SOC Estimation for Blended Cathode Batteries
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Solution Overview
Problem
Existing methods for estimating the state of charge (SOC) of secondary batteries with blended cathode materials face challenges due to unusual voltage behaviors, making it difficult to accurately determine SOC, especially when the battery is in a no-load state and undergoing voltage relaxation.
Innovation Solution
The method involves measuring the key-on voltage and key-on discharge voltage of a secondary battery with blended cathode materials, using these parameters to estimate SOC through a predetermined relationship, such as a look-up table or function, which accounts for the specific discharge conditions and cathode material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If blended cathode materials are used to optimize battery performance, then energy capacity and temperature stability are improved, but voltage behavior becomes unusual making SOC estimation difficult
Solution Approach 1:
The patent changes the parameters used for SOC estimation from relying solely on voltage to using a combination of voltage, current, and temperature parameters. By measuring multiple parameters simultaneously and using their combined variation patterns, the system can accurately estimate SOC even when voltage behavior is unusual due to blended cathode materials.
Solution Approach 2:
The patent implements a feedback mechanism where the estimated SOC is continuously updated based on measured voltage, current, and temperature data. The system compares the measured parameter variations with expected patterns and adjusts the SOC estimation accordingly, creating a closed-loop system that compensates for unusual voltage behavior.
2Measurement precision
If voltage relaxation phenomenon is considered for accurate SOC estimation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-storing the relationship between voltage relaxation patterns and SOC states in lookup tables or as characteristic curves. During operation, the system only needs to measure the current voltage and compare it with the pre-stored data, avoiding complex real-time calculations while maintaining high accuracy.
Solution Approach 2:
The patent uses copying by creating simplified representations of the complex voltage relaxation phenomena through lookup tables and characteristic curves. These copied data structures capture the essential relationships without requiring the system to model the complex physical processes in real-time, thus reducing computational complexity.
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 even in cases of unusual voltage behavior, enabling the blending of cathode materials that were previously incompatible, and optimizing battery performance for various applications by accurately determining SOC.
Implementation Method 1
the voltage relaxation phenomenon by transferring operating ions between the first cathode material and the second cathode material
Implementation Method 2
the voltage of the secondary battery may be gradually changed until reaching the equilibrium state voltage while following a voltage relaxation profile determined by the SOC
Implementation Method 3
secondary batteries which allow repeated charge and discharge since their electrochemical reaction is at least partially reversible
Data Source
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AI summary
Disclosed is an apparatus and method for estimating a SOC of a secondary battery containing a blended cathode material. The SOC estimating apparatus estimates a SOC of a secondary battery including a cathode having a blended cathode material containing a first cathode material and a second cathode material with different operating voltage ranges, an anode having an anode material, and a separator for separating the cathode from the anode, and the apparatus includes a sensor configured to measure a discharge inception voltage and a final discharge voltage when the secondary battery is discharged for a predetermined time, and a control unit configured to estimate SOC of the secondary battery corresponding to the measured discharge inception voltage and the measured final discharge voltage by using a predetermined relationship between the discharge inception voltage and the final discharge voltage and the SOC of the secondary battery.