Battery Pack State of Health Estimation Using OCV and Aging Factors
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Solution Overview
Problem
Existing methods for estimating battery pack deterioration require extensive test results and can produce errors when the change rate of charging capacity differs from tabulated values, leading to unclear mileage reduction and output issues in electric vehicles.
Innovation Solution
An apparatus and method that estimate battery pack deterioration by sensing state information, converting it into open circuit voltage (OCV), estimating state of charge (SOC), calculating battery aging factors, and applying these to a lookup table to generate a final state of health (SOH) using a combination of coulomb counting and least mean square schemes, while filtering for accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If extensive test results are used to table the change rate of charging capacity to the change in battery voltage, then the estimation accuracy is improved, but the device complexity and time required increase
Solution Approach 1:
The patent extracts the essential estimation function from extensive physical testing by using a mathematical model based on the relationship between open circuit voltage (OCV) and state of charge (SOC). The model uses only voltage measurements during charging/discharging cycles, eliminating the need for extensive capacity testing while maintaining estimation accuracy.
Solution Approach 2:
The patent replaces physical testing with a mathematical/electrical model. Instead of performing extensive capacity tests to create lookup tables, the system uses the theoretical relationship between OCV and SOC to estimate battery health, substituting mechanical testing with electrical measurement and calculation.
2Ease of operation
If a lookup table is used for estimating battery deterioration, then the estimation process is simplified, but errors occur when actual battery behavior differs from tabulated values
Solution Approach 1:
The patent introduces dynamic adjustment to the estimation process by calculating a correction factor based on the current state of charge (SOC) and comparing it with reference SOC values. This allows the system to adapt to actual battery behavior deviations from standard lookup tables, correcting estimation errors in real-time while maintaining the simplicity of the lookup table approach.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual voltage behavior during charging and discharging, comparing it with expected values from the lookup table, and adjusting the estimation accordingly. The system uses the difference between actual and expected OCV-SOC relationships to correct SOH estimates, ensuring reliability even when battery behavior deviates from standard characteristics.
3Productivity
If the battery is continuously used, then the vehicle operates normally, but the battery deteriorates leading to mileage and output reduction
Solution Approach 1:
The patent performs preliminary estimation of battery health status during normal vehicle operation by continuously monitoring voltage, current, and temperature. The system calculates SOH in real-time using the OCV-SOC relationship and correction factors, allowing deterioration to be detected and managed before it significantly impacts vehicle performance, enabling proactive maintenance decisions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate estimation of battery health without extensive testing, minimizing errors and providing clear insights into battery capacity degradation, thus improving vehicle performance and customer satisfaction.
Implementation Method 1
a conversion operation unit configured to convert into an open circuit voltage (OCV) using the generated state information and estimate a state of charge (SOC) using the converted OCV
Implementation Method 2
The SOC may be estimated by converting the OCV into the SOC using a coulomb counting scheme and the coulomb counting scheme may represent a value obtained by integrating a current value input by a unit time and then dividing the integrated current value by the total battery capacity as an SOC value fluctuated for a unit time
Implementation Method 3
The first estimation operation unit may calculate the first SOH by assigning a threshold condition to the primarily estimated SOH and applying a least mean square scheme to the SOH satisfying the threshold condition
Data Source
AI summary
An apparatus for estimating a deterioration may include a battery pack, a state information sensing unit configured to sense a state of the battery pack to generate state information, a conversion operation unit configured to convert into an open circuit voltage (OCV) using the generated state information and estimate a state of charge (SOC) using the converted OCV, a first SOH estimation operation unit configured to estimate a first state of charge (SOH) using the estimated SOC, a battery aging factor calculation unit configured to calculate a battery aging factor using the estimated SOC, a second SOH operation unit configured to apply the calculated battery aging factor to a preset lookup table to calculate a second SOH, and a filtering unit configured to filter the first SOH and the second SOH to generate a final SOH.