Calculation method and system for display SOC of lead-acid battery

Abstract

The invention provides a calculation method and system for the displayed SOC of a lead-acid battery, and the method comprises the steps: calculating an average voltage value and an average current value when the real-time electric quantity percentage is smaller than a first set value, calculating the average voltage value and the average current value once every time the real-time electric quantity percentage is reduced by 1%, and updating the lower limit percentage (battery internal resistance parameter) of the discharge capacity based on the average voltage value and the average current value, the SOC is calculated and displayed based on the discharge capacity lower limit percentage and the real-time electric quantity percentage, the method can dynamically and adaptively follow the theoretical SOC, the battery internal resistance parameter is introduced, the display SOC automatically adjusts the following slope of the display SOC along with the increase of the internal resistance, and the display SOC is more authentic.

Description

Technical Field

[0001] This invention relates to the field of battery tube technology, and in particular to a method and system for calculating the state of charge (SOC) of a lead-acid battery. Background Technology

[0002] State of Charge (SOC) is a key parameter characterizing the remaining capacity of a lead-acid battery. Its accuracy directly affects the battery's efficient and safe use, and is of paramount importance in preventing overcharging and over-discharging, and extending battery life. Accurate SOC estimation is particularly crucial for applications such as electric vehicles, uninterruptible power supplies (UPS), backup power for communication base stations, and various energy storage systems.

[0003] Typically, a high-precision "theoretical SOC" is calculated and maintained internally by the Battery Management System (BMS), usually through methods such as open-circuit voltage method and time-integration method. However, for the sake of user experience and system stability, the "displayed SOC" shown to the user should not change arbitrarily or frequently. When the "theoretical SOC" and "displayed SOC" deviate due to accumulated errors, traditional calibration methods usually only perform a "hard" and large-amplitude synchronization under specific conditions (such as after full charging and resting). This synchronization method is too abrupt, leading to "SOC jumps" in the user experience (e.g., SOC suddenly jumps from 70% to 85%), causing user confusion and distrust. At the same time, between two calibration opportunities, the displayed SOC may become out of sync with the battery's actual state for a long time, failing to provide users with an accurate reference and potentially leading to misoperation, causing the battery to over-discharge or prematurely disconnect. Existing "displayed SOC" can smoothly, continuously, and adaptively follow the "theoretical SOC," gradually eliminating accumulated errors and avoiding drastic jumps in the displayed value, thus improving user experience and system reliability.

[0004] Theoretical SOC, calculated using methods such as the open-circuit method and time-integration method, is derived from the open-circuit voltage and the battery's OCV curve to obtain an initial theoretical SOC, which is then updated using the time-integration method. However, as the battery's internal resistance increases, the battery's usable capacity gradually decreases, and the percentage deviation between the theoretical SOC and the battery's actual usable capacity becomes increasingly larger. Similarly, the displayed SOC will also deviate increasingly from the battery's actual capacity. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the present invention aims to provide a method and system for calculating the SOC of a lead-acid battery that can smoothly and continuously follow the "theoretical SOC" and adjust as the battery's internal resistance increases.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for calculating the State of Charge (SOC) of a lead-acid battery, wherein the lead-acid battery pack includes at least one battery cell of the same specification, the battery cells being connected in series, comprising: The terminal voltage of the lead-acid battery pack is acquired in real time, and the integral value of the terminal voltage over time is calculated. Real-time acquisition of the discharge current of the lead-acid battery pack, and calculation of the discharge capacity integral based on the discharge current; During the discharge process of the lead-acid battery pack, the real-time charge percentage is updated based on the integral of the discharge capacity. When the real-time battery percentage is less than the first set value, the average voltage and average current values ​​are calculated once for every 1% decrease in the real-time battery percentage. During the process of a continuous 5% change in the real-time battery percentage, when the average current value, average voltage value, and discharge time of two adjacent real-time battery percentages meet the set conditions, the lower limit percentage of discharge capacity is updated. The discharge time is used to indicate the discharge time when the remaining battery decreases by 1%. The State of Charge (SOC) is calculated and displayed based on the lower limit percentage of discharge capacity and the real-time percentage of battery charge.

[0007] As a further improvement of the present invention, the step of updating the real-time charge percentage based on the integral of the discharge capacity during the discharge process of the lead-acid battery pack includes: When the integral of the discharge capacity exceeds the third set value, the real-time power percentage decreases by 1%. The discharge capacity integral is reset to zero, the discharge capacity integral is recalculated, and the real-time power percentage is updated.

[0008] As a further improvement of the present invention, the conditions include: Within a 1% change period of real-time battery percentage: The average current value is greater than 0; The discharge time is greater than 0 and less than or equal to the fourth set value; The discharge time is greater than or equal to the fifth set value and less than or equal to the sixth set value; The difference between the average voltage value within the previous 1% change period of real-time battery percentage and the average voltage value within the current 1% change period of real-time battery percentage is greater than or equal to the seventh set value.

[0009] As a further improvement of the present invention, the fifth setting value is equal to 0.9 times the discharge time within the previous real-time power percentage change 1% cycle, the sixth setting value is equal to 1.1 times the discharge time within the previous real-time power percentage change 1% cycle, and the seventh setting value is equal to the internal resistance multiplied by the average current value within the current real-time power percentage change 1% cycle.

[0010] As a further improvement of the present invention, the step of updating the lower limit percentage of discharge capacity includes: Define a lower discharge capacity percentage array, which contains six lower discharge capacity percentages with the same initial value; If the condition is met twice during five consecutive changes of 1% in the real-time battery percentage, the lower limit of the discharge capacity percentage will be updated based on the latest real-time battery percentage. The updated discharge capacity lower limit percentage is stored in the discharge capacity lower limit percentage array according to the first-in-first-out principle; After removing the maximum and minimum values ​​from the lower discharge capacity percentage array, the average of the remaining three lower discharge capacity percentages in the lower discharge capacity percentage array and the first lower discharge capacity percentage in the updated lower discharge capacity percentage array is taken to update the lower discharge capacity percentage.

[0011] As a further improvement of the present invention, before the step of calculating the internal resistance value when the lower limit percentage of discharge capacity changes, the method further includes: correcting the updated lower limit percentage of discharge capacity based on the average voltage value and the average current value.

[0012] As a further improvement of the present invention, the step of correcting the updated discharge capacity lower limit percentage based on the average voltage value and the average current value includes: When the average current is greater than or equal to 0 and less than or equal to the eighth set value, and the average voltage is less than or equal to the terminal voltage corresponding to the zero charge during the discharge process of the lead-acid battery pack, if the real-time charge percentage is greater than the updated discharge capacity lower limit percentage. Based on the latest real-time battery percentage, after reassigning values ​​to all discharge capacity lower limit percentages in the discharge capacity lower limit percentage array, the discharge capacity lower limit percentage is updated again.

[0013] As a further improvement of the present invention, the step of correcting the lower limit percentage of discharge capacity based on the average voltage value and the average current value includes: When the average current is greater than or equal to 0 and less than or equal to the eighth set value, and the average voltage is greater than the terminal voltage corresponding to the zero charge during the discharge process of the lead-acid battery pack, if the real-time charge percentage is less than or equal to the updated discharge capacity lower limit percentage. Based on the latest real-time battery percentage, after reassigning values ​​to all discharge capacity lower limit percentages in the discharge capacity lower limit percentage array, the discharge capacity lower limit percentage is updated again.

[0014] As a further improvement to the present invention, the step of calculating and displaying SOC based on the lower limit percentage of discharge capacity and the real-time battery percentage includes: The display shows SOC=100%. (Real-time battery percentage - Lower discharge capacity percentage) / (1 - Lower discharge capacity percentage).

[0015] The present invention also provides a calculation system for displaying the state of charge (SOC) of a lead-acid battery, for implementing the above-mentioned calculation method, comprising: A voltage sampling circuit, connected to the lead-acid battery pack, is used to obtain the terminal voltage of the lead-acid battery pack. The current sampling current is connected to the lead-acid battery pack and is used to obtain the discharge current of the lead-acid battery pack. The processing unit is connected to the voltage sampling circuit and the current sampling circuit, and is used to receive the terminal voltage and discharge current. The processing unit includes a processor, a communication interface, a memory, and a communication bus. The processor, the communication interface, and the memory communicate with each other through the communication bus. The memory is used to store computer programs. The processor is used to execute the programs stored in the memory to implement the above-mentioned calculation method.

[0016] The beneficial effects of this invention are as follows: This invention introduces a discharge capacity lower limit percentage (SOC0), which represents the percentage of the lower limit capacity of the series lead-acid battery pack, i.e., the maximum discharge lower limit of the battery. By tracking the pairwise changes of the real-time charge percentage (SOCi), the relationship between the average voltage change, the internal resistance voltage division, and the discharge capacity is calculated, and the discharge capacity lower limit percentage (SOC0) is continuously updated. When the discharge capacity lower limit percentage (SOC0) changes, i.e., the battery internal resistance changes, the slope of the displayed SOC curve is dynamically adjusted to make the displayed SOC more realistic. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is a flowchart of the calculation method described in this invention; Figure 2 This is a graph showing the relationship between SOC / S in this invention. Figure 3 This is a schematic diagram of the current sampling current structure described in this invention; Figure 4 This is a schematic diagram of the voltage sampling current structure described in this invention. Detailed Implementation

[0019] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The present invention provides a method for calculating the displayed SOC of a lead-acid battery. The lead-acid battery pack includes at least one battery pack of the same specifications connected in series. That is, the present invention is applicable to the calculation of the displayed SOC of a lead-acid battery in which a single or N battery packs of the same specifications are discharged in series.

[0021] First, the parameters required for this invention are defined: (1) Define the specifications of lead-acid battery packs: rated voltage of a single cell V_R, rated capacity Q_R; (2) Define Vi as the real-time terminal voltage of an N (N≥0) series lead-acid battery pack; (3) Define Ii as the real-time discharge current of an N (N≥0) series lead-acid battery pack; (4) Define Qi as the integral of the real-time discharge capacity of an N (N≥0) series lead-acid battery pack; (5) Define R0 as the initial internal resistance of an N (N≥0) series lead-acid battery pack, with R0 = 0 by default; (6) Define SOCi as the real-time charge percentage of an N (N≥0) series lead-acid battery pack. The initial value of the real-time charge percentage SOCi is calculated based on the battery terminal voltage Vi and the OCV curve before discharge. (7) Define SOC0 as the lower limit percentage of discharge capacity for an N (N≥0) series-connected lead-acid battery pack. The default initial value is 2%, the minimum value is 2%, and the maximum value is 40%. As the battery internal resistance increases, the usable battery capacity decreases, and SOC0 gradually increases. The lower limit percentage of discharge capacity array is stored using an array of length 6 (SOC0_1, SOC0_2, SOC0_3, SOC0_4, SOC0_5, SOC0_6), with a default initial value of 2% for each array. When the lower limit percentage of discharge capacity SOC0 is updated, it is recursively stored in the array, replacing the old value with the new one. The maximum and minimum values ​​are removed, and the average of the remaining intermediate values ​​and the latest stored value (SOC0_1) is taken. The lower limit percentage of discharge capacity SOC0 is used as a parameter of battery internal resistance. (8) Define ti as the real-time discharge time of N (N≥0) series lead-acid battery packs, in milliseconds; (9) Define Ti as the discharge time of an N (N≥0) series lead-acid battery pack from the change of real-time charge percentage SOCi to the change of real-time charge percentage SOCi-1, that is, the cycle time of the charge percentage SOC decreasing by one percent, in milliseconds; (10) Define Vm as the terminal voltage when the real-time charge percentage SOCi=0 during the discharge process of an N (N≥0) series lead-acid battery pack.

[0022] (11) Define the displayed SOC as SOC / S, SOC / S = 100%. (SOCi - SOC0) / (1 - SOC0).

[0023] Please see Figure 1 The present invention provides a method for calculating the state of charge (SOC) of a lead-acid battery, comprising the following steps: S1. Obtain the terminal voltage Vi of the lead-acid battery pack in real time and calculate the integral value of the terminal voltage over time, ∫⊿t. Vi.

[0024] S2. Obtain the discharge current Ii of the lead-acid battery pack in real time, and calculate the discharge capacity integral Qi based on the discharge current.

[0025] S3. During the discharge of the lead-acid battery pack, the real-time battery percentage SOCi is updated based on the discharge capacity integral Qi. Specifically, when the discharge capacity integral Qi is greater than the third set value, the real-time battery percentage SOCi decreases by 1%; the discharge capacity integral Qi is cleared to zero, and the discharge capacity integral Qi is recalculated from the next percentile to update the real-time battery percentage SOCi; the third set value is one percent of the rated total capacity Q_R.

[0026] S4. When the real-time battery percentage SOCi is less than 40%, calculate the average voltage value 1 / Ti for every 1% decrease in the real-time battery percentage SOCi. ∫⊿t Vi, average current value 1 / Ti ∫⊿t Ii is used to track changes in voltage and current values ​​because the smaller the state of charge (SOC), the greater the influence of internal resistance, and the more obvious the real-time change in SOCi.

[0027] S5. During the process of a continuous 5% change in the real-time energy percentage SOCi, the average current value 1 / Ti of two adjacent real-time energy percentages SOCi. ∫⊿t Vi, average voltage value 1 / Ti ∫⊿t When the discharge time Ti meets the set conditions, the lower limit percentage of discharge capacity SOC0 is updated. The discharge time Ti indicates the discharge time required for the remaining capacity SOCi to decrease by 1%. This step enables the tracking of changes in internal resistance.

[0028] Furthermore, the conditions include: Within a 1% change period of real-time battery percentage: 1. Average current value 1 / Ti ∫⊿t Vi > 0; 2. The discharge time Ti is greater than 0 and less than or equal to the fourth set value; here, the fourth set value can be 6 minutes, that is, 0≥Ti≥6 minutes; 3. The discharge time is greater than or equal to the fifth setting value and less than or equal to the sixth setting value; the fifth setting value is equal to 0.9 times the discharge time within the previous 1% real-time battery percentage change cycle, and the sixth setting value is equal to 1.1 times the discharge time within the previous 1% real-time battery percentage change cycle, i.e., 0.9. (Discharge time Ti-1) ≤ Discharge time Ti ≤ 1.1 (Discharge time Ti-1); 4. The difference between the average voltage value during the previous 1% change period of real-time battery percentage and the average voltage value during the current 1% change period of real-time battery percentage is greater than or equal to the seventh set value. The seventh set value is equal to the internal resistance multiplied by the average current value during the current 1% change period of real-time battery percentage, i.e., (1 / (Ti-1)). ∫⊿t (Vi-1)-1 / Ti ∫⊿t Vi) ≥ R0 (1 / Ti) ∫⊿t Ii), where the initial value of the internal resistance R0 is 0.

[0029] If the condition is met twice during five consecutive 1% changes in the real-time battery percentage, proceed to the next step.

[0030] Specifically, a discharge capacity lower limit percentage array (SOC0_1, SOC0_2, SOC0_3, SOC0_4, SOC0_5, SOC0_6) is defined. This array contains six discharge capacity lower limit percentages with the same initial value, resulting in a discharge capacity lower limit percentage array (2%, 2%, 2%, 2%, 2%). When the condition is met, if the condition is met twice during five consecutive 1% changes in the real-time battery percentage, the first discharge capacity lower limit percentage is updated based on the latest real-time battery percentage SOCi; specifically, the real-time battery percentage SOCi is... After 0.7, the new discharge capacity lower limit percentage SOC0_1 is assigned.

[0031] The updated discharge capacity lower limit percentage SOC0_1 is stored in the discharge capacity lower limit percentage array according to the first-in-first-out principle.

[0032] After removing the maximum and minimum values ​​from the discharge capacity lower limit percentage array, the average of the remaining three discharge capacity lower limit percentages in the discharge capacity lower limit percentage array and the first discharge capacity lower limit percentage SOC0_1 in the updated discharge capacity lower limit percentage array is taken to update the discharge capacity lower limit percentage SOC0.

[0033] S6, based on the average voltage value 1 / Ti ∫⊿t Vi, average current value 1 / Ti ∫⊿t Ii, the updated discharge capacity lower limit percentage SOC0 is corrected, which includes two parts: Correction for low discharge capacity lower limit percentage SOC0: when 0 ≤ average current 1 / Ti ∫⊿t Ii≤5A, and average voltage 1 / Ti ∫⊿t Vi≤ the terminal voltage Vm corresponding to the zero charge during the discharge process of the lead-acid battery pack, if the real-time charge percentage SOCi> the updated discharge capacity lower limit percentage SOC0.

[0034] Based on the latest real-time battery percentage SOCi, after reassigning values ​​to all discharge capacity lower limit percentages in the discharge capacity lower limit percentage array, the discharge capacity lower limit percentage is updated again. Specifically, the real-time battery percentage SOCi is... 0.7 is assigned to all SOC0_1, SOC0_2, SOC0_3, SOC0_4, SOC0_5, and SOC0_6, and the lower limit percentage of discharge capacity SOC0 is updated again, where the maximum value of SOC0_1, SOC0_2, SOC0_3, SOC0_4, SOC0_5, and SOC0_6 is 14%.

[0035] That is, in the subsequent real-time change of the SOCi percentage by 1%, when the average current 1 / Ti ∫⊿t Ii is greater than zero and less than or equal to 5A, and the average voltage is 1 / Ti ∫⊿t If Vi is less than or equal to the terminal voltage Vm when the charge percentage is zero during the discharge process of the series battery pack, and if the real-time charge percentage SOCi is still greater than the updated discharge capacity lower limit percentage SOC0, then it is determined that the discharge capacity lower limit percentage SOC0 is too small. In this case, the charge percentage SOC0 is multiplied by 0.7 (the maximum value is 14%, which cannot exceed the maximum value) and assigned to all values ​​in the discharge capacity lower limit percentage array, and the discharge capacity lower limit percentage SOC0 is updated at the same time.

[0036] Correction for excessively high discharge capacity lower limit percentage (SOC0): When 0 ≤ average current 1 / Ti ∫⊿t Ii, and average voltage 1 / Ti ∫⊿t Vi > the terminal voltage Vm corresponding to the zero charge during the discharge process of the lead-acid battery pack. If the real-time charge percentage SOCi ≤ the updated discharge capacity lower limit percentage SOC0.

[0037] Based on the latest real-time power percentage SOCi, after reassigning values ​​to all discharge capacity lower limit percentages SOC0_6 in the discharge capacity lower limit percentage array, the discharge capacity lower limit percentage is updated again. Specifically, SOC0_1 in the discharge capacity lower limit percentage array is... 0.7, SOC0_2 0.7, SOC0_3 0.7, SOC0_3 0.7, SOC0_3 0.7, SOC0_6 0.7 is reassigned to all values ​​in the lower discharge capacity percentage array, and the lower discharge capacity percentage SOC0 is updated again. The minimum value of all values ​​in the lower discharge capacity percentage array is 2%.

[0038] That is, in the subsequent real-time battery percentage (SOCi1%) battery change, when the average current 1 / Ti ∫⊿t Ii is greater than zero and less than or equal to 5A, and the average voltage is 1 / Ti ∫⊿t Vi is greater than the terminal voltage Vm corresponding to the zero charge percentage during the discharge process of the series battery pack. If the charge percentage SOCi is still less than the lower limit of discharge capacity SOC0 at this time, it is determined that the lower limit of discharge capacity SOC0 is too large. Then, each value in the lower limit of discharge capacity array is equal to itself multiplied by 0.7 (the minimum value is 2%, which cannot be less than the minimum value), and the lower limit of discharge capacity SOC0 is updated.

[0039] S7. Calculate and display SOC / S based on the lower limit percentage of discharge capacity (SOC0) and the real-time percentage of charge (SOCi). The display shows SOC (Solution Oxygen Content) = 100%. (Real-time battery percentage SOCi - Discharge capacity lower limit percentage SOC0) / (1 - Discharge capacity lower limit percentage SOC0).

[0040] This invention introduces a discharge capacity lower limit percentage (SOC0), which represents the percentage of the lower limit capacity of a series lead-acid battery pack, i.e., the maximum discharge lower limit of the battery. By tracking the pairwise changes of the real-time discharge capacity percentage (SOCi), the relationship between the average voltage change, the internal resistance voltage division, and the discharge capacity is calculated, and the discharge capacity lower limit percentage (SOC0) is continuously updated. When the discharge capacity lower limit percentage (SOC0) changes, i.e., the battery internal resistance changes, the slope of the displayed SOC curve is dynamically adjusted to make the displayed SOC more realistic.

[0041] The calculation method of this invention can achieve smooth and continuous dynamic following of "displayed SOC" to "theoretical SOC", avoiding sudden changes and jumps in the displayed value. It can also adjust the slope of the curve that follows the change of SOC according to the actual capacity after battery degradation, so as to reflect the true usable capacity of the battery.

[0042] The invention will now be further explained using six lead-acid batteries connected in series as an example, as follows: Each lead-acid battery has a capacity of 12V 23Ah. A six-cell series-connected battery pack has a total voltage of 72V and a total capacity of 32Ah. When fully charged, a single lead-acid battery has an open-circuit voltage greater than or equal to 13.2V; when the charge is 0%, the open-circuit voltage is less than or equal to Vm, at which point Vm = 11.8V. When fully charged, the six-cell series-connected battery pack has an open-circuit voltage greater than or equal to 79.2V; when the charge is 0%, the open-circuit voltage is less than or equal to 70.8V.

[0043] Step S1: Obtain the terminal voltage Vi of the lead-acid battery pack in real time, and calculate the integral value of the terminal voltage over time, ∫⊿t. Vi.

[0044] Step S2: Obtain the discharge current Ii of the lead-acid battery pack in real time, and calculate the discharge capacity integral Qi based on the discharge current.

[0045] Step S3: Update remaining capacity SOCi. When the discharge capacity integral Qi is greater than or equal to 1% of the total capacity 32Ah, the real-time capacity percentage SOCi is decremented by 1, and the discharge capacity integral Qi is equal to the discharge capacity Qi minus 32Ah. 1%, continue with the capacity integration in step S2, and calculate the next real-time power percentage SOCi.

[0046] Step S4: Voltage and Current Change Tracking. When the real-time battery percentage (SOCi) is below 40%, calculate the average voltage 1 / Ti for every 1% decrease in SOCi. ∫⊿t Vi and average current 1 / Ti ∫⊿t Ii. Where Ti is the time it takes for SOCi to decrease by 1%, Vi is the real-time terminal voltage of the battery, and Ii is the real-time discharge current; Step S5: Tracking internal resistance changes. Continuously monitor the pairwise changes in the real-time charge percentage SOCi every 5 percentage points, condition ①: average current 1 / Ti ∫⊿t Ii > 0; Condition ②: 0 ≤ discharge time Ti ≤ 6 minutes; Condition ③: the time taken for every two 1% intervals of real-time charge percentage SOCi satisfies 0.9. (Discharge time Ti-1) ≤ Discharge time Ti ≤ 1.1 (Discharge time Ti-1), where (Ti-1) is the time taken for SOCi-1 to change; Condition ④: The average voltage of the real-time charge percentage SOCi in every two 1% intervals satisfies (1 / (discharge time Ti-1)). ∫⊿t (Vi-1) - 1 / Ti ∫⊿t Vi) ≥ Internal resistance R0 (1 / Ti) ∫⊿t Ii), where 1 / (Ti-1) ∫⊿t (Vi-1) is the average voltage of SOCi-1.

[0047] If, in five consecutive pairwise changes of the real-time battery percentage SOCi, conditions ①, ②, ③, and ④ are all met twice, then the percentage point at which the latest real-time battery percentage SOCi appears is used as the basis for determining the real-time battery percentage SOCi at that point. 0.7 is assigned the new lower limit capacity SOC0_1 and stored in the array. The maximum and minimum values ​​in the lower limit percentage of discharge capacity are removed, and then averaged with the newly stored first lower limit capacity percentage SOC_1 to obtain the updated lower limit percentage of discharge capacity array.

[0048] Step S6: Correction for low discharge capacity lower limit percentage SOC0: When the average current 0 ≤ (1 / ti) ∫⊿t Ii), and the average voltage (1 / ti) ∫⊿t If Vi ≤ Vm, Vm = 11.8V, and the real-time charge percentage SOCi > the lower limit of discharge capacity SOC0 is still satisfied, then the real-time charge percentage SOCi will be set to... 0.7 is directly assigned to all discharge capacity lower limit percentages SOC0_1~SOC0_6 (maximum value 14%), and the discharge capacity lower limit percentage SOC0 is updated again.

[0049] Discharge capacity lower limit percentage SOC0 over-correction: 0 ≤ when average current (1 / ti) ∫⊿t Ii), and the average voltage (1 / ti) ∫⊿t If Vi) > Vm, and Vm = 11.8V, and the real-time charge percentage SOCi ≤ discharge capacity lower limit percentage SOC0 still satisfies this condition, then the SOC0_1 value in the discharge capacity lower limit percentage array will be adjusted. 0.7, SOC0_2 0.7, SOC0_3 0.7, SOC0_3 0.7, SOC0_3 0.7, SOC0_6 0.7 Reassign each value to all values ​​in the lower discharge capacity percentage array (minimum value 2%), and update the lower discharge capacity percentage SOC0.

[0050] Step 7: Display SOC. The SOC / S calculation is based on the discharge capacity lower limit percentage SOC and the real-time energy percentage SOCi, and the SOC / S is displayed. like Figure 2 As shown, SOC / S = 100%. (Real-time battery percentage SOCi - Discharge capacity lower limit percentage SOC0) / (1 - Discharge capacity lower limit percentage SOC0).

[0051] The displayed SOC / S will follow the "theoretical SOC" change in real time and linearly. The lower limit percentage of discharge capacity, SOC0, will affect the slope of the displayed SOC / S. The greater the internal resistance, the greater the slope of the displayed SOC / S.

[0052] When the lower limit of discharge capacity SOC0 = 2%, the displayed SOC SOC / S is at most 100%. As the real-time charge percentage SOCi decreases to 2%, the displayed SOC SOC / S also decreases to 0%. When the real-time charge percentage SOCi is less than 2%, the displayed SOC SOC / S remains unchanged (minimum 0%).

[0053] When the lower limit of discharge capacity SOC0 = 8% (increased battery internal resistance), the displayed SOC SOC / S is at most 100%. As the real-time charge percentage SOCi decreases to 8%, the displayed SOC SOC / S also decreases to 0%. When the real-time charge percentage SOCi is less than 8%, the displayed SOC SOC / S remains unchanged (minimum 0%).

[0054] When the lower limit of discharge capacity SOC0 = 40% (maximum value), it indicates that the battery has degraded significantly. At this time, the displayed SOC / S ratio is at most 100%. As the real-time charge percentage SOCi decreases to 40%, the displayed SOC / S ratio decreases to 0%. When the real-time charge percentage SOCi is less than 40%, the displayed SOC / S ratio remains unchanged (minimum 0%).

[0055] Based on the same inventive concept, the present invention also provides a lead-acid battery pack internal resistance estimation system, such as... Figure 3 and Figure 4 As shown, the method for estimating the internal resistance of a lead-acid battery pack as described above includes: a voltage sampling circuit, a current sampling circuit, and a processing unit. The voltage sampling circuit is connected to the lead-acid battery pack and is used to obtain the terminal voltage of the lead-acid battery pack. The current sampling circuit is connected to the lead-acid battery pack and is used to obtain the discharge current of the lead-acid battery pack. The processing unit is connected to the voltage sampling circuit and the current sampling circuit and is used to receive the terminal voltage and the discharge current. The processing unit includes a processor, a communication interface, a memory, and a communication bus. The processor, the communication interface, and the memory communicate with each other through the communication bus. The memory is used to store computer programs. When the processor executes the program stored in the memory, it implements the above calculation method.

[0056] In summary, the present invention has the following beneficial effects: (1) The implementation circuit is simple, requiring only a voltage sampling circuit, a current sampling current and a processing unit, resulting in low cost.

[0057] (2) It can smoothly follow the changes in theoretical SOC and dynamically adjust the slope of the curve according to the changes in battery internal resistance, so that the capacity displayed by "SOC" is more realistic.

[0058] (3) It is applicable to most common lead-acid batteries and has strong applicability.

[0059] In this description, references to terms such as "an embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0060] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0061] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for calculating the State of Charge (SOC) of a lead-acid battery, characterized in that, The lead-acid battery pack includes at least one battery cell of the same specification, which are connected in series, including: The terminal voltage of the lead-acid battery pack is acquired in real time, and the integral value of the terminal voltage over time is calculated. Real-time acquisition of the discharge current of the lead-acid battery pack, and calculation of the discharge capacity integral based on the discharge current; During the discharge process of the lead-acid battery pack, the real-time charge percentage is updated based on the integral of the discharge capacity. When the real-time battery percentage is less than the first set value, the average voltage and average current values ​​are calculated once for every 1% decrease in the real-time battery percentage. During the process of a continuous 5% change in the real-time battery percentage, when the average current value, average voltage value, and discharge time of two adjacent real-time battery percentages meet the set conditions, the lower limit percentage of discharge capacity is updated. The discharge time is used to indicate the discharge time when the remaining battery decreases by 1%. The State of Charge (SOC) is calculated and displayed based on the lower limit percentage of discharge capacity and the real-time percentage of battery charge.

2. The calculation method according to claim 1, characterized in that, The step of updating the real-time battery percentage based on the integral of the discharge capacity during the discharge process of the lead-acid battery pack includes: When the integral of the discharge capacity exceeds the third set value, the real-time power percentage decreases by 1%. The discharge capacity integral is reset to zero, the discharge capacity integral is recalculated, and the real-time power percentage is updated.

3. The calculation method according to claim 1, characterized in that, The conditions include: Within a 1% change period of real-time battery percentage: The average current value is greater than 0; The discharge time is greater than 0 and less than or equal to the fourth set value; The discharge time is greater than or equal to the fifth set value and less than or equal to the sixth set value; The difference between the average voltage value within the previous 1% change period of real-time battery percentage and the average voltage value within the current 1% change period of real-time battery percentage is greater than or equal to the seventh set value.

4. The calculation method according to claim 3, characterized in that, The fifth setting value is equal to 0.9 times the discharge time within the previous 1% change cycle of real-time battery percentage, the sixth setting value is equal to 1.1 times the discharge time within the previous 1% change cycle of real-time battery percentage, and the seventh setting value is equal to the internal resistance multiplied by the average current value within the current 1% change cycle of real-time battery percentage.

5. The calculation method according to claim 3, characterized in that, The step of updating the lower limit percentage of discharge capacity includes: Define a discharge capacity lower limit percentage array, which contains six discharge capacity lower limit percentages with the same initial value; If the condition is met twice during five consecutive changes of 1% in the real-time battery percentage, the lower limit of the discharge capacity percentage will be updated based on the latest real-time battery percentage. The updated discharge capacity lower limit percentage is stored in the discharge capacity lower limit percentage array according to the first-in-first-out principle; After removing the maximum and minimum values ​​from the lower discharge capacity percentage array, the average of the remaining three lower discharge capacity percentages in the lower discharge capacity percentage array and the first lower discharge capacity percentage in the updated lower discharge capacity percentage array is taken to update the lower discharge capacity percentage.

6. The calculation method according to claim 1, characterized in that, Before the step of calculating the internal resistance value when the lower limit percentage of discharge capacity changes, the method further includes: correcting the updated lower limit percentage of discharge capacity based on the average voltage value and the average current value.

7. The calculation method according to claim 6, characterized in that, The step of correcting the updated lower limit percentage of discharge capacity based on the average voltage value and the average current value includes: When the average current is greater than or equal to 0 and less than or equal to the eighth set value, and the average voltage is less than or equal to the terminal voltage corresponding to the zero charge during the discharge process of the lead-acid battery pack, if the real-time charge percentage is greater than the updated discharge capacity lower limit percentage. Based on the latest real-time battery percentage, after reassigning values ​​to all discharge capacity lower limit percentages in the discharge capacity lower limit percentage array, the discharge capacity lower limit percentage is updated again.

8. The calculation method according to claim 5, characterized in that, The step of correcting the lower limit percentage of discharge capacity based on the average voltage value and the average current value includes: When the average current is greater than or equal to 0 and less than or equal to the eighth set value, and the average voltage is greater than the terminal voltage corresponding to the zero charge during the discharge process of the lead-acid battery pack, if the real-time charge percentage is less than or equal to the updated discharge capacity lower limit percentage. Based on the latest real-time battery percentage, after reassigning values ​​to all discharge capacity lower limit percentages in the discharge capacity lower limit percentage array, the discharge capacity lower limit percentage is updated again.

9. The calculation method according to claim 6, characterized in that, The step of calculating and displaying SOC based on the lower limit percentage of discharge capacity and the real-time battery percentage includes: The display shows SOC=100%. (Real-time battery percentage - Lower discharge capacity percentage) / (1 - Lower discharge capacity percentage).

10. A calculation system for displaying the State of Charge (SOC) of a lead-acid battery, characterized in that, To implement the calculation method as described in any one of claims 1 to 9, comprising: A voltage sampling circuit, connected to the lead-acid battery pack, is used to obtain the terminal voltage of the lead-acid battery pack. The current sampling current is connected to the lead-acid battery pack and is used to obtain the discharge current of the lead-acid battery pack. The processing unit is connected to the voltage sampling circuit and the current sampling circuit, and is used to receive the terminal voltage and discharge current. The processing unit includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; the memory is used to store computer programs; and the processor is used to implement the calculation method as described in any one of claims 1 to 9 when executing the program stored in the memory.

Images