Battery Condition Assessment via Voltage Discharge Slope Analysis
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Solution Overview
Problem
Existing battery condition assessment methods are limited by unique voltage discharge curves, lack of direct energy measurement, requirement for controlled temperature, high equipment costs, and complexity in interpreting results, making it difficult for laypersons to accurately determine battery damage levels without resting the battery in an open-circuit voltage state.
Innovation Solution
A method involving measuring terminal voltage over time while discharging the battery at a predetermined current, calculating the slope of the natural logarithm of voltage change, and comparing it to a threshold slope based on similar batteries with known conditions, using an apparatus with a data acquisition board and processor to determine the damage level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage sensing is used to determine battery condition, then voltage discharge curves can be measured, but each voltage discharge curve is unique and changes as the battery ages, making comparison difficult
Solution Approach 1:
The patent transforms the voltage measurement from absolute voltage values to a normalized voltage change rate (slope of voltage vs. time). This parameter transformation makes the measurement comparable across different batteries by focusing on the rate of change rather than absolute values, thereby resolving the issue of unique discharge curves.
2Measurement precision
If coulomb counting is used to determine remaining capacity, then current integration over time provides SOC, but it does not directly measure energy in the battery and assumes initial charge based on Peukert's law
Solution Approach 1:
The patent replaces the electrical measurement approach (coulomb counting) with a temporal measurement approach (voltage change rate over time). Instead of integrating current over time, the method measures how quickly voltage changes during discharge, providing a more direct indicator of energy content without relying on Peukert's law assumptions.
3Measurement precision
If cranking test is used to determine state of health, then voltage comparison during engine cranking provides SOH, but it requires controlled temperature conditions
Solution Approach 1:
The patent extracts the essential measurement (voltage change rate during discharge) from the complex cranking test procedure. By focusing only on the voltage-time relationship during a simple discharge test, the method removes the requirement for controlled temperature conditions while maintaining measurement precision.
4Measurement precision
If AC conductance test is used to measure dynamic conductance, then time-varying AC signal response provides conductance data, but repeated tests at multiple frequencies are needed and accuracy diminishes when testing more than one battery
Solution Approach 1:
The patent uses a simple, low-cost measurement approach (voltage-time slope during discharge) that can be quickly performed on multiple batteries without requiring complex AC signal generation and analysis equipment. Each test is simple and quick, allowing efficient testing of multiple batteries with consistent accuracy.
5Measurement precision
If electrochemical impedance spectroscopy is used to evaluate battery condition, then impedance at different AC frequencies provides detailed information, but expensive equipment and training to interpret results are required
Solution Approach 1:
The patent replaces expensive EIS equipment with simple voltage and time measurement tools. The measurement method produces straightforward slope values that can be directly compared against reference values, eliminating the need for complex impedance spectrum interpretation while maintaining measurement precision.
6Measurement precision
If traditional methods are used to determine battery condition, then various measurements can be taken, but the battery needs to be in a rested open-circuit voltage state during testing
Solution Approach 1:
The patent performs the measurement during the discharge process itself rather than requiring the battery to be rested beforehand. By measuring the voltage change rate during active discharge, the method obtains accurate condition assessment data without the time loss associated with resting the battery to reach open-circuit voltage state.
Data Source
AI summary
Systems and methods for determining the damage level of a battery are provided. An exemplary method includes measuring a terminal voltage of the battery over time while discharging the battery at a predetermined current; calculating a slope of a natural logarithm of a rate of change of a first voltage of the battery over time based on the terminal voltage of the battery; and comparing the calculated slope to a threshold slope that is based on measurements of a plurality of similar batteries with known conditions. The first voltage of the battery may correspond to a voltage across an RC component of an equivalent circuit model for the battery.