Battery State of Health Estimation Without Full Discharge
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Solution Overview
Problem
Lithium-ion batteries in battery electric vehicles (BEVs) experience capacity fade due to time-dependent and cycle-dependent factors, leading to premature degradation and high costs, as they are not fully discharged after operation, and existing methods fail to accurately track the state of health without full discharge.
Innovation Solution
A system that determines the remaining capacity of lithium-alloying material cells by calculating time-dependent and cycle-dependent fade components using temperature, voltage, and cycle count data, allowing for the estimation of state of health without requiring full discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full discharge is performed to accurately measure battery capacity, then measurement precision is improved, but battery life is reduced due to increased degradation from complete discharge cycles
Solution Approach 1:
The patent applies partial action by performing capacity estimation without requiring full discharge. The system estimates remaining capacity based on partial discharge data combined with time-dependent and cycle-dependent fade models, thereby avoiding the harmful effects of complete discharge while still achieving accurate capacity assessment.
2Duration of action of stationary object
If battery capacity is tracked without full discharge, then battery life is extended, but measurement precision deteriorates due to insufficient discharge data
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors voltage, temperature, and discharge characteristics, then updates fade component estimates and remaining capacity calculations in real-time. This closed-loop approach allows accurate capacity tracking without full discharge by constantly refining estimates based on observed battery behavior.
Solution Approach 2:
The patent changes the measurement parameters from requiring full discharge voltage-capacity curves to using partial discharge data combined with time and cycle counters. By shifting from complete characterization to incremental monitoring with fade modeling, the system achieves accurate tracking while preserving battery life.
3Measurement precision
If time-dependent and cycle-dependent fade components are separately calculated, then capacity prediction accuracy is improved, but device complexity increases due to multiple calculation components
Solution Approach 1:
The patent segments the capacity fade phenomenon into distinct time-dependent and cycle-dependent components. Each component is calculated separately using specific formulas and input parameters, allowing the system to capture different degradation mechanisms independently and combine them for comprehensive capacity prediction.
Data Source
AI summary
A method may determine a remaining capacity of a cell that includes a lithium-alloying material in an electrode using a controller. The method includes receiving a temperature signal representing a temperature of a partially discharged cell and receiving a voltage signal representing a voltage of the partially discharged cell. The method further includes determining a time-dependent fade component and a cycle-dependent fade component of the cell. The time-dependent fade component of the cell is determined based on the temperature, the voltage, and an operating time of the cell. The cycle-dependent fade component of the cell is determined based on a depth of discharge of the partially discharged cell and cycle count data representing cycle-dependent fade from previous cycles of the cell. The method further includes determining a remaining capacity of the cell based on the time-dependent fade component, the cycle-dependent fade component, and a reference capacity of the cell.