Battery Internal Resistance Measurement by Switched DC Load
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Solution Overview
Problem
Existing methods for determining battery impedance are either cost-intensive due to the need for complex AC measurements or inaccurate for higher battery capacities using DC measurements, making it difficult to assess the condition of batteries with different capacities efficiently.
Innovation Solution
A method involving periodic switching between two current intensities to measure the internal resistance of rechargeable energy storage devices, allowing for accurate determination across various capacities using a simple and cost-effective DC measurement approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC measurement is used to determine battery impedance, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the complex AC measurement system with a simpler DC measurement system. Instead of using alternating voltage and current to determine impedance, the invention uses direct voltage measurements at two different current intensities to calculate internal resistance, thereby eliminating the need for complex AC measurement circuitry while maintaining measurement capability
Solution Approach 2:
The patent changes the measurement parameters from AC voltage/current to DC voltage measurements. By measuring voltage at two different DC current intensities (I1 and I2) and calculating the difference, the system determines internal resistance without requiring AC signal generation and detection circuitry, thus simplifying the device
2Device complexity
If DC measurement is used to determine battery impedance, then device complexity is reduced, but measurement accuracy deteriorates for higher battery capacities
Solution Approach 1:
The patent employs periodic switching between two different current intensities (I1 and I2) to stimulate the battery. This periodic variation in current allows the measurement system to capture voltage differences that occur during the switching transitions, enabling accurate determination of internal resistance even for high-capacity batteries where conventional DC measurements fail
Solution Approach 2:
The system uses the measured voltage values from both current intensity levels to calculate internal resistance through a feedback mechanism. By continuously monitoring the voltage at different current levels and applying the calculation formula R = (U2 - U1) / (I2 - I1), the system compensates for the limitations of DC measurement in high-capacity batteries
3Adaptability or versatility
If a single measuring device is used for all battery capacities, then adaptability is improved, but measurement accuracy deteriorates for higher capacities
Solution Approach 1:
The patent creates a universal measuring device that can accurately measure internal resistance across a wide range of battery capacities (from low to high capacity). The device achieves this by using a standardized measurement procedure involving two current intensities and voltage differential calculation, eliminating the need for capacity-specific measurement circuits or multiple different devices
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
Enables accurate measurement of internal resistance for batteries with capacities between 1 Ah and 200 Ah, improving measurement accuracy and reducing the need for multiple measuring devices, while maintaining cost-effectiveness.
Implementation Method 1
determining the internal resistance based on the detected first and second voltages
Data Source
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AI summary
According to a first aspect, a method for determining the internal resistance of a rechargeable electrical energy storage device is presented. The method includes measuring a first voltage of the energy storage device while a first current is drawn from it. Furthermore, the method includes measuring a second voltage of the energy storage device while a second current, greater than the first, is drawn from it. Additionally, the method includes periodically switching between the drawing of the first and second currents. Optionally, the method further includes determining the internal resistance based on the measured first and second voltages, which are recorded during the periodically switched first and second currents.