Battery State-of-Charge Determination via Tafel Slope Analysis
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Solution Overview
Problem
Current methods for determining the state-of-charge of batteries, such as lead-acid batteries, are impractical, inaccurate, or too complex and expensive, lacking a simple and effective means for precise measurement during formation and operation.
Innovation Solution
A method involving measuring electrical potential at initial and subsequent current states, determining ohmic resistance, calculating the Tafel slope, and comparing it to a predetermined target value to assess the state-of-charge, using a system with a control module and analysis module to control current flow and compute Tafel slope from voltage and current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If advanced modelling techniques or laborious scientific experimentations are used to determine U0, I0, and η, then measurement precision is improved, but device complexity and ease of operation deteriorate
Solution Approach 1:
The patent extracts and measures only the Tafel slope parameter from the complex electrochemical system, isolating this specific kinetic parameter from other complicating factors. By focusing measurement on the Tafel slope rather than attempting to determine all individual parameters (U0, I0, η) separately, the system achieves accurate state-of-charge determination with simpler measurement procedures
Solution Approach 2:
The patent changes the measurement approach from determining multiple complex parameters to measuring a single transformed parameter (Tafel slope) that directly correlates with state-of-charge. This parameter transformation simplifies the measurement while maintaining or improving accuracy, as the Tafel slope inherently encapsulates the electrochemical kinetic information needed for SOC determination
2Measurement precision
If advanced modelling techniques or laborious scientific experimentations are used to determine U0, I0, and η, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The patent extracts and measures only the Tafel slope parameter from the complex electrochemical system, isolating this specific kinetic parameter from other complicating factors. By focusing measurement on the Tafel slope rather than attempting to determine all individual parameters (U0, I0, η) separately, the system achieves accurate state-of-charge determination with simpler measurement procedures
Solution Approach 2:
The measurement system uses the battery's own electrochemical response during normal charging or discharging to self-determine its state-of-charge. The Tafel slope is calculated from voltage and current measurements taken during regular battery operation, eliminating the need for separate complex experimental procedures or external calibration processes
3Loss of information
If methods such as deep discharges, coulombic counting, electrolyte density, open-circuit voltage, loading response, ohmic resistance, or electrochemical impedance spectroscopy are used, then state-of-charge information is obtained, but practicality, accuracy, or complexity increases
Solution Approach 1:
The patent transforms the measurement approach from determining multiple complex parameters to measuring a single transformed parameter (Tafel slope) that directly correlates with state-of-charge. This parameter transformation simplifies the measurement while maintaining or improving accuracy, as the Tafel slope inherently encapsulates the electrochemical kinetic information needed for SOC determination
Solution Approach 2:
The Tafel slope measurement method serves multiple functions: it determines state-of-charge, characterizes electrochemical kinetics, and works during both charging and discharging processes. This single measurement approach replaces the need for multiple specialized techniques, providing a universal solution that simplifies the overall measurement system while delivering comprehensive battery information
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 simple, accurate, and practical method for determining the state-of-charge, enabling precise control during battery formation and operation, and can be used in both charging and discharging processes.
Implementation Method 1
The Tafel equation is shown in Eq. (1), which describes the overvoltage (U−U0) of an electrochemical reaction generating an electric current
Implementation Method 2
The battery exhibits during charging or discharging at least one electrochemical main reaction system and at least one electrochemical side reaction system
Implementation Method 3
there is an unavoidable ohmic voltage drop whenever current is flowing, which is separate from the electrochemical overvoltage. This ohmic voltage drop is directly proportional to the current (I) and the ohmic resistance (RΩ)
Data Source
AI summary
Apparatus, systems, and methods for battery charging and formation are disclosed herein that charge, or discharge, one or more batteries and stop charging or discharging each battery once it has reached a desired state-of-charge, as determined by comparing calculated Tafel slope to a reference Tafel slope for the battery. Computer-readable instructions and/or hardware are also provided for installation upon a previously existing battery charging system or battery discharging system.