Battery OCV Estimation via Transient Resistive Correction
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Solution Overview
Problem
Current methods for determining the open-circuit voltage (OCV) to state-of-charge (SOC) relationship in battery cells are time-consuming and provide limited data points, making them inefficient for characterizing the OCV vs. SOC relationship, especially in battery-powered devices like hybrid-electric vehicles.
Innovation Solution
A controller-programmed method that uses differences and root values of charge and discharge voltage measurements during continuous charge/discharge cycles at higher rates, allowing for faster and more accurate characterization of the OCV vs. SOC relationship, including the use of bi-directional power supplies and sensor modules to monitor battery cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pulse method is used to determine OCV vs. SOC relationship, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent applies continuous charge/discharge cycles instead of discrete pulses, maintaining continuous measurement and data collection throughout the process. This eliminates idle settling time between measurements while continuously advancing the battery through its SOC range, thereby reducing total test duration while maintaining measurement precision through continuous monitoring of voltage, current, and temperature parameters.
Solution Approach 2:
The patent performs preliminary characterization of transient resistive effects by measuring voltage responses at multiple time points during charge/discharge transitions. These preliminary measurements of resistive behavior are then used to correct subsequent OCV measurements, allowing the system to compensate for transient effects without requiring extended settling times, thus reducing overall test duration while maintaining accuracy.
2Productivity
If high magnitude pulse current is chosen, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
By maintaining continuous charge/discharge operation without discrete high-magnitude pulses, the system achieves high productivity through sustained current flow while avoiding the measurement distortions caused by large transient currents. The continuous operation allows for steady-state measurements at each SOC point, preserving measurement precision while maximizing testing speed.
Solution Approach 2:
The patent dynamically adjusts charge/discharge current magnitudes based on measured transient resistive effects and battery state. By modifying current parameters in response to real-time measurements of voltage responses and resistive behavior, the system optimizes the balance between testing speed and measurement accuracy, using higher currents when appropriate but correcting for their effects through measured resistive parameters.
3Measurement precision
If the pulse method is used, then measurement precision is improved, but quantity of substance decreases
Solution Approach 1:
The continuous charge/discharge process generates measurements at every increment of SOC rather than only at discrete pulse endpoints. This continuous data generation dramatically increases the quantity of data points obtained throughout the battery's operating range, providing a detailed characterization of the OCV vs. SOC relationship with high precision at numerous SOC levels simultaneously.
Data Source
AI summary
A vehicle is disclosed that includes a battery and a controller programmed to calculate a battery voltage characteristic from previously measured charge and discharge data. The battery voltage characteristic is based on differences between the previously measured values when state of charge falls in a range in which the differences are approximately equal. Outside of the range, the charge and discharge voltage data are corrected based on a square root of time to obtain the battery voltage characteristic. The characterization may be performed with a high-rate continuous charge and discharge cycle. Also disclosed is an apparatus for generating the battery characteristic that includes a bi-directional power supply. The battery voltage characteristic is obtained based on the differences of the charge and discharge voltage data and corrected data based on the square root of time. A method is also disclosed based on the same.