Secondary Battery Capacity Estimation via Differential Curves
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods struggle to accurately estimate the maximum capacity of secondary batteries, particularly in battery modules with cells of varying degrees of deterioration, leading to incomplete charging and operational inefficiencies in battery management systems.
Innovation Solution
A secondary battery capacity measuring system that calculates differential characteristic curves from historical data and fits a reference differential curve to estimate the maximum capacity of non-deteriorated cells using coefficients derived from deteriorated cells, accounting for material characteristics and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charging process is stopped when any cell reaches upper-limit voltage, then overcharging is prevented, but cells with smaller capacity cannot be fully charged
Solution Approach 1:
The patent applies partial action by selectively charging only those cells that have not yet reached the upper-limit voltage. The charging controller identifies cells with capacity greater than the minimum capacity cell and continues charging them even when the minimum capacity cell reaches the voltage limit, thereby partially charging the battery module rather than completely charging all cells uniformly.
2Measurement precision
If maximum capacity is measured by complete discharge through minute current, then accurate capacity value is obtained, but operational efficiency is reduced due to long measurement time
Solution Approach 1:
The patent substitutes the mechanical/discharge-based measurement method with an estimation method based on voltage-capacity relationship curves. Instead of physically discharging the battery through minute current over extended periods, the system uses differential voltage measurements and curve fitting algorithms to estimate maximum capacity, replacing a time-consuming physical process with a computational approach.
3Ease of operation
If SOC is acquired by integrating charging/discharging current, then SOC value is obtained, but error accumulates over long-term operation
Solution Approach 1:
The patent implements feedback by using the estimated maximum capacity to continuously correct and update the SOC calculation. The system compares the integrated current-based SOC with the capacity-based SOC derived from voltage measurements and the estimated maximum capacity, using this feedback to correct accumulated errors and maintain accurate SOC values over long-term operation.
4Adaptability or versatility
If battery module contains cells with different deterioration levels, then battery can continue operation, but charging management becomes complex
Solution Approach 1:
The patent applies local quality by treating each cell individually based on its specific capacity characteristics. The charging controller identifies the minimum capacity cell and uses it as a reference, then calculates individual charging control values for each cell based on its capacity relative to the minimum. This allows differential charging management where each cell receives appropriate charging control based on its local quality or individual state.
Data Source
AI summary
A secondary battery capacity measuring system that estimates maximum capacities of other cells using characteristics of a deteriorated cell even when a charging process in the deteriorated cell having a smaller maximum capacity than the other cells in cells constituting a battery module ends and data for measuring the maximum capacities of the other cells cannot be acquired is provided.