Low-temperature charging method, system and equipment for power battery and storage medium

Abstract

The invention discloses a power battery low-temperature charging method, system and device and a storage medium, and relates to the technical field of power batteries. When the temperature is smaller than a first temperature threshold value, entering a high-frequency awakening charging and discharging mode; when the temperature is greater than or equal to the first temperature threshold value and less than or equal to a preset second temperature threshold value, entering a heating charge-discharge mode; the charging current of the high-frequency awakening charging and discharging mode is smaller than the discharging current and is smaller than the charging current of the heating charging and discharging mode; the discharge current of the heating charge-discharge mode is greater than the charge current thereof and greater than the discharge current of the high-frequency wake-up charge-discharge mode. According to the invention, no additional heating device is needed, the battery cost is relatively low, the low-temperature service life of the power battery can be prolonged, and the usability of the power battery under extremely cold working conditions in winter is improved.

Description

Technical Field

[0001] The present application relates to the technical field of power batteries, and in particular to a method, system, device and storage medium for low-temperature charging of power batteries. Background Art

[0002] With the continuous advancement of the industrialization of power batteries, the requirements for power batteries are getting higher and higher. In the field of electric vehicle applications, power batteries are not only required to have high energy density and power density, but also need to be able to further adapt to the extreme working environment brought about by different regions and seasons. Currently on the market, power batteries mainly include lithium-ion batteries and sodium-ion batteries. It is difficult to charge power batteries at low temperatures, which can easily cause permanent capacity loss and lead to safety accidents, which seriously limits the scope of use of electric vehicles and their application and promotion in high-cold areas.

[0003] In the related technology, a low-temperature charging and discharging method of a battery based on temperature compensation and a temperature compensation device are provided. By installing a heat preservation device on the outside of the battery to maintain the temperature of the sodium-ion battery, the power battery can be used normally in a low-temperature environment.

[0004] However, the above method not only increases the cost of the battery, but also the excessive polarization voltage during the charging process will cause capacity loss, shorten the battery life, and even bring safety hazards. Summary of the invention

[0005] The present application provides a method, system, device and storage medium for low-temperature charging of a power battery, which can solve the technical problems in the prior art that the low-temperature charging method has high battery cost and shortens the battery life.

[0006] In a first aspect, the present application provides a method for low-temperature charging of a power battery, the method comprising:

[0007] Get the current temperature of the power battery;

[0008] When the temperature is lower than a preset first temperature threshold, the high-frequency wake-up charging and discharging mode is entered;

[0009] When the temperature is greater than or equal to the first temperature threshold and less than or equal to the preset second temperature threshold, the heating charging and discharging mode is entered;

[0010] The charging current of the high-frequency awakening charging and discharging mode is smaller than its discharging current, and smaller than the charging current of the heating charging and discharging mode; the discharging current of the heating charging and discharging mode is larger than its charging current, and larger than the discharging current of the high-frequency awakening charging and discharging mode.

[0011] In combination with the first aspect, in one embodiment, before obtaining the current temperature of the power battery, the method further includes: obtaining polarization voltage and equivalent impedance of the power battery at different temperatures, and obtaining first current values ​​at different temperatures according to the polarization voltage and equivalent impedance;

[0012] When entering the high-frequency wake-up charge and discharge mode or the heating charge and discharge mode and charging for the first time, it also includes: obtaining the charging start voltage and the charging internal resistance at the temperature to obtain the second current value;

[0013] The charging current is obtained according to the smaller value of the first current value and the second current value at the temperature.

[0014] In combination with the first aspect, in one implementation, obtaining the charging current according to the smaller value of the first current value and the second current value at the temperature specifically includes:

[0015] The product of the smaller value and the current health of the power battery is used as the charging current;

[0016] The second current value I cc1 for:

[0017]

[0018] Among them, U P is the polarization voltage, U 1 is the charging start voltage, R cc is the charging internal resistance, and A is a constant.

[0019] In combination with the first aspect, in one embodiment, before obtaining the current temperature of the power battery, the method further includes: obtaining a safe use voltage threshold and an equivalent impedance of the power battery at different temperatures, and obtaining a third current value at different temperatures according to the safe use voltage threshold and the equivalent impedance;

[0020] When entering a certain charge and discharge mode and discharging for the first time, the method further includes: obtaining a discharge starting voltage and a discharge internal resistance at the temperature to obtain a fourth current value;

[0021] The discharge current is obtained according to the smaller value of the third current value and the fourth current value at the temperature.

[0022] In combination with the first aspect, in one implementation, obtaining the discharge current according to the smaller value of the third current value and the fourth current value at the temperature specifically includes:

[0023] The product of the smaller value and the current health of the power battery is used as the discharge current;

[0024] The fourth current value I dc1 for:

[0025]

[0026] Among them, U max is the polarization voltage, U 2 is the discharge starting voltage, R dc is the charging internal resistance, and B is a constant.

[0027] In combination with the first aspect, in one implementation, after obtaining the current temperature of the power battery, the method further includes:

[0028] According to the above temperature and charge and discharge mode, the charge and discharge frequency and discharge duty cycle are determined, and then the single charge and discharge time is determined; the above single charge time is greater than the single discharge time.

[0029] In combination with the first aspect, in one implementation, when the temperature is greater than the second temperature threshold, the method further includes:

[0030] The power battery voltage is obtained, and when the power battery voltage is greater than or equal to a first voltage threshold, a normal charging mode is entered until the power battery voltage is greater than or equal to a second voltage threshold.

[0031] In a second aspect, the present application provides a power battery low-temperature charging system, the system comprising:

[0032] An acquisition module is used to obtain the current temperature of the power battery;

[0033] A charging module, which is used to enter a high-frequency wake-up charging and discharging mode when the temperature is less than a preset first temperature threshold; and enter a heating charging and discharging mode when the temperature is greater than or equal to the first temperature threshold and less than or equal to a preset second temperature threshold;

[0034] The charging current of the high-frequency awakening charging and discharging mode is smaller than its discharging current, and smaller than the charging current of the heating charging and discharging mode; the discharging current of the heating charging and discharging mode is larger than its charging current, and larger than the discharging current of the high-frequency awakening charging and discharging mode.

[0035] In a third aspect, the present application provides a power battery low-temperature charging device, which includes a processor, a memory, and a power battery low-temperature charging program stored in the memory and executable by the processor, wherein when the power battery low-temperature charging program is executed by the processor, the steps of the power battery low-temperature charging method are implemented.

[0036] In a fourth aspect, the present application provides a computer-readable storage medium, on which a power battery low-temperature charging program is stored, wherein when the power battery low-temperature charging program is executed by a processor, the steps of the power battery low-temperature charging method are implemented.

[0037] The beneficial effects of the technical solution provided by this application include:

[0038] By obtaining the current temperature of the power battery, the corresponding high-frequency wake-up charge and discharge mode or heating charge and discharge mode is entered, wherein the charging current of the high-frequency wake-up charge and discharge mode is smaller than its discharge current, and smaller than the charging current of the heating charge and discharge mode; the discharge current of the heating charge and discharge mode is larger than its charging current, and larger than the discharge current of the high-frequency wake-up charge and discharge mode, so as to complete high-frequency pulse charge and discharge in extremely cold temperature domain and heating charge and discharge mode at low temperature. Not only does it not require additional heating device, the battery cost is lower, but it can also improve the low-temperature service life of the power battery and enhance the usability of the power battery in extremely cold working conditions in winter. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of a flow chart of an embodiment of a method for low-temperature charging of a power battery of the present application;

[0040] Figure 2 This is a flow chart of another embodiment of the low-temperature charging method for a power battery of the present application;

[0041] Figure 3 A schematic diagram of the current of positive and negative pulse charging and discharging in the embodiment of the present application;

[0042] Figure 4 This is a schematic diagram of the structure of an embodiment of a low-temperature charging system for a power battery of the present application;

[0043] Figure 5 This is a schematic diagram of the hardware structure of the power battery low-temperature charging equipment involved in the embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0045] Because under extreme low temperature conditions in winter, the acceptable discharge rate of sodium-ion batteries and lithium-ion batteries is generally higher than the charging rate. In addition, sodium-ion batteries can also be discharged to 0V. Therefore, it is crucial to use the low-temperature performance advantages of sodium-ion batteries and lithium-ion batteries to reasonably formulate a charging strategy for power batteries under low temperatures.

[0046] In a first aspect, an embodiment of the present application provides a method for low-temperature charging of a power battery.

[0047] In one embodiment, referring to Figure 1 , Figure 1 The figure is a flow chart of an embodiment of a method for charging a power battery at low temperature of the present application. The method for charging a power battery at low temperature comprises:

[0048] S1. Get the current temperature of the power battery;

[0049] S2. When the temperature is lower than the preset first temperature threshold, the high-frequency wake-up charging and discharging mode is entered;

[0050] S3. When the temperature is greater than or equal to the first temperature threshold and less than or equal to the preset second temperature threshold, enter the heating charge and discharge mode.

[0051] The charging current of the high-frequency awakening charging and discharging mode is smaller than its discharging current, and smaller than the charging current of the heating charging and discharging mode; the discharging current of the heating charging and discharging mode is larger than its charging current, and larger than the discharging current of the high-frequency awakening charging and discharging mode.

[0052] In this embodiment, by acquiring the current temperature of the power battery, the corresponding high-frequency wake-up charge and discharge mode or heating charge and discharge mode is entered, wherein the charging current of the high-frequency wake-up charge and discharge mode is smaller than its discharge current, and smaller than the charging current of the heating charge and discharge mode; the discharge current of the heating charge and discharge mode is larger than its charging current, and larger than the discharge current of the high-frequency wake-up charge and discharge mode, so as to complete high-frequency pulse charge and discharge in extremely cold temperature range and heating charge and discharge mode at low temperature. Not only does it not require additional heating devices, the battery cost is lower, but it can also improve the low-temperature service life of the power battery and enhance the usability of the power battery in extremely cold working conditions in winter.

[0053] Furthermore, in one embodiment, before obtaining the current temperature of the power battery, the method further includes: obtaining polarization voltage and equivalent impedance of the power battery at different temperatures, and obtaining first current values ​​at different temperatures based on the polarization voltage and equivalent impedance.

[0054] The first current value at any temperature is: the ratio of the polarization voltage to the equivalent impedance at the temperature.

[0055] In this embodiment, when entering a certain charge and discharge mode and charging for the first time, it also includes:

[0056] First, the charging start voltage and the charging internal resistance at the temperature are obtained to obtain a second current value;

[0057] Then, the charging current is obtained according to the smaller value of the first current value and the second current value at the temperature, and then the power battery can be charged with the charging current.

[0058] In this embodiment, the charging current is obtained according to the smaller value of the first current value and the second current value, so as to ensure the charging effect and charging safety.

[0059] Furthermore, in this embodiment, obtaining the charging current according to the smaller value of the first current value and the second current value at the temperature specifically includes:

[0060] The product of the smaller value mentioned above and the current health of the power battery is used as the charging current.

[0061] In this embodiment, further constraints are imposed on the charging current according to the current health of the power battery, which can further adapt to the health of the power battery and facilitate the charging process to be carried out effectively and accurately.

[0062] In other embodiments, the smaller value of the first current value and the second current value at the temperature may be used as the charging current.

[0063] In this embodiment, the second current value I cc1 for:

[0064]

[0065] Among them, U P is the polarization voltage, U 1 is the charging start voltage, R cc is the charging internal resistance, and A is a constant.

[0066] Furthermore, in one embodiment, before obtaining the current temperature of the power battery, the method further includes: obtaining a safe voltage threshold and an equivalent impedance of the power battery at different temperatures, and obtaining a third current value at different temperatures based on the safe voltage threshold and the equivalent impedance.

[0067] The third current value at any temperature is: the ratio of the safe operating voltage threshold at the temperature to the equivalent impedance.

[0068] In this embodiment, when entering a certain charge and discharge mode and discharging for the first time, it also includes:

[0069] First, the discharge starting voltage and the discharge internal resistance at the temperature are obtained to obtain a fourth current value;

[0070] Then, the discharge current is obtained according to the smaller value of the third current value and the fourth current value at the temperature. Subsequently, the power battery can be discharged with the discharge current.

[0071] In this embodiment, the discharge current is obtained according to the smaller value of the third current value and the fourth current value, so that the discharge effect and discharge safety can be guaranteed.

[0072] Further, in this embodiment, obtaining the discharge current according to the smaller value of the third current value and the fourth current value at the temperature specifically includes:

[0073] The product of the smaller value mentioned above and the current health of the power battery is used as the discharge current.

[0074] In this embodiment, the discharge current is further constrained according to the current health of the power battery, which can further adapt to the health of the power battery and facilitate the discharge process to be carried out effectively and accurately.

[0075] In other embodiments, the smaller value of the third current value and the fourth current value at the temperature may be used as the discharge current.

[0076] In this embodiment, the fourth current value I dc1 for:

[0077]

[0078] Among them, U max is the polarization voltage, U 2 is the discharge starting voltage, R dc is the charging internal resistance, and B is a constant.

[0079] Furthermore, in one embodiment, after obtaining the current temperature of the power battery, the method further includes:

[0080] According to the above temperature and charge and discharge mode, the charge and discharge frequency and discharge duty cycle are determined, and then the single charge and discharge time is determined; the above single charge time is greater than the single discharge time.

[0081] In this embodiment, the charge and discharge frequency of the high-frequency wake-up charge and discharge mode is 800Hz to 2000Hz, and its discharge duty cycle is 5% to 40%, thereby determining the single charge and discharge duration in the high-frequency wake-up charge and discharge mode. The charge and discharge frequency of the heating charge and discharge mode is 0.1Hz to 1000Hz, and its discharge duty cycle is 1% to 20%, thereby determining the single charge and discharge duration in the heating charge and discharge mode.

[0082] Furthermore, in one embodiment, when the temperature is greater than the second temperature threshold, the method further includes:

[0083] The power battery voltage is obtained, and when the power battery voltage is greater than or equal to a first voltage threshold, a normal charging mode is entered until the obtained power battery voltage is greater than or equal to a second voltage threshold.

[0084] Furthermore, in one embodiment, when the temperature is greater than the second temperature threshold, the method further includes:

[0085] The power battery voltage is obtained, and when the power battery voltage is less than a first voltage threshold, a heating charging and discharging mode is entered, until the obtained power battery voltage is greater than or equal to the first voltage threshold, and a normal charging mode is entered.

[0086] The low-temperature charging method of this embodiment can improve the low-temperature charging performance of the power battery at low temperatures through high-frequency wake-up charging and discharging mode and heating charging and discharging mode and segmented constant current charging, so that the power battery can be charged and discharged even in extremely cold conditions (-60°C), and is also conducive to promoting the industrial application of sodium-ion batteries in the field of power batteries.

[0087] In one embodiment, the above-mentioned power battery low temperature charging method includes:

[0088] Step 1. Determine whether an external power source is connected, monitor the battery parameters during the battery charging process, obtain the temperature and voltage of the battery cell, and determine the charging mode entered by the power battery;

[0089] Among them, the monitored battery data mainly includes battery cell temperature, voltage and current, etc. For electric vehicle power battery packs, the lowest battery cell temperature in the battery pack is used as the current temperature of the power battery.

[0090] Step 2. When the temperature of the battery is lower than the set first temperature threshold T1, a high-frequency wake-up positive and negative pulse charging and discharging charging mode, i.e., a high-frequency wake-up charging and discharging mode, is started;

[0091] Among them, the first temperature threshold T1 of sodium ion battery is -40℃~-20℃, the first temperature threshold T1 of lithium ion battery is -30℃~-10℃, the usual frequency of high-frequency wake-up charge and discharge mode is 800Hz~2000Hz, and the discharge duty cycle is 5%~40%. The high-frequency wake-up charge and discharge mode is mainly at high frequency and small current. At this stage, the battery impedance is mainly reflected in ohmic impedance and electrolyte transfer impedance. Ohmic impedance can achieve a small temperature rise, and high-frequency ion transfer is conducive to battery wake-up at low temperature.

[0092] Step 3. When the first temperature threshold T1 ≤ the current temperature of the battery ≤ the second temperature threshold T2, the charging mode of heating positive and negative pulse charging and discharging, i.e., heating charging and discharging mode, is entered;

[0093] Among them, the second temperature threshold T2 is 0℃~5℃. In this heating charge and discharge mode, since the discharge current is several times higher than the charging current, the charging time is several times longer than the discharging time, so as to achieve heating while charging. The frequency is 0.1Hz~1000Hz, and the discharge duty cycle is 1%~20%.

[0094] Step 4. When the battery temperature is greater than the second temperature threshold T2, the voltage monitoring unit monitors the power battery voltage. If the voltage is greater than or equal to the first voltage threshold, the heating charge and discharge mode is terminated and the normal battery charging mode is started; if the voltage is less than the first voltage threshold, the heating charge and discharge mode is continued until the power battery voltage reaches the first voltage threshold, and then the normal charging mode is entered;

[0095] Step 5. When the power battery is charged from the normal charging mode to a second voltage threshold, charging is terminated; wherein the second voltage threshold is greater than the first voltage threshold.

[0096] Among them, the normal charging mode includes constant current and constant voltage charging, step-by-step constant current charging and AC charging and other charging modes, charging the battery to the second voltage threshold, or SOC to more than 95% with an acceptable charging current.

[0097] Preferably, the first voltage threshold of the sodium ion battery is 2.8V~3.1V, and the second voltage threshold of the sodium ion battery is 3.9V~4.0V; the first voltage threshold of the iron-lithium battery in the lithium ion battery is 2.0V~2.2V, and the second voltage threshold is 3.4V~3.65V; the first voltage threshold of the ternary battery in the lithium ion battery is 2.9V~3.15V, and the second voltage threshold is 4.0V~4.4V.

[0098] Optionally, the battery SOC can be estimated in combination with the initial and real-time voltage and current collected by the monitoring unit, and the charging mode is controlled by judging the battery SOC state. The first voltage threshold is equivalent to 10% to 30% SOC, and the second voltage threshold is equivalent to 95% to 100% SOC.

[0099] In this embodiment, according to the Thevenin equivalent circuit model and Joule's law, during the process of applying pulse excitation to the battery, the internal resistance of the battery is usually equivalent to real impedance and imaginary impedance. The impedance model is as follows, reflecting the relationship between impedance and frequency:

[0100]

[0101] Where f is the frequency of the sinusoidal AC, Z is the equivalent impedance of the battery at frequency f, and R e is the ohmic internal resistance of the battery, L is the inductance of the battery, R ct is the charge transfer resistance of the battery, Q ct is the capacitance coefficient of the constant phase element corresponding to the charge transfer process, and α is the phase factor of the charge transfer.

[0102] Based on the Maas current curve, the polarization voltage U was obtained by three-electrode test. P , and then obtain the first current value I cc0 :

[0103]

[0104] When the battery is charged and discharged at different frequencies, the internal impedance increases with the frequency. During low-temperature pulse heating, there is a difference in the internal impedance of the battery when comparing the initial high-frequency charge and discharge with the final low-frequency charge and discharge, so the battery current needs to be corrected.

[0105] By obtaining the measured data of the battery at different temperatures, the charging current corresponding to different temperatures can be calculated. The measured data at different temperatures are summarized to obtain the measured database of the battery at different temperatures. The measured database of batteries with the same chemical system is summarized to form a database set, and the constant A under the chemical system can be obtained.

[0106] Optionally, the measured data sets of batteries of different chemical systems can be aggregated into a database cluster, and the data can be classified according to the temperature threshold intervals mentioned above, and the charging data of lithium-ion batteries at different temperatures and different voltages can be classified. cc1 and I cc0 Tests are carried out to obtain the constant A under different chemical systems.

[0107] In addition, the charging internal resistance R at different temperatures can be determined by combining the HPPC (Hybrid Pulse Power Characterization) method or the JEVS (Japan Electric Vehicle Society) method. cc .

[0108] Therefore, the minimum charging current I cc for:

[0109] I cc =min(I cc0 ,I cc1 )

[0110] in, U 1 It is the charging start voltage that is monitored instantaneously during charging.

[0111] In this embodiment, the real impedance generates Joule heat during charging, and the expression Q of the Joule heat is:

[0112]

[0113] In this embodiment, based on the premise of safe use of the battery, the safe use voltage threshold U of the battery at different low temperatures is determined. max The initial discharge current, i.e., the third current value, is obtained by the voltammetry method, and then the third current value I at each temperature is obtained by the interpolation method.dc0 .in,

[0114]

[0115] Combined with HPPC method or JEVS method to determine the charging internal resistance at different temperatures, and then use interpolation method to obtain the charging internal resistance R at each temperature. dc .

[0116] Based on the electrochemical model and measured data of battery pulse charge and discharge, the battery is adjusted to different specific voltages, and instantaneous pulse tests are completed at different temperatures. The pulse endpoint potential and threshold potential (polarization voltage or voltage discharge threshold) are close, usually recommended to be ≤0.05V, to determine the limit power and limit discharge current values ​​at each temperature and voltage. Similarly, combined with the cluster analysis method, the constant B value is calculated to determine the fourth current value I dc1 The calculation formula is:

[0117]

[0118] Therefore, the minimum discharge current I dc for:

[0119] I dc =min(I dc0 ,I dc1 )

[0120] Furthermore, since the internal resistance of the power battery will inevitably increase and the capacity will decay during use, the current can be further limited by the SOH, i.e., the health of the battery. With k as the SOH calculated by the battery main controller, the final charging current I is obtained. ccSOH , and the discharge current I dcSOH ,in:

[0121] I ccSOH = k × I cc

[0122] I dcSOH = k × I dc .

[0123] Based on the actual measurement and calculation, the charging current I of the high-frequency wake-up charging and discharging mode is obtained. 1 The range is 0.05C~1C, and the charging current I 3 The range is 0.05C~3C.

[0124] In this embodiment, the temperature of the power battery is monitored by a temperature monitoring unit to determine the charging mode entered by the power battery under low temperature conditions, and the maximum achievable pulse frequency is obtained. As the temperature rises to a value greater than or equal to the first temperature threshold and less than or equal to a preset second temperature threshold, the maximum pulse charging current amplitude and the maximum discharge current amplitude allowed by the power battery are obtained to realize charging modes under different temperature ranges.

[0125] In some embodiments, polarization is more obvious during constant current charging at low temperature. Sodium deposition and lithium precipitation at the negative electrode of the battery are also caused by excessive accumulation of sodium ions or lithium ions at the interface. In addition, sodium ion power batteries charge slowly under low temperature conditions.

[0126] In this embodiment, the high-frequency wake-up charge and discharge mode of small current and the heating charge and discharge mode of large current destroy the polarization layer inside the battery through the intermittent charging and discharging process, which can alleviate the battery polarization to a certain extent, promote the flow of electrolytes in the electrolyte, balance the problem of uneven distribution of sodium ion or lithium ion concentration in the electrolyte, reduce the depletion of sodium or lithium at the interface, and inhibit the reduction reaction between the solvent and the interface electrons, thereby effectively inhibiting the growth of the SEI film and the increase of the interface resistance of the battery, and improving the charging efficiency and cycle life. At the same time, during pulse charging, by periodically applying voltage pulses during the charging process, the migration and embedding / de-embedding of sodium ions or lithium ions between the positive and negative electrodes are promoted, so that the sodium ions or lithium ions in the graphite are more evenly distributed, and the formation of sodium or lithium plating is avoided, thereby reducing the precipitation of sodium salts or lithium salts on the electrode surface. In addition, the temperature rise rate of the heating charge and discharge mode of large current is fast, which can also effectively improve the low temperature performance of the battery.

[0127] In this embodiment, a new type of supercapacitor is also provided, namely a new type of flexible solid-state capacitor, which has a wide operating temperature range and supports operation at extreme temperatures below -40°C. The new type of flexible solid-state capacitor has an anti-freezing electrolyte, a carbon nanotube electrode with vertically arranged channels, and a backup power supply for the high-frequency wake-up stage at low temperatures. Compared with commercial capacitors, the new type of flexible solid-state capacitor has a wider operating temperature range, which is conducive to further broadening the lower limit of the applicable ambient temperature of the power battery. Combining the above control strategy and the new type of supercapacitor, the problem of sodium electrolysis and lithium electrolysis at low temperatures can be further alleviated.

[0128] like Figure 2 As shown, in this embodiment, taking a sodium ion cylindrical battery as an example, its 1C nominal capacity is 9Ah, the first temperature threshold T1, the second temperature threshold T2, and the current temperature of the power battery is less than or equal to T2, the above-mentioned power battery low temperature charging method specifically includes:

[0129] A1. Get the current temperature of the power battery;

[0130] A2. Determine whether the temperature is less than T1. If so, go to A3; otherwise, go to A4.

[0131] A3. Enter high-frequency wake-up charging and discharging mode;

[0132] A4. Determine whether the temperature is greater than or equal to T1 and less than or equal to T2. If so, go to A5; otherwise, go to A3.

[0133] A5. Enter heating charging and discharging mode;

[0134] A6. Determine whether the temperature is greater than T2 and the power battery voltage is greater than or equal to the first voltage threshold. If so, go to A7; otherwise, go to A5.

[0135] A7. Enter normal charging mode;

[0136] A8. Determine whether the power battery voltage is greater than or equal to the second voltage threshold. If so, it indicates that charging is complete and ends. Otherwise, go to A7.

[0137] Among them, in the above step A3, the first temperature threshold T1 is -20°C. When the current temperature of the power battery is lower than -20°C, the acceptable discharge rate of the sodium ion battery is greater than the charging rate, and the set discharge current can be greater than the charging current. At this time, the charging current is 0.1C, the discharge current is 0.2C, the discharge duty cycle is 10%, and the battery charge and discharge frequency is controlled to be 1500Hz, ensuring that the capacity attenuation rate of the sodium ion battery is reduced after low-temperature charge and discharge cycles, and the battery can also be quickly awakened and heated.

[0138] In one embodiment, the temperature of the sodium ion battery is higher than -20°C, the battery charge and discharge frequency is controlled to be 400Hz, the maximum charging current allowed by the battery is 0.3C, the maximum discharge rate is 1C, the charging current is 0.2C, the discharge current is 1C, and the duty cycle is 8%, which can achieve rapid battery heating.

[0139] In another embodiment, when the temperature of the sodium ion battery is higher than -20°C, the battery frequency is controlled to be 300Hz, the charging current is 0.3C, the discharging current is 1C, and the duty cycle is 10%. The low temperature charging capacity attenuation rate of the sodium ion battery is reduced by 0.5%.

[0140] Among them, in the above step A6, when the battery temperature is greater than the temperature threshold T2, the voltage monitoring unit monitors the power battery voltage, and when the voltage is greater than or equal to the first voltage threshold, the heating charge and discharge mode is ended and the normal charging mode of the battery is started; when the voltage is less than the first voltage threshold, the heating charge and discharge mode is continued until the voltage of each cell reaches the first voltage threshold.

[0141] Specifically, when the sodium ion battery voltage is greater than or equal to the first voltage threshold and the battery temperature is greater than or equal to T2, segmented constant current charging is entered, the first voltage threshold ranges from 2.8V to 3.1V, and T2 is 0°C to 5°C. When one of the voltage or temperature conditions is not met, the heating charge and discharge mode is continued until both the voltage and temperature meet the requirements.

[0142] When the battery control system has a high-precision SOC estimation function, it can replace the voltage judgment based on the SOC value. The first voltage threshold range is 2.8V~3.1V, which is equivalent to a 30% SOC state of the battery. At low temperatures, the battery voltage changes with the temperature. At the same 30% SOC state, the voltage of different batteries fluctuates, and the voltage range is 2.8V~3.1V.

[0143] In the above steps A7 and A8, the battery is charged to the second voltage threshold by the normal charging mode, and the charging is terminated; the normal charging mode involves multiple charging modes such as constant current and constant voltage charging, step-by-step constant current charging and AC charging, and the battery is charged to the second voltage threshold or SOC to more than 95% with an acceptable charging current.

[0144] Optionally, the second voltage threshold range of the sodium ion battery is 3.9V to 4.0V.

[0145] Furthermore, in one embodiment, taking a lithium-ion battery as an example, the 1C nominal capacity is 20Ah, but is not limited thereto.

[0146] Optionally, the first temperature threshold T1 of the lithium-ion battery is -15°C. When the battery temperature is -16°C, the high-frequency wake-up charge and discharge takes a charging current of 0.1C, a discharging current of 0.13C, a discharge duty cycle of 10%, and a control battery frequency of 1500Hz, so as to achieve a short-time rapid wake-up and temperature rise of the lithium-ion battery under extremely cold conditions.

[0147] like Figure 3 The current trend shown in the figure shows that both the high-frequency wake-up charge and discharge mode and the heating charge and discharge mode are a reverse discharge followed by a charge. ccSOH For I 1 , its discharge current I dcSOH For I 2 , its single charging time t1 is greater than the single discharging time t2; the charging current I ccSOH For I 3 , its discharge current I dcSOH For I 4 , its single charging time is also longer than the single discharging time.

[0148] In this embodiment, the small current positive and negative pulse charging and discharging in the high-frequency wake-up charging and discharging mode can quickly activate the battery at an ambient temperature below -40°C, which can slow down the concentration polarization and electrochemical polarization to a certain extent, avoid the loss of battery capacity caused by direct high current charging, and also help to increase the battery temperature. The high current positive and negative pulse charging and discharging in the heating charging and discharging mode is also conducive to reducing the capacity attenuation rate of the battery after low-temperature charging and discharging cycles, and realizing rapid heating of the battery.

[0149] In a second aspect, an embodiment of the present application also provides a low-temperature charging system for a power battery.

[0150] In one embodiment, referring to Figure 4 , Figure 4 The schematic diagram of the structure of an embodiment of a low-temperature charging system for a power battery of the present application is shown in FIG. The low-temperature charging system for a power battery includes an acquisition module and a charging module.

[0151] The acquisition module is used to acquire the current temperature of the power battery.

[0152] The charging module is used to enter a high-frequency wake-up charging and discharging mode when the temperature is lower than a preset first temperature threshold; and to enter a heating charging and discharging mode when the temperature is greater than or equal to the first temperature threshold and less than or equal to a preset second temperature threshold.

[0153] The charging current of the high-frequency awakening charging and discharging mode is smaller than its discharging current, and smaller than the charging current of the heating charging and discharging mode; the discharging current of the heating charging and discharging mode is larger than its charging current, and larger than the discharging current of the high-frequency awakening charging and discharging mode.

[0154] Optionally, the acquisition module includes a temperature monitoring unit, a current monitoring unit and a voltage monitoring unit, wherein the temperature monitoring unit is used to collect the temperature value of the battery; the current monitoring unit is used to collect the current value of the battery; and the voltage monitoring unit is used to collect the voltage value of the battery.

[0155] The charging module is a main control module, which is used to perform basic data storage, data judgment and charge and discharge control on the battery according to various battery parameters and preset strategies.

[0156] Optionally, the system further comprises a capacitor control module and a power control module, wherein the capacitor control module is used to control the charging and discharging circuit of the novel supercapacitor; and the power control module is used to control the charging and discharging circuit of the power battery.

[0157] Furthermore, in one embodiment, the acquisition module is also used for:

[0158] Before obtaining the current temperature of the power battery, obtaining the polarization voltage and equivalent impedance of the power battery at different temperatures, and obtaining the first current value at different temperatures according to the polarization voltage and equivalent impedance; and,

[0159] When entering the high-frequency wake-up charge and discharge mode or the heating charge and discharge mode and charging for the first time, obtaining the charging start voltage and the charging internal resistance at the temperature to obtain the second current value;

[0160] The charging current is obtained according to the smaller value of the first current value and the second current value at the temperature.

[0161] Furthermore, in one embodiment, the acquisition module is also used for:

[0162] The product of the smaller value mentioned above and the current health of the power battery is used as the charging current.

[0163] Furthermore, in one embodiment, the acquisition module is also used for:

[0164] Before obtaining the current temperature of the power battery, obtaining the safe use voltage threshold and equivalent impedance of the power battery at different temperatures, and obtaining the third current value at different temperatures according to the safe use voltage threshold and equivalent impedance; and,

[0165] When entering the high-frequency wake-up charge and discharge mode or the heating charge and discharge mode and discharging for the first time, obtaining the discharge start voltage and the discharge internal resistance at the temperature to obtain a fourth current value;

[0166] The discharge current is obtained according to the smaller value of the third current value and the fourth current value at the temperature.

[0167] Furthermore, in one embodiment, the acquisition module is also used for:

[0168] The product of the smaller value mentioned above and the current health of the power battery is used as the discharge current.

[0169] Furthermore, in one embodiment, the charging module is also used for:

[0170] According to the above temperature and charge and discharge mode, the charge and discharge frequency and discharge duty cycle are determined, and then the single charge and discharge time is determined; the above single charge time is greater than the single discharge time.

[0171] Furthermore, in one embodiment, the acquisition module is further used to: acquire the power battery voltage when the temperature is greater than the second temperature threshold;

[0172] The charging module is also used to: when the temperature is greater than the second temperature threshold and the power battery voltage is greater than or equal to the first voltage threshold, enter a normal charging mode until the power battery voltage is greater than or equal to the second voltage threshold.

[0173] Among them, the functional implementation of each module in the above-mentioned power battery low-temperature charging system corresponds to the various steps in the above-mentioned power battery low-temperature charging method embodiment, and its functions and implementation processes are no longer repeated here one by one.

[0174] In a third aspect, an embodiment of the present application provides a low-temperature charging device for a power battery. The low-temperature charging device for a power battery may be a personal computer (PC), a laptop computer, a server, or other device with a data processing function.

[0175] Reference Figure 5 , Figure 5 Schematic diagram of the hardware structure of the power battery low temperature charging device involved in the embodiment of the present application. In the embodiment of the present application, the power battery low temperature charging device may include a processor, a memory, a communication interface and a communication bus.

[0176] The communication bus may be of any type and is used to interconnect the processor, the memory, and the communication interface.

[0177] The communication interface includes input / output (I / O) interface, physical interface and logical interface, etc., which are used to realize the interconnection of devices inside the power battery low temperature charging equipment, and the interface used to realize the interconnection between the power battery low temperature charging equipment and other devices (such as other computing devices or user devices). The physical interface can be an Ethernet interface, a fiber optic interface, an ATM interface, etc.; the user device can be a display (Display), a keyboard (Keyboard), etc.

[0178] The memory can be various types of storage media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), flash memory, optical storage, hard disk, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), etc.

[0179] The processor may be a general-purpose processor, which may call the power battery low-temperature charging program stored in the memory and execute the power battery low-temperature charging method provided in the embodiment of the present application. For example, the general-purpose processor may be a central processing unit (CPU). The method executed when the power battery low-temperature charging program is called may refer to the various embodiments of the power battery low-temperature charging method of the present application, which will not be repeated here.

[0180] Those skilled in the art will understand that Figure 5 The hardware structure shown in the figure does not constitute a limitation on the present application, and may include more or less components than shown in the figure, or combine certain components, or arrange the components differently.

[0181] In a fourth aspect, an embodiment of the present application also provides a computer-readable storage medium.

[0182] A power battery low-temperature charging program is stored on the computer-readable storage medium of the present application, wherein when the power battery low-temperature charging program is executed by the processor, the steps of the power battery low-temperature charging method as described above are implemented.

[0183] Among them, the method implemented when the power battery low-temperature charging program is executed can refer to the various embodiments of the power battery low-temperature charging method of the present application, and will not be repeated here.

[0184] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0185] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.

[0186] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0187] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; the “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0188] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0189] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0190] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for charging a power battery at low temperature, characterized in that: The method comprises: Get the current temperature of the power battery; When the temperature is lower than a preset first temperature threshold, the high-frequency wake-up charging and discharging mode is entered; When the temperature is greater than or equal to the first temperature threshold and less than or equal to a preset second temperature threshold, entering a heating charge-discharge mode; The charging current of the high-frequency wake-up charge and discharge mode is smaller than its discharging current, and smaller than the charging current of the heating charge and discharge mode; the discharging current of the heating charge and discharge mode is larger than its charging current, and larger than the discharging current of the high-frequency wake-up charge and discharge mode.

2. The low temperature charging method for a power battery according to claim 1, characterized in that: Before obtaining the current temperature of the power battery, the method further includes: obtaining polarization voltage and equivalent impedance of the power battery at different temperatures, and obtaining first current values ​​at different temperatures according to the polarization voltage and equivalent impedance; When entering the high-frequency wake-up charge and discharge mode or the heating charge and discharge mode and charging for the first time, it also includes: obtaining the charging start voltage and the charging internal resistance at the temperature to obtain the second current value; The charging current is obtained according to the smaller value of the first current value and the second current value at the temperature.

3. The low temperature charging method for a power battery according to claim 2, characterized in that: Obtaining the charging current according to the smaller value of the first current value and the second current value at the temperature specifically includes: The product of the smaller value and the current health of the power battery is used as the charging current; The second current value I cc1 for: Among them, U P is the polarization voltage, U1 is the charging start voltage, R cc is the charging internal resistance, and A is a constant.

4. The low temperature charging method for a power battery according to claim 1, characterized in that: Before obtaining the current temperature of the power battery, the method further includes: obtaining a safe use voltage threshold and an equivalent impedance of the power battery at different temperatures, and obtaining a third current value at different temperatures according to the safe use voltage threshold and the equivalent impedance; When entering a certain charge and discharge mode and discharging for the first time, the method further includes: obtaining a discharge starting voltage and a discharge internal resistance at the temperature to obtain a fourth current value; The discharge current is obtained according to the smaller value of the third current value and the fourth current value at the temperature.

5. The low temperature charging method for a power battery according to claim 4, characterized in that: Obtaining the discharge current according to the smaller value of the third current value and the fourth current value at the temperature, specifically includes: The product of the smaller value and the current health of the power battery is used as the discharge current; The fourth current value I dc1 for: Among them, U max is the polarization voltage, U2 is the discharge starting voltage, R dc is the charging internal resistance, and B is a constant.

6. The low temperature charging method for a power battery according to claim 1, characterized in that: After obtaining the current temperature of the power battery, it also includes: According to the temperature and the charge and discharge mode, the charge and discharge frequency and the discharge duty cycle are determined, and then the single charge and discharge time is determined; the single charge time is greater than the single discharge time.

7. The low temperature charging method for a power battery according to claim 1, characterized in that: When the temperature is greater than the second temperature threshold, the method further includes: The power battery voltage is obtained, and when the power battery voltage is greater than or equal to a first voltage threshold, a normal charging mode is entered until the power battery voltage is greater than or equal to a second voltage threshold.

8. A power battery low temperature charging system, characterized in that: The system comprises: An acquisition module is used to obtain the current temperature of the power battery; A charging module, which is used to enter a high-frequency wake-up charging and discharging mode when the temperature is less than a preset first temperature threshold; and enter a heating charging and discharging mode when the temperature is greater than or equal to the first temperature threshold and less than or equal to a preset second temperature threshold; The charging current of the high-frequency wake-up charge and discharge mode is smaller than its discharging current, and smaller than the charging current of the heating charge and discharge mode; the discharging current of the heating charge and discharge mode is larger than its charging current, and larger than the discharging current of the high-frequency wake-up charge and discharge mode.

9. A power battery low temperature charging device, characterized in that: The power battery low-temperature charging device includes a processor, a memory, and a power battery low-temperature charging program stored in the memory and executable by the processor, wherein when the power battery low-temperature charging program is executed by the processor, the steps of the power battery low-temperature charging method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a power battery low-temperature charging program, wherein when the power battery low-temperature charging program is executed by the processor, the steps of the power battery low-temperature charging method according to any one of claims 1 to 7 are implemented.

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