Battery Stress-Strain Sensor for SOC and SOH Measurement
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Solution Overview
Problem
Current methods for determining the state of charge (SOC) and state of health (SOH) of batteries, particularly lithium-ion batteries, are imprecise and unsuitable for consumer applications due to reliance on voltage measurements, coulomb counting, and complex models, which are sensitive to temperature and current, and require offline testing and recalibration.
Innovation Solution
A battery management system using a container with a stress/strain sensor and a processor to measure mechanical expansion, which correlates stress/strain with SOC and SOH, allowing for accurate determination without the need for complex mathematical computations or offline testing, using linear or non-linear approximations for relationship data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage-based measurement is used to determine SOC, then the measurement is simple, but the precision is poor because voltage is insensitive to SOC and dependent on temperature and current
Solution Approach 1:
The patent introduces a mechanical intermediary (stress/strain sensor) that indirectly measures SOC through the physical expansion/contraction of battery materials during charge/discharge cycles. This mediator provides a more precise measurement signal than direct voltage measurement while maintaining system simplicity.
2Measurement precision
If coulomb counting method is used to determine SOC, then the measurement precision is improved, but the device complexity increases due to mathematical intensity and periodic recalibration requirements
Solution Approach 1:
The patent replaces the complex electrical/mathematical coulomb counting system with a simpler mechanical measurement system using stress/strain sensors. This substitution eliminates the need for mathematical integration and periodic recalibration while providing direct physical measurement of charge state through material expansion.
3Measurement precision
If controlled capacity measurement is used to determine SOH, then the measurement precision is improved, but the loss of time increases because the battery must be offline for many hours
Solution Approach 1:
The patent enables the battery to be measured during normal operation without requiring external testing equipment or taking the battery offline. The stress/strain sensor continuously monitors mechanical properties during charge/discharge cycles, allowing SOH determination while the battery remains in service.
4Measurement precision
If controlled capacity measurement is used to determine SOH, then the measurement precision is improved, but the productivity decreases because the battery cell must be offline for the duration of measurement
Solution Approach 1:
The patent maintains continuous useful action by enabling SOH measurement during normal battery operation. The stress/strain sensor provides continuous monitoring without interrupting charge/discharge cycles, ensuring the battery remains productive throughout the measurement process.
5Device complexity
If conventional SOC measurement methods are used, then the device complexity is low, but the loss of energy increases due to power loss from periodic full charge/discharge recalibration
Solution Approach 1:
The patent replaces electrical recalibration methods with mechanical measurement that requires no energy-intensive full charge/discharge cycles. The stress/strain sensor provides continuous SOC tracking during normal operation, eliminating periodic recalibration energy losses.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a more accurate and efficient method for determining SOC and SOH, accounting for self-discharge and reducing power loss, suitable for various battery types, including lithium-ion cells in electric vehicles, with improved battery pack performance and longevity.
Implementation Method 1
measure mechanical expansion, which correlates stress/strain with SOC and SOH
Data Source
AI summary
A battery management system for use with a battery under test is disclosed. The system includes a container configured to hold the battery. The system also includes a stress/strain sensor. The container is configured to hold the battery in fixed relationship with respect to the stress/strain sensor. A processor is coupled to the stress/strain sensor, the processor being configured to measure the stress/strain on the battery and determine the state of health (SOH) of the battery based on the measured stress/strain and previously stored SOH relationship data for the battery. The processor may be configured to determine a state of charge (SOC) of the battery based on the measured stress/strain, the SOH of the battery and previously stored SOC relationship data for the battery.