TWI509270B - Method and system of state of health of battery - Google Patents

Description

Method and system for estimating battery health status

The invention relates to a method and a system for estimating the health status of a battery pack, and in particular to a method and a system for estimating the health status of a battery pack without erecting a database.

With the rising awareness of environmental protection and energy conservation, the related technologies of special power vehicles are booming. Special power vehicles use gaseous fuel or electric energy to assist or even replace liquid fuel as a power source for vehicles. Current special power vehicles are classified into oil-electric hybrid, oil-gas hybrid or pure electric drive.

Among them, the hybrid electric vehicle has the advantage of reducing the fuel consumption of the vehicle. Compared with the general gasoline-driven vehicle, the hybrid electric vehicle has more electric motors and rechargeable batteries, and some of the power when the engine is started is used to drive the tires. A portion of the power is charged by the generator into the rechargeable battery, which in turn supplies power to the electric motor to operate the vehicle.

Therefore, how to effectively control the rechargeable battery and improve the performance of the rechargeable battery is the focus of the research and development of the hybrid electric vehicle and the electric vehicle on the market, and the battery management system (Battery Management System, BMS) is the main development technology. The battery management system's function is to estimate the State Of Charge (SOC) and State OF Heath (SOH) of the rechargeable battery, allowing users to predict the charging time, vehicle mileage and battery life.

However, the current research on battery management systems can be roughly divided into open circuit voltage method, Coulomb power integration method and load voltage method, etc., but all of the above methods take a lot of time to construct a measurement database of rechargeable batteries. In order to estimate the charge state and health status of the rechargeable battery. In addition, the open circuit voltage method can be measured only when the rechargeable battery is stopped charging and discharging, which is extremely inconvenient for the user.

Accordingly, it is an object of the present invention to provide a method and system for estimating the health of a battery pack that substantially reduces the time it takes for conventional battery management techniques to construct a large database. In addition, the present invention utilizes the method of measuring the loop voltage, instead of using the open circuit voltage method or the internal resistance method, thereby estimating the health state during the discharge process of the battery pack, without being limited to the estimation during the charging process. There is no need to use special instruments to pre-measure the temperature or internal impedance of the battery pack.

According to an embodiment of the present invention, a battery pack health state estimation method is provided, the method comprising: a measuring step of repeatedly measuring a plurality of battery cells of the battery pack by using different predetermined discharge conditions Complex loop voltage. a discretization step for calculating loop electrical power of each battery cell according to a statistical distribution of a standard deviation (Standard Deviation) formula Press to obtain a voltage standard deviation of each cell. A differential step, which obtains a discrete curve according to the discharge electric quantity and the standard deviation of the voltage, and uses a differential formula to calculate a standard deviation wave trough value of one of the discrete curves. An estimation step of calculating a rated discharge power of the battery pack and a discharge power corresponding to the standard deviation wave trough according to a health state (SOH) calculation formula to obtain a health state of the battery pack.

According to the foregoing battery pack health state estimation method, wherein the preset sampling condition in the measuring step is to measure the loop voltage of each battery cell of the battery pack once every 100 milliampere-hours (mAH), and each discharge battery of the battery pack It is obtained by the Coulomb counting method. The standard deviation formula in the discretization step is And X _i is a random variable of the loop voltage, u _i is the average value of the loop voltages corresponding to the respective battery cores, Z _i is the standard fraction of the loop voltage values of the battery cores, and n is the total number of loop voltages corresponding to the respective battery cells. In the differential step, the differential formula is dσ ( AH ) / dAH , and σ ( AH ) is the voltage standard deviation versus discharge capacity function, and AH is the discharge capacity. The health state calculation formula in the estimation step is k( AH _valley )/( AH _original )×100%, where k is the discharge coefficient, AH _valley is the discharge capacity corresponding to the standard deviation wave valley, and AH _original is the rated discharge capacity of the battery pack. .

Another embodiment of the present invention provides a battery pack health state estimation system including a battery pack, a voltage detecting circuit, a current detecting circuit, and an arithmetic module. The battery pack has a plurality of battery cells. The voltage detecting circuit is electrically connected to the battery pack, and the voltage detecting circuit repeatedly measures the complex loop voltage of each battery cell by using a different complex discharge quantity of a predetermined sampling condition. The current detecting circuit is electrically connected to the battery pack, and the current detecting circuit measures One of the battery packs discharges current to calculate each discharge. The computing module is electrically connected to the battery pack, and the computing module comprises a discretization unit, a differential unit and a health state (SOH) calculation unit. The discretization unit calculates the voltages of the respective loops of each battery cell according to a statistical deviation of a standard deviation (Standard Deviation) formula to obtain a voltage standard deviation of each of the battery cells. The differential unit obtains a discrete curve according to each discharge electric quantity and each voltage standard deviation, and uses a differential formula to calculate one standard deviation wave valley value of the discrete curve. The health state calculation unit calculates a discharge power of one of the battery packs and a discharge power corresponding to the standard deviation wave value according to a health state calculation formula to obtain a health state of the battery pack.

According to the foregoing battery pack health state estimation system, wherein the preset sampling condition is to measure the loop voltage of each battery cell of the battery pack once every 100 milliampere-hours (mAH), and each discharge power of the battery pack is a current collector. Obtained by the Coulomb counting method. The standard deviation formula is And X _i is a random variable of the loop voltage, u _i is the average value of the loop voltages corresponding to the respective battery cores, Z _i is the standard fraction of the loop voltage values of the battery cores, and n is the total number of loop voltages corresponding to the respective battery cells. The differential formula is dσ ( AH ) / dAH , and σ ( AH ) is the voltage standard deviation versus discharge capacity function, and AH is the discharge capacity. The health state is calculated as k( AH _valley )/( AH _original )×100%, where k is the discharge coefficient, AH _valley is the discharge capacity corresponding to the standard deviation wave trough, and AH _original is the rated discharge capacity of the battery pack. The battery health assessment system further includes a memory module, a display module, and a load. The memory module is electrically connected to the computing module. The display module is electrically connected to the computing module to display the health status of the battery pack. The load is electrically connected to the voltage detecting circuit and the current detecting circuit for connecting the load, the battery pack, the voltage detecting circuit and the current detecting circuit in series to form a loop.

The method and system for estimating the health status of the battery pack of the present invention utilizes the standard deviation change of the battery core circuit voltage of the battery pack and the discharge power to obtain the health status of the battery pack, thereby instantly correcting the residual of the battery pack Battery status.

100‧‧‧Battery Health Status Estimation System

110‧‧‧Battery Pack

111‧‧‧ battery core

120‧‧‧Voltage detection circuit

130‧‧‧ Current detection circuit

140‧‧‧ Computing Module

141‧‧‧Discrete unit

142‧‧‧differentiation unit

143‧‧‧Health State Calculation Unit

144‧‧ ‧ integral unit

150‧‧‧ memory module

160‧‧‧ display module

170‧‧‧load

AH ‧‧‧discharge

V ‧‧‧ loop voltage

I ‧‧‧discharge current

AH _{oringal ‧‧‧rated} discharge capacity

AH _valley ‧‧‧ discharge capacity corresponding to the standard deviation wave valley

SOH‧‧‧Health status

210‧‧‧Measurement steps

220‧‧‧ Discretization steps

230‧‧‧Differential steps

240‧‧‧ Estimation steps

The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; A block diagram of the measurement system.

FIG. 2 is a block diagram showing the operation module according to FIG. 1.

3 is a flow chart showing a method for estimating a health state of a battery pack according to an embodiment of the present invention.

4 is a discrete graph showing a battery health state estimation system in accordance with an embodiment of the present invention.

Please refer to FIG. 1 and FIG. 2 , wherein FIG. 1 is a block diagram showing a battery pack health state estimation system according to an embodiment of the present invention, and FIG. 2 is a diagram showing a computing module according to FIG. 1 . Block diagram. The battery health state estimation system 100 includes a battery pack 110, a voltage detecting circuit 120, a current detecting circuit 130, an operation module 140, and a memory The module 150, a display module 160, and a load 170 are recalled.

The battery pack 110 has a plurality of battery cells 111. The present invention is described with respect to the lithium iron battery pack as an embodiment, but is not limited thereto.

120 is electrically connected to the battery voltage detection circuit 110, the voltage detecting circuit 120 to a plurality of different samples under the conditions of a predetermined discharge capacity AH is repeated a plurality of measurement loop voltage V of each battery cell 111. In the following description, the actual embodiment will be described with reference to the preset sampling conditions.

The current detecting circuit 130 is electrically connected to the battery pack 110, and the current detecting circuit 130 measures the discharging current I of the battery pack 110 for calculating the discharging power AH .

The computing module 140 is electrically connected to the battery pack 110. The computing module 140 includes a discretization unit 141, a differentiation unit 142, a health state calculation unit 143, and an integration unit 144.

The discretization unit 141 calculates the loop voltages V of the respective battery cells 111 according to a standard deviation formula statistical distribution to obtain a voltage standard deviation of each of the battery cells 111.

The differentiating unit 142 obtains a discrete curve according to each discharge electric quantity AH and each voltage standard deviation, and calculates a standard deviation wave trough value of one of the discrete curves by using a differential formula.

The health state calculation unit 143 calculates a rated discharge power amount AH _{original of the} battery pack 110 and a discharge power amount AH _valley corresponding to the standard deviation wave valley value according to a health state calculation formula to obtain a health state SOH of the battery pack 110.

The integrating unit 144 calculates the generated discharge amount AH based on the discharge current I of the battery pack 110.

The memory module 150 is electrically connected to the computing module 140.

The display module 160 is electrically connected to the computing module 140 for displaying the health status SOH of the battery pack 110.

The load 170 is electrically connected to the voltage detecting circuit 120 and the current detecting circuit 130 for connecting the load 170, the battery pack 110, the voltage detecting circuit 120 and the current detecting circuit 130 in series to form a loop.

The standard deviation formula and the differential formula used above will be more clearly described below. Please refer to FIG. 3 and FIG. 4 at the same time. FIG. 3 is a schematic diagram showing a method for estimating the health state of the battery pack according to an embodiment of the present invention, and FIG. 4 is a diagram showing the differential unit according to FIG. Discrete curve graph. The battery pack health state estimating method includes the steps of the battery pack 110 being fully charged and performing the following health state estimation, including: a measuring step 210, which utilizes the voltage detecting circuit 120 to discharge the different amount of power in a predetermined sampling condition. The AH repeatedly measures the complex loop voltage V of the plurality of battery cells 111 of the battery pack 110. In the present embodiment, the preset condition is to record the loop voltage V of the battery cell 111 in units of measurement per 100 mAh, and define the discharge current I of the battery pack 110 to be 1 current per 12 amps (Current, C). That is, the battery pack 110 has a discharge current of 1200 milliamperes (mA) per hour. Specifically, the discharge electric quantity AH according to the voltage detection circuit 120 is calculated by the discharge current I measured by the current detection circuit 130, and the discharge electric quantity AH is calculated and obtained by the current integration method.

A discretization step 220 calculates a voltage standard deviation of the loop voltage V of each of the battery cells 111 according to a standard deviation formula statistical distribution. The standard deviation of the voltage is: X _i is a random variable of the loop voltage V , u _i is an average value of the loop voltage V corresponding to each battery cell 111, Z _i is a standard fraction of the loop voltage value of the battery core, and n is a loop voltage corresponding to each battery cell 111 The total number of V , where n can be 0~1000. Thereby, the voltage standard deviation of each of the battery cells 111 can be obtained.

The differential step 230 is to obtain a discrete curve according to the discharge electric quantity AH and the voltage standard deviation of the measuring step 210. In the embodiment, the battery unit 110 has been degraded 20 times, 30 times, 40 times, and 50 times to draw the fourth picture. For example, the discharge electric quantity AH is the horizontal axis, and the voltage standard deviation is the vertical axis. Then use the differential formula to calculate the standard deviation wave valley of the discrete curve. The differential formula is: Where σ ( AH ) is the voltage standard deviation versus discharge power AH function.

The estimation step 240 calculates the rated discharge power AH _{original of the} battery pack 110 and the discharge power AH _valley corresponding to the standard deviation wave valley according to the health state calculation formula, thereby obtaining the health state SOH of the battery pack 110. The health state SOH calculation formula is: Where k is a proportional constant of a certain value, AH _valley is the discharge capacity corresponding to the standard deviation wave trough, AH _original is the rated discharge capacity of the battery pack 110, and different battery packs 110 have different proportional constants K , which may be different The type and the brand of the battery pack 110 are different, and may be 0 to 1000, particularly preferably 1 to 100. As shown in FIG. 4, the standard deviation wave troughs of the battery pack 110 which has been degraded 20 times, 30 times, 40 times, and 50 times correspond to the range of 1700 mAH to 3300 mAH of the discharge electric quantity AH .

Thereby, the health state SOH of the battery pack 110 can be quickly corrected under the above-mentioned steps without having to construct the database of the battery pack 110.

Therefore, the method and system for estimating the health status of the battery pack of the present invention have the following advantages: the measurement of the standard deviation of the battery core circuit voltage and the discharge power of the battery pack are used to obtain the health status of the battery pack. This allows you to instantly correct the residual battery status of the battery pack without having to spend a lot of time building the database.

Moreover, since the invention measures the voltage of the circuit, the health state of the battery pack can be estimated when the battery pack is discharged, without stopping the battery pack discharge behavior.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

100‧‧‧Battery Health Status Estimation System

110‧‧‧Battery Pack

111‧‧‧ battery core

120‧‧‧Voltage detection circuit

130‧‧‧ Current detection circuit

140‧‧‧ Computing Module

150‧‧‧ memory module

160‧‧‧ display module

170‧‧‧load

SOH‧‧‧Health status

Claims (11)

A method for estimating a health state of a battery pack, the method comprising: a measuring step of repeatedly measuring a plurality of loop voltages of a plurality of battery cells of a battery pack by using a different plurality of discharge powers of a predetermined sampling condition; a discretization step, Calculating the loop voltages of each of the battery cells according to a standard deviation formula statistical distribution to obtain a voltage standard deviation of each of the battery cells; a differential step, which obtains one according to the discharged electrical quantities and the voltage standard deviations Discrete curve, and adopting a differential formula to calculate one standard deviation wave valley of the discrete curve; and an estimation step of calculating a rated discharge power of the battery pack according to a health state calculation formula and corresponding to the standard deviation wave valley value The discharged electric quantity is used to obtain a healthy state of the battery pack; wherein the health state is calculated in the estimation step as k( AH _valley )/( AH _original )×100%, where k is a proportional constant, and AH _valley is The discharge capacity corresponding to the standard difference wave trough, AH _original is the rated discharge capacity of the battery pack. The battery pack health state estimating method of claim 1, wherein the predetermined sampling condition in the measuring step is to measure the loop voltages of the battery cells of the battery pack once every one hundred milliamperes. The battery pack health state estimating method of claim 2, wherein the discharging power of the battery pack in the measuring step is obtained by a current integration method. The battery pack health state estimation method of claim 3, wherein the standard deviation formula in the discretization step is And X _i is a random variable of the loop voltages, u _i is an average value of the loop voltages corresponding to each of the battery cells, and Z _i is a standard fraction of loop voltage values of each of the battery cells, and n is corresponding to each The total number of loop voltages of the battery cells. The method for estimating the health status of the battery pack according to claim 4, wherein the differential formula in the different step is dσ ( AH )/ dAH , and σ ( AH ) is a function of the voltage standard deviations of the voltages, AH is the Some discharge power. A battery pack health state estimation system includes: a battery pack having a plurality of battery cells; a voltage detecting circuit electrically connected to the battery pack, wherein the voltage detecting circuit repeats a different number of discharges with a predetermined sampling condition Measuring a plurality of loop voltages of the battery cells; a current detecting circuit electrically connecting the battery pack, the current detecting circuit measuring a discharge current of the battery pack for calculating the discharge power; and an operation module Electrically connecting the battery pack, the computing module includes: a discretization unit that calculates the loop voltages of each of the battery cells according to a standard deviation formula statistical distribution to obtain a voltage standard deviation of each of the battery cells a differential unit that obtains a discrete curve according to the discharged electrical quantities and the standard deviations of the voltages, and calculates a standard deviation wave valley value of the discrete curve by using a differential formula; and a health state calculating unit according to a health state Calculating formula for calculating the rated discharge capacity of one of the battery packs and the discharge amount corresponding to the standard deviation wave trough to obtain one of the battery packs Kang state; wherein the health condition is calculated as _{k (AH valley) / (AH} original) × 100%, where k is a proportionality constant, AH _valley for the trough should be the standard deviation value of the discharge power, AH _original cell for The rated discharge capacity of the group. The battery pack health state estimation system of claim 6, wherein the preset sampling condition is to measure the loop voltages of the battery cells of the battery pack once every one hundred milliamp hours. The battery pack health state estimation system of claim 7, wherein the discharge power of the battery pack is obtained by a current integration method. The battery pack health state estimation system of claim 8, wherein the standard deviation formula is And X _i is a random variable of the loop voltages, u _i is an average value of the loop voltages corresponding to each of the battery cells, and Z _i is a standard fraction of loop voltage values of each of the battery cells, and n is corresponding to each The total number of loop voltages of the battery cells. The battery pack health state estimation system of claim 9, wherein the differential formula is dσ ( AH )/ dAH , and σ ( AH ) is a function of the voltage standard deviations of the voltages, and AH is the discharge power. The battery pack health state estimation system of claim 10, further comprising: a memory module electrically connected to the computing module; a display module electrically connected to the computing module for displaying the battery pack The health state; and a load electrically connected to the voltage detecting circuit and the current detecting circuit for causing the load, the battery pack, the voltage detecting circuit and the current detecting circuit to form a loop in series.