Battery Cell SOH Estimation via CC-CV Phase Current Analysis
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Solution Overview
Problem
Existing methods for determining the State of Health (SOH) of a battery cell require complete discharge and recharge cycles, which are restrictive and may not provide reliable estimates with partial recharge variations.
Innovation Solution
A method using a CC-CV recharge process to measure charging currents and charge variations, calculating coefficients α and β, and determining SOH through a stored function g^-1, allowing for SOH estimation without full charge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complete discharge and recharge cycles are used to determine SOH, then measurement reliability is improved, but time consumption and operational restrictiveness increase
Solution Approach 1:
The patent applies partial action by performing SOH determination during only a portion of the charging process (constant voltage phase) rather than requiring complete charge-discharge cycles. This allows reliable SOH estimation to be obtained from partial charging data, significantly reducing the time and operational restrictions while maintaining measurement reliability through careful selection of measurement points during the CV phase.
2Measurement precision
If complete discharge and recharge cycles are used to determine SOH, then measurement reliability is improved, but ease of operation deteriorates
Solution Approach 1:
The method enables SOH determination during normal charging operations without requiring complete discharge-recharge cycles. By measuring currents at specific points during the constant voltage charging phase and calculating based on partial charge data, the system maintains measurement reliability while greatly improving ease of operation and eliminating operational restrictiveness.
3Loss of time
If partial recharge is used to estimate real capacity, then time consumption is reduced, but measurement precision deteriorates due to high variation requirements
Solution Approach 1:
The patent utilizes the continuous constant voltage charging phase to perform SOH determination. By measuring currents at multiple points during the ongoing CV charging process and continuously calculating the coefficient α and real capacity, the method achieves both time efficiency and measurement precision without requiring high variation in charge levels or interrupting the charging process.
Data Source
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AI summary
The invention relates to a method for determining the health status of a battery cell, implemented by an electronic diagnostic device, comprising the following steps: a) controlling the charging of the cell according to a CC-CV type charging process, comprising a CC phase of cell charging at constant current, followed by a CV phase of cell charging at constant voltage; b) during the CV phase, measuring the charging current Il in the cell at a first instant, measuring the charging current I2 in the cell at a second instant subsequent to the first instant, and measuring the change in charge ΔQ of the cell between the first and second instants; c) calculating a coefficient α representing the ratio ΔQ/(I2-I1); and d) determining a SOH value representative of the health status of the cell taking into account the coefficient α.