Battery SOC Estimation Using Interruption-Time OCV Analysis
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Solution Overview
Problem
Existing methods for estimating the State Of Charge (SOC) of battery cells, particularly lithium batteries, are inaccurate when the battery voltage graph exhibits a nonlinear pattern, leading to incorrect Open Circuit Voltage (OCV) estimation and subsequent SOC diagnosis issues.
Innovation Solution
A SOC estimating apparatus and method that uses a control unit to estimate SOC by analyzing voltage information during charging and discharging interruptions, incorporating a reference time to distinguish between short-term and long-term polarization components, and employing function optimization techniques to accurately estimate OCV and SOC, even in nonlinear voltage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If linear analysis method is used to estimate OCV, then estimation is simple, but accuracy deteriorates when voltage graph is nonlinear
Solution Approach 1:
The patent changes the estimation approach from linear analysis to dual-time-point analysis, measuring voltage at two specific time points (immediately after current interruption and after a predetermined time) to capture both short-term and long-term polarization effects. This parameter change enables accurate OCV estimation for both linear and nonlinear voltage graphs.
2Measurement precision
If sufficient rest period is provided for SOC estimation, then accuracy is improved, but productivity deteriorates due to longer time required
Solution Approach 1:
The patent applies partial action by measuring voltage at two specific time points rather than requiring complete rest period. The first measurement is taken immediately after current interruption (capturing short-term polarization), and the second measurement is taken after a predetermined time (capturing long-term polarization). This partial measurement approach achieves accurate SOC estimation without requiring full rest period, thus improving productivity.
3Speed
If voltage measurement is taken immediately after current interruption, then response time is improved, but measurement precision deteriorates due to polarization effects
Solution Approach 1:
The patent segments the voltage measurement process into two distinct time points: the first voltage measurement is taken immediately after current interruption to capture the state with short-term polarization, and the second voltage measurement is taken after a predetermined time to capture the state with long-term polarization. By segmenting the measurement into these two parts, the system can separately analyze and compensate for different polarization effects, achieving accurate OCV estimation despite the short response time.
Data Source
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AI summary
The present disclosure is directed to providing an SOC estimating apparatus and method, which may accurately estimate OCV and SOC of a battery cell even when a voltage rough graph of the battery cell exhibits a nonlinear rough graph. According to an aspect of the present disclosure, the SOC estimating apparatus has an advantage of estimating the SOC of the battery cell more accurately and more reliably. In addition, the SOC estimating apparatus has an advantage of estimating the final SOC of the battery cell quickly even in an environment where it is difficult to secure a sufficient rest period, by estimating the second SOC based on voltage information obtained during the charging and discharging interruption time.