SOC Estimation for Blended Cathode Batteries
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Solution Overview
Problem
Existing secondary battery technologies face challenges in accurately estimating the State of Charge (SOC) of lithium secondary batteries, particularly when using blended cathode materials, due to unusual voltage behaviors in transition regions, leading to increased estimation errors during repeated charging and discharging cycles in hybrid electric vehicle modes.
Innovation Solution
A method and apparatus that utilize a blended cathode material with different operating voltage ranges, incorporating a sensor to measure dynamic voltage and a control unit to identify transition region voltage patterns, calculate parameters, and estimate SOC using a predetermined relationship, such as a look-up table or function, to accurately determine the SOC even in transition regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blended cathode material is used to improve battery performance, then energy capacity and stability are improved, but voltage behavior becomes unusual in transition regions leading to increased SOC estimation error
Solution Approach 1:
The voltage range of the blended cathode material is segmented into multiple regions (first voltage range, second voltage range, and transition region between them). Each region corresponds to different active cathode materials, allowing the system to identify which region is currently active and apply appropriate SOC estimation methods for each region, thereby resolving the measurement accuracy issue in transition regions
Solution Approach 2:
The system changes the parameter used for SOC estimation based on the voltage region. In non-transition regions, conventional voltage-SOC relationships are used, while in transition regions, the system identifies the unusual voltage behavior and applies corrected estimation methods, effectively adapting the estimation parameter to the current operating condition
2Ease of operation
If conventional SOC estimation methods are used, then the system is simple to operate, but estimation error increases in transition regions with distinctive voltage behaviors
Solution Approach 1:
The system continuously monitors the voltage-SOC relationship and identifies when the battery enters a transition region by detecting unusual voltage behaviors. This feedback mechanism triggers a switch from conventional estimation methods to region-specific estimation methods, maintaining both simplicity and accuracy by only applying complex methods when necessary
Solution Approach 2:
The system pre-establishes multiple voltage-SOC relationship models corresponding to different voltage regions and cathode materials. Before SOC estimation, the system determines which region is currently active and selects the appropriate pre-prepared model, avoiding real-time complex calculations while ensuring accuracy for the current operating condition
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 reliable SOC estimation in secondary batteries with blended cathode materials, reducing estimation errors and improving accuracy even in regions with distinctive voltage behaviors, thus enhancing the performance and reliability of electric vehicles operating in hybrid electric vehicle modes.
Implementation Method 1
a sensor configured to measure a dynamic voltage of the secondary battery during charging of the secondary battery
Implementation Method 2
A battery generates electric energy by oxidation and reduction reactions
Implementation Method 3
a control unit configured to identify a dynamic voltage profile of the secondary battery as a transition region voltage pattern, calculate a parameter of the transition region voltage pattern, and estimate a SOC of the secondary battery from the calculated parameter
Data Source
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AI summary
Disclosed is an apparatus for estimating a state of charge (SOC) of a secondary battery which includes (i) a cathode comprising a blended cathode material having a first cathode material and a second cathode material, wherein the first and second cathode materials have different operating voltage ranges; (ii) an anode comprising an anode material; and (iii) a separator for separating the cathode from the anode. The apparatus includes a sensor configured to measure a dynamic voltage of the secondary battery during charging of the secondary battery, and a control unit configured to identify a dynamic voltage profile of the secondary battery as a transition region voltage pattern, calculate a parameter of the transition region voltage pattern, and estimate a SOC of the secondary battery from the calculated parameter by using a predetermined relationship between the parameter and the SOC.