Battery SOH Estimation via High-Voltage Charging Curve Analysis
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Solution Overview
Problem
Current methods for estimating the State of Health (SOH) of power battery packs in electric vehicles rely heavily on accurate initial values and ampere-hour integral calculations, which are prone to errors due to cumulative inaccuracies and dependence on operating conditions, leading to inaccurate SOH predictions.
Innovation Solution
A method and apparatus that analyze the charging curve of a power battery pack to determine high-voltage and high-voltage platform charging stages, calculate remaining capacity, and estimate SOH without requiring full charging and discharging cycles, initial SOC values, or being influenced by operating conditions, thereby improving accuracy and convenience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ampere-hour integral method is used to calculate electricity amounts, then the method is simple to implement, but cumulative errors accumulate over time resulting in inaccurate SOH estimation
Solution Approach 1:
The charging process is segmented into distinct stages (constant current charging, constant voltage charging, and high-voltage platform charging) based on voltage and current characteristics. By identifying transition points between stages and calculating capacity for each segment separately, the method avoids cumulative errors from continuous integration while maintaining implementation simplicity.
Solution Approach 2:
The method performs preliminary identification of charging stage transition points (such as the end of constant voltage charging and entry into high-voltage platform charging) before calculating capacity. By pre-determining these critical points during charging, the system establishes accurate boundaries for capacity calculation, eliminating the need for post-processing correction of cumulative errors.
2Measurement precision
If full charging and discharging cycles are performed to estimate SOH, then the accuracy of SOH estimation is improved, but the time consumption and operational disruption increase
Solution Approach 1:
The method uses partial charging information (specifically the high-voltage platform charging stage characteristics) to estimate SOH without requiring complete charge-discharge cycles. By focusing on the distinctive high-voltage platform phase that occurs during normal charging operations, the system obtains sufficient data for accurate SOH estimation while minimizing time loss and operational disruption.
Solution Approach 2:
The method utilizes charging data that is naturally generated during normal vehicle operation and charging processes. By analyzing the high-voltage platform charging characteristics that occur during routine charging, the system performs SOH estimation using self-generated data without requiring external testing equipment or dedicated test cycles, thereby eliminating time loss and operational disruption.
3Device complexity
If SOC initial values are used for SOH estimation, then the calculation process is simplified, but the accuracy deteriorates due to dependence on accurate initial values
Solution Approach 1:
The method extracts SOH estimation from dependence on SOC initial values by focusing on the high-voltage platform charging stage characteristics. By isolating and analyzing the specific voltage-current-time relationships during this stage, the system calculates capacity based on observable charging behavior rather than requiring accurate initial SOC values, thereby eliminating the trade-off between simplicity and accuracy.
Data Source
AI summary
Provided is a method for calculating the SOH of a battery power pack. The method comprises the following steps: acquiring a charging curve of a cell of a battery power pack, and determining a current charging phase according to the charging curve, wherein the charging phase comprises a high voltage charging inflection point and a high voltage charging phase (S1); acquiring a battery pack power amount corresponding to the high voltage charging inflection point and a battery pack power amount corresponding to the high voltage charging phase (S2); calculating the remaining capacity of a cell according to the battery pack power amount corresponding to the high voltage charging inflection point and the battery pack power amount corresponding to the high voltage charging phase (S3); and calculating the SOH of the cell according to the remaining capacity (S4).