Battery SOH Estimation Using Pause-Period Voltage Derivatives
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Solution Overview
Problem
Existing battery state estimation methods assume uniform battery temperature and require complex circuit configurations for impedance measurement, failing to accurately estimate the state of health (SOH) distribution across battery cells, which leads to accelerated degradation and reduced system performance.
Innovation Solution
A battery state estimation device that uses the correspondence between the time derivative of output voltage during a pause period and battery temperature to estimate the SOH of individual cells, allowing for the consideration of temperature distribution across the battery system, thereby estimating the deterioration state of the entire battery system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance measurement using sine wave or rectangular wave is used to estimate battery state, then measurement capability is improved, but circuit configuration becomes complicated
Solution Approach 1:
The patent extracts the impedance measurement function from complex AC signal generation and instead uses the natural pause period during battery operation. By measuring voltage change during this pause without applying external AC signals, the method eliminates the need for complex impedance measurement circuits while retaining the ability to estimate battery state through voltage-based impedance calculation.
Solution Approach 2:
The battery system's own pause period is utilized for measurement purposes. Instead of requiring external measurement signals, the natural pause in battery operation serves as the measurement window, allowing the system to self-diagnose its state without additional complex measurement infrastructure.
2Measurement precision
If frequency response processing is used to measure temperature characteristic of impedance, then measurement accuracy is improved, but analysis process becomes complicated
Solution Approach 1:
The patent extracts the temperature characteristic information directly from voltage measurements during pause periods at different temperatures. By correlating voltage change rates during pauses with battery temperature, the method obtains temperature characteristics without requiring frequency response analysis or complex signal processing.
Solution Approach 2:
The patent replaces complex frequency domain analysis with time domain voltage measurement during pause periods. Instead of processing frequency responses, the method directly measures voltage changes in the time domain and correlates them with temperature, simplifying the analysis process while maintaining measurement accuracy.
3Ease of operation
If average SOH is measured without measuring SOH distribution, then measurement simplicity is improved, but battery system performance prediction becomes inaccurate
Solution Approach 1:
The patent segments the battery system into individual battery cells for separate SOH evaluation. By measuring voltage characteristics of each cell during pause periods, the method obtains SOH distribution across all cells rather than just an average, enabling accurate identification of weak cells that could limit overall system performance.
Solution Approach 2:
The patent implements feedback by continuously monitoring voltage changes during pause periods and updating SOH estimates for individual cells. This feedback mechanism allows the system to track SOH distribution over time and identify cells that are deteriorating faster than others, providing accurate predictions of overall system performance based on the weakest cell.
Data Source
AI summary
An object of the present invention is to provide a battery state estimation device capable of accurately estimating a deterioration state of an entire battery system in consideration of an SOH distribution of battery cells. The battery state estimation device according to the present invention estimates an SOH of a battery cell by using a correspondence between a time derivative of an output voltage during a pause period of the battery cell and a battery temperature, and estimates a deterioration state of an entire battery system by using the SOHs of a plurality of battery cells (see FIG. 1).