Cell Balancing Using Voltage Variation Pattern for OCV Estimation
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Solution Overview
Problem
Existing methods for balancing State Of Charge (SOC) in batteries, such as electric vehicles, face challenges in accurately measuring SOC due to non-linearity in battery behavior, leading to low accuracy and error accumulation, especially when using output voltage or current integration methods.
Innovation Solution
A cell balancing apparatus and method that estimates Open Circuit Voltage (OCV) and SOC using a voltage variation pattern, incorporating a voltage measuring unit, temperature measuring unit, and a mathematical model to correct for temperature effects, allowing for accurate SOC balancing by comparing estimated OCV and SOC across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If output voltage is used to estimate OCV, then SOC estimation can be performed, but measurement accuracy deteriorates due to IR drop
Solution Approach 1:
The patent stores historical voltage data before the current measurement point, allowing the system to analyze voltage variation patterns that occurred prior to the current state. This preliminary data collection enables the calculation of OCV by referencing how voltage changed in previous states, thereby separating the true OCV from transient IR drop effects.
Solution Approach 2:
The patent introduces voltage variation pattern as an intermediary element between the measured voltage and the OCV estimation. By analyzing the pattern of voltage changes over time rather than relying on a single voltage point, the system uses this intermediate representation to filter out IR drop disturbances and extract the true OCV value.
2Device complexity
If current integration method is used to estimate SOC, then estimation process is simplified, but measurement accuracy deteriorates due to error accumulation
Solution Approach 1:
The patent replaces the current integration method (which accumulates errors over time like a mechanical counter) with a voltage-based estimation method. Instead of continuously summing current measurements, the system uses voltage variation patterns and stored historical voltage data to estimate OCV and SOC, thereby eliminating the cumulative error problem while maintaining reasonable complexity.
3Measurement precision
If mathematical models are used to estimate SOC, then estimation accuracy is improved, but computation time increases and hardware requirements increase
Solution Approach 1:
The patent performs preliminary data collection and storage by maintaining a database of historical voltage measurements and their corresponding OCV values. This pre-collected data allows the estimation process to reference stored patterns rather than performing complex real-time calculations, significantly reducing computation time while maintaining accuracy.
Solution Approach 2:
The patent creates a simplified representation of the voltage-OCV relationship by storing historical data patterns. Instead of using complex mathematical models that require heavy computation, the system copies and references previously observed voltage variation patterns, enabling fast estimation by matching current patterns against stored examples.
Data Source
AI summary
Disclosed is a cell balancing apparatus and method using a voltage variation pattern of a battery cell, which measures voltage of each cell, estimates OCV or SOC of each cell using a voltage variation pattern of each cell including a present voltage and a past voltage, and eliminates a deviation in OCV or SOC between the cells through comparison of the estimated OCV or SOC of each cell. In estimating the OCV of each cell, an output voltage error due to IR drop is corrected. Thus, SOC of each cell may be accurately estimated. And, an accurate estimation of SOC may render substantial elimination for a SOC deviation of each cell. Furthermore, SOC estimating using an output voltage leads to an active cell balancing even during charge and discharge of battery, thereby minimizing an SOC deviation of each cell.