Battery State-of-Health Estimation via Resistance and Temperature Mapping
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Solution Overview
Problem
Current methods for estimating the state of health (SOH) of motor vehicle batteries are inefficient and lack consensus, particularly for lead-acid batteries, as they often require intrusive tests and do not accurately account for degradation due to sulphation and corrosion.
Innovation Solution
A method that measures the internal resistance and temperature of the battery after a rest phase, using a predetermined map to estimate SOH through linear interpolation, allowing for precise estimation of battery health by considering voltage and current samples collected at high frequency during discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If intrusive tests are used to measure battery internal resistance, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The patent performs preliminary measurements of open-circuit voltage and short-circuit current during normal battery operation before the actual SOH estimation. These preliminary actions capture the necessary electrical characteristics without requiring intrusive testing, allowing the battery to remain in its normal operational state throughout the process.
Solution Approach 2:
The battery management system uses the battery's own operational electrical signals (voltage and current measurements during normal operation) to perform self-diagnosis and SOH estimation. The system leverages existing operational data rather than requiring external testing equipment or intrusive procedures.
2Ease of manufacture
If simple SOH evaluation based on internal resistance is used, then ease of manufacture is improved, but measurement precision deteriorates
Solution Approach 1:
The patent transforms the simple internal resistance measurement into a more precise SOH estimation by changing the parameters used: instead of directly measuring resistance, the system measures open-circuit voltage and short-circuit current, then calculates SOH using the ratio of these parameters. This parameter transformation maintains ease of manufacture while significantly improving measurement precision.
Solution Approach 2:
The patent introduces intermediate calculation steps using open-circuit voltage and short-circuit current as intermediary parameters. Rather than directly evaluating internal resistance, the system uses these intermediate measurements to derive SOH, thereby improving precision while maintaining system simplicity.
3Measurement precision
If multiple measurement parameters are collected, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing battery management system multi-functional by enabling it to perform both normal operational monitoring and SOH estimation using the same voltage and current measurement infrastructure. The system universally uses available electrical signals for multiple purposes, improving precision without adding dedicated measurement hardware.
Solution Approach 2:
The battery management system serves multiple functions using its existing measurement capabilities. The same voltage and current sensors used for operational control also provide data for SOH estimation, eliminating the need for additional measurement devices and reducing overall system complexity.
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 method provides a fine estimate of battery health, accounting for sulphation and corrosion, and is suitable for integration with on-board automotive applications, offering improved accuracy and reduced intrusiveness compared to existing methods.
Implementation Method 1
calculating the internal resistance of the battery from the voltage-current measurement pair obtained and from another pair of voltage-current values of the battery measured during the rest phase
Data Source
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AI summary
The invention relates to a method of the type for estimating state-of-health (SOH) based on a measurement of the internal resistance (Rb) of the battery. According to the invention, the state-of-health is also estimated using a measurement of an internal temperature (Tb) of the battery and the state-of-charge (SOC) thereof. The state-of-health (SOH) of the battery is obtained by means of a pre-established cartography to which the resistance, the measured temperature and the state-of-charge of the battery are applied as input. The invention also relates to a battery measurement sensor and a battery management system adapted to carry out the method of the invention.