Battery Capacity Fade Estimation via Temperature-Potential Ratio
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Solution Overview
Problem
Lithium-ion batteries experience capacity fade due to side reactions and active material loss during charge/discharge cycles, making it difficult to accurately determine their state of charge and capacity without complete discharge, which is impractical for applications like hybrid-electric vehicles.
Innovation Solution
A method that estimates the open-circuit potential and capacity fade of lithium-ion batteries by measuring temperature and state of charge, using a battery management system to regulate charging/discharging based on these estimates, and utilizing the ratio of change in open-circuit potential relative to temperature to collect data points for accurate capacity fade analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complete discharge is performed to diagnose battery capacity, then measurement precision is improved, but loss of time and productivity deteriorate
Solution Approach 1:
The patent applies partial action by measuring battery capacity using only a limited capacity range or state-of-charge range sampled during normal operation, rather than requiring complete discharge. The method uses open-circuit potential measurements at specific state-of-charge points to estimate total capacity, achieving accurate diagnosis without the time-consuming complete discharge process.
2Productivity
If open-circuit potential measurements are taken at limited state-of-charge ranges, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The patent changes the measurement parameters by using temperature-compensated open-circuit potential measurements and utilizing the relationship between open-circuit potential and state of charge. By measuring dU/dT (change in open-circuit potential with temperature) and using this ratio along with potential measurements, the system achieves accurate capacity fade determination from limited state-of-charge data points.
3Measurement precision
If temperature measurements are incorporated into capacity fade analysis, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses temperature as an intermediary parameter to improve capacity fade measurement. Temperature measurements serve as a mediator that, when combined with open-circuit potential measurements and used to calculate dU/dT ratios, enables more accurate capacity fade determination. The temperature data acts as an additional dimension of information that enhances the precision of capacity estimation without requiring complex additional measurement systems.
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
Enables precise estimation of battery state of health and capacity fade, allowing for optimal battery usage and potential cost savings by using smaller batteries while maintaining performance and lifetime targets, without requiring complete discharge.
Implementation Method 1
estimating, by the battery management system, a capacity fade of the at least one battery cell based on the open circuit potential of the at least one battery cell and a ratio of a change in the open circuit potential relative to a change in the temperature
Data Source
AI summary
Methods and systems are described of managing a battery system. The battery system including at least one battery cell and one or more sensors configured to measure a temperature of the at least one battery cell. The method includes receiving a measurement of the temperature of the at least one battery cell, estimating an open circuit potential of the at least one battery cell, estimating a capacity fade of the at least one battery cell based on the open circuit potential of the at least one battery cell and a ratio of a change in the open circuit potential relative to a change in the temperature of the at least one battery cell, and regulating at least one of charging or discharging of the at least one battery cell based on the estimation of the capacity fade.