Battery State of Health Estimation via Partial Charge Calibration
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Solution Overview
Problem
Current methods for estimating the state of health (SOH) of batteries are either invasive, time-consuming, or unreliable, as they either require direct capacity measurement or indirect estimation through resistance or impedance monitoring, which does not accurately reflect capacity loss.
Innovation Solution
A method involving a calibration phase to identify a favorable voltage or charge range where the derivative of charge with respect to voltage is maximized, allowing for linear interpolation to determine the state of health based on charge or energy measurements within this range, enabling rapid and non-intrusive SOH estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complete charge and discharge test is performed to measure true SOH, then measurement precision is improved, but loss of time and productivity deteriorate
Solution Approach 1:
The patent applies partial action by performing SOH estimation during only a portion of the battery charge/discharge cycle rather than requiring a complete cycle. Specifically, the method estimates SOH during constant current charge or discharge phases, avoiding the need to wait for complete cycling while still obtaining accurate measurements during the most informative portion of the operation.
Solution Approach 2:
The patent implements preliminary action by continuously monitoring battery parameters (voltage, current, temperature) during normal operation and pre-calculating SOH estimates using stored calibration data. This allows the system to have SOH information ready before a full capacity test would be needed, eliminating waiting time while maintaining accuracy.
2Measurement precision
If a complete charge and discharge test is performed to measure true SOH, then measurement precision is improved, but device complexity and operational disruption increase
Solution Approach 1:
The patent ensures continuity of useful action by enabling SOH measurement during normal battery charge or discharge operations without requiring the battery to be taken offline. The method continuously monitors voltage, current, and temperature during routine charging/discharging and performs real-time SOH estimation, allowing the battery to remain in service throughout the measurement process.
Solution Approach 2:
The battery management system performs self-service by using the battery's own operational data (voltage, current, temperature during normal charge/discharge) to calculate SOH estimates. The system leverages calibration data stored in memory and applies it to real-time measurements, allowing the battery to monitor its own health without external intervention or specialized testing equipment.
3Ease of operation
If resistance or impedance monitoring is used to estimate SOH, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent applies parameter changes by using multiple battery parameters (voltage, current, temperature) simultaneously rather than relying on a single parameter like resistance or impedance. The method combines these parameters during constant current charge or discharge phases to calculate charge quantity, providing a more comprehensive and accurate SOH estimate that accounts for the complex electrochemical behavior of lithium-ion batteries.
Solution Approach 2:
The patent introduces an intermediary approach by using charge quantity calculation as a mediator between simple voltage/current monitoring and direct capacity measurement. The method integrates current over time during constant current phases to determine charge quantity, which serves as an intermediate metric that correlates strongly with capacity and SOH, bridging the gap between easy-to-measure parameters and accurate SOH estimation.
Data Source
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AI summary
The invention relates to a method for estimating the state of health (SOH) of a battery, characterised by comprising the following steps: a first phase of calibrating (P1) one or more batteries of the same family of batteries, making it possible to determine a favourable range for estimating the state of health of a certain family of batteries, the favourable range corresponding to a partial charge or discharge of a battery, and to determine reference data; a second phase of measuring and estimating (P2) the state of health of the battery, comprising the steps of measuring (E14) at least one value linked to the quantity of charge or energy supplied or delivered by the battery in a partial discharge or charge phase of the battery over the favourable range, and estimating (E16) the state of health of the battery based on the result of the measurement step (E14) and the reference data established during the first calibration phase.