TWI809941B - Capacity calculating method of battery affected by low temperature environment - Google Patents

Abstract

A capacity calculating method of a battery affected by a low temperature environment is provided. The evaluating method includes steps of: detecting a temperature of the battery before the battery discharges; integrating the temperature of the battery over time to calculate temperature integration values respectively of the integration time periods; subtracting the temperature integration values of high temperatures from the temperature integration values of low temperatures to calculate a total temperature integration value; and calculating an actual capacity of the battery according to the total temperature integration value.

Description

Calculation method of battery capacity affected by ambient low temperature before discharge

The invention relates to a method for estimating battery capacity affected by temperature, in particular to a calculation method for battery capacity affected by ambient low temperature before discharge.

With the rapid development of new energy vehicles, people have higher and higher requirements for the calculation accuracy of battery capacity. Since the capacity of the battery is greatly affected by the temperature of the environment, it is necessary to design a battery capacity compensation mechanism. The current battery capacity compensation mechanism on the market only considers the increase in battery capacity as the battery temperature rises during the battery discharge process to estimate the battery capacity.

However, before the battery is discharged, it may be placed in a low-temperature environment for a long time, causing the electrolyte in the battery to condense at a low temperature. The actual capacity still cannot be fully recovered to 100% of the ideal capacity. Therefore, the existing battery capacity compensation mechanism needs to be improved, and the temperature-time factor before the battery discharge needs to be considered, so as to accurately calculate the actual capacity of the battery.

The technical problem to be solved by the present invention is to provide a calculation method for the influence of battery capacity by the low temperature of the environment before discharge, which includes the following steps: Detect the temperature of the battery in the previous time interval; integrate the temperature of the battery with the times of multiple integration time ranges divided by the time interval to calculate the multiple temperature integrals of the multiple integration time ranges; Whether the temperature of the battery within each integration time range is lower than the temperature threshold value, if so, determine that the temperature integral in this integration time range is a low temperature integral, if not, determine that the temperature integral in this integration time range is a return temperature integral; add Sum all the low temperature integrals within the time interval to calculate the total low temperature integrals; add up all the return temperature integrals within the time interval to calculate the total return temperature integrals; combine the total low temperature integrals with the total return temperature Subtracting the integrals to calculate the total temperature integral of the battery in the time interval before discharge; and based on the total temperature integral, to estimate the temperature of the environment where the battery is discharged and the time it is placed in the environment, and the impact on the capacity of the battery Level, according to which the actual capacity of the battery is calculated.

In order to further understand the features and technical content of the present invention, please refer to the following detailed description and drawings related to the present invention. However, the provided drawings are only for reference and description, and are not intended to limit the present invention.

S101~S119, S201~S207, S301~S307, S401~S409, S501~S505: steps

BAT: battery

100:Battery capacity evaluation device

10: Temperature detector

20: Processor

t1~t7: time

A12, A23, A34, A45, A56, A67: integral area

Y1: linear curve

Y2: nonlinear line taking

Qmax: ideal capacity

PreCap: reserved capacity

FCC: actual capacity

TempCap: temperature variable

RsvdCap: reserved capacity

FIG. 1 is a flow chart of the steps of calculating the battery capacity according to the low temperature integral and the return temperature integral in the method for calculating the battery capacity affected by the low temperature of the environment before discharge according to an embodiment of the present invention.

Figure 2 is a block diagram of calculating the battery capacity based on the product value of the low temperature integral value and the low temperature activation coefficient and the product value of the return temperature integral value and the return temperature activation coefficient of the calculation method of the battery capacity affected by the low temperature of the environment before discharge according to the embodiment of the present invention .

FIG. 3 is a flow chart of steps for calculating the temperature variable of the battery capacity changing with the ambient temperature before discharge in the method for calculating the battery capacity affected by the low temperature of the environment before discharge according to an embodiment of the present invention.

4 is a flow chart of steps for calculating the temperature variable of the battery capacity as the environment temperature changes during the discharge process in the method for calculating the battery capacity affected by the ambient low temperature before discharge according to an embodiment of the present invention.

FIG. 5 is a flow chart of the steps of calculating the battery capacity according to the battery reserved capacity, total temperature variable and reserved capacity of the method for calculating the battery capacity affected by the ambient low temperature before discharge according to the embodiment of the present invention.

FIG. 6 is a schematic diagram of a battery capacity evaluation device considering the impact of low temperature before discharge according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of the integration of temperature versus time before the battery is discharged.

FIG. 8 is a schematic diagram of linear curves and nonlinear curves established by the calculation method of the battery capacity affected by the ambient low temperature before discharge according to the embodiment of the present invention.

9 is a schematic diagram of the battery capacity calculated by the calculation method of the battery capacity affected by the ambient low temperature before discharge according to the embodiment of the present invention.

The implementation of the present invention is described below through specific specific examples. The present invention can be implemented or applied through other different specific embodiments, and various modifications and changes can be made to the details in this specification based on different viewpoints and applications without departing from the concept of the present invention. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the protection scope of the present invention.

Please refer to Fig. 1, Fig. 6 and Fig. 7, wherein Fig. 1 is a flow chart of calculating the battery capacity according to the low temperature integral and the return temperature integral of the calculation method of the battery capacity affected by the low temperature of the environment before discharge according to the embodiment of the present invention; 6 is a schematic diagram of a battery capacity evaluation device considering the impact of low temperature before discharge according to an embodiment of the present invention; FIG. 7 is a schematic diagram of the integral of temperature before discharge of a battery versus time. The method for calculating the battery capacity affected by the low temperature of the environment before discharge in the embodiment of the present invention may include steps S101 to S119 as shown in FIG. Actual capacity.

In step S101 , the temperature detector 10 of the battery capacity evaluation device 100 is used to detect the temperature of the battery BAT within a time interval before the battery BAT is discharged.

其中F(t)代表總溫度積分量，t1~t2為一積分時間範圍，t2~t3為另一積分時間範圍，t(n-1)-tn為又另一積分時間範圍，t1~tn代表多個積分時間範圍的時間，T代表電池BAT的溫度，t代表時間。 In step S103 , the processor 20 of the battery capacity evaluation device 100 is connected to the temperature detector 10 to obtain the temperature of the battery BAT from the temperature detector 10 . Using the processor 20 to integrate the temperature of the battery BAT with the times of the multiple integration time ranges cut out from the above time interval, to calculate multiple temperature integral values in the multiple integration time ranges, expressed as:

Among them, F(t) represents the total temperature integral, t1~t2 is an integration time range, t2~t3 is another integration time range, t(n-1)-tn is another integration time range, t1~tn represents The time of multiple integration time ranges, T represents the temperature of the battery BAT, and t represents time.

If necessary, the processor 20 can be used to establish a curve as shown in FIG. 7 in a graph according to the time within multiple integration time ranges and the temperature of the battery BAT at different times. The vertical axis of the graph is the temperature of the battery BAT, and the horizontal axis of the graph is time, that is, the curve in the graph is a temperature-time integral curve.

Utilize the processor 20 to calculate an integral area that the curve covers in the graph within each integration time range, which is a temperature integral amount of each integration time range, such as calculating the first integration time range t1-t2 shown in FIG. 7 Integral area A12, integral area A23 of the second integration time range t2~t3, integration area A34 of the third integration time range t3~t4, integration area A45 of the fourth integration time range t4~t5, fifth integration time range t5~ The integration area A56 at t6 and the integration area A67 in the sixth integration time range t6-t7 are only for illustration here, and the present invention is not limited thereto.

In step S105, the processor 20 is used to determine whether the temperature of the battery BAT within each integration time range is less than a temperature threshold. If the temperature of the battery BAT is less than a temperature threshold within an integration time range, execute steps S107 and S111. Conversely, if the temperature of the battery BAT is not less than a temperature threshold within an integration time range, then steps S109 and S113 are executed.

In step S107, if the temperature of the battery BAT is less than a temperature threshold within an integration time range, it is determined/classified as a low temperature integral within the integration time range. For example, using the processor 20 to determine that the integrated area below the horizontal axis of the graph is a low-temperature integrated area, the integrated area A12 of the first integrated time range t1~t2 and the integrated area of the third integrated time range t3~t4 shown in Figure 7 The area value of the area A34 and the integrated area A56 of the fifth integration time range t5-t6 is the low temperature integral.

In step S109 , if the temperature of the battery BAT is not less than a temperature threshold within an integration time range, it is determined/classified as a warm-up temperature integral within the integration time range. For example, utilize the processor 20 to determine that the integrated area above the horizontal axis of the graph is a warm-up integrated area, as shown in Figure 7, the integrated area A23 of the second integration time range t2~t3, the area of the fourth integration time range t4~t5 The integrated area A45 and the integrated area A67 in the sixth integration time range t6-t7 are the integral values of the temperature recovery.

In step S111, the processor 20 is used to sum up all the low temperature integrals within a time interval to calculate a total low temperature integral. For example, use the processor 20 to add up the area value of the integral area A12 in the first integration time range t1~t2, the area value of the integration area A34 in the third integration time range t3~t4, and the fifth integration time as shown in FIG. The area value of the integral area A56 in the range t5~t6 is used to calculate a total low temperature area value, that is, a total low temperature integral value.

In step S113 , the processor 20 is used to sum up all the return temperature integrals within a time interval to calculate a total return temperature integral. For example, use the processor 20 to add up the area value of the integral area A23 in the second integration time range t2~t3, the area value of the integration area A45 in the fourth integration time range t4~t5, and the sixth integration time as shown in FIG. The area value of the integral area A67 in the range t6~t7 is used to calculate a total return temperature area, that is, a total return temperature integral.

In step S115, a total low temperature integral calculated in step S111 is subtracted from a total return temperature integral calculated in step S113 to calculate a total temperature integral of the battery BAT in a time interval before discharge, as follows Equation representation: F(t)=TLW-THG, Among them, F(t) represents the total temperature integral, TLW represents the total low temperature integral, and THG represents the total return temperature integral. If the calculation result of the total temperature integral is negative, it will be directly replaced by 0.

For example, using the processor 20 to subtract the total return temperature integral of the integral area A23, the integral area A45, and the integral area A67 from the total low-temperature area value of the integral area A12, the integral area A34, and the integral area A56 shown in FIG. 7 , To calculate a total temperature integral of the battery BAT before discharging.

In step S117 , according to the total temperature integral, the influence degree of the battery BAT's capacity on the battery BAT's capacity is estimated by the ambient temperature where the battery BAT is discharged and the time it is left in the environment (ie, the temperature-time factor).

In step S119, the actual capacity of the battery BAT when it starts to discharge is calculated according to the degree of influence of the ambient temperature and time factors on the capacity of the battery BAT before the battery BAT is discharged.

Please refer to Fig. 1, Fig. 2 and Fig. 6, in which Fig. 2 shows the calculation method of the battery capacity affected by the low temperature of the environment before discharge according to the embodiment of the present invention. The flow chart of the steps to calculate the battery capacity by multiplying the activation coefficient. The method for calculating the battery capacity affected by the low temperature of the environment before discharge in the embodiment of the present invention may further include steps S203 and S207 as shown in FIG. The evaluation device 100 is executed after steps S101 to S113.

In step S201, the processor 20 is used to set a low-temperature activation coefficient according to the (chemical) characteristics and (aging) state of the battery BAT.

In step S203 , the processor 20 is used to set a warm-up activation coefficient according to the (chemical) characteristics and (aging) state of the battery BAT.

In step S205 , the processor 20 multiplies a total low temperature integral by a low temperature activation coefficient to calculate an activated low temperature integral.

In step S207 , the processor 20 multiplies a total return temperature integral by a return temperature activation coefficient to calculate an activated return temperature integral.

In step S115, the processor 20 subtracts an activation cycle from an activation low temperature integral The temperature integral is used to calculate a total temperature integral, which is used as the basis for calculating the actual capacity of the battery BAT in step S119.

The calculation of the above steps S205, S207 and S115 is expressed by the following equation: F(t)=a×TLW-b×THG, wherein F(t) represents the total temperature integral, a represents the low temperature activation coefficient, and TLW represents the total low temperature integral Amount, b represents the temperature recovery activation coefficient, THG represents the total temperature recovery integral.

Please refer to Fig. 1, Fig. 3, Fig. 6 and Fig. 8, wherein Fig. 3 is a flow chart of the steps for calculating the temperature variable of the battery capacity with the change of the ambient temperature before discharge in the calculation method of the battery capacity affected by the low temperature of the environment before discharge according to the embodiment of the present invention Figure; Figure 8 is a schematic diagram of the linear curve and nonlinear curve established by the calculation method of the battery capacity affected by the low temperature environment before discharge according to the embodiment of the present invention.

The method for calculating the battery capacity affected by the ambient low temperature before discharge in the embodiment of the present invention may further include steps S301 to S307 as shown in FIG. 3 , which can be executed by the battery capacity evaluation device 100 shown in FIG. After step S115 and before step S119.

In step S301, the processor 20 is used to calculate the percentage of the actual capacity loss of the battery BAT affected by the environment of the battery BAT before it is discharged according to a total temperature integral within a time interval before the battery BAT is discharged, as the first capacity loss percentage .

In step S303, the processor 20 multiplies the actual capacity by the first capacity loss percentage to calculate the first capacity loss amount.

In step S305, the processor 20 subtracts the first capacity loss from the actual capacity to calculate the first temperature variable in step S307, and the first temperature variable serves as the basis for calculating the actual capacity of the battery BAT in step S119.

If necessary, the processor 20 can be used to calculate the percentage of capacity loss of the battery BAT in each time range according to the temperature integral of the battery BAT before discharging in each time range, and then it can be based on multiple time ranges as shown in FIG. 8 Separate multiple temperature integrals and their separate multiple capacities Loss percentage, to establish a linear curve Y1 as shown in Figure 8, take a nonlinear line Y2, or establish a curve equation.

Please refer to Fig. 1, Fig. 3, Fig. 4 and Fig. 6, wherein Fig. 4 is the step of calculating the temperature variable of the battery capacity with the change of the ambient temperature during the discharge process in the calculation method of the battery capacity affected by the low temperature of the environment before discharge in the embodiment of the present invention flow chart. The method for calculating the battery capacity affected by the ambient low temperature before discharge in the embodiment of the present invention may further include steps S401 to S409 as shown in FIG. 4 , which may be performed by the battery capacity evaluation device 100 as shown in FIG. Before S119.

In step S401, the battery BAT is discharged.

In step S403, use the processor 20 to calculate the temperature variable when the battery BAT generates heat due to the discharge and the temperature of the battery BAT gradually increases with time during the discharge process of the battery BAT, as the second temperature variable. The technical content related to the temperature variation of the temperature of the battery BAT after discharge has been clearly stated in the previous application, so it will not be repeated here.

In step S405, the processor 20 adds the first temperature variable before the discharge of the battery BAT calculated in step S307 to the second temperature variable after the discharge of the battery BAT calculated in step S403, so as to calculate the battery temperature variable in step S407. Total temperature variation before and after discharge of BAT.

In step S409, the processor 20 subtracts the total temperature variable from the ideal capacity to calculate the actual capacity of the battery BAT in step S119.

The calculation of steps S301~S307, S403~S407 can be expressed by the following equation: TempCap=(FCC×(100%-TempHour))+(FCC×(100%-TempRise)), where TempCap represents the total temperature variable and FCC represents The actual capacity of the battery BAT, TempHour represents the first temperature variable before the battery BAT is discharged (that is, before the battery BAT is discharged, for example, the temperature change from the total storage time of the battery BAT in a low temperature environment to one second before discharge, the capacity of the battery BAT caused Poor), TempHour room temperature preset 100%, TempRise represents the second temperature variable after the battery BAT starts to discharge (that is, the temperature change after the battery BAT starts to discharge, resulting in the capacity difference of the battery BAT), TempRise normal temperature preset 100%.

Please refer to Fig. 1, Fig. 4 to Fig. 6 and Fig. 9, wherein Fig. 5 shows the calculation method of the battery capacity affected by the low temperature of the environment before discharge according to the reserved capacity of the battery, the total temperature variable and the reserved capacity of the battery according to the embodiment of the present invention. Flow chart of the steps of capacity; FIG. 9 is a schematic diagram of the battery capacity calculated by the calculation method of the battery capacity affected by the low temperature of the environment before discharge according to the embodiment of the present invention. The method for calculating the battery capacity affected by the ambient low temperature before discharge in the embodiment of the present invention may further include steps S501 - S505 as shown in FIG. 5 , which may be executed by the battery capacity evaluation device 100 as shown in FIG. 6 .

In step S501, the processor 20 can determine the reserved capacity PreCap of the battery BAT as shown in FIG. For example, in the battery specification, the full charging voltage is 4.2V, but the actual charging voltage of the charger can only reach 4.18V, and the reserved capacity is equal to or about the capacity gap between 4.2V and 4.18V. Or for example, even though all the cells in the battery pack are of the same type, some cells will also have obvious bifurcated voltage when they are close to being fully charged, that is, the voltage difference between the cells in the battery pack is very large, showing an unbalanced imbalance. In a steady state, it is easy to increase the loss of the battery pack and shorten the life, so it should be avoided as much as possible. Therefore, when the algorithm takes the voltage at the bifurcation point as the full charge voltage, the reserved capacity is equal to or approximately the capacity gap between the voltage at the bifurcation point and the standard voltage of the cell.

In step S503, the processor 20 determines the reserve capacity RsvdCap of the battery BAT as shown in FIG. 9 . In order to avoid the cells being discharged to a place with a lower voltage as much as possible, so that the life of the cells decays faster, the algorithm expects to set the voltage of the battery pack’s Under Voltage Protection (UVP) as high as possible, but at the same time It is necessary to take into account the customer's discharge needs, so UVP will set it according to customer needs, and let the reserved capacity depend on the total capacity of the battery cells, reserved capacity and customer needs.

For example, the customer's demand for the battery pack is 200Ah, and the total discharge capacity of the battery cell is 214Ah, and the reserved capacity caused by setting the charging voltage according to the bifurcation point is 6.5Ah, then the reserved capacity is 7.5Ah (=214-200 -6.5), and the UVP voltage point is obtained by comparing the open circuit voltage and the depth of discharge with DOD 3.5% (7.5/214).

In step S505, the ideal capacity Qmax of the battery BAT as shown in Figure 9 is subtracted by the processor 20 from the reserved capacity PreCap, the reserved capacity RsvdCap and the total temperature variable TempCap (as the total temperature variable calculated in step S407) to calculate The actual capacity of the battery BAT.

The calculation of step S505 can be expressed by the following equation: FCC=(Qmax-PreCap-RsvdCap)-TempCap, wherein, FCC represents the actual capacity of the battery BAT, and Qmax represents the ideal capacity of the battery BAT (i.e. designed according to the characteristics of different batteries The ideal capacity will be updated as the battery ages), PreCap represents the reserved capacity of the battery BAT, RsvdCap represents the reserved capacity of the battery BAT, and TempCap represents the total temperature variable of the battery BAT calculated as described above.

If necessary, the battery capacity evaluation device 100 shown in FIG. 6 may further include a storage element, such as but not limited to a memory, for storing the above-mentioned calculated data.

To sum up, the present invention provides a calculation method for the influence of battery capacity by the low temperature of the environment before discharge, which is based on the temperature-time factor in the environment where the battery is placed before discharge, especially considering the long-term placement of the battery in a low-temperature environment that causes the electrolyte in the battery to Condensation, the characteristic that the battery does not activate with temperature, causes the difference between the actual capacity of the battery and the ideal capacity, so as to accurately calculate the actual capacity of the battery.

The content disclosed above is only a preferred feasible embodiment of the present invention, and does not therefore limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made by using the description and drawings of the present invention are included in the application of the present invention. within the scope of the patent.

S101~S119: steps

Claims (8)

A method for calculating the capacity of a battery affected by the low temperature of the environment before discharge, comprising the following steps: detecting the temperature of the battery within a time interval before the discharge of the battery; dividing the temperature of the battery into the time interval Integrate the time of each integration time range to calculate a plurality of temperature integrals in a plurality of integration time ranges; determine whether the temperature of the battery within each integration time range is less than a temperature threshold, and if so, determine the temperature of the battery in each integration time range. The temperature integral in the integration time range is a low temperature integral, if not, it is determined that the temperature integral in the integration time range is a return temperature integral; add up all the low temperature integrals in the time interval to obtain Calculate a total low temperature integral; add up all the temperature integrals within the time interval to calculate a total temperature integral; subtract the total low temperature integral from the total temperature integral to obtain Calculate a total temperature integral of the battery in the time interval before discharge; and estimate the temperature of the environment where the battery is discharged and the time it is placed in the environment based on the total temperature integral, and the capacity of the battery degree of influence to calculate the actual capacity of the battery. The method for calculating the battery capacity affected by the low temperature of the environment before discharge as described in Claim 1 further includes the following steps: according to the characteristics and state of the battery, a temperature recovery activation coefficient is set; the total temperature recovery integral is multiplied by the The temperature recovery activation coefficient is used to calculate an activated temperature recovery integral; and the total low temperature integral is subtracted from the activation temperature recovery integral to calculate the total temperature integral. The method for calculating the battery capacity affected by the ambient low temperature before discharge as described in claim 2 further includes the following steps: setting a low temperature activation coefficient according to the characteristics and state of the battery; multiplying the total low temperature integral by the low temperature activation coefficient to calculate an activated low temperature integral; and subtracting the activated low temperature integral from the activated low temperature integral to calculate the total temperature integral. The method for calculating the battery capacity affected by the low temperature of the environment before discharge as described in claim 1 further includes the following steps: according to the total temperature integral, calculate the percentage of the actual capacity loss of the battery affected by the environment before the battery is discharged, as a first capacity loss percentage; multiplying the actual capacity by the first capacity loss percentage to calculate a first capacity loss; and subtracting the first capacity loss from the actual capacity to calculate a first temperature variable. The calculation method for the battery capacity affected by the low temperature of the environment before discharge as described in claim item 4 further includes the following steps: discharge the battery; calculate that during the discharge process of the battery, the temperature of the battery will increase with time due to the self-heating of the battery due to discharge. The gradually rising temperature variable is used as a second temperature variable; and the first temperature variable and the second temperature variable are summed together to calculate a total temperature variable affected by the ambient temperature before and after the battery is discharged. The method for calculating the battery capacity affected by the ambient low temperature before discharge as described in Claim 5 further includes the following steps: subtracting the total temperature variable from an ideal capacity to calculate the actual capacity of the battery. The method for calculating the battery capacity affected by the low temperature of the environment before discharge as described in Claim 1 further includes the following steps: according to the temperature integral amount in each of the integration time ranges, the actual impact of the environment in which the battery is located before discharge on the battery is calculated. the percentage of capacity loss as a percentage of capacity loss for each of the integration time ranges; and a plurality of the temperature integrals and a plurality of the capacity loss percentages of the plurality of integration time ranges respectively to establish a linear curve or A non-linear curve. The method for calculating the battery capacity affected by the low temperature of the environment before discharge as described in Claim 1 further includes the following steps: according to the times within the multiple integration time ranges and the temperature of the battery, a curve is established in a graph, The vertical axis and horizontal axis of the graph are the temperature and time of the battery respectively; calculate the integral area of the curve covered in the graph within each integration time range; determine the integral area below the horizontal axis of the graph is a low temperature integral area; determine that the integral area above the horizontal axis of the graph is a return temperature integral area; and subtract all the low temperature integral areas in the graph from all the return temperature integral areas to calculate a The total temperature-integrated area is taken as the total temperature-integrated amount.

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