to the aging coefficient to obtain an initial value of the correction current, wherein the aging coefficient is a health state of the sodium battery; Fully charge the sodium battery sample under a preset room temperature condition, and discharge the sodium battery sample to a preset battery state of charge; The discharged sodium battery sample is allowed to stand at a preset cell temperature for a first preset time; charging the sodium battery sample after standing still using the initial value of the correction current, and dissecting the sodium battery sample when the battery is fully charged; According to whether metallic sodium is precipitated in the sodium battery sample, the initial value of the correction current is adjusted by a preset step size to obtain an adjusted value of the correction current; wherein the initial value of the correction current is adjusted to a smaller value when metallic sodium is precipitated, and the initial value of the correction current is adjusted to a larger value when metallic sodium is not precipitated; Using the correction current adjustment value as the correction current initial value, returning to the step of charging the sodium battery sample after standing using the correction current initial value, and dissecting the sodium battery sample when the battery is fully charged; Until the maximum correction current adjustment value when no metallic sodium is precipitated is obtained, and the maximum correction current adjustment value when no metallic sodium is precipitated is used as the correction maximum charging current.

4. The method according to claim 1, wherein When the theoretical maximum charging current value is a current limit value at which the temperature rise of the sodium battery does not exceed a temperature warning value under a preset high-temperature charging condition, determining the theoretical maximum charging current value according to a preset battery state of charge and a preset cell temperature of the sodium battery sample includes: Fully charging a plurality of sodium battery samples under a preset normal temperature condition, and discharging the sodium battery samples to a preset battery state of charge, wherein the preset normal temperature condition is greater than a preset temperature threshold, and the preset temperature threshold is used to indicate a boundary between low temperature and non-low temperature scenarios; The discharged sodium battery sample is left standing for a second preset time at a preset battery cell temperature, wherein the preset battery cell temperature is greater than the preset normal temperature condition; Charging the rested sodium battery samples with different test charging currents, and detecting during the charging process whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to the temperature warning value, wherein the test charging current is greater than 1C; Acquire a second target sodium battery sample when the temperature of the sodium battery or the temperature of the sodium battery management system rises to the preset temperature warning value; The theoretical maximum charging current value at the preset battery state of charge and the preset battery cell temperature is determined according to the minimum test charging current of the second target sodium battery sample.

5. The method according to claim 4, characterized in that The amplifying the theoretical maximum charging current value based on the aging coefficient to obtain a corrected maximum charging current under a preset battery state of charge, a preset battery cell temperature condition, and a current aging condition includes: Calculating a ratio of the theoretical maximum charging current value to the aging coefficient to obtain an initial value of the correction current, wherein the aging coefficient is a health state of the sodium battery; Fully charge the sodium battery sample under a preset room temperature condition, and discharge the sodium battery sample to a preset battery state of charge; The discharged sodium battery sample is allowed to stand at a preset cell temperature for a second preset time period; charging the sodium battery sample after standing still using the initial value of the correction current, and detecting during the charging process whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to the preset temperature warning value; According to whether the temperature reaches the preset temperature warning value, the initial value of the correction current is adjusted by a preset step size to obtain a correction current adjustment value; wherein when the temperature reaches the preset temperature warning value, the initial value of the correction current is adjusted down, and when the temperature does not reach the preset temperature warning value, the initial value of the correction current is adjusted up; Using the correction current adjustment value as the correction current initial value, returning to the step of charging the sodium battery sample after standing using the correction current initial value, and detecting whether the internal temperature of the sodium battery or the internal temperature of the sodium battery management system rises to the preset temperature warning value during the charging process; Until the maximum correction current adjustment value when the internal temperature of the sodium battery or the internal temperature of the sodium battery management system does not rise to the preset temperature warning value is obtained, and the maximum correction current adjustment value when it does not rise to the preset temperature warning value is used as the correction maximum charging current.

6. The method according to claim 1, characterized in that The method further comprises: Obtain the current temperature, current state of charge, current aging coefficient and terminal voltage of the target sodium battery; querying a corresponding target corrected maximum charging current based on the current temperature, the current state of charge, and the current aging coefficient; The charging voltage of the target sodium battery is adjusted to be within a charging protection interval, where the charging protection interval is a voltage interval greater than the terminal voltage and less than or equal to a target voltage, and the target voltage is a voltage value corresponding to the target corrected maximum charging current.

7. The method according to claim 6, characterized in that The step of adjusting the charging voltage of the sodium battery to be within a charging protection interval includes: Determining whether the current charging current is less than the target corrected maximum charging current; If the current charging current is less than the target rectified maximum charging current and lasts for a third predetermined time period, increasing the charging voltage by a first step; If the current charging current is greater than or equal to the target corrected maximum charging current and lasts for a fourth predetermined time period, reducing the charging voltage by a second step size; determining whether the charging voltage is less than or equal to the terminal voltage; If the charging voltage is less than or equal to the terminal voltage and lasts for a fifth predetermined time period, increasing the charging voltage by a third step size; Determining whether the charging voltage is greater than the sum of the terminal voltage and a preset voltage threshold; If the charging voltage is greater than the sum of the terminal voltage and the preset voltage threshold and lasts for a sixth preset time period, the charging voltage is reduced with a fourth step length.

8. A device for calibrating maximum continuous charging current, characterized in that: The device comprises: an aging module, used to obtain an aging coefficient of a sodium battery sample, where the aging coefficient is used to represent the aging degree of the sodium battery sample relative to a brand new state; A theoretical protection current acquisition module is used to determine a theoretical maximum charging current value according to a preset battery state of charge and a preset cell temperature of the sodium battery sample; The correction protection current module is used to amplify the theoretical maximum charging current value based on the aging coefficient to obtain the corrected maximum charging current under the preset battery state of charge, preset battery cell temperature condition and current aging condition.

9. A vehicle, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method according to any one of claims 1 to 7 by executing the computer instructions.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the method according to any one of claims 1 to 7.

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