Battery charging tail end SOC display control method

Abstract

The invention discloses a battery charging tail end SOC display control method, which comprises the steps of obtaining the maximum voltage of a single battery and the real SOC of the battery, and if the maximum voltage is greater than or equal to a voltage threshold value and the real SOC of the battery is smaller than an SOC threshold value, correcting the real SOC of the battery; after the real SOC of the battery is corrected, the charging current is controlled to be reduced; and after the charging current is reduced, if the maximum voltage rises to the voltage threshold value, the current real SOC of the battery is greater than the SOC threshold value and the displayed SOC is smaller than the SOC threshold value, controlling the displayed SOC to be smoothly increased to the current real SOC of the battery.

Description

Technical Field

[0001] This invention relates to the field of charging control technology, and in particular to a method for controlling the state of charge (SOC) display at the end of battery charging. Background Technology

[0002] Lithium iron phosphate (LFP) batteries are widely used in electric vehicles and energy storage systems due to their high safety and long cycle life. However, LFP batteries have a wide voltage plateau region, making it impossible to calibrate the State of Charge (SOC) during vehicle operation, leading to potential deviations in SOC. In practical applications, due to prolonged vehicle operation with incomplete charging or shallow charging and discharging, the individual battery cell voltage remains within the plateau region without any opportunity for correction. Furthermore, the battery management system relies solely on ampere-hour integration calculations, and its SOC value may accumulate errors that increase significantly compared to the actual value. Currently, most methods on the market correct SOC errors by charging the battery to the cutoff voltage, causing the SOC to jump to 100%. However, this method has the following drawbacks:

[0003] Rapid fluctuations in SOC during full charge correction have caused user confusion and complaints; inaccurate SOC at the end of the charge can easily lead to excessive charging current at the end, causing lithium plating problems and affecting battery life. Summary of the Invention

[0004] This invention provides a battery charging terminal SOC display control method to address at least one defect in the prior art.

[0005] This invention provides a method for controlling the state of charge (SOC) display at the end of a battery charging process, comprising:

[0006] Obtain the maximum voltage and true SOC of a single battery cell. If the maximum voltage is greater than or equal to a voltage threshold and the true SOC is less than a SOC threshold, then the true SOC is corrected.

[0007] After correcting the actual SOC of the battery, control the reduction of the charging current;

[0008] After the charging current decreases, if the maximum voltage rises back to the voltage threshold, the current actual battery SOC is greater than the SOC threshold, and the displayed SOC is less than the SOC threshold, then the displayed SOC is controlled to smoothly increase to the current actual battery SOC.

[0009] Optionally, determining whether to correct the actual SOC of the battery further includes:

[0010] Obtain the change in battery capacity and the maximum temperature of individual battery cells;

[0011] If the change in battery capacity is greater than the change threshold, the maximum temperature of the battery cell is greater than the temperature threshold, the maximum voltage is greater than or equal to the voltage threshold, and the actual state of charge (SOC) of the battery is less than the SOC threshold and the actual SOC of the battery is not corrected, then the actual SOC of the battery is corrected.

[0012] Optionally, controlling the displayed SOC to smoothly increase to the current actual battery SOC includes:

[0013] Get charging current, maximum temperature of individual battery cells, and display SOC;

[0014] If the maximum voltage rises back to the voltage threshold, the displayed SOC is less than the voltage threshold, the charging current is less than the current threshold, the current battery true SOC is greater than the voltage threshold, the maximum temperature of the battery cell is greater than the temperature threshold, and the battery true SOC has been corrected, then the displayed SOC is controlled to smoothly increase to the current battery true SOC.

[0015] Optionally, before controlling the reduction of the charging current, the charging current is determined using a charging ammeter based on the battery cell voltage and battery cell temperature.

[0016] Optionally, controlling the reduction of charging current includes:

[0017] The charging current is reduced to 0.1C.

[0018] Optionally, the SOC threshold is 99%.

[0019] Optionally, controlling the displayed SOC to smoothly increase to the current actual battery SOC includes:

[0020] Within 10 seconds, the displayed SOC is smoothly boosted to the current actual battery SOC.

[0021] Optionally, correcting the actual SOC of the battery includes:

[0022] Set the battery's true SOC to the SOC threshold.

[0023] Optionally, the voltage threshold is 3.6V.

[0024] Optionally, if the battery is not in a charging state, the SOC correction flag is set to 0, which indicates that the actual SOC of the battery has not been corrected.

[0025] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention proposes a battery charging end-SOC display control method. In this method, the actual SOC of the battery is corrected under specific conditions, which can eliminate SOC calculation errors caused by factors such as battery polarization, temperature changes, and aging. When the conditions of the maximum voltage rising back to the voltage threshold, the current actual battery SOC being greater than the SOC threshold, and the displayed SOC being less than the SOC threshold are met, the displayed SOC is controlled to smoothly increase to the current actual battery SOC. Smooth display SOC changes prevent abrupt changes in the displayed SOC. In this method, after correcting the actual battery SOC, the charging current is also controlled to decrease, which helps to reduce battery polarization at the charging end. This slows down battery aging and extends battery life. Attached Figure Description

[0026] Figure 1 This is a flowchart of the battery charging terminal SOC display control method in the embodiment;

[0027] Figure 2 This is a flowchart of another battery charging terminal SOC display control method in the embodiment;

[0028] Figure 3 This is a flowchart of another battery charging terminal SOC display control method in the embodiments;

[0029] Figure 4 This is a schematic diagram of the charging curve of the lithium iron phosphate battery in the embodiment;

[0030] Figure 5 This is a schematic diagram of the charging end correction charging curve in the embodiment. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0032] Figure 1 This is a flowchart of the battery charging terminal SOC display control method in the embodiment, for reference. Figure 1 The methods include:

[0033] S101. Obtain the maximum voltage of the battery cell and the actual SOC of the battery. If the maximum voltage is greater than or equal to the voltage threshold and the actual SOC of the battery is less than the SOC threshold, then correct the actual SOC of the battery.

[0034] In this scheme, the true SOC of the battery refers to the true SOC of the battery estimated by the Battery Management System (BMS). The true SOC of the battery is used internally by the BMS, and this value can change.

[0035] For example, in this scheme, the SOC threshold is a set value (e.g., 95% to 99%), which represents the power boundary target at the end of charging. The voltage threshold is the voltage judgment standard for achieving this target. The two are theoretically one-to-one correspondences.

[0036] For example, in this solution, the SOC threshold is set to a fixed value (e.g., 99%). Depending on factors such as battery type, battery usage status, and environment, the voltage threshold corresponding to the same SOC threshold may be different.

[0037] For example, in this solution, the correspondence between the voltage threshold and the SOC threshold can be determined by the Open Circuit Voltage (OCV)-SOC curve, which can be determined experimentally. For lithium iron phosphate batteries, the OCV-SOC curve shows that as the SOC increases from 90% to 100%, the OCV slowly increases from approximately 3.55V to 3.65-3.7V. The OCV corresponding to 99% SOC is approximately 3.68V, therefore the voltage threshold is typically set between 3.6 and 3.7V. For ternary lithium batteries, the OCV-SOC curve shows that the OCV corresponding to 99% SOC is approximately 4.15V, and the OCV at full charge is approximately 4.2V, therefore the voltage threshold can be set between 4.1 and 4.15V. For lead-acid batteries, the OCV at full charge is approximately 2.1V, and the OCV corresponding to 99% SOC is approximately 2.08V, therefore the voltage threshold can be set between 2.08 and 2.1V.

[0038] For example, in low-temperature environments (e.g., -10°C): battery polarization intensifies (increased ohmic and electrochemical polarization), and the terminal voltage (load voltage) during charging will be higher than the OCV. For instance, when charging a lithium iron phosphate battery at -10°C, the load voltage at 95% SOC may reach 3.7V (the load voltage at 95% SOC at room temperature is approximately 3.65V), in which case the voltage threshold needs to be appropriately increased. In high-temperature environments (e.g., 50°C), battery activity is enhanced, and the OCV decreases, so the OCV corresponding to 95% SOC may decrease, in which case the voltage threshold needs to be lowered.

[0039] For example, in fast charging scenarios (such as 2C to 3C), the polarization voltage is higher and the terminal voltage rises faster, so the voltage threshold needs to be appropriately reduced (e.g., for 99% SOC, lithium iron phosphate is reduced from 3.65V to 3.6V).

[0040] In this scheme, the correction of the battery's true SOC can be achieved by directly correcting the battery's true SOC to the SOC threshold (using the SOC threshold as the current battery's true SOC).

[0041] Alternatively, the actual state of charge (SOC) of the battery can be corrected by estimating the polarization voltage Up based on the RC equivalent circuit model, using the current charging current and model parameters, with the following formula:

[0042] U p =I×R×(1-e^(-t / τ))

[0043] In the formula, I represents the charging current, R represents the polarization resistance, t represents the charging time, and τ represents the polarization time constant.

[0044] The equivalent OCV is calculated using the following formula: Equivalent OCV = Terminal Voltage - Polarization Voltage - Ohmic Voltage. After obtaining the equivalent OCV, the corresponding SOC is found through the OCV-SOC curve and used as the corrected true SOC of the battery.

[0045] S102. After correcting the battery's true SOC, control and reduce the charging current.

[0046] In this solution, after correcting the battery's true SOC, the current charging stage can be considered the end of the charging process. Reducing the charging current at this stage prevents the terminal voltage from rapidly exceeding the threshold due to high current, which could trigger overvoltage protection, forcibly stop charging, and ultimately lead to charging interruption and insufficient charge. Furthermore, reducing the current eliminates polarization interference, allowing the battery to absorb charge more fully and preventing incomplete charging.

[0047] S103. After the charging current decreases, if the maximum voltage rises back to the voltage threshold, the current actual battery SOC is greater than the SOC threshold, and the displayed SOC is less than the SOC threshold, then control the displayed SOC to smoothly increase to the current actual battery SOC.

[0048] In this scheme, after the charging current is reduced, the battery can continue to absorb power, the battery's true SOC gradually increases, and the corresponding open circuit voltage (OCV) also increases. Finally, the maximum voltage of the battery cell recovers from the state below the threshold after the current reduction to the voltage threshold.

[0049] In this scheme, when the maximum voltage recovery threshold, the actual battery SOC is greater than the SOC threshold, or the displayed SOC is less than the SOC threshold, the display SOC is smoothed. When the SOC is smoothly increased, the displayed SOC can be gradually increased to the current actual battery SOC at a preset rate (e.g., 0.1% / second).

[0050] When the displayed SOC reaches the current actual SOC, the smoothing operation stops, and the displayed value remains consistent with the actual value until charging is complete.

[0051] For example, in this solution, if the conditions in S103 are not met, the displayed SOC can be determined in the following way:

[0052] When the displayed SOC and the actual battery SOC are inconsistent, the rate of change of the displayed SOC during charging is: (100 - displayed SOC) / (100 - actual battery SOC); the rate of change of the displayed SOC during discharging is: (displayed SOC - 0) / (actual battery SOC - 0).

[0053] In this scheme, when the maximum voltage of a single battery cell reaches the voltage threshold, but the actual SOC of the battery is still lower than the SOC threshold, SOC correction is triggered to reduce SOC error. After correcting the actual SOC of the battery, if the maximum voltage of the single cell rises back to the voltage threshold, the current actual SOC is greater than the SOC threshold, and the displayed SOC is still lower than the SOC threshold, the displayed SOC is smoothly increased to the current actual SOC to avoid display jumps, improve user experience, and ensure that the displayed value is consistent with the actual value.

[0054] This embodiment proposes a method for controlling the display of State of Charge (SOC) at the end of battery charging. This method corrects the actual SOC of the battery under specific conditions, eliminating SOC calculation errors caused by factors such as battery polarization, temperature changes, and aging. When conditions are met—such as the maximum voltage returning to a voltage threshold, the current actual SOC being greater than the SOC threshold, and the displayed SOC being less than the SOC threshold—the displayed SOC is smoothly increased to the current actual SOC. This smooth SOC change prevents abrupt changes in the displayed SOC. Furthermore, after correcting the actual SOC, this method also controls and reduces the charging current, which helps reduce battery polarization at the end of charging, slowing down battery aging and extending battery life.

[0055] Based on any of the aforementioned solutions, in one possible implementation, determining whether to correct the actual SOC of the battery further includes:

[0056] Obtain the change in battery capacity and the maximum temperature of a single battery cell; if the change in battery capacity is greater than the change threshold, the maximum temperature of a single battery cell is greater than the temperature threshold, the maximum voltage is greater than or equal to the voltage threshold, the actual SOC of the battery is less than the SOC threshold and no correction has been made to the actual SOC of the battery, then the actual SOC of the battery is corrected.

[0057] In this scheme, when determining whether to correct the battery's true SOC, two additional conditions are added: the change in battery capacity and the maximum temperature of a single battery cell.

[0058] In this scheme, the change in battery capacity refers to the cumulative change in capacity during a single charge. At the beginning of battery charging, the voltage surges due to the instantaneous charging current surge, reaching the voltage threshold; however, the accumulated charge at this time is minimal, and the true State of Charge (SOC) remains low, far from the SOC threshold (e.g., 99%). Without the condition of a cumulative capacity change, a correction may be falsely triggered.

[0059] With this condition added, corrections can only be triggered when the cumulative charge exceeds the change threshold and the effective charging phase is confirmed, thus eliminating transient interference in the early stages of charging.

[0060] In this scheme, the condition that the maximum temperature of a single battery cell is greater than a temperature threshold is added. The purpose is to eliminate the interference of low temperature environment on the electrochemical characteristics of the battery and ensure that SOC correction is only carried out within the temperature range where the battery performance is stable.

[0061] For example, in this solution, when the temperature is below a temperature threshold, the rate of change of OCV with SOC increases significantly. If SOC correction is triggered below the temperature threshold, the correction result will deviate from the true value due to distortion of the OCV-SOC baseline relationship. By adding the condition of the maximum temperature of the battery cell, it can be ensured that the correction is only performed in the temperature range where the OCV-SOC curve is relatively stable, thus improving the reliability of the correction.

[0062] Based on any of the aforementioned solutions, in one possible implementation, controlling the smooth ramp-up of the displayed SOC to the current actual battery SOC includes:

[0063] Get charging current, maximum temperature of individual battery cells, and display SOC;

[0064] If the maximum voltage rises back to the voltage threshold, the displayed SOC is less than the voltage threshold, the charging current is less than the current threshold, the current battery true SOC is greater than the voltage threshold, the maximum temperature of the battery cell is greater than the temperature threshold, and the battery true SOC has been corrected, then the displayed SOC is controlled to smoothly increase to the current battery true SOC.

[0065] In this scheme, after the current reduction charging, the maximum voltage of the battery cell rises back to the voltage threshold. If the displayed SOC is still lower than the SOC threshold, the charging current is less than the current threshold, the temperature is within the adaptation range, and the actual SOC has been corrected, then the display SOC will be smoothly increased to avoid display errors or safety risks caused by a single condition triggering the error.

[0066] In this scheme, the purpose of keeping the charging current below the current threshold is that if the charging current does not drop to the current threshold, the large current will cause fluctuations in the individual cell voltage of the battery. At this time, the maximum voltage may rise to the threshold temporarily, and the calculation of the battery's true SOC is easily disturbed. When the charging current is below the current threshold, the charging current fluctuation is small, the correspondence between voltage and SOC is stable, the calculation error of the battery's true SOC is small, and the jump in the displayed SOC can be avoided.

[0067] In this scheme, the temperature threshold (e.g., 10℃) is the lower limit range where the OCV-SOC curve is relatively stable. When the maximum temperature of a single battery cell is greater than the temperature threshold, the accuracy of the battery's true SOC is higher, avoiding the display of an incorrect SOC value due to low temperature distortion.

[0068] In this solution, the purpose of adding a correction to the battery's true SOC is that if the true SOC is not corrected, triggering the smoothing of the displayed SOC may lead to an incorrect displayed SOC. After the battery's true SOC is corrected, smoothing the displayed SOC can avoid using an uncorrected erroneous SOC to guide the display, ensuring that the displayed value is consistent with the actual battery level.

[0069] Based on any of the aforementioned schemes, in one possible implementation scheme, before controlling the reduction of the charging current, the charging current is determined using a charging ammeter based on the battery cell voltage and battery cell temperature.

[0070] For example, in this solution, when the battery is being charged normally, a charging current meter is used to determine the charging current corresponding to the current battery cell voltage and temperature. The current is determined by directly looking up the table, without the need to calculate the charging current in real time.

[0071] For example, in one possible implementation, taking a lithium iron phosphate battery as an example, the charging current meter can be as shown in Table 1.

[0072] Table 1

[0073]

[0074]

[0075] Based on any of the aforementioned schemes, in one possible implementation scheme, controlling the reduction of charging current includes: reducing the charging current to 0.1C.

[0076] In this scheme, after correcting the battery's true SOC, the battery is considered to be entering the charging phase, and 0.1C is defined as the charging current at the charging phase (e.g., close to 99% SOC). At the charging phase, the battery is nearly fully charged, and its current-accepting capacity decreases significantly. Using 0.1C as the charging current allows for slow replenishment and precise control of the SOC rising to 100%.

[0077] Based on any of the aforementioned schemes, in one possible implementation, the SOC threshold is 99%.

[0078] In this scheme, the SOC threshold is set to 99%, which serves as the boundary value for whether to perform battery true SOC correction. This effectively solves the SOC deviation problem when the battery is close to full charge. When the maximum voltage of a single cell is greater than or equal to the voltage threshold, and the battery's true SOC is less than 99%, it indicates a large error in the battery's SOC. At this point, battery true SOC correction is triggered. This eliminates SOC calculation deviations caused by factors such as polarization and temperature, providing an accurate SOC benchmark for subsequent recharging to 100%.

[0079] In this scheme, the electrochemical characteristics of the battery charging end (SOC 95%~100%) determine that the closer to full charge, the easier it is for the SOC calculation deviation to increase, and 99% can be used as the boundary value.

[0080] When a battery's State of Charge (SOC) increases from 95% to 100%, the internal polarization of the battery exhibits a non-linear growth. For example, the polarization voltage of lithium iron phosphate batteries is approximately 0.03V at 95% SOC, but rises to over 0.08V at 99% SOC. This polarization leads to an artificially high terminal voltage. If the SOC is calculated based on the terminal voltage, it's easy to see a voltage display showing the value corresponding to 99% (3.68V), while the actual SOC deviates by only 97.5%. Triggering a correction at this point can accurately eliminate this error.

[0081] At 99% SOC, the OCV-SOC curve is steep (e.g., for lithium iron phosphate, the OCV jumps sharply from 3.67V to 3.70V between 98% and 100% SOC). A small voltage change (0.01V) corresponds to a 0.5% to 1% fluctuation in SOC. If correction is not triggered at 99%, the small voltage error will be amplified into a significant deviation in SOC when replenishing power to 100%.

[0082] Based on the 99% trigger correction, the SOC error can be precisely controlled. When the power is replenished to 100% at 0.1C, the final SOC error can be ≤0.5%, meeting the user's accuracy requirement for 100% full charge.

[0083] Based on any of the aforementioned solutions, in one possible implementation, controlling the displayed SOC to smoothly increase to the current real battery SOC includes: controlling the displayed SOC to smoothly increase to the current real battery SOC within 10 seconds.

[0084] In this solution, when the displayed SOC is smoothly increased to the current actual battery SOC within 10 seconds, a linear and uniform method can be used to break down the deviation value into multiple equal-length steps, so that the user does not perceive any jump during the increase, while ensuring that the correction is completed within 10 seconds.

[0085] For example, in this solution, the displayed SOC is smoothly corrected to the true SOC value within 10 seconds. For instance, if the displayed SOC is 98.3% and the true SOC of the battery is 99.3%, the displayed SOC is smoothed to 99.3% at a rate of 0.1% per second.

[0086] Based on any of the aforementioned schemes, in one possible implementation, the correction of the battery's true SOC includes setting the battery's true SOC to a SOC threshold.

[0087] In this scheme, when the conditions for correcting the battery's true SOC are met, the battery's true SOC is directly brought up to the SOC threshold, quickly eliminating SOC deviations caused by factors such as polarization and current measurement errors.

[0088] For example, in this solution, since the SOC threshold is already bound to the battery voltage threshold (e.g., 99% SOC corresponds to a static OCV of 3.68V for lithium iron phosphate), assigning the battery's actual SOC to the SOC threshold can balance efficiency and accuracy.

[0089] For example, in this solution, taking lithium iron phosphate battery as an example, if the change in battery capacity is greater than the change threshold; when the maximum voltage of the battery cell is between 3.6V and 3.685V (the voltage range corresponding to 99% SOC); when the maximum temperature of the battery cell is between 5 and 45℃; when the actual SOC of the battery is less than the SOC threshold; and when the SOC correction for this charge has not been triggered, then the SOC threshold is directly assigned.

[0090] For example, if the SOC threshold is 99%, then the SOC threshold (e.g., 99%) is read, and the actual battery SOC is directly assigned to 99%.

[0091] This solution uses a direct assignment method, which does not require complex algorithms. It only requires condition judgment and assignment operations, and has a short processing time, making it suitable for scenarios with high speed requirements, such as fast charging terminals.

[0092] Based on any of the aforementioned schemes, in one possible implementation scheme, the voltage threshold is 3.6V.

[0093] In this scheme, the battery is set as a lithium iron phosphate battery. Based on the OCV-SOC curve characteristics of lithium iron phosphate batteries, 3.6V is at the end of a flat period close to full charge. At room temperature (25℃), 3.6V corresponds to a SOC of approximately 98.5%-99% at rest, which is close to the SOC threshold (99%). Using 3.6V as the voltage threshold that matches the 99% SOC threshold can avoid assignment errors caused by voltage fluctuations. In addition, when the maximum voltage of a single battery cell is 3.6V, when correcting the battery's true SOC, a direct assignment of 99% is not required, and subsequent 0.1C trickle charging can be quickly connected to bring the battery to 100%.

[0094] Based on any of the aforementioned schemes, in one possible implementation scheme, if the battery is not in a charging state, the SOC correction flag is set to 0, and the SOC correction flag being 0 indicates that the battery's true SOC has not been corrected.

[0095] In this scheme, the SOC correction flag (set to 1 to indicate correction) is only set after the actual SOC correction of the battery is triggered, but its effectiveness is limited to the current charging cycle. When the battery enters a non-charging state, the SOC will change due to the following factors, causing the flag state to become disconnected from the actual SOC:

[0096] When lithium iron phosphate is left to stand at room temperature, if the flag bit is 1 after charging (corrected to 99%), and the SOC drops to 98% after 2 days of standing, but the flag bit is still 1, the 3.6V correction will be skipped during the next charge because it has been corrected, resulting in an error in the SOC calculation.

[0097] If the device is not used after charging, the flag will be set to 1 (99%). Then it will be discharged to 90%. If the device is still processed according to the correction method during the next charge, it will miss the accurate assignment under the 3.6V threshold, resulting in a mismatch between the SOC and the voltage (3.6V corresponds to 98.5%~99%).

[0098] In this scheme, the premise for correcting the battery's true SOC is that the SOC at the end of charging is close to 99%. When the SOC deviates from this range in the non-charging state, the corrected flag becomes meaningless and needs to be reset to 0 to re-trigger the correction to adapt to the current SOC.

[0099] Figure 2 This is a flowchart of another battery charging terminal SOC display control method in the embodiment, see reference. Figure 2 Based on any of the aforementioned solutions, in one possible implementation, the method includes:

[0100] S201. Determine if the battery is in fast charging mode.

[0101] S202. When the battery is in fast charging mode, obtain the maximum voltage of the battery cell, the actual SOC of the battery, the change in battery capacity, and the maximum temperature of the battery cell.

[0102] S203. If the change in battery capacity is greater than the change threshold, the maximum temperature of a single battery cell is greater than the temperature threshold, the maximum voltage is greater than or equal to the voltage threshold, the actual SOC of the battery is less than the SOC threshold, and the SOC correction flag is 0, then the actual SOC of the battery is corrected.

[0103] S204. After correcting the actual SOC of the battery, control the reduction of the charging current, and set the SOC correction flag to 1.

[0104] When the S205.SOC correction flag is 1, if the change in battery capacity is greater than the change threshold, if the maximum voltage rises back to the voltage threshold, the displayed SOC is less than the SOC threshold, the charging current is less than the current threshold, the current actual SOC of the battery is greater than the SOC threshold, or the maximum temperature of a single battery cell is greater than the temperature threshold, then the displayed SOC will be smoothly increased to the current actual SOC of the battery.

[0105] S206. When the battery is not in fast charging mode, the SOC correction flag is set to 0.

[0106] Figure 3 This is a flowchart of another battery charging terminal SOC display control method in the embodiments, see reference. Figure 2 and Figure 3 In this scheme, the SOC correction flag is set to SOCCorFlag, the maximum voltage of a single battery cell is Vmax, the maximum temperature of a single battery cell is Tmax, the charging current is I, the actual SOC of the battery is RealSOC, and the displayed SOC is DispSOC.

[0107] In this solution, the setting method is applicable to scenarios where the battery is a lithium iron phosphate battery. The voltage threshold is set to 3.6V, the SOC threshold is set to 99%, the temperature threshold is set to 10℃, the change threshold is set to 2%, and the current threshold is set to 0.125C.

[0108] In this scheme, the initial value of the SOC correction flag is 0. When the battery system is fast charging, the BMS collects the individual cell voltage, individual cell temperature, charging current and SOC of the battery.

[0109] If the cumulative capacity change during a single charge exceeds 2%, then it is further determined whether the following conditions are met: Vmax >= 3.6V, Tmax > 10℃, RealSOC < 99%, and SOCCorFlag is 0. If so, RealSOC will be corrected to 99%, and the SOC correction flag SOCCorFlag will be set to 1.

[0110] After correcting RealSOC, according to the charging current table (Table 1), the charging current I is reduced to 0.1C and charging continues.

[0111] After the current drops to 0.1C, the voltage decreases. When the cell voltage rises back to 3.6V (the second time it reaches 3.6V), it is determined whether the following conditions are met: DispSOC < 99%, I ∈ [0, 0.125C], RealSOC > 99%, cell maximum Tmax > 10℃, and SOCCorFlag is 1. If so, the DispSOC is smoothly corrected to the current RealSOC within 10 seconds.

[0112] Figure 4This is a schematic diagram of the charging curve of the lithium iron phosphate battery in the embodiment, for reference. Figure 4 In this scheme, the charging voltage plateau of lithium iron phosphate is relatively flat, with a rapid voltage rise phase before full charge. The orange curve in the figure eventually approaches 3.6V marked by the blue line. This is the voltage threshold for SOC correction at the end of charging of lithium iron phosphate batteries. When the voltage of a single cell reaches 3.6V, the SOC correction logic is triggered.

[0113] The light blue curve represents the final SOC correction. In the 99% to 100% range at the end of charging, when the displayed SOC is inconsistent with the battery's actual SOC, the displayed SOC will be smoothly corrected to the current actual battery SOC within 10 seconds, achieving a smooth display of the displayed SOC without jumps.

[0114] The dark green curve indicates that the correction to 99% is triggered at 3.6V. When the single cell voltage reaches 3.6V and meets the battery's true SOC correction conditions, the BMS forces the battery's true SOC to be assigned 99%, correcting the error of the conventional algorithm and ensuring accurate SOC display when fully charged.

[0115] from Figure 4 As can be seen, when the maximum voltage of a single cell reaches 3.6V, it triggers the correction of the battery's true SOC, bringing it to 99%. At the same time, other parameters (such as current, voltage of each cell, etc.) also change accordingly with time or operating conditions. These curves together provide data support for battery state monitoring, control strategy verification, etc.

[0116] Figure 5 This is a schematic diagram of the corrected charging curve at the charging end in the embodiment, for reference. Figure 5 The gray curve represents the maximum single-cell voltage. At the end of charging, as the single-cell voltage gradually increases, approaching and reaching approximately 3.6V, the curve shows an initial rise, followed by fluctuations and then stabilization. This reflects the voltage changes during charging, especially the voltage characteristics when approaching full charge.

[0117] The purple curve indicates that the charging current gradually decreases from a higher level during the charging process. When the battery's true SOC correction condition is triggered, it drops to about 0.1C, and then the full charge is completed.

[0118] Towards the end of the charging process, the displayed SOC undergoes a rapid correction. The displayed SOC is quickly adjusted to more closely approximate the true value.

[0119] Once the battery's true SOC correction conditions are met, the battery's true SOC rises directly from its previous state to approximately 99%. This process reflects the correction of the battery's true state of charge, ensuring the accuracy of the SOC at full charge, and also conforms to the characteristic of lithium iron phosphate batteries where the SOC is closely related to voltage at the end of charging.

[0120] from Figure 5 As can be seen, in the final stage of charging a lithium iron phosphate battery, the voltage of each individual cell gradually increases while the charging current gradually decreases. When relevant voltage and other parameters meet the set conditions, the battery management system corrects the displayed SOC and the battery's actual SOC to ensure that the SOC accurately reflects the battery's full charge state. Simultaneously, it completes the final full charge process with a small current, ensuring the battery is fully charged while avoiding overcharging that could damage it, thus protecting the battery's performance and lifespan.

[0121] In this solution, for lithium iron phosphate batteries, the voltage characteristic correction point of charging the lithium iron phosphate cell to 3.6V is used. Combined with temperature and current data, the true SOC of the BMS is corrected to correct the SOC error, smooth the display of SOC changes, and prevent the displayed SOC from jumping.

[0122] This method can solve the problem of SOC jump at the end of charging; this method increases the timing of SOC correction at the end of charging, which can improve the accuracy of SOC estimation when the vehicle is not fully charged; this method is simple and efficient, does not rely on too many limiting parameters, and can be used in various lithium iron phosphate battery systems; this method corrects the SOC at the end of charging, controls the allowable charging current, and improves battery life.

[0123] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A battery charge end SOC display control method characterized by, The method comprises: acquiring a maximum voltage of a battery cell, a real SOC of the battery, and correcting the real SOC of the battery if the maximum voltage is greater than or equal to a voltage threshold and the real SOC of the battery is less than an SOC threshold; after the real SOC of the battery is corrected, controlling a reduction of a charging current; after the charging current is reduced, if the maximum voltage rises to the voltage threshold, the current real SOC of the battery is greater than the SOC threshold, and a display SOC is less than the SOC threshold, controlling the display SOC to be smoothly increased to the current real SOC of the battery.

2. The battery charge end SOC display control method according to claim 1, wherein The method further comprises: acquiring a battery capacity change amount and a maximum temperature of the battery cell; if the battery capacity change amount is greater than a change amount threshold, the maximum temperature of the battery cell is greater than a temperature threshold, the maximum voltage is greater than or equal to the voltage threshold, the real SOC of the battery is less than the SOC threshold, and the real SOC of the battery is not corrected, correcting the real SOC of the battery.

3. The battery charge end SOC display control method according to claim 1, wherein The method further comprises: acquiring a charging current, a maximum temperature of the battery cell, and a display SOC; if the maximum voltage rises to the voltage threshold, the display SOC is less than the SOC threshold, the charging current is less than a current threshold, the current real SOC of the battery is greater than the SOC threshold, the maximum temperature of the battery cell is greater than the temperature threshold, and the real SOC of the battery is corrected, controlling the display SOC to be smoothly increased to the current real SOC of the battery.

4. The battery charge end SOC display control method according to claim 1, wherein Before the charging current is controlled to be reduced, a charging current table is used to determine the charging current based on a battery cell voltage and a battery cell temperature.

5. The battery charge end SOC display control method according to any one of claims 1 to 4, characterized by, The method further comprises: reducing the charging current to 0.1C.

6. The battery charge end SOC display control method according to any one of claims 1 to 4, characterized by, The SOC threshold is 99%.

7. The battery charge end SOC display control method according to any one of claims 1 to 4, characterized by, The method further comprises: controlling the display SOC to be smoothly increased to the current real SOC of the battery within 10 seconds.

8. The battery charge end SOC display control method according to any one of claims 1 to 4, characterized by, The method further comprises: setting the real SOC of the battery to the SOC threshold.

9. The battery charge end SOC display control method according to any one of claims 1 to 4, characterized by, The voltage threshold is 3.6V.

10. The battery charge end SOC display control method according to any one of claims 1 to 4, characterized by, If the battery is not in a charging state, an SOC correction flag is set to 0, and the SOC correction flag being 0 indicates that the real SOC of the battery is not corrected.

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