Battery Internal Resistance Measurement via Voltage-Current Correlation
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Solution Overview
Problem
Existing methods for measuring internal resistance of vehicle batteries are cumbersome, costly, and difficult to implement in embedded environments, especially when batteries are mounted within vehicles, and struggle with defining selection criteria for current dispersion-based resistance estimation.
Innovation Solution
A system and method that measures current-voltage pairs, calculates the correlation between current and voltage, and estimates internal resistance using a preset threshold, employing regression analysis and temperature consideration to accurately determine the resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate apparatus is connected to measure internal resistance of the battery, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The battery management system measures internal resistance using its own existing voltage and current sensors without requiring external measurement apparatus. The system utilizes its built-in capability to monitor voltage and current to calculate internal resistance through correlation analysis, making the battery self-diagnostic for this parameter.
Solution Approach 2:
The voltage and current sensors originally designed for general battery monitoring are made multi-functional by using them not only for state-of-charge estimation but also for internal resistance measurement through correlation analysis of voltage-current pairs.
2Measurement precision
If a separate apparatus is mounted within the vehicle to measure internal resistance, then measurement capability is improved, but part cost increases
Solution Approach 1:
The battery management system performs internal resistance measurement using its own existing voltage and current sensors, eliminating the need for separate measurement apparatus and reducing part costs while maintaining measurement capability.
3Measurement precision
If modeling analysis is used to estimate internal resistance from voltage output, then measurement capability is improved, but ease of operation deteriorates due to difficulty in embedded environment application
Solution Approach 1:
The complex modeling analysis approach is replaced with a simpler statistical correlation method that analyzes the relationship between voltage and current pairs. This substitution makes the estimation process more suitable for embedded environments by reducing computational complexity while maintaining estimation capability.
4Measurement precision
If statistical method with current dispersion threshold is used to obtain resistance, then measurement capability is improved, but ease of operation deteriorates due to difficulty in defining selection criteria
Solution Approach 1:
The system calculates the correlation coefficient between voltage and current pairs and uses this feedback to objectively determine when sufficient data has been collected for accurate internal resistance calculation, eliminating the need for subjective threshold selection criteria.
Data Source
AI summary
A system and method for more accurately measuring an internal resistance of a battery for a vehicle are provided. The method includes measuring, by a controller, current-voltage pairs for the battery and calculating a correlation between current and voltage in the measured current-voltage pairs. In addition, the internal resistance of the battery is measured using the current-voltage pairs having the correlation equal to or greater than a preset threshold.