Method and device for calibrating soc value of iron-lithium battery cell and electric vehicle
By connecting lithium iron phosphate (LFP) cells in series with ternary lithium batteries, and using the SOC value of the ternary lithium batteries to calibrate the SOC value of the LFP cells, the problems of high difficulty and abrupt changes in SOC value estimation for LFP batteries are solved, resulting in more accurate SOC calculation and longer battery life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-20
- Publication Date
- 2026-03-27
AI Technical Summary
The SOC value of lithium iron phosphate batteries is difficult to estimate and has poor accuracy, which causes the SOC value displayed by electric vehicles to fluctuate, affecting the user experience.
By connecting lithium iron phosphate (LFP) cells in series with ternary lithium batteries, the voltage value is detected during charging and discharging. The SOC value of the LFP cells is calibrated using the SOC value of the ternary lithium batteries through calibration modes of voltage plateau period and non-voltage plateau period. Current integration method and special voltage point correction are used to prevent SOC value jumps.
It improves the accuracy of SOC value calculation for lithium iron phosphate cells, prevents SOC value jumps, enhances user experience, reduces overall vehicle weight, and extends the lifespan of power batteries.
Smart Images
Figure CN116087852B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The embodiment of the present application relates to the technical field of battery, in particular to a kind of iron lithium battery SOC value calibration method, device and electric vehicle. BACKGROUND
[0002] In recent years, with the increase of iron lithium battery in the electric two-wheeled vehicle market, the problem of inaccurate SOC (State of Charge, battery charge state) of iron lithium battery is also obviously increased; That is, due to the existence of voltage platform period in the open-circuit voltage curve of iron lithium battery, the SOC value of iron lithium battery is difficult to estimate and the precision is poor, so that the user cannot obtain accurate SOC value; In addition, even in the non-voltage platform period of iron lithium battery SOC value can be determined, due to the existence of inflection point in the curve of iron lithium battery SOC value with voltage, the SOC value displayed by electric vehicle exists the problem of jumping, which seriously affects the user experience. SUMMARY
[0003] The embodiment of the present application provides a kind of iron lithium battery SOC value calibration method, device and electric vehicle, to solve the problem of inaccurate iron lithium battery SOC calculation, avoid the jumping phenomenon of SOC value, improve user experience.
[0004] According to one aspect of the present application, a kind of iron lithium battery SOC value calibration method is provided, comprising:
[0005] The iron lithium battery and the ternary battery are connected in series, and the voltage value of the iron lithium battery and the voltage value of the ternary battery are detected during charging or discharging of the iron lithium battery and the ternary battery;Wherein, the capacity of the iron lithium battery and the ternary battery is same;
[0006] According to the voltage value of the iron lithium battery and the voltage value of the ternary battery, the calibration mode of the iron lithium battery SOC value is determined;The calibration mode of the iron lithium battery SOC value includes voltage platform period calibration mode and non-voltage platform period calibration mode;
[0007] When in voltage platform period calibration mode, then according to the SOC value of ternary battery, the SOC value of iron lithium battery in voltage platform period is calibrated;
[0008] When in non-voltage platform period calibration mode, then according to the preset voltage value of the ternary battery and the preset voltage value of the iron lithium battery, the SOC value of the iron lithium battery in non-voltage platform period is calibrated.
[0009] Optionally, according to the voltage value of the iron lithium battery and the voltage value of the ternary battery, the calibration mode of the iron lithium battery SOC value is determined;It includes:
[0010] determining whether the detected voltage value of the ternary battery is greater than 3.3V and less than 4.0V, and the voltage value of the iron lithium battery is greater than 3.0V and less than 3.5V, if yes, triggering the voltage platform period calibration mode; if no, triggering the non-voltage platform period calibration mode.
[0011] Optionally, if the iron lithium battery is in the voltage platform period, the SOC value of the iron lithium battery in the voltage platform period is calibrated according to the SOC value of the ternary battery, comprising:
[0012] The SOC value of the ternary battery is calculated by using the current integration method, and the SOC value of the iron lithium battery is corrected based on the calculated SOC value of the ternary battery.
[0013] Optionally, during the charging process and in the non-voltage platform period calibration mode, the SOC value of the iron lithium battery in the non-voltage platform period is calibrated according to the preset voltage value of the ternary battery and the preset voltage value of the iron lithium battery, comprising:
[0014] When the voltage value of the ternary battery is charged to 4.0V, or the voltage value of the iron lithium battery is charged to 3.5V, the SOC value of the iron lithium battery is corrected to 95%, and the current charging current is adjusted at the same time;
[0015] The SOC value of the iron lithium battery is calculated by using the current integration method, and the SOC value is corrected based on the calculated SOC value of the iron lithium battery;
[0016] When the voltage value of the ternary battery is charged to 4.2V or the voltage value of the iron lithium battery is charged to 3.65V, the charging is carried out by using the pressure balance method, and when the charging current is less than 1 / 10C, the SOC value of the iron lithium battery is corrected to 100%.
[0017] Optionally, during the discharging process and in the non-voltage platform period calibration mode, the SOC value of the iron lithium battery in the non-voltage platform period is calibrated according to the preset voltage value of the ternary battery and the preset voltage value of the iron lithium battery, comprising:
[0018] When the voltage value of the ternary battery is discharged to 3.3V, or the voltage value of the iron lithium battery is discharged to 3V, the SOC value of the iron lithium battery is corrected to 10%;
[0019] The SOC value of the iron lithium battery is calculated by using the current integration method, and the SOC value is corrected based on the calculated SOC value of the iron lithium battery;
[0020] When the voltage value of the ternary battery is discharged to 3.0V for a preset time, or the voltage value of the iron lithium battery is discharged to 2.75V for a preset time, the SOC value of the iron lithium battery is corrected to 0%.
[0021] Optionally, the calibration method of the SOC value of the iron lithium battery cell further comprises:
[0022] After the battery management system is powered on and initialized, the open circuit voltage of the iron lithium battery cell and the open circuit voltage of the ternary battery cell are detected;
[0023] When the open circuit voltage of the ternary battery cell is less than or equal to 3.0V, or the open circuit voltage of the iron lithium battery cell is less than or equal to 2.75V, the SOC value of the iron lithium battery cell is corrected to 0%;
[0024] When the open circuit voltage of the ternary battery cell is greater than or equal to 4.2V, or the open circuit voltage of the iron lithium battery cell is greater than or equal to 3.65V, the SOC value of the iron lithium battery cell is corrected to 100%;
[0025] When the open circuit voltage of the ternary battery cell is greater than 3.0V and the open circuit voltage of the iron lithium battery cell is greater than 2.75V, and the open circuit voltage of the ternary battery cell is less than 4.2V and the open circuit voltage of the iron lithium battery cell is less than 3.65V, the corresponding SOC value is obtained from the SOC-OCV table according to the open circuit voltage of the ternary battery cell, and the SOC value of the iron lithium battery cell when the system is powered on for the first time is corrected based on the obtained SOC value.
[0026] Optionally, the number of the iron lithium battery cells and the number of the ternary battery cells are both multiple; the number of the iron lithium battery cells is greater than the number of the ternary battery cells, and the ternary battery cells are connected in series among the multiple iron lithium battery cells.
[0027] According to another aspect of the present application, a calibration device for the SOC value of the iron lithium battery cell is provided, which is used for the calibration method of the SOC value of the iron lithium battery cell according to any one of the embodiments of the present application, comprising:
[0028] A voltage value detection module is configured to detect the voltage value of the iron lithium battery cell and the voltage value of the ternary battery cell during the charging or discharging process of the iron lithium battery cell and the ternary battery cell; wherein the iron lithium battery cell and the ternary battery cell are connected in series, and the capacity of the iron lithium battery cell and the ternary battery cell is the same;
[0029] A calibration mode confirmation module is configured to determine the calibration mode of the SOC value of the iron lithium battery cell according to the voltage value of the iron lithium battery cell and the voltage value of the ternary battery cell; the calibration mode of the SOC value of the iron lithium battery cell includes a voltage platform period calibration mode and a non-voltage platform period calibration mode;
[0030] A calibration module is configured to calibrate the SOC value of the iron lithium battery cell according to the SOC value of the ternary battery cell when the voltage platform period calibration mode is used; and calibrate the SOC value of the iron lithium battery cell according to the preset voltage value of the ternary battery cell and the preset voltage value of the iron lithium battery cell when the non-voltage platform period calibration mode is used.
[0031] According to another aspect of the present application, there is provided an electric vehicle comprising: a battery management system module, a voltage sampling line, a current sensor, a relay, a ternary cell and a lithium-iron cell;
[0032] The battery management system module comprises the calibration device for the SOC value of the lithium-iron cell according to any one of the embodiments of the present application; the ternary cell and the lithium-iron cell are connected in series, and the number of the lithium-iron cells is greater than the number of the ternary cells; the voltage sampling line is used to send the collected voltage of the ternary cell and the voltage of the lithium-iron cell to the battery management system module; the current sensor is used to send the detected series current to the battery management system module; and the relay is used to control the on-off state of the ternary cell and the lithium-iron cell.
[0033] Optionally, the electric vehicle further comprises a temperature control module, and the battery management system module is further used to enter different working modes according to the ambient temperature of the battery and the current power, and control the temperature of the cell through the temperature control module to ensure that the ambient temperature of the cell is within a preset safe temperature range; wherein the working modes include a low-temperature working mode, a normal-temperature working mode and a high-temperature working mode.
[0034] The technical solution provided by the present application calibrates the SOC of the lithium-iron cell based on the SOC value of the ternary cell when the lithium-iron cell is in the voltage plateau period, by mixing and connecting the lithium-iron cell and the ternary cell in series (equal-capacity cells). The calculation method of the SOC of the ternary cell is relatively accurate, and can fundamentally solve the problem of inaccurate SOC of the lithium-iron cell. When the lithium-iron cell is in the non-voltage plateau period, the current integration method is used to calculate the SOC value of the lithium-iron cell, and the SOC value of the lithium-iron cell is corrected by setting a special voltage point, to avoid the phenomenon of jump of the displayed SOC value. That is, a suitable SOC value is calibrated for the set voltage value (the voltage value at the inflection point), and when the voltage value of the ternary cell or the voltage value of the lithium-iron cell is the preset voltage point, the calculated SOC value of the lithium-iron cell is corrected according to the calibrated SOC value, to prevent the problem of jump of the SOC value of the lithium-iron cell existing in the non-voltage plateau period. BRIEF DESCRIPTION OF DRAWINGS
[0035] Figure 1 is a flowchart of a calibration method for the SOC value of a lithium-iron cell provided by an embodiment of the present application;
[0036] Figure 2 is a structural block diagram of a battery power system of an electric vehicle provided by an embodiment of the present application;
[0037] Figure 3 is a flowchart of another calibration method for the SOC value of a lithium-iron cell provided by an embodiment of the present application;
[0038] Figure 4is a flow chart of another iron lithium battery cell SOC value calibration method provided by the embodiment of the present application. DETAILED DESCRIPTION
[0039] The present application will be further described below in conjunction with the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the present application are shown in the drawings, but not all the structures.
[0040] The embodiment of the present application provides a kind of iron lithium battery cell SOC value calibration method, Figure 1 is a flow chart of another iron lithium battery cell SOC value calibration method provided by the embodiment of the present application. Figure 1 The iron lithium battery cell SOC value calibration method comprises:
[0041] S110, iron lithium battery cell and ternary battery cell are connected in series, the voltage value of iron lithium battery cell and the voltage value of ternary battery cell are detected in the charging or discharging process of iron lithium battery cell and ternary battery cell;Wherein, the capacity of iron lithium battery cell and ternary battery cell is same.
[0042] Specifically, iron lithium battery cell and ternary battery cell are mixed in series to form the power battery of electric vehicle. Wherein, the capacity of iron lithium battery cell and ternary battery cell is same. That is, at least one iron lithium battery cell in the power battery of electric vehicle is replaced by ternary battery cell. Figure 2 is a structure block diagram of another electric vehicle battery power system provided by the embodiment of the present application. Figure 2 The number of iron lithium battery cells 20 and the number of ternary battery cells 10 can be multiple. However, since the cost of iron lithium battery cell 20 is higher than the cost of ternary battery cell 10, the number of iron lithium battery cell 20 is greater than the number of ternary battery cell 10 in the embodiment of the present application to reduce the cost of electric vehicle power battery system. In addition, a plurality of ternary battery cells 10 can be arranged in series in a plurality of iron lithium battery cells 20, for example, in the first string (which can be understood as the first position in the battery string) of the series battery cells of the power battery system, the Nth string (the last string), the N / 4th string and the 3N / 4th string. A suitable amount of ternary battery cells 10 can also be arranged at other positions. By arranging ternary battery cells 10 in series in a plurality of iron lithium battery cells 20, the accurate SOC values of the battery cells at different positions in the battery string can be obtained when the battery cells in the power battery system are charged / discharged, so that the problem of uneven charging / discharging of the battery cells at different positions in the power battery can be found in time when the SOC value of ternary battery cell 10 is used as a reference to calibrate the SOC value of iron lithium battery cell 20.
[0043] S120, determine a calibration mode for the SOC value of the iron-lithium battery cell according to the voltage value of the iron-lithium battery cell and the voltage value of the ternary battery cell; the calibration mode for the SOC value of the iron-lithium battery cell includes a voltage plateau calibration mode and a non-voltage plateau calibration mode.
[0044] Specifically, the SOC is generally corrected by using an open circuit voltage method in the prior art. The OCV (Open Circuit Voltage) refers to the open circuit voltage of the battery, that is, the voltage of the battery after long-term static. There is a one-to-one corresponding relationship between the open circuit voltage and the remaining capacity SOC of the battery. By experimentally determining the relationship between the open circuit voltage of the single battery and the SOC, the open circuit voltage curve (i.e., the OCV curve) of the battery cell can be obtained and written into the BMS software program. When the battery system is powered on, the BMS first analyzes the static time of the battery system. When the static time is greater than or equal to 1 hour (1 hour is a typical value, and it can also be 3 hours), the BMS obtains the true SOC of the battery system by table lookup method, and compares it with the displayed SOC. If there is a difference between the two, the SOC of the battery system is corrected.
[0045] However, the iron-lithium battery cell has a difficult-to-overcome defect, that is, there is a voltage plateau in the open circuit voltage curve of the iron-lithium battery cell, which leads to a greater difficulty in estimating the SOC and a poor accuracy, which will seriously affect the user experience. It can be understood that, in the open circuit voltage state (OCV-SOC) curve of the iron-lithium battery cell, the open circuit voltage curve is very flat in some regions (before about 3.2V). In the vicinity of this region, as the battery is charged and discharged, the battery maintains a relatively stable open circuit voltage, which leads to a large error in SOC estimation. In the embodiment of the present application, in the calibration process of the SOC value of the iron-lithium battery cell, whether the iron-lithium battery cell is in the voltage plateau is distinguished according to the voltage value of the iron-lithium battery cell and in combination with the voltage value of the ternary battery cell, so as to perform targeted calibration mode. The calibration mode for the SOC value of the iron-lithium battery cell includes a voltage plateau calibration mode and a non-voltage plateau calibration mode.
[0046] S130, when in the voltage plateau calibration mode, the SOC value of the iron-lithium battery cell in the voltage plateau is calibrated according to the SOC value of the ternary battery cell; when in the non-voltage plateau calibration mode, the SOC value of the iron-lithium battery cell is calibrated according to the correction SOC value corresponding to the preset voltage value of the ternary battery cell and the preset voltage value of the iron-lithium battery cell.
[0047] Specifically, when the iron lithium battery cell is in the voltage platform period, the SOC of the iron lithium battery cell is calibrated based on the SOC of the ternary battery cell. The calculation method of the SOC of the ternary battery cell is relatively accurate, and can fundamentally solve the problem of inaccurate SOC of the iron lithium battery cell. When the iron lithium battery cell is in the non-voltage platform period, the SOC of the iron lithium battery cell is calculated by using the current integration method, and the SOC of the iron lithium battery cell is corrected by setting a special voltage point, so as to avoid the phenomenon of jump of the displayed SOC. That is, the appropriate SOC value is calibrated for the set voltage value (OCV-SOC, voltage value at the inflection point), and when the voltage value of the ternary battery cell or the voltage value of the iron lithium battery cell is the preset voltage point, the SOC value calculated by the iron lithium battery cell is corrected according to the calibrated SOC value, so as to prevent the problem of jump of the SOC value of the iron lithium battery in the non-voltage platform period. It should be noted that when the number of iron lithium battery cells and the number of ternary battery cells are both multiple, the minimum value of the SOC of the multiple ternary battery cells is corrected (which can be corrected according to the OCV-SOC curve of the ternary battery cell) and used as the correction value displayed in the voltage platform period of the iron lithium battery cell; and when the iron lithium battery cell is in the non-voltage platform period, the minimum value of the SOC of the multiple iron lithium battery cells is corrected (which can be corrected according to the OCV-SOC curve of the iron lithium battery cell, and the calibrated SOC value is used for correction at the inflection point of the curve) and displayed.
[0048] The calibration method of the SOC value of the iron lithium battery cell provided by the embodiment of the present application includes connecting the iron lithium battery cell and the ternary battery cell in series, detecting the voltage value of the iron lithium battery cell and the voltage value of the ternary battery cell during charging or discharging of the iron lithium battery cell and the ternary battery cell; wherein the capacity of the iron lithium battery cell and the capacity of the ternary battery cell are the same; determining whether the iron lithium battery cell is in the voltage platform period according to the voltage value of the iron lithium battery cell and the voltage value of the ternary battery cell; if the iron lithium battery cell is in the voltage platform period, correcting the SOC value of the iron lithium battery cell in the voltage platform period according to the SOC value of the ternary battery cell; and if the iron lithium battery cell is in the non-voltage platform period, correcting the SOC value of the iron lithium battery cell in the non-voltage platform period according to the preset voltage value of the ternary battery cell and the preset voltage value of the iron lithium battery cell. The problem of inaccurate calculation of the SOC of the iron lithium battery cell is solved, and the problem of jump of the SOC is prevented, which facilitates the use of the user and improves the product recognition. In addition, the available power of the system is increased (the energy density of the ternary battery is higher, 206Wh / kg, and the energy density of the iron lithium battery cell is lower, 140Wh / kg), and the mass of the whole vehicle is reduced. Moreover, after the SOC calculation is relatively accurate, the phenomenon of overcharging and overdischarging of the battery cell does not occur, and the service life of the power battery in the electric vehicle is increased.
[0049] Figure 3 is another flowchart of the calibration method of the SOC value of the iron lithium battery cell provided by the embodiment of the present application, referring to Figure 3 The calibration method of the SOC value of the iron lithium battery cell includes:
[0050] S210, connect the iron lithium battery cell and the ternary battery cell in series, detect the voltage value of the iron lithium battery cell and the voltage value of the ternary battery cell during charging or discharging of the iron lithium battery cell and the ternary battery cell; wherein the capacity of the iron lithium battery cell and the ternary battery cell is the same.
[0051] S220, judge whether the detected voltage value of the ternary battery cell is greater than 3.3V and less than 4.0V, and the voltage value of the iron lithium battery cell is greater than 3.0V and less than 3.5V, if yes, trigger the voltage platform period calibration mode; otherwise, trigger the non-voltage platform period calibration mode.
[0052] S230, in the voltage platform period calibration mode, calibrate the SOC value of the iron lithium battery cell according to the SOC value of the ternary battery cell; in the non-voltage platform period calibration mode, calibrate the SOC value of the iron lithium battery cell according to the correction SOC value corresponding to the preset voltage value of the ternary battery cell and the preset voltage value of the iron lithium battery cell.
[0053] Specifically, the OCV-SOC curve of the iron lithium battery cell has a voltage platform period, the SOC value of the iron lithium battery cell is about 10% to 90%, and the voltage of the iron lithium battery cell is maintained at about 3.2V. The range of the voltage value of the iron lithium battery cell less than 3.5V and greater than 3.0V can be set as the trigger condition of the voltage platform period calibration mode of the iron lithium battery cell, and the voltage of the voltage platform period of the iron lithium battery cell is included to ensure the calibration of the iron lithium battery cell.
[0054] Since the capacity of the ternary battery cell is the same as that of the iron lithium battery cell, and each battery cell is discharged and charged at the same time during the operation of the electric vehicle power battery, the difference between the SOC of the ternary battery cell and the SOC value of the iron lithium battery cell should be small, even the same. When judging whether the iron lithium battery cell is in the voltage platform period, the voltage value of the iron lithium battery cell can be judged in combination with the voltage value of the ternary battery cell, so as to further improve the accuracy of the judgment. According to the voltage value of the iron lithium battery cell and the voltage value of the ternary battery cell, the calibration mode of the SOC value of the iron lithium battery cell is determined, including: judging whether the detected voltage value of the ternary battery cell is greater than 3.3V and less than 4.0V, and the voltage value of the iron lithium battery cell is greater than 3.0V and less than 3.5V, if yes, trigger the voltage platform period calibration mode; otherwise, trigger the non-voltage platform period calibration mode.
[0055] In the charging and discharging process, if the measured voltage value of the ternary battery is greater than 3.3V and less than 4.0V, and the voltage value of the iron lithium battery is greater than 3.0V and less than 3.5V, the SOC value of the iron lithium battery in the voltage platform period is calibrated according to the SOC value of the ternary battery. Optionally, the SOC value of the iron lithium battery in the voltage platform period is calibrated according to the SOC value of the ternary battery, including: the SOC value of the ternary battery is calculated by using the current integration method, and the SOC value of the iron lithium battery is corrected based on the calculated SOC value of the ternary battery. At high voltage, if the detected voltage value of the ternary battery is greater than or equal to 4.0V, or the voltage value of the iron lithium battery is greater than or equal to 3.5V; the non-voltage platform period calibration mode is triggered. At low voltage, if the detected voltage value of the iron lithium battery is less than or equal to 3.3V, or the voltage value of the iron lithium battery is less than or equal to 3.0V, the non-voltage platform period calibration mode is triggered.
[0056] Optionally, during the charging process and in the non-voltage platform period calibration mode, the SOC value of the iron lithium battery in the non-voltage platform period is calibrated according to the preset voltage value of the ternary battery and the preset voltage value of the iron lithium battery, including:
[0057] When the voltage value of the ternary battery is charged to 4.0V, or the voltage value of the iron lithium battery is charged to 3.5V, the SOC value of the iron lithium battery is corrected to 95%, and the current charging current is adjusted;
[0058] The SOC value of the iron lithium battery is calculated by using the current integration method, and the correction is made based on the calculated SOC value of the iron lithium battery;
[0059] When the voltage value of the ternary battery is charged to 4.2V or the voltage value of the iron lithium battery is charged to 3.65V, the charging is carried out by using the pressure balancing method, and when the charging current is less than 1 / 10C, the SOC value of the iron lithium battery is corrected to 100%.
[0060] Specifically, during the charging process, the charging of the iron lithium battery and the ternary battery is faster, so as to prevent overcharging of the battery that charges faster. For example, if the ternary battery is first charged to 4.0V, the SOC value of the iron lithium battery is corrected to 95%. Or the iron lithium battery is first charged to 3.5V, and the SOC value of the iron lithium battery is corrected to 95%. After correcting the SOC value of the iron lithium battery to 95%, the current charging current is adjusted to reduce the charging speed and further prevent overcharging. When the voltage value of the ternary battery is charged to 4.2V (charging cutoff voltage) or the voltage value of the iron lithium battery is charged to 3.65V (charging cutoff voltage), the charging is carried out by using the pressure balancing method, at this time the voltage is unchanged, the charging current gradually decreases, and when the charging current is less than 1 / 10C, the SOC value of the iron lithium battery is corrected to 100%.
[0061] Optionally, during the discharging process and in the non-voltage plateau calibration mode, the SOC value of the iron lithium battery in the non-voltage plateau is calibrated according to the preset voltage value of the ternary battery and the preset voltage value of the iron lithium battery, and the method comprises the following steps of:
[0062] When the voltage value of the ternary battery is discharged to 3.3V or the voltage value of the iron lithium battery is discharged to 3V, the SOC value of the iron lithium battery is corrected to 10%;
[0063] The SOC value of the iron lithium battery is calculated by using the current integration method, and the SOC value of the iron lithium battery is corrected based on the calculated SOC value.
[0064] When the voltage value of the ternary battery is discharged to 3.0V for a preset time or the voltage value of the iron lithium battery is discharged to 2.75V for a preset time, the SOC value of the iron lithium battery is corrected to 0%.
[0065] Specifically, during the discharging process, the electric quantity is first calculated by the integration method, and the temperature and voltage of each battery are detected. When the voltage of the ternary battery reaches 3.3V or the voltage of the iron lithium battery reaches 3V, the current SOC value is quickly corrected to 10%. The system continues to calculate the electric quantity by the integration method, and when the voltage of the ternary battery reaches 3.0V (discharge cutoff voltage) or the voltage of the iron lithium battery reaches 2.75V (discharge cutoff voltage), and continues for a preset time, for example, after 30 seconds according to the current voltage, the SOC value is quickly corrected to 0%. After the preset time, the SOC value is corrected to 0% again, which can prevent the situation that the SOC value is actually not 0% but displayed as 0% due to the too fast voltage drop.
[0066] Optionally, the calibration method of the SOC value of the iron lithium battery further comprises:
[0067] After the battery management system is powered on and initialized, the open circuit voltage of the iron lithium battery and the open circuit voltage of the ternary battery are detected;
[0068] When the open circuit voltage of the ternary battery is less than or equal to 3.0V or the open circuit voltage of the iron lithium battery is less than or equal to 2.75V, the SOC value of the iron lithium battery is corrected to 0%;
[0069] When the open circuit voltage of the ternary battery is greater than or equal to 4.2V or the open circuit voltage of the iron lithium battery is greater than or equal to 3.65V, the SOC value of the iron lithium battery is corrected to 100%;
[0070] When the open circuit voltage of the ternary battery is greater than 3.0V and the open circuit voltage of the iron lithium battery is greater than or equal to 2.75V, and the open circuit voltage of the ternary battery is less than 4.2V and the open circuit voltage of the iron lithium battery is less than 3.65V, the corresponding SOC value is obtained from the SOC-OCV table according to the open circuit voltage of the ternary battery, and the SOC value of the iron lithium battery is corrected based on the obtained SOC value.
[0071] Based on the above embodiments, Figure 4 is another flowchart of the method for calibrating the SOC value of the iron-lithium battery cell provided by the embodiments, referring to Figure 4 , the method for calibrating the SOC value of the iron-lithium battery cell comprises:
[0072] S310, the BMS is powered on and initialized.
[0073] S320, the open-circuit voltage of all the battery cells is detected.
[0074] S330, it is judged whether the open-circuit voltage of the ternary battery cell is less than or equal to 3.0V, or the open-circuit voltage of the iron-lithium battery cell is less than or equal to 2.75V; if yes, step S340 is executed; if not, step S350 is executed.
[0075] S340, the SOC value of the iron-lithium battery cell is corrected to 0%, and step S380 is executed.
[0076] S350, it is judged whether the open-circuit voltage of the ternary battery cell is greater than or equal to 4.2V, or the open-circuit voltage of the iron-lithium battery cell is greater than or equal to 3.65V; if yes, step S360 is executed; if not, step S370 is executed.
[0077] S360, the SOC value of the iron-lithium battery cell is corrected to 100%, and step S390 is executed.
[0078] S370, the corresponding SOC value is obtained from the SOC-OCV table according to the open-circuit voltage of the ternary battery cell and stored, and the SOC value of the iron-lithium battery cell is corrected based on the obtained SOC value.
[0079] S380, it is judged whether all the battery cells enter the charging mode; if yes, step S3110 is executed; if not, step S390 is executed.
[0080] S390, it is judged whether all the battery cells enter the discharging mode; if yes, step S3110 is executed; if not, step S3100 is executed.
[0081] S3100, the current SOC value is kept unchanged.
[0082] S3110, the charging mode is performed, and step S3130 is executed.
[0083] S3120, the discharging mode is performed, and step S3130 is executed.
[0084] S3130, it is judged whether the detected voltage value of the ternary battery cell is greater than 3.3V and less than 4.0V, and the voltage value of the iron-lithium battery cell is greater than 3.0V and less than 3.5V; if yes, step S3140 is executed; if not, step S3150 is executed.
[0085] S3140, calibrating the SOC value of the iron lithium battery in the voltage platform period according to the SOC value of the ternary battery.
[0086] S3150, calibrating the SOC value of the iron lithium battery in the non-voltage platform period according to the preset voltage value of the ternary battery and the preset voltage value of the iron lithium battery.
[0087] Optionally, during the charging or discharging process, further comprising: entering different working modes according to the ambient temperature of the battery and the current power, and controlling the temperature of the battery through the temperature control module to ensure that the ambient temperature of the battery is within the preset safe temperature range; wherein the working modes include: low temperature working mode, normal temperature working mode and high temperature working mode.
[0088] Specifically, when the BMS is powered on, the temperature value and the current voltage of each battery are read first, if the temperature is less than K1, the low temperature working mode is entered and the heating function is started, if the temperature is greater than K2, the high temperature working mode is entered and the cooling function is started, if the temperature is between K1 and K2, the normal temperature working mode is entered. Wherein K1 is less than K2.
[0089] During the charging or discharging process:
[0090] When the temperature is greater than K2, the high temperature working mode is entered (according to the program setting lookup table, different temperatures correspond to different charging and discharging currents) and the cooling function is started, when the temperature is less than K2-5, the normal temperature working mode is entered (according to the program setting lookup table, different temperatures correspond to different charging and discharging currents);
[0091] When the temperature is between K1 and K2, the normal temperature working mode is entered (according to the program setting lookup table, different temperatures correspond to different charging and discharging currents);
[0092] When the temperature is less than K1, the low temperature working mode is entered (according to the program setting lookup table, different temperatures correspond to different charging and discharging currents) and the heating function is started, when the temperature is greater than K1+3, the normal temperature working mode is entered (according to the program setting lookup table, different temperatures correspond to different charging and discharging currents).
[0093] The embodiment of the application also provides a calibration device for the SOC value of the iron lithium battery, which is used for executing the calibration method for the SOC value of the iron lithium battery in any of the above embodiments, and comprises:
[0094] A voltage value detection module is configured to detect the voltage value of the iron lithium battery and the voltage value of the ternary battery during the charging or discharging process of the iron lithium battery and the ternary battery; wherein the iron lithium battery and the ternary battery are connected in series, and the capacities of the iron lithium battery and the ternary battery are the same;
[0095] The calibration mode confirmation module is configured to determine a calibration mode for the SOC value of the iron-lithium battery cell according to the voltage value of the iron-lithium battery cell and the voltage value of the ternary battery cell; the calibration mode for the SOC value of the iron-lithium battery cell includes a voltage plateau calibration mode and a non-voltage plateau calibration mode.
[0096] The calibration module is configured to, in the voltage plateau calibration mode, calibrate the SOC value of the iron-lithium battery cell in the voltage plateau according to the SOC value of the ternary battery cell; and in the non-voltage plateau calibration mode, calibrate the SOC value of the iron-lithium battery cell in the non-voltage plateau according to the preset voltage value of the ternary battery cell and the corrected SOC value corresponding to the preset voltage value of the iron-lithium battery cell.
[0097] The embodiment of the present application also provides an electric vehicle, which comprises a battery power system, and the battery power system of the electric vehicle comprises a battery management system module 30, a voltage sampling line 40, a current sensor 70, a relay S1, a ternary battery cell 10 and an iron-lithium battery cell 20. Figure 2
[0098] The battery management system module 30 is integrated with the calibration device for the SOC value of the iron-lithium battery cell in any of the above embodiments. The ternary battery cell 10 and the iron-lithium battery cell 20 are connected in series, and the number of the iron-lithium battery cells 20 is greater than the number of the ternary battery cells 10. The voltage sampling line 40 is used to send the collected voltage of the ternary battery cell 10 and the voltage of the iron-lithium battery cell 20 to the battery management system module 30; the current sensor 70 is used to send the detected current of the ternary battery cell 10 and the iron-lithium battery cell 20 to the battery management system module 30. The relay is used to control the on-off state of the ternary battery cell and the iron-lithium battery cell.
[0099] In addition, the electric vehicle further comprises a temperature detection line 50, which is used to send the detected temperature of the ternary battery cell 10 and the temperature of the iron-lithium battery cell 20 to the battery management system module 30; and a temperature control module 60, which is used to control the temperature of the ternary battery cell 10 and the iron-lithium battery cell 20 according to the instruction of the battery management system module 30. The battery management system module 30 is further used to enter different working modes according to the ambient temperature of the battery cell and the current power, and control the temperature of the battery cell through the temperature control module 60, so as to ensure that the ambient temperature of the battery cell is within a preset safe temperature range; wherein the working modes include a low-temperature working mode, a normal-temperature working mode and a high-temperature working mode.
[0100] Note that the above merely describes preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, modifications and substitutions can be made without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims.
Claims
1. A method for calibrating the SOC value of a lithium iron phosphate battery cell, characterized in that, include: A lithium iron phosphate (LFP) battery cell and a ternary lithium battery cell are connected in series. During the charging or discharging process of the LFP and ternary lithium battery cells, the voltage values of the LFP and ternary lithium battery cells are detected. The LFP and ternary lithium battery cells have the same capacity. The calibration mode for the SOC value of the lithium iron phosphate battery cell is determined based on the voltage value of the lithium iron phosphate battery cell and the voltage value of the ternary lithium battery cell; wherein, the calibration mode includes a voltage plateau calibration mode and a non-voltage plateau calibration mode; When in voltage plateau calibration mode, the SOC value of the lithium iron phosphate cell is calibrated based on the SOC value of the ternary lithium battery cell. When in non-voltage plateau calibration mode, the SOC value of the lithium iron phosphate cell is calibrated according to the preset voltage value of the ternary lithium battery cell and the corrected SOC value corresponding to the preset voltage value of the lithium iron phosphate battery cell. During charging, and in non-voltage plateau calibration mode, the SOC value of the lithium iron phosphate cell during the non-voltage plateau period is calibrated based on the preset voltage values of the ternary lithium battery cell and the lithium iron phosphate battery cell, including: When the voltage of the ternary lithium battery cell is charged to 4.0V, or the voltage of the lithium iron phosphate battery cell is charged to 3.5V, the SOC value of the lithium iron phosphate battery cell is corrected to 95%, and the current charging current is adjusted. The SOC value of the lithium iron phosphate battery cell is calculated using the current integration method, and a correction is made based on the calculated SOC value of the lithium iron phosphate battery cell. When the voltage of the ternary lithium battery cell is charged to 4.2V or the voltage of the lithium iron phosphate battery cell is charged to 3.65V, the constant voltage method is used for charging. When the charging current is less than 1 / 10C, the SOC value of the lithium iron phosphate battery cell is corrected to 100%.
2. The calibration method for the SOC value of lithium iron phosphate battery cells according to claim 1, characterized in that, The calibration mode for the SOC value of the lithium iron phosphate battery cell is determined based on the voltage values of the lithium iron phosphate battery cell and the ternary lithium battery cell; including: If the detected voltage value of the ternary lithium battery cell is greater than 3.3V and less than 4.0V, and the voltage value of the lithium iron phosphate battery cell is greater than 3.0V and less than 3.5V, then the voltage plateau calibration mode is triggered; otherwise, the non-voltage plateau calibration mode is triggered.
3. The calibration method for the SOC value of lithium iron phosphate battery cells according to claim 2, characterized in that, If the lithium iron phosphate (LFP) battery cell is in a voltage plateau period, then the SOC value of the LFP battery cell in the voltage plateau period is calibrated based on the SOC value of the ternary lithium battery cell, including: The SOC value of the ternary lithium battery cell is calculated using the current integration method, and the SOC value of the lithium iron phosphate battery cell is corrected based on the calculated SOC value of the ternary lithium battery cell.
4. The calibration method for the SOC value of lithium iron phosphate battery cells according to claim 2, characterized in that, During discharge, and in non-voltage plateau calibration mode, the SOC value of the lithium iron phosphate cell in the non-voltage plateau period is calibrated according to the preset voltage values of the ternary lithium battery cell and the lithium iron phosphate battery cell, including: When the voltage of the ternary lithium battery cell is discharged to 3.3V, or the voltage of the lithium iron phosphate battery cell is discharged to 3V, the SOC value of the lithium iron phosphate battery cell is corrected to 10%. The SOC value of the lithium iron phosphate battery cell is calculated using the current integration method, and a correction is made based on the calculated SOC value of the lithium iron phosphate battery cell. When the voltage of the ternary lithium battery cell is discharged to 3.0V and continues for a preset time, or when the voltage of the lithium iron phosphate battery cell is discharged to 2.75V and continues for a preset time, the SOC value of the lithium iron phosphate battery cell is corrected to 0%.
5. The calibration method for the SOC value of lithium iron phosphate battery cells according to claim 1, characterized in that, Also includes: After the battery management system is powered on and initialized, it detects the open-circuit voltage of the lithium iron phosphate cell and the open-circuit voltage of the ternary lithium battery cell. When the open-circuit voltage of the ternary lithium battery cell is less than or equal to 3.0V, or the open-circuit voltage of the lithium iron phosphate battery cell is less than or equal to 2.75V, the SOC value of the lithium iron phosphate battery cell is corrected to 0%. When the open-circuit voltage of the ternary lithium battery cell is greater than or equal to 4.2V, or the open-circuit voltage of the lithium iron phosphate battery cell is greater than or equal to 3.65V, the SOC value of the lithium iron phosphate battery cell is corrected to 100%. When the open-circuit voltage of the ternary lithium battery cell is greater than 3.0V and the open-circuit voltage of the lithium iron phosphate battery cell is greater than 2.75V, and when the open-circuit voltage of the ternary lithium battery cell is less than 4.2V and the open-circuit voltage of the lithium iron phosphate battery cell is less than 3.65V, the corresponding SOC value is obtained from the SOC-OCV table based on the open-circuit voltage of the ternary lithium battery cell, and the SOC value of the lithium iron phosphate battery cell at the first power-on of the system is corrected based on the obtained SOC value.
6. The calibration method for the SOC value of a lithium iron phosphate battery cell according to any one of claims 1 to 5, characterized in that, The number of lithium iron phosphate cells and the number of ternary lithium-ion cells are both multiple; the number of lithium iron phosphate cells is greater than the number of ternary lithium-ion cells, and the ternary lithium-ion cells are connected in series with intervals among the multiple lithium iron phosphate cells.
7. A calibration device for the SOC value of a lithium iron phosphate battery cell, characterized in that, The calibration method for the SOC value of lithium iron phosphate cells according to any one of claims 1 to 6 includes: A voltage detection module is used to detect the voltage values of the lithium iron phosphate battery and the ternary lithium battery during the charging or discharging process; wherein the lithium iron phosphate battery and the ternary lithium battery are connected in series, and the lithium iron phosphate battery and the ternary lithium battery have the same capacity; The calibration mode confirmation module is used to determine the calibration mode of the SOC value of the lithium iron phosphate battery cell based on the voltage value of the lithium iron phosphate battery cell and the voltage value of the ternary lithium battery cell; the calibration mode of the SOC value of the lithium iron phosphate battery cell includes a voltage plateau calibration mode and a non-voltage plateau calibration mode; The calibration module is used to calibrate the SOC value of the lithium iron phosphate battery cell according to the SOC value of the ternary lithium battery cell in voltage plateau calibration mode; and to calibrate the SOC value of the lithium iron phosphate battery cell according to the preset voltage value of the ternary lithium battery cell and the corrected SOC value corresponding to the preset voltage value of the lithium iron phosphate battery cell in non-voltage plateau calibration mode.
8. An electric vehicle, characterized in that, include: Battery management system module, voltage sampling line, current sensor, relay, ternary lithium battery cell and lithium iron phosphate battery cell; The battery management system module includes the calibration device for the SOC value of the lithium iron phosphate cell as described in claim 7; the ternary lithium battery cell and the lithium iron phosphate cell are connected in series, and the number of lithium iron phosphate cells is greater than the number of ternary lithium battery cells; the voltage sampling line is used to send the collected voltages of the ternary lithium battery cell and the lithium iron phosphate battery cell to the battery management system module; the current sensor is used to send the detected series current to the battery management system module; and the relay is used to control the conduction state of the ternary lithium battery cell and the lithium iron phosphate battery cell.
9. The electric vehicle according to claim 8, characterized in that, It also includes a temperature control module. The battery management system module is also used to enter different working modes according to the ambient temperature of the cell and the current charge, and to control the temperature of the cell through the temperature control module to ensure that the ambient temperature of the cell is within a preset safe temperature range. The working modes include: low temperature working mode, normal temperature working mode and high temperature working mode.
Citation Information
Patent Citations
Hybrid battery control method and device, storage medium and electronic device
CN114889491A