EV Battery SOH Measurement Using Enhanced Charge Depth
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Solution Overview
Problem
Existing battery health measurement methods for electric vehicles are inaccurate due to varying depths of charge and discharge, leading to errors in assessing the state of health (SOH) and range capabilities.
Innovation Solution
A method and system that control the discharge depth of the battery to a minimum SOC and charge it to a maximum SOC, providing an enhanced charge depth for more accurate SOH measurement, which includes determining normal and enhanced charge depths and using these to calculate driving and enhanced SOH, respectively, to improve range estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the battery is discharged to a normal driven SOC for driving operations, then the vehicle can operate normally, but the SOH measurement accuracy is reduced due to insufficient charge depth
Solution Approach 1:
The system performs preliminary full charging of the battery to maximum SOC before conducting SOH measurements. This preliminary action ensures the battery is in an optimal state for accurate measurement, separating the measurement preparation phase from normal driving operations. The battery is charged to maximum SOC, then discharged to minimum SOC specifically for measurement purposes, rather than attempting to measure during normal partial charge cycles.
2Measurement precision
If the battery charge depth is increased to improve SOH measurement accuracy, then measurement precision improves, but the complexity of the charging control process increases
Solution Approach 1:
The charging control system dynamically adjusts charge depth based on the measurement phase. During normal operation, the battery is charged to a normal SOC appropriate for driving. During SOH measurement phases, the system dynamically switches to charging at maximum SOC to ensure adequate charge depth for accurate measurements. This dynamic adjustment resolves the contradiction by adapting charge depth to operational requirements.
Solution Approach 2:
The charging control process is segmented into distinct operational modes: normal driving mode with standard charging, and measurement mode with full charging to maximum SOC. This segmentation allows the system to optimize for measurement accuracy during measurement phases without permanently complicating the overall charging system, as each mode has its own simplified control logic.
3Measurement precision
If the battery is discharged beyond normal driven SOC to achieve enhanced charge depth, then SOH measurement accuracy improves, but the time required for complete charge cycles increases
Solution Approach 1:
The system implements periodic full charge cycles for SOH measurements rather than requiring continuous full charging. Normal operations use efficient partial charging to normal SOC, while periodic measurement cycles perform complete charge to maximum SOC followed by discharge to minimum SOC. This periodic approach achieves accurate measurements without extending the time of everyday charging operations.
Data Source
AI summary
A method and system for estimating state of health (SOH) of a battery configured for providing electrical power to a motor for driving a vehicle. The method and system configured for measuring an enhanced SOH for the battery according to an enhanced SOH process. The enhanced SOH process including maximizing a discharge depth of the battery to maximize accuracy of the enhanced SOH measurement.