CN107861075B

CN107861075B - Method for determining SOP of power battery

Info

Publication number: CN107861075B
Application number: CN201711412872.9A
Authority: CN
Inventors: 李世明; 王世强; 胡庆军; 张叶鑫
Original assignee: Jiangxi Special Automobile Technology Co Ltd
Current assignee: Jiangxi Special Automobile Technology Co Ltd
Priority date: 2017-12-24
Filing date: 2017-12-24
Publication date: 2020-03-27
Anticipated expiration: 2037-12-24
Also published as: CN107861075A

Abstract

The invention discloses a method for determining SOP of a power battery, which comprises the following steps: step 1, selecting the temperature, the polarization voltage, the duration time, the SOC and the SOH of a measurement target; step 2, adjusting the temperature, SOC and SOH of the battery to the target temperature; step 3, adjusting the battery to the initial polarization voltage of the target; step 4, obtaining the discharging coulomb efficiency of the set time under the specified multiplying power; step 5, obtaining the charging coulomb efficiency of the selected duration under the specified multiplying power; step 6, fitting a curve and a curved surface function according to the results obtained in the steps 4 and 5; and 7, obtaining the battery damage evaluation of the given power under the given condition according to the fitting result, and obtaining the maximum bearable power of the battery. The method has the advantages that the coulombic efficiency is adopted to directly and quantitatively evaluate the capacity loss of the battery, reliable basis can be provided for the control strategy to use the battery power, the initial polarization voltage condition is set, the influence of the use history on the SOP is included, and the measurement is more accurate and reliable.

Description

Method for determining SOP of power battery

Technical Field

The invention relates to the field of electric automobiles, in particular to the field of power battery management of electric automobiles.

Background

Due to the aggravation of energy crisis and environmental crisis, new energy automobiles are rapidly developed in the year, and lithium batteries are used as mainstream energy storage energy sources of electric automobiles, and management systems of the lithium batteries are also widely concerned. In battery management, SOC (state of charge), SOH (remaining life), and SOP (power handling capability) are all important state parameters of a battery, and SOC and SOH technologies are developed and are receiving wide attention. But there are few techniques available for real-time estimation of the state of power (SOP) of lithium batteries. The SOP represents the bearing capacity of the battery to charge and discharge power, and the accurate estimation of the SOP can ensure that the electric automobile obtains larger power freedom on the premise of protecting the battery, such as available power for starting and accelerating, climbing speed, recovered power of brake electric energy and the like. The power state of the battery is related to various factors and states such as the SOC, SOH, and temperature of the battery, and thus has a high degree of non-linear characteristics.

The prior art mainly has a method of impulse response for predicting the power bearing capacity of a battery, for example, a method of power response for a power-assisted hybrid electric vehicle power battery test manual (HPPC) of the U.S. free-CAR project applies specific impulse excitation to the battery under different SOCs to obtain corresponding voltages to predict the power, but the method only considers the static characteristics of the battery and has low prediction accuracy in dynamic conditions. The electrochemical model method uses a large amount of chemical partial differential and utilizes various approximate combinations for estimation, but the application range after simplification is very limited, and the application requirements are difficult to meet. Electrical models simulate the behavior of a battery through a combination of electrical components, but these models are more suitable for performance simulation than SOP estimation. Other prior art methods, such as patent application 201610799603.1, obtain maximum power a priori, but there is no specific method to obtain maximum power.

Disclosure of Invention

The invention aims to solve the technical problem of realizing reliable and effective measurement of the maximum bearable power of a power battery.

In order to achieve the purpose, the invention adopts the technical scheme that: a method of determining power cell SOP:

step 1, selecting the temperature, the polarization voltage, the duration time, the SOC and the SOH of a measurement target;

step 2, adjusting the temperature, SOC and SOH of the battery to the target temperature;

step 3, adjusting the battery to the initial polarization voltage of the target;

step 4, obtaining the discharging coulomb efficiency of the set time under the specified multiplying power;

step 5, obtaining the charging coulomb efficiency of the selected duration under the specified multiplying power;

step 6, fitting a curve and a curved surface function according to the results obtained in the steps 4 and 5;

and 7, obtaining the battery damage evaluation of the given power under the given condition according to the fitting result, and obtaining the maximum bearable power of the battery.

In the step 1, the selected target temperature points are 0 ℃,5 ℃,10 ℃, 20 ℃, 35 ℃, 45 ℃,50 ℃ and 55 ℃;

in step 1, the selected target SOC points are 10%, 20%, 30%,50%,80%,90%, and 100%.

In step 1, the selected target SOH is 100%, 90%, 85%, 80%, 70%. The selected durations are 10 seconds, 20 seconds, 35 seconds.

In the step 1, the selected target polarization voltage is fully charged according to a standard working condition, the battery is discharged by respectively using a rated cycle life multiplying factor, an 80% cycle life multiplying factor, a 50% cycle life multiplying factor and a 30% cycle life multiplying factor to obtain a polarization voltage curve, and the polarization voltage corresponding to the SOC point is selected as a test polarization voltage.

The setting time of the step 4 is 20 seconds.

And 5, repeating the steps 1 and 2 to obtain the charging coulombic efficiency, repeatedly selecting different parameters each time, and obtaining the charging coulombic efficiency according to the selected duration under the specified multiplying power of the point.

And 4, repeating the steps 1-3 to obtain the discharging coulombic efficiency, repeatedly selecting different parameters each time, and measuring the charging coulombic efficiency and the discharging coulombic efficiency of the selected duration time under the selected temperature, SOC, SOH and initial polarization voltage.

The method has the advantages that coulombic efficiency is adopted to directly and quantitatively evaluate the capacity loss of the battery, reliable basis can be provided for the control strategy to use the battery power, the initial polarization voltage condition is set, the influence of use history on the SOP is included, the measurement is more accurate and reliable, and the battery use strategy can select a variable maximum power control strategy on the premise of controlling the total loss of the battery capacity.

Drawings

The following is a brief description of the contents of each figure in the description of the present invention:

fig. 1 is a flow chart of a method of determining the SOP of a power cell.

Detailed Description

The invention discloses a method for determining SOP of a power battery, which is a method capable of essentially determining the maximum bearable power of the battery, and takes a ternary lithium battery 8Ah battery core as an example, and the specific processing steps are as follows:

the method comprises the following steps: the selected temperature points are 0 ℃,5 ℃,10 ℃, 20 ℃, 35 ℃, 45 ℃,50 ℃ and 55 ℃;

the selected SOC points were 10%, 20%, 30%,50%,80%,90%, 100%. Selecting SOH as 100%, 90%, 85%, 80%, 70%;

the selected durations are 10 seconds, 20 seconds, 35 seconds. And (3) selecting the polarization voltage, fully charging according to the standard working condition, discharging the battery by respectively using rated cycle life multiplying power, 80% cycle life multiplying power, 50% cycle life multiplying power and 30% cycle life multiplying power to obtain a polarization voltage curve, and selecting the polarization voltage corresponding to the SOC point as the test polarization voltage.

Step two: the battery is adjusted to target temperature, SOC and SOH.

And step three, adjusting the battery to the initial polarization voltage of the target.

And step four, measuring the 20-second discharging coulomb efficiency of the point under the specified multiplying power.

And step five, repeating the step two, and measuring the charging coulomb efficiency of the selected duration under the specified multiplying power of the point.

And step six, repeating the steps one to four, and measuring the charging coulombic efficiency and the discharging coulombic efficiency of the selected duration time under the selected temperature, SOC, SOH and initial polarization voltage.

And seventhly, performing curve surface equal function fitting according to the test result.

And step eight, designing the battery capacity attenuation damage evaluation of the given power under the given condition according to the fitting result, and using the battery charge and discharge control strategy.

Claims

1. A method of determining the SOP of a power cell, characterized by:

step 7, obtaining the damage evaluation of the battery with given power under given conditions according to the fitting result, and obtaining the maximum bearable power of the battery;

in the step 1, the selected target temperature points are 0 ℃,5 ℃,10 ℃, 20 ℃, 35 ℃, 45 ℃,50 ℃ and 55 ℃.

2. Method to determine the SOP of a power cell according to claim 1, characterized in that: in step 1, the selected target SOC points are 10%, 20%, 30%,50%,80%,90%, and 100%.

3. Method to determine the SOP of a power cell according to claim 1, characterized in that: in the step 1, the selected target SOH is 100%, 90%, 85%, 80% or 70%;

the selected durations are 10 seconds, 20 seconds, 35 seconds.

4. Method to determine the SOP of a power cell according to claim 1, characterized in that: in the step 1, the selected target polarization voltage is fully charged according to a standard working condition, the battery is discharged by respectively using a rated cycle life multiplying factor, an 80% cycle life multiplying factor, a 50% cycle life multiplying factor and a 30% cycle life multiplying factor to obtain a polarization voltage curve, and the polarization voltage corresponding to the SOC point is selected as a test polarization voltage.

5. Method to determine the SOP of a power cell according to any of the claims 1-4, characterized in that: the setting time of the step 4 is 20 seconds.

6. Method to determine the SOP of a power cell according to claim 5, characterized in that: and 5, repeating the steps 1 and 2 to obtain the charging coulombic efficiency, repeatedly selecting different parameters each time, and obtaining the charging coulombic efficiency according to the selected duration under the specified multiplying power.

7. Method to determine the SOP of a power cell according to claim 1 or 6, characterized in that: and 4, repeating the steps 1-3 to obtain the discharging coulombic efficiency, repeatedly selecting different parameters each time, and measuring the charging coulombic efficiency and the discharging coulombic efficiency of the selected duration time under the selected temperature, SOC, SOH and initial polarization voltage.