Secondary Battery SOC Estimation via OCV Table Averaging
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Solution Overview
Problem
Existing methods for estimating the state of charge (SOC) of secondary batteries require extensive investigation of battery characteristics to correct terminal voltage, leading to inefficiencies in accuracy and time consumption.
Innovation Solution
A secondary battery system that uses an SOC table to correlate open circuit voltage (OCV) with SOC, allowing for real-time SOC calculation without the need for complex corrections or extensive battery characteristic investigation, by averaging SOC values during charging and discharging cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If terminal voltage correction is performed using existing methods, then SOC accuracy is improved, but investigation time and device complexity increase
Solution Approach 1:
The patent pre-calculates and stores correction values in a correction value storage unit during battery manufacturing or initial setup. These correction values are derived from battery characteristics and are ready for immediate use without requiring real-time investigation. This preliminary action eliminates the need for time-consuming on-site battery characteristic analysis while maintaining accurate SOC correction.
Solution Approach 2:
The patent creates a simplified model or lookup table of battery characteristics that can be easily stored and referenced. Instead of performing complex real-time voltage corrections requiring detailed battery investigations, the system uses pre-copied correction data that approximates the effect of thorough battery characterization. This copying approach maintains accuracy while dramatically reducing the time and complexity of investigation.
2Measurement precision
If terminal voltage correction is performed using existing methods, then SOC accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex correction calculation algorithms with pre-stored correction values in a lookup table or database. The correction value storage unit contains pre-computed values that can be directly applied without performing complex mathematical operations or real-time battery model simulations. This copying approach maintains correction accuracy while significantly simplifying the device architecture and reducing computational requirements.
Solution Approach 2:
The system performs the complex correction value derivation during battery manufacturing or initial setup, storing the results for later use. This preliminary calculation eliminates the need for complex real-time processing in the operational system. The battery control device simply retrieves pre-computed correction values rather than performing complex calculations during SOC estimation, thereby reducing device complexity.
3Speed
If current integration method is used for SOC estimation, then real-time SOC calculation is achieved, but SOC error increases over time
Solution Approach 1:
The patent employs a feedback mechanism where the battery control device continuously monitors terminal voltage and compares it with expected voltage values based on the integrated current measurements. When discrepancies are detected, the system retrieves appropriate correction values from the correction value storage unit and applies them to adjust the SOC estimate. This feedback loop maintains accuracy over time while preserving the real-time calculation capability of current integration.
Solution Approach 2:
The patent dynamically adjusts the SOC estimation by changing the voltage parameter used in calculations. Instead of relying solely on integrated current values, the system incorporates corrected terminal voltage measurements at charging/discharging switching points. These parameter changes, guided by pre-stored correction values, compensate for integration errors and maintain SOC accuracy without sacrificing real-time performance.
Data Source
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AI summary
A secondary battery system capable of acquiring an SOC of a battery with a simple computation without acquiring battery characteristics is to be provided. The secondary battery system according to the present invention is adapted to acquire a momentary SOC (charging SOC) by obtaining an initial value of an SOC from a CCV acquired during a charging period and adding an integrated value of a charge or discharge current to the initial value of the SOC, acquire a momentary SOC (discharging SOC) by obtaining an initial value of an SOC from a CCV acquired during a discharging period and adding an integrated value of a charge or discharge current to the initial value of the SOC, and acquire an SOC close to a true value by averaging the charging SOC and the discharging SOC.