Battery Cell State of Health Estimation via End-of-Discharge Voltage
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Solution Overview
Problem
Existing methods for estimating the state of health (SOH) of battery cells require memorizing voltage evolution throughout discharging or charging, which is restrictive, especially for large batteries due to the high quantity of data needed.
Innovation Solution
A method that measures voltage at each cell's terminal during discharging or charging, interrupts when a predefined condition is reached, and uses a mathematical function to calculate the capacity of other cells based on end-of-discharge/charge voltages, reducing data storage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage evolution is memorized throughout discharging or charging phase, then SOH estimation can be performed, but data storage requirements become high for large batteries
Solution Approach 1:
The patent extracts only the essential information needed for SOH estimation by interrupting the discharge/charge process when a first cell reaches end-of-discharge or end-of-charge condition. Instead of storing complete voltage evolution curves for all cells, the method stores only end-of-discharge/end-of-charge voltages and uses these to calculate capacities through mathematical functions, thereby extracting minimal necessary data while preserving estimation accuracy
Solution Approach 2:
The patent performs preliminary characterization of the battery to determine mathematical functions that relate cell voltages to capacities before actual SOH estimation. These pre-determined functions (including polynomial regression models) are stored instead of complete voltage curves, allowing rapid SOH calculation without requiring extensive data storage during operation
2Measurement precision
If complete voltage curves are stored for all cells, then accurate capacity determination is possible, but measurement and storage complexity increases
Solution Approach 1:
The method extracts only critical voltage measurements (end-of-discharge/end-of-charge voltages) rather than storing complete voltage curves. This extraction approach maintains capacity determination accuracy while dramatically reducing storage and processing complexity by eliminating redundant data points
Solution Approach 2:
Instead of storing actual complete voltage curves for each cell, the patent creates simplified mathematical representations (copies) of the voltage-capacity relationships through predetermined functions. These mathematical models serve as compact substitutes for full voltage curves, enabling accurate capacity calculation without complex data storage
Data Source
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AI summary
This description relates to a method for determining the health status of the cells (Ci) of a battery, comprising: a) during a phase (101) of battery discharge, measuring the voltage Ui across each cell (Ci); b) when a first cell (Ci_lim) reaches a predefined end-of-discharge condition, interrupting (102) the discharge and recording, for each cell (Ci), the voltage Ui of the cell at the end of the discharge phase; c) determining (103) a value QCi_lim representative of the capacity of the first cell; and d) determining (104), for each other cell of the battery, from the value QCi_lim determined in step c) and the end-of-discharge voltages Ui recorded in step b), using a predetermined mathematical function f, a value QCi representative of the cell's capacity.